es dogs

ay.

ta dF

Pe 4
Ob ae
ease

Ay)

ov

Mie N Sa PLOWS

OF THE

ROYAL SOCIETY OF EDINBURGH.

PRANS ACTIONS

OF THE

PO YA SOCIETY

OF

EDINBURGH.

VOL. XXX.

EDINBURGH:

PUBLISHED BY ROBERT GRANT & SON, 107 PRINCES STREET,
AND WILLIAMS & NORGATE, 14 HENRIETTA STREET, COVENT GARDEN, LONDON.

MDCCCLXXXVII.

Part I. published . Dee. 3, 1883.
PARm ‘ : ; . Nov. 29, 1884.
Part III. 53 ; . Feb, 13, 1886.
Part IV. 3 ; . duly 9, 1887.

TT.

IV.

VII.

VIII.

CONTENTS.

PART I. (1882-83.)

. The Pycnogonida dredged in the Fare Channel during the Cruise

of H.M.S. “ Triton” (in August 1882). By Dr P. P. C. Hoex,
Member of the Royal Academy of Science of the Netherlands.
(Plate 1),

. Bright Clouds on a Dark Night Sky. By Professor C. P1azzi SMytu,

Astronomer-Royal for Scotland. (Plates II.—XIV.),

Note on the Little b Group of Lines in the Solar Spectrum and the
New College Spectroscope. By C. Piazzt Smytu, Astronomer-
Royal for Scotland. (Plate XV.),

Observations on the Annual and Monthly Growth of Wood in
Deciduous and Evergreen Trees. By the late Sir Rosert
CHRISTISON, Bart., and Dr CHRISTISON, .

. A Contribution to the Chemistry of Nitroglycerine. By MattHew

Hay, M.D., Assistant to the Professor of Materia Medica in
the University of Edinburgh,

. The Elementary Composition of Nitroglycerine. By MattrHrtw

Hay, M.D., and Orme Masson, M.A., B.Sc.,

Report on the Tunicata collected during the Cruise of H.MLS.
“Triton” in the Summer of 1882. By W. A. Herpmay, D.Sc.,
Professor of Natural History in University College, Liverpool.
(Plates XVI.-XX.), ; :

Report on the Pennatulida dredged by H.M.S. “ Triton.” By A.
Mines MarsHatt, M.D., D.Se., M.A., Fellow of St John’s

College, Beyer Professor of D olony 3 in Ona — (Plates
XXI.-XXV.), ;

PAGE

ia:

37

45

67

78

93

119

vi

XI.

XII.

pGHOE

ZY

XV.

XVI.

CONTENTS.

Asteroidea dredged in the Faerie Channel during the Cruise of
H.M.S. “Triton” in August 1882. By W. Percy SLApEn,
F.L.S., F.G.S. Communicated by Joun Murray, F.R.S.E.
(Plate XXVI_), .

. On a New Species of Pentastomum (P. protelis) from the Mesentery

of Proteles cristatus; with an Account of tis Anatomy. By
W. E. Hoyiz, M.A. (Oxon.), M.R.C.S., Naturalist to the
“Challenger” Commission. (Plates XXVITI., XXVIII),

On Superposed Magnetisms in Iron and Nickel. By Professor
C. G. Knott, D.Sc. (Plate XXIX.),

On the Relative Electro-Chemical Positions of Wrought Iron, Steels,
Cast Metal, &c., in Sea Water and other Solutions. By THomas
AnpreEws, A.M., Inst. C.E., F.C.S. (Plates XXX.-XXXIV.),

PART II. (1883-84.)

Report on the Tunicata dredged during the Cruises of H.M.SS.
“ Porcupine” and “ Lightning” in the Summers of the Years
1868, 1869, and 1870. By Professor Hrerpman, F.R.S.E.
(Plates XXXV., XXXVTL),

Note on Sir David Brewster's Line Y in the Infra-Red of the Solar
Spectrum. By Professor Piazzi Smyvu, F.R.S.E., Astronomer-
Royal for Scotland. (Plate XX XVII),

On the Formation of Small Clear Spaces in Dusty Air. By JoHN
AITKEN, F.R.S.E. (Plate XX XVIII),

On Stichocotyle Nephropis, a New Trematode. By J. T. Cun-
NINGHAM, B.A. (Plate XX XIX.),

XVII. The Enumeration, Description, and Construction of Knots of

fewer than Ten Crossings. By Rev. T. P. Kirkman, F.R.S.
(Plates XL.-XLIIT.),

PAGE

153

193

204

219

233
239

273

281

XVIII.

XIX.

XXIV.

XXV.

XXVL
XXVIL.

xx viLE

CONTENTS.

On the Approximation to the Roots of Cubic Equations by help
of Recurring Chain-Fractions. By Epwarp Sane, LL.D.,
F.R.S.E.,

On Knots. Part II. By Professor Tarr, Sec. R.S.E. (Plate
XLIV.),

Appendiz.—Note on a Problem in Partitions. By Professor

Tait, Sec. R.S.E.,

. On the Philosophy of Language. By Emeritus Professor

BLACKIE, F.R.S.E.,

. The Old Red Sandstone Volcanic Rocks of Shetland. By

B. N. Peacu, F.R.S.E., and Joun Horne, F.R.S.E. (Plates
XEV XLVI.) : ; : :

. Observations on a Green Sun and Associated Phenomena. By

Professor C. Micuiz Smits, F.R.S.E. (Plate XLVIL),

. An Example of the Method of Deducing a Surface from a Plane

Figure. By Professor L. Cremona, LL.D. Edin., Hon.
F.R.SS. Lond. and Edin.,

PART III. (1884-85.)

Micrometrical Measures of Gaseous Spectra under High Dis-
persion. By Professor C. Prazzi SMytu, F.R.S.E., and Astro-
nomer-Royal for Scotland. (Plates XLVIII-LXXVIIL.),

On Bipartite Functions. By Tuomas Murr, LL.D., .

The 364 Unijilar Knots of Ten Crossings, Enumerated and
Described. . By Rev. Toomas P. Kirxman, M.A., F.R.S,

On Knots. Part III. By Professor Tarr. (Plates LX XIX.-
LXXX1.), ;

A New Graphic Analysis of the Kinematics of Mechanisms.
By Professor Roserr H. Smirx, Mason College, Birming-
ham. (Plate LXXXI1.),

Vil

PAGE

311

327

340

343

309

389

411

415

461

483

493

507

vill

X XIX.

XXX.

XXXII.

XXXII.

XX XI.

XXXIV.
XXXV.

CONTENTS.

The Visual, Grating and Glass-lens, Solar Spectrum (in 1884).
By Professor C. Prazzi Smytu, F.R.S.E., and Astronomer-
Royal for Scotland. (Plates LX XXIII.-CXLIIL),

Observations on the Recent Calcareous Formations of the
Solomon Group made during 1882-84. By H. B. Guppy,
M.B., F.G.S., Surgeon H.M.S. “Lark.” Communicated by
JOHN Murray, Ph.D. (Plates CXLIV., CXLV.),

Observations on Atmospheric Electricity. By Professor C.
Micuig Suiru. (Plate CXLVL),

Note on Ectocarpus. By Joun Rarrray, M.A., B.Sc., Scottish
Marine Station, Granton, Edinburgh. Communicated by
JoHN Murray, Ph.D. (Plates CXLVII., CXLVIIL),

Anatomy and Physiology of Patella vulgata. Part I. <Ana-
tomy. By R. J. Harvey Grsson, M.A. Communicated by
Professor HERDMAN, D.Sc. (Plates CXLIX.-CLIIL),

Detached Theorems on Circulants. By THomas Mutr, LL.D.,

On the Hessian. By Professor CuRystTAt,

APPENDIX —

The Council of the Society,

Alphabetical List of the Ordinary Fellows,

List of Honorary Fellows,

List of Ordinary Fellows Elected during Sessions 1883-85,

Laws of the Society,

The Keith, Brisbane, and Neill Prizes,

Awards of the Keith, Makdougall-Brisbane, and Neill Prizes,

Proceedings of the Statutory General Meetings,

List of Public Institutions and Individuals entitled to receive Copies

of the Proceedings and Transactions,

Index,

PAGE

519

545

583

589

601
639
645

654
655
668
674
681
688
690
693

701
707

TRANSACTIONS

ROYAL SOCIETY OF EDINBURGH.

VOL. XXXII. PART IL—FOR THE SESSION 1882-83.

CONTENTS.
: Page
Art. I.—The Pycnogonida dredged in the Farce Channel during the Cruise of H.M.S.
“Triton” (in August 1882). By Dr P. P. C. Horx, Member of the Royal
Academy of Science of the Netherlands. (PlateI), . . . : : 1
Il.— Bright Clouds on a Dark Night Sky. By C. Prazz1 Suyru, Astronomer-Royal for
. Scotland. (Plates II. to XIV.), ‘ : ; ¢ P ; 11
III.—WNote on the Little b Group of Lines in the Solar Spectrum and the new College
Spectroscope. By C. Prazzt Smyru, Astronomer-Royal for Scotland.
(Plate XV.), . ‘ : ‘ ; : ; : ‘ 37
IV.— Observations on the Annual and Monthly Growth of Wood in Deciduous and Ever-
green Trees. By the late Sir Ropert Curisrison, Bart., and Dr Curistisoy, . 45

V.—A Contribution to the Chemistry of Nitroglycerine. By MartHew Hay, M.D.,
Assistant to the Professor of Materia Medica in the University of Edinburgh, . 67

Vi—The Elementary Composition of Nitroglycerine. By Mattunw Hay, M.D., and
Orme Masson, M.A., B.Sc, . wis : ; : : " 78

VII.—Report on the Tunicata collected during the Cruise of H.M.S. “Triton” in the
Summer of 1882. By W. A. Herpman, D.Sc., Professor of Natural History
in University College, Liverpool. (Plates XVI. to XX.), : ? 5 93

VIII.—Report on the Pennatulida dredged by H.M.S. “ Triton.” By. A Mitnes MarsHatn,
* M.D., D.Sc., M.A., Fellow of St John’s College, Beyer Professor of Zoology in
Owens College. (Plates XXI. to XXV.), . : ; ‘ or eS

IX.—Asteroidea dredged in the Faerie Channel during the Cruise of H.M.S. “ Triton”
in August 1882. By W. Percy Suapen, F.L.S., F.G.S. Communicated by
JoHN Murray, F.R.S.E. (Plate XXVI.), . ‘ : < eae 855)

[For remainder of Contents, see last page of Cover. ]

TRANSACTIONS.

I.—The Pycnogonida dredged in the Faroe Channel during the Cruise of H.MLS.
“ Triton” (in August 1882). By Dr P. P. C. Hox, Member of the Royal
Academy of Science of the Netherlands. (Plate I.)

(Communicated by Mr Joun Murray.)

During the cruise of H.M.S. “ Triton” a small but very interesting collec-
tion of Pycnogonids was made. Mr Joun Murray sent it over to me, and
asked me to prepare a report on it, which I gladly undertook to do.

The thirteen stations of the “Triton” cruise are situated about 60° lat.
north, and between 6° and 9° 6’ long. west of Greenwich. At six of these
stations Pycnogonids were obtained. The depth of the sea at these stations
varies from 433 to 640 fathoms; at two of them the bottom was hard
ground or stones, at three the bottom was mud, at one ooze. At three of the
stations the bottom temperature was about 45°, at the three others about 30°.
The first three being in the so-called warm area, the latter in the cold area.

The number of species collected amounts to eleven. Three of them inhabit
the cold area, and were not found in the warm area (Vymphon Stromiz, Kroyer ;
Colossendeis proboscidea, Sab. spec.; and C. angusta, G. O. Sars); five species
were observed only in the warm area (Nymphon hirtipes, Bell; N. macrum,
Wilson ; NV. longitarse, Kroyer; Pallene malleolata, G. O. Sars ; Pallenopsis
tritonis, n. sp.). The remaining three seem to inhabit the cold as well as the
warm area. Nymphon macronyx, G. O. Sars, however, is represented by several
hundred specimens from the cold area, and by one specimen only from the
warm area; and this is also the case with Nymphon robustum, Bell. Of both
species the number of specimens collected at stations in the cold area was so
large, that the occurrence of one specimen at astation in the warm area
seems rather unimportant-—it must be considered as a specimen which has got
astray ; but whether this happened before or after its being dredged, I cannot
say with certainty. As in both instances the station in the warm area
from which the single specimen was obtained follows one in the cold area,

VOL. XXXII. PART I. A

2 DR P. P. C.. HOEK ON’ THE

at which several hundred specimens of the one, and upwards of fifty of the
other, species were collected, it is even probable that—the same fishing appara-
tus (trawl) being used—one specimen was overlooked either remaining between
the meshes of the trawl or clinging to the rope. The nature of the animals,
with their long and numerous legs, each furnished with a claw, favours this
‘suggestion. The only specimen which remains as inhabiting both areas is
Nymphon grossipes, Oth. Fabr.: it 1s represented by eight specimens, four of
which are from the cold water area, and four from the warm water area.

Comparing these facts with those furnished by the cruise of the “ Knight
Errant” (1880), of the “ Véringen” (1876 and 77-78), and of the “ Willem
Barents ” (1878 and 1879), and also with what is known about the Pycnogonids
of the North American coast (for which knowledge we are much indebted to
the studies of Mr E. B. Witson), we have made the following table, from
which those species are excluded which have hitherto been only once
observed :—

Area in which | A7@® it Which | jyeq in which| _ Does it inhabit the
Name of the Species. H. M.S. ‘Triton’ ‘Kinichtekcant G. O. Sars inhabit the | Atlantic near
caught it. b aught it. caught it. Arctic Sea ? teins
Nymphon robustum, Bell, . : Cold Cold Cold Yes No
“A macronyx, G. G. Sars, . Cold Cold Cold 2 No
S Stroma, Kroyer, . : Cold Both Cold Yes Yes
7 hirtipes, Bell, . : Warm ey Cold Yes Yes
. macrum, Wilson, . A Warm ae Bi. No Yes
Fe longitarse, Kroyer, : Warm why ine Warm Yes Yes
" grossipes, Oth. Fabr., . Both Cold Cold Yes Yes
sj serratum, G. O. Sars, . iis ah Beth Yes No
Colossendeis proboscidea, Sab. spec., Cold Cold Cold Yes No
.) angusta, G. O. Sars, . Cold 3 Cold ? Yes
Pallene malleolata,G.O. Sars, . Warm bis Both 2 No
Pallenopsis tritonis, n. sp... : Warm as “ No Probably

From this table the following conclusions may be deduced :—

1. The species which inhabit the cold area in the Atlantic occur also in the
Arctic Ocean (NV. robustum, C. proboscidea) ; those which have not yet been observed
in the Arctic may be expected to be found there (N. macronyx, C. angusta).
They are not found near the American coast, or only at a very considerable
depth (Colossendeis angusta at a depth from 810 to 1242 fathoms).

PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. “TRITON.” 38

2. The species which inhabit the warm area in the Atlantic occur also at a
much lower latitude near the American coast (NV. macrum, Pallenopsis, spec.).
They are not found in the Arctic Ocean.

3. The species which inhabit both areas in the Atlantic occur in the Arctic
Ocean as well as near the American coast (NV. Strdmii, N. hirtipes, N. grossipes).
Nymphon serratum inhabits both areas in the Atlantic ; it has been observed in
the Arctic, and will probably be found at a much lower latitude. Pallene
malleolata inhabits both areas also, and will probably be found to have a wide
northern as well as southern distribution.

4, The only species whose distribution does not seem to be in accordance with
the temperature of the water it inhabits is V. ongitarse. Hitherto it has only
been observed in the warm water area, yet it inhabits the Arctic as well as the
New England coast. However, I think this exception is of no consequence :
in the first place, because it always, in the northern parts of the Atlantic at
least, lives rather solitary, and therefore may be found in the future in the cold
area also ; and in the second place, because it is a somewhat uncertain species,
and perhaps will turn out to bea variety of NV. grossipes.

A few notes on the species submitted to my examination are appended
here :—

1. Nymphon robustum, Bell.

A very large number of specimens of this species was obtained at
Stations 8 and 9, fourteen specimens were dredged at Station 6, and one specimen
was taken from the bottle which contained the Pycnogonids of Station No. 10.
The specimens show the same difference with those of higher northern latitudes
as do those dredged by the “ Knight Errant ” in 1880; they are not nearly so
stout, and are smaller. Numerous specimens had attached to the legs a Scal-
pellum, for which I proposed the name Scalpellum nymphocola. It is a
curious fact, that the specimens of the Barents Sea (and I studied also those of
the third and fourth cruise of the Dutch schooner “ Willem Barents”) never
had this Cirriped on their legs.

2. Nymphon hirtipes, Bell.

Only one small specimen of this species was dredged at Station No. 5. Mr
Epmunp B. WILson and Professor G. O. Sars apply to this species the name J.
hirtum, Fabr. But the description of Fasricius (Lntom. System., 1794) is not
only very brief, but it is totally insufficient to recognise the species. The
species which Kroyer (1845) described under the name WN. hirtwm, Fabr., no
doubt differs from the present species (as is stated by Professor Sars and by

4 DR P. P. C. HOEK ON THE

Witson also). I therefore retain the name of Fasricrus for KRoyEr’s species,
the first that has been described recognisable under that name, and I give to
the other the name of Bet1, whose figures and description doubtless refer to it.

Although this species is common in high northern latitudes (Bett, Miers,
Hoek), it seems to be rather scarce in the North Atlantic (Professor G. O. Sars
only observed it once; it was not obtained by the “ Knight Errant”; and the
“Triton” collected only one specimen). Off Halifax it was taken in great num-
bers by the U.S. Fish Commission in 1877 (Wilson).

3. Nymphon Strémi, Kroyer.

During the cruise of H.M.S. “Triton” this species was met with on three
different occasions. At Station 9 about forty specimens of it were taken ;
at Station 8, three, and at Station 6, one specimen. It was not observed at
one of the stations of the warm area, as happened during the cruise of the
“ Knight Errant.”

4. Nymphon macronyx, G. O. Sars.

This species was first observed by Professor Sars during the first cruise of
the “ Voringen” (1876); it was again collected in the Faroe Channel during the
summer of 1880 (“ Knight Errant”) ; and it is now dredged for the third time
by H.MLS. “Triton.” Professor Sars collected four specimens; the “Knight
Errant” took about thirty specimens; and the “Triton” several hundreds.
These specimens were obtained in about lat. 60° north, whereas Sars got his
specimens at 62° 44’ 5”. Whether its distribution will be found to extend still
further north, I cannot say with certainty. I only think it very probable, as
this species is an inhabitant of the cold area.

At Station 8, several hundred specimens of this species were taken,
y 9, about fifty specimens 5) 4
fe G) ive 7 3 ”
and one specimen (see p. 1) was found in the bottle containing the Peis
gonids from Station 10.

One of the specimens of Station 8 has no eyes; or, better perhaps, has no

pigment in its eyes.

5. Nymphon macrum, Wilson.

Witson, Pycnogonida of New England, Report U.S. Commission of Fish and Fisheries, vi.
(1878), 1881, p. 487, pl. iv., figs. 21-23.
Syn. Vymphon brevicollum, Hideke Report “Challenger” Pycnogonida, 1881, p. 45, pl. iii.
figs. 13-15; pls. xv. figs. 12 and 13.
The general appearance of this species is much like MW. Strémii. When

studying the details as to the length of the joints of the palpi, of the tarsal joints

PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. “TRITON.” 5

of the legs, the structure of the first segment of the body, of the oculiferous
tubercle, &c., it is, however, easily distinguished not only from the above named,
but also from other species of the genus.

The eggs of NV. Strémii are small and very numerous; those of NV. macrum
are very large, each egg-mass containing a few eggs only.

This species inhabits the warm water area. Four specimens were collected
at Station 10; nineteen specimens at Station 11.

The U.S. Fish Commission took this species at a few localities in the Gulf
of Maine, in from 85 to 115 fathoms; the “Challenger” south of Halifax, in 83
fathoms. The depth at which it was collected during the cruise of H.M.S.
“Triton” was between 516 and 555 fathoms.

6. Nymphon grossipes, Oth. Fabr.

In all, eight specimens which I refer to this species were collected. In
most of its characters this species is very variable; its conical and acutely
pointed oculiferous tubercle, the length of the third joint of the palpus, which
is longer than the second joint, and the armature of the second tarsal joint of
the leg, are, I think, the best marks for its distinction.

Hitherto, this species was, in the Northern Atlantic, only observed in the
cold area. H.M.S. “Triton ” collected four specimens in the warm and four in
the cold area, viz., three at Station 6, one at Station 9, and four at Station 10.

7. Nymphon longitarse, Kroyer.

At Station 11, at a depth of 555 fathoms, two specimens of this species were
dredged. They are very small specimens, having an extremely attenuated
appearance, with blunt oculiferous tubercles, and with the first tarsal joint
* twice as long as the second.

8. Colossendeis proboscidea, Sab. spec.

This robust species is represented by a single specimen taken at Station 9,
at a depth of 608 fathoms. For a figure of this species I refer to my paper on
the Pycnogonids of the “ Willem Barents,”

9. Colossendeis angusta, G. O. Sars.
G. O. Sars, Prodromus descriptionis, Arch. for Math. og Naturv., ii. p. 268, 1877.
(Plate I. fig. 8.)

This species is known from a short (Latin) description by Professor G. O.
Sars. Mr Witson (Bull. Mus. Comp. Zool., viii. 1881, p. 243) got specimens of
what he believes to be the same species from deep water in the Atlantic,
between N. lat. 38° and 41°, and W. long. 65° and 73°, and points out several
differences of greater or less importance between his specimens and those of
SARS,

6 DR P. P. C. HOEK ON THE

Some of these differences may be due to variation of the species, the others
to the provisional character of the paper of Professor Sars. Nor would I have
insisted upon this disagreement had not the specimens collected with H.M.S.
“Triton” shown also some of the variations from the description of Sars pointed
out by WILson.

The largest specimen collected by the “Triton” measures 20 mm.; the
proboscis, which is slightly swollen a little behind the middle, is not quite
10 mm. The abdomen, according to Sars and WILsoN, is one-third the length
of the trunk ; in the “Triton” specimens, however, it is only one-fourth that
length. The third (second, Sars) joint of the palpus is a great deal longer than
the fifth (fourth, Sars). The eighth joint of the palpus is globose, and much
shorter than the two last. The claw of the ovigerous leg is not confluent with
the last joint (SARs) : in my specimens, as in those of Wixson, there is a distinct
articulation between them. The colour of the specimens is beautiful orange.

There are in all eight specimens. Of these five are from 16 to 20 mm., and
about, or quite, full grown. The three other specimens measure from 9 to
12 mm., and are furnished with very slender and three-jointed mandibles (fig. 8).
The last joint of these mandibles terminate in minute rudimentary chelee.

I observed the same in a young male specimen of Colossendeis gracilis
collected during the cruise of H.M.S. “Challenger” (vide Report “ Challenger ”
Pycnogonida, p. 69). It is a very curious fact that some of the species of
the genus Colossendeis retain a pair of appendices of the larval state almost
till the animal has reached the size of the adult; and these appendices do
not remain in the extremely small and feeble condition of larval life, but
grow with the proboscis till the length of this part of the body surpasses half
its length when full grown. Probably the mandibles are only lost when the
animal comes to maturity.

This species is an inhabitant of the cold water area; the highest latitude
at which it has been observed is 63° 10’ 2”: it has not been found as yet in
the Arctic region. Sars obtained it from 417, the “Triton” from 466 to 640
fathoms. Off the eastern coast of the United States Mr Acassiz has dredged
it at a depth of from 810 to 1242 fathoms—a striking instance of the southward
extension of Arctic forms in deep water, as Mr WILSON says ; for though it has
not been found in the Arctic Ocean as yet, we may safely conclude, from its
occurrence in the cold water area, that hereafter it will be met with there.

Seven specimens were taken at Station No. 8 and one at Station No. 6.

10. Pallene malleolata, G. O. Sars.
G. O. Sars, Crustacea et Pycnogonida nova, Arch. for Math. og Naturv., iv. p. 469, 1879.
(Plate I. fig. 7.)
I know this species only from the description of Professor G. O. SARs,

PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S “TRITON.” 7

Four robust specimens were taken at Station No. 10 at a depth of 516
fathoms. It is the only representative of the genus found at a considerable depth
in high northern latitudes. Professor Sars collected it between N. lat. 72°
27’ and 80°; the station at which the “ Triton” dredged itis N. lat. 59° 39’ 30",
in the warm area.

11. Pallenopsis tritonis, n. sp.
(Plate I. figs. 1-6.)

Animal slender, the lateral processes, at the end of which the legs are
inserted, being distinctly separated from each other. Dark yellow coloured,
smooth: no tubercles or hairs are visible on the surface of the body even when
studied with a lens. Legs not very hairy; the structure of the hairs, as in
numerous species of Pallene and Pallenopsis, furnished with small barbs
pointing towards the tip.

Proboscis nearly cylindrical, slightly swollen a little behind the middle.
Mouth large, as in the other species of the genus (Pallenopsis oscitans, Hoek,
spec. &c.). The length of the proboscis is not quite equal to that of the
oculiferous and two succeeding segments taken together.

Oculiferous segment longer than the two following taken together, somewhat
swollen in front, where it overhangs the base of the proboscis, and where it is
furnished with the rounded oculiferous tubercle. Of the eyes the two anterior
ones have very large clear lenses; the other two are a great deal smaller and
are placed at the back side of the tubercle, a dark reddish and rhombiform
pigment spot being placed at the tip of the tubercle.

The form of the other segments is the same as in other species of the
genus; the abdomen is cylindrical, its length corresponds with that of the
second and third segments taken together (fig. 1).

The mandibles are very slender, the two basal joints extend beyond the
tip of the rostrum, third joint considerably swollen, with the claws curved and
not so long as in P. longirostris, Wilson (fig. 2).

The palpi are represented by very small globular knobs implanted laterally
near the base of the proboscis.

The ovigerous legs (figs. 3 and 4) have the first joint almost globular, the
second, fourth, and fifth joints of considerable and nearly equal length, the
third a great deal longer than the first, and also a little longer than the sixth
joint, which is swollen at the distal extremity. Seventh to tenth joints gradually
diminishing in length, and at the same time growing more slender. Tenth joint
rather elongate. Joints first to fifth are sparsely hairy, joints sixth to tenth
covered with numerous spines; those at the distal extremity of the sixth joint
are a great deal stouter, and are placed in a complete ring.

The legs are exactly thrice as long as the body (with the proboscis enclosed) ;

8 DR P. P. C. HOEK ON THE

the length of the different joints is as follows :—First and third joint as long as
the lateral process, at the end of which the leg is inserted. Second joint more
than thrice as long as the first, slightly swollen towards its distal extremity.
Fourth joint more than twice as long as the second, and even a little longer than
the fifth joint. Sixth, seventh, and eighth joints combined once and a half as
long as the fifth. First to fourth joint almost of the same thickness, fifth to
eighth joint gradually growing more slender ; all the joints are furnished with
a longitudinal darker coloured stripe, as is common in Pycnogonids. The first
three joints of the legs are almost quite smooth, the outer joints rather hairy.
The structure of the last two joints of the leg can be judged from fig. 5. They
are not so slender as the same joints of P. longirostris as figured by WILson.
The armature, however, is much the same as in that species.

The only specimen of this species which was collected by the “ Triton” is
a male; as far as I could make out without mutilating the animal, the small
genital pores are only present on the two hindermost legs, and situated ventrally
near the distal extremity of the second joint. The ovigerous leg contains a
glandular organ with small opening near the beginning of the fourth joint, and
so does the fourth joint of all the legs. Of the latter the porus is placed at the
end of a tubular process* inserted about the middle of the jomt. As shown
in fig. 6, the excretory canal, which passes through the tubular process, has a
vesicular swelling at its base. Most probably these glandular organs do not
occur in the females of this species.

The intestinal cecum which enters the mandible in this species is well
developed (fig. 2); it can be traced till in the last, the claws bearing joint.
The total length of the body is 83 mm., that of a leg of the hindermost pair
26 mm.

Together with Pallene malleolata, Numphon macronyx, and N. macrum, this
interesting Pycnogonid was dredged at Station 10 of the cruise of H.M.S.
“Triton.” A young Lamellibranch mollusc (an oyster ?) is affixed to one of its
legs.

Mr E. B. Witson (1881) proposed a new genus for those Pycnogonids
which come near to Phowxichilidium, M. Edw., but which are characterised by
three-jointed (four-jointed, Witson) mandibles and ten-jointed ovigerous legs
present in both sexes. Moreover, it is distinct on account of the existence of
rudimentary palpi. WiLson describes two species as belonging to this genus,
P. forficifer and P. longirostris, and he supposes that KRroyeEr’s Phoxichilidium
Jluminense should also be referred to this genus. No doubt he is right in
this supposition, although the extra articulation of the mandible is wanting

* Witson hints that this glandular duct might be a character of generic significance, It occurs,
however, in numerous genera, as in Phowichilidium, Oorhynchus, &c.

PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. “ TRITON.” 9

in this species. If the genus Pallenopsis be accepted, four other species of
deep-sea Pycnogonids, collected during the voyage of H.M.S. “Challenger,”
and described in my report on the Pycnogonids as belonging to Phoxichildium,
Milne Edw., belong doubtless to it also. So we have eight species of this
genus, the range of depth and geographical distribution of which may be judged
from the following list :—

Name of the Species. Depth in Fathoms. Geographical Distribution.
Pallenopsis fluminensis, Kroyer, spec., 7-20 Patagonia, Brazil.

y patagonica, Hoek, spec., 45-175 Patagonia.

- forficifer, Wilson, 262-333 Otf South Carolina,

.. longirostris, Wilson, 500 South of Cape Cod.

e tritonis, N. Sp., 516 Faroe Channel.

% pilosa, Hoek, spec., 1600-1950 Southern Indian Ocean.

.; oscitans, Hoek, spec., 1675 Atlantic, West of Azores.
| i: nollissima, Hoek, spec., 1875 Off Yeddo (Japan).

Of these, six are true deep-sea species, the two others are shallow-water
inhabitants. The deep-sea species have the mandibles three-jointed (as are those
of the young of Colossendeis and Ascorhynchus) ; the two shallow-water species
show a transitory form between those with three and those with two-jointed
mandibles. In the mandible of P. patagonicu a trace of an articulation is
visible dorsally, but totally wanting when seen from the ventral side; in P.
Jluminensis, a little beyond the middle, the basal joint of the mandibles is
furnished with a row of hairs, and seems to be divided into two.

Within the limits of the genus Pallenopsis the change of three-jointed into
two-jointed mandibles has taken place. That the three-jointed mandible must
be considered as the original form is shown by the mandibles of different
species of Ascorhynchus and Colossendeis ; though they exist in these genera as
rudimentary or larval organs only and are too small and too weak to be of use to
the animal, they are distinctly three-jointed. Larval parts, or parts which have
grown rudimentary, are no more strongly influenced by circumstances ;
hence they often retain their original condition. No doubt it is a very
curious coincidence, that the deep-sea species show the original condition of
the mandibles, whereas the shallow-water forms are furnished with these
organs in the more robust condition of most of the other genera of Pycnogonids.

Finally, I wish to point out that the new species for which I have proposed
the name P. tritonis comes very near to P. longirostris, Wilson. Iwas long uncer-
tain whether I should refer my specimen to that species or should describe it as
a new one. I chose the latter, because of numerous, though perhaps not
very important, differences between his description and my specimen. Should

VOL. XXXII. PART I. B

10 PYCNOGONIDA DREDGED DURING THE CRUISE OF H.M.S. “ TRITON.”

the two forms prove identical—as I think it very probable they will do when
examined comparatively—they give new evidence of the wide range of deep-

sea species.

LIST OF THE STATIONS at which Pycnogonids were taken by H.MS. “ Triton.”

Station No. 5, August 9, 1882.—Lat. 60° 11’ 45” N., long. 8° 15’ W.; 433 fathoms. Bottom,

hard ground ; temp. 43°, 5 (Trawl).
Station No. 6, August 17, 1882.—Lat. 60° 9’ N., long. 7° 16’ 30” W.; 466 fathoms. Bottom,

stones; temp. 30°-29°, 5 (Dredge).
Station No. 8, August 22, 1882.—Lat. 60° 18’ N., long. 6° 15’ W.; 640 fathoree Bottom,

mud; temp. 30° (Trawl).
Station No. 9, August 23, 1882.—Lat. 60° 5’ N.; long. 6° 21’ W.; 608 fathoms. Bottom,

mud; temp. 30° (Trawl).

Station No. 10, August 24, 1882.—Lat. 59° 40’ N., long. 7° 21’ W.; 516 fathoms. Bottom,
mud; temp. 46°-49°, 5 (Trawl).

Station No. 11, August 28, 1882.—Lat. 59° 39’ 30” N., long. 7° 13’ W.; 555 fathoms.
Bottom, ooze ; temp. 45°, 5 (Trawl and Dredge).

EXPLANATION OF PLATE IL.

Figs, 1-6, illustrating Pallenopsis tritonis, n. sp.

Fig, 1. Animal, dorsal view; magnified 7 diameters.

Fig. 2, Last joint of the mandible; magnified 41 diameters.

Fig. 3. Ovigerous leg; magnified "7 diameters.

Fig. 4, Last five joints of the ovigerous leg; magnified 41 diameters.

Fig. 5. Last two joints and claw of one of the legs; magnified 41 diameters.

Fig. 6. Tubular process of one of the legs; magnified 94 diameters,

Fig. 7. Pallene malleolata, G. O. Sars, dorsal view ; magnified 6 diameters.

Fig. 8. Colossendeis angusta, G. O. Sars, lateral view of the anterior part of the body ;

magnified 7 diameters.
(All the figures are drawn with the camera lucida.)

s. Roy. Soc. Edin? Vol. XXXILE Plate I.-

AJ. Wendel lith.
PYCNOGONIBDA OF THE CRUISE OF H.M.S. TRITON.

foeldiya)

Il.— Bright Clouds on a Dark Night Sky. By C. Ptazzi Smytu, Astronomer-
Royal for Scotland. (Plates II. to XIV.)

(Read 18th June 1883.)

Parr I. Statement of the case, and first reference to Meteorological Observations, 5 ° alg
Part II. Further reference to Meteorology and its computations, A 5 . “3 15
Part III. Supposed physical cause of the phenomenon. Diagram on p. 18, : é : 17
AppEeNnDIx I. Scottish bi-diurnal Meteorological Observations, April 6-10, 1882, . - ‘ 22
AppENDIx II. Projections of the same in Plates II. to IX., : 5 ; 29
Apprenpix III. Continuous hourly observations and their Serene in Plates xe i XIV., : 30
Apprenpix IV. Further testimony from Royal Observatory, Greenwich ; Gordon Castle ; and Royal
Observatory, Edinburgh, touching Aurora, : : . . : . : 34
gh G

On a moonless night, whenever clouds of an ordinary elevation in the
atmosphere appear upon, or pass across, the star-spangled sky behind them,
they exhibit themselves, as a rule, dark, sometimes even black, in comparison
therewith, And no wonder, when every-part of the open sky from visible star to
visible star therein must be lit up to some, though doubtless a very small, extent
by the faintest general and cumulative radiance of those myriads and myriads
of lesser stars, which only a large telescope can show to be individually
existent as actual stellar points of light, but in their aggregate more nearly
eternal, and still more constant from age to age, than our gigantic Sun itself.

If the heavens become entirely covered by such clouds, a very dark night is
the usual and natural result. That at least is my experience on the Calton
Hill through thirty years of observation; and something very like it is probably
so generally recognised as fact over the whole country, that this formal state-
ment about it, may appear to many persons a needless truism.

Yet such darkness of elevated midnight clouds is not without exception.
For on April 8, 1882, on looking out Northward about 9.30 p.m. from an upper
chamber in the house No. 15 Royal Terrace, to see if there was any Aurora to
observe, I saw indeed no Aurora, but in-place of it two or three decidedly
luminous clouds, on an otherwise dark by comparison, but star-bearing, sky.

The rounded forms of these clouds were so contrary to the regular arcs and
needle-shaped darts of Aurora, and there was so marked an absence of the
very dark regions which usually appear on the Northern horizon, low down
underneath an Auroral display, that I went next to the South side of the house,
and there, to my greater surprise, saw that all the clouds visible from thence
were luminous with a white, moon-like radiance. Any portions of sky between

VOL. XXXII. PART I. c

12 C. PIAZZI SMYTH ON

them appeared by contrast of pitch-like darkness, though without preventing
a good sized star from shining forth ;—and the brightness of the clouds con-
tinually increased from the Zenith down towards the Southern direction, so far
as the neighbouring Calton Hill allowed one to look into that quarter.

The affair was so unusual, that I immediately made my preparation for
going expressly to the top of the said Calton Hill, in order to look further down
South, and see what strange source of light there could be there, illuminating
the clouds so strongly ;—for the Almanac declared that there was no Moon in
the position at that time, nor would be for several hours.

The ascent of the hill under such circumstances was rather tantalising ;—
for the first part of the way, by bringing one closer thereto, produces a higher
angle of obstruction for the summit,—and meanwhile the clouds overhead and
around,glowed with such an unnatural glare of light,as made me fear it could not
last long, and that I might be too late after all to see its origin in full force, and
behold whence it came. Tree tops of neighbouring gardens projected on some
of these clouds, showed their detail of twigs with almost daylight minuteness ;
and on coming into view of Nelson’s Monument, though still a long way off,
there was not only the Time-Ball on its summit, but there were its staff and
cross-arms, each and every one clearly visible and even black and sharp against
one of these preter-naturally bright clouds. But on reaching the top of the hill,
and getting a view from thence right down to the Southern horizon, there was
nothing there in the heavens, or apparently anywhere else to account for the
strange scene up above. The effect so very strong up there, simply died away
from inanition in the distance towards the South.

Baffled then and disappointed I entered the Royal Observatory enclosure
and watched the strange bright clouds overhead or nearly so, as they were
wafted about, but chiefly from East to West, for nearly a couple of hours. The
air was cold and dry. The clouds were of the massive, but irregular figure of
cumuli when seen at a high angle of altitude, and their light gave to spectro-
scopic examination nothing but the faintest continuous spectrum in the green
region, Not in the slightest degree therefore like Aurora, with its sharp citron
line; but rather like the faintest trace of carbon-flame illumination,

Gradually the disastrous and humbling idea grew in my mind,—that this
wondrous phenomenon of luminous night clouds was nothing but their reflection
of the gas-lights of Edinburgh and Leith, Portobello and Granton ; and I tried
to dismiss the matter from my mind. But every subsequent night that showed
the usual rule of clouds dark against a starry sky,—though said clouds were
illuminated by just the same city gas-lights,—brought up the further and per-
haps more important question “why and how were clouds able to reflect such
abundant light on that one night of April 8 alone ?” |

Besides the postulate that the air must have been very clear, two other

BRIGHT CLOUDS ON A DARK NIGHT SKY. 13

possible reasons suggested themselves. One was, that the clouds were low, and
therefore nearer the lights that iJuminated them. The other, that they affected
on that night some peculiar physical structure which enabled them to reflect
with far more than their wonted degree of brilliance. i

The first of these two reasons, however, did not seem very important; for
though cumulus clouds are never very high in the atmosphere, say about 3000
feet, rain-clouds are often lower and show no such light; indeed they are
usually the blackest of night-clouds. This very circumstance therefore led to
expecting that the bright appearance of April 8, might be due to just the
opposite condition of the atmosphere, which moreover did then to some extent
prevail, in the shape of dry, Scottish spring weather and its undesirable “clouds
without water.” That is without any to fall as rain, though there must have
been some retained to.form the visible mass of the cloud and reflect light with
extra force.

Such an idea may bring into play our reason No. 2; but before launching
on that hypothesis, it will be well to ascertain whether there was anything
extraordinary in the dryness, or indeed in any of the other meteorological con-
ditions of that one night, contrasting strongly with those of the nights imme-
diately before and after.

To this end I have been kindly permitted by the Secretary of the Scottish
Meteorological Society to make use of the Schedules of that hard-working body.
And after having selected 24 of them on account of either their topographical
neighbourhood or high character, I have extracted their bi-diurnal observations
from April 6 to April 10, or for two days before, as well as two days after, the -
phenomenal night of April 8, as will be seen in Appendix I., and have graphi-
cally represented their Hygrometry in Appendix II.

One and one only of the 24 observers says there was Aurora that night ;
and I have requested the Secretary to communicate with him, and ascertain
exactly what he saw and how he knew it to be Aurora.* But otherwise there
was nothing remarkable in any of the returns except the Hygrometric. The
Barometer was high, about 30°3 inches; the Thermometer low, about 41°:0; the
mean Depression of the Wet-bulb about 2°°5, and the Wind generally from the
Kast.

Now so far as Barometer, Thermometer, and wind are concerned the
observers were, probably all of them, perfectly competent. But in the more
delicate and sensitive matter of the Depression of the Wet-bulb by evaporation,
—TI have found it needful to reject three of them for reasons wherein I trust to
be supported. Thus in a certain case which I will only allude to as No. 14, and
wherein that usually most varying quantity (Depression of Wet-bulb), is made
to read exactly 1° degree both morning and evening and day after day through

* See Appendix IV.

14 C, PIAZZI SMYTH ON

almost the whole period,—there was too evidently something, somewhere want-
ing in that observer.

Again in No. 9 the differences from morning to evening are better ex-
pressed, but the wet-bulb is too often higher than the dry-bulb, to be fully
credible. And in No. 11, the observer, by simply entering the depression as
always 1 degree, unless when he sometimes makes it just 2 degrees, shows that
he is not aware of either the refinement, the truth, or the power of this beau-
tiful method of arriving scientifically at the Hygrometric state of the air about
him.

But of the remaining 21 stations, a notable majority does show a very
remarkable depression of the wet-bulb to have occurred on the 8th of April,
1882; and without anything similar to it on the other days, either before or
after.

Thus North Esk Reservoir, height 1150 feet, had a wet-bulb depression that
night of 5°:8, in place of a 3° average.

Wanlockhead, 1334 feet high, had a depression of 6°8 in place of its
average 3°°5,

Moffat, 350 feet high, had 6°°9, in place of 2°°5.

Greenock, 233 feet high, had 12°:2, in place of 4°'5.

Paisley, 88 feet high, had 5°:0, in place of 3°°5. And

Glasgow, 54 feet high, had 5°-0, in place of 2°°5.

While at other stations, the anomaly occurred earlier in the day, or at the
9 A.M., in place of the 9 p.m. observation: thus—

Braemar, 1114 feet high, had 4°-5, in place of an average 3°°0.

New Pitsligo, 495 feet high, had 2°°6, in place of 1°°2.

Stobo Castle, 600 feet high, had 7°:0, in place of 3°:0.

Stronvar, 428 feet high, had 4°:0, in place of 2°-2.

Dalkeith, 190 feet high, had 3°°5, in place of 2°:3.

Callton Mor, 135 feet high, had 13°:0, in place of 4°:0.

Balloch Castle, 93 feet high, had 5°°3, in place of 2°:2.

Eallabus, 71 feet high, had 8°-0, in place of 4°:0.

Aberdeen, 66 feet high, had 2°°9, in place of 2°°3.. And

Gordon Castle, 104 feet high, had 7°:9, in place of 3°:8.

Taken only so far, though very confirmatory on the whole, there are larger
anomalies among the stations, both as to quantity and time, than is desirable.
I therefore applied next to Mr W. H. M. Curistiz, Astronomer-Royal, at
Greenwich, for the hourly observations of the self-recording dry and wet bulb
thermometers there; and made the same request to Mr Rozert H. Scort, for
the returns from the Meteorological Council’s Observatories of Glasgow and
Aberdeen, They kindly responded, and their communicated observations are
contained in Appendix ITI.

BRIGHT CLOUDS ON A DARK NIGHT SKY. 15

But before using them in the whole, I extracted their 9 A.M. and 9 P.M.
observations, and projected them in the same manner as had been done with
the 24 Scottish Stations ; when there came out a most puzzling result ;—viz.

At Glasgow, in place of the expected evening depression, there was posi-
‘tively an elevation. And

At Aberdeen, in place of the small morning depression of 2°°9, there was
the immense one of 6°°7 ; the average one being only 2°'3.

On using, in place of the single observations of 9 A.M. and 9 P.M., the means
of the whole 12 hours of observations a.m. and P.M.,—the anomalies of the
curves were largely removed. And at length on projecting every observation,
and obtaining a nearly continuous history of the wet-bulb depression through
the whole 24 hours of each of the 5 days—the anomalies were all most
abundantly and exquisitely explained.

An enormous depression, it was thus ascertained, had really occurred at
Glasgow on the evening of April 8, amounting to no less than 12°°8 ; but it was
of short duration, and comprised so completely within the interval from 9 A.M.
to 9 p.M., as not to have affected either of these observations. While at
Aberdeen, where the Depression had occurred earlier, and to the smaller
extent of 6°°7 only, and lasted less than two hours,—its maximum had just
struck on the 9 a.M. observation and made that appear excessive.

The Greenwich observations, very much as might have been expected from
their great distance, were not sensibly affected by our peculiar Scottish pheno-
menon of April 8; but are extremely instructive for study, and the proof they
' give that 9 a.m. and 9 p.m. observations anywhere, are not sufficient for arriving
at a knowledge of all the laws of Nature in this department of Meteorology.

Part II.

Thus far I have described only the simple results of rude, instantaneous
observation, viz., the depression of the wet, below the dry, bulb thermometer as
actually seen by the observer. And though that quantity by itself does not
give the full or exact Hygrometric state of the atmosphere, it does show forth
to so large an extent any variations in the same, that I could wish our Scottish
bi-diurnal observers were instructed to enter that quantity, viz., the depression
of the wet, below the dry, bulb, as they might so easily do, at the time they
enter the latter.

For then, having only one column necessary to look at for instant Hygro-
metry, they would be far sharper in appreciating changes therein, and the tinal
results their observations might lead to,—than when their present two columns
of mere thermometer figures rather confuse them at the time, and are relegated
to the Royal Observatory, Edinburgh, at the end of the month, for some one

16 C. PIAZZI SMYTH ON

there to find out by computations of another kind, what their instrumental
readings were equivalent to touching “ Humidity;” but on days then so long
passed by, as to have ceased to have any vivid interest for the observer.

To bear on, or illustrate this proposition, all my graphic projections in
Appendix ITI. have been arranged so as to give, jirst, the raw depression of the
wet, below the dry, bulb ; and second, the computed Humidity, taking account
of the Temperature at the time ; and it will be seen that there is no important
abnormal wave in the latter, that has not its crest, or hollow sufficiently, and
sometimes more strikingly, marked in the former. The former therefore, which
every observer can enter for himself at the time with a living interest in it, is
quite near enough to the scientific truth for all current weather discussions
whether for agriculturists or gardeners, sailors or country gentlemen.

But in this particular inquiry of ours on the present occasion, we must do
something more. Wherefore Mr HeAtu, ist Assistant Astronomer in the
Royal Observatory, has obligingly assisted me by both computing three forms
of the Hygrometric expression, and also projecting their curves, together with
that of the Temperature, for all the hourly observations of the three continuously
working Observatories alluded to.

Now the projection of the Humidities does not differ much, as already indi-
cated, from the mere Depressions of the Wet Bulb. Nor does the projection
of the Grains-weight of water in a cubic foot of air, except in the way of dull-
ing and flattening all the curves. But the map of the Grains-weight of water
still required to saturate each cubic foot, gives an immense result for our par-
ticular phenomenon of the night of April 8; as well as a notable insight into
some permanent characteristics of climate.

These permanencies are, that in the North there is very little change
between day and night either as to quantity of watery vapour in the air, or the
further amount required to saturate it. But in the South, teste the Royal
Observatory, Greenwich, there is an intensity of difference between day and
night, not in the amount of watery vapour contained in the air, but in the
further quantity which the air could take up without being saturated thereby,—
which is not only surprising but warning too; as it is a condition that lies at
the root of many of the movements of the atmosphere, and promotes also the
disruptive, in place of the silent or slow, discharge of atmospheric electricity.

Looking next to the particular phenomenon of April 8, we find it occurred
at 9 A.M. at Aberdeen; and at 4 p.m. at Glasgow; or crossed the country from
N. East to 8. West at the rate of about 14 miles per hour, increasing in quan-
tity as it went; for while it attained to only 0°80 grains at Aberdeen during 2
hours, it reached 1:80 grains at Glasgow and lasted there for nearly 8 hours.
That is, the increased number of grains of watery vapour per cubic foot, which
the air could take up without being saturated.

BRIGHT CLOUDS ON A DARK NIGHT SKY, 17

Now as that is the very effect which is experienced in the South every day
at Noon, as contrasted against Midnight, we might expect that our pheno-
menon was produced by an elevation of temperature in the air, without time
given to it to pick up moisture equivalent to its then increased Humidity
requirements, And this appears to have been the case to some extent, but
was certainly preceded at Aberdeen on the morning of the 8th, where the
influence began, by a very unusual decrease of the absolute amount of watery
vapour contained in the air,—however that decrease was operated.

Hence in one way or another, dryness of the air was an eminent character-
istic of the atmosphere though for a limited period, near, or about, or shortly
preceding the time when the night clouds over Edinburgh appeared Juminons
by excess of brilliancy in their reflection of the city’s gas-lights.

But what does that lead us to, as to the physical manner in which the
reflection was produced ?

Part ITI.

Before entering on this last portion of the inquiry, let me further state, that
after many and many nights of clouds black on a gently translucent starry sky
subsequent to April 8, 1882 ;—there was another-most remarkable example of
clouds bright on a black but still starry sky on Monday April 30,1883. Those
unnatural looking bright midnight clouds, as they were wafted hither and
thither over the heavens by stray currents of air rather than regular winds, had
almost a fearful splendour,—reminding one of Salvator Rosa’s dark Noon-day
pictures of white clouds overhanging deep rocky gorges among Calabrian
mountains black as midnight and teeming with treacherous banditti; and I
much wondered that honest Edinburgh folk were not out on the streets in
crowds gazing at, and discussing the strange spectacle. So short-lived too ;
for the very next night was eminent for the normal blackness of its clouds
contrasted against the pellucid and star-bearing heavens between them.

I wrote therefore to the Astronomer-Royal at Greenwich, inquiring whether
any of the more wide-spreading influences, causes or accompaniments of Aurora,
were manifested there, on the nights of April 8, 1882, and April 30, 1883, as
compared with the nights and days immediately before and after these two
dates. But the reply, as will be seen in Appendix 4, was entirely negative ;
for neither in Terrestrial Magnetism, Earth currents, atmospheric electricity, or
Sun-spots was there anything noteworthy going on at either of those times.

Relieved therefore of any Cosmical phenomenon to attend to,—let us now
look at the matter in its more ordinary terrestrial character.

On June 25, 1882, at the rather elevated station of Buxton, in high Derby-

18 C. PIAZZI SMYTH ON

shire, I witnessed a remarkable proof that “cumulus” clouds can assume, and
keep up for a short time, an excessive brilliancy of reflection.

The case was this; at 6 P.M. when walking in the Park there, and looking
S. East, I noted and sketched the half-Moon and a great thunder-cumulus*
cloud close to it thus,

The Moon was exceedingly pale as compared with the great mass of the
cloud on which the Sun was shining out of a clear sky in the West. The
cloud was indeed estimated at 7 to 10 times as bright as the Moon! This
extreme brightness of the cloud however only lasted about half an hour; when
its brighter part went down to something like 3 times that of the Moon.

But as Sir Joun Herscuet well remarked in his “ Cape Observations,” and
when contrasting telescopically the brightness of the Moon setting behind the
summit-cliff of Table Mountain, with that cliff then illuminated by the brilliant
rising Sun of South Africa,—their then brightnesses were equal, just as their
illuminations by the Sun, at the same distance therefrom in space, were equal
also. But the solid surface of the Moon must be a nearly constant of reflect-
ing power; therefore when it was so vastly transcended in brightness by the
Buxton cloud in daylight,—the said cloud must have been an anomaly surpass-
ing all ordinary terrestrial surface materials in reflective power, just as did the
Edinburgh night clouds when distinctly luminous from their reflection of gas-
lights far below them.

What enabled clouds then, on these two or three occasions, to reflect so
very strongly whatever light, whether Solar, or artificial, that struck upon
them? The only reason I can suggest powerful enough for the occasion, but
one that seems to fulfil all the conditions, is,—that the molecules of the clouds
were then in a hollow, vesicular condition, rather than drops or spherules of
water. ‘The former state is evidently most compatible with their floating in

* The thunder-cumulus, when weather is approaching a condition for electric discharge differs
from the ordinary cumulus cloud, by being more tightly made up as it were, and with smaller or sort
of cauliflower figures.

BRIGHT CLOUDS ON A DARK NIGHT SKY. is:

the air for any length of time and dropping no water ; whereas the latter is the
very preparation for rain-fall. This latter too is the condition of least reflection
and most absorption of light, while the former is that of least absorption and
most reflection.

These propositions may be practically established most easily by earth-sur-
face examples, where the nature of the molecules may be most easily examined.
Falling rain drops, even when directly shone on by the Sun and forming a rain-
bow, are anything but bright, unless indeed they are mixed with hail. And if
we take water in the largest shape, what is there so dark as the deep blue sea,
whence comes to our eyes only a faint, “first surface” reflection, from a sphere
of stupendous size; and yet what is so brightly white as the foam of the same
material when arranged in numerous, small coalescing convex vesicles, every
one of them reflecting from both the first, and more especially the second,
surface of its film, whatever point or gleam of light there may be in the whole
hemisphere illuminating them.

Or again how dark brown is the water of a peaty hill in the Highlands when
in a placid state, reflecting by means of only its first surface; and yet how
brightly white is the course of a stream of it viewed from a distance on the
mountain side and even under a cloudy sky, when it has to chafe and
tumble down rocky channels, wherein it covers itself with foam, or in-
numerable little hemispherical bubbles on bubbles, each of which gives us,
both the weak first, and the strong second, reflection of a film of water, or glass
plate in air.

That is, such a frothy surface is bright when we look upon it from above,
or the side whence, by day, comes its chief, or only illuminating light; as snow
also then appears mostintensely white. But when we look at either snow,
or froth of water between us and the chief light, they appear dark rather
than bright; for they reflect far too well, to allow much to be transmitted
through them.

But still more particularly what can be brighter than those fields of apparent
snow, the upper surfaces of the clouds composing the great cloud stratum of
the low N. East, or commencing Trade, wind, as seen day after day in the
summer season from the summit of the Peak of Teneriffe, at a depth of several
thousand feet below: and they are known to be in the watery, as contra-dis-
tinguished to the frozen, condition. And yet what is darker and more threaten-
ing than the appearance of the same clouds, when seen from below, or between
the observer and the Sun-illumined hemisphere of sky.

There too, at or near the sea level, in a moist air, rain does sometimes fall
from those clouds’ lower dark surfaces, where their component molecules may
be increased in size with acquired outside moisture until they become practi-
cally drops of water. But above, on their upper surfaces, where to an observer

VOL. XXXII. PART I. D

20 C. PIAZZI SMYTH ON

higher still, they appear so blindingly white, they come into contact with “the
Teneriffe air above the clouds” (ze., the clouds of the lower N. East wind),
which air is dry to the last degree ; dry even to a depression of from 25 to 30
degrees Fahr. of the wet, below the dry, bulb Thermometer. Now this is a
state of things which must evaporate the outside of the watery cloud-molecule;
and if there be, as I believe has long since been generally held, a hollow or air
centre to it, must leave the watery coating portion only as a thin shell sur-
rounding such air particle. In which case such shell will reflect from a second
surface almost as large as the first, and with a very minimum of absorption by
fluid material.

Such thinning indeed of the vesicle, as pointed out lately by Professor ALEX.
HERSCHEL, must not be carried too far; or, like the black centre of NEwron’s
rings, there will supervene an incapacity to reflect any light ; immediately after
which, the vesicle must burst, and cease to be a visible existency. As this
termination of the life of cloud molecules—which are seen by travellers who
ascend the peak, to be continually rising into the upper air, but never getting
beyond a certain level therein,*—must take place more rapidly the drier the
medium, it results that the whole cloud seen in the distance will have a harder,
better defined ontline, on the side where the air is dry, than that where it is
moist; or according to Nature’s general law, above, rather than below, the level
of the N. East wind’s clouds.

Now the night clouds of April 8, 1882, which belonged to such N. East
weather, showed well-compacted, almost case-hardened surfaces below, or when
looked at from below, which was also at that time, the direction from which
their chief illumination came, viz., the city gas-lights. And if their lower
surfaces were then so compact, and could then reflect so powerfully, as they
undoubtedly did that: night, it must have been because there was at that time
a stratum of air below them, as remarkably dry as the classic stratum which is

* This feature is well set forth by Dr Marcer, F.R.S., in his recent book Southern and Swiss
Health Resorts, p. 262; except that he speaks of the return S. West current as being immediately
above the cloud, in place of, as it is throughout all the summer season, separated from it by a thickness
of full 5000 feet of a gradually decreasing strength of N. East wind, the same in direction as what prevails
both below, and in, the cloud level, but differing hygrometrically therefrom exceedingly, in being extra-
ordinarily dry. This important physical peculiarity is afterwards, however, fully acknowledged by Dr
Marcet at pp. 296 to 306 of his useful book. For he there sets forth in a fuller and more serious
manner that the N. East cloud level is never so low as 1209 feet, but nearer to 3000 feet high; and
by its shade moderates both the temperature, the radiation and the moisture of the country below it.
But at his Guajara station, 7090 feet high and therefore altogether above that N. East cloud level, he
found there was still a prevailing tendency of the wind to blow from the North East, but accompanied
by a terrific dryness, amounting on one occasion to 30°'5 depression of the wet, below the dry, bulb
thermometer. Even on the higher central Peak, at 10,700 feet elevation, he says that “the S. West
current, bringing back moisture from between the tropics,’ was only beginning to be felt; and the
traveller would have to ascend several thousand feet higher still, if he could, to reach the full force and
volume of that important stratum, at that season. All which exactly agrees with my own experience,
described in Teneriffe, an Astronomer’s Experiment, in 1856,

EE

BRIGHT CLOUDS ON A DARK NIGHT SKY. 21

otherwise always above, any massive cumulus clouds, as testified by the
Teneriffe observations of 27 years ago.

But the whole purport of the Meteorological data we have collected and
discussed from 27 Observatories, large and small, shows without contro-
versy that a most unusual wave of dryness did pass across Scotland on that
particular 8th of April day. Below the level of the clouds too, because so
distinctly perceived and felt on the inhabited surface of the earth; but having
its maximum probably at 2000 feet or more above the sea-level, because
recorded as greater in amount at the hill, than the valley (but everywhere beneath
the clouds), stations of the Scottish Meteorological Society.

22 C. PIAZZI SMYTH ON

APPENDIX IL

Br-DIURNAL OBSERVATIONS FROM APRIL 6-10, 1882, at 24 STATIONS OF THE ScoTrTisH METEOROLOGICAL
SocreTy, AND 3 GOVERNMENT OBSERVATORIES. ~

g 3 | Hygrometer iyepomenicnl Wind
Date. 4° Raa Computed Results, bar es Clouds.
ne
ieee SSS :
oe . 3 3 r g
SraTron. gS : 3 ee z be Zs S = g g REMARKS.
Bz) 4 | 4 |, |F 3|z8s seq) 2 | jegisu es
gS | BR) @ | B | So ieee | He) so] a | 8a) S 4) =
wo Sh > 2 aQ |e) o|] 2 So] Sco S an 73) =|
= | Be| A | F | ds [= S/Se8/ a1 | 8 | #8 2 g
= ag a> 4s: D4 J <
“a | 3? Bree Se Sse ee ae
ins. _ . Z gr. brs.
F { 30°54| 4-7 | 4-3 | o-9 02| 93 | & | 26 63 Nicaea 2a 08
30°60| 41-1 | 38-7 | 24 06] 81 | EB | 22 es | &
. 67| 43-2 | 40°8 | 2-4 6 | 81 F | RG 23 |
MESURE, it { 30°71 | 39-0 | 38:7 | 0:3 o1| 93 | E | 2-9 aes ca
30-68 | 43:2 | 408 | 2-4 o6 | 81 | B | 2-2 05 | a. 0 | 0-0
162 feet. 8 | 30-67 | 39-2 | 38-3 | 0-9 0-2] 9 |NE| 26 LO
Tats GiT) Nil ee FEETNrria| Ex a aa an ee ea Se
Tong. 81". | {|8052/ $87 | 867 | 20 05 | 84 | SE. | 17 35 | g5| 4 | 00/0 e eee
30°37 | 36-7 | 35-7 | 1-0 02 | 92 |S.E. | 20 - a |.) 1) eee acy
19 §| 80°25 | 38-4 | 37-7 | 0-7 o2| 24/1] | 22 BBall ee | 0
30°17 | 36-9 | 34-7 | 22 05 | 92 | E | 20
Means,.. 30:52 | 39:9 | 38-4 | 15 0-4 | 88 23
~ §|30°52| 39-7 | 37-9 | 1°8 05 | 86 |N.E.| 1-0 8 ,
6 { 30°57 | 35-0 | 343 | 0-7 02| 93 | NE} 0-2 i \ Clear and fair.
BRAEMAR, 7 §| 3059) 30-0 | 28-8 | 12 o4| 8 | & | oO Fog. \ 7
No. 2. { 30-64 | 36-9 | 33:5 | 3-4 os | 73 | BE. | oO cs .
1114 feet. 30°60 | 36-7 | 321 | 4-6 09 | 6 | BE | 0
8 | 30-54 | 37-7 | 35-2 | 2-5 06 | 80 | E | 0 ; Clear and fair.
Lat. 57° N. Le peeks eae | ee ee Se ee ee
Long. 3° 24’ W. 30-41 | 37-7 | 325 | 5-2 11| 6 | B | oO
E 9 { 30°31 | 39-4 | 36-7 | 27 06| 79 | & | o ' Clear and fair.
19 §| 30716 | 422 | 37-7 | 45 10| 69 |SE. | 0-2 3 a
{ 30-14 | 34-4 | 32:8 | 1-6 o4| 84 | BE | O 1 .
Means, . ; 30°45 | 37:0 | 34:2 | 2°8 OO affth 01

4 30:47 | 40°5 | 39°5 | 1-0 0-2 | 92 | N.E.| 4-0 Mist.| 9
Pe By 30-53 | 37-5 | 36:5 | 1:0 02] 91 | BE | 4-0 Nimb.
a Hass " 30°60 | 40°5 | 38:1 | 2-4 06 | 81 |SE. | 4-0 Bt ap
cra pod ‘ {| 30°63 | 32:5 | 31:5 | 1:0 02] 88 | B 4-0 0
80°61 | 42°5 | 36°8 57 1:2 62 a0) 4-0 0 Sad 1c Hoar frost.
1150 feet. 8 1| 30-54] 33:5 | 29:5 | 4-0 08 | 61 | EB | 40 o | 2] : \ Clear fine day.
Lat. 55° 48°. [ rac gl aes Para hic <=.
oh 30°43 | 321 | 31-5 | 0-6 o1| 92 |SE. | 4-0 Fog. an ee
Long. 3°21’ W. | 9 { 30-29 | 31-5 | 29:5 | 2-0 0-6 | 74.| N. | 10 0 7 Cirro-stratus, fine.
10 { 30°18 | 47-5 | 43:5 | 4-0 10 | 74° | N. | 1-0 pages
30°10 | 35:5 | 33:5 | 2-0 0-4 | 82 | Var. | 4-0 5
Means, . 30°44 | 37:4 | 35-0 | 24 0:5 | 80 34

BRIGHT CLOUDS ON A DARK NIGHT SKY.

2 = | Hygrometer Rivuamncissanll Wind
Date. ae fee Con ee Besnles, rae Cicer.
ne
——| e= :
oa , 3 5 8 g é
STATION. g 2 S aS ef si Z é 3 a zg 3 REMARKS.
Ba| 4 | 4/3, ]£ 2/225 See eee (|e eel gS
a Bt a & gS fuego] sse| x. . 28 5 ry
allese is | o | Se ee oboe | ee eeetbecasiie ti) Be
Spee l(e | 6 | £3 PS 8) Soca eee tesail s | “E
= 2: a= Io ales] Es etic fa) 4
2 | a a le ale alee baer & |
ins. 4 6 e grs.| gr hrs.
30°39 | 41 | 401 | To] 37] 63] 92 | B | 40] B | 10 | 45
30-48 | 39-0 | 36-4 | 26] 22| 06] 8| & | 10} B | 2 | @
WANLOCKHEAD, 7 30°55 | 42°9 | 88°5 | 4:4 7 2:2) 10) 70 E. CON Ieee 0 12
No. 4. { 30°58| 37:0 | 365 | 05 1°24] 02] 96 | & | o2| 2. | o | *@
ist tect. | (| 3057| 403 | 360 | 43] 20] 10) 68 | w. | 02 0 | 45
{ 30-47| 40:5 | 33-7] 68] 15 | 14] 53 |S.w.] 0-2 ie) Be
ca oe ns Paik eae) ii «eaters A Sane tas 3 inl Ta
Long. 3°48 W. | {|30-40| 302 | 299] 03 | 19] 01] 9 | w. | o2] .. | © | a3
30-29 | 36-3 | 35-21 11] 221 03| 90 | w.| 02] w.] 1
iy f\oote| 28 )| 20-00 28] 625! OF | ayo low. |or | s. |) a |g
{ 30-08 | 36-1 | 36-0 | 0-1 | 25 | 0-0 | 99 |N.w.| 0 6 i
Means. .| |30-40| 386 | 362 | 24] 22] 06 | 82 |... | 1-0
g {| 30°49) 43° | 39° 23 | 009) | elem eGo} [m0 fh og
{ 30°57 | 43° | 42: 29| 03/92 | & | 90/ BE | 8
MaRrcHMONT 7 { 30°66 | 41° 39° 2°5 0°5 84 i. 1:0 E. 8 6
(Berwick), 30°66 | 38° | 37° 24) 03] 91 E. 4:0 0
0. 5. eas Bouees Shee | rian sees = aa = BNE sees
g §|30:67| 41° | 39° Paylh O | ra4 "| Pw) [| Ptoh ls L. ||i8 |b og
500 feet. { 30°59 | 39: | 38° 25 | 031 92 | E | 40] & | 10
Lat. 55°44” N. | 4 {|30°50| 39° | 36: Pen | Aw. le-ol |B. p10 |) ay
Long. 2° 25’ W. { 30°34 | 34° | 34° 23 | 00/100 | B. | 40] B | 5
10 §|30-24| 35° | 34° 21 | 03 | 90 | NE} 40/NE/ 10] 4
{ 30-14] 36- | 35° 22 | 03] 91 |NE.| 40] N-E.| 10
Means. 30-49 | 38-9 | 37°3 2-4 | 0-4 | 87 eI |
4 30°54] 45-7 | 41-3 | 44 | 25 | 10 | 70 | NE
30-60] 43-0 | 405 | 25 | 26) 06 | 1 | NE
30°68 | 45°3 | 41-5 | 88 | 26 | 09 | 74 | NE
1 ee Ta 30-68 | 39°5 | 385 | 10 | 26 | 02 | 92 | NE
30°69 | 45:5 | 42-0 | 35 | 26 | 08 | 7 | NE etl <=:
piece. 8 4) 30-61 | 37-0 | 35-5 | 15 | 22] 0-4 | 87 | N, a
Meme mOtONG se co lancco|l age | a7 tal a
ee 30-521 39:5 | 375] 20] 23 | 05 | 84 | B ts
eet We | 9 { 30°36 | 360 | 35:5 | 0-5 | 2-4 | O-1 | 96 [BNZ, im
10 { 30-26 | 38:5 | 37-7 | 08 | 26 | 0-2 | 94 [HSE ie
30-18 | 37:3 | 355 | 1:8 | 22 | o5 | 85 | w. es
Means,. 30°51 | 40-7 | 386 | 2:2 |.25 | 05 | 84
g §|30:50| 445 | 482°) 18. | 30 | 03 | 90 | F a1 eee AN aca
30-61] 423 | 402] 21 | 26 | 05 | se | E 8 6
30-67 | 44:5 | 42:2 | 23 | 28 | 06 | 83 | E 3 Siete
re 7 { 30°68 | 38-0 | 37-0 | 10 | 24 | 03 | 91 | E ee Bes a pile a0 Rs
30-70| 44-5 | 42-71] 18 | 29 | 05 | 87 | E 2 4
mUvOHfeet. 8 { 30°63 | 37°5 | 36-2 | 13 | 23 | 03 | 89 | & 34 lms bes
Lat. 56°3'N. [| 7 Ft nc oc |
OG Ae 30°51] 405 | 382 | 23 | 24 | 06 | 82 | B 8 4
Long. 2° 40''W. | 9 { 30°39 | 36-5 | 352 | 13 | 22103 | 89 | B 2 ee Tes
0 { 30-27 | 39:0 | 382 | 0-8 | 26 | 0-2 | 94 | B G blame let
30-19 | 33:5 | 32:8 | 0-7 | 21 | o1 | 92 | E 2 5
Means, . ci 30°52 | 40-1 | 38°6 | 1°5 2°5 0-4 88

24 C. PIAZZI SMYTH ON

3 a Hygrometer cose ‘ical Wind
Sx 9 AM. yeTemeticr 9 ass. Clouds.
3s oe a bane Computed Results. ee WSS
Six ; 3
a = =z 3 ZS 5
STATION. 3 = 2 Peles fa 2 s a E é REMARKS.
2) Ee ih. Pelee = fhe | S| 4
B24] 13 2 /¢.15 8/382 £2 a He
: eres a oat ac 8$|FzE8 os § S
2 |g.| | 3 | 22 [S52 |225| fe] 2 | gz| s | §
= | ee | & | © | Bs [e(ai28| 271] = | es) 2) &
SSE Be Js vo 2°) er |B ise 1 wea Mos
yo ey aye i= Ves St NsiI a 8
re ins. A - grs.
‘ { 30°53 | 43-0 | 40-5 26 0-2 0-10
30°57 44:8 | 393 22 0-2 a.
: 67 | 46-0 | 43-0 0-2
man ie 7 \|30-67 | 39-0 | 37-0 2°3 0-2
. 30°67 | 46-2 | 43-5 29 | 0 0-2 —
90 feet. 8 { 30-62 | 38-0 | 36-0 22 | 05 | 83 0-2
Eat, 55°59! N. 30°51 | 41-0 | 37-9 23 | 07 | 76 0-2
Long. 216 W. | 9 4) 30-35 | 363 | 355 19 | 07 | 76 0-0
* { 30:25 | 40-0 | 38-0 2-4 | 0-5 | 84 0-2
30°15 | 35°5 | 32-8 18 | o¢6 | 76 0-0

Means, . : 30°50 | 41-0 | 38-2

iS)
o
°
wa
a
=
re)

jected
faedeodetihs 5

present Inquiry.

Sa!

44:2 | 43-7
41-2 | 40°5
30°66 | 46°0 | 44-5
30°67 | B85 | 39-0
240 feet. 8 { 30°68 | 45:2 | 44-0
Sy ee 30°58 | 36°2 | 37-0
top e OTN | ——— ee ee
Long. 2° 47’ W.. 9 { 30°49 | 48-5 | 48-2
30°35 | 36°5 | 36°5

10 ‘ 30°21 | 43-2 | 44:2
30°16 | 86°0 | 35-2

HADDINGTON,
No. 9.

O1) 98 |K.N.E} 1-0
0:0 | i100 | N.E.} 1:0
aa! oct E. 1:0
02 | 93 E. 1:0

Means, . “ 30°49 | 41°6 | 41°3

in the

This Station’s results are re

7 30-47 | 420 | 41-0 | 10 | 28 | 08 | 92 | B.
30°57 | 40-0 | 38-0 | 20 | 24 | 05 | 84 | BE
-61| 42:0 | 40:0 | 2:0 | 26 | 05 | 85 | E
se ey 7 { 30°65 | 38-0 | 36-0 | 20 | 22 | 05 | 98 | E.
wie esol) (eat laschcee Dace Mh eae beta, sMecseces ates 8 Ines | 3 | are
30°63 | 40-0 | 33-0 | 70 | 5 | 1-4 | 51 | Nw e
600 feet. 8 4/30:55| 36-0 | 35-0] 10 | 22] 03] 91 | o | .. 5
Lat. 55° 35° N. Sree ee a | > Soa eee
ay ape 30-49 | 36-0 | 33:0 | 3:0 | 1:8 | 0-7 | 74 | &.
Long. 3° 25" W. 30°33 | 34-0 | 33-0 | 1-0 | $1 | 02 | 89 | BE
30-20 | 40-0 | 32-0 | 80 | 1-4 | 15 | 46] S.
30°13 | 390 | 37-0 | 20 | 23 | 05 | 84 | E
Means, k 30-46 | 38:7 | 35-8 | 29 | 22 | 0-6
Ko} PL ee SOS 2S a a |
uy
3 |
ee 30°54| 44- | 43: 0 BE. | 40
aa 30-52| 45: | 44° 0 BE. | 1-0
&o|| Cupar (Fire), 30°69 | 44: | 43- 0 BE. | 1-0 .
$3 No. 11. 30-69 | 45- | 43- 0 E. | 1-0 3
Ba}| 210 feet. 3071| 45° | 44- | 1-0 BE. | 10 a
oo || 30°63 | 46° | 44- 0 Bt ead ss iS
*|! Lat. 56710'N. aie ES lin es sna a Hane __
26.1! Long, 376’ W. 30°49 | 37: | 36° 0 BE. | 1-0
&e 30:36 | 38: | 37: 0 BE. | 1-0
35 30:26 | 38 | 36° 0 E. | 1:0
on 30°17 | 39: | 38: 0 E. | 1-0
| Means, . 30:51 | 42-1 | 40-8 3 ena |
BE \

BRIGHT CLOUDS ON A DARK NIGHT SKY.

REMARES,

{ Hard frost at
night.

oe Hygrometer Hvenometrical Wind
Date. PE ban es Gomnited Results. Sic. ‘Clouds.
aes
SraTIon. B< 5 z be; 53 ge e c= é
See | 2 is [be elgs® ae = 1 =) ap oS
eapes. | 2 | So tee slays Sembee se |e | eo |
os ee | A A | 82 |[sselesal so Ha | ie) is =
apes |e | & | Be Ter Sls ee betes fea loeemie ss: || s
2 | o|iA | © | es |S Blas] elie | ge) 2 | gz
& as oF 2 3 = ae
& | &* AY |e ale Sige jaa 5
ins s é grs.| gr. hrs.
g {| 30°50 | 45°0 So} 29 | 05 E.S.E| 9:0 is
{ 30°57 | 42°5 3-0 | 2-4 | 0-7 ES.E.| 40
Grascow, , | 30°64) 44:5 35 | 26 | 0-8 B. | 4-0
No. 12. ( { 30-67 | 40-5 25 | 24] 0-6 SE] 10] 1. ‘
54 feet. g f | 80°67 | 44-0 3-0 | 26] o-7 E | 40 3
{ 30-60 | 41:5 50 | 20] 1-41 E. | 10 a
Lat. 55°53’N, |__— = = 2 lee oe ee ee S
Long. 4°18 W. | {| 30°51] 39°5 25 | 22] 06 ESE] 1-0
{ 30°34 | 41-5 15 | 2:6 | 0-4 ES.E| 1-0
19 § | 30°23 | 34-0 0-0 | 2:3 | 0-0 | 100 |S.S.B.| 0-2
{ 30-14 | 39:5 2-0 | 2:4 | 0-5 E.S.E| 0-2 A
Means, . | 30-49 | 41-2 a5] 24] 0-6 25
g § | 30°83 | 45° m4 | 3-1] ond N.E.| 9-0 | ... :
| 30-63 | 41-7 2:6 | 24) 06 N.E.| 90 | ...
BALLOCH CASTLE, a 30°67 | 44-5 2°9 27 rd N.E.| 4:0 A W
No. 13. 30°71 | 40-5 19 | 25] 0-5 we | #0) 2.
98 feet. g {| 80°70 | 46-0 54 | 23 | 13 N.E.| 40 a
30-63 | 41-0 24 | 2-4 | 0-6 BE. | 0-0 a
12 eh a a eae Be | antes Rained Readbetl Es
Long. 4°35’ W. | ; 30-54 | 37-0 12 | 23] 03 BE. | 0-0 6
30°39 | 47-5 19 | 3-2] 0-5 S.E. | 0-0
19 §| 3027 | 37-0 0-4 | 25] O71 SE. | 0-0 7
30-18 | 41-5 17] 26] 0-4 SE. | 00] ...
Meons, . ~ | 30-52 | 42-2 2-2 0-5 . | 30
g f| 80°48 | 42-1 0-5 0-1 saa ee
30°55 | 37-1 10 03 see: Nez
CaAsTLE-DouGLAS, 7 { 30°61 | 36-1 1-0 0:3 d Mies ee
No. 14. 30-65 | 35-1 1-0 03 : sak Be
783 feet. ; 30-64 | 38-1 1-0 0-3, 7 ea R=
...,.. 30°56 | 35-1 1-0 0:3 ee Ih Be
Aa ase ———— a a ee
Long. 3°52 W. | 9 {| 30-45] 31°6 1-5 05
30°35 | 37-1 1-0 03
19 § | 30°24| 33-1 1-0 0-2
{ 30°14 | 34-1 1-0 0-2
Means, . 30°47 | 36-0 1-0 0:3
&
.. | 45°8 7 ee ae
6 { 30°54 | 42-0 7 a4
Morrat, 7 { 30°62 | 46°8 2
No. 15. 30-63 | 43-0 BT ie
350 feet. g § | 30°61 | 53-0 -0 | 100 ey
cy 30°54 | 42°8 5
AiO ean | \\————— | \ aa | eae
Long. 3°27’ W. | 9 {| 30-48| 43-5 1-2
{ 30-35 | 40-0 0:5
‘te j 30-22 | 45-0 0-5
30-11 | 40-5 18 6 S
Means, . 30-46 | 44-2 0-7 |

ected

J

ivy.

in the present Inqu

This Station's results are re

—

26 ©, PIAZZI SMYTH ON

| g a Hygrometer Hygrometrical Wind
| Date. 3 e a ae Gap Results. rahe Clouds.
A 5 -
3 = ay eel & 3 5g 3 Ss
S?ation. Ty 3 < 3 : Ze S cs s sg REMARKS.
Be.) eS We feu ie) iliges Boge eas el &
z a. a 5 s class gS = i
3 ee | & A $3 [Sse |/25e| be a | se] 8 E
= [eo 0 2 © | 28/2 elss2|s4 | 2 | 22] 8 5
a2 |[Es| 2 | F | es |S Biee3| 21] 2 | gale | &
a a5 a= JP Oso) sa tea ESS a <
< [-2) (=) Fale | Ba a i)
na ell ys : ES.) ete hrs. 7
{ 30°52 | 44: 41 Bb 3:6 07 77 E. 4:0 be
30°59 | 39° 36 3 2 0-7 77 = ae
7 { 30°66 | 42° 39 3 2-4 07 78 E. 0-2
STRONVAR, 30°64 | 37° 35 2 21 0°5 83 xi a
No. 16. = Sees (eae ee See |e ees meen aie, coeiien ey Eee Se a
8 30°66 | 42° 38 4 2°2 0-9 72 E. 1:0
428 feet. 30°57 | 36° 34 2° 2°0 0°5 82 ae 3a
Lat. 5620.N. | 9 { 30:49| 32° | 3l- | 1 | o2| 87 | BE | 02 BE
Long. 4° 20 W. 30°33 | 34 33 I: 0-2 89 Pe
10 { 30°23 | 36° 35 iE 0:3 91 N.E 1:0
30°13 | 42° 39 3° 0:7 78 oan =
has. 30-48 | 38-4 | 36-1 | 05 | 81 ee es er ae ;
6 { 30°51 | 44:2 | 42:2 0°5 84 E. D2, 4 10: =
30°54 | 47°2 | 42°7 ior} 70 E. 1:0 0
GREENOCK, 7 { 30°64 | 42:2 | 38-7 0:3 | 7 E. 2:2 5
No. 17. 30°61 | 53°2 | 46°7 uc7f 62 E. 0:2 0 was
233 feet. 8 30°66 | 43:2 | 37°9 1:2 63 E. 22, 5
30°57 | 55°2 | 42:9 31 40 E. 1:0 0
Lat. 55°57’ N.| | ———/—_ —|—__ —|—_— —— |_| — | — | | ——_.
Long. 4° 45’ W. 9 { 30°52 | 36:0 | 383°9 0°5 81 i. 0-2 10
30°35 | 49:0 | 44:9 ial 72 W.. 1:0 0
10 { 30°22 | 37:2 | 36°7 01 96 E. 1:0 Nimb.
30°14 | 48:2 | 43:7 alae 70 i. 0-2 5 an
Means,. . 30-48 | 45-6 | 41-0 li] 7 ie | aere al De

4 30-49 | 45-1 27 | 071 78 | BE 20 bg :
30°56 | 43°6 23 | 10! 6 | a
PAISLEY, 7 j 30-62 | 44-1 23|10| 6 | E 10st aa ;
No. 18. 30°65 | 426 22 | 10] 69 |-S.B. iy mi
88 feet. J 30°65 | 37-6 | 36-1 23 | 041 87 | SH. LO di
30°56 | 42°6 | 37°6 21| 11| 66 | E. es
acts BO" GO NE [ed Laan ESIGN PARAGARGO pc Penh Pei APA | Bee eee Se)
Long. 4°27 W. | g 30-48 | 39-1 | 36-1 21 | 07 | 77 | B. 1610 |) be
30-43 | 43°6 | 40-1 25 | 08 | 74 | NE. 4
10 | 30-21 | 35-1 | 39-1 17/07] 72 | Be Ldm || tg 7
30°14 | 41-1 | 38-6 24 | 08] 81 | E.
‘Means, . | 30°48 | 41-4 | 38-0 08 | 74
i { 30-48 | 52-0 | 47-0 14] 6 | BB | 10 2 ‘
30°57 | 87°5 | 36-0 0-4 | 87 | NE] 1-0 0
Canutox-Mor, | j | 49°0 | 43-0 15 | om |) ar |) 1 1 .
No. 19. 30-65 | 41-5 | 39-0 06 | 81 | BE | 10 0
135 feet. g § | 30°63 | 546 | 41-5 30] 38 | B | 10 Seel! ig a
Sa oes 1 | 30°55 | 42:5 | 41-5 0-2 | 92 | N.EB.| 10 0 a
at. 56° 5’ N. ——— | —_— | | FS - | | -—- —_ — —_-
Long. 5°28 W. | g 30-48 | 45:5 | 40-0 12] 6 | B-| 1-0 fiom)
30°34 | 37-5 | 36-0 04 | 87 | EB. | 10 0
10 { 30-23 | 47°5 | 45-0 06 | 88 | E. | 1-0 9 .
30°12 | 36:5 | 35-0 o4| 87 | N | 10 0
2-4 | 1:0 | 75 1-0 | |

Means, . . ated 44°4 | 404

BRIGHT CLOUDS ON A DARK NIGHT SKY.

27

Sa Hygrometer Hepraietrieal Wind
Date. 3% aes Coniputed Results fades et
|| eae
38 :
oa ae oS & =3 | b
3 4 ag tia = Ze es 4 3 REMARKS.
Sration. se i ok Me a o|2,°3 Zo 7 g S 4
ieee = lie | Sele ee lees cose || = tS lice ly &
d | ge) @ | 2 | 22 [see/Eze/ ee | 2 | 2a] 2 | :
B S ay Ss ol ae a x jae A <
ey) 43 Bees? > dee pea hs
ins 5 é " ers. | gr. hrs.
g {\s048| 4 fae | s | oe) on me] Bm | 10 3
30°53| 43: | 40° | 3: | 25] 07] 78 | & | 1-0
EALLABUS, 7 { 30°61] 47° | 42° 5: pee lees Gr E. 1-0
No. 20. 30-62| 47° | 43- | 4 | 27] 10] 73 | B | 9-0
71 feet. /g s/goe1{ 49° [a | 8 | 21] 19] 53 | B | 9-0
30-51 45> | 46 ob 52 |Pos | 14 bes |) me |) 10
Lat. 55° 47' N. Le i oii sae i Se | Eee eee eee
Long. 6°15" W. | 0-46] 58 | 4 | 9: | 28) 22) 51 [Calm] 0-0
30-351 36° |-35° | 1: | 22 | 0-3 | 91 |Calm| 0-
10 {| 3025] 43° | 43° | 0: | 3:2 | 0-0 | 100 |Catm| 0-0
30-12| 38° | 37° | 1- | 24 | 0:3 | 91 | Calm] 0-0
Means, '30-45| 446 | 40-7 | 39] 25 | 0-9 | 75 2-2
4 { 30:56| 45-5 | 426 | 29 | 28 | 07 | 79 | S.B
30-60 | 381 | 36-0 | 21 | 2-2 | 0-5 | 82 | SB.
30-64| 44:8 | 40-0 | 4:8 | 23 | 11 | 67 |S.w.
Seon CASTLE, De 30-64 | 43-0 | 36-5 | 65 | 1:8 | 1-4 | 56 |S.W.
c ae eee | Se eee ee be Lee <i
30-65 | 48:9 | 41-0 | 79 | 21 | 19 | 53 |S.w. ‘3 vi
104 feet. 8 1|30-56| 39-1 | 37-0 | 21 | 23 | 05 | 83_|S.w. Pa Aurora.
Loe nl i Sd SS ee —— Fc A a
: 30-47| 37-0 |321 | 49 | 1-6 | 1-0 | 62 |s.w.
Long. 3°2’)W. | 9 { 30-36 | 35-0 | 33-5 | 1-5 | 2:0 | 0-4 | 85 |S.W.
- 30-24| 42:8 | 393 | 3:5 | 2-4 | 0-8 | 74 |N-W.
30-14 | 38°5 | 37-0 | 15 | 24 | o-4 | 88 |N-W.
Means, . 30-49 | 41:3 | 37-5 | 3-8 | 2-2 | 0-9 | 73
A 30°56 | 42:1 | 40-7 | 1-4 | 2-7 | 0-4 | 89 | SB.
30°60 | 89-0 | 880 | 10 | 25 | 08 | 92 | Su
30°65 | 41-4 | 40-4 | 10 | 28 | 03 | 92 | 8.
Wuw Prmstieo, | 7 { 30-67 | 35:6 | 35-2 | 0-4 | 2-4 | 0-2 | 96 | 8. % fr
No. 22. DU Oe eg OR ee ee ee ~
30-65 | 47-4 | 448 | 26 | 31 | 06 | 82 | 8.
495 feet. 8 { 30-58 | 36-8 | 36-0 | 0-8 | 2-4 | 0-2 | 93 | S.B. | ie
ee a eter ee ss rk ee Pe cc Un eee
: 30-48| 38:3 | 373 | 1-0 | 25 | 03 | 92 | S.B. FF
Bong. 2°9'W. | 9 { 30-33 | 33°8 | 33-1 | 0-7 | 2-0 | 02 | 93 | 8. -
a { 30-23 | 37:3 | 36-0 | 13 | 23 | 04 | 89 | & bos
30-14 | 38-0 | 363 | 1-7 | 23 | o4 | 85 | NW.
ion. 30-49 | 39-0 | 37-8 | 1-2 | 25 | 03 | 90 :
A { 30:59 | 40-0 | 38-0 | 2:0 | 24 | o5 | g4 | zs. Ol Fe 2
30:55 | 47°0-| 45:0 | 20 | 32 | 05 | 86 | EE 0 6
30°68 | 37-0 | 355 | 15 | 2:2 | 0-4 | 87 | w. 10 4
EN 74 30-79 | 44:0 | 43-0 | 1:0 | 30 | 03 | 92 |nw] . | 2. | o | 8 | 6
——————| = = oa S| || d
30-64| 41-0 | 39-0 | 2-0 | 25 | o5 | 84 | NE. 0 Gms
Bieter: 8 { 30°57 | 43-0 | 41:0 | 20 | 27 | 05 | 84 | Bm | Omar || a. |
rae eros wT : Hii aes Sasa oo bose
Bete glass as [| ee | eae eae © 2 al as
i { 30:27 | 38-0 | 36-0 | 2-0 | 22 | 0-5 | 93 | NE. LOMA) Gel) 6
30-14| 46-0 | 41-0 | 5-0 | 24 | 12 | 67 | E- 0 8
Means, . 30-50| 41-3 | 39-4 | 1-9 | 26 | 05 | 86 % T.)

VOL. XXXII. PART I,

C. PIAZZI SMYTH ON

g a Mypeomioier Hygrometrical
Date. me anne Gomten Results.
az
28 3
<a » & i
SraTron. 3< ag 5 zo
3e|(4 | 4/3. 2 /225
: 5 = a 3 e|s5e
e | gs] 8 | 8 lee eae lFse| ..
” S 25 — ae = .
“ins = S 2 grs. | gr.
{ 30°59 | 45°8 | 43-2 | a% | 39 | O-7 | 82
80°63 42-9 |'40-4 | 2:5 | 26 | 0-6 | 82
‘68 | 44-5 | 41:3 | 3-2 | 26 | 0-7 | 76
ABERDEEN, 7 { 30°70 | 41-0 | 39°8 | 1-2 | 2-7 | 03 | 90
No. 24. faecal ah)! Sa el eames! | arapeetl|| Sk lh Sel Peal
30°68 | 39-7 | 36-8 | 2-9 | 2:2 | o-7 | 78
66 feet. 8 1|30:60| 415 | 39-2 | 23 | 25 | 08 | 83
bat BOON alenue | ae leon Eee lea
ee 30°49| 40:3 | 38:2 | 21 | a4 | o5 | 84
Long. 2°6'W. | 9 { 30°36 | 38-2 | 37:0 | 1-2 | 2-4 | 0-3 | 90
“ j 30-25 | 39-0 | 37-6 | 1-4 | 2-4 | 0-4 | 89
30°16 | 42°6 | 39-1 | 3-5 | 23 | 0-8 | 74
Seats, 30°51| 41:6 | 393 | 23 | 25 | 06 | 93
f 30° | 436 | 41-7 | 1:9 | 2:8 | 0-5 | 85
30: | 41°6 | 39-4 | 22 | 25 | 0-5 | 84
ABERDEEN 7 { 30° 43°2 | 40-4 | 2°8 2°6 0-7 79
METEOROLOGICAL 30° 39°5 | 38°6 | 0:9 2°6 0'2 93
CoUNCIL ——|§ J fd Fare
OBSERVATORY, 8 { 30° 40:2 | 33°6 | 6:6 15 1:4 54
No. 25. 30° | 40-7 | 38-9 | 18 | 25 | 0-5 | 86
Lat. 57° 9 N. 5 30° | 39:7 | 37-7 | 2:0 | 2-4 | 05 | 84
Long. 2° 6’ W. 30 38-9 37-4 15 | 24 | 0-4 | 88
- 137-7 | 36-7 | 1-0] 2-4 | 02 | 92
10 { 30° | 41-1 | 382] 29123 | o7 | 78
Means, 40-6 | 383 | 2-4 | 24 | 06 | 82
- { 30: | 45-0 | 428 | 22 | 2-9 | 0-5 | 84
30° | 42:9 | 39:9 | 3-0 | 2:5 | o7 | 78
GLAscow ; j 30° | 43-4 | 40-4 | 3-0 | 2:5 | 0-7 | 78
METEOROLOGICAL 30° 42:0 | 39°3 | 2°7 9°5 06 80
CouNCcIL la | ee EO I I
OBSERVATORY, 8 { 30° 42°8 | 40:0 | 2:8 2°5 0-7 79
No. 26. 30° | 41°8 | 39:8 | 2-0 | 2-6 | 0-5 | 86
Lat. 55°53’ N. | 30° | 3921368 | 94122106 | 81
| Se eee eh
10 { 30° | 40-0 | 37-6 | 2-4 | 23 | 06 | 81
Means, . 41:3 | 39:0 | 23 | 25 | 06 | 83
ee
g §| 30° | 48-4 | 463 | 21 | 3-28 | 0-56 | 85
Royat Opserva- 1}... | 443 | 42-0 | 2:3 [2-77 | 0-56 | 82
TORY, GREENWICH | ,~ { | 30° 51:0 | 474 | 3°6 | 3-22 | 0:98 | 76
(LonpDon). J x 45°7 | 43:0 | 2-7 | 2°83 | 0-71 | 81
No. 27. | Ss a PL. | kL ae
3 {| 80° 53:0 | 49:2 | 3-8 [3-44 | 1-06 | 75
— feet. |... | 44-9 | 42-2 | 9-7 12-75 | 0-64 | 80
Lat. 51.29N. | 9 (|30° | 48:3 45-1 | 3-2 13-00. 0-86 2
Long. 0° 0’ Uline 410 | 39°4 | 1:6 | 2°59 | 0-4
10 30° | 46-9 | 44-3 | 2-6 | 2-98 | 0-71 | 82
43°38 | 41-2 | 2-6 | 2-66 | 0-62 | 80
Means, . | 467 | 44-0 | 27 | 295 | 0-71 | 81

Wind
at 9 A.M. Clouds.
and 9 p.m.
re é Ee :
as : =| 8 c=
ar | 2/8 |
ies a o na
2 ei 3 =]
g/ef| | =
S ace o (>)
= 2s iI i=
Ae A <q
(=) s)
hrs.
S.E. | 0:2 At pe
he | te | 8 at
nap 2 9 Sep
be le aie
Tae eae 10
SE. | 1-0 re
N. 1-0 10
N. 0-2 10

REMARKs.

BRIGHT CLOUDS ON A DARK NIGHT SKY. PAs)

APPENDIX IL.

Prosxctions of the preceding Observations, see Plates II. to IX., viz. :—
Plate II. Map of the Scottish Meteorological Stations referred to.
Plate III. Observations at Edinburgh.

Do Wanlockhead.
Do. North Esk Reservoir.
Do. Braemar.
Plate IV. Do. Douglas Castle.
Do.. Stobo Castle.
Do. Marchmont, Berwick.
Do. New Pitsligo
Plate V. Do. Stronvar,
Do. Moffat.
Do. Haddington.
Do. Greenock.
Plate VI. Do. Cupar (Fife).
Do. Dalkeith.
Do. Callton-Mor.
Do, Smeaton.
Plate VII. Do. Balloch Castle.
Do. East Linton.
Do. Paisley.
Do. Kallabus.
Plate VIII. Do. Glasgow, No. 1. ‘
Do. Glasgow, No. 2.
Do. Aberdeen, No. 1.
Do. Aberdeen, No. 2.
Plate IX. Do. (Greenwich, Royal Observatory, London, communicated.)
Do. Gordon Castle.
Do. Inverness.

[Apprnp1x IIT.

30 C. PIAZZI SMYTH ON

APPENDIX III.

I. Numertcat Tasies of Hourly Observations of Temperature, Depression of Wet-bulb, and
Hygrometrical Deductions for
Aberdeen,
Glasgow, and
Greenwich,

IL Puatzs X. to XIV. of Grarutcoan Prosections of the preceding Hourly Observations, viz. :—

Plate X. Temperature Curve at Aberdeen.

Do. Glasgow.
Do. Greenwich.
Plate XI. Depression of Wet-bulb Therm. at Aberdeen.
Do. do. Glasgow.-
Do. do. Greenwich.
Plate XII. Weight of Vapour in 1 cubic foot of Air at Aberdeen.
Do. do. Glasgow.
Do. do. Greenwich.

Plate XIII. Vapour required to saturate 1 cubic foot of air at Aberdeen.

Do. do. Glasgow.

Do. do. Greenwich.

Plate XIV. Humidity Curve at Aberdeen.
Do. Glasgow.

Do. Greenwich.

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34 C, PIAZZI SMYTH ON

APPENDIX IV.

1, GREENWICH TESTIMONIES AS TO CosMICAL ACCOMPANIMENTS OF AURORA BEING DEFICIENT
ON APRIL 8, 1882, AND APRIL 30, 1883.—Letters 1 and 2..

Royal Observatory, Greenwich,
London, S.E., May 12, 1883.

Dear S1r,—In regard to unusual phenomena on 1882, April 8, and 1883, April 30, as compared
with adjacent days, I am requested by the Astronomer-Royal to inform you as follows :—

The magnetical registers (Declination, Horizontal Force, and Vertical Force) indicate nothing
unusual, neither do the Meteorological (Barometer, Thermometer, Electrometer).

Wind 1882, April 6 to 10, steady E.N.E. and N.E. throughout the greater part of the five days,
changing on afternoon of April 10.

Wind 1883, April 29 to May I. Change on April 30 from N. to S.W. at 4%, and from S.W.
to E. at 64". On April 29 change in opposite direction about same times. On May 1, steady
N.E. wind.

1882, April 8. Brilliantly fine and cloudless throughout, similar on April 6 and 7, very little
cloud on April 9, cloudy but fine on April 10.

1883, April 30, A very similar day (in all respects) to May 1.

I am, Dear Sir,
Yours very truly,

(Signed) WILLIAM ELLIS.
Prof. C. P. Smyth..

Royal Observatory, Greenwich,
London, S.E., May 14, 1883.

Dear Sir,—With reference to your inquiry as to whether there was anything unusual on the
Solar photographs of 1882, April 8, and on 1883, April 30, as compared with photographs taken
on neighbouring days, the Astronomer-Royal requests me to say that there are no noteworthy changes
in the spots shown on pictures taken on 1882, April 7, 8, and 9. Small spots were constantly
forming or disappearing, but nothing unusual is shown.

The picture taken on 1883, April 30, shows a group of several very small spots which disappeared
before 1883, May 1. Two small groups not visible on 1883, April 30, are shown on the picture
taken on May 1. The changes are not at all unusual in character or amount.

I am, Dear Sir,
Yours very truly,

(Signed) FE. Dunkin.
Prof. C. Piazzi Smyth.

2. OF THE AURORA SAID TO HAVE BEEN OBSERVED AT 1 STATION OUT oF 24 IN SCOTLAND
ON APRIL 8, 1882.

Letter from the Gordon Castle Observer to Mr Buchan, Seeretary Scottish Meteorological Society.

Dear Str,—I am in receipt of your note inquiring about “ Aurora” entered in my notes of daily
readings in 1882. I have looked up the Schedule, and find there are no particulars dated; simply
Aurora. ‘The time is too far back to bring my memory to it, but I see by the readings under, that
it had been the precursor of a considerable depression of the atmosphere at the period.

I am, Sir,
Yours faithfully,

(Signed) JOHN WEBSTER.

BRIGHT CLOUDS ON A. DARK NIGHT SKY. 30

3. Or AURORZ SPECTROSCOPICALLY OBSERVED IN EDINBURGH AT THE ASTRONOMERS’
HOoUvsE IN 1882 AND 1883.

The concluding remark in Mr Wessrter’s letter, that the date of his stated Aurora, April 8, 1882,
was followed by a considerable depression of the atmosphere, is perfectly true; for the record of
Barometer (uncorrected), wind, rainfall, and clouds, kept at the Royal Observatory, Edinburgh, in
connection with Time signalling, runs thus from April 5 to April 15, 1882 :—

Wind. ‘ .
: Wind. Rainfall, Clouds.
pay EMGAGE ees Direction. Depth of. 0 to 10.
April. Inches. Inch.
5 29°99 3 N.E. 000 10
6 30°10 2 N.E. 013 6
U 30°23 4 N.E. 000 0
8 30°22 2 N.E. 000, 0
9 30°02 2 N.E. 000 3
10 29°77 3 N.E. ‘000 0
11 29°58 2 N.N.E. “000 10
12 29°45 3 8.8.E. 000. 9
13 29°06 8 EK. 035. 10
14 | 28°83 10, N.E. “424 10
15 29°29 1 N. ‘230 10

That circumstance, however, does not prove that the luminosity Mr Wester observed in the sky
at Gordon Castle was a real Aurora. It certainly could not have been one of the grander Aurore, or
it would have been noted at some of the 23 other stations; would have imprinted itself indelibly on
the observer's memory, and would have marked itself on the continuous photogtaphic curves of the
magnetic needles at Greenwich.

Whether it was, however, a faint Aurora, or perhaps some other luminous manifestation, I do not wish
to suggest a word either for or against; but if the observer could have said that he spectroscoped it
with a pocket spectroscope, and saw the Auroral Citron line,—I should have accepted the testimony
immediately. For I myself have never yet spectroscoped any decided Aurora, without its showing
that line ; and have never seen that line in any other light, though I have, on one occasion, elicited
the line out of a full-Moon, mid-night sky, when at the time there was no appearance of Aurora or
any of its usual accompaniments,—but where, an hour before, there had been some unmistakable
needle-shaped jets and darts of its light on the Northern horizon.

The opportunities I have had for good numerical observations of the Auroral spectroscopic line,
during the last 15 months have not. been many; but may form a useful addendum to the present
paper,—as follows :—

© October 22, 1882, at 11" p.m.; the moon ten days old, and the sky bright with moonlight;
Aurora seen as a faint but regularly-shaped arc on the N.W. horizon ; spectrum place of its Citron line
=45 511 of Wave Number per Brit. Inch.

h October 28, 1882, at midnight; past full-Moon; sky clear and frosty. No Aurora visible to
the naked eye at the time, though there had been earlier in the evening. The place of Aurora line,
doubtfully observed, came out 45 350 (2) W.N. Place.

3 November 14, 1882. Aurora lasted through much of the night, but chiefly behind clouds.

9 November 17, 1882. A grand Aurora; but barely seen here by reason of clouds, smoke, and
irection.

Fh November 25, 1882, 11" 30™ p.m.; Moon just past the full. No Aurora to naked eye,
but its line was clearly seen in the spectroscope, followed by a broad band of continuous spectrum of
the Moonlight. Place of the line observed at 45593; while the continuous band of Moonlight
began at 46 610, culminated in intensity near 48 200, and ended gradually near 52 610 W.N. Place.

( March 26, 1883, at 10° p.m.; a rather bright Auroral are northwards, its central portion
rising 10° or 15° high, and having dark shade underneath. Its Citron line’s place measured 45 558
W.N. Place.

3 March 27, 1883, at 10° p.m.; a long low quiescent, or blandly-shining faint arch of Aurora
on the northern horizon. Its Citron line’s spectrum place measured 45 542 W.N. Place.

VOL, XXXII. PART I, F

36 BRIGHT CLOUDS ON A DARK NIGHT SKY.

This latter was the best Auroral manifestation I have seen this season. Many others I believe
have been noted in Sweden and Norway; but those countries seem to be situated over one of the
Earth’s invisible quasi voleanoes, or rather perhaps “maelstroms” of Aurore; so that as Professor
Anestrom noted many years ago, and Professor Lemsrrom more recently, there is sometimes an Auroral
phosphorescence there on everything about them, air, earth, ice, and water.

Such phosphorescence, however, as Professor Lemstrom has well remarked, is recognised by its
giving to the spectroscope the well-known Citron Aurora line, whose place is close, according to my
observations, to 45 550 W.N. Place,

But other kinds of phosphorescence, so far as I have observed them, give only a band of continuous
spectrum in the green and glaucous regions, necessarily more refrangible than the Aurora line; or

Stick phosphorus in a chamber, has the maximum brightness of its -

broad, faint, band at : . 49000 W.N. Pl.
Animal phosphorescence at sea, has the similar centre at... 50 300 y
Carbo-hydrogen blue flame, when too faint to show its individual

lines, has its chief brightness near . : ; . 49 200 ‘5
The Zodiacal light has the same, at or near , ‘ . 48150 ss
Twilight has the same, at or about : : : . 48150 A
While Moon light, as above, has it at or near ; : . 48200 a

The last three therefore can hardly fail to be of one and the same Solar origination; but the two
first are quite different from them; and still more different are they from the chief Auroral line, both
in appearance and spectrum place; while the third suits our faintly bright night clouds of April 8,
1882, with a broad slit perfectly.

TRANS. Roy. Soc. EpDIN® Vou. XXXII. Pvare II.

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TII.—Note on the Little b Group of Lines in the Solar Spectrum and the New
College Spectroscope. By C. Piazzt Smytu, Astronomer-Royal for Scot-
land. (Plate XV.)

(Read June 1883).

Every spectroscopist is perfectly aware that the group of dark Fraunhofer
lines in the Solar Spectrum, known as “little b,” is composed of the biggest,
broadest, most colossal lines in all the brighter part of any and every spectrum
depending on Sunlight, whether direct from the Sun or reflected from the earth’s
atmosphere, the Moon, or any of the planets.

How the apparent misnomer came about, was not on the principle of the
biggest gun ever made by our military, being termed “the Woolwich infant ;”’
but because after FRAUNHOFER had spaced out the spectrum into nearly equal
lengths, so far as the majority of the chief lines allowed, and called them by
capital letters, beginning with great A in the ultra red and ending with great
H in the ultra violet,—he then began again at the red end, and marked all the
notable intervening lines by small letters. Whence it came about that those
sometimes very imposing bands of telluric water-vapour lines “little a” are
found between great A and great B; and those grand and truly solar lines
in the green, little 6, are found, by accident as it were of Nature, between great
E and great F.

In the smaller class of pocket spectroscopes and on the faint light of the
Sky, observers merely recognise two strong lines ; the first from the red end is
b*, and the second, considerably thicker, is 67. A very little increase of power,
however, easily shows b? to be composed. of two lines, 6? and 63; and Fraun-
HOFER himself had announced it. But that such J? was still further composed
of two lines was I believe first discovered by Professor Swan, and published in
our Transactions as part of his now classical spectrum paper of 1855 and 1856.
For therein (vol. xxi. p. 427) he mentions most clearly—though calling our
b*, 67, b? by the names 8, 0’, b? that “on the 20th of May, about 7° 10™ p.m.
when the sun was rather low on the horizon, but free from clouds, he observed
with a magnifying power of 21 (on his large theodolite telescope, directed to a
single prism of 60°) the line 6? (our 63) to be very finely but distinctly double ;
so that,” he adds, “ the group consists of 4 lines” (our 0", b?, 63, and b*). While
on page 426 he had already expressed his admiration for the group “as being
one which, whether we regard the singular configuration or the strength of the
lines which compose it, is perhaps the most notable in the solar spectrum.”

In the Philosophical Transactions of the Royal Society (London) for 1860,

VOL, XXXII. PART I. | G

38 C. PIAZZI SMYTH ON THE

there is a picture by Sir Davip Brewster and Dr GLapsTONE confirming these
four grand lines of little b, and adding some thinner intervening lines and faint
broad bands. But before that could produce much effect on men’s muids, it
was utterly eclipsed by the far grander Solar Spectrum map, first of Prof.
Kikcuorr, and then of Professor ANGsSTROM, whose exquisitely engraved, and
certified, map still remains for many purposes the Normal Solar Spectrum Map
of all the human race.

Now let us take a new start from that last map, date 1868, in order to
ascertain something of our present degree of knowledge touching the visible
characteristics of these four remarkable lines ; for however many thinner ones
there may be, the principal members of the group are four only, and have over-
whelming importance. Two of these moreover, viz., b' and b? were represented
by Anastrom physically different from the others, be slightly bordering them
with haze.

In -1875 the Royal Society published a map in their Philosophical Transac-
tions, where they represented (though by a very exceptional kind of symbolic
marking, looking really like something else very different but very important if
true) these haze borders of 0* and b? as still broader; but made b? and 54, pale
in a high, dark in a low, sun, as though they were atmospheric or telluric lines,
which they certainly are not.

In 1880 M. Fievez, in the R. Observatory of Brussels, represented several
lines hazy, though he left 6* quite sharp and black.

But in the same year Professor VoGEL, of the Astro- Physicalischen Onsen
tory at Potsdam in Prussia, and armed with a new spectroscope of immense
power, published a very superior spectrum map wherein he represented 0", b?
and 6‘ all equally and very broadly hazy, but kept b? quite sharp, well defined
and black, besides adding many thin lines, some single and others double.

In the following year at Madeira I had the opportunity, besides confirming
Professor VoGEL on all the four great lines, of adding thereto the further physi-
cal distinction that the lines themselves, inside the envelopes of haze of b', b?-
and 6* were all of a peculiarly faint material; and of presently still further
discovering both that the 6* line, within the compass of its own haze, was
double ; and that 6’, without any haze, appeared not actually double, but to
promise certain resolvability into it, had my apparatus been only of a slightly
better order.

At the time I could hardly believe my eyes; but have learned since then
that the duplicities of b? and b+ had been just previously to that date ascer-
tained with some of the splendid spectroscopes in America; as they were also
subsequently by a second very powerful spectroscope built up, and employed
by M. Frevez at the Royal Observatory, Brussels, in 1882.

But perhaps I am going on too fast; for certain learned parties, to whose

LITTLE 6 GROUP OF LINES IN THE SOLAR SPECTRUM. 39

extensive knowledge implicit respect has hitherto been generally paid, have not
yet taken any notice of either M. Frevez or the American observers. <A
particular case of such neglect is to be found in the new, or third edition, of
Dr ScHELLEN’s German work on “Spectrum Analysis” published during the
present year, 1883, in 2 volumes, and an atlas filled with excellent engravings.

The number of different spectroscopes illustrated in those volumes is legion.
But amongst them all, the highest opinion seems to be entertained for the
spectroscope of Professor. VocrL, already alluded to. The instrument was
made by the celebrated M. ScuropeEr of Berlin, contains 6 large compound
prisms of heavy glass, with powerful telescope, collimator and automatic move-
ments to match. It is represented accordingly with pride in three pictures on
pp. 243, 244 and 245; while on p. 247, to prove beyond doubt how advanced
are its powers, a pair of diagrams of the little b group are given; first, as
they were represented by ANGsTrom in his day; and second, as they are
now seen by Professor VocEt. But though the latter, as I have already stated,
introduces several more thin lines, he leaves the four classic members of the
little b group, as given by ANcsrrom at the early spectroscopic date of 1868,
untouched ; for Dr ScHELLEN, by some inadvertence having imparted haze to
Anestrom’s view of bt, has destroyed. (on his own plate) the rightful claim
of Professor VoGEL to that physical discovery.

Now let us contrast that state of things with some observations I have just
been able to make in Edinburgh through the sunshine there, all smoky as it
unhappily is, at No. 15 Royal Terrace, but with an admirable spectroscope, kindly
left in my hands for a few weeks by Professor P. G. Tait,—after he had, by a
marvellous chance, been able to acquire it for the Natural Philosophy Labora-

tory of the Edinburgh University. It is of English make, by Messrs T. Cooxr
& Sons of York, but constructed for the late eminent Belgian scientist, Dr Van
MOoNCKHOVEN, on a plan arranged between himself, Mr Lockyer and Messrs
CooxeE ; though he had hardly received it when sudden death by angina pectoris
cut short his splendidly energetic and promising career, to the terrible grief of
his family and friends. The instrument thrown thus open to purchase again,
was sent here by Messrs Cooke, and I could not but admire exceedingly the
compactness of its arrangement, by which it was enabled in a remarkably small
compass and with absolute directness of vision throughout the whole spectrum,
to employ virtually any number of prisms from 2 to 20. Every prism too
-being “simple,” and of white flint glass; a feature in happy opposition to the
compound prisms of brown or green flint glass, cemented to crown-glass anti-
prisms, which are far too frequent favourites elsewhere.

But how did the Cooke spectroscope acquit itself, when tried with the
maximum number of its prisms, and highest magnifying power of eye piece ?
I was over and above delighted to find that it focussed more sharply than any

40 C. PIAZZ{ SMYTH ON THE

spectroscope I had ever used ; and on bringing in our old friends of the little b
group, there was not only all that Dr ScHELLEN and Professor VoGEL have
recorded for the latter—not only too all the physical features which I had noted
with difficulty at Madeira,—but there were b? and b*, each of them as clearly
doubled, and their components clean separated, as any observer could possibly
desire. Of 6? one line was shown to be much stronger than the other, but
equally sharp ; while of b* one line, the stronger also of the pair, was evidently
hazy, and just as accurately concentric with that cloud of haze, as were the
old 6' and b? with regard to their clouds of haze; but the new and weaker
component of b* was evidently excentric to the haze of b*; a further test now
of performance, but whose additional utility will presently appear.

So far then as mere optical definition was concerned, nothing could be more
satisfactory, or rather I should say transcendent, than this trial of the new
College spectroscope on the little b group; though it had been preceded in its
detection of duplicities merely, by the American observers, and also by M.
THOLLON in France, and M. Fievez in Belgium. But those gentlemen have
not, so far as I know, taken the further step of investigating chemically and
physically the ultra nice points of optical discovery which they have added to
the b group.

I do not of course by this allude to what every one may read in ANGSTROM’S
admirable normal map, as to b’, b? and 64, all of them now known to be endued
with a remarkable haze, being the reversals of magnesium metal burning in the
Sun, and b?, so strikingly without haze, being a similar representative of iron;
—hbut to this further detail, that under and coincidently with b*, ANnastrom
placed an iron, as well as a magnesium line; and under b?, a nickel, as well as
an iron line. Or, as his followers are delighted to assert, b? and b* are basic
lines ; viz., one line standing as a base for two metals. The principle therefore
of any such basic line represents .a new chemistry, where two earthly elements
are, by long roasting in Solar heat, resolved into one element, forming a
common base to them both. So that certain reputed simple and original
elements of the chemists hitherto, are really compound bodies; and the list of
elements in the Sun, is shorter than that which is accepted on the earth.

It is something of a check to that system, to he enabled to say from mere
optical observation, that in the two instances in little b, where basic lines had
been thought to be met with, superior spectroscopes have shown there are two
lines in each case; but much more than that is necessary for full proof; for
who can be certain that any two given spectrum lines seen very close together,
in place of representing a mere chance, or optical, coincidence of two perfectly
unconnected elements’ lines, may not be a physically double line of some one
metal.

I have therefore been trying the Cooke Spectroscope on this point, by

—_—

LITTLE b GROUP OF LINES IN THE SOLAR SPECTRUM. 41

deflagrating before it with condensed induction spark the several metals con-
cerned. My apparatus for that purpose is unfortunately very primitive and

- weak, not more than 15-inch sparks in air, and 1 quart Leyden jar to condense ;

but by placing the spark in front of the slit, obtaining the solar spectrum
between the points of the sparking metals, and correcting by eye for the neces-
sarily curved spectral lines of 20 simple prisms,—certain definite results were
obtained on some of the points required, as thus—

(1) For Magnesium. The metal spark line corresponding to b* is just as
certainly a single line, as those corresponding respectively with b* and 6; and
further it falls on the second, more refrangible, and stronger component of the
Solar 4, quite suitably to its hazy physical appearance in the Sun.

These three Magnesium spark lines moreover form an ordered triple,
remarkably like the Oxygen triples which I announced to the Society some
two years ago, in so far that the 2nd and 3rd are closer together than the 1st
and 2nd, and the intensities of each go on decreasing from Ist to 2nd, and from
2nd to 3rd, but the arrangement is on a far grander scale.

(2) For Iron. Two of its spark lines appear in the field of view in places |
evidently belonging to b3 and bf in a general way; but they are both sadly
faint, 7.¢. in my weak sparking apparatus. However the stronger one is
remarkably sharp and may be certainly said to coincide with the first, or least
refrangible component of b‘ in the Solar spectrum; which is that one which
simple observation had already shown to be excentric to the characteristic
magnesium haze. With not by any means so much certainty, unfortunately, the
fainter iron line may be said to coincide with the stronger of the two recently
discovered components of the Solar b?.

(3) For Nickel. Here the result was poor to utter disappointment ; the
tabular Nickel line concerned has only an intensity of 2 attributed to it, against
many that are classed as 10, by the great spectroscopists with powerful
apparatus ; and it appeared to me to deserve even less. Indeed I had only to
wander a little further on into the blue regions of the spectrum to find Nickel
lines there that were a pleasure and a certainty to compare with Solar lines ;
but the particular Nickel line in or near b? was so faint as to be utterly hazy and
undecided ; wherefore I must relegate this question of the b? supposed basic line
to those who can produce brighter sparks of Nickel and Iron than I can.

And there is another point touching Nickel that I would also recommend
to their earnest attention. Every one has heard of the Nickel line between the
two D lines of the Solar spectrum; and many persons will have read in Dr
MarsHaL Warts most useful Index of Spectra that both THaLten and
Krrcuorr have assigned their maximum for intensity, or 10, to that Nickel
line. Being desirous therefore to see what such a grand line would look like in
the Cooke spectroscope when sparked by my apparatus, I brought it into the

42 C. PIAZZI SMYTH ON THE

field, together with the Sun spectrum; but behold, although it was much
clearer than the little 6? Nickel line, it was yet a very poor thing ; so poor, that
I wandered off into the Citron regions, amongst the groves of hazy air lines, to
see if something better could not be found there ; and sure enough I stumbled
almost immediately on a magnificent line, a line which for brightness, beauty
and definition was far beyond everything else in the field of view, though that
was a pretty full one too. It proved to be the line at 46 380 W.N. Place, which
Dr Warts has entered in his tables on the authority of both THALEN and
KircnorrF as of intensity only equal to 6, when the trifling line between D* and
D? was called by them 10.

On turning to ANestrom’s Normal Solar map with its chemical references,
I was encouraged by finding the D Nickel line and its Solar representative also,
far fainter than the 46 380 W.N. line of Nickel and iés Solar reversal. But on
still further referring to that most able observer M. Lecog DE BoIsBAuDRAN, he
represents the 46 380 line, as the very maximum, or the a, of the whole Nickel
spectrum ; gives no place to the D Nickel line at all; and only the faintest
imaginable marking to the Nickel line in the place of b®?. His deflagrating
method was however different ; for he used simple, uncondensed electric sparks,
and employed them not on metal points, but on a solution of a salt of the
metal. Perhaps too, bearing in mind the extreme modesty of his ‘“spectro-
scopic installation,” it is wrong to refer to him,—master hand though he
undoubtedly is, so far as it accords with his plan to go into any subject,—for
more than the testimony he gives to the magnificent lustre of the a line at
46 380 W.N. Place. So that the only remaining anomaly, but a most important
one, to be cleared up by those who have plenty of electrical energy at their
command and a good spectroscope, is, the immense intensity attributed to the
D Nickel line by MM. Tuaten, Kircuorr and Warts! Is there a numerical
error there, or is that line capable of peculiar intensification with increased
electric temperature 4

But meanwhile though I may have failed in that inquiry, what an extension
of the powers of pure and simple spectroscopic observation (when we have
light enough) does not the new College Spectroscope already exhibit !

A few years ago some of our best men thought the ne-plus-wltra of accurate
observing had already been reached with the Dispersion of a single prism of 60°
and magnifying power on a telescope of about 20: for after that, they found
that whatever was gained in Dispersion by adding a second or third prism, was
lost by bad definition. But here, thanks to the super-excellence of our British
optical house, Messrs T. Cooke & Sons of York, no less than 20 prisms are -
virtually employed, and the limits of fine definition, even when tested by high
magnifying power, are not yet reached.

All that Dispersive power too, and all that Definition are perfectly necessary

LITTLE b GROUP OF LINES IN THE SOLAR SPECTRUM. 43

in the present day. For as this Note must have shown, if it has shown anything,
the most radical and fundamental questions in all Chemistry and the very

constitution of the Cosmos depend upon the most recently elicited and minutest

of all the phenomena yet observed.

P.S. September 28, 1883.

The above position will become still more distinct on considering two sets of first rate observations in this
part of the Spectrum, contained in the Proceedings of the Royal Society (London), and the present paper should
by no means be allowed to close without honourable mention of both of them.

The first to be noticed of these sets, is by Professors Lrvernc and Dewar, working in the magnificent
Cavendish Laboratory at Cambridge ; and writing at-p. 229 of said Proceedings for May 1881, of 0%, that it is
“a close double, but the Iron is less refrangible than the Nickel, line.”

While of b¢ they state with greater fulness :—

“ By examining the are of a battery of 40 Grove cells, or that of a Siemens’ machine, taken in a crucible of
lime, under the dispersion of the spectrum of the fourth order given by a Rutherfurd grating of 17,296 lines
to the inch, we are able to separate the iron and magnesium lines which form the very close pair b* of the solar
spectrum. Either of the two lines can be rendered the more prominent of the pair at will, by introducing iron
or magnesium into the crucible. The less refrangible line of the pair is thus seen to be due to iron, the more
refrangible to magnesium. Comparison of the solar line and the spark between magnesium points confirms
this conclusion, that the magnesium line is the more refrangible of the two.”

This accords well enough with, and indeed overshadows, my imperfect experiments in Edinburgh. But
what are we to think, on turning to p. 443 of the same. Society’s Proceedings for the earlier date of March 20,
1879, where that distinguished spectroscopist Mr Norman Lockyrr, working with all the resources of the
Government Department of Science and Art at South Kensington, implies, of 6°, that there is no Iron there,
only Nickel ; but of bt, that there are besides Iron and Magnesium, no less than 9 other metals, viz., Mo, W, Co,
Mn, Ca, Li?, Na?, Cu, and Al, coincident with it.

The beginning of some explanation of this difference undoubtedly is, that at the time of his observation,
the accomplished observer had not heard that both b? and 6* were double lines, and had not a spectroscope of
sufficient power to show them so.

The second part of the explanation is probably due to the admission in the last par. of p. 442, that
compulsory “rapid surveys of the arc spectra of most of the metallic elements” have led to approximate, being
sometimes assumed as exact, coincidences,

This is an almost necessary feature in the earlier stages of any inquiry ; but now that we are happy to
learn, on one side, that Mr Lockyer has come into possession of one of Professor RowLanv’s (U.S.Am.) grand
concave Gratings, and on the other, know that the Natural Philosophy Laboratory of the Edinburgh University
possesses the Monckhoven-Cooke Spectroscope, together with a 4-horse power Gas-engine, Dynamo, Grand
Tnduction-Coil and Condenser to suit,—we may expect something very important from either one or both those
parties revising that list of so many metals supposed, four years ago, to have one common meeting place

in the Spectrum.
C. P.S.

EXPLANATION OF THE PLATE REPRESENTING THE COURSE OF DISCOVERY
TOUCHING THE LITTLE 6 GROUP IN THE SOLAR SPECTRUM.

This plate is rough and rude to a degree, and that is partly intended ; because, to attempt
to reproduce the infinite refinement of shades, tints and lines shown by Nature in the Solar
spectrum, belongs more to the department of artistic beauty, than scientific work; and already
every high Solar scientist has utterly discarded the trouble and expense of introducing that
leading element of the Spectrum’s beauty, colour, into his maps; and has taken that very
strong step towards a symbolic, rather than realistic, representation, partly on ‘account of the
absence of colour-pigments from his paper enabling him to bring out the more useful black or
grey of the Fraunhofer lines with greater force and more ease of recognition.

But even then, in mere black and white, the question comes up once again, should we
attempt to reproduce every such refinement the spectrum itself shows, and in the manner in
which it appears there——which would necessitate the most ultra microscopic engraving on

4t C. PIAZZI SMYTH ON THE LITTLE b GROUP OF LINES, ETC.

copper or steel plates ;—or shall we adopt a short, easy, symbolic method by which in the tenth
of a second we can make a mark anywhere, on paper as well as copper-plate, signifying merely,
or standing for, such and such an artistic, or realistic, effect ?

A splendid example of the former method is to be seen in M. Cornv’s fine engravings of
the ultra-violet portion of the Solar Spectrum; for there, thin. lines are successfully repre-
sented of every degree of shade from lightest to darkest; but without the mechanical means by
which they are executed appearing to the eye, until reinforced by a powerful magnifying glass ;
and they are then seen to be the effect of minute dots more or less closely packed, and without
ever recurring to “the vulgar expedient” of ruling an actual line, in one uniform degree of
blackness. When any person donates the science of his time with such a Solar spectrum map,
whether in whole or part, the public ought to be very grateful to him; and it is to be hoped
they are so, in this case, to M. Cornu, the distinguished Parisian scientist, for his unmatched
portraiture of “the region of fluorescence.”

But the daily work of the world requires an interim employment of some easier method,
something akin to writing by the letters of the alphabet as signifying sounds, in place of paint-
ing pictures of the things intended. One method already extensively in use and much to be
commended, is to express the different degrees of darkness of a Fraunhofer line, whatever
the breadth, by different heights or depths of the line; and this it will be seen I have availed
myself of in several instances.

The same principle may be applied to the shadings by which bands are represented in the
Spectrum. Shadings of some kind are necessary there with the very faint bands, to prevent
straining the symbol too far; which would result, if we had only the device of shortening the
height of a band in positive black ink, to represent an ultra faintness of shade. Such shade
being, in reality, at the telescope, just as high necessarily as any of the blackest lines,
because they are all reproductions of one and the same slit in front of the spectroscope.

Faint bands therefore have long since been generally represented by a shading of thin
parallel lines; and the method is unequivocal when the lines are ruled in any direction except
that, in which they might be repetitions of the slit of the Spectroscope, or stand for separate,
independent, thin Fraunhofer lines.

Hence I have represented the hazy borders of the 6 lines, by either horizontal, or 45° inclined
lines, and no spectroscopist will take them, or the knots in them, as anything else than
symbols of shade. It is necessary too, to be very particular on this point, because the Royal
Society, London, in both its Philosophical Transactions and Proceedings, has most pertinaciously
set, and is still setting, the opposite example of representing shade in the spectrum, by thin lines
ruled parallel to each other and in the direction of the slit; so that when many and many a
close double, or treble, or quadruple Spectral line appears in a Royal Society engraved
Spectrum plate, it may mean, either that their observer did see a double, or treble, or quad-
ruple line in that place; or, that he only saw a faint, unimportant haze.

Finally in our present plate, one mcre difficulty has to be compassed; for it is to be an
historic memento, from the earliest spectroscopic times to.the latest. In my last year’s publica-
tion, “Madeira Spectroscopic” I attempted to meet a similar case, by representing every
observation, of whatever date, on one and the same scale. But I have been told that some
persons do not like the necessarily resulting effect of that plan, in so far as it makes the earlier
observations, taken with very small dispersive power, look colossal in coarseness. In the
present case therefore, I have decreased that appearance by adopting a smaller and smaller
scale for every earlier Spectrum view; but so arranging them one over the other, each with
its own sized numerical graduation above it, that I trust there will be the least difficulty and
the most satisfaction practically possible, in comparing details of the one with the other, and
fixing the dates when real advances of observation—knowledge were made.

C. Bas:

; Roy. Soc. Epirn® VoL. XXXII. PLATE XV.

Chronolog ical Plate of the Course of Discovery , Touching the
Zettle 6 group in the Solar Spectrum; 1830 — (82.

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( 45 )

IV.—Observations on the Annual and Monthly Growth of Wood in Deciduous
and Evergreen Trees. By the late Sir Ropert Curistison, Bart., and
Dr CHRISTISON. |
(Read 19th March 1883,)

Having undertaken to continue the observations on the growth of trees
commenced by my father in 1878, and carried on by him with unflagging zeal
until a few months before his death in 1882, I give in the present paper the
measurements made by him in 1881, which he did not live to publish, and those
made in 1882 by myself. I shall also endeavour to point out the conclusions
which may be drawn from the whole series of observations, beginning in 1878,
arranging them under the heads of—

I, ANNUAL OBSERVATIONS.
II. MontHiy OBSERVATIONS.
III. InFLuENCE oF WEATHER ON THE GROWTH OF Woop.

Thus the deductions already arrived at by my father in this branch of his
investigations on the growth and measurement of trees will be again reviewed
and tested by the experience of two additional years. The other branches of
his subject, including his inquiry as to the proper mode of measuring the girth
of trees, the kind of information to be derived from such measurements, his
discussion of DECANDOLLE’s rule for estimating the age of trees by.the annual
rings, the modes of doing so recommended by himself, and his description of
the Fortingall Yew, have been so fully treated in his earlier papers, published
in the Transactions of the Botanical Society of Edinburgh, as to require little
further elucidation. Very different is it however with the yearly and monthly
measurements. These can only become truly reliable after a prolonged series
of observations ; and even the present review of five years’ experience must be
considered as to a considerable extent provisional and subject to correction.

Before proceeding with the proper subject of this paper, it is advisable to
state that the observations and deductions in it rest entirely on the possibility
of making accurate measurements of the girth of trees. Previous to Sir
RoBeERt’s observations measurements of the kind were made in the vaguest and
most unreliable manner. It was reserved for him, in extreme but vigorous old
age, to make the simple discovery that such measurements could be depended
upon to within a tenth or even a twentieth of an inch, and that consequently
not only the annual but even the monthly increase could be accurately recorded.
I thought it was desirable however on taking up the subject as it dropped
from his hands to retest this question, and to ascertain whether my measure-

VOL. XXXII. PART I. H

46 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

ments might not, from some difference of manipulation, disagree with his.
Accordingly, with the aid of my brother, I remeasured early in 1882 the forty-
one trees in the Botanic Garden measured by Sir Ropert at the end of the
growing season in 1881. The result was satisfactory. In nineteen instances
there was no appreciable difference between the two measurements ; in seven-
teen the difference did not exceed a twentieth of an inch; in three it
amounted to a tenth, and in two to a seventh of an inch. Thus in only five
cases were the discrepancies so great as to be of material consequence ; and,
on investigation, these discrepancies were found to be evidently due either to
extreme roughness or a tendency to scale in the bark. So great a degree of
accuracy as this however cannot be obtained with ordinary tapes. I have found
some of the inches marked on these a tenth of an inch too large, others a tenth
too small. Another source of error with them is the terminal ring with the
fastenings by which it is attached to the tape. If the measurement be taken over
the ring, and it happens to be sunk in a depression of the tree, no error results ;
but if the rg be on a projection of the bark, its bulk may cause an error in
excess amounting to a twentieth or even a tenth of an inch. A different result
from either of these will probably be got if the measurement is kept clear of
the ring altogether. In the early part of his experiments Sir RoBeErt used a
tape, painted so as to avoid stretching, and graduated by himself; an extra
inch graduated to tenths served for taking the fractions of an inch, so that it
was unnecessary to graduate the tape throughout into tenths. But mistakes
were apt to arise from the necessity of reckoning the tenths in a direction con-
trary to the numbering of the inches, and ultimately he used a steel tape, —
graduated throughout to tenths, made specially for him by Messrs CHESTERMAN.
This is certainly the kind most to be recommended.

I. ANNUAL OBSERVATIONS.

Following Sir Rosert’s example, I give the increments for 1881 and 1882
in a tabular form, along with those already published for previous years. As in
the course of time however several of the trees originally selected have ceased
to be eligible, I have found it necessary to remodel the table to a considerable
extent. Thus the Scots fir, No. 19 in his list, and the Picea Lowei, 32, having
ceased to grow, have been cut down; the Scots firs, 11, 36, 37, have also
ceased to grow for three years; and the yew, 47, is almost in the same predica-
ment. As it was obviously useless to retain these, they have been struck out ;
and the Pinus Laricio, 17, the aged sycamore, 13, and walnut, 14, having bark
either so scaly or so rugged as to be unsuitable for minute measurements, have
shared the same fate. In compensation for these losses in the Botanic Garden,
a larger number of trees growing at Craigiehall, five miles from Edinburgh, have
been selected for observation and added to the list. No confusion need be
feared from these changes in making comparisons with former years, as the

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 47

increments are computed on the average increase per tree in the different
classes. For the sake of clearness it has also been judged advisable to divide
the table into two parts, the first comprising the twenty-eight deciduous and
the second the twenty-three evergreen trees under observation.

I have ascertained that the results obtained from this new list do not differ
materially from those derived from the former list by Sir Ropert. But as it
would be useless to cumber these pages with more than one set of observations,
I have resolved to give the results of the new list alone, as being both more
reliable when corrected so as to apply to the past, and forming a more accurate
basis for the future,

TABLE I.—ANNUAL INCKEASE IN GIRTH OF DECIDUOUS TREES,

All in the Botanic Garden or Arboretum, except those marked “ Craigiehall.”

Increase.
Date and Girth

Trees. when first measured.

1878. 1879. 1880. 1881. 1882.

Inches. Inches. | Inches. | Inches. | Inches. | Inches.

Birch, ; 1878 55°35 0°25 0:05 0:05 O80.) “O10
“ (Craigiehall), ? 1880 56°30 o oe 040 |) 0:55 | 0-45
Beech, . ‘ ; 1878 71°40 L206 -0°95+) 0°65 0°85 1:15
a ; 4 60:50 1:20 | 080] 0:90 0:90 | 1:10

» rs 75°80 0-60 | 0-60 0:25 0:50 | 0:60

me it , : : > 60°30 0°60 | 0:45 015 0:50 | 0:50

» (Craigiehall), . 1880 | 135-00 = ang 0-50" |, 60765.) 0:60

és ni, Ce ; 1878 116°35 0:80 | 060] 040] 035 | 0°65

# - is 61°75 0:60 | 0:30 O50). 30:50 (0°70

3 co Oi ; 1. 71:85 0-70 | O50] 0:55 0°65 0°85
Lime, . 3 : ; 1878 76°10 050) 0-15 0:00 065 | 0°55
Birt} 5 ’ : i 42°70 O70) O40!) O15 0°25 0.40

» (Craigiehall), . a * 99°65 0-20), Oris O08) 20:25.) 5 Ora
Sweet chestnut, . F ;, 70°80 LO; 0:90) 0:65 5 LO) 0-90
Tulip tree, . , ; me (5770 K-00") 040) 030 0°55 | 0-50
Horse chestnut, . ; ‘ 48°75 O°75) 07505 10-35) 0°70. |b O10
Hawthorn, . : 3 aA 38°00 0:80 0:10 0:75 0:35 0:65
Flowering ash, . 4 ; 75°30 Co0n SO405 0:30) 0775 | 0°50
Sycamore, : as _58°60 0:50 0:20 0:15 0°30 0:40
English oak (Craigiehall, 4 69°45 0°65 0:50 0°20 0°35 0°35
Turkey oak, 4 1880 73:00 ae Se 0°70 P25 0:90
: : 1878 41:90 0-60. |. 0:65 | 0:35 0°60 | 0:65

American ‘oak, : ; Ks 30°80 050 | 040] 030 0:30 | 0:40
Hungary oak, : i 23°60 ISO? es P70. |) L40"+> TPSb Ie ess
x f 3 : 1880 16°45 5 abs, TLO|, S EGON Hile-90!.

. ‘ ; : 33 13°50 ee me 110i OR eet 50
Hornbeam, . ‘ : 1878 44:50 O40 | 035°" 0-10) 5 Oboe" 0°50
Total increase of 22 trees
first marked in 1878, ee Ke. L500; P05 1 8 fomiei2- 90. | 13°75
Average per tree, its oF 068 | 050] 040] 058 | 0-62
The same, with 5 added

in 1880, . 7 box a. . a Ae 12°55 | 18°65 | 19:10
Average per tree, we seg - one 0°46 0°69 0°71

48 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

TABLE IJ,— ANNUAL INCREASE IN GIRTH OF EVERGREEN TREES,

All in the Botanic Garden or Arboretum, except those marked “ Craigiehall.”

Increase,
Date and Girth

Trees. when first measured.
1878. 1879. 1880. 1881. 1882.
Inches. Inches. | Inches. | Inches. | Inches. | Inches.
Douglas pine, . . | 1878 | 5610 | 0-60] 0:45] 045] 0:60] 0°50
‘i a : : » 64:30 080 | 0:30 | O35): 0:35) 040
Pinus excelsa, . ; 5 30°90 035 | 020) 005 0:30} 015
ce ie ; . > 32°70 040 |} 0:20] 035 | 0:35) 0-40
Sequoia gigantea,. . » 23°95 Ti5| 0:30) 1:00) 035 | 070
a hae : » 23°95 75s ps6. SO, SO ee
ay oD A . ”» 18°95 1°85 1:50 1:50 1:30 179
. 5 : 5 » 23°85 1:25 170 1:55 1°35 1°65
Deodar, 5 : “ » 26:10 1-10 |, 0°70.) 0°45 |. 0:35.) 0:95
. : ; . oe 64:00 1:20 0°60 0:40 0°25 0:70
Picea Lowei, : F » 15:00 40) 1:25) 1:40) 0:90)" G05
_Araucaria, . : : ” 18:10 0:60_|...0°50.| 0:55 | 050 |. 0-45

: f ; 3s 20°20 050} 0:90] 075] 0601] 0:85
- (Craigiehall), 1879 17:90 tie 0-85 | 065 | 0-45 | 0-70
Atlas cedar, . ; ; 1878 27-55 | 1°65 | 1:40 | 1:75. ). 240)) “60
Evergreen oak, . 1879 29:05 ie 0-40} 010] 010} 0:25
Yew, .. ; : 1878 |- 67:60 0:60 | 060) 0:35 | 050] 0:50
34:10 0:50] 015] 020] 0:30] 0:45

. : ¢ : ; 1879 37°50 060 |} 040] 0-40] 0:55
se ' 4 ; ; 9 23°50 ie, 030 | 035] 045) 0:55
o ; : ; : 2 33°30 on 045} 040] 035 | 0-45
copula Mpa nd 1880 SAD. Ot = hae = 015 | 0-15 |) (O26,
Cypress (Craigiehall), . 1879 14:20 <> =| O80) 15.) 270:'36. | > 085
Total increase of 16
trees first measured
in 1878, . ; ‘ at A 15°70 | 12°90 | 12:90 | 10:90 | 13:50
Average per tree, me or 0:98 | 080; 080] 068] 0-84
The same, with 7 added |
in 1880, . ; ‘ at oy -. gfe 16°10 |" 13% | T7-2s
Average per tree, fet hie .* ee 0-70 | (0:59 |. O75

The most remarkable result from the whole series of observations is the
want of correspondence between the deciduous and evergreen classes in the
increase and decrease of the growth of wood in the different years under review.
Thus, as the tables show, a remarkable decline took place in both classes in
1879 as compared with. 1878, the average growth of each tree for these years
in the deciduous class being 0°68 in. and 0:50 in., and in the evergreen class
0°98 in. and 0°30 in. But in 1880, while the deciduous average declined still
further,—to 0°40, the evergreens remained quite stationary ;* and in 1881, when

* Sir Rozerr Curistison believed that they also had declined, although to a less extent, but he was
misled by an error in the figures of his MS.

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 49

the deciduous average rose decidedly,—from 0°40 to 0°58, the evergreens
suffered a decided fall,—from 0°80 to 0°68. In 1882 the difference was not so
remarkable, as the average of both rose, but in the case of the evergreens to
much the greater extent of the two.

I shall endeavour to explain the causes of these differences at the conclu-
sion of this paper, under the head of the connection of weather with the growth
of wood.

Sir Ropert CHRIstiIson was inclined to attribute to the oak tribe a greater
power of resisting inclement winters than other leaf-shedding trees possessed.
At page 84, part iv. of his paper, he states that while leaf-shedding trees in general
suffered a reduction of 41 per cent. in their increment in 1879 as compared with
1878, seven oaks measured by him lost only 10 per cent. Unfortunately, for
various reasons, all these oaks are not available for comparison in subsequent
years, but at page 168, part v., he showed that the average increments of fifteen
leaf-shedding trees in three successive years down to 1880 were 0°80 in., 0°45 in.,
and 0°35 in., and that the corresponding numbers for four of the oak tribe were
0°82 in., 0°77 in., 0°54 in., a result still favourable to the oaks, although not so
much so as in the previous instance. But if the facts be examined in detail, it
is evident that this apparent superiority of the four members of the oak tribe is
really due to one of their number—the hardy and quick-growing Hungary oak
—and that the other three, although they suffered little loss in 1879, fell off
greatly in 1880. It must be considered also that all these trees, with the
exception of the hornbeam, which Sir Rosert classed with the oaks, are of
foreign origin. If we reckon the growth of the hornbeam with that of the only
two British oaks whose measurements are at all reliable, the result is most
disastrous for our native oaks; for while their united growth in 1878 was 2:05
in. and in 1879 1°65 in., it was only 0°70 in. in 1880. In these experiments
the number of trees may be too small to give thoroughly reliable results, but it
certainly seems probable that the foreigners—the Hungary, American, and
Turkish oaks—stand severe winters, in our neighbourhood at least, better
than our native oaks, the Hungary oak being much the hardiest of ail,
while the British oak comes out worse than any other species of tree under
observation.

The yew seems to form an exception to the rule that the increment of wood
in evergreen trees continued to decline in 1881, notwithstanding the remarkable
rally made in the leaf-shedding class in that year. We have seen that the
average growth of all the evergreen trees declined from 0°80 in. in 1880 to 0°68
in 1881 ; but if we take the yews alone, five in number, we find that their
average growth rose from 0°35 in. in 1880 to 0°40 in 1881. Thus in the wave
of decline and rise during the three severe winters they followed the deciduous
group, and not their relations the evergreen Pinacee.

50 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

II. MontTHLty OBSERVATIONS.

- Encouraged by the results of his annual measurements, Sir Roserr
CuristTison selected in 1880 five deciduous and six evergreen trees, already
ascertained to be quick growers, as suitable for monthly observations. These
trees comprised two beeches, three Hungary oaks, four Sequoias, one Araucaria,
and an African cedar. They were measured at the end of May, June, July,
August, and September. The operation was repeated by himself in the same
months, with the exception of May, in 1881; and again by me in 1882,
with the exception of August. Thus a tolerably complete record of the
monthly increments of these trees was obtained for three seasons. As the
number experimented upon, however, was both too limited and comprised too
few species to give altogether reliable results, I commenced in 1882 to make
monthly measurements of a considerably larger number, and henceforth twenty-
eight- deciduous and eighteen evergreen trees, including twenty-two species,
will be under observation.

I shall now proceed to consider the conclusions to be derived from these
measurements in the solution of the following questions :—1. What are the
months to which the growth of wood ts confined (a) in deciduous trees as a class
and (b) in evergreens as a class? 2. In which month is the growth of wood
most active in these two classes (a and b)_ respectively? 3. What are the
peculiarities in these respects of different species of trees ?

In the Tables III., IV., and V. the facts will be found in detail on which
the subsequent conclusions are founded. Table III. gives the three years’
measurements and average growths of the smaller number of trees originally
selected by Sir Rosert; Tables IV. and V. the results of a single year’s observa-
tions on the larger number, measured for the first time in 1882. The trees in
this list only partially correspond with those used for annual observations, as a
considerable number of the latter, from growing too slowly or from other causes,
are not reliable for minute measurements,

1, a. The Months to which the Growth of Wood is confined in Deciduous Trees,

From the measurements made in 1880 on his five selected trees, Sir RoBERT
came to the conclusion that the growth of wood in leaf-shedding trees is con-
fined in general to the months of June, July, and August. I think however
that he underrrated the importance of the May growth, It amounted to 12 per
cent. of the annual total, which it must be admitted is a substantial sum. It
was due however almost entirely to the three Hungary oaks, the increase in
the two beeches having been scarcely appreciable. Unfortunately the measure-
ments for 1881 were not taken till the end of June, so they are not available
for this inquiry. But after the unusually mild winter of 1882 the May growth

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 51

was nearly twice as great as in 1880, amounting to 21 per cent. of the annual
increase. Again no doubt it was mainly due to the Hungary oaks, their pro-
portionate growth for May having been 24 per cent. of their annual increase ;
still the beeches were not idle, their corresponding growth amounting to 10
per cent. And although the Hungary oak—exceptional among deciduous

TABLE IJ].—MontTHLY INCREASE IN GIRTH, IN HUNDREDTHS OF AN INCH, OF FIVE DECIDUOUS
AND S1x EVERGREEN TREES IN THE BOTANIC GARDEN.

—

trees for its early vigour—unduly raises the average in so small a number of
trees, a substantial increase in May nevertheless did take place among deciduous
trees in general. For if we include the whole of them, twenty-five in number,
other than Hungary oaks, which were measured for the purposes of this inquiry
for the first time in this same year, their average growth in May proves to be 12
per cent. of the annual increase. Including the three Hungary oaks the pro-
portion amounted to 16 per cent.

1880. | 1881. 1882.

May May | Lay Agee

May. June. and | July.| Aug. |Sept. |) and | July. |} Aug.|Sept.|| May. June and jJuly.} and

June. June. June Sept.

Deciduous Trees—

Beech, . (00 == 25) = -25 | 50 | 10-00 | 20) -25'| -35'| 051) 10: + -35 — 45} 40 | -30
is HiOe-= SO 410) 20) -She-Oael oo 1 Sa) 15) 05") tb 4-30 = 451-30) 35
Hungary oak, { 30 + 40 = ‘70| 40] -30) 00 || 60] 50] -65| -05 | 30 + -45 = -75) -60| ‘50
# Re Oh = 420) = 45 130) 30-05 | 765) 45) 50) 00) 85 + 50 = -85 1) 55 | -50

f , Ors or == >) 50") 25) 05 I-60!) soa) 50") 00 “65 + “15 = -80) 50) 20
Total, . |0°65+1:65=2:30 |1:70 |1:30 |0°15 ||2°40 12°10 [2°15 0-15 11:55 +1:753= °30 |2°35 |1°85
peer | 0-13 +.0°33=0°46 |0-34 |0-26 [0:03 ||0-48 [0-42 |0-43 |0-03 || 0:31-+0:35=0°66 [0°47 |0°37
Monthly aa 12+ 30= 42/31] 24] 3 | 35/31/32] 2 | 214 23= 44] 31 | 25

centage, ;
Evergreen Trees—

Sequoia, 40+ -25= -65| -40/ 05} -00|| -40/] -00] 15) -00 |) 25+ -30= -55] 10] -05
+ = 5+ *50=1:05} :70| 15] :00 |1°00) 05) 45) 00] 45+ -65=1:10)| -20 | -10

ss F OS 40 — tO) | 008-00 I-85) “2 20) 00) “To 65=1-40)5:25.| 10

x , 5+ 40= 95] 45) 00) -00} "75| :30] 30) 00) °55+ -55=1:10} -40] 15
Araucaria, 40 olor —e oon lpclion | OoNeO0) e-SonpeOnmaton "OON) “Abit TO" 5:5) elon) “15
Atlas cedar, . A oOo 0) | SO Obes) 35) 505) “O0N) Bo-ee40—. "75 40 | 45
Total, . |3:05+2-00=5-05 |2:40 |0°75 |0-05 |/3-90 |1:05 [1-75 10-00 | 2804+ 2°65=5-45 |1-50 |1-00
agg at 0-51+0:33=0°64 |0:40 |0-12 |0-:01 110-48 |0-17 |0-29 |0-00 |) 0-46 +.0:44—0-90 |0-25 |0:17
Monthly per- ye one es) eee ae ees Tips eae
Eoatage, \ oie 24— 61730 | 9 0 | De Pisco | O Sb-EeSSs— GSO ie

on
Wo

SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

At the conclusion of the growing season the limit is probably more fixed.
Neither in 1880 nor in 1881 was a greater increase than a twentieth of an inch
recorded in any tree in September. So small an amount as this comes within

TABLE [V.—MoNTHLY INCREASE IN GIRTH OF TWENTY-EIGHT LEAF-SHEDDING TREES IN THE
BoranNic GARDEN, ARBORETUM, AND AT CRAIGIEHALL IN 1882.

_ Increments in hundredths of an inch.
No. Trees. Girth 31st
March.
May. June. July. August.
7 | Beech, : ; c : 5 75°05 ‘10 35 ‘40 30
8 o ; ; : , : 64:30 “15 30 30 35
14 x ; : ; ; ; 13D 05 ‘20 ‘20 “15
38 . : ; : ; : 62:00 00 “185, 30 =) "05
8 -|..,, Craigiehall, . : . | 1386-15 ‘00 sof “25 15
9 = 5 : ; . | 118°45 ‘10 “15 25 15
14 te 5 , , : 63°70 a5 ‘10 "25 ‘20
15 D » : ; : 74:30 15 ‘20 30 20)
22 Rs ‘ 4 : : 98°35 ‘10 ‘10 ‘20 ‘05
40 | Hungary oak, . : ‘ : 30°35 30 “45 ‘60 50
54 ms aes A ; ; ; 19°15 ‘OO ‘50 "HD 50
55 i tealg 3 ; ; : 16°30 65 "12 ‘50 20
44 | American oak, . : , ; BI 1515) ot) ‘10 1 00
43 |Turkish oak, . , 2 : 44:20 ‘10 “15 30 “L!5)
10 ; » Craigiehall, . : 74:95 ‘20 20 30 “20
12 | English oak, : : ; TL'15 05 05 ‘10 “5
33 | Hornbeam, ; 2 ‘ 45°90 "15 "15 15 05
28 | Sycamore, . mie ; . 59°75 00 25 15 05
58 mB. Y ; : 63°50 ‘00 05 05 00
7 wf Craigiehall, : ee Pala TD ‘00 “25 aii 05
18 | Lime, ; : : : ; 44°20 05 5) ‘20 ‘00
21 » Craigiehall, . ; ~* | 100-35 ‘00 05 “15 25
3 } Ash; . ; ; : , : YW 3) ‘20 “5 “ey 00
6 » Craigiehall, ' ‘ 2) aAOe te iO 15) 05 05
4 |Spanish chestnut, . : “ 74:75 ‘05 ‘20 "30 "39
9 | Horse chestnut, ; 5, ; 51:05 ‘00 05 “05 ‘00
6 | Tulip tree, : : ; P 78:15 1 £00 05 20 25
5 | Birch, Craigiehall, . ; : 57-15 ‘00 "15 20 ‘10
Average of the 28 trees, e at 18 "24 ‘16
. 3 Hungary oaks, : re ee lb) ‘37 ‘53 ‘40
_ 25 others, . ; ; : = ‘O7 alts) ‘20 gi)
e 9 Beeches, . 5 ; : ae 09 "19 27 18
- Monthly percentage of 28 trees, . F oe 16 26 35 23
‘3 - 3 Hungaryoaks| ... 25 20 31 24
: a 25 others, 5 TH 13 27 36 24
‘ 53 9 Beeches, . Ra 12 26 hi 25

the limit of probable error ; it may be doubted, therefore, whether any increase
really took place in that month ; but as the differences between the records of

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 53

August and September, trifling though they were, all indicated an increase, it is
probable that a slight and altogether immaterial growth did occur, Measure-
ments kindly made for me by Mr Sap.er in 1882 to test this question further

TABLE V.—MontTHLY INCREASE IN GIRTH OF EIGHTEEN EVERGREEN TREES IN THE BOTANIC
GARDEN, ARBORETUM, AND AT CRAIGIEHALL IN 1882.

Increments in hundredths of an inch.
No. Mapas Girth 31st ;
H March.
May. June. July. August.
Inches.

25 | Sequoia, . : . : ; 27°55 "25 30 ‘10 05
27 - : : . : : 30°65 45 65 ‘20 10
if Z : ; é : 25°10 25 65 “25 10
2 % : : , ’ : 29°70 55 55 i EO oh 05)
29 | Deodar, . ; 3 L i 28-70 10 20 30 st)
30 : ' ; : ; 66°45 ‘00 20 30 "20
34 | Araucaria,. ; 3 : ; 20°25 AD ‘10 05 05
35 a ! . f : : 22°95 “45 ‘10 5 5s
+ - Craigiehall, : ; 19°85 25 25 ‘10 ‘10
31 | Picea Lowei, . 5 ; : 19°95 45 ‘20 20 20
5 | Douglas pine, . : : 58°20 15 25 10 05
2 | Austrian pine, Craigiehall, , ‘ 21°55: 65 “40 20 30
39 | African cedar . Re 33°75 cats “40 “40 ‘45
1 | Cypress, Craigiehall, . ; : 17-00 35 "25 “20 05
41 | Yew, : : F ; 69°65 10 hd 10 AS
48 5 F . ; 2 , 38°90 gid ay ‘20 05
49 a 4 ; : j : 24-60 “20 10 od a) 10
eel 45 : : : : ; 32°50 ‘20 00 05 Ny
Average of 18 trees, . : : ; ee 31 i 19 15
4 Sequoias, . : 2 sige ‘50 "bo "24 ‘10
3 Araucarias, . : : ve | 15 10 10
4 Yews, . : : : ae 16 10 “LA: ‘11
2 Deodars, . : : ir 05 ‘20 30 27
Monthly percentage of 18 trees,. Ace 34 29 21 16
4 Sequoias, . ice 36 39 28 7
3 Araucarias,. O54 47 23 15 15
4 Yews, ; ee 33 20 25 Dy,

2 Deodars, . Se 6 24 37 35 |

proved unfortunately unavailable, owing to inaccuracies in the tape used. But
as the increment for August and-September combined was less than in the two
previous years, it is fair to conclude that there could have been no material
growth in the latter month.

1, b. The Months to which Growth of Wood is confined in Evergreen Trees.

From the monthly measurements in 1880 of the six originally selected trees,
Sir RoBert concluded that the evergreen class begins to increase materiallyin girth
VOL, XXXil. PART I. I

54 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

in May, a month earlier than leaf-shedding trees. This conclusion is amply con-
firmed by the measurements of the two succeeding years. In 1881, indeed, the
proof is not positive, as the first measurements did not take place till the end of
June; but as 51 per cent. of the whole annual growth was accomplished by that
date, it is fair to conclude that a considerable proportion of the increase must
have taken place in May. In 1882 there is no room for doubt. The increment
till the end of that month actually exceeded the increment of any other month,
and the only question is whether a portion of that remarkable growth was
not due to April. Unfortunately, as no measurements were taken at the end of
that month, this point must remain doubtful.

But the reliability of results obtained from so limited a number of trees and
species may justly be questioned. At all events, it may be held that, although
true of these species, they may not be true of evergreens in general. Fortunately,
however, these results are amply corroborated by observations on the larger
number of evergreen trees, first measured for monthly comparison in 1882.
The proportion of annual increment in these eighteen trees due to May was 34
per cent., almost identical with that of the selected six, which was 35 per cent.

The limit of the growing season in evergreen trees is better ascertained at
the end than at the beginning. Of the six selected trees only one—the African
cedar—showed the slightest trace of increase in September, and that only in
one of the two years in which observations are available. The increment
recorded, moreover, was so slight as to come within the limit of probable
error.

In August the proportionate growth seems to be much less in evergreen
than in deciduous trees. In August 1880 the increment of the six selected
evergreen trees was only 9 per cent. of the annual increase, while in the
deciduous group it was 27 per cent. In 1881 there was a greater equality, the
respective percentages being 31 and 34, But in 1882 that of the evergreens
again fell to 13, while the deciduous percentage reached 25. The results for
the latter year were confirmed by the observations on the larger number of
eighteen evergreen trees, whose proportionate growth for August was only 15
per cent. of the annual increase.

On the whole, the conclusions to be drawn from all these observations are—
First, that in ordinary seasons the growth of wood in deciduous trees is mainly
confined to June, July, and August. In September it is scarcely appreciable.
In May however a small growth does take place, which in favourable seasons
may become of no insignificant amount. The Hungary oak not only grows
with exceptional vigour in May, but probably in favourable seasons makes a
start in April. Secondly, that evergreen trees as a class begin to grow probably
a month earlier than the deciduous group. They make substantial progress
in May, and some of them perhaps make a start in April. On the other

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 55

hand, the measurements indicate that they stop growing somewhat earlier
than the deciduous class.

Thus Sir Ropert Curistison’s conclusions are substantially confirmed;
although the growth of deciduous wood in May is probably of somewhat
greater importance than he supposed. It must be remembered, however, that
these rules apply only to the neighbourhood of Edinburgh. In the milder
climate, aided by a richer soil, of the south-western districts of Britain, where
the leaves expand two or three weeks earlier than here, it is to be expected
that the growth of wood will also be correspondingly earlier. Other leaf-
shedding species besides the Hungary oak may also be found to be exceptional
in the early vigour of their growth, as Sir RoBeErt’s observations and my own
include but a small proportion of the numerous native and foreign trees which
thrive in our islands.

A greater irregularity in the distribution of the monthly growth of the
evergreens as compared with the deciduous trees occurred in all the three
years during which monthly measurements were made. Thus, while the July
percentages of growth in deciduous trees as shown in Table III., were 31, 31,
and 31 in these three years, in the evergreen group they were 30, 18, and 19. In
August the differences were still more striking, the respective figures being
24, 32, 25 for the deciduous group, and 9, 31, 13 for the evergreen.

It is remarkable that in 1881 the growth of the six evergreens, which in
July amounted to only 18 per cent. of the annual increment, became vigorous
again in August, when it reached 31 per cent. The deciduous group seemed
to partake in this exceptionally vigorous growth in August 1881, but to a much
less degree, the proportions being 31 per cent. for July and 34 per cent. for
August. In treating of the influence of weather on the growth of wood I
shall endeavour to explain these apparent anomalies.

2, a. The Months in which the Growth of Wood is most active in Deciduous Trees.

TABLE VI.—MontTHLY PERCENTAGES OF INCREASE IN GIRTH OF DECIDUOUS TREES.

May
May. June. and July. | August | Sept.
June ;
5 Selected deciduous trees, 1880, . 12 + 30 = 42 31 24. 3
ps = 1881, . nae ane 35 31 32 2
z ie SoZ 21 + 23 = 44 Sill 25 a?
28 Deciduous trees, 1882, ; : 6-226 = 42 35 2a

To elucidate this subject I give in Table VI. the percentage of growth due
to each month of the years 1880, 1881, and 1882, in the five originally selected

56 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

deciduous trees, and the corresponding results for the growing months of 1882
in the larger number of trees then under observation. |

The Table shows that in 1880 June and July were the best growing months
for the five selected trees. The amount in these two months was nearly equal.
The united growth of August and September, of which September’s share was
very trifling, was not much less than that of June or July, while that of May
was only half that of August.

The year 1881 is not fully available for this inquiry, no measurements
having been taken for May; but as the united growth of May and June but
little exceeded that of July or August, it is fair to conclude that the increase in
June alone was less than in either of the subsequent months.

In 1882 the growth of the five trees in question was apparently distributed
over a longer period. May takes a more prominent place with 21 per cent.
The growth for June and combined August and September is not much
greater, while July takes a decided lead with 31. The preponderance of the
early-growing Hungary oak in the small number of selected trees, however,
gives a false impression of the increased deciduous growth in May of this year.
If we consider the whole number of deciduons trees, twenty-eight in all, under
observation in 1882, the percentage for May is reduced to 16, which is still,
no doubt, a substantial and probably an unusual amount.

2, b. The Months in which the Growth of Wood is most active in Evergreen
Trees,

TABLE VII.—MoNTHLY PERCENTAGE OF INCREASE IN GIRTH OF EVERGREEN TREES.

May. June et bent July August.
6 Selected evergreen trees, 1880, OF i 24. ee 6) 30 9
. * ? *: ake 51 18 31
: 3 1882, a0 = Sos. =o oo 19 1s
18 Evergreen trees, 1882,. 34 + 29 = 63 ini 16

It is more difficult to determine from the available data the month of
greatest growth in evergreen than in deciduous trees. Not only are the varia-
tions in this respect in different years greater in the former than the latter, but
it is doubtful whether a part of the increment attributed to May ought not to
be credited to April in the case of evergreen trees. This doubt arises from
Sir Roper having concluded, probably too hastily, that no growth takes place
in April. I can find no evidence in his papers of his having ascertained this by
measurement, and I do not know how he came to form and act upon that con-
clusion. Further observations are evidently necessary to settle this doubt, and

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 57

these I hope to undertake in future years.* At present all that we can safely
say is that the increase of wood in evergreen trees from the beginning of
spring till the end of May probably exceeds on an average that of every subse-
quent month. Table VII. shows that it did so in the case of the six selected
trees in 1880 and 1882, also in the eighteen trees measured in the latter year.
In 1881 the observations are incomplete, as separate measurements were not
made for May and June, but August—with 31 per cent.—has a strong claim
to the highest place, due I believe to exceptional circumstances.

One of the most remarkable conclusions that may be drawn from the three
years’ monthly observations on evergreen trees, as a class, is that they appa-
rently accomplish the greater part, and sometimes much the greater part, of
their growth by the end of June. Thus in 1880, 64 per cent., in 1881, 51 per
cent., and in 1882, 68 per cent. of the annual increment of the six selected trees
was finished by that date, and the increment of the eighteen trees measured in
1882 was almost identical with that of the six in the same period, amounting to
63 per cent. Apparently then it is not heat alone which regulates the growth of
wood in many evergreen trees. By some inherent vital power they complete the
greater part of their growth before the commencement of the two warmest
months in the four which constitute the growing period, or else their vital power
is so exhausted in the early part of the season that growth cannot be carried on
with vigour when the real heat of summer comes on.

In conclusion, it must be allowed’that further observations, both on deciduous
and evergreen trees, are required to determine which is the best growing month
in each class. At present the indications are in favour of July for the former
and May for the latter, if the whole, or nearly the whole, of the growth hitherto
ascribed to that month really belongs to it.*

3. Monthly Increase in certain Species of Trees.

There is considerable variety in the vigour of growth in different species
both of deciduous and evergreen trees in the different months of the growing
season. My observations on this point indeed, on any considerable number of
trees, extend only to a single year, but the results are sufficiently striking to
deserve attention. In Table VIII. are given the percentages of monthly growth
in seven species, which, either from the number of specimens under observation,
or from the certainty of their measurement, yield the most reliable results.

The Hungary oak begins to grow earlier than any other of the deciduous
trees under observation. In the backward spring of 1880 the three specimens
marked in the Botanic Garden were well clothed with foliage on the 15th May,

* Since this paper was read, the spring measurements for 1883 show a growth in April amounting

to two-fifths of that in May in twenty evergreens under observation. It appears probable therefore that
June is the month of greatest growth for evergreens.

58 _ $IR ROBERT CHRISTISON AND DR CHRISTISON ON THE

and after the wonderfully mild winter of 1882 one of them was beginning to
expand its leaves on the 27th of March. Their growth was more evenly dis-
tributed over the four growing months than that of any others of the deciduous
group, and among the evergreens the yews alone rivalled it in that respect.
The Turkish and American oaks seem also to be early growers. The propor-
tion of their May growth was not much less than that of the Hungary oaks,
still in both the first and last months of the growing season they were less active
than the latter. The British oak grows poorly in this district, and besides,
from the roughness of its bark, it is not suitable for minute measurements.
The only one experimented upon showed no appreciable increment in May.
The beeches made only 12 per cent. of their annual increment in May, about
half the proportion of the foreign oaks, and as this was in an unusually early
season it is probable that in ordinary years their May growth must be very trifling.

TABLE VIII. MonTHLY PERCENTAGE OF INCREASE IN GIRTH OF SEVEN SPECIES OF
TREES IN 1882.

Tier Se June. July. August.
3 Hungary oaks, ; 25 21 31 23
2 Turkish and 1 American oalk, : Die 22 38 18
9 Beeches, . : : s ; 12 26 ot 25
4 Sequoias, : ; 5 ’ 36 39 18 i
3 Araucarias, . : 3 : : ~ 48 22 15 15
2 Deodars, . : : , Z : 6 24. on 33
4 Yews, . : : j ; 5 33 20 25 22

Among other deciduous species, which being less reliable do not find a
place in this Table, the ash and the hornbeam alone showed an appreciable
growth in May. It is fair to state however, that in the Edinburgh district the
horse chestnut leaves were almost universally destroyed in 1882 by early frost
and the ravages of insects. It is no wonder therefore that the specimen
measured in the Botanic Garden grew only a tenth of an inch in the year.

The Sequoias were remarkable, even among evergreens, for the early vigour
of their growth. No less than 75 per cent. of their annual growth was finished
by the end of June. But they ceased to increase earlier than any of the other
species, their growth in August being only 7 per cent.

The Araucarias also grew rapidly in the early part of the season, accomplia
ing very nearly one half of their annual increment by the end of May, and 70
per cent. by the end of June.

With the Deodars it was exactly the reverse, 70 per cent. of their increment
taking place after June. If the observations for a single year on two trees may
be trusted, the Deodar is an exception to the general rule of early growth in
evergreens

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES, 59

The increase of the yews was nearly equally divided between the first and
second periods of the season. The former had indeed a slight advantage, but
the spring of 1882 was unusually early, and a longer experience may show
that yews do not follow the rule of early growth which appears to hold
good in most of the Pinaceez.

As it may be of some interest to show the comparative rate of growth of
wood in certain species of trees under observation, I give the following Table :—

TABLE [X.—AVERAGE INCREASE IN GIRTH OF EIGHT SPECIES OF TREES FOR THREE YEARS.

1880. 1881. 1882. Average.
Average of— Inch. Inch. Inch. Inch,

3 “Hungary oaks, : 1:20 1°72 1°75 1:55
1 American and 2 Turkish oaks, j 0:45 0°75 0°65 0:62
9 Beeches, . : Z 0°53 0°64 0°79 0°65
4 Sequoias, . : ; . 1:46 sz 1:40 1:01
3 Araucarias, F ; ' ‘ 0°65 0-51 0:66 0-61
2 Deodars, . ‘ : : ; 0:42 0°30 0:82 0:51
4. Yews, 3 : ; : . 0°31 0:37 0°50 0:39
1 African cedar, . : 5 1:75 1°40 1:60 1°58

III. INFLUENCE oF WEATHER ON THE GROWTH OF Woop.

This is a complicated inquiry, so many and various are the influences which
may come into play. Extreme frost, prolonged frost, the amount of heat and
sunshine, drought or excessive rain, strong winds, all no doubt affect the
growth of wood, their influence varying with the seasons, and not necessarily
showing their effects immediately.

Of all these agents cold is probably the most energetic; I have there-

fore looked to it mainly for explanation of the differences in annual growth,

adopting Mr Sap.ier’s record of temperature in the Botanic Garden as my
guide, because the greater number of the measured trees are situated either
there or in the adjoining Arboretum. The thermometers used by him are four
feet from the ground, and being unprotected the readings are not strictly
accurate, but for purposes of comparison with each other the observations are
sufficient.

Sir Roperr Curistison showed that the remarkable cold and absence of
sunshine in the spring and summer of 1879 caused a great deficiency in the
growth of wood, both in deciduous and evergreen trees, in that year as com-
pared with the previous one ; that the deficiency was greatest in the deciduous
class ; and least of all, so far as his observations went, in oaks.

In 1880 the spring was favourable to the opening buds, the temperature

60 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

being considerably above average in February and March, while although
April was cool it was free from severe frosts. The summer was also of an
average character. The foliage was therefore, in general, rich and abundant.
Nevertheless there was again a great falling off in the growth of deciduous
wood. This Sir Rosert attributed to the extraordinary low temperatures of
the previous December, succeeding an autumn unfavourable to the ripening of
wood and formation of buds. He believed that evergreen trees had also
suffered, although not to the same extent; but I find that he had been deceived
by an error in copying his figures, and that their growth in 1880 was almost
identical with that of 1879.

It is not easy to explain why both classes should have suffered a diminution
in the growth of wood in 1879, and only the deciduous class a further decline
in 1880. In the first of these years the cause of deficiency was no doubt, as
‘Sir Rosert believed, the inclement spring and summer, as the cold of the
previous winter although prolonged was not remarkably intense; under these
circumstances both classes of trees were unfavourably influenced. In 1880
on the other hand the cold of the previous winter was both prolonged and
intense, and in all parts of the country its effects were visible in the killing
of tender young wood or even of whole trees. It is no wonder then that
the deciduous trees showed a marked decline in addition to the serious loss
they had suffered in the previous year. But why did the evergreen class
escape this further loss? Possibly the explanation of this difference may
be found in the earlier activity of growth in evergreens in spring. In their
exposure to the intense frost of winter their circumstances must have
been much the same as those of the deciduous class, but their compara-
tively early buds would probably come under the influence of the genial March
and April to a greater degree than the later buds of the leaf-shedding trees,
which, on the other hand, would encounter a rather inclement May. Another
cause that may be suggested is that the previous autumn, which was highly
unfavourable to the ripening of wood, may have in some way prejudiced the
evergreens less than the deciduous trees. That the evergreen trees under
observation were not really hardier than the deciduous ones was proved by
their fate in the following year.

The winter of 1880-81 was even more protracted and severe than that of
1879-80. Both the lowness of the average temperature and the number of
extremely low readings at the Botanic Garden in January, the coldest month of
1880-81, were more remarkable than in December, the coldest month of the pre-
vious winter, Thus the lowest temperatures recorded in the latter month were
1°, 4°, 15°, 17°, 19°, but those of January 1881 were 0°, 4’, 7°, 10°, 11°, 12°, 12°, 12°,
13°, 14°. And this greater cold was prolonged far into the spring. On the last
day of February and first few days of March 15°, 15°, 18°, and 19° were recorded,

——

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 61

and another wave of cold brought the thermometer below the freezing point on
twelve nights in the first fortnight of April, the lowest readings being 21°, 22°,
and 23°. On the other hand, the lowest readings in the same months of 1880
were only 23° in February, 22° in March, and 27° in April. Moreover, the total
number of nights of frost in these three months in 1880 was only thirty-four,
while in the corresponding period of 1881 it was fifty-three.

After so severe a winter and spring it might have been expected that even
more disastrous effects on the growth of wood would have resulted than after
the less extreme cold of the previous year. But, on the contrary, the deciduous
trees, at least, made a remarkable rally, the average growth of twenty-seven
of them having risen from 0°46 in. in 1880 to 0°69 in. in 1881, an increase of
nearly one-third. Very different however was the fate of the evergreen trees.
Unlike the deciduous class they had successfully resisted the efforts of the
previous hard winter, but now they suffered seriously, thus differing once more
from the leaf-shedding trees, but in the opposite way, for their average growth,
which in 1880 had been 0°70 in., was now only 0°59 in.

The wonderful rally made by the leaf-shedding trees in 1881, notwithstanding
the almost unprecedentedly low temperatures of the previous winter, can only be
accounted for, I believe, by the favourable character of the preceding autumn,
which allowed the growth of wood of 1880 to be perfectly matured, and so enabled
it to withstand the rigour of the winter in 1881. But why was a similar effect
not produced upon the evergreens? Is it because the maturing of wood is not
so effectual with them as it appears to be with the deciduous trees in enabling
them to resist a severe winter? Or shall we find the reason in the compara-
tively early growth of evergreens which might expose their tender buds to the
frequent low temperatures of March and April, a danger from which the buds
of the deciduous class, coming out later, would be free, while they would benefit
by the geniality of May? The latter seems the most probable cause, but
further observations are required to settle the question.

The winter of 1881-82 was one of the mildest on record. It was well
suited therefore to test Sir Ropert’s suggestion that evergreens might in an
unusually mild winter show some trace of growth; but none could be detected
in any of the twenty-eight measured trees. Vegetation however was very
early. A sycamore and a Hungary oak among the marked trees in the Botanic
Garden began to expand their leaves on the 27th of March. The sycamore
paid dearly for its temerity. Caught by an early frost and afterwards attacked
by insects, its leaves were irretrievably injured, and its increase in girth for the
year only amounted to a twentieth of an inch. A similar fate befell nearly all
the horse chestnuts near Edinburgh, including a fine specimen, one of my
measured trees, which grew only a tenth of an inch in the year. The Hungary

oak, on the other hand, did not suffer at all. The deciduous class as a whole.
VOL. XXXII PART I. K

62 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

however, were not injured in this way ; but notwithstanding the mild winter they
only maintained their improvement of the previous year, without attaining the
standard of growth of 1878. The reason of this failure, no doubt, was the
unfavourable nature of the previous autumn for the ripening of wood, combined
with the ungenial nature of the growing season, both of which were well-marked
evils at the Botanic Garden, as I was informed by the late lamented Mr Sap.er
shortly before his death.

The evergreens, on the other hand, recovered their loss of the previous
year. Apparently the frost of April had not injured them, and they had been
stimulated by the mildness of May, as their growth till the end of that month
bore a high proportion to the whole annual increase.

This attempt to connect the annual variations in the increase of wood with
temperature, and to explain the curious contrasts between deciduous and
evergreen trees in their annual erowth by the effects of temperature alone,
cannot be considered as altogether satisfactory. Neither are the difficulties
cleared up by considering other causes which must manifestly affect the
growth of wood. Violent winds, for example, must be prejudicial not only by
tearing down important branches, but by damaging the leaves. Every one
must have observed the injury done to foliage by storms, particularly in spring
and the beginning of summer. Multitudes of leaves are blown away, and
those which remain hang limp and shrivelled from the branches, their petioles
twisted by the wind, and the circulation through them thus hindered by bruis-
ing of the vessels. In the records of the Scottish Meteorological Society many
gales are reported as having occurred at Edinburgh in the years with which
we have to do, but I cannot clearly trace a connection between them and any
diminution in the growth of wood. I should have expected the greatest
damage to have been done in 1881. In the previous year, indeed, there were
three gales in May, but it was a backward spring, and the leaves may thus
have escaped. At all events we know that Sir Rosert remarked the richness
and abundance of foliage in June, and there were no gales in that or the sub-
sequent growing months. In 1881, on the other hand, one gale in May, three
in June, two in July, and four in August were recorded ; yet this was the year
in which, with all the disadvantage of a previous winter of almost unprece-
dented severity, the growth of deciduous wood made a remarkable rally. But
the fact is that the effects of each gale must be watched in order to know
whether any general damage has been done to the leaves or not, so much
depends on the strength of the wind, its direction, and the shelter which may
protect the trees concerned. I should expect that differences between the
annual increase of deciduous and evergreen trees might sometimes be due to
this cause, as the leaves of the latter, from their shape, cannot be exposed to

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 63

the same injury as those of the former ; but in the years now under considera-
tion I cannot trace any such effect.

In a climate such as ours, with frequent variations from the average in the
monthly rainfall, considerable effects on the growth of wood may be expected
from excess or deficiency of rain at the growing season. To trace these effects
may be difficult, from the possible simultaneous action of other causes immediate
or remote ; nevertheless I think something may be made of an examination of
the principal abnormalities in the rainfall during the three years in which
monthly observations of growth were taken. I owe to the kindness of Mr
Bucuan the following Table, showing the excess or deficiency of rain during the
months of the period in question. The means from which these are calculated
are derived from twenty-eight years’ observations at Charlotte Square, whereas
the monthly rainfall is taken from observations at Cumin Place, Grange ; but
the general results are not likely to be seriously affected by this difference.

TABLE X.—MonTHLY Excess oR DEFECT OF RAIN AT EDINBURGH IN 1880, 1881, AND 1882.

Jan. Feb. | March. | April. | May. | June. | July. | Aug. | Sept. Oct. Noy. Dec.

1880, . |-1:69} +0°03) —0-09) +0°11) —1:05 — 0-46) +1:91) — 2°46) +0°17) + 1°66) + 1°54) +1:01

1881, . |—0°70) + 2°81) +.0°13) — 0°32) — 0:04) — 0°61) + 0°52) + 3:06) +0-97) — 0°50) +.0°60) - 0°83
1882, . |—0°55| +0°01| + 1:04) + 1-00) + 0°29) +. 0-28) — 0°51) — 0°85 ef oho

In comparing the rainfall with the tree-growth, I shall make use of the
proportion which the monthly percentage of the latter bears to the whole annual
growth. These will be found in Table VI. and VII.

1880.—The rainfall of May was less than half the average, and that of June
was deficient by about a third ; but the increase of wood in both classes of trees
was quite up to the average of the same period for three years. In July the
rainfall was much in excess: the deciduous growth was an average one ; but
the evergreen growth was much above the average. In August there was a
great deficiency of rain, — 2°46, and an excess of heat, + 3°'3 ; the deciduous
growth was about an average, the evergreen greatly below average.

1881.—In April, May, and June there was a deficiency of rain, but it only
amounted to an inch in all, and as vegetation was completely checked by severe
weather till the middle of April, the small proportionate growth of both classes _
of trees in May and June may fairly be attributed to the latter cause. In July
the rainfall was slightly in excess: the deciduous growth was again an average,
but the evergreen under average. In August, the memorable month of the
Volunteer Review at Holyrood Park, no less than 6 inches of rain, double the

64 SIR ROBERT CHRISTISON AND DR CHRISTISON ON THE

average, fell at Edinburgh; then the evergreens made a surprising rush, no
less than 31 per cent. of their annual growth taking place, whereas in August
1880 the portion was only 9 per cent., and in 1882, 13 per cent. This result
was the more remarkable, as the temperature of the month was 2°'3 below the
average. The deciduous trees were also apparently benefited by this excessive
rain, although accompanied by deficient temperature, their proportion being 34
per cent. in August and September of 1881, while it was only 27 per cent. in
1880, and 25 per cent. in 1882.

1882.—The rainfall of March, April, May and June was abundant, exceeding
the average by an inch in each of the first two months, and being rather above
the average in the third and fourth. In the same period the growth of ever-
ereen wood was large, but this may easily be accounted for by the mild winter
and early spring, without calling in the aid of the rainfall.

Taking a general view of this investigation, it appears as if an abundant
rainfall were favourable to the growth of wood, but much more favourable to
the evergreen than the deciduous class. It must be admitted however that a
longer series of observations, taken on a larger scale, are necessary to determine
this point. The most striking fact shown is the extraordinary increased growth
of the evergreens in August 1882, along with a very heavy rainfall and low
temperature, whereas in the previous August, when the conditions were
reversed, the rainfall beimg 2°46 inches in default and the temperature 3°:3 in
excess, the evergreen growth was very deficient.

SUMMARY.

To give a better idea of the general scope of this paper, the details of which
are necessarily of a somewhat dry and tedious character, I now give a summary
of the chief conclusions which are scattered throughout the text. It must be
remembered however that these conclusions are strictly applicable only in the
Edinburgh district, and that some of them are only indications of the probable
truth, and require to be confirmed by a larger series of observations.

1. The effects upon the growth of wood of the severe winters preceding the
growing seasons of 1879, 1880, 1881 were not the same in deciduous and ever-
green trees. In 1879 both suffered: the former more than the latter. In
1880 a further decline took place im the deciduous class, but not in the other.
In 1881 the deciduous class recovered their loss of the previous year, but it was
now the evergreen’s turn to fall off. After the unprecedentedly mild winter of
1882 they again differed. For while the deciduous trees made no further
recovery, the evergreens regained the loss sustained in 1881; neither class
however attaining to the standard of growth in the favourable season of 1878.

2. Evergreen trees probably do not increase their wood at all in winter,

GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES. 65

however mild it may be, as not the slightest trace of growth could be detected
in the measured trees after the wonderfully mild winter of 1882.

3. The British oak probably suffered a greater decline in its growth of
wood from the severe winters than any other tree under observation. The
Hungary oak, on the other hand, was less affected than- any other tree; and
the Turkish and American oaks less than our native oak.

4. In the wave of increase and decrease in wood growth through these
years the yews followed the deciduous class, and not their congeners the ever-
green pines.

5. The appreciable growth of wood in deciduous trees is mainly confined to
June, July, and August in ordinary seasons ; but a material increase does take
place in May, particularly when the spring is unusually mild.

6. The growing season in evergreen trees includes May, and probably an
appreciable start is made even in April, when the spring is favourable.

7. The proportionate monthly growth seems to vary more in evergreens
than in deciduous trees.

8. The growth of wood is probably greatest in July in deciduous trees, and
in June* in evergreens ; but further observations are required to settle these
points.

9. On an average of three years the evergreen trees as a class accomplished
60 per cent. of their annual increase of wood before the end of June, the deciduous
60 per cent. of theirs after that date. Deodars appear to be exceptional, as
they agreed with the latter instead of the former group. In yews the growth is
probably pretty equally divided between the two periods.

10. Of all the species measured, the Hungary oak and African cedar proved
much the quickest growers. Then followed the ‘Sequoia gigantea.

11. Thorough ripening of wood in autumn seems to be of immense con-
sequence in enabling deciduous trees to stand extremely low temperature in
winter. Evergreens however do not seem to be so dependent on it.

12. An excessive rainfall seems to be favourable to the increase of wood,
particularly in evergreen trees. A great excess of rain in August 1881 appar-
ently stimulated the growth of wood in these to a remarkable degree, although
the temperature of the month was decidedly low.

In conclusion, I cannot help expressing a wish that others who have better
opportunities than I can command would take up a line of inquiry which Sir
Rosert CuristTison has made easy by the practical rules he has laid down for
its prosecution. ‘The necessary observations are not difficult to make, merely
requiring precision ; and they take up little time when the trees experimented
upon are near at hand. The work is interesting, and the results may prove to

* See foot note, page 57.
VOL. XXXII. PART I. L

66 GROWTH OF WOOD IN DECIDUOUS AND EVERGREEN TREES.

be of importance in unexpected ways. I must also repeat the surprise which
Sir Rosert often expressed, that little or nothing seems to have been done to
ascertain the effects of manuring on tree growth. ‘ Mulches” have indeed
been applied to favourite trees when in a sickly state, and often with the best
results, but the farther step of trying the effect of manures in stimulating the
crowth of healthy trees has not, so far as Iam aware, been taken. Perhaps
the want of any reliable method of ascertaining the rate of growth of wood has
hitherto stood in the way of such experiments ; but surely there is the greatest
encouragement to undertake them, now that Sir Roperr has shown the ease
and accuracy with which minute measurements of the girth of trees can be
made, and their rate of growth thus ascertained in comparatively short periods
of time. If such application of manures proved useful, but at the same time
too expensive to be employed on the great scale, it should at least be welcomed
by the landed proprietor to secure a more rapid growth of young ornamental
wood.

Note.—In Table III. the average growth of the Evergreen trees for May and June 1881
should be 0°65 instead of 0:48, and the monthly percentages 59, 15, 26, instead of 51, 18, 31.
The latter errors occur also in Table VII. The conclusions in the text are not materially
affected by these errors, except that the claim of August to the highest average monthly growth
in 1881, mentioned on page 57, becomes very doubtful.

(ares 3}

V.—A Contribution to the Chemistry of Nitroglycerine. By Marruew
Hay, M.D., Assistant to the Professor of Materia Medica in the
University of Edinburgh. .

(Communicated by Professor Crum Brown.)

Introductory.—In the course of an inquiry into the physiological and
therapeutical action of alkaline nitrites, and allied substances, I was struck
with the strong resemblance which the action of nitroglycerine bears to that
of the nitrites.* The resemblance is, indeed, so well marked, that the action of
the one may be held to be identical with that of the other, unless in respect of
intensity. The suggestion, therefore, naturally occurred to me, that nitro-
glycerine is not a nitrate of glyceryl, as it is always represented, but a nitrite.
For no ordinary nitrate, as an alkaline nitrate or nitrate of ethyl, nor any
compound of glyceryl with another acid, as sulphuric acid, produces an action
on the body at all resembling that of nitroglycerine. On referring to the
various investigations which had been made for the purpose of ascertaining the
chemical constitution of nitroglycerine, I found that none of them was
sufficiently extended and exact to place beyond doubt its precise nature. The
danger in manipulating so explosive a body had evidently prevented the
various chemists from making a thorough examination of its composition. I
at first thought that nitroglycerine might be a nitrite of glyceryl, having its
nitrous acid so ‘intimately combined with the glyceryl, that the acid did not
exhibit its reactions when tested for in the usual way ; just as the acids of other
ethereal compounds will not yield their usual reactions, unless special means
are taken to forcibly dissociate the acid from the base; for example, the acid
of acetate of ethyl, or of chloride of ethyl. Certainly nitroglycerine gives no
blue colour with a solution of starch and iodide of potassium and sulphuric
acid, a.very delicate test for the presence of nitrous acid. In order, however,
to apply the test to the separated acid of nitroglycerine, I mixed an alcoholic
solution of nitroglycerine with an alcoholic solution of pure caustic potash. The
potash was ascertained to be free from nitrite, which I have frequently found
present in small quantity in various specimens of ordinary potash. Decomposi-
tion of the nitroglycerine quickly occurred, and the fluid, when now tested for
nitrous acid, was found to contain the acid in abundance, and so much of it,
that for the moment I believed that nitroglycerine was, in reality, a nitrite of

* MartnHew Hay, Practitioner, March and June 1883.
VOL. XXXII. PART I. M

68 DR MATTHEW HAY ON THE

glyceryl ; and hence the nature of its physiological action. Some estimations,
however, of the quantity of the nitrous acid proved to me that whilst the larger
portion of the nitrogen of the nitroglycerine appeared as nitrous acid in the
decomposed products, yet a considerable portion was present in some other
form.

The production of a large amount of an alkaline nitrite, when nitroglycerine
is decomposed by an alkali, is a fact which, very strangely, has hitherto
escaped the observation of chemists. MULLER and Dr LA Rue™* have, indeed,
remarked the formation of nitrous acid in the spontaneous decomposition of
badly-washed nitroglycerine ; and Hess and Scuwast have even stated that
nitrite of potassium is formed in addition to nitrate of potassium when potash
is allowed to act on nitroglycerine, but they appear to have believed that the
nitrite was formed in small quantity, and was quite a subsidiary product of the
decomposition. Ever since Rarrron,{ in 1855, published his paper on ‘ Nitro-
glycerine and its Products of Decomposition by Caustic Potash,” the
decomposition has been invariably represented, and even in the most recent
works on chemistry, by the equation :-—C,H, .3(0.NO,)+3HKOH=C,H,
.30H+3(KO.NO,) ; that is, caustic potash decomposes nitroglycerine with
the formation of glycerine and nitrate of potash ; and it is mainly from the
supposed correctness of this equation that the formula for the constitution of
nitroglycerine has been derived. Wu.i1Amson,§ in the following year, gives
an account of an investigation of nitroglycerine, and with results so exactly
similar, even in detail, to those of Rarron, that it is apparent that these
chemists had made the investigation conjointly, although they published their
results separately. Ratton supplies a more minute account of his method of
analysis of the products of decomposition, and it is not difficult to understand,
from a careful perusal of it, how he was led to suppose that the nitrate of |
potash, which he obtained by crystallisation, was the only salt present. He |
applied no tests for nitrous acid, and he made no quantitative estimation
either of the nitrate of potash or of the glycerine ; and I may anticipate some
of the results of the present investigation, and say that it is highly improbable -
that he obtained any glycerine at all, as he probably mistook for glycerine a
syrupy residue consisting of other substances. No succeeding investigator of
the chemistry of nitroglycerine has examined much more minutely the decom-
position products ; and the equation, therefore, remains as yet unaltered. It is
evident that the constitution of nitroglycerine and the action of alkalies on
nitroglycerine afford room for further investigation.

* Muttver und De ta Ror, Liebig’s Annalen. d. Chemie., CIX. 122.
} Hess und Scuwas, Berichte d. deutsch. chem. Gesellschft. Bd. XT. (1878), 8. 192.
} Ramon, Qu. Journ. of Chem. Soe., vol. vii. p. 222.

~ § Witiiamson, Proc, Roy. Soc. Lond., vol. vii. p. 130.

CHEMISTRY OF NITROGLYCERINE. 69

Action of Fixed Alkalies on Nitroglycerine.—The nitroglycerine used was
made by myself and not extracted from dynamite, as has been very frequently
the case with previous investigators. I shall afterwards describe the mode of
preparation employed. It is sufficient in the meantime to state, that whatever
was the variation practised in the method of the production of the nitro-
glycerine, the products were perfectly uniform in character. The action of the
alkali was examined both in aqueous and in alcoholic solutions. Nitro-
glycerine is so insoluble in water that it was decidedly preferable to make use
of an alcoholic solution of the ether and mix it with an alcoholic solution of
pure caustic potash (crystallised from its solution in alcohol). Absolute ethylic
alcohol was employed in every instance.

When a moderately strong solution of caustic potash (1 in 10) is added to
a solution of nitroglycerine of similar strength, the following phenomena are
observed. The first few drops of the alkaline solution produce an_ orange-
coloured precipitate, which, on the addition of more of the potash, assumes
along with the whole fluid a deep reddish-brown colour. A large amount of
heat is developed during the mixture, amounting almost to ebullition of the
alcohol; a strong aldehyde-like odour is evolved, without any perceptible
odour of ammonia or acrolein. The fluid quickly separates into two layers—
the lower, and much the smaller, being partly of the nature of a solid
precipitate, yet in great part syrupy and of a very deep reddish-brown colour,
and containing nearly all the colourmg matter formed by the decomposition of
the nitroglycerine. The upper layer constitutes the bulk of the fluid, and is
yellowish in colour, and at first muddy, but, after a few minutes, becomes quite
transparent. The application of external heat is, as I have ascertained, quite
unnecessary to complete the decomposition, although in most of my
experiments I have with this object boiled the fluid over the water-bath
for several minutes, sometimes to the entire dissipation of the alcohol, water
being added as the alcohol is evaporated. When water is so added, the syrupy
precipitate, in proportion to the amount of alcohol still present, becomes
partially or completely dissolved, yielding a deep reddish-brown solution. If
sufficient water is added to the fluid without previous removal of the alcohol,
it is still possible to obtain a perfect solution of all the substances present. It
was in such diluted solutions, obtained either in the one way or the other, that
I estimated the amount of nitrite of potassium formed. This was effected by
means of starch, potassium iodide, and dilute sulphuric acid, a thoroughly
well-boiled 5 per cent. solution of starch, and containing 2 per cent. of
potassium iodide, being employed. The blue colour obtained on the addition
of these reagents was compared, as regards its intensity, with the colour
produced by a similar amount of the reagents added to standard solutions of
nitrite of sodium placed in test-tubes of the same diameter and used in the

70 DR MATTHEW HAY ON THE

same quantity as in the case of the nitroglycerine solution. The purity of the
nitrite of sodium was previously ascertained by titration. with a standard
solution of permanganate of potash; and the strengths employed of the
standard solutions of the nitrite were 1 in 500,000, and 1 in 1,000,000. The
solution of decomposed nitroglycerine was diluted with distilled water until,
on the addition of the starch reagent, a depth of blue was obtained precisely
similar to that given by the strongest of the standard solutions of the nitrite.
The solution was then diluted with an equal bulk of water, and, for the
purpose of control, compared with the weaker standard solution. From the
amount of dilution needed it was easy to estimate the quantity of nitrous acid
present in the solution of the decomposed nitroglycerine. This method is
only approximately correct, but it is the only method available. Any error
was as far as possible eliminated by making the dilutions and comparisons with
extreme care, and by occasionally repeating the estimation of. the nitrous acid.
The following were the results obtained. (The letters following the various
specimens of nitroglycerine are for the purpose of identifying each specimen
with its mode of preparation, which will be afterwards stated.)

I. Nitroglycerine, A.—1:1533 grms. dissolved in about 5 cc. of alcohol,
and treated with fully 1:5 grms. of caustic potash dissolved in about
12 c.c. of alcohol. Boiled over water-bath for half an hour, water
being added to replace the evaporated alcohol, and heating
continued until the whole of the alcohol was driven off. Fluid
diluted to 30 ¢c.c. 1c.c. of this was further diluted, and employed
for the estimation of the nitrous acid. A dilution corresponding to
1 of the original nitroglycerine in 620,000 of water was found to
contain the same proportion of nitrous acid as the 1 in 1,000,000
standard solution of nitrite of sodium. The nitroglycerine had,

7205) corre-

therefore, produced a quantity of nitrous anhydride

sponding to 62 per cent. of the anhydride in Na.O.NO, or 34°143 per
cent. of the weight of the nitroglycerine.

A second estimation of the nitrous acid in the same solution
of decomposed nitroglycerine gave 35°244 per cent. of N,Os.

II. Nitroglycerine, A.—1 c.c. of a 10 per cent. solution heated to the
boiling point with a small excess of alcoholic solution of potash ;
diluted with two volumes of water and again heated to the boiling
point, and the nitrous acid then estimated.

The nitroglycerine yielded 35°24 per cent. of ee

III. Nitroglycerine, A.—Same in all respects as IT.
The yield of nitrous anhydride was 35:24 per cent.

LY’.

vel.

ELT.

VIII.

XII.

CHEMISTRY OF NITROGLYCERINE.

r@!

Nitroglycerine, A.—Same as II., except that caustic soda was used

instead of caustic potash. The decomposition presented the same
appearances as when potash was used.
The yield of nitrous anhydride was 35:24 per cent.

diluted with water two minutes after the addition of the potash.
The yield of nitrous anhydride was 33°04 per cent.

. Nitroglycerine, A.—Same as II., but no heat applied, and fluid freely

Nitroglycerine, B.—1 grm. dissolved in. about 6 c.c. of alcohol, and

heated with 12 c.c. of 124 per cent. alcoholic solution of caustic

potash.

being added to replace the alcohol.
The yield of nitrous anhydride was 34°96 per cent.

with excess of potash solution.

The yield of nitrous anhydride was 34°41 per cent.

estimation gave 34°96 per cent,

as in VIL.

The yield of nitrous anhydride was 34:96 per cent.

. Nitroglycerine, G.—Same proportions as VII.

The yield of nitrous anhydride was 35:24 per cent.

. Nitroglycerine, G.—Same proportions as IX.

The yield of nitrous anhydride was 34°96 per cent.

. Nitroglycerine, N.—Same proportions as X.

The yield of nitrous anhydride was 35:24 per cent.

Nitroglycerine (from Noset’s dynamite).—Same proportions as X.

The yield of nitrous anhydride was 35:24 per cent.

Boiled over water-bath to dissipate the alcohol, water

Nitroglycerine, D.—1 grm. dissolved in 15 c.c, of alcohol, and heated

Another

Nitroglycerine, F.—Same proportions of nitroglycerine and alkali

SuMMARY OF ESTIMATIONS OF NiTROvus ACID IN THE ALKALINE DECOMPOSITION-
Propucts oF NITROGLYCERINE.

No. of Analysis.

Specimen
of

Nitroglycerine.
|

Percentage of
Nitrous
Anhydride.

L
A A
341°43) 35°24

IDEM.

35°24

IV.

35°24

33:04

AVI iyi): ViLLT. s}) - TEX

34°96 | 34°41 | 34:96 | 35:24

xX. XI.
G N
34°96 | 35-24

xa:

Dyna-
mite.

35°24

72 DR MATTHEW HAY ON THE

These analyses are amply sufficient to show that the amount of nitrous acid
formed during the alkaline decomposition of nitroglycerine is neither small
nor variable ; and, assuming that nitroglycerine is a trinitrate of glyceryl, it
corresponds remarkably with the supposition that two out of tLe three parts
of nitric anhydride, which nitroglycerine contains, are reduced to nitrous
anhydride; for the trinitrate of glyceryl ought theoretically to yield, if so
reduced, 33°48 per cent., an amount which agrees very closely with that
actually obtained, if due allowance be made for experimental error in a method ©
which, although the best available, cannot claim to be exact. _

It is open to suggestion, reasoning alone from these estimations of nitrous acid,
that nitroglycerine is perhaps a di-nitrite of glyceryl, or a mono-nitrate di-nitrite
of glyceryl. As opposed to its being one or other of those bodies, the fact
that specimens of nitroglycerine, as B and D, prepared in presence of urea, were
found to yield the same proportion of nitrous acid as the others, is of importance.
Another weighty objection to its being a nitrite is that on passing nitrous
anhydride.gas into glycerine no substance at all resembling nitroglycerine was
obtainable ; although there was formed an oily liquid containing nitrous acid
in combination, which, however, quickly decomposed in contact with water.
This body has recently been investigated by Mr Masson,* and he- believes it to
be the tri-nitrite of glyceryl. It is not probable that the di-nitrite will possess
greatly different properties. Were nitroglycerine the di-nitrite, it ought to
yield a much higher proportion of nitrous acid than was actually obtained.
For these and various other reasons, it is not the di-nitrite, and much less the
tri-nitrite. As to the possibility of its being a mono-nitrate di-nitrite, the
objection as to the yield of nitrous acid is not by any means strong. For

such a body ought theoretically to yield 30:89 per cent. of a 3 (nitrous

anhydride), an amount tolerably close to what was actually obtained. And
amongst the alkaline decomposition products of nitroglycerine, it is not difficult
to separate nitrate of potassium by crystallisation. But, on the other hand,
the mono-nitrate di-nitrite ought to yield 21:5 per cent. of nitrogen, whereas, —
by actual experiment, Mr Masson and myself have found that nitroglycerine
contains a inuch lower percentage of nitrogen.

From these and other considerations, which will be referred to later on, it
is impossible to avoid concluding that nitroglycerine is a tri-nitrate of glyceryl,
and that two-thirds of its nitric acid is reduced to nitrous acid during the
decomposition of the ether.t

I shall now give a brief account of the other substances, besides nitrite of
potassium, which are formed when an alcoholic solution of potash acts on an
alcoholic solution of nitroglycerine.

* Masson, Journ. Chem. Soc., August 1883.
+ Vide accompanying communication on “'The-Elementary Composition of Nitroglycerine,”

CHEMISTRY OF NITROGLYCERINE. 13

Nitrate of potassium is, as I have mentioned, present in considerable
quantity, and with the nitrite constitutes the larger portion of the reddish-brown,
partly viscid, partly crystalline precipitate, which is formed in the decomposing
fluid. I have not estimated the nitrate quantitatively; but there is every
reason to believe, from the estimation of the total nitrogen by SCHLOESING’s
method and from other circumstances, that the amount of the nitric acid cor-

responds very closely to one-third of the nitrogen present in nitroglycerine.

But nitrite and nitrate of potassium are not the only substances formed. I
have also proved the presence of acetate of potassium, oxalate of potassium,
and, doubtfully, of formate of potassium, neither of the two latter appearing to
be present in large quantity. There is alsoa small amount of ammonia, and ofa
reddish-brown, resinous body, which imparts the dark colour to the decomposing
fluid. There is likewise present a very curious and very interesting substance,
which possesses the unusual power of forming a firm jelly with a very large
proportion of absolute alcohol. In contradiction to Ratton and WILLIAMSON,
and previous investigators, I have found no glycerine, or only the merest trace

of it. This is a new and most important fact.

In order to ascertain the presence and nature of these various decomposition-
products, 6°67 grammes of pure nitroglycerine were decomposed with excess of

potash in the usual manner, the mixture being allowed to boil for five minutes,

and afterwards set aside for one day, to permit of the deposition of certain of
the substances dissolved in the hot absolute alcohol. The supernatant fluid,
which was transparent and of an orange colour, was then decanted, and the
residue was again boiled with a fresh quantity of absolute alcohol, and again set
aside for a day, when the alcohol was decanted and added to the previously
decanted alcohol. This process was repeated a third time. The mixed alcoholic
fluids ought to have contained the excess of caustic potash and the whole of
the glycerine, were any present; and in the deep reddish-brown residue I
expected to find nearly all the colouring matter, and.all the salts‘insoluble in
absolute alcohol, as the nitrite and nitrate of potassium.

The mixed alcoholic fluids were neutralised with.alcoholic sulphuric acid in
order to precipitate the potash as sulphate of potash. A voluminous white
precipitate formed, which, after standing for some hours, was separated by
filtration. The filtrate, although faintly acid, yielded another tolerably copious
precipitate of sulphate of potash on the further addition of sulphuric acid, which
was now added in distinct excess. Salts of potash were evidently present, dis-
solved in the alcohol; certainly, amongst others, the nitrite and acetate, as proved

by testing. The precipitate was again removed by filtration, and the alco-

holic fluid was now distilled fractionally in order to remove the more volatile
substances, as the alcohol and acetic, formic and nitrous acids, the less volatile
glycerine, if present, remaining in the retort. Distillation was continued until

74 DR MATTHEW HAY ON THE

four-fifths of the fluid had been evaporated. An equal bulk of water was now
added to the residue, and distillation was continued until the alcohol was almost
completely expelled. The residue was now saturated with pure barium hydrate,
in order to remove the sulphuric acid, and then filtered; and the excess of
barium -was precipitated by a stream of carbonic acid gas, and the fluid was
again filtered. The filtrate was now evaporated over the water-bath, and was
quickly reduced to five or six drops of a golden yellow viscid residue. Treated
with absolute alcohol, in which glycerine is freely soluble, it at once hardened,
and was almost entirely insoluble in alcohol. It evidently consisted in part of
a barium salt, as ascertained by testing. The alcoholic solution or extract was
filtered, and, on evaporation, yielded about one drop of a yellowish syrup, much
more viscid than glycerine, and pungent rather than sweet to the taste. A few
minutes’ further drying dessicated it to a hard scale. The syrup gave merely
the faintest odour of acrolein when heated with acid sulphate of potash. J
therefore concluded that this residue, which ought to have contained the greater
part of the glycerine, were any present, contained practically none of that sub-
stance. The absence of glycerine from the alkaline decomposition products of |
nitroglycerine was confirmed by a second experiment, made with a still larger
quantity of nitroglycerine, and in which no distillation was practised, and less
opportunity therefore afforded for the decomposition or evaporation of the
glycerine.

The deep reddish-brown residue, laid aside at the commencement, after
being well washed and extracted with boiling absolute alcohol, was next
examined. Dried at 100° C. for 24 hours, it weighed 14°65 grms., and was
probably not even then absolutely dry, although very nearly so. The large
amount of the residue is remarkable, as it weighs considerably more than the
sum of the weights of the nitroglycerine decomposed, and of the potash neces-
sary, according to Rariron’s equation, for the decomposition of the nitro-
glycerine. This point will shortly receive an explanation.

The dried residue was perfectly soluble in water, forming even with a large
volume of water a deep reddish-brown solution. A portion of the residue was
dissolved in boiling water, and, after standing for some hours, large needle-
shaped crystals of nitrate of potassium separated, which by re-solution and
re-crystallisation were obtained in a perfectly pure form, and distinctly recognised
to be nitrate of potassium. From another measured portion of the residue it
was attempted to remove the nitrite of potassium and formate of potassium (if
present), by treatment with strong acetic acid, and extraction with boiling
absolute alcohol, in order to remove the acetate of potash and free acids thus
formed, and to obtain in a tolerably pure state the nitrate of potassium for the
purpose of a quantitative determination ; but the method did not succeed.

One-half of the original dried residue was next dissolved in water, and

CHEMISTRY OF NITROGLYCERINE. 15

treated with moderate excess of dilute sulphuric acid, and heated for a few
minutes. Red fumes were evolved with brisk effervescence; and a dark
_ reddish-brown precipitate was formed, which evidently constituted the colouring
matter of the decomposition products of nitroglycerine, although the colour
was not wholly removed by the addition of the acid. The precipitate was
collected on a filter, and washed with dilute acid and dried ; it weighed 0°040
eram. It was insoluble in acid solutions, but freely soluble in dilute solu-
tions of allxalies or alkaline carbonates, and was of a resinoid character, and is
probably similar in nature to aldehyde-resin, or even to caramel.

As regards the peculiar alcohol-gelatinising body which I have mentioned
as existing amongst the products of the alkaline decomposition of nitro-
glycerine, it was met with in the course of an examination of the decomposed
products of 15 grms. of nitroglycerine, obtained in the usual way. The
supernatant alcoholic fluid was treated with excess of dilute alcoholic sulphuric
acid, in order to precipitate all the potash, both free and combined. The filtrate
was afterwards neutralised, and the sulphuric acid precipitated by means of
pure carbonate of barium. The evaporated filtrate yielded a residue which
crystallised on cooling, and contained no glycerine, and which was very freely
soluble in water without gelatinisation. It was also freely soluble in hot
absolute alcohol ; but on allowing the solution to cool, even if the proportion of
the residue to the alcohol was 1 to 20 or 30, the solution became a firm, partly
erystalline-looking jelly, which could not be poured out of the test-tube in which
it formed. This body, whatever be its exact constitution, is certainly a very
exceptional organic substance, and deserves further examination.

No gases are generated when potash acts on nitroglycerine in alcoholic
solution. This was ascertained by placing the solution of nitroglycerine in a
retort connected with a tube inverted over mercury, and boiling to drive out
all the air. Alcoholic potash was then added, precautions being taken to
prevent the simultaneous admission of air, and the boiling was continued for
some time without any gas being formed. -

These are the products formed when alcohol is the medium through which
the potash attacks the nitroglycerine. Similar products are obtained when
water is employed, and the only apparent difference is that, on account of the
very sparing solubility of nitroglycerine in water, the decomposition proceeds
with great slowness, fully two hours’ boiling over the water-bath being required
to effect the decomposition of one gram. of nitroglycerine in a strong solu-
tion of pure potash. Less red colouring matter is formed than when alcohol is
employed, and much more oxalic acid seems to be produced ; but the amount
of nitrous acid is the same.

From this detailed account of the decomposition of nitroglycerine by caustic
potash, it will be seen that the usual equation is very. far from representing

VOL. XXXII. PART ‘I. , N

76 DR MATTHEW HAY ON THE

what actually occurs. It is almost regarded as a fixed law in the chemical
decomposition of compound ethers by alkalies, that the alkali unites with the
acid of the ether and liberates the alcohol. This does not appear to be the —
case with nitroglycerine. For no glycerine is formed, and the acid is in great
part reduced. But there is no doubt that the reduction of the greater portion
of the acid is to be associated with the disappearance of the glycerine, which is
evidently oxidised by the oxygen lost by the acid. Therefore, instead of
glycerine, we have oxidation products of it, as acetic acid, oxalic acid, formic
acid, &e. When nitroglycerine is being decomposed by potash, nitric acid and —
elycerine or glyceryl occur in a nascent and very active condition, the one as a
powerful oxidising substance, the other as a readily oxidisable substance. As
a consequence they act on each other, and two out of the three molecules of
the nitric acid part each with an atom of oxygen to the glycerine or glyceryl,
and this amount of oxygen is sufficient to completely oxidise and break up the
glycerine, mostly, if not entirely, into certain organic acids, which, of course,
will combine with a portion of the excess of. the alkali used for the decomposi-
tion. That is one view; but there is another view, according to which the
caustic potash may be regarded as taking an active part in the decomposition
of the nascent glyceryl. When pure glycerine is melted with potash, it is well-
known that acetate and formate of potash are produced along with _
hydrogen.* The action is represented by the equation,—

C,H, (OH), +2KOH = KO. CHO + KO.C,H,0 + OH, +2H,.

The decomposition effected by potash under these conditions may occur even
in dilute solution if the glycerine be in a nascent state, more particularly if
there be present at the same instant a highly oxidising body like nascent nitric
acid, which is promoting the same form of decomposition, and is ready to grasp
the nascent hydrogen. The amount of hydrogen set free is precisely the
quantity needed to reduce two-thirds of the nitric acid of the nitroglycerine,
and the other decomposition products of the equation given correspond toler-
ably closely with those ‘actually ascertained to be formed. But if such a
decomposition occurs, it implies that five, not three, molecules of hydrate of
potash are required to decompose one molecule of nitroglycerine. In accord-
ance with these views the action of caustic potash on Saiki may be
represented thus :—

(1) C,H,:3(0-NO,) + 3KOH=C,H, (OH), +3(K:O-NO,).
Nitroglycerine. Potash. Glycerine. Potassium
and Nitrate.
(2) C,H, (OH), + 2KOH=KO-CHO+KO-C,H,0 + 0H, +2H,.
Glycerine. Potash. Potassium Potassium Water. Hydrogen,
Formate. Acetate. :

* Dumas et Stas, Ann. Chim. Phys., 1xxiii., 148,

CHEMISTRY OF NITROGLYCERINE. 4

(3). 3(KO.NO,)+2H,=KO.NO, + (2KO.NO)+20H,.
Potassium Hydro- Potassium Potassium Water. |
Nitrate. gen, Nitrate. Nitrite.

or, combining these stages of the supposed reaction into one equation :—

(4) ,H,.3(0.NO,)+5KOH=KO.NO,+2(KO.NO) +KO.CHO+KO.0C,H,0+30H,,

Nitroglycerine, Potash. Potassium Potassium Potassium Potassium Water.
Nitrate. Nitrite. Formate. Acetate.

In equation (1) it might have been more in harmony with the view ad-
vanced that the glycerine should have been represented as glyceryl and water,
to indicate more completely its nascent state.

There is every reason to believe that equation (4) is substantially and
approximately correct, although in respect of the oxidation products of
glycerine these may vary in their nature and proportions. Besides being in
accordance with the results of the examination of the products of decomposi-
tion, it is supported, as regards the amount of potash required, by the following
experiments :—

According to RariLTon’s equation, one part of nitroglycerine requires for its

complete decomposition 0°741 parts of potassium hydrate; according to the
equation just given the proportion isas1:1:235. If less of potash is used than
in the latter proportion, then, if the latter equation be correct, complete decom-
position will not occur, and a quantity of nitrous acid will be produced corre-
sponding to the amount of potash employed ; and the solution of the products
of decomposition will remain neutral until more than the requisite proportion
_ of potash (1°235 to 1) has been added. In the following four experiments
nitroglycerine, F’., was employed in every instance, and a certain quantity of it
was dissolved in alcohol and decomposed by an alcoholic solution of a given
weight of pure potash, freshly crystallised from alcohol, and as free as possible
from carbonate ; the mixture being boiled for ten minutes, diluted with water,
and again boiled for ten minutes.

: Weight of Yield of Nitrous Anhydride :
No. of Weight of De, J = Reaction of Decom-
; : 5 Potassium ressed ¢ rcentage of F
Experiment. Nitroglycerine. i carat 7 SS Niomlncenine need: y posed Fluid.
Calculated accord-
Grms. Grms. ing to Author’s Found;
equation.
i al 0:80 21:68 23:23 Neutral.
1p 1 1:00 27AL 28°68. Neutral.
IIL. 1 1-24 33-48 34-69 VO a,
: alkaline,
I. li 1:50 33°48 34:69 Alkaline,

78 DR MATTHEW HAY ON THE

The degree of alkalinity of (IV.) was ascertained by titration with a stand-
ard solution of sulphuric acid (30 in 1000). 6-2 cc. of standard acid were
required for complete neutralisation, which is equivalent to 0-203 grms. of
potassium hydrate, which, subtracted from 1°50 erms., the quantity of potash
originally added, gives 1:297 grms. as the amount of potash actually used up,
or a little more than the theoretical quantity. It is noteworthy in these
experiments that where less than five molecules of potash, although more than
three, were added to one of nitroglycerine, a quantity of nitroglycerine could
be observed to remain undecomposed, as it was precipitated on the addition of
water to the alcoholic mixture, proving that when potash acts on nitroglycerine
in presence of excess of the latter, according to the equation I have adopted,
the potash is used up in thoroughly decomposing each molecule of the nitro-
glycerine, and does not partially decompose a greater number of molecules.
The respective yields of nitrous acid are alone sufficient to prove this.

The amount of potash required for the decomposition ‘of nitroglycerine is
‘interesting in connection with a method described by BeckERHINN * a few years
ago for the estimation of the degree of acidification of the ether, whether tri-,.
di-, or mono-nitrate, in which, after adding what he considered to be excess of
caustic potash, he titrated the excess with normal oxalic acid. But his calcula-
tions were based on the accuracy of Ramron’s equation. It is very difficult,
therefore, to understand how he could possibly have obtained satisfactory results,
although he claimed to have done so, and quoted two analyses. In the follow-
ing year Hess and Scuwast denied the correctness of his method, and made
analyses according to it, but obtained widely different results, yet still acknow-
ledging Rartton’s formula, .and ascribing the faultiness of me method to various
minor circumstances.

Action of Ammonia—The volatile alkali seems to act on nitroglycerine in
the same manner as the fixed alkalies, but not so ener getically. When excess
of strong ammonia was added to an alcoholic solution of nitroglycerine, there
was no immediate decomposition of the nitroglycerine; as is the case when
potash or soda is added. The resultant mixture-remained colourless and
showed no precipitate. It was then placed over the water-bath and heated all
but to ebullition for one hour ; and in order to preserve excess of ammonia, more
of the reagent was added from time to time. It now gradually assumed a deep
reddish-brown colour, almost deeper than that observed in decomposition with —
potash. The maximum intensity of colour was reached after half an hour’s
heating, so that ammonia acts much more slowly than potash. The amount of
nitrous anhydride obtained was equivalent to 345 per cent. of the nitroglycerine

* Beckeruinn, Sitzwngsb. d. Wien. Akad., Bd. 1xxiii. (1876), Abth. 2, S. 235.
+ Hess u. Scuwas, bid., Bd. lxxv. (1877), Abth. 1, S. 702.

CHEMISTRY OF NITROGLYCERINE. 79

used, or a proportion exactly similar to that produced by the action of a fixea
alkali.®

Action of Alkaline Carbonates.—Nitroglycerine was dissolved in slightly
diluted alcohol in order to permit the solution in it of carbonate of potash,
which was afterwards added in the form of a concentrated aqueous solution.
The mixture slowly assumed a reddish colour even in the cold. Heated over
the water-bath, the nitroglycerime tolerably rapidly underwent decomposition,
and the fiuid became of a fairly deep reddish-brown colour. The, fluid was
heated for one hour, and water was added as the alcohol became evaporated.
The yield of nitrous anhydride was 35:24 per cent., or the same as when
caustic potash is used. In a second experiment the yield was exactly the
same. Using a five per cent. alcoholic solution of nitroglycerine, and boiling
it with excess of carbonate of potash, it was ascertained that complete
decomposition occurs in about ten minutes.

Action of Phosphate of Soda (Na,HPO,).—This salt is acid in constitution,
but alkaline in reaction. Added in concentrated aqueous solution to a one
per cent. alcoholic solution of nitroglycerine, and heated over the water-bath, the
phosphate commenced to decompose the nitroglycerine three to four minutes
after the mixture was fully heated, as was evidenced by the appearance of a

yellowish tint gradually deepening to an orange-red. After heating for an
hour and a half, slightly diluted alcohol being added occasionally, a yield of
13:76 per cent. of nitrous anhydride was-obtained. In another experiment,
after heating a similar mixture for forty minutes, 13-21 per cent. of nitrous
anhydride was obtained. On both occasions the nitrous acid was estimated
in one half of the fluid, and it was observed, in diluting the fluid with
water, that a considerable amount of nitroglycerine was precipitated. In
the second experiment, by adding potash to the remaining half of the fluid,
and heating for a few minutes, and then estimating the nitrous acid, 34°41 per
cent. of nitrous anhydride was obtamed, proving that no nitrous acid had been
set free by the phosphate of soda, which, in the absence of sufficient alkali,

* Tt is somewhat remarkable that the yield of nitrous acid was as great as when a fixed alkali
_ was used; since it is well known that a solution of nitrite of ammonia readily undergoes decom-
* position when heated ; and it was to be expected that the estimated yield of nitrous acid would have
been diminished by the occurrence of such a decomposition in the heated fluid. In order to make
certain that the result obtained was correct, and that under the conditions of the experiment such a
decomposition did not occur, or occurred only to a limited extent, I have, since the paper was read,
repeated the experiment. This I have done on two occasions, and with separate quantities of pure
nitroglycerine. On the first occasion only 29°6 per cent. of nitrous anhydride was obtained, but, on
the second, 34.1 per cent., or very nearly what was obtained in-the experiment recorded in the text.
The nitrite of ammonia formed by the splitting up of the nitroglycerine would appear, therefore, to
undergo very little decomposition under the conditions in which it is placed. This may be due to
the excess of free ammonia always maintained in the decomposing mixture, or to the low degree of
heat applied, as, in order to prevent the rapid escape of gaseous ammonia, heat was applied short of
ebullition of the fluid, or, more properly, of the escape of ammonia in the form of bubbles of gas ; or
it may be that the highly concentrated alcohol in which the nitroglycerine was dissolved hindered the
decomposition of the nitrite.

80 DR MATTHEW HAY ON THE

might have been decomposed into nitric acid and nitric oxide, or evaporated
off. This form of control-analysis is the more necessary when the salt or
substance employed to act on the nitroglycerine is neutral; and in such
circumstances I have always made use of it. |

Phosphate of soda appears, therefore, to act on nitroglycerinein much thesame
manner as alkalies and alkaline carbonates, only very much less powerfully.

Action of Chloride of Sodium.— Excess of a concentrated solution of the pure
salt was mixed with a one per cent. alcoholic solution of nitroglycerine. The
salt was not precipitated, as the alcohol contained a little water. The mixture
was heated for thirty-five minutes. There was no perceptible change of colour,
and the quantity of nitrous acid did not amount to more than a fraction of a_
per cent. of the nitroglycerine used. The starch reagent yielded no blue
colour with the fluid until sulphurie acid was added. The trace of nitrous acid
was therefore present as a nitrite. One half of the fluid was treated with
potash, and from it was procured an amount of nitrous anhydride correspond-
ing to 35°25 per cent. of the nitroglycerine. The chloride of sodium had not,
therefore, decomposed the nitroglycerine and lost the nitrous acid by
decomposition or evaporation.

Chloride of sodium possesses, therefore, extremely little action on nitro-
glycerine.

Action of Hydrochloric Acid.—1'6 c.c. of the strong acid were diluted with
2 c.c. of water and added to 10 cc. of a one per cent. alcoholic solution of
nitroglycerine ; and the mixture was heated over the water-bath for half an
hour. It was then found to contain a trace of nitrous acid, not exceeding a
small fraction of a per cent. of the nitroglycerine. One half of the fluid,
heated with excess of caustic potash, and thus completely decomposed, yielded
nitrous anhydride corresponding to 13°5 per cent. of the nitroglycerine.
This showed that the hydrochloric acid had decomposed about 39 per cent.
of the nitroglycerine, but whether with the formation of nitrous acid, it is
quite impossible to say. For even had nitrous acid been formed, it would have
been driven off by the boiling, or decomposed in contact with the water of
the fluid. {

Hydrochloric acid, therefore, in large excess, decomposes nitroglycerine
much more slowly than a caustic alkali or even an alkaline carbonate, and not
much more quickly than phosphate of soda.

Action of Sulphuric Acid.—0°5 c.c. of strong sulphuric acid was diluted
with 1 c.c. of water, and mixed with 10 c.c. of a one per cent. solution of
nitroglycerine, and heated for half an hour. At the end of this period the
fluid did not contain more than the merest trace of nitrous acid. One half
of the fluid, boiled with potash, yielded nitrous anhydride corresponding to
29°'7 per cent. of the nitroglycerine. The sulphuric acid had, accondiaaa
decomposed 11°3 per cent. of the nitroglycerine employed.

CHEMISTRY OF NITROGLYCERINE. 81

Sulphuric acid, in the proportion used, would appear, therefore, to act less
energetically than hydrochloric acid on nitroglycerine. Concentrated sulphuric
acid in the cold seems to have almost no action, as is proved by the method
of the preparation of nitroglycerine.

Action of Sulphuretted Hydrogen—According to De Vris,* an ethereal
solution of nitroglycerine is readily decomposed by sulphuretted hydrogen with
a copious precipitation of sulphur.

In order to test the truth of this observation, I submitted two ten per
cent. solutions of nitroglycerine—the one in absolute alcohol, the other in
ether—to the action of a stream of sulphuretted hydrogen gas. But although
the gas was allowed to pass in a rapid stream through each solution for fifteen
minutes, yet not the slightest trace of decomposition occurred, as was evidenced
by no change of colour, and the absence of nitrous acid and precipitated sulphur
and other decomposition products ; even although, in the case of the alcoholic
solution, its temperature was raised to near the boiling point and the gas passed
for fifteen minutes longer. Nitroglycerine was precipitated abundantly from
both solutions on thé addition of water. These experiments were more than
' once made, and aiways with the same result.

It must, therefore, be concluded that sulphuretted hydrogen has no action,
or at most a very slow action, on pure nitroglycerine. The opposite experience
of De Vris was probably due to his having used an impure nitroglycerine.

Action of Alkaline Sulphides.—Vhese act very energetically on nitro-
glycerine, and decompose it, if in alcoholic solution, as rapidly as alkalies alone
do. On adding a solution of ordinary sulphide of potassium, or sulphide of
ammonium, to an alcoholic solution of nitroglycerine, the mixture quickly
assumes a deep reddish-brown colour, and its temperature rises; and the
action of the sulphide is conipleted with a sudden and most abundant
precipitation of sulphur in every part of the mixture simultaneously. No gas
is given off; and, contrary to expectation, after being boiled with excess of
the sulphide for half an hour, filtered to remove the sulphur, and treated: with
acetate of lead and again filtered to remove the sulphuretted hydrogen of the
sulphide, it yielded evidence of the presence of nitrous acid to the extent of a.
little less than half the proportion yielded by a purely alkaline decomposition.
It would appear, therefore, that the whole of the nitrous acid set free in the
decomposition of the nitroglycerine by the alkali of the sulphide is not acted
on by the sulphuretted hydrogen of the sulphide. For we may assume, since
sulphuretted hydrogen does not of itself attack nitroglycerine, that it is the
alkali of the sulphide which takes the initial step in the decomposition of the
nitroglycerine ; the sulphuretted hydrogen playing a subsidiary part, and merely
acting on the nascent products of the decomposition effected by the alkali,

* De Vai, Journ. Pharm. [3], xxviii, 3; and Gmutin’s Handbook of Chemistry, x. p. 562.

82 DR MATTHEW HAY ON THE

But why the whole of the nascent nitrous acid should not thus be decomposed
by the sulphuretted hydrogen I do not, in the meantime, attempt to explain,
beyond suggesting that the nascent nitrous acid may in part combine with
the alkali; and, once so united, it is incapable of being acted on by the
sulphuretted hydrogen. |

But the sulphuretted hydrogen does not play an aiaeeihen passive part in
the actual decomposition of the nitroglycerine itself, for when an aqueous
solution of an alkaline sulphide, such as potassium sulpbide or ammonium
sulphide, is poured over pure undissolved nitroglycerine, and the mixture
vigorously shaken, the solution gradually becomes reddish, and the tempera-
ture rises, and apparently, when the temperature has risen sufficiently, the
whole or nearly the whole of the nitroglycerine suddenly decomposes with a
copious formation of sulphur. In fact, the nitroglycerine seems to become
suddenly converted into a mass of sulphur. It will be remembered that when
potash alone is allowed to act on nitroglycerine under. similar circumstances,
the decomposition proceeds very slowly. The presence, therefore, of
sulphuretted hydrogen very greatly promotes the decomposition of nitro-
glycerine ; but in what particular manner I have not endeavoured to ascertain. ~

Action of Water.—In order to ascertain to what extent water when boiled
with nitroglycerine is capable of decomposing it, a given quantity of a saturated
aqueous, and, owing to the insolubility of nitroglycerine in water, a necessarily
weak, solution of nitroglycerine was heated over the water-bath. After ten

minutes’ active heating, the fluid exhibited no signs of decomposition, and con- —

tained no trace of nitrous acid. It was then continuously heated for three
hours. It still remained colourless, and-on the addition of starch and -iodide of
potassium gave no blue; but when these reagents were added along with
dilute sulphuric acid, a distinct blue was obtained. The nitrous acid present
was. evidently combined with some other decomposition product of the nitro-
glycerine ; it was estimated and found to amount to 1°7 per cent. of the whole
nitroglycerine employed. A given portion of the fluid was heated with potash,
in order to learn how much of the nitroglycerine remained undecomposed, and
a quantity of nitrous acid (nitrous anhydride) was obtained, equivalent to 8°88
per cent. of the whole nitroglycerine ; from which it is to be concluded that
73°48 per cent. of the nitroglycerine had been decomposed by heating with
water for three hours. It is to be considered that a portion of this may have
been lost by simple evaporation, although this was to a certain extent avoided
by heating in a long-necked Florence flask.

Action of Alcohol.—A one per cent. solution of nitroglycerine in absolute
alcohol was heated over the water-bath for one hour, the alcohol being renewed’
from time to time. There was no change in colour, and nitrous acid could not
be detected, even when sulphuric acid was added along with the usual reagents.
A portion of the fluid was decomposed with potash, and the nitrous anhydride

CHEMISTRY OF NITROGLYCERINE. 83

obtained was found to be equivalent to 33°45 per cent. of the whole nitro-
glycerine, proving that the nitroglycerine had not been apparently decomposed
by heating with alcohol.

From this it is evident that the alcohol used as a menstruum in ascertaining
the action of other substances on nitroglycerine did not of itself aid in the
decomposition of the nitroglycerine.

Preparation of Nitroglycerine.—After I had observed that nitroglycerine
yielded, when decomposed with an alkali, a large amount of nitrous acid, and being
fully sensible of the insufficiency of existing analyses to determine the elementary

composition of nitroglycerine, doubts arose in my mind, as I have already

stated, as to whether nitroglycerine was actually a tri-nitrate of glyceryl. I
have already given some important reasons in connection with its alkaline
decomposition products for regarding it as the tri-nitrate, and not as any form
of a nitrite. But I have thought it advisable to supply what additional proof
could be obtained of its composition from a consideration of the yield of nitro-
glycerine from a given weight of glycerine. For this purpose I prepared nitro-
glycerine with various proportions of glycerine and acids, in order to ascertain

the highest possible yield of nitroglycerine. Another important object which I

had at the same time in view was to learn how far such variations in the method
of the preparation of nitroglycerine might affect its composition. The latter
object was very desirable, owing to the very discrepant statements which have
been made by previous investigators as to nitroglycerine consisting entirely of
tri-nitrate of glyceryl, or of a mixture of the tri-nitrate with the di-nitrate and
mono-nitrate. |

In the preparation of the nitroglycerine, Pricr’s pure glycerine, dried for
six hours in the air-bath at a temperature of 120°C, was always employed ; the
specific gravity, after drying, was 1:260 at 14°C. The acids were each of two
strengths—nitric acid, of a specific gravity of 1:422 (referred to as strong nitric
in what follows), and 1:494 (referred to as fuming nitric acid) ; sulphuric acid,
of a specific gravity of 1844 (referred to as strong sulphuric acid), and 1:984
(referred to as fuming sulphuric acid) ; all at 15:5°C. In every instance the
nitric and sulphuric acids were first mixed and placed in a vessel containing
salt and ice, and cooled to below 0°C. In certain cases where urea was also
used, it was added to the nitric acid previous to mixture with the sulphuric
acid. Into the cooled mixture of the acids the glycerine was slowly dropped
and well mixed by constant stirring, the temperature, as ascertained by a ther-
mometer, never being permitted to rise above 10°C. After standing for a
variable time, the mixture was poured into a large and measured quantity of
cold water, when the nitroglycerine was precipitated. It was now very care-
fully collected, after thorough stirring with the water, and was in this slightly
impure state dried in the air-bath at 70°C. It dried quickly, but assumed a
yellowish tint, and had a pungent acid odour. The weight of the dried nitro-_

VOL, XXXII. PART I. 0

84 DR MATTHEW HAY ON THE

glycerine, increased by the weight of the nitroglycerine known to be lost by
solution in the water into which it had been thrown, and which was calculated
from a solubility of 1 in 800, gave the total yield of nitroglycerine. The nitro-
glycerine before being used for any other purpose, as for analysis, was thor-
oughly shaken with successive quantities of distilled water until it was perfectly
pure. The first precipitation and washing was, I am satisfied, quite sufficient
to remove by far the largest part of the impurities, and the trace of these left
did not interfere to any noteworthy extent with the actual weight of the nitro-
glycerine. In certain cases I checked the weight of the raw nitroglycerine by
weighing the product after it had been thoroughly purified, and, again allowing
for loss by washing, according to the quantity of water used, I obtained almost
the same weights. A note of the time for which the mixture of the acids and
glycerine was allowed to stand before being thrown into water was always kept.

Figure . Weight of Nitric Weight of Time ; Yield of

Of Weight Acid. Sulphurie Acid. of Nitroglycerine,

Reference oe Standing

fa the par ceame. Strong. Fuming. Strong. Fuming. after Absolute.

| Various Grms. Si: = — = complete x Percentage.

Products. Grms. Grms. Grms. Gims. Mixture. Grms.
A. 12°4 mas 30 75 nes 10 mins.
B. 6:1 jurea,2 grms. 15 30 ae Stitt; an “ot
C. 10-4 30 urea, 1 grm. 30 a A» 1m, 16°3
D. 8:8 25 = furea,lSgrm-| 50) ba Spopes 9-486 | 107°8
E. 10°2 30 ee 60 3 Bee 16°71 163°8
EF, 10°8 30 oe 90 ee se 18°79 1756
G. 10°6 30 sn 90 eis OOo; 19°11 180-2
Hy: 9-4 be 20 20 20 BO Ay 19-06 202°7
i, 10:2 at 20 10 30 30g 18°80 184:3
J. 9°6 30 300 30 anys BO) 9s, 2°89 30°1
K. 10°3 tt 30 90 ae a et 23°40 2271
L. 10°5 is a0) b- 30 30 30)», 24:50 233°3
M. 10°25 B56 30 20 40 50S, 23°75 Jol
MN; 10:0 x07 30 60 Bi ou a 25°40 234:0

The specific gravity of each nitroglycerine was taken, and was found to vary
from 1°601 to 1°604, depending on the temperature. From this fact alone, of
the close agreement in specific gravity exhibited by the various products, it
might be fairly concluded that they were all one and the same body. Their
uniformity has, however, been more certainly proved by their all having been
ascertained to contain the same percentage of nitrogen.* Indeed, in whatever
way tested, whether as regards specific gravity, yield of nitrogen and of nitrous
acid, and behaviour towards solvents, they were all found to agree precisely.
The great difference in the amounts of the various products cannot therefore be
regarded as being due to a difference in the nitroglycerine. It seems to be
almost entirely caused by the differences in the quality and proportion of the

* Vide Hay and Masson’s Paper on “The Elementary Composition of Nitroglycerine.”

CHEMISTRY OF NITROGLYCERINE. 85

acids. The highest yield of nitroglycerine is that of N., where 234 parts of
nitroglycerine were procured from 100 parts of glycerine. Now, glycerine,
C,H,.(O0H);, ought theoretically to produce 246 per cent. of tri-nitrate of
glyceryl, C,H,.8(0.NO,). Making allowance for inevitable loss from
various intelligible causes, it may, therefore, be fairly deduced that the experi-
mental yield of nitroglycerine strongly favours nitroglycerine being regarded
as the tri-nitrate. If it were the tri-nitrite, C,H;.3(0.NO), the theoretical
yield would be 194 per cent.; if the di-nitrite, C,H;.HO.2(O.NO), 163 per
cent.; and if the mono-nitrate di-nitrite, C,H;.(O.NO,).2(0.NO), 211 per cent.
The actual yield very distinctly exceeds any of these.

With regard to the conclusions of practical and commercial importance
which may be drawn from these various methods of preparing nitroglycerine,
it is to be observed that there is a distinct advantage, as is generally recognised,
in employing fuming nitric acid (compare (F) and (G) with (K)); that where
fuming nitric acid is used, no benefit is to be obtained from the employment of
fuming sulphuric acid (compare (L) and (M) with (K) and (N)); that two parts
of ordinary sulphuric acid to one part of fuming nitric acid appears to give as
good a yield as any other proportion of acids, and quite as large a yield as
when more sulphuric acid is used (compare (N) with (K)); and that the yield

is not to any considerable extent increased by allowing the acids and glycerine |
to remain in contact for some time after mixture, as some chemists have
advised (compare (F) with (G), and (L) with (M)).

Characters of Nitroglycerine—I have been somewhat surprised to find
that a large number of contradictory statements exist as to the ordinary physical
characters of nitroglycerine. Whilst a few authors describe it as colourless,
by others it is referred to as a pale yellow oil, even in the most authoritative
modern works on Chemistry, as FeHtine’s Mewes Handworterbuch der Chemie*
and Bremsrem’s Handbuch der Organischen Chemie.t Now nitroglycerine is per-
fectly colourless when pure. As obtained from dynamite, it is certainly yellow,
but the colour is due to decomposition having taken place, which, I believe, is
to little or no extent spontaneous in character, but rather proceeds from the
presence of a little of the weak soda which is invariably employed in the manu-
facture of nitroglycerine for the purpose of removing the traces of the acids.
The soda neutralises the acids, but it at the same time decomposes the nitro-
glycerine, and imparts the colour so commonly ascribed to it as an inherent
property. Nitroglycerine washed with distilled water has in my possession
never become in the slightest degree coloured, even although kept in an open
capsule, freely exposed to the air, but away from dust, for two months; in
stoppered bottles it has not during the last seven months showed the least sign of
decomposition. Even in solution in water, or in alcohol, it keeps almost equally
well. More than one author states that it decomposes and becomes red on

Bo, ii Lene) + S. 529, 1881.

86 DR HAY ON THE CHEMISTRY OF NITROGLYCERINE.

being heated over the water-bath. I have heated pure nitroglycerine to the
highest possible temperature over the water-bath for four hours, and have
never observed the development of the slightest colour or decomposition.
When it decomposes under such circumstances it probably contains free acid
or alkali. Again, it is stated by Rartton* that when placed in the bell-jar of
the air-pump it rapidly undergoes decomposition. In the course of the investi-
gation by Mr Masson and myself, we have kept nitroglycerine for twelve days
in vacuo without its exhibiting the slightest signs of decomposition. The
decomposition of RarLron’s preparation must have been due to its impurity.

Nitroglycerine has no odour when cold, but emits a pungent odour when
heated. Although odourless in the cold, it nevertheless seems to be under-
going slight volatilisation; for after working with it for a short time, and without
directly touching it with the fingers, I have generally experienced its physio-
logical effect in a slight degree. Its taste is sweet, and not unlike that of
glycerine, but is more pungent.

As regards its solubility, 1 gram. dissolves in about 800c.c. of water ;
with difficulty in 3¢.c. of absolute alcohol, easily in 4c¢.c.; in 10°5¢.c. of
rectified spirit (sp. gr. 0°846); in lec. of methylic alcohol (sp. gr. 0°814); in
4c.c. of methylated spirit (sp. gr. 0°830) ; in 18 ¢.c. of amylic alcohol ; in every
proportion in ether ; so also in chloroform, in glacial acetic acid, and in carbolic
acid ; in less than 1c.c. of benzol; in 120c.c¢. of carbon bisulphide ; and to a
very limited extent, if at all, in glycerine.

Method of Estimating Nitroglycerine.—In cases where nitroglycerine
cannot be estimated gravimetrically after extraction with one of its solvents,
a method based on the evident constancy of the amount of the nitrous acid
produced in its decomposition with potash may be safely adopted. I have
made use of this method for ascertaining the degree of its solubility in water,
and for other quantitative estimations in the course of this investigation,
and it is not difficult to apply. The materials necessary are a standard
solution of pure nitrite of sodium (titrated with permanganate) of the
strength of 1 in 1,000,000, a well-boiled solution of starch and iodide of
potassium, dilute sulphuric acid, and pure potash, ascertained to be free from
nitrous acid. Heat the fluid containing the nitroglycerine with excess of
potash, and dilute with water until, in comparison with the standard solution of
nitrite of sodium, it yields a blue colour with the starch mixture and sulphuric
acid of precisely the same depth. From the degree of dilution required the
amount of nitrous anhydride present can be readily calculated, and this amount

eel de 10 ; ‘ F :
multiplied by 3.. 2 (33°48 being the percentage of nitrous anhydride yielded by
nitroglycerine) will give the quantity of nitroglycerine.

* Op, cit.

L870)

VI.—The Elementary Composition of Nitroglycerine. By Matturw Hay, M.D.,
and OrME Masson, M.A., B.Sc.

(Communicated by Professor Crum Browsx.)

Nitroglycerine is commonly described as the tri-nitric ether of glyceryl, and
the formula C,H;(O.NO,), is accorded to it. This theory of its composition
is based (1) upon its mode of formation; (2) upon the statement, made by
RAILToN, WILLIAMSON, and others, that it is decomposed by potash into
potassium nitrate and glycerine ; (3) upon several estimations of the nitrogen
which it contains, and one comparative estimation of its carbon. The second
argument cannot be accepted, as it has been shown by one of us that the
decomposition does not take place in the way stated;* and the analytical
results which have been obtained by the various investigators are so incomplete
and mostly so imperfect, and differ so greatly among themselves, that they
cannot be taken as affording any proof of the composition of the substance. It
seemed to us, therefore, desirable that some accurate estimations should be
obtained, not only of the nitrogen but of the carbon and hydrogen. A brief
résume of previous analytical results will show that this is the case. .

RaitTon,t in 1855, attempted to estimate the relative quantities of carbon
and nitrogen by Liepic’s method. The ratio of the volume of carbonic acid to
that of nitrogen required by the formula is 2:1. Rariron obtained results
varying from 2°156:1 to 1°912:1; so that, although they are on the whole in
favour of the formula, they cannot be regarded as satisfactory. He made no
attempt to estimate the carbon and hydrogen absolutely, as he found it
impossible to dry his nitroglycerine, even in an exhausted receiver, on account
of its great tendency to decompose. This proves that the substance was
impure, as we have found pure nitroglycerine to be perfectly stable in the air
and in vacuo.

WILLIAMson,{ in the following year, gave an account of the composition of
nitroglycerine, which agrees so exactly with Razron’s in every detail, that
there can be no doubt that their experiments were made in conjunction,
although published separately and without reference to each other.

Hess,§ in 1874, estimated the nitrogen in commercial nitroglycerine

* See the preceding paper : ‘‘ Contribution to the Chemistry of Nitroglycerine,” by MartHew Hay.
+ Ratton, Quart. Jour. Chem. Soc., vol. vii. p. 222,

~ Wuu1amson, Proc. Roy. Soc., vol. vii. p. 130.

§ Huss, Zeitschr. f. anal. Chen, 1874, S. 257.

VOL, XXXII. PART I. le

88 MATTHEW HAY AND ORME MASSON ON THE

obtained from various sources. He used different methods and got results
varying from 13:7 to 16°6 per cent., the percentage required by the formula of
elyceryl tri-nitrate being 18°5. From this he concluded that commercial nitro-—
elycerine contains the mono- and di-nitrate, as well as the tri-nitrate.

BECKERHINN,* in 1876, described an extremely elaborate method for the
estimation of the carbon and hydrogen, but gave no results.

Hess and Scuwas,t in 1877-78, made some nitrogen determinations by
Dumas’s method. In one sample they found 15°72 and 15:65 per cent., and in
another (from Nose.’s Zamky manufacture of 1872) they found 16°13, 16-12,
and 16°12 per cent., though this was the same liquid which four years earlier
had yielded Hess only 14:0 per cent.

SAvER and Apor,{ in 1877, estimated by three methods the nitrogen in nitro-
elycerine obtained from dynamite. First they used Reicuarpr’s modification
of ScHLoEsine’s method, after decomposing the liquid with potash, and obtained
from 12°3 to 14 per cent. Next they tried the ignition with soda-lime process,
but found that only 2 to 8 per cent. of the nitrogen was evolved as ammonia.
Finally they made four determinations by Dumas’s method, using nitroglycerine
obtained from three different samples of dynamite; and in this case they
obtained from 18°35 to 18°52 per cent., which agrees very closely with the per- _
centage calculated from the formula, but differs widely from that obtained by
Hess and Scuwas by the same method.

The nitroglycerine which we employed in our - analyses was made by adding,
drop by drop, one part by weight of Price’s pure glycerine to a mixture of two
parts of nitric acid (sp. gr. 1°49) and six parts of sulphuric acid (sp. gr. 1°84),
the mixture being surrounded with ice and kept at a temperature never
exceeding 10°C. Five minutes were allowed to elapse before pouring the
mixture into water ; and the precipitated nitroglycerine was then well washed
eight times with large volumes of distilled water, and dried for seven hours in
an air-bath at a temperature of from 70° to 80° C. Finally, it was allowed to
stand twelve days over sulphuric acid in the exhausted receiver of an air-pump.
Not the slightest sign of decomposition ensued ; and it was found that. the
nitroglycerine, after standing one week in vacuo, had lost less than one-tenth
per cent. of its weight, which shows that it was practically dry from the first.
It was perfectly colourless and transparent. Its specific gravity at 14°5C.
was 1°601.

The carbon and hydrogen were estimated by ignition in a tube closed and
drawn out at one end and filled with copper oxide and metallic copper in the
usual manner. At the termination of the ignition the drawn-out point was

* Beckerninn, Sitzgsber. Wien. Akad., Bd. xxiii, Abth. ii, S. 240.

+ Hess wv. Sonwan, Ber, Deutsch. chem. Gesellschft., Bd. xi, 8. 192.
¢ Saver w, Avor, Jbid., Bd. x. S. 1982.

ELEMENTARY COMPOSITION OF NITROGLYCERINE. 89

broken, and a stream of oxygen was passed through to ensure the complete
combustion of the carbon. In our first experiment the nitroglycerine was
weighed out in a short glass tube, and this was dropped into the combustion
tube; but an explosion occurred at an early stage of the ignition, which,
although damaging the furnace and slightly injuring one of us who happened
at the moment to be within a few inches of the tube, satisfied us that the
explosive force of the quantity of material employed (0°23 grm.) was not so
ereat as to prevent our continuing the experiments with the adoption of very
ordinary precautions. It was next attempted to burn the nitroglycerine in the
form of dynamite, using pure and previously ignited Kveselguhr as the
absorbent ; but this also gave rise to an explosion, though of greatly diminished
violence. Ultimately it was found that the combustion could be performed
without any risk of explosion by adopting the following method. A quantity
of the liquid (from ‘2 to ‘4 grm.) was weighed out in a porcelain boat con-
taining finely-divided copper oxide, and was then covered with another layer of
the oxide. The boat was dropped into the combustion tube, and its contents
were scraped out and well mixed up with the granulated copper oxide by
means of a long bent copper wire. . The tube was then filled up in the
customary manner. The chief difficulty attending this method is to avoid the
introduction of moisture by the copper oxide and consequent raising of the
hydrogen percentage. The precautions taken against this were increased in
each experiment, so that the last hydrogen determination is probably the most
reliable, while the first is considerably too high. All the combustions were
conducted with unusual slowness. The same means was employed for filling
the tube in the nitrogen determinations by Dumas’s method.

Calculated. Found.
“2 ; 15°86
Be a: ; 9:90 =
Ne . : ; 18°50 an oe we 17:93 17:97
a 63-44

Two nitrogen determinations were also made with the same nitroglycerine
before it had been placed im vacuo, and the results, though slightly higher,
hardly warrant the belief that there was any difference in the Gaeanostbion.
They were (1) 18:25 and (2) 18-06.

We consider that the above figures prove nitroglycerine to be glyceryl
trinitrate, the slight deficiency of nitrogen being possibly due to the presence

90 MATTHEW HAY AND ORME MASSON ON THE

of traces of impurities (oxidised derivatives of glycerine) irremovable by the
water with which the nitroglycerine was washed.

We have also estimated the nitrogen in other samples of nitroglycerine,
prepared with different proportions of acid, in order to ascertain whether a
difference in the method of preparation causes any corresponding difference in
the composition of the liquid. The results show that it is not so. In these
cases Dumas’s method was not employed, but a modification of ScHLOESING’s
process, which we have found to give equally good results, in spite of the
contrary experience of Hess and Scuwas and of SAvER and Apor.

The weighed quantity of nitroglycerine was dissolved in absolute alcohol
and decomposed by boiling for ten minutes with excess of an alcoholic solution
of caustic potash. Water was then added, and the whole of the alcohol was
driven off by evaporation ; after which the fluid was made up to a given
volume, of which a measured portion was taken for experiment. The volume
of nitric oxide evolved by the reducing action of the ferrous chloride and
hydrochloric acid (the reagents employed in ScHLOESING’s method) was, in each
case, compared with the volume of gas obtained under precisely the same
conditions of temperature and pressure from a standard solution of pure
potassium nitrate, aud also, in certain instances, of pure sodium nitrite; and
from these data the percentage of nitrogen was calculated. A correction is,
however, necessary, inasmuch as a small portion of the nitrogen is always
evolved as ammonia on boiling the nitroglycerine with potash. The amount
of this was determined in a preliminary experiment, as follows :—

1:1533 grm. of nitroglycerine was dissolved in 5 c.c. absolute .alcohol and
a solution of 1:5 grm. of potash in absolute alcohol added, the flask being
immediately connected with a modified BoussincAvuLt’s apparatus and then
boiled. After half an hour an equal volume of water was added, and boiling
then continued three-quarters of an hour more. The distillate was received
into standard acid; and, at the end of the operation, this was titrated with
standard soda. By this means it was found that 0053 grm. of ammonia had
been evolved ; so that nitroglycerine loses nitrogen during decomposition with
potash to the extent of 0°38 per cent. of its weight. This amount was,
therefore in each case, added to the percentage of nitrogen found by
ScHLOESING’s method.

In the following table the letters in the second column refer to the various
samples of nitroglycerine employed. A detailed description of their manu-
facture will be found in the preceding paper,* where they are lettered in the
same order. Experiment IX. was made with nitroglycerine obtained from
a NoseEL’s dynamite cartridge by displacement with water and desiccation over
the water-bath.

*

A Contribution to the Chemistry of Nitroglycerine,” by Matruuw Hay,

ELEMENTARY COMPOSITION OF NITROGLYCERINE, 91

No. of Nitroglycerine Percentage Corrected for loss Percentage

Experiment. Employed. Nitrogen found. of NH. Calculated,
I; A EGE 18:15
EE A 17-47 17°85
ITI. A 17°76 18:14
TRV. B 17°76 18:14

V. C 17°76 18:14 18°50

VI. F 17-41 agers)
Vii. J 17°81 LS*19
VILL N 17°73 18°11
IX, Nobel’s gerd 18°15

These figures agree closely not only with each other, but with those obtained
by us by Dumas’s method. Our analyses already given prove nitroglycerine
to be glyceryl tri-nitrate : these analyses render it highly probable that it is
invariable in composition, and that therefore the statements of some previous
investigators, particularly those of HEss, are erroneous. If nitroglycerine at
any time does contain the lower nitrates of glyceryl, it is probably owing to the
nitroglycerine having been very imperfectly washed in the process of its
manufacture. Nitroglycerine is only very slightly soluble in water ; glycerine
is freely soluble in water; and, reasoning from chemical analogies, it is highly
| probable that the intermediate nitrates possess intermediate degrees of
solubility, which will readily permit of their removal by an ordinarily complete
washing of the nitroglycerine with water, but may allow only of their partial
removal if a limited quantity of water is used. According, however, to the
published description of the various commercial processes for the preparation
of nitroglycerine, the washing appears to be sufficiently thorough to remove
the lower nitrates; for the amount of washing necessary to remove traces of
the free acid used in the manufacture of nitroglycerine is certainly quite
sufficient to dissolve out the lower nitrates.

VOL, XXXII. PART 1. ; Q

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VIL. — Report on the Tunicata collected during the Cruise of H.M.S.“ Triton” in
the Summer of 1882. By W. A. Herpman, D.Sc., Professor of Natural
History in University College, Liverpool. (Plates XVI. to XX.)

(Read 16th July 1883.)

This collection was sent to me for examination some months ago by Mr
Murray. It may be conveniently divided into two very natural groups :—

1. Ascip1AceA, including the forms dredged or trawled: from the bottom
of the sea.

2. THALIACEA, including the free-swimming pelagic forms captured by
the tow-net at or below the surface.

The small group of AscripIACcEA contains no Compound Ascidians, and only
two* of the four families of Ascidiae Simplices known are represented init. The
one of these families (the Cynthiidze) is represented by a single species only, while
the other (the Ascidiidz) contains the remaining three species, referred to the
two genera Ascidia and Ciona. One of those species of Simple Ascidians
_(Aseidia tritonis) is new to science, the other three are well-known British
forms.

This little collection of Ascip1acza is chiefly interesting (1) on account of
the depths at which the specimens were procured, and (2) on account of the
locality being one in which the Ascidian fauna had not been previously investi-
gated. Ascidia tritonis, though a new species, is not in any way aberrant or
strikingly peculiar, and hence, as far as the Simple Ascidians of the collection
go, the region explored by the “'I'riton” may readily be regarded as an exten-
sion of the British fauna.

The second group—the THALIACEA—is a very considerable collection, as may
be seen from the following list of the different localities. The most remarkable
circumstance in regard to it is that, with the exception of two specimens of
Salpa, the whole series is composed of one species, Doliolwm denticulatum, of
which between five and six thousand specimens were collected.

List of “ Triton ” THALIACEA.

1882.
August 3rd—4th. Surface. Doliolwm denticulatwm, about 100 specimens, 1 small one (2 mm. long).
Ath. Tow-net at a depth of 12 fathoms. Dol. denticulatum, 8 specimens, in absolute

alcohol.
» 4th—5th. Tow-net at a depth of 12 fathoms. Dol. denticulatum, about 1000 specimens; and
1 specimen of Salpa runcinata (aggregate form).

* See “ Postscript,” page 114.
VOL. XXXII. PART I, R

94

DR W. A. HERDMAN ON

August 5th (Station 2). Nets at the weights and trawl, 530 fathoms. Dol. denticulatum, about 1000

)

7th.
7th—8th,
8th.
9th.

”

13th—30th.
18th.

20th.

”
22nd.
22nd—23rd.
24th.
28th.

specimens ; also 6 specimens in absolute alcohol.

Surface. Dol. denticulatum, about 30 specimens.

Surface. FS 3 specimens, in absolute alcohol.

Surface. 3 20 specimens.

Tow-nets at a depth of 100 to 150 fathoms. Dol. denticulatum, 60 specimens ;
also 20 in absolute alcohol.

Tow-nets at trawl at a depth of 327 to 430 fathoms. Dol. denticulatwm, 20 speci-
mens.

Surface to 40 fathoms. Dol. denticulatum, 9 specimens.

Surface. Dol. denticulatum, 1 specimen; and 1 specimen of Salpa runcinata (soli-
tary form).

Surface. Dol. denticulatum, 1 large and 3 small (2-3 mm. long) specimens.

Tow-net at a depth of 40 fathoms. Dol. denticulatum, about 50 specimens.

Tow-net at a depth of 300 fathoms. Dol. denticulatum, about 40 specimens,

Tow-nets with 400 fathoms of line out. Dol. denticulatum, 75 specimens.

Tow-nets at a depth of 400 fathoms. Dol. denticulatum, 12 specimens.

Surface. Dol. denticulatum, 1 specimen, stained brown,

Tow-net at a depth of 40 fathoms. Dol. denticulatwm, about 50 specimens.

Tow-nets from surface to 400 fathoms. :, ime col0) >
Ps atadepth of 600 ,, 3 st 450 :
Tow-nets between surface and 40 ,, x 25 specimens.
Surface, at night. 2 75 Mi
Tow-nets at a depth of 40 fathoms. > 1 specimen.
Surface. z 50 specimens.
Surface down to 40 fathoms. “ about 40 specimens.
Tow-nets at a depth of 40 fathoms. 35 30 specimens.
Surface. Dol. denticulatum, 28 specimens, in osmic acid and absolute alcohol.
» about 100 2 picrie _
” » 180 ” osmic ”
3 ye LO, a chromic 3

Tow-net at a depth of 5to 10 fathoms. Dol. denticulatum, about 1200 specimens.
Tow-nets at a depth of 10 fathoms. Dol. denticulatum, about 150 specimens, in
chromic acid.
Tow-nets at a depth of 13 fathoms. Dol. denticulatum, 1 specimen, in chromic
acid.

Tow-nets at a depth of 12 fathoms. Dol. denticulatum, about 100 specimens, in
picric acid.

Tow-nets at a depth of 20 fathoms. Dol. denticulatum, about 100 specimens.

” 40 ” ” 200 ”
Tow-nets with 400 fathoms of line out. Dol, denticulatum, about 130 specimens.
Tow-nets at weights (Station 12), 580 fathoms. Dol. denticulatum, 50 specimens.
Surface. Dol. denticulatum, 100 specimens,

Surface down to 40 fathoms. Dol. denticulatum, about 100 specimens, one of
them small (3 mm. long).

Tow-net at trawl (Station 13), depth 570 fathoms. Dol. denticulatum, 20 speci-
mens.

Also, obtained during the cruise of the “ Knight Errant ”: —
August 10th, 1880, From a depth of 20 fathoms. Salpa zonaria, 10 specimens.

The localities of most of these dates, namely, 7, 7-8, 8, 9, 18, 20, 21, 29, and

THE ‘ TRITON ” TUNICATA. 95

30, are over the ‘‘ Wyvilie-Thomson” ridge, 7, 7-8, 8, 9, and 30 being towards
the NW. end, and 18, 20, 21, and 29 near the centre. 22 and 22-23 are
situated in the “cold area” near its southern end; while 24, 28, and 31 are
in the “warm area” near the SE. end of the ridge. 3-4, 4, 4-5, and 5 are
between the island of Rona and the southern end of the ridge.

OrpER I.—ASCIDIACEA.
Family CyNTHIID.

Polycarpa pomaria, Savigny (Pl. XVII. figs. 5 and 6).

I have referred a small specimen from Station 3 to this widely distributed
and apparently highly variable species. I have not examined a sufficient
number of specimens to be able to say much as to the range of variation from
my own experience ; but from a comparison of the descriptions of other inves-
tigators, it is obvious that this is one of those interesting forms out of which it
is possible to make either one or half a dozen “species,” according to the state
of one’s critical faculties. TrausTEpT* describes it as Styela pomaria, and gives
as synonymous Cynthia pomaria, Sav., C. coriacea, Alder, C. tuberosa, Macgill,
and Polycarpa varians, Heller ; while HELLERt suggests that Cynthia sulcatula
and C. granulata of Alder may also be varieties merely.

There can be little doubt that Savigny’s Cynthia polycarpa and C. pomaria
are merely varieties of the one species now known as Polycarpa pomaria,
Say. (=P. varians, Heller), and Cynthia tuberosa of Macgillivray is certainly
the same species; while Alder’s Cynthia sulcatula and C. granulata may
possibly be young individuals. But I cannot agree with TRAUSTEDT and
HELLER in regarding Cynthia coriacea, Alder and Hancock, as another variety.
The description in Alder’s Catalogue f states (1) that the ovaries are large and
white, and line the mantle with cylindrical convolutions, and (2) that the
branchial sac has about ten longitudinal folds, two important characters either
of which would be sufficient evidence to exclude the species from the genus
Polycarpa, while the second alone, if “ about ten” may be taken as meaning
more than eight, cuts it off even from the sub-family Styeline.

The Triton specimen, which is a small one (2 cm. in length, 1°6 cm. dorso-
ventrally, and 1:2 cm. in thickness), was trawled at Station 3 (8th August 1882,
at the NW. end of the Wyville-Thomson ridge, and north of the ‘‘ warm area,”
bottom s. sh.) from 87 fathoms. Viewed from the side, it is rudely quadrate

* Oversigt over de fra Danmark og dets nordlige Bilande kjendte Aseidice Simplices. Vidensk. Meddel,
Nat. For., Kjobenhayn, 1880, p. 415.

+ Untersuchungen tiber die Tunicaten des Adriatischen und Mittelmeeres, Abth. iii. p. 19, Wien, 1877,

{ Cat. Mar. Moll. Northumb. and Durham, Trans, Tynes. Nat. Field Club, vol. i. 1850.

96 DR W. A. HERDMAN ON

rather than hemispherical in outline, the anterior end being truncated and
almost as broad as the base of attachment. The most projecting point of the
anterior end is placed midway between the two apertures, which are far apart,
and distinctly upon the right side of the extremity (see Pl. X VII. fig. 5). Probably
on account of extreme contraction, they are also sessile, rather inconspicuous,
and irregularly lobed:

The test is thick, strong, and leathery ; greyish-white on the outer surface,
and white in section. At the posterior end it has several root-like prolonga-
tions from 1 to 1'2 cm. in length. The mantle is thick, strongly muscular, and
closely united to the inner surface of the test.

The branchial sac has eight very prominent folds, four upon each side. The
two dorsal folds on each side are more closely placed than the ventral ones,
and the clear spaces bordering the endostyle are considerably wider than those
beside the dorsal lamina. As the branchial sac of this species has never, so
far as I am aware, been figured, I give a view (Pl. X VII. fig. 6) from the inside
of a part showing two folds and the interspace in their natural relations, while
at the right-hand side another interspace is represented as more exposed by the
removal of the next fold. The sac isa very thick one, the folds being prominent,
the internal longitudinal bars numerous, and the stigmata comparatively small.
Occasional wider transverse vessels occur; in some places (see fig., t7) they
alternate regularly with three smaller ones (¢7’). Delicate membranes dividing
the meshes are only present here and there (¢r”). At the base of each fold
lies a series of large meshes (mh), each of which I found contained about
six stigmata. ELLER mentions meshes with ten to twelve stigmata each; I
found such only in the series adjoining the endostyle.

The simple tentacles are numerous and closely placed. The dorsal tubercle
is small and nearly circular in outline, being slightly elongated laterally. The
aperture is anterior, and both horns are coiled inwards.

The margin of the anus is expanded, and cleft into a number of blunt pro-
cesses.

The yellow polycarps and grey endocarps are so numerous as almost com-
pletely to hide the inner surface of the mantle.

Family Ascrprip/.
Ascidia tritonis, n. sp. (Plate XVI.).

External Appearance.—Shape ovate, flattened laterally, attached by posterior
half of left side, especially towards the ventral edge; anterior end rather
narrower than posterior but blunt. Dorsal edge slightly more convex than
ventral. Branchial aperture terminal, sessile, wide, lobes distinct. Atrial

THE “TRITON” TUNICATA. 97

aperture on dorsal edge, halfway from anterior to posterior end, sessile, wide,
indistinct lobed. Surface even and soft, but finely roughened all over. Colour
ereyish-brown.

Test soft, cartilaginous, not stiff; thin on right side, much thicker on left,
especially at the area of attachment, where it increases to 15 cm.; smooth and
glistening on inner surface ; clear and transparent in section. Vessels not con-
spicuous.

Manile.—Shape long and narrow; siphons long, especially atrial, which is
placed nearly halfway down the dorsal edge ; musculature strong on right side,
almost absent on left, where the mantle is thin and membranous; sphincters
moderately developed.

Branchial Sac rather delicate and not plicated. Transverse vessels alter-
nately larger and smaller, the larger ones with broad membranes hanging
from them. Internal longitudinal bars narrow, bearing large curved papill
at the angles of the meshes. Stigmata long and narrow, usually five in each
mesh.

Dorsal Lamina narrow, slightly ribbed transversely, and toothed on the
margin ; double for a short distance at the anterior end.

Tentacles numerous, of several sizes, some very long (up to 1°5 cm.), stout
at the base.

Dorsal Tubercle small, irregularly ovate in outline, aperture anterior, horns
not coiled.

Alimentary Canal not large, placed on the left side of the body about the
middle. Cisophageal aperture two-thirds of the way down the dorsal edge of
the branchial sac; stomach irregularly pyriform; intestine rather wide, and
forming a narrow loop.

Genitalia in intestinal loop. Sudrbatie vesicles extending over the greater
part of the intestine. Vas deferens wide and prominent, running along the
posterior and dorsal side of the rectum towards the atrial aperture.

Three large specimens and one small one of this new species of Ascidia
were obtained in the second haul of the dredge at Station 13 (81st August 1882,
in the centre of the “warm area”), from a depth of 570 fathoms, bottom ooze.
All of the specimens were more or less incrusted, especially upon the left side,
with fragments of sponges and worm tubes; one of them had a few specimens
of a small Tubularian zoophyte adhering, while the smallest individual had
several specimens of Anomia ephippium attached to its test.

The largest specimen is 13°5 cm. in length and 8 cm. in breadth, the smallest
5 cm. in length and 3 cm. in breadth. The remaining two are 9°5 cm. and
10°5 cm. respectively in length, while both measure 6°5 cm. across at the widest
point. In general shape, and especially.in the position of the atrial aperture

98 DR W. A. HERDMAN ON

(see Pl. XVI. fig. 1), this species shows resemblances to Ascidia lata* and
Ascidia meridionalis,t but it differs greatly from both these species in internal
structure.

The shape of the body when the test is removed (Pl. XVI. fig. 3) is remark- |
able on account of its great antero-posterior elongation, and the position of the
stomach and the intestine so far from the posterior end. The appearance
presented by the body when seen from the left side suggests that this peculiar
relation is caused by the branchial sac having extended posteriorly beyond the
stomach.

The muscular pad at the base of the branchial siphon, from the lower edge
of which the tentacles spring (Pl. XVI. fig. 6), is very strong. The tentacles
are large, and so numerous that their bases touch.

The dorsal tubercle (Pl. XVI. fig. 6) is peculiar, inasmuch as the left horn
is bifurcated ; however, this is very possibly merely an individual variation.

With the exception of Ascidia meridionalis, obtained during the “Challenger”
expedition at 600 fathoms, off the south-eastern coast of South America, the
present species was found at the greatest depth from which the genus Ascidia
has been recorded.

Ascidia virginea, O. F. Miiller (Pl. XVII. figs. 3 and 4).
= Ascidia sordida, Alder & Hancock, Cat. Mar. Moll. Northumb., &c.)

At first sight, and after a hasty examination, I was inclined to consider this
‘specimen as a new species, but after a more careful investigation of its anatomy
I prefer to regard it as merely an abnormally-shaped individual of Ascidia
virginea. If this form should be found to occur with sufficient frequency it
might be distinguished as variety pedunculata. I remember dredging a
similar individual a few years ago in the Firth of Forth, but cannot now
find the specimen in my collection.

The body is pyriform, shortly pedunculated, and attached by the posterior
end (Pl. XVII. fig. 3); it is slightly compressed dorso-ventrally. The anterior
end is narrow, but widens rapidly, especially on the right side ; the widest point
is reached at a little more than one-eighth of the distance from the anterior to
the posterior end. The anterior half is moderately swollen, the posterior
half is much narrower, and forms a short stalk. The apertures are both near
the anterior end, not distant, sessile, but conspicuously lobed. The surface
is rather irregular, but smooth ; it is somewhat incrusted by foreign objects.
The peduncle is slightly enlarged at its lower extremity to form a disc of

* HerpMan on British Tunicata, Linn. Soc. Jour., Zool., vol. xv. p. 277.
+t HerpMan, Report upon the Tunicata of the “Challenger” Expedition, part i, p. 207.

Se

THE “ TRITON ” *TUNICATA, 99

attachment. The colour is dirty grey. Length, 5 cm.; greatest breadth,
2 cm. ; thickness of peduncle, 1 cm.

The test is thin, except at the top of the peduncle, where it is considerably
thickened. The peduncle is solid, and formed of test alone. The vascular
trunks enter the test at the top of the peduncle.

When the test is removed the body has the appearance usual in Ascidia
virginea, and the mantle is in a normal condition, strongly muscular on the
right side, but thin and weak upon the left.

The branchial sac corresponds in all respects with what I have found in
other specimens of the species. It is longitudinally plicated to a slight degree,
has strong internal longitudinal bars with no papille, and square meshes with
five or six stigmata each.

The dorsal lamina is strongly ribbed transversely. The tentacles are
numerous, closely packed together, and of several sizes. Those of the first
order are long and slender. The dorsal tubercle is simple, and elongated
antero-posteriorly. The posterior three-fourths or so is enclosed in the small
peritubercular area, and the end is pointed. The aperture is anterior, and
the horns are not coiled (Pl. XVII. fig. 4). Ascidia virginea is one of the
most variable species known, in regard to the shape of the dorsal tubercle.*
The present form is rather simpler and more symmetrical than usual, and is
peculiar in having the posterior end pointed.

The single specimen was trawled off the Butt of Lewis, 25th August 1882,
depth, 40 fathoms.

Ciona intestinalis, Linn. (Pl. X VII. figs. 1 and 2).

Sixteen specimens of this common British species were in the collection sent
to me, four of them being preserved in absolute alcohol. They were all obtained
by the trawl at Station 3 (8th August 1882, at the north-west end of the
Wyville-Thomson ridge, and north of the “ warm area,” bottom s, sh.) from
a depth of 87 fathoms. This is the greatest depth known to me at which this
species has been found, but it is quite possible that it may have been obtained
in Scandinavian seas, or in the Mediterranean at greater depths, though I have
been unable to find records of such instances. The “Triton” specimens are
all of fair size, and as some of them are much corrugated it is probable that
they were large individuals when alive and expanded.

The tests are more colourless than is usual with shallow water specimens
from our own coasts, and have almost none of that dull green tint which may
generally be observed even after preservation in spirit. On the other hand,

* See Hzrpman, ‘‘On the ‘Olfactory Tubercle’ as a Specific Character in Simple Ascidians,”
Proc. Roy. Phys. Soc. Edin., vol. vi. session cx. p. 256, 1881,

100 DR W. A. HERDMAN ON

the red pigment spots at the branchial and atrial apertures and the pigment on
the aggregation of glands at the opening of the vas deferens are as bright and
conspicuous as is usual in the living animal. In one of the specimens preserved
in absolute alcohol, which was dissected, the inner surface of the test was found
to be closely ribbed longitudinally and less conspicuously so transversely. This
has been caused by the test having remained attached to the mantle during the
contraction of the latter, and having become impressed by the subjacent
strongly developed longitudinal muscles.

The papille at the angles of the meshes in the ‘iantial sac seemed
larger than is usual in the species, and were certainly much larger than those
represented by HEtLer* from a Mediterranean specimen. In some places
their length equalled the space between two neighbouring internal longi-
tudinal bars, so that when laid flat they stretched across the mesh.

I have observed considerable individual variation in the branchial sac of
this species. In 1881+ I noted a variability in the number of stigmata con-
tained in each mesh, and since then I have met with several other points in
which individuals differed. The specimens examined have been from various
parts of the British seas—the Firth of Forth on the east ; Lamlash Bay, Loch
Fyne, and the Sound of Mull on the west ; and Poole, Portland, and Dartmouth
on the south coast. I have also specimens from the Channel Islands, the
Chausey Archipelago, and the coast of Brittany, in addition to those collected
by the “Triton” in the North Atlantic.

I have very rarely seen the arrangement figured by Heiter { where the
meshes are represented as being greatly elongated transversely, and occupied
by two rows of extremely short stigmata. Usually the meshes are nearly
square, and are divided into two areas by a delicate transverse membrane,
which, however, does not generally interrupt the stigmata. This is shown at
tr” in fig. 2, where the membrane crosses the mesh, while the stigmata extend
behind. In the mesh below no transverse membrane is present, while
in fig. 1 three are seen, the central one being much the strongest. This
last arrangement was found to be very prevalent in the sac of the “Triton”
specimen examined. In some specimens the meshes, in place of being square,
are considerably elongated longitudinally—the reverse of the variation figured
by HeELLER—and the contained stigmata are very long and narrow. In this
case the meshes are always divided by from one to three transverse membranes.

The papillae upon the internal longitudinal bars appear liable to considerable
variations in their size and arrangement. In some cases they are present only
at the angles of the meshes, as shown in the lower part of fig. 2, and are then
all of much the same size. Where the meshes are divided there is usually a

* Untersuchungen tiber die Tunicaten des adriatischen Meeres, Abth. ii. Taf. iv. fig. 6, Wien, 1875.
t Jour, Linn. Soc., Zool., vol. xv. p. 332. t Loc. cit.

THE “TRITON” TUNICATA, 101

papilla placed at each point of intersection with the median or chief trans-
verse membrane (¢7” in the figs.) and the internal longitudinal bars. These
papille are usually rather smaller than those at the angles of the meshes,
but in some cases (as is shown in the upper part of fig. 2) the papillae may be
all of the same size. I have found the chief papille varying in size from a little
less than one-half* the breadth of the mesh to (in the case of the “ Triton”
specimen) the entire breadth. In fig. 1 the papillae have been omitted, in
order that the transverse membranes might be clearly seen.

Returning to the “Triton” specimen, the margin of the anus was expanded
and more deeply indented than is shown in HELuEr’s figure.t The oviduct was
found full of ova, some of which were also discovered in the peribranchial
cavity ; and the pigmented glands at the aperture of the vas deferens seemed to
form a larger and more conspicuous mass than usual.

Orpver II.—THALIACEA.

Both families of this order, the Doliolide and the Salpide, are represented
in the collection.

Family I.—Do.totw 2.

Doliolum denticulatum, Quoy and Gaimard (Pls. X VIII, XIX., and XX.).

The five or six thousand specimens of Doliolwm in the collection are, I was
astonished to find, all one form, and this I have identified with the sexual
generation of Doliolum denticulatum.{ This species was first described and
figured by Quoy and GaAtmaArp, the founders of the genus, in the zoology of
the voyage of the “ Astrolabe,”§ in 1835. It had been found in the Malay
Archipelago near the islands of Amboyna and Vanikoro. Sixteen years later
Hoxtey || published his observations made upon certain Tunicata during the
voyage of the “ Rattlesnake.” In this paper very considerable additions are
made to the knowledge of the structure of Doliolum, and the relations in

* Tn Heller’s figure they are about one-fourth of the breadth of the mesh.

+ Loe. cit., Taf. v. fig. 8. .

{ As will be pointed out in the following description, there are a number of details, especially in
the branchial sac, in which these “Triton” specimens differ from the accounts of Doliolum denticula-
tum given by Kererste1n and Exnurs (Zoologische Beitriige, 1861) and by GropBen (Arbeiten aus
dem Zoolog. Instit. der Univ. Wien, 1882). As, however, they agree with those authors’ descriptions
in the more important anatomical features, and as they could not be referred to any other known
species, I prefer to consider them as a variety of Doliolum denticulatum. It is improbable that they are
an undescribed species, since they are apparently so common in the North Atlantic. Doliolum den-
ticulatum is probably rather a variable form.

§ “ Voyage de découvertes de l’Astrolabe,”’ Zoologie, T, iii, pt. 2, p. 599; Atlas, Mollusques,
pl. Ixxxix. figs. 25-28. Paris, 1835.
|| “Remarks upon Appendicularia and Doliolium,” &¢., Phil. Trans. for 1851, part 2, p. 599, pl.
XVili, ;
VOL. XXXII. PART I. s

102 DR W. A. HERDMAN ON

which the genus stands to Sa/pa and Pyrosoma are pointed out. Huxtey’s
specimens had been obtained in the South Pacific between Australia and New
Zealand. During the next few years Kroun,* GEGENBAUR,t and LeucKkartT{
worked at the Pelagic Tunicata, but their efforts, and especially those of the
two former investigators, were mainly directed towards the elucidation of the
remarkably complex life-history of Doliolum, and the additions made to the
knowledge of the adult structure were comparatively few and unimportant.

KEFERSTEIN and Euters,§ during the winter of 1859-60, investigated several
Mediterranean forms of Doliolum, both as regards their anatomy and life-
history. As the chief subject of their observations was Doliolum denticulatum,
it has been of great advantage to have their description and careful figures
with which to compare the “Triton” specimens. No works of importance
upon Doliolum have appeared since, with the exception of ULrantn’s || and
GROBBEN’s‘ papers, published during the last two years. These are mainly
devoted to the development and life-history, which is now almost completely
cleared up. GRoBBEN, however, treats also of the anatomy and histology, and
to his memoir, as well as to that of KEFERSTEIN and EHLERs, I shall have to
refer in the following description.

Commencing with the body form, most of the “Triton” specimens are of
the characteristic barrel shape (see Pl. X VIII. figs. 1, 2, 3, 4, and 9), some of
them (as fig. 9, which was drawn from a specimen obtained August 4-5 from
12 fathoms) being rather wider than others. Some specimens, however (see fig.
10, which represents two specimens obtained on August 5th from a depth of 530
fathoms), are very different in shape, being narrow, elongated, and almost
cylindrical. At first I separated out a number of these forms, under the
impression that they were a distinct species from the barrel-shaped individuals,
but found afterwards, when examining their structure, that the two kinds
agreed perfectly in all the details of their anatomy. Since then I have found
various intermediate shapes between those shown in figs. 9 and 10, and have
consequently no hesitation in considering them all as one species. As a rule, I
find it is the specimens from considerable depths, and those which have been
closely packed in a tube or bottle, which diverge most from the typical barrel

* “Ueber die Gattung Doliolum,” &c., Archiv fiir Naturgeschichte, 1852, p. 53.

+ “Ueber die Entwicklung von Doliolum,” Zeitschrift fiir wissensch., Zoologie, 1853, Bd. v. p. 13;
and “Ueber die Entwicklungscyclus von Doliolum,” &c., Zeitschrift fiir wissensch., Zoologie, 1855,
Bd. vii. p. 283.

+ Zoologische Untersuchungen, Heft ii., “Salpen und Verwandte,” Giessen, 1854.

§ Zoologische Beitrage, iii., “ Ueber die Anatomie und Entwickelung von Doliolum,” Leipzig, 1861.

|| “ Ueber die embryonale Entwicklung des Doliolum,” Zoologischer Anzeiger, iv. No. 92, p.
472, and No. 96, p. 575, 1881; also “ Zur Naturgeschichte des Doliolum,” Zoologischer Anzeiger, v.
p. 429 and p. 447, 1882.

{| “ Doliolum und sein Generationswechsel,’ &c., Arbeiten aus dem Zoolog. Instit. der Univ.
Wien, &c., t. iv. h. 2, 1882.

THE “TRITON”. TUNICATA. 103

shape, hence it is probable that the abnormal form is due either to the
animal not having been killed suddenly enough or to imperfect preservation.
All of the “Triton” specimens, with the exception of the five small ones
mentioned in the list on page 93, are between 6 mm. and 12 mm. in length,
and most of them measure 1 cm. This size is apparently much greater than
that of Mediterranean specimens, as GROBBEN speaks of his as being about
2°5 mm., while KEFERsTEIN and Eaters figure one 3 mm. in length.

Most of the specimens are in ordinary rectified spirit, while a few have been
treated in each of the following methods :—.

1. Preserved in absolute alcohol.

. Put first into chromic acid solution and then into absolute alcohol.

. Preserved in a saturated solution of picric acid.

. Put first into solution of osmic acid and then into absolute alcohol.

. Put first into solution of picric acid and then into absolute alcohol.

. Preserved in solution of chromic acid.

These specimens were all in excellent condition for examination, and the
different methods appear to give almost equally good results. Perhaps the best
preparations for most histological points were obtained from the specimeris
preserved in chromic acid by thoroughly washing in alcohol, staining in picro-
carmine, and mounting in Farrant’s solution; while for some few special
points the specimens preserved in osmic acid solution and absolute alcohol
excelled.

The test is almost absent, being represented merely by a delicate structure-
less layer over the ectoderm, which covers the surface of the mantle. The
mantle contains the muscular bands or hoops, which, in this form, are eight
in number (m' to m*® in the figs.). The first and last of these bands form
sphincters for the apertures, and usually appear to terminate the body anteriorly
and posteriorly, as shown in Plate XVIII. fig. 4, the delicate denticulated
margins of the branchial and atrial apertures being almost invariably turned
in or directed across the opening. This denticulated margin was turned out
in the chromic acid specimens examined, and was more perfectly preserved
than in any of the others. It is divided into twelve lobes around the branchial
aperture and ten around the atrial. The muscle bands are composed of very
long non-striped fibres, closely and regularly placed, as shown in Plate XVIII.
fig. 6. Sometimes, as in fig. 5 (from a picric acid specimen), the fibres are
thrown into undulations.

The wide branchial aperture leads into the branchial siphon, which, as there
is no diaphragm and no circlet of tentacles, may be considered as extending back
to the peripharyngeal band. This band, in all the specimens which I have
examined, runs in most of its course between the 2nd and 3rd muscle bands, or
in the 2nd intermuscular space (Pl. XVIII. fig. 11, p.p), and marks the anterior

SO OF BP OD LY

104 DR W. A. HERDMAN ON

end of the branchial sac, which extends back usually to between the 5th and
6th muscle bands. GRroBBEN, however, describes and figures* the peripharyngeal
band as lying in the 1st intermuscular space. KEFERSTEIN and EHLERS also
representt the branchial sac as extending anteriorly into the Ist intermuscular
space, an arrangement which I have been unable to find in the “Triton”
specimens.

The arrangement of the stigmata is as follows :—A series commences on
each side of the median dorsal line, close behind the 3rd muscle band (see
Pl. XVIII. figs. 8 and 11, sg), and extends posteriorly for a variable distance
—usually to about the 6th muscle band. The stigmata in this series differ
greatly in size among themselves. The most anterior one is very short—in
fact, almost circular. The next three or four increase rapidly in length till
the level of the nerve ganglion (.g.) is reached, and then the increase becomes
less marked. Towards the posterior end there is a slight diminution in size.
Considered asa whole, the two series of stigmata diverge somewhat posteriorly,
so that the space between them in the dorsal middle line is narrow in the 3rd
intermuscular space, the region of the ganglion, but widens posteriorly (PI.
XVIIL. fig. 11). As a result of this arrangement, when the branchial sac is
seen from the side, the dorsal series of stigmata appear to slope downwards and
backwards from the region of the ganglion (see PI. X VIII. fig. 4). There is also
a series of stigmata upon each side of the ventral median line. These, how-
ever, do not extend so far anteriorly as the dorsal series do. They commence
behind the 4th muscle band, near the posterior extremity of the endostyle,
and extend backwards, increasing in length rapidly at first, and then maintain.
ing their size till they come to the sides of the cesophageal aperture. Here
they commence to curve dorsally, and then towards each other, finally uniting
in the dorsal middle line, usually near the 6th muscle band, so as to forma curve
surrounding the membranous area in which the cesophageal aperture is placed
(see Pl. XIX. fig. 10, sg).

The membranous side wall of the branchial sac is very wide anteriorly,
where it extends from the endostyle almost to the ganglion dorsally. In the
4th intermuscular space it is encroached upon by the development of the
ventral series of stigmata, and as it is traced posteriorly from this point, it
becomes narrower and narrower, till finally it merges upon each side into the
median dorsal area through the failure of the dorsal stigmata. The exact
number of stigmata in the different series varies of course according to the
size of the individual. In mature specimens there are usually from thirty
to fifty in the dorsal row on each side, and about thirty as an average in each
ventral series.

* Loc. cit., p. 13, woodcut, and pl. i. fig. 1, wb.
+ Zoologische Beitrdge, pl. ix. figs. 1 and 2.

THE ‘“‘ TRITON” TUNICATA, 105

A glance at Plate [X. of Kerrerstern and Enters’ work suggests that the
specimens there figured may have been young, and the number of stigmata
shown (thirteen to fifteen in the dorsal row) is just about the number present
in the smallest “Triton” specimens (2 mm. long). Perhaps this may also
account for the great anterior extension of the dorsal rows of stigmata which
are represented as reaching in front of the 2nd muscle band, while in the
“Triton” specimens they were never seen in front of the 3rd (see Pl. XVIII.
figs. 8 and 11). The ventral band, containing fifteen stigmata, is shown by
KEFERSTEIN and EHLERS extending to the front of the 3rd intermuscular
space, while in all the specimens which I have examined, it has terminated
some place in the 4th intermuscular space. GRoBBEN* speaks of forty-two as
the largest number of stigmata upon each side which he observed, KEFrERSTEIN
and ExLerst say that the number may vary from twenty-six to forty-three,
while the usual number in the “Triton” specimens was about seventy !
GROBBEN also describes and figures{ the series of stigmata as extending exactly
one intermuscular space further anteriorly than I found to be the case. As
they appear always to terminate posteriorly in the neighbourhood of the 6th
muscle band, it is obvious that there must be a greater number of stigmata in
each intermuscular space in the “ Triton” specimens than in those from the
Mediterranean, and a comparison of my figures on theone hand, with those of
GROBBEN and of KEFERSTEIN and EHLERs on the other, shows that this is the
case.

The bars separating the stigmata are covered in the usual manner with
ciliated cells placed in such a position that the cilia project across the
stigmata. These cells are not placed in a single row, as a surface view of the
branchial sac such as that shown in fig. 2, Plate XIX. might lead one to
imagine, but are placed in groups of four or five elongated cells placed closely
side by side§ (see Pl. XIX. fig. 3). This arrangement can only be made out
by viewing the bar upon which the cells are placed from the interior of the
stigma. An osmic acid preparation showed with a Zeiss ;4,-in. oil immersion
objective that these cells were nucleated and nucleolated, and had a striated
band upon the free edge, from which the cilia project (Pl. XIX. fig. 4). At the
rounded ends of the stigmata the ciliated cells are very numerous, forming
many rows. They also change their character (see Pl. XIX. fig. 2), and become
cubical, spherical, or polygonal in shape.

The endostyle is always a well-marked feature in the ventral middle line
of the branchial sac. It extends from midway between the 2nd and 8rd
muscle bands anteriorly (Pl. XVIII. figs. 7 and 11, en) to somewhere in the

7 Lae cit., p. LG. + Loe. cit., p. 57. t Loe. cit., p. 16, and pl. i. fig. 1.
§ Grossen has figured a similar arrangement in the case of the asexual forms of the same species
(Loe. cit., pl. v. figs. 34, &c.).

106 DR W. A. HERDMAN ON

4th intermuscular space posteriorly. KeErerstein and EHLERS represent it as
extending rather further anteriorly, but terminating at the 4th muscle band
posteriorly ; while in GrosBeEn’s figures it commences as in mine, but terminates
in the 3rd intermuscular space. At its anterior extremity the endostyle is
joined by the ventral ends of the two peripharyngeal bands (see Pl. XVIII.
figs. 7 and 11), while posteriorly it is continued into a membrane with a free
projecting edge which runs backwards over the heart, and then round the left
hand side of the cesophageal aperture (Pl. XIX. fig. 10, mb). The histology of
the endostyle has been minutely described by GroBBEN (loc. cit.).

The prebranchial zone, the region anterior to the peripharyngeal band, is
covered by squamous epithelium. In osmic acid preparations the protoplasm
in these cells is found to have become contracted and aggregated around the
distinct nuclei, so as to present the appearance, shown in Plate XIX. fig. 6,
of stellate cells united by their processes to form a network.

On the surface of the peripharyngeal band this epithelium has become
modified into long fusiform cells (Pl. XIX. fig. 5) all placed with their long axes
directed along the band. When not so highly magnified, or not stained
properly, they give rise to the appearance shown in Plate XVIII. fig. 13. The
dorsal ends of the two peripharyngeal bands meet, but at this point they are
twisted round so as to form a double spiral towards the right, the left hand
band performing one and a half turns, and the right a single turn only. This
arrangement is shown in figs. 8, 11, and 12 on Plate XVIII., and at once
suggests the form of the dorsal tubercle found in a similar position in the
Ascidiacea, That organ is represented, however, in Doliolum, not by the curved
dorsal part of the peripharyngeal band which has been described, but by the
anterior end of the deeply funnel-shaped depression indicated by .a in figs. 8
and: 12.*

The part of the prebranchial zone which is enclosed by the dorsal spirals’ of
the peripharyngeal band has its epithelium modified into large polygonal cells,
the outlines and nuclei of which are strongly marked. In the preparation from
which fig. 7 on Plate XIX: was drawn, the protoplasm in most of the
cells was aggregated around the nucleus in a stellate form.

The nerve ganglion is placed in the mantle, and indicates the median dorsal
line. It is small, but very distinct from its opacity. It is usually rudely cubical
or nearly spherical in shape, and gives off four large nerve trunks, two at its
anterior and two at its posterior angles, besides smaller nerves between. It
usually lies a short distance behind the 3rd muscle band, as shown in figs. 8

* Possibly the cavity (v.a in the figures) represents merely the opening of the duct from the
neural gland into the dorsal tubercle of the Ascidiacea, while the spirals (d.t, in Pl. XVIII. fig. 11)
indicate the sense-organ, which I believe the dorsal tubercle to have formerly been (see Proc, Roy.
Soc. Edin., p. 144, 1882-83, : - :

THE “TRITON” TUNICATA. 107.

and 11 on Plate XVIII., but may be further back as represented by KEFERSTEIN
and Enters in their pl. ix. fig. 1. It may advance forward, so as to touch
the 3rd muscle band (see Pl. XIX. fig. 1), but is never found outside the 3rd
intermuscular space.

The ganglion is very opaque, and it is difficult to make out its constitution.
Fig. 8 on Plate XTX. shows its anterior end with four nerves, two large and
two small, arising from it. GroppEn * has apparently not noticed the smaller
pair (Pl. XIX. fig. 8, v’), but he describes a median anterior nerve which I could
not find in any of my specimens, unless it be the nerve shown at n in Plate
XVIII. fig. 12, which is drawn from an individual having apparently only
three anterior nerves. As in other Tunicates, where the matter has been
investigated, the nerve cells are all in the outer layers of the ganglion, and the
centre is formed of a mass of delicate interlacing fibres and granular matter.
Fig. 12, Plate XIX., shows this arrangement well. The nerve cells are
ovate, unipolar, bipolar, or multipolar, rarely the latter. They are finely
granular, and have distinct nuclei and nucleoli (see Pl. XIX. fig. 13).

On the ventral surface of the ganglion there lies a dark mass which must be
the neural gland, but of which I was unable to make out the structure definitely.
It gives rise anteriorly to a very delicate duct which runs directly forwards to
open at the prebranchial zone into the funnel-shaped depression mentioned
above (see Pl. XVIII. figs. 8 and 12). This duct is wide where it emerges from
below the ganglion, and its wall is formed of distinct polygonal cells (see Pl.
XIX. fig. 8 2.d). It rapidly narrows, however, as it runs forwards, and the
cell elements lose their distinctness, so that in the part immediately in front
of the 3rd muscle band (Pl. XVIII. fig. 8, xd) it is very difficult to make
out any structure in the wall. In front of this point it again becomes more
distinct, and the cells vary from fusiform to squamous in their character (PI.
XIX. fig. 9, n.d) up to the point where the duct joins the funnel-shaped de-
pression.

The length of this neural duct varies with the positions of the ganglion and
of the aperture in the prebranchial zone. The normal arrangement is shown in
figs. 8 and 11, Plate XVIII., while in fig. 1, Plate XIX., it is abnormally
short, on account of the unusual position of the ganglion. The aperture
in the prebranchial zone is always placed in the median dorsal line upon the
most anterior point of the spirals formed by the peripharyngeal band, and
therefore in the 2nd intermuscular space. GRoBBEN and also KEFERSTEIN and
EHLERS figure it in the 1st intermuscular space, an arrangement which I have
never seen. Although the peripharyngeal bands encroach upon the Ist inter-
muscular space at the two sides (see Pl. XVIII. fig. 11), they always, in the
specimens which I have examined, dip posteriorly at the ventral and dorsal

Loe, seit.spa 9

108 DR W. A. HERDMAN ON

ends, and hence the anterior end of the endostyle and the dorsal spirals come
to be situated in the 2nd intermuscular space.

The aperture in the prebranchial zone is small, and leads into a funnel-
shaped cavity continuous with the neural duct (Pl. XIX. fig. 9). At the posterior
narrower end of this cavity, the flat cells lining the duct become gradually
cubical and then low columnar, and bear each a long cilium which projects into
the centre of the cavity, and is directed posteriorly, This funnel-shaped
cavity is apparently merely the aperture of the neural duct. I have searched in
vain for any trace of a sensory apparatus. In several specimens I have suc-
ceeded in tracing one of the smaller nerves given off from the anterior end
of the ganglion in its entire course forwards (see Pl. XVIII. fig. 12, »). It
runs alongside the duct and close to it, but passes the funnel-shaped cavity
upon its left side without giving off any branch, and continues its way
anteriorly to supply the lobes around the branchial aperture.

The heart is situated on the ventral surface of the posterior end of the
branchial sac, just between the termination of the endostyle and the cesopha-
geal aperture and in the posterior part of the 4th intermuscular space
(Pl. XIX. fig. 10,2). In chromic acid specimens the transverse muscle bands
of the wall of the heart were well shown (see Pl. XIX. fig. 11), but each band
appears to me to be composed of a large number of very fine fibres placed side
by side, and not of one fibre only as supposed by KEFERSTEIN and EHLERS.*

The alimentary canal, omitting the pharynx or branchial sac, which has
been already considered, consists of cesophagus, stomach, and intestine, and
forms a curved tube, lying mainly in the 5th and 6th intermuscular spaces
(Pl. XVIII. fig. 4).

The cesophageal aperture is placed at the posterior r end of the branchial sac
in the middle line, and nearer to the ventral than to the dorsal surface. It
lies in the membranous area prolonged back from the region around the
posterior extremity of the endostyle (Pl. XIX. fig. 10), and is surrounded
laterally and dorsally by the posterior end of the ventral series of stigmata.
This is a notable point, since it is usual in the Ascidiacea for the oesophageal
aperture to be placed on the dorsal edge of the sac, and invariably so amongst
Ascidize Simplices, in some of which it is placed nearer to the anterior than
to the posterior end of the dorsal edge.

The cesophageal aperture is surrounded by a membranous rim, which on its
left anterior edge is continued forwards to join the posterior extremity of the
endostyle, while at its other end, after surrounding the aperture (see Pl. XIX.
fig. 10, mb), it is continued as a spiral ridge into the cavity of the cesophagus.
The cesophagus is short, and leads downwards and backwards to the anterior
end of the large irregularly quadrangular stomach (Pl. XX. fig. 1, sé). From

* Loc, cit., p.-58,

THE “TRITON” TUNICATA. 109

the posterior end of this the short curved intestine emerges. The stomach
lies in the 5th intermuscular space, and the intestine runs backwards till it
almost or quite reaches the 7th muscle band, and then turns dorsally and to
the right, and finally runs forwards to terminate in the anus placed in the 5th
intermuscular space, over the stomach (Pl. XVIII. fig. 4). According to
KEFERSTEIN and EnLers the anus is situated at the posterior part of the 5th in-
termuscular space, or upon the sixth muscle band, while according to GROBBEN
it lies in the 6th intermuscular space. Huxtey figures it in the fifth inter-
muscular space. The epithelium lining the intestine is polygonal in surface
view (Pl. XX. fig. 4) and very distinctly nucleated. In the wall of the stomach
the cells are columnar and more darkly coloured.

Two glandular systems, which seem to be quite distinct, are found in
connection with this alimentary canal. First, along the ventral surface of the
stomach, especially towards the pyloric end, and more or less scattered over
the first portion of the intestine, may be found masses of rather darkly coloured
glandular-looking czeca (see Pl. XX. fig. 1, g/). These branch and apparently
anastomose occasionally, forming rude networks, but the branches are short
and stout, and the meshes small and irregular. No duct or opening into the
alimentary canal was visible. With a higher magnification the ceca present
somewhat the appearance shown in Plate XX. fig. 5—masses of cells rounded
or polygonal in outline, but rarely angular, having small indistinct nuclei and
granular cell-contents. These clumps of branched ceca have apparently not
been noticed previously, as I find nothing in the published descriptions and
figures which could represent them.

The second glandular apparatus is the system of fine clear-walled tubules
ramifying over the intestine, which was first pointed out in Doliolum by
HUXtLey,* and has since been more or less completely described by Leuckarr,
GEGENBAUR, KEFERSTEIN and Enters, and GropBen. It has also been recently
investigated by CHANDELONt in Perophora and Salpa, where it has very much
the same arrangement as in Doliolum. CHANDELON comes to the conclusion
that the system can be compared neither with a kidney nor a liver, but
that it is probably a digestive gland of some kind.

In the specimens which I examined this system appeared generally well
developed, although it was sometimes difficult to make out, owing to the
opacity of the alimentary canal caused by its food contents. In Plate XX.
fig. 1, d indicates the duct of this system, which is a clear-walled, almost
transparent vessel, entering the pyloric end of the stomach. From this point
it may be traced upwards and backwards (Pl. XX. fig. 1, represents a specimen

* Phil. Trans., 1851.

+ ‘‘Recherches sur une annexe de tube digestif des Tuniciers,” Bulletins de V Academie Royale de
Belgique, 2™° ser. t. xxxix. No. 6, 1875.

VOL. XXXII. PART I, T

110 DR W. A. HERDMAN ON

in which the intestine has been turned ventrally so as to expose the whole
alimentary system) to about the middle of the intestine. At this point the
duct divides, and its two branches run over the wall of the intestine, subdivid-
ing as they go. The twigs branch freely and sometimes anastomose (Pl. XX.
fig. 3). Many of them end in short cecal projections, and in some cases these
are enlarged to form terminal knobs (see Pl. XX. fig. 3, ¢), which may contain
irregularly rounded bright bodies (concretions ?) similar to those described eee
CHANDELON in Pevophora.

The wall of the main duct is lined by regularly arranged fusiform cells
placed with their long axes parallel to the length of the duct (Pl. XX. fig. 2),
The tubules on the intestine are lined by flattened epithelium bulging into the
lumen where the nuclei occur, and enlarged into cubical cells in the terminal
knobs.

The apertures of the reproductive organs lie at the posterior end of the
body behind the alimentary cunal, and usually in the 6th intermuscular space.
All the “Triton” specimens of Doliolum denticulatum examined belong to the
sexual generation, KrrersTEIN and EHLers’ “generation A,” and have both
male and female organs well developed.

The ovary is an ovate mass placed usually in front of the 7th muscle band
(Pl. XX. fig. 7, ov), but occasionally behind it (Pl. XX. fig. 6, ov). Ova of
different sizes were almost always distinctly visible in it (Pl. XX. fig. 1, g, and
fig. 13, ov). It opens on its dorsal edge into the atrial cavity.

The testis, as Huxuey~* first correctly described, is in the form of a greatly
elongated tube, usually nearly as long as the body, terminating posteriorly on
the anterior face of the ovary, and extending forwards for a variable distance
with rather an irregular course (Pl. XX. figs. 6, 7, &c.,and Pl. XVIII. figs. 1-4).
At its posterior end, where it abuts against the ovary, it turns dorsally,
forming a tube which may be called the vas deferens, and opens into the atrial
cavity (Pl. XX. figs. 13 and 14, «d.).

- The anterior end of the testis is very variable. NJEFERSTEIN and EHLERS
state that it may terminate any place between the 3rd and the Ist inter- —
muscular space, and they figure it at the posterior end of the 3rd in one case
and the anterior end of the 4th in another. GRoBBeEn states that it extends
‘orward to the 4th muscle band, while Huxtey figures it as reaching nearly to
the 1st. In most of the specimens which I have examined the anterior end is
placed close to the 2nd muscle band, as shown in Plate XX. figs. 6 and 9. No
previous investigators, so far as I am aware, either describe or figure the extra-
ordinary variability in form of this anterior end of the testis. A glance at
figs. 6, 7, 8, 9, 10, and 11 on Plate XX. shows the extent of this variability.
In fig. 6 the tube becomes rapidly smaller opposite the 3rd muscle band, —

* Phil. Trans., 1851, part ii. p. 602.

THE “TRITON” TUNICATA. 111

and, after a short undulating course as a very fine tubule, enlarges into a
pear-shaped dilatation extending to the 2nd muscle band. In fig. 9, which
is drawn on a larger scale, there are two dilatations on the narrow part of the
tube, while in fig. 11 the narrow part is long and convoluted, and extends
forward to the 2nd muscle band. In fig. 10 the testis reaches the 2nd
muscle band without any diminution in its calibre, and then, narrowing slightly,
forms a loop extending almost to the 1st band, after which it curves back to-
wards the 2nd, and ends in a narrow filament. The two remaining cases figured
are the most remarkable of all. In fig. 8 the tube narrows rapidly opposite
the 3rd muscle band, and from this point forwards almost to the 1st it remains
very narrow, but with two large ovate dilatations and several smaller ones upon
its course. Fig. 7 shows a case where the wider tube extends to the 2nd
band and then suddenly narrows, but the fine tubule, in place of running
forwards, turns posteriorly, and eventually reaches the 4th muscle band after
passing through several irregular dilatations, Throughout, this male system
was filled with minute granular cells (Pl. XX. fig. 12), but no distinct sper-
matozoa could be made out.

The most remarkable feature of this “ Triton ” collection of Doliolide is, that
such vast numbers should prove to be entirely one generation of the same
species, and all, with a very few exceptions, of much the same size. Questions
naturally arise such as, Where have they come from? Where are the asexual
forms from which they have been produced? and Why are such quantities of
that species found in that locality at that time? We are not yet in a position
to answer any of these questions fully. Mr Murray tells me that when
captured, they were all drifting from the south-west to the north-east. This
would carry them from the “‘ warm area” across the “ Wyville-Thomson ” ridge
into the “ cold area,” but what part of the Atlantic they came from, or how far
north they are carried, is not known. Mr Murray states that “they were
abundant during the whole time of the cruise, except when we touched upon
the Faroe bank water.” As far as I can judge from the numbers of specimens
in the tubes collected on the different days, the configuration of the bottom
and the division of the region explored into “warm” and “cold” areas has
no effect whatever upon the abundance of the Doliolide. There are large
quantities of specimens in the collection from the 3rd to the 5th August,
halfway between Rona Island and the south-east end of the ridge; on the 29th
August, over the centre of the ridge; on the 28th and 31st August, in the
“warm area ;” and on 20th to 23rd August, in the “cold area.” The region
from which the smallest numbers have been brought back are those explored
on the 7th to the 9th August at the north-west extremity of the ridge.

Mr Murray has kindly supplied me with the following extracts from his

112 DR W. A. HERDMAN ON

journal, which bear upon the abundance of the Doliolide at different times, and
relatively to other surface forms :—

“ August 5, 1882.—Doliolums were quite as abundant to-day as yesterday;
they appeared to be chiefly about 10 fathoms beneath the surface. Diatoms
in the stomach as usual. The immense mass of these in this portion of the sea
at this time is very astonishing.

“The last year (1880), in the “Knight Errant,” the most characteristic
thing in the surface gatherings was the enormous multitude of Acanthometre,
and now these are almost absent.

“ August 7.—There- was quite a change this morning in reference to the
general character of the tow-net gatherings. The Doliolums had quite dis-
appeared, and Acanthometre were now very abundant, and the most charac-
teristic animals.

“In the afternoon, after we had moved south from the Faroe Bank, we got
again the same surface animals as yesterday and the day before, viz., vast
numbers of Doliolums, some Medusze, larvee of Medusee or other Ccelenterates
and Copepods. .

“This is a somewhat remarkable change, and would perhaps indicate a |
current of water from a different source than the more northern water of this
morning. .

“ August 18—The Doliolums also were observed to be phosphorescent,
emitting electric-like discharges which were divided like forked-lightning, and
appeared to me to follow the direction of the nervous cords or filaments... .
Doliolums and Actiniz were again abundant throughout the day, sometimes in
enormous abundance.

“ August 24.—There are no Doliolums, and only a few Arachnactis in the ©
nets this morning, from about 30 or 40 fathoms. ... . Doliolums were got in
some hauls at a depth.of 10 fathoms during the day.

“ August 29.—There were a large number of Doliolums on thé surface
during the day, indeed they masked all the other things in most of the hauls,
In general, the Doliolums were most abundant about 5 or 6 fathoms beneath
the surface.

“ August 30.—During the day, in the tow-nets at and near the surface,
Doliolums and Arachnactis were most abundant, filling the nets each time.

“It is remarkable that in the tow-nets, at the weights, there were not over
one or two Doliolums, but many Copepods, apparently Arctic forms, &ec.

“In summary, Doliolums most abundant, masking all the other things for
weeks. At times the Doliolums appeared to be in vast banks, where they

were very numerous; between these banks there were always a few
stragglers. J. M.”

THE “ TRITON” TUNICATA. £5

Family I1.—Sa.pip-.

During the “Triton” expedition only two specimens of Salpa were obtained,
but curiously enough these show the two conditions—solitary and aggregated
—of the same species, Salpa runcinata. In August 1880, during the cruise of
the “Knight Errant” in the same neighbourhood, some large specimens of
Salpa zonaria were the only Tunicata captured.

Salpa runcinata, Chamisso.

1. Solitary form. One specimen, measuring 2'2 cm. in length, was obtained
on the surface on the 18th August 1882.

2. Ageregated form. A single member of a chain was captured in the
tow-net at a depth of 12 fathoms, 4th—-5th August 1882.

This is the Salpa fusiformis of Cuvier, and has the body prolonged both
anteriorly and posteriorly beyond the branchial and atrial apertures into long
tapering appendages. The body proper measures 1°5 cm. in length and 1 cm.
in breadth, while the anterior appendage extends beyond the branchial aper-

ture for 1:4 cm., and the posterior appendage beyond the atrial aperture for
1°7 cm.

Salpa runcinata is a well known Scandinavian form, and has been obtained
in British seas before now. Early inthe present century, Dr Jonn MAccuLLocH
described (Western Isles,* vol. ii. p. 187) and figured, under the name of
Salpa monilifornis, a form which may have been the aggregate condition of S.
runcinata. He found the chains occurring in abundance in autumn in the
harbours of Canna and Campbellton. In the spring of 1821 Dr FLemine found
many chains a foot and more in length upon the Caithness coast ; and about
thirty years later Professor Epwarp Forses identified with Salpa runcinata,
both solitary and aggregated, some specimens captured by Lieutenant THomas,
R.N., in the Orkney Seas. In 1868 Professor M‘INrosut came upon vast quan-
tities of both the solitary and the chain form of Salpa runcinata upon the east
shores of North Uist, im company with both forms of Salpa spinosa, Otto, a
species which ForseEs had predicted would probably be found in the Hebrides.

Salpa zonaria, Chamisso.

Ten specimens of this form were obtained in the tow-net, at a depth of 20
fathoms, on 10th August 1880, during the cruise of the “KnightErrant.” The
specimens are well preserved, and are all about 4 cm. in length.

* See Forses and Hanuzy, History of the British Mollusca, vol. i. p. 50, 1853.
+ See Jour. Linn. Soc., Zool., vol. ix. p. 41.

114 _DR W. A, HERDMAN ON

POSTSCRIPT.

Since the above was written, I have received from Mr Murray another -
“Triton” specimen. This necessitates the following addition to my report —
which should be inserted between “ Ascidiacea” and “ Family Cynthiide,” near
the top of page 95 :—

Family MoLeuLip-.

Eugyra glutinans, Moller.

A single specimen of this widely distributed species was obtained in the
second haul of the trawl on the 22nd August 1882, at Station 8 (in the “ cold
area,” near the S.E. end of the ‘‘ Wyville-Thomson ” ridge), from a depth of 640
fathoms. This is a greater depth than any from which Molgulide were
obtained during the ‘ Challenger” Expedition.

The incrusting sand is very fine, and the bare area around the apertures is
conspicuous. In the branchial sac there are usually about eight coils in the
spiral forming each infundibulum. The specimen measures 9 mm. in breadth —
by 6°5 mm. in length.

EXPLANATION OF THE PLATES.

The objectives employed while drawing the figures were as follows :—
Swift, 1 inch—magnifies about 45 diameters.

nee OM rs 55 225 Fr

bik een " 300 By
Hartnach, No. 4 2 50 ys
4 iS = 180 s

32 r oe BOO 4

Zeiss ,!5, oil immersion ,, 950 “i

The following system of lettering has been adhered to in all the figures :—

at, atrial aperture.
br, branchial aperture.

- brf, fold in branchial sac.
c, enlarged end of tubule of intestinal gland.
d, duct of intestinal gland.
dl, dorsal lamina.
d.t, dorsal tubercle.
en, endostyle.

, genital mass.

g!, gland at pylorus of stomach.
gc, nerve cells in outer part of ganglion.
h, heart.

THE “TRITON” TUNICATA. 115

h.m, horizontal membrane of branchial sac.
2, intestine.

4.1, internal longitudinal bar of branchial sac.
Z, lobe at branchial aperture.

1.v, fine longitudinal vessel of branchial sac.
am to m8, the muscle bands in Doliolwm.

mb, membrane.

m.b, muscular bundle.

mh, mesh of branchial sac.

nN, 2’, nerves.

n.a, aperture of duct from neural gland.

n.d, duct from neural gland.

ng, nerve ganglion.

@, esophagus.

@.a, cesophageal aperture.

ov, ovary.

p, papilla; p’, smaller intermediate papilla.
p-p, peripharyngeal band.

sg, stigmata.

st, stomach.

t, testis ; ¢’, anterior prolongation of testis.
in, tn’, tn”, tentacles of 1st, 2nd, and 3rd order.
tr, transverse vessel; ¢7’, tr”, smaller transverse vessels.
v.d, vas deferens.

2, prebranchial zone. ,

Piatt XVI.

Ascidia tritonis, n. sp.

Fig. 1.—Ascidia tritonis, seen from the right side. Natural size.
Fig. 2—A small portion of the surface of the test. Slightly magnified.

Fig, 3.—Another specimen, after the removal of the test, seen from the left side. Natural size.
Fig. 4.—Part of the branchial sac, from the inside. Objective, Swift, 1 inch.

Fig. 5.—Small portion of dorsal lamina, showing free edge. Objective, Swift, 1 inch.

Fig. 6.—Dorsal part of anterior end of branchial sac, showing tentacles, dorsal tubercle, peri-

pharyngeal bands, &c. Objective, Swift, 1 inch.

PEATE Neville

Figs. 1 and 2, Ciona intestinalis, Linn, Figs. 3 and 4, Ascidia virginea, O. F. Miiller.
Figs. 5 and 6, Polycarpa pomaria, Sav.

Fig. 1.—A small portion of the branchial sac of Ciona intestinalis, Linn., seen from the inside ;
papillz not represented. Objective, Swift, 1 inch.

Fig. 2.—Another small portion of the branchial sac of Ciona intestinalis, from the inside.
Objective, Swift, 1 inch.

Fig. 3.—Ascidia virginea, O. F. Miiller, var. pedwnculata, from the left side. Natural size.

116 DR W. A, HERDMAN ON

Fig. 4—Dorsal part of ee end of branchial sac of Ascidia virginea var. pediment 4
showing tentacles, dorsal tubercle, &c. Objective Swift, 1 inch.
Fig. 5.—Polycarpa pomaria, Savigny, seen from the left side. Natural size.
Fig. 6.—Part of the branchial sac of Polycarpa pomaria, seen from the inside, and showing
two folds and two interspaces. Objective, Swift, 1 inch,

PiatTe XVIII.
Doliolum denticulatum, Quoy and Gaimard.

Fig. 1.—Doliolum denticulatum from the right side. Natural size.

Fig. 2.—A specimen preserved in chromic acid and absolute alcohol, from the left side.
Natural size.

Fig. 3,—The same specimen seen from the ventral surface.

Fig. 4—A young individual (2 mm. in length) seen from the right side. Objective, Hart. 4.

Fig. 5.—Part of a muscle band from the mantle of a specimen preserved in picric acid.

_ Objective, Hart. 5.

Fig. 6.—Another muscle band from the same specimen. Objective, Hart. 5.

Fig. 7.—Anterior half of endostyle, seen from the interior of the branchial sac, from specimen
stained in picro-carmine. Objective, Hart. 4.

Fig. 8.—Nerve ganglion, dorsal part of peripharyngeal band, &c., seen from interior of branchial
sac. Objective, Hart. 4. .

Fig. 9.—Broad barrel-like form of Doliolwm denticulatwm, from left side. Natural size.

Fig. 10.—Two specimens of the narrow elongated form. Natural size.

Fig. 11.—Right side of branchial sac, &c., from interior. Reduced from Objective, Hart. 4.

Fig. 12.—Nerve ganglion, neural duct, peripharyngeal band, &c. Objective, Hart. 5.

Fig. 13.—Small part of peripharyngeal band, from specimen stained in osmic acid. Objective,
Hart. 7.

PLATE XIX.
Doliolum denticulatum, Quoy and Gaimard.

Fig. 1.—Nerve ganglion and dorsal part of peripharyngeal band, from a specimen preserved |
in chromic acid and absolute alcohol, and stained in picro-carmine. Objective,
Hart. 4.
Fig. 2.—The ends of some of the stigmata, from a specimen preserved in picric acid. Objective,
Swift, + inch.
Fig. 3.—Some of the ciliated cells bounding the stigmata, stained in picrocarmine. Objective,
Hart. 7.

g. 4—Some of the ciliated cells bounding the stigmata, stained with osmic acid. Objec-
tive, Zeiss, 5, oil immersion.

Fig. 5.—Some of the cells from the surface of the peripharyngeal band of a specimen pre-
served in chromic acid, and stained in picro-carmine. Objective, Zeiss, 45, oil
immersion.

Fig. 6.—Part of the prebranchial zone in a specimen preserved in osmic acid and absolute

alcohol. Objective, Hart. 7.

Fig.

Fig.
Fig.

Fig.

Fig.

THE “TRITON” TUNICATA. 11%

7.—Part of the prebranchial zone enclosed by the coiled dorsal ends of the peripharyngeal
band, from a specimen preserved in chromic acid and absolute alcohol, and stained
in picro-carmine. Objective, Zeiss, p, oil immersion.
8,—The anterior half of the nerve ganglion, showing the origin of the neural duct, from
specimen stained in osmic acid. Objective, Zeiss, ps, oil immersion.
9.—Anterior end of the duct from the neural gland, showing its ciliated expansion and
terminal aperture, from specimen preserved in osmic acid and absolute alcohol.
Objective, Zeiss, 75, oil immersion.
10.—Posterior end of endostyle, cesophageal aperture, and the neighbouring part of the
branchial sac, seen from the interior, from a specimen preserved in chromic acid
and absolute alcohol, and stained in picro-carmine. Objective, Hart. 4.
11.—Part of the heart, from specimen shown in fig. 10. Objective, Hart. 7.
12.—Part of the ganglion, showing the origin of one of the nerves, from a specimen pre-
served in picric acid and absolute alcohol, and stained in picro-carmine. Objective,
Zeiss, 75, oil immersion.
13.—A group of nerve cells from the ganglion shown in figure 12. Enlarged from Zeiss,
Objective >, oil immersion, ocular 4.

PLATE XX.
Doliolum denticulatum, Quoy and Gaimard.

1.—(CEsophagus, stomach, intestine, digestive glands, reproductive organs, &c., of an
individual preserved in alcohol, and stained in picro-carmine. Reduced from
Objective, Swift, 1 inch.

2.—Part of the duct (d) crossing from intestine to stomach in last figure. Objective,
Zeiss, =}, oil immersion,

3.—Part of the digestive gland forming a network of tubules over the intestine, from
same specimen as fig. 1. Objective, Swift, 4 inch.

4.—Part of the wall of the intestine, surface view. Objective, Hart. 5.

5.—Part of the organ (g/) seen ramifying over the stomach and first portion of the
intestine in fig. 1, from specimen stained in picro-carmine. Objective, Zeiss, 74,
oil immersion.

6.—The reproductive system dissected out. Reduced from Objective, Swift, 1 inch.

7.—The same in another specimen, showing a curious anterior termination. Reduced from
Objective, Swift, 1 inch.

8.— Anterior extremity of the testis of another individual, stained in picro-carmine. Objec-
tive, Swift, 1 inch.

9.—Anterior extremity of the testis in another specimen, preserved in solution of
osmic acid. Objective, Hart. 5.

. 10.—Anterior extremity of the testis in another specimen, stained in picro-carmine. Objec-

tive, Swift, 1 inch.

. 11.—Anterior extremity of the testis iu another specimen. Objective, Hart, 5.

. 12.—Small part of the edge of the testis near the posterior end. Objective, Hart. 7.
. 13.—Opening of vas deferens close to ovary. Objective, Hart. 4.

. 14.—Aperture of vas deferens. Objective, Hart. 7.

VOL. XXXII. PART I. U

it

Vol. XXXII, Plate XVI.

Ba

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Trans. Roy. Soc. Ed

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Trans. Roy. Soc. Edin’ Vol. XXXII, Plate XVII.

‘Herdman del. ¥. Huth, Lith” Edin?
EIGSI&2 ClONA INTESTINALIS, Linn. FIG? 3&4 ASCIDIA VIRGINEA var. PEDUNCULATA,
FIG? 5&6 POLYCARPA POMARIA, Sav

Trans. Roy. Soc. Edin™

Vol. XXXII, Plate KVIII.

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Trans. Roy. Soc. Edin™

Vol. XXXII, Plate XIX.

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Vol. XXXII, Plate XX.

F Huth, Lith Baint

Cetin 2)

VIIL— Report on the Pennatulida dredged by H.M.S. “ Triton.” By A. MILNES
Marsuatt, M.D., D.Sc., M.A., Fellow of St John’s College, Cambridge,
Beyer Professor of Zoology in Owens College. (Plates XXI. to XXYV.)

(Read 16th July 1883.)

INTRODUCTION.

The Pennatulida obtained by H.M.S. “Triton,” and placed in my hands for
description, are of six genera only, each genus being represented by a single
species. The interest of the collection is, however, far from commensurate
with its size, for of the six species two are altogether new to science, a third
has hitherto been met with only off the Norwegian coast, while concerning the
remainder, which are well known species, the “Triton” specimens have furnished
important additions to our knowledge, either of their anatomy or distribution.
In arranging the species I have followed the system of classification pro-
posed by KOLLIKER in his “ Report on the Pennatulida dredged by H.M.S.
|*Challenger.’”* This scheme, though representing the latest results of our
greatest authority on the group, cannot be considered altogether satisfactory,
inasmuch as but very little attempt is made to express the mutual relations of
the several groups, and highly specialised forms are mixed up with more primitive
ones in a very confusing manner. I have, however, thought it better to adopt
it here rather than attempt to frame a new scheme on inadequate material.
The following outline of KOLLIKER’s classification shows the position
occupied by the genera with which we are concerned :—

Order PENNATULIDA.
Section I. PENNATULEH: polyps fused together to form leaves.
Sub-section 1. Penniformes: leaves well developed.
Family 1. Pteroeidide.
Family 2. Pennatulide.
Genus Pennatula.
Sub-section 2. Virgulariew : leaves small.
Family 1. Virgularide.
Genus Virgularia.
Family 2. Stylatulide.
Genus Diibenia.

* Zool. Chall. Exp., part ii. pp. 38-35, 1880.
VOL, XXXII, PART I. x

120 DR A. MILNES MARSHALL ON THE

Section II. Sprcat#: no leaves ; polyps sessile.

Sub-section 1. Funiculinew: polyps arranged in distinct rows.

Family 1. Funiculinidee.
Genus Puniculina.

Family 2. Stachyptilidee.
Family 3. Anthoptilide.

Sub-section 2. Junciformes: polyps in single series or in indis-
tinct rows.

Family 1. Kophobelemnonide.
Genus Kophobelemnon.

Family 2. Umbellulide.
Genus Umbellula.

Family 3. Protocaulide.
Family 4. Protoptilide.

Section III. Renitte#: rachis expanded, in form of a leaf.

Section IV. VERETILLE&: polyps arranged on rachis in radiate manner. —

The following table shows the localities at which the specimens were
obtained, the number taken at each, and the instrument employed in each case. —
The specimens taken at Stations 6 and 7 do not belong to the “ Triton” collec-
tion, but were dredged by the “ Knight Errant” in 1880 :—

Station. Locality. ve Date. Name. Number.

6 | 59°37'N.,, 7°19 W. | 530 | Aug. 11, 1880 | Kophobelemnon 1
7 do. do. 530 | Aug. 12, 1880 Pennatula 1
8 | 60°18'N., 6°15’ W. 640 | Aug. 22, 1882) Kophobelemnon 2
10 | 59°40'N., 7°21’ W. 516 Aug. 24, 1882 ) 3
2
11 /59°29’30’N.,7°13'W.| 555 | Aug, 28, 1882 Pennatula 18
» 1
Virgularia 2

% 1 fragment
Diibenia i
Kophobelemnon 13

s 11 & 6 heads
; Umbellula 1

Sith ee \ 35-37 2 Funiculina 10 fragments

Off Butt of Lewis, 40

>
=
Q

g. 25, 1882 Pennatula 4

PENNATULIDA DREDGED BY H.M.S. ‘“‘ TRITON.” 121

Concerning the mode of capture, it will be seen from the above table that
the trawl was distinctly more successful than the dredge; and the difference
between the two is greater than appears from a mere comparison of the number
of specimens taken, for the proportion of imperfect and mutilated specimens
brought up by the dredge far exceeds that yielded by the trawl, the mutilation
being in many cases clearly caused by the dredge itself.

For such forms as Pennatulida the dredge is indeed a very unsuitable
instrument of capture ; a point that deserves a greater amount of practical
attention than it appears yet to have received.* It is certainly worthy of note

that the three most interesting forms collected by the “Triton” were all
_ brought up by the trawl.

Concerning the nomenclature adopted, I have retained the terms polyp and
zooid for the two kinds of individuals, sexual and asexual, of which a Pennatulid
colony normally consists, since these names are in general use. Strictly
speaking, the names are objectionable, for the term zooid is commonly and con-
veniently employed in zoology to indicate any member of a colony that is
produced asexually, and in this sense both kinds of individuals of the Penna-
tulid colony are zootds. :

For the tubular cavity into which the mouth leads, and which is commonly
spoken of as the stomach, I have adopted the term stomodeum. ‘This cavity is
| im no sense of the word entitled to the name of stomach, inasmuch as diges
tion is effected, not in it, but in the body cavity into which it opens below.
KOLLIker has proposed to call it cesophagus,t but the term stomodwum seems
preferable, as indicating at once its origin by involution of the outer layer of the
body or ectoderm.

DESCRIPTION OF THE SPECIMENS.

Order PENNATULIDA.
Section I. PENNATULEA,

Sub-section 1. Penniformes.

Family 2. Pennatulide,

Pennatula, L.
; Pennatula phosphorea, L. (Pl. XXI. figs. 4-7, and Pl. XXII. figs. 8-16.)
| This species was obtained by the “Triton” at two localities, off the Butt of
Lewis in 40 fathoms water, and at Station 11 at a depth of 555 fathoms. The
collection also includes a single specimen obtained by the “Knight Errant” in
“11980.

* Cf. Nature. A new dredging implement, vol. xxvii. p. 11.
} Koutixer, Anatomisch-systematische Beschreibung der Alcyonarien, p. 416, 1872.

122 DR A. MILNES MARSHALL ON THE

Of this very variable species K6LLIKER distinguishes three well-marked
varieties, characterised as follows :*—

1. Var. angustifolia: Leaves long and narrow; polyp heads few and wide
apart.

2. Var. lancifolia: Leaves lancet-shaped ; polyp heads numerous, and close
together. Of this form, which should probably be considered the typical
P. phosphorea rather than a distinct variety, KOLLIkER further distinguishes
four sub-varieties.

3. Var. aculeata: Leaves slender, and placed close together ; on the ventral
surface of the rachis are four to six rows of long spines, connected with the
zooids.

Of the “ Triton” specimens those obtained off the Butt of Lewis belong to
the second variety Jancifolia; while the more numerous specimens from the
deeper water of Station 11 are typical examples of the variety aculeata. The
two forms are so distinct that it will be well to describe them separately.

P. phosphorea var. lancifolia, Koll.

All four specimens are small, and of somewhat stunted appearance, the
leaves being twisted in an irregular manner, so that sometimes the dorsal and
sometimes the ventral border of the leaf is turned upwards. The four speci-
mens, though of nearly the same absolute size and all obtained at one haul,
differ a good deal among themselves as to the shape of the leaves and the
breadth of their attachment to the rachis, and also as to the extent of separa-
tion between the component polyps of a leaf.

The zooids, which are uniform in size, cover the whole ventral surface of

the rachis, except the mid-ventral eroove, and extending upwards between
the leaves, become continuous with small groups of three or four zooids each
situated on the dorso-lateral angles of the rachis between the leaves.

In all four specimens the stalk, with the exception of the terminal dilatation,
which is yellowish, is of a dark red colour, due, as in the rachis and leaves,
to the calcareous spicules imbedded in it. In one specimen the colour is a deep
purple of exceptional intensity.

The measurements of the four specimens in millimétres are as follows :—

A. B. C. D.

Length of colony, i | 60 mm. 56 mm. 58 mm. 58 mm.
. rachis, ; : a) 27 31 30
» stalk, : ; 28°5 29 27 28

leaves, ; ; 13 13 12 11°5

Greatest width of leaves, ; 2 2°5 3 3
No, of leaves on each side, ; 20 rail 22 20
» polyps per leaf, 3 10 9 9 10

* KOLLIKER, Anatomisch-systematische Beschreibung der Alcyonarien, pp. 130-134.

— ee oa eee eee

PENNATULIDA DREDGED BY H.M.S. ‘‘ TRITON.” 125

From these figures it will be seen that specimens A and B approach very
closely K6OLLIKER’s variety angustifolia.

P. phosphorea var. aculeata, Koll. (Pl. XXI. figs. 4-7, and Pl. XXII. figs. 8-16.)

This very well-marked variety, which does not appear to have been hitherto
recorded from British seas, is characterised by the long and slender shape of
the leaves (Pl. XXI. figs. 4 and 5), the small number of their component
polyps, their distance apart, and the extent to which they are separate from one
another ; and above.all, by the fact that a number of the zooids of the veutral
surface (figs. 4 and 5, f) are very exceptionally developed—assuming the form
of conical spines, which project from the rachis for a distance in some speci-
mens of 3°5 mm., or even more.

This variety was first described in 1858 by Koren and DANIELSSEN,* who
found it at a single locality near Christiansund, where it occurred rather
abundantly on clay bottom at the depth of 80 to 100 fathoms. Since then it
has been taken by Sars at Christiansund at a depth of 30 to 70 fathoms, and
in the Throndhjemsfjord in 100 fathoms water; by CARPENTER and WYVILLE
Tomson, during the “‘ Porcupine” expedition in the Atlantic Ocean, 48° 26’ N.,
9° 44’ W., at a depth of 358 fathoms; and by Wurreaves in the Gulf of St
Lawrence, at a depth of 160 to 200 fathoms.

Of the “Triton” specimens of P. phosphorea, all those, 19 in number,
obtained at Station 11, depth 555 fathoms, belong to this variety, as also does the
single specimen from the “ Knight Errant” collection dredged at Station 7, in 530
fathoms water. As the variety is a very interesting one, and has not yet been
satisfactorily described, I have taken the opportunity afforded by the large number
of specimens available to investigate in some detail the more important structural
details, directing my attention more particularly to the large ventral zooids.

The following table gives the measurements of the single specimen from the
“Knight Errant” and of two of the “Triton” specimens. All the latter are of
small size, the specimen B being one of the largest.

A. iE C.
‘ eee ‘ “Triton ” Collection.
Length of colony, : : : 70 mm. 62 mm. 48 mm.

A rachis, ; ; 3 31 28:5 24

x stalk, ‘ : : 39 33°5 24.

» ., leaves (longest), . , 12 13 10
Greatest width of leaves, ; 4 3 1:5 1195;
Number of pairs of leaves, . ; 19 14 10
Number of polyps per leaf, . ; Y 6 t
Length of largest zooids, 5 ‘ 3 35 3

* Koren and Danretssen, Forhandlinger 7. Videnskabsselskabet 1. Christiania, p. 25, 1858 ; also
Fauna Littoralis Norvegie, part iii. pp. 86-88, and pl. ii. figs. 8 and 9, Bergen, 1877.

124 DR A. MILNES MARSHALL ON THE

KoreEN and DANIELSSEN, WHITEAVES and VERRILL, maintain the specific
distinctness of this form from P. phosphorea. The measurements of the
different specimens I have been able to examine show so great variability in
the essential characters of the form, such as the length of the large zooids,
width of leaves, &c., that I can have no hesitation in agreeing with KOLLIKER*
in regarding it as merely a variety, though a very well-marked one. I cannot,
however, accept Ricurarpi’st conclusion that it is not even a variety, “ma uno
stato puramente accidentale di certi exemplari.”

The general appearance of the form is shown in Pl. XXII. fig. 4, representing
an entire specimen seen from the right side and twice the natural size. Fig. 5 is
a transverse section through the rachis about the middle of its length, with one
of the attached leaves and the base of the corresponding leaf of the opposite
side. For the sake of comparison, I have given in fig. 6 a similar view of a
normal specimen of P. phosphorea obtained from Oban.

If these two figures be compared together, it will be seen that the points in
which the variety aculeata (fig. 5) differs from the typical P. phosphorea (fig. 6)
are the following :—The leaf is longer and much narrower; the polyps are fewer —
in number, are placed further apart, and are independent of one another for a
greater portion of their length. The walls of the rachis are much thicker, a
condition associated with the presence of larger and more numerous spicules ;
the axial calcareous stem is thicker, and the main longitudinal canals of the
rachis much smaller than in the typical form. Concerning the zooids, it will be
seen that a very large one (fig. 6, f) arises from the rachis immediately below —
each leaf, with the ventral border of which it is fused for about a third of its —
length. Nearer the mid-ventral line of the rachis there is on each side a second _
row of large zooids, usually slightly smaller than those of the outer row, but
sometimes equalling them in size; and within these again other zooids occur
intermediate in size between the large ones and the normal small ones, The
largest zooids, those attached to the ventral borders of the leaves, have an
average length of rather over 3 mm. in the “Triton” specimens; in exceptional
cases they reach 4 mm.

Between the large zooids are numerous small ones of the normal size and
character, which extend up the sides of the rachis between the bases of the
leaves.

That the connection of the large ventral zooids with the leaves is of a purely
secondary nature is clearly seen by tracing their gradual development in passing.
upwards from the lower end of the rachis. At their first appearance they —
are small, identical in all respects with the normal zooids, and quite inde-

* KOLLIKER, Op. cit., pp. 134 and 366.
¢ Ricutarpi, Monografia della famiglia dei Pennatularii, p. 24.

PENNATULIDA DREDGED BY H.M.S. “TRITON.” 125

pendent of the leaves, with which they become connate a) after they have
attamed a considerable size.

The structure of the large zooids, which does not appear to have been
examined with any care hitherto, is shown in the series of figures on Plate XXII.
Of these fig. 8 represents a median longitudinal section through the whole
length of one of the zooids, and through the part of the rachis from which it
springs ; while figs. 10 to 16 are transverse sections through a zooid at different
parts of its length, fig. 10 being near to the apex and fig. 16 passing pater
the base of attachment of the zooid.

The general anatomy of the large zooid is well shown in fig. 8, from which
it will be seen that while agreeing in essential structure with the smaller and
more typical zooids, it yet presents some points of special interest.

The zooid is conical in shape, arising by a broad base from the rachis and
tapering upwards rather sharply, ending in a pointed apex. As shown in figs.
4 and 8 the zooid does not project horizontally outwards, but obliquely upwards,
so that we can distinguish between an inner or axial surface, directed
toward the rachis, and an outer or abaxial surface facing outwards.

On the inner or axial surface, and nearer the base than the apex of the zooid,
is the mouth (fig. 8, 2). This leads into the stomodzum s, which is lined by
columnar ciliated ectoderm cells, the cilia clothing the outer or abaxial wall
being of very great length, and forming with the surface of the stomodeum
from which they arise the structure which Mr Hickson has recently proposed
to speak of as the siphonoglyphe.*

The stomodzeum opens below into the general body cavity h, which is lined
by endoderm, and is in communication with the cavities of the adjacent zooids
and with.the main lateral canals of the rachis, and so indirectly with the
polyps. The stomodéeum is attached to the body wall by the usual eight septa,
which are well shown in the transverse section (fig. 15). Below the stomodeum
the two septa of the inner or axial surface, bounding the axial] interseptal cavity,
remain of considerable width, and bear at their free edges the two mesenterial
filaments (figs. 8 and 16, p), which are very long and much convoluted, and
extend down to the bottom of the zooid cavity.

The other six septa become reduced immediately below the stomodzeum to
very narrow ridges (fig. 16, m), which disappear altogether a short way lower down.

The body wall of the zooid consists of an outer layer of short columnar ecto-
derm cells, below which is the firm gelatinous mesoderm. This latter is much
thicker on the outer or abaxial surface than it is on the inner or axial, and is
strengthened by a great number of large calcareous spicules (figs. 8-16, 4).
These spicules are straight rods, thickest in the middle, and with rounded ends ;

* Hickson, on the “Ciliated Groove (Siphonoglyphe) in the Stomodzeum of the Aleyonarians,” Proc.
Roy. Soc., 1883.

126 DR A. MILNES MARSHALL ON THE

the largest attain a length of 1:6 mm., with a width of ‘13 mm. In transverse
section (figs. 10-16, 7) the spicules are triangular, with rounded angles, and a
shallow groove running somewhat obliquely down the middle of each face.
They are exceedingly numerous along the whole length of the abaxial surface
of the zooid, and are arranged with their long axes parallel, or nearly so, to
that of the zooid.

The mesoderm is traversed by a system of irregularly branching nutrient
canals continuous with those of the rachis. The muscular system of the body
wall of the zooid seems to be completely absent.

The relations of the inter-septal chambers in the part of the zooid above the
stomodzeum are rather curious. Fig. 14 represents a transverse section through
the mouth opening; it shows that at this point only five of the eight inter-
septal chambers are present, viz., the abaxial, or as it is commonly called, ventral
cavity, the two latero-ventral cavities bounding it on either side, and the two
lateral cavities; the axial or dorsal and the two latero-dorsal cavities not
extending above the mouth. In a section taken a little higher up, through
the upper part of the mouth (fig. 13), the two lateral cavities have dis-—
appeared, and the mid-ventral and latero-ventral cavities are alone present.
Tracing them further up towards the apex of the zooid, we find that all three
persist for some distance, but that after a time the middle abaxial or ventral
cavity, which has been from the start the smallest (cf figs. 15 and 14), loses
its lumen (fig. 12), and then disappears altogether, the two latero-ventral
cavities alone persisting (fig. 11).

Further up still (fig. 10), one of the two latero-ventral cavities disappears
and one alone is left, which can be traced nearly, or in some cases quite, up to
the apex of the zooid.

The prolongations upwards of the interseptal chambers above the mouth —
correspond, not to the tentacular cavities of the fully formed polyps, but to
the cavities of the calyx processes ; and the whole of the part of the large
zooid above the mouth is to be regarded as formed by a special unilateral
development of the calyx, corresponding at its base to five, and along the
greater part of its length to three calyx processes fused together, but with
their axial cavities remaining distinct.

That the spine of the large zooid really consists of calyx processes and not
of tentacles, is, I think, proved by the perfect continuity between the wall of —
the zooid itself and the spine; by the unbroken series of exceptionally large
spicules extending along the abaxial wall of the whole length of the zooid,
including the spine ; and by the absolute identity between a transverse section
across the upper part of the spine, and one through a calyx process of a normal
polyp. This latter point is well shown in figs. 9 and 10, the former being a
section of a calyx process, and the latter of the spine of one of the large zooids. —

‘
‘

PENNATULIDA DREDGED BY H.M.S. “TRITON.” 127

The agreement will be seen to be absolute, even as regards the actual size
and arrangement of the spicules, which in both cases are far larger and more
abundant on the abaxial or outer surface than on the axial or inner one. It
is also worthy of note, in connection with the point in question, that in the
development of the polyps the calyx processes appear earlier than the
tentacles (vide fig. 7). |

The large zooids of P. phosphorea var. aculeata agree, therefore, with the
zooids of Pennatulida generally in the complete absence of tentacles, as well as
in the absence of reproductive organs and the possession of but two mesenterial

filaments. They are peculiar merely in their very great absolute size, and in
the prolongation of the abaxial surface to form the spine.

The structure of one of the normal small zooids is shown in fig. 8, ¢. It will
be noticed that here also the mouth, which in the early stages of development is
terminal (as shown in the rudimentary zooid between ¢ and the large zooid),
becomes thrown over to the axial surface by growth forwards of the abaxial
side, which forms a prominence above the mouth clearly comparable to the

spine of the larger zooids. The figure shows also that the smaller zooids, like
the large ones, possess the clothing of exceptionally long cilia on the abaxial
surface of the stomodzeum (siphonoglyphe of Hickson).

The small zooid in question (fig. 8, ¢) is an immature one, as there i is as yet
no communication between the stomodzum and the body cavity of the zooid;
the septa and mesenterial filaments have also not yet appeared.

PANCERI™ has described and figured an interesting abnormality occurring in
a specimen of P. phosphorea, in which four of the latero-ventral zooids, three
on the left side of the rachis and one on the right, have the form and structure
of fully developed polyps, inserted independently into the rachis, and attaining
a length of 10 mm. and a diameter of 1 to 2 mm. In describing this curious
modification, Panceri discusses briefly the mutual relations of polyps and zooids,
points out the fundamental and essential correspondence between the two, and
infers that the zooids must be regarded as abortive polyps, and that such cases
as the one he describes are to be viewed as examples of reversion from the
abortive to the fully developed condition. |

In this view Panceri is undoubtedly right. In a colony of individuals
formed by continuous gemmation, 7.¢., by a process of budding in which the
several zooids remain organically connected together to form the colony, the
several component individuals must be supposed to be primitively all alike and

jequivalent to one another. Differences in structure and function could clearly
only have arisen after the habit of forming colonies had been established for
some time. Hence those colonies will be the most primitive in which there is

* Pancerl, “Intorno ad una forma non per anco notata negli zooidi delle pennatule,” Rendiconto
dell Academia delle scienze fisiche € matematiche, pp. 23-28, Napoli, Febbrajo, 1870.

VOL. XXXII. PART I, i

128 DR A. MILNES MARSHALL ON THE.

in the adult form the smallest amount of difference between the constituent
individuals ; while those forms in which this differentiation reaches its greatest
development will be the most highly modified forms. These principles are of
great importance in framing a scheme of classification of a colonial group such
as the Pennatulida, and have not received sufficient attention in the classifica-
tion at present in use. - |

In the ordinary P. phosphoreathe amount of differentiation is comparatively
slight, and is brought about in the simplest possible manner ; the asexual zooids
being simply arrested at what is merely an early stage of development in the
case of the polyps. This is well shown in Pl. XXI. fig. 7, representing a
side view of the lower end of the rachis, and showing the early stages of
development of the polyps and zooids.

The figure shows that the young polyps d are at first quite independent of
one another, and that in their earlier stages they are absolutely identical with
the zooids ¢; and that the differences arise from the zooids becoming arrested
at this early stage, while the polyps advance further, increase in size, acquire
calyx processes /, and tentacles ¢, fuse with one another at their bases, so that
their further increase in length gives rise to the leaf of the adult, and acquire
the full number of mesenterial filaments, and ultimately reproductive organs.’ —

The differentiation is thus of the simplest possible character, the zooids
being simply arrested or abortive polyps, whose function is apparently to main-
tain currents of water circulating throughout the colony, for which purpose they
have retained the sole structure peculiar to them—the clothing of exceptionally
strong cilia on the abaxial surface of the stomodeum. As the siphonoglyphe is
present in the mature polyps of many Alcyonarians, such as Alcyonium (vide
Hickson, loc. cit.), it seems certain that in the Pennatulida it is a structure that
has been lost by the polyps, but retained by the zooids.

In the variety aculeata differentiation has advanced further; and it is a
point of importance to note that the points in which the large zooids differ
from the small ones cannot be considered as repetitions of any part of the
process by which the polyp is developed from the zooid condition. In the
young polyp all the calyx processes arise simultaneously (fig. 7), as do also all
the tentacles, so that the asymmetrical development of the calyx in the large
zooids must be regarded as peculiar to and acquired by them. ‘The lateral
position of the mouth in the large zooids has apparently been acquired inde-
pendently of and previous to the formation of the calycular spine, inasmuch as
it is an equally prominent feature in the normal small zooids (fig. 8, ¢).

Judging from their structure, the large zooids would seem to be protective —
in function, but as to the special circumstances which determine their develop-
ment in particular forms, we are in complete ignorance. Were our knowledge
confined, so far as these forms are concerned, to the “ Triton” specimens, we

“

PENNATULIDA DREDGED BY H.M.S. “ TRITON.” 129

should be greatly tempted to suppose that as one set of specimens—the typical
P. phosphorea—is obtained from a depth of only 40 fathoms, and the other,
_the variety aculeata, from 555 fathoms, that the structural differences between
the two forms may be at any rate in part due to the different external condi-
tions of pressure, &c.

Although, however, the variety aculeata does appear to occur as a rule
in deeper water than the more normal form, yet this rule is not universal, for,
as we have seen above,* Sars obtained specimens of aculeata off the Norwegian
coast at depths of 30 to 70 fathoms. The determining cause therefore that
leads to the production of the variety aculeaia must be some other than mere
depth, though this would appear to have some influence.

It may be noticed, finally, that the vertical range of P. phosphorea, which
K6LLIKERt puts at 30 to 300 fathoms, has been nearly doubled by the “ Triton”
dredgings, which show that the species lives in abundance, though in a rather
diminutive form, as low as 555 fathoms.

Sub-section 2. Virgulariee.
Family 1. Virgularide.
Virgularia, Lam.

Virgularia tuberculata, n. sp. (PI. XXI. figs. 1-3.)

Specific Characters.—Polyps nearly sessile, united at bases in groups of
three, the groups alternating on the two sides of the rachis. Calyx completely
obliterated when the polyp is fully protruded ; calyx margin marked by eight
small tubercular processes placed opposite the tentacles. Reproductive organs
in the immature leaves at the lower part of the rachis. Stem cylindrical. Colour
of colony, yellowish-white. No calcareous spicules in any part.

Habitat.—Station 11.

Of this species three specimens were obtained, all of which are imperfect.
The largest specimen (Pl. XXI. fig. 1) measures 68 mm. in length, and consists
of the stalk and lower part of the rachis ; its upper end is abruptly truncated,
and the upper 10 mm. of the stem are denuded of the fleshy sarcosoma.

The second specimen is similar to the first, but smaller in all its dimensions ;
it has a total length of 36-4 mm., and consists of the stalk and lower end of
rachis, the upper end of which is abruptly truncated.

The third specimen is 46 mm. long, and consists of the middle portion of
the rachis of an apparently rather larger specimen than either of the other two ;
truncated at both ends.

* Supra, p. 123.
t Zool. Chall. Hxp., part ii. p. 38, 1880.

130 DR A. MILNES MARSHALL ON THE

The stalk of the first specimen (Pl. XXI. fig. 18) is cylindrical, with an
average diameter of 2:1 mm. It presents a slight terminal dilatation at its
lower end, and is marked on both dorsal and ventral surfaces by shallow median
longitudinal grooves. The stalk has a length of 15 mm., and is continuous
above with the rachis, the transition from one to the other being marked by
the first appearance of the leaves.

The lower part of the rachis is flattened dorso-ventrally, and has a transverse
diameter of 26 mm. It is marked by upward continuations of the median
dorsal and ventral grooves of the stalk.

As we pass from the region with immature leaves to the part of the rachis
bearing fully developed polyps, the rachis gradually becomes reduced in width,
and in the upper part, where the polyps have attained their full size, it becomes
cylindrical, with a diameter in the first specimen of 0°5 mm., forming in fact
a very thin fleshy investment to the stem.

The stem is cylindrical at its upper end, with a diameter of 0-4 mm.; it
remains of nearly uniform size throughout the whole length of the rachis, but
tapers gradually as it passes down the stalk. It is of considerable brittleness,
especially in its upper part.

The polyps commence in the lower part of the rachis as small transverse
ridges placed very close together, the first 6 mm. of the rachis having 20 of
these ridges on each side. Passing upwards, the ridges become more pro-
minent, wider, and situated further apart, each being divided at its free edge
into three polyps.

Of the three polyps of a ridge, the dorsal one is from the start the smallest
of the three, and the ventral one the largest; and these proportions are retained
throughout.

As the polyps get larger, the groups move further and further apart, until the
interval between successive groups on the same side of the rachis is about
3 mm., which appears to be the limiting distance.

The ridges on the lower part of the rachis are so placed that while the
dorsal polyps of the ridges of the two sides are almost in contact with one
another in the mid-dorsal line, the ventral polyps are separated from one
another by nearly the whole width of the ventral surface of the rachis, an
arrangement which persists also in the fully formed polyps (fig. 2). .

The groups of polyps are from the first placed, not opposite one another, but
alternately, as shown in figs. 1 and 2, the right hand group being a little in
advance of the left one.

The polyps of each fully developed group are almost completely independent
of one another, their bases alone being united together, so that it is hardly
possible to speak of distinct leaves. The inclusion of the species in the genus
Virgularia is fully justified, however, by the general mode of development of

\

PENNATULIDA DREDGED BY H.M.S. ‘“‘ TRITON.” 131

the polyps, especially the simultaneous appearance of the component polyps of
a group ; by the position of the reproductive organs in the immature polyps,
the proportions of the stem at different heights, and by the existence of such
forms as Virgularia bromleyi* in which the separation of the polyps is not
carried quite so far as in V. tuberculata. From V. bromleyt, the new species is
distinguished at once by the absence of calcareous spicules, and the presence of
the tubercles marking the calyx margin.

Concerning the development of the polyps, it can be ascertained by examina-
tion of the immature polyps at the lower end of the rachis, that the stomodeum
arises as usual as an involution of the ectoderm, appearing before the tentacles,
which latter all develop simultaneously. In the early stages of development one
tentacle is very commonly rather larger than the other seven, but whether this
is an accidental feature or not I have been unable to determine, nor have I
detected any constancy of position of the larger tentacle. In each group
the ventral polyp is always the furthest developed, and the dorsal one the
least so.

In the smaller of the two specimens in which the stalk is perfect, the
change from the immature to the fully developed polyps is a very abrupt one ;
not gradual asin the larger specimen figured (Pl. XXI. fig. 1). The stalk in this
smaller specimen is 8 mm. long; the first 4 mm. of the rachis bear immature
leaves only, and above this point the fully formed polyps commence abruptly.

The fully expanded polyp (fig. 2) measures about 2°5 mm. in length, of
which the tentacles form rather more than half; its width is about 0°2 mm.
Opposite the insertion of the polyp, and for some little distance above and
below it, the sarcosoma of the rachis is markedly thickened (fig. 2), giving the
rachis at these places a quadrangular shape. The boundary line between the
body of the polyp and the tentacles is indicated in the fully expanded polyp by
a row of eight small knob-like processes placed opposite the tentacles (fig. 2).

_ These processes are hollow, and consist of all three layers of the body wall—

ectoderm, mesoderm, and endoderm ; they appear to correspond to the calyx
processes of other Pennatulida.

When the polyp is retracted, as in the lower specimens of fig. 2, these pro-
cesses mark the line of invagination, and become much more conspicuous,
appearing as knobs placed round the edge of the calyx.

In the “ Triton” specimens, retraction of the polyp is never carried further
than is shown in fig. 2, the fully retracted polyp being about half the length of
the fully expanded one. Retraction is probably effected slowly, as the great
majority of polyps have died in an almost completely expanded state.

The tentacles are rather longer than the body of the polyp; are pinnated as
shown in fig. 2, and present no special features of importance.

* KoiiiKer, Zool, Chall. Exp., part ii. p. 9, 1880.

132 = DR:A. MILNES MARSHALL ON THE .

The anatomy of the polyp, so far as I have had the chance of investigating
it, agrees with that of other Virgulariw. The reproductive organs, as in
Virgularie generally, are contained, not in the mature polyps, but in the im-
mature ones at the lower end of the rachis.

The large specimen (fig. 1) is a male, and a small part of the rachis removed
from a point 22 mm. from the lower end of the stalk, showed the mature male
organs or spermatospheres. These (fig. 3) have the typical structure of the
male organs of Pennatulids. They are oval or spherical bodies, the largest of
which have a diameter of 0°38 mm.° Each is enclosed in a very thin capsule, the
contents of which are a mass of very minute brightly refracting bodies—the
heads of the spermatozoa; these are more closely packed at the periphery than
in the centre, where a number of fine radiating filaments can be seen, which are
probably the spermatozoa tails.

The smaller specimen, in which the lower end of the rachis is present, was
also examined for reproductive organs, but none were found. The third
specimen, consisting of the middle part alone of the rachis, is of course devoid
of reproductive organs.

This specialisation of the reproductive organs to the immature polyps is
undoubtedly a sign of considerable differentiation, and marks Virgularia as a
less primitive genus than such a form as Pennatula. For while in the latter
the component individuals of the colony are of two kinds only—zooids and
polyps—in Virgularia they are of three kinds—zooids, nutrient individuals, and
reproductive individuals. Whether all the immature polyps ultimately develop
into mature ones is uncertain ; probably not, inasmuch as all recorded specimens
of Virgularia have immature polyps at the lower end of the rachis. The
abrupt transition from the immature to the mature polyps described above as.
occurring in the second example of V. twberculata, may perhaps indicate the
existence of a sharp line of demarcation between the sexual and the nutrient
individuals.

Whether zooids are present or not in V. tuberculata, I ee been unable to
determine with certainty without destroying the specimens. Certain very small
knob-like projections on the rachis near the base of the polyps may perhaps
prove to be zooids ; if so, they are in an exceedingly rudimentary condition.

As noticed above, all three specimens of V. twberculata are imperfect, and
their imperfection is of some interest, inasmuch as it is very characteristic of
dredged specimens of Virgularia generally. Of the type species, V. mirabilis, a
perfect specimen has never yet been seen, all the specimens recorded being
fractured either at one or bothends. The lower ends or stalks are occasionally
found perfect, but the upper end never, the only known exception being a
single specimen in the Glasgow Museum.

The cause of this mutilation has been elsewhere discussed. It has been

‘

PENNATULIDA DREDGED BY H.M.S. “ TRITON.” 133

suggested * that the lower fracture, which usually occurs about the junction of
stalk and rachis, 7.¢., about the point of emergence from the mud of the sea’
bottom, is caused by the dredge at the moment of capture; while the upper
fracture is almost certainly effected quite independently of the dredge, and is
perhaps due to the tops being browsed on as food by other animals. The
great brittleness of the calcareous stem probably accounts for the readiness
with which the specimens become broken, and the fact that of the three
specimens of V. tuberculata, the one brought up by the dredge is broken at
both ends, while the two taken with the trawl have their lower ends entire, speaks
strongly in favour of the correctness of the first part of the above explanation. -
The measurements of the three specimens are as follows :—

A. 3 C.
Upper end imperfect. Upper end imperfect. Both ends lost.

Total length, are ; ; 68 mm, 36°4 min. 46 mm,
Rachis, . : - : 53 28°4 46
Stalk, . : 5 : 15 8 ole
Diameter of rachis, ; » Oia tor26 0:4 to 2:1 0°52

= stalk, : ; 21 It 3

e stem, ‘ : 0°4 0°38 0:4
No. of polyps per leaf, . ; 3 3 3
Length of polyp, ; 8 Eel

+ tentacle, ; iL ne 1-4
Distance of polyps apart (greatest), 3 8g 31,
Diameter of spermatospheres, 0:38

Family 2. Stylatulide.

Diibemia, Kor. and Dan.
Diibenia abyssicola var. smaragdina (Kor. and Dan.). (Pl. XXIIT. figs. 17-21.)

A single fragment of this species was obtained from Station 11 at a depth
of 555 fathoms. The specimen, which is imperfect at both ends, and has a total
length of 61 mm., is represented from the ventral surface three times the natural
size in Pl. XXIII. fig. 17; while figs. 18 and 19 represent on a larger scale
portions of the rachis as seen from the lateral and dorsal surfaces respectively.

Inasmuch as the sole description that has yet appeared of this very beautiful
form is the extremely short and imperfect account given by Koren and
DANIELSSEN,+ I have thought it well to investigate and describe the “Triton ”
specimen as fully as could be done without injury to it.

The rachis (figs. 17, 18, and 19) is cylindrical, and only slightly exceeds in
diameter the cylindrical stem by which it is traversed throughout its length.
At the upper end of the specimen the stem projects bare for a length of about

* Vide Report on the Oban Pennatulida, by A. M. Marshall and W. P. Marshall, 1882, pp. 57-60.
+ Fauna littoralis Norvegic, part iii. p. 26, and pl. x. figs, 7 and 8, 1877.

134 DR A. MILNES MARSHALL ON THE

3 mm. above the uppermost polyps, ending in an abruptly truncated and
evidently broken extremity. At the lower end the fracture appears to have
occurred about the junction of stalk and rachis, but the fleshy sarcosoma has
been stripped off the lowermost 8 mm., leaving this part of the stem bare, and
rendering it impossible to localise exactly the seat of fracture. The stem is
quite as brittle as that of Virgularia, so that there can be little doubt that the
cause of fracture is the same in the two cases.

The entire specimen is of a pale yellowish-white colour, but has become a
good deal discoloured in parts, apparently from the action of the spirit in which
it was preserved.

The polyps (figs. 17, 18, and 19) are arranged in pairs along the sides of the
rachis, each pair being embraced at its base by the fan-shaped plate of cal-
careous spicules 4, so characteristic of the family Stylatulide. The pairs of
polyps are not inserted opposite one another, nor do they strictly alternate’; but
those of the left side are situated a little further forward, nearer the upper end
of the rachis, than the corresponding pairs of the right side.

The intervals between successive pairs of polyps on the same side of the
rachis (fig. 17) gradually increase in passing upwards. At the lower end of the
specimen the successive pairs are almost in contact with one another, but in
passing upwards they move further and further apart, the intervals attaining a
maximum a short way below the upper end of the specimen, above which point
they decrease slightly, the polyps themselves also becoming smaller.

The characters and relations of the fan-shaped spicular plates are well shown
in figs. 18 and 19. Each plate is triangular, with the apex directed downwards
and inserted into the rachis, and with its free upper edge surrounding the ‘base
of the pair of polyps to which it belongs. The plate is formed by the fusion of
a number of radiately arranged spicules, of which the more deeply placed ones
are smaller and completely fused together, while some of the more superficial
ones are much larger, and not so closely fused. One of these large spicules is
represented in fig. 21; it is widest near its lower end, and gradually tapers
upwards to a point, which (figs. 18 and 19) projects freely for a short distance
above the upper edge of the plate. These large spicules may attain a length
of 2°3 mm. and width of 0-15 mm. From the apex of the spicular plate a
number of smaller rod-like spicules (fig. 18) are continued for a variable distance
down the rachis.

The two polyps of each pair have their bases, which are covered by the
spicular plate, fused together so as to form a rudimentary leaf. Above the
level of the top of the spicular plate they are, however, completely free from
one another. Of the two polyps, the dorsal one is always slightly smaller than
the ventral one in accordance with the general rule among Pennatulida. The
dorsal polyps of corresponding pairs are separated from one another by but a

\

PENNATULIDA DREDGED BY H.M.S. “ TRITON.” 135

slight interval (fig. 19), while the ventral polyps are separated by the whole
width of the ventral surface of the rachis.

The polyps are retractile, and the extremes of contraction and expansion
are represented in the two polyps of the upper pair in fig. 18. As the figure
shows there is no calyx formed during retraction, and the tentacles appear to
contract to a less extent than the bodies of the polyps. As in the case of
Virgularia tuberculata, the fact that the majority of the polyps have died in an
expanded or half-expanded condition may be taken as evidence that contraction
is effected slowly.

Each tentacle is supported on its outer or aboral surface by a strong rib of
calcareous spicules shown on a larger scale in fig. 20. These spicules are placed
for the most part obliquely, running upwards and outwards; they have an
average length of 0°13 mm. and diameter of 0°02 mm. They do not extend
into the pinnules.

At intervals along the body walls of the polyps spicules are found similar to
those of the rachis, but rather smaller and less abundant.

Concerning the reproductive organs I have no observations. According to
Koren and DAniELssEN,* these are normally situated in the body cavities of the
fully developed polyps in the genus Diibenia ; but a large polyp from the middle
of the colony, which I opened for the purpose, had no trace of reproductive
organs.

The zooids are few in number, and very small and inconspicuous. They
occur (fig. 19, e) as small rounded swellings on the dorsal surface between the
pairs of polyps, and also on the sides of the rachis just above the polyps.

The genus Diibenia was established by Koren and DANIELSSEN in 1874,t and
was at first named Batea, but that name being already appropriated for a genus
of Crustacea, it was changed in 1877 to Diibenia. It includes those members
of the family Stylatulide in which the polyps, though fused at their bases, do
not form distinct leaves, the fusion not extending above the calcareous fan-
shaped spicular plate. The validity of the genus has been questioned by
VERRILL and by RicuiArp1, but is accepted by K6LLIKER in his Report on the
“ Challenger” Pennatulida, and may be considered as established.

The “Triton” specimen has all the characters of Diibenia abyssicola vay.
smaragdina, as defined by Koren and DANiELssEN.[ This variety differs from
the typical D. abyssicola in its more slender form, in its pale colour, and in
having the polyps in groups of two instead of three or more. KoreEN and
DANIELSSEN express a doubt as to whether it should not be considered a
distinct species rather than a mere variety, a doubt which I must share without

* Op cit., p. 24.
+ Magazin for Naturvidenskaberne, 1874.
{ Koren and Dantetssen, Fauna littoralis Norvegic, part iii. p 96, 1877.

VOL. XXXII, PART I, Z

136 DR A. MILNES MARSHALL ON THE

attempting to remove, as I have had no opportunity of ae specimens of
the typical D. abyssicola.

The variety smaragdina has hitherto only been recorded from the Rams-
fjord close to Alveerstrémmen, two miles from Bergen, where it was found “at
a depth of 100 to 120 fathoms on a clayey sand bottom,” in company with the
typical D. abyssicola, but in smaller numbers.

The measurements of the “ Triton” specimen are as follows, those of two
specimens described by Koren and DANIELSSEN being given for the sake of
comparison :—

A. B. C.
2 phat aes aa Swedish specimens, entire.

Total length, ; ; 3 61 mm. 268 mm. 200 mm.
Rachis, . : : : : : 61 197 148
Stalk, . ; : . absent fell 62
No. of pairs of alae : ; : 34 54 44
Diameter of rachis, : : ; 0:36 . oe
Diameter of stem (at top), : , 0°32
Length of fully expanded polyp, _.. 4:5

tentacle, . 2-4
Length of retiectal polyp (incl. tentacle), 2 -
Size of large spicules of calyx, ; 2°3 x 0:15

tentacle, . 0:13 x 0:02

Size of See of body wall of polyp, 0°56

Section IT. Sprcata.
Sub-section 1. Funiculinee.
Family 1. Funiculinide.
Funiculina, Lam.

Funiculina quadrangularis, Pall. (Pl. XXIII. fig. 22.)

Ten fragments of this species were obtained by the “Triton” in Loch
Linnhe, off Castle Walker, in 35 to 37 fathoms of water, and at a distance of
31 miles from the shore.

All the specimens are small and imperfect. Two of them, of 9:4 and
12°5 cm, length respectively, have the stalks perfect, and are broken short
above at the lower part of the rachis. The remainder are all mere fragments
broken at both ends, and varying in length from 5 to 34 cm..

None of the specimens have the upper ends perfect, a very unusual circum-
stance with this species, which is usually obtained in perfect condition. The
specimens have, however, evidently been roughly handled, and were probably —
damaged at the time of capture. ‘

PENNATULIDA DREDGED BY H.M.S, “ TRITON.” 137

All the fragments belong to small and young specimens. Inasmuch as F.
quadrangularis is found at other parts of Loch Linnhe in great profusion and
of large size, specimens having been obtained up to 162 cm. in length, it
would appear that the locality from which the “Triton” specimens were
obtained is not one favourable to this species.

The portion of rachis of one of the young specimens drawn in fig. 22 shows
some points of interest. In the first place, it will be noticed that the calcareous
spicules, which in F. quadrangularis are usually confined to the calyx, here
extend down the whole length of the polyps along the lines of attachment of
the septa. These spicules, which also occur in the rachis, though in smaller
numbers, have an average length of 17 mm. The unusual abundance of these
spicules, and their presence in such young specimens, are points of interest.

The middle polyp of the figure is shown in a condition of extreme contrac-
tion ; the tentacles being completely withdrawn within the calyx, the processes
of which meet one another so as to form an acutely pointed cone. This figure
agrees very closely with one given by K6LLIkERr,* the accuracy of which has been
doubted, owing to the shape being so very unlike that of the expanded or half-
expanded polyp, and the apparently exaggerated length of the calyx processes.

Fig. 22 shows also the gradual increase in size of the polyps in passing
from the dorsal (right-hand surface in the figure) to the lateral surface ; also
the entirely independent insertion of polyps and zooids—a primitive feature ;
and the total absence of distinction between the young polyps and the zooids ;
also the quadrangular shape of the stem.

Sub-section 2. Junciformes.
Family 1. Kophobelemnonide.
Kophobelemnon, Asbjornsen.

Kophobelemnon stelliferum var. durum (Koll). (Pl. XXIV. figs. 23-28.)

Thirty-three entire specimens of this species and seven heads (the upper
polyp-bearing part of the rachis) were obtained, one of these being from the
“Knight Errant” collection, the remainder from the “Triton” one. They
were dredged at four different localities, Stations 6, 8, 10, and 11, and at
depths varying from 516 to 640 fathoms.

K. stelliferum was first found by O. F. MULLER in 1775, near Droébak, in the
Christianiafjord, and described by him in the Zoologia Danica, under the name
Pennatula stellifera. It has been dredged in various parts of the Christiania
fjord by Loven and by Aspsornsen,t the latter of whom obtained it in con-

* KouurKer, op. cit., pl. xvii. fig. 153.
7 AspsérnsEN, “ Beskrivelse over Kophobelemnon Miilleri,” Fauna littoralis Norvegie, Andet
Hefte, pp. 81-85, and Tab, 10, figs. 1-8, 1856.

138 DR A. MILNES MARSHALL ON THE

siderable numbers at a depth of about 40 fathoms, and of sizes varying from
20 mm. long, with only a single polyp, to 125 mm. long, with 24 polyps.

A single specimen was obtained by PAnceri from the Bay of Naples,* and
during the “‘ Porcupine ” expedition two specimens were obtained by CARPENTER
and WYVILLE THomsont off the N.W. coast of Scotland,—one in 59° 41’ N.,
and 70° 34’ W., at a depth of 458 fathoms, the other in 59° 34’ N., and 7° 18
W., and at 542 fathoms depth.

External Characters.—The “ Triton” specimens vary much in size, and in
the number and arrangement of the polyps. The smallest specimen is 26 mm.
long, and has only two polyps; the largest specimen in the collection, the
single specimen obtained by the “ Knight Errant,” is 88 mm. long, and bears
18 polyps.

The general appearance of one of the average specimens of the “ Triton”
collection is well shown in Pl. XXIV. fig. 23; the specimen being drawn from
the dorsal surface, double the natural size.

The rachis, which is somewhat club-shaped, is widest a short distance below
its upper end, from which point it tapers upwards to a blunt point. It bears
on its dorsal and lateral surfaces the polyps, which are few in number, and of
large size. Between the polyps the surface of the rachis is studded on all
sides with zooids, excepting a short tract immediately below each of the
polyps, which is destitute of zooids.

The stalk (fig. 23, >), which forms rather more than half the entire length of
the colony, and which is distinguished from the rachis by bearing no zooids,
is oval in section, as shown in fig. 27, and of tolerably uniform size along its
whole length, except at its lower end, which presents a terminal thin-walled
dilatation.

The arrangement of the polyps differs a good deal in different specimens, and
it is difficult to make out any definite system. In all cases the uppermost
polyps, those nearest the top of the rachis, are the largest, and the lowest ones
the smallest. The most usuai arrangement is that shown in fig. 23. Here
there are six fully developed polyps arranged in two sets, an upper and a lower
one, each of three polyps. Of these three, one is inserted in the dorsal surface
of the rachis very close to the mid-dorsal line, or actually in it, while the other
two are inserted on the sides of the rachis a little way below the dorsal polyp,
and not quite opposite one another, the right hand polyp being as a rule a little
above the left hand one. The three polyps of each set are of about equal size,
but those of the upper set are much larger than those of the lower set. Below
the lower set can be seen in many specimens, as in the one figured, a third set of

* Panceri, “Intorno a due Pennatularii l’uno non per anco trovato nel Mediterraneo, Valtro
nuovo del nostro golfo,” Rendiconto dell’ Academia delle scienze fisiche @ matematiche, Napoli,
Giugno, 1871.

t, Vide Koutixer, op. cit., p. 306.

PENNATULIDA DREDGED BY H.M.S. ‘“ TRITON.” 139

very small and as yet rudimentary polyps, arranged in a manner exactly corre-
sponding to the upper sets.

It is clear that this arrangement might also be described by saying that the
polyps are arranged in three longitudinal series, one dorsal and two lateral, the
members of each series decreasing in size from above downwards, and this is
indeed the method usually adopted. I am disposed, however, to prefer the
former mode of description, because it seems to me from an examination of a
number of specimens, that the three polyps of each set arise simultaneously, or
very nearly so, the dorsal polyps being often a little ahead of the lateral ones,
and the right lateral polyps appearing sometimes a little earlier than the
left ones.

There appears, indeed, to be a fair amount of constancy in the arrangement
and order of appearance of the polyps. Of twelve specimens, four had 3 polyps
only, which were clearly the three of the upper set ; five had 6 polyps arranged
as in fig. 23 ; one had 4 polyps, 7.¢., the 3 of the upper set and the second dorsal
one ; and the other two had 4 and 5 polyps respectively arranged in an irregular
manner. In specimens with a larger number of polyps than six, it is very
difficult to make out any definite plan of arrangement.

Structure of Polyps.—This has been very fully described by KOLLIKER,* and
will not be considered here in any detail. The main points are shown in the
figures 24 to 28. The mesoderm is everywhere, both in stalk, rachis, and
polyps, of considerable thickness, and has an immense number of calcareous
spicules imbedded in it (figs. 27, 28). Each tentacle (figs. 24 and 25) has
along its outer surface a prominent rib, made up of closely packed spicules,
while smaller ones extend along the pinnules, as first noticed by PANCERI.

The spicules of the tentacular rib, which may attain a size of 0°66 by 0-11
mm., are of the shape shown in fig. 26, and in transverse section in fig. 25.

The polyps project from the rachis nearly at right angles, as shown in fig.
23, and the polyp cavities on reaching the rachis do not stop, but bending
down at right angles to their former course, are continued for some distance
down the rachis, ending blindly below; the lower part of the stomodzeum, and the
whole of the organs below the stomodeum being thus contained within the
rachis. The greater part of the thickness of the rachis is, in fact, made up
of these lower ends of the polyps, which in a transverse section of the rachis
will be seen cut at various levels.

Fig. 28 represents such a section. On the left side it cuts one of the
lateral polyps longitudinally and horizontally (¢/ fig. 13) ; on the right side it
cuts the corresponding polyp of that side lower down, the section passing
transversely through the lower part of the stomodzeum. The dorsal polyp
of the set is cut at a still lower level, the section passing through the two
long mesenterial filaments and the ova.

* Op. cit., pp. 297-304.

140 DR A. MILNES MARSHALL ON THE

The section also shows four zooids cut, like the polyps, in different planes.
and at different levels.

Plane of Symmetry.—Each polyp of a Pennatulid colony can be divided.
longitudinally into two perfectly similar halves by one plane only, which is
spoken of as the plane of symmetry. This plane passes between the two long
mesenterial filaments, bisecting the septal chamber bounded by the two septa
which bear these filaments; it also bisects the septal chamber immedi-
ately opposite to this one, and passes along the long axis of the stomodzeum,
which in transverse section (fig. 28, s) is oval, not circular in shape. In
Kophobelemnon this plane of symmetry of each polyp has a very definite
relation to the rachis. The plane is a vertical one, and is perpendicular to the
surface of the rachis to which the polyp is attached, so that if prolonged it
would pass through the centre of the calcareous axis or stem. These relations
will become more obvious from an inspection of fig. 28. In the case of all three
polyps shown in this figure, the planes of symmetry, being vertical when the
specimen is placed upright in its natural position, will be at right angles to the
plane of the paper. In the case of the dorsal polyp the plane of symmetry
must pass through the centre of the polyp cavity, and must also (by definition)
pass midway between the two long mesenterial filaments p ; it is obvious from
this figure that this plane, if prolonged, will pass through the centre of the
calcareous stem ¢.

So also in the case of the right hand polyp of the figure. In order to
divide the retractor muscles 7m symmetrically, it is clear that the plane of
symmetry must bisect the septal chamber next to the stem c, and also the
chamber immediately opposite to this one; such a plane will pass along the
longer axis of the stomodzum s, and will, if prolonged, pass through the
centre of the stem ce.

So with. all the other polyps, the plane of symmetry will always be a
vertical one, will be at right angles to the surface of the rachis at the point of
insertion of the polyp, and will, if prolonged, pass through the centre of the
calcareous stem.

It is further evident from fig. 28 that the two long mesenterial filaments are
on the side of the polyp next to the stem, so that the surface of the polyp
which, when the polyp becomes free from the rachis (cf fig. 23), is continuous
with its upper surface, may conveniently be called the axial surface; while the
opposite surface, which is furthest from the stem, and which is continuous with
the lower surface of the polyp when this becomes free from the rachis, may be
called the abaxial surface.

I have already used the terms agial and abaxial when describing the
surfaces of the Pennatula zooids,* and have done so in exactly the same sense

* Supra, p. 125.

,

PENNATULIDA DREDGED BY H.M.S. “ TRITON.” 141

as that here proposed, the axial surface being that which bears the long
mesenterial filaments. As these words express a real and an important rela-
tion, they would appear preferable to the very misleading terms dorsal and
ventral, which are commonly employed to denote the surfaces in question.

The plane of symmetry of the zooids obeys exactly the same laws as that
of the polyps, the mesenterial filaments being placed on the axial wall.

Concerning the arrangement of the zooids on the rachis, it will be seen from
fig. 28 that the reason of the existence of a short tract devoid of zooids imme-
diately below each polyp is that this tract is really part of the abaxial wall of
the polyp; and as the zooids are developed on the rachis itself and not on the
polyps, there can clearly be no zooids on these tracts.

Retraction of Polyps.—In spite of the great rigidity of the wall both of the
polyp itself and its tentacles, due to the enormous number of spicules contained
in it, the polyps can, as shown on the right-hand side of fig, 23, be withdrawn
almost completely into the rachis, the tentacles entirely disappearing from
sight in the fully retracted state. During the process of retraction the body
wall of the polyp is thrown into transverse folds, and one specially deep fold
at the junction of body and tentacles (vide the left-hand polyp of fig. 28) corre-
sponds to the calyx of other Pennatulida.,

Structure of Stalk.—This is well shown in fig. 27, representing a transverse
section taken about the middle of its length. The mesoderm is of great
thickness, and is divided into inner and outer zones by the well-developed
layer of longitudinal muscles Im, which forms a deeply corrugated sheath
extending round the whole stalk. Of the two zones the outer one is very
richly studded with calcareous spicules 7, crossing one another in all possible
directions ; while the inner zone is devoid of spicules, and is traversed by a
dense network of nutrient canals. The stem c is quadrangular, with rounded
angles and grooved lateral surfaces. In the rachis, as we have seen (tig. 28), the

stem is cylindrical; but this change in shape is by no means exceptional,

occurring in Pennatula and several other genera, as well as in Kophobelemnon.

The stem is invested by a mesodermal sheath, which is prolonged outwards
to the body wall as four vertical septa, which separate from one another the
four main longitudinal canals of the stalk, of which the dorsal dc, and ventral
wc, are considerably larger than the lateral ones Jc. If these canals, which are
lined by endoderm, be traced upwards towards the rachis, the two lateral ones
are soon found to disappear; the dorsal one extends a short distance up the
rachis, and then in its turn disappears, while the ventral one (fig. 28, vc)
persists of considerable size throughout the whole length of the rachis.

Of Kophobelemnon stelliferum KOLLIKER* distinguished at first two varieties,
which he named mollis and dura respectively, the difference consisting chiefly

* KOLLIKER, op. cit., p. 305.

142 DR A. MILNES MARSHALL ON THE

in the greater number and size of the spicules of the latter, which reach in the
tentacles a length of from 0°64 to 0°89 mm. and width of 0°09 to 0:12 mm.
The muscular layers are also far less strongly developed in the var. dura than
in var. mollis. ;

At a later period* he described a specimen from the Atlantic at a depth of
690 fathoms, which was in all its characters intermediate between the two
other forms, and seemed to prove them to be merely varieties, and not, as once
supposed, specifically distinct.

The “Triton” specimens belong clearly to the variety dura, though they
differ a good deal among themselves as to the size of the spicules. The single
specimen from the “ Knight Errant ” collection has much smaller spicules than
any of the others, and is to be referred to the variety intermedia.

The following table gives the measurements of the ‘“ Knight Errant” speci-
men and of one of the typical “ Triton” specimens :—

A. B.
Var. intermedia Var. dura

from “ Knight Errant.” from “Triton.”

Total length, . : ‘ 82 mm, 45 mm.
Length of rachis, : 43°5 21
a stalk, ; : 38°5 (broken at lower end) 24
No. of polyps, . ; ‘ 18 6

Size of spicules (largest), : 0:31 x 0:018 0°66 x 0-11

All the specimens of XK. stelliferum were encrusted rather thickly with sand,
which adhered somewhat firmly to the ectoderm, and doubtless acted in part
as a protective envelope. The internal cavities, both stomodzum, body cavity,
and tentacular cavities, also contained large quantities of sand, which rendered
the preparation of sections a matter of some difficulty. Whether this indicates
a habit of retraction into the sand in which they live planted by their stalks, or
whether the sand is purposely swallowed for the sake of food matters that may
be mixed with it, I have had no opportunity of determining.

Family 2. Umbellulidee.

Umbellula, Lam.
Umbellula gracilis, n. sp. (Pl. XXV. figs. 29-35.)

Specific Characters.—Distinctly bilateral. Polypg forming a cluster on the
upper end of a club-shaped rachis ; greyish in colour with dark reddish-brown
tentacles. Stalk long, very slender and exceedingly flexible ; ending below in
a dilated vesicular portion. Zooids numerous on the rachis between the polyps, —

* Op. cit., p. 320.

,

PENNATULIDA DREDGED BY-H.M.S. “ TRITON.” 143

and extending a short distance below them; zooids of upper part of rachis

much the largest, and each provided with a tentacle bearing a double row of
pinnules ; zooids of lower part of rachis are smaller,—they may have tentacles,
but these do not bear more than a single pinnule. Stem cylindrical along the
ereater part of its length, becoming quadrangular in the terminal dilated part.
No calcareous spicules at any part of the colony.

Habitat.—Station 11; depth 555 fathoms.

External Characters.—A_ single specimen of this species was obtained
with the trawl. This specimen, which is in perfect condition, is represented
of the natural size, and from the dorsal surface in Pl. XXV. fig. 29. It hasa
total length of 290 mm., of which the upper 26 mm. are expanded to form the
club-shaped rachis. This ends above in a blunt point (fig. 30), and is widest about
the middle of its length, where it measures 6 mm. from side to side, and 5 mm.
from the dorsal to the ventral surface.

The rachis bears the polyps on the upper two-thirds of its length, and below
the lowest polyp tapers somewhat rapidly, and passes without any sharp line of
demarcation into the stalk.

The stalk is cylindrical and very slender, with a diameter about the middle
of its length of 0°8 mm. At its lower end it presents a distinct enlargement,
35 mm. long and 3°5 mm. in diameter. For the greater part of its length the
stalk is extremely flexible, so much so that it can readily be coiled in circles of
5 mm. diameter without the slightest danger of breaking.

The stem or calcareous axis is cylindrical along the greater part of the
length of the stalk, with an average diameter of 0°5 mm. Shortly before
reaching the terminal dilatation of the stalk the stem enlarges somewhat
suddenly to 0‘9 mm. in diameter, becoming at the same time quadrangular in
shape, and very much more rigid than in the upper part. In the terminal
dilatation it gradually tapers towards the lower end.

The polyps, which are confined to the upper 18 mm. of the rachis (figs. 29
and 30) are 13 in number, and gradually increase in size from above down-
wards. They are inserted on all sides of the rachis, with the exception of a
narrow strip 1°5 mm. wide along the mid-ventral surface (fig. 30), aud even this
is somewhat encroached upon by the lowest polyps.

It is difficult to make out any definite plan of arrangement of the polyps.
Commencing at the top, the first polyp, which is the smallest of the lot, is
inserted in the left latero-dorsal surface just below the apex. The second
polyp is placed on the right latero-dorsal surface, a little way below the first.
Then comes a rather irregular whorl of six polyps, of which two are dorsal,
two lateral, and two latero-ventral; and finally a lower whorl of five polyps,
the largest of all, of which one is mid-dorsal, two lateral, and two latero-ventral,
the left one of the last pair almost reaching the mid-ventral line.

VOL. XXXII. PART I. 2A

144 DR A. MILNES MARSHALL ON THE

The body of the polyp is greyish in colour, and from 10 to 15 mm. in length.
It is widest at its base—4 mm. in the larger polyps, and gradually narrows in
its upper third to 25 mm. The upper part is marked by very distinct longi-
tudinal grooves opposite the septal attachments, and is also slightly corrugated
transversely.

The tentacles are of a dark reddish-brown colour, and of about the same
length as the polyp body. Lach is fringed by a double row of pinnules, which
exhibit an irregular alternation of larger and smaller ones (fig. 31); the larger
pinnules being inserted rather nearer the inner or oral surface of the tentacle
than the small ones. LinDAHL™ has directed special attention to this inequality
of the pinnules in the case of U. Lindahli (KOll.)+, where it appears to be much
more marked than in U. gracilis.

The polyps and tentacles are non-retractile, or can at most be withdrawn to
a very slight extent, and there is no trace of a calyx.

Structure of Polyp.—One of the polyps was removed fu the sake of
studying its structure, and cut into a series of transverse sections. The
anatomy presents no points of special importance. The body wall is of only
moderate thickness, the body cavity and tentacular cavities being of large size.
As in Kophobelemnon the polyp cavities are prolonged into the rachis, but a
larger proportion of the polyp is free than in this genus; the stomodeeum and
upper part of the mesenterial filaments being contained within the free part of
the polyp, and the reproductive organs and lower part of the mesenterial fila-
ments being alone situated within the rachis.

The plane of symmetry in the case of the one polyp examined, and pre-
sumably in the others as well, obeys the same laws that have been found above
to apply to Kophobelemnon and Pennatula, 7.e., it is vertical and at right angles
to the surface of the rachis at the point of insertion of the polyp. The axial surface
of the polyp, moreover, is that which bears the two long mesenterial filaments.

The single specimen obtained is a female, and the arrangement of the
reproductive organs is the same as in other Pennatulida, the ovaries being the
free edges of the six septa which bear, higher up, the six short mesenterial
filaments. Fig. 34 represents a section of one of these fertile septa and of the
part of the body wall from which it springs. The figure shows the largely
developed retractor muscle of the polyp rm, and at the edge of the septum ova
in various stages of development, each with a large nucleus and nucleolus, and
invested in a distinct epithelial capsule. The ripe ova have a diameter of
0-1 mm.

* LinDau, “Om Pennatulid-sligtet Umbellula,” Kongl. Svenska Vetenskaps-Akademiens Handlingar,
Bd. xiii. No. 3, Stockholm, 1874.
+ Kouuker, Die Pennatulide Umbellula, Wurzburg, 1875. K6xi1Ker proposes to group together

Linpauw’s U, miniucea and U, pallida under the name U. lindahli.
,

‘
1

PENNATULIDA DREDGED BY H.M.S. “TRITON.” 145

The specimen being in excellent histological condition, I have been enabled
to make some observations on the development of the ova. Fig. 35 represents
a transverse section through one of the ovigerous septa close to its free inner
edge. The septum is seen to consist of a central mesodermal lamella z, clothed
on each side by a thick layer of endodermal cells y. Of these cells the super-
ficial ones form a layer of short columnar or cubical cells, while the remainder
of the endoderm consists of larger cells of irregular polygonal shape, closely
packed together, with large granular but rather ill-defined nuclei and granular
protoplasm.

Among these cells certain ones are conspicuous by their larger size and
granular appearance, o’. These, which are the germinal cells or primitive ova,
appear to arise in the deeper parts of the endoderm layer close to the meso-
derm lamella, and as they increase in size gradually move outwards towards
the surface.

Together with this increase of size the ova become spherical in shape, the
protoplasm becomes very granular and opaque, and the nucleus, which at first
was an ill-defined granular body, becomes vesicular, and acquires a distinct
nucleolus and a very well-marked nuclear reticulum. In some of the larger
Ova 0, a reticular appearance is also evident in the protoplasm.

The ovum, by its continued growth, reaches the surface of the septum, and
pushing before it the surface layer of columnar epithelium, which forms the
follicular investment, projects freely from the surface to which it remains
attached by a short stalk (fig. 34).

In Sagartia, according to the HErtwias,* the ova arise in the deeper layer
of the endoderm, but sink into and become invested by mesoderm before com-
mencing their outward passage towards the surface of the ovary. I have seen
no trace of such a mesodermal investment in Umbellula, neither have I seen the
peculiar polar fibrillar apparatus described in Sagartia.

Structure of Zooids—The zooids of U. gracilis are unique among Penna-
tulida, so far as at present known, in possessing pinnated tentacles.

As shown in fig. 30, the zooids cover all parts of the rachis not occupied by
the polyps. The largest zooids are those at the upper end of the rachis, and
it is in this situation alone that the zooids with pinnated tentacles occur. Below
the polyps the zooids get gradually smaller and smaller.

Fig. 32 represents on a larger scale a group of zooids from the ventral
surface of the upper extremity of the rachis, drawn with the camera. The
zooids are seen to be conical, in the best marked cases tubular, projections with
a mouth at the free end overhung by a single tentacle, which bears a variable
number of pinnules. The pinnules may occur on one side only or on both,
and in some cases form a row of five or six on each side of the tentacle.

* O. und R. Hertwic, Die Actinien, pp. 95 seq.

146 DR A. MILNES MARSHALL ON THE

In fig. 33 one of these zooids is represented in longitudinal vertical section,
together with the part of the rachis from which it springs.

The tentacle, which is hollow, overhangs the mouth on the abaxial side,
a point of some interest, inasmuch as the calycular processes of the large
ventral zooids of P. phosphorea var. aculeata were also found to be abaxial
(of. Pl. XXII. fig. 8).

The mouth leads into the stomodzum s, the abaxial wall of which is
clothed with very long cilia 7. At its lower end the stomodzum opens into
the body cavity h, which is lined by endoderm, and is prolonged into the
tentacle. The body cavity is, at any rate in some cases, in direct communication
with that of adjacent zooids.

As in zooids generally, there are only two mesenterial filaments present, of _
which one is shown in the figure. These are borne by the axial septa, and are
extremely long and much convoluted.

In some of the larger zooids I have noticed a slight notching of the margin
of the mouth, which may possibly indicate the rudiments of additional ten-
tacles. )

Below the polyp-bearing part of the rachis the zooids become much smaller.
The tentacles at first increase slightly in length, but become much more slender,
and lose their pinnules, with the exception of a single one, which is often
retained, giving a bifid appearance to the tentacle. These tentaculiferous
zooids are, as shown in fig. 30, almost confined to the lateral margin of the
rachis, the zooids of the dorsal and ventral surface becoming very early reduced
to the condition of small wart-like knobs. These become ‘smaller in size and
more irregular in arrangement as we pass downwards, and finally cease about 50
mm. from the upper end of the rachis.

In possessing single tentacles the zooids of U. gracilis resemble those of U.
Hucxleyi and U. Carpenteri,* two of the species obtained by the “ Challenger ”
from the North Pacific and South Polar seas respectively, but differ from
all other species, and indeed from all other Pennatulida yet described.
In possessing pinnated tentacles the zooids of U. gracilis stand absolutely
alone. “a

I have pointed out above, when discussing the nature of the zooids of P.
phosphorea, that zooids must be considered as abortive polyps arrested in an
early stage of development.

It becomes now an interesting inquiry how this unitentacular condition of
the zooids of Umbellula arose. So far as is at present known, the earliest rudi-
ments of all eight tentacles arise simultaneously in the Pennatulid polyps. I
have described this above in the case of the asexually formed polyps of Pennatula

, * KotuKer, Zool, Chall. Exp., part ii. 1880, pp. 21-24.

erm,

PENNATULIDA DREDGED BY H.M.S. “ TRITON.” 147

and Virgularia, and Witson * has recently shown that the same applies to the
sexually produced young of fenil/a. It appears, therefore, that the unitenta-
cular condition of the Umbellula zooid is not a repetition of any stage occurring
in the ontogeny of the normal Pennatulid polyp. It is, however, just possible
that such a stage once existed in the phylogeny of the group, but has dropped
out of its ontogeny. So far as is known, a unitentacular condition does not
obtain in the ontogeny of any Alcyonarian, though we must bear in mind that
very few forms have as yet been studied adequately. Among Zoantharia a_
temporary unitentacular condition occurs in Actinia mesembryanthemum,t while
in Cerianthus and Arachnitis four tentacles arise simultaneously, and in other
cases all eight.

The definite relation of the single tentacle of the Umbellula zooid to the
plane of symmetry seems to indicate that it has some morphological signi-
ficance, though at present we have not evidence to determine what that
significance is. I would, in conclusion, direct attention to the. remarkable
condition of the polyps in Scytalium tentaculatum, Koll.,t one of the “ Chal-
lenger ” species, in which each polyp has but a single tentacle, as showing that
a unitentacular condition may be more widely spread than is at present
suspected.

Our knowledge of the genus Umbellula has been very greatly increased of
late years. Two specimens taken off the coast of Greenland in 1752, and very
imperfectly described, were for more than a century the only examples recorded.
In 1871 Linpaut obtained two specimens, one in Baffin’s Bay in 410 fathoms,
and the other at the entrance to the Omenakfjord, in N. Greenland, at a depth
of 122 fathoms. An Umbellula was also obtained by NorDENSKIGLD in the
Kara Sea, to the east of Novaya Zemlya, during the ‘“ Vega” expedition.

The ‘Challenger ” expedition added enormously to our knowledge of this
genus, no less than seven new species being obtained from widely different
parts of the world. Concerning the geographical distribution of this genus
KOLLIKER says :—‘‘ After having known for more than a century only one
locality, the North Polar Sea, near the coast of Greenland, we have now learned
that this form is far and widely distributed. Umbellule have now been
obtained from the North Atlantic Ocean (between Portugal and Madeira);
from the North Polar Sea, coast of Greenland; from the Atlantic Ocean, under
the Equator, between Africa and America, and from the west coast of Africa,
north of Sierra Leone (Stud.) ; from the South African Sea, west of Kerguelen
Island ; from the South Polar Sea; from the coasts of New Guinea and of

* Witson, “‘ The Development of Renilla,” Proc. Roy. Soc., 1882.

7 Lacaze-Durtuiers, “ Développement des Coralliaires,” Archives de Zoologie expérimentale et
générale, vol. 1. 1872, and vol. ii. 1873.

{ KouuiceEr, Zool. Chall. Exp., part ii, 1880, pp. 10, 11, and pl. iii. fig. 12, pl. iv. fig. 13.

148 DR A. MILNES MARSHALL ON THE

Japan; and from the middle of the North Pacific Ocean. Umbellula has,
therefore, of all genera of Pennatulida, the widest distribution.”*

The “ Triton” specimen makes a very interesting addition both to the list —
of species of Umbellula and to the localities in which it has been found.

The measurements of the sole specimen of Umbellula gracilis yet known are
as follows :—

Total length, . 2 : . : 290 mm.

Length of rachis (aieced “sea ; . ; : 26
Length of polyp-bearing part of rachis, : : ; 18
Width of rachis at widest part, ; : . . 6
Thickness, . ‘ : ; 5
Length of terminal aleiatsert of cialis : : ‘ oo

Diameter, . : : ; 3°2

Diameter of stalk (middle of length), : ! 0-7

i stem, . d : : 0°5

Ee stem (widest ao , : f ; 0-9
Number of polyps, . 5 ‘ ; : ‘ 13
Length of polyp (shortest), . —.. F f : 15

a body, . . , E TS

E tentacle, . , 4 . ee
Length of polyp (largest), . : ; : ; 26
pi body, . : ; ; 13
tentacle, . ; : . 18
iamaire of polyp, base, : ‘ : : 5

just below feiss s : , 2°8

Length of zooid, largest, 3 ; = : 1:8

Length of tentacle of zooid, ieee ; ; : : 13

GENERAL OBSERVATIONS.

Geographical Distribution.

Horizontal Distribution.—The most noteworthy point is the great abundance
and variety of specimens dredged at one particular locality,—Station 11. At
this place there were obtained, from a depth of 555 fathoms, nineteen specimens
of Pennatula phosphorea var. aculeata; three specimens of Virgularia tuber-
culata, a new species ; one specimen of Diibenia abyssicola var. smaragdina, a
form hitherto found only off the Norwegian and Swedish coasts ; thirty speci-
mens of Kophobelemnon stelliferum var. dura; and one specimen of Umbellula
gracilis, a new species ; 7.¢., example of five out of the fourteen known families
of Pennatulida, of three distinct subsections, and two of the four sections of
the order were obtained at this one spot.

, * KouuiKer, Zool. Chall. Exp., part ii. 1880, p. 37.

PENNATULIDA DREDGED BY H.M.S. “ TRITON.” 149

This extraordinary profusion mark the locality as a very exceptional one.
At each of the other stations only single species were obtained.

Vertical Distribution.—The “Triton” observations have increased the ver-
tical range of Pennatula phosphorea to 555 fathoms, its previously recorded
limit being 340 fathoms; of Diibenia abyssicola, from 120 to 555 fathoms ; of
Kophobelemnon stelliferum v. durum, from 300 to 640 fathoms; and have added
a new deep water Virgularia, V. tuberculata, extending to 555 fathoms, to the
sole one previously known, V. bromleyi.

These results, so far as they go, do not lend any very material support to
KO6LLIKER’s conclusion, that “the simpler forms of Pennatulida, especially those
with sessile polyps, inhabit great depths.”*

KO6LLIKER ranks among primitive forms of Pennatulida the Umbellulida,
which are an essentially deep water family, seven out of the twelve known
species being found below 1000 fathoms and five below 1800 fathoms, and cites
this distribution in evidence of the view that the lower forms of Pennatulida
are, as a rule, deep water forms.

Umbellula appears to me, however, to be not a primitive form but a highly
modified one. This is shown by the great length of the non-polypiferous as
compared with the polyp-bearing part of the colony, 7.¢., the great prepon-
| derance of the purely colonial portion ; by the great difference between the
polyps and the zooids ; by the extreme differentiation of some of the zooids ;
and, above all, by the polymorphism of the zooids themselves, an almost unique
condition among Pennatulids. In all these respects Umbellula is far less pri-
mitive than Funiculina, which is essentially a shallow water form, attaining its
maximum of development at about 30 fathoms depth.

A point of considerable interest concerns the influence of increase in depth on
| the structure and habits of Pennatulids. On this point but little can be said at
, present for want of sufficient evidence.

We have seen above that some of the deep water forms (below 500 fathoms)
have much thicker body walls and layers, and more numerous spicules, than
| those from less depths. If we compare different genera together there would
appear to be no relation whatever between depth of water and development of
| spicules; thus Umbellula gracilis and Virgularia tuberculata from 555 fathoms
| have no spicules at all; while P. phosphorea and K. stelliferum, brought up in
| the same dredge with the preceding species, have exceptionally large and
numerous spicules. If, however, we confine ourselves to one species, we seem
to find such a relation; thus the specimens of Pennatuia phosphorea from below
| 500 fathoms have very much thicker walls, and larger and more abundant
spicules, than those from 20 to 40 fathoms. In this case we have strong reason

* Kouuiker, Zool. Chall. Exp., part ii. 1880, p. 39.

150 DR A. MILNES MARSHALL ON THE

for thinking, from the small size and somewhat stunted appearance of the deep
water specimens, that the species is typically a shallow water one, and it is very
possible that the increase in development of spicules is due directly to the
change of environment.

All the specimens of Kophobelemnon and also those of Pennatula obtained
below 500 fathoms contain large quantities of sand mixed with Foraminifera
shells, both in the polyp cavities and in the tentacular cavities, and also
encrusting the exterior. The specimens of Umbellularia, Diibenia, and Virgu-
laria brought up at the same time are, however, perfectly clean and free from
sand. Whether this indicates difference in habits or is merely accidental, I
have no means of ascertaining; the specimens of Pennatula from shallow
water have no sand in the polyp cavities, or but very little.

Morphology.—The chief points of morphological interest on which light is
thrown by the “ Triton” specimens appear to concern the structure of the
zooids of Pennatula and Umbellula ; and the relations of the plane of symmetry
of the polyps established in Pennatula, Kophobelemnon, and Umbellula.

DESCRIPTION OF THE FIGURES ON PLATES Kee xRy,

All the figures were drawn with the camera. -Figures 8, 28, and 33 are not taken from
single sections, but are constructed from a number of separate camera drawings of the several
parts shown. The numbers beneath the figures indicate in diameters the magnifying power —
employed in each case.

Alphabetical List of References,

a, rachis. nm, mouth.

b, stalk. 0, ovum.

c, stem. o’, germinal cell or primitive ovum.
d, polyp. p, long mesenterial filament.

dc, main dorsal canal of rachis. 7, cilia of siphonoglyphe.

dl, leaf. rm, retractor muscle of polyp.

e, zooid. s, stomodzeum.

t, tentacle.

t’, cavity of tentacle.

u, pinnule of tentacle.

v, spermatosphere.

ve, main ventral canal of rachis.
w, ectoderm.

J, large zooid.

g, body cavity of polyp.
h, body cavity of zooid.
i, spicule.

k, spicular plate.

1, calyx process,

I’, cavity of calyx process.
lc, main latera) canal of rachis.

Im, longitudinal muscles of rachis and stalk.

m, tneseutery or septum.
,

“, mesoderm.
z’, nutrient canals of mesoderm.
y, endoderm.

PENNATULIDA DREDGED BY H.M.S. “‘ TRITON.” 151

PLATE XXI.

Fig. 1.—Virgularia tuberculata ; ventral surface. x 3.

Fig. 2.—Virgularia tuberculata ; portion of rachis, ventral surface, showing arrangement of
polyps in groups of threes; also the tubercular calyx processes and the varying
conditions of the calyx during retraction of the polyp. x 17.

Fig. 3.—Viryularia tuberculata ; two spermatospheres from lower part of rachis of the speci-
men shown in fig. 1. x 70.

Fig. 4.—Pennatula phosphorea var, aculeata ; from right side. Shows characteristic shape of
leaves, also both small and large zooids, x 2.

Fig. 5.—Pennatula phosphorea var. aculeata ; transverse section of rachis with one entire leaf
and the base of the corresponding one of the other side. Shows shape of leaf;
shape and arrangement of zooids both large and small; great thickness of wall of
rachis, and small size of its main canals. x 4.

Fig. 6.—Pennatula phosphorea ; transverse section of rachis with entire leaf of normal form, for
comparison with fig. 5. Shows great width of leaf, absence of large zooids, thinness
of walls of rachis, and large size of main canals. x 4.

Fig. 7.—Pennatula phosphorea var. aculeata ; lower end of rachis from left side. Shows stages
in development of polyps, and especially the simultaneous appearance of the
calyx processes and of the tentacles; also the primitive independence of the
polyps of one another. x 17.

PLATE XXII.
Illustrating the anatomy of the large ventral zooids of Pennatula phosphorea var. aculeata.

The reference letter ¢! in the figures on this plate should be 7.

| Fig. 8.—Longitudinal section of large ventral zooid and of the part of the rachis from which

it arises. Shows structure of large zovid and of one of the small zooids. x 50.

Fig, 9.-—Transverse section of a calyx process of a polyp, for comparison with the succeeding
figure. x 150.

Figs. 10 to 16.—Transverse sections through one of the large ventral zooids at various parts of
its height, fig. 10 being close to the apex and fig. 16 at the base of attachment to
the rachis. x 150.

‘Fig. 10.—Through upper end of zooid, showing one calycular cavity.

| Fig. 11.—Lower down; shows two calycular cavities.

| Fig. 12.—Lower down still; shows three calycular cavities.

Vig, 13.—Through upper part of mouth; shows long cilia of siphonoglyphe.

| Fig. 14.—Through lower part of mouth; shows five calycular cavities.

| Fig. 15.—Through stomodzeum about the middle of its length. Shows eight septa and septal

chambers.

| Fig. 16.—Through lower part of polyp cavity, showing the two mesenterial filaments, and the

remains of the other six septa.

PLATE XXIII.
Fig. 17.—Diibenia abyssicola var. smaragdina. Ventral surface. x 3.
| Fig. 18.—Diibenia abyssicola var. smaragdina. Portion of rachis from left side. Shows
arrangement of polyps in pairs, each pair embraced at base by a fan-shaped spicular
plate. .x 17.
VOL. XXXII. PART I: 2B

Fig.

ig. 19.—Diibenia abyssicola var. smaragdina. Portion of rachis from dorsal surface. Shows —
. 20.—Diibenia abyssicola var. smaragdina. Tentacle of polyp, showing rib of calcareous

. 21.—Diibenia abyssicola var. smaragdina, one of large spicules of spicular plate. x 55, —
. 22.-Funiculina quadrangularis. Portion of rachis of young specimen from left side.

. 23.—Whole specimen, dorsal surface; showing typical arrangement of polyps. x 2.
. 24,—Tentacle of polyp; showing rib of calcareous spicules extendirig whole length of

ig. 25,—Transverse section of tentacle, showing tentacular cavity and extension into pinuules, |

. 26.—Two large spicules from spicular rib of tentacle. x 55,
g. 27.—Transverse section of stalk; showing arrangement of spicules and muscles; also

. 28.—Transverse section of rachis passing through three polyps at different portions of

. 29.—Whole specimen; dorsal surface. x 1.

. 30.—Rachis; ventral surface. Shows arrangement of polyps and zooids. x Q.
. 31.—Tentacle of polyp; shows alternation of large and small pinnules. x 10.
. 82.—Apex of rachis; ventral surface. Shows shape and arrangement of large zoids

ig. 33.-—Longitudinal section of one of the large zooids; shows the tentacle with its pinnules,

34.—Section of septum bearing ova, and of the part of the body wall of the polyp from

DR A. MILNES MARSHALL ON THE PENNATULIDA, ETC.

arrangement of polyps and zooids. x 17.

spicules. x 70.

Shows shape of polyp in state of extreme contraction; also extension of apioules 4
down whole length of polyps and on to rachis. x 7.

PLATE XXIV.

Kophohelemnon stelliferum var. durum.

tentacle and along pinnules. x 20. 7

also arrangement and shape of spicules. x 70.

shape of stem and of main longitudinal canals. x 30.

their length. The left-hand polyp is cut horizontally (¢f. fig. 23), and shows stomo-
dum, mouth, and tentacles; the right-hand polyp is cut transversely through the
lower portion of the stomodzeum, and shows arrangement of retractor muscles and
position of plane of symmetry of polyp; the third or dorsal polyp is cut trans-
versely at a still lower level, and shows the two mesenterial filaments and a
number of ova. The section also shows several zooids and the shape and position
of the stem and of the main ventral canal. x 30.

PLATE XXV.

Umbellula gracilis,

with pinnate tentacles. x 14.
mouth, stomodzeum, mesenterial filament, &e. x 55. .

which the septum arises. Shows also the disposition of the retractor muscle,
x 70. ‘ :
35.—Section of ovigerous septum close to its free edge, showing various stages in the
early development of the ova. x 470.

Vol. XXXIL, Plate XXL

Marshall del.ad nat.

¥. Huth, Lith Edin®

VBR GUA Rola EN SNCA st UME eas

Trans. Roy. Soc. Edin? Vol. XXXI1, Plate XXII.

1

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JA.M. Marshall del.ad nat F Huth, Lith® Edi

PUESN-NeA T UCL A:

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Fig. 18.
X17

farshall,del.ad nat.

ans. Roy. Soc. Edin?

‘vans. Roy. Soc. Edin® Vol. XXXII, Pl. KXIV.

Fig. 23.

xX 2

oe

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RAIA

aaa

-Marshall,del ad nat. F.Huth, lntht Edin®

KO-Pe hOB Ev vE.E MN ON.

Trans. Roy. Soc. Edin®

. Vol. AXXI, Plate XXV.

—————

Marshall del. ad nat.

F Huth Lath’ Edin®

VOW EB Ee UA.

1X.—Asteroidea dredged in the Faerie Channel during the Cruise of H.M.S.
“ Triton” in August 1882. By W. Percy Siaven, F.L.S., F.G.S.
Communicated by Joun Murray, F.R.S.E. (Plate XX VI.)

(Read 16th July 1883.)

The star-fishes recorded in the present communication were dredged by Mr
JoHN Murray during the cruise of H.M.S. “ Triton” (under the command of
Staff-Commander Tizarp, R.N.), whilst investigating the nature of the Wyville-
Thomson Ridge and the adjacent portions of the Faerée Channel. All the
forms, excepting these from Station 3, were obtained from deep water, and the
collection, as a whole, is both rich and interesting. One species and two well-
marked varieties have not hitherto been described, and two other species have
only been found once previously. The series consequently forms a valuable
supplement to the collections made during the cruises of H.M.S. “ Porcupine ”
and the “ Knight Errant,” and is an important addition to our knowledge of the
fauna of this region of the Atlantic. I propose to reserve any remarks upon
the general character of the asterid fauna of the Faerdée Channel until treating
of the collections obtained during the “‘ Porcupine” and “ Lightning” cruises.

I am indebted to Mr Murray for his kindness in placing this collection in
my hands. | |

I. List oF THE SPECIES COLLECTED.

1. Pteraster militaris (O. F. Miller), Miiller and Troschel.

Station 2. August 5, 1882. Lat. 59° 37’30” N., long. 6° 49’ W.
Depth, 530 fathoms ; bottom temperature, 46°-2 Fahr.

2. Pteraster militaris, var. prolata, nov. (Plate X XVI. fig. 1.)

Station 9. August 23, 1882. Lat. 60° 5’ N., long. 6° 21’ W.
Depth, 608 fathoms ; bottom temperature, 30° Fahr.

This is a remarkable form, differing greatly in general appearance from the
normal type of P. militaris; and although it accords in the main with the
diagnostic formula of that species, the majority of the characters differ more or '
less in degree. It is not improbable that a series of examples might ultimately

warrant its being ranked as a distinct species ; but for the present I prefer to

WO, XMMIL PARI" T. pa OF

[54 MR W. PERCY SLADEN ON THE

place the solitary specimen as a variety of P. militaris until further material is —
available—a course which is sufficient to identify the form, and at the same time
indicate the nearest specific affinities.

The variety is characterised by the following points :—The great length and
narrowness of the rays; R>37; R=58 to 60 mm., 7=18 mm. ; breadth of a ray
at the base, 18 to 22 mm. extreme measure. The dorsal paxille appear usually

to have one of their spinelets much more robust than the two or three com- —

panion spinelets, which are remarkably fine and delicate, and the tips of the
spinelets can scarcely be said to protrude through the supradorsal membrane,
notwithstanding that this latter is placed rather loosely upon them, and much
wrinkled. Two or three lineal series of paxillee are more or less clearly distin-
guishable along the. sides of the rays. On the actinal surface the segmental
apertures are remarkably large, and the aperture-papille are much broader and
more robust at their proximal portion than in P. militaris. In the ambulacral
spines the three inner spines of each transverse comb form a line oblique to the
furrow, the comb being curved aborally at the margin of the furrow, and the
position of these spines upon the adambulacral plate being also oblique in rela-
tion to the plane of the ray. The actino-lateral spines are very short, and the —
outer portion of the web which proceeds from the outermost ambulacral spine,
i.é., the membranous continuation of the transverse comb upon the actinal
membrane, is much more prominent than in the typical form of the species, and
extends up to the margin of the lateral fringe. Although these differences may
appear insignificant verbally, they produce when combined a striking facies, the
characters of which can hardly be explained, as being simply the modifications
of the normal form consequent on the conditions of a deep water habitat, since
the example of P. militaris from 530 fathoms (Station 2), recorded above, differs
in no way from the normal form.

3. Archaster lenuispinus (Diiben and Koren), Sars.

Station 9. August 23, 1882. Lat. 60° 5’ N., long. 6° 21’ W.
Depth, 608 fathoms ; bottom temperature, 30° Fahr.

4. Archaster bifrons, Wyville Thomson.
Station 10. August 24, 1882. Lat. 59° 40’ N., long. 7° 21’ W.
Depth, 516 fathoms ; bottom temperature, 46° Fahr.
Station 11. August 28, 1882. Lat. 59° 29’ N., long. 7° 13’ W.
Depth, 555 fathoms ; bottom temperature, 45°°5 Fahr.

5. Astropecten Andromeda, Miiller and Troschel.

Station 10. August 24, 1882. Lat. 59° 40’ N., long. 7° 21’ W.
Depth, 516 fathoms ; bottom temperature, 46° Fahr.

ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. “TRITON.” 155

Station 11. August 28, 1882. Lat. 59° 29’ N., long. 7° 13’ W.
Depth, 555 fathoms ; bottom temperature, 45°°5 Fahr.

The propriety of retaining this form in the genus Astropecten appears to be
questionable. I propose to reserve the discussion of the subject until dealing
with some allied forms obtained by the “ Challenger ” expedition.

6. Luidia ciliaris, Philippi.
Station 3. August 8, 1882. Lat. 69° 39’ 30” N., long. 90° 6’ W.
Depth, 87 fathoms ; bottom temperature, 49°°5 Fahr.

I consider this form separate from LZ. Sarsii, D. and K. Both species were
comprised in Forbes’ LZ. fragilissima. I regard L. Savignyi, Audouin, distinct
from either.

Rhegaster, gen. nov.

Marginal contour subpentagonal; rays slightly produced. Abactinal sur-
face more or less convex, actinal flat. The whole body covered with mem-
brane, beset with crowded spinelets.

Abactinal skeleton composed of irregular plates, crowded and subimbricated
in places, which leave small irregularly disposed meshes. The whole skeleton
is hidden in a thick membrane, and furnished with a compact covering of

_ small, uniform, crowded spinelets. Papule small, numerous, isolated, irregu-

larly distributed over the whole area. Infero-marginal plates large, forming
the margin of the test. Supero-marginal plates superficially invisible, concealed
-in the dorsal membrane. Actinal interradial areas with large subregular plates,
hidden by a superficial membrane, with small crowded spinelets.
-Adambulacral plates broader than long. Ambulacral spines short and
thickly invested with membrane, forming a regular furrow-series and several

| . . . : .
subregular longitudinal rows externally. Ambulacral sucker-feet in simple pairs,

with small sucker-disk.
Madreporiform body small, midway between margin and apex. Anus sub-
central. No pedicellariz.

This genus comes within the scope of the family Asterinidw as defined by
Dr VicuiEr, and appears to be well distinguished from the other genera of the
group. In addition to the species now described, I include in the genus the
interesting form named by Dr StuxBere* Solaster tumidus, but which has more
recently been referred to the genus Asterina by Drs DANIELSSEN and Koren.t
| The latter naturalists have given an admirable description, and two detail

* Ofversigt af Kongl. Vet.-Akad. Férhandl., Arg. 35, 1878 (1879), No. 3, p. 31, pl. vi.
+ Nyt Mag. f. Naturvidensk., Bd. xxvi. hft. 2, p. 182, pls. i. and ii. figs. 6-10.

156 MR W. PERCY SLADEN ON THE

figures of specimens dredged during the Norwegian North Atlantic Expedition,
and a well-marked variety (var. twberculata, D. and K.) is also defined. DAntEL- —
ssEN and Koren state that they place the S. twmidus provisionally as an
Asterina, and mention at the same time a number of important points wherein
the form differs from that genus. The determination appears to have been
published with cautious hesitation, and I feel bound to express regret that the
circumstance of the discovery of the new species should force upon me the
undesired course of forestalling the Norwegian savants in the establishment of —
a genus for the reception of a form upon which they have bestowed such care- |
ful study. oe

' Through the kindness of Professor Lovin, I had the privilege of examining —
Dr StuxBErG’s type specimens when in Stockholm last autumn, and I am able ©
to confirm the opinion of Drs DANIELSsSEN and Koren in regarding the original
reference of the form to Solaster as altogether untenable.

7. Rhegaster Murrayi, n. sp. (Plate XXVI. figs. 2-7.)

Station 5. August 10, 1882. Lat. 60° 11’ to 60° 20’ N., long. 8° 15/ to
S 8 WW.
Depth, 433 to 285 fathoms ; bottom temperature, 43°:5 to 40°°8 Fahr.

Marginal contour subpentagonal, rays slightly produced; the lesser radius
in the proportion of 77 per cent., or as 5:6°5. R=14'3 mm., r=11 mm.

Interbrachial angles aGrsaitia indented at the median eee line, from
whence the contour curves outward faintly, consequent on a slightly tumid swell-
ing at the base of the ray, and is then gracefully incurved towards the tip, which
is obtuse and rounded. Abactinal area high and convex over the disk, sloping
down regularly to the extremity of the rays, the height at the centre of the disk
being 11°75 mm. A feeble sulcus or depression is present on the outer part of
the median interradial line, which emphasises the tumid character of the base
of the rays. Actinal surface more or less flat, excepting that the rays are
slightly turned up at their extremity, and that a rather sharp depression occurs -
in the interbrachial areas along the inner reel of the median interradial line, —
behind the mouth-plates.

Dorsal area covered with short, delicate spinelets, all of uniform length and
size, their lower portion being apparently sunken in membrane. The spinelets
stand perpendicular and are closely placed, presenting to the naked eye the
appearance of a fine and uniformly granular surface. When magnified the
spines are seen to be slightly expanded or flaring outwardly, and to be com-
posed of many rods or lamelle, with the extremity of each individual lamella
terminating in a short thorn-like point.

ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. ‘‘ TRITON.” 157

The spinous dorsal area is punctured with numerous small but conspicuous
pores, which are irregularly distributed at small but unequal distances apart
over the whole area, excepting the extremities of the rays and a narrow band
along the median interradial line; towards the margin the apertures are
smaller, wider apart, and less frequent. Through these apertures the papulz
are protruded, and under magnification a small but definite circlet of the dorsal
membrane surrounding the puncture of the papula, and unencroached upon by
spinelets, may be seen. No grouping of the dorsal spinelets occurs, which in
any way indicates the outlines.of the underlying plates of the abactinal floor ;
and the only break in this perfectly uniform covering consists of a number of
most minute channel-lines, which run irregularly here and there amongst the
spinelets, the only one of these maintained with any regularity being a long
straight channel, similar in breadth to all the others, extending along the
median interradial line. The anal aperture is subcentral and distinct, and is
surrounded by slightly larger spinelets. The madreporiform body is very
small, round, and with numerous strive. It is situated rather nearer to the
_ margin than midway to the centre of the disk, and the surrounding portion of
the test is slightly prominent.

Actinal interradial areas extensive, and with their outer margin conspicu-
ously festooned by the infero-marginal plates. Infero-marginal plates eight to
nine in number from the interbrachial line to the tip of the ray; the contour of
their outer margin is rounded, and bears a group of eight to twelve spinelets,
rather larger and more robust than those of the dorsal area above described.
The plates are entirely covered with spinelets—the part which falls in the
side of the ray with spinelets similar to those on the dorsal area, and the
ventral portion with spines similar to those on the ventral area. When
the starfish is viewed in profile, the marginal plates are seen to be clearly
marked out by vertical furrows as well as by their prominent tumidity ;
but the junction of the infero-marginal with the supero-marginal plates, or
indeed the presence of these latter at ail, is indiscernible to superficial obser-
vation. Seen on the actinal side, the marginal plates are clearly defined by
well-marked channels or furrows, and these run in oblique lines from the
margin up to the adambulacral plates. The furrows are almost regularly
parallel, hence the areas or columns they define are of nearly uniform
breadth throughout. Consequent on their diagonal direction, a triangular
space occurs in the median interbrachial line in the inner portion of the area,
which is not conformable to the arrangement above described, the channels
which traverse it converging towards the apex of the triangular space, a short
distance removed from the margin of the disk. The whole ventral area is
covered with small, almost spicular, spinelets, which are short, sharply pointed,
and with their bases buried in membrane. The spinelets are all nearly uniform

158 MR W PERCY SLADEN ON THE —

in size, rather widely spaced, and are directed outward, almost horizontally,
the angle at which they stand to the actinal surface being very small.

Ambulacral furrows narrow and almost uniform in breadth throughout.
Adambulacral plates broader than long, bearing from five to eight spines.
The ambulacral spines form a regular inner or furrow series, which arches over
and almost conceals the ambulacral sucker-feet, and three sub-regular outer
rows more or less clearly defined. The following is the arrangement of the
spinelets on the plates :—Of the inner or furrow series there are two on each
plate, which stand side by side and slightly oblique, especially towards the
end of the ray. These two spines are regular throughout the ray, and are of
equal size, short, compressed, lanceolate, tapering to a sharp point, and invested |
in membrane, which adds to the apparent breadth of their base. The outer
spines are subject to a considerable amount of variation, both in number and
position. Three only may be present, each placed behind the other, external
to the furrow spines, forming a transverse series on the adambulacral plate, or
one, two, or even all three of these spines may be reduplified--the companion
spine usually standing rather oblique. These variations do not appear to be
dependent on position in the ray, but may occur in any part. All the outer
spines are of uniform size, cylindro-conical in shape, rather obtusely pointed,
and covered with membrane. i

Mouth-plates form a triangular mouth-angle, not prominent or protuberant
superficially, and perfectly conformable with the triangular outline of the inter-
radial area. ‘The mouth-aperture is completely closed, and the arrangement of
the armature of the mouth-plate is suggestive of that in certain Gonzasteride.
The mouth-spines are short, robust, and-stand perpendicular. One odd spine
is placed at the extreme angle, at the junction of the two plates of a mouth-
angle, and five similar spines, all closely placed, occupy the free or furrow
margin of the plate, decreasing in size as they recede from the mouth ; the odd
spine being the largest, the next three slightly smaller, and the two outer ones
much smaller. All the spines are cylindrical, slightly taper, and obtusely
rounded at the tip. Upon the surface of the plates, and on a line with the
two small outer mouth-spines, stand two short secondary or superficial mouth-
spines, one on each plate, very robust at the base, conical and pointed ; and,
further outward again, a second, but much smaller, spine behind each of the
secondary mouth-spines; this small pair perhaps belonging to the adambu-
lacral plate adjacent to the mouth-plates. A single minute spinelet, situate
on the median or sutural line of the mouth-plates, stands midway between
each of the pairs of secondary mouth-spines; and no other spines of any
description are present on the mouth-plates.

Remarks.—The form above described is nearly allied to Rhegaster tumidus
(Stuxberg, sp.). The following appear to be the chief points of difference :—

ASTEROIDEA DREDGED DURING CRUISE OF H.MS. “ TRITON.” 159

The length of the ray is much less in the new species, the radial proportions
being for A. Murrayi, R=1°37r, and for R. tumidus R=1°97, in specimens of
the same size. The rays are consequently much less defined, and are more
widely expanded at the base. In &. Murrayi the marginal contour is dis-
tinctly festooned by the infero-marginal plates, and each of these bears a group
of enlarged spinelets, neither of the characters being present in R. tumidus.
The ambulacral spines appear to be more numerous in the new form, the arma-
ture of the mouth-plates somewhat different, the distribution of papule more
numerous on the dorsal surface, and the character of the spinelets, both on
the abactinal and actinal areas, more simple.

I have great pleasure in associating this interesting species with the name
of Mr Joun Murray, whose zealous labours in connection with deep-sea
dredging are well known.

8. Mimaster Tizardi, Sladen.

Station 10. August 24,1882. Lat. 59° 40’ N., long. 7° 21’ W.
Depth, 516 fathoms ; bottom temperature, 46° Fahr.

Station 11. August 28, 1882.~ Lat: 59° 29’ N., long. 7° 13’ W.
Depth, 555 fathoms ; bottom temperature, 45°°5 Fahr. .

9. Hippasteria plana (Linck), Gray.

Station 3. August 8, 1882. Lat. 60° 39’ 30” N., long. 9° 6’ W.
Depth, 87 fathoms ; bottom temperature, 49°°5 Fahr.

10. Cribrella oculata (Linck), Forbes. (Plate XXVI. fig. 8.)

Station 1. August 4, 1882. Lat. 59° 51’ 30” N., long. 6° 21’ W.
Depth, 240 fathoms ; bottom temperature, 47°°6 Fahr.

Station 10. August 24,1882. Lat. 59° 40’ N., long. 7° 21’ W.
Depth, 516 fathoms ; bottom temperature, 46° Fahr.

Station 11. August 28, 1882. Lat. 59° 29’ N., long. 7° 13’ W.
Depth, 555 fathoms ; bottom temperature, 45°°5 Fahr.

The specimens from Stations 10 and 11 have an abnormal appearance, even
for this variable species, probably, consequent on their deep-water habitat.
The variation is characterised by the comparative smallness of the disk and the
greater length and narrowness of the rays, which are subcylindrical and almost
uniform in breadth throughout, especially in the small examples where the
expansion at the base is very slight. The single example from Station 11
| measures R=39 mm., r=5 mm., breadth of ray at the base 5°75 mm. The
spinelets of the abactinal area are very small, and rather more widely spaced
than in the normal form. They are conically pointed, and have the appearance

160 MR W. PERCY SLADEN ON THE

of being rooted in membrane and rather thickly invested at their base, which
gives the spine-groups a larger and somewhat more expanded character than
usual in shallow water specimens. The three examples from Station 10 are
much smaller, and their spinulation is very minute and scanty, seldom more
than two to four spinelets being present in a group. The effect of this is
perhaps most striking in the armature of the adambulacral plates, where the
group of spines external to the furrow-series becomes - abnormally small and
insignificant. The comparative length of the ray and its almost uniform
breadth is very conspicuous in comparison with small specimens of similar size —
of the ordinary form, in which the ray is proportionally shorter in the -young
stage than in the adult. The coiour in alcohol of the specimens under notice is"
a dirty greyish- brown.

Considering the known variability of the species, I do not at annie feel
justified in doing more than placing on record the character of the variation
above noted. If a larger supply of material should ultimately necessitate the
nominal recognition of this form as a deep-sea PANe it might appropriately
be called cylindrella.

11. Zoroaster fulgens, Wyville Thomson. (Plate XX VI. figs. 9-11.)
(Zoroaster fulgens, Wyv. Thoms, (1873), The Depths of the Sea, p. 154, fig. 26.)
Station 11. August 28, 1882. Lat. 59° 29’ N., long. 7° 13’ W.
Depth, 555 fathoms; bottom temperature, 45°5 Fabr. A young
example.
Station 13. August 31, 1882. Lat. 59° 51’ 2” N., long. 8° 18’ W.
Depth, 570 fathoms ; bottom temperature, 45°-7 Fahr.

A brief description and a woodcut of this handsome starfish were given by
Sir WyviLLe THomson in the work cited above. As no detailed description of
the species has yet been published, the following may not be unacceptable :—

Rays five. R=125 to 130 mm.; r=14 to 15 mm.

Rays very long, narrow, subcylindrical, and tapering throughout to a finely
pointed extremity ; arched on the abactinal surface, and tumid on the actinal —
surface on either side of the furrow, which is deeply sunken. Interbrachial
angles acute. Breadth of a ray at the base 17 mm.

The disk is rather higher than the.rays and slightly tumid. The calcareous
skeleton of the whole test is formed of suboval or subhexagonal plates, disposed
in perfectly regular longitudinal and transverse series. The following is the
arrangement they present. Surrounding a dorso-central and five small radially
placed plates are five large plates interradial in position; and outside and
alternating with these are five similar but rather smaller radially placed plates.*

* It will be noted that these plates represent in a remarkable manner the dorso-central, the under
basals, the basals, and the radials respectively of the crinoid calyx.

ASTEROIDEA DREDGED DURING ORUISE OF H.M.S, “‘ TRITON.” 161

Outward from each of the radial plates proceeds a longitudinal series of plates
which extends along the median dorsal line of the ray, each plate regular in
form (subhexagonal) and touching or slightly imbricating upon its next serial
companion. On either side of this median line of plates is a parallel line of
smaller plates, and these are succeeded bya line or series of plates nearly equal
in size to those of the median line ; the outer of these lines of plates standing
on the rounding which separates the dorsal and lateral areas of the ray.
Between this dorso-lateral line and the adambulacral plates are five longi-
tudinal and parallel series of plates, the three upper rows forming the sides of
the ray and the two lower being on the tumid actinal surface. The plates of

the two upper rows of the lateral series are broader than those in the three

lower series. The longitudinal arrangement of all the series is perfectly
regular, and the plates diminish gradually in size as they proceed outward.
Excepting the median dorsal line, the plates of all the other rows form regular
transverse series, as well as longitudinal. The plates of the median dorsal line
are slightly larger than the others, and consequently do not correspond. All
the plates are contiguous, but leave a small diamond-shaped or sub-circular
mesh between the rounded corners of adjoining plates. This is covered with
membrane, through which one or more small papulze proceed, and on which are
usually borne one, or occasionally two, small forficiform pedicellarie. The
meshes form perfectly regular longitudinal lines, and this character, as well as

_ their presence, is rendered more conspicuous by the slightly tumid surface of

I.

.

|

:

|

the plates. The surface of all the plates is studded with a number of small,
uniform, well-spaced miliary granules, on which are articulated very short
ciliary spinelets thinly covered with membrane. The plates of the median
dorsal line are sub-mammillated, rising to a small but definite tubercle in the
middle, which gives attachment to a short, robust, conical spinelet, the sur-
rounding portions of the plate being covered with the same small miliary

granules and spinelets as the other plates. Isolated dorso-lateral plates are

occasionally similarly mammilated and spined, and the large interradial plates
on the disk are also usually thus furnished. On the plates of the three rows
which succeed the adambulacral plates, there are usually one to three spinelets
much longer and more robust than the accompanying miliary spinelets. These
are naked, delicate, cylindrical, and taper to a fine extremity, and are generally
arranged in slightly oblique lines, with the middle spine often more forward
and longest when three are present, near the lower margin of the plate, and
they are directed upward and appressed to the ray. The next row on the sides
of the ray, 7.¢., the fourth from the adambulacral plates, has one larger spine on
each plate, of equal size to the afore-mentioned. The adambulacral plates are
quite within the furrow, and are short but broad, extending far upward almost.
vertically. Each alternate plate is developed into a thin prominent ridge,
VOL, XXXII. PART I. 2D

162 MR W. PERCY SLADEN ON THE

which extends far into the furrow and entirely separates neighbouring suckers,
whilst the intermediate plates are smooth, and appear to form the true furrow-
wall. Four ambulacral spines, which are moderately long, cylindrical, and
slightly tapering, are placed in single file at intervals along the edge of the
ridge, the innermost being usually the most delicate, and the outermost is
usually the shortest. Two to five small forficiform pedicellariz are attached by
membrane to the extremity of the delicate innermost spine. One or two small
ciliary spines may be present on the extreme outer edge of the adambulacral
plate, adjacent to the first row of longitudinal plates ; and two or three similar
small spines are present in the same position at the outer edge of the non-
prominent intermediate plates, but no spines whatever are present on the
surface of these plates within the furrow.

The actinostome is deeply depressed, and the mouth-plates are entirely
within the cavity, and are not apposable. They are armed only with pointed,
moderately robust spines similar to the larger spines on the ridges of the
adambulacral plates.

The madreporiform body is small and inconspicuous, and is placed external
to one of the interradial plates.

The anal aperture is small, distinct, surrounded by a circlet of small ciliary
spines, and is placed at the side of the dorso-central plate, and consequently
slightly excentric in position.

The ambulacral sucker-feet form four rows. They are rather small, sub-
conical, and terminated with a small but distinct fleshy sucker.

Premature Phase.—The young form, measuring R=11 mm. and 7=2'25 mm.,
has a very remarkable appearance, owing to the prominence and distinctness of
the component plates of the skeleton. The disk is much higher than in the
adult. The dorso-central plate is prominent, and assumes the shape of a
rounded cone. The interradial and first radial plates are of nearly equal size,
and are very tumid or almost semi-globular in form. The plates of the median
dorsal line are large and distinct, occupying a large portion of the abactinal
surface of the ray. The so-called dorso-lateral series of plates form the margin
of the ray, and the intermediate plates are small. Between the ‘dorso-lateral”
series and the adambulacral plates there are not more than two fully-developed
longitudinal rows of plates, with a partially-developed series commencing to
appear between the latter and the adambulacral plates. The terminal (ocular)
plates are very large, somewhat resembling the shape of a serpent’s head, and —
are armed with one or two pairs of comparatively large robust spinelets, near
the extremity, which are directed outwards.

The large plates of the disk and the median dorsal line have already a small
tubercle, but only some of these bear spinelets. All the plates have a few
widely spaced and very minute granules and microscopic ciliary spinelets. The

ASTEROIDEA DREDGED DURING CRUISE OF H.M.S. ‘‘ TRITON.” 163

spinelets on the lower rows of plates are comparatively long and well developed.
The character of the alternate prominent adambulacral plates is already dis-
cernible, although not more than one or two ambulacral spinelets are present
on each.

The madreporiform body is outside and external to the interradial plate, and
almost in the ravine of the interbrachial angle. The anal aperture is excentral,
and situated between the dorso-central plate and an interradial plate, standing
in the right posterior interradius when the madreporiform body is placed in the
right anterior interradius.

12. Asterias Miilleri, Sars.

Station 5. August 10,1882. Lat. 60° 11’ to 60° 20’ N., long. 8° 15’ to
8° 8’ W.
Depth, 433 to 285 fathoms ; bottom temperature, 43°°5 to 40°:8 Fahr.

Il. Stration-Lists.

The following lists show the species associated at the respective stations :—

Station 1. August 4, 1882. Lat. 59° 51’ 30” N., long. 6° 21’ W.
Depth, 240 fathoms ; bottom temperature, 47°°6 Fahr.
Cribrella oculata.

Station 2. August 5, 1882. Lat. 59° 37’ 30” N., long. 6° 49’ W.
Depth, 530 fathoms; bottom temperature, 46°:°2 Fahr.
Pteraster militaris.

Station 3. August 8, 1882. Lat. 60° 39’ 30” N., long. 9° 6” W.
Depth, 87 fathoms ; bottom temperature, 49°°5’ Fahr.
Hippasteria plana.
Luidia ciliaris.

Station 5. August 10,1882. Lat. 60° 11’ to 60° 20’N., long. 8° 15’ to 8° 8’ W.
Depth, 433 to 285 fathoms ; bottom temperature, 43°°5 to 40°8 Fahr.
Rhegaster Murray..
Asterias Miilleri.

Station 9. August 23, 1882. Lat. 60° 5’ N., long. 6° 21’ W.
Depth, 608 fathoms ; bottom temperature, 30° Fahr.
Pteraster militaris var. prolata.
Archaster tenuispinus.

164 MR W. PERCY SLADEN ON THE ASTEROIDEA, ETC.

Station 10. August 24,1882. Lat. 59° 40’ N., long. 7° 21’ W.
Depth, 516 fathoms ; bottom temperature, 46° Fahr.

Archaster bifrons.

Astropecten Andromeda.

Mimaster Tizard.

Cribrella oculata var. cylindrella.

Station 11. August 28, 1882. Lat. 59° 29’ N., long. 7° 13’ W.
Depth, 555 fathoms ; bottom temperature, 45°°5 Fahr.
Archaster bifrons.
Astropecten Andromeda.
Mimaster Tizardi.
Cribrella oculata var. cylindrella.
Zoroaster fulgens. .

Station 13. August 31, 1882. Lat. 59° 51’ 2” N., long. 8° 18’ W.
Depth, 570 fathoms ; bottom temperature, 45°°7 Fahr.
Zoroaster fulgens.

DESCRIPTION OF PLATE XXVL.

1. Pteraster militaris var. prolata, Abactinal aspect; natural size.
2. Rhegaster Murrayi. Abactinal aspect; magnified 2 diameters.

3. . - Actinal aspect; magnified 2 diameters.
4
5

* Portion of the dorsal surface ; magnified 20 diameters.
ss One of the spines of the dorsal surface, seen in profile; highly

magnified.

5a. 2 The same spine seen from above ; highly maguified.

6. et Adambulacral plates and portion of the adjacent ventral sur-
face ; magnified 8 diameters.

i€ 5 Mouth-plates; magnified 10 diameters.

8. Cribrella oculata vay. cylindrella, Abactinal aspect; natural size.

9. Zoroaster fulgens. A young example. Abactinal aspect ; magnified 3 diameters.
. 10. ;, Outline of the profile of the same specimen.
ea. A Diagram of the plates of the disk, showing their correspondence

with the crinoid calyx. The respective plates are marked as
follows :—
1. Dorso-central.
2. Under Basals.
3. Basals.
4. Radials.

:
|

ta

ATS,
LAS

Be

Dy Wapier

roy

af
We

RHEGASTER MURRAYI,

var. PROLATA. hea

PTERASTER MILITARIS,

1.

& Sou Edin‘

ATitchie

ZOROASTER FULGENS,

lati,

CYLINDRELLA,

var.

CRIBRELLA OCULATA,

8.

( 165 )

X.—On a New Species of Pentastomum (P. protelis), from the Mesentery of
Proteles cristatus; with an Account of its Anatomy. By W. E. Hoyts,
M.A. (Oxon.), M.R.C.S., Naturalist to the “Challenger” Commission.
(Plates XXVIT. and XXVIII.)

(Read June 4, 1883.)

For the parasites which form the subject of the present communication, I
am indebted to my friend Professor Morrison Watson, who found them in a
male specimen of Proteles cristatus, Sparrman, of whose myology he has since
published an account.* Before entering upon a description of the entozoon, it
may be allowable to say a word or two with respect to its host, which is not
an animal of everyday occurrence. It was first described a little more than a
century ago by SPARRMAN,t the Swedish traveller, as occurring in South Africa,
where it is known to the farmers as the “ grey jackal”; he gave it the name
Viverra cristata. The only point in his description of any present interest is
that its stomach “had nothing but ants in it, or to speak more properly, the
white termites,” which might be a valuable hint for any one who had the will
and opportunity to investigate the life history of the parasite before us.

Since the time of SPARRMAN, it was erected into a separate genus by
Gerorrroy St Hinaire, and the name Proteles was chosen as expressing the fact
that its anterior extremities were each provided with five, or the perfect
number, of toes. It is now generally regarded as a type intermediate between
the Hyzenidee and Viverride, its appearance when alive being strikingly like

that of small hyzena.{

The animal dissected by Professor Fina remained some days before the
abdomen was opened, a circumstance which affected very prejudicially the
histological preservation of its inhabitants, and made me hesitate for some time
as to whether it would be worth while to attempt a complete account of the
creature’s anatomy ; however, in consideration of the rarity of the specimens, it

was resolved to make the effort, and the result has been the discovery of some

interesting anatomical relations, although the account of the minute structure
is in many particulars less complete than it would otherwise have been.

* Proc. Zool. Soc. Lund., p. 579, 1882.

t Sparrman, AnpREw, M.D., A Voyage to the Cape of Good Hope, Sc. Translated from the

Swedish original, London, 1786, vol. ii. p. 177.
t Fuowsr, Proc. Zool. Soc, Lond., p. 474, 1869.

WOL, XXXII, PART. I, QE

166 MR W. E. HOYLE ON

THE ENCcLosING Cyst.

The Same! to the number of about ten, were enclosed in cysts in the
mesentery, and their appearance is shown in the accompanying
woodcut (fig. 1). Each is coiled into a more or less complete
circle, and, in every case examined except one, the ventral sur-
face formed the convexity of the curve.

Fig. 1. General appear- The cyst itself presents nothing in its structure worthy of
ance of the encysted : ° . Pee 5
parasite, special note ; it consists of closely interwoven fibrils of connec-

tive tissue, imbedded in a quite homogeneous matrix; the wall is about 0:05
mm. thick, and it is more compact towards the inner than the outer surface.

THE EXTERNAL APPEARANCE.

The form of the body is (Pl. XX VII. fig. 1), speaking generally, cylindrical
in the anterior half, and slightly tapering in the posterior, until it ends in a
blunt cone. In some specimens the last two segments presented an appear-
ance which may be aptly described in the words used by Dixstne in speaking of |
another species, “‘cute externé in forma preeputii”; but this was by no means
constant.

The head is hemispheroidal, and is followed by a smooth cylindrical portion,

gz ~=which is of very variable length ; in some cases it scarcely seems ’

to exist at all, whilst in others it measures from 2 to 3°5 mm. (cf

Pl. X XVII. fig. 1, and woodcut, fig. 2). ;

This is succeeded by a number of annuli, which give the

a Lie ae body a decidedly vermiform appearance, although, as will be

seen in the sequel, this segmentation is scarcely at all reproduced in the internal
organisation.

The number of the annuli varies with the sex, and also, though to a less
extent, with the individual ; it amounts in the males to 16 or 17, in the females -
to from 18 to 22. Each of these rings is separated by a constricted portion of
the body, which may conveniently be termed the “interannular space”; these
are somewhat less than the annuli, not only when measured transversely to the
creature, but also longitudinally, except when it is very fully extended, under
which circumstances the two sets of rings become about equal. Furthermore,
the interannular spaces are of much weaker consistency than the annuli, as will
be explained in treating of the internal anatomy ; and in correlation with this fact,
it is to be noticed that when the animal is coiled up, it is the interannular spaces
which give way to allow of this, the annuli scarcely undergoing any change at
all in breadth, but approaching each other on the concave aspect of the curve. —

On the ventral surface of the head, and about 1 mm, from its anterior

A NEW SPECIES OF PENTASTOMUM. 167

margin, in the middle line, can be readily seen, even with the naked eye, a
circular or slightly oval mark ; this is the lime which indicates the boundary of
the oral papilla (woodcut, fig. 2). On either side of it are two slits, about 0°5
mm. in length, whose anterior extremities converge towards the middle line ;
these are the orifices of depressions of the cuticle which contain the hooks,
and the points of these may generally be seen, under a low magnifying power,
protruding from them.

The orifices of the sexual glands are somewhat difficult to observe, but in
many cases they can be made out by careful examination, after the spirit has
been allowed to evaporate from the specimens. The male genital openings are
two in number, and are situated about 1 mm. behind the mouth, close to the
middle line, and one at either side of it (Pl. X XVII. fig. 1, 4.0). The female
genital apparatus opens also in the middle ventral line, but within less than
1 mm. of the posterior extremity. All three are perfectly simple orifices, with-
out any prominence.

These were all the points worthy of note observed on the external surface.
I could find no tactile papille, such as are to be seen in Linguatula tenioides,
although I looked for them with great care.

THE Bopy- WALL.

The wall of the body consists of three distinctly marked layers—

1. The Cuticle.
2. The Epidermis.
3. The Subepidermic Layer.

1. The Cuticle (Pl. X XVII. fig. 9, cw) is a thin even layer which covers
the whole surface of the body, including the invaginations in which the hooks
are situated, and sends inwards prolongations which line the cesophagus, the
rectum, and the genital ducts. Its thickness is on the average about 0°01 mm.,
and presents no noteworthy changes in different parts of the body, except that
it is slightly thinner in the invaginated portions.

There can be little doubt, from the analogy of different forms of life, that
it is composed of chitin, although I attempted no investigation on this point,
beyond ascertaining the fact that it did not dissolve in boiling solution of

| caustic potash. It is to all appearance quite structureless, even when

a

examined under high powers of the microscope ; no trace could be found of

| the pores mentioned by Leucxarr in L. tenioides,* nor did the cuticle appear
to be divided into two distinct layers, which was probably owing to the
| immaturity of the specimens.

* Bau u, Entwick. d. Pentastomen, Leipzig u. Heidelberg, 1860, p. 30.

168 MR W. E. HOYLE ON

The aunuli, however, are perforated by large pores or “ stigmata,” arranged _
in from 6 to 8 irregular rows, but none of these are found in the interannular _
spaces. ]

These stigmata are about 0°014 mm. in diameter, and almost circular in
form, and when seen en face present a double contour, which is due to the
difference in density of the cuticle immediately surrounding the stigma ; when
seen in section they appear very slightly constricted, so as to approach an
hour-elass in shape (Pl. XX VII. figs. 9 and 11); the cuticle immediately sur-
rounding the stigma is more highly refractile, and therefore probably also of
greater density than the other portions ; but there is no clear line of demarca-
tion between these as indicated by Leuckart in L. teemoides.* In some cases”
the portion of cuticle around the stigma is slightly thickened, although this is
by no means constant.

A surface view of the cuticle shows, moreover, a number of small irregularly
oval markings, arranged in fairly even rings around the pores, and producing
an appearance which recalls that of a transverse section of bone with its
Haversian canals and lacune (Pl. XX VII. fig. 2). These marks are due to
the extremities of the epithelial cells, which form the next layer of the body-
wall, as was very distinctly visible in one small portion of the cuticle which
had this layer still attached to it. “

While treating of the cuticle it will be well to describe the hooks which are
modified portions of it. Their form is shown in the drawing (Pl. XXVIL.
figs. 3 and 12) better than it can be described in words; they are seen to be —
composed of two separate joints, moved by appropriate muscles, which will be
treated of in the sequel. Their homology has been fully discussed by Lruckart
in his classic monograph, and my investigations have not enabled me to add
anything to what he has written upon this head.

2. The Epidermis, which follows immediately upon the cuticle, is a
single layer of columnar epithelial cells, 0-012 to 0°02 mm. in thickness (PI.
XX VII. fig. 9, ep). The cells contain a distinct nucleus, generally oval in form,
and situated in varying positions in different cells ; in some cases a nucleolus
was visible.

3. The Subepidermic Layer (P\. X XVII. fig. 9, par) composes the greater
part of the body-wall of the animal. It varies greatly in thickness, but on an
average may be taken at 0°2 mm., the extremes being about 01 mm. and 0°35
mm. ; as a general rule, it is thinnest along the dorsal surface, and in the
narrow ventral intermuscular space (see p. 169) it is not unfrequently absent
altogether.

The cells of which it is made up are of very various sizes and shapes ;
occasionally their diameter nearly equals the length of the epithelial cells, but

* Loc. cit., p. 31, Tab, i, figs. 7 and 8,

A NEW SPECIES OF PENTASTOMUM. 169

in most cases they are only almost one-third the size of these. They contain a
finely granular protoplasm, and a small spheroidal, ovoid, or somewhat irregu-
larly shaped nucleus. They are packed closely together, and occupy the whole
space between the subcuticular epithelium and the longitudinal muscle bundles.

Among them are scattered the large glandular cells which will be described
as part of the secretory apparatus (see p. 178); and they are traversed by many
of the muscle-fibres, which will also be described in a special section of the
paper.

Towards the body cavity this layer, or the longitudinal muscle-bundles
where they interpose, is marked off in the sections by a clear definite line,
which becomes deeply stained. This I take to be the ccelomic epithelium
(endothelium), but unfortunately none of my specimens were sufficiently well-
preserved to enable me to speak with confidence on this point.

THe Muscuitar SYSTEM.

When the animal is opened by a median dorsal incision, and the body-wall
spread out and examined from within, an appearance is seen such as is shown
in Pl. XXVII. fig. 17.

Longitudinal bands are crossed by transverse bands, and interspaces,
roughly speaking, rectangular in form, are left between them. The ventral

median line is marked by a series of square gaps, towards the margins of which

|

|
|

are placed a number of radiating fibres. Along the lateral sides of the suc-
cessive squares there stretch two broad bands (fig. 17, m./’, m./’), which are com-
posed of longitudinal muscular fibres, and, though somewhat variable in their
breadth, are nearly as wide as the squares. Beyond these, again, are a number
(commonly 8-10) of very much narrower longitudinal bands (fig. 17, m.0).

A closer examination confirms the view that these longitudinal bands are

composed of muscular fibres, but the case is otherwise with the transverse

bands. ‘These, as was pointed out by LEucKarr,* are cellular in structure,
and consist largely of the glandular cells which will be alluded to when treating
of the subepidermic cell-layer (p. 178). They correspond with the external
annulations of the animal, and on focussing deeply through these bands the
stigmata are seen, whilst none are visible in the spaces between them.

The muscular system of this parasite cannot, however, be fully understood
by means of such a preparation as has just been described; to render our
knowledge complete, transverse sections are necessary ; and, when the informa-
tion derived from these is taken into account, there are seen to be present
three systems of muscular fibres—

* Levckart, loc. cit., p. 39.

170 MR W. E. HOYLE ON

1. Transverse fibres, immediately underlying the epidermis.
2. Longitudinal fibres, arranged in bundles, lying for the most part imme-
diately below the coelomic epithelium.

3. Oblique fibres, placed obliquely, however, both to the dorso-ventral
plane of the body and to planes cutting it transversely.

1. The Transverse Layer of muscular fibres is very thin, it being only one
fibre thick ; in some cases there seemed to be two or even three such layers,
but this appearance was probably owing to a slight obliquity of those particular
sections.

It is situated immediately within the epithelium, so that its fibres are for
the most part parallel to-the cuticle, and they lie in planes which are approxi-
mately transverse to the body of the animal. 3

The appearance of this sheet of fibres is seen in Pl. X XVII. fig. 14; the
fibres branch dichotomously, and at intervals unite with each other so as to
form a fine network with elongated meshes, in which the cells of the parenchyma
of the body-wall may be noticed.

In the body proper of the animal this layer is developed almost exclusively
on the sides, its fibres not often crossing the ventral, and hardly ever the dorsal
median line.

in one specimen about 1 mm. from the caudal extremity, I noticed a small
patch of these fibres dorsally situated, but this might have been an individual —
peculiarity. The cephalic region, however, shows a great change in the
arrangement of this layer, for there it is best developed on the dorsal and ~
ventral aspects of the body, and to a much smaller extent on the sides.

With respect to the nature of the individual fibres, but little can be said.
They are very thin (about 0:001 mm.), and I could not detect in them that
transverse striation which was noticed by Lruckarr.* Some of the better
preserved specimens showed, however, a kind of sarcolemma, an exceedingly
thin sheath with a well-defined outline, and with small ovoid nuclei (Pl. XX VII.
fig. 16, nz).

2. The Longitudinal Layer varies a good deal in its arrangement in different
parts of the animal, and it will be advantageous to describe it as seen at about
the middle of the body. <A section taken in this situation is shown in PI.
XXVII. figs. 10 and 13, m./), and it willbe at once noticed that the longitudinal
muscles are situated at some distance from the external surface, being separated
from it by the whole thickness of the body-wall. Its fibres, moreover, are
grouped into definite bundles, which in the ventral region present a more or
less elongated oval section, while in the lateral and dorsal regions they are —

* Loe. cit., p. 40.

A NEW SPECIES OF PENTASTOMUM 171

more nearly circular. A space free from muscles passes down the middle line
ventrally, and this space, as we shall see, extends throughout the whole length
of the animal.

The bundles are thus arranged :—About four or five thin band-like portions
are placed in the compartments formed by the splitting of the ventral margin

of the oblique muscle-layer (fig. 10), and a somewhat thicker one lies on the

inner surface of this layer close along its ventral margin. It is these bands
which, overlapping each other by their outer margins, produce the appearance
of a broad band, seen when the body-wall is examined from within (Pl. XX VII.
fig. 17, m./’).

Passing outwards there are next noticed smaller bands, of somewhat
irregular figure in section, lying between the oblique muscles and the body-
wall; and then, after passing the point where the former of these are inserted
into the latter, we come to a number (8-12) of rounded bundles which stand
out from the body-wall, and would lie free in the body-cavity were they not
covered with a thin membrane (ccelomic epithelium 7).

In Levcxarr’s* description of these muscles in P. proboscideum, he
mentions a space free from muscles extending down the dorsal median line of
the animal similar to that above mentioned on the ventral aspect ; this state of
things certainly did not obtain in the species at present under consideration,
the longitudinal bundles succeeded each other quite regularly across the dorsal
surface, and there was no thinning out of the mesoderm towards the median
line (Pl. XX VII. fig. 10). Leucxarr furthermore alludes to a division of each
lateral muscle-mass into a dorsal and a ventral portion, but this also was not
to be noticed in my specimens.

Towards the tail (Pl. XX VII. fig. 13) the muscular system gradually becomes
less and less strongly developed, until at distances of less than 0°5 mm. clearly
defined fibres are not to be found. The longitudinal and oblique systems
appear to arise almost side by side, and the former is seen in sections a little

less than 1 mm. from the hinder extremity to consist of about nine bundles on

each side, which at this point show much less variety in size and shape than in
other parts of the animal. Even here, however, there are a certain number of
bundles, somewhat broader and more flattened, connected with the ventral
margin of the oblique layer of fibres. The number of fibres in each bundle varies
from about 10-30, but I could not make out satisfactorily any constant relation
between the size of the bundles and their position.

The fibres of which the longitudinal muscles are composed are almost
0008 mm. in diameter, usually oval in transverse section, except where they
are rendered polygonal by mutual pressure. In most cases the inner portion
of the fibre is pale in colour, and bordered by a fine deeply stained line

* Loe. cit., p. 41.

172 MR W. E. HOYLE ON

(sarcolemma ?), in which is often seen an ovoid thickening which may be due
to the presence of a nucleus. When they are well preserved these fibres show
a clear transverse striation, the striz being separated from each other by a
distance somewhat greater than the diameter of the fibre; thus resembling
those of the oblique fibres shown in Pl. XX VII. fig. 9

3. The Oblique System of muscles does not form a complete layer encircling
the body, but consists of two muscular planes, which take origin near the
ventral median line, and pass upwards and outwards, diverging at an angle of ©
sixty degrees or more (Pl. X XVII. fig. 10, m.0). Each plane appears in trans-
verse section as a thin line, never thicker, and usually somewhat thinner, than
a single fibre of the longitudinal muscles, but it shows a longitudinal striation
as if composed of several fibrils. Near the ventral margin, and to some extent
also near the dorsal, this lamella is seen to split into a varying number of
thinner portions, between which are situated the longitudinal muscle-bundles
as already described.

This muscular group, however, is Saintes in two senses ; as we have just
seen, its fibres form two lamelle inclined towards the median plane of the
body, but in addition to this, they pass obliquely downwards and forwards
from one segment of the body into the next, as is shown in Pl. XXVIL
fig. 17. These fibres appear to be homologous with one half of the cruciform
systems, which Leuckarrt describes and figures in P. proboscideum,* but of the
other half, those, namely, which proceed downwards and backwards, no trace
was to be found.

If it be correct to assume that the crucial aie are the remains of one or
two complete coats of oblique fibres, if we suppose the process of degradation
carried still further, then the fibres passing downwards and backwards, not
being of so great utility in the movement of creeping as those passing in the —
other direction, would be the first to disappear, and these latter only would
remain.

The fibrils of which this layer is composed are about 0°003 mm. in diameter,
but they frequently exhibit a longitudinal striation, as though made up of still
finer elements, and rarely the transverse striation was clearly exhibited
(fig. 9, m.0). At intervals along the fibrils small darkly-stained nuclei are to be

observed, but whether these belong to the sarcolemma or to the connective
tissue, I was unable to discover.

With respect to the mode of termination of the fibrils J can say but little ;
it was often quite easy to follow them as far as the subcuticular epidermis, and
in a few cases an appearance was presented such as is shown in P]. XXVII.
fig 16, giving decidedly the impression that they passed between the cells of
this layer and are inserted directly into the cuticle. It would hardly be safe

* Loc, cit, p. 41, Tab. i. fig. 10.

A NEW SPECIES OF PENTASTOMOM. Lie

to assert that this was generally the case, without an examination of fresh
specimens, but it receives corroboration from LrucKartT’s account of P. probos-
cideum. Some of these oblique fibres, on reaching the inner surface of this
epithelium, turn and pass along it, thus assisting in the formation of the trans-
verse muscular coat already described (fig. 16).

Before quitting the muscular system, three points require a brief considera-
tion,—the modifications which it undergoes in the tail and in the head, and
its disposition with respect to the cephalic hooks.

In the tail about the point at which the longitudinal fibres first became
noticeable, the two lamelle have a somewhat different disposition ; instead of
being inclined to each other at a considerable angle, they are much more nearly
parallel, but separating from each other to give place to the intestine, they
again approach slightly as they are inserted into the body-wall dorsally (Pl.
XXVII. fig. 13).

The second point may be dismissed in a very few words ; on approaching
the anterior extremity of the body, the splitting of the layer of oblique fibres
towards its ventral margin is much further carried out (Pl. XX VIL. fig. 10, m.0),
and the bundles of longitudinal muscle-fibres in relation with it are more nume-
rous and larger, so that the ventral band of muscles is much more prominent.
Concurrently with this change, but proceeding much more slowly, is a gradual
diminution of the bundles of longitudinal fibres in the remaining portions of the
body. As we reach points still more anterior in the animal (about on a level
with the cesophagus) the ventral longitudinal bands undergo a similar diminu-
tion, until in the neighbourhood of the hooks the regular longitudinal muscle-
coat is represented only by a few isolated fibres.

The oblique fibres, on the contrary, become more numerous, and are dis-
posed more nearly parallel to the median plane of the body, until finally they
come into relation with the hooks, and there become adapted to a special

function, as will presently be seen.

The Muscles of the Hooks.—The muscles which act upon the hooks have
been studied by means of almost complete series of sections, both longitudinal
and transverse, and though the general result of this inquiry is to corroborate
LeEvucKaArt’s * account of the matter, there are one or two differences which
require to be noticed.

Attached to the hook itself are four muscles, one to the dorsal and three
to the ventral extremity of its base.

The Extensor unci (Pl. XXVII. fig. 12, we), as the first of the muscles
above mentioned may conveniently be called, arises from the inner or ventral
surface of the basal joint of the hook, and its fibres pass forwards and inwards,

* Loe. cit., pp. 46, 47.
VOL. XXXII. PART I.

i)
ey

174 MR W. E. HOYLE ON

to be inserted pinnately into a tendon which is attached to the dorsal angle of
the hook.

The Flexor unci (fig. 12, uf) is inserted into the opposite angle of the hook,
and arises,as LEucKART has well described, from the basal joint of the hook, its
fibres crossing those of the muscle last mentioned.

The Flexor accessorius unci (fig. 12, u.f.a) is a long thin band which appears
to arise in the mesoblastic tissue of the body, and passes forwards approaching
the flexor unci on its ventral aspect ata slight angle, and is inserted close
beside it.

The Retractor wnci (fig. 12, ur) passes forwards and slightly towards the
dorsal surface, and is inserted close to the two last. It acts to some extent asa __
flexor, but in conjunction with other muscles, more particularly the extensor, it
produces that movement of retraction of the hook as a whole which LEucKARtT |
has described as occurring in the living Pentastomum, but which unfortunately
I have not had the opportunity of witnessing. ¢

In addition to these four muscles are two attached to the extremity of the
basal joint of the hook.

The Protractor basis unci, arises from the anterior surface of the head, and
passes backwards to be inserted into the posterior extremity of the basal joint
of the hook. It consists generally of more than one slender bundle, and its
action can be readily inferred from an inspection of the drawing (fig. 12, w.b.p).

The Adductor basis unci (if it be allowed to use the word in the sense of
drawing towards the ventral surface) is inserted along with the last named, but _
its fibres pass inwards from an origin near the ventral surface of the body
cavity (fig. 12, w.b.a).

In addition to the definite muscular bundles above described, a set of fibres —
arises from the cuticle all round the invagination in which the hook is situated;
these muscles, which may be termed “ retractors of the cuticle,” are obviously
charged with the function of facilitating the egress of the point of the hook
from its sac and increasing the extent of its protrusion.

THE DIGESTIVE TRACT.

This portion of the animal’s anatomy consists only of four well-defined
portions—
1. The Oral Papilla.
2. The Gésophagus.
3. The Stomach.
4. The Rectum.

1. The Oral Papilla.—In the description of the outside of the animal, men-
tion has been made of a small circle lying between the two pairs of hooks.

—_—_ c s

A NEW SPECIES OF PENTASTOMUM. 175

This is the external opening of an annular groove, whose depth is generally
about equal to the diameter of the circle, though it is sometimes a little deeper.

_ The two sides of the groove are almost in contact, so that its breadth is quite

infinitesimal.

From this it follows that the papilla, which is separated by the groove from
the surrounding tissues, is a short cylinder, of about equal length and diameter.
It is not quite regular in form, however, but the base is a little contracted from
side to side, while the antero-external angle is sometimes a little rounded off
(Pl. X XVII. fig. 8).

The cuticle which covers the free extremity of the papilla is not to be dis-

| tinguished from that covering the remainder of the body, while that upon the

sides of the groove is a little thicker, and absorbs the staining material (hemat-
oxylin) more greedily, and is provided with a number of small spines (fig. 4).

The subcuticular epithelium of this organ presents no note worthy of modifi-
cations, but its muscles are rather complex, and indicate that it is an organ of
considerable functional activity.

The papilla itself contains two (possibly three) sets of muscular fibres—the
first traverses it almost parallel to the longitudinal axis of the body, slightly
approaching the ventral surface as it passes backwards (Pl. XXVII. fig. 8);
the second passes from its base towards the free extremity, bending slightly
inwards as it proceeds. Some of the sections of the papilla seemed to show
a thin marginal layer of fibres, divided transversely, which would of. course
constitute a sphincter, but these appearances were so uncertain, that I do not
feel justified in doing more than merely alluding to them.

In addition to these, a clearly-defined retractor bundle runs obliquely for-
wards from the middle of the body into the papilla (Pl. XX VII. fig. 8), while
all around it slender groups of fibres pass outwards, and are inserted into the
cuticle. |

From a consideration of the structures above described, it seems probable that
this papilla can be protruded after the manner of a proboscis ; the last named
muscles being specially efficacious in assisting this action ; the subsequent retrac-
tion also is amply provided for. Furthermore, the intra-papillary antero-posterio
fibres will, by their contraction, increase the space behind the papilla, which
the retraction and consequent swelling of this latter will again diminish, thus
obviously aiding the operation of deglutition. A third function possible to this
organ is that of a sucker, to secure the adhesion of the parasite to its host.

No structure of this kind would appear to exist in L. twnioides, whose
mouth is merely “a widely gaping orifice” (eine grosse und klaffende

| Oeffnung),* followed by a funnel-shaped pharynx, along which the chitinous

lining is continued as far as the stomach itself.

* Leuckart, loc. cit. p. 55.

176 MR W. E. HOYLE ON

2. The Gsophagus commences at the bottom of the groove posteriorly, and
after a variously curved course, opens into the ventral surface of the stomach
some distance behind its anterior extremity (Pl. XX VII. fig. 8, w). Its course
is at first obliquely upwards and backwards, and its transverse section is cres-
centic, the horns being directed ventrally (fig. 6, 7); the dimensions of this
crescent are 0'16 mm. across the horns, while the lumen of the passage is only
0°012 mm. in width. This portion of the cesophagus is lined with chitin pro-
longed from the external covering of the body; and its wall is composed of a
mass of cells in which distinct muscular elements could not be made out,

The cesophagus then turns directly backwards to pass beneath the anterior
nerve commissure (fig. 8, a.72.c), and at this point its structure undergoes a
change ; the cuticular lining after becoming gradually thinner, entirely dis-
appears, and outside the cellular wall there lies a covering of muscular fibres
arranged as a sphincter ; while, in addition to all this, the section of the tube
becomes irregularly elliptical instead of crescentic, the transverse and dorso-
ventral diameters being 0°1 mm. and 0:012 mm. respectively. .

When the cesophagus has passed through the nerve collar, its direction
tends more upwards, and very slightly forwards, and its lumen assumes an
irregularly stellate form, owing, probably, to the contraction of the sphincter
muscles, and consequent puckering of the cellular lining (fig. 6, 7). It now ~
turns backwards, and at the same time comes to lie in a mass of cells situated
immediately below the intestine. The elements composing this mass are for
the most part of ovoid form, the greatest diameter averaging 0-016 mm. ; they
have a finely granular content, and a large deeply-stained spheroidal nucleus,
with a nucleolus. Their function must remain to a large extent the subject of
conjecture ; their histological characters and situation would suggest that they
form a gland, but none of the sections examined have revealed any trace of
duct or of excretory openings in the cesophageal wall.

After a short course through this gland-like organ, it turns directly upwards,
and opens upon a small elevation in the floor of the intestine, at a point about
1 mm. behind its anterior extremity (Pl. XX VII. fig. 8).

3. The Stomach (Chylusmagen of Leuckart) needs only a few words of
description. As stated above, it presents anteriorly a rounded ccecal extremity
about 0°5 mm, in length, behind which is the opening of the cesophagus (Pl.
XXVII. fig. 8). Its form is, speaking roughly, cylindrical, slightly tapering, —
however, as it passes backwards, and it lies evenly in the middle of the body
cavity ; its greatest diameter being about 0°75 mm. A little less than 1 mm.
from the posterior extremity of the body the stomach terminates by opening —
into the rectum.

Of all the organs of the body the digestive tract was, unfortunately, the
worst preserved, so that I am unable to give information of any great value as

A NEW SPECIES OF PENTASTOMUM. 177

to its histology. It is lined by a single layer of nucleated epithelial cells, and
the remainder of the wall is made up of two indistinctly cellular layers, in
which I failed to distinguish any definite muscular elements (figs. 5 and 10).

The wall thus composed is about 0-042 mm. in thickness near the head, but
it commonly increases to about double this, and is much more compactly con-
stituted in the more posterior portions of the body.

Two mesenteries (fig. 5) support this portion of the alimentary canal; these
are not diametrically opposite to each other, but are separated by an angle of
90° to 120°. They are thin lamella (0021 mm. thick), made up either of small
rounded cells, or else of fibres placed longitudinally ; on an average, two of
these make up the thickness of the lamina. The mesenteries commence as
continuous membranes about one and a half millimetres from the hinder
extremity of the body, although traces of them are visible in transverse sections
posteriorly to this.

In addition to the stomach, they support the hook-glands (Pl. XXVII. fig.
10), and in the anterior portion of the body the vasa deferentia come into rela-
tion with them, as will be more fully explained when speaking of those organs.

There would appear to be in LZ. tenioides nothing homologous to the struc-
ture just described, unless it is to be found in a number of distinctly muscular
fibres which arise from the stomach, and spreading out in the form of a fan,
unite with the muscular wall of the body ;* but the differences between these
two sets of structures are so many, that it would scarcely be justifiable to
regard them as homologous, save as the result of an embryological inquiry.

4. The Rectum (Pl. XXVII. fig. 7) is about 0°75 mm, in length ; in section
it is compressed dorso-ventrally, its transverse diameter being 0:17 mm., while
its upper and lower surfaces are almost in contact; it is lined with cuticle,
0°015 mm. in thickness, prolonged from the external surface of the body, below
which is a layer of cells, forming part of the chitincogenous layer. Muscular
_ elements seem to be entirely absent.

SECRETORY ORGANS.

Three distinct sets of organs must, in the present state of our knowledge,
be grouped together under this head, although they differ widely in structure
and probably in function also.

They are—

1. The Hook-Glands.
2. The Parietal Cells.
3. The Stigmatic Cells.

1. The Hook-glands (Hakendriisen, Leuckart) are undoubtedly the same

* Lot. Ctt., Dp: Oo

178 MR W. E. HOYLE ON

structures as VAN BENEDEN described in his P. Diesing ‘7,* and as those to which
Leuckart alludes in P. cylindricum, P. oxycephalum, &c.t They are elongated
bolster-shaped bodies, tapering slightly towards either end and flattened ‘on the
median surface which is in relation with the intestine (Pl. XX VII. fig. 10, 1.9).
They extend forwards into the head, but about the poimt where the cesophagus
opens into it they leave the intestine, and passing outwards unite with the
body-wall; posteriorly they extend to within a few millimetres of the hinder
extremity of the body. .

Their length is thus very little less than that of the entire animal, while
their average diameter is about 0°7 mm., so that they fill up the greater part of
the body-cavity on either side of the intestine,

Each gland is covered by a delicate membrane, and within is made up of
very large cells varying 0:07 mm. to 0°15 mm. in diameter, of very diversified
shapes and packed closely together.

The cells were found to contain a coarsely granular protoplasm, and a
large nucleus (0°02 mm. in diameter) in which a nucleolus could only very rarely
be distingnished,

In the centre of the gland may be seen the duct (fig. 10, 4.9’), a tube 0:02 mm.
in diameter, with a lumen of 0°008 mm., lined with a very delicate layer of
chitin. This duct was traced forwards through a series of transverse sections
nearly as far as the bases of the hooks ; beyond this point, however, it could not
be followed; but there can be no reasonable doubt that it opens in the invagina- —
tion of the cuticle in which the hook is situated, as described by Levcxart. I
could detect no ducts passing towards the mouth, but only the two pairs pro-
ceeding in the direction of the hooks; neither the duct nor any portion of the
gland passes through the nerve ring, as in P. oxycephalum.t

These glands would seem from their position and relations to be homologous
with the salivary glands of other Arthropoda; the fact of their opening at the
base of the appendages and not into the cavity of the mouth might be an
obstacle to the adoption of this view, unless perhaps these are to be regarded
as homologous with the jaws rather than with the limbs of allied forms.

2. The Parietal Cells (Pl, XXVII. fig. 9, p.c) I propose for the present to
term a number of large oval cells scattered in the mesoderm of the body-wall,
because at present no opinion can be offered as to their function. They consti-
tute one of the most conspicuous characters seen in the examination of sections,
both longitudinal and transverse.

In form they are ovoid, generally flattened by mutual contact, and averaging
0-03 mm. in diameter; they contain a deeply stained spheroidal nucleus of

* Ann. d. Sci, Nat., sér. 3, t, xi. p. 324, 1849.
+ Levoxart, loc. cit., p. 67.
+ Loe, cit., p. 67.

A NEW SPECIES OF PENTASTOMUM. 179

about 0008 mm, in diameter, within which a small nucleolus is generally to be
seen ; the protoplasm is finely granular and faintly stained.

These cells are arranged in groups of 2-5, and very commonly at the point
where several cells meet may be observed an oval speck, from which fine radi-
ating lines branch out (figs. 9 and 15). _ The similarity between this appearance
and that depicted in some of Leucxanrt’s figures will be at once apparent.*

The distribution of these cell-groups next demands attention; they lie
among the smaller mesodermic cells constituting the body-wall, about
midway between its inner and outer surfaces, and are disposed in zones, corre-
sponding with the annuli of the body, and consequently with the stigmata, none
being found in the interannular spaces. It is, in fact, the presence of these cells
which causes the swelling of the annular regions of the body and the greater
stiffness of the wall in those parts, which has been already alluded to.

In the annuli, however, these cell-groups are very closely placed, and in a
transverse section they seem to form an almost continuous zone; more than
fifty can often be seen in a single circumference.

The homology of these cells next demands our attention. Their position
would seem to show that they correspond to those cells of ZL. tenioides which
Levuckar® has called the hook-gland (Hakendriisen, see Tab. i. fig. 11 of his
monograph), and this view is strikingly confirmed by a study of their appear-
ance (cf fig. 15 with Tab. i. fig. 17). The form of the cells is the same, as also
their arrangement in acini composed of 2-5; the radiating apparatus also,
which Leucxart regards as the commencement of the excretory apparatus, is
the same in both. But if we admit this hypothesis we are placed on the horns
of a dilemma, for we have in the creature before us a structure which is homo-
logous with the hook-gland of L. teenioides, and another organ which is beyond
all question the homologue of a gland which LeucKart finds in P. proboscideum
and other species, and which VAN BENEDEN has described in his L. Diesingzi,
_and which, again, is declared to be the homologue of the hook-gland of L.
tenioides.t Thus we have two separate organs both corresponding to the same
organ. It appears to me that at present the only course open to us is to assume
that we have here a condition in which there is a double set of organs, one of
which is lost in certain forms, while the other disappears in others. This does
not seem satisfactory, however, because both structures appear to be very well
developed, and have by no means the aspect of rudimentary structures.

In the face of this difficulty, I regret the more that I was unable to trace the
course of the excretory apparatus of these peripheral gland cells, even after the
_ most careful scrutiny of the sections. This knowledge might have solved the
mystery, but at present it must be left until some future occasion may furnish
a supply of better preserved material.

* Loe. cit., Tab. i, fig. 17. fp LGGn Cit, De Owe

180 MR W. E. HOYLE ON

With regard to the function of this cell-system, I have, as will be inferred
from what has just been stated, no theory to offer; if it be really a portion of
the hook-gland, then the suggestions of LeucKArT seem the most apt that can
be offered, and if not, the discovery of the destination of the secretion must
precede any further hypothesis.

3. The Stigmatic Cell-groups (P\.'XXVII. figs. 9 and 11, s.c) have been
already alluded to as situated immediately within the stigmata. They are —
spheroidal in form, and their inner surface projects only a little beyond that of
the subcuticular epithelium, so that they have an average diameter of about
0-02 mm. They are not very transparent, and take up the straining material
eagerly, so that their structure is somewhat difficult to make out. Each con-
sists of from six to nine small cells, with clear or clouded protoplasmic contents,
and a comparatively large variously-shaped nucleus. ‘The outer aspect is
moulded into a kind of short neck which lies within the stigma, and is closed
by a fine very darkly stained line.

Such being the appearance of these structures, it becomes necessary to
inquire into their homology and function. In LeucKart’s classic* work there
are described in the earlier developmental stages of ZL. teentoides vesicles of
clear fluid in relation with the stigmata, and these in the adult are replaced by
large cellular processes which project into the body-cavity. It would seem,
then, that we have in the subject of the present investigation a condition inter-—
mediate between the two just described, and this is rendered more probable
inasmuch as Levokart speaks of and figures an incipient segmentation.

These cell-groups are possibly homologous with the subcuticular glands
described by KOLLIKER in certain insects ;+ it is scarcely possible that they have
any relation other than a merely analogical one with glands, which they closely
resemble in structure, described by ANDREAE in Stipunculus nudus.t

With respect to the function discharged by these structures it seems quite
possible that they take part in the formation of the cyst which encloses the
animals, unless they be excretory in nature, and destined only to come into
full activity on the further development of the animal; it is not impossible,
however, that both these suggestions may be true.

THE NERVOUS SYSTEM.

As might have been anticipated, the nervous system of the subject of this
paper shows but slight differences from that of any similar forms which have
hitherto been examined. It consists of a single median ganglion, showing,
however, traces of a primitive division into two lateral halves, and of about

* Loc. cit., p. 33. ;

+ Verhandl. d. phys. med. Vereins Wiirzburg, p. 76, 1857.
t Zeitschr. f. wiss. Zool., Bd. xxxvi. p. 201, Taf. xii., figs. 1 and 4, 1881.

A NEW SPECIES OF PENTASTOMUM. 181

equal length and breadth (0:28 mm.), while its thickness amounts to about
014mm, A general view of its form and position, with the branches given
out from it, is given in the dissection depicted in Pl. XXVIII. fig. 16, ng.
The two larger branches, which pass backwards, can be traced for more than
half the length of the animal ; they lie in the main parallel to each other, one
on either side of the ventral median line. From either side of the large ganglion
a branch passes along the cesophagus, and probably reaches the oral papilla.

In connection with the structure described by Liknarp~* in several other
Arthropods (Spirocyclistus, Cossus), it is interesting to note that the preeceso-
phageal commissure in my specimens was double, and from the anterior cord
two branches proceeded forwards.

The minute structure of the nervous system was so ill-preserved that no
observations of value could be made upon it.

THE GENERATIVE ORGANS,

Both male and female specimens were fortunately present among those I
had for examination, but while the genital apparatus of the former presented
some noteworthy arrangements, that of the latter was not specially remarkable.

The Male Organs.

These may conveniently be described under the following heads :—

1. The Testis.

2. The Vesicula seminalis,
3. The Vas deferens.

4, The Cirrus Sac.

1. The Testis (Pl. X XVII. fig. 5; Pl. XXVIII. figs. 1-6, ¢) is situated on the
dorsal surface of the intestine ; it is an unpaired, long, very thin walled sac,
extending from a point some 4-5 mm. behind the head, to within about 1 mm.
of the posterior extremity, where it ends in a mass of small parenchymatous
cells, which lie on the dorsal aspect of the intestine. Its greatest breadth
(measured from side to side) is 0'7 mm., whilst its thickness (dorso-ventral)
will be rather more than one-third of this.

The wall of this gland consists of a thin, and to all appearance, structureless
| membrane, which becomes very deeply stained by hematoxylin, and measures
0004 mm. in thickness. It is attached to the dorsal wall of the body-cavity
by a thin cellular mesentery (PI. XX VIII. fig. 3, m.¢) which is precisely similar
| in structure to those supporting the intestine, already described.

In the immature specimens under consideration, the gland contained only
* Lisnarp, ‘“ Constitution de l’anneau cesophagien,” Archiv. d. Biol., t. 1. p. 381, 1880.
VOL. XXXII, PART J, ) ore

182 MR W. E. HOYLE ON

a few masses of protoplasm of very variable size and shape, each usually
possessing several nuclei, but not divided into distinct cells (fig. 2); they clearly
represent the earlier stages in the development of the spermatozoa as figured by
Leuckart.* Anteriorly, as well as posteriorly, the testis becomes narrower
though not to the same extent, and its inferior wall becomes thickened by a
deposition of small cells on its outer surface. Farther forward two grooves
appear in this mass of cells, which gradually become deeper until eventually —
they become roofed in, and thus converted into two tubes (figs. 4 and 5).
The tissue in which these tubes lie is composed of small rounded cells, which
vary from 0-004 mm. to 0-008 mm. in diameter, and are provided with small
spheroidal nuclei. In the tubes they seem to form a single layer of columnar

epithelium, but this was so badly preserved that I can give no further
particulars concerning it.

The lumen of these tubes gradually becomes regularly oval and very nine
smaller, being in some sections barely perceptible, and in certain cases the cells
seem to have a tendency to segregate into a separate covering for each tube,
as indicated by a splitting in the cell mass; these fissures do not, however,
extend far, and may be due only to the shrinking of the tissue in hardening
(fig. 6).

On examination of Pl. XXVIII. figs. 4-6, it will be noticed that the cavity
of the testis extends forwards some distance over this tube, but it becomes
gradually smaller and eventually terminates blindly.

These two tubes continue separate although enclosed within a common
investment for a distance of 0°2 mm., and then fuse into a thinner walled
cavity, roughly oblong in section, and supported by a continuation of the same
mesentery as the testis. At this poimt we may consider the second part of the
genital tract to begin.

The two tubes are, of course, indications of the primitive symmetry of the
sexual organs, and it may be worth while to mention that in Z. tenioides the
testis is double (though both glands eventually open into an unpaired tube),
while in P. oxycephalum and P. proboscideum only a single gland is present.

2. The Vesicula seminalis (Pl. XXVIII. fig. 1, v.s), (Samenblase, Leuckart).
I apply this name to the structures now to be described, because they seem
to correspond to a tube, bifurcated at its extremity in LZ. twnioides, and near
its commencement in P. proboscideum. In the present instance the lumina of
the two tubes become united, and also first enlarged, for as may be seen by
comparing figs. 6 and 7, the cavity of the single vessel is much greater than
those of its two components. The wall is made up of cells of precisely the
same character, but is only about 0°024 mm. in thickness on the average.
The layer of columnar epithelium is distinct in its interior.

* Loc. cit., Tab, ii, fig. 14.

A NEW SPECIES OF PENTASTOMUM. 183

After a course of about 0°01 mm. this vesicula seminalis becomes divided
into two by a septum which rises from its ventral surface (fig. 7), and very
shortly it divides into two quite distinct tubes (figs. 8 and 9). This junction

between the two vesicule seminales is of considerable morphological interest,
because it is the first trace of a condition which is carried further in P. pro-
boscideum, and reaches its fullest expression in the large median sac found in
| iL. tenioides (cf. Levexart, loc. cit., Tab. ii. figs. 9 and 10).
At this point the dorsal mesentery splits, and a portion accompanies each
- tube. |
| The two branches of the vesicula seminalis now diverge from each other,
/ and passing round the intestine, become united with the copulatory apparatus
| which lies upon its ventral surface ; as they separate they first of all lose their
| mesenteric connection with the dorsal body-wall, although the rudiment of the
| mesentery is still to be seen after they have become detached from it. In their
| further course they approach the hook-glands, which they gradually traverse,
| passing through the middle of the gland and not between it and the intestine.
The rudimentary mesentery now demands a moment’s notice; it passes
| forwards, becoming slightly wider, and just at the point where the vesicula
seminalis emerges from the hook-gland, it becomes connected with this latter ;
so that now each hook-gland is supported by two mesenteries, one which it has
had throughout the whole length of the body, and another which it has derived
from the genital organs.

In this connection it may be well to say a word or two with respect to the
size and structure of the vesicula seminalis. It is about 2 mm. long, and
of a regular oval section, its greater and lesser diameters being 0°178 mm.,
and 0-1 mm. respectively, being slightly larger about the middle of its length.
Its wall is made up of two layers of about equal thickness (0°02 mm.); the
outer of which consists of a mass of cells very similar to those mentioned at
_ its commencement, but rather more irregular in outline, and varying consider-
ably in size, and provided with distinct ovoid nuclei. The inner coat consists
of a single layer of elongated columnar epithelial cells, also nucleated and
separated from each other by an undulating boundary line.

The vesicula seminalis now lies free in the body-cavity for a short distance,
and then becomes attached to the vas defereng, which will be presently
described.

At this point one of the most remarkable peculiarities in the organisation of
the animal comes into notice. The lumen of the vesicula seminalis becomes
excluded, and is not continuous with that of the vas deferens.

This last is a tube regularly elliptical in section, of sharply-defined even
contour and compact walls ; applied to the dorsal wall of this is a mass, oval in
section, of much looser tissue, which is in fact the wall of the vesicula seminalis,

184 MR W. E. HOYLE ON

but there is no intimate union between the two, which are separated by a clear |
line of demarcation.

The truth of this observation, so exactly opposed to what might have bedi
expected, has been confirmed by the preparation of a very careful series of
transverse sections, which show the one tube lined with a perfectly smooth
layer of epithelium, passing by the other, utterly ignoring, if the expression may
be allowed, its proximity, while the vesicula seminalis fades away in a mass of
rather loose cells without showing the least desire to unite with its companion.

Pl. XXVIII. fig. 15, shows the last section which contains a trace of the
vesicula seminalis, in the one next behind the lumen, though small, was quite
apparent, and in the next anterior there is no trace of it whatsoever.

Observations suggested by this arrangement will be deferred until the next
portion of the generative system has been described.

3. The Vas deferens (PleX XVIII. figs. 1,10, and 12, v.d)is a short tube which —
passes forwards from the termination of the vesicula seminalis and opens into
the cirrus sae; this portion of it is about 1°5 to 2 mm. in length, but it is pro-
longed backwards into a ccecal process (blindschlauchartiger Anhang, Leuckart)
whose length commonly exceeds that of the anterior portion by two to three
times ; it is variously curved, and in ane case was observed to open again into
itself, and thus to form a complete tubular ring.

The structure of this vessel is the same throughout, its average diameter is
about 6°08 mm., that of its lumen 0:024 mm.; within it is lined by a thin layer
of chitin derived from the external covering of the body, externally to which is
seen a compact mass. of nucleated cells radially disposed and to all appearance
epithelial in nature. Iwas unable to discover with certainty the presence of
muscular elements in this wall, although LevcKkart observed them in L. tenioides,
and based upon that fact the hypothesis that the ccecal prolongation is an organ
for the propulsion of the semen.* For the greater part of its length it possesses —
a further adventitious covering of tissue similar to that in which the vesicula
seminalis terminates.

The opening of this organ into the cirrus sac will be described under that
heading (p. 185).

The want of continuity between the vesicula seminalis and the vas deferens —
becomes comprehensible when we consider what is known of the developmental
history of this group of animals, for it would appear from the researches of
Leuckarr that one portion of the generative apparatus takes origin by the
segregation of cells within the body, while another portion is formed by
invagination of the external surface. When it is remembered that the vas
deferens is connected with the external surface, and bears further marks of its
origin in its chitinous lining, and that the vesicula seminalis presents a marked

* Loc. cit. p. 75.

A NEW SPECIES OF PENTASTOMUM. 185

contrast in appearance, and has no such lining, it would seem justifiable to
assume that the point where these two come into relation with each other is
also the point where what may be termed the inward and outward growing
portions of the generative apparatus meet. Furthermore, the immaturity of
the specimens before us, indicated by their encysted condition, is in support of
this, for it is quite conceivable that, as sexual maturity apprvaches, a connec-
tion might be formed between these two canals, It is to be noted, however,
that in LEuckart’s figures of the sexual organs of L. teenioides, the channel is
shown as quite pervious from the exterior to the testis even in so early a stage
as that known as P. denticulatum,* which measures only 4°5-5 mm. in length ;
but in describing the stage immediately preceding, which has a length of
3 mm., he mentions that the communication with the cirrus sac and the hinder
portion was not clearly observed (“Kine Communication mit den dahinter
gelegenenen Leitungsapparaten wurde mit Bestimmtheit nicht beobachtet ”).+
If this explanation be the correct one, it is curious that the species before us
should present such a striking embryonic feature when the remainder of its
organisation has attained such a comparatively advanced stage of development.
4, The Cirrus Sac is shown in longitudinal section in Pl. XXVIII. fig. 10,
and may be seen to be roughly divisible into two portions,—a solid part through
which the vas deferens passes, situated on the dorso-lateral aspect, and a
hollow part placed nearer to the ventral line. The latter portion is, speaking
ects, ovoid in form and slightly flattened in the radial direction of the
animal’s body, as seen in the section (fig. 11): anteriorly it gives off a tube
_ from either side (fig. 10). One of these is the eaculatory duct, the position of
whose aperture near the middle line of the body has been already described ;
its lumen becomes gradually smaller until it reaches 0:005 mm.

The other tube-duct of what seems to be a gland, which, under the name of
accessory, will be presently described.

The wall of this saccnlar portion is on the average about 0°036 mm. in
thickness ; its innermost layer is of chitin so thin that it appears only as a fine
though very distinct line under a power of 400 diameters; next follows an
epithelial layer, 0°008 mm. in thickness, of nucleated columnar cells; the
remainder of the wall being composed of small cells among which run a number
of muscular fibres, these last being confined to the anterior portion of it.

The solid portion of the cirrus sac is an ovoid mass somewhat smaller than
\the other part, the wall of which covers it to a certain extent, though even-
tually it fuses with it. Through the middle of this mass of cells passes the canal
of the vas deferens, slightly widening as it approaches the sac until it ends in a
\short groove (Pl. XXVIII. fig. 10; also in section fig. 11, v.d).

A short distance posterior to this is another orifice leading into a cavity

* Loe. cit, Tab, iv. fig. LW. t Loe. cit., p. 134.

186 MR W. E. HOYLE ON

which contains the “Chitinzapfen” of Lrucxart (fig. 10, ¢2). This is a
cylindrical body, pointed at its free extremity, and for the greater part of its
length attached by one side to the interior of the cavity in which it lies
(fig. 12, ¢.z); this cavity is only just large enough to contain the organ, whence
in section its lumen appears as a slit almost annular in form. Between this
part of the cell-mass and that which contains the vas deferens there is very
often a fenestra, as in the case shown in the drawing.

With respect to the structure of this portion of the cirrus sac, it consists in
the main of small (0:°002-0:005 mm.) nucleated cells, closely packed. In the
“ Chitinzapfen” these show a tendency to a radial arrangement, and often leave
in the centre an irregular gap, which does not seem, however, to be of any
morphological signification.

The epithelial lining of the vas deferens here assumes a most distinctly
radial arrangement (fig. 12, v.d), the cells being very long and slender, and
with nuclei either at one extremity or the other, rarely in the middle; exter-
nally to this is a thinner layer of cells, which is an extension of the common
wall of the cirrus-sac.

Of the cirrus itself I could find no trace whatsoever, and am consequently
led to imagine that it has not yet made its appearance ; if this be so, we have
here another point in which this animal corresponds with a very early stage of
L. tenioides. It is possible, however, that in this species no cirrus is ever
formed, and that the “ Chitinzapfen” does duty as a copulatory organ ; in any —
case, I should be disposed to regard this as a kind of dilator for opening up the
sexual canal, either for the immediate flow of the semen, or as a preparation
for the passage of the slender cirrus, which by itself would hardly seem to be
fitted for such a purpose. In this process a very important service would be —
rendered by the muscles which pass transversely across the sides of the cirrus
sac, for they would approximate the “ Chitinzapfen ” to the sexual orifice.

The Accessory Gland (Pl. XXVIII. fig. 13), above alluded to, is a flattened
mass of cells lying beside the intestine about the spot where the cesophagus
enters it, and stretching in a dorsal direction as far as the hook-gland. The
duct passes upwards and forwards through the middle of it, and is surrounded
by a space, crossed by numerous fine threads which are probably minute rami-
fications of the duct, although it could not be made out with certainty that they
were hollow. At the extremities of these are groups of cells (0:008-0:014 mm.
in diameter), rendered polyhedral by mutual pressure, and provided with
relatively large nuclei, in some of the larger cells 0°008 mm. in diameter.

As to the secretion of this gland and its function, I have been able to make
no observations. .

A NEW SPECIES OF PENTASTOMUM, 187

The Female Organs.

But little is to be said on this subject, because these organs were in a very
unsatisfactory state of preservation. They consist of—

1. The Ovary.

2. The Oviducts.

3. The Receptacula Seminis.
4. The Vagina.

1. The Ovary (Pl. XXVIII. fig. 18) occupies a position exactly corresponding
to that of the testis, but is very much smaller. It is in fact at this stage of the
animal’s growth merely a narrow tube, about 0°015 mm, in diameter, passing
with a sinuous course down the median dorsal line. It is attached by a
mesentery similar in structure to, but much thicker than, those which support
the testis and intestine (Pl. XXVIIL. figs. 3, 14, &.).

It consists of a thin layer of small nucleated cells, and has a considerable
lumen ; but I was unable to make out anything regarding the development of
the ova.

2. The Oviducts are two in number, and like the vasa deferentia, pass round
the intestine, and eventually meet in the middle line below it (Pl. XXVIII.
fig. 16, 0.d), where they open into the vagina.

In structure they seem to resemble the ovary itself.

3. The Receptacula Seminis (Pl. XXVIII. fig. 16, 7s) are two flattened
oval sacs, nearly 1 mm. in length, and situated one on either side of the middle
line immediately posterior to the oviducts. Anteriorly, and towards the
median line, the cavity of the sac enlarges, and into this dilated portion projects
a papilla on which opens, by a stellate orifice, the tube by which the sac com-
municates with the vagina.

The cuticular lining of the vagina could be followed to this orifice, but I
could find no trace of it on the interior of the sac; the wall of which consists
of a very compact mass of minute nucleated cells; it is about 0:025 mm. thick
on the average, and is lined with what appear to be the remains of an epithelial
layer.

4, The Vagina (Pl. XXVIII. fig. 16, v) is simply a narrow tube, which
passes directly backwards from the point of union of the oviducts to open in

| the ventral line within a millimetre of the anus. Typically it lies in the ventral

median line, but in one specimen of which I made sections, it lay at one side,
between the hook-gland and the muscles of the body-wall.

It has a lumen of about 0:008 mm., and is lined by a delicate layer of
cuticle, immediately external to which is found as usual a layer of columnar
epithelial cells, These again are surrounded by another layer, made up of

188 MR W. E. HOYLE ON

rounded nucleated cells about two deep, and having a diameter of some
0-007 mm,

SYSTEMATIC POSITION.

The parasite which has just been described finds its nearest congener in
Pentastomum polyzonum, Harley.* It is distinguished from it, however, by
the number of segments, which in the females under consideration amounts to —
18-22, whilst in the adult females of P. polyzonum hitherto described t it does
not exceed 19, and it is very unlikely that an immature form should have more,
though it would very probably have fewer segments than the adult. In this
case the difference in size is of course valueless as a specific character.

I propose therefore to make the specimens above described the type of a
new species, whose diagnosis would be provisionally as follows :—

Pentastomum protelis, n. sp.

Body cylindrical in the anterior half, slightly tapering posteriorly, terminal —
segment obtusely pointed. No clear distinction between cephalothorax and
abdomen. Head hemispheroidal, equal in diameter to the body. Mouth fur-
nished with a papilla, perhaps a protrusible proboscis. No accessory hooks.
Stigmata arranged in numerous irregular rows on all the segments. Male,
13-17 mm. in length, with 16 or 17 annuli. Female, 20-25 mm. in length, with
18-22 annuli. Habitat, the mesentery of Proteles cristatus, enclosed in a con-
nective tissue cyst.

It is, of course, possible that some future investigator will demonstrate the
identity of this form with an early stage of P. polyzonum, and this possibility
is increased by the fact that specimens of this species were found in an
African serpent,t of which part of the globe Pvoteles cristatus is also an
inhabitant.

If such should be the case, Leuckart’s opinion that P. Diesingii, v. Ben., is”
the immature forni of this would be untenable, for this form exhibits distine-
tions in its body form, oral papilla, and muscular system, sufficient to prove
its specific distinctness from the subject of this paper. .

I propose now to make a few concluding observations on the subdivision of
the family Pentastomide.

In the brief systematic portion of LEucKART’s 5 work, the species are grouped
under two headings, which are regarded as being of sub-generic value—

* Proc. Zool. Soc. Lond., part 25, p. 115, 1857.
+ Ber, Ann. and Mag. Nat, Hist., ser. 5, vol. vi p. 176, 1880.
+ Bass loc, cit. p. 173. § Lue. cit, p. 152.

A NEW SPECIES OF PENTASTOMUM. 189

Linguatula, “Corpus depressum.” ‘‘ Cavitas corporis in latera annulorum
porrecta, pectinata.”

Pentastomum, “ Corpus teretiusculum. Cavitas corporis continua.”

It appears to me, however, that we see now sufficient anatomical distinc-
tions in the works of previous authors,* and in the research which has just been
recorded, to justify the elevation of these two groups to the position of distinct
genera.

In the first group, for example, the hook-gland is diffuse, the cesophagus
opens into the anterior termination of the intestine, the testis is double, and the
vesicula seminalis single, while in the second group the hook-gland is collected
into two masses, one on either side of the intestine ; the cesophagus opens on
the inferior surface of the intestine, the testis is single, and in most cases the
vesicula seminalis seems to be double (P. oxycephalum would appear to be an
exception).

It would seem only reasonable to suppose that such an amount of difference
in structure ought to be anatomically expressed by at least a generic difference ;
but further investigations into the anatomy of other members of the group
are very desirable to show whether they agree in the possession of these
characters. |

With respect to the names which these divisions should have, I do not
think it possible to improve upon those suggested by LruckarTr. As VAN
BENEDEN has pointed out,t Zinguatula has a claim to recognition on the score
of priority, having been applied by Frouiicu] in the case of L. serrata.

The two genera would then be diagnosed thus, the characters of the family
remaining as given by LEUCKART :—

Linguatula, Frohlich.

(Type, Pentastomum teenioides, Rudolphi.)

Body flattened ; body cavity sending out lateral processes into the annuli ; hook-
gland diffuse; opening of esophagus into the extremity of the intestine ; testis
| double; vesicula seminalis single.

Pentastomum, Rudolphi.

(Type, P. proboscideum, Rudolphi.)
Body cylindrical ; body cavity even, without lateral prolongations ; a hook-gland
on either side of the intestine ; testis unpaired ; vesicula seminals single (2).

er

* Van Benepen, Ann. Sci. Nat., sér. 3 (Zool.) t. xi. p. 3138, 1849; Dimsine, Ann. des Wien.
Mus., Bd. i. p. 1, 1836.
+ Loe. cit., p. 314. :
t Frouuicu, Naturforscher, Bd. xxiv. p. 148, 1789 (fide Diesing).
VOL. XXXII. PART I. 2H

Se

190 MR W. E. HOYLE ON

EXPLANATION OF THE PLATES.*

Explanation of Reference Letters the same in both Plates,

a.g, accessory gland; a.g’, duct of same. o.d, oviduct.

a.n.c, anterior nervous commissure. o.p, oral papilla.

¢.8, Clrrus Sac. ov, ovary.

cu, cuticle. par, subepidermic cellular layer.

c.2, “ Chitinzapfen.” p.c, parietal cells.

ep, epidermis. 7.8, receptaculum seminis,

g.o, genital openings. s.c, stigmatic cells.

hg, hook-gland ; h.g’, duct of same. t, testis.

i, intestine. v, Vagina.

me, mesentery. v.d, vas deferens ; v.d’, cecal portion of same.
m.l, longitudinal muscles. v.s, vesicula seminalis.

m.o, oblique muscles. w.e, extensor unci muscle,

m.t, transverse muscles. u.f, flexor unci muscle.

n, Nerves. u.f.a, flexor accessorius unci muscle.
ng, nerve ganglion. u.r, retractor unci muscle.

nu, nucleus of sarcolemma. u.b.a, adductor basis unci muscle.

w, cesophagus. u.b.p, protractor basis unci muscle.

PLATE XXVIT,
MUSCLES, DIGESTIVE AND SECRETORY ORGANS.

Fig. 1.—View of Pentastomum protelis, ventral surface (small male specimen).

Fig. 2.—Surface view of the cuticle.

Fig. 3.—Hooks: J, lateral; m, median.

Fig. 4.—Side view of oral papilla.

Fig. 5.-—Transverse section of intestine and mesenteries, with posterior portion of testis.
Fig. 6.—Transverse sections of cesophagus.

Fig. 7.—Transverse section of rectum.

Fig. 8.—Median longitudinal section of head.

Fig. 9.—Transverse section of body-wall.

Fig. 10.—Transverse section of body, posterior to union of vas deferens and vesicula seminali
Fig. 11.—Stigmatic cells.

Fig. 12.—Muscles of hook.

Fig. 13. —Transverse section near the posterior extremity.

Fig. 14.-—View of transverse muscles.

Fig. 15.—Large glandular cells from the body-wall.

Fig. 16.—Terminations of muscular fibres in the cuticle.

Fig. 17.—Arrangement of muscles are seen from within the body-cavity.

* The drawings were for the most part made by the aid of the camera with Zeiss’ microscope.
magnifying power employed is marked on the plate beside every drawing. 7

A NEW SPECIES OF PENTASTOMUM. 191

PLate XXVIII.
GENERATIVE ORGANS.

Fig. 1.-—General view of male organs.

Fig. 2.—Portion of contents of testicle.

Figs. 3-7.—Transverse sections of testis at different points as far as the commencement of the

vesicula seminalis.

Fig. 8.—Section of vesicule seminales prior to the separation of the two tubes.

Fig. 9.—Section of vesiculze seminales after the separation.

Fig. 10.—Longitudinal section of cirrus sac.

Fig. 11.-—Transverse section of cirrus sac along the line « a.

Fig. 12.—Transverse section of cirrus sac along the line y y.

Fig. 13.—Transverse section of accessory gland and duct.

Fig. 14.—Transverse section of vesicula seminalis, hook-gland, &c.

Fig. 15.-—Transverse section of vas deferens at the point of termination of the vesicula semi-
nalis. ;

Fig. 16.—General view of part of the female organs and nervous system.

Fig. 17.-—Longitudinal section of the receptaculum seminis.

Fig. 18.—Transverse section of ovary and its mesentery.

SS

5

VOL. XXX 11, PLATE XX VIL

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ANATOMY of PENTASTOMUM PROTELIS.

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bY. Soc. EDINe Vou. xxxi1, PLATE XXVIII,

ZO89 SLD

193

XI.—-On Superposed Magnetisms in Iron and Nickel. By Professor C. G.
Knott, D.Sc. (Plate XXIX.)

(Read 2nd July 1883.)

The experiments which form the subject of this paper are designed, in the
first place, to test the relation pointed out by MAxweLi* between JouLr’s
discovery of the lengthening of iron in the direction of magnetisation,t and
WIEDEMANN’S later researches into the twisting of iron under the influence of
longitudinal and circular magnetisations,{ and, in the second place, to investi-
gate the corresponding properties of nickel.

According to JouLE’s discovery, an iron bar or wire lengthens in the direc-
tion of magnetisation, and contracts in directions at right angles thereto.
The extension is greater for a stronger magnetising force, and, if the metal is
subjected to traction in the direction of lengthening, is smaller for a greater
traction. In the experiments:to be described a wire was fixed at its upper
end, and stretched vertically by means of an appended mass. It passed cen-
trally through a glass tube of nearly the same length, round which a helix of
wire was wound. The length of the helix was 34°3 centimetres, and the total
number of coils 196. A current passed through the helix magnetised the wire
longitudinally. At the lower end of the wire was fixed a short copper wire,
which dipped into a pool of mercury. By this means a current could be passed
along the wire so as to magnetise it circularly. The twist produced under the
joint influence of the longitudinal and circular magnetisations was measured by
the deflection of a spot of light focussed upon a millimetre scale after reflection
from a mirror attached to the lower end of the wire.. Both the magnetising
currents were measured on a Helmholtz tangent galvanometer.

The method of experimenting was as follows :—One of the currents was
kept steady, while the other was varied through a considerable range. When
both currents were flowing the free end of the wire came to rest in a definite
position, which was registered by the reading on the seale. -One of the currents
was then reversed, and a second reading obtained. The difference between
these readings was approximately four times the angle.of twist. By successive

* See Maxwewt’s Electricity and Magnetism (2nd edition, vol. ii. § 448). The first edition comesto
a wrong conclusion, in-consequence of a misprint in WIEDEMANN’s Galvanismus (1st edition, Bd. ii. § 491).
See also Curystat’s article on “‘ Magnetism” in the Encyclopedia Britannica (vol. xv. pp. 269, 271).

+ Srurceon’s Annals of Electricity, vol. viii. p. 219; and Phil, Mag., 1847.

{ Wrepemann’s Galvanismus, 1st edition, Bd. ii. § 491.

VOU. XXXII. PARTI. Ail

194 PROFESSOR C. G. KNOTT ON THE

reversings and re-reversings of the current, a series of readings was obtained
whose differences gave a good mean. From the numbers so deduced the true
twist expressed in radians was easily calculated.

The first experiments were made with an iron wire, ‘00435 square centi-
metres in cross section. The most important are those in which the current
along the wire (the linear current) was kept constant, while the helical current
was made to vary from under half an ampere to nearly six amperes. Five
different series were taken with different values of the steady current. In the
following tables the upper row gives the successive values of the helical cur-
rents in amperes, and the lower the corresponding twists in radians x 10°.

Group A.

Experiment J. Linear Current = 575 Amp.

Helical Current, 0377 Oval PF 1889 2-045 2°573 5019

Experiment II. Linear Current = “723.

Helical Current, | 0°368 | 0°758 | 1:289 | 1676 | 2°025 | 2°436 | 2902 | 3:°375 | 5-019

SS ee Oe ee eee

Twist, ‘ 4 307 597 816 877 907 900 881 832 703

Experiment III. Linear Current = 1891.

Helical Current, 0°393 | 0-741 |1:254 | 1566 |1:987 | 2-488 | 2°925 | 3-527 | 4-068 | 5°781

:

pees ‘ ; 372 | 762 | 1179 | 1335 | 1389 | 1389 | 1387 | 1345 | 1279 | 1077

Experiment IV. Linear Current = 3°157.

Helical Current, | 0:460 0-700 1:254 1991 2488 | DB Lo7 4:592

Rf | a |

| Twist ; 342 775 | 1251 1567 1680 | 1710 1682

SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 195

Experiment V. Linear Current = 4-068.

Helical Current, 0-410 0-700 1:254 1:891 2°385 3039 4:214

Twist, é 5 | 390 810 1303 1678 1802 1886 1884

Three series were taken with steady helical current and varying . linear
current. They are as follows :—

Group B.

Experiment I. Helical Current = ‘611 Amp.

Linear Current, 0-410 0-716 1:272 | . 1943 2°395 3051 3°899

Twist, : p 126 357 ‘TAQ 1030 1125 1197 1225

Experiment II. Helical Current = 1:987 Amp.

Linear Current, 0:418 0-750 1:276 1-948 2°364 2:970 3°803
Twist, ; : | 127 312 | 767 1190 1358 1576 1754
Experiment. III. Helical Current = 3:229,

Linear Current, 0:505 | 0:893 1:320 1°703 2-724
Twist, : ; 152 | 387 718 877 1367

In both these series the wire was under a tension of 1950 grammes’ weight.
The representative curves are shown on Plate XXIX., iron groups A. and B.
The current strengths of the varied current are laid down horizontally, and
the corresponding twists vertically. The two series differ markedly, the
A group showing a maximum twist for an intermediate current strength, the
B group giving no such indication. That such a difference between the two
cases should exist is not to be wondered at, since the magnetisation due to a

196 PROFESSOR C. G. KNOTT ON THE

linear current follows a different law from that due to a helical current. Indeed,

it is impossible to magnetically saturate an iron wire by means of a linear
current. Further than this, experiments of the B type need no discussion.

The maximum point in the curves of group A is a constant characteristic

of all similar cases, as will be seen by reference to the curves of groups C and

D. These represent further experiments with iron wires, in which is studied |
more particularly the effect of tension upon the amount of twist. In the fol-
lowing tables there are three distinct series under each experiment correspond-

ing to three different tensions. The last column contains the tensions expressed

in grammes’ weight. i

Group C.—Cross Section of Iron Wire = ‘00276 sq. cc.
Experiment I. Linear Current = 033 Amp.

Helical Current, 0:952 1657 2-489 3'°039 a v3) 5'198 || Tension,

561 632 632 607 523 413 1360
Twist, . : 1013 1148 1161 1097 1013 875 712
1123 1284 1258 1265 1097 923 388

Experiment II. Linear Current = 1:476 Amp.

Helical Current, 0°533 |0°952 | 1657 | 2 489 | 3:039 | 3°723 | 5:198 |) Tension.

484 | 1213 | 1471 | 1484 | 1406 | 1299 | 1097 1360
Twist, . 5 458 | 1077 | 1452 | 1594 | 1529 | 1426 | 1187 712
439 | 1045 | 1503 | 1658 | 1684 | 1561 | 1323 388

Experiment III. Linear Current = 2°412 Amp.

| Helical Current, | 0°533 | 0-952 | 1-657 2°489 | 3-039 | 3°723 | 5:198 || Tension.

| 0484 | 03677 | 1332 | 1445°| 1510 | 1555 | 1394 1360
Twist, - ‘O< | 0490 | 1187 | 1742 | 1974 | 1974 | 2019 | 1800 712
| | 0394 | 0923 | 1394 | 1723 | 1820 | 1800 | 1645 388

SUPERPOSED MAGNETISMS IN IRON AND NICKEL.

Group D.—Cross Section of Iron Wire = ‘000714 sq. cc.

Helical Current,

Twist,

0508

103
142
129

Experiment I. Linear Current = 0°65 Amp.

197

Helical Current, |0°508 | 0°995 1598

Twist, ae
252

The direction of twist was as. found by WIEDEMANN.
passed down the wire from the fixed to the free end, and the wire is mag-
netised with north pole downwards, the free end, as looked at from above,
twists in the direction of the hands of a watch. As pointed out by MAxweE.Li

and CuRyYSTAL, this agrees with JouLe’s discovery mentioned above.

0995 |1:593 | 2262 | 2°615 |3:157 | 4-068 || Tension.

290 | 368] 348 | 336] 329 | 265 388

400 | 613°} 619 | 613] 574] 484] 258

484} 697 | 761) 787} 761 | 723 |) 129

Experiment II. Linear Current = 0:973 Amp.

2:262 |2°615 | 3157 |4:068 || Tension.

794 | 839 | 865 | 807] 774 | 388

o 923°} 1090 | 1077 | 1013 | 884] 208

613 | 916 | 1045 | 1123.| 1084 | 1045 | 129

If the current is

For the

circular magnetisation due to the down current is right handed with reference

to the current.

Hence the resultant magnetisation lies in a direction inter-

mediate to the circular and longitudinal magnetisations at any point; and as
the iron extends in the direction of magnetisation, and contracts at right angles
thereto, there will be a lengthening of the wire in a direction oblique to the
axis, such as to cause a twist in the direction specified. The amount of twist
depends not only on the magnetising force in this oblique direction, but also
upon the obliquity, so that a maximum twist for an intermediate value of the
helical current is quite in accordance with JouLe’s result that the extension
Suppose, for example, that the circular and
longitudinal magnetisations at a point on the wire are a and £, and that these
give a resultant magnetisation ,/a?+ 6? in a direction making an angle, whose
tangent is a/8, with the vertical line through the point.
along this direction be represented by » (a? +"), an assumption approximately

‘increases with the magnetisation.

Let the extension

198 PROFESSOR C. G. KNOTT ON THE

true according to Jounr’s researches. Then the amount of twist per unit
length of the wire will be
r=p(a? + f?)a/B=(a*/B+ a8).
If a is constant, 7 has a maximum value when
p=a:
If B is constant, there is no such maximum value of 7. A comparison of curves
A and B (Plate X XIX.) bear this out fully.

Hence, in the case of constant circular magnetisation and varying longi-
tudinal magnetisation, the twist will first mcrease and then diminish as the
latter is increased to its saturation point. For a stronger circular magnetisa-
tion the maximum point is pushed further on, until, when the circular
magnetisation has reached the saturation point, there will be no subsequent
fall off in the twist, z.e., no true maximum point. These remarks apply strictly
to a thin iron cylinder. In the case of a wire the effects are complicated.
Still the curves on Plate I. bear out in a remarkable way these conclusions.
Thus in fig. A the maximum point obviously occurs further to the right in the
higher curve. In the following table a direct comparison between the linear
current strength and the helical current strength, which corresponds to the
maximum twist, is established :—

Linear Current, ; : : : ‘ 0575 | 0°723 | 1°891 | 3:157:| 4-068
Helical Current for Maximum Twist, ; 2 Die, 2°4 3:1 3°5 +

The highest curve has no distinctly marked maximum, a result in close agree-
ment with the foregoing deductions. The other series of curves bear out the
same conclusion.

JOULE also found that the extension for a given magnetisation was smaller
when the wire was subjected to a greater tension. Hence, in general, we
should expect the twist in a wire due to superposed circular and longitudinal
magnetisations to be less for the greater tension, since the longitudinal exten-
sion will be diminished. This conclusion is quite borne out by curves C and
D. ,With only one exception (namely, C III.) an increase in tension is
accompanied by a decrease in twist. This result is not in accordance with
WIEDEMANN’S, who found the twist to be nearly independent of the tension.
Possibly, however, he worked with a thickness of wire which for the special
combination of current strengths and tensions was not sufficiently sensitive to
the change of tension. A glance at the curves C and D shows how much
greater is the sensitiveness to tension change for certain combinations than for
others.

SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 199

JOULE further discovered that when the tension exceeded a certain value,
there was contraction instead of extension in the direction of magnetisation.
This ought to give in these experiments a reversed twist under tensions higher
than this critical value. Of this, however, there was no indication, although
the thicker iron wire broke under a tension of 2600 grammes’ weight, and was,
therefore, subjected in experiments A to a comparatively high tension.

It remains now to consider nickel. The experiments were conducted in
precisely the same manner as in the case of iron. The following are the
tabulated results for a nickel wire of cross section, ‘0056 sq. cc., length 36 cc.,
and tension 1950 grammes’ weight ; first, for a steady linear current and varied
helical current, and second, for a steady helical current and varied linear cur-

-rent. As before, the currents are in amperes, and the twists in radians x 10°,

Group A. (Linear Current Steady.)

Experiment I. Linear Current — 0°674 Amp.

Helical Current, | 0°368 |0°700 | 1-210 |1:891 | 2°303 | 2°616 |3:016 | 3:997

Twist, ; | 109} 200; 429} 765 952 | 1077 | 1206 | 1458

Experiment II. Jinear Current = 0°995 Amp.

Helical Current, | 0°307 | 0-410 | 0-741 |1:276 | 1-680 2084 2°594 3s

Twist, , ‘ Doe LOSa) 281s oO}. 8704 L052.) 1303 | 1897

Experiment III. Linear Current = 2'510 Amp.

Helical Current, | 0°268 | 0°700 | 1:210 |1:891 | 2:303 | 2-616 | 3-016 | 3-997

Twist, , : 152 268 596 | 1119 | 1410 | 1923 | 2145 | 2552

Experiment IV. Linear Current = 3:039 Amp.

Helical Current, | 0°205 | 0°393 | 0°741 | 1:°313 |1°726 | 2°084 | 2594 | 3-591 | 5-384

948 | 1310 | 1553

Twist, . ; | 20 | 74 | 436

1894 | 2345 | 2819

200 PROFESSOR C. G. KNOTT ON THE

Experiment V, Linear Current = 4441 Amp.

| Helical Current, | 0205 | 0°451 ors 1:298 | 1°750 | 2°084 | 2°594 | 3565 | 5-479

Twist, : ; 123 |. 219 | 584 | 1145 }~1535 | 1797 |. 2126 | 2626 | 31o2
Experiment VI. Linear Current = 5-578 Amp.

Helical Current, 0:368 0-576 0:952 1521 1:938 2°784 4:519

Twist, 5 5 171 345 855 1442 7,

Group B. (Helical Current Steady.)

‘Experiment I. -Helical Current = 0°658 Amp.

Linear Current, | 0°368 | 0°578 007 1:815 | 2°368 | 2°724 | 3:277 | 3°815 | 4°796

Twist, . ; 39 v4 132 204 383 | 505 | 702} 897 | 1019

Experiment II. Helical Current = 1:891 Amp.

Linear Current, | 0°327 | 0°582 | 1:141 |1:891 | 2°891 | 3-463 | 3-927 | 5-019

| | FE | | |

Twist, . ; 57 89 | 180]; 420} 954 | 1871 | 1700 | 1991

ExperimentIII. Helical Current = 2°702 Amp.

Linear Current, 0°327 | 0582 |1:141 |1°891 | 2°891 | 3-463 |3:927 | 5-019

ee ee ee ee

Twist, .. : | 29 89 | 216] 457 | 1126 | 1545 | 1948 | 2322

SUPERPOSED MAGNETISMS IN IRON AND NICKEL. 201

Experiment IV. Helical Current = 2:405 Amp.

Linear Current, 0:893 1:520 Wigs Vas 2°812 4334 4-680

ee

Twist, . : 368 819 1355 1561 1865 1890

Experiment V. Helical Current = 3°338 Amp.

Linear Current, 0:867 1:494 1-797 2°298 2°702 3°277 4519

Twist, . : | 439 929 1226 1639 1909 2168 2374

The representative curves are shown on Plate XXIX., nickel groups
Aand B. The chief points of difference between the behaviour of iron and
nickel are these: first, the direction of twist in the nickel is the reverse of that
in the iron; and second, there is no maximum in the nickel A group of curves.
The free end of the nickel wire twists.in the direction opposite to the hands
of a watch, as looked at from above, when the wire is traversed by a down
current, and is magnetised with north pole downwards. This agrees with
BarRETT’s discovery,* that nickel contracts when magnetised. The possibility
of a maximum, again, depends upon how the amount of contraction varies
with the magnetisation, and also, since the abscisse represent currents and not
magnetisations, upon the relation which holds between these last,

The B curves are very similar in form to the B curves of the iron. It will
be noticed that curve IV. of this series lies for the most part higher than curve
III., although the steady helical current is smaller in the former ; also that L.,
IL, and III. seem to fall together, as belonging to the same set, while IV. and
Y. form a system by themselves. The reason of this would seem to be that
between the dates, June 2nd and 4th, namely, on which these sets were taken,
the nickel wire underwent some physical change. Probably this was of the
nature of a change in temper, since on the latter date the nickel wire was for
an instant traversed by a current of sufficient strength to make it glow red hot.
|Taking this consideration into account, and neglecting curve A, III., which is
\obviously a bad experiment, we conclude that the twist due to the superposi-
jtion of circular and longitudinal magnetisations in nickel wire increases with

* See Mature, vol. xxvi. 1882,
VOL. XXXII. PART I. 2K

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( 205 )

XIT.—On the Relative Electro-Chemical Positions of Wrought Iron, Steels,
Cast Metal, &c., in Sea-Water and other Solutions. By THomas ANDREWS,
Assoc. M. Inst. C.E., F.C.S. (Plates XXX. to XXXIV.)
(Read 15th January 1883.)

The experiments contained in this memoir were made by the author with
the galvanometer on wrought iron, steel, cast metal, &c., bars and plates,
arranged in galvanic circuit in sea-water and various other waters and solutions,
to determine the relative electro-chemical position of these metals under such
circumstances.

These varieties of the same metal iron are of such vast and universal utility
that accurate information respecting any of the properties possessed by them
cannot fail to be of interest.

A knowledge of the relative electro-chemical positions assumed by wrought
iron, steels, and cast metal when in galvanic connection in sea-water is of
importance as determining their respective liability to electrolytic disintegration
when combined in marine works and structures, and a research of this kind
presents features of interest capable of practical application In many ways.

When plates or bars of wrought iron, steel, &c., are connected in circuit
and immersed in sea-water or other solution, and attached to a delicate galva-
nometer, an electric current is set up of varying power according to the
difference of chemical composition or mechanical or physical properties, &c., of
the wrought iron and steels employed.

The following experiments were undertaken by the author to measure, if
practicable, the extent of this action, and to endeavour to determine the relative

electro position of the various steels, wrought iron, and cast metal, with some
degree of exactness.

TABLE A.
Analyses of Steel, Wrought and Cast-Iron Bars. Percentage Composition.
Descripiion. ore Combines Silicon. Sulphur. |Phosphorus.| Manganese. Tungsten. (by eee ce).
Soft Siemens-Martin steel, aa bai de des a sg ae i
Wrought iron, A ; ot Trace | ‘224 None ‘239 ‘071 ess 99-466
Soft steel (Firth’s), . alla Miata: 570 032 Trace 066 147 side 99°185
Bessemer steel, P : Ree 550 None 032 175 216 ae 99-027
Puddled steel, 5 : ate "440, 144 048 149 Trace av 99-219
Puddled steel (chilled), . Peete 490 140 004 ‘073 ‘215 a 99-078
Hard steel (Firth’s), : ihe 1600* | +145 002 025 183 one 98-045
Cast metal, . ; ‘ 2:400 | 1:000* | ‘570 ‘140 580 860 ahs 94-450
Tungsten steel, . 6 ous 1°750* | +135 069 139 “720 9-270 87°917
* By combustion.
VOL. XXXII. PART I. 21

206 MR THOMAS ANDREWS ON THE RELATIVE

One interesting fact observed in the course of these experiments is that
wrought iron and steels, &c., are not static in their relative electro-chemical posi-
tions, and when immersed in sea-water, or other solutions in connection with each
other, cannot exactly be regarded as constant elements. The relative electro-
chemical position is also varied, according to the nature of the solutions employed.

The chemical composition of the iron and steel bars and plates employed in
the following experiments is shown by the accompanying analyses.

TABLE B. .
Analyses of Steel, Wrought and Cast-Iron Plates. Percentage Composition.

Description. Grarhile Compings ilicon, | Sulphur. | Phosphorus. | Manganese. (by atone
Soft Siemens-Martin steel, . ie 170 ‘071 ‘117 ‘077 "627 98'938
Soft steel (Firth’s),. Relies oo “460 074 025 210 184 99:047
Wrought iron, : : F 500 Trace. 206 024 454 396 98-920
Soft’ Bessemer, é : : ane 150 015 ‘lll 064 ‘540 99°120
Hard Bessemer, . . ; het 510 068 113 ‘087 1153 98:069
Hard Siemens-Martin steel, . ong 720 ‘080 102 143 1:239 97°716
Hard steel (Firth’s), . .| ... | 1-407*| -121 | -036 080 360 97-976
Cast metal, . . . . 1500 2:010* “410 ‘250 450 *650 94-730

* By combustion.

Some of the physical properties of the bars employed are indicated by the
following tests to which they were submitted :—

TABLE C.
Original, Ultimate Stress. Fractured. iabanenes
Stress
i per Square a Appearance
Description Difference, Inch of ole
Fractured i re.
Size.| Area Total, | Per Square Inch Size.) Area. [= a)pom "Area, Inch Per =
‘ * | of Original Area. . ne Por neh. ! Cent.
Area Cent.
Inch.} Sq. in. Ibs. Lbs. Tons.|Inch.| Sq. in. Ibs.

Tungsten steel, |-30 | -0 = 8011: : ; eC S : 10 ¥ silky
8 ’ 70 |12,561 179,443 =80°1)'27 | -057 013 {18-6 | 220,368 [0°73 | 7:3 90 % granular

Hard steel, —. |-298 | 0697 |10,967 |157,346 = 70-2)-289 | -0656 | 0041 | 5°8| 167,179 | -12| 1:2] 100 % granular
Bessemer steel, |-297 | -0693 | 9,851 |142,150 =63'4|-275 | 0594 | -0099 |14-2| 165,841 | -16| 16] 100 % granular

Puddled steel, |-296 | 0688 7,180 |104,361 = 46°6)-257 | 0518 | ‘0170 |24°7 | 138,610 | -27| 2°7) 100 % silky

Puddled steel
(chilled),

298 | 0697 | 6,322| 90,703 = 40°5/-295 | 0683 | -0014 | 2°0| 92,562 | -07| 0-7 (i? ee

Wrought iron, |-296 | 0688 6,028 | 87,618 = 39°1)-284 | 0633 | 0055 | 7°9| 95,229 | 11] 11} 100 % fibrous

Soft Siemens-
Martin steel, I 28 ‘113 | 8,328 | 73,699 =32'9|-25 |:049 |:064 [56:6] 169,959 |1°97 |19°7| 100 % silky

100 % granular |
(mottled)

Cast metal, —. |-293) 0674 | 1,436] 21,305= 9-6|-293] 0674 |-0000 | 0:0] 21,305 | 00] 0-0

A

ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC. 207

GALVANOMETER EXPERIMENTS.

The bars of wrought iron and steels, &e., used in the experiments were
exactly 297jths of an inch (7°5 millimetres) in diameter, and were cut as test
pieces from near the centre of bars of wrought iron and steel, manipulated as
near alike as possible for purposes of comparison.

All the wrought iron and steel, &c., plates employed in
the following experiments, except where otherwise de-
scribed, were exactly three inches square (representing a
total surface area of exposure of eighteen square inches
for each plate, exclusive of the edges which were alike
in each case), and were of uniform thickness, and in shape
as shown in fig. No. 1.

The bars and plates were of the chemical composition and
possessed of the general physical properties, as shown in the preceding tables,
and with the exception of those covered with scale (magnetic oxide), were
all smoothly polished bright.

The experiments on the various samples were conducted in each case in
precisely the same manner for purposes of exact comparison, and very many
times repeated, but in the same manner for corroboration, the results being
derived from exactly corresponding experiments in each case, the bars and
plates in the solutions being kept exactly the same distance apart, &c., in fact,
every precaution was adopted to insure accuracy.

The records in the following tables of galvanometer experiments are the
result of some 3000 carefully made observations by the author, some of which
were thirty or forty times repeated to insure accuracy.

It should be understood that the following experiments do not represent
fixed or permanent deflections ; but they are the results of a number of observa-
tions made in precisely the same manner in each case for purposes of exact
comparison between the various steels employed.

In cases where necessary the author has recorded the highest and lowest
deflection noticed, in addition to the averages to illustrate the variations better.
In the galvanometer experiments the bars and plates were all immersed, one
pair at a time, in an equal measured quantity of sea-water, or other solutions,
and placed in galvanic connection at equal distances apart. The wrought iron,
&c., bar or plate, was connected with one terminal of a delicate galvanometer,
to the other terminal of which was attached the bar or plate of steel, &c. The
connections were made with insulated copper wires properly secured to the ends
of the bars or plates with screw clips.

The measurement of the galvanic action is recorded in the tables.

[Inserted April 5, 1883.—The galvanometer selected for these experiments

208 MR THOMAS ANDREWS ON THE RELATIVE

was a low resistance galvanometcr, with jewelled centre, accurately graduated
throughout the circle.

To observe the fractional parts of degrees with accuracy, the author took
the observations through a powerful lens fixed above the galvanometer, by
means of which arrangement and from the author’s experience in using it in
this manner, and from repeated check experiments, it was found that variations.
of the needle could be taken to about the ;th of a degree of deflection.

The galvanometer was examined by the Wheatstone Bridge arrangement
with standard resistance coils, and the resistance was found to be 220 ohms.

A Daniells cell through a resistance of 9180 ohms (including the resistance
of the galvanometer) gave a deflection of one degree, or 5;gpth of an ampére
produces a deflection of one degree (taking the electromotive tone of the
Daniells cell as unity).

From these observations, therefore, the strength of the electric current
represénted by the deflections recorded in this paper may be calculated ; and
as the resistance in the cells containing the sea-water would not exceed
3 ohms, an indication of the E.M.F. can be obtained.

In taking all readings the galvanometer was very carefully adjusted before
each observation, and all deviations from vibration, tremor, or other causes,.
carefully guarded against; the greatest care was exercised in the experiments,
the point of the needle being under constant observation, and the slightest
variations were carefully watched as the differences to be dealt with in course
of these experiments were sometimes small.

The author is satisfied that the observations recorded represent accurately
differences arising from the nature of the metals and solutions employed. |

The experiments on bars, recorded in tables D, E, F, represent the average
of the deflections observed on first immersion of the steel and iron bars in the
sea-water, the bars on each repetition of the experiment being carefully washed
and wiped dry before re-immersion.

A very marked feature in the other galvanometer experiments, recorded in
table and diagram G, J, Plate XXXII. (these observations extending over
longer periods of time), is the steadily changing deflections noticed from the —
commencement; this appears to indicate a tendency in the various steels and
irons to polarise each other’s electric action, so that in course of time, as.
submerged iron and steel becomes coated with oxides, galvanic activity is con-
siderably reduced from its first force; but it does not wholly subside. When
plates of iron and steel, &¢., in galvanic connection were taken out of the sea-—
water (the oxides being washed off) and were re-immersed, the deflections of —
the galvanometer arose for a time, afterwards reducing again.

The experiments in this memoir indicate that the galvanic relationships 0
the various steels and wrought iron do not remain the same, in sea-water or
other solutions, but they appear capable of an interchange of electro-chemic

ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC. 209

position; for instance, in the experiment with the plates, some of the steel
plates took a negative position compared with the wrought iron ; but afterwards
the position was reversed.

This change of electro-chemical position is a fact of considerable interest,
and the author has therefore given as typical some of the full records of the
deflections observed in some of the experiments between steels, wrought iron,
cast metal, &c.

These diagrams, &c., illustrate this tendency in detail. A reference to some
of the tables will also show that in many instances the interchange is greatly
varied and influenced by the nature of the solutions in which the steels, &c.,
were immersed. When the steels, &c., were immersed in an acid solution
instead of one containing neutral salts, such as sea-water, a noticeable result
was, in some instances, an almost complete reversal of electro-chemical position.
(See table and diagram G, I, Plate XX XII.)

Although the soft steel and Bessemer steel bars in table D are recorded
thereon as in the negative position compared with wrought iron, this is not
contradictory to the results of similar soft steels in table G, because the results
in table D are the first deflections, whereas those in table G indicate the same
negative position at the commencement of the experiment; but the electro-
chemical position afterwards changes by prolonged exposure.

An explanation of this change in the electro-chemical position of the soft
steels may be that, as the solution gradually penetrates and acts on the metal,
it meets with crystalline networks of higher carbides, &c., and other consti-
tuents of varying composition, which would pr ppabh offer varying resistance to
the action of the solution,

This view of the case would appear to derive support from the observations
made “ On the Microscopical Structure of Iron and Steel,” by HENry CLirron
Sorsy, Esq., LL.D., F.R.S., from which it would appear that iron or steel of
the finest manufacture cannot be regarded as of purely homogeneous composition.

The experiments recorded in the following tables were made not only with
the object of endeavouring to ascertain the relative electro-chemical position of
wrought iron, steels, and cast metal, but also to throw light, if possible, on the
amount of galvanic action which takes place practically where these metals are
combined in marine or other structures. It will be seen, therefore, that the
observations are roughly arranged with this object.

Amongst other experiments, measurements were not only taken using zinc,
copper, and wrought iron as standards in combination with iron and steel and
cast metal, &c., but it will be also observed that bars and plates covered with
magnetic oxide were employed, as practically the action of this oxide upon
wrought iron, steels, and cast metal in sea-water, &c., is frequently a source of
electrolytic disintegration, to ascertain the extent of which forms one object
of the following experiments :—

MR THOMAS ANDREWS ON THE RELATIVE

210

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212 MR THOMAS ANDREWS ON THE RELATIVE

TABLE F.

Galvanometer Experiments with Bright Steel, Wrought Iron, Cast Metal Bars, &c.

| SOLUTION IN WHICH THE BARS WERE IMMERSED,

}- Onr-Firta NORMAL STANDARD SULPHURIC ACID.

Percentage! 7:16 Rod formi Wroueht Iron Bat ; Tron Scale (Magnetic
| soe te Cer ea erg oee | gotaimg one Slemene | ,OSHe) forming one:
Cations | following. with each of following. following,
| Deflection | Electro- | Deflection | Electro- | Deflection | Electro-
; of Galvano-| Chemical | of Galvano-| Chemical | of Galvano-| Chemical

| meterin | Position of} meter in | Position of | meter in | Position of
| Degrees. | the Metals.) Degrees. | the Metals.| Degrees. | the Metals.)
Soft Siemens-Martin steel, ; : .. || 890 N 0°62 Pp 14:15 Pas
Wrought iron, . ; ; : ; Trace | 10°10 N 14-90 P
E |
Soft steel (Firth’s), . : J 2 0570 | 8°89 N 0°25 N 14:87 12
| Bessemer steel, ; (0F5)5) ) 9:03 N 0°55 N 13°80 P
|
Puddled steel, . | 0-44 || 8:08 N 0°60 N 13°90 12)
Puddled steel (chilled), . q 5 | 049 | 9:97 N 0:90 N 13°77 Pp
Hard steel (Firth’s), . | 1:600 8°84 N O57 N 14:95 P
Cast metal (graphitic carbon, 2°40 ; 1:00 12°50 N 0-95 N 15-07 P
per cent.), : ; c ‘
' Tungsten steel, . 4 ; : ; Eres) | 9°40 N 0:16 N 14:27 P
REMARKS.

Each result is the average of ten observations made in the same manner fr exact compivison,

A reference to the analyses of the steel plates shows that, as rezards
manufacture, they were selected from three of the most important classes
of steel, viz., Bessemer, Siemens-Martin, and cast steel, and a sample of the
softest and hardest temper was taken from each kind.

ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC. 213

TABLE G.
Galvanometer Experiments with Bright Steel, Wrought Iron, and Cust Metal Plates, &c.
WATERS IN WHICH THE PLATES WERE IMMERSED.
|
| Sea-WATER.
l Bars
= : 56 A Plates covered with Scale (Magnetic
Percentage W monet Han Epes (Bright) forming Oxide) placed & Galvanic connection
Description. ee oa following Bright Steel, &c. Plates. with lle eras Betas
Carbon.
Deflection of Deflection of
Galvanometer in c Galvanometer in
Degrees. Electro-Chemical Degrees. Electro-Chemical
Position of the Position of the
SS Metals. SS Metals.
Average.| Highest. \verage.| Highest.
Soft Siemens-Martin steel, . . | 0-170 2°69 | 300 N 351] 4:00 IP
N for 3 minutes,
: 1:25 | 1:50 |afterwards P to
f : A . “4 i : 2 3°75 P
Soft steel (Firth’s), 0:46 0-77 | 225 | end of Experi- 3°27 7
ment
Wrought iron, . ‘ ; . | Trace 2:92) 3:00 P

Soft Bessemer, . ; Pe |e O50 0°83 | 2°75 |Pfor120 ,, 3°96} 5:00 P

0°28 | 0°50 N afterwards

1:05 | 1°50 'N for 20 minutes

Hard Bessemer, . : : . | 0°510 0-75 | 1-25 |P afterwards 3°27) 4:25 ne

1:25 | 1°50 Nfor 10 minutes

Hard Siemens-Martin steel, . Os 420 014 | 025 [Pfor85 ,,

0°15 | 0°50 |N afterwards
1:06 | 1°75 \N for 15 minutes

0-21 | 0:50 |Pfor80__,,
012] 015 [Nfor55 ,,

Hard steel (Firth’s) . ; 5 1-407

0°37 |. 0°50 |N for 3 minutes
y
)
| 100 3°75 P

| : : ; 0:93] 2°75 |N for 30 minutes
Cast metal,*. : : . | 2010 | 150) 2:00 Ie { 0-471 0-60 |P afterwards
t é

* Graphitic carbon, 1°50.

REMARKS.

+ Each result is the average of about thirty observations which were taken at regular intervals extending
over three hours.

+ Each result is the average of twenty-three observations taken in each case at equal distances of time,
each experiment extending over two hours.

VOL. XXXII. PART I. 2M

214 MR THOMAS ANDREWS ON THE RELATIVE

TABLE H.
Galvanometer Experiments with Copper, Steel, Wrought Iron, and Cast-Metal Plates, §c.

Sea-WATER.

Ferner ee of | Copper Plate (Bright), forming one Element with each of #

Description Combine following Bright Steel, &e., os tes.
Canon
Deflection of Galvanometer in Degrees. |, Pere
. p tion of the
Metuls.
Average. Highest. Lowest.
Soft Siemens-Martin steel, , : 0170 617 9°50 4:50 P
_ Soft steel (Firth’s), 0-460 615 9:00 425 Pp
Wrought iron, . Trace 8°62 | 9°75 4:50 |
Soft Bessemer, . 07150 674 | 9:50 5:25 P |
Hard Bessemer, : 07510 (33 9°75 5-40 pas in
Hard Siemens-Martin steel, | 0-720 725 9:50. 5°75 P a
Hard steel (Firth’s), . | 1-407 7:05 8:00 5°50 Pf
Cast metal,* | 2010 7°26 10°50 | 5°75 12

* Graphitie carbon, 1°50 per cent.

REMARKS.

Fach of the above results is the average of nineteen observations, each taken at equal d'stances of ti
each experiment extending over three hours.

ELECTRO-CHEMICAL POSITIONS OF WROUGHT-IRON, ETC.

TABLE I.

215,

Galvanometer Experiments with Bright Steel, Wrought Iron, and Cast-Metal Plates, Sc.

| SOLUTION IN WHICH THE PLATES WERE [MMERSED.

OneE-FirrH NORMAL STANDARD SULPHURIC ACID.

Wrought-Iron Plates (Bright), forming |
one Element with each of the following
Bright Steel, &e., Plates,

Plates covered with Scale (Magnetic
Oxide) placed in Galvanic Connection
with Bright Plates from the same

piece of Steel, &e.

Hlectro-Chemical
Position of the
Metals.

Deflection of
Galyanometer in
Degrees,

Average.

Highest.

Eleetro-Chemical
Position of the
Metals,

Description. eae
Carbon.
Deflection of
Galvanometer in
Degrees.
Average.) Highest.
5 ; Oa We 225)
Soft Siemens-Martin steel, 0170 0.0 1-00
: 0°25 | 0:25
Soft steel (Firth’s), 0-460 Sei all sae
Wrought iron, Trace
: 0°40 | 2°00
Soft Bessemer, 0150 0-24 | 0:25
Hard Bessemer, 0510 Lien Sele ie)
Hard Siemens-Martin steel, 0°720 1:62 | 2:00
Hard steel (Firth’s), . 1-407 O74 | 2:00
4 0744 | 1-25
Cast metal,* . é ‘ : 2:010 0:63 | 0:90

P for 26 minutes
N afterwards

P for 2 minutes |
N afterwards

P for 60 minutes)
Nitornl200y.

te

12)
P

P for 12 minutes

N afterwards

1:00
0-25

P for 5 minutes
N afterwards

* Graphitie carbon, 1°50 per cent.

REMARKS.

Each result is the average of about forty observations, taken at equal distances of time, each experiment

extending over three hours.

It is interesting to compare the results of the above table and diagram I with table and diagram G,
A partial reversal of the galvanic positions of some of the steels appears to take place, when an
acidsolution is employed instead of sea-water, as previously pointed out.

Experiments to ascertain the Galvanic Action caused by Plates of Wrought Iron
(the half of every Plate being Bright, the other half left with ats Scale on).

Eleven plates of wrought-iron (cut from the same large plate) were each
bent double, thus, the half of every plate polished bright, and the

other half left covered with scale just as it left the rolls, they were
then placed in a clean porous cell, Daniells battery, filled with sea-

water.

Each plate was 4:12 inches square, and as there were eleven in
the whole series, this represents a total superficial area of 373°48

BRIGHT SIDE
SCALED S/DE

Fig. 2.

sq. inches of scaled surface, and 373°48 sq. inches of bright surface,
though, of course, the action of a voltaic series like this would be different to

216 MR THOMAS ANDREWS ON THE RELATIVE

that of two large plates of such superficial area. This arrangement, however, ,
illustrates intensified galvanic action.
The whole were arranged in a voltaic series, as shown in sketch —

TT

LM

DH
i
x=
Ss
ical
ssa)

Fig. 3.

and attached to the terminals of a galvanometer, the deflections were as
recorded under

TABLE J.
Time of Deflection in Electro-Chemical
Observation Degrees. Position of Bright Part.

June 3rd, 7.35 17:00 Positive.

7 7.4) 1400 ;

a 7.50 11:00 x

= 8.0 9:00 5

. 8.10 7°50 ‘

i 8.20 6°75 —

% 8.30 6-00 .

) 8.40 5:00 =

z 8.50 4:75 ¥s

5 9.0 4°50 >

bs 9.10 4:00 sf

9.20 3°75 :

9.30 3°50 m;

> 9.40 3:25 ~

53 9.50 3°25 a

om ROO 3-00

,, 10.10 3°00 >

of 10.20 2°75 z

i ehvnolso 2°50 io Vinal

5; 10 35 2°50 .
June 4th, — 1:00 x

5 cote ae 1-00 7

, 6th, — 0°75 ks

The galvanic mischief induced by iron scale is a matter of such importance —
that special attention has been directed to the measurement of this, as will be
seen in these experiments (see Tables).

ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETU. Die

> Hxperiments on the Gulvanic Action set up by a series of Burs of Wrought
Iron and various Steels immersed in Sea-Water.

The sample bars were portions cut from the same rods whose composition
and general properties have been previously described.

The deflections of the needle of the galvanometer are shown in the accom-
panying tables K and L.

TABLE K,

Deflection of the Galvanometer Needle, produced when Bars of Wrought Ivon and Hard Cast
Steel (all of the same size and polished bright) were immersed in Sea-Water forming the

elements of Galvanie Action. Average of eight Experiments in each case.,

Deflection of Needle. |

3 Bars of wrought iron connected with 3 Bars of hard cast steel, 1:28 degrees

ee +3 ; 4, 5 138i,
an; : ; ony 3 2s 15
Owls fs 5 Onges +5 ETON, hs
ates > » ieee ‘i PA 55
Se 3 55 Ole ies . ZEAOF « . 55

The wrought iron was the electro-positive metal.

TABLE L.
Deflections of the Galvanometer Needle produced wien Polished Bars of the Wrought Tron ail
the Sott Steel, the same size, were immersed in Sea-Water forming the elements of Galvanic
Action. Average of six Experiments in each case.

Deflection of Needle.

3 Bars of the wrought iron connected with 3 Bars of the soft 1:00 degrees
+ » ”» ” 4 » » 1:50 »
5 5 =e

” ”» » Pe) oh)

cast steel,

The wrought iron was the electro-positive metal.

The whole of the preceding galvanometer experiments afford some compari-

| son of the galvanic action set up by the exposure of combinations of wrought

iron, steel, &c., to sea-water, colliery mineral waters, or river waters, &c., of

known composition, and are so far interesting, because in actual practice

wrought and cast iron and steel bars, plates, &c., are frequently exposed to
similar destructive influences.

218 RELATIVE ELECTRO-CHEMICAL POSITIONS OF WROUGHT IRON, ETC.

In experiments made by the author to ascertain the galvanic action taking
place between wrought iron and steels, &c., over more extended periods of
time, it was found that galvanic action between these metals had a tendency
to be reduced from various causes during prolonged exposure to sea-water and
other solutions.

The general deductions from the foregoing observations are that—

1st, The electro-chemical position of wrought-iron, steels, and cast metal
appears capable of changing according to the nature of the solution in which
they are immersed, an acid solution producing frequently different results from
‘one containing only neutral salts, This interchange of electro-chemical position
between the metals being also frequently observable both when immersed in
an acid and neutral solution, as indicated by the preceding tables.

2nd, A measurable difference is noticeable in the behaviour of the various.
steels, &c. employed under the conditions recorded in the experiments. This.
would lead to the conclusion that the danger from the greatly increased
corrosion in sea-water, &c, through galvanic action, is a factor not to be
disregarded in compound structures of the preceding metals. The tendency to
polarise each other’s action, and the consequent interchange of electro-chemical
position, would appear to exert a considerable influence in retarding and
reducing this source of danger. Galvanic action between wrought iron and
steels, &c., appears (from experiments on hand by the author) also to be -
materially reduced in course of extended periods of time, otherwise the liability
to destructive corrosion through such action, though never inconsiderable,
would be a more formidable matter to encounter than in engineering practice
it really is. At the same time, it need scarce be remarked, this source of dis-
integration should not be overlooked in constructive works of wrought and
cast iron and steel.

It is not now necessary for the author to attempt to enter into the further
practical application of the results deducible from the experiments contained in
this memoir; he has, however, great pleasure in being permitted the honour
to present the results herein recorded as a contribution to the chemistry of
iron and steel.

Soc. Enin® PLATE XXX.

DIAG RA M..-D.

/Ilustrating some of the Comparative Results in Table D.

WATERS 1N WHICH THE BARS WERE IMMERSED.

Sea WaTER. An Acip CoLLiERY WATER.

[PTION POSITIONS OF THE STEELS, &c. POSITIONS OF THE STEELS, &C.

Positive Positive
position Negative position of Metals. position Negative position of Metals.
of Metals. of Metals.

Degrees of Deflection of Galvanometer.

Curves SHOWING THE COMPARATIVE ELECTRO-CHEMICAL CURVES SHOWING THE COMPARATIVE ELECTRO-CHEMICAL
i]
Degrees of Deflection of Galvanometer. |

123 465 67 8 910 Zr. 1 23 45 6 T 8 9 10

21 4.
fs ah
=NS-MARTIN 5

7
\-

v4 if 4

IT-IRON he 7
bs
~

in

NS

Tron Scale in connection with
Wrought-Iron in connection with
Zinc in connection with

'

Wrought-Iron in connection with
Zinc in connection with

Tron Scale in connection with

A. RITCHIE & SON, EOIN®

a te eee

Soc. Epin® D I A G R ix M G. RATE; eXOXONal:

lustrating the change of Electro-Chemical position between some Steel and Wrought-I/ron Plates, see Table G.

WATERS IN WHICH THE PLATES REMAINED CONSTANTLY
IMMERSED DURING THE EXPERIMENT.

CURVE SHOWING THE VARYING ELECTRO-CHEMICAL POSITION OF THE
STEELS IN GALVANIC CONNECTION WITH WROUGHT-IRON.

Sea WATER.

Plate (bright) forming one Wrought-Iron Plate (bright) forming one Positive position Negative position of

dard Cast Steel Plate (bright). } element with a Soft Bessemer Plate (bright). Time of Steels. Steels.
from . . n
ralvano- | Fyectro-Chemical | Deflection of Galvano- | Blectro-Chemical eee G 2 3 a o a
grees SetOeS Ie meter in Degrees “ih f Py ais Py o
: position of the - : position o of 6 |
a Hard Cast Steel. at interes gf time | the Soft Bessemer QA é 3 A A
; uring three hours. Steel. 1 0= 1 9 Z
w
——
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PrAG RA M —-G, I.
lustrating the change of Electro-Chemical position between Cast Metal and Wrought-/ron Plates, see Table G I.

SOLUTIONS IN WHICH THE PLATES REMAINED CONSTANTLY
IMMERSED DURING THE EXPERIMENT.

PLATE XXXII.

CurRVE SHOWING THE VARYING ELECTRO-CHEMICAL POSITION OF THE

Cast METAL IN GALVANIC CONNECTION WITH WrovuGHT-IRON,
Sea WATER. 4th Norma STaNpARp SutrHuric Aci.
n Plate (bright) forming one Wrought-Iron Plate (bright) forming one Positive position of Negative position of
ha Cast Metal Plate (bright). element with a Cast Metal Plate (bright). Time Cast Metal. Cast Metal.
7 he z from 4 é onl § 3 2
on o Q eflection o ‘ F Commencement & ‘S18 5 5 5
in Degrees eueo eo Chemical Galvanometer in Degrees | Electro-Chemical a Bb ) 2 | o fy ios}
als of BORO ® at intervals of position of Z Q (a) bol A Ss :
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Soc. Iprn®

DIAGRAM H.

WATER IN WHICH THE PLATES REMAINED CONSTANTLY
IMMERSED DURING THE EXPERIMENT.

;

CURVE SHOWING THE VARYING ELECTRO-CHEMICAL
STEELS IN GALVANIC CONNECTION WITH COPPER PLATES.

PLATE XXXIII.

trating the change of Electro-Chemical position between Steel, Wrought-/ron, and Copper Plates, see Table H.

|

POSITION OF THE

SEA WATER.
bright) forming one element | Copper Plate (bright) forming one element Positive position of the Steels.
iemens-Martin Steel Plate. with a Wrought Iron Plate (bright). Time
= from By g 8 4 g rs S
zalvano-| Electro-Chemical | Deflection of Galvano-| Electro-Chemical Commencement, 5 5, 2 E, 5 2 5, s s
egrees position of meter in Degrees position of oe o o a oy o oO By o oy By ef
of time | the Soft Siemens- at intervals of time the Wrought A A A A A A A Qa A SUS
hours. | Martin Steel. | during three hours. hark Eperimet.gg 9 § 7 6 5 4 3 2 1 20% f
Hii a 4-50 P | a bo
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PLATE XXXIV.

Le

DIAGRAM

‘lustrating the change of Electro-Chemical position between some Steel and Wrought-/ron Plates, see Table I.

Soc. Eprn®

The Black Line ______ indicates the deflections caused by the Soft Siemens-Martin Steel in Galvanic connection with Wrought-Iron in #th Normal Standard Sulphuric Acid.

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Soft Bessemer ” ” ” oe ” ” ” ” ” ”

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Positive position of
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STEELS IN GALVANIC CONNECTION WITH WROUGHT-IRON.

CURVE SHOWING THE VARYING ELECTRO-CHEMICAL POSITION OF THE

Time
from
Experiment.

commencement
of

osition of
ft Bessemer.

Electro-Chemical
(c}

the g

0-00
0-00

0

meter in Degrees

Wrought-Iron Plate (bright) forming one
at intervals of time
during three hours.

element witha Soft Bessemer Plate (bright).

Deflection of Galvano-

IMMERSED DURING THE EXPERIMENT.

@ 4

Be Bia
ESE?
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4th Normat STanparpD SutpHuric Acip.

SOLUTION IN WHICH THE PLATES REMAINED CONSTANTLY

Mv

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a Plate (bright) forming one
Soft Siemens-Martin Steel Plate

H

A, RITCHIE & SON, LOIN®

ar

XIIL.— Report upon the Tunicata dredged during the Cruises of H.M.SS.
“Porcupine” and “Lightning,” in the Summers of 1868, 1869, and 1870.
By W. A. Herpmay, D.Sc., Professor of Natural History in University
College, Liverpool. (Plates XXXV. and XXXVL)

(Read 7th January 1884.)

A few years ago the late Sir C. WyviLLe THOMSON gave me for examination .
some specimens of Ascidians which had been obtained during the cruises of
the “Porcupine” and “ Lightning,” and last summer I received from Mr Jonn
-Morray the remainder of the Ascidiz Simplices and two species of the
Ascidize Composite from the same deep-sea dredging expeditions.* Some
additional specimens of the “ Porcupine ” Ascidize Composite have been placed
in my hands during the last few days (January 1, 1884). The present paper
contains a detailed account of the Simple Ascidians alone; the Compounc.
forms will be worked up along with the “Challenger” Ascidize Composite,
and will be described and figured in the second part of my Report upon the
Tunicata of the ‘Challenger” Expedition. It may, however, be useful to
state here that the “ Porcupine” Compound Ascidians include :—

Distaplia rosea, Della Valle.
One colony from Tangier Bay ; 35 fathoms.

Aplidium Jallax, Johnston.
Two small colonies from Loch Foyle; 10 fathoms.

Leptochinum, sp.
One colony from Station 12 (“‘ Lightning,” 1868, Feerde channel) ;. 530
fathoms.

Leptoclinum, sp.
Several colonies ; locality unknown.

_Leptoclinum albidum.
Several colonies from Tangier Bay ; 35 fathoms.

* In the summer of 1868 H.M.S. ‘‘ Lightning” explored the region of the North Atlantic lying
between the Hebrides and the Feriées. In 1869 H.M.S. ‘‘ Porcupine” made three cruises, the first off
the north-west and west coasts of Ireland, the second off the south and south-west of Ireland, and the
third off the north of Scotland as far as the Ferées. In 1870 the “Porcupine” dredged down the
west coasts of France and Spain and in the neighbourhood of Gibraltar Strait, and explored the African
coast of the Mediterranean as far east as Sicily.

VOL. XXXII. PART II. 2N

220 DR W. A. HERDMAN ON

Leptoclinum, n. sp. .
One colony from Tangier Bay ; 35 fathoms.

Didemnum, sp.
One colony from Station 54 (Ferée channel, “cold area”); 363 —
fathoms.

Botryllus, sp.
One colony from Tangier Bay; 35 fathoms.

Botryllus, sp. .
One colony from Station 54 (Ferée channel, “cold area”); 363
fathoms.

Some of these possess an interest, apart from their morphological pecu-
liarities, on account of the considerable depths from which they were obtained.

ASCIDLZ SIMPLICES.
Family AscipmIp&.

This family is represented in the collection by three species of Ascidia,
The common Ciona intestinalis was apparently not dredged at any ae the
localities visited.

Ascidia scabra, O. F. Miiller. ;

About thirty specimens of this well-known species, most of them attached —
to Lamellibranch valves, were dredged in Lough Foyle, Ireland, from a depth of
10 fathoms, during the first cruise of the ‘‘ Porcupine” in 1869. Most of them
are small. They range from 5 mm. to 25 mm. in greatest length. The shape —
varies considerably. The small individuals are ovate and much flattened;
the larger ones are usually irregularly orbicular, but a few are oblong, and
resemble the typical form of Ascidia virginea. The mantle is strong, and the
muscle bands run very irregularly.

In some remarks upon this species published in 1880, I showed how vari-
able the branchial sac might be in the arrangement of the stigmata.* The
“Porcupine” specimens exhibit this irregularity, and, in addition, show in
some places an imperfect development of the internal longitudinal bars, which
is frequently observed in Corella parallelogramma, and which I have figured
in Ascidia triangularis.t In 1880 I described the meshes in Ascidia scabra

* “Notes on British Tunicata,” Journ. Linn. Soc. Zool., vol. xv. No. 85, p. 274.
+ Loc. cit., pl. xvi. fig. 6.

THE “ PORCUPINE”. AND “ LIGHTNING ” TUNICATA. DA

as being usually transversely elongated, and as containing each about twelve
stigmata; but in some of the “Porcupine” specimens the meshes are occa-
sionally square, and have only 6-7 stigmata. Here and there at the angles of
the meshes very short hemispherical papille may be found on the internal
longitudinal bars, otherwise the ‘“ Porcupine” specimens agree with the
description and figure in the Journal of the Linnean Society.

The large tentacles are rather stouter than those in my former figure,* but
the arrangement is the same. The dorsal tubercle is somewhat variable -in
this species, but is always very simple. Two of the “‘ Porcupine” specimens
have it intermediate in shape between those figured by myself in 1880T and
by JuLin{ in 1881.

In several of the specimens large masses of ova are present in the peri-
branchial chamber.

Ascidia plebeia, Alder, var. nov. (?) (Plate XX XV. figs. 1-8).

External Appearance.—The body is irregularly ovate or pyriform, greatly
compressed laterally, and attached by the posterior half, or more, of the left
side. The anterior end is narrow and produced, the posterior considerably
wider. The dorsal and ventral edges are irregular, but nearly equally curved;
both sides are flattened. The branchial aperture is terminal and prominent;
the lobes are well marked. The atrial aperture is from one-third to half way
down the dorsal edge, prominent, projects laterally, and has well-marked
lobes.

The surface is somewhat irregular, but not rough. There are adhering sand
and shell fragments at the posterior end and over part of the left side.

The colour is yellowish-grey.

Length of the body, 4:2 cm.; breadth, 1°9 cm.

The test is moderately thick and strong, of a firm gelatinous consistency,
translucent, smooth, and glistening on the inner surface, and richly supplied
with blood-vessels. The left side and posterior end are thickened and made
stiff by the presence of many imbedded sand grains and fragments of shells.

The mantle is moderately strong. The musculature is well developed on
the right side and the anterior end of the left, but is very slight over’the
visceral part of the body. The sphincters are fairly strong.

The branchial sac is slightly plicated longitudinally. The transverse
vessels are all of the same size. The internal longitudinal bars are strong, and
bear large curved and sometimes forked papille at the angles of the meshes, and
smaller simple ones between. The meshes are slightly elongated vertically, and

* Loe. ctt., pl. xvii. fig, 2. + Loe. cit., pl. xvii. fig. 1.

t ‘Recherches sur l’organisation des Ascidies Simples, &c.,” Archives de Biologie, t. ii. fase. 1,
pl. iv. fig. 2.

222 DR W. A. HERDMAN ON

contain each four to six stigmata. The horizontal membranes are slight; there
are none between the smaller papillee.

The dorsal lamina is slightly ribbed transversely, and has small denticula-
tions on the free margin.

The tentacles are numerous, and so closely placed that their bases touch.
There are 80 or 82 large, with about the same number of intermediate smaller
ones.

The dorsal tubercle is small and simple, ovate in outline, and with the
narrower end anterior. The aperture is anterior, with the right horn rather
longer than the left, but neither of them curved. No peritubereular area is
present.

Locality.—Two specimens, one large and one small, were obtained, during
the second cruise of the “ Porcupine,” at Station 33, 20th July 1869, lat. 50°
38’ N., long. 9° 27’ W.; depth, 75 fathoms; bot. temp., 9°°8 C.

These specimens are exceedingly like the common Ascidia plebeia, Alder, but
differ from it in some details. They have no trace of the greenish tinge so
characteristic of Ascidia plebeia even after preservation in alcohol, and the test
is firmer and stiffer. The general shape, however, and the positions of the aper-
tures (see Pl. XXXV. fig. 1) recall the characters of Ascidia plebeia. The
measurements in the above description are those of the larger specimen ;
the smaller one is 2°6 cm. in length and 1:4 cm. in breadth. In the smaller
specimen the atrial aperture is not distant from the branchial, and is turned
forwards.

The body, when the test is removed, is long and narrow, and the branchial
sac extends slightly beyond the viscera posteriorly (see Pl. XX XV. fig. 2). The
stomach is large and the intestine rather wide. It is covered with renal vesicles
and the reproductive ceca. The ovary forms thick swollen masses, and the
spermary small dendritic tubules scattered chiefly over the anterior part of the
intestine. The oviduct and the vas deferens are both greatly distended in
the larger specimen, and form conspicuous curved tubes on the left side of
the body (see Pl. XXXYV. fig. 2). Large quantities of ova were found in
the peribranchial chamber.

The branchial sac resembles that of Ascidia plebeta in every particular.*
The primary papille are large (Pl. XX XV. fig. 3), and in some cases bear
pinne or small tubercles on the sides. Smaller transverse vessels connecting
the intermediate or secondary papille appear never to be present.

The tentacles are numerous and closely placed, more closely than I have
found before in Ascidia plebeia, and I can only distinguish two sizes, with an

occasional very much smaller one here and there. The dorsal lamina is very -

slightly ridged and denticulated. The prebranchial zone is papillated all over,

* Compare description in Journ. Linn. Soe. Zool., vol. xv. No. 85, p. 288.

THE “PORCUPINE” AND “LIGHTNING” TUNICATA. 208

and rather wide. There is no peritubercular area, and the dorsal tubercle is
small and simple, just as in Ascidia plebeia. It only occupies about one-fourth
of the breadth of the prebranchial zone.

After taking all the characters into consideration, I am inclined to refer the
specimens to Ascidia plebera, Alder, of which they may be considered as a
variety until more is known about the range of variation in the species.

Ascidia, sp.

A torn test of a single individual of the genus Ascidia was found adhering
to some fragments of Annelide tubes dredged at Station 45, lat. 35° 36’, long.
2° 29’; “ Porcupine” 1870; depth, 207 fathoms ; bot. temp., 12°°4 C.

As the test only is present, it is, of course, impossible to identify the
species, but there can be no doubt as to the genus. I consider it worthy of
record simply on account of the depth from which it was obtained.

Family CynTHuDs.

No members of the sub-families CyntHIN& and BoLTENIN« are in the collec-
tion, but the STYELIN# are represented by the common Styela grossularia, van
Beneden, and four species of Polycarpa, three of which appear to be unde-
scribed. One of these is from the Mediterranean, one from the Ferée channel,
and the other from the North Atlantic 8.W. of Ireland, and from outside the
_ Strait of Gibraltar, in rather deep water.

Siyela grossularia, van Beneden.

A large number of small individuals of this species were found attached to
specimens of Polycarpa pomaria, dredged near Belfast on 4th August 1869, at a
depth of 70 fathoms. |

They vary from 2 mm. to 3 mm. in greatest length. Although they are
so small, all of those I have examined are sexually mature and contain ripe
| Ova, and in some cases tailed larve, in the peribranchial cavity.

Also half a dozen small specimens of this species were found on a fragment
of shell from Station 54, lat. 59° 56’ N., long. 6° 27’ W., during the third cruise
of the “ Porcupine” in 1869; depth, 363 fathoms ; bot. temp. —0°'3 C.

They are of the blister-like form, flattened ‘antero-posteriorly, and with
| expanded margins. So faras I am aware, this is the greatest depth at which

Siyela grossularia has been obtained. It is usually regarded as a shallow water
species, and in some localities extends up between tide marks further than
any other species of Tunicate.

There are also in the collection one large and six small specimens, labelled
“* Lightning,’ off Valentia.”

224 DR W. A. HERDMAN ON

Polycarpa pusilla, n. sp. (Plate XXXV., figs. 4-6).

External Appearance.—The body is spherical, ellipsoidal, ovate, or pyriform,
- is not compressed, and is unattached. The anterior end is narrower if not the
same as the posterior, which is wide and rounded. When the shape is ellipsoidal,
the long axis is dorso-ventral. The apertures are not distant, on the anterior
end; in some cases prominent, in others sessile and inconspicuous; no lobes are
visible.

The surface is even, but completely covered by an incrusting ie of fine
sand. MHair-like processes are present on the posterior half or so of ‘the body,
and bear sand grains.

The colour is ight brown.

Length of body (in an average sized specimen), 5 mm.; breadth, 6 mm.;
thickness, 4 mm. |

The test is moderately thick and tough, completely concealed externally by
the sand, and smooth internally, it is continued posteriorly into the hair-like —
processes bearing sand grains.

The manile is rather strong. The muscle bands are numerous, though fine,
and form a close network. Most of them compose a strong longitudinal layer
internally, and a weaker circular layer externally. The sphincters are well
developed.

The branchial sac has four folds upon each side. The internal longitudinal
bars are very broad, ribbon-like membranes; there are four or five on each fold,
and one or two in the interspace. The meshes are rather large and square, and
contain each five or six stigmata. In the mature sac the stigmata are long
and narrow, and each mesh is divided transversely by a narrow horizontal
membrane.

The tentacles are of two sizes, with occasional smaller ones between. There
are usually upwards of fifty altogether in the circle.

The dorsal lamina is a narrow membrane with slight transverse ribs, which —
begin a short way from the anterior end. The edge is thickened, but has no
denticulations.

The dorsal tubercle is simple, and ovate in outline; the aperture is directed
anteriorly and to the left. The horns are not coiled, but almost touch ; the long
axis is vertical.

Locality.—Thirty-five specimens of this species were obtained 40 miles off
Valentia, at a depth of 110 fathoms in the North Atlantic ; and one specimen
was obtained at Station 31,‘ Porcupine.” 1870, lat. 35° 56’ N., long. 7° 6 WH
at a depth of 477 fathoms; bot. temp., 10°3 C.

This is a curious little species, in external appearance bearing considerable
resemblance to Polycarpa pilella, a species discovered during the “Challenger”
Expedition at Bahia, in shallow water. The present species is usually spherical,

THE “ PORCUPINE” AND “ LIGHTNING” TUNICATA. 225

and most of the specimens look like little rough bullets covered with sand (see
Plate XXXV. fig. 4, e. and f.). They feel quite hard, the test being rather firm.
The specimens collected vary from 2 mm. to 9 mm. in ‘greatest diameter.
Most of them are small. In the majority, the apertures are not visible
externally, and it is impossible to distinguish the ends and sides without dissec-
tion. Ina few, however (see Plate XX XV. fig.4, a and b.), the apertures are pro-
minent, terminating short conical projections from the anterior end of the body.
No lobes are visible, but when the test is removed in apertures are seen to be
distinctly cross-slit.

The mantle does not adhere to the test, and BehskGaenely the body can
be readily shelled out. The musculature is well developed all over, and consists
of two distinct layers, the internal longitudinal, starting anteriorly in bundles
of fibres radiating from the apertures, and the external circular. Besides these,
there are also a few oblique and irregularly running bundles. |

The branchial sac appears variable. In small (young) specimens (see
Plate XX XV. fig. 6), the stigmata are short and rounded, and the transverse
_ vessels very wide; while in the larger specimen examined, the stigmata are
long (see Plate XX XV. fig. 5) and closely placed, and the transverse vessels all
very narrow. The internal longitudinal bars are wide and ribbon-like. In the
part of the sac of the large specimen examined (see Plate XX XV. fig. 5) there
were five bars on each of two folds next the endostyle, and only a single bar in
the interspace, while the two rows of meshes formed by this bar with the adjacent
folds had from five to six stigmata in each mesh. The series next to the endo-
style was wider, each mesh containing nine or ten stigmata. In the young speci-
men examined and figured (Pl. XX XV. fig. 6) the first or dorsal fold (67. f I)
has seven bars, and is separated by a single row of meshes from the dorsal
lamina; and by four rows of meshes from the second fold—hence this interspace
has three bars. The second fold (b7. f J.) has three bars, and is separated
from the third by three rows of meshes, hence this, the second interspace, has
two bars only. The third fold (d7. f. ZZZ) has five bars, and is separated
from the fourth by three rows of meshes, hence this third interspace has also
two bars. The fourth fold (07. 7 ZV.) has also five bars, and is separated from
the endostyle by two rows of stigmata, or an interspace with one bar. The
stigmata in this sac are all short and rounded, and placed far apart. There
are usually three or four in a mesh.

The tentacles (Plate XX XV. fig. 6) are rather irregular, Three sizes are pre-
sent, but members of the third order are often absent, as seen near the endostyle
at the left hand end of the figure. The polycarps are fairly numerous. Some
are male, others female, and others hermaphrodite. The endocarps are rare.
The stomach is globular, and deeply sulcated.

226 | DR W. A. HERDMAN ON

Polycarpa curta, n. sp. (Pl. XXXVI. figs. 7-11).
External Appearance.—The body is ovate, ellipsoidal, or elongated trans-
versely; not compressed laterally, and unattached. The anterior end is wide
and convex, the posterior is usually still wider, and flat or irregular; the dorsal
and ventral edges are short and similar. The apertures are rather far apart,
being placed at the opposite extremities of the anterior end. They are equally :
anterior, and are sessile and inconspicuous. There are ‘no apparent lobes.
The surface is smooth, and fairly regular, but is slightly incrusted with
small sand grains.
The colour varies from yellowish- grey to light brown.
Greatest length of the body, dorso-ventrally (in an average specimen), 9
mm.; breadth (antero-posteriorly), 7 mm.; thickness, (laterally), 5 mm.
The test is thin, but very tough and leathery. It is quite opaque. The
outer surface is slightly sandy, and the posterior end has a few hair-like pro-
longations, to which sand grains are attached.
The mantle does not adhere to the test. The apertures are slightly cross-
slit, and the sphincters surrounding them are strong. The musculature else-
where on the mantle is well developed, the muscle bands forming a close net-
work not clearly divided into longitudinal and circular layers.
The branchial sac has four well-marked folds on each side. The most dor- |
sally placed is larger than the others, and has about twelve internal longitudinal
bars. The rest of the folds have about six bars each, and there are two bars
in each interspace. All the internal longitudinal bars are flat, ribbon-like
membranes of considerable width. The transverse vessels are all of the same
size. ‘The meshes are about square, and contain each four or five stigmata.
The dorsal laminais a narrow membrane, with no ribs and no denticulations.
The tentacles are not very numerous. There are eighteen or twenty larg
tentacles, and the same number of smaller intermediate ones.
The dorsal tubercle is simple. It is fusiform in outline, with the long axis
vertical, There is an irregular slit down the middle, but there is no curva
hence no horns are present.
Locality.—Sixteen specimens of this species were dredged at Station 12;
‘« Lightning,” 1868; lat. 59° 36’ N., long. 7° 20’ W.; depth, 530 fathoms ; bos
temp., 6°°4 C.
This species is allied to Polyeaa ‘pa pusilla, but differs both in external appear-
ance and in internal structure. It is not so much incrusted with sand, and the
shape, though variable in both species, is here more decidedly elongated dorso-
ventrally (Plate XX XVL. figs. 7 and 8), the result being the apertures come to b
placed far apart at the opposite extremities of the wide anterior end (see Plat
XXXVL. fig. 7). The greatest length is always dorso-ventrally, and this ranges i
the specimens collected from 5 mm. to 13 mm.

THE “PORCUPINE” AND “LIGHTNING” TUNICATA. 227

The branchial sac has the folds (Plate XX XVI. fig. 9) better developed than

in Polycarpa pusilla. In one sac examined the arrangement, starting from the
dorsal lamina along the right hand side, was—one row of wide meshes con-
taining 8 to 10 stigmata, then the 1st fold with 12 bars, then the 1st interspace
with 2 bars, then the 2nd fold with 7 bars, then the 2nd interspace with 2 bars,
then the 3rd fold with 7 bars, then the 3rd interspace with 3 bars, then the 4th
fold with 6 bars, and then a row of wide meshes separating the ventral fold from
the endostyle. Figure 10 on Plate XXXVI. shows the narrow dorsal lamina
and the wide row of meshes separating it from the commencement of the first
fold on the left side of the sac. A large number of fine muscle fibres are
| present in the branchial sac, chiefly in the transverse vessels.
The peritubercular area (Plate XXXVI. fig. 2) is large and triangular in
| shape. It is almost perfectly symmetrical. The tubercle is very different
| from that of Polycarpa pusilla. It is comparatively simple, since the slit,
| though irregular in shape, is not curved to form horns or spirals (see Plate
| XXXVI. fig. 11, d.7.). The polycarps are irregularly rounded; they are herma-
phrodite. Endocarps are not numerous.

Polycarpa pomaria, Savigny.

Twelve moderately large specimens of this common species were dredged
| on August 4, 1869, near Belfast, at a depth of 70 fathoms. The largest indi-
| vidual measures 3 cm. in length and 2 em. in breadth.

Three or four of the specimens differ somewhat in appearance from the
rest ; their tests are thinner and smoother, but otherwise they appear to be
exactly the same.

_ A single individual of this species was also obtained in 1870 in Tangier Bay
| from a depth of 35 fathoms. The test is stiff, giving a solid appearance and
| feel to the specimen, and the exterior is somewhat incrusted with sand. The
| difference in external appearance between this individual and those with smooth

thin tests from near Belfast is very considerable, but the species is a variable
| one, and intermediate forms are common.

Polycarpa formosa, nu. sp. (Plate XX XVI. figs. 1-6).

External Appearance.—The body is elongated antero-posteriorly, and varies
from pyriform to oblong in shape. There is almost no lateral compression, and
} attachment is by the posterior extremity. The anterior end is moderately
wide, but narrower than the middle of the body. The posterior end is narrower
| than the anterior. The widest region is usually a little behind the middle of
| the body. ‘The apertures are both anterior, and not distant. They form slight
papillze, and are each distinctly four-lobed.

The surface is even, but considerably incrusted with sand grains, especially

VOL. XXXII. PART II. 20

228 DR W. A. HERDMAN ON

at the posterior end, where there are also root-like prolongations of the test,
to which sand is attached.

The colour is light grey where the test is exposed; reddish-brown from
the sand elsewhere.

Length of the body (average specimen), 1°5 cm.; breadth, ‘7 cm. ; length
of the root-like appendages, 1 cm. to 2 cm.

The test is thin, but moderately tough. It is translucent where free from
sand. The posterior end from which the sandy prolongations spring is some-
what thickened.

The mantle is rather slight. The muscle bands are feeble, and not very
numerous; they form an open irregular network.

The branchial sac has four folds upon each side. Each fold is formed by
the aggregation of from six to twelve internal longitudinal bars. There are
two to four bars in each interspace. The transverse vessels are of two sizes,
alternating regularly. The meshes are much elongated vertically, and contain
about three or four stigmata each. The stigmata are long and narrow, and the
meshes are divided transversely by a narrow horizontal membrane.

The dorsal lamina is rather wide, and has irregular and partial transverse
ribs ; the margin is smooth.

The tentacles are numerous, and closely placed. They are large, and all of
much the same size.

The dorsal tubercle is a simple, slightly-curved band, with the extremities
directed posteriorly.

Locality. Six specimens were dredged in Tangier Bay, on the 5th August
1870, from a depth of 35 fathoms.

There is a characteristic appearance about the specimens of this species,
although they all differ somewhat in shape (see Plate XX XVI. figs. 1-3). In
all, the apertures are closely placed at the anterior end, the body is elongated
antero-posteriorly, and the posterior end is prolonged into a mass of branched
projections covered with sand. The dimensions of the six specimens are as
follows :—

A. B. C. D. E. F,

Length of body alone, . .| 20cm. | 150m. | 15cm. | 16cm. | 10cm. | 14cm.

Length of posterior projections, | 1‘lem. | 07cm. | 22cm. | 10cm. | 14cm. | 25 cm.

Breadth of body, . ; » | lcm. | 0:9em. | 0°7 cm. | 0°7 cm. | 060m, | 05iomm

The folds in the branchial sac (Pl. XX XVI. fig. 5), although they have a con-

THE ‘“ PORCUPINE” AND “LIGHTNING” TUNICATA. 229

siderable number of internal longitudinal bars, do not project much into the
cavity. The sac, as a whole, is very similar in structure to those of Styela
oblonga, S. flava and S. glans.*

The dorsal tubercle is very simple, the prebranchial zone is narrow (Plate
XXXVI. fig. 6), and the peritubercular area small, and not occupied by the
tubercle. The tentacles are of considerable size, and have large bases.

Polycarps are not very numerous. They are scattered over the inner surface
of the mantle (Plate XX XVI. fig. 4, g.). They are unisexual. The male poly-
carps are deeply cleft into lobes.

The alimentary canal lies on the dorsal part of the left side of the body.
The stomach is pyriform, and is strongly ribbed externally ; the intestinal loop
is moderately open, and the rectum is long and narrow (see Plate XXXVI.
ne 4. 7):

Family Mo.euip..

This family is represented in the collection by two species of Molgula and
the common ELugyra glutinans.

Molgula, sp.

A single small specimen of a Molgula, slightly torn, was found adhering to
one of the specimens of Polycarpa pomaria from near Belfast ; 70 fathoms.

The shape is nearly globular; 8 mm. in diameter, and slightly compressed
laterally. Short hair-like processes project all over, and have a few grains of
sand and other foreign bodies attached to them, but there is no incrusting coat.
The test is moderately thin, soft, and nearly transparent. The colour is light
yellowish-grey. Possibly this may be Molgula nana, Kupffer.

Molgula ampulloides, van Beneden.

One specimen of this rather widely-diffused species was dredged in Lough
Foyle, during the first cruise of the “ Porcupine” in 1869, from a depth of 10
fathoms. It measures 1‘7 cm. in length, and 1:4 cm. in greatest breadth.

Hugyra glutinans, Moller (Plate XXXVI. figs. 12-14).

Eighteen specimens of this common and apparently gregarious species were
dredged in Donegal Bay, Ireland.

None of the specimens are large. They range from 4 mm. to 12 mm. in
greatest diameter. The incrusting sand is very fine and comes off readily, the
result being that most of the specimens have very little left, and in some the
delicate test is almost completely exposed.

* See Report upon the Tunicata dredged during the voyage of H.M.S. “Challenger,” Part I.
Plate XX. figs. 4, 8, and 11.

230 DR W. A. HERDMAN ON

In the branchial sacs of several of these specimens, the vessels forming the
apices of the spiral infundibula are considerably swollen, attaining as much as
twice their normal calibre (Plate XXX VL. figs. 12 and 13); and the epithelium

on the edges of the corresponding stigmata is greatly thickened (see Plate
XXXVI. fig. 14).

Postscript, May 30, 1884.—Since the above paper was written and the
plates finished, I have received, through the kindness of Dr P. HeErpert
CARPENTER, three specimens of an interesting and apparently undescribed
Molegulid, which was dredged from a depth of 440 fathoms in the Ferée
channel during the third cruise of the ‘ Porcupine” in 1869. This species will ©
be described and figured in the Report on the “ Challenger ” Tunicata, Part IL. —

EXPLANATION OF THE PLATES.

The following system of lettering has been adhered to in all the figures :—

at. Atrial aperture.
br. Branchial aperture.
br. f. Fold in the branchial sac.
d.l, Dorsal lamina.
d.t. Dorsal tubercle.
en. Endostyle.
g. Genital organ.
h. m. Horizontal membrane of the branchial sac.
7. l, Internal longitudinal bar of the branchial sac.
m. The mantle,
p., p'. Papille of the branchial sac.
p. p. The peripharyngeal bands.
vy, The rectum.
sg. The stigmata of the branchial sac.
st. The stomach.
tn., tn’. The tentacles.
tr., tr’., tr”. The transverse vessels of the branchial sac.
z. The prebranchial zone.

PLATE XXXV.

Figs. 1-3, Ascidia plebeia, Alder, var. nov.
Figs. 4-6, Polycarpa pusilla, n. sp.

Fig. 1. Ascidia plebeia, var., seen from right side; natural size. ‘i
Fig. 2. Ascidia plebeia, var., the test removed, body seen from the left side ; natural size,

THE “ PORCUPINE” AND “ LIGHTNING” TUNICATA. 231

Fig. 3. Small part of the branchial sac of Ascidia plebeia, var., seen from the inside ; magnified
50 diameters.

Fig. 4, a.-—f. Six specimens of Polycarpa pusilla, n. sp.; natural size.

Fig. 5. Small part of the branchial sac of Polycarpa pusilla, seen from the inside; magnified 50
diameters,

} Fig. 6. Right half of the anterior part of the branchial sac, showing also the tentacles, the

endostyle, the dorsal tubercle, the prebranchial zone, &c.; magnified 50 dia-

meters.

PLATE XXXVI.

Figs. 1-6. Polycarpa formosa, n. sp.
Figs. 7-11. Polycarpa curta, nu. sp.
Figs. 12-14. Zugyra glutinans, Moller.

Fig. 1. Polycarpa formosa, from the right side ; natural size.

Fig. 2. Another specimen of the same species.

Fig. 3. Group of one small and two large specimens of the same species; natural size.

Fig. 4. Specimen of Polycarpa formosa, dissected from the left side to show the alimentary

canal, &c.; slightly enlarged.

Fig. 5. Small part of the branchial sac of Polycarpa formosa, seen from the inside ; magnified
50 diameters.

Fig. 6. Dorsal tubercle, &c., of Polycarpa formosa ; magnified 50 diameters.

Fig. 7. Specimen of Polycarpa curta; natural size. The arrows indicate the branchial
(inhalent) and atrial (exhalent) apertures.

Fig. 8. Two other specimens of the same species.

Fig. 9. Small part of the branchial sac of Polycarpa cwrta, seen from the inside ; magnified 50
diameters.

Fig. 10. Small part of the dorsal lamina and branchial sac of Polycarpa cwrta, from inside ;

magnified 50 diameters.

Fig. 11. Dorsal tubercle and peritubercular area of Polycarpa cwrta ; magnified 50 diameters.

Fig. 12. Centre of a spiral from branchial sac of Lugyra glutinans ; magnified 50 diameters.

Fig. 13. Centre of another spiral from the branchial sac of Hugyra glutinans ; magnified 50
diameters.

Fig. 14. Another similar spiral from Lugyra glutinans ; magnified 300 diameters.

iS)
ru

VOL. XXXII. PART II.

| Roy. Bece sain Vol XAAI. Plate XXXV.

dman del. figs, /-3, ASCIDIA PLEBEIA, A/der var nov
FIGS. 4-6. POLYCARPA PUSILLA, 7, 5.

T.Dobb & C° Luth® Lpool.

Plate XXXYJ

OY, Soc. Edin't Vol XXXIL

2 6, POLYCARPA FORMOSA» sp
Figs, 7-//, POLYCAKPA CURTA 17.52.

|
T.Dobb & C? Lith’ L'sool

Hman del,
Figs, /2-/4, EUCYRA GLUTINANS, Mo//er

XIV.—WNote on Sir David Brewster's Line Y, in the infra-Red of the Solar
Spectrum. By C. Piazzt Smytu, Astronomer Royal for Scotland. (Plate
XXXVIT).

(Read 17th December 1883. )

Of all known examples in physical science, of simplifying, and at the same
time “ precisionising” some of its fundamental data, which might otherwise
fall to be entangled in high numbers, none has been happier than FRAUNHOFER’S
application of the letters of the alphabet to certain chief lines in the solar
spectrum. Happy both in its conception by the inventor, and its universal
acceptance since then by the world. Whence it comes to pass now, that in every
country, whoever observes the solar spectrum at all, with whatever instrument,
large or small, diffracting or refracting, and whether he holds tothe undulatory,
or any other theory of light, and catalogues spectral lines either in Wave-lengths
or Wave-numbers, or merely in terms of the brass scale screwed to his instru-
ment by a maker,—yet whenever he speaks of the line A, or B, or C, or
any other so named by FRAuNHoFER, he singles out thereby from among
thousands, exactly the same identical line which any and every other spectro-
scopist alludes to under the same simple letter.

Hardly less happy was the extension of the system made by our great

specialist in optical physics, Sir Davin Brewster, when, having discovered

several lines in the infra-red of the solar spectrum, beyond or before Fraun-
HOFER’ commencing line “ great A”’—he named them with the later letters of
the alphabet, whose stock of symbols had not been more than half used up
by FRAUNHOFER in reaching toward the further violet end of the spectrum.
Hence, without disturbing any one of FRAUNHOFER’S lettered lines from red
through green, to blue and violet, Brewster called his new line next beyond,
or before great A in the “infra red,” by the letter Z; the next before and
outside that, Y; and the next before that again, X.

In so far, BREwsTER’s proceeding was quite as happy as FRAUNHOFER’s ; and
if his assigned letters have been lately misused or omitted in certain high
quarters, that is not his fault, and perhaps not intentional on the part of those
who have done so, but has arisen jirst/y from the difficulty that many observers

_ have in seeing his lines in the ultra-red, on account of their exceeding faint-

ness; and secondly,from some of them being Solar, and others Telluric, to a degree

that even he himself had not fully anticipated. It would seem, therefore, to be

high time, in BrewsTER’s own Society and Country, to come to a clearer under-

standing on the facts of his nomenclature, touching at least those three chief
VOL. XXXII. PART II. 2Q

234 C. PIAZZI SMYTH ON NOTE ON SIR DAVID BREWSTER’S

lines X, Y, Z; and the case is all the more claimant just now, seeing that a
very grand chemical identification has just been made out in France for one of
them; but one, unhappily of late called after one letter by some persons, and
another letter by others, a fruitful source of future trouble unless corrected
speedily. I propose, therefore, to inquire here, by help of a few recent obser-
vations, and reference to many old ones, which is the right letter to employ for
each of those three lines.

Sir Davin BrewstTer’s activities in Solar-spectrum observation were in full
force at his favourite Border seat of Allerly, in 1833, as evidenced by three
spectroscopic papers in our volume of 77-ansactions for that year ; but the fullest
and most authoritative publication on his new lines in the infra-red is that con-
tained in his joint paper with Dr GLApsToNE in the Philosophical Transactions
of the Royal Society, London, in 1860.

Of the longest spectrum-view contained in a plate accompanying that paper,
I submit a portion copied by myself, as Strip No. 1 of my own plate now pre-
sented, with very little alteration, except slightly expanding it to suit my scale ;
and freely crossmg and recrossing the lines representing both shade and the
inevitable darkness at and about the very origin of spectrum light, which,
beginning on the left-hand side of the picture, rapidly increases in intensity
towards the right—FRAUNHOFER lines and bands therein always excepted.

As an observer, I like Sir Davin’s drawing much, for its truthful representa-
tion of the real and necessary degree of darkness, in midst of, or antagonistically
to, which the new lines had to be detected; a feature of Nature, this darkness
at either end of the spectrum, so rarely introduced in modern spectrum draw-
ings. And though the shade bands are rather too sharply defined on either
edge, I recognise, in spite of the depreciatory comments of M. Kircuorr, that
it is exceedingly like what appears at that end of the spectrum, when a spec-
troscope is under-prismed and over-telescoped. So too it must most eminently
have been in Sir Davin’s case, when he seems to have employed but one simple
prism of not very heavy glass, and no less than a 5-foot achromatic telescope
to look into it. But then it was Brewsrer’s eye that looked; so no wonder
that he saw with it more than any of his predecessors, and most of his suc-
cessors as well.

“The light less refrangible than A,” say the conjoint authors at their page
150, “is red, but extremely faint, so faint indeed, that few observers of the spec-
trum have perhaps ever seen it; and the only drawing hitherto published of lines
in it appears to be in a map of the solar spectrum by M. MarrutEsen of
Altona. He represents a few lines which, on comparison with fig. 1, may be

identified as the band anterior to Y, Y itself, and the band Y'. In order to map"

the lines and bands in this portion of the prismatic image, Sir Davin BrewsTER
was obliged to take extraordinary precautions. The telescope was lined with

LINE Y, IN THE INFRA-RED OF THE SOLAR SPECTRUM. 235

black velvet, in order to exclude any reflected light ; a low power was em-

ployed; the slit was made about the eighth, or tenth, of an inch wide,* and
the eye of the observer was washed with water to cleanse the fluid that lubri-
cates the cornea. The most prominent line in this space is that marked Y.”
That last remark is quite to our purpose, and I trust the drawing-strip,
No. 1, of the Plate now given, illustrates it perfectly, remembering that “ great
A” and “‘little a” are introduced merely to give milestone references to known
parts of the spectrum, and a measuring test universally understood for scale.
Strip No. 2 represents some rude efforts of mine in 1871, with very unequal
apparatus, to see something of this rare region of the ultra-red. The drawing
is slightly altered from that in Vol. XIII. of the Edinburgh Astronomical Obser-
vations, inasmuch as the mere general appearances of many close, thin lines
unmeasured, and of shading, improperly represented there by vertical lines, are
here crossed diagonally and horizontally in such a manner that they cannot be
understood to imply true, resolved spectral lines, or anything but shade only,
symbolically expressed. And the chief result is thereby plainer than ever, v7z.,
that the Y line was better seen ina high summer, than a low winter, sun; a

~ feature indicating it to be of Solar origin, and not of Earth’s atmosphere, or

“Telluric ” intervention.
Strip No. 3 gives the two views of high and low sun, contained in the Royal
Societys Himalaya spectrum, in their Philosophical Transactions for 1875.

This drawing is on a smaller scale than their’s ; and their questionable shadings

With vertical lines have been changed by me into diagonal lines ; but otherwise
it represents in exactly the same manner their very surprising negation of the
visibility of Y in a high sun, but its abundant visibility, and that of BREwsTER’s
Z also, in a low sun.

Strip No. 4 represents on a reduced scale my own observations (from
Vol. XIV. of £d. Ast. Obs.) made in Portugal in 1877, with a far more powerful
spectroscope than I had ever possessed before, and which I had had constructed
specially to look into this particular question of the visibility, or non-visibility,
of the Y line in a very high, indeed almost Zenithal, sun. The result, as will
be seen in the drawing, was to confirm the previous Edinburgh observation, and
to show that Y was, with the sun near the zenith, most notably visible; Brew-
stER’s X appearing next in strength ; but Z only in the faintest manner possible,
if at all.

Strip No. 5 is a very reduced copy of part of a magnificent work derived
from photography by Captain Apnry and Colonel Festinc, forming the
Bakerian Lecture at the Royal Society for 1880.

* The distance of this slit is unfortunately not stated. It may have been at the other end of a
long room, and was apparently unfurnished with any kind of collimator lens, in the improved manner
introduced by Professor Swan.

2356 C. PIAZZI SMYTH ON NOTE ON SIR DAVID BREWSTER’S

By dint of Captain ABNeEy’s really wonderful processes of changing the colour
of silver for transmitted light, he was enabled to photograph not only all that:
part of the infra-red end of the solar spectrum discovered with so much pain
and labour by Brewster, but to procure records of other lines, some of them
very grand ones too, extending nearly three times as far away, and into what
is, to the human eye, absolute, unmitigated darkness. There is, therefore, not
the slightest intention here to compete with him in spectral range ; and I have
purposely left his spectrum strip bright and of full height up to the extreme left
hand end of my paper, to indicate that his view extends very much further still
in that same direction. The only point of difference in fact which I have with
him and his distinguished fellow-labourer, or the Central Metropolitan Society
which publishes their work, is,—that the very strong line, which from its place
in the spectrum can be no other whatever than Y, he calls Z; and the letter Y
he gives no place to.

Apparently Captain ABNey and Colonel Festive had not seen the real Z line
at all; and with little doubt because they worked in a too high Sun for #,
though excellent for their other, and chief, objects. For Strip 6 shows the result
of three observations which I had the fortune to make during an unusually long,
bright sun-shiny afternoon on the 30th of May last at the house No. 15 Royal
Terrace, Edinburgh. The apparatus was moderate in power; there was
no attempt to resolve bands into their very thin component lines; but only

mile-stone.
At 5" 50™ p.m. then, of distinct lines, Y alone was visible outside Great A.

But

At 8" 0™ p.m., with a very much lower Sun, there, besides Y nearly as before,
stood out Z as quite a strong line, accompanied too with bands, and proving
itself to be Telluric without a doubt.

Finally, Strip 7 represents what the ancient Greeks might have called th
apotheosis of line Y, in its glorious identification at last by M. HENRI BECQUEREL
with a bright emission line of the same Solar Sodium (Na), which produces that
grand turning-key to all the modern developments of Spectrum analysis, viz.
the Solar lines D’ and D’. a

The fullest account of this final confirmation of the Solar character of Y
that I have yet seen is that contained in the Compies Rendus for July 9, 1883
pp. 71-74, by M. Henrr Becqurret himself. He had been researching the
infra-red spectrum of chemistry by his celebrated Father’s method of the pheno:
mena of Phosphorescence, and found two new distinct and widely separatec
salt lines to exist therein. He next proved the correspondence of both of them
with?two extra strong and equally widely separated lines at the same points of

LINE Y, IN THE INFRA-RED OF THE SOLAR SPECTRUM. 3H

the Solar spectrum. One, and the fainter of these two lines, was an immense
distance further into visual darkness than any of the lines in my plate. It was
even beyond Captain ABNEy’s and Colonel Festine’s furthest photographic,
being at 23 130 Wave Number. But the other, at 31 010 W.N.—to be freely
taken as equivalent to our 30 860—is no less than BrewstTErR’s Y, and is
honourably mentioned by M. BecquEreEt as being such.

It is indeed so instructive, as well as encouraging, to find the line thus
alluded to in Paris as “ BrewstTer’s Y line,” three years after that letter was
expunged in London from the Solar spectrum, that I beg to conclude with
M. Henri BECQUEREL’S own words thus :—

“La vapeur de sodium, qui est principalement caracté¢risée dans le spectre
lumineux par la double raie D, présente dans l’infra-rouge deux tres fortes raies
caractéristiques dont les longeurs d’onde sont 819 (=W.N.Br. 31 010) et 1098
(=W.N.Br. 23 130). Ces raies sont les mémes lorsqu’on volatilise dans larc,
du sodium métallique ou du chlorure de sodium; elles coincide avec deux fortes
raies du spectre solaire.

“Ta raie \ 819 (W.N. 31 010) que l’on peut voir a l’ceil nu avec un spectro-
scope ordinaire, coincide avec une des plus fortes raies du spectre infra-rouge
du Soleil que BREWSTER avait vue, et désignée par la lettre Y.

“Dans les conditions ou lon dédouble les raies D, je n’ai pu dédoubler
distinctement la raie Y.”

POSTSCRIPT.

The above concluding remark of M. H. BEcQUEREL is instructive to those
who would desire to see for themselves this salt representative of BREWSTER’s
Y line; for it shows that even in his “Arc” light, notwithstanding its necessary
brilliance, that particular line must have been too faint for neat physical
notation; and, indeed, unless an arc light can be prepared as bright as, or
possibly still brighter intrinsically than, a high summer sun, such almost must
be the result.

With the most powerful Bunsen gas burners, consuming any amount of
Chloride of Sodium, the trial is quite hopeless; and even with 1-inch induction
Sparks, condensed by a half-gallon jar between platinum points, of which one
Tises through moistened salt, with the effect of making the D lines painfully
bright, I have not succeeded in causing the same salt’s Y line, or lines, to
certainly appear.

I bave, however, in the search found three air lines much further towards
the infra-red than any of the standard list of air lines entered in Dr Wart’s
invaluable Index of Spectra, as compiled by him from the observations of the
greater spectroscopists.

VOL. XXXII. PART IL. 2R

238 c. PIAZZI SMYTH ON NOTE ON SIR DAVID BREWSTER’S LINE Y.

Though not quite so far to that end of the spectrum as certain two lines of
Rubidium, yet being much more constant and more easily procured, these new
lines may be useful to other researchers as references for spectrum place in
that rather barren region. I give their approximate Wave-number readings
therefore here, and have depicted their appearance in the last or “appended ”
spectrum strip of our table, desiring to remark only, in addition, that the
middle line of the three is triple, the distance between its first and second
components being rather greater, and between its second and third rather less,
than the potassium a’**’ pair, whose Wave-number places are 32988 and
33 128, respectively ; while all the three air lines appear fairly sharp, with a
narrow slit, and under a dispersion of 12° A to H, combined with a magnifying
power on the inspecting telescope of 15.

Air Line 1, Rel. Intensity=5, Wave-number place in Brit. Inch=32 693

Its “a” component, Intens.=5, W.N.PI. if =33 944
Air Line 2, eb: = so =a) ps cs — 34 071
a? a c (i oP) 9) = 2, 9 9 = 34 157
Continuous spectrum begins soon after this, and goes on increasing towards the violet.
Air Line 3, Rel. Intensity=6, W.N.PI1. in Brit. Inch, =35 404

First Air Line in Dr Warts’ Index of Spectra, Intens=6, W.N.Pl.=38 470

NOTE ADDED ON May 30, 1884.

In the course of sundry spectroscopic experiments on vacuum tubes
through the winter of 1883-4, and now communicated to Royal Society,
Edinburgh, I have had abundant testimony that the first of the lmes noted
above, viz., at 32 693 Wave-number place, is an oxygen line ; a very remarkable
one too, for though like all other “tube,” or simple-spark, oxygen lines, it is
very faint,—yet it is well-defined, and is further towards the ultra red than any —
line or band I have yet come across in any of the other gases.

The triple line which follows I have equally proved to belong to nitrogen.

But to what gas, air line 3, at 35 404 Wave-number place belongs, I have
obtained no indication as yet from vacuum tubes. C.: Pass

Rv. Soc. EDINE. : PLATE XXXVII.

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OAL ALLNE

NDip. New AIR LINES descovered en Edinburgh i SWVevernvber , 7883.
avi PHOTO-LITHO. BY A. RITCHIE & SON, EDIN. Thomas Heath el,

( 239 )

XV.—On the Formation of Small Clear Spaces in Dusty Air. By
Mr Joun AlTKen. (Plate XX XVIII.)

(Received December 27, 1883 ; read January 21, 1884.)

The dust particles floating in our atmosphere are every day demanding
more and more attention. As our knowledge of these unseen particles in-
creases, our interest deepens, and I might almost say gives place to anxiety,
when we realise the vast importance these dust particles have on life, whether
it be those inorganic ones so small as to be beyond the powers of the
microscope, or those larger organic ones which float unseen through our
atmosphere, and which, though invisible, are yet the messengers of sickness
and of death to many—messengers far more real and certain than poet or
painter has ever conceived.

As the great importance of these dust particles is gradually being realised,
we are from time to time increasing our efforts to protect ourselves from these
invisible enemies. Professor, now Sir JosePH, Lister has shown us how to
contend successfully with those organic germs, which, falling on our wounds,
there find a suitable resting-place, and, if not killed, germinate and grow to
our destruction. Sanitary societies are every day being formed, one of whose
objects is to combat these floating particles by better appliances directed
towards the prevention of the conditions suitable for the germination, growth,
and increase of these germs, and against their spread from infected centres,
while other societies are directing their energies against the artificial produc-
tion of those inorganic forms of dust which pollute our atmosphere.

The immense importance of everything connected with dust must be my
excuse for bringing before this Society observations on phenomena which I fear
must appear to many as trivial and uninteresting; as the clear spaces to
which I shall direct attention are on almost a microscopic scale, and require to
be magnified to enable us to see them clearly.

Professor TyNDALL has made many experiments on the light-reflecting par-
ticles floating in our atmosphere. He found these particles were destroyed by
heat, and that by placing a flame under a brilliant beam of light, which revealed
by illuminating the dust in the air, there was seen rising from the flame wreaths
of darkness resembling intensely black smoke. He then found it was not
necessary to burn the particles to produce this stream of darkness. This was
observed when a hot metal ball was placed under the beam of light, and per-
mitted to remain till its temperature had fallen below that of boiling water. It

VOL. XXXII. PART II. 28

240 MR JOHN AITKEN ON THE

was then found that, though the dark current was much enfeebled, it was still
produced. To study this effect, Professor TyNpALL stretched a platinum wire
transversely under the beam, the two ends of the wire being connected with
the poles of a voltaic battery, and the necessary appliances for regulating the
strength of the current. “ Beginning with a feeble current, the temperature of
the wire was gradually augmented; but long before it reached the heat of
ignition a flat stream of air rose from it, which, when looked at edgeways,
appeared darker and sharper than one of the blackest lines of FRAUNHOFER in
a purified spectrum” (see fig. 5). He goes on to say—“ Right and left of this
dark vertical band the floating matter rose upwards, bounding definitely the
non-luminous stream of air. What is the explanation? Simply this: The hot
wire rarefied the air in contact with it, but it did not equally lighten the float-
ing matter. The convection current of pure air therefore passed upwards
among the inert particles, dragging them after it right and left, but forming
between them an impassable black partition.” *

This explanation of Professor TyNDALL’s has been received by most of us
without question ; yet I think that if we try to form a mental picture of the
process which is here supposed to go on, we shall have some difficulty in doing
so. Professor TYNDALL supposes the distribution of the floating matter is due
to the heat, which lightens the air, but does not in the same degree lighten the
floating dust ; the tendency, therefore, he says, is to start a current of clear air
through the mote-filled air. No doubt the lightening of the air will slightly
increase the tendency of the motes to fall, but the increased freedom to fall
from this cause will be extremely slight and inappreciable, and will be entirely
negatived and overruled by the upward movement of the hotter air, and the
result will be simply to cause the particles to lag a little behind the air in
their movements.

Our confidence in Professor TYNDALL’s explanation was not, however, shaken
till Lord Rayerau, in going over Professor TYNDALL’s experiments and extend-
ing them, discovered that the explanation given of the formation of the dark
plane was not correct, and showed that it could not be due to heat lightening
the air, and so enabling it to shake itself free from the dust motes, because he
discovered that cooling the air produced a precisely similar result (see fig. 2).
Lord Raytercu introduced a cold glass rod into smoky air, and then found
that “a dark plane extending downwards from the rod, clearly developed itself,
and persisted for a long while.” + He says—“ This result not merely shows that
the dark plane is not due to evaporation, but also excludes any explanation —
depending upon an augmentation in the difference of densities of fluid and

* Proc. Roy. Inst., vol. vi. p. 3, 1870; also Essays on the Floating Matter in the Air, p. 9.
Loigmans, Green, & Co., 1881.
+ Paper read before Royal Society, December 21, 1882; also Natwre, vol. xxviii. p. 139,

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 241

foreign matter.” Lord Ray eicH also offers as a suggestion that the particles
may be thrown out by the centrifugal force, as the mixture flows in curved
lines round the obstacle.

In a letter to Nature of July 26, 1883, Dr LonGe gives an account of some
experiments he made on the dark plane and on dusty air. Dr Lopcr says—
“We are now pretty well convinced that differences of temperature have
nothing to do with the real nature of the phenomenon ; we jind that solid bodies
have sharply defined dust-free coats or films of uniform thickness always surround-
ing them, and that these coats can be continually taken off them, and as con-
tinually renewed, by any current of air.” Dr Lopcer also describes a number
of interesting electrical experiments on the dust, and makes many very valuable
suggestions, but comes to no definite conclusion. He says—‘‘ Why,the air near
a solid is free from dust we are. not prepared to say.”

From these quotations it will be seen that the whole matter is involved in
considerable obscurity; and as the subject already had considerable attractions
for me, I determined to undertake an investigation in this particular direction.
My experiments were begun in summer, but it was not till November that the
greater part of the work was done.

I have considerable difficulty in determining how it will be best for me to
place the result of this investigation on record. Asa rule, it is best to take
the reader over the road traversed by the investigator, as the probability is the
difficulties of the one will be the same as those of the other, and the results
generally unfold themselves best when treated in this way. In the present
occasion this method is not suitable. The subject, though apparently simple
enough, was found to be much more intricate and complicated than was
expected. The result was, many a false scent was followed only to be given
up, so that I would be taking the reader to my conclusions by a long, winding,
and uninteresting path. It will therefore be better for me simply to describe
the result of the investigation from my present point of view.

Apparatus used.

The apparatus used was all of the simplest and least expensive kind. The
dust-box in which the experiments were made was a cigar-box, the lid of
which was removed and a piece of glass put in its place. When in use the
box was placed on its end, with the glass to the front. A window was cut out
of the left side of the box, extending from close to the bottom to near the top,
and coming close to the front of the box. The box was then painted black
inside. Holes were cut in the back of the box, or wherever required for the
introduction of the different pieces of apparatus, which shall be afterwards
described. Asa source of illumination, two gas jets, placed close to each

242 MR JOHN AITKEN ON THE

other, were used ; these jets were enclosed in a dark lantern, having an opening
towards the dust-box. To concentrate the light, two double convex lenses were
fitted into a short tube. This tube was loosely attached to the front of the dark
lantern, and could be directed to, and focused on, any part in the interior of the
dust-box. For observing the phenomena two magnifying glasses were employed
—one a simple double convex lens, which was used for getting a general view
of the phenomena; the other a more powerful compound glass, strong enough
to enable me to see and follow the movements of the individual dust particles.

For observations on the effects of slight differences of temperature, metal
or glass tubes in some form or other were generally used. Straight tubes closed
at one end were found most convenient; these tubes were introduced through
the back of the box, and the closed end projected inwards to within a short dis-
tance of the glass front, so as to admit of observation under the strong magni-
fying glass. The tubes were heated or cooled by means of water or steam
introduced into them through a small tube which passed down their interior.
This small tube was connected by an india-rubber tube to a glass filler, into
which the water was poured, and from which it flowed down the small tube to
the front end of the experimental one, and returned to the outside of the box
by the space between the tubes. In this way the experimental tube could be
easily heated or cooled, and the space all round it left free for observation.
For higher temperatures, a fine platinum wire, heated by means of a small
bichromate of potash battery, was employed.

Different kinds of dust were used in the experiments, such as dust made
in the usual manner with hydrochloric acid and ammonia, and by burning
sulphur in the presence of ammonia; this last was used when very dense
fogging was required ; smoke of paper and other substances were experimented
with; also dusts made by burning sodium or magnesium; and for experiments
with dust which would not change with heat, calcined magnesia and lime
were employed. Charcoal powder was also used in some experiments. The
powders of these last three substances were stirred up by means of a jet of
air. These dusts were also varied by the addition of water vapour.

Suppose now that the gas is lit in the lantern, and the dust-box in its place
Let us introduce into the box through the opening in the back one of the glass
or metal tubes, closed at the front end, and introduce into this tube from the
back the smaller one, and connect this latter with the filler, so as to enable
us to pour hot or cold water through the tube, to heat or cool it. If we
are going to use smoke, a piece of smouldering brown paper is introduced into

the box, by removing the glass front, which is kept easily removable for this and

other purposes ; or, if we are going to use sal-ammoniac dust, the ammonia
and hydrochloric acid can be introduced on glass or wooden rods through
small openings in the box, or the acid and ammonia may be placed in small
open vessels inside the box. If the dense sulphate dust is required, the sulphur

FORMATION OF SMALL CLEAR SPACES IN DUSTY ATR. 243

may be placed on a match and introduced into the box after being lighted.
When the dust is thick enough, and uniformly distributed through the box,
bring the light to a focus on the tube. For the present the tube must be
neither heated nor cooled.. Using the magnifying glass ; it will in all proba-
bility be found that there is a clear space all round the tube or on some part
of it, and that the air currents are carrying off the clear space in an irregular
manner, or there may be seen rising over the tube a regular dark plane, depend-
ing on the relative temperatures of the air and the tube.

Now remove the beam of light from the dust-box and leave it for some time.
If left long enough, and the box kept free from changes of temperature, it
will be found that all air currents have ceased, and a close examination of
the experimental tube will show that the dust is now in contact with it at the
sides and on the top. But if we look on the under side of the tube we shall
there see a clear space, like that shown in fig. 1, which represents the tube seen
endways.* It will be observed that this does not agree with Dr Lopar’s
observations ; but I think I have taken every precaution, and the conclusion
which I have come to is, that bodies have not sharply defined dust-free coats,
and that when the bodies and the air have the same temperature, the dust
comes into contact with the sides and top of the bodies.t Now what is the
cause of this clear space under the tube? Clearly

Gravitation,

which brings me to the first of the causes of the dark plane. When the air
comes to rest, the temperature of the air and the tube being the same, there is
nothing to keep the dust from coming into contact with the tube. But gravita-
tion is at work on the particles, and while the air is still the particles are all
falling, and as the upper surface of the tube stops those falling on it, there are
no particles to supply the place of those falling from the space under the
tube, and the result is that a dustless space is here formed. If now we pour
into the tube some cold water we can study the

Kifects of Cold.

At once a downward current is started, and this downward current carries with
it the clear air under the tube; the two currents of dustless air from the sides

* In the figs. the white surface represents the light-reflecting dusty air, while the black represents
the transparent air, free from reflecting particles.

+ The only reason I can imagine for this difference between Dr Lopen’s results and mine is that
he worked with more powerful sources of illumination than I did. He used either the sun’s light, an
oxyhydrogen lamp, or a Serrin arce-lamp, while I only used gas. Now one result of this difference
would evidently be that the illuminating beam used by him would have a much greater heating effect
than the one used in my experiments, and would therefore heat the surfaces under examination. I
found this effect even with gas. If the body had a small capacity for heat, it was only necessary to
keep the light focused on it for a short time to heat it sufficiently to cause a clear space to form over
the part where the light acted.

244 MR JOHN AITKEN ON THE

of the tube meet underneath it, and forma dark plane in the centre of the
descending current, as represented in fig. 2.

It might be thought that gravitation would not act quickly enough to keep up
a supply of dustless air sufficient for this purpose. This however does not seem
to be the case, and gravitation appears to be the only cause of the distribution of
the dust, causing this dark plane in the descending current. One reason for
supposing this is, that if we only cool the tube very slightly, the dark plane is
very thick and well marked; but the more we cool the tube the thinner does
the dark plane become, intead of thicker, which would be the result if it was
due to difference of temperature. The effect of the increased cold is to increase
the velocity of the descending current, and draw out and thin down the dark
plane. Further, if we closely examine the air round the tube with the strong
magnifying glass, we shall see the particles of dust descending and settling on
the horizontal part on the top of the tube, while the particles which fall a little
to each side of the centre line are carried on by the current, and continue to clasp
the tube closely till the current begins to turn under the tube, where the particles
being free to fall, drop away from the tube, and leave a clear space (see fig. 2).
This clear space only begins to be perceptible when the current begins to turn
underneath the tube, and gradually becomes thicker as it travels underneath
towards the centre where the two currents join, and form the descending
dark plane.

The rate at which dust settles out of air by gravitation is much quicker
than we might imagine. Dust is kept in suspension by ascending currents, and
when these are removed it settles remarkably quickly. There was an oppor-
tunity for seeing this in these experiments. If the experimental tube was
cooled, then the cold gave rise to currents descending on the side of the box
where the tube was, and rising on the other side; but the rising current only
came up to the height of the tube, and all the air above the tube was still and
currentless, because its temperature increased towards the top of the box, and
then was produced a condition of stable equilibrium. Under these circum-
stances, I have frequently seen the whole of the upper part of the box above
the cold tube become quite clear, and with a sharp line of demarcation between
the clear still air above, and the dusty currents underneath. It is, of course,
the vertical component of the currents that keeps the dust in suspension, the
horizontal component having no such action. This may be seen when we
cause a current of dusty air to flow along the under side of a horizontal flat
surface. At the point where the current starts, the dust is in contact with the
under surface of the body, but falls further and further from it as it flows —
along. |

In order to study the effect of temperature alone, it was necessary to
arrange the experiment so as to get rid of this gravitation effect. For this
purpose I prepared another piece of apparatus. The ideal shape of body for

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 245

this purpose would be one having some length and breadth, but infinitely thin
and flat, so that when placed vertically, the air in passing over it would never
have to move in a horizontal direction. ‘The nearest approach I could make to
this was made with a piece of copper foil folded on itself, soldered all round
its edges, and fixed to the end of a brass tube. It was heated and cooled by
passing into it hot or cold water. This instrument presented at the front edge
extremely little thickness, and was found to answer well, but was rather delicate
and easily put out of shape. As it is only necessary to examine one side of the
test plane or surface, a different form of apparatus was afterwards adopted. It
_ was made of a piece of brass tube the same as used in the previous experi-
ments, and a flat plate of copper was soldered to one side of it at the front
end. This plate was filed perfectly flat and smooth, and sharpened at the top
and bottom edges, all the bevel being on the tube side of the plate. The side
of the plate presented towards the source of illumination was thus a perfectly
flat surface, and when placed vertically, the air passing over the front surface
could not have its dust separated from it by gravitation, as a// the horizontal
movement went to the back of the plate.

Placing either of these test surfaces in the dust-box with the plate vertical,
cold was applied. At once a downward current was produced, but no dark
space was formed on the vertical test surface ; and if the copper foil apparatus,
which is flat on both sides, is used, no dark plane whatever is formed, as
shown in fig. 3. More intense cold was tried, and a temperature of —10° C. in
air of a temperature of 15° C. was found to produce no effect save an increased
rate of current, and an increased brightness in the particles near the plate,
due to water vapour being deposited on them by the lowering of the tem-
perature, an effect observed by Lord RAy1eicH on the dust bounding his cold
dark plane. Different dusts were tried, and the experiment varied in many ways,
‘but when the gravitation effect was removed, not the slightest tendency to the
formation of a dark plane by cold could be detected. The tendency seemed
to be the other way. The dust particles in all cases tended to keep close to
the cold body. This indicates that Lord Ray.eren’s dark plane formed in the
descending current from a cold body is not an effect of the cold, but is due to
the separating action of gravitation.

What I am about to state may at first seem a contradiction of this conclusion.
When varying the conditions of the experiment, and altering the amount of water
vapour present, I was much surprised to find that under certain conditions the
dark plane had a decided tendency to make its appearance in the descending
current even from a thin vertical surface. On repeating t he experiment and
varying it, it was found that the conditions best suited for getting this dark plane
were when there was nothing but ordinary atmospheric dust in the box, and
the air was saturated with water vapour. Under these conditions, there was
generally all through the box a haziness, but in the space in front of the cold test

246 MR JOHN AITKEN ON THE

surface the cold thickened this haziness into a dense cloudiness, which extended —
for some distance from the plate and showered down from it. But between
the fog and the test surface there was a well-marked dark space. To what was
this due? I had already satisfied myself that cold did not tend to drive away
the particles. Then why did these particles conduct themselves differently
from the others? While the test surface was vertical, the motion of the
particles was too quick to be followed with the magnifying glass. The surface
was, therefore, placed nearly horizontal, with a slight slope towards the light
(see fig. 4). Still the dark space remained, and the current flowed on, but the —
particles did not come close up to the plate, though gravitation was acting on
them. The cold could surely not be repelling the particles and keeping them
off the plate. A short examination with the strong magnifying glass, which it
was now possible to use as the particles were moving slowly enough, showed
that this was not the case. The particles were seen flowing along in the
current, but at the same time they were seen falling into the dark space and
disappearing when they came within a certain distance of the surface. The
explanation was evident. The surface, by its very low temperature, had robbed
the air close to it of its moisture, which it deposited on itself in ice crystals.
Into this cold but drier air the particles evaporated as they fell, and in this
case the dark plane would contain the dust of the atmosphere, which, however,
is black, compared with the brilliancy of the surrounding fog. In this case the
dark plane was produced by

Evaporation,

and this explains why it is not visible when artificial dusts are present, the
larger particles of the artificial dusts not being sufficiently reduced by evaporation
to make them comparatively invisible. We shall now pass on to consider the

Effects of Heat.

For this purpose let us remove the flat test surface from the smoke-box,
and put in its place a round tube of metal or glass. A glass one is preferable,
as it permits the illuminating beam to pass through it, and we are thus enabled
to see what is taking place all round. After the box is filled with dust, leave it
for some time, till the tube has acquired the same temperature as the air. On
examination we shall find, as before, the particles evenly distributed, and coming
close up to the surface of the tube on the top and at the sides, while underneath
we shall see the clear space produced by gravitation. We shall first examine
what the effect is of a slight difference of temperature. For this purpose
we shall pour some slightly heated water through the tube, so as to raise its
temperature a very little—a degree or two. When this is done the equilibrium
is destroyed, and currents begin to form. The clear space formed by gravita-
tion under the tube rises up, closely clasping and encircling the tube m

aa

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 247

a dustless envelope. The two currents of clear air which started from the
under side of the tube, reunite at the top after passing round the sides,
and ascending in the centre of the upward current, form a well-marked dark
plane (see fig. 5). Here again gravitation seems to be the principal cause of
the distribution of the particles. This certainly is the case when the difference
or temperature is very slight, but we shall see that, as the temperature rises, the
gravitation effect bears a less and less proportion to the heat effects, which we
shall presently consider. It will be as well to note here the difference in the
clear space surrounding the tube in this case and when cold was applied, as
shown in figs. 2and 5. When cold was applied (fig. 2), the dark space was only
on the under side of the tube ; but with heat it is all round the tube, because it
has its origin in the air under thé tube. |

When making these experiments a somewhat peculiar effect was often
noticed, which seems worth recording, as it forms a good illustration of the
influences at work here. If, after the tube had been warmed and a well-
marked dark plane formed over it, no more hot water was added, and
the tube allowed to cool, the upward current became sluggish after a time,
and the dark space presented the appearance shown in fig.6. The two sides of
the tube now differed. The left side was bounded by a clear space, which
ascended as before, but on the other side, the dark space did not continue to
the top of the tube. As shown, the particles here came into the dark space
and obliterated it. The explanation of this peculiar effect, which so often
repeated itself, is this. The falling temperature had allowed the current on the
right side to become so slow that gravitation had time to act on the particles
after the current turned to the upper side of the tube, and the particles had
time to fall through the clear space before they were carried into the ascending
current over the tube. In other words, gravitation undid on the upper part over
the tube what it did at the under. The left side of the tube continued to keep
its clear space, because the light used for illuminating it was focused on this
side; it, therefore, was slightly warmer than the other.

Gravitation, while it explains the formation of the dark plane in such cases
as above described, where the difference of temperature is slight, is evidently
not the whole explanation. Gravitation can obviously have little to do with
the formation of the dark plane formed over a thin wire, as the time occupied
in horizontal movement when going round so small a body is not enough for it

| to have any appreciable effect. In order to study the effects of heat apart from

those of gravitation, the tube with the flat surface fixed on it, employed in the

experiment with cold, was used, as it eliminates the gravitation effect and

shows the heat effect alone. Fixing this piece of apparatus in the smoke-box

with the test surface carefully adjusted in a vertical plane, heat was slowly

applied to it. An upward current at once started, and it was noticed that at
VOL, XXXII. PART II. aT

248 MR JOHN AITKEN ON THE

the same time a clear space was formed on the hot surface, and rose up from
it, producing a dark plane in the ascending current (fig. 7). This clear space
was evidently entirely due to the heat in some way driving the particles away
from the hot surface.

When working with this flat test surface it is necessary to be careful about
the adjustment of it ina vertical plane. Ifthe surface leans either to the one side
or to the other, a clear space is, of course, formed on the side to which it inclines
by the separating action of gravitation, and gravitation also acts on the particles
on the other side, and tends to counteract the effect of the heat. Further, if
the surface is inclined enough, the gravitation effect overcomes the heat effect,
and destroys the dark space by causing the particles to fall towards the hot
surface. At the same time, the gravitation dark space on the under side
becomes thicker and thicker the more the plane of the test surface approaches
the horizontal. This instrument may be made capable of measuring the relative
effects of different temperatures, &c., by providing it with a scale to indicate its
angle with the vertical. The greater the angle at which the dark space is
visible the greater will be the repelling force.

By the construction of the instrument, when placed vertically, the gravita-
tion effect is entirely removed. The dust particles can be seen coming straight
up, and no purified current coming from the under side (compare figs. 5 and 7).
The clear space begins to show itself with a very slight rise of temperature.
Indeed, it would appear that it is formed by the slightest rise of temperature, —
as it always begins to be visible just when the temperature is high enough to
cause an ascending current. With a slight difference of temperature it is
extremely thin, and requires careful observation to detect it, but as the tem-
perature rises it becomes thicker and thicker. For the present I shall not enter
into the question as to why the dust particles move away from a hot body, but
shall leave the consideration of this subject till after describing some experi-
ments which seem to throw some light on the mechanism of these movements. —
For the present I shall simply speak of it as repulsion due to heat.

The following experiments will help us to understand the action of this
repulsion. Fix a piece of glass in front of, and parallel to, our flat test
surface, and ata distance from it of two or three millimetres. Glass is used
because it is transparent, and allows the illuminating beam to penetrate and
show us what is taking place at the different surfaces. If we now warm the
test surface, the dust particles all move away from it towards the glass plate, and
many of them attach themselves to the glass. After a short time the glass
gets warmed by radiation, &c., from the hot test surface. If we now cool the
test surface a change takes place, the dust particles move away from the glass,
and crowd up towards the colder test surface.

A better form of the experiment is shown at figs. 8 and 9. A glass plate

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 249

A, 12 cm. long and about 4 cm. broad is attached by means of cement, near its
upper end, toa metal tube, to enable us to heat it while in the dust-box.
Another plate of glass B, of the same size as A, is placed opposite and parallel
to it, at a distance of about 5mm. The plate attached to the tube is first put
in its place in the box, and after it has acquired the temperature of the air,
the other plate B is warmed and put in its place, opposite to A, as shown in
sketch. The box is now filled with dust. If we now carefully examine the
air between the two glass plates, we shall find that the warm plate B (fig. 8) is
bounded on each side by a clear space, its high temperature having driven all
the dust particles to a distance, while the other plate has no clear space round
it. Now let us put a little warm water into the tube to heat the upper part of
the cold glass plate A, and note the change in the distribution of the dust.
As before, the lower part of B is bounded by a clear space (see fig. 9), but the
upper part of A being now warmer than B, the dust is driven from A towards B,
and a clear space opened in front of the hot part of A, while the clear space
formerly in front of the upper part of B is closed. The heat has thus caused
the dust particles to move across the direction of motion of the air. These
experiments have been made with different dusts, and always with the same
result.

For the purpose of studying the effects of higher temperatures than that of
boiling water, a fine platinum wire was fitted up inside the dust-box and heated
by means of a small bichromate battery. The arrangement of wire which I
prefer for this purpose is made by bending it into a U-shape and bringing the
two legs close together, say one or two millimetres apart. The wire is placed
horizontally in the dust-box, with the bend to the front, and the legs at the same
level, the two copper wires to which it is attached being carried backward and
out of the box. By this arrangement a clear end-view is obtained all round
the wire, and the effect of the heat conveniently observed, and further, the
wire doubled in this manner, tells us more than a single wire can. .

In experimenting with this arrangement of apparatus, the results are as
varied as the dusts employed. Each dust gives a different size of dark plane
for the same temperature. The previous experiments with less intense heat
seemed to point to repulsion as the cause of the clearing away of the particles.
If this were the case, it seemed very unlikely that some dusts would be
repelled further away than others, at least to the extent that actually took
place. To see if repulsion was the explanation in this case also, instead of a
single wire, which I used in my first experiments, I doubled the wire into a
U-shape, as already explained, and placed the length horizontally, with the legs
at the same level. When this wire was heated in the sal-ammoniac or in sulphate
dust, it was at once evident that repulsion was not the cause of the dark plane
in these dusts. With either of them, when the temperature of the wire was not

250 MR JOHN AITKEN ON THE

very high, the dark plane rising over each leg was very thin (see fig. 10), but as
the temperature rose, the planes extended on each side till the two planes met and
formed one large one (see fig. 11). An examination by means of a magnifying
glass showed that this broad dark plane was due to the evaporation, or to the
disintegration of the particles, as they could be seen streaming upwards and
disappearing into the dark space under the wires. They there arrived at a
space the temperature of which was sufficient to convert them into gases or
vapours. The dark plane in this case was thus due to a change of the particles
from the solid to the gaseous state. Hence the great differences in the size of the
dark planes of different dusts, each kind of dust having a different temperature
at which it evaporates or becomes disintegrated. The sulphate dust, for instance,
gives a smaller dark plane than the chloride, because the sulphate requires a
higher temperature to drive it into the gaseous state than the chloride.

This result is quite different from that got with temperatures which were
not sufficient to vaporise the particles and make them invisible. It was there-
fore now desirable to make experiments with some substance which a high
temperature could not destroy. For this purpose I selected calcined magnesia
and calcined lime, also soda and magnesia dusts, produced by burning the metals.
With these dusts a different result was obtained. A high temperature had no
other effect than forming a thin dark plane over each wire (see fig. 10). But
even these stable forms of dust were subjected to a repulsion, the particles
passing near the wire being driven to a small distance from it on each side. It
may be possible that some of the particles of these dusts are vaporised, but if
so, the amount must be very small, and can have but little influence on the
formation of the dark plane.

Another effect noticed in these, and in the experiments at lower tempera-
tures, was that whenever there was much water vapour present, there was a
faintly indicated dark plane formed by the evaporation of the water from the
particles. If nothing but the dust of the air was present in a fog formed with
steam, then the wires were surrounded by a very thick dark plane, due to the
evaporation of the fog particles ; and if any artificial dust was present, then the
thick dark plane was still visible, but not black, as the particles were only
reduced in size by the evaporation of the water from them. All these different
effects of the hot wire can be illustrated at one time, if we put into the dust-
box some indestructible dust, also some sal-ammoniac and sulphate dusts, in
proper proportion, and then add some water vapour. When the wire is heated
in such a mixture, we get a result like that shown in fig. 12. In the centre we
have the true dark plane, in the wider space there is only the indestructible
powder present. The next boundary shows the vaporising zone of the sulphate,
the next the vaporising zone of the sal-ammoniac dust, and the last that of water.
In fig. 12, @ is the true dark plane, in which there is nothing but gases and

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 2351

vapours ; in the wider space b, both the chloride and sulphate dusts are
vaporised, and we have nothing visible save the indestructible dust ; in the
next space ¢ the chloride is vaporised, and there are present the sulphate and
indestructible dusts; while in the space d all the dusts are present, but dry,
the condensed water being evaporated.

Conclusion.

The conclusion we have arrived at from these experiments is, that for the
formation of the dark plane in dusty air, there are various causes which may
be classed under the following heads :—With cold, producing the downward
dark plane, we have—1st, the distributing effect of gravitation; and 2nd, the dis-
appearance of the particles by evaporation, when falling into a space rendered
dry by condensation produced by cold. With heat, producing the upward dark
plane, we have—lIst, the distributing action of gravitation; 2nd, the distributing
action of repulsion due to heat ; 3rd, evaporation of the particles; and 4th, dis-
integration of the dust. In the last two cases the dust is rendered invisible by
the heat changing it from the solid light-reflecting condition to the transparent
gaseous state.

Effect of Centrifugal Force.

We may here ask ourselves, Are these the only ways in which the dark
plane may be produced? It is, of course, impossible to give a definite answer
to such a question. There are, no doubt, other ways in which it seems possible
that this phenomenon might be produced, and it seemed worth while to consider
| Lord Ray eicu’s suggestion as to the effect of centrifugal force. On consider-
| ing the action of this force in the experiments described, it is evident that it
can have but little to do with the distribution of the particles, because the air,
in rising and passing round the wires and tubes, is curved first in one direction,
and before it again takes up its original direction of motion, it is curved to an
equal amount in the opposite way. So that whatever sifting action the centri-
fugal force may have at the one part of its course, will be undone at the other.
| 1, however, thought it worth while to arrange an experiment, to see if the par-
| ticles really were thrown out by centrifugal force at any part of their passage.
|| With this object, I fixed inside the dust-box a piece of thin sheet metal, with
its plane vertical. Arrangements were made so that a current of dusty air was
\caused to flow down the one side of the plate, round the lower edge, and up
the other side. In this way the air was caused to curve through an angle of
/180°, and no curving in the opposite direction took place. When this was
\done, it was seen to be possible to give an appearance very like as if the cen-
rifugal force did throw the particles away from the centre of motion. In front,
nd just above the lower edge of the plate, there was formed a clear space,

—————E—E————— oo

.

iw)

52 MR JOHN AITKEN ON THE

very near the centre of rotation of the air. On examination, however, it was
seen that this was caused by an eddy, due to the upward channel in which
the air was confined being wider than the space under the plate. In the eddy
so formed the particles were soon sifted out by gravitation, and a clear space
formed. On contracting the breadth of the upward channel, and making it
equal to the passage under the plate, this eddy disappeared, and the clear space
was no longer formed. In this experiment, though the air was caused to curve
through a considerable angle, yet there was no satisfactory evidence of any —
distributing action due to centrifugal force. It seems probable that, even
under these conditions, a certain amount of sifting action does take place,
though not enough to make it observable; and though there are reasons
for supposing that if the particles were heavy enough, and the velocity of
the current great enough, there would be a visible effect, yet it is evident
that centrifugal force plays no part in the formation of the dark plane, in the
experiments with heat and cold. The fact that the dark plane has a sharply
defined boundary is proof that centrifugal force is not the cause of the distri-
bution, as this force would not give such a result. Its tendency would be
to throw the heaviest particles furthest out, and thus give rise to a shaded
outline.

Effect of Electricity.

Electricity is another force which might be supposed to play some part in
the formation of the dark plane. It was difficult to believe that the attraction
of the particles was a thermal effect when making the experiments with the hot
and cold surfaces placed opposite each other, and observing the way in which
the particles were repelled by the one plate and attracted to the other; and on
making other experiments, which will be presently described, in which the dust
rising in the current from the heated platinum wires was attracted to, and
deposited itself on, the surfaces of bodies placed in its path. The dust particles
conducted themselves in a waystrongly suggestive of electricaldisturbance. They
seemed to be attracted by the cold surfaces in exactly the same way as if they
had become electrified at the hot surface. It was, therefore, thought advisable
to make experiments to ascertain whether electricity had anything to do with the
formation of the dark plane. Experiments were first made to see if the hot sur-
face became electrified in the dust-box by the passage of the air over it, or from
other causes. For this purpose I used a small cylindrical conductor of solid
metal, about 1 cm. in diameter, and with rounded ends. This conductor was
fixed to the end of a glass tube, and a conducting wire connected to it and
carried through the tube. The conductor was then introduced into the dust-
box through an opening in the back, after which its connecting wire was jomed
to a gold-leaf electroscope. Before the conductor was put in its place it was

FORMATION OF SMALL CLEAR SPACES IN DUSTY ATR. 253

heated, and the box was filled with dust. Examined with the magnifying glass
in the usual way, the dark plane was found to be well marked and the repulsion
going on as usual, but not the slightest sign of electrification showed itself at
the electroscope. No signs of electricity having shown themselves at the hot
surface, it was sought for in the ascending current. This was done by first
removing the insulated heater and putting in its place the platinum wire, to get
a more intense effect from the high temperature. Over the wire was placed a
large insulated flat-shaped conductor for the dust to deposit itself upon. The
conductor was then connected to the electroscope, the box filled with dust, and
the electric current turned on to heat the wire. The leaves of the electroscope,
however, remained close together, so that the dust deposited on the conductor
could not have been charged with electricity.

It may be objected to these experiments that the electroscope used was not
sensitive enough for the purpose, and that if a more sensitive instrument had
been employed, signs of electricity might have been obtained. It is quite
possible that another instrument might have shown signs of electrical disturb-
ance, but I think that if electricity was the cause of these phenomena, and was
sufficiently strong to repel the particles and to cause them to adhere to bodies,
it would be quite powerful enough to separate the leaves of the electroscope.
Any electrification less than would affect the leaves would only be a secondary
matter, and could not be the cause of the phenomena. Another reason for
supposing that electricity has little to do with these effects is that the dust tends
to settle only on cold surfaces.

Experiments were now made to see what the effect is of electrifying the hot
surface. The small cylindrical conductor was heated, placed in the box, and
connected with the electroscope. A Leyden jar charged very slightly, but
enough to cause the full divergence of the leaves of the electroscope, was then
connected with the apparatus, and the effect on the dust surrounding the electri-
fied conductor noted. While the body was hot enough to cause a well-marked
dark plane, there was not the slightest effect produced by the electricity, though
the leaves of the electroscope were wide apart, and showed that the hot surface
had a decided charge. The electroscope was then removed, and a much higher
charge given to the conductor. This time an effect was evident, but it was
difficult to say what was taking place. The general appearance of the air round
the hot conductor had quite changed. The sharp outline of the clear space
round it was destroyed, and the dark plane over it had lost its clear and sharp
outline, and had become much thicker, though not so dark, as before. All
round the conductor there seemed to rage miniature storms, and the particles
had much the appearance as if they were seen all out of focus. This effect was
produced by either positive or negative charge.

To find out what was taking place in the air round the electrified body, I

954 MR JOHN AITKEN ON THE

had recourse to large-sized particles of dust to enable me to follow the move-
ment of each particle. Calcined magnesia was selected for this purpose.
When the air in the dust-box was filled with this powder, the reason of the
change in the dark space at once became evident. The particles in the ascend-
ing current could be seen rushing towards the electrified surface and adhering
to it. The dark space was thus broken in upon, and its outline destroyed
by the attracted particles ; the air round the body was at the same time
deprived of a great quantity of its dust ; and over the conductor there rose a
thick and ill-defined band of clearer air, the particles which formerly were in it
having attached themselves to the electrified body. All the particles did not
seem to be equally attracted, but some much more than others. This gave rise
to the irregular movements seen all round the body. The dust particles
frequently deposited themselves on the conductor in small needle-like radial
columns, which grew by the addition of the particles till they got to a certain
size, when they were shot off and flew through the air with surprising velo-
city. If, after the conductor had been electrified a short time, the supply of
electricity was cut off and the conductor connected with the electroscope, the
charge given to the air and the dust in the box was given back. The leaves of
the electroscope expanded quickly, and if discharged, rapidly became charged
again, the dust at the same time being attracted to and deposited on the con-
ductor in needle-like columns.

After looking at this last experiment, and seeing the tendency which particles

in electrified air have to deposit themselves on bodies, we cannot help asking —

the question, Does this experiment throw any light on the well-known tendency
to the development of certain forms of bacteria resulting in the putrefaction of
our foods, and in the appearance of increased quantities of certain ferments
during thundery weather? Can it be that the germs of these forms of life

floating in our atmosphere have a far greater tendency to settle upon the —

surface of bodies from electrified air than when there is no electrical disturb-
ance? No doubt this electrical attraction must have some effect in this
direction, but whether it is the principal cause or not I shall not venture
to say.

If we use still higher degrees of electrification than those used in the above
experiments, other effects are produced, but they have no relation whatever to
the formation of the dark plane. From the experiments described it will be

seen that the effects of electricity are of quite a different kind from those of —

heat. The electrified body, instead of repelling the particles like a hot one,
attracts them, and clears the air in a partial way by attracting some of the par-
ticles to itself, while heat acts by repelling all of them to a distance. This anta-
gonism between the two forces may be illustrated by heating the conductor and
electrifying it slightly. At first no effect is produced by the electricity ; the

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 255

dark plane remains quite clear, but as the temperature falls, a stage is arrived
at when the electrical effect overcomes the heat effect, and the particles break
in on the dark space and destroy it.

In making electrical experiments, most of us have noticed the tendency which
dust in the room has to settle on the different parts of the electrical apparatus,
and to destroy the insulation, and many have noticed the excited and rapid
movements of electrified dust. Dr Lopae, in the letter already referred to,
remarks on the rapidity with which the dust-box, in his experiments, was cleared
of its dust by means of electrified bodies placed inside it. I have made some
experiments on this subject, to determine the conditions most favourable for the
clearing of air by means of electricity. For these experiments I preferred to
use a large glass flask about 30 cm. in diameter. Placing this flask with its
mouth downwards, I introduced into it an insulated metal rod, fixed vertically,
and passing through the open neck of the flask. Ifa dense cloudiness was
made in the flask with any dust, by preference it was generally made by burn-
ing sulphur and adding a little ammonia. After a dense whiteness had been
produced, the conductor was electrified. Seen from a distance, no change
seemed to have taken place, but on examination it was found that all the dust
was deposited on the inside of the flask ina nearly uniform white coating. To
enable me to see what was taking place, the inside of the flask was wetted.
When. the electrification began, the dust could now be seen driven about
as by a violent wind, and, after a few turns of the machine, it had disap-
peared from the flask. The conditions found most suitable for producing this
result quickly were a rapid discharge of the electricity into the dusty air by
means of a point or points. If the conductor terminates in a ball inside the
flask, the electrification has but little effect. In addition to the conductor
terminating in a point, it is also necessary to have near the electrified point
surfaces to aid in the rapid electrification of the dust. When the point is
surrounded by surfaces the air currents are violent, but if we remove the sur-
faces the currents are not nearly so strong. This may be seen by allowing a
cloud of dust to rise round a conductor placed in an open space, when but little
effect will be observed on electrification. After the dust has been electrified,
it ought to be brought near some surface, towards which it may be attracted,
otherwise it may lose its charge before meeting a place to deposit itself.

Experiments have also been made to determine whether the very fine and
invisible dust of the atmosphere is also caused to deposit itself when electrified.
With this object the large glass flask had an india-rubber stopper fitte] to it,
through which passed a tube to connect the interior of the flask with an air-
pump, to test the condition of the air in the flask by reducing its pressure,
while it was kept moist by the presence of water, and to observe whether any
cloudy condensation took place after electrification. A conductor insulated in

VOL, XXXII. PART IL 2U

256 MR JOHN AITKEN ON THE

a glass tube passed through the stopper, and terminated in a point inside the
flask. Means were taken to insure the insulation of this conductor inside the
flask. This was done by surrounding the insulating tube with another tube, and
causing the entering dry air to pass into the flask through the space between
the tubes. The insulation was thereby kept good, and the glow of the dis-
charge at the point was quite visible in the midst of the moist air.

On experimenting with this apparatus, it was found that electrification for a
short time by means of an ordinary cylindrical electrical machine was sufficient
to deposit almost all the dust, only the very slightest signs of condensation being
visible after electrification. What formed the nuclei of the very few cloud par-
ticles which appeared it is difficult to say. Whether they were undeposited dust
particles, or particles thrown off the conductor, or some product of the electric
discharge, this experiment does not determine. That they may be some pro- —
duct formed from the air by the electric discharge is suggested by the following
experiment. First purify the air in the flask, either by passing it through
a cotton-wool filter, or by electrification, then reduce the pressure to super-
saturate it, and now electrify. At once a cloud forms all round the conductor,
and extends to near the sides of the vessel. This cloud is evidently not
formed by anything thrown off the conductor, forming nuclei, as it appears at
the same moment all round the point. It is more probable that the nuclei of
these cloud particles are formed by the discharge of the electricity producing
in the air nitric acid, or ozone, on which the supersaturated vapour condenses.
That the nuclei so formed are not solid particles there seems to be but little
doubt, because if we allow filtered air to enter so as to increase the pressure
and evaporate the particles, cloudiness does not reappear on again reducing
the pressure, which it certainly would do if the nuclei had been solid particles,
The number of nuclei that remain after electrification is very small, if the air
is not supersaturated with vapour; and practically we may say that electrifica
tion deposits all the very fine dust, and I may remark here that it does it in a
very rapid manner. The air in the flask can be purified much quicker by means
of electricity than by the air-pump and cotton-wool filter. It may be noted
here that the dust of the atmosphere has but little effect on the brilliancy
of the glow of the point discharge. With a large amount of dust, with the
ordinary dust, with no dust, and with the electrification used, no difference
of importance in the brightness of the glow was detected.

The Lungs and Dust.

When we see a beam of sunlight shining into a darkened room through a
small opening, and revealing, by illuminating, the suspended dust, making the
beam look like a solid body, we have great difficulty in realising that our atmo-

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. Vi

sphere can be so full cf dust, as this experiment shows it to be, as it escapes our
observation under ordinary conditions of lighting, and it gives us a feeling of
discomfort to realise that we are breathing that dust-laden air. This uneasiness
was by no means decreased when my experiments on cloudy condensation
revealed the fact that, in addition to that mass of visible dust, there are enormous
multitudes of particles so small that even the concentrated light of the sun does
not revealthem. These minute particles are so numerous that hundreds of them
are crowded into every cubic centimetre of air. On realising these facts our
feelings are those of wonder that our lungs can keep so clean as they do, while
such vast quantities of impurities are constantly ebbing and flowing through
them. Atthat time I was not aware that there is an influence ever at work tend-
ing to protect the lungs by preventing, to a certain extent, the particles of dust
coming into contact with their surfaces,—that nature had provided a subtle form
of mechanism possessing some of the advantages of a filter without any of its
disadvantages. The experiments here described show that a hot surface
repels the dust particles in the air. The heat of our bodies will, therefore,
exert a protective influence on the lungs, and tend to keep them free from
dust.

Our lungs, however, are not only hot, they are also wet. What influence
will the constant evaporation which takes place at the surface of the tubes
and passages have on the dust? To answer this question, I fitted the flat test
surface in the dust-box, and through an opening in the top introduced a brush
dipped in water, with which one-half of the surface was kept wet, the other half
being dry, to compare the effects under the two conditions. When the surface
was heated a few degrees, to even less than the temperature of our bodies, the
result was most decided, the dust being driven more than twice as far from the
plate in front of the wet part as it was from the dry. The evaporation, there-
fore, of the water from the surface of the bronchial tubes tends strongly to
ward off the dust, and keep it from coming into contact with their surfaces.
We must not, however, imagine that the heat, or the heat and the evaporation,
are sufficient entirely to prevent the dust coming into contact with the surfaces
of our bronchial tubes and passages, because dust really does come into contact
with them, but it does not do so nearly to the extent to which we have been in
the habit of supposing.

The necessary conditions for this repulsive effect to be active are, that the
air is acquiring heat and moisture. If the air has the same temperature as
our bodies, and is saturated with vapour, this force no longer exists, and gravi-
tation and other forces are free to act.

Although the repulsion due to heat and evaporation are not powerful
enough to form a perfect protection to the lung surfaces against the contami-
nation of dust, yet it is very evident that their protective influence will have a

258 MR JOHN AITKEN ON THE

most important effect on the condition of our Jungs, and one towards which I
wish to direct the attention of those who make this organ a special study.
There seems to be but little doubt that we have here an explanation of some of
the effects of different climates. For instance, what a difference there must be
in the amount of dust deposited on the lungs from air breathed at, say, St
Moritz or Davos Platz, and at such places as Madeira or other similar health
resorts! These remarks are altogether apart from the question of the amount
of dust in the air at the different places, and refer only to the action of the
lungs on the dust which may be present.* In the Alpine resorts the air is cold
and dry, and the tidal air, which flows backwards and forwards through the
bronchial tubes, is in the very best condition for preventing the dust coming into
contact with their surfaces, as the difference in temperature between the air
and the body is great, and the air is also capable of causing a rapid evaporation.
Whereas, at such places as Madeira, where the air is hot and moist, the repelling
forces are both at a minimum. The effects of these different conditions on the
lungs seems well worth study. :

In illustration of the protective influence of heat and moisture many experi-
ments may be made, but the following is perhaps the easiest. Take an ordinary —
paraffin lamp, raise the flame till a very dense cloud of smoke rises from it.
Over the lamp place a very tall metal chimney, to produce a quick current
of air and also to cool it. Have ready two porous cylindrical jars (porous ©
jars are used because they keep up a supply of water for evaporation), one
jar filled with water slightiy heated, and the other with cold water. Cover
both jars with wet white paper. Now introduce the hot one into the top of the
chimney, and leave the black wreaths of smoke to stream over it for say half a
minute, then take it out and put in its place the cold one, and leave it for the
same length of time. The result will be, the hot one will be quite clean, not a
speck of soot on it, while the cold one is covered with soot. It is not, however,
so black as a cold dry surface would be, as the slight evaporation from its
surface tends to protect it.

We must not, however, suppose that the lung surfaces are so well protected
as the paper in this experiment. In the lungs the currents are quicker,
they do not flow over such uniform surfaces, and further, they pass round
curves, so that in the lungs dust tends to deposit where the currents flow
quickly where they strike on the concave side of curved passages and on pro-
jecting edges. Further, all dust which penetrates beyond the tidal air and gets
into the residual air will ultimately fall on the surfaces of the tubes and air

* The amount of dust breathed by invalids at the two places will not be greatly different, as
most of their time is spent in the house, and the air in the rooms at the two places will be nearly
ejually dusty. The higher temperature inside will slightly reduce the thermal effect, but will no
diminish tlie rate of evaporation.

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 259

cells. This tendency of the dust in the residual air to settle is increased by the
load of water deposited on it by the moist air.

The amount to which our lungs are protected by heat and evaporation can
scarcely be solved in a physical laboratory, and will be best determined by
anatomical examinations of lungs which have lived under different conditions of
temperature and moisture.

A Thermic Filter.

Having observed that the dust particles tended to move away from hot
bodies and to attach themselves to cold ones, I made some experiments
on the subject to study the movements of dust particles when placed between
hot and cold surfaces. Most interesting results were obtained by placing near
the hot platinum wires, already referred to, a piece of glass or a plate of metal,
and getting the dust deposited upon it. One arrangement of the experiment
is to place the glass with its plane vertical and transversely over the wires,
at such a height that its lower edge almost touches the wires, and fill the
box with dust by blowing up some calcined magnesia or other fine powder.
After all the currents have settled, and while the air is still full of dust, the
electric current is turned on and the wire heated. A well-marked dark plane
at once rises over the wire, and in its upward passage it is cut transversely
by the glass plate. After the plate has been left for some time with the air
current streaming over its surface, it is found to have a very beautiful impres-
sion of the dark plane imprinted on it. The warm air, in streaming upwards
over the surface of the glass, deposited its dust on it, and the fact of there being
no dust in the dark plane is recorded by a well-defined line of clear glass,
the deposit of dust on each side of the clean line being thickest just along
the edge, and thinning away on each side. These impressions of the dark plane
may be made permanent by causing the dust to be deposited on a plate newly
coated with black varnish, and used while the varnish is still soft.

It is not necessary to put anything on the surface of the glass to cause the
dust to adhere, as it attaches itself to a clean surface of glass with considerable
firmness, but some adhesive substance on the plate enables the impression to
stand rougher treatment. Impressions of the dark plane have also been made
with charcoal dust deposited on opal glass. These black impressions are, of
course, “negatives” of the magnesia ones, the plane in the former case being
white, surrounded by black dust. The charcoal dust was securely fixed by first
coating the glass with a thin solution of gum, which was dried before the
dust was deposited on it, and the dust fixed by breathing on the surface.

If in place of putting a plate vertically over the wires, we place two plates
vertically—one at each side of the wire—we then get the dust deposited on the
plates, thickest opposite to the wires and thinner higher up. Arrangements

260 MR JOHN AITKEN ON THE

were made for studying the action of surfaces placed on both sides of the wires.
Fixing the plates parallel to each other, and at a distance of 2 or 3 mm. apart, —
with the platinum wire between them, I carefully watched the motions of the
particles carried up in the air current. As the particles approached the wires
they gradually changed the direction of their motion, and instead of coming
straight up they curved towards the sides, some of the particles striking and
adhering to the side plates at a point below the wire. Some rose higher and
stuck opposite to it, others went higher still, while others passed on to the top
and escaped.

I had for some time been trying to arrange an experiment in which I should
be able to watch the movements of the individual particles of dust, so as to see
them moving away from the hot surface. My intention was to examine the
movements of the particles with a microscope of low power, or with a powerful
magnifying glass. My great difficulty, however, was to get the movements
due to the convection currents sufficiently slow to enable me to follow the
moving particles when much magnified. After making the experiment last
described, I saw it was possible to arrange for this much-desired observa-
tion. The use of the large particles of magnesia enabled me to dispense with
the microscope, and use only a magnifying glass of moderate power; and by —
bringing the plates on each side of the wire close together, the velocity of the
upward convection current could be greatly reduced by the friction of these
surfaces, and by their cooling effect on the gases. The two side plates of glass
were accordingly brought closer together, to a distance of about 1 millimetre.
Fig. 13 represents the arrangement magnified five times, the U-shaped wire
being shown in section between the plates. The ascending current was now
very slow, and no difficulty was experienced in following the movements of the
individual particles, so I had at last the satisfaction of seeing the particles
being repelled by the hot wire.

When the wire, heated to a red heat in air filled with magnesia dust, was
examined by means of a magnifying glass, the spectacle which presented itself
was most curious and interesting. At a distance below the wires, the particles —
could be seen coming straight up between the glass plates, but as they approached —
the wires they seemed to get uneasy, and as if wishing to avoid the heat,
some of them attached themselves quickly to the glass, others went further up,
but soon curved towards the sides and adhered to them; while others boldly —
advanced straight up, almost to the wires, when their motion was suddenly
arrested and they were driven downwards and sideways, and attached themselves
to the glass. If the wires were hot enough, not a single particle got past them,
and the glass plates had each a patch of magnesian powder adhering to
its surface below the level of the wires. The direction of movement of the par-
ticles is roughly indicated by the lines in fig. 13.

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 261

These experiments naturally suggested the possibility of constructing
an air filter on thermic principles. They showed that the visible particles
of dust could be thrown out of the air, as the particles tended to move from
the hot parts, and to attach themselves to cold surfaces. But the question
which naturally suggested itself was, Are the very small invisible particles also
arrested ? If the thermic filter turned out to be a success, it appeared to
me it would also be the best way to get an answer to this question. In order
to filter air on thermic principles, all that appeared necessary was to pass the
air through a space or channel, the two sides of which were kept at different
temperatures. In this way I hoped the dust would be driven from the hot
side and attach itself to the cold one. Practically to carry out this idea, the
simplest method that suggested itself was to pass the air through the space
between two concentric tubes, the one tube being kept hot, and the other cold.
In the preliminary instruments which have been made, the distance between
the tubes forming the space through which the air passes, is in one instrument
less than 1 mm., but in other instruments this space is nearly as much as 3mm.
The length of the passage in the different instruments is about 35 cm. One of
these instruments has the outer tube jacketed by means of a larger pipe for the
purpose of heating it with steam. The other instruments were heated simply
by means of a gas flame. The filter is shown in section, fig. 14. A is a tube
about 13 mm. diameter. B is another tube slightly larger, and allowing a space
C, between the two for the passage of the air to be filtered, which enters and
leaves by the tubes D,D. The outer tube E forms a steam jacket round B.
F, F are pipes for steam entering, and for condensed water leaving the jacket.
The pipe A is kept cold by means of a stream of water. In working the instru-
ment it is not, however, necessary to keep to this arrangement ; steam may be
admitted to the centre tube A, and cold water to the outside jacket; both
arrangements do equally well. For the purpose of cleaning and examining the
surfaces of the air channel, the centre tube was not permanently fixed in its
place, but was so arranged that it could be easily taken out, and the joints
were made tight by means of the short pieces of india-rubber tube H,H. The air,
after passing through the space C, was conveyed by means of a tube to a glass
flask, in which there was a little water. The flask in turn was connected by
means of another tube to an air-pump, in order to test the condition of the
air after passing through the instrument. If cloudy condensation is produced
when the pressure is reduced in the flask, we know that the air is not filtered;
and, on the other hand, if the air remains perfectly clear on exhausting, we
know that no dust, not even the invisible particles, have passed into it.

The apparatus was fitted up for trial, all the connections being made and
tested. Using the instrument heated with flame, the first effect of the heat,
as expected, was a great increase in the fogging. The temperature was raised

262 MR JOHN AITKEN ON THE

as high as it safely could be, to cleanse the instrument thoroughly ; after which,
as we know, it will cease to give off nuclei at a lower temperature. When the
tube was thoroughly cleansed by means of heat, and all the impurities swept
out of it by a current of air, the temperature was lowered slightly, and the air
allowed to pass slowly through the tube on its way to the test-flask. After
this, the fogging in the flask gradually diminished, and after passing through
the rainy stage, it ceased entirely, proving that the filter was doing its work
thoroughly, not a single particle— not even one of the very minute and invisible
ones—escaping it. On equalising the temperature, either making both tubes
hot or both cold, the filtering action of course ceased.

It does seem somewhat strange that air should be freed from all its
dust in passing through a channel large enough for a fly to pass, if it has
sufficient intelligence to keep always on the cold side. All who have
experimented on this subject know that dust can get through any opening,
however small. On testing this filter for the first time, I failed to get a satis-
factory result. I however felt convinced that it ought to work, and the
failure was attributed to some imperfection in the tubing or joints. Arrange-
ments were therefore made for testing the tightness of the whole apparatus.
The one end of the filter being connected, as described, to the glass flask in
which the air was tested, I now connected a cotton-wool filter to the other
end of the thermic filter, and proceeded to test ifall was tight, by drawing in air —
from the cotton-wool filter through the apparatus, while it was cold. At first,
I could not succeed in getting air free from dust; fogging always took place on
reducing the pressure in the flask, showing that dusty air was leaking in some-
where, and mixing with the filtered air. After much time spent in remaking
all the joints, it was discovered that the air-pump valve was not quite tight ;
by allowing the leakage to bubble through the water in the flask, it was found to
be very slight, only about 2 or 3 c.cm. per minute. After this was put right,
fogeing still appeared, showing that there was still leakage. This time it was
traced to the stop-cock between the filter and the test-flask. This leakage was
smaller than the other, yet it let in dust. After all leakages had been stopped,
the cotton-wool filter was removed, and the thermic filter being heated, was now
found to do its work satisfactorily, though more slowly than a cotton-wool filter.
The ease with which dust passes through small openings is surprising ; indeed,
I have found that any opening which admits air, also allows these less than
microscopic particles to pass, and yet the air in its passage through the wide
channel of this filter had every particle of dust. taken out of it by the thermal
conditions to which it was subjected.

If we cause the filter to purify air into which we have intentionally put a
good deal of dust, such as dust of calcined magnesia, we find all the dust
collected on the surface of the cold tube, near the end where the air entered,

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 263

while the hot tube is quite clean. If we send the smoke of a cigar through the
filter, nothing but perfectly transparent gases come out at the other end. The
effect of coating the cold surface with glycerine has been tried, as it seemed pos-
sible that the dust deposited on the clean surface might be carried on by the air
current. The dust, however, seems to be firmly held on a cold clean surface, and
no decided improvement was got by the addition of the glycerine. No accurate
experiments have been made to determine the best size of the filtering channel.
The filters with very narrow passages and those with much wider ones all work
well, but no quautitative experiments have been made as to their relative values.
It is not easy to determine what influence difference of temperature has on
the action of a cotton-wool filter. Heating the cotton-wool has little effect in
reducing its filtering powers. We might expect this, as the cotton and the air
passing through it rapidly acquire the same temperature ; and it is extremely
difficult to say how much of the action of this filter depends on the slight
differences of temperature produced by the air in passing through the cotton.

Diffusion Effects.

I shall now describe two experiments on diffusion, which were made in the
hope they would throw some light on this repelling action of hot bodies. For this
purpose a tube similar to those used in the previous experiments was taken,
and an opening made in the side of it, at the front end. Into this opening was
fitted a thin plug of plaster of paris. The surface of the plug was made flat,
and when put in the dust-box was placed vertically, as in the experiments on
the heat effect, to get rid of the distribution due to gravitation. This diffusion
diaphragm was blackened, to enable the effect to be better observed, as a white
surface reflects so much light, it makes it difficult to see what is taking place.

After the diffusion apparatus was fitted in its place, the dust-box was filled
with sulphate dust, and left till everything had acquired the same temperature.
Carbonic acid gas was then introduced into the tube. At once a downward
current was produced in front of the diaphragm, the dust particles kept
close up to its surface, and if there was any tendency to the formation of a
clear space the carbonic acid at once closed it. The apparatus for supplying
the carbonic acid gas was then removed, and a small pipe connected with the
gas pipes was then led into the diffusion tube, so as to get the effect due to the
diffusion of gases lighter than air. The effect in this case was the opposite of
that given by the carbonic acid. An upward current at once started, and a
thin clear space formed in front of the diffusion diaphragm. These experiments
prove that the dust particles move in the direction in which the greatest rate of
diffusion takes place. This at first sight looks very self-evident; but we must
remember that in front of the diffusion diaphragm, when hydrogen is coming

VOL. XXXII. PART II, 2x

264 MR JOHN AITKEN ON THE

through it, that the ascending clear space is not composed entirely of the lighter
gas which has come through the diaphragm. In that clear space the larger
proportion of the molecules are air molecules; and while the air molecules
advance up to and pass through the diaphragm, the dust particles are driven
away from it. I shall presently have to refer to this.

When speaking of the action of heat and moisture in protecting the lung
surfaces from contact with the suspended dust in our atmosphere, no mention
was made of this diffusion effect, as it can be better considered here. In our ©
lungs the small quantity of tidal air, which flows backwards and forwards,
carrying in the oxygen, and out the carbonic acid, never gets further than the
main bronchial tubes, and does not penetrate to the air-cells; the carbonic
acid, set free into the residual air in these cells, is carried outwards to the tidal
air by diffusion, and at the same time oxygen is diffused from the tidal air
towards the residual air. Now, what is the effect of this diffusion on the
distribution of the dust? We have seen that in diffusion through a porous
diaphragm the dust moved towards the carbonic acid. If this was the case
in our lungs, then the dust would tend to penetrate towards the air-cells
and come into contact with their surfaces. In our lungs the exchange between
the carbonic acid and the oxygen does not, however, follow the law of diffusion
through a porous diaphragm, but those of osmose; and the rate of passage
of these gases through the lung surfaces does not depend upon their relative
densities, but on much more complicated conditions, of which solubility is in
this case one of the principal. The result is, that in our lungs for every volume
of oxygen that passes inwards, exactly or almost exactly one volume of
carbonic acid passes outwards. These diffusion effects balance each other, and
the result is that diffusion has no tendency to cause dust to penetrate towards
the air-cells, or to adhere to the surfaces of our lungs.

Repulsion due to Heat.

We shall now consider the cause of the repulsion of the dust particles by
hot bodies, and see if we can make out the mechanism by which the particles
are driven away. This is a subject of considerable difficulty, and one on which
I fear there will be much difference of opinion, and I shall simply state here
what appears to me at present to be the cause of the particles moving away
from a hot and towards a cold surface. The simplest explanation, and the one
which offered itself first, was that possibly it might be a radiation effect, and
that the particles are repelled in the same way as the vanes of a Crookes’
radiometer by the reaction of the heated gas molecules in the way explained by
Professors Tarr and Dewar. We might suppose the side of the particles next
the hot surface to be warmed by radiation, and the gaseous molecules on that

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 265

side getting heated by contact, would rebound from it with greater velocity
than those on the other side, the dust particles being thus driven away in a
sort of rocket fashion. On examination, however, this explanation does not
appear satisfactory ; because the particles are so very near the hot surface that
they will not be heated principally by radiation, but by contact with the hot
gases near the heating surface, radiation having but a slight effect.

So far as I have been able to form a mental picture of the mechanism of
this repulsion, it seems to be produced in the following way :—First, let us go
back to the diffusion experiments. We saw that when hydrogen was diffused
into air, a clear space was formed over the diffusing surface. Now why was
this? The air molecules were moving towards the diaphragm and passing
through it, yet they did not carry any dust particles with them. The reason
seems to be this. In the air in front of the diaphragm there are two currents
of molecules—one of hydrogen, moving outwards from the diaphragm, and one
of air, moving inwards ; but as the hydrogen current is the stronger, it carries
the dust particles along with it, and the difference in the strength of these two
currents in this case gives rise to a thin clear space over the diffusing surface.

Let us now apply the same reasoning to the heat effect. When we re-
member that hot and cold gases tend to diffuse into each other, the explanation
given does not require to be greatly altered. The molecules of air on the surface of
the hot body get heated by contact, and these molecules tend to diffuse themselves
outwards into the colder molecules. In imagination, let us look at a section of
the air close to the hot body. The air there is no longer homogeneous. Some
of the particles have more kinetic energy than others. Those molecules with
the greatest kinetic energy have the greatest amount of their motion in a direc-
tion away from the hot surface, while the cold ones have the greater amount of
their motion in a direction towards the hot surface. Now what will happen to
any particle of matter hung among these heterogeneous molecules? ‘The side of
the particle next the hot body will be bombarded by a larger proportion of hot
molecules than the other side, and the result will be to drive the particle away
from the hot body. It may be objected that, as the air pressure is the same on
the front and back of the particles, therefore the total energy of the molecules on
the front and on the back must be the same, and therefore there will be no
tendency to cause the particles to move. I think, however, this does not cor-
rectly represent the case. Near the heating surface the hot molecules are
moving outwards and the cold ones inwards. If there were more cold ones
moving inwards than hot ones outwards, so that the total energy of the inward
moving ones was equal to the total energy of the outward moving ones, which
would be necessary in order that the pressures might be equal, then no motion
would be produced in the dust particles. We must, however, remember that
there are exactly the same number of molecules moving each way. One effect

266 MR JOHN AITKEN ON. THE

of the hot surface seems to be to differentiate the movements of the molecules,
causing the greater amount of the movement of the hot ones to be outward
and of the cold ones inward, and the outward moving molecules, having the
greater kinetic energy, exert a greater pressure on the dust particles and drive
them outwards. In the hydrogen diffusion effect the particles of dust were
driven away, because a greater number of hydrogen molecules were moving one
way than air ones the other. In the heat effect they are driven away, because
the molecules moving from the hot surface have a greater kinetic energy than
those moving towards it, and the particles are bombarded on the one side by a
greater number of hot molecules than on the other.

We have the same effect intensified when the hot surface is wet. When
this is the case, the vapour molecules diffusing outwards carry with them the
dust particles to a much greater distance than the heat alone, as there is no
inward current of vapour molecules to contend with the outward one, and tending
to drive the dust particles inward; the result is, we get a dark plane at
least twice as thick with heat and vapour as with heat alone. Of the two, the
vapour seems to be the more powerful, as very little heat with moisture gives a
thicker dark plane than double the heat would do. If we carefully fix the
experimental test surface in a vertical position and simply wet it, the effect is
to cool it by evaporation, and a downward current is produced ; but, at the
same time, a clear space is formed, showing that in this case the outward
effect of the vapour is greater than the inward effect of the cold.

There seemed to be a possibility of getting an answer by experiment as to
whether the radiation or the diffusion theory is the correct one. If radiation is
the cause of the repulsion, then we should expect that a good radiator would
cause the particles to be driven further away, and thus cause a thicker dark
plane than a bad radiator. For the purpose of testing this, another experi- —
mental flat test-surface was prepared. ‘This test-surface was made of silver and
highly polished. One-half of it was then covered with lamp-black. After the
test-surface was fixed in the dust-box heat was applied to it, and the thickness
of the clear space over the two halves of the test-surface carefully noted. To
do this, the dust-box was so arranged that I could look down the test-surface—
not across it as usual—and could thus see down the boundary line between the
dark plane over the polished surface and over the lamp-black. The result was,
not the slightest difference could be detected between the two. The boundary
line of the dark space in front of the plate was a straight line parallel to the
surface of the plate. This experiment, while it gives no support to the diffusion
theory, shows us that radiation is not the principal cause of the dark plane.

If the explanation here given of the repulsion of the dust by a hot surface is
correct, then this effect is not produced in the same way as the repulsion of the
discs of a Crookes’ radiometer when heat is falling on them, but is similar to

FORMATION OF SMALL CLEAR SPACES IN DUSTY AIR. 267

the repulsion of the discs by a hot surface placed inside the radiometer bulb, as
in the apparatus described by Mr Crookes in Nuture, vol. xv. p. 301. In this
radiometer the vanes were made of very clear mica, and they did not rotate
when light fell on them. Inside the bulb, and just clear of the discs, was fixed
in a vertical plane a blackened plate of mica. When the light was allowed to
fall on this fixed and black plate, the vanes instantly rotated as if a wind were
issuing from this surface. The energy which causes the repulsion of the dust
and of the discs of this radiometer is transferred in both cases from the
hot surface to the repelled surface by the kinetic energy of the gas molecules,
and not by radiation. ,

Another consideration which indicates that the force causing the movement
of the dust is not transferred by radiation is the well-known fact that radiant
heat is not much intercepted by dust. When we concentrate a strong beam of
light and heat in dusty air by means of a lens, perhaps one of the things which
strikes us most is the very slight heating effect which is developed at the focus.
The dust is not destroyed, and no rapid upward current is formed. But if we
place a piece of paper at the same focus it is at once charred, and a rapid
current of air rises from its heated surface.

The rate at which vapour molecules diffuse under the conditions existing
in the experiments is very great, and seems to be quite sufficient to account for
the results. Take, for instance, the water molecules when they pass into
vapour. Vapour molecules are selected because we can follow their move-
ments. Ina small fraction of a second they diffuse to a distance of nearly
lem. This can be seen in the experiment described with the flat test-surface
when moistened. With a slight rise of temperature, fog particles are seen
forming in the current, rising in front of the wet surface. Even at the lower
edge of the plate these particles are seen at some distance from the plate, and
separated from it by a dark space, showing that even at that point the
vapour molecules have already diffused outwards to a distance and far beyond
the dark space, while probably other molecules have gone further than the fog
‘boundary, but are under conditions which keep them in the state of vapour.

Or take the reverse of this diffusion process, seen in the evaporation of fog
particles. Let us blow some steam into the dust-box, so as to form a regular
fog, but without adding any dust. Into this fog introduce a piece of very
dry wood; if it is charred so much the better, as its blackness enables us to see
more easily what is taking place. It will be observed that there is formed all
round the wood a clear space, in which not a particle of fog can be seen. If
Wwe watch the air currents we shall see the particles approaching, but vanishing
at some distance from the wood, and over the wood the particles will be seen
falling into the clear space and disappearing. This clear space is caused by
the wood absorbing the vapour in the air near it, thus surrounding itself with

268 MR JOHN AITKEN ON THE

a space of dry air, into which the fog particles evaporate as they approach, and
so rapid is the diffusion towards the wood that the air is kept dry enough to
evaporate the particles as quickly as they approach.

Attraction Due to Cold.

To explain the attraction of the dust particles by cold surfaces, we have only
to reverse the explanation given of the repulsion due to heat. At the cold sur-
face the outward moving molecules of air have less kinetic energy than the
warmer inward moving ones, and the dust is thus driven towards the cold
surface by the greater energy of the hot molecules.

This explanation of the action of hot and cold surfaces may not at first
sight seem satisfactorily to account for the peculiar movements of the dust
particles as they approached the hot wire, in the experiment shown in fig. 13.
We might here ask ourselves, for instance, Why were some of the particles
carried close to the wire, and then driven away from it? The inertia of
the particles is clearly not sufficient to cause them to advance against the force
which produced their rapid repulsion. Then why did they approach so close
to the wire, and then appear driven away with such violence? It looks as if
the particles had become heated to a temperature sufficient to drive off their
occluded gases and condensed vapours, and that the repulsion in this case was
due to the rapid escape of these gases and vapours. No doubt, something
will be due to their escape, but I do not think it is the principal cause of the —
repulsion, because the particles are so small, the gases and vapours will escape
from their surfaces all round them, and their effects will therefore nearly balance.
Further, the escape of these gases will not explain why the particles were
always driven towards cold surfaces. The following seems to be the principal
reason why the particles are always driven sideways and not downwards. The
rate at which a particle of dust will be repelled from the surface of a body is
not necessarily the same in all directions round the body, but will depend on
the closeness of the isothermal lines at the different places; and as in the experi-
ment the temperature varies very much more rapidly towards the cold glass
at the sides than it does downwards, the result is, a more powerful impulse is
given sideways than downwards; and further, the cold glass surfaces diffe-
rentiate the molecular movements near them, and cause an attraction.

Let me illustrate this point further, and show by a parallel case in the action
of gravitation, why it is that the particles of dust when repelled move towards.
the side, and not downwards. Suppose there is a very long, but narrow and
regularly shaped mountain, with its highest point near the middle, and the sides
sloping regularly and quickly to the summit, while the ridge descends slowly.
In ascending such a mountain, we can either go up the long easy slope of th

;

FORMATION OF SMALL CLEAR SPACFS IN DUSTY ATR. 269

ridge, or up the steep sides. Now, suppose a stone to be rolled up the
ridge of this mountain, by a force acting in a direction along the ridge,
it is evident that if the stone gets off the ridge, that it will fall down the
quicker slope towards the side; and if the stone keeps the ridge, and we
succeed in rolling it nearly to the summit, but there meet a slope too steep
for us to push the stone up, then the stone will obviously be in a position of
unstable equilibrium, and the slightest fall will cause it to leave the easy slope
of the ridge, and, once started on the quick descent of the sides, its motion will
be rapidly accelerated in a direction at right angles to that in which we are
pushing ; thus the stone will descend the quick slope of the side with great
velocity, even while the force which pushed it up the ridge is still acting on it.
The direction in which the force now acts on the stone is such that it no longer
tends to prevent it falling; and further, supposing it was directly opposed to
its motion, it would have but little effect against the steep slope of the
side. Now draw the contour lines of this mountain. It will be found that
they exactly correspond to the isothermal lines round the hot wire placed
between the cold plates. The dust and the stone each fall towards the side,
because that is the direction of steepest slope.

General Remarks.

This tendency which the dust in our atmosphere has to move away from
hot bodies, and attach itself to cold ones, will, I have no doubt, help to explain
many phenomena which are not at present well understood. No doubt, many
things will suggest themselves to different minds as receiving their explanation
im this somewhat curious liking of dust for lodging in cold places. Among
other things, it explains the reason why stove and hot-air heated rooms are
always so much dirtier than those warmed by open fires. Ina stove-heated room
the air is warmer than the walls and than the objects in the room, the dust there-
fore tends to leave the air, and to deposit itself on every object colder than
itself in the room ; whereas, in a room warmed with an open fire, the heating
being principally done by radiation, the walls and furniture are hotter than the
air, they therefore tend to throw off the dust, and even when it does fall on them,
it does not adhere with that firmness with which it does to a cold surface, and
any breath of air easily removes it.

Diffusion also, no doubt, plays some part in determining whether dust
shall or shall not adhere to the walls and ceilings of rooms.

Again, a knowledge of this tendency of dust to settle on cold surfaces is
necessary to enable us fully to explain why so much soot adheres to the inside
surfaces of chimneys. If the smoke were cold, so much soot would not settle in
the chimneys, nor would it adhere so firmly.

A simple experiment to illustrate this tendency of dust to leave warm, and

270 MR JOHN AITKEN ON THE

to settle on cold surfaces, is made in the following way :—Take two narrow

strips of glass mirror, any substance will do, but the mirror surface shows the
result best. Arrange so as to hold these strips of glass face to face, and with
their surfaces at a distance of a few millimetres, but before putting them in
their places, heat one of them to a temperature of say 100°C. Have ready
a tall glass vessel, large enough for the glass strips to enter freely. Now
fill this vessel with some dust, by burning sodium or magnesium, or by shaking
up some calcined magnesia or other powder. By the time the air in the vessel
is settled and cooled, but before the dust settles, have ready the glass strips,
one of them hot as directed, and placed in front of the other, face to face,
with an air space between. Now put the mirrors into the vessel among the
dust. After a minute or so examine them. The following will be the result.
The hot one will be quite clean, while the cold one will be white with dust.
That the dust has no tendency to settle on the cold one, may be proved by
putting at the same time in the vessel another cold strip some distance from the
hot one, when it will be seen that this one is almost entirely free from dust,

depending upon whether it was a little hotter or colder than the dusty air.

When one looks at the enormous amount of dust deposited on the cold
mirror in this experiment, we cannot help associating the result in some way
with the condensation of vapours, and it takes some time before we can arrange
our ideas and realise that the thick white deposit was truly thrown out of
suspension and settled on the mirror in the solid state, and was not in the state
of vapour before coming into contact with the cold glass.

A somewhat curious experiment may be made with light calcined magnesia
powder, which shows the action of this force in a marked way. The magnesia
is heated to a good red heat in an iron vessel. If we now take a metal
rod 5 or 10 mm. diameter and heat it as hot as the powder. We may then
dip in into the powder, and stir it as much as we please, but on taking the rod
out, it will be found to be quite clean. But if the rod is cold, it comes
out of the powder with a club-shaped mass of magnesia adhering to it,
so thick that the magnesia-coated end is twice as thick as the rod itself.
If the rod is kept in the hot powder for a short time, and then taken out,
with its coating of powder adhering to it, whenever the powder gets outside
the hot vessel, and exposed to the cold, it falls away, as the inside of the
powder is now hotter than the outside.

Most of us have noticed when heating powders, particularly if they are
light, that while they are heating they take on a peculiar semi-fluid appear-
ance if stirred, or if the vessel is tilted back and forwards. This I have
always supposed was due to the escape of occluded gases from the powder,
keeping it in a state of semi-suspension. Now, however, I think this peculiar
effect is a result of the repulsion due to heating. My reason for supposing this

FORMATION OF SMALL CLEAR SPACES IN DUSTY ATR. 271

is, that if after the powder is heated it is cooled quickly, and again heated
before there is time for it to absorb gases, the same semi-fluid appearance
is again produced while heating. Further, if the powder, instead of being
heated in a closed vessel, is placed in a cup, so that the under side of
the powder is kept hot, while the top is cooled by radiation, so long as
these conditions are kept up the powder retains its fluid-like properties,
moving about on the slightest tilting of the cup, and conducting itself in a way
very suggestive of the spheroidal condition, but without any generation of
vapour to give rise to the irregular movements seen in liquids. It seems
possible that something of the spheroidal condition may receive its explanation
in this repulsion between hot and cold surfaces. This repulsion may be illus-
trated by placing a hot and a cold surface together. A piece of cold glass, for
instance, slides about in a remarkably easy way on a hot surface of glass.

Many practical applications of this attraction and repulsion will no doubt
be found. It might be easily applied to the condensation of those fumes from
chemical works which at present are allowed to pollute the air. But perhaps
the application of most general interest would be towards the prevention of
smoke, or rather the prevention of the escape of smoke into the atmosphere.
Whatever interest, however, it may have in this way, it is clear it can never
meet with general adoption, save under compulsion, as it will effect no saving
in fuel, such as would result from more perfect forms of combustion.

I have, however, made some experiments in this direction, and find that by
placing a tall metal chimney over a very smoky paraffin lamp, surrounding
this chimney with another tube slightly larger, and causing the products of
combustion to rise up the centre tube, and descend through the annular
space between the two tubes, the soot is all taken out, and nothing but a white
Vapour is seen escaping. On examining the tubes after they have been in use

“some time, the inside surface of the inner one is found to be slightly coated
with soot, while its outer surface is perfectly clean and bright, not a speck of
dust on it, and the inside of the outer tube, which is only a short distance from
it, is thickly coated with soot. This arrangement, however, is too complicated,
Save for special purposes.

It has been already stated that the reason why so much soot collects in
chimneys is that the gases are hotter than the sides of the chimney. In cases
where the gases are allowed to escape at a high temperature advantage might
be taken of this tendency. If we simply cooled the smoke in the presence of
plenty of depositing surface, much of its soot would be trapped out, and the
escaping smoke made less dense. The amount that might be trapped in this
way will depend on the extent to which the gases could be cooled.

For works with large chimneys this plan evidently could not be adopted,
and in their case the purification would require to be down at the bottom of the

VOL. XXXII. PART II. 2Y

272 MR JOHN AITKEN ON CLEAR SPACES IN DUSTY AIR.

chimney. The evident objection to this is, that as the gases are cooled in the
depositer, the draught in the chimney will be destroyed. This, however, ca
be avoided by the use of “regenerators.” The impure air would be led toa —
cold regenerator, where it would be cooled and its impurities deposited; and
when purified it would be led through another chamber, where it would be heated
before being sent up the chimney. This arrangement would not require heat to
be spent in working it, as the process would be reversed, and by simply revers-
ing the direction of currents from time to time the heat stored up in cooling
would be used for heating the purified gases before being sent up the chimney,
This purifying process by heating and cooling would require to be done a
number of times, and the air sent through a succession of regenerators before it
could be made perfectly pure.

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XVI.—On Stichocotyle Nephropis, a new Trematode. By J. T. CUNNINGHAM,
B.A., Fellow of University College, Oxford, and Naturalist in charge of
the Marine Station, Granton, Edinburgh. (Plate XX XIX.)

‘J, (Read 5th May 1884.)

The Norway lobster, Nephrops norvegicus, on account of its abundance in
the Firth of Forth, and the consequent ease with which it can be obtained from
the Newhaven market, is given to the practical classes in the Natural History
Laboratory of Edinburgh University for dissection, as an example of the de-
capodous Crustacea. One day in December last, while I was superintending
the work of a class engaged in the study of this animal, one of the students,
whose name I have unfortunately forgotten, called my attention to some glob-
ular protuberances on the intestine of the specimen he was dissecting. At the
time I was unable to answer his questions any further than to say that the

_ protuberances were the cysts of a parasite, and I put the specimen by for sub-
sequent examination. On opening the cysts afterwards I found in them a
small white worm, which proved to be a Trematode possessing novel charac-
teristics. In the following paper I shall describe this parasite, and show that

‘it is so distinct from all Trematodes hitherto known as to constitute a new

genus. On several occasions I had the pleasure of examining the animal in
the company of my friend and former colleague, Mr DuncAN MatTTHEws, and
some of the points in its structure were first noticed by him.

I will first describe the animal as completely as possible, and then deal with
the manner of its occurrence and its relation to other Trematodes.

The worms when taken out of the cysts are elongated and cylindrical in
shape, one surface, the ventral, being slightly flattened; they vary in length
from ‘75mm. to 80mm. They are white in colour and somewhat opaque, so
that there is considerable difficulty in making out their internal anatomy under
the microscope. The body tapers towards each end, the thickest part being
| near to the oral or anterior extremity. The arrangement of the organs is bi-
laterally symmetrical. The mouth is a small simple circular aperture, situated
on the ventral surface, close to the anterior end of the body. Behind it,
along the median line of the ventral surface, is a single row of large muscular
| suckers, which diminish gradually in size towards the posterior end. The
|margins of the mouth are muscular, and its cavity can be dilated and con-
tracted, so as to act as an additional sucker. When the animal is viewed with
| its ventral surface upwards, slightly compressed by a cover-glass, and under a
VOL. XXXII. PART II. | OM:

274 MR J. T. CUNNINGHAM ON

low power, it presents the appearance shown in Plate XX XIX. fig. 1. The
ventral series of suckers is seen along the median line; each of them has a
central depression varying in size according to the state of contraction, and
round this is the projecting rim, in which can be seen the radiating muscles by
which the sucker is dilated. The number of suckers present varies in different
individuals according to their age and size,—the smallest specimens, such as the
one shown in fig. 4, may have as few as 7, the larger usually have 15 or 16,
while in the largest I have counted as many as 22. No doubt specimens
might be found the totals of whose suckers would supply all the intermediate
numbers between these.

The suckers are always more difficult to distinguish at the posterior end of
the series, where they are very small, and they evidently increase in number
at this end, just as the segments of a Chaltopod. It is this approach to meta-
merism which renders the creature specially interesting. The metamerism,
however, does not extend to any of the other organ systems, and consequently
the animal cannot claim among the Trematodes so isolated a position as the
Gunda segmentata, described by LANG, among the Turbellarians. From the
disposition of the system of suckers, I have named the animal Stichocotyle,
adding Nephropis for the specific name, from the name of its host.

The surface of the body is marked by closely set transverse folds, which are
indicated in fig. 1, between the suckers. These folds, seen in optical section,
give the body a crenated outline, which is also indicated in the figure. When
the body is much extended, either by compression or by the muscular move
ments of the animal, the folds disappear; they are probably due to the pre-
sence of an inelastic cuticle, although neither in the opticle nor actual section
of the integument can a separation between cuticle and epidermis be dis-
tinguished. The external layer of the body wall, as seen in optical section
in the living animal, is homogeneous and transparent, and of considerable
thickness.

The most conspicuous of the internal organs are the main canals of the
water-vessel, or excretory, system. These are two in number, one running
down each side of the body through its whole length. Their size, in compari-
son with that of the whole animal, is extremely large; their walls are throwt
into transverse folds. The interior of the canals is crowded with large spherical
concretions similar to those found in the excretory system of other Trematodes
and of Cestodes. These concretions, during the examination of the living
animal, are continually moving with considerable rapidity, the contractions of
the body forcing them suddenly from one part of the canal to another. In the
middle line, between the main excretory canals, is the intestine. From the
mouth can be traced a narrow cesophagus, dilating into a muscular pharynx,
with thick walls, and this leads into an intestine which diminishes slightly it

+

STICHOCOTYLE. NEPHROPIS, A NEW TREMATODE. 2795

diameter towards the posterior end, where it ends blindly. The intestine is
quite simple, and has no branches or diverticula.

When a specimen is examined with its dorsal side upwards, and consider-
ably compressed, the intestine and lateral excretory canals are seen with great
distinctness, as there are no muscular thickenings dorsally to form suckers.
Fig. 2 shows somewhat diagrammatically the view thus obtained. At the pos-
terior end the two lateral canals terminate in muscular portions, which pass in-
wards behind the intestine, and unite to form a single median chamber with thick
muscular walls. This chamber opens in the usual way by a pore on the dorsal
surface, close to the end of the body. The rhythmical dilatation and contrac-
tion of the terminal chamber is very pronounced, and it commonly happens,
when the animal is under compression, that one of the spherical bodies con-
tained in the lateral canals passes into the terminal chamber, and is expelled
from the dorsal pore with some force. The appearance of the terminal part of
the excretory system under a high power is shown in fig. 3.

When the living animal is very attentively examined with an objective of
high power, by careful focussing fine ciliated canals can be made out be-
tween the large lateral canals and the dorsal surface. It is probable that, like
the corresponding fine canals in other Trematodes, these open into the main
lateral canals, and are, on the other hand, in communication with the inter-
cellular spaces of the body-parenchyma; but owing to the opacity of the
tissues, I have not yet succeeded in tracing out these relations. The cilia, whose
motion alone enables one to trace the tubules in question, are of great length,
and are situated on the walls of the tubules at intervals. I have not been able
to discover any “ éntonnoirs ciliés” at the ends of the branches of the system
of tubules, like those described by Fraivont.* I have followed the ciliated
tubules sometimes for considerable distances. Their course is somewhat irre-
gular, but maintains a longitudinal direction. They branch occasionally, but
the branches never extend into the median region of the body above the intes-
|time. I have not found any tubules on the ventral side of the body, but they
| extend forwards beyond the anterior limit of the main lateral canals.

Ihave now described the general disposition of the digestive, excretory,
and integumentary systems of the animal, and have hitherto mentioned nothing
| which cannot be made out in living specimens. No reference has been made
\to the generative or nervous systems. In the stage of the animal’s history’
| which is passed within the body of Nephrops neither of these systems is
jdeveloped. I shall refer to structures which may be their rudiments. Special
Sense organs are altogether absent.

In order to examine the histological structure of the tissues, I have pre-

* “ Rech, sur l'appareil excréteur des Trém. et Cestoides,” Junin Fratpont, Are. de Biologie, Tom. i.
1880,

276 MR J. T. CUNNINGHAM ON :

pared transverse sections in continuous series from specimens preserved with
picro-sulphuric acid, and stained with borax-carmine. The specimens chosen
for this purpose were of the medium size, carrying about 16 suckers. The
sections are all very similar to one another, differing chiefly in the relation
which they bear to the series of suckers. In one taken from the middle of the
series, the intestine is seen in the centre, elliptical in outline, the long axis of
the ellipse being dorso-ventral. The epithelium of the intestine is thick, and
composed of large nucleated cells, which form sometimes more than one layer,
and are not quite regular in arrangement. Both in the living animal and the
prepared section it can be seen that the cells of the intestinal epithelium are
rapidly proliferating ; the free ends of the cells project into the lumen in various
degrees, and a number of detached cells are seen lying free in the interior, |
In the living animal these cells float about under the influence of the move-
ments of the body, and are occasionally expelled from the mouth. Some of
them contain minute round granules.

On each side of the intestine is the section of one of the main lateral
excretory canals, in which there is no distinct epithelium to be seen. There
are nuclei in the walls, and the cavity may be lined by an epithelium of ex-
tremely thin cells, to which these nuclei belong. The walls of the canal are
extremely thin.

The parenchyma of the body, or mesenchyma, appears in the sections as a
fine reticulum with deeply stained nuclei at the nodes. The actual structure of
the mesenchyma in Trematodes has been much disputed,* some observers
maintaining that the intercellular spaces are globular and the cells stellate;
others, vice versa, that the cells are globular, and the intercellular spaces reticu-
late. In the living Stichocotyle the mesenchyma is seen to be crowded with
minute bright refringent granules, which seem to be contained in intercellular
spaces, as they move through considerable distances in parts of the animal
which are in active contraction. They are shown in fig. 3.

The muscular layers of the body wall are imperfectly differentiated; they
are represented by a zone of closely crowded nuclei at the periphery of the
mesenchyma, and, external to this, a zone of small dots, which are probably.
the sections of longitudinal fibrils. The account of the muscular layers of the
integument in the young of Amphilina, given by SALENsky,t agrees pretty

there are no nuclei.
The sucker is composed chiefly of elongated cells, whose long axis is per-
pendicular to the epidermis. These are simple muscular cells which dilate the

* Vide Fratpont, loc. cit., p. 428.
{ Zeit. f. wis. Zool., Bd, xxiv., 1874.

STICHOCOTYLE NEPHROPIS, A NEW TREMATODE. 2G

cavity of the sucker. Nuclei are scattered through the tissue, each cell pro-
bably possessing one. The muscles which contract the cavity of the sucker are
not so conspicuous. The tissue of the sucker is separated from the tissues of
the body by a thin limiting membrane, which is continuous at its periphery
with the limiting membrane of the epidermis. This is an arrangement which
is not easily explained, as, the muscles of the sucker being probably a special-
isation of the ordinary muscles of the body wall, it would be expected that the
continuity between the two would be maintained.

Beneath the lateral excretory canal of the right side, in the anterior sec-
tions, is an area occupied by very closely crowded nuclei. This can be traced
through successive sections of the series as far as the end of the fifth sucker.
It passes from its first position, under the right main canal, to the left side of
the same canal, at the same time becoming thicker, and towards its termination
becomes so broad as to extend beneath the intestine from the right canal to the
left. There is thus an irregular cord of small unmodified cells extending
through a considerable part of the length of the body, and it is possible that the
generative organs of the adult are derived from this.

The most external layer of the body representing the epidermis and cuticle,
is in sections, as in the living animal, quite homogeneous. I have not yet been
able to distinguish in it either nuclei or cell boundaries, or a separation between
epidermis and cuticle. The layer becomes thinner where it lines the cavity of
the sucker. In the living animal small funnel-shaped openings are seen in the
epidermis, which may be the apertures of glands, but as they are not visible
in the sections it is possible that they are only fractures produced by com-
pression.

The only trace of tissue which may belong to the nervous system is a tract
composed of very fine fibrils in some of the sections anterior to the mouth.
This tract forms a band extending horizontally across the body near to the
dorsal side. ‘The fibrils of which it is composed are extremely minute, and the
whole tract is destitute of nuclei. It is shown in fig. 6, and may represent the
cerebral ganglion. <A pair of processes from this mass of tissue can be traced
through the succeeding two or three sections, which are probably the rudiments
of a pair of lateral nerve-cords. They pass downwards towards the under side
of the main excretory canals.

The cysts in which the animal occurs are scattered on the extremely thin
| walls of the posterior part of the intestine of Nephrops, in the region of the
abdomen. They sometimes contain more than one worm, as many as six
having been taken by Mr Marruews on one occasion from a single cyst.
| Usually the wall of the cyst is soft and opaque, and white or light yellow in
colour. It is of a cellular nature, and is apparently a pathological product of
the tissue of the intestine of the host.

278 MR J. T. CUNNINGHAM ON

The cysts vary in size with the age and size of the worm within, and the ©
youngest and smallest ones are brittle and dark brown in colour. <A very —
young worm taken from such a cyst is shown in fig. 4. It has only seven —
suckers. The worm in all cases, when placed on a slide in a little water,
exhibits movements of contraction and extension, and coils or straightens its —
body, but is not able to travel over much space. When an infected crayfish is
opened which has been twenty-four hours out of water, the worms are often
found to have escaped from the cyst, and are found lying on the muscles; but
I think this does not take place while the Nephrops is living. The number of
cysts varies considerably. I have sometimes found them covering the posterior —
part of the intestine completely; and in other cases only two or three of the
very smallest brown cysts were present. The diameter of the cysts varies from
‘5mm. to2or 3 mm. I have taken as many as forty worms from a single
Nephrops. ,

The proportion of specimens of Nephrops infected is not small. In one
case I found three out of eight contained the parasite. Usually out of a dozen
opened three or four are infected; but sometimes a dozen may be searched
without a single parasite being found. My observations have extended now -
over nearly four months, and I have not yet found any variations in the state of
the parasite. .

I have not found the parasite in any other part of the body of Nephrops
except the intestine; and I have no evidence to show whence it is derived,
what is its mature state, or in what conditions its adult stage is passed. ,

It seems probable that the eggs are taken into the stomach of Nephrops_
with its food, and that an embryo escapes from the egg, which pierces the wall
of the intestine, and there develops into the stage of the worm which I have
examined. The further development most likely takes place in the body of
some large fish which feeds on Nephrops; but hitherto no 'Trematode is known.
living inside the body of a marine fish except the Calicotyle Kroyeri, which is
found in the cloaca of rays, and Encotyllabe Pagelli in the mouth of Pagellus
centrodontus,*

In passing on to consider the affinities of the parasite, it may be set down
as obvious that it is in every respect a typical Trematode. The characters of
the water-vessel system and of the suckers could not be found outside that
class. But the arrangement of the suckers is entirely novel. A serial arrange-
ment of the suckers is not uncommon among Trematodes; but there is no
other genus in which they form a single series extending along the median
ventral line through nearly the whole length of the body. The series when
present is usually double. Microcotylet has in the posterior third of its body

* Van Benepen et Hesse, Mém. Acad. Roy. de Belg., Tom. xxxiv.
+ Ibid.

STICHOCOTYLE NEPHROPIS, A NEW TREMATODE. 279

a series of small suckers on each side. They are very numerous, and all of the
same size. In Octocotyle* there are, near the aboral extremity, four pairs of
lateral suckers, one pair behind the other. The suckers of Gastrocotylet form
a single series along the edge of a projecting membrane on the right side of the
body. Ernst ZELLER describes a serial repetition of pairs of suckers as an
occasional abnormality in Diporpa.{ At the posterior extremity of this genus
there is a pair of large suckers forming divergent projections. ZELLER met
with a specimen in which the single pair was replaced by three pairs, one
behind the other. In all these cases the suckers are provided with chitinous
hooks, as in nearly all the Polystomide. Stichocotyle is without chitinous
armatures in any part of its body. Until the adult form is found and its
anatomy examined, it is impossible to say anything more definite about the
position of Stichocotyle than that it belongs to the Polystomide, though it
differs from all other Polystomide in passing through an encysted stage within
the body of another animal.

I hope before long to trace out the whole life history of this interesting
form, as at the Granton Marine Station I shall have good opportunities for
carrying on the search after its earlier and later stages. In concluding the
present account I have to express my warmest thanks to Dr ArnoLp LANG, of
the Naples Zoological Station, who kindly sent me some valuable suggestions
and references.

EXPLANATION OF PLATE XXXIX.
Letters of Reference.

bis. Cord of blastema.

cz. ca. Ciliated tubules of water-vessel system.
CO. Spherical concretions in lateral canals.
ep. Epidermis and cuticle.

e. ap. External aperture of water-vessel system.
jf. ce. Free cells in lumen of intestine.

gl. Openings of dermal glands (?).

ont. Intestine.

int. ep. Epithelium of intestine.

1. ca. Lateral canals of water-vessel system.

me. Mesenchyma.

mu. su. Muscles of sucker.

mM. Mouth.

me. gr. Granules in mesenchyma.
ne. Cerebral ganglion.

ph. Pharynx.

Sil. Series of suckers.

te. ch. Terminal chamber of water-vessel system.

* Van BENEDEN et Hussz, Mém. Acad. Roy. de Belg., Tom. xxxiy.
+ Ibid.
t Zeits. f. wiss. Zool., Bd. xxii. 1872.

280 MR J. T. CUNNINGHAM ON STICHOCOTYLE NEPHROPIS.

Figs. 1, 2, 3, 4 were drawn from fresh specimens. All were drawn without the aid of a .
lucida, ;

Fig. 1. Ventral view of Stichocotyle, as seen under slight pressure.
Fig. 2. Optical section of the whole animal, seen with dorsal surface upwards.

. 4. Very young specimen, with seven suckers. Se
Fig. 5. Transverse section, passing through middle of first sucker of moderate-sized specimen. |
Fig. 6. Section through pre-oral region of same specimen,

iy
2.
Fig. 3. Optical section, showing termination of water-vessel system.
4.
5.

's. Roy. Soc. Edin?

Vol. XXXII, Pl. XXXIX.

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XVIL—The Enumeration, Description, and Construction of Knots of Fewer
than Ten Crossings. By Rev. THomas P. Kirkman, M.A., F.R.S. (Plates
XL,-XLIIT.)

(Read June 2, 1884.)

1. By a knot of 7 crossings, I understand a reticulation of any number of
meshes of two or more edges, whose summits, all tessaraces (ax7), are each a
single crossing, as when you cross your forefingers straight or slightly curved,
so as not to link them, and such meshes that every thread is either seen, when
the projection of the knot with its m crossings and no more is drawn in double
lines, or conceived by the reader of its course when drawn in single line, to
pass alternately under and over the threads to which it comes at successive
crossings.

The rule for reading such a reticulation of single lines meeting in tessaraces
only is this—Coming by the edge or thread pg to the tessarace g, you leave it
by the edge of g which makes no angle with pq, nor is part of thread under or
over which you pass at gq.

2. It is not necessary, after what Professor Tair has written on knots, to
prove that every reticulation having only tessarace summits, whether polyedron*
or not, if it be one continuous figure and projected to show all its crossings and
no more, can be read all through by this alternate under and over, so that all
_ its closed circles, one or more, can be written down in numbered summits, and
that the knot can be labelled as unifilar, bifilar, or trifilar, &c.

3. If a thread @ of a knot, after passing under or over a thread J, passes
over or under b before it meets a third thread ¢, there is a linkage of two cross-
ings and a flap between them. This flap is the small eyelet seen between two
links of a slack chain as it lies on the table: it is a 2-gon, a mesh of two edges
and of two crossings. Here see art. 9.

4. In our enumeration of knots of n crossings, two, C and CO’, are counted
as the same one, whenever and only when, in the number, polygonal rank, and
order of their meshes C’ is either the exact repetition or the mirrored
image of C; and I consider the threads of all the circles of a knot to be tape
untwisted.

5. Nothing general seems to have been written upon knots of more than
seven crossings. Nor, fortunately for the claims of those knots upon the inte-

* J hope to be pardoned for omitting the 2. It annoys me to hear the learned say polyhédron.
Why not perthodic also? or, more learnedly, perthodic ?

VOL. XXXII. PART IL. ok

282 ~REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

rested attention of the student, has unanimity been even so far secured. In
what Listinc and Tair have contributed to this theory, there is an affirmation
of identity, or of equivalence, denoted by the symbol =, between two knots of
seven crossings which, by the above definition of sameness, are as unlike as
they can be. This, of course, is due to a mere difference in definitions. The
right definition in the view of Listinc and Tair I find not easy to seize, and I
cannot work on reticulations between equivalence and identity, nor pause to
consider the deformations of a knot A into an equivalent knot B that can be
effected by twisting the tape of A. I content myself by exhausting the forms
that differ according to my definition; and I leave to a more competent hand
the reductions to be made by twisting.

6. The reader will judge for himself whether the number of different unifilar —
knots of seven crossings is twelve, as I am compelled to believe, or at —
most eight, as Tart prefers to say. Whatever be the decision cf the reader,
I am highly delighted, while attempting to write on a theme so dry and tire-
some, that we have, at the outset, such a pretty little quarrel as it stands —
wherewith to allure his attention.

7. Every polyedron which is an n-acron having only tessarace summits is a_
solid knot of ” crossings, on which is neither linkage nor flap. Such a knot
can be projected on any of its triangular or m-gonal faces, so as to show all its
m crossings, and no more, within that face or at its summits. It has no linear
section, @.é., no plane can cut it in space, nor can any closed curve be drawn
upon lines of its projection, without meeting it in more than two points, on edge
or at crossing.

In a knot which is no polyedron, we call a section that meets it in only two
projected summits or crossings, linear, as passing through two points only of
the figure; although no crossing of a mesh in space can be cut through its —
opposite angles without making four ends.

8. No projected knot, solid or unsolid, can have a linear section through
one edge &/ only, and through one crossing g only. For, if it can, let the two”
threads at g on the left hand of the section be pq and 79, pq passing over 7'¢ at
q; then pq at the crossing p passed under a thread, and rg at 7 passed over one.
Cut at g, making four ends; reunite into one thread 7p the two ends on the
left ; this shortened thread passes over a thread at * and under one at p, as
before, and its further course is unaltered in either direction. The same is”
true of the shortened thread made by reuniting the two threads on the right of
the section, /"

The figure is now the projection of a knot of n—1 crossings having two
portions, L on the left and R on the right, which are connected by a single
thread 4#/, the law of under and over being observed in both L and R.
The course of the thread 4/, pursued along its circle small or great through R

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 283

from # upon R, must bring it back to 7 upon L through L. But this is clearly
impossible from want of a second connecting thread ; which proves the proposi-
tion.

9. Knots Solid, Subsolid, and Unsolid.—A. solid knot is a polyedron,
art. 7.

Subsolid knots admit of no linear section but through the two crossings of
a flap; through the projections of these a closed curve can be drawn meeting
the knot in no third point.

The projections of an unsolid knot admit one or more linear sections either
through two crossings not on a flap, or through two edges coming from two
crossings not on the same flap.

If a projected unsolid V admits a hnear section through two edges coming
from two crossings on the same flap, V is made up of two portions, K and L,
connected like two links of an ordinary chain, so that K (or L) can be set free
in its completeness by breaking only one thread of the other. No knot V
constructed in these pages is such a compound of K and L. Such a compound
is easily drawn; in such a V either K or L can be slipped along the thread of
the other, without twisting a tape, so as to occupy, if the other be unifilar, any
position upon it. All our unsolids are composite; but no severing of a single
_ thread will ever set free on one of them a portion which is a complete knot.

Of solid knots we are not treating. If the apparent dignity of knots so
maintains itself as to make a treatise on these m-acra desirable, it will be no
difficult thing to show in a future memoir how to enumerate and construct

‘them to any value of x without omission or repetition. The beginner can
amuse himself with the regular 8-edron, which is trifilar, or with the unifilar of
eight crossings made by drawing within a square a square askew, and filling up
with eight triangles.

10. I consider a knot as given by its projection upon and within any one,
2-gonal or m-gonal, of its meshes drawn large, and as having the symmetry of
that projection. Nor do I trouble myself with inquiring how far that symmetry
is affected by the law of under and over at the crossings, because, in reading
the circle or circles of a projected knot, we can take any crossing q as our first,
and can on beginning to read take either of the threads at g as passing under
and over the other. A knot in space can be read only as given.

In my description of the symmetry of our reticulations, I shall assume that
| the reader understands the terms employed. They, with others not wanted
here, are necessary and sufficient ; they are the only such terms that ever have
been proposed; and, for more than twenty years since they were introduced,
no more suitable terms have offered in their stead. Iam quite ready to use
better ones when they are invented. The symmetry, however, of the figures
handled in this paper is of itself so evident that the reader will easily satisfy

284 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

himself, without debate about the terms employed, as to the truth or error of
my enumerations.
11. All that we need to add here is on the symmetry of flaps, which are
2-gons, correctly drawn as two curved lines through the same two points.
A flap has the symmetry of its undrawn diagonal d through its two cross-
ings, and may be conceived as standing symmetrically about d, in either of two
planes at right angles to each other, which contain d. This d may be asym-
metric, or epizonal, or zonal, or zoned polar, or zoneless polar ; and the flap is
accordingly asymmetric, or epizonal, &c. The two edges of a flap are unlike
only when it is asymmetric or epizonal.
In a zonal flap, a single zonal trace passes through the two crossings ; in an —
epizonal flap, a single zone passes between the crossings. In a zoned polar
flap, two zonal traces intersect in the centre, the termination of the 2-zoned
axis.
In the centre of a zoneless ere flap, an axis of 2-ple repetition termin-
ates.

3A and ,A have each one zoned polar flap.

;A has one epizonal flap.

gf has one epizonal and one asymmetric flap.

«@ has two different polar, and one zonal flap.

gH has one zonal flap and no other.

so and ,Q have each one zoneless polar and one asymmetric flap ; so has ,Aj.
sAk has one asymmetric flap and no more,

sAm has one zoned polar flap and none other—art. 45.

gb has one epizonal, two zonal, and one asymmetric flap.

3bg has one zoned polar and one asymmetric flap,

,bu has three zonal flaps only.

gbv and ,Bw have each one epizonal and two asymmetric flaps.
gby has one zoned polar and one zonal flap.

12. The construction of polyedra and of other reticulations of summits is

best apprehended by studying their reduction by fixed rules to antecedents or
bases of 2-7 summits. We proceed to the reduction of knots.

Reduction of an Unsolid Knot Q of n Crossings.

In this are two processes,—the clearing away of concurrences, and
removal of least marginal subsolids.

13. Concurrences.—Two or more continuous flaps, each having a crossing
common to the next, are a concurrence of two or more, except when two 0
three flaps are collateral with the same pierre mesh, Three such omy i

dba’ a concurrence. a

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 285

When a concurrence of n stands about the (n+ 4+2)-gonal mesh F, their
common collateral, F is reduced by deletion of n—1 flaps, each conceived to
vanish by the union of its two summits, to the (£+3)-gon F’, carrying one only
of those flaps.

If their collateral F is an (n+ 1)-gon, it is reduced by the vanishing of » —2
of the concurrent flaps to a triangle f carrying the remaining two. This f cannot
lose a flap without losing an edge and disappearing.

Every concurrence on the unsolid Q of art. 12, whether standing on a
marginal or non-marginal component of Q, is to be thus reduced, and Q now
becomes an unsolid Q’ without a concurrence, of m —7 crossings.

14. Least Marginal Sections and Least Marginal Subsolids.—Our unsolid Q’,
obtained by deletion of 7 flaps, has one or more /inear sections, marginal or not.

By a marginal linear section of Q’ can be cut away one and only one
marginal subsolid, on which (art. 9) lies no linear section except through the
two crossings of a flap.

By a least marginal section of Q’ can be cut away a least marginal subsolid.

A marginal subsolid of & crossings all untouched by any possible least
section, is a least marginal, when no marginal subsolid of fewer than / cross-
ings untouched by the section can be cut away from Q’ by any kind of section.

15. The Five Kinds of Linear Section of an Unsold Knot.—These are,

fc, which is read, flap on flap close ;

t ss s flap on flap ;

eee 15 F flap on edge;
ef, i, o edge on flap ;
Covet ssi » €dge on edge.

The first letter in these symbols denotes the flap or edge of the least
marginal subsolid cut away from, or in construction imposed on, the unsolid or
subsolid charged.

16. The linear section fc is the only one that passes through two crossings.
After making the section jc, there is a pair of truncated crossings, both on the
diminished @’ and on the subsolid removed. These are completed into
tessaraces in the severed portions by replacing each portion on the other by the
two pairs of edges of two flaps, at the cost of which two flaps the portions were,
in construction at the section 7c, united to form Q’.

These pairs are conceived to be so united to the broken threads at the
| truncated crossings as to complete both the severed portions into two knots.
This can always be done, and needs not trouble us, when we are reducing a
projected figure of simple lines making tessaraces only.

If the subsolid S removed at this section jc has, when completed by its
restored flap, / crossings, the n—7 crossings of the undiminished Q’ are made
fewer by s—2; for Q’ has lost only the crossings of S not on the section.

286 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

This S in construction of Q’ was counted as a least marginal charge of /—2
crossings. Two crossings are always lost when in construction a subsolid
having / crossings is imposed at a section je.

In reduction at this section je, this S is a least marginal subsolid of s—2
crossings along with others of /—2 removed by any section ff; fe, &c.

17. Our unreduced Q’ of n—7 crossings may have in it every kind of least
marginal section, art. 15. Such section, not fc, always cuts two edges, making
four ends. In every case, ff, fe, ef, or ee, those pairs of ends are conceived to
be united on either hand into one edge, by which is restored the half-flap or
the edge cut away in each portion when united by construction, in order that
every summit should be a tessarace in the completed unsolid.

The imposition of a least marginal charge by je costs four edges of two
flaps; by 7; fe, ef, or ee it costs only two edges, one on each of the united
knots. |

No crossing is lost when a charge is imposed by a section f% fz, ef, or ee.
All this will be found very clear and easy when we come to constructions, and
examples will abound.

18. In this reduction of Q’ all least marginal baibiahiae say of / crossings,
are to be removed without regard to the number of their meshes, which may —
differ while each has added & crossings. And care is to be taken that none is
cut away which has been loaded with another either on flap or edge, and thus
made non-marginal.

When our Q is thus reduced, it has become Q, an unsolid of x—y crossings

(/>?).

This Q, will in general have one or more concurrences due to the flaps sub-
stituted for subsolids removed. All these are to be cleared away (art. 13),
whereby Q, becomes Q;, an unsolid without a concurrence; and Q) is to be —
treated as we treated (’ in art. 14.

We shall finally arrive by these reductions either at an unsolid of two
portions, neither of which is least, which is to be reduced by a final section to
two subsolids each of ¢ crossings ; or at a ring of flaps which is reducible to the
fundamental ,A ; or to a nucleus subsolid or solid knot. We have now to set
about the reduction of subsolids.

19. Reduction of a Subsolid of n Crossings by its Leading Flap.—The rule
is—Remove both edges of a leading flap, or of a leading flap when there are_
co-leaders. By this removal, the two meshes covertical with the deleted flaps
lose each a crossing; and if one or both coverticals are triangles, that one or
both become flaps. The result obtained is a subsolid of m— 2 crossings.

20. Every flap can be written AB,CD, where A and B (ASB) are col-
laterals, and C and D (CSD) are coverticals, of the flap. |

We compare first the collaterals of the flaps whose leader is to be found,

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 287

If A,B,, A,B, &c., are the pairs of collaterals, the leader has the greatest A, no
matter what be the coverticals. If several flaps have the greatest A, the leader
has the greatest B. If several have both A and B greatest, we compare co-
verticals. If one has the greatest C, it leads; if more than one, the greatest D
gives the lead. If no leader can thus be determined, we have to examine the
collaterals of the A’s. The leader has more than any other of the greatest of
these collaterals; and so on we go over the collaterals of the B’s, the C’s, and
the D’s. The leader, if there is only one, is certain to be found.

I have never had occasion to examine the collaterals of AB,CD. If two
competitors have these all equal, it is almost a certainty that there is symmetry,
and no leader, but a set of co-leaders. Where there is no symmetry, no two
edges or flaps on a knot are alike.

It suffices, after writing two or more flaps as equally claiming by their AB,
CD to lead, to place a note of interrogation, and to examine the symmetry,
which readily betrays itself. The deletion of any one of the co-leaders com-
pletes the reduction.

A flap can neither be removed from a knot nor added to it without cutting
of threads and reunion of ends. But this does not trouble us here, as by art. 2
we know that every projection making tessaraces only is a true knot, that its
circles can be read by the rule of under and over, and that the threads of all
the circles can be drawn in double lines as narrow untwisted tapes visibly
passing under and over at alternate crossings.

21. In the converse problem of construction, the question is, in how many |
ways to add, on a knot P’ of n—2 crossings, a leading flap, so as to construct
without risk of repetition a subsolid of m crossings. The note of interrogation
written after the comparison of two flaps that can be drawn across two meshes
of P’ is a presumption of symmetry, which is pretty certain to be verified when
we come to draw in turn our new flaps on P’, and to examine the constructed
P of n crossings as to the leadership of the doubted flap which turns P’ into P.

22. Two things are to be noted here, both in reduction and construction.
Ifa flap f on any subsolid is covertical at its crossing @ with a triangular mesh
abe, which carries a flap /’ on the edge dc, since abe cannot lose a crossing by
the deletion of /, it thereby becomes itself a flap f” collateral with the flap /”.
Now a pair of collateral flaps is excluded from all our constructions, because it
is a circle of two crossings, whose projection represents nothing in space but a
| movable ring through which one thread once passes. Wherefore the flap /is
indelible or a jived flap. It cannot be removed, nor be a competitor for the
lead, either in reduction or construction.

When two flaps are collateral with the same triangular mesh, both are jized ;
for the deletion of either leaves the other hanging by a nugatory crossing which
admits a forbidden punctual section. The reader can easily verify this.

288 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

By continuing this reduction of a subsolid by removal of the leading flip, we
must at last arrive either at a solid knot, or at one of the two irreducibles ,A
and ,A, of three and of four crossings.

23. Construction of Knots of n Crossings—The rules for this are the exact
converse of those above given for reduction.

First, to construct the subsolids of n crossings, all inferior knots being given
with their symmetry, we have in the first place to take in turn every subsolid
P’ of n—2 crossings, and to determine before we draw them the different lead-
ing flaps that can be added on P’. Knowing its symmetry, we can write down
and mark on its edges every different pair of points on flap or edge that can be
joined as the crossings of a new flap, and also the collaterals and coverticals
which this will have. We make a table of the possible leading flaps, with the —
notes of interrogation that presume symmetry in the P of m crossings to be
built on P’. Next we draw the leading flaps, thus constructing and registering
the resulting subsolids P.

A caution is required here, for the examination of the claim of a new flap,
ab=8M, to leadership ; a and 0 being the crossings of the flap, when one of its -
collaterals is a triangle abc. If ¢ in this triangle is the crossing of a flap cd, ed
becomes fixed (art. 22), for it is covertical with a trianglegsab, which carries a
flap on its edge ab. Care must be taken to exclude this flap cd from claim to —
leadership over ab.

I was caught in this trap in the art. 41, for I had entered the flap (dd) as
led by (56), and thus missed the unifilar ,G. Professor Tarr found this knot, —
adding one to my first list of 8-fold knots, He first found also the unifilars
»Al, Ak, and ,Bg, omitted by a like error in arts. 51 and 56. He also first
found ,Dm, which I ought to have constructed along with ,D/ in art. 61.

24. In the second place, we take in turn every unsolid P” of n—2 crossings
on which a leading flap or flaps can be drawn so as to abolish all concurrences,
and to block linear section. Such leading flaps will be few. Next we draw
them all, and thus complete without omission or repetition our list of subsolids”
P of a crossings. This. list is. the only difficulty of our work ; what follows is
for every value of m all easy routine, as we shall see; but it soon becomes toe
tedious. by the enormous number of results to be registered and figured.

25. Next, to construct the wnsolids of n crossings which have no concurrence,
we impose in the first place on the solids and subsolids, and in the second on —
the unsolids, of »—7 crossings, each taken in turn as the subject Q’ to be

pleting an unsolid Q of 2 crossings. without a concurrence.
The ¢ charges may be all or none alike, or all but one alike, &. ; and from
our list of subsolids of & crossings must be selected with or without repetition

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 289

every possible set of e charges. These, as well as their reflected images when
required (although such images are neither registered or figured by us), have to
be imposed in every different posture, by every kind of possible section, jc, 7
&c., on every different set of ¢ flaps or edges that can be selected on the subject
knot, and in every different order that symmetry permits without repetition of
results (art. 4), so that when the work is done not one of the unsolids Q of n
crossings shall have a least marginal subsolid besides the e that we have just
imposed, nor have a concurrence upon it.

26. The linear sections by which the charges are imposed may be any of the
five of art. 15. But, observe, when we use the section /f¢, we are to select the
charge from our list of subsolids of /+2 crossings ; because (art. 16) two will
be lost. For other sections our selection of the charges will be from those of
k crossings.

27. The number of different postures in which a charge can be imposed on
Q’ depends on the symmetry of the united portions of the Q completed by the
union. Let « denote the edge or flap of the subject and ¢’ that of the charge in
all the five sections fc, 77, fe, ef, ee. The rules are three—

(1) If one or both of « and & be zoned polar, only one configuration is pos-
sible by the union; no second and different (art. 4) can be formed by turning
the charge C through two right angles about ¢’, nor by using C’, the reflected
image of C, when C is not C’.. Every knot on which is a zone is its own
mirrored image.

(2) If neither e nor < be zoned polar, and if they are not both asymmetric,
two and two only different configurations can be made by the above variation
of posture of the charge.

(3) If both « and ¢ are asymmetric, four different configurations can and
| must be made and registered, due to such variation.

No more results can be obtained by putting for Q’ the reflected image of
Q’: nothing is so attainable but repetitions or reflected images of knots already
Tegistered.

On almost every subject Q’ and charge C, though having any symmetry,
may be found asymmetric, 7.¢., zoneless and non-polar, flaps and edges, which
are to be dealt with by the above rules.

28. The subject Q’ to be charged with a set of least marginal subsolids may
have or not have concurrences. All that is required in order that the com-
pleted Q shall have no concurrence, is that our number e of charges of &
crossings shall be large enough to spoil all concurrences on Q’, as well as to
cover at least once every marginal subsolid on Q’ which has fewer than +1
crossings.

In the constructions of this paper, Q and C are one or both symmetric.
When asymmetrics come to be handled both as subject and charge, the number

VOL. XXXII. PART. II. 3B

290 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

of results becomes unmanageably vast long before m the number of crossings is
out of its teens.
29. The jinal operation, after construction of all knots of » crossings with-
out concurrences, is to take every subsolid and unsolid R in our lists which has
m—c crossings and no concurrence, and to add to it in every possible different
way ¢ flaps making with one or more on R concurrences of every possible
number of two or more flaps, thereby adding ¢ crossings, and completing the
number 2. This last operation soon becomes impracticable from the number
of results.
30. Nothing can be here added that will give so much insight into our
subject as the actual construction of knots, to which we now proceed, first to
that of subsolids, and next to that of unsolids of the number 7 in hand of —
crossings. :
_ Two Fundamental Subsolid Knots.—The only subsolids that cannot be
reduced by deletion of a leading flap (art. 19), are those of three and of four
crossings. These, ,A and ,A( vide Plate XL.), are irreducible and fundamental.
3A is a 3-zoned monarchaxine, whose principal poles are triangles not plane,
which have three common summits and no common edge.
The unsolid ,B is formed on ;A by art. 29, and has a symmetry of like
description. The secondary 2-zoned poles on either are alternately flaps and —
erossings, being heteroid poles in ;A and janal in ,B.
31. Subsolid and Unsolids of Five Crossings.—The subsolid must be built on
3A. The only points that can be here joined by a flap, are either on one flap of —
3A or on two. We cannot obtain a subsolid by joining the former pair, because
the constructed knot would be an unsolid having a concurrence of two (art 13).
We join the latter pair, and it matters not whether we draw our flap in the
upper or in the lower of the two triangles whose summits are the same three
crossings, and whose edges are different halves of the three flaps of ;A.
Drawing the flap 54, the two flaps of ;A connected by it become triangles, and
sA is constructed, a 2-zoned monarchaxine heteroid, whose zoned poles are a
tessarace and an opposite tetragon. ‘This is the only subsolid of five crossings.
The unsolid ;B is by (29) formed on ,A, and ,C is made on ,A.
32. Knots of Six Crossings.—The subsolids ,A, &c., must be formed on ,A
and ,B. This ,A has a janal 2-zoned axis through thie
z centres of the flaps, and two like 2-ple janal zoneless axes
through two pairs of opposite mid-edges. It has only one
mesh, the monozone triangle 342, and the only pair of point
that can be joined are 5a and 56.

Drawing 5a, or rather conceiving it drawn, we write

» to determine the leading flap,
(5a)=43,43 ; (12)=43,43; (5a)>(12)?

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 291

This is read thus—the flap on 5a has for collaterals 3 and 4, and for coverticals
3 and 4; so has the flap on 12: which leads ?
Next, conceiving 56 drawn, we write,

(56)=43,44; (12)=44,43; (43)=43,44.

Here by art. 19 (12) appears to be leader, until we observe that it is fixed by
art. 22, and cannot be a competitor.
We therefore write more correctly,

(56) =43,44>(43)=43,44 ? (12) is fixed ;

which inquires, Does (56), which is 43,44, lead (48), which is also 43,44?
We consider this second as well as the preceding note of interrogation a pre-
sumption of symmetry (art. 21).

Drawing the flap (5a) we obtain ,A, and the flap (56) gives us ,B, on both
of which the leading flap so drawn is marked 56. Observe that in our figured
subsolids of m crossings, the leading flap is always marked n(n—1). Our pre-
sumptions of symmetry are verified in the two results ,A and .B.

The polar edges of the heteroid zoneless axis of ,A are evident in the figure.
The two-zoned axis of ,B has for faces a flap and an opposite 4-gon. The
other two flaps of ,B are like epizonals.

It was possible to connect by a flap the two edges of the flap 43in,A. But
this could have completed an unsolid having a linear section through 3 and 4;
and completed it wrong, because no unsolid is ever made by so adding a flap.

33. We next take the unsolid ,B, considering whether or no a flap can be
drawn on it to make it a subsolid of six crossmgs. Readily we perceive that
by joining two opposite flaps we can both spoil the concurrence and block the
linear section. This gives us ,C, which has all the symmetry of the wedge which
it becomes when an edge is removed from every flap. The three, ,A ,B and .C,
are all the subsolids of six crossings.

34. We seek now the unsolids of six crossings. To obtain them by least
marginal charge or charges (art. 25), we have to lay 2 upon 4 and 3 upon 3.

There is but one charge that can add two crossings only, ,Afc, which means
4A imposed (art. 15), by the section fv. Imposing this on ,A we get ,.D, a zoned
triaxine, whose three janal 2-zoned axes have for poles, one two tessaraces,
a second two flaps, and the third two 4-gons symmetrical but not plane, which
have two common summits and no common edge.

Laying next on ;A the charge ,A/ (art. 15), we obtain ,E, another zoned
triaxine, whose janal poles are two edges, two tessaraces, and two hexagons
alike and non-planar. There is in truth no least marginal subsolid in either
sD or .E, the two halves of the knot being identical in each. But it is instruc-

292 REV.T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

tive, and involves no error, here to consider them as cases of the linear sections
fe and ff.

35. We have constructed all the knots of six crossings that are without a
concurrence, viz., «A, «B, «C, ~D, .—E. Those having concurrences are obtained,
sF on ;A, ,G and ,H on ,A, and ,I on ;A. These nine, ,A...,I, along with the
solid knot ,J, are the ten possible knots of six crossings. Four of them, as
Tait has found and drawn them, are unifilar, viz., ,A, sH, «F, «G4; and this is
read on the figures. The number 12 on each shows that there are 12 steps in
the circle of the knot, which passes twice through every crossing, once over —
and once under. ,B, ,D, and ,H are bifilars; ,C and ,J are trifilars.

36. Knots of Seven Crossings.—The subsolids ,A, &c., must be built on ;A,

: ‘&c. The only lines that can be drawn on ,;A here ©
NRE given are jf and aa, each 44; and af, ae’, ee’ be, bh,
iaripgres each 34.

2
By 7, which has no rival, we get ,A ; whose 2-zoned
VW ; poles are the flap and the tessarace 3333,
4
(aa) =44> (12), or (34) =48 ;
(af) =53, 43 >(12)=53, 43 ?
(bh) =48, 43>(12)=48, 43 ?

For the:rest, ae’, be, and ee’,
(43) =53 > (ae) =43 ;
(43) =44> (be) =43 and >(ce')=43.
We ‘have to draw, besides ff, the flaps (aa) (af) and (bh), expecting symmetry
with the two last, which we soon find,
By (aa) we get »B,
whose 2-zoned poles are this flap and a tessarace.

By (af) comes ,C, monozone ;
By (0h) , ,D,

whose zoneless 2-ple poles are a 4-gon and a 4-ace. Thus there are four sub-
solids, ;A, ;B, ;C, ;D, reducible by the leading flap to ,A.
37. On ;B, annexed, as we cannot allow a concurrence, we can draw only
' (if) and (b/),
(af)=53>(12)=43, and (45) is fixed (art. 22).
(2f)=44, 43 > (45) =44, 43 2 ((12)=34),

for (45) is not fixed when (Lf) is drawn.
3 % 5 We have to draw (af) and (2/) looking for symmetry
in the latter.

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 293

(af) gives us ,H, asymmetric ;
(of) ” /F, monozone.

Thus there are six subsolids, ,A ;B...-F, of which we read on their figures
that ,C, ,D, and ,E are unifilar. f

38. To obtain the unsolids ,G, &c., without concurrences, we have to lay 2
upon 5, 3 upon 4, and 2.2 upon 3,

sAfe on ;A gives ,G, monozone,

This is 2 upon 5. We cannot lay the same charge on ;B destroying the con-
currence, without completing an unsolid having two marginal charges of which
we have just imposed only one; which is forbidden (art. 25).

For 3 upon 4,

; 34f on ,A gives ;H:
3Afe on ,A gives ,I; vide the figures.
Observe that we can impose ;A only by the sections fand fe; for it has no
edge to lose at a section ef or ee; and if we attempt to lay it on a flap h by fc,
we merely turn / into a concurrence of two, which is not permitted as a result
of any charging operation.

In ;H and ,I the 2-zoned and the zoneless 2-ple axes of ,A, after being
loaded symmetrically by ;A, retain their repeating polarity, but from being
janal have become heteroid, not janal.

For 2.2 upon 3, we lay on;A the two charges ,A?fc, which stands for
twice ,Afe. The result is ,J, in which one flap is zoned polar, and two are
epizonal. Thus there are four unsolids, ;G, ;H, ;I, J, without concurrence.

39. For unsolids, ,K, &c., having concurrences, we obtain on ,A, ;K; on
al.and ;M; on .C,,N; on,D,,P; on,H, ,Q; on;A,Rand,S; on,A, ;r
and ,U; on,A,,V; eleven of them.

Thus we have 21 knots of seven crossings, of which 6 are subsolids and 15
are unsolids. ‘Their symmetry and circles are to be read on their figures.

Twelve of them, ,C, ,D, ,E, ,G, 7H, -I, -L, ;P, S, ;T, ,;U, ,V, are unifilar, of
which all but ,I have been found and figured by Tair. See Plate XV., Trans.
L.S.#., 1876-77, for his eleven figured unifilars, and his reduction of them to
eight.

40. The meaning of the symbols jv, 7; and fe is clear from the figures
7G, ;H, ;I. In reduction of ,G, after making the linear section, two flaps have
| to be restored. Also after section of the two parallels in ,H, the cut portions
have to be united to make two flaps on the severed knots; and after section
in ;I they have to be united to restore the flap on the charge ;A and the edge
on ,A.

We shall see an example of the section ef in ,Dg, and of ee in ,A/ and ,Di;
vide the figures.

294 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION , AND

41. Construction of Knots of Eight Crossings—For the subsolids ,A, &¢., we
have to draw leading flaps on ,A, &c. In A, which is

nae figured here, the 2-ple zoneless heteroid axis passes
sf through @ and e. The only faces are 5641, 634, and

4 563, and there is one flap which is asymmetric, hay-
ing different edges marked f and f’. The only different
lines that can be drawn are

fa, fb, ca, cb, each 35;

fc and ab, each 44; and
fd, fe, be, bd, de, de, each 34,

The two d’s are the same point repeated in the repeated triangles 563 and 124.

(fa) =53, 53 >(12)=58, 53 ?

(fb) = 58>(12)=43;

(ca) =53, 54>(56)=53, 53; (12) is fixed (art. 22) ;

(cb) =53, 44>(56)=53, 44 ?

(fe) =44, 43 >(12)=—44, 43 ?

(fd) —43, 43> (12) =43, 43 ?

(bd) =43, 54>(12)=43, 53; (56) is fixed (art. 23),
For the rest,

(12) leads (ab); and (56) leads (fc) (be), (de) and (dc).

We have to draw seven flaps, expecting symmetry in four cases—

(fa) gives us A; (ca) gives us .H;
(fc) ” 3B; (cb) » alths
(7) 5 (0d) yg
(fd) gD;

whose symmetry and circles are read on their figures, where the zoneless poles
on ,A, ,B, and sD are 55 and =) 44 and 33, 44 and 44, and the leading flaps
are marked 78.
42. We take next ,B, whose only faces are the 2-zoned polar 1256, and the

monozone faces 4253 and 124. The only lines drawable

are,
Ja, ba, hb, each 35,
ff, aa, bb, ha, each=44,
and Jb, bb, each=43.

3 Here (43) is fixed for every flap that we can draw,
{The 6 should be at the base corner.] except (7) and (6b), each = 44.

(ba) = 53, 54>(56)=53, 54? (12) and (43) are fixed (arts, 22, 23).
(hb) = 53>(12)=—44 and >(56)=—43,

(bb) =44, 44>(12) or (56) or (43)? each=44, 44,

(ff) =44, 33 > (43) =44, 33 ?

(aa)=44 >(12)=48 and >(56)=43.

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 295

For the rest,
(56) leads (fa) and (7b) from the flap (12),

and (12) leads (bb) =43,
We have to draw five flaps, presuming symmetry with (ba), (6b), and (7).

(f) gives us .H,

whose three 2-zoned janal axes terminate in the centres of the zoned polar
flaps and of two pairs of edges 44, 44; and 33, 33.
(ib) gives us ,J, asymmetric,
(db) gives us ,J,
whose two janal zoned poles are 4-gons, the four like janal zoneless 2-ple poles
being edges 44. We often mean by pole the polar face summit or edge in
which an axis ends.
(aa) gives us .K,
having two different zoned polar flaps :
(ba) gives us ob,

whose zoneless poles are 44 and 55.

43. Our next base is ,C, which has one flap, one triangle, and one 4-gon.
The only different lines that can be drawn are jf and aa, : f
each 44, and fa and aa, each 43. The two /’s are alike. | Gre bitn Bea |

(ff) =44, 33> (23) =43, 33 2
(aa)=44 >(382) or (56) or (14)? each =44;

not (fa)=53 >(14)=54; a OS,

Meemor (a0)=—43 >(14)=—54. 3 4

We have two flaps only to draw.
(7) gives .M,
| whose zoned poles are the flaps, the four like zoneless 2-ple poles being
tessaraces.
(aa)=44 gives ,N,

whose eight janal secondary 2-zoned poles are alternately flaps and 4-gons.

44. We have no more subsolids of six crossings. Of the unsolids, we
. find only four, ,D, ,E, .F, and ,G, on which a flap can be drawn to block linear
section.

We have on ,D, in laa, and 14aa,

3
(aa)=53>(34) and >(56), each=43.,
(aa) =44> (34) or (56) each=43.
2
By (aa)=53 we get ,P.
By (aa) =44 we get ,Q, wide the figures, )
6

296 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND
We have on ,E,

(aa) =64 >(23) or (45)—63.
(aa)=55>(12) or (45)=—53.
By (aa)=64 we get ,R, and
by (aa)=55 we get ,S.

Upon ,I we see that (ab), (ad), (ac), are the only flaps that ean block linear
section and exclude concurrence,

J 74
7 (ab) =54, 33>(43)—54, 33 ?
SS (ac)=54 >(43)=44,
2s a A

not (ad)=63 >(43)=64.

4 3 Drawing the flaps (ab) and (ac) we get ,T and ,U.
Upon .G only (a) can exclude concurrence. Here (84) is fixed (art. 22).

(ab)=54>(56)=54? (12)—34,

Drawing (ab) we obtain ,V symmetric as we expected,
having three different flaps, one zonal, one epizonal, and
AS, one asymmetric.
One more subsolid, ,W, is built on J, which has only

one edge and one angle.
We have constructed twenty-two subsolids of eight crossings, Ae ~3We
whose symmetry and circles are seen on their figures. Seven of har are
unifilar. :
In naming these knots I use an alphabet of 25 letters, omitting the letter O.

Thus
. A, B,...%: Aa, Ab... Mow Be Bh Bee

are each a set of 25.
45. For the unsolids ,X, &c., of eight crossings which have no concurrence,
we have to lay 2 upon 6, 3 upon 5, 4 and 2:2 upon 4.
For 2 upon 6 we can impose ,Af% on ,A once, on ,B twice, on ,C once, on
, once, and on ,F once, but on no other of six crossings, without violating the

rules in arts. 25, 28.
sAfe on ,A gives ,.X ;
yp eek A ic

” ae » sAa ;
4 Que stg
” ae ” gAc >

whose descriptions are read on their figures. The monozone ,Aé has four
different flaps, one epizonal upon the marginal charge, and three zonals, in the
zonal plane.

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 297

For 3 upon 5,
sAf on ,A gives ,Ad;
3Afeon ;A gives ,Af and Ae;
3Afe on ;B attempted gives ,Z

erroneously, or leaves a concurrence. ;Afe on ;A gives ,Ag, by arts. 16, 17,
and ,AA, art. 27.

For 4 upon 4,
sAff on ,A gives ,Az;
AVON. AL 54 SAYS
zAeeon,A ,,* Ak and ,Al.

The janal zoned poles on ,A7 are two flaps, two edges of the 4-gon, and two
opposite not plane 6-gons. The two poles of ,A/ are a flap and an edge 33:
on ,A& the janal zoneless poles are edges 33: on ,A/ are two pairs (66)
and (33) of janal zoneless 2-ple poles; and a third pair are two 6-gons not
plane.

There are two constructions by the charge ,Ace, because neither e nor ¢
(art. 27) is zoned polar.

For 2-2 on 4 (art. 38),

6 :
,A’fc on ,A gives ,Am,

which has all the symmetry of ,A ; the four 2-ple zoneless janal poles are where
they were, and the zoned janal poles are the two flaps of the imposed charges.
Finally,

i ;
,A’ffc on ,B gives ,An,

ee a janal zoned pole in each flap, and another pair in opposite non-plane
6-gons.

sAp is the only solid knot of eight crossings, a 4-zoned monarchaxine
homozone, whose eight identical janal 2-ple zoneless poles bisect eight polar
edges 33. Thus we have constructed seventeen unsolids without concurrence,
eX -¥..., An, of which nine are unifilar.
46. We complete our list of unsolids by art. 29—

7A gives Aq; J gives .By, .Bh ;

7B ae Ce or way ey,

2 See _Br a.) ABE, .BL..Baan Bn:
7D , Au; 66 gbp, .Ba;

AB yy «= gAv; thw Aw; (Dee sbi abs

aly evel Baevs ae ADM a lb lees

BG, gb, gb03 pa. «6g, g BU;

pte abe, bd ; Jee Be gis DY, abe:
Pla. | abe, .b/5 Ve IE ee Oli

Of these 36 we have figured only half, the 18 of them which are unifilar ;
VOL, XXXII, PART II. 3

298 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

as in the unifilars appears to lie mainly the interest of these knots. The 18
plurifils (if ever they deserve a name) can easily be drawn by the student with —
the aid of the above list ; and they must be figured by him who constructs the —
10-fold knots, for on many of them flaps can be drawn to make subsolids of ten
crossings.

We have found of eight crossings,

1 solid knot, unifilar,
22 subsolids, A... .W,
17 unsolids without concurrences
36 unsolids with concurrences ;

in all 76 8-fold knots, of which 35 are unifilar.
47. Construction of Knots of Nine Crossings.—The subsolids ,A, &c., are to
be formed by drawing leading flaps on ;A, &c.

5 4
ee The only lines that differ on ,A here figured are,
Jb and dd, each=44;

b df, dd, db, dq, ge, ee, eb, each=34 :
2376, 347, 123, and 134 are the only faces. The d’s
Sp . . 5
6 7 are alike, all on the same asymmetric edge 34, which

has two different sides.
(fb) = 44, (fd) =43, and (dd)=438, have no competitors ; for this (dd) fixes
(67) (art. 23),
(ddl) =44, 44>(67)=44, 44?

All the lines =34, except fd and dd, are led by (67). We have four flaps to
draw, expecting symmetry with (dd)=44.

By (dd)=44 we get ,A; by (dd)=43 we get ,D;
7 (fb) =44 ” gb 5 ” (fd) ? oC.

The symmetry and circles of these four knots are read on their figures,
48. We consider next ;B, here drawn. This has the faces 1473, 6745, an
Z 541, with one zoned polar and one epizonal flap.

oe different lines that can be drawn are,
“ : ab, aa, fb, bb, and cb, each=53, ~
ab, fc, and bb, each=44,
EZ es aa and ae, each=43.
In 07 (bb) =53, 55>(23) or (54) each 53 54; (67) is fixed (art. 23)
(aa)=53 >(23, 67 or 54) each=44;

(fe) =44 >(23)=43;
In 67b (bb) = 44, 55>(67)=44, 55? (45) =(23) = 43.

oe 9a

—

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS, 299

For the rest,
(54) leads (fb), (aw) =44 and (ab) =44,
(67) leads (ab)=38, (ea) and (cd),

We have to draw (0b) =53, (aa), (fc) and (bb)=44, expecting symmetry
with the last,
(bb) =583 gives ,E; (bb) =44 gives ,G;
(fo) » oF; (aa) » oH;

_ whose symmetry and circles are on their figures.

49. ,C annexed has monozone faces 1357, 12467, 354, and asymmetric
faces 456, 567, and the flap.
The different lines on it are,

ab, ac, cc, each 36;
ad, ac, be, each 45 ;
bd, ec, each 44;
ed, eb, each 35 ;

besides lines 34 that can be drawn in triangles.

(aa) has no rival :

in lab, (ab) =63, 53 >(67) =63, 53 ?

in 2ac, (ac) =63, 43 > (67)=—63, 43 ?

in 24ca (ac)= 54>(67)=53;

in 12cbd (bc) = 54>(67)=53 or (12)=43;

(cc) =63, 44>(12) or (67) each=63, 44 ?

For the rest, (12) or (67) leads them all, as well as all flaps on lines 34.
We have to draw six flaps, looking for symmetry with three,

(aa) gives us gl ; (ab) gives us oJ ;
In 2ace (ac) bolt sul I (ac) » gl in 24ea.
in 21be (bc) ap as (ce) Pe ON

The symmetry and circles of these are on the figures.

50. Next comes ;D here drawn. The polar 4-gon is 5217, and the asym-
metric faces are 5234, 123, 143. The only different
lines to be drawn are,

fa, fh, ch, ed, dg, in 1dg, and dg, in 7dg, all 53 ;

fe, dd, dh, gg, all 44 ; g 7
eg, et, gt, he, hi, ci, all 43 ; 16 lines. y)
(fd) =53>(67) =43;

(fh) =53>(67)=43;

(ed) =53, 54>(82)=58, 53; (67) =48 ;

(dg,)=53, 54>(67)=53, 53, or (82) =44 ;
(dgy)=53 >(82)=43; and (67) is fixed (art. 23);

300 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

inc4h, (ch) =53, 44>(32)=53, 44? (67) is 43 ;

(fc) =44 >(76)=43;

(dh) =44 >(76 or 32)=43;

(gg) =44, 44>(76 or 32) =44, 43

(eg) =43, 53>(76)=43, 53 ?

(ei) =43, 43>(76)—438, 43 2

(hi) =48, 54>48, 43; (23) is fixed (art. 23).
For the rest,

(32) leads dd, gi, ct, and he=43.

We have twelve flaps to draw, expecting with three at least symmetry :

(fd) gives oP; (je) gives ,V;
(fh) » Q; (dh) » W;
(cd) 4 oR; (99) » 9&3
(94,) » 993 (9) oo» 9X;
(ch) 4» of; (c?) » 94}
(49_) » 9U; (Mm), gAa.

The poles of ,X are a tessarace and the leading flap. The symmetry and
circles of all are read on figures.

51. Our next subsolid base is E, appended, on which no two edges are
alike. Thirty-one different flap-lmes can be drawn
on it, namely,

bd, bf, ed, ec, fe, all 63;
be, be, ef, fd, de, all 54;
ae, ah, lm, Yj, hm, hy, hi, te, all 53 ;
ai, hl, eh, jm, all 44;
Sm, nf, nm, gk, gt, ik, jd, jk, kd, all 48 ; %

the lines /m, &c., in the base being supposed dotted.

(bf) =63, 43>(67)=63, 432? 54=44;

(ed) =63 =>(54)=43,;

(ce) =63 >(54)=53;

(bc) =54 = >(54)=43;

(be) =54 >(54 or 67)=53;

(cf) =54, 48 >(23)=54, 482? (54)=44;
(fd)=54 >(23 or 54)=44 and >(67)=53;
(de) =54 >(54)=53, or (67)=43; (23) is fixed ;
(lm) =53, 43>(67)=53, 43? (67)=44;

(dk) =43, 64>(54)=43, 64? (67) and (23) are fixed
(ie) =538, 64>(54)=53, 64? 5

”

For the rest,
(23) leads nf, ah, ae, ai, mh, ef, mj, mn;
(67) ,, Al, he, hi, bd, Yj, jd, my;
(54) ,, gt, gk, tk, jk, jh.

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 301

We have eleven flaps to draw, with five queries about symmetry, which
speedily reveals itself,

(of) gives ,Ab; (fd) gives ,Ah;
(ed). gAes (dae i, +g Awe
(ae). gad; my 4 GA;
(00) oy) ge (die .,, gAhs
(UE) OP 2) Ur ris; Ade
(Ff) » Ag;

The symmetry and circles of all are written on their figures. The poles of
»Aj are the tessarace common to the two 5-gons, and the flap which connects
them: those of ,A‘ are a 6-gon and a 4-ace.

52. The sixth and last subsolid is ;F, which has only one asymmetric face
(1567), and one asymmetric flap (67). The flap (25) is
epizonal, Eighteen different flap-lines can be drawn:

ae, bd, W’e, 07, be, ef, ec, fd, all 53 (bj and be dotted below) ;

ac, bb, U’f, ee, ed, cj, all 44 ;

f af, dd, dj, all 43.

(bb) =44>(25)=43;
('d) in Vd7 =53>(23)=43 and (34) =44,

For the rest,

(25) leads b’e, Of, cj, ed ;
(34) leads ae, ce, ec, ac, af, dd, and dj in 7dy ;
(67) leads fd, be in 3be, ff, fe, and by in 40).

We have two flaps to draw,
(bb) giving ,Am and (0d), giving ,An,

whose circles and symmetry are read on the figures.
53. We betake ourselves next to the unsolids of seven crossings, which, by
a leading flap, can become subsolids. These are

WG, 7H, 7, wd, 7K, 7L, >M, iN, 7, 7R, a)
On ,G annexed can be drawn to block the linear section only three lines,

which are

(ab) =54> (12) =43;
in @b7, (cb) =63,44>(54) = 63,43 and >(12)=43;
in cb17, (cb) =54>(54)=53 and >(12)=43.

We draw three flaps,

(ab) giving ,Ap, (cb) giving ,Ag, and (cb) giving ,Ar;

whose description is seen on their figures.

302 REV. T, P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

54. On ,H, here seen, we can draw two flaps only,

= (ab) = 64 (in 56ba)>(43)=63 or (21)=43.
(ab) =55 (in 562ba) >(43)=53 or (21)=43.

One (ab) gives ,As, the other gives ,Az.

Zoe Four flaps can be drawn on ;I annexed,

(ab) = 64 >(56)=63 or (13)=53;
eee (db) = 55 >(57)=53 or (13)=53;

(ac) =55>(24 or 56)—53 and >(13)=54;

(de) =64>(57 or 24)=68 and >(13)=54.

/ wea
— Here (ab) gives ,Aw ; (ac) gives ,Aw;
s

(GO) O53. ghd (dc) , Am.

Professor Tart does not allow ,H and ,I to be different knots, giving a reason
at p. 158, Trans. RSE. 1876-7, which appears to me sufficient wherever it can
be verified without twisting the tape, or breaking the law of alternate over and _
under. It is true that on the knot in space whose projection is ;H, the three
crossings 543 which are found on the thread 67 between 6 and 7, can by
slipping of the thread be made to appear on the thread 71; so that the order of
the crossings shall be changed from 165435437 .., the thread passing over at
15347, to 167543543 .., the thread passing over at 17534, 7.e., making two
consecutive overs at 7 and 5. The resultant figure in space, although it would
have ,I for its projection, would, if I am in the right, be no knot. If I had not
drawn both ,H and ,I, I should have missed some unifilar 9-fold knots, both
here and in art. 63.

55. On ,J, annexed, can be drawn only two lines to make a subsolid,

(ab) =54,44(67) =54,44% (54=12)=43.
(ac) = 54,44>(12 or 54)=43; (67) is fixed.
(ab) gives Ay, and (ac) gives ,Az.

2 both concurrence and linear section,

(fa) =54, 43 >(54) =54, 33; (12) =44;
(fo)=54 >(54)=44; (12)=43;
(ga) =54, 43>(57)>54, 43? (12)=44;
: (gc)=54 >(57)=44, or (12) =53.

A flap (fy) can be drawn, but the linear section 74 would remain. For t]
rest,
(45) leads fe, he, hd; (75) leads bg, ic, id,

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 303

Here
(fa) gives ,Ba ; (ga) gives .Be ;
CO) 33 ob ; (ge) oBd.
The circles and symmetry are on the figures.
56. On ;L, here given, no line can be drawn to spoil the concurrence and
the linear section but from « or 8,

(ae)=54 >(23)=44 and >(67)=53; (54) is fixed (art. 22).
not (ac)=63 >(23)=64;
not (ad) =54, 33>(23) =54, 43;
not (6g)=53, 53>(67) =53, 54; 2
not (bf)=44 >(67)=53.

Here

(ae) gives us Be.

mae
(ad)=63 >(12)=44, or (34)=43; \ ape fer
(ab)=54 >(12 or 34)=53; (56) is fixed (art. 22). a lie

On ;M, here seen, the leading flap must be drawn from a.

(ac) = 54, 43 >(56) =54, 43? (34)=44,
Here { 4

(ad) gives ,B/, (ab) ,Bg, and (ac) ,BA, the latter symmetrical.

57. On ,N, annexed,
(ad) =54>(42, 26, 17)=54?
(26) leads (ab), and (45) leads (ae).

=
Ww

x
M
ae +

The only leader

(ad) gives us ,Bi, symmetric.

On ;P no flap can spoil both concurrence and linear section.
On ,Q there can be drawn only one leading flap—

IN

(ab)=56, giving .By.

\
7

On ;R, here given,

(ac) =55 >(32 or 17)=55 ?
(ab) is led by (17).

~
to

Be

Here (ac) gives us ,Bk, symmetric.
On ;S, annexed,

s
Q

(ac)=55>(76 or 34)—54.
(ab) =64>(56 or 34)=64 2

Here (ac) gives ,B/, and (ab) ,Bm, the latter symmetric. 1 >
We have constructed by their leading flaps sixty-three subsolids of nine
crossings, of which thirty are unifilars, bearing on their figures the number 18.

.

304 REY. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

58. We demand next the number of the unsolid 9-fold knots, and first,
of those which have no concurrence.

To construct these we are to lay 2 upon 7, 3 upon 6, 4 and 2°2 upon 5, and
32 upon 3.

For 2 upon 7 (art. 34) imposing ,Ajfc, we get

On ,A , ,Bn; Ony,I,.,00., cco;
» 7>, bp and.ba; » ye pe sees
ye ptelee Renee
el og DS's yy op pone
3 pls gbb), pbs .bUs 5 UN Oks
peg! sigh a; PA pacts
» 72 5 By; » 7B, GJ.
Dateh iprinen Cael,

On ,J we do nothing, because we cannot cover both its least marginal
charges ; and nothing on ,P, because we cannot both spoil the concurrence and
cover the least marginal charge.

59. For 3 upon 6, the charge must be ;A/e (art. 26) or ;Af;, or Age

sAffe on ,A gives ,Ck and ,C/;
te). Bay One Cr | cep
» Ae) ” 9 .

On ,D we cannot cover both marginals ,Aj.

On ,E we cannot cover both.

On ,F, ;Age imposed to spoil the concurrence would be ;A?fc on A
wrongly constructed by one charge ,A/¢ only.

On .G we cannot both spoil the concurrence and cover the least marginal.

On .H it requires two charges to spoil the two concurrences.

Next, for 3 upon 6 again,

3Af on ,A gives ,Cr;
gAjeon pA 5° BCs ener, (ev. .cls ews

for the e charged on ,A (art. 41) is in turn every different edge, a,,c,d,e.

3Af on _B gives ,Ca , ,Cy;
sAfeon ,.B 4 »C2,,Da;
sAf on .C .» D8;
sAve on C °,,' (Des
pAf on GF» 5, 5D;
sAfeon WJ 4, De.

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 305

60. We have next to lay 4 and 2:2 upon 5,
sAf on ,A gives ,D/;
sAgfon A ,, Dg;
jAjeon A, Dh;
gAceon A ;, Dz.
sA’ffc on .A gives ,D7 (art. 38).
,A-feon ~B 3. Wis
5B was made (art. 31) by adding a concurrence to ,A ; but it is also ,Afe
on ;A, though improperly made (art. 38); and as we have two charges to im-
pose, we can both spoil the concurrence and cover the least marginal of ;B,
thus making ,D/.
61. Finally, we have to lay 2:3 and 3:2 upon.3,

;A7fc on A gives ,D/ and ,Dm.
3A2f on ,A gives ,Dn. These lay 2°3 on 3.
sA%fe on A gives yDp. This lays 3:2 on 3.

In ,D/, ,Dm, and ,Dz the symmetry is maintained about one of the 2-zoned
axes of ,A, though not a 2-zoned symmetry.

We have constructed 115 9-fold knots without concurrences, of which 63
are subsolids, and 52 are unsolids without concurrences. Among the 63 are
30 unifilars, and among the 52 are 25, making 55 unifilars without concurrences.

62. There remain only the 9-fold unsolids which have concurrences.
The number of ways in which a knot K’ of x-c crossings can be made by add-
ing ¢ concurrences of flaps into K of m crossings is easily seen when the
symmetry of K’ is given, K’ having no concurrence—

gA gives Dg; gV gives oFc , 9Fd , ,Fe;

3B 5 9D7; oh ” bE
gC nS 9Dt 2g g& » gk , ohh ;
BON Bf) Dus Yew Mobos dip gees
abe 3. 2Do, Dw, Dz; 32 on gl, gm;
a 5 Dy ; De; Re Ga ge Ds
SG) gay ,Ed , Hes pAb ,, oF ,oFr, oFs;
BED 4G, Vola: phe 5 oF¥, 9Fus glu;
ple as lle poEy oligs sAd ,, okw, Fa;
Sy gh; ple 5, volYi, oft
pieiee oa, oly, ok; Say a gad , 6G .gac,
tines, oll, Ban: GAO sz, gO 5
a 6 (ok; sAh , Ge;
aN » oiip ; gAt » AC yi 3
gh ” og ? gH ? Ay ” Gg ? oGh ;
BO oS gH; gAk ,,° ,Gt;
Blu; oli, sw; pA ow odin
RSM pte 5g ha 5 sAm , Gk;
st ky; wAn ,, ,Gl,,Gm.
Us, Be 2 Ha ,ghOs

VOL. XXXII. PART II.

306 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

63. We have next to add two concurrences of flaps to all of ,A, &., on
which is no concurrence—

yA gives Gn ;,

vB 3, GGP sigG@ s gots Gs; ;

WO 5, gGt), gas

yD page ows

Ea, ca e ey np oo Gy o1 bg gules
EF 3, god. lei. be

Go 5, wl, Ghd ey

pil ays gles gtlly, pian.

1 rr 8 emer shay ale lobar 872

0 © 5. legis gigi’, Surtees

The number of results in any of the above cases of this article is that of the
different flaps which can be made a concurrence of three plus the number of
different pairs of flaps that can be made each a concurrence of two.

64. We have next to place three concurrences of flaps on ,A, &c., foun on
5A, five on ,A, and six on ,A—

gA gives Hw , Hx;
goo Sgt ciple gta, glo ghes la
gC » gle ) olf ? lg 3

pit Grrglts oles

get Pau Viewlen

5A gives oI/ , Im, oIn;
yA ” olp ? olg ? gl;
fee Bost Balls:

Finally, there is one solid knot, ,I¢.

The number of 9-fold knots that have concurrences is 128, of which y
have figured only the 70 of them which are unifilars. The rest will have to”
drawn if the census of unifilars is carried to higher values. This can easily
done.

We have found 244 knots of nine crossings, viz. :—

1 solid knot,
63 subsolids,
52 unsolids without concurrences,
128 unsolids with concurrences.

Of these 244—

30+25+70+1=126 are unifilar.

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 307

I think that no difficulty will present itself in the construction of higher
n-fold knots, which has not been met in the preceding pages.
Here follow the abbreviations used in the descriptions of symmetry :—

Monch. for Monarchaxine. . Mox. for Monaxine.

Triax. or Tri. for Triaxine. Moz. for Monozone.

Triarch. for Triarchaxine. Hom. for Homozone,

Zo. for Zoned. Het. for Heteroid, not janal.

Az. for Azonal, or Zoneless. 2p. for 2-ple, repetition about an axis.

POSTSCRIPT, SepremBer 1, 1884.

65. As it is a brief matter, it may be worth the while to show how all solid
knots can be constructed without omission or repetition.

Solid Knots, Prime and Non-prime.—aA solid knot Q of crossings is prime
or non-prime according as it has or has not a crossing or summit A3B3, A and
B being any meshes.

Lowest Triangle of a Solid Knot Q.—It is easily proved that no solid knot
has fewer than eight triangles. The triangle L of Q is ABC, DEF, where
ABC are the three covertical faces and DEF the collaterals of L, the lesser
being written before the greater in both triplets.

If L’ be another triangle of Q, the lower of LL’ has the least A, whatever
be the other five faces. If A=<A’, the lower has the least B. If also B=B’,
the lower has the least C. If ABC and A’B’C’ are alike, the lower has the
least D, and so on.

If the six faces are alike in both, it is wisest, and almost sure to be right in
construction, to presume that L and L’ are identical, or one the reflected image
of the other, by the symmetry of Q, which is soon decided. If they are not thus
proved alike, an examination of the collaterals of ABCDEF cannot fail to
determine the lower triangle. The one whose A, or, if required, whose B, &c.,
has the lowest collaterals is the lower.

66. Reduction of a Solid Knot Q.—The simple rule is, efface the edges of

the lowest triangle L of Q, or of a lowest when Q has a symmetry.
Such reduction of a prime solid knot Q of 7 crossings gives us a subsolid or
jan unsolid knot P of n-3 crossings, which has one, two, or three flaps,
according as the effaced L had one, two, or three covertical triangles: and L
|must have one, or, by our first definition (65), it cannot be lowest on Q.
Such reduction of a non-prime Q gives either a non-prime P’ or a prime
_\solid knot P of n-8 crossings ; but I am not certain that this can ever be P’.

308 REV. T. P. KIRKMAN ON THE ENUMERATION, DESCRIPTION, AND

67. Construction of Solid Knots Q of n Crossings.—The rule is the converse
of the preceding. Add to the subject P of »-3 crossings, whether P be solid,
subsolid, or unsolid, a lowest triangle of the result Q, occupying three mid-
edges of a mesh of P. I any not certain that when P is non-prime such addi-
tion can ever be made.

In order that Q may be solid, P must have fewer than four flaps, which, if
more than one, must be collaterals of one mesh. If P has only one flap, it is
collateral with two meshes, alike or different. Such a P must not be unsolid.

It may be that several different lowest triangles of Q may be drawn upon P, —
giving as many different Q, or that no lowest of Q can be drawn on P. In this
case P is no base, and in construction is useless. No knot Q is reducible to it
by deletion of a lowest triangle of Q. Examples are given below.

68. We proceed to construct on our figured knots P every possible solid
knot Q.

Our only knots which have fewer than four flaps, all of which stand about
one mesh, are ,A; ,A; ¢F, oJ; 7A, C3 gR, oT, ,W, ,Ad, ,Ag, ,Ap, ,Ag, Abs
oAs 9B, oC, oI, oJ, sK, ol, oN, »Bm, .Bn, ,De, ,D/, Ey, Ff, ,Gd, ,I¢; thirty of
them, of which ,Ag, ,Ey, ,E/ are not figured, but can easily be drawn (arts. 46,
62) on ,A, ,T, and spW—

3A gives the solid J ;

5A ” sAD ;

gE 3 git; see the three figures ;

yA wA, 20. tri. 443°, (446) ;

7C 3 iP, 5 zo. monch. hom. 5731, (20) ;

and also ,,C, az. tri. 4438, (6, 14);
sR gives the solid ,,A , 2 zo, mox. het. 4°38, (6, 6, 10) ;

sAd 7 uB, 2 zo. mox. het. 574319, (4, 4, 14);
gAt . n0, moz. 54939, (22);

oA 5 pA, moz. 54439, (4, 20);

ob 43 wb, az, tri. 4°38 , (24) ;

oJ 3 0, asym. 574731, (24) ;

1D, 6 zo. hom, 673%, (888) ;

ok Pe ww, moz. 54439, (10, 14) ;

gl: 5 wi, 2p. mox. het. 4°38, (6, 18);

gu 55 2%, 3 zo. monch. 4°38, (6666) ;

obm sy 1H , 20. triarch. 493°, (6, 6, 6, 6) ;
Ve y wl, 2p. mox. het. 5747310, (4, 4, 16) ;
gly 35 19 » 2 20. mox. het. 57473", (10, 14);
Nig 5 wk , 2p. mox. moz, 4°38 , (24).

We have thus twenty prime solid knots, of fewer than thirteen crossi

CONSTRUCTION OF KNOTS OF FEWER THAN TEN CROSSINGS. 309

made on eighteen of our thirty inferior knots. The remaining twelve, viz.—
Pee teW gain, Ag, Cy gl, bm ,aDh, Ge, lf,

are found to be no bases.

In ,,A above, 4* means 4444, and the circles are in parentheses.

No non-prime solid knot has fewer than sixteen crossings. The simplest is
43° , 4 zo. monch., in which two opposite 4-gons are each covertical with four
triangles, the triangles being four pairs of collaterals.

In order that a prime solid knot P may be a base, it must have not more
than three summits A3B3, which must be so placed that, by drawing a lowest
triangle of the non-prime Q to be formed, every pair of covertical triangles
shall disappear.

All non-primes can be easily constructed by our simple rule without
omission or repetition when the primes of more than twelve crossings are
before us.

This may suffice on solid knots until their value in electricity and magnetism
is so enhanced as to call for a formal treatise on the whole subject.

‘VOL. XXXII. PART II. ORE

y. Soc. Edint

5B 10
vs

2 zo.Mox.Hef.

4 z0.Monch. 2 zo.Mox. Het. 5 zo.Monch.

Vol. XXXI, PLXL.

12/6B

b—~{

2 zo.Mox. Het.

2 p. Mox. Het.

61 6.6 |6d 4.4.4

6 zo. Monch. zo. Triarch.

6H. 6.6
zo. Triax. Hom. Tri
TGs nes |) Sf 10) 14 Cis 4.10
en Se
7
«Het.| 2 zo.Mox. Het. Moz 2 p. Mox. Het.

2 zo. Mox. Het.

Het. | 2 zo. Mox.Het.

2 zd.Mox.Het.| 2 zo.Mox. Het 7 zo. Monch. 2 p. Mox. Het.

14
2 ae Mox. Het.
7 eee

ale 4.10

2 zo.Mox.Het.| 2 zo.Mox.Het.

16

2 p. Mox. Het.

(A 72(0)- Mox.Het.

8G 8.8
We LAN
ee nee re
2 p.Mox. Het. | asym.
sJ 4.4.8
Hom Tri. 2 zo.Mox.Het.
2 p. Mox. Het.
sAa 4.12 |}8 Ab 16
Moz
i 8 Aj 16
r 2 p. Mox. Het.

F Huth, Lith* Edin®

yc. Edin?

18 Ba

>

>)
N

NN

9Bec

Vol. XXXII, Pl. XLII.

4.6.8|9Be

ypN

4.14

4.10

a / L
_2 iia
9
asym. Moz asym. asym.
9Bi 4.4.10 | 9 Bj 4.6.8/9Bk ig |9 Bl 3 |9Bm 6.12

eS

a:
=

9Bf 4.14 | 9B$ 18
AW
asym asym
9Bn 4.14 |9Bp 4.14

ry

2 zo. Mox. Het 3 zc. Mox. Het. 2 p. Mox. Het. |. 3 zo. Mox. Het. Moz Moz
;.i2|}9Br 8.10|sBs 8.10} 9Bt 6.12 |}9Bu is | 9 By 8.10 |} 9Bw ig |9 Bx 4.14
| asym. asym asym asym. asym. asym. Moz

9Bz ig|o9Ca 6.12} 9Cb 18 9Cd ig |9Ce ae i
Moz asym ae sa SO | asym. asym. asym.
a 1
9Ci is | 9 Cj ig See oe acl ig|9Cm 8.10|/9Cn 6.12
Moz Moz asym. asym. Moz | Moz
9Cr is|}9Cs ig | 9Ct is|9Cu is | 9CV ig|9Cw 18
Moz 2p. Mox. Het. 2 p. Mox. Het. asym. asym. asym.
ae
Cy a. 14 oDa 4.14|9Db aDe 4.4.10} 9Dd ig |9De 4.4.10
2z0. Mox. Het. asym Moz. asym. 2 zo. Mox. Het.
9Di 6.12 he 2Dm

aot

©
1s]
x
®

st

o

o
n=)
ie
id
o

teil a

asym. asym 2 zo. Mox. els asym. Moz 2 p. Mox. Het.
9Ds 18 ice is|9Dv is|}9Dw 18
——— a
SS Re ——
oN WS 5
| ESS | ee ee ee
a am | Cg ema =
3 zo. Monch. asym asym. asym. asym. asym.

F. Huth, Lith? Edin*

Soc. Edin*

Vol. XXXU, Pl. XLII.

sEl ig | 3Em 1g |3Eq ig
asym. asym. asym.

gEz 18 18 re 8
2 p. Mox. Het. asym. asym asym. asym

18 18 3Fw 18
asym. Moz

aS
ES

2 z0. Mox. Het.

2 zo. Mox. Het.

i:
=
ae

asym.
asym. asym.

9HI 18
. Mox. Het.

2 zo. Mox. Het.
———I|

Sek
DIDI
AA

2 zo. Mox. Het. | a za. Mox. Het. 2 zo. Mox. Het.

2 zo. Mox. Het.

glb 18

a Mox. Het.

=
Al

2 zo. Mox. Het

O

3 zo. Monch.

¥. Huth lith® Edin”

( 311 )

XVIII.—On the Approximation to the Roots of Cubic Equations by help of
Recurring Chain-Fractions. By Epwarp SAnc.

(Read 7th January 1884.)

In the twenty-ninth volume of the Society’s Transactions, at page 59, Lord
BrounckEr’s process for finding the ratio of two quantities (commonly known
as the method of continued fractions) is extended to the comparison of three or
more magnitudes. It is there shown that recurrence, which was believed to
belong exclusively to equations of the second degree, extends to those of higher
orders, and examples of this extension are given in determining the proportions
of the heptagon and enneagon.

In the present paper it is proposed to show the application of this extended
method to equations of the third degree.

| If there be a progression of numbers A, B,C,D,E,.... formed by
means of the multipliers p, g, 7, according to the scheme :—

rA+qB+pC=D
7rB+qC+pD=E
rC+qD+pE=F,

and if the number p be greater than either g or 7, the terms will approach to
be in continued proportion, and their ultimate ratio will be the positive root of
the equation

a —px?—qu—r=0, : : A ; : (1)

—

independently of the values assumed for the initial A, B, C. The actual pro-
| gression may be regarded as the sum of three series having the initials A, 0, 0;
0,B, 0; and 0, 0, C respectively. On developing the term, we find that the
| coefficient of A in the mth term is 7 times that of C in the preceding or n—1st
term; while the coefficient of B is compounded of g times the n—1st, and r
times the n — 2d coefficients of C. Hence we need only to compute the series
| beginning with 0, 0, 1, in order to have the means of compounding any term
of a progression formed with the same multipliers.
VOL. XXXII. PART II. 3F

312 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF

The successive terms of the elementary progression are easily found to be

[0]=1

ie

[2]=p" +9

[3J=p* +2pq +7

[4]=p* +3p’¢ +2pr +9”

[5]=p° +4p°¢ +3p"r +3pq? +2qr

[6] =p° Popty Papin pep? -H6pgr NP pr

[7T]=p" +6p°¢ +5p'r +10p%¢? +12p’or +4 pg? +3pr? +3927

[8]=p® + 7p°¢ +6p’r +15ptg? + 20p%97r +10p7q? 4+ 6p?7? +12p9?r +94 +397?

and the general form of the mth term of the progression having the initials
A, B,C, is, C being regarded as the zero term,

[v—1]rA+ {[r—1]g+[n—2]7}B+[n]C
or
[n—2]rB+[n—1]{rA+qB}+[n]C.

But the elementary progression alone suffices to determine the value of the
ultimate ratio 1:2.

This process is applicable directly only to equations having suitable coeffi-
cients. In the case of pure equations, those whose queesitum is the cube root
of some number, the coefficients p and q are both zeroes, and the progression
becomes

02-01 OR OF 0 Us On ae euioces

which contains the truism that the ratio 1:7; 7:7"; is triplicate of that of
which we are in search. !

In order so to change the form of an equation as to fit it for the application
of this method, we modify LAGRANGE’S process in a manner which may be best
explained by examples.

Let it be proposed to extract the cube root of the number 2.
In the equation

w—Oz?—0x—-2=0,
we may write - in place of x, so as to give to it the form

a? — 0a*b—Oab?— 20? =0,

in which, if 6 represent the side of a cube, a@ stands for the side of the double q
cube.

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 313

Here, in order to find the ratio of a to b, we, following BrouncKEr’s plan,
try how often } is contained in a. Clearly it is only once, with something
over. We therefore write a=1b+c, and get, by substitution,

108 — 3b%e— 30e?—cF =0 ,

an equation easily managed. The ratio of ¢ to 6 is now obtained from a
progression regulated by the multipliers 7=1, ¢g=3, p=3; thus

0, 0, 1, 3, 12, 46, 177, 681, 2620,°10080, &e.;
so that if any one term—say 177—be assumed for c, the succeeding term, 681,

is approximately the corresponding value of 6; but ~a=1b+c¢, wherefore 858 is
the corresponding value of a. In this way we form the series—

oO ©@ @® & ® 6) (6) (7) (8) (9)
eo ot 0 OU 1K CB 223858 8 B01 HE TROD | 44861
ioe 68” CD” ECT” Ss GBL* «2 620" 10080" 38781’

(10) (11) (12) (13) (14) (15)

187984 723235 2782518 10705243 41186518 158 457 801 ee
149203’ 571032’ 2208486” 8496757’ ' 32689761’ 125768040’ ~’

approaching very rapidly to the cube root of 2.
Among these we notice that each member of the terms (3), (6), (9), (12),
(15) is divisible by 3, On simplification, these terms, with the prefixes

ae 2 form a series progressing according to the scheme r=1, g=—3
p=57; thus
(0) @) (2) (3 (4) (5)

+1 0 5 286 16287 927506 52819 267
St 0 A 227 go27,” ‘s6i62 47922680’

converging still more rapidly to the required root. The term (2) is true to
within the accuracy of five-place logarithms, the defect being ‘000 0032. The
next term (3) passes beyond the exactitude of seven-place tables, its loga-
rithm being in excess by 00000 00157. The excess in the case of (4) is
00000 00000 31409, which could not be detected with the ten-place tables;
while (5) gives a defect of 00000 00000 00053, as tested by my manuscript
tables to fifteen places. The errors are two in defect, two in excess, and so on.

The roots of numbers immediately above or below a cube are very readily
found. Thus for the cube root of 9 the equation becomes a@—9?=0; whence
a=2b+c, and

b3— 126%e— 66c?++1e=—0.

314 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF

Hence for a progression converging to the ratio 6: ¢ we have the multi--
pliers r=1, g=6, p=12, giving the series

0,.0, 1, 12, 190, 1 8¥s:, 23'388.,- &e. ;

and hence, converging to the ratio of a: b, we have the progression

(0) ()erae@) (3) (4) (5) (6) (7) (8)
1 0 2 25 312 3896 48649 607476 7855502 941719529
0’. 0’ 1’ +18 150’: 1873” 23°388° °292 044° 31646°729" 455aqnueee

(9) (10) (11) (12)
1182754836 14768960708 184418777041 2302 821 843 576

568 609 218’ 7100175745’ 88659 300 648’ 1107 081 271 464’ a

Here the terms (3), (6), (9), (12) are reducible by the common divisor 6,
and form the progression

(0) (@) (2) (3) (4)
2 0 52 101246 197125806 383 803 640596
—1’ 0’ 25’ 48674’ 94768203’ 184513 545 244’

which proceeds according to the multipliers 7=1, g=-—3, p=1947.

This convergence is so rapid that the error of the term (2) cannot be
detected by help of the ten-place logarithms; that of (3) is beyond the
precision of the fifteen-place tables.

In the case of the number 7, which is less by unit than the cube of 2, the
convergence is somewhat slower. For the equation

a—Te—0

it is convenient to take the first measure in excess, and to write a=2b—¢
which gives
b§— 126%e+ 6bc?—?’=—0;

so that the progression, by help of the multipliers r=1, g=—6, p=12,
becomes

(0) a) (5) (6) (7)
-1 0 2 23 264 3032 34823 399948 4593470
0’ 0’ I” 12’ 188’ 1585’ 18204’ 209076" 2401276"

(8) (9) (10) (11) Oo
52756775 605920428 6959097956 79926409679 917 968 248 840 4.
27579 024’ 316749726’ 3637923 841’ 41782166760’ 479 875 207 800°

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 315

of which the terms (3), (6), (9), (12) give, on being simplified, the pro-
gression

(0) (1) (2) (3) (4)

0 44 66 658 100 986 '738 152994 '708 140
ad’ «00 o23”)-84846” 52791621" - 79 979 201 300’

for which the multipliers are r=1, g=—3, and p=1515.

In order to get a clear view of the general principles here involved, we
shall propose to extract the cube root of n’+1.

The equation a°—(n?+1)b?=0, gives, for the first approximation, a=nb+c,
whence

b8 — 3nb?c— 3nbe?—c =0,

so that the multipliers are r=1, g=3n, p=3n’, which give, converging to the
ratio of 6: c, the progression

0,0, 1, 3n?, 9nt+3n, 27n°+18n3+1, &c.,

and consequently, converging to ./(7?+1), the series of fractions

One () (2) (3) (4)
eo 0 n 3n? +1 9n> + 6n? 27n7 +27 nt +4n
0.” 0’ atte 3n? 7 = Ont+3n’ 27n8+18n3+1 ’
(5) (6)
81n9+ 108° + 33n2+1 243nU+ 4058+ 189n°> + 21 n?
81n8+ 81nd +1522 ’ 243n10 4+. 324n7+108nt+6n ”
(7)

729n!8 +1 458n29+ 918774 189nt+7n
729n +1 215n9+594n8+81n?+1 ’

(8)
2187n%+5 103n'!? +4 050n9+1 2428+ 117n3 +1
2 187n4#+44 374n" + 2 835n?+648n°436n? =”

(9)
| 6 561n 417 496n*+16 767m" +6 885n8+1 107254 45n?
| 6 561n ©+15 309n% +412 393n%+4 050? +459nt+9n *

Here we observe that the numerators of the terms (3), (6), (9) are divisible

316 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF

3 3
by 37, the denominators by 32, and hence, for the value of a there

comes out the progression

+1 0
Sau Or

81n9+ 13575 + 63n3+7
81n®+ 108% + 36n3 +2’

bn? +2
3n8+17

2 187n4 +5 832n124+5 589n9+ 2 295843693 +15
2 1875+ 5 103n!+ 4 131n?+ 1 350n5+1538n4+3 ’

the multipliers for which are
r=1, g=—38, p=2in+27n +3,

w/ (nm? —1)
N

and similarly we find for , the multipliers to be

r=1, q=—3, p=272' —27nF +3 ,
with the initial terms

ieee
3n3 —1’

ea a
+1 0’
these results agreeing with what has been found in the cases of 9 and of 7.

It may also be observed that each third term of these second series is

reducible by 3, and that they form a progression converging still more rapidly.

When the proposed number differs from a complete cube by more than
unit the extraction of the root is more complicated. As an example, we shall
take the number 3.

In the equation a?—3?=0, on putting a=1b+¢ we get

— 23+ 367+ 3b? +1c=0,
or
3 3 rt
(eS / 0.) IE el 5 ee eae
b 7 be 3 OC 7° =(() .

whence the multipliers

or, more conveniently

ws OVS gi
WS goed ae hare ap 8
from which the progression
3 1b. 67... B05. 1371) 6189) 28 035
9+, 05 te go a2. BM teilby? bebe? + aed Semel

'
4
;
‘
;

)

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 317

the numerators being got from the multipliers 4, 6, 3, while the denominators are
powers of 2. From this, since a=0)+<¢, we have the approximations to ./3

Cy (3) (4)- ..(5) (6) (7) (8) (9)

ee Ob OF. 437 OTT sO4t AN 439 189.853

is ~6 CG oe eal 90". 28085” TIE783 ”
(10) (11) (12)

826921 3739613 16911777

573355 2592903’ 1725071 **

Here, as in the preceding cases, each third term may be simplified,,the pro-
gression being

7 659 60951 5637259
=) GP doa’ sgogeer &

i0.7 457’ 42261’ 3908657’

_ for which the multipliers are 7=64, g= — 48, p=98.

Here the approximation is comparatively slow, the less accurate terms being
_ largely combined with the more accurate ones.

_ To carry BRouNCKER’s process one step farther, let us try how often 6 con-
tains c; for b=1c, the above equation gives + 5c? instead of zero; for b=2c,
the result is + 3c? ; but for b=3c, we get —17c*?, wherefore 6 contains c twice
with something over ; we therefore write b=2c+d. The substitution gives

+3 —9c?d —9ed?— 2d? =0,

or

—3e'd— Bed?— +d =(0.

The multipliers hence resulting are

giving the progression for d:c
2 4
O70) 135 12. 45-5 175, 670, 2565-5 &e.,

but a=3c+d, b=2c+d, wherefore the ratio of a:b is given by the pro-
gression

318
(OF, Moti (2) fC) wae (5)
Ons Bro h0 ol B8rAt dd9.5 4 ae
OAcweawa 272 sre Bons”
(8) (9) (10) (11)
320344 122659 4696572 11798306
92 211g’ 85047’ 32562218 1246806

converging much more rapidly.
LAGRANGE’S application of BRouNCKER’s meth
tinued, as in the following scheme :—

0= a— 0ab— Oab?— 38°;

0O=— 269+ 30%+ 36c?+ 10;

0O=+ 38— 9e?%d— 9ed?— 23 ;

0 = —29d°+18d?e+18de?+ 32°;

0= + 10e—33e?f — 69 ef2— 297% ;
&e.

—e=4f4g

EDWARD SANG ON THE APPROXIMATION TO THE ‘ROOTS OF

(6) (7)
2185 83662
1515’ 5 8008’

(12)
26 6 885 6678

Hh? 2774955 ° >

od may be still farther con-

a=1b+e ;
b=2c+d;
c =3d+e ;
d=le +f ;

&e.

until we arrive at some equation promising greater facility or greater rapidity.

The last of the above gives

r=2.9; q=6.9; p=3.3;

with the condition a=13¢+10/; b=9e+7/7

For the cube root of the next number, 4, we have

a— O0a>— O0ab?—40> =0,
— 30+ 30%+ 3bc?+ 1e°=—0;
+ 438— 0cd— b6ed?—"3d2=0 ;
— 5d?+ 6d’e+ 12de?+ 4c? =0;
+ 12e— 24e?f— 24ef2— 5f3=0;
— 5373+ 24f%9+ 48f9?+1293 =0 ;
+ 319 — 639°h—135gh?—53h7=0 ;

—188h3 + 324h77 + 216/27 +318 —0 ;

&e.

The equation in e and f put in the form
SG YON NL Gy toy 5 ys
eo — 26?f— ef i af Ss 0

5

a1? G—2. 4.) —25 8

gives the multiplications 7=

ditions
a=3e+3f; b=5e+2f

a=1b+c;
b=1ce+d;
c=ld+e ;
d=2e +f ;
e=aftg;
fHlgth;
g=sh+t ;
A=2+hk;
&e.

nd these, along with the cor

>

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 319
produce the progression
g “19 “54 140 414 11508
ee ot 9 94 ogee? 74a
converging rapidly to the value of 4/4.
For the cube root of 5 the equations are
e@— 0ab— Oab?— 50°=0; a=1b-+e ;
— 48+ 30%+ 3027+ 1°=0; b=1ce+4+d;
+ 32— 3d— Y9ced?— 40°=0; c=2d+e ;
—10d?+ 15d?e+ 15de?+ 32 =0; d=2e4+f ;
+13¢ — 45f— 45ef?-10f7=0; e =4ft+y;
—78f? +219729 + 111/72 +137=0; f=39+h;
&e. &e,
The equation in d and e gives the multipliers
f= =the pal D5
while a=5d+2e; b=3d+1e; hence for %/5, we have the progression
1D Sa 21.75 48.375 108.0375 241.14575 538 . 284375 ee
eee §6©6- 12275" 28.275’ Gauls7> ” .-141.01875 - 314.'791875 ’ ;

Here the error is reduced about 5 times at each successive step.
The equation in ¢ and / gives

wetegon 585 45
me siae st ae BES igh
while a=12¢e¢+5/; b=7e+3/.
The progression thence resulting is
12 605 34245 1915230 107 241125 en
De soe 20025) e045.” 627714910: *,

converging more rapidly than the former.

From these instances it is clear that the cube root of any number, or the
root of any cubic equation with integer coefficients, may be represented by a
series of chain-fractions of the third order; and not by one only, but by many
of such series. Since the successive steps of the Brounckerian process neces-
sarily depends on the peculiarities of the case, it would be difficult to make a
general analysis beyond the first step; but a symbolical investigation that far
may lead to important results.

VOL. XXXII. PART Il. 3G

320 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF

Let us take the general case of a number exceeding a perfect cube by, say,
a; that is a number of the form v’+a. We have here a=nb+c, and the
equation
a—(n8+a)8=0 F
becomes
—ob + 3n%e+3nde+e=0 ;

- which gives the multipliers

1 37 3n?
r=— ) GS ? = ?
a a a
or more conveniently
Nae 3an, Sn?
Te ra ge te

from which we have the elementary progression

Owe Ie 2. Ont+8an Bint + Bani +a* ge,

a a a®
and thence the progression of fractions

as 0 3+a 9n' + ban? 27n§ + 27an?+ 4a?
0 O- 3n2 *? =9Ont4+B8an ? 27 n®+18an?+a2 ’

convergence to the cube root of the ratio v’—a : n’, is aheaeed from a oral
sion of which the multipliers are
v=a°; g=—3at; p=27n® + 27an*?+ 3a",

the initials being‘

+a” , 0, 3n3+2a
a? 0’ 3n3+1a°

This formula may be generalised by substituting for 2° any number K.
pe = “ is obtained with the multipliers

a®; —3at; 27K2+27aK + 3a?
from the initial terms

+a-*?, 0. 8K+2a
—q"*’ 0’ 3K+1la’

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. o21

sae a ; 8/7 L :
And again, if we write K+a=L or a=L—K, NA K results, with the
multipliers,

(L—K)*; 3(L—K#; 3L24+21KL+3K?2;
from the initials

+(L-K=. 0. K+2L. 2K3430K®L+42K12+71L!
=k s” OI e ROL sOKie IF

These inquiries have been confined to the components of two terms
only of the elementary progression, whereas in chain-fractions of the third
order three terms are admissible. For the purpose then of giving the utmost
generality to our research we shall suppose the three initial terms of a progres-
sion to be

the multipliers being, as before, 7, 7, p. Then, according to what has been
already shown, the xth subsequent terms is

\

|

| [n—2rB+[n—1]{rA+qB}+[n]C _
| [n+2]r6+[n—-1]{ra+o8}+[rly

|
|

If then z be the asymptote of the elementary progression, while S is that of
the series of fractions, we must have

7B+(rA+qB)0+Co? _«
7B+(ratgByot ye

RM a ee BO)

-}and we wish now to express S directly in terms of the nine data, A, B, C; a,

By: p,9,7. For this purpose we must eliminate x from the two equations
| (1) and (2).

Equation (2) may be written im the form
(C—yS8)x2+{7(A —aS8)+9(B—8)}a+-7(B—B8)=0 . . . . . (2)
from which and

2 — Or age m—iO" ue! fo ig rk en Ue) ae ne eee GO)

we have to eliminate z, The elimination gives

322 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF

S8{7°a8 + 2gra°B+ pra*y + (pr+¢q’)aB + (py—sr)aBy—gay*+ (py +7) 6°
+(p?— 9) By — 2pBy* + y°}
—S*{A[87°a? + 4qraB+ 2pray + (pr+9°)B? + (pq—sr)By—ay’]
+ Bl2gra’+ (2pr+29")aB + (v9 —8r)ay + (Bp9 + 37)B? + (2p? — 29) By —2py?]
+C[ pra’ + (pq—87)aB — 2gay +(p*—9)8°—4pBy + 3y"]}
+S{a[37r?A?+ 4qrAB + 2prAC + (¢?+p7)B? + (pg —37)BC—qC?]
+ B[2qrA?+ (2pr+ 2¢°)AB+ (pq —38r)AC + (3p¢ + 37) B? + (2p? — 2¢) BC — 2pC?]
+ y[prA?+(pq—3r)AB—2qAC + (p?—q)B*—4pBC + 8C?]}

—S°{r? AS + 2qrA?B + prA2C + (pr+q7)AB? + (pq— Seals —9AC?+( hae --
(p?—q)B?C —2pBC?+C33}=0 . . .. . A; came : ee

Thus it appears that, while the root of every cubic equation may be reached
by help of a recurring chain-fraction of the third order, every such fraction has
for.its asymptote the root of a cubic. The above equation (3) gives us directly
the form of the cubic when the initials and the scheme of progression are
known ; and, inversely, it contains the means for discovering the progression
suiting a proposed cubic. Thus for such an equation as

GS*— HS?+KS—L=0,

we must equate the above coefficients to G, H, K, L respectively. Here,
among the nine unknowns, p, 7g, 7; A, B, C; a, 8B, y, we have only four
conditions, so that we are at liberty to make five arbitrary assumptions. Now
of the six, A, B, C; a, 8, y, the third power of each occurs; hence the
ultimate equation must contain at least one cube. Thus we are again thrown
back on the solution of a cubic; but in this case we know that it is always
possible so to make the assumptions as that the root may be integer, providec
the coefficients of the given equation be so.

The preceding very involved expressions may be replaced by others con-
siderably simpler. The xth term of the progression may be written

D[v]+ E[n—1]+F[n—2]
d[n|+e[n—1]+F[n—2] ’

where D takes the place of rB, E that of (rA+qB), and F that of C; an
similarly for the denominator. ‘The asymptote then is

Da? +Ezr+F

da* + ea +f i

whence
(D--dS)a?+(E eS)e—(F—/f)ce=0.

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 323

The elimination now gives

S*{77a? —qrd’e+ (q?— 2pr) dif + prde’ — (pg + 3r)def+ (p* + 29)df?+ re —geft pef? +f}

— $?{373Dad? — qr(2Dde + Ed?) + (q?— 2pr)(2Ddf + Fad?) + pr(De? + 2Ede) — (pq +37)
(Def+ Edf + Fde) + (p?+ 29)(Df? + 2Fdf ) + 37He?— q(2Hef + Fe”) + p(Ef? + 2Fef)
+3Ef%}

+81{3r3D?d — gr(D?e + 2D Ed) + (9? — 2pr)(D?f+ 2DFd) + pr(2DEe + Ed) — ( pg +37)
(DE/+ DFe+ EFd) + (p?+ 2¢)(2DF/+ Fd) + 37 Ee — q(E2f+ 2EFe) +p
(2EFf+ Fe) +3F7/ }

—§$°{ 72D — grD?E + (q? — 2pr)D?F + pr DE? — (pg + 387) DEF + (p?+ 2q)DF?+7E? —qE°F
ee 0) ts NO Gwe Susss, “ent ge gact @acsrt ts we * oe nt AAD

It may be interesting to apply this method to some problems in geometry ;
and we may take the construction of the heptagon as a first example.

The ratio of the diagonal to the side of a regular pentagon is given by the
well-known series0,1,1,1,2, 3, 5, 8, 18, 21, &c, in which each term
is the sum of the two preceding, this being a progression of the second order
having the multipliers g=1, p=1

The relation between the long diagonal, a, and the side, b, of a heptagon
is easily shown to be

a3 — 2a7b — ab? +03=0,

which gives at once the multipliers r=1, g=+1, p=2, whence tbe pro-
gression
(re Opetiie2 oe il 825). OO), 120, 289, O50... &E..,

each new term being the double of the last found together with the difference
between the preceding terms. The convergence here is slow; to make it more
rapid we may write a=2b+c, and so get the equation

~ a adieeelionenes

—034+-3b%e+ 4b7+=0.

This gives the multipliers =1, g=4, p=3; whence the progression

324 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS OF

and a still more rapid convergence is obtained by putting b=4c+d; we then
find
b&—20ced—9e?—- B=0,
while
a=9e+2d, b=4e+4+1d.

Here r=1, g=9, p=20, and the rapidly converging series is

0 182 3721 76067 185805

9
> O° 4 BL’ Te56’ 33853’ e2eg1? &*

Enneagon.

If we contract an isosceles triangle, having each angle at the base quadruple
of the angle at the vertex, and if we lay off along the side two parts, each equal
to the base, and from the vertex one part, the three measures overlap by a
distance easily shown to be the fourth term of a continued proportion, of which
the side and the base are the first and second terms.

Hence, if @ be the long diagonal of an enneagon, and 0 the side,

a:b? ::b: 38b-—a,
or
“—8ab+b?=0.

This equation gives at once a series having r=—1, g=0, p=8 for the
multipliers, viz.—

F

0,0, 1, 3, 9, 26, 75, 216: 622, 1791, S157 padeee

which converges pretty rapidly to the ratio of the base to
the long diagonal. Here, from thrice the term last found,
we subtract the ante-penult, in order to get a new term;
that is, from thrice AB we subtract PN to obtain AF.
From thrice AF we should subtract KB to get the
long diagonal of an enneagon having FA for its side,
and so on, the distances PN, KB, BA, AF being
continued proportion.

The figures FMNP and FABK are evidently similar;
so if in the continued direction FB we measure from K,
twice FB, to M’, we shall obtain an enlarged edition of th
figure FM NP.

The convergence becomes more rapid if we put a=3
—c, so as to get the equation

b—9b2c+6bce—c2=0.

CUBIC EQUATIONS BY HELP OF RECURRING CHAIN-FRACTIONS. 325
The multipliers 7=1, g=—6, p=9 thus found give the progression

ele 0 3 26 216 1-791 14849
en ee i Oe? Oe > Ley

&e.,

which contains each alternate term of the preceding.

| The construction of a regular polygon of eleven sides involves an equation

_ of the fifth order, and would introduce chain-fractions also of that order. The
extension of the present method to that case offers no difficulty, but would
pass beyond the scope of this paper.

In the preceding examples we have several times examined the progression
formed by each third term of the series; and in the last example we have
noticed the progression of the alternate terms. This brings us to the general
law, that the terms taken at equal intervals along a series of recurring chain-
fractions form a series of the same kind. Thus [0], [2], [4], [6], &c., are
connected by the law

| [~—4] {07} x [w—2]{2pr—9?} + [a] ip? + 2g} =[n—2],

| the multipliers being

| R=7?, Q=29r—-¢@, P=p? +2¢.

And, similarly each third term forms a progression according to the law
[n—6]{r3} +[n—3] fg? — 3pqr—3r°} —[n]{p + 3p9 +37} =[n+3],

where
R=; Q=@—d8pgr —37°; P=p?+3pq+3r.

In the same way, for the terms four steps apart, we have

R=—1*; Q= — 2p'r? + 4pq?r— 9 + 497° ;
P=p'+4p7q+4pr+2¢’.

This law of recurrence extends to chain-fractions of all orders, and even to
periodic continued fractions. Thus, in seeking the square root of 7 by the usual
\process, we get the successive quotients 2;1,1,1,4;1,1,1, 4; &,
occurring in groups of four, and giving the converging fractions,

4 1 il + 1 it i
Se 3m 6 45 C82 aT 00. ih, SO 0
3

ae 7? SY AR? 208” 6 OF “AO rer

326 EDWARD SANG ON THE APPROXIMATION TO THE ROOTS, ETC.

If we select here the last term of each group as = = hs a , &., or the

2 37 590
first term as [> 77° 593° &c., we form a progression with the multipliers g=1,

p=16. Similarly, for the square root of 20, we get the quotients 4; 2, 8;
2,8; &c., occurring in groups of two, the successive approximations being

A 2° 962 8 2
1.4 = 76 161.1364 2889 é ° 1 9. Lely 2.883
0° LT’ ; T7’ 36 ) 305 > 46’ &C., nN which the terms 0 ’ Dp} ’ 36 5) 646 ) &e )

progress with the multipliers g=—1, p=18.
This circumstance greatly facilitates our investigations in quadratics; thus

if the indeterminate equation
e=Ty? +1

were proposed, we have at once the solution by seeking ,/7, and taking the
last term of each group; thus
¥ Mellel Wal) =e
(= 7 Y= 48 >
xv=2024, y=1765, and so on,

are the solutions. “
When the group of quotients consists of two terms a, 8, the order of

recurrence is given by g=—1, p=a8+2.

For a period with the three quotients a, 8, y, we have g= Sek p= aBy
+a+Bt+y. }
For one with the four, a, B, y, 8, we have q=—1, p=aByd+(a+y)

(B+8)+2.

The subject, however, is too extensive to be treated as an syecnds to the
present paper. q

(327%)

XIX.—On Knots. Part I. By Professor Tarr. (Plate XLIV.)
(Read 2nd June 1884. )

One main object of the present brief paper is to take advantage of the
results obtained by Kirkm4n,* and thus to extend my census of distinct forms
to knottiness of the 8th and 9th orders; for the carrying out of which, by my
own methods, I could not find time. But I employ the opportunity to give, in
a more extended form than that in the short abstract in the Proceedings, some
results connected with the general subject of knots, which were communi-
cated to the Society on January 6, 1879, as well as others communicated at a
later date, but not yet printed even in abstract.

L Census of 8-Fold and of 9-Fold Knottiness.

1. The method devised and employed by Kirkman is undoubtedly much
less laborious than the thoroughly exhaustive process (depending on the
Scheme) which was fully described and illustrated in my former papert; but it
shares, with the Partition method, which I described in § 21 of that paper and
to which it has some resemblance, the disadvantage of being to a greater or less
extent tentative. Not that the rules laid down, either in KirkmAn’s method or
in my partition method, leave any room for mere guessing, but that they are too
complex to be always completely kept in view. Thus we cannot be absolutely
certain that by means of such processes we have obtained all the essentially
different forms which the definition we employ comprehends. This is proved
by the fact that, by the partition method, I detected certain omissions in
Kirkman’s list, which in their turn enabled him to discover others, all of which
have now been corrected. And, on this ground, the present census may still
err in defect, though such an error is now perhaps not very probable.

On the other hand, the treatment to which I have subjected K1rkman’s col-
lection of forms, in order to group together all mere varieties or transformations
of one special form, is undoubtedly still more tentative in its nature; and
thus, though I have grouped together many widely different but equivalent
forms, I cannot be absolutely certain that all those groups are essentially
different one from another. :

Unfortunately these sources of possible error, though they tend (numeri-
cally) in opposite directions, and might thus by chance compensate one another

* Ante, p. 281. + On Knots, Trans. R.S E., 1876-7.
VOL. XXXII. PART II. 3 H

328 PROFESSOR TAIT ON KNOTS.

so far as to make the assigned numbers of essentially different forms accurate,
cannot in any other sense compensate. In other words, there may still be
some fundamental forms omitted, while others may be retained in more than
one group of their possible transformations. Both difficulties grow at a fear-
fully rapid rate as we pass from one order of knottiness to the next above ; and
thus I have thought it well to make the most I could of the valuable materials
placed before me ; for the full study of 10-fold and 11-fold knottiness seems to
be relegated to the somewhat distant future.

2. The problem which Krrxman has attacked may, from the point of view
which I adopt, be thus stated :—“ Form all the essentially distinct polyehdra*
(whether solids, quasi-solids, or unsolids) which have three, four, &e., eight, or
nine, four-edged solid angles.” Thus, in his results, there is no fear of ©
encountering two different projections of the same polyhedron; or, in the
language of my former paper, no two of his results will give the same scheme. —
Thus there is no one which can be formed from another by the processes of §5 —
of my former paper.

3. But, when a projection of a knot is viewed as a polyhedron, we necessarily
lose sight of the changes which may be produced, by twisting, in the knot itself —
when formed of cord or wire; a process which (without introducing nugatory |
crossings) may alter, often in many ways, the character of the corresponding
polyhedron. This subject was treated in §§ 4, 11, 14, &c., of my former paper. —
But it is so essential in the present application that it is necessary to say some-
thing more about it here. It would lead to great detail were I to discuss each
example which has presented itself, especially in the 9-folds ; but they can all
be seen in PI. XLIV., by comparing together two and two the various members
of each of the groups.

The following example, however, though one only of several possible trans-
formations is given, is sufficiently general to show the whole bearing of the
remark, so far at least as we at present require it. ]

It is obvious that either figure may be converted into the other, by merely
rotating through two right angles the part drawn in full lines, the dotted part
of the cord being held fixed. Also, the numbers of corners or edges in the
right and left handed meshes in these two figures are respectively as below :—

* This word is objectionable, on many grounds, in the present connection. But a more suitable
one (loes not oceur to me; and the qualification (given in brackets) will prevent any misconception.
Of course no projection of a ¢rue polyhedron can be cut by a straight line in two points only.

PROFESSOR TAIT ON KNOTS. 329

55332 nq 04882
443322 ® 433332,

These numbers would necessarily be zdentical if the forms could be repre-
sented by the same scheme. As will be seen by the list below, § 6, these are
respectively the second, and the sixth, of the group of equivalent forms of
number vit of the ninefold knots. (See Plate XLIV.)

The characters of the various faces of the representative polyhedra (so far at
least as the number of their’sides is concerned) are widely different in the two
cases. [Mr KirKxman objects to this process that it introduces twisting of the
cord or tape ztse/f, No doubt it does, or at least seems to do so, but the
algebraic sum of all the twists thus introduced is always zero; 2.¢., by “ iron-
ing out” the tape in its new form, all this twist will be removed. I have often
used a comparison very analogous to this, to give to students a notion of the
nature of the kinematical explanation of the equal quantities of + and — elec-
tricity, which are always produced by electrification. If the two ends of a
stretched rope, along whose cylindrical surface a generating line is drawn, be
fixed, and torsion be applied to the middle by means of a marlinspike passed
through it at right angles, one-half of the generating line becomes a right-
handed, the other an equal left-handed cork-screw. Thus the algebraic sum
of the distortions is zero. And, in consequence, if the rope be untwistable
(the Universal Flexure Joint of § 109 of Thomson and Tait’s Natural Philosophy)
and endless, the turning of the spike merely gives it rotation like that of a
vortex-ring. Such considerations are of weighty import in many modern
physical theories. |

As will be seen, by an examination of the latter part of Plate XLIV., even
among the forms of 9-fold knottiness there are several which are capable of
more than one different changes of this kind. Some of these I may have failed
to notice. But it is worthy of remark that the 8-folds seem, with two excep-
tions, to resemble the 7-folds in having at most two distinct polyhedral forms
for any one knot.

4. KirkMAn’s results for knottiness 3, 4, 5, 6,7, when bifilars and composites
are excluded, agree exactly with those given in my former paper. I have
figured these afresh in Plate XLIV., in the forms suggested by KirKman’s
drawings, omitting only the single 6-fold, and the single 7-fold, which are com-
posite knots.

As will be seen in the Plate, where they are figured in groups, there are but

18 simple forms of 8-fold knottiness. Besides these there are 3 not properly

8-fold, being composite (¢.¢., made up of two separate knots on the same string) ;
either two of the unique 4-fold, or a trefoil with one or other of the two 5-folds.
These it was not thought necessary to figure, especially as they may present.
themselves in a variety of forms.

330 PROFESSOR TAIT ON KNOTS.

And the Plate also shows that there are 41 simple forms of 9-fold knotti-
ness. Besides these, and not figured, there are 5 made up of two mere separate
knots of lower orders, and one which is made up of three separate trefoils.

5. Thus the distinct forms of each order, from the 8rd to the 9th inclusive,

are in number

AL hie ok 2h nase
or, if we exclude combinations of separate knots,

1 Ae oe dk Oe AL.

The later and larger of the numbers in these series, however, would be con-
siderably increased if we were to take account of arrangements of sign at the
crossings, other than the alternate over and under which has been tacitly
assumed; and which are, in certain cases, compatible with non-degradation of
the order of knottiness. This raises a question of considerable difficulty, upon
which I do not enter at present. Applications to one of the 8-folds and to one
of the 9-folds will be found in my former paper, § 42 (1).

Another interesting fact which appears from Plate XLIV. is, that there are
six distinct amphicheiral forms of 8-fold knottiness: at least if we include one,
not figured, which consists of two separate 4-folds; in which case we must
consider that there are two six-fold amphicheirals, the second being the com-
bination of right and left handed trefoils, described in § 13 of my former paper.
Thus the number of amphicheirals is, in the 4-fold, 6-fold, and 8-fold knots
respectively, either 1, 2, 6, or (if we exclude composites), 1, 1, 5. All but two
of these 8-fold amphicheirals were treated in my former paper, two having been
separately figured, and the other being a mere common case of the general
forms of § 47. |

Finally, as a curious addition to the paragraphs on the genesis of amphicheiral
knots, given in my first paper, I mention the following, which is at once suggested
by the amphicheiral 6-fold :—Keeping one end of a string fixed, make a loop on
the other; pass the free end through it and across the fixed end; pass the free
end again through the external loop last made, then across the fixed end,
and so on indefinitely. The second time the fixed end is reached we have
the trefoil (if the alternate over and under be adhered to), the third time we
have the amphicheiral 6-fold; and, generally, the mth time, a knot of 3(m-1)
fold knottiness, which is amphicheiral if » is odd. Three of these were, inci-
dentally, given in my former paper.

But, reverting to the main object of my former paper, we now see that the
distinctive forms of less than 10-fold knottiness are together more than sufficient
(with their perversions, &c.) for the known elements, as on the: Vortex Atom
Theory.

6. From the point of view of theory, as suggested in §§ 12, 21, of my

PROFESSOR TAIT ON KNOTS. 331

former paper, it may be well to give here the partitions of 2n which correspond
to true knots—for the values of m from 3 to 9 inclusive. The various parti-
tions, subject to the proper conditions, are all given, in the order of the number
of separate parts in each; those which have a share in one or more of the true
knots, as given in the Plate, are printed in larger type.

co N= 6 (contd.) N =8 (contd.) n=9 N =9 (contd.)
33 42999 772 99 66222
22:2 33222 763 972 65322
222222 754 963 64422
664 954 64332
N=4 a 655 882 63333
——- = 8429 873 55422.
44 77 8332 864 55332
422 752 7522 855 54432
332 743 7432 774 54333
2222 662, 7333 765 44442
653 6622 666 44433
644 6532 9522 822222
N=5 554 6442 9432 732292
7322 6433 9333 642222
55 6422 5542 8622 633222
532 6332 5533 8532 552222
442 5522 5443 8442 543222
433 5432 4444 8433 533322
4229 5333 82229 7722 444929
3322 4442 73229 7632 443322
22222, 4433 64222 7542 433332
62222 63322 « 7533 333333
53222 55222. 7443 6222229
nN=6 442922, 54322 6642 5322229
ae 43322 53332 6633 442922292
66 33332 44422 6552 4332222
642 422222 44332 6543 3333222
633 332222 43333 6444 42222999
552 22929299 622229 5553 33222222
543 532222 5544 222222222,
444 nN=8 442229 93222
6222 — 433222 84222
5322 88 333322 83322
4499 862 4229229 75229
4332 853 3322222, 74322
3333 844 22222222 73332

The whole numbers of available partitions are thus in order :—
2, 4, 7, 14, 23, 40, 66.
Of these there are employed for knots proper only
Ie. 4 A We 17. 36.
respectively. The remainder give links, or composite knots, or combinations
of these. (See Appendiz.)

To enable the reader to identify, at a glance, any knot of less than 10-fold
knottiness, I subjoin the partitions corresponding to each figure in Plate XLIV.
It is to be remembered that (as in § 15 of my former paper) deformations which
are compatible with the same scheme, however they may change the appearance

¢

332 PROFESSOR TAIT ON KNOTS.

of a knot, do not alter the partitions. But it is also to be remembered that
identity of partitions, alone, does not necessarily secure identity of form.
The 3, 4, 5, and 6-folds may be disposed of in a single line.

n=3 n=4 n=) n=6
33 sen 442 55 543 552
222 332 3322 , 22222 4332 , 3838222. ., .33222

Here the bar indicates not only that the right and left-handed partitions
are alike in number and value, but also that they are similarly connected, 7.¢.,
that the knot is amphicheiral.

For the Sevenfolds, we have

if II, - UL
5333, 4433 5482 5432 5432 4433
45322 43322 43322 33332 44992 44229
IV. Vv. VL VIL.
644. 5522 662 77
332222 44222 ga0202° 9222999
For the Eightfolds,
L re Til.
54322 | 54322 | 54322 53332 | 44332
44332 53332 44332 43333 44499 44499
IV. Vv. Wal: Vile
5443 54322 m 6532, 6532
333322 44332 54322 44332 333322 433222 43333
VIII. TX: ae <r
6433 5443 5542 54322 54322 55222 9, 55222.
433222 °* 433999 433222 44332 54322 44332 54329
RL RAUL: xy: XV. XVI XVIL. XVIIL.
6532 655 763 754 772
543.22 433222 3322229 3322292 3322222 55222 3322999

Finally, for the Ninefolds, the list is

I. II.
44433 63333 63333 | 54333 9 54333 | 44433 0 4d
433332 533322 °° 443322 °° 533322 °* 443322 °° 533322 — 443322

PROFESSOR TAIT ON KNOTS. 3390

WT TN
54333 44433 54439 54432 54432 54482
443322 °' 443322 533322 °' 533322 °F 443399 °° 443322
V. VI. Vik
44449 64332 |, 85332 | 64332 54432 54432
AAB2DD, 443322 °' 443322 ° 443399 433339 °° 433339
VIL

64332 55832 64332 | 55332 | 55332 64332
443322 °§ 443399 °' 593399 %* 599999 ©F 43939999 OF 499299

EX. x: x xa0e
54432 5553 5544 64422 | 64422 64422 64422
443322 3333222 3333222 433332 °* 3333383 °F 533392 ° 443392
XIE ARIE
55422 55422 55429 65322 |. 65322 | 65322 65322
443399 °* 539392 °' 433332 433332 °" 433332 ° 533329 °F 443392
KV, XVI.
65322 55332 58332 | 65322 7632 7632 7682
443322 °F 443322 © 543992 °F 543222 3333222 °° 3333222 ° 4339999
XVII. XVIII.
64332 64332 64432 54432 64332 54333 54432
533322 ° 443392 ° 533322 © 443329 543222 ° 543222 °F 543299
xX Oe
55422 55422 55832, 54432 54432
533322 ° 443322 543992 % 543992 © 543999
XI. Oa0e
7443 7443 6543 6543 7533 6633 7533 6633

4332222 ° 3333222 ° 3333292 °° 4339992 4332222 °° 4332292 % 3333999 3333999

DX IIT, XXIV. XXKV.
6543 5553 6552 6552 64422 | 44d? | dddd2 64429
4332222 9 4332292 4332222 * 3333222 443322 © 543999 °F 443329 °F 543999
XXVI. XORVIL XXVIII.
66222 | 66222 | 66222 5544 6543 7533 , 6543
443322 543222 °F 443322 4429292 * 4499999 4332222 °° 4339999
maxX. Sexxy 09.4
64422 64422 7542 7542 65322 55332

543222 °F 443322 4332222 ©" 3333222 543222 °" 543999

«

334 PROFESSOR TAIT ON KNOTS.

XXXII. XXXIII. XXXIV. XXXV.
AAMAD or 64422 7632 a 6633 7542 5544 44433
552222 552222 4422222 ~ 4422222 449992 °T 4499999 333333

XXXVI. XXXVII. XXXVIII. XXXIX. XL. XLI.

666 864 882 66222 7722 99
33222222 33222222 33222222 552222 4422222 222222222

It will be seen that the above list suggests many curious remarks. Thus,
in the eightfolds, we have two diferent amphicheirals, each having the parti-

tions 44332. Again, we have es for a knot which is not amphicheiral,

as well as 54322 for one which is amphicheiral. (See §47 of my former paper.)

And we have : ees standing for two quite distinct knots. All these apparent

difficulties, however, are due to the incompleteness of the definition by parti-
tions merely (z.¢., as by Listine’s Type-Symbol). For, in addition to this, it is
requisite that we should know the relative grouping of the right-handed or of
the left-handed partitions.

In the Plate I have inserted the ee given in my former paper to
the various forms of 6-fold and 7-fold knottiness:—and I have also appended to
each form the designation of the corresponding figure in KirKMAn’s drawings.

The Plate contains a great deal of information of a kind not yet alluded to
in this paper. It gives, for instance, an excellent set of examples of Knot-
Sulness. This term implies (§ 35 of my former paper) “ the number of knots of
lower orders (whether interlinked or not) of which a gicen knot is built up.” It is
to be understood as applied to s¢mple forms only ; for we have set aside, as
composite knots, all such as have any one component separable, so that it may
be drawn tight without fastening together two laps belonging to one or two of
the other components.

Thus, as a few of the examples of 2-fold knotfulness among the 8-folds, we
have

vi. and x1. (3-fold and once-beknotted 5-fold) ;
and i. and v. (each two 4-folds) ; while
Ill., 1x., and xtv. are different forms of two (linked) 3-folds.

Among the 9-folds we have, for instance,

xxx. and xxx. (4-fold and clear-coiled 5-fold),
xvi. and xxvi. (3-fold and 6 6-fold),
XIV., XV., Xvi, and xxv. (4-fold and once-beknotted 5-fold).

But we have also

IV., XIII, XXII, and xxIv. (linked 3-fold and 4-fold),
XX., XXvil. (two 3-folds, linked, and with one kink).

PROFESSOR TAIT ON KNOTS. 335

The analysis of self-locked knots, such as rv. and vi. of the 8-folds, and 11, 1x.,
X., XIx., &c., of the 9-folds, is considered below.

Il. Beknottedness.

7. The question of Beknottedness (on which I have occasionally made short
communications to the Society since my papers of 1876-7 were printed in a
brief condensed form) has been again forcibly impressed on me while
endeavouring to recognise identities among KIrKMAN’s groups. I still con-
sider that its proper measure is the smallest number of changes of sign which
will remoce all knottiness. But, shortly after my former paper was published, I
. was led to modify some ideas on the subject, which were at least partially
given there. J had been so much impressed by the very singular fact of the
existence of amphicheiral forms, that I fancied their properties might in great
measure explain the inherent. difficulties of this part of the subject. I have
since come to see that this notion was to some extent based on an imperfect
analogy, due to the properties of the 4-fold amphicheiral, and that the true
difficulty is connected with Locking.

8. The existence and nature of this third method of entangling cords were
first made clear to me by one of the random, sketches which I drew to
illustrate Sir W. THomson’s paper on Vorter-Motion [ Trans. R. S. E., 1867-8 |.
I had not then even imagined that the crossings in any knot or linkage could
always be taken alternately over and under, though I found that I could make
them so in all these sketches. The particular figure above referred to again
presented itself, among others possessing a similar character, while I was
studying the peculiar group of plaited knots whose schemes contain the lettering
- n alphabetical order in the even as well as in the odd places. (See {§ 27, 42,
of my former paper.) But I soon saw that, though I had first detected locking
in those members of the group of plaits where. three separate strings are
involved, essentially the same sort of thing occurs in the other members of the
group, though they are also proper knots in the sense of being each formed

with a single continuous and endless string. And, as the above very simple

example sufficiently shows, we can have locking, independent of either knotting

or linking, with two separate strings. For it is clear that the irreducibility
VOL, XXXII. PART II. 31

3936 PROFESSOR TAIT ON KNOTS.

of this combination depends solely upon the sign of the central crossing.
There is no real linking of the two cords, and there is obviously no knotting.
But if the sign of any one of the crossings, except the central one, be changed,
the whole becomes the simple amphicheiral link, the linking having been
introduced by the change of sign. [This, as will be seen in § 14 below, is an
excellent example of a case in which the key-crossing of a locking is also a
root-crossing of a fundamental loop. |
9. We may therefore define, as one degree of locking, any arrangement, or
independent part of an arrangement, analogous to that above (whether it be
made of one, two, or three separate strings), the criterion being that the change
of one sign unlocks the whole. But it is well to notice, again, that if, in the
above figure, we change the sign of any crossing except the central one, we
have one degree of linking left, and that this has in reality been introduced by
the change of sign. This remark extends, with few exceptions, to more
complex cases.
- 10. Thus, though the following 8-fold knot (which I reproduce from
Trans. R. S. E., 1877, p. 188) does not, at first sight, appear to depend on

|
.
|

locking, we have only to make a simple transformation (as ante, § 3) to re-
duce it to the symmetrical form in which the single degree of locking is

at once evident. It was by considering this knot, with its (quite unex-
pected) single degree of beknottedness, that I first saw the true bearing
of locking in the present subject. (It is given as x. of the 8-folds in Plate
XLIV.) 2
Other excellent instances of the same difficulty are the following. The first
of these is completely resolved, the second changed to the 3-fold, while the third
becomes apparently two linked trefoils, all by the change of the single crossing
in the middle of the lock. But with the 9-fold knot (which is merely a different

PROFESSOR TAIT ON KNOTS. SOF

projection of Pl. XLIV. fig. xxxv.) the trefoils are so linked after: this
operation, that the change of. sign of one crossing of either resolves the whole.

8 8 &

This is, however, much more easily seen by at once changing the signs of the
middle and of the lower (or the upper) crossing, for the whole is thus resolved.
[This course is at once pointed out by the process of § 13 below, if we choose
as fundamental crossings the three highest in the figure.| Hence the beknotted-
ness is 1, 2, 2 in the last three figures respectively.

11. Another instructive example is afforded by the 8-fold knot below,
which is figured as Iv. on Plate XLIV. :—

At a first glance it appears to be made of two once-linked trefoils, and there-
fore to have three degrees of beknottedness. But a little consideration shows
that neither the trefoils nor the link have alternations of signs (7.¢., there is
neither knotting nor linking), but that the whole is kept from resolution solely
by the lap of cord which has been drawn as a straight line in the figure. This
forms, as it were, the tail of a Rupert’s drop; break it, and the whole falls to
pieces. A change of sign of either of the interior crossings on that lap makes
one trefoil; of either of the 4 lateral external crossings, the 6-fold amphi-
_cheiral ; of the upper crossing, the 4-fold amphicheiral ; and of the lower axial
crossing, the 5-fold of one degree of beknottedness. All these modes of resolu-
tion lead to the result that the knot is of 2-fold beknottedness.

12. It is now obvious why, in consequence of locking and not of amphi-
cheiralism as I first thought, the electro-magnetic test fails in certain classes of
cases to indicate properly the amount of beknottedness. For it is clear that
in pure locking there is no electro-magnetic work along the locked part of any
one of the three courses involved. Hence, for the part of a knot or link which
is locked, the electro-magnetic test necessarily gives an incorrect indication of
beknottedness, Perhaps it may be said that, in such cases, beknottedness is
not the proper name for this numerical feature of a knot:—but it is obviously
correct if defined as in §7 above.

-

338 PROFESSOR TAIT ON KNOTS.

13. A simple but thoroughly practical improvement on the methods given
in my first paper for the graphical solution of Gauss’ problem (extended) is as

follows :—Draw the knot or link, as below, with a double line, like the edges ~

of an untwisted tape, and dot (or go over with a coloured crayon) one of the

motes,

two lines. Now it is easy to see that, of the four angles at a crossing, one
angle is bounded by full lines, and its vertical angle by dotted lines. These
will be called the symmetrical angles. Also it is clear that the electro-magnetic
work has one sign for the crossings when the symmetrical angles are right-
handed, and the opposite sign when they are left-handed. Thus we can at once

mark each crossing as 7 or /, silver or copper, at pleasure. If the figure bea

knot, and if we cut it along a line dividing a symmetrical angle, re-uniting the
pairs’ of ends on either side of that line, the whole remains a knot (still with
alternations of over and under if the original was so), but of knottiness at least
one degree lower. When the line divides an unsymmetrical angle, the whole
becomes (after re-uniting the ends, as before) two separate closed curves, in
general linked and, it may be, individually knotted. [When we treat a link in
this way at any of the linkings (2.¢e., where two diferent strings cross one
another), it becomes a knot. It is curious that by this process a knot is
equally likely to be changed into a knot or into a link, while a link always
becomes a knot.| This method has the farther advantage of showing at

a glance the various sets of crossings which we may choose for omission —

(in the electro-magnetic reckoning), as due merely to the cozling of the figure,
not to knotting, linking, or locking. For each such crossing must belong to a
simple loop, which, for reference, we will call fundamental. Such a loop is
detected immediately by its having (throughout) the full line or the dotted line
for its external boundary, and therefore is necessarily closed at a symmetrical

angle. If we now erase these fundamental loops in succession, till no crossings

are left, the crossings at their bases form one of the groups which may be tried.
When part of the knot has locking, it is sometimes necessary to try more than

one of these groups before we arrive at the true measure of beknottedness. —

As this is a matter of importance, it may be well to discuss it a little farther.
14, When there is no beknottedness (whether true, or depending on linking

or locking), the electro-magnetic work, with the proper correction for mere —

coiling, is certainly ni. But this proper correction requires to be found, and
where there is locking its discovery sometimes presents a little difficulty.

When there is no locking, all we need do is to draw the knot afresh, beginning

(i

PROFESSOR TAIT ON KNOTS. 399

at a point external to each of the fundamental loops, and making each crossing
positive when we jirst reach it. It is evident that the fundamental loops or
coils will now be simply laid on one another. The signs of a// the crossings on
any one loop may be changed, while that of the base of the loop is immaterial,
and this process may be carried out with some or all of the other fundamental
loops in any order. Compare the various signs in any state thus produced
with those (alternate or not) of the original knot, so as to find the smallest
number of changes necessary for its full resolution. The sign of the crossing
at the base of each fundamental loop is simply to be disregarded. Another
mode of going to work is to alter the signs at pairs of points where two funda-
mental loops cross, so as to diminish as far as possible the necessary number of
real changes of sign. But we must be very careful in using this process, to see
that it does not introduce locking.

15. When there is locking in part of the knot, the real difficulty is met with
only if the crossing or crossings which form as it were the key of the locked
part, must also be taken as the base or bases of fundamental loops. In this
case we commence the fresh drawing of the knot at a point exterior to the
locking, but on the fundamental loop of which one of the key crossings forms
the base. This ensures that the completion of the fundamental loop is effected
by the dast of the operations on the locked part. But the application of the
method can be learned far more easily from an example or two than from any
rules which could be laid down. Thus the following drawings represent the
results of this method as applied to two of the knots already figured. In the

first of these the two lower external crossings are taken for the fundamental
loops, and we see that the knot (if originally over and under alternately) re-
quires for its full resolution only the change of sign of each of the two cross-
ings which lie in its axis of symmetry. But, if we had chosen the crossings
last mentioned as bases of fundamental loops, we should at once have felt the
difficulty due to locking.

In the second, all four crossings in ‘the axis of symmetry close fundamental
loops ; but the change of the sign of the Jowest of these, alone (which is the
key of the locked part), is required for the full resolution.

340 PROFESSOR TAIT ON KNOTS.

AP PEW DTXK:

Note on a Problem in Partitions. By Professor Tarr.
(Read July 7, 1884.)

In the partition method of constructing knots of any order, n, of knottiness, we have to select from _
the group of partitions of 2n those only in which no part is greater than n, and no part less than 2,

Thus, as given in the text, § 6, we have for sevenfold knottiness the series of partitions of 14;—
but they are now arranged below in classes according to the value of the largest partition.

77 662 554 4442 33332 2222222
752 653 5522 4433 332222
743 644 5432 44222
7322 6422 5333 43322
6332 53222 422222
62222

It is an interesting inquiry to find how many there are in each class, for any value of x. The number —
of classes is obviously n—1; and, if we remove from each the first partition (z.e., that which is not in-
ferior to any of the others), the remainders form a new set of classes of partitions which we may desig-
nate as
Di» Pugh» Pagds +++ Pinas

respectively ;—where py is defined as the number of partitions of s, in which no partition is greater than
7, and none less than 2. }

Without explicitly introducing finite differences or generating functions it is easy to calculate the
values of the quantity p{;—and to put them in a table of double entry which can be developed to any
desired extent by the simplest arithmetical processes. The method is similar to one which I employed
some years ago for the solution of a problem in Arrangements (Proc. R.S.L., viii. 37, 1872).

In the first place we see at once that if r>s

Vs =D -

Thus, if 7 denote the column, and s the row, of the table in which py! occurs, all numbers in the row
following p' are equal to it. Thus the values of p{ enable us to fill up half the table. In the remain-
ing half 7 is less than s; and by a dissection of this class of partitions, similar to that which was given

«

above, we see that

Pi =Di-e FPiregr ts ee FP ot Pit ps;

where the two last terms obviously vanish ; and the first term is obviously 1 in the case of r=s, unles
r<2, when it vanishes.

PROFESSOR TAIT ON KNOTS. 341

Hence, if the following be a portion of the table, the crosses being placed for the various values of
pi, mil or not,
Values of 7.
Sw 16 1708

—

Values of s.
= ii iat a a cae ©
ttt ee + +

ADO FR WD H OS
Pett+tt+t+t+ tio
Uy 02M at i ceo ps meer

a © Ce a)

H+tt+tt
H++4 +4

+K

it will be seen at a glance that the above equation tells us to add the numbers A, B, C, D, E together,
to find the number at K. This is quite general, so that L, in the second last column, is the sum of
A, B,...., H; and all the numbers beyond it, in the same row, are equal to it. In the table on next
page, each number corresponding to the jirst L is printed in heavier type, and its repetitions are taken
for granted.

Thus it is clear that simple addition will enable us to construct the table, row by row, provided we
know the numbers in the first row and those in the first column. Those in the first and second columns
are all obviously zero, as above. The rest of the first row consists of units. These are the values of
p:, %.¢., the first term of the expression above for p?. Hence we have the table on the following page,
which is completed only to 7=17, with the corresponding sub-groups.

From the table we see that p}=8. Hence the partitions of 18, subject to the conditions, are in

number

84+114+114+14+104+8+34+1=66,

_ which agrees with the detailed list in § 7 above.
[The rule is to look out the number p”, and add it to all those which lie in the diagonal line drawn

form it downwards towards the left. But the construction of the table shows us that this is the same
as to look out pz, at once. |

Similarly we verify the other numbers of partitions given in the text.

And it is to be remembered that p” is the number of required partitions in which m occurs, and that
every one of the class p>" has for its largest constituent »—7. Thus, looking in the table for p/ and
the numbers in the corresponding downward left-handed diagonal, we find the series

4 6 5 5 2 i

which will be seen at once to represent the dissection of the partitions of 14 given above.

The investigation above was limited by the restriction, imposed by the theory of knots, that no par-
tition should be less than 2. But it is obvious that the method of this note is applicable to partitions,
whether unrestricted, or with other restrictions than that above. The only difficulty lies in the border-
ing of the table of double-entry. Thus, if we wish to include unit partitions, all we have to do is to put
unit instead of zero at the place »=1, s=0, and develop as before. Or, what will come to the same
thing, sum all the columns of the above table downwards from the top, and write each partial sum
instead of the last quantity added, putting unit at every place in the second column.

Similarly, we may easily form the corresponding tables when it is zequired that the partitions shall

be all even, or all odd.

342

Table of the values of »{; the number of partitions of s in which no one is

PROFESSOR TAIT ON KNOTS.

less than 2, nor greater than 7,

(The values of r are in the first row, those of s in the first column.)

0 2 ae
0 1
1
2
3 Te
4 1 2
5 1 4
6 De
7 1 2
8 om
9 of)
10 2 5
11 Q 4
12 7
13 5
8
7

10

—
for)
So © 9S 6496707080 OC (OZOcS OFCnO (ORO So Ono OVO OLORron OOo ao oO 1S
AA nKWInar or Fr PP WOR WW DH Wb &
—
bo

(RSIS SSS SS) SS OS) CS SS SS) SS) OOS Se OS] OS SS Se ea Ss SD SS SS)
KH OrorcororortorortorororcorororororF:

From what has been stated in the previous pages, it is easy to see how to
extend this table ; forming the successive terms of each row by adding step by
step upwards to the right along a diagonal, thence upwards to the top, zig-zag
along the row of heavier type as soon as it is reached.

5

22

42

6

7

8

113
126
155

2 0) al

95
110
134
155
189

171 215

207

107
123
154
eG
220

115
135
168
197

12:73 14. to 16 my

21
23
33
39
52
61
81
94
122
143
180

24
33
40
53
63
83

98 100 102

34
40
54
64
85

126 130

150

'

3 aa

54 55.
65 65 66
86 87

Amphich! Amphich? o forms Il Two forms
mG. WW ve Il,
IV Unique Sie i Unique aE aes iA aes a fie: ae orms Ill Two fee IV ae
mS , a os eed a , ie VII at ree Vill te forms X pe forms sf — mene

plo SERS Dat

8 Bb 8 Ax

sy XII be XLV id XV Unique XVI_ Unique oor ie wit: ( Il Six forms
sBj sBz oJ 9K 2P 9Q

IL Two ieee IV Four ae a4 Unique VI_Three forms
9 Ab ] 9Aq
rm: a Six areas IX hea X Unique Xl Unique
3Au o AV 2Bec
XIII Three forms a Four forms
eAz 2Bw 2Dw
ee Three forms XVII Four forms XVII1 Three forms
9Fj ]
XX_ Three ea aoe a oe cae Four ioeg
9D1 3D
si a Aan pe Four ee can Three a: ” 35 Two forms
9Fa 9Fc 9Fn 9 Fi 9 Fk 9Gk 9Em 9 Gl 9Hz oHt 9Gp 2Gq
| forms XXIX Two forms XXX Two forms XXXI Two forms XXXII Two forms XXXII Two forms
9Gv 9 Hi 9Gz 9Hh 9Ha a 9Hs oHy
XXXIV Two forms XXXV Unique XXXVI Unique XXXVII Unique soe ne XXXIX Unique re ey XLI Unique
gIt gle oll

F. Huth, Lath® Bdin®

—
©o
i
(Sy)

—

XX.—Philosophy of Language. By Emeritus Professor J. S. BLAckteE.
(Read 7th April 1884.)

The UNIVERSE, as we have it, is an organised system of rational or reasonable
forces and forms; of which the former are the product of the plastic, self-
energising, productive power within, the latter the external presentation or
manifestation of that power.

I. Language is a form of the fluid element, the air, moulded into shape by the
vital forces of any living creature acting under the constraint of a determined
organism, and significant of the sensations, emotions, sentiments, or thoughts of
the creature; transmitted to and made appreciable to other similarly consti-
tuted creatures by the instrumentality of the ear, an organ nicely sensitive to
all the affections of the fluid element, and thus faturally fitted to be the
medium of intelligible communication between creature and creature in a
system of social interdependence.

II. The simplest elements of language which we have in common with the
lower animals are of the nature of cries ejaculated or instinctively sent forth
from the vocal organs of the creature, under the stimulus of some sensations of
pain or pleasure, either arising altogether from within, or called into action by
some external agency, as the pricking of a pin,—such cries as the cawing of
rooks, the purring of cats, the grunting of pigs, the braying of asses, the cackling
of geese, the shrieking of women, and the roaring of men,—cries which arise
necessarily from the nervous constitution and vocal organism of the creature,
and which are naturally intelligible to all creatures of a kindred nature, and
endowed with a responsive susceptibility. These cries in human language
are, in the language of grammar, interjections: such as ha, ha! ho,ho! 4 po,
BaBot. But they are in fact verbs, or at least the soul of a certain class
of verbs, performing, as a means of communication between creature and
creature, the complete function of verbs, and becoming perfect verbs in
grammatical ‘form directly they are tied down by certain modifications to
definite relations of personality and time ; of which anon.

III. Were a human being only a bundle of sensibilities, human language would
consist merely of such ejaculatory words; but this sensibility is only the starting
point of his existence, the point which he has in common with a mouse, a midge,
or a monkey ; he soon becomes a perceptive animal, and after that a mimetic or
imitative animal; being moved by an unfailing instinct to reproduce, in some
form or other, whatever striking forms or energising forces from without may

VOL. XXXII. PART II. 3K

344 EMERITUS PROFESSOR J. 8S. BLACKIE ON

have strongly affected his nature. Hence, the whole family of words, in
grammars stupidly called onomato-poetic, in which we recognise the germ of the
dramatic element in literature, as in the ejaculatory element we may recognise
the germ of the lyrical element. This whole class of words, representing
originally all sorts of natural sounds, is manifestly the product of the native
dramatic instinct of the human creature, and, though starting originally from im-
pressions of sound, readily adapts itself by analogy to cognate impressions of the
other senses, and even to emotions of the mind, and in this way claims a much
larger domain in the field of every cultivated speech than would at first sight seem
to belong to it.

IV. Our next proposition brings us to a higher and a characteristically
human platform. When I call an ox, bo—bov—baa, as in Greek, Latin, and
Gaelic, this, as a mere echo of an animal sound, might be repeated by a parrot,
or any other animal with imitative instinct and apt vocal organisation. But
the moment I use this imitative sound to express the name, not only of the indi-
vidual animal which I just heard utter the sound, but the notion, idea, or type of
a whole class of animals uttering the sound, I plant myself on a platform of in-
tellect of which no animal, not even the cleverest monkey, is capable. The
genesis of the idea in the human soul is a matter of which neither sensation nor
sensibility can give any account; sensation is always the occasion, never
the cause, of the idea. Four eggs, for instance, are no doubt felt to be four by
a dog, or bull, or by a man; but the leap from that to the mathematical
proposition, 2+2=4, is infinite, and cannot be overbridged by any ingenuity.
In forming the idea of an ox or a cow, the vovs or Adyos, which differentiates a
man from a brute, acts plastically from its own dominant centre, and uses
sensuous impressions merely as a multiform material on which the unity of an
intelligent type is impressed; here we have the birth of human, that is intellec- —
tual language, a language expressive, not of sensations or of feelings, but of —
thoughts and ideas, which are as general as mathematical definitions, and are the
pure creations of thinking. In forming them man acts as a god creating an |
organism ; and this truth, so habitually ignored by a certain narrow school of
physical scientists in these latter days, is not the least striking manifestation of
the philosophic depth which lies at the bottom of that text—Gen. i. 27, “God
made man in his own image.” Here we see distinctly the reason why brutes
have no language in the sense that we talk of human language. The vital
forces which belong to them, being purely of sensational and emotional origin,
are satisfied by the lowest form of vocal expression which we call cries ; their .
language is in the main ejaculatory, and in some part also imitative. But
there being no Adyos or vods in them that craves for expressing in intelligible
form, the words significant of types and general ideas, of course no such form
appears ; and man stands emphatically differentiated from them as the only

THE PHILOSOPHY OF LANGUAGE. 345

speaking, because the alone thinking animal ; the Adyos of speech being in part
only the outside of the Adyos of thought, and both expressed significantly in
Greek by the same word. We say, therefore, distinctly that the mass of
human language consists of an array of articulated sounds elevated by the
power of self-acting imperial mind—Bacwkkds vovs, as Plato calls it—from their
original sensous significance into the region of thought, and made thus
to serve as an organ of thinking in the communications of a specifically
thinking animal.

V. That the vows in the formation of language acts in its own imperial style,
and not at all in the manner of Locke’s unhappy simile of the sheet of blank
paper, will appear plainly on considering the nature of that class of words
which, in all languages, is found to express purely mental operations. They
are, of course, formed by a secondary application of originally sensuous
terms; but the point lies not in their origin, but in the selection made from
a host of words of the same origin. Thus, in Greek—xaradapBavo, cvvinnn,
ovddoyilw; in Latin—comprehendo, concipio, intelliyo; in German—/assen,
beyreifen, plainly imply a very distinctly energetic forthputting of the
internal moulding faculty to lay hold of the material presented by the
senses, as a potter lays hold of the clay. And in this regard it is not without
interest to remark that, whereas verbs of sensation generally in Greek govern
the genitive case, verbs of seeing, which is pre-eminently the intellectual sense,
always govern the accusative ; for the same reason evidently that active verbs
generally govern that case, viz., because the accusative is a case of motion
towards a point; that is the appropriate case to mark the invasion, so to speak,
of the external material world, by the internal vital force of the observer in the
act of cognition.

VI. The steps by which language grows from the original simple elements
into the luxuriant expanse of significant sounds found in our dictionaries is not
difficult to trace. The original stock, either in its single nakedness or with
some modifications and slight additions, is adapted to new and very diverse
uses by the law of similitude acting along with the law of parsimony. The law
of parsimony, or a Wise economy and a wise laziness, forbids to invent absolutely
new words when old ones can serve the purpose; and the law of similitude,
which the mind constantly follows in the classifications of science, as in the
inspirations of poetry, by easy steps of transference, leads to an unlimited
variety of uses of the same root, just as in the world of colour dark green may
pass into light yellow. The changes of meaning which the root undergoes in
this process of adaptation to new objects and new circumstances are always
instructive and often amusing. We shall content ourselves with two familiar
examples. The word prick, for instance, whether as a noun or a verb, is, I have
no doubt, derived from the slight sharp sound made by a pin or a drop of rain

346 EMERITUS PROFESSOR J. S. BLACKIE ON

falling on a dry surface. The various forms which it has assumed in its passage
through the millions of millions of human mouths during long centuries, from
Sanscrit, through all the Teutonic languages, will be found in Skeat. They all
signify a dot or spot, or the point that makes it, or the act of making it ; and
the last of the large progeny of small dots or points is one which is said to be
produced either by native virtue of the academic soil at Oxford, or, as Lord
Reay had it, by a peculiar metamorphosis which the rude unkempt Scot some-
times undergoes when he is transplanted to that atmosphere compounded
curiously of the four elements of Greek, Episcopacy, Aristocracy, and Plutocracy ;
so that, to use the language of geologists, a prig is a metamorphic Scot, having
in West End estimation the same relation to a normal Scot that a dainty
Alderney cow has to a shaggy Highland stirk. This is the bright side of the
creature, and the side of course from which he habitually contemplates himself.
The dark side is revealed by the etymology which plainly sets him forth as a
creature of small points and proprieties—a creature mighty in small matters—
a sort of dainty drawing-room pedant—in whom the 76 ceuvdv of true manhood
has been altogether swallowed by the 76 zpérov of smooth convention, and the
To Kopabov of petty elegance and superficial polish. Opposed to him is the
sumph, a creature with neither points nor polish, from the German swmpf, a bog,
coudos, porose, a boggy-brained animal, whose depth, when he has any, is only
a profundity of soft and sinking stupidity. Take now the word bu//—not the
animal which is kin to Bo, but the Pope’s bull, which has nothing to do with
the bovine cousinship in which the model Englishman glories. The Latin
bulla, as every schoolboy knows, was a sort of boss or knob hung round the neck
of patrician boys, and pet lambs sometimes, by fond Romish mamas ; its original
meaning was a bubble of water, from bullio, English bod. This round boss or
knob, in a leaden avatar, came in the Middle Ages to be attached, as a sort of
seal or stamp, to the thundering ordinances which his Holiness of the seven hills
used to thunder over Europe largely, in order to crush kings and frighten fools ;
hence transferred to the document itself; and as the good old gentleman, with
all his infallibility, sometimes blundered, a bull came to signify a blunder; and
as Irishmen are famous for blunders, the little gilded ornament on the baby
patrician’s neck became metamorphosed into a blunder very closely akin to the
bubble out of which the word arose.

VII. The modifications, in verbal form, which the root underwent, in order
to adapt itself to new applications and to acquire new shades of meaning form —
two classes—those of which the origin and significance are either perfectly
plain or can reasonably be presumed, and those of which the significance is
altogether unknown, and in all probability not to be recovered. The general rule
is, in the words of Horne Tooke: “ Nothing in language is arbitrary or conven-—
tional.” Language, like political constitutions and national character, is a growth,

THE PHILOSOPHY OF LANGUAGE. 347

not a convention or an institution. The most superficial dissection of the
familiar forms of words, as we have them in our grammars, distinctly shows this.
Amo amas means merely love I, love thou; the Sancrit asmz, the Latin swum,
and the Greek «iui, being merely the two interflowing elements which are
presented separately in the Gaelic tha mi and the English Jam. So the case
terminations in Greek and Latin are merely significant attachments expressive
of local relationship which have grown into the root in these terminational
languages, but of which the meaning stands clear in that detached form
which these agglutinated postpositives present as independent propositions ;
the sign of the genitive in English of being manifestly = 07, Greek amd, Latin abd,
away from, It matters nothing that we cannot in all cases, or in the majority
of cases, distinctly put our fingers on the original significant form of the abbre-
viated or polished case termination ; enough that man is a reasonable animal,
and that from his reasonable proceeding in known cases we can certainly divine
it in where the formative action is hidden from our view. Words as we have
them, especially terminations, conjunctions, and other such frequently used and
much abused elements of the vocal currency of a country, are like old shillings
from which the image and superscription has been defaced, but which certainly
was there, as it lies in the very nature of a coinage to bear some stamp and
authoritative signature on its face.

VIII. That some modifications made in the root are without separate signi-
ficance, and may without impropriety be called arbitrary and conventional, I
think we must admit ; and so Horne Tooxe’s rule, like other rules, will have its
exceptions, and must not be pressed urgently in all cases. Any child could tell
how rubefacio signifies to make red ; it is merely two words run into one, in the
same way that the Greek use movea in dpromows, a baker; but no man can tell
me how fell came to signify to cause to fall, or how the plural of man should
be men. No doubt in this latter case you may say that the a of the singular
was changed into the e of the plural by the reflex contagion of the ¢ in the plural
termination Manner ; but this is merely the description of a process of contagion
or infection taking place between two contiguous emissions of articulated breath,
not the laying bare of any natural significance in the change which has taken
place. There is nothing in the word /e// that should cause it to mean to cause
to fall; it is a pure matter of convention—an ingenious device, let us say, to
make one word serve two purposes, as faces have been made by ingenious
draughtsmen representing two different persons, according as you look at them
from this side or from that. In the same way no conceivable reason can be
given why wre in German, were in English, should be the subjunctive mood of
was ; or, what is similar, why the a of the indicative of the Sanscrit or Greek
should be softened into y in the subjunctive. It is for the sake of variety and
distinction alone that such changes are made ; and they are in this view perfectly

348 EMERITUS PROFESSOR J. 8 BLACKIE ON

analogous to the change of accent which takes place in English when a verb and
a substantive are in all other respects identical, as in prétest and protést, or in the
case of proper names in Greek— A toyernjs, born of Jove ; Avoyévys, a man’s name;
deEdpevos, having received; Aecéapevds, Mr Receiver. A phenomenon somewhat
different from these cases presents itself in the case of diminutives, which are
made in most languages by the addition of terminations, which, though possessing
no separate meaning in themselves, do really suggest the idea of littleness by the
character of the differentiating syllables. Thus the terminal /, being a pleasant
soft letter, and easy to dwell on prettily with a kindly tongue, seems to have
been used in various languages to express diminutives—as in Latin puer, puella,
puerulus; German Magd, médl; Italian donna, donzella, dama, damigella. The
same explanation may apply to the vowel p in the Greek taddépu, from avd.
It is impossible, however, to see the same propriety in the termination foxos
used to diminish substantives in Greek, as ish is to diminish adjectives in
English, and zke in Scotch, as in lass, lassie, lassikie. It is probable that all
thése terminations, as also the Greek ixdés adjectival termination, are only
varieties of the verb éuxew, to be like, in which case they belong not here, but to
our previous section.

IX. Before proceeding further, it may be well to make two remarks
about roots. (1) However remote the single Sanscrit monosyllabic roots in dha,
tha, ma, &c., may appear from any ejaculatory or mimetic origin, I most firmly
believe that they are merely the curtailed forms of words which had such an —
origin, starting from the impressions made on the senses or from external
sensations; as, for instance, when Max MULLER says that pater, a father,
comes from the root pa, to nourish—even if that be true—I am not at all sure
that the root pa, to nourish, did not first come from the kindly babble of infantile
lips which produced papa, mama, Amme, pata, and py. (2) All roots are, and
must have been verbs originally, for the simple reason that substantives could
not receive names except from certain qualities residing in them; but qualities,
so long as they are quiescent, do not strike the senses sufficiently to stir the soul
to that vocal utterance which is the word ; therefore adjectives, being quiescent
qualities, could not be the first words, but verbs, which are energising qualities or
functions. But the first word, though a verb, while the language-forming
instinct is yet in its infancy, would answer all the three purposes of verb, sub-
stantive, and adjective; as happens in our bald and unterminational English
every day—jire, to fire, fireman—which, had the Englishman spoken Greek,
would infallibly have assumed the triple form of zip, tupéve, and supeurys.

X. Hitherto we have spoken of language only as a useful machinery for the
purpose of communication among social creatures; but language is also a fine’
art, and that in a double sense: a fine art fashioned by Nature under the
influence of that striving towards the Beautiful which is apparent in all the

THE PHILOSOPHY OF LANGUAGE. 349

Divine workmanship, and again cultured and improved by man in virtue of his
divine origin and divine mission on earth, so beautifully expressed by the Stoics—
Contemplari atque imitari mundum. Now, in this view, the perfection of a
language will depend in the first place, as in a musical instrument, on the
number and variety and completeness of the notes which it contains, and again
on the quality of these tones, and lastly on the skill with which they are used by
a natural genius and a practised player. With this high ideal before us, we
shall certainly find no human language perfect ; for, besides that the organs of
utterance in some cases may be of less perfect construction and of inferior
capacity, the most highly gifted peoples in the use of language are apt to have
pet tendencies and to fall into mannerisms, which are not only bad in them-
selves, but do an additional harm by excluding other less-favoured elements of
a perfect vocal gamut from fair exercise. Thus the language becomes lopsided,
and, as in the case of a body palsied in one limb, presents an appearance of
completeness which its power of action does not warrant. It appears to have
two arms, but can strike only with the right or with the left. Any vital
function rarely used is used with difficulty, which gradually hardens itself into
an impossibility ; and so we find whole nations of the highest organic accom-
plishment unable to pronounce certain letters; as the Germans cannot pro-
nounce 7h at all, and the English regularly change the y of the Greeks and the
Scotch ch into &. Some nations cannot even distinguish 7 and /, both liquids,
no doubt, and so akin, but considerably different, both in the movement of the
tongue by which they are pronounced, and in their musical effect on the ear.
On the otber hand, the aspirate which the German cannot enunciate is so
familiar to the Celt that he introduces it regularly where it does not belong,
and not rarely allows it, as in the Gaelic ha for ta, to override and delete the
consonant which it modifies. There is hardly a nation that does not get into a
bad habit of using one part of the machinery by which vocal breath is emitted
with such preference as to impart a mannerism so strong as to become a
distinctive mark of nationality ; thus the Englishman, by the preferential use of
the back of his mouth, gets into what is called the ha-ha style, and the curtailing
of the 7 of its fair proportions, so that

I saw
A beautiful sta-aw = star,

is a perfectly good rhyme to a London, but not to an Edinburgh ear. The
| Greek, on the other hand, gave a preference to the front of the mouth, which
produced the vjrcv and the ov=o0, which the Englishman in his ignorant
| insular fashion refuses to recognise. The Yankee nasalism is another familiar
‘instance of the same kind; and the vocalisation even of the liquid J, as
in Versailles, of the modern French, is the most recent instance of the

350 EMERITUS PROFESSOR J. 8. BLACKIE ON

polished feebleness in which that emasculated offspring of the Latin language
delights.

XI. The quality of the vowels, and the choice and combination of consonants
by which the music of language is specially affected, must depend partly on the
delicacy of the original senses and organic tissue ; and that this is influenced in
a considerable degree by the climate, that is, by the atmosphere which the
speaker breathes from his cradle, can scarcely be doubted. Hence the greater
fulness and sweetness of the English vocalisation compared with the Scotch ;
hence, perhaps, the less musical character of the Teutonic languages generally as
compared with the Greek and Latin. But, though climate no doubt asserts its
sway here, as in a matter as much physical as moral, national character, at the
same time, as the moral element which affects enunciation, cannot fail to make
itself felt; so the Germans and the Scotch, being a more emotional people than
the English, put more soul into their syllables, and draw out their words with a
more kindly moral emphasis ; and it seems impossible not to deduce the nos
tamen sumus fortiores of Quinctilian, spoken in contrasting Latin with Greek,
from the radically different character of the two peoples. But here we must
remark, that the ideal of harmony in a language consists not merely in rich-
ness and sweetness, but in that grand and curiously varied combination of
strength and sweetness by which the great compositions of a BEETHOVEN ora —
HANDEL distinguish themselves from a pleasant or a plaintive popular ditty.
Now the strength or the bones of a language are in the consonants ; and the
trunk, so to speak, of the word lies in the root ; so that the typical language is
that which has always at hand a strong combination of consonants to express
strong feelings, and a rich flow of vowels to express the more delicate emotions.
Now, as we have already said, it is extremely difficult for a language to possess
all excellences ; as the French avez for habetis, pére for the Italian padre, peut
for potest, not to mention the systematic deletion of the mz in the final syllable
of the present indicative of verbs, are a strong proof of how apt polish in this
region is to degenerate into feebleness. Nay, it seems absolutely impossible,
even in the best constituted languages, to combine sweetness with strength in
the degree which an ideal type would demand ; for, as the most significant and
dramatically most effective part of a word lies in the root, it follows that when-—
ever a strong utterance is to be fairly given, then the root which dramatically
expresses the strong word ought to be made prominent. On the other hand,
as the music of a language depends very much upon the cadence of the termina-
tions, which in fact have only their vocalic element to recommend them, itt
follows that, whenever sweetness is to be expressed, these terminations ought
not to be cheated of their natural emphasis. But, as a matter of fact, these
terminations being affixed without distinction to all kind of roots, either,
being accented, will swamp the root, or, being unaccented, will be apt to lose

THE PHILOSOPHY OF LANGUAGE. 351

part of their full musical value, or; at all events, prevent the root from standing
so emphatically on its own legs, and producing its full dramatic effect. One
line from Homer will show this—

4 AS 4 > A tA te) >
Sovmnoe O€ Tec av apabyae Se TEVXE ET AUTH,

and this may stand to verify the general proposition that the English language,
besides being superior generally to either Greek or Latin in the dramatic truth
and vigour of its roots, by virtue of its very lack of terminations, has a dramatic
power in its daily use, which it is as impossible for Greek to emulate as it is
impossible for English to emulate Greek in the volume of sentences and the
cadence of periods.

XII. In the music of language, as the vowels are more sonant than the conso-
nants, so the long vowels and the broad vowels, as a@ and o and w, are more musical
than the short vowels and the slender vowels. Next to the quantity or volume
of sound, the pitch of sound, accompanied as it naturally is with an emphatic
dominance of the accented syllable, has a notable effect on the music of spoken
address, and cannot be transposed or neglected without doing violence to the
genius of the language. In respect of accent, the Greek, as noted by the ancient
rhetoricians, has a decided advantage over the Latin, in allowing the accent to
ride freely, according to certain laws, over the three last syllables ; while the
Latin, like the Gaelic, altogether excluded the accent from the last syllable of
the word, where it is most musical. As the accent is one of the most character-
istic, so it is one of the most persistent elements of the vocal life of a people ; and
in the case of Greek is, accordingly, prominent alike in the books of the ancient
grammarian and in the mouths of the modern people ; a fact which renders
inexcusable the practice of English Hellenists in transferring wholesale the
Roman system of accentuation to the Greek. We have no more right to tamper
with the music of any language than with the colouring of a great painter or
the diction of a great poet.

XIII. A written alphabet, or a body of visible signs significant of sounds, is
| no doubt a grand invention, and a great convenience, but belongs to the philo-
| sophy of language only in a very indirect fashion. A written, graven, or
printed language is for record primarily, not for expression ; like a photograph,
it is an exact likeness, but without the expression which is the soul of the living
image. An OrpPHEUS, therefore, and a Homer, the highest form of lyrical and
epic poetry, was possible to Greece, if not before a written alphabet was known,
certainly before it was used for purposes of writing and reading. Neverthe-
less, it seems certain that without the habit of writing and reading books,
certain forms of literature which appeal to calm introspection, rather than to
present excitement, could not have existed; without a written alphabet, Homer

VOL. XXXII. PART II. a0

352 EMERITUS PROFESSOR J. S. BLACKIE ON

and Hestop could never have been followed in due season by the large range of
historical survey in Heroportus, and the condensed summation of political wisdom
in THucypipEs. <A printed alphabet, therefore, we may say, is the mother of
prose literature, and of the wide expansion of intellectual sympathy and linguis-
tic expression which a prose literature implies. A people that does not read and
write will never demand and never acquire any form of intelligent utterance
beyond the historical ballad, enlarged, it may be, into the popular epic, the
sacred hymn, the secular song, and the popular harangue. An example of this
we have at our own door in the Highlands. The only other remark that occurs
to me to make on the alphabet is, whether it ought to be a system of visible
symbols distinctly representing articulate sounds, as in all the languages with
which European civilisation is familiar, or indirectly by means of abbreviated
pictures of the things which the words represent, as in the ideographic writing of —
the Chinese. This method, compared with the other, is evidently the product of
an earlier stage of civilisation, crude, clumsy, and cumbrous, having neither the
poetry of a picture, nor the flexibility of an alphabet of spoken signs to recom-
mend it. But whether the use of it entails on the people who have not
advanced beyond this first stage of visible speech, any other disadvantage than
the necessity of cumbering the mind with a more complex array of memorial —
signs, I do not know, and shall be happy to learn.*

XIV. Language, as noted above, is not a convention, but a growth; and as
a growth, like the human individual, has its infancy, its youth, its manhood, its
age, its decrepitude, and its death; and the same circumstances that favour or
stunt the growth of the individual affect in a similar way the growth of a lan-—
guage. The best parentage for a language is a fine climate and a great story
teller, in its infancy and youth. The Greeks had both. Homer was at once
their secular and their sacred Bible; and as such acted powerfully from the
first, and without any diminution of action even to the present hour, both as a_
spur and a rein; a spur to exertion so brilliantly begun, and a rein to unre-
gulated, unchastened, and unfraternising exertions in future fields of intellectual
glory. The next condition of the luxuriant growth of language—of course,
always supposing rich natural endowments—is that the national mind, the
outcome of the national life, should not be disturbed in the natural progress of
its evolution. This disturbance usually occurs from some extraneous influence,
acting either violently in the way of conquest, or peacefully in the voluntary sub-
mission which a weak nation is always apt to pay to a stronger. From both
these disturbing forces the Greek language remained free. Escaping trium-
phantly by the heroic struggles of Marathon and Salamis from the threatened

* Since this paper was read I have seen Professor Lecer of Cambridge, who expressed himself

decidedly of opinion that the ideographie writing of the Chinese acts as a hindrance to the rich develop-
ment of the spoken language. |

THE PHILOSOPHY OF LANGUAGE. 300

despotism of Asia over Europe, Greece had full time to put forth her intellec-
tual strength in all departments, according to the law of a natural growth, before,
from internal dissensions, she was obliged to submit politically to the world-wide
influence of Rome. But here again the importance of an early and ripe culture
of the national language showed itself in the most brilliant style. The con-
queror, instead of crushing, stooped to adopt the language of the conquered;
and when the Western Empire fell to pieces by the incursion of northern
barbarians, Greek still flourished in the oldest half of the Christian Church
and the Eastern half of the Roman Empire. It thus obtained a lease of life
more than 1000 years beyond what might have been supposed to be the epoch
of its natural demise ; and when, by the overthrow of the Byzantine Empire in
1453, its complete collapse seemed almost certain, the repulsion between the
Turkish faith and the Christian preserved the language from the amalgamating
and absorbing force which, under the common circumstances of conquest, must
have worked its dissolution. It remains, therefore, at the present hour, a
wonder of linguistic longevity unique in the history of language, and bidding
fair, in spite of the artificial life in which Latin is preserved by the Roman
Church, to spread out the branches of a green old age over every part of the world
that is not too wise in its own conceit, or too isolated in its own narrowness,
to own the civilising influence of the moral culture which belongs to the present,
only when it bears with it the most valuable inheritance of the past.

XV. The disturbing forces alluded to in the previous section either produce
what may be called a violent death, if the resisting forces, as in the case of Gaul
and Spain when conquered by Rome, are weak, or they produce a fusion more
or less complete between the superimposed and the underlying stratum, and
a mixed language of greater or less heterogeneousness of structure is produced,
Such is the character of our own English tongue. Now, though it is quite sure
that chance cannot make a language any more than a world, yet out of a chanceful
throwing together of two languages, a mixed product of very excellent character
may procced ; just as when two good puddings are thrown together, the com-
pound result will at all events contain all the good that is in each of the constitu-
ents, a good resulting not from the chance fashion of the mixture, but from the
cunning preparation of the materials out of which the mixture was made. With
all this, however, it is quite certain that this blind way of throwing two good pud-
dings into one is not the way to make the best pudding ; there is no certainty
in such a process that the two puddings may harmonise and coalesce into a
congruous, classical unity of the pudding genus. And so the English language,
however excellent, and however worthy of the commendation of such a distin-
guished philologer as Jacop Grimm, and however glorified by its having been
made the organ of expression by the greatest dramatist the world ever saw, has
some very manifest defects, which, both from a philological and a practical point

354 EMERITUS PROFESSOR J. S. BLACKIE ON

of view, place it on a lower platform than such self-developed languages as
Greek and German. For (1) by the violent disturbance of its growth at an early
period of its development, its power of compounding simple words and using its
own roots has been so maimed and curtailed, that it is constantly obliged to borrow
from all sources, in a fashion often clumsy and inelegant, and without that com-
plete assimilation which is necessary to enable borrowed forms to satisfy the
demands of a cultivated linguistic taste. (2) The linguistic instinct of the people
acts so weakly that any irregularity creeps easily into it, and a subjection to the
whims of fashion, that mar its esthetic effect, and render it very difficult for a
stranger to follow its vagaries. This remark applies particularly to the pronun-
ciation and accentuation of our tongue. (3) What is worst of all, the immense
mass of borrowed materials, taken and constantly being taken into our language
from foreign sources, distinct both in space and time from our colloquial cur-
rency, issues in the creation of a stratum of language, running parallel to the
vulgar English, which only scholars and persons of large foreign culture can
readily understand ; thus planting a prickly fence between the learned and the
unlearned, in the highest degree unfavourable to the diffusion of scientific
knowledge. It is an evil similar in kind, though less in degree, to that under
which the whole of Europe suffered before the appearance of DANTE in Italy,
SHAKESPEARE in England, and LEssine in Germany, viz., that, while social inter-
course was carried on in the language of the country, knowledge of every kind
was acquired and accumulated and stored in the language of the ancient Romans.
XVI. But the phenomena caused by the violent invasion of one language
by another are not exhausted either by the complete extinction of the invaded
language on the one hand, or by its hybrid mixture with the invading language
on the other. It is possible, on the one side, that the language of the invaders,
though maintaining its acquired dominion, and remaining in all its constituent
elements substantially the same, may, through the combined effects of time,
change of atmosphere, and action of new circumstances, undergo such extensive
modifications as to become, not a new language indeed to the eye of the philologer, —
but an old language with a new face ; and, on the other side, it is equally possible
that the language of the invaded country, partly from its own inherited strength,
partly from the intellectual weakness of the invader, may maintain its ground
firmly, and yet, as in the previous case, from the influence of time and action of
new social forces, become practically to the vulgar eye a new language, while
to the scientific eye it is only a modification of the old. Of these two classes of
what we may call, not mixed but metamorphic languages, the Romanesque
languages—French, Spanish, Portuguese, and Italian—form familiar examples.
To understand their formation we must bear in mind that, as all things in the
world, specially all living things, in HEractitus’ phrase, pe wavra, are in a
constant flux, so specially language, from being a very fluid material, and easily

THE PHILOSOPHY OF LANGUAGE. 355

yielding to slight and accidental influences, when it has once acquired a fixed and
what may be called a classical type, can preserve this type only so long as the con-
tinuity of political and intellectual forces to which it and the type belong is not
broken. The moment this continuity is broken, which acts as a restraining and
conservative authority, the loose elements of which every language is composed
are set adrift, so to speak, and left to be affected in every possible way by incal-
culable and often capricious forces, of which action, continued through genera-
tions, a metamorphic type of the original tongue must necessarily be the out-
come. The changes thus produced on the old classical type of the language
may be classed partly under the head of what Max MULLER calls phonetic
decay; that is, a smoothing and rubbing down of the language, by a process
similar to attrition in the mineralogical world—a process which is always in one
sense a corruption, and which often arises from no nobler cause than the
laziness or carelessness of the speaker, but which, in the result, according to the
degree of its action and the character of the materials acted on, may either be an
emasculated enfeeblement or a musical improvement of the original tongue. But
these changes are not all processes of decay; along with the decay a process
of reconstruction is largely going on, in which the most active element is the
coming to the surface and emphatic self-assertion of certain original vital and
plastic forces in the popular tongue, which had been over-ridden and suppressed
so long as authority and fashion maintained the cultivated type of the language
in a position of acknowledged superiority. Add to these elements a very
slight sprinkling of strange elements in the metamorphic tongue—such as of
Arabic in Spanish, of Teutonic in French and Italian—and we have dis-
tinctly before us the conditions under which all metamorphic languages of
the two classes represented by French and Italian assume their new type. Both
languages are substantially Latin; but in the one the invading element became
subject to the metamorphic action from the downfall of the Roman Empire, and
the loss of all linguistic guidance thereon consequent; while in the latter
the language of the invaded survived in a metamorphic shape, partly from the
partial and irregular action of the invading powers, but principally from
the ecclesiastical and intellectual supremacy which, under the most unfavourable
circumstances, the invaded language did not fail to assert. It need scarcely be
remarked also that, in proportion as the native Latin form of the language
acted with more potency and with less disturbance on its native Italian ground
than when transferred to Celtic France, in the same proportion, Italian would be
a less corrupted, a more masculine, and a more majestic form of the old Roman
tongue than that which is now wielded so dexterously by the brilliant wits and
clever writers of the old insula Parisiorum.

XVII. Under this section, which has led me to talk of phonetic decay, I may
put a question which has often occurred to me, but to which I felt I had no

356 EMERITUS PROFESSOR J. 8. BLACKIE ON

materials for supplying a satisfactory answer, viz., whether is the extremely
vocalic structure, and the weakness of the consonantal element observable in
the language of certain savage or semi-savage peoples, owing to the attrition of
time, or to an original defect in the lingual organisation of the race?
Analogy leads to the former alternative ; but both answers are possible; and
local record alone, in the form of old inscriptions, or translations by missionaries
in early times, could supply materials for deciding definitely on one side rather
than on the other.

XVIII. The peaceful disturbance of the national process of growth, in any
language, by the process of quiet decay and obliteration, takes place when a
small people with an inferior literature finds itself in close geographical con-
junction and in overpowering social connection with a people vastly superior in ~
number, in wealth, in intelligence, in policy, and in every element that consti-
tutes a highly developed social organism. In this case the language is doomed
to a slow, it may be, but to a certain death; for as certainly as coals will be
imported from Newcastle or Fife or Mid-Lothian by those who have none in
Ross-shire or Caithness, so certainly will English ideas and English speech
penetrate into the remotest glens of the Celtic Highlands; and though, as in
Ireland, from obvious causes, the people may assert a distinct and well-marked
nationality, the language in which their most cherished traditions have been
handed down will not be able to maintain its ground. Not that there is any-
thing desirable in the extinction of an old and venerable form of speech; quite
the contrary. Let dying languages be preserved with pious care by those who
love them, and those to whom they belong; there is no reason why we should
kick our grandmother into her grave merely because she is old; let her tell her
old stories and sing her old songs, nothing could be better—better even than
sermons sometimes; but however good they may be, they can serve only for
our occasional recreation, not for our daily food. The Celtic languages in
Europe, with the miraculous facility of communication now everywhere to be
found, will certainly die out in a very few generations; first in Ireland, strangely, —
where the Celtic blood is most hot; second, in the Scottish Highlands; and, lastly,
in Wales. The Scottish language, again, though daily dying out, even among
the lowest classes, as a medium of social intercourse, hasa better chance of sur-
viving, in its lyrical Avatar, as the Doric dialect of the English, if only the
Scottish people would be true to themselves, and not submit so tamely to the —
process of Anglification which, from obvious causes, is spreading so rapidly
over the land. A very little decent attention to the national music in our
highest as well as in our lowest schools would act powerfully in preserving in a
green old age the most pleasant manifestation of our existence as a separate
people ; but the mass of men in all countries are lazy and cowardly—oi zrod\ot_
kakot—and incline always to swim with the current rather than to ask whither

THE PHILOSOPHY OF LANGUAGE. 357

the current is driving them ; and in a town like Edinburgh, which, though metro-
politan by public law and by historical tradition, must, since the Union, be more
or less provincial in respect of London, there will always be in influential
quarters a considerable majority of persons who, under the influence of aristo-
cracy, plutocracy, bureauocracy, and other potent forces working from above,

will prefer the meretricious glitter of borrowed accomplishments to the healthy
glow of home-grown virtues.

( 359 )

XXI—The Old Red Sandstone Voleanic Rocks of Shetland. By B. N. Peacu
and J. Horne, of the Geological Survey of Scotland. (Plates XLV. and
XLVI.)

CONTENTS.
PAGE PAGE
Introduction, : : SBS 5. Necks on Bressay and Noss, . 5 ait
I, GEOLOGICAL Saenger OF THE VOLCANIC 6. Summary of Events indicated by
Rocks, . : ; 4 SXoll Volcanic Phenomena of Shetland
A. Contemporaneous Lavus Bh Puffs, : ol Old Red Sandstone, . : 4) B78
I Porphyritic Lavas and Tuffs of North-
mavine, 361 II. Microscopic CHARACTERS. . : . 3879
2. Diabase Lavas and Tufts of ieee 1. Porphyrite Lavas
and Sandsting, . 364 3. Diahise Lawas ; L
3. Probable ina of the Tee ed 2s. ‘intrusive aise Basic Rocks, . 379
Tuffs of Aithsting and Sandsting, 365 Rocka
4, Lava of the Holm of Melby, . . 266 ie Tape heats ‘ ‘ - 381
5. Bedded Lavas and Tuffs of see Rooeness Sheet, . 382
Stour, . . : 366 Sandsting Sheet, : : a oe?
6. Band of Tuff in Brose, : > oor Papa Stour Sheet 389
B. Intrusive Igneous Rocks, . : 368 5. Dykes— ; A cialis Rocks. 383
1. Intrusive Sheet of Binary Granites Binary Granites ; : 383
in Northmavine, . : 368 and Quartz-fel-
2. Intrusive Sheet of Granite in Send sites, ’ : + ges
sting, . 370 Rhyolites, ® wiht l 384
3. Intrusive Sheet of shiveatinge Fel- Summary of Results, . F ‘ : _ 386
sitein Papa Stour, . : Sasa
4, Dykes— ; ‘ ‘ snore APPENDIX.—Table of Chemical Analyses of
a. Binary Comics : : OS: eight Specimens of Shetland Old Red
b. Quartz-felsites, : : one Voleanic Rocks, by R. R. Tatnock,
c. Rhyolites, : : : . 374 F.R.S.E., . : ; - : . 387
d. Diabase Rocks, : ‘ = ext)

Perhaps the most interesting feature connected with the Old Red Sandstone
formation in Shetland is the evidence of prolonged volcanic activity in those
northern isles. The great development of contemporaneous and intrusive
igneous rocks, which gives rise to some of the most striking scenery in Shet-
land, is all the more important when compared with the meagre records in the
Lower Old Red Sandstone of Orkney and the Moray Firth basin. Not till we
pass to the south of the Grampians do we find evidence of a far grander
display of volcanic action during this period, in the sheets of lava and tuff in
the Sidlaws and Ochils and in the great belt stretching from the Pentlands
south-westwards into Ayrshire. The relations of the Shetland igneous rocks
are admirably displayed in the various coast sections, especially in the mural
cliffs of Northmavine and some of the Western Islands. From these records,
though they have been subjected to much denudation, it is possible to con-
struct a tolerably complete sketch of the volcanic history of this formation, as
developed in that region.

VOL. XXXII. PART IL. 3M

360 B. N. PEACH AND J. HORNE ON THE

No previous attempt has been made to furnish a chronological account
of the Old Red volcanic phenomena of those northern isles. In H1BBERT’s
admirable volume * there are various references to the granite masses of the
Mainland and the amygdaloidal claystones in the south-west of Northmaviue.
He also refers to the porphyritic and amygdaloidal rocks in Papa Stour, which
were likewise described by Dr FLemine.t In various papers published in the
Mineralogical Magazine,{ Dr HeppLe notes the existence of interbedded and
intrusive igneous rocks of this age in Shetland, with descriptions of the minerals
obtained from them. The first attempt, however, to connect these Old Red
volcanic rocks with their representatives south of the Grampians, was made by
Dr ArcuiBaLp GEIKIE, the present Director-General of the Geological Surveys.
In 1876 the geological structure of Papa Stour, which is almost wholly com-
posed of volcanic rocks, was solved by him in company with Mr Bb. N. Peacu;
and, as the result of that traverse, an account of the geology of that interesting
island was given in his celebrated paper on “The Old Red Sandstone of
Western Europe,” published in the Zransactions of this Society.§ Though
unable to visit the voleanic rocks on the north side of St Magnus Bay, he
ventured to suggest that,the amygdaloidal claystones referred to by H1BBERT
would turn out to be merely a repetition of those in Papa Stour,—a suggestion
which has been amply verified by subsequent investigations.

During our successive visits to Shetland, which were undertaken mainly
with the view of examining the glacial phenomena of the group, we were
induced to pay close attention to the distribution and geological structure of
the Old Red Sandstone rocks, on account of the important bearing which they
have on the ice-carry during the glacial period. A brief sketch of the develop-
ment of the contemporaneous and intrusive igneous rocks was given in the
paper which we communicated to the Geological Society in 1879.|| But since
that paper was read we have twice visited the islands in the course of our
holiday rambles, in order to work out in greater detail the volcanic history of
that period. Our last visit was specially devoted to the investigation of an
interesting series of rhyolites, which have not hitherto been described, though
at certain localities they have a remarkable development. A large number of
microscopic sections have been prepared and examined, while detailed chemical
analyses of the typical volcanic rocks have been made for us by our friend Mr
RR. R. Tatrock, F.R.S.E., one of the public analysts for Glasgow. We now
propose to lay the results of these investigations before the Society.

* Hispert’s Shetland Isles, pp. 341, 474, 484, 491.

Tt Mem. Wernerian Soc., vol i. p. 162.

t Mineralog. Mag., vol. ii. pp. 160, 170 et seg., 253 ; vol. iii. p. 32.
§ Trans. Edin. Roy. Soc., vol. xxvii. p. 345.

|| Quart, Jour. Geol. Soc., vol. xxxv. p. 786.

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 361

I. GEOLOGICAL STRUCTURE OF THE VOLCANIC Rocks.

The records of volcanic activity are mainly confined to the west and north-
west portions of the Mainland and the islands adjoining the western seaboard.
They may be grouped in two divisions,—first, the contemporaneous igneous
rocks, comprising the lavas and tuffs which were erupted and spread over the
sea-floor during the accumulation of the sedimentary deposits ; second, the in-
trusive igneous rocks, which were injected at a later date, probably towards
the close of the Old Red Sandstone period in Shetland. The result of the
chemical analysis of typical examples of these divisions clearly proves that
the former belongs wholly to the basic series, while the latter includes both
acidic and basic rocks.

A. Contemporaneous Lavas and Tuffs.

Beginning first with the interbedded volcanic rocks, the best development
of them is to be found in the south-west part of Northmavine, between Stenness:
and the mouth of Rooeness Voe. No finer sections could be desired than
those exposed along the storm-swept cliffs of the Grind of the Navir. Here
and there the observer sees narrow “gios” which have been excavated in the
tough lavas and ashes and occasionally a subterranean passage or tunnel, com-
municating with the surface by a funnel-shaped aperture, from which, during
storms, a column of spray issues with the advancing tide. The best examples
of this latter phenomenon are to be seen at the “ Holes of Scraada.”

The tract of ground occupied with this series of ancient lavas and tuffs
measures about six miles in length from Stenness to Ockren Head. It is evi-
dent, however, that they must originally have covered a larger area, from the
isolated fragments which have escaped denudation, in the islet of Doorholm,
and Esha Ness Skerry. In the southern part of this tract, between Stenness
and Hamna Voe, the terrace-shaped features which are characteristic of vol-
canic areas are so apparent, that the eye can easily follow the successive out-
crops of the lavas and tuffs. This area is almost entirely occupied with
contemporaneous volcanic rocks, there being but few intercalations of sedimen-
tary deposits. Along the east side, between Rooeness Voe and Brei Wick, the
lavas and tuffs are bounded by a great sheet of granite and quartz-felsite, which
will be described in a subsequent page. On the south bank of Rooeness Voe,
rather more than a mile from Ockren Head, the relation between the two is
admirably exposed in a steep grassy “gyo.” At this locality the slagey por-
phyrites, which form a cliff about 300 feet high, with a beautifully slicken-sided
| surface, are brought into conjunction with the pink granitoid rock by a fault.
Owing to the covering of peat, we were unable to trace this fault across the

362 B. N. PEACH AND J. HORNE ON THE

peninsular tract. On the shores of St Magnus Bay at Brei Wick, the inter-
bedded and intrusive igneous rocks are not found in such close proximity ; the
junction between the two being concealed by a sandy beach. From the
admirable coast sections there is little difficulty in determining the geological
structure of the volcanic masses. They form a great syncline, the centre of
which is occupied by a coarse volcanic breccia or tuff and from underneath this
breccia there crops out a series of slaggy diabase-porphyrites, with occasional
beds of red ashy sandstones and flags. Such is the general arrangement of the
strata, though the succession is occasionally disturbed by faults of greater or
less magnitude. The order of succession is best displayed in the cliffs bounding
St Magnus Bay, and we shall therefore describe first of all the section between
Brei Wick and Stenness. On the west side of Brei Wick Bay, which is the
eastern limit of the interbedded volcanic rocks, the following section is visible.

Fic. 1.—Section in Brei Wick Bay, Northmavine.

At the east end of this section occurs a bed of coarse tuff (2), with bombs
of porphyrite, averaging 6 inches across, which is succeeded by finer tuff (1);
the strata forming a small synclinal fold. Towards the west they are under-
laid by red sandstones (3), which are pierced by a mass of pink quartz-felsite
(4), like the intrusive igneous rock to the east of Brei Wick. Fragments of the
sandstones are seen adhering to the felsite, which have been slightly indurated —
by the intrusive mass. On the west side of the felsitic intrusion, the sand-
stones are repeated with a westerly dip, and they are succeeded by the beds of
coarse and fine tuff already described. These are overlaid in turn by coarse
ashy sandstones, in which masses of tuff are curiously intermingled with layers
of sand in the same bed. Grey sandy flags rest on these ashy sandstones,
which are abruptly truncated by a fault bringing in the porphyrites. For a
short distance the order of succession is disturbed by intrusive dykes; but near
Tang Wick Ness the lavas are seen dipping in a north-west direction.

In the little bay beyond Tang Wick Ness a bed of dark purple diabase-por-
phyrite passes underneath coarse volcanic breccia, containing blocks of schist
and porphyrites ; the latter being most numerous. These included fragments
of schist were doubtless derived from the sides of the old vents, and though we ~
cannot now point to the sites of the volcanic orifices, still the existence of these
blocks of schist in the tuffs clearly indicates that they must have pierced the
metamorphic rocks of the district.

Not far to the west of this locality, pale slaggy porphyrites rest on dark
purple lavas; the latter being overlaid near Stenness by coarse volcanic breccia,

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 063

occupying the centre of the syncline. From Stenness northwards towards
Hamna Voe this volcanic breccia is traceable, being inclined at a gentle angle
to the south of east and on the west side of the synclinal fold the porphyrites
reappear, with a gentle easterly dip. They occupy the strip of rising ground
bordering the sea at the Grind of the Navir, and in this neighbourhood the
terrace-shaped features are most characteristically developed. Along the coast-
line, from Stenness to the Grind of the Navir, there is an excellent exposure of
the successive lava flows with few intercalations of tuff. The numerous isolated
stacks and the more distant islet of Doorholm, which are formed of the same
materials, plainly indicate the great denudation which the contemporaneous
volcanic rocks have undergone.

A traverse along the south bank of Rooeness Voe confirms the general
arrangement of the strata just described. The fault bounding the interbedded

| Fic. 2.—Four successive lava flows overlaid by tuff. Ovkren Head, Rooeness Voe,
Rooeness Hill cliff in the distance.

series in Rooeness Voe, which has already been referred to, has not produced
much effect on the inclination of the bedded masses. <A. short distance to the
north-west of the fault, in a small stream draining two lochans, a section is
exposed of red micaceous flaggy sandstone, overlaid by coarse tuff, dipping to
the north-west at an angle of 3°. Following the coast-line, we have a con-
tinuous exposure of diabase-porphyrites, lying nearly flat or at gentle angles,
till we reach Ockren Head at the mouth of the Voe, where the lava flows are
admirably shown, piledon each other in regular succession. On the headland
and also in an outlying stack to the north, there are four sheets of lava
overlaid by coarse tuff. The diabase-porphyrites present the usual scoriaceous
‘\character on the upper and under surfaces of the flows, and they likewise
thicken and thin out rapidly. The lavas have a purple tinge, and perhaps

364 B. N. PEACH AND J. HORNE ON THE

appear more sombre than they really are when contrasted with the bright
red cliffs of granite on the opposite side of the Voe. Some of the beds are
highly involved, and show clearly how the partially solidified crust has been
caught up and rolled forwards in the advancing current of the still molten
lava. |
From the evidence afforded by these sections, it is manifest that in the
peninsular tract of Northmavine, west_of Hillswick, there is an important
development of ancient lavas and tufts, which attain a thickness of not less than
500 feet. The absence of any intercalations of sandstones, flagstones or shales,
save near the fault at Brei Wick and Rooeness Voe, is also a feature worthy of
notice, as indicating that the subaqueous eruptions must have been well-nigh
continuous for a time in that portion of the basin.

The interbedded volcanic rocks which now fall to be described, occur in the
midst of a great series of sedimentary deposits, in the peninsular tract of —
ground lying to the west of Weisdale. These sedimentary deposits have under-
gone so much alteration that Hissert regarded them as forming part of the
metamorphic series, though he noticed that the strike of the former was dis-
cordant with that of the latter. This classification was adopted till the summer
of 1878, when in the course of our investigations we stumbled on a rich
assemblage of plant remains in the beds north of Walls. Many of the speci-
mens were badly preserved, but some of them were sufficiently distinct to
permit of identification. Upwards of twelve specimens of Lepidodendron —
nothum, Unger and several examples of Psilophyton princeps, were obtained—
forms which are typical of the Old Red Sandstone as developed in other parts _
of Shetland, Orkney, Caithness, and other regions. There can be no doubt,
therefore, that these altered strata, which with the associated volcanic rocks
cover an area of about 50 square miles, really form an important development
of the Old Red Sandstone of Shetland. While engaged in mapping the bound-
aries of these altered strata, we detected certain lavas and tuffs which are
regularly intercalated with the series; the former, however, differing consider- —
ably from their representatives in Northmavine. From their microscopic
characters, as well as from their chemical analysis, it is apparent that the lavas
have shared to some extent in the partial metamorphism of the area. But, —
before defining the localities in which they occur, it may be desirable to indicate
their probable geological position.

Disregarding minor folds, the altered strata seem to form a great synclinal
trough, the axis of which runs approximately from Fontabrough Voe on
the west coast, east by the village of Walls to the head of Bixetter Voe.
On the northern side of the syncline we have a gradually ascending series”
exposed on the coast from the cliffs of Sandness Hill southwards towards Fonta-
brough Voe, Similar ascending sections are to be met with on the shores of

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 365

Vaila Sound and Gruting Voe on the south side of the axis; but a large portion
of the area on this side is occupied by a great sheet of intrusive granite, which
will be referred to in a subsequent paragraph. By means of two powerful
faults, the altered Old Red strata are brought into conjunction with the meta-
morphic series on the east and north sides, and hence the unconformable relation
between the two is nowhere visible. A line drawn from a point not far to the
east of Aith Ness in Aithsting, southwards by Bixetter and Symbister Church
in Selie Voe, Sandsting, marks the course of the great north and south fault
bounding the area on the east. On the north side the fault runs from a point
west of Aith Ness in Aithsting, south-west by Sonso Ness, thence by Brindister,
Burrafirth, to Snarra Voe and Sandness Hill. Over a great part of this penin-
sular tract the beds consist of grey and blue indurated sandstones or greywackes
with green and pale shales. The sandstones are abundantly traversed with
joimts, which are frequently coated with peroxide of iron, and in places they
have a marked schistose character. Sometimes the sandstones are converted
into genuine quartzites, and the shales interbedded with them are distinctly
cleaved. The plant remains which we found at various points on the moors
between Walls and Sandness Hill occur in green and blue jointed sandstones
weathering with a yellowish or pale white crust. At certain localities the beds
are distinctly conglomeratic, especially on the rocky hills overlooking the head
of Snarra Voe and West Burrafirth Voe. Characterised by massive bedding
and containing more or less rounded pebbles of quartz, quartzites and various
metamorphic rocks, they remind one of the thick-bedded conglomeratic sand-
stones at Lerwick on the eastern seaboard. Indeed, after several extensive
traverses we came to the conclusion that much of the altered series west of
Weisdale is the counterpart of the Lerwick series. The exact position of the
latter in the order of succession which we established on the eastern seaboard
will be readily seen from the following table :—

5. Flaggy series of Bressay and Noss, consisting of alternations of
sandstones, flags and shales. At the base of Noss Head (577 feet)
there is a zone of dark calcareous shale with limestone nodules,
which has a striking resemblance to the well-known fish-bed of the
Moray Firth basin.

4. Lerwick series, consisting of massive false-bedded sandstones, which
throughout are markedly conglomeratic.

3. Rovey Head conglomerates.

2. Brenista series, consisting of well-bedded red flags.

1. Basement breccia.

If we are right in inferring from the resemblance in lithological characters
| and the identity of the plant remains, that the altered strata west of Weisdale

366 B. N. PEACH AND J. HORNE ON THE

are on the same geological horizon as the Lerwick series, then we are able
to fix the date of the ejection of the contemporaneous volcanic rocks in
Aithsting and Sandness. The latter are admirably seen on the shores of
North and South Clouster Voe, whence they can be followed north-east- —
wards towards Aith Ness. The volcanic rocks consist in that region of dark
green diabase lavas, which only occasionally exhibit vesicular cavities on the
surface of the flows. But from this feature, as well as from their perfect
parallelism with the sedimentary strata, there can be no doubt of their con-
temporaneous origin. In chemical composition they are highly basic, and
strongly resemble the diabase-porphyrites of Northmavine, though there is a
difference in one important particular, which will be subsequently referred to.
Again, on the western shores of Sandness the quartzites and flagstones are
associated with bands of tuff, which are exposed on the coast at the mouth of
Dale’s Voe and further south near Watt’s Ness. The volcanic ash can be
traced inland in a north-east direction by the Stourbro Hill. The lavas and
tuffs now referred to dip to the 8.S.E., like the altered strata with which they
are associated. They are not exposed on the south side of the synclinal axis ;
at least we saw no indications of them in the course of our traverses. Their —
absence may be accounted for by the occurrence of the great intrusive sheet of
granite which was intruded along the lines of bedding at a period subsequent to
the ejection of the lavas.
The small tract of unaltered Old Red strata at Melby contains no into
bedded volcanic rocks, but in the Holm of Melby—a small island between the
Mainland and Papa Stour—there is an interesting relic of volcanic activity.
The arrangement of the strata is shown in the following section :—

1

Fic. 3.—Section across the Holm of Melby. 1, Sandstones and flags; 2, porphyrite.

Along the east coast runs a well-marked anticline of grey flags, which,
towards the west, pass underneath a bed of dull purple porphyrite, forming
the ridge in the centre of the Holm. This sheet of lava is overlaid by another
series of grey flags, strongly resembling some of the flagstones in the Sound of
Noss, east of Bressay. Possessing the usual amygdaloidal characters, this
bed strongly resembles the type of porphyrites developed in Northmavine.

Crossing the Sound of Papa to the island of Papa Stour, further evidence
is obtained of the intercalation of diabase-porphyrites in the flagstones, sand-
stones and conglomerates. The geological structure of this interesting island
has been graphically described by Dr ArcuiBaLD GEIKIE in the Transactions of
this Society, and little else remains to be added to the account given by him.

OLD RED SANDSTONE, VOLCANIC ROCKS OF SHETLAND. 367

In the course of our subsequent visit we obtained some additional evidence
regarding the intrusive character of the sheet of felsite which forms such a
prominent feature in the geology of the island. At various points on the coast-
line, sometimes at the base of the cliffs, sometimes forming the whole cliff from
top to bottom, there are certain red sandstones, flags and conglomerates which
are clearly interbedded with purple slaggy porphyrites. - That these lavas were
ejected during the time of the formation of the sedimentary deposits is proved
by the occurrence of blocks of diabase-porphyrite in the conglomerates.
Neither the sandstones nor the interbedded porphyrites are traceable for any
distance, as they are cut through and overlaid by a sheet of pink felsite, which
covers nearly the whole of the island. The lavas occur in Hamna Voe on the
south side of the island, on the shore east of the church in Housa Voe, on
both banks of Culla Voe, and again on the headlands of Bordie in the north-
west of the island.

The only relic of interbedded volcanic materials on the east side of Shetland
is met with on the east coast of the island of Bressay in Noss Sound. Opposite
the north end of the island of Noss, on the east side of the fault skirting the
shore below Ander Hill, a bed of brecciated tuff about seven feet thick is asso-
ciated with grey flags. The strata dip to the east at a low angle and are
repeated by small faults, as shown in the accompanying ground plan.

Fic. 4.—Intercalation of tuff (2) with grey flags (1), S.E. shore of Bressay.

There can be little doubt that this band of tuff is directly connected with
the remarkable series of volcanic necks which occur not far to the south on
| the same island. When we come to describe the nature of the materials which
| now fill these vents, we shall see that it is highly probable that no lavas were
| ever ejected from these orifices. It is more likely that they mark but a feeble
development of volcanic energy, during which occasional showers of tuff were
spread over the sea-floor. If this be true, then, this band of tuff may be
regarded as a relic of this sporadic outburst. Occurring near the top of the
flagey series of Bressay, it is evident that this tuff occupies a high geological
position in the order of succession in the eastern seaboard. It is not improb-
able, therefore, that it may represent portions of the contemporaneous volcanic
series of Papa Stour and Northmavine.

' We have now completed the sketch of the interbedded volcanic rocks, and,
| from the foregoing descriptions, it is manifest that only portions of the ejecta-
| VOL. XXXII. PART II. oN

368 B. N. PEACH AND J. HORNE ON THE

menta discharged from the volcanoes of the period are still preserved to us,
From the manner in which they are truncated by faults in Northmavine and
overspread by intrusive felsite in Papa Stour, we are justified in inferring that
their original limits must have been much greater than now. But the proofs

Ww
Cliff Hills _ Wart of Bressay

Lerwick
VS

f —_ Ne >

Fic, 5.—Generalised section across the Old Red Sandstone on the east side of Shetland, showing the position
of the voleanic rocks in Bressay. 1, Schists of the Cliff Hills; 3, Brenista flags; 4, Rovey Head con-
glomerates; 5, Lerwick sandstones: 6, flaggy series of Bressay and Noss; 7, volcanic rocks;
J, faults.

of volcanic activity are not confined to those materials which were accumu-
lated simultaneously with the sediment on the sea floor. The phenomena con-
nected with the intrusive igneous rocks furnish even more striking proofs of

the display of volcanic energy which characterised that period. q

B. Intrusive Igneous Rocks.

These may be grouped in three divisions—(1) Sheets, (2) Dykes, (3) Necks.
Of these divisions the first is the most important, as the sheets cover extensive
areas in Northmavine and Sandsting on the Mainland, nearly the whole of Papa
Stour, the greater portion of Meikle Rooe and a portion of the island of
Vementry. An interesting feature connected with these intrusive sheets is
the evidence which they furnish of the vast amount of denudation which has
taken place since Old Red times. It is only by working out the physical
relations of these intrusive masses that we can form an approximate idea of
the extent of this denudation.

By far the largest area occupied by these intrusive rocks is in Northmavine,
where they extend from the northern headlands of the Mainland opposite Uya
Island to Rooeness Voe and onwards to the Heads of Grocken, near Hills-
wick. The isolated columns of the Drongs are composed of the same intrusive
rocks and likewise the eastern part of Meikle Rooe and the northern portion
of Vementry. It is highly probable that the masses just indicated, though
now isolated from each other, once formed parts of the same intrusive sheet.
Lithologically, as well as microscopically, the rocks bear a close resemblance to
each other. The length of this sheet, when measured from its northern limits
to Vementry, is about twenty miles, and its breadth in Northmavine varies
from three to four miles. This mass is brought into conjunction with the

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 369

metamorphic series at the Heads of Grocken by a fault, which is admirably
seen on the shore.

In Meikle Rooe the granite mass is also faulted against the older rocks,
which consist mainly of diorite with occasional patches of mica schists. In
all likelihood, the fault at the Heads of Grocken and in Meikle Rooe is merely
the northern prolongation of the great north and south dislocation bounding
the altered Old Red strata west of Weisdale. On the shores of Rooeness Voe,
however, and northwards by the Biurgs, on the eastern seaboard of North-
mavine, the granite spreads over the ancient crystalline rocks in the form of a
great sheet, without deflecting the strike of the metamorphic series, and termin-
ates along the eastern margin in a great escarpment 200 feet high. The North-

Fic. 6.—Binary granite faulted against the ancient crystalline schists, Heads of Grocken, Northmavine. The
Headlands of Stenness, and the Islet of Doorholm in the distance, formed of bedded lavas and tufts.

Mavine mass consists mainly of a binary granite or aplite, composed of quartz
and pink orthoclase felspar, shading occasionally into salmon-coloured quartz-
felsite. Generally the rock is coarsely crystalline and highly siliceous, and
there can be no doubt that the mass must have consolidated under great
pressure, though the materials under which it lay buried have been wholly
removed by denudation. The presence of so much silica has no doubt retarded
the general denudation of the Rooeness plateau, but it has been ineffectual in
preventing the waste caused by the sea. But apart from the coarsely crystalline
character of the rock, the marked columnar structure suggests the idea that it is
a great intrusive sheet which has consolidated underneath the surface. Those
who wish to study this feature would do well to sail down Rooeness Voe or
along the shores of St Magnus Bay from the Heads of Grocken to Brei Wick
(see Sketch of Heads of Grocken, fig. 6). Along the cliffs the observer is
confronted by symmetrical columns rising from the sea-level, which are tra-

370 B. N. PEACH AND J. HORNE ON THE

versed by a series of vertical joints. Hence it follows that the vertical face
of the cliff is preserved, though constantly assailed by the sea and subjected
to continual recession by the removal of huge slices of rock. Frequently the
columns are isolated and left to battle with the denuding agencies as_ best
they may. The columns of the Drongs are beautiful relics of the Rooeness
Hill sheet which have hitherto been able to resist complete demolition.

We have already referred to the fact that the only place where this intru-
sive mass is seen in contact with the interbedded volcanic rocks of North-
mavine is on the south bank of Rooeness Voe, where the latter are thrown
down by a fault against the former. We have therefore no indication of the
thickness of strata which originally covered the plateau. But, from the
columnar structure, the coarsely crystalline texture, from the manner in which
it spreads over the metamorphic series like a great cake, we have come to the ©
conclusion that the Rooeness mass is an intrusive sheet which forced its way —

Ww ; ,
Ockren Head Rooeness alee RooenessHit The Biurgs Skeal
| " arate ZS ’
H NAVAN im ZLIEE 2
ay in j Y \ \ ZZ LZR DD B
ea | Soe aces pe TT LT - Lie py, WV RGE ce oD

Fic. 7.—Section across Northmavine from Ockren Head to Skea Ness. 1, Metamorphic rocks; 2, serpentine ;
3, granite and quartz-felsite ; 4, breccia of serpentine fragments ; 5, bedded porphyrite and tuff ; /, faults.

upwards and laterally between the metamorphic strata on the one hand, and
the members of the Old Red Sandstone on the other, at the time when the Main-
land lay buried under tke deposits which accumulated during that period. It
is right to state, however, that, so far as our observations went, there are no ,
beds underlying this igneous mass which could be referred to the Old Red
Sandstone. At one locality, to the north of Colafirth Voe, a curious brecciated
serpentinous mass occurs, which might, on further examination, prove to be a
basal breccia of this age. Be this as it may, it is evident that the underlying
platform consists mainly of diorite and various metamorphic rocks. The fore- —
going conclusion is confirmed, as we shall presently point out, by an examina-
tion of the relations which the Sandsting granite mass and the Papa Stour
felsite bear to the Old Red strata. |
The age of the granite mass of Sandsting is placed beyond doubt by a study
of its relations to the altered Old Red strata of that district. It covers a
triangular area, extending from Selie Voe to Gruting Voe. <A portion of the
sheet is also met with in the south-east of the island of Vaila. When
measured along a line from Vaila to Selie Voe, the mass is 6 miles long, ax d
its eget breadth is about 4 miles. Presenting the same columnar structure
as the Rooeness sheet, it immediately suggests the idea of a common origin.
Lithologically it approaches the type af an ordinary granite, save at certain

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. . 371

localities, where, through the disappearance of the mica, it resembles the binary
g anite of Rooeness Hill) The upper limit of the sheet is clearly defined by
the altered Old Red strata between Gruting and Selie Voes. Along this line
the observer cannot fail to note how the slope of the upper surface of the
intrusive sheet coincides with the angle of inclination of the sedimentary rocks.
This feature is admirably displayed on the east bank of Gruting Voe, at the
foot of Cullswick Hill. The hardened quartzose flags dip to the north at an
angle of about 20°, which is about the inclination of the boundary line between
the two. When followed along the junction line, however, the granite cuts
across the successive beds, resembling, as we shall see, the behaviour of the
sheet of pink felsite on Papa Stour. But in addition to this fact, it frequently

Fic. 8.—Junction of granite and altered Old Red Sandstone strata in Gruting Voe.

happens that the altered Old Red strata and the intrusive sheet are firmly
welded together along the junction. In some instances it is possible to dislodge
fragments a few square inches across, showing the junction between the two—
a phenomenon which conclusively points to the intrusive character of the mass.
There is no passage from the sedimentary rocks into the granite, indicating a
probable metamorphic origin. On the contrary, the junction line is sharply and
clearly defined. This feature, which is characteristic of the Rooeness and
Sandsting sheets, is thus referred to by Dr HeppLe—“ Holding firmly to the
view which regards much of the granite in Scotland as the completion of the
metamorphism of the gneiss, I am unable to adopt for a moment any such view
as regards the granite of Shetland. The nature of the rock itself, the abutments
of the stratified rocks against its flanks and the disturbances it has produced
among their adjacent layers forbid such a view.” *

The island of Papa Stour is covered for the most part with a sheet of
pink spherulitic felsite, forming noble cliffs which rival those of Rooeness Voe
and the Heads of Grocken. The same columnar structure is everywhere
| apparent, not only in the island itself, but in the outlying stacks and skerries,
| which have been severed from the main sheet by denudation. Fortunately the
| evidence is sufficiently clear to show that this sheet must have been injected
between the underlying diabasic lavas and tuffs and an overlying series of
| sedimentary deposits, only a fragment of which has escaped denudation. In his

* Mineralog. Mag., vol. 1. p. 160.

372 B. N. PEACH AND J. HORNE ON THE

description of the geology of Papa Stour, Dr ArcHIBALD GEIKIE has referred
to two sections, one on the north side of Hamna Voe and the other on the
cliffs at the headland of Bordie, where the bedded lavas and grey tlaggy sand-
stones are traversed by this sheet of pink felsite. In the course of our subse-
quent visit, we observed that, in Culla Voe, the sheet steals across the edges
of the lavas, while a thin lenticular offshoot from the main mass is forced in
like a wedge at a lower level between the diabase-porphyrites. Further, on the
south-eastern headlands, about a mile east of Hamna Voe, the pink felsite cuts

Vic. 9.—Pink spherulitic felsite showing marked columnar structure, north-west side of Papa Stour with outlying
stacks—Foula in the distance.

across the sandstones, and passes from a lower to a higher horizon, as shown in
the accompanying section. These and other sections which might be adduced,
plainly indicate the intrusive character of the Papa Stour sheet, since it not
only occurs on various horizons, but frequently eats its way upwards, when
traced along the base of the cliffs. There can be no doubt that the sandstones
and conglomerates with the associated lavas form the platform over which the

Fic. 10.—Pink felsite injected among red sandstone, on shore one mile east of Hamna Voe, Papa Stour. 1, Red
aud purple amygdaloidal diahase-porphyrites ; 2, red sandstone and flags ; 3, pink spherulitic felsite.

felsite spreads. It is equally clear, however, from the evidence obtained at
the Horn of -Papa, that the sheet must have been covered by sedimentary de-
posits. There, on the cliff top, the pink felsite is overlaid by a patch of red
felspathic sandstones which are nearly horizontal. The sandstones in immediate
contact with the felsite have been hardened and altered to some extent by the
intrusion of the igneous mass, and in some places portions of the sandstone an

felsite may be seen adhering together, clearly showing the effects of contact
metamorphism. The occurrence, therefore, of this isolated patch of sandstone is
invested with special interest, inasmuch as it helps us to realise the denudation

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 373

which has taken place. It is evident that the sandstones must originally have
covered the whole of the sheet, and may probably have been continuous with
the sedimentary deposits of the Mainland. But though the evidence now
adduced shows that the felsite has been injected among the members of the

Fic. 11.—General section across Papa Stour. 1, Red sandstones and flags ; 2, purple diabase-porphyrites ;
3, great sheet of pink spherulitic felsite.

Old Red Sandstone, there is an important lithological difference between the
Papa Stour rock and the granitoid masses of Sandsting and Rooeness Hill.
This divergence will be discussed when we come to treat of their microscopic
characters.

2. Dykes and Veins.—One of the most interesting features connected with
the great intrusive sheets is the number and variety of the dykes and veins
radiating from them as centres. Along the boundary of the Northmavine sheet
from North Rooe southwards by Hillswick, Mavis Grind, to Aith Voe in
Aithsting, these dykes occur in great - numbers. Throughout that wide area
they traverse the ancient crystalline rocks, the diorite and the altered Old Red
strata. In addition to this, we find thin veins and bosses of the same materials
penetrating the interbedded volcanic rocks between Brei Wick and Stenness.
This latter point is of some importance, as it shows that the intrusion of the
sheet, with its branching veins, was subsequent to the ejection of the basic
lavas and tuffs. In many cases it is possible to trace the branching veins till
they coalesce with the parent sheet ; but more frequently they are completely
isolated at the surface, though it is probable that a subterranean connection
may exist. The same phenomena are repeated in the case of the great mass in
Sandsting and in a less conspicuous form in connection with the Papa Stour
sheet. The dykes and veins belonging to the acidic series may be grouped
under three divisions—(1) Binary granites and ordinary ternary granites, (2)
Quartz-felsites, (3) Rhyolites. In the case of the first group, the dykes still
preserve the lithological character of the parent sheet, being coarsely crystalline
and consisting mainly of pink orthoclase felspar and quartz with hardly any
mica. Some characteristic examples occur in Northmavine, more especially
along the coast-line from Mavis Grind to Hillswick. Indeed, the isthmus at
Mavis Grind exhibits a curious network of these granitoid dykes interlaced
with the diorite. The quartz-felsites are still more numerous than the preceding
group. Possessing a fine-grained ground mass with quartz, in distinct crystals
or amorphous forms, they are readily distinguishable from the granitoid type.
They are typically developed on the shores of Gruting Voe in Sandsting, in

374 B. N. PEACH AND J. HORNE ON THE

contact with the granite mass, and in the altered Old Red. strata at some
distance from the main sheet.

By far the most interesting of these intrusive dykes, however, are the rhyo-
lites, which are conspicuously developed in the small island of Papa Little,
on the neighbouring shore of the Mainland, and also round the granite mass of
Sandsting between Bixetter Voe and Loch Skeld. Possessing a fine-grained
semi-vitreous texture, they exhibit in hand specimens a characteristic banded
arrangement of the partially devitrified felsitic matter. The constituent bands
sometimes display slight variations of tint, which serve to make them more dis-
cernible by the eye. This banded arrangement, which, as we shall presently
show, is due to fluxion structure, maintains a constant direction in the case of
the dykes in the south-east corner of Papa Little. Even when the main dyke
sends branching veins into the adjoining strata, the lines of flow have the same
trend in the offshoots as in the parent dyke,—a feature which is interesting
and suggestive. The rhyolites are usually of a pale grey or yellowish colour,
but some of them possess a marked pink or flesh-red tint. This interesting
series was detected by us in the course of our third visit to Shetland when
tracing the faults bounding the altered Old Red strata west of Weisdale.
A subsequent visit was paid to the islands solely for the purpose of determining
whether they might represent acidic lavas which had been ejected at the sur-
face. The microscopic examination plainly showed that some of the dykes
possess fluxion structure in a remarkable degree, and we were therefore anxious
to learn whether this might be due to extravasation at the surface and the
rapid consolidation of the glassy magma. During this visit our observations
were mainly confined to the magnificent sections round the southern shores of
Papa Little, where the strata consist of well-bedded but considerably altered
flags and shales belonging to the Old Red Sandstone. The two great faults
dounding the altered Old Red area in the Mainland cross each other in this island,
the one trending towards the north in the direction of Meikle Rooe, while the
other preserves an E.N.E. direction. Only the south half of the island is made —
up of strata of Old Red age, the remainder being composed of gneissose rocks
belonging to the series which is so well developed in the centre of the Mainland.
The rhyolite dykes are most strikingly represented on the south-east shore,
northwards to the point where the fault brings the Old Red strata into con-
junction with the metamorphic series. The altered flagstones have a persistent
strike about N. 10° W., which is more or less parallel with the north and south
bounding fault, and they dip about W. 10° S. at angles varying from 70° to 80.
This strike is quite abnormal, however, and is evidently caused by proximity
to the great north and south fault, for when we cross to the south-west shore
of Papa Little the strike of the flagstones is E.N.E., which is identical with
the trend of the altered Old Red strata over much of the area west of Weisdale.

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 379

On the south-west shore the dip of the strata varies from S.S.E. to S.E. The
indurated flagstones and shales pierced by the rhyolites are frequently coated
with a green chloritic or serpentinous substance. The dykes are of variable
breadth, some of them measuring 12 feet across, while others are considerably
in excess of this amount. Generally they preserve a course more or less
parallel with the lines of bedding of the flags and shales, but not infrequently
they pass transgressively across the edges of the flags. In one instance, the
dyke enclosed lenticular patches of altered shales, which were injected with
thin branching veins of rhyolite, varying from a few inches to 2 feet in
breadth. When traced northwards, this mass rises along the edges of the
shales on the cliff. Not far to the north of this locality similar evidence
is obtained on the shore of the intrusive character of the rhyolites. The fol-

‘lowing ground plan exhibits the relation of the intrusive dykes to the Old Red

strata on this part of the shore.

At Aith Ness some of the dykes exhibit in a less perfect form the banded
structure of those just described, and in this case also they occur close to the
north and south boundary fault. It is possible that in some cases this fluxion
structure might be partly due to shearing, which might have caused subsequent
rearrangement of the materials in connection with the faulting and metamorphism

A ig Se
GEN > A\ a \ Direction of dip of strata.
Hardened sandstone Rhyolite. Shingle,

and flagstone.

Fic. 12.—Ground Plan of rhyolite dykes intruded among Lower Old Red Sandstone strata, south-west shore
of Papa Little, Shetland.

of the beds; but we shall now point out that the same feature is observable in

the dykes near Loch Skeld, about 3 miles from the bounding fault. In the

Laxa Burn, to the south-west of Bixetter Voe, a dyke of rhyolite was observed,

which, on the roadside near the cottage as well as in the burn below the road,

merges into a crystalline granitoid rock with quartz, felspar and mica. Again,

in the neighbourhood of Loch Skeld, near the granite boundary, we found typical

examples where the dykes display fluxion structure as perfect as in Papa Little.
The three preceding types of intrusive veins belong to the acidic series, and

closely resemble each other in chemical composition, as may be seen at a glance
VOL. XXXII. PART II. 30

376 B. N. PEACH AND J HORNE ON THE

by referring to the table of chemical analyses appended to this paper. Nay
further, it may be noted that the rhyolites are, so far as their chemical com-
position is concerned, closely allied to the great intrusive sheets. Taking this
important point into consideration, as well as their behaviour in the field, it is
evident that the former are merely offshoots from the latter. We are inclined
to believe that the rhyolites formed ducts leading in all probability to the sur-
face, and that in these subterranean fissures the banded structure was originally
developed. Had the molten matter reached the surface, it would have been
ejected as highly acidic and glassy lava. When we come to describe the
microscopic characters of these rocks, it will be seen that they have undergone
considerable devitrification.

But there is another series of dykes of a highly basic type, which have
been injected through the great sheets of granite and quartz-felsite, and are
therefore of a later date. This material is also met with in the form of bosses

Fic. 13,—Diabase dykes traversing pink granite, north shore of Rooeness Voe, Northmavine,

piercing the granitoid masses, as in the case of Skeld Hill in Sandsting. These
rocks consist of diabase of a fine-grained character when occurring in the form
of dykes, but very granular and coarsely crystalline when developed in bosses.
The dykes are prominently developed on the Rooeness plateau, where they
have been noted by Hispert and Dr HEDDLE, on the shores of Rooeness Voe,
and on the cliffs of Meikle Rooe. At these localities they have a north and
south trend ; and, owing to their dark colour, they form a striking contrast to
the pink granite in which they occur. Sometimes, owing to rapid decay, they
leave great clefts, indicating their course; sometimes they project abov:
the general level of the acidic rock on either side. In the Sandsting granite
mass we likewise noted several dykes of the same rock. In the burn neat
Garder House, close to Selie Voe, several examples occur. The granite an

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 377

felsite through which these diabase rocks are injected are occasionally very
hornblendic, but not always so. Notwithstanding this feature, the boundary is
clearly defined. On the Skeld Hill the boss of diabase has a well-marked
boundary separating it from the granite which surrounds it. In this instance
the granite is micaceous, with pink orthoclase felspar and quartz, the mica
being very dark-coloured and abundant close to the basic rock. The diabase,
on the other hand, hardly contains any quartz, and the felspar is only
sparingly developed ; while the green mineral is very abundant. In a subse-
quent paragraph we shall point out the resemblance in chemical composition,
and, to a certain extent, in microscopic characters, between these basic
intrusions and some of the diabase lavas. From the manner in which they
traverse the intrusive sheets, there can be no doubt that they mark a later
phase of volcanic activity, if, indeed, they do not mark the close of volcanic
action in the Old Red Sandstone of Shetland.

3. Necks.—The occurrence of volcanic pipes of Old Red age in Shetland is
another proof of the manifestation of volcanic activity which characterised that

5 «

NIE I Tp UU — A) —
SSS ro &

Z |

© 10 20 30 40 50 100 , ee ae P Wu, LANL
SS eS ee a ighly incline 0.
; Sandstone Volcanic Porphyrite
i+ peri calietnate: and ahales agglomerate. dyke.

big. 14.—Plan of Volcanic Pipes or Necks on East Shore of Bressay.

|

.

| period. Strange to say, they occur on the eastern seaboard of Shetland, where
the interbedded volcanic materials hardly exist. So far as our observations

a gone, no trace of these volcanic orifices is to be found in the western
districts of the Mainland or the adjoining islands, where the igneous rocks are
best developed. At the entrance to Noss Sound, on the south-east shore of
Bressay, and also in the island of Noss, a series of necks is exposed. The vent
in the island of Noss was noted by Dr HEpDLE in 1848,* though, so far as we
are aware, no previous description of it has been given. The necks are arranged
in a linear manner, and have evidently come to the surface along a line of fissure.

* Mineralog. Mag., vol. ii. p. 253,

oyrites

LM

378 B. N. PEACH AND J. HORNE ON THE

The beds surrounding the necks consist of red sandstones, which are much
shattered and baked along the lines of junction with the agglomerate. They
dip seawards (towards the east) at angles varying from 20° to 25°; but towards
the edge of the fissure they are highly inclined. When the sandstones are
followed inland, the alteration which is so apparent at the line of junction
gradually disappears. As may -be seen from the accompanying ground plan
(fig. 14), the outline of the vents is very irregular.

The materials filling the vents consist of a coarse agglomerate, made up of
angular fragments of sandstones, flags and shales, imbedded in a finely-
comminuted paste. Occasionally large masses of the surrounding sandstones
are enclosed in the agglomerate, which are highly crystalline. Besides these,
there are masses of red calcareous and highly-baked mudstones, which have
been torn from the sides of the vent. No bombs of porphyrite occur in the
agoelomerate,—at least, none was observed by us. A vein of porphyrite a few
inches thick is traceable along the margin of the orifice for a short distance,
and coatings of a diabasic lava occur on the surfaces of the indurated sandstones.
We also noticed a thin vein of copper pyrites traversing the agglomerate and
the altered sandstones.

Crossing the Noss Sound, another neck is visible, which resembles that just
described in the nature of the material filling the vent and in its mode of —
occurrence. Round the neck the gradual folding inwards of the flags near the
edge of the agglomerate is worthy of note, as it forms a characteristic feature
of the stratified rocks in immediate contact with the Carboniferous volcanic
vents in central Scotland. From the nature of this volcanic agglomerate it is
highly probable that no lavas were ejected from these orifices. It is more
likely that they served mainly as blow-holes, discharging occasionally showers —
of triturated materials derived from the sides of the vents.

We shall now briefly summarise the succession of events as indicated by the
volcanic phenomena described in the foregoing pages. ‘The earliest ejections —
consisted of basic lavas and tuffs, which were spread over the sea-floor, and in —
several instances were: intercalated with the ordinary sediment. In North-
mavine the volcanic accumulations were nearly continuous, save towards the
horizon of the lowest beds, where flagstones and ashy sandstones alternate with
the lavas. In the Aithsting and Sandness district the ejections were limited
to a few sheets of diabase and some bands of tuff, which are interbedded with
a great succession of altered sandstones, flags and shales. The sheet of
porphyrite in Melby Holm indicates a recurrence of volcanic activity, which
became more pronounced as the conglomerates, sandstones and flags of Papa
Stour were deposited. In the latter case the discharge of volcanic materials
must have been intermittent. The band of tuff and the necks in Bressay

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 379

indicate a sporadic outburst during the deposition of the flaggy series of
Bressay and Noss.

The discharge of these highly basic lavas and tuffs and the deposition of
the associated sediment, were followed by the injection of three great sheets of
highly acidic rocks. The relations of the sheet in Papa Stour to the basic rocks
plainly show that the eruption of that mass was later than the ejection of the lavas.
Similar evidence is supplied by the granite mass in Sandsting, and there is every
probability that the great Rooeness plateau was erupted at a later date than
the basic lavas of Northmavine. Numerous veins of granite, of quartz-felsite,
and of rhyolite radiate from these intrusive sheets, which doubtless belong to the
same period of intrusion. The last phase was characterised by the eruption of
a series of highly basic rocks, consisting of diabase, which traverse alike the
ancient crystalline rocks, the Old Red strata and the great intrusive sheets.

II. Microscopic CHARACTERS.

The microscopic examination of the bedded lavas proves that there is a con-
siderable difference between the so-called porphyrites and the diabase rocks,
which both occur in the series. A typical example of the former group, taken
from the neighbourhood of Ockren Head in Rooeness Voe, shows that it is
composed mainly of very minute columnar crystals of plagioclase felspar, which,
as a rule, are much altered, and only occasionally show traces of the twin
striation. Between these closely aggregated crystals there is a fine ground
mass, and some of the minute interspaces are also occupied with a bright green
decomposition product, which may be green earth. After the felspar, however,
magnetite is the most abundant mineral,—so much so, indeed, that it might be
grouped with the class of felspar-magnetite rocks described by Dr ArcuiBaLp
GEIKIE in his paper on the “ Carboniferous Volcanic Rocks of the Basin of the
Forth.” *

The sections prepared from the lavas in the altered Old Red area, between
Clouster and Aith Voes, show that plagioclase felspar is the chief constituent.
Augite, however, is also present, though it is only occasionally recognisabie, by
far the larger portion having been converted into chlorite. In one instance
| where this alteration has been considerably developed the augite has a granular
appearance ; but in other sections a few larger crystals of augite remain which
are quite distinguishable. The magnetite, which is also largely distributed, has
been converted to a great extent into limonite. This type is a true diabase, and
were it not for the great alteration which has taken place in the pyroxenic

mineral, it might be compared with some basaltic lavas of later paleeozoic age.

* Trans. Roy. Soc. Edin., vol. xxix. p. 508.

380 B. N. PEACH AND J. HORNE ON THE

There is one noteworthy feature connected with the sections prepared by us
from the Shetland lavas, and that is the absence of olivine in recognisable
forms. In this respect they differ from the diabase lava of the same age in
Shapinshay, Orkney, which we detected in 1879. One of the sections from
this locality shows that, in addition to the plagioclase felspar, there is much
olivine distributed in crystals and crystalline grains, which, for the most part,
has been converted into serpentine. Chlorite is also present, but the augite is
hardly represented at all. The magnetite, which is very abundant, frequently
envelopes the crystals of olivine either wholly or in part only. This type is
very different from any we have met with in Shetland. It might be termed a
felspar-diabase, rich in olivine and poor in augite.

On referring to the table of analyses appended to this paper, it will be seen
that of the two types—the one taken from the porphyrites in Northmavine, and
the other from the diabase lava in Clouster Voe—the latter is the more basic.
The proportion of silica in the porphyrite lava from Rooeness Voe is 51°82,
while in the diabase from Clouster it is 48°36 per cent. The alumina in the
former is 14:14, while in the latter it is 19°73 per cent. Another difference of
some importance is in the relative quantities of magnesia: in the porphyrite
lava it is 1°76, while in the diabase lava it amounts to 5:97 per cent. It would
seem, therefore, that the diabase lavas from the altered Old Red area west of
Weisdale were not only more basic originally, but the greater proportion of
magnesia points to considerable alteration at a subsequent date.

A section of volcanic ash from Dales Voe, Sandness, when examined micro-
scopically is found to consist of angular and subangular quartz grains, with a
few fragments of orthoclase and plagioclase felspar. It also contains fragments
of felsite, and a rock exhibiting an ill-defined micro-crystalline structure re-
sembling that of some of the devitrified rhyolites. A fine dusty felspathic
substance separates the individual grains.

It may be more convenient to describe here the microscopic characters of
the intrusive diabase rocks, as they have close affinities both chemically and —
microscopically with the interbedded lava just referred to. These affinities
are all the more interesting when we remember that the respective eruptions
of the two groups were separated by a considerable interval of time, during
which highly acidic rocks were ejected. The microscopic characters of the
diabase from the boss in Sandsting resemble those of the dykes in North-
mavine, with this exception, that the former are more coarsely crystalline.
The sections from the Skeld Hill show that the felspar crystals are much
decomposed, but in some cases it is possible to determine that they are plagio-
clase. Instead of presenting the usual clear faces, they have a dusty brown —
appearance, which has almost obliterated their twin structure. It is observable
that the triclinie felspars, though larger than in the interbedded lavas, do not

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 381

form the main constituent. They are associated with a green fibrous mineral,
which is largely represented, and has apparently replaced the augite. In one
of the sections, the augite occupying the interspaces still occurs in forms which
are recognisable; parts of the original crystals being quite fresh, while the
remainder has been converted into chlorite and a yellowish green mineral which
may be epidote. The unaltered portions show the characteristic play of colours
with polarised light. A little magnetite is diffused through the sections, but to
a much more limited extent than in the diabase lavas. It occupies quite a
subordinate position compared with the felspar and the green chlorite mineral.
We have already called attention to the fact that the boundary line between
the diabase and the granite is well defined. A section of the granite from the
junction contains triclinic felspars, clear quartz with fluid inclusions, and mica
partially converted into a green decomposition product. Numerous specks of
limonite occur, resulting from the hydration of the iron oxide. The rock
associated with this in the same microscopic section is a diabase similar to those
described. It contains no quartz, and the augite is faintly recognisable.

The sections taken from the stream near Garder House, on the west bank
of Selie Voe, are coarsely crystalline like those from Skeld Hill. The plagio-
clase felspars are much kaolinised, and the pyroxenic mineral has undergone
intense alteration.

Compared with these, the sections taken from the dykes in Northmavine
traversing the binary granite and felsite are exceedingly fine-grained. In one
instance, the crystals of plagioclase are very fresh, and the interspaces between
the crystals are filled with a bright green mineral, probably chlorite, there being
no fresh traces of the original augitic constituent. Magnetite is not abundant,
and small needles of apatite are disseminated through the mass. Another
example taken from Rooeness Voe exhibits much granular augite along with
the triclinic felspar, which has only undergone slight alteration. Magnetite is
also present in very small grains.

The chemical analysis of a typical example of the Skeld Hill rock proves
that it is closely allied to the basic lavas; the proportion of silica being 50°58
per cent. The percentage of magnesia is even larger than in the two examples
of the interbedded lavas, amounting to 8°90 per cent. This feature plainly
indicates the great alteration which the pyroxenic mineral has undergone, and
the consequent development of magnesian silicates. It is worthy of note that
while the specific gravity of the bedded lavas is 2°7, that of the Skeld Hill rock
is 2°9 per cent.

The microscopic characters of the great intrusive sheets in Northmavine
and Sandsting have many points in common. A section from the Heads of
Grocken shows that the rock is coarsely crystalline, consisting essentially of red
orthoclase and quartz. The felspar is much kaolinised; but in one instance

382 B. N. PEACH AND J. HORNE ON THE

a crystal of orthoclase displays the Carlsbad type of twinning, polarising with
different colours on different sides of the median line. The quartz occurs in
erains and in crystals, clear and colourless, with numerous fluid inclusions. A
small quantity of apatite is present in the section. There is no trace of any
felsitic ground mass, and it is therefore evident that the rock most nearly
approaches the character of a binary granite or aplite. Another section from
the north bank of Rooeness Voe exhibits the same coarsely crystalline charac-
ter as the preceding example; the felspar predominating over the quartz.
Besides the orthoclase, which is also kaolinised, there is some microcline which,
with polarised light, displays that peculiar rectangular arrangement of the
striations traversing the mineral. Magnetite is also present, merging in some
instances by hydration into limonite. The microscopic examination of sections
taken from various localities throughout this mass only confirms the conclusion
previously arrived at by Hispert and Dr Heppie. The rock is essentially
granitic, but owing to the singular absence of mica over the greater portion of
the sheet, it is different from the older granites in Shetland, represented by
the masses at Dunrossness and Bixetter Voe.

A section taken from near the margin of the Sandsting sheet in Gruting
Voe contains much orthoclase which has been considerably kaolinised, large
grains of quartz, and a little black mica. In short, it is a typical granite.
Another specimen from the hills west of Skeld closely resembles the foregoing,
with the addition of a small quantity of microcline. At Laxa Burn the rock
consists of an admixture of red orthoclase and quartz.

The rock occurring near the diabase on Skeld Hill shows, under the micro-
scope, prisms of orthoclase and plagioclase ; the latter predominating, and less
altered than the former. With these are associated clear quartz and dark
mica, which are strongly dichroic. Needles and prisms of apatite occur abun-
dantly in the section, while magnetite is also present along with some crystals |
of sphene. A specimen, not far removed from the foregoing, exhibits a fair
proportion of green hornblende, which is dichroic, along with biotite, the other
constituents being the same. In the sections prepared from the Sandsting
sheet no trace of a felsitic ground mass has been observed. The only note-
worthy microscopic difference between the Sandsting and Rooeness sheets is
in the development of mica and hornblende in the former mass.

Far more interesting and exceptional are the microscopic characters of the
Papa Stour sheet of pink or salmon-coloured felsite. Instead of presenting a
marked crystalline aspect, it shows a felsitic ground mass of a reddish-brown
colour, in which few felspar crystals are discernible. This ground mass is
highly decomposed, and hence, even with a high power, it is impossible to
define the fine granular constituent, as the base has little action on polarised
light. The characteristic feature of the rock is the well-marked spherulitic

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND, 383

structure which it presents under the microscope. A section prepared from
the knobs of this rock, near the church, on the east side of the island, displays
this spherular arrangement with singular beauty. The spherulites do not
traverse the section in regular bands, but in wavy lines and in groups. No
nucleus is observable in the centre of the spherules, nor are they enclosed by a
periphery, as in the spherulitic glassy lavas of younger date. When magnified
120 diameters, some of these spherular developments exhibit very clearly the
fine radial fibres diverging from a common centre, while others have lost all
traces of these fibres. In the latter case they are supplanted by an exceedingly
fine-grained ground mass, but the rude outlines of the original spherules are
still visible. The ground mass is stained by minute ferruginous particles,
resulting from the decomposition of iron pyrites. There are numerous small
nests or cavities in the ground mass, filled chiefly with quartz of secondary origin
and small crystals of orthoclase.

Another section, taken from the cliff at the Horn of Papa, exhibits a
similar spherular structure, though of a less perfect type. The divergent fibres
are not so characteristically developed, and in the parts of the section where
they are absent, the ground mass is more granular. The nests filled with
secondary quartz do not form such a striking feature in this section ; but one
large crystal of clear quartz, with fluid inclusions, occurs in the mass.

Attention has been previously directed to the microscopic characters of
this felsite by Dr ARcHIBALD GeErxKIE, who has pointed out the spherular group-
ings of the constituents and the absence of any crystalline structure in the
rock. From the evidence now adduced, we are inclined to believe that the
felsite originally possessed a vitreous character, which has to a large extent
disappeared through devitrification. In all likelihood the great alteration
which the rock has experienced may have been partly coincident with, and
partly subsequent to, this molecular change. If the vitreous material had
reached the surface originally, it would have been ejected in the form of a
glassy lava.

The dykes radiating from the intrusive sheets present microscopic characters
of a varied type. The coarse-grained aplites or binary granites are identical
with the Northmavine and Sandsting sheets. A typical example occurs at
Mavis Grind, in which the felspar is mainly orthoclase with some Carlsbad
twins. Some microcline is also present, but the felspars have undergone con-
siderable alteration. The quartz occurs in isolated crystals and in groups
enclosed in the felspars. A number of sections of the quartz-felsites have been
prepared, displaying very uniform characters. A typical example from Aith
Ness, in Aithsting, shows a micro-crystalline ground mass of felsitic matter, with
small crystals of orthoclase porphyritically developed. Quartz occurs in small

| grains and nests, and magnetite is also present in minute grains. Another sec-
. VOL. XXXII. PART II. 3 P

4

J84 B. N. PEACH AND J. HORNE ON THE

tion from a dyke close by the former locality exhibits a similar ground mass,
but more coarsely crystalline, which is traversed by veins of secondary quartz
and lamin of chlorite, with magnetite grains more abundantly developed.
All the’specimens have been much kaolinised.

The rhyolites possess certain microscopic characters which readily distin-
euish them from the preceding group. They exhibit fluxion structure of a
more or less perfect type and possess a micro-crystalline base. In this base,
erystals and grains of quartz and felspar are arranged in parallel but wavy
lines, round which the felsitic matter curves in continuous streams. The
parallel and wavy bands of felsitic matter vary considerably in density. Some
of them are extremely fine-grained, parts of them remaining dark under
crossed nicols. The coarser bands do not remain dark with crossed nicols,
and with polarised light many of the particles exhibit the play of colours
characteristic of quartz. It is evident, therefore, that much of the base of the
coarser bands consists of minute grains of quartz. The felspar and quartz fre-
quently exhibit rounded edges in the midst of the streams of devitrified mat-
ter. Another feature of these ancient rhyolites is the absence of microlites
in the ground mass, which are so characteristic of the younger vitreous
rocks.

A section (59 ¢) from the north-east corner of Papa Little exhibits most of
the foregoing characters. The wavy bands of micro-felsitic matter are ad-
mirably shown, along which are arranged lines of quartz and felspar, but not —
continuously. Plagioclase is of less frequent occurrence than the orthoclase,
and many of the quartz and felspar crystals have distinct rounded edges. A
few crystals of iron pyrites occur in the section, which decompose into fine
grains of limonite. A green dichroic mineral, probably hornblende, occurs in —
one of the denser bands. There are also minute grains of viridite, which
are evidently decomposition products. No microlites are observable in this
section. In one section (2 e), taken from a dyke close by the foregoing instance,
the bands of fine micro-felsitic matter enclose small oval-shaped masses of a —
coarse-grained material otherwise similar in character to the surrounding base.
The quartz is frequently elongated in the direction of the flow of the molten
matter. Throughout the base there are abundant dark grains, probably
opacite. The section (3 ¢) from the same neighbourhood possesses a very fine-
grained and dense band of micro-felsitic matter, in which a prism of orthoclase
lies obliquely across the direction of the flow, round which the stream of
devitrified matter curves in continuous lines. With crossed nicols, this dense
band exhibits patches which remain dark when the stage is rotated.

The section from near Skeld,in Sandsting, close to the edge of the granite —
mass, exhibits very distinct fluxion structure, but the micro-felsitic base con-

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 385

tains hardly any crystals of quartz and felspar. The sections from Laxa Burn,
near Sand Church, in Sandsting, display similar characters.

From the foregoing descriptions it cannot be doubted that this well-marked
fluxion structure is due to movement of the molten magma which originated
in the fissures radiating from the intrusive sheets.

The evidence seems to point to the conclusion that the materials originally
existed in a glassy form, and that the rock when it consolidated was a rhyolite.
Since that period a process of devitrification has been in operation, which has
converted the glassy matrix into the micro-felsitic matter. The fact that only
portions of the denser bands remain persistently dark under crossed nicols,
while the coarser bands transmit the light, would seem to indicate that the
devitrification has advanced so far as nearly to destroy all traces of the original
glass. Nay more, in one instance (65 ¢), from near Aith Ness, in Aithsting,
the fluxion structure is hardly traceable, save with polarised light. This section
shows a crystalline felsitic ground mass, with occasional crystals of orthoclase
and quartz; the iatter being minutely distributed in the ground mass, though
much of it appears to be of secondary origin, filling cracks in the section.
The whole mass has been much kaolinised, and is darkened by the presence of
minute specks of ferrite. Indications of fluxion structure are observable in
the neighbourhood of the isolated felspar crystals, but the rest of the ground
mass has lost all trace of this structure. It seems reasonable to infer, there-
fore, that this example displays an extreme type of devitrification, and that
possibly many of the quartz-felsites belonging to the Old Red Sandstone forma-
tion of Shetland may represent what originally were rhyolitic rocks, though all
traces of the original structure have disappeared.

We have been favoured with the following note from Professor RENARD,
who has kindly examined the typical sections showing fluxion structure from
Shetland :—‘‘ L’examen que jen ai fait a porté sur deux points: 1. Je crois
qu il n’y a pas lieu de douter que les echantillons, spécialement les sections
typifiques 2, 3, 5, 59, montrent avec beaucoup d’evidence une structure fluidale.
2. Je ne vois pas dinconvenient a’nommer cette roche rhyolite ancienne, et je
crois en effet comme vous, que c’est une rhyolite dont la base s’est devitrifiée,
et que ne contient guere d’elément vitreux apres les modifications auxquelles
elle fut soumise. Sion admet cette maniere de voir, d’apres la classification
que nous suivons sur le continent on la grouperait peut-étre parmi les /eszt
pechsteine, mais cest la un terme de nomenclature sur laquelle il y a beaucoup
a distinguer. Vous savez, mieux que je ne puis vous le dire, que les /elsit ’
pechsteine représente les rhyolites anciennes et apres tout lun nom vaut
Yautre.”

On referring to the table of chemical analyses, it will be seen that the
members of the acidic series—both the intrusive sheets and the branching

386 B. N. PEACH AND J. HORNE ON THE

veins—are closely allied to each other in chemical composition. The granites
of Rooeness and Sandsting, the spherulitic felsite of Papa Stour, and the
rhyolites of Papa Little, yield similar results. The percentage of silica in the
Sandsting granite is 70°96, in the Papa Stour felsite 69:12, in the grey and
pink varieties of rhyolite 73°70 and 72°32 respectively. There is no appreci-
able difference in the other ingredients, save in the quantity of potash in the
Papa Stour felsite, which amounts to 10°17 per cent. The specific gravity of
the granites and rhyolites is 2°6, while that of the Papa Stour felsite is 2°5.

In conclusion, we might thus briefly summarise the results of these inves-
tigations.

1. The porphyrite and diabase lavas of Shetland belong to a basic series, and
present microscopic characters akin to the great volcanic series of Lower Old
Red Sandstone age in central Scotland.

2. The intrusive diabase dykes and bosses resemble the foregoing in chemi-
cal composition and microscopic characters, though they are separated from each
other by a considerable interval of time. .

3. The great intrusive sheets of Rooeness Hill and Sandsting consist of
binary granite and ordinary micaceous granite respectively, while the Papa
Stour sheet is composed of pink spherulitic felsite. The dykes of devitrified
rhyolite, associated with the binary granites, closely resemble the granites and
felsites in chemical composition, and hence the divergence in lithological and
microscopic characters is due to the different conditions under which they con-—
solidated.

4. The well-marked fluxion structure displayed by the rhyolites seems to
indicate that they originally possessed a glassy ground mass, which has to a
large extent disappeared through devitrification.

5. The mere presence of fluxion structure in igneous rocks does not by
itself prove that the lavas were ejected at the surface, as the physical relations
of the Shetland rhyolites clearly show that they are intrusive.

Norr.—Our best thanks are due to Professor Renarp and Mr T. Davies for the assistance they
kindly rendered in the microscopic examination of these rocks.

OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND. 387

City Awnatyst’s LABORATORY,
138 Bato Srrezt, Guascow, 22nd June 1881.

ANALYSES of eight Specimens of Shetland Igneous Rocks received from
J. Horne, on the 4th February 1881.

3a. :
aby 2c, 3b, 3c. . : : pe Vari bun te
eee ecu e eer: | oss | We. | Re
ese | 28ss | ace Spewheces | 2@b | £25. | sae
per cent. | per cent. | per cent. | per cent. | per cent. | per cent. | per cent. | per cent.
Silica, . : : : ‘ 51°82 48-36 50°58 71°66 70°96 69°12 73°70 72°32
Alumina, . . : . 14:14 19°73 15°51 13°28 15:18 14°55 13°34 14-02
Peroxide of iron, . : ; 5°50 7-71 5°74 1:24 1:69 1:70 1:06 1-11
Protoxide of iron, : F 5°76 4:68 3°06 "10 | absent 14 14 ‘47
Bisulphide of iron, . . | absent | absent ‘45 | absent | absent | absent | absent | absent
Oxide of manganese, . : ‘25 | trace 29 | absent | absent | absent ‘10 | trace
Lime, . - : : ; 6°10 6°63 9°52 2°24 1°52 1:57 2°33 114
Magnesia, . : : 5 1°76 5:97 8:90 64 “70 52 1:24 48
Potash, : z ; : 7°81 2°57 85 4°84 4°68 10°17 5°05 7°44
Soda, . : : ; : 1:09 3°47 2°89 5°37 4:32 1:27 2°43 2°53
Phosphoric acid (Anhydride) ‘56 05 13 18 | trace 05 | trace trace
Sulphuric acid, <5 : 05 | absent ‘08 | absent ‘ll 12 22 | absent
Titanic acid, S . | absent | absent | absent | absent | absent | absent | absent | absent
Carbonic acid, 55 F 4:05 ‘10 1-28 | absent | absent | absent | absent | absent
Water of combination, : “91 53 “51 “30 66 67 27 “40
Moisture, . : - “20 20 21 15 18 “12 12 ‘09
100: 100° 100: 100° 100° 100° 100° 100°
SPECIFIC GRAVITY, . : 2°743| 2°788*| 92-911* 2-609 2618 2540 2°652 2°621

* Mean specific gravity of three pieces.

Ropert R. TATLocK.

VOL. XXXII. PART II. 3Q

388

Fig.

Fig.

Fig.

Fig.

. Porphyrite, Rooeness Voe, Northmavine, showing minute columnar crystals of plagioclase fel- —
. Diabase, Clouster Voe, Aithsting. A contemporaneous volcanic rock seen with polarised light,

. Diabase, Skeld Hill, Sandsting. An intrusive rock seen with polarised light. This section

. Rhyolite, Papa Little. An intrusive rock showing dense bands of micro-felsitic matter, with a

. Rhyolite, Papa Little. An intrusive rock seen between crossed Nicol prisms, showing wavy

. Spherulitic felsite, Papa Stour. An intrusive rock seen with polarised light, composed of reddish-

. Felsite, Dales Voe, Sandness. An intrusive rock seen with polarised light, showing a fine

. Binary granite or aplite, Heads of Grocken, Northmavine, seen with polarised light, consisting

THE OLD RED SANDSTONE VOLCANIC ROCKS OF SHETLAND.

EXPLANATION OF PLATES XLV. AND XLVI.

spar, abundant magnetite, with a green decomposition product. A fine ground mass is
interposed between the felspar crystals. This is a typical example of the porphyrite lavas of
Old Red Sandstone age in Shetland (30 diameters).
The crystals of plagioclase felspar are well preserved and abundant, the augite has been con- —
verted to a large extent into chlorite. Magnetite is very abundant throughout the section
(70 diameters).

shows the marked distinction between the interbedded and intrusive diabase rocks. The
plagioclase felspar crystals are larger than in the preceding section, but much decomposed.
The augite has been largely replaced by a green fibrous mineral, but fresh crystals are recog-
nisable in the section. Magnetite is also present (20 diameters).

prism of orthoclase lying obliquely across the direction of the flow. This section exhibits”
very perfect fluxion structure, the movement being from right to left (20 diameters).

bands of micro-felsitic matter, which partly remain dark and partly transmit a faint light.
Lines of quartz and felspar are arranged more or less parallel with the wavy bands of vitreous
matter. The quartz is elongated in the direction of the flow (20 diameters).

brown felsitic matter, arranged in well-marked spherules, in which the fine radial fibres are
prominently developed. In some parts of the section the diverging fibres have been sup-.
planted by a fine grained ground mass. Nests or cavities filled with a secondary quartz are
visible. The ground mass is stained with minute ferruginous particles (70 diameters).

felsitic ground mass, with large irregular grains of quartz containing fluid inclusions. Strings
of quartz also traverse the section. A well-marked prism of orthoclase forms a prominent
feature near the centre of the drawing, and minute grains of magnetite are evenly distributed
through the mass (30 diameters).

of-reddish-brown orthoclase, which is much kaolinised, and quartz with fluid inclusions ( y
diameters).

. Roy. Soc. Edin’ Vol. XXXII, Pl. ALV

achle] F Huth, Lith” Edin®

oy.Soc. Kdin* . Vol. XXX1i PL. XI

F Huth, Lith’ din"

( 389 )

XXII.—Observations on a Green Sun and Associated Phenomena. By Professor
C. Micuiz SmiruH. (Plate XLVILI.)

(Read July 7, 1884.)

The appearance of a green or blue sun, though not unknown, is of sufficiently
rare occurrence to make a full investigation of all the phenomena connected
with it highly desirable. I have therefore tried to obtain as accurate and
complete information as possible concerning the appearance of a green sun in
India during several days in September 1883..

The general features of the phenomena were well seen in Madras, and will
probably be best described by my notes taken at the time. On September 9th
the sun before setting assumed a peculiar silvery appearance, and its brightness
was so much decreased that for about half an hour before sunset it could be
observed with the naked eye. This was observed, I believe, though to a less
extent, on the two days preceding, but I did not myself see it on these days.
On September 10th, from 5.0 to 5.30 p.m., the sun could easily be looked at
with the naked eye, yet the limbs were sharply defined. At 5.30 the sun
entered a low bank of clouds, and did not fully reappear again, but a narrow
strip seen through a rift in the cloud at 5.43 was coloured a bright pea green.
Round Madras this colour had been seen in the morning, but in Madras itself
_ clouds concealed the sun till it had risen to a considerable altitude. Of the
| morning of the 11th I have no record, but in the evening the green colour was
_ very brilliant, and was visible for more than half an hour, being preceded, as on
the former night, by the silvery white appearance of the sun’s disc. On this
_ evening a large sunspot about one foot long was so conspicuous an object that
| it attracted the attention of even the most casual observers.
| September 12th, at 12.35 a.m., the moon, which was near the horizon, appeared
| apale green. Bright stars near the horizon showed the same tint. From 5.15
to 5.30 the clouds to the east were coloured reddish-brown. At 5.55 the sun
rose with a yellowish-green colour, but was almost instantly lost in clouds. | It
reappeared at 6.4, and was then of a bright green colour ; this colour rapidly got
fainter, but was quite perceptible till 7 o'clock. In the afternoon, the phenomena
of the previous nights were repeated, and the horizon being free from clouds,
the actual sunset was observed. The entry in my notes is—‘‘6.3, the sunset
as a greenish-yellow ball, cumulus, stratus, and nimbus clouds near the horizon,
but moon fairly clear. Some blue sky, but hazy.” The change from green to
greenish-yellow was evidently due to the great increase in the strength of the

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390 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

low-sun band close to the horizon, which left the strip of yellow between that —
band and the rain-band by far the most prominent feature in the spectrum.
September 13th.—In the early morning there was a good deal of distant light-
ning. The sun rose of a bright golden yellow colour; no green was seen. In
the afternoon there were slight showers. A most remarkable observation
made this morning by Mr Pocson seems very difficult to explain, except by
some form of auroral display. I give his notes in full :—
“ September 12, 1883, 17" 0", Madras mean time.—The sky a most
remarkably intense reddish-yellow, so unusually bright that I called up my ~
daughter Isis to witness it. A dark cloud bank from about east to south, and —
the vivid light above uncommonly auroral in appearance; more so than anything
I have seen here before.
“At 17" 10", the red hue considerably diminished, and bright orange
yellow the prevailing tint. The light quite bright enough to make notes by.
“ At 17" 20", the dark blue-black stratum now from about north to east,
and very near the horizon. Sky tolerably clear to about 20° altitude, but of a
rich red tint, with bright yellow clouds above, beginning at about 30° and
covering the east of the sky.
“At 17" 30", all changed within the last four or five minutes, and
writing now difficult without a lamp. A thick dark red stratum over the
sunrise point, and everywhere else a very greenish-yellow.
“At 17° 40", the low cloud stratum now sea-green. Light only enough ©
to write by with difficulty.
“ At 17" 50", sun rising a bright yellowish-white, and otherwise nothing
extraordinary, all unusual tints having disappeared with the sunrise.”
September 14th.—Before sunrise the clouds were blue and grey, with patches
of red. Clouds of all sorts,—cirrus, nimbus, stratus, cumulus, and mare’s tails.
Two bright flashes of lightning about 5.30 a.m. In the evening there was a
slight green tinge, and after sunset the sky was golden red till 6.50, while
mercury seen through the red haze was twinkling strongly.
September 15th.—The sun rose golden. In the evening the sunset was very
fine ; in the west the colour was golden to orange yellow, in the east it was
greenish; red clouds remained till 7.5; there were very brilliant red “ rayons de-
crépuscule.”
From September 15th to September 20th the sunrises and sunsets were very
fine, with red and gold for more than half an hour before sunrise and after us
September 21st.—Sunset normal. ;
September 22nd.—The sun rose as a yellow ball, and showed distinct —
yellow afterwards, From ten minutes before till sunset, the sun was greenish-
yellow, but the sun was much brighter than on the 10th and 11th. ‘
September 23rd.—The sun rose very green. At 5.37 p.m. the sun appeared

A GREEN SUN AND ASSOCIATED PHENOMENA. 391

from under clouds very green. Strong absorption in the red end of the spectrum
to C, low-sun bands weak. 5.45, clouds greyish-purple. There was only one
bank of clouds which was near the horizon; above this was a peculiar greyish
haze. At 6.0 the clouds were of a marked purple colour; breaks near the
horizon were reddish-brown. During the night there was a great deal of sheet
lightning in the south.

September 24th.—The sun rose bright yellow. The spectrum showed
complete absorption up to B; the rain-band, a and 8 were very thick, and the
low-sun bands less marked than usual. There was lightning all night, beginning
in the south and working round tothe south-east. It consisted chiefly of sheet
lightning, with occasional zigzag flashes, but no thunder; the stars were fairly
clear except near the horizon. Saturn and the moon, when near the horizon,
were both very dim.

September 25th.—Sunrise golden green. In the afternoou the shadows cast
on white paper were still quite pink, but the sunset was bright yellow.

September 26th.—Much the same as yesterday.

September 27th.—Before sunrise C, B, a, the rain-band and the dry-air band
were very strong, but the dry-air band was less than half as dark as the rain-
band. The sun rose golden red. The-spectrum showed signs of clearing up;
glimpses of A could now be obtained. After dark there was very bright light-
ning in the west—sheet lightning, with a good deal of zigzag, and at least one
_ very fine specimen of a flash such as is obtained a
| by discharging a Leyden jar through a spangled BOR ay ig
| tube, the flash being broken upintoa number of : ee os ei
_ detached pieces. During the day there were “ !
| slight local showers in parts of the town.
| September 28th.—Spectrum still showed great absorption. Lightning at
_ night.

September 29th.—Absorption still very strong. After dark there was a
| display of luminous clouds, specially towards the east. After 11 p.m. there
| was very heavy rain, with much lightning and some thunder.

| September 30th._Sunrise golden. The spectrum on the sun showed A
| clearly, and was very thick.

October 2nd.—In the morning from about seven to nine, there was a thunder-
storm, in which the thunder was almost continuous for above an hour and a
half; but though the storm was almost vertically overhead, hardly any lightning
| was visible. Apparently the discharges were chiefly from cloud to cloud, and
the thick layers of heavy clouds overhead shut out the flashes. The thunder
was followed by heavy rain. The official Meteorological Report contains the
following reference to this storm—‘The weather on the 2nd instant was
decidedly remarkable; thunder in the morning; heavy rain at noon, exactly

392 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

three inches being recorded by 1 p.M., and continuing less heavily, but stor
till 10 p.m. The total rainfall for ie day was 4°88 inches.”

To complete the description of the phenomena, I will now quote from the
accounts of some reliable observers in other parts of the Presidency. The
following is from the diary of the superintendent of the lighthouse at Muttum,
in the south of Madras, for September 1883 :—

“6th, 7th, 8th.—After sundown on these days there was a very peculiar
saffron glare, which faded as it became dark. On 8th it was very marked.

“9th (Sunday).—This day, from about 4 p.m., the sun became perfectly green,
and could be looked at without any inconvenience. The saffron glare after
sunset seen. The green appearance of the sun continued several days, both in
the morning and the evening.

“13th, 6.30 p.M.—A large meteor [? a fire-ball] passed from west to north-
east. It burst three times and faded away.

“15th.—There were observed on this day five clusters of spots on the sun ;
the green tint has been lost, and the sun is of a natural colour.

“22nd.—Sun again appeared of a very green colour, which continued every
day up to the 28th.”

The next account is from Bellary :—

“ Sunday, 9th September.—Sun set as usual, but after sunset a lurid glare
spread over the sky, the colour being red with mauve in it. [Another corre-
spondent writes that.he thought the infantry lines were on fire. ]

“ Monday, 10th. —Sun, both at rising and setting, emerald green.

« Tuesday, 11th. —Again the same appearance both at rising and setting.

“12th, 13th, 14th.—Emerald green at sunset. After this week no record.”

From Coonoor, on the Nilgiris, more than 6000 feet above sea-level, I have
the following notes from Mr J. F. Gri :—

“Sunday week (9th) was remarkable chiefly for a persistent red glow,
likened by many to the reflection of some great fire. Our sunsets have been —
gorgeous for several days, always abounding in the peculiar pea-green tints.
Last evening (20th) the eastern sky and the whole landscape showed a most
lovely and unusual greenish glow. After sunset a few clouds in the east were
tinted lilac. The more distant mountains stood out very distinct against the
green—clear but somewhat deep—of the sky. All near trees and other objects
at hand had a ‘scene-painty’ (chromium oxide suggested) green tint. Red
predominated in the western sky on the many clouds; but there was an
intensely luminous area of hardly yellowish light near where the sun had set,
which must have continued an hour. The ‘shimmery’ appearance of the sum,
and the ease with which it could be looked at during Monday to Thursday,
were remarked everywhere. There has been a good deal of bright lightning
seen at some distance over the plains on many days.” if

A GREEN SUN AND ASSOCIATED PHENOMENA. 393

This is particularly interesting on account of its close resemblance to the
description so often given of scenes in hill countries just before heavy rain.

Mr MAntey’s observations at Ongole, which is the farthest north point at
which satisfactory observations seem to have been made, have already been
published in Nature, and need not be repeated here.

The Spectrum.

_ The observations on the spectrum were made partly with a direct vision
spectroscope, with a lens in front of the slit (HILGER’s rain-band spectroscope),
but chiefly with my zodiacal light spectroscope, which has a single large dense
glass prism and a collimator three feet long. The great length of the collimator
permits the use of a very wide slit, which was found to be a great advantage in
this case. The only means of recording the positions of the lines is by reference
to a reflected scale; and since all the lenses of the instrument are quartz, the
focus of the observing telescope, and consequently of the scale also, has to be
changed for different parts of the spectrum. This was found very inconvenient
when it was necessary to take a number of readings in different parts of the
_ spectrum in rapid succession. The positions of the bands cannot be considered
as strictly accurate, but they cannot be far wrong, as they were fixed by refer-
ence to known lines near them, and the scale values for the different parts of
_ the spectrum were obtained by plotting the scale readings for known lines in
terms of wave-lengths, and smoothing the curve. The main features of the
_ spectrum taken on the sun when green were—

(1) A very strong general absorption in the red end.

(2) A great development of the “ rain-band” and of all other lines which are
ascribed to the presence of water vapour in the atmosphere, more especially of
the group C, of a, and of the band at W.L. 504.

The absorption in the red end was of very varying intensity; but when the
phenomenon was at its maximum phase it gradually crept up from about B till
past C, as the sun sank towards the horizon. On the 12th, when the sun was
within a few degrees of the horizon, the absorption was well marked up to
| W.L. 621—i.¢., to beyond a, while at the violet end the visible spectrum ended
at W.L. 428, or just beyond G.

The lines A and a were never visible, even on the sun, when it was green,
and even B could be made out with difficulty from half an hour before sunset
| onwards ; and before it vanished it grew intensely prominent, with enormously
| thick bands on the less refrangible side. The band C, on the more refrangible
| side of C, became very broad and black, while the fine line between this and C
remained thin and sharp, and C itself thickened out on the less refrangible side.
The rain-band was stronger than I have ever before observed it on the plains ;

394 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

and even with the dispersion produced by a single prism, at least eight lines
could be measured in it, while many more were visible.

The low-sun band was not very conspicuous; but this was partly due to
contrast with the very strong rain-band. The line W.L. 568 at the more
refrangible side of the low-sun band was very well marked, and the band itself
seemed to consist of a series of equidistant lines. The apparently much ~
stronger absorption in the red than in the blue end was a very marked feature,
which became still more conspicuous when a photograph of the blue end was
examined.

A photograph was taken on the evening of the 23rd September, when the
sun was very green, and the visible spectrum extended between W.L. 645 and
W.L. 410. Half of the slit was exposed for twenty seconds, and the other half
for thirty-three seconds. Both gave good photographs, extending from about
F to a distance beyond H, twice as great as the distance between F and H.
This is very nearly the same length as I obtain under similar circumstances in
ordinary weather, though not nearly so long as I obtained last summer at an
altitude of 6000 feet. The lines were sharp and well defined, and contained no
bands that were specially prominent, though some seemed darker than usual.
I have, unfortunately, no means at present of making an accurate determination
of these lines. The atmospheric band C was very strongly marked, and was
decidedly more conspicuous than C itself. It was thick and dark even at an
altitude of 60° or 70° in the middle of the day, and formed then, next to the —
general absorption, the most characteristic feature of the spectrum. The
contrast of the thin line between C and C’ with these lines was most interesting.

Since the passing away of the abnormal conditions, I have made careful
observations of the sunset spectrum with the same apparatus, and I find that
ordinarily A and @ are clearly visible, as well as B, though at times they are
strongly marked, and a good deal of shading is observable between them. C
is much thinner, and the rain-band is less prominent than the low-sun band,
which, however, does not now have the appearance of a number of fine lines.
The nearest approach to the green sun spectrum was observed recently during ©
a severe thunderstorm, which was accompanied by a fall of about 14 inch of
rain.

A very similar though less intense spectrum can be observed almost any
evening by taking advantage of the passage of a small thin cloud over the sun’s
disc. Ifa lens is used in front of the slit of the spectroscope, the absorption
due to the cloud will be seen as a band in the middle of the bright spectrum
from the unclouded part of the sun; and, owing to the strong contrast, the
details of the absorption will be well seen, just as in the case of a spectrum of
a sunset.

A GREEN SUN AND ASSOCIATED PHENOMENA. 395

Meteorological.

My attention was first called to the peculiar state of the atmosphere on
September 3rd, when making observations on atmospheric electricity. Observa-
tions made at 10 a.m. on August 31st showed a normal but rather low
electrification ; no observations were made on the 1st or 2nd September, the
electrometer being out of order. On the 3rd, after the instrument had been
carefully dried, observations were begun at 1.10 P.m., when the air potential
was found to be negative, the electrometer readings varying from —28 to —17
divisions. By 2.45 it had become positive, amounting, however, to only +6,
which was also the reading at 4.45. During the succeeding days numerous
readings were taken, and these show a remarkable state of electrification (see
Appendix A). The general results of the observations may be summed up
thus :—In the early morning the potential of the air was positive ; it continued
positive, but gradually decreased in strength till some time between 9 and 10 A.m.,
when it fell to zero, and then became negative. The strength of the negative
charge varied greatly and with remarkable rapidity, and the maximum readings
were obtained either just before or during strong gusts of wind. The negative
charge continued till the sea breeze set in in the afternoon, when it became
positive, and continued so all night, and in all cases, I believe, the change of
sign coincided with a change in the direction of the wind. Very high readings
were at times obtained; in one case the reading was —459 divisions of the
scale (=about 1900 Daniell cells or 2100 volts) at about 5 feet above the
ground, in bright sunshine with a clear sky, but with a gusty wind, which
raised clouds of dust. At other times there would be scarcely a trace of
electricity perceptible. In all cases in which the potential was negative it
decreased with height, but when it was positive it increased with height.
Another point worth noticing is that, when negative, the potential might vary
very much, but with two exceptions (and these are a little doubtful) it did not
change sign, as one finds so often in a thunderstorm. This state of affairs
continued from September 3rd to September 6th. On the 7th the potential
was positive all day, the day being cool and cloudy throughout. On the
8th it was negative for a short time; on the 9th it was again positive all day;
jon the 10th, 11th, and 12th, it was as from the 8rd to the 6th; from the 13th
|to the 19th it was normal, though on the last of these days it fell to zero
jat 11 a.m. From the 20th to the 27th it was again abnormal,—positive till
jabout 9.30 a.m., then negative and then positive again,—except on the 23rd,
-\when the lowest reading obtained was zero. After the 27th the readings were
jall positive.

It will be observed that all the negative readings were obtained when the

396 PROFESSOR (C. MICHIE SMITH ON OBSERVATIONS ON

wind was westerly, and after the day had so far advanced that the ground had
begun to grow hot. This westerly wind is a hot land-wind, and on a previous”
occasion I obtained negative readings during its prevalence (Proc. Roy. Soc. Edin.,
vol. ix. p. 615), but then there were local showers a few hours afterwards.
Thinking at the time that this was probably a similar case, I wrote a note to
the local papers on the 6th, asking particulars of the weather within a radius of ©
100 miles of Madras, especially with reference to rain, thunder, and lightning,
and wind direction between the Ist and 6th of the month. In reply to this I
got information from various stations which was of considerable interest, but
apparently no rain fell within 100 miles of Madras up to the 6th, but on that
day there were a few showers in and around Madras (0°03 inches at Madras
Observatory). On the same day there was a storm at Tindivanum, about
75 miles south of Madras, which is thus described by a correspondent :—* At
about 3 p.m. on the 6th a severe storm passed over this place, direction west by
a little south to east by a little north. Wind preceded rain by a quarter of an
hour, and blew steadily (not in gusts) for an hour ; velocity not known, but must —
have been very great..... Rain fell in torrents from 3.15 to 3.45, and from
this time till 6 p.m. it continued to drizzle. There was only one clap of thunder,
which lasted some two or three minutes, and seemed to roll on eastward; it
took place about 3.30. This seemed to break the violence of the storm. .... a
Of this storm, which seems to have been very violent and local, I received
another account from a gentleman who passed through it in the train, and who
stated that the storm was such as he had seldom, if ever, experienced before.
From Canajore in Mysore I received the following :—“..... Here, 6 miles”
from the Western Ghauts, altitude 3100 feet, the weather during the first week
of this month was abnormally wet. The average rainfall for September is
about 12 inches, but between the Ist and the 9th I gauged 18-04 inches, the
aggregate on the 6th, 7th, and 8th being 10°85 inches. No thunder.” From
the Koondahs, near Coonoor on the Nilgiris, another correspondent reports
that he was awakened about 4 a.m. on the 9th by a terrific gale, which lasted
for only about half an hour, and passed off as suddenly as it began. The
reports show an abnormal state of the atmosphere, which tended to give rise to —
local disturbances. This abnormal condition is also shown in a report from —
Kodaikanal, on the Pulney Hills, kindly sent me by Mr Levinas, who has kept
a rainfall register since 1873. He writes—“There was the same peculiar
colour of the sun at rising and setting here which was noticed in other places,
and on the same dates as recorded in the newspapers. The atmosphere here
all the time was very hazy. The only other remarkable events were that we
had frosts in the beginning of September, which I never observed before at
that time of the year. The rainfall for September was also the lowest I have
any record of; it was as follows :—1st to 13th, none; 14th, 0°40; 15th, 135,

A GREEN SUN AND ASSOCIATED PHENOMENA. 397

19th, 0-40 ;—total, 2°15 inches. [Average for September, 6°65 inches on thirteen
days.| During the month we had no thunder or lightning. Early in the
month the wind was from the north, which was unusual.” An examination of
the daily weather reports for the month shows that in the earlier. part the
“eneral weather” to the north was threatening or overcast, in the central
parts of the Presidency it was fine with passing clouds, and in the south sultry.
From about the 7th onwards for some days there are frequent reports of “ dust
haze,” “sultry,” and “dark gloomy weather ” in the reports ; while, on the other
hand, at two stations the report is, “atmosphere unusually clear.”

The rainfall for September over the whole Presidency was much less than
‘usual. The average for fifteen stations for which reliable data are available is
| 3°24 inches, instead of 6°90, the average for preceding years. The monsoon
| rainfall, on the other hand, was much above the average for the same fifteen
| stations. The rain at some stations continued into January, but taking only
‘the months of October, November, and December, the average rainfall was
| 21°75 inches, while the average due for the same time is 17°36. This includes
| Bellary, at which the fall was 11-90 inches below the average. |

The barometric variations during the month also seem worth a careful
study. Except for Madras, I have only the 10 a.m. readings, but these may
| generally be taken as yielding a fairly accurate, though rather less smooth,
barometric curve than that which would be obtained from the mean of the
| corrected three daily observations. The accompanying diagram shows the
/ curves for Colombo, Madras, Belgaum, Allahabad, and Calcutta (Alipore).
| The first point that strikes one on examining the curves is their strong general
resemblance, showing the same causes at work in producing change of pressure
over the whole area of India. We have first a minimum, which was on the
| 6th at Colombo, Madras, and Allahabad, and on the 7th at Belgaum and Cal-
| cutta, The delay at these two last places was exceptional, for out of ninety-
three stations sending in reports only thirteen show a falling barometer on the
7th, and these are connected with small local areas of depression. The rise to
a maximum is rather irregular, but it is reached for most stations on the 18th,
and the report for the 19th shows a fall at every station except Sholapur and
Moulmein. The fall continued till the 21st, when a rise took place at the great
majority of stations. A third minimum falls on the 27th. Observations made
with the black bulb solar radiation thermometer in vacuo and the grass mini-
mum thermometer will be referred to further on,

In any attempt to discover the cause of the phenomena observed it is of
importance to determine exactly the dates at which they were first seen at
different places. This, however, is a very difficult thing to do, inasmuch as
most of those who have reported on the subject have been untrained in exact

VOL. XXXII. PART II. 38

398 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

observations, and in many cases have made more definite statements than their
observations warranted. Thus, for example, I watched the sunset on the 9th,
and certainly there was no trace of green in the silvery colour of the sun’s dise;
yet several people in Madras told me that they had seen the sun set green on —
that night ; but this was after they had seen the green sunsets on the following
nights. I believe this is only an illustration of what happened in many cases,
the peculiar sunset on the evening of the 9th was observed casually, then when
people began to talk about the green sunsets of the 10th and 11th, the casual —
observer recollected that he had seen something peculiar, and his imagination
gave the silvery whiteness a green tinge. This has made me careful to sift as
far as possible the various statements which I have received, and, though I
cannot claim that the dates which I have accepted are im all cases absolutely
accurate, I think that they come very near the truth.

The general result of my investigation into the dates of occurrence of the —
phenomenon is, that in Ceylon, in the south part of the Madras Presidency, and
at Ongole, in the north, the sun first appeared green on the evening of the 9th,
and that over the rest of the Presidency, where seen at all, it was first seen on
the morning of the 10th. At Belgaum it is reported to have appeared on the
8th, and if this is accurate it isthe earliest date on which it was seen anywhere
in India, and would at once negative the idea of a gradual propagation either
from south to north or from east to west. I have no good reason to doubt the
accuracy of my Belgaum correspondent, but as no notes seem to have been
taken at the time, it is possible that he is not strictly correct. Beyond India
I have two reports from ships at sea—one from the captain of the “ Cleomene,”
who reports that there was a green sun and moon on the 9th, 10th, and 11th,
when his position was from lat. 8° N. to lat. 16° N., and from long. 83° 30’ E. to
long. 88° 40° E. In the same letter he reports that his ship was struck with
lightning on the Ist. The other report is from the chief officer of the ss.
“Pelican,” who has given me the following extract from his log :—‘‘ September
10th—The sun rose this morning looking quite green; never saw the like
before. Last evening the sky had a greenish haze, making the moon lock
sickly pale green, and a few peculiar black clouds like wisps or mare’s
tails. Light breeze from S. to S.W. with high S.E. swell. Position at noon,
lat. 10° 4° N., long. 64° 12° E. It was preceded by squally weather,
with strong 8.W. wind and very damp weather ;—heavy dews at night.”
Thus at two places—Madras and the position of the “ Pelican”—more than
1000 miles apart, the phenomenon appeared simultaneously, while to the
south and east it appeared on the previous day. At Ongole, lat. 15° 30° N.,
long. 80° 8’ E., Mr Manpey saw the green sun on the 10th, and was informed
that it had been seen on the 9th by one whose evidence he thinks entirely
satisfactory. I have no information to show that the green sun was seen at

A GREEN SUN AND ASSOCIATED PHENOMENA. 399

any stations farther north except Vizagapatam, Rajamundry, and Simla, and
unfortunately I cannot obtain the dates at which it was seen at these places.
At Bombay it cannot have been at all conspicuous, for though noticed by some
persons it was not seen at the Observatory, and so I cannot obtain any accurate
details as to the date of first appearance, &c. Beyond India we have several
dates which seem to be fixed with considerable certainty. In Honolulu, on
September 5th, the sun’s disc before setting was seen to be green (Nature,
vol. xxix. p. 549). On September 4th, at 5 p.m., the master of the “Jennie
Walker” “noticed the strange appearance of the sun, which was greenish.”
The ship’s position then was long. 155° 28’ W., lat. 8° 20’ N. A passenger
travelling from San Francisco to Sydney, three days out from Honolulu, writes:
—“On Wednesday, September 5th, we witnessed a most curious phenomenon.
The sun set perfectly blue, and next morning it rose a flaming ball of blue”
(Nature, vol. xxix. p. 181). From Barinas, in Venezuela, we have a report
that “on September 2nd, from daylight until noon, and from 3 p.m. to sundown,
the sun appeared like a globe of burnished silver ; between noon and 38 o’clock
it was of a bluish-green colour” (Nature, vol. xxix. p. 77). At Trinidad, on
| September 2nd, the sun was observed as a blue globe at 5 o'clock (Nature,
vol. xxviii. p. 577). It was seen at Panama on the 2nd and 3rd, and at Cape
Coast Castle, apparently, on the Ist. All these dates refer to the first appear-
ance, but we have a series referring to the second. Of these the earliest that I
can find is in an extract from the log of the P. and O. s.s. “ Nizam,” with which
Captain Harvey has favoured me :—‘“‘September 20th, in lat. 12° 50° N., long.
48° 26’ E., and the sun at the time being about 15° high, a greenish haze was
noticed gathering over it and the sky generally in the west. As the sun
decreased in altitude the green became more distinct, until a bank of green
cloud, of various shades, formed on each side of the sun, and as the sun
disappeared below the horizon so the cloud closed over the point of its setting.
This peculiar sky lasted nearly an hour after sunset, and made a greenish twi-
light most wonderful to look at. The light air blowing at the time was from
the eastward, and the weather fine and clear.” On the 21st the same pheno-
mena were observed, but not so clearly, owing to the ship’s proximity to
Socotra, “the wind at this time was 8.S.W. and the air moist.” The entry for
the following day is also of interest. “September 22nd, in lat. 12° 00’ N.,
long. 58° 00’ E., the S.W. monsoon blowing fresh in this position and the sky
cloudy, but there was unmistakably a greenish tinge in the west at sunset,
From this date until September 25th the weather was overcast and cloudy, so
that no observations were made; but in lat. 8° 50’ N., long. 71° E., the sun was
again observed to set with a green tinge over it. The weather at this time was
fine and clear, with a light northerly wind.” At almost all stations in South
India the greenness reappeared on the 22nd. Finally, we have the letter from

400 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

Hicks Pasna, dated Duem, September 24th-—“ To-day, when it [the sun] rose
it was of a pale green colour.” There is no proof, of course, that this is the
date of its first appearance in the Soudan, but if the green was nearly as
brilliant there as it was here, it could not have escaped observation.

Before discussing the causes of the phenomena that have been described, ©
it will be well to point out that we must distinctly separate the green sun and
the sunsets that appeared along with it from the remarkable sunsets which
occurred nearly all over the world some time later, and which were visible
here till at least the end of April. My reasons for making this separation are
—1. The general appearance was quite different in the two cases. The sunsets
accompanying the green sun were peculiarly lurid, and were, so far as I could
judge, simply an exaggerated form of what we usually have some time before
the bursting of the monsoon, and round the horizon we had then a most
decided fog, in which stars were lost some time before setting. The main
features of the subsequent sunsets, on the other hand, were the delicacy of the
colours, and the beautiful rosy afterglow reflected apparently from very light —
cirrus clouds high up. The horizon at this time was remarkably clear, as is
shown by the circumstance that Mr Pocson was able to make accurate measure-
ments of the faint comet “Ross” within less than 5° of the horizon. 2. The
spectrum was totally different in the two cases, for in the latter case the red
end was very free from general absorption A, @, and B standing out clear and
sharp, while the rain-band was slight, or altogether wanting, and the low-sur
bands were strong-—a complete contrast to what I have described as being
visible in the former case. I may add, that any increase in the strength of the
rain-band has been accompanied by a decrease in the brilliance of the after.
glow. :
To account for the green sun, three hypotheses have been put for-
ward—

1. That it was due to vapours or dust from the volcanic eruption at
Krakatao. First suggested by Mr Pogson. (

2. That the cause was the presence of an abnormal amount of aqueous
vapour. An explanation which I offered at the time of the occurrence.

3. That it was caused by a cloud of meteoric dust.

Mr Lockyer has taken up the first of these theories, and starting with the
assumption that the sunset effects were due to the same cause as the green
sun, has attempted to trace the general propagation of the dust round the
earth. His first line passes through Mauritius, the Sechelles, Cape Coast
Castle, Brazil, Trinidad, Panama, and Honolulu. His second is a line passing
from south to north through India. Taking the dates of the appearance of the
phenomena which can be relied on, we find that they would require approxi
mately the following velocities of propagation—

A GREEN SUN AND ASSOCIATED PHENOMENA. 401
Krakatao to Mauritius, é ; ; . 161 miles per hour.
a Cape Coast Castle, . E : ; a! “
" Trinidad, . ; : ' : . 74 ix
a Near Honolulu, lat. 8° 21’ N., long. 155° 28’ E., 85 is

These are the velocities if we assume that the column of dust was sent up
by the great explosion which took place between 8 A.M. and 9 A.M. on the 27th;
and even the plutonists seem to hesitate to affirm that the violence of the
| previous explosions was sufficient to send the dust up to the required height,
though the first great shower of dust must have been ejected some time
| previous to that hour. When we consider that, from the nature of the case, the
deduced velocities can only be very rough approximations, being in each case the
minimum value, it must be admitted that the more distant ones agree fairly
| well with each other. Here, however, we are met by two difficulties, viz., is
_ there any reason to believe in the existence of an upper current moving with
_ anything like the requisite velocity? and, if it moved so fast along the one
| track, how was it so long of reaching Southern India? Regarding the first of
| these difficulties, it seems absolutely certain that no such uniformly strong
currents exist, at least at any altitude to which the dust could possibly have
been projected. Mr Locxyrr attempts to overcome the second difficulty by
| assuming an upper current from east to west, nearly along the equator. It
| crossed to the north however to reach Cape Coast Castle and Trinidad—and
| an under current from south to north. If, however, Mr MANLEY’s observations
| are accurate, as there seems every reason to believe they are, it appeared at
| Ongole as soon as in Colombo, and at least twelve hours sooner than in
Madras; and, if the Belgaum observations are accurate, it appeared there a day
| before it was seen in Colombo. Taking, however, only those observations about
| which there can be no doubt we get the following velocities, taking the shortest
lines between Krakatao and the various stations :—

To Colombo, : . 2000 miles, 6-7 miles per hour.
ee vindiras. . ' Be een mere oF
3, Bellary, ». : ‘ eZ. once oO 0s

Lat. 10° 4’ N., long. 64° 12’, 3100 ,, 98 Ps

velocities increasing with the distance from the source.

Taking these along with the Japan observations, which require a velocity
of over 40 miles per hour, it seems very difficult to believe that dust would
have travelled in these different directions with such very different velocities.
Finally, we have the negative evidence, which in this case seems to have some
weight, that the first rain which fell after the appearance of the green sun
contained no volcanic dust. I collected several gallons of the rain which fell
on the night of the 29th, and had the sediment which it contained carefully

402 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

examined under the microscope by Dr T. K. Rocrrs, a skilled chemist, but no —
trace of volcanic matter could be detected in it. Ido not suppose that the —
asserted discovery of volcanic ejecta in rain and snow in Europe will be allowed
to have much weight in the decision of the question, since, even if the volcanic
nature of the materials found is proved, it still remains an open question where
they came from.
With regard to the water vapour theory, there is at least some definite
evidence upon which to found an argument. The spectroscopic evidence
detailed above shows that all the prominent lines in the spectrum which are
due to the presence of aqueous vapour were stronger than usual, and that there
was, in addition, a strong general absorption in the red. This general absorp-
tion might doubtless be produced by the presence of dust of a suitable fineness
suspended in the air, but that it may also be produced by water vapour, or at
least by clouds, is amply proved by observations which I have since made on
several occasions. In a recent thunderstorm, to which I have referred above,
and which was predicted spectroscopically forty hours before it developed, I
found almost exactly the same spectrum as in the case of the green sun, but —
the absorption in this case was produced by the passage of the sunlight through —
a comparatively thin stratum of dense cloud, instead of through a fairly trans-
parent atmosphere. We know, too, that the absorption produced by aqueous —
vapour in certain conditions is capable of producing the observed appearance.
On this point we have the observations made by Mr Lockyer, confirmed by —
other observers, of the sun being seen green through the steam escaping from
the funnel of a steamboat, and his further observation of a green sun seen
through a mist on the Simplon. We have also an observation made by
Professor Prazzt Smyta (Edinburgh Astronomical Observations, vol. xiv.
Appendix, p. 29), represented in a plate of which the following description is”
given :—‘“ Two eye views of varieties of daylight, whereof the first represents a
remarkable case of the sun looking blue rather than yellow, red, or the colours
usually given to it by extra thickness of atmosphere; and the second shows
a peculiarly green sunset sky—both of them proving to be forerunners of the
sirocco’s stifling wind and its concluding warm rain.” The spectrum of the
cloud light on this occasion shows a strong similarity to the spectrum observed
here, only the absorption in the red end is less, and in the blue end rather
more strongly marked. For my own part, I do not believe that a more or less
green sunset is so rare an occurrence as has been supposed, and since my
attention has been called to it, I have seen it several times and very markedly
on the 13th and 14th of May, when it was perhaps the earliest symptom of the
coming monsoon.
The abundance of water vapour present is also shown by the very heavy
monsoon which followed the appearance under discussion, when in Madras

A GREEN SUN AND ASSOCIATED PHENOMENA. 403

itself the rainfall was 19°17 inches, and in Masulipatam 15°71 inches above
the average. We see then that aqueous vapour was present in large quantities,
and that the presence of aqueous vapour is sufficient to account for the
phenomena, so that it seems unscientific to call in the aid of any other agents,
such as dust or sulphurous vapours, unless their actual presence can be proved,
which, I submit, has not yet been done. Assuming then that the cause was
aqueous vapour, the farther question arises, Why the phenomena should not be

' more frequently observed? This question cannot perhaps be fully answered at
_ present, but some light can, I think, be thrown upon it by the following con-
_ siderations:—In most cases, where we have an excessive amount of vapour

present in the atmosphere, part at least is condensed into clouds, and these

_ even when light, form a screen near the horizon which shuts out the sun at the
| time when the greenness would be observed. In the present case, on the other
_ hand, the vapour was almost entirely uncondensed, only a very light haze being
_ observed, and a few clouds low down on the horizon. The vapour was also at
_ a greater height than usual, and was probably diffused through a great depth of
| the air; while in India, at least, the meteorological conditions near the surface
_ of the ground prevented the formation of low clouds.

An interesting question arises as to whether electrical action may not have

had something to do with this distribution of moisture. The observations
_ already described, both those made with the electrometer and those made on
| lightning, show that the air was very highly charged with electricity. I am
' not prepared to lay much stress on the electrometer observations, however,

until I have had an opportunity of investigating more fully the ordinary state

_ of the atmosphere during the prevalence of west and south-west winds. The
| circumstance that the potential of the air was negative only when the wind was
| westerly, and even then only when the surface of the ground was hot, seems
| to indicate that the chief cause of the peculiar electrical state lay in the lower
| parts of the atmosphere. At the same time, it seems well to record these
electrical observations along with the other meteorological ones. Even
neglecting the electrometer observations, we have still various indications of
| an abnormal electrical state, for all the clouds that were formed about this time

were evidently highly electrified, and the abundant displays of sheet lightning—
which I ventured to say were not due to the reflection from distant storms—
accompanied by occasional flashes of forked lightning, were indications of the
great storm which burst on October 2nd, when the vapour had at length con-

| densed into clouds. In this connection, it ought to be noticed that the storm

of October 2nd was one in which the discharges took place almost entirely
between cloud and cloud. Ido not know that there is sufficient experimental
data to show whether or not highly electrified vapour would be less ready to
condense into clouds than non-electrified vapour, but it seems probable that

404 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

this would be the case. The experiments made by Dr OLIvEer Lopce (Nature,
vol. xxix. p. 612) seem quite insufficient to found any theory upon, inasmuch
as they deal simply with the effect produced on a mass of very fine particles of
water in an enclosed space by a highly electrified point.

The presence of abundance of vapour seems to be explained, naturally
enough, by the setting in of the moist monsoon currents in the upper parts of
the atmosphere; or at least by the conflict between the north-east and south-
west monsoons, which was apparently begun by that time.* It is by no means
impossible that the Krakatao eruption may have had some influence on the
direction of these currents, for we have proof of the immense displacement of
the air caused by the eruption in the barometric waves which were traced three
times round the earth. Further, the ascent of a heated column of air and
vapour over the volcano would tend to produce an area of low pressure round
it, and thus to set up a cyclonic influx of air from other places, and it is quite
possible that this influx is indicated in the oscillations of the barometer shown
in the accompanying diagram, the sudden cessation of the cause of inflow after
the eruptions ceased, causing a series of decreasing waves—direct and reflected.
The eruption may also have had something to do with the electrical state of
the air, for we know from observations made on the spot, that much electricity
was generated by the eruption, and Professor PALMIERI’s observations show
that the material ejected from Vesuvius is negatively electrified. A hypothesis
connecting the phenomena with the eruption at Krakatao in this way would not
be liable to the same difficulties regarding the velocity of propagation as one
which involves the actual transport of dust, for the delay at one place relatively
to another might be caused by the absence of a sufficient quantity of vapour.
The theory which I have suggested would also account naturally for the second
appearance of the green sun, the interval being due to one of the familiar lulls
in the contest between the two monsoons. On the dust theory, it seems very
difficult to account for this second appearance.

At one time I was inclined to think that the theory which made the
phenomena depend on cosmic dust was an extremely probable one, and that
the dust formed nuclei, about which the vapour condensed in the manner
shown by Mr Airxen. Various observations, however, seem to negative this.
It seems hardly possible that vapour was condensed in any quantity, else the
absorption of solar heat would have been considerable. Observations made
with the black bulb thermometer im vacuum are not very satisfactory, yet when
carefully made with the same instrument under similar circumstances, they
have some value. The Madras observations show that the readings were
above the average for the month, and that on the 28rd, one of the days of

* See Mr Levine's remarks, ante, p. 396, and the extract from the log of the “ Nizam,” p. 399. ;

A GREEN SUN AND ASSOCIATED PHENOMENA. 405

maximum greenness, 160°°7 was reached. ‘The mean for the month was 147°°3,
against an average of 136°°5. The presence of either dust or condensed
moisture in quantities sufficient to have produced the observed effect would, it
seems certain, have intercepted the solar heat to a great extent, but vapour,
on the other hand, probably would not. Admittedly the question of the
absorption of radiant heat by aqueous vapour is still a moot one, but the recent
experiments made by Professor M‘Grecor, by Professor Tarr’s new method,
show conclusively that the absorption cannot be nearly so great as many people
have supposed; and we find such an experienced meteorologist as Mr BLANForRD
stating, as the most probable conclusion from meteorological observations,
that “both air and vapour, as compared with other gaseous bodies, are
moderately good absorbers of heat, and in nearly equal degree.”* The
minimum temperatures, which are perhaps a safer guide to the transparency
of the air, yield results similar to those of the black bulb thermometer ; and
observations of double stars showed that the atmosphere was clearer and
steadier than usual. We must therefore, I think, give up any theory involving
the presence of sufficient dust to render the sun green. Whether or not the
following sunset glows were due to the presence of dust I cannot discuss here,
but I would point out that an amount of dust sufficient to produce these effects
would probably not materially affect the transparency of the atmosphere.

* Indian Meteorologist's Vade Mecum, part ii. p. 24.

| APPENDIX.

VOL. XXXII. PART It. oT

406

Date. Hour.
Sept. 3 1.10 P.
5 2.45
Sept. 4 10.5 a
| 10.10
” to
10.17
i Noon
i 1.10 Pp
i 3.0
as 6.30
Sept. 5 5.50 a
bs 9.0
x 10.0
”
53 11.5
i 15 P.
s Du)
‘ 2.10
os 3.15
5.0
‘ 6.20
e 10.10
Sept. 6 6.0 a.
bs 8.0
8 9.0
Fp 9.45 a.
10.5
3 10.10
: 1.10 P
( 9.5
ts to
{210
3 2.20
+ 4.20
¥ | 6.15

Lt. S.W.
Do.

Fr. Sx E.

it! We As:

Very light.

10
31

PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

APPENDIX A.
Electrometer.
Remarks.
Positive.| Neg.
28
ad | to
VG
6 sie
136
to On roof.
ih
a Ground—wind in gusts with much dust flying; |
495 bright sun,
ila e When wind light, R. B, 2.
: 67 Very fine and bright.
ue 11 Ground.
35 re Do.
5 bas Do.
5 a Roof—clear.
on 2 Ground—bright.
~+-+ || onaee.|| oor.
tL 72 Do.
86
- to Ground—dust flying.
122
325
Me } to Wind gusty.
368
2 40 Calm.
3 20
Bee 35 Cloudy.
sve 1 Roof—wind going round to S.E.
12 Ate Ground.
10 03 Cloudy.
29 12 feet above ground—thin arts
2 Do.—starry, with light clouds.
5
Le spe |» o.—cloudy.
a Le
+ 74 Ground—cloudy.
188
to Do.—just before slight dust-cloud.
432
ec 18 Steady.
Sr 24
ie From window about 40 feet high—dust-storm, |
6< | 105 and a few drops of rain, followed by heavy]
1 06 J rain,
560 hate eeie ceased. This was followed by o one

clap of thunder. R. B. 8. i
Roof—followed almost immediately by a shower.
Steady—dry.

Date.

Sept. 7

—

:

A GREEN SUN AND ASSOCIATED PHENOMENA. - 407

APPENDIX A.—continued.

Electrometer.
Hour. Wind. i ee | Remarks.
Positive.) Neg.
6.0 a. Mod. W. | 25 ine Steady—cloudy and cool.
Very light
9.0 { ae \ a Pe. Do. da
10.0 Lt. do, 16 aie Do. do.
11.30 Do. 15 aCe Do. do.
1.35 Bb Trace. ;
2.45 S.W. 15 Bs
6 A. Lt. W. 14 wis Roof—steady.
9.0 Do. i
aie ey ic aia | Some clouds, but sun pretty bright. R. B. 5 to 6.
2.0 P. 5 $n |)
4,20 nee 146 ae Cloudy, apparent thunder cloud overhead.
6.15 S. fresh. 38 ies Rain at 7 P.M.
6.35 a. Lt. W. 32 dae Cool and cloudy.
8.10 Fresh. 16 Ste Steady.
9,0 Do. 14 fed R. B. 3 to 4.
0.0 Do. 16 ashe Thin clouds.
For the rest of the day maximum 16, minimum 13.
5.40 a. | Lt. W. 16 sh Cloudy.
9.0 Do. 8 a3
10.0 Very light.| ... 21 Very little dust.
46
11.30 Light. si f to Do.
10
2.10 P, Calm. Grace}; «6. Cloudy.
5.10 Do. as 31 Do.
a he 7 Ey \ hin clouds—very close and still. ;
6.104. | Light W. | 27 ag Steady.
9.0 Ss 8 Cee Roof.
9.10 ads 2 oF Ground.
9.30 one No | trace.
10.15 5
to oF ae to Cloudy, but hot.
10.22 23
1020 | | a | | p Bight clouds
12.354. | Lt. W.S.W.| 10 He Light haze.
5.30 Lt. W. 18 cbs
6.30 ag 23 ap R. B. 4 to 5.

10.15
to
10.45
3.507, | Lt SE. | 42
5.30 Lt. E. 56

143 i
as to Ground—thin haze, and plenty of dust.
4 Roof.

at 1.5 Pp.
Do. Max. 60 at 5.45 a.m; min. 11 at 9.40 a.
Do. Max. 60 at6p.m.; min. 47 at1.10P. No
{ observations in forenoon.
Do. Max. 74 at 11.50 a.m.; min, 37 at 9 a.m.
\ Cloudy.

| Positive all day. Max. 66 at 2.30 p.; min. 8

408 PROFESSOR C. MICHIE SMITH ON OBSERVATIONS ON

APPENDIX A.—continued.

Electrometer.
Date. Hour. Wind. ae Se Remarks.
Positive.| Neg.
Positive all day. Max. 78 at 310P.mM.; min.
Pep 1 33 { trace at 11 a.m, Bright. |
Sept. 20 6 A. Light W. | 63 38
+ 9.0 sis 18 a Light clouds. R. B. 5.
5 9.55 at se 34 Cloudy.
53 11.55 Very Lt. E) 44 ae Clear.
Sept. 21 6 A. Lt. W'ly. 29 sar Do.
35 OA: see Trace.
10.10 i
7 to Very Lt. W. 9to} 19
10.15
a 11.0 Ane No | trace. Hazy.
19
A 11.50 Light E. {i
34
+» 4.30 P. ots 49
Sept. 22 8 a. Light W. No | trace.
ae 9.0 Ss ... | Trace. | Cloudy.
5 10.0 ae pak 4
5 11.0 ses No | trace. Ground.
# wh siete 6 Vi Roof.
“y ao at 4 Sus At 12 feet above ground.
Positive all day, Max. 11 at 3.30 P., min. 0 at}
Sept. 23 . 50 oe 3: { 10.20 a.
Sept. 24 5.45 Light W. | 35 oe Fine—slight mist.
a 9.0 .. 15 ce Hazy.
os 9.50 axe oak 25 Ground—bright.
” aes bor 8 Roof.

J 11.30 | LightE&. | 25 | ... | Lightning all night to S. and SE.
Sept. 25}. 7.15 Light W. | 18 ie Cloudy and hazy.
bs 9 Very Lt. 8 5a Hazy.

33
oF 9.55 Light W. ob to Cloudy.
27
a 11.45 Light E. to ar Sun very hot.

Slightly negative between 9 and 10, but positive
Sept. 26 at all other times. Thereafter no negative read-

; o is ih a ings were got except in storms ; but the read-
ings have been low, except in stormy weather.

A GREEN SUN AND ASSOCIATED PHENOMENA. 409

APPENDIX B.

Rainfall for October, Difference fom
November, and 3
Station. December. Average.

Actual. | Average. | Above. Below.
Vizagapatam, : : : 19°40 20°13 ae 0:73
Masulipatam, ; , ; 28°12 12°41 ere das
Bellary, . : : : : 5°47 17:37 moe 11:90
Madras, . : : 48°21 29:04 Ilia ace
Salem, : ; : ; 19°48 10°17 9°31
Wellington, : : : : 25°11 18-98 6:13
Coimbatore, ’ : ; : 15°73 9:92 581 Bs
Trichinopoly, é : ! : 14°25 16:07 a 1:82
Negapatam, ‘ ; ; 32°48 31:27 1:21
Madura, . 5 : : p 22°57 16:01 6°56
Cochin, . 5 : 22°44 17:94 4:50 ao
Mangalore, : : : 8-47 10°50 50 2°03
Mercara, . : ‘ : ‘ V2 10°58 6°63
Bangalore, : : : : 17°43 8°58 8°85 A
Colombo, . : : ‘ : 29°82 31:43 aS 1-61
Average, . : : : F 21°75 17°36 4°39

APPENDIX C.

Abstract of the Mean Meteorological Condition of Madras in September 1883, compared with the
Average of past Years.

Mean Value of 1883. Difference from Average.

Reduced atmospheric pressure, . 29°791 0-017 above. 29:°774
Temperature of air, : : : 84°7 16 do. 83:1

Do. of evaporation, : : 76°6 0-6 do. 76:0
Percentage of humidity, : 68 | 5 below. 73
Greatest solar heat in vacuo, : : 147°3 10:8 above. 136°5
Maximum in shade, é : : 95°9 3°8 do. 92-1
Minimum in shade, : : : TS) 0-6 clo. 103

Do. on grass, ‘ : : 76:1 i) do: 74:4
Rainfall in inches on six days, . : 0°56 4:24 below. 4°80

Do. since January Ist on fifty-two days, 12°54 (AE) Glo 19°73
General direction of wind, : ; S. by W. | 2 points South. | S.W. by S.
Daily velocity in miles, . ? 5 190 30 above. i. 160
Percentage of clear sky, . : F 40 4 do. 36

N. R. POGSON, Government Astronomer.

MOL, XXXII, PART IT, 3 U

Vol. XXXII. Pl. XLVIL

September 1883.
18

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Roy. Soc. Edin*

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GREEN

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XXIII.—An Example of the Method of Deducing a Surface from a Plane Figure.
By L. Cremona, LL.D. Edin., Hon. F.R.SS. Lond. and Edin., Professor of
Mathematics in the University of Rome.

(Read 21st April 1884.)

Let there be given, in a plane z, six (fundamental) points 1, 2, 3, 4, 5, 6, of
which neither any three lie in a right line, nor all in a conic ; and consider the
six conics [1] = 23456, [2] = 13456, [3] = 12456, [4] = 12356, [5] = 12346,
[6] = 12345, and the fifteen right lines 12, 18,.., 16, 28,.., 56.

There is a pencil of cubics 1°23456 (curves of the third order, having a
node at 1 and passing through the other fundamental points) ; their tangents at
the common node form an involution, viz., they are harmonically conjugate
with regard to two fixed rays. Five pairs of conjugate rays of this involution
are already known; for instance, the line 12 and the conic [2] have conjugate
| directions at the point 1, for, they make up a cubic 1723456.
| Each other fundamental point is the centre of a like involution. And also
on each conic [1], [2],..., and each line 12, 13,... points are coupled har-
monically with regard to two fixed points. The involution on the conic /1] is
cut by the pencil of rays through 1; for instance, the point 2 is conjugate to
the second intersection of [1] with 12, &c. The involution on the line 12 is
cut by the pencil of conics 3456; for instance, the points 12.34, 12.56 are
conjugate, as 34 and 56 make up a conic through 3456; and the point 1 is con-
jugate to the second meeting of 12 with the conic [2]; &c.

The Jacobian of a linear twofold system (réseau) of cubics 123456 is a
sextic K = (123456) having six nodes at the fundamental points. Since any
réseau of cubics 123456 contains 1° a cubic 4== 1723456; 2° a cubic breaking
up into a ray 7 through 1 and the conic [1]; 3° a cubic made up by the line 12
and a conic ¢ through 3456, &c.; we see immediately that the (sextic K)
Jacobian of the réseau 1° has the same tangents as the cubic /£ at the common
node 1; 2° and 3° passes through the intersections of 7 with [1], and the inter-
sections of c with 12, &c.

The Jacobians K form a linear threefold system of sextics (123456)’

MCN EN KY WK = 0,
| therefore we have the following theorem :
If six points 1, 2, 3, 4, 5, 6 are given in a plane 7z, as said above, we may
VOL. XXXII. PART Il. 3X

412 DR L. CREMONA ON AN EXAMPLE OF THE

construct a threefold linear system of sextics K = (123456), whose tangents
at each of the six common nodes are coupled in involution, and which cut, also
in involution, each of the six conics [1], [2],..and of the fifteen right lines
12,18,... Any sextic of this system is the Jacobian of a réseau of cubics
123456.

Among these o’ cubics, there are o' curves possessing a cusp (stationary
point), and the locus of the cusps is a curve 6 = (123456)‘ of the twelfth order,
which touches each conic [1], [2],... and each line 12, 13, ... in two distinct
points, and has (only) two distinct tangents at each quadruple point 1, 2,... :
those points and these tangents being the double elements of the twenty-seven
involutions mentioned above.

Let us start now from the foregoing plane diagram, without any further —
reference to its origin; and consider 7 as representative of a surface ® whose
plane sections shall have the sextics K as their images.* We see at once that
the order of ® is 12, for, two sextics K meet in (6.6—6.4=) 12 more points.
Thus we get a (1, 1) correspondence between the points of 7 and those of ®;
any point M on zw being common to ow?’ sextics K, it is the image of a point M’
on ®, in which the co? corresponding planes meet. But if M lies on one of the
six conics [1], [2], .. or of the fifteen lines 12, 18, .. or infinitely near to one of
the six points 1, 2,..., then all the o? sextics K passing through M contain
also another common point M, , which is conjugate to M in one of the twenty-
seven involutions. Therefore, in such case, M’ isa double point on ®: this
surface has an infinite range of double points, whose locus, as easy to see, is
constituted by twenty-seven right lines, having as their images on z the six
fundamental points and the six conics and fifteen lines connecting them.

If M falls at the intersection of 12, 34 viz., if it belongs to two involutions,
it will have two conjugate points M, = (12) (56), M, = (84) (56); and the
three points M M, M, will be common to ow’ sextics K corresponding to
planes, whose point of intersection M’ (where the nodal lines of ® meet, which
answer to 12, 34, 56) is consequently a treble point on ®. Thus, cur surface
possesses forty-five treble points, in each of which three nodal lines meet.

Let a cubic 123456 have a cusp M; then, every sextic (123456)’, which is
the Jacobian of a réseau including that cubic, shall pass through M and touch
there the tangent at the cusp. Hence the ’ sextics K through M will have
the same tangent at this point. Accordingly the corresponding point M’ will
be a double point on ® with coinciding tangent planes, viz., a cuspidal or
stationary point. Thus we see that ® has a cuspidal curve, whose image on 7
is the locus of cusps of cubics 123456, viz., the curve © = (123456)* of the
twelfth order. The order of the cuspidal curve on ® is (6.12—6.2.4=) 24. ©

* See Caroraui’s paper in Collectanea Math. in memoriam D. Chelini.

METHOD OF DEDUCING A SURFACE FROM A PLANE FIGURE. 413

The class of ®, that is to say, the number of the tangent planes drawn
through two arbitrary points in space, is equal to that of the intersections of
the Jacobians of two linear twofold systems of sextics K. The Jacobian of
such a system is of the order 3(6—1)=15, and passes 3.2—1=5 times through
each fundamental point ; but the curve © is clearly included in the Jacobian,
therefore, this latter will break up into a fixed curve, 9, and a variable one,
being of the order 15-—12=3, and possessing the multiplicity 5-4=1 at the
fundamental points. So the residual Jacobian is a cubic curve 123456. Two
such curves meet in 9—6=3 more points ; hence the class of ® is 3.

The surface ®, being of the twelfth order and third class, and having
twenty-seven nodal right lines and a cuspidal curve of the twenty-fourth degree,
is the reciprocal of the general cubic surface. It was very easy to foresee this
conclusion, in accordance with the (1, 1) correspondence between any surface
and its reciprocal. But I wished to give an instance of the method of deducing

-a (unicursal) surface from a plane figure assumed as its representative.

3
;

Art. XX.—On the Philosophy of Language. By Emeritus Professor Buackig, E.R.S.E,

XXI.—The Old Red Sandstone Volcanic Rocks of Shetland. By B. N. Peaon, Esq., ni
F.R.S.E., and Jonn Horne, Esq., F.R.S.E. Read March 17, 1884. (Plates

XXII. — Observations on a Green Sun and Associated Phenomena. By Professor C. Micute
Smira, F.R.S.E. Read July 7, 1884. d

XXIUL—An Example of the Method of Deducing a Surface from a Plane Figure.
‘Professor L, Cremona, LL.D. Edin., Hon. F.R.SS. Lond. and Edin., .

The TRANSACTIONS of the Royau Sociery or EDINBURGH will in future

Vol.

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Read April 7, 1884, .

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VOL. XXXII. PART IIL—FOR THE SESSION 1884-86.

el

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CONTENTS.

SEIN OE! MTT
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PAGE

XXIV.—Micrometrical Measures of Gaseous Spectra under High Dispersion. By C.
Prazzt Suytu, F.R.S.E., and Astronomer-Royal for Scotland. Read June

16, 1884, (Plates XLVIII.-LXXVIIZ.), : F : . 415

XXV.—On Bipartite Functions. By Tuomas Muir, LL.D, Read February 16,1885, 461

—The 364 Unifilar Knots of Ten Crossings, Enumerated and Described. By
__ Rev. Tuomas P. Kingman, M.A., F.R.S. Read July 20,1885, . . 483

Knots. Part Ill. By Professor Tarr. Read June 1 and July 20, 1885,

(Plates LKXIX.-LX XXL), 493

A New Graphic Analysis of the Kinematics of Mechanisms. By Professor
Rosert H. Smits, Mason College, Birmingham. Read January 19, 1885.
(Plate LXXXIL), . : 4 ; : : P we BOT

-The Visual, Grating and Glass-lens, Solar Spectrum (in 1884). By C. Prazzi
_ Smyru, F.R.S.E., and Astronomer-Royal for Scotland. Read June 1, 1885.
(Plates LXXXITI.-CXLIIL.), ? 3 : ‘ 3 og

— Observations on the Recent Calcareous Formations of the Solomon Group made

during 1882-84. By H. B. Guppy, M.B., F.G.S., Surgeon H.M.S. “ Lark.”
Communicated by Jonny Murray, Esq. Read June 15, 1885. (Plates
CXLIV., CXLV.), . an 2 : ; , : . 545

— Observations on Atmospheric Hlectricity. By Professor C. Micuin Smiru.
Read June 1, 1885. (PlateCXLVIL), . : . 583

-Note on Ectocarpus. By Joun Ratrray, M.A., B.Sc., Scottish Marine Station,
Granton, Edinburgh, . Communicated by Jonn Murray, Esq., Ph.D. Read
February 2, 1885. (Plates CXLVII., CXLVIIL), i ; REY

— Anatomy and Physiology of Patella vulgata, Part I, Anatomy. By R. J.
Harvey Gipson, M.A. Communicated by Professor Hurpman, D.Sc.
Read January 5 and July 20, 1885. (Plates CXLIX.-CLIIL), . cy OO

XX! 'V.—Detached Theorems on Circulants. By Tuomas Muir, LL.D. Read May 4,
rt, 1885, : : : : rie : , ; . > 639

.—On the Hessian. By Professor Curystat, Redd May 18, 1885, : . 645 -

ee

XXIV.—Micrometrical Measures of Gaseous Spectra under High Dispersion.

APPENDICES.

~I for) Ord Go bo

By C. Prazzt Smytu, F.R.S.E., and Astronomer-Royal for Scotland.
(Plates XLVIII. to LX XVIII.)

(Read 16th June 1884.)

CONTENTS. PAGE

INTRODUCTION, : 416
Part I.—The first Gas to 8 astednneay ia ade what Gpanttons? : : 4 ; + PAIS
The Candle-Spectrum, or CH gas in Blow-pipe Flame, : : : ; . 419

The Spectrum plates employed here, .« : : é ; : . 420

Principles of Spectrum representation, ; : ; : ; : pel

Maps of the CH Spectrum in Flame, . : : : ; : . 422

Advantages of Electric-lighted Gas- Vacuuin Tubes, ‘ ; E ‘ : . 424

A London objection to my testimony therein, : : ¢ ; ; . 425

Part IJ.—Citron and Green bands of CH in Vacuum Tubes, ‘ : ‘ : eA 7,
Orange band of CH and effects of Pressure, . : : : ; : . 428

Blue and Violet bands of CH, . ; : ‘ : ; : : J 86431

Marsh Violet band of CH, : ‘ ; : : s = 432

Chemical Interpretation of the CH Spectrom, : ‘ : - ‘ . 432

Part II[].—The CO Spectrum, : ? : : : ‘ ; : : . 435
Statical differences, ! 2 F : ; ‘ : : : . 485

Green band of CO, : : d : . 5 ' : : » 4386

Its numerical explication, : : : ; ; ‘ : : . 488

Remaining bands of CO,. , : ; ‘ F : : : . 439

Part IV.—Elementary Gases, Subject 1,or H, . : : : : : : . 440
Elementary Gases, Subject 2, or O, . : : ; ; . : . 444
Elementary Gases, Subject 3,or N, . ; : ‘ ‘ ‘ : . 446

Part V.—Conceluding Noteson H,O,andN, . - : ‘ F : ‘ . 450

Appmnpix I. Professor Alexander 8. Herschel’s letter on the Green Band of CO and its
explications (eventually condensed into Plate 31), . 454
Aprrenpix II. Professor Alexander 8. Herschel’s letter, on a theoretical point in Plate 31, a) 4D
Apprmnpix ITI. Mr Charles F. Casella’s letters on the f aeae and Purification of some of
his Vacuum Tubes, . F : ‘ : ; c : . 458
Apprnpix IV. Plates 1 to 31, as follows:—
PLATES.
XLVIII. 1 ; CH in Blow-pipe Flame, Orange band thereof, and Citron band, adapted to a 40-foot

Spectrum length.
" " Citron band continued and Green band.
" " Green band continued and Blue band.
" Violet band thereof.
Sreessive methods of Incandescence tested by the D! and D? Sodium lines, on an
enlarged scale.
CH in Vacuum tubes, Citron band thereof, and Green band, adapted to a 40-foot Spec-
trum length.
" " Gren pang continued, Blue band, Violet band, and Marsh Violet
and.

VOL. XXXII. PART Ill. ai one

416 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

AprenpDIx IV. Plates—continued.

PLATES.
LV. 8 | CO in Vacuum tubes, Red band thereof, and Scarlet band, on a 40-foot Spectrum length.
LVI. 9 " " Orange band and Yellow band,
LVIL. 10 " " Yellow band and Citron band.
LVIILI. 11 " " Green band thereof and Blue band.
LIX. 12 " Indigo band and Violet band.
LX. Uys |p Bl abet Vaouum tubes, Early Red, Red to Scarlet, region ; on a 40-foot Spectrum length.
LXI. 14 " " Orange, Yellow, and Citron.
LXII. 15 " " Citron to Green.
LXIII. 16 " " Green, Glaucous, and Blue.
LXIV. 17 " " Blue, Indigo, and Violet.
LXV. 18 " " Violet continued.
LXVI. 19 | O in Vacuum tubes, Ultra-Red, Red, and Scarlet, regions on a 40-foot Spectrum length.
LXVII. 20 " " Orange and Yellow.
LXVIII. 21 " " Citron to Green.
LXIX. 22 " Glaucous to Violets
LXX. 23 | N in Veouum tubes, Ultra-Red regions thereof, adapted to a 40-foot Spectrum length.
LXXI. 24 " " Ultra Red, Red, and Scarlet.
LXXIL. 25 " " Yellow and Citron.
LXXIII. 26 " " Citron and Green.
LXXIV. 27 " " Glaucous and Blue.
LXXV. 28 " " Blue and Indigo.
LXXVI. 29 " " Violet ; all the above Plates have scales in terms of Wave-number
per British Inch.
LXXVII. 30 | Folding Index Map of all the above, and some other, gases, at both high and low tempera- ;
5 tures, and throughout the visible Spectrum, but greatly reduced in scale.
LXXVIII. 31 | Folding plate of Green CO's extra-green-CH portion ; full size of original record, viz., for
a 120-foot Spectrum length, with explication of its double arithmetical series.

AprEnDiIx V. On the numerical Wave-number Spectrum Scale adopted here.

INTRODUCTION.

After the Royal Society, Edinburgh, had been pleased in 1880 to accept and
print my paper on the general appearance of Gaseous spectra as seen on a very
small scale, but complete on that scale from one end to the other of the visible
spectrum, I was desirous to present them with some very highly Dispersed
and much magnified views of the more interesting and probably crucial por-
tions of the most important of those spectra. 4

An example of acting on that principle had already been set in the admir-
able essay of MM. Ancsrrom and THALEN, published in the Upsala Trans-
actions for 1875, For there, both in the Plates and letterpress, the final
portions entitled “Mesures Micométriques” are very largely magnified
representations of certain small parts of what went before. _

But just as occurred in the earlier division of that great work, so also
this later portion of it, there appeared to me to be too few gases, and too few
portions of their spectra treated of, to supply a sufficiently comprehensive basis
for this branch of science.

GASEOUS SPECTRA UNDER HIGH DISPERSION. 417

or definition to bring out many of the exquisite and close-set details which
spectroscopy is beginning to demand in the present day for any and every gas
that is now observed. And this, too, although those Upsala results did most
honourably transcend all others at the time they were published, and for
many years afterwards, indeed almost, if not quite, up to the present time.

Hence I have felt it incumbent on myself, before venturing to trouble this
Society with new versions of any old phenomena, not only to increase the range
of subjects treated of, but to improve the instrumental apparatus employed on
all of them, until it was capable of some very remarkable performances in the
way at least of differential mensurations in the field of view or near it.

Of such differences, however, only. For temperature changes in the fluid
prisms, although greatly reduced by a variety of contrivances, were yet continu-
ally at work, altering to so sensible an extent the value of the Dispersion scale
from its distant zero, as to prevent the absolute places given by this very
lately put-together apparatus being anything better than extremely rough when
over long ranges.”

But condoning that one weakness, for the sake of other advantages, the
strength of the instrument for micrometrical detection and record of small
differences may be indicated thus—

(A) The one-prism spectroscope employed in my collective and rudimentary
paper of 1880, possessed a little more than 3° of Dispersion from A to H, with
a magnifying power on the telescope of 10 diameters; virtually broadening
those 3° to 30°.

(B) The apparatus employed by MM. Ancstrom and Tuaten for their
Mesures Micrométriques, as nearly as I can gather in a general way, must have
had at the utmost a Dispersion A to H of 24°, with a magnifying power of
nearly the same number of diameters; or equivalent virtually to a spectrum
600° long.

(C) While my present arrangement has 60° of Dispersion A to H, with
magnifying powers on the telescope of inspection rising from 12 to 36, and a
further mechanical magnifying in the recording apparatus of 5 times;
equivalent to 9000 of the same degrees altogether; or to the action of 1800
simple prisms of 60° refracting angle in white flint-glass, viewed with the
naked eye.+

* By observations on Green CO on November 3, 4, and 5,it was ascertained that, after every-
thing had been done at the place that could well be done to secure constancy of temperature in the
bisulphide of carbon prisms employed, a slow fall of 1° Fahr. increased the Dispersive power of the
collective train of prisms by 0°727 of a Revolution of the very coarse screw motion ; or by close upon
10 inches on the surface of the recording barrel. The interval of time therefore between any two
Mutually dependent observations was, after that, made as short as possible.

+ The diameter of the objectives was the same as in my.earlier apparatus, viz., 2°25 inches, and
the refracting faces of the prisms presented nearly the same breadth to the entering ray.

418 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

To which qualities were added, when assisted however by certain more
intense illuminations, a transparency nearly as great, and a definition in certain
parts of the spectrum considerably better, than I have seen in almost any
smaller instrument.

For this latter excellence I have chiefly to thank Mr Apam Hui1cer, and to
laud the extreme skill and perfection wherewith he constructed both the glass
cores of the bisulphide prisms, and their all-important anti-prisms out of
admirably hard, white, and uniform crown glass. The Micrometrical recording
apparatus was exquisitely constructed by Messrs T. Cooke & Sons of York,
to whom I am therefore much obliged; while I am further quite unspeakably
indebted to the progress of Chemical Science, which has, in recent years
entirely freed bisulphide of carbon from the horrors of its ancient smell, and
has given us a fluid perfectly colourless, nearly inodorous, exceedingly trans-
parent, and endued with less refraction but more concomitant Dispersion, than
anything else under the Sun. ta

In discussing therefore the results obtained with all these advantages, I
shall not only refer to MM. Anesrrom and THALEN’s now nine year old, yet
still most excellent, essay, but shall consider it a duty to seek out later and
more advanced works, if they exist, elsewhere. Paying particular attention to
the recent Reports of the British Association’s very powerfully constituted
Committee * for reporting on our present knowledge of Spectrum Analysis in
1880, 1881, 1882, and 1883.

For their admirable digests of all that has gone before, and all that has
come up to their own time, in the now voluminous bibliography of the
spectrum, enables every one to locate the place, and assign the value of any
new observation both with high certainty and the least loss of time.

4

PART I.

THE First GAS TO BE EXAMINED, AND UNDER WHAT CONDITIONS.

As my object has been to a large extent to pass over superficial variations,
and arrive, if possible, at the great constants of Nature in this department,—

* The Members of the Committee are given thus—

Professor Drwar. Professor A. K. Huntineton.

Dr WiiAMson. Professor Emerson REYNOLDS.

Dr Marssaatyt Warts. Professor Reinoup.

Capt. W. pp W. Asney, R.E. Professor Livni.

Mr Sroney. Lord Ray.eieu.

Professor HartLey. Dr Scuuster, and

Professor M‘Lrop. Mr W. CHanvier Roserts, Secretary.

Professor Carny Fosrmr. ,

GASEOUS SPECTRA UNDER HIGH DISPERSION. 419

it would seem that I ought to begin with the simple, elementary gases; and
afterwards touch on their compounds if desired.

But the practical methods of inductive inquiry into Nature, cblige me to
proceed in exactly the opposite manner, and begin, as did also the great Upsala
leaders, with the manufactured compound gas most immediately at hand in
any and every situation in life, viz., illuminating gas, whether of coal, oil, wax,
or tallow.

There may be, as we shall see presently, some difficulty in deciding on the
chemical interpretation to be put on the spectrum thence obtained, but there
is none in procuring a view of it; for whether we observe the blue flame of a
blow-pipe of coal-gas and air, or the blue base of an upright flame of either
those or any other of the ordinary illuminants of night employed by man,
| burning in the open air,—there appears to be always the same identical
| spectrum present, differing in no one case from another, except in ‘degree of
brilliancy.

Were we to burn the illuminant in a current of pure oxygen, something
additional might be seen. But I have purposely refrained from doing that, and
| confined myself, in this part of the inquiry, to the grand aerial constant for all
| men, compound though it be, of the earth’s atmosphere, for the sole elementary
aid to combustion, as a mode of obtaining incandescent temperature.

To make the effects of that, however, more visible than usual, I have em-
| ployed a blow-pipe nearly a foot long; with coal-gas in quantity from the
| service pipes of the house, but urged in intensity by air from a bag under
pressure equivalent to 6 or 8 inches of water: and have further always
| placed the flame thence procured “end-on” to the spectroscope’s slit, in the
| manner described to, and approved by, the Royal Scottish Society of Arts
_ several years ago. Thence results what the Brittish Association calls,

THE CANDLE-SPECTRUM, IN AIR,

or, as named here, for reasons presently to appear, CH, 7.e., CARBO-HYDROGEN,
IN Biow-Pire FLAME.

Having been introduced to this Society nearly thirty years ago, by our
respected Fellow, Professor Swan, this particular spectrum will doubtless be
well known to every one present, as offering a charmingly simple arrangement
of five bands, most aptly to be compared to the human hand. For the first of
| them, orange coloured, and therefore in the orange region of the spectrum, is
comparatively thin and weak, say like the little finger. The second, citron
coloured, much stronger like the next finger. The third in the green, the
| brightest and strongest of the whole, like the middle finger. The fourth, in
| the blue, intermediate for strength between the first and second, like the index

420 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

finger; while the fifth, in the violet, is not of the build of any of the other
bands; you may say not a finger at all, but shorter, broader, sturdier, like
the thumb.
Viewed in any ordinary single-prism spectroscope, each of the first four
of these bands begins on the red side with a strong line, followed by two,
three or more similar lines, but in decreasing brightness and lessening distance,
interspersed with haze; while the fifth band seems to be composed of nothing
but haze. . ;
This luminous hazy mist has, however, been occasionally seen by some
individuals with powerful spectroscopes to be more or less resolvable into
faint and exceedingly close lines or linelets. And now, with my new ~
spectroscope, I have not only seen it all so resolved, but have been able to
measure almost every linelet by micrometer, until at last they became too
faint to be distinguished in any manner whatever.
The record thus procured, proving so neatly that there is no waste,
neglected, unordered or accidental material in the spectrum of this cheapest of
all the gases, was obtained on the instrument in so very magnified a condition,
that the whole visible spectrum, or from red to violet on the same scale, would —
extend to 120 feet in length.
But this being supposed a rather longer scale than the world is as yet quite -
ready for, though demanding far more for certain parts of the Solar Spectrum,
the original record has been reduced on subsequent working sheets to a 40—
foot spectrum length. And as only the portions with very visible lines and
linelets for the five bands of CH in air, are given,—this particular subject
will yet be found in larger and fuller representation than it has probably ever
enjoyed before, though packed away in four only of our plates. -

THE SPECTRUM PLATES EMPLOYED HERE, THEIR METHODS AND SYMBOLISM.

For the original observations and records on both the long 120 foot scale,
and the first reduction to the forty-foot, I am answerable myself. But the
drawing out of the final and finished plates, thirty-one in number for the whole
paper, and all save three on the same exact 40 foot Wave-number per British
inch scale, has been confided to Mr Tuomas Hearn, First Assistant in the
Observatory ; because his handling of the pen and pencil is finer than mine;
and, under photo-lithographic treatment will give something like the perfection
of copper-plate engraving, without its superior expense.

The said plates are intended moreover to serve more than the usual purpose
of such data. For though it is customary, and was actually done by Messrs
Ancstrom and THALEN in their classical case, to give both a printed list of the
numbers representing their micrometrical measures, and also an engraved, and

GASEOUS SPECTRA UNDER HIGH DISPERSION. 421

most beautifully engraved, map, or picture of the same—yet I have invariably
found a mere list of printed numerical spectrum places, by whomsoever issued,
to be but very little instructive,—without spending a lamentable amount of
time over its interpretation, application and meaning on every occasion of
using it; while it is also not a little expensive to print. Hence I have tried
on this occasion to save the cost of figure printing, by throwing the whole
burden of what is needed for final results, on the Plates alone.

Spectroscopic plates of some kind, on account of peculiar virtues of their
own for such subjects, must be introduced in some shape, or to some degree.
The following characteristic sentence occurs in a British Association Report
for 1883, p. 123 :—“ Three such spectra have been photographed, but without
the aid of maps their peculiarities are not capable of description.” Wherefore
now, by keeping our plates sufficiently large, and with very clear and distinct
scales, we may hope that they will not only preserve their own peculiar attri-
bute of showing at a single glance the groupings and general bearings of
multitudes of lines far better than any other known method,—but they will
allow, on close examination and longer inquiry, the numerical places of any
particular lines to be read off to nearly as minute a degree of exactitude, as
the original observations were capable of giving.

This good quality would have been absolutely so with the 120 foot records ;
and if not quite so with the 40 foot size, that is why I specially request that
Mr Hearn’s drawings shall not be reduced any further, as no smaller scale can
pretend either to do justice to the originals, see especially Plates LX XII.
and LX XIII., or impart confidence to those who may use them. To which
apology I have only now to add, that the following principles of representation
have been strictly followed throughout all the plates of this series.

PRINCIPLES OF SPECTRUM REPRESENTATION.

Rule 1. The representation is negative, in so far as it shows light by black ;
and darkness by white.

Rule 2. A vertical black line, whether thick or thin, tall or short, on the
plate, represents, and is devoted to representing, nothing else than a true
spectral line of light, seen and measured as such in the spectroscope, and is
considered as precious a result of observation or discovery to the spectroscopist,
as a real star is to the Astronomer. |

Rule 3. Different degrees of brightness in the real lines of light in these
gaseous spectra, where all lines are necessarily of an equal height,—are
represented in the drawings, approawimately by different thicknesses of the
black lines employed there; and more exactly, by adding thereto the further
method of different heights or depths of the lines so drawn.

422 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

Rule 4. When lines of light in the spectrum are so faint or ill-defined that —
they no longer give the appearance of solid or liquid light, and are no longer
sharp and smooth-edged like knife blades, or stretched silver wires, but look
more like faint, uncertain, granular, worsted threads,—the lines representing
them on the plates are not drawn in full ink or with parallel sides, but of a
conical shape, or in dots, or in wavy lines, and in extreme cases with
cross lines. . ;

Rule 5. Faint broad bands in the spectrum, and its occasional portions of
continuous spectrum light, are never indicated in these drawings by any kind or
arrangement or succession of vertical lines, but by either horizontal, or oblique
lines; and these may be crossed over and over again to produce the required
degree of intensity in any case. For the lines of such shadings can evidently
be never confounded with true spectral lines; which, being images of the slit
of the spectroscope, must all be vertical and parallel, when the spectrum
range is horizontal.

Rule 6. Shading by either inclined or horizontal lines being symbolic and
abstract only; such lines may, for facility of execution, be of almost any
degree of coarseness or width apart; provided only that the amount of ink
contained in them shall, if symbolically supposed to be smeared up and down
within the upper and lower limits of the horizontal spectrum strip,—indicate
only a grey shade, not a full degree of blackness. And exceeding refinements
of such shade or faint-light surfaces in the spectrum itself, may be indicated on
the drawings by making the shading lines there cover more or less of height or —
depth in the spectrum strip, as already adopted for the easier representation of —
different degrees of brightness in the spectral lines alluded to under Rule 3.

DRAWINGS OF THE CH Spectrum IN BLOW-PIPE FLAME.

Now all the latter of these rules came into play at once with our first
subject, or the blue-grey blow-pipe flame of coal-gas and air; for there is not
light enough in it to give off any lines of real, liquid light, only haze of
different degrees of rarefaction.

Considering indeed the proverbial faintness of the blue base of flame, as
when a candle burns low and blue, it is rather surprising to find that so very
small a portion of it as enters between the almost closed jaws of the
spectroscope’s slit, can yet be distinguished as made up into upwards of 400
parcels, separated one from the other always by different and definite spectrum
place ; and sometimes also by instantly recognisable features of physiognomy
or gradated intensity. | :

Yet such is the case, for the plates now exhibited of the coal-gas and air
blow-pipe spectrum (Plates XLVIII. to LI.), show 81 separate existences in th

GASEOUS SPECTRA UNDER HIGH DISPERSION. 423

Orange band, 94 in the Citron, 97 in the Green, 107 in the Blue, and 71 in the
Violet. Their distribution in each band appearing thus—

Orange band—1st leader consists of lines 2, followed by linelets 27

2nd n is . 14

3rd A 2 o 11

| 4th Ss De ie

5th : my 4 5
6th a. iy i 62

Citron band—1st - 2 Pe aS.

2nd 4 2 - UP

3rd ‘. 2, 6 9

Ath . 2, ie 7
5th i 2; Hs 31?

Green band—1st leader, “Green giant” 2, a Al

2nd lines consists of 2, id sf

3rd 4 in ' fb

4th A We F 7

5th . 22, - 4

6th 12, : 17

Blue band—H1st eo DE 4 Zl

2nd Dy. é 14

3rd " ae ' 12

’ Ath es PAP i, 5

5th ad 22, . 55

Violet band—Preliminary band has linelets 20

Subsequent and chief band contains iheaee and
linelets of various kinds, certainly . hae |
and probably many more; each being
fainter and faimter in every successive
repetition beyond.

This is also probably the case with the linelets of the more refrangible ends
of each of the earlier bands, for they are all vanishing series to that side.
Hence to record more, or fewer of them, tells nothing new in the theory, but
speaks only to the brightness of the optical images ; and as I usually stopped,
not when a definite end was arrived at, but when the linelets had become so
‘| faint and diffuse that it did not seem worth while to go on any longer,—other
persons may succeed with better apparatus in chronicling more lines and
linelets than I have done ;—-such gatherings however being always fainter than
those now tabulated.

But even with them, the strain on the eye to measure their places micro-
| metrically was often so great, that I was not unfrequently afraid I might be
deceiving myself, and undoubtedly must have made many mistakes, particularly
in setting the pointer between the close linelets, instead of upon one or other
jof them. Yet after completing the measurement of any band, there was found
jon the whole such a decided order, or law of increasing distance from linelet to
@eyVvOL. XXXII, PART Itt. 3 Z

424 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

linelet, in proceeding from the red to the violet end, and of decreasing distance
at the same time between the leading lines, or rather pairs of lines in each
band,—as could not have arisen from mere accidental error, or blind fancy ;
and did seem to testify to a considerable portion of the interesting arrangements —
of Nature, in this branch of her handiworks, having been secured on this
occasion in linear record.

If the leading lines too in each band, notwithstanding their faintness and
haziness, have been represented by me as double, though single to all former
observers, we may find strong confirmations thereof in our next subject, viz.,

ADVANTAGES OF ELEcTRIC-LIGHTED GAS Vacuum TUBES.

These tubes are usually illumined for observation by that variety of electri-
city contained in the spark from an Induction coil, actuated by a Bichromate
Galvanic battery. Such was the kind employed here, and was capable of
giving sparks from 2 to 4 inches long in the open air: the size of the immersed
portions of the plates being 4”°2 by 46 ; and the number of cells 12, but only 6
of them having fresh exciting fluid each observing night. The coil was by Mr
Apps, said to be a6 inch spark coil if used with five quart-sized Bunsen, or
Grove, cells. It was also furnished with a quantity, as well as an intensity,
primary ; one or other to be employed alternatively ; but*after many trials with —
little or no difference on spectra, I settled down to the intensity arrangement
alone, and to carefully attending to the state of the spring brake ; its freedom
from oxidation ; or from becoming self-soldered, and being in the best state of
strain for illuminating sparks, without stopping dead.

Employing these sparks then on vacuum tubes, they may of course be
expected to show higher temperature effects than mere blow-pipe flame. But
they have other advantages over both that method of incandescence, and
induction electric sparks in the open air, whether taken direct from the
coil or with the interposition of a condenser, in the shape of “the jar dis-
charge.”

To illustrate the nature of these advantages for our particular purpose of
Micrometrical measures of precision, I submit on Plate LII. four views of the
salt lines (D! and D? of the Solar spectrum) rendered incandescent in as many
different modes, and viewed under high dispersion.

No. 1 is the effect of burning a solution of Na (chloride of Sodium) ona
small spiral of iron wire in the flame of a Bunsen burner of coal-gas and air,
the usual manner of all ordinary Spectroscopists. The effect will be seen to
be broad, dull and hazy in the extreme; there is much continuous spectrum
paling the lines, and the outer envelopes of vapour of the flame produce on
each line an inversion of the direct action; or cause a black line to run do wn

GASEOUS SPECTRA UNDER HIGH DISPERSION. 425

the middle of each big bright line,—represented here by a white line on a broad
black band, splitting it into two, but foggily and uncertainly.

This whole result is of course most unsatisfactory and untoward to sharp,
micrometric bisection.

No. 2 exhibits the spark drawn from a solution of Na forming one of the
poles, the other being a platinum wire. There is here no continuous spectrum,
there is also something sharper and more intense than before in the picture
which it gives of the D lines; but the abnormal central line down the middle
of each standard line is repeated; and the whole is in a peculiar, crackly,
continually exploding, condition, also opposed to very nice bisection.

No. 3 shows the same identical spark, but altered in quality by the intro-
duction of a half gallon Leyden jar. The change is immense, the whole field
being now filled with fervid light of the general air glow, also with certain
hazy air-bands palpitating in their heated atmosphere, and which I have not
attempted to show, while the D lines are still split through the middle and are
hazy both inside and out. Finally,

No. 4 shows the D lines in an end-on vacuum tube. The field here is
absolutely black about them; the D lines absolutely bright, sharp, compact,
steady, well defined, and everything-that a micrometrical observer could
desire.

In a second tube with the D lines still as above, there were a few faint,
low temperature, Hydrogen lines. These were just as sharp and steady as
the Na lines, but being vastly fainter were exceedingly thin; so that, over-
looking linear, in place of disc-point, figures, the whole field of view gave one
the impression of gazing upward into illimitable stellar space, where one star
differeth from another in glory, but all of them exist in the quietude of heaven,
the calm of eternal peace and distance ineffable.

A Lonpon OBJECTION TO MY TESTIMONY WHEN USING THAT METHOD.

The tube incandescence then is pre-eminently favourable for accurate micro-
metrical observations. But before I can expect to have my descriptions of
what it has revealed to me listened to elsewhere, it will be necessary to meet
Openly an accusation lately printed against me by that very same British
Association Committee whom I have already on other points alluded to most
honourably for their ability, and presumed sense of justice. Yet the following
is what appears at p. 12 of their Report for 1880, published in London, when
speaking of certain of my observations at that date in vacuum tubes :—

“ Professor Prazzi SMYTH has however not filled his own tubes, and we must
be careful not to attach too much value to the labels put on vacuum tubes by
the glass-blower who has filled them.”

426 ©. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

Of course this a delicate insinuation that I have been trusting to such
labels : if it is not also intended to indicate that he who fills his own tubes, as
the actual writer of that sentence for behoof of the Committee of fifteen had
done for himself, may take a very high place among the philosophers of the
land. While any one who falls short of that particular tubular operation by
the smallest item, no matter in what company, or under what system of
friendly or scientific co-operation with others,—instantly pitches headlong down
a social precipice, and may only bring up afterwards among glass-blowers.

Now it is perfectly true that I did not either make or fill my own tubes ;
and there has never been any secret about it; for I have from the first joyfully
proclaimed who did that for me; and did it at last so well, that I could
conscientiously recommend them elsewhere.

For as to the persons concerned, I have been very fortunate in interesting
in this matter intellectually, several gentlemen of education, ability, and
experience in both chemistry, scientific instrumentation, and business, viz.,
first, M. SALLERON, and then his successor M. DEMICcHEL in Paris; next Mr
Louis P. Casetia, and then Mr Cuarues F. Casetua in London; and finally I
believe I may add, to name one deficient to none in persevering enthusiasm to
conquer every chemical difficulty that arose in his path, though with little
leisure and less of laboratory appointments, Mr W. H. Suarp of Messrs Kemp
& Co. in this city.

With one or other of these gentlemen I have been in nearly continued
correspondence for the last six years, discussing and trying experiments for the
quality of the glass, size and shape of the tubes, materials of the electrodes,
strength of sparks, arrangement and bore of capillary, as well as the methods
of preparing the several gases, purifying them when made, removing occluded
gases from the electrodes both before and during the filling, and then finally
sealing. Sealing too not a single tube only, but a series at several stated and
pre-determined steps of pressure.

But did I even then trust to either the necessary labels of some kind put
on these tubes, or to the long descriptive letters also sent to me ?

Certainly not, after the first few days of experience.

For my plan ever since then has invariably been, on receiving a batch of
fresh tubes from any maker, to put them one by one into a testing apparatus; —
find out there what is in them by their stronger lines compared with the —
general literature of the subject, put my own labels on them, and perhaps send
i of the batch back to the maker for faults that had escaped him; and then
would begin a correspondence to try and find out where, either in the making —
of the gas, or the steps of its purification, the fault originated, and how it —
might be avoided in a new set. |

Again, even with tubes that have passed this examination, I have usually

GASEOUS SPECTRA UNDER HIGH DISPERSION. 497

reviewed a number of them before any night of final observation for the
present paper, in order to find out if any changes with time and use were
going on amongst them, and to ascertain more particularly for the service of
the great spectroscope, which tube of them all, whatever its original label, was
just then capable of showing a particular part of the spectrum of some specially
required gas, with the greatest purity and the utmost vigour.

If this is still to be held up to public reprobation by London central and
immovable scientific authority, as my “trusting to a label put on by a glass-
blower,’—and because I did not fill my own tubes,—there is nothing left for
me but to request the Royal Society, Edinburgh, to judge between us,—if I
shall yenture to set forth, before the close of this paper, how much more of the
undoubted phenomena, of at least one particular gas I have succeeded in
discovering, identifying, and micrometrically recording on an extended scale,
than have any of those London and British Association gentlemen ever been
able to observe in their tubes, although they filled them for themselves.

Resuming then, by this Society’s leave, we come next to

PART II.
CITRON, AND GREEN, Banps or CH, 1n Vacuum TUuBEs.

After preliminary experiments with Alcohol, Marsh gas, Turpentine, Coal
gas and Olefiant gas—I settled down to working chiefly the two last of these
Carbo-hydrogen vapours or gases.

Of these gases much desired, pure CH spectrum, by electric light, but
under atmospheric pressure,—MM. Anesrrom and THALEN have given the two
brightest bands, viz., the Citron and the Green, in their Mesures Micrometriques.

Those well-known bands make therein a very brilliant picture, especially
as they are engraved in ne plus ultra style of both refinement and force ;
in the positive manner too, or with the lights white, on a field of black for
darkness, and with an effect that RemBpranpT might have envied.

The Swedish scientists do also there give a considerable indication of hazy,
fluted linelets, continually getting closer, and brighter as they approach the
least refrangible side of each band. But, strange to say, they have wholly
omitted the vastly superior brilliancy of the leading /ives in each band!

These strong Jeading lines are the first exact features which a beginner in
spectroscopy makes out, to his great delight, when studying each CH Blow-
pipe band; though at first sight, and with a too broad slit, said bands had
probably appeared to him as only composed of smooth haze. And I can now
further vouch, that those CH bands’ leading lines, whether in blow-pipe or
vacuum tube, remain equally conspicuous over the linelets, in all my subsequent

428 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

magnifyings up to a size fully 12 times larger than that of the Swedish
Philosophers. These lines moreover in the vacuum tubes, are very distinctly
double, and get wider and wider in their duplicities, though they decrease
their whole distances of double from double, with every succeeding line.
There must therefore, in their omission, be an error in the work of those
otherwise unexceptionable authorities; and it is pretty certainly owing in large
part to the bad definition, or broad slit of the spectroscope there employed,
as well as the greater practical difficulties in the positive mode of representing
bright-line spectra. For the Upsala linelets are ultra hazy things, running one
into the other and making only a confused and slightly undulating surface of
luminous fog; culminating too soon, on the red-ward side, into the perfect
light, or whiteness, of white paper. Whereas in my Vacuum tubes, far beyond
the Blow-pipe’s hazy separations already alluded to, the linelets, however faint,
are thin and linear; and in some new tubes are capable of exquisite sharpness
of definition, on an almost absolutely black field of view.
‘That however is not all that has to be noted with a very high Dispersion
power ; for after further working these tubes, the linelets became double, and ~
after that even treble! Such a change however being always the beginning of
a tube failing, or going altogether wrong: and was first testified to, as will be seen
in Plate No. LIII., by the very superior optical power of a fine Grating which
I had the honour of receiving from Professor RowLanp, of Johns Hopkins
University, Baltimore, U.S. ; but corroborated afterwards only too abundantly —
by the older prismatic apparatus. Hence some advantage will be found, when
comparing my different views of any of these CH bands, to note the name of
the tube employed on the occasion, and the date of observation ; a single day, —
of hard work, often showing great progress in the work of deterioration.

ORANGE Banp or CH; anp Errects oF PRESSURE, IN VACUUM
TUBES SO-CALLED.

For testing my own views of any other than the Citron and Green bands —
just disposed of,—we must fall back on the general map of the Upsala
scientists, small though it be. But it is beautifully engraved ; in the negative
manner fortunately as to representing light by black; and professes to give
the Orange, Citron, Green, Blue and Violet bands. Shading them, however,
into striking relief by adding to others closely ruled vertical lines, which are a
mere engraver’s easy method of producing shade, and mean nothing, while they
mislead much, in spectroscopy.

Comparing it, however, first of all with my own Index Map of CH im
vacuum tubes (Plate LX X VII.)—what is the meaning of the immense force ol
the Orange band, and at the same time the dwindling down to a mere trace of

GASEOUS SPECTRA UNDER HIGH DISPERSION. 429

the Violet band in the Upsala Memoir,—so very differently to what occurs in
that grand constant, viz., the Blow-pipe flame’s spectrum of coal-gas and air.

In this last material nothing is easier on any occasion, and for any
length of time, than to get all 5 bands to show; but the Orange band is
always weak; and did therefore altogether escape some of the earlier
' observers.
| In the tubes also, by electric light, the Orange band is far weaker than
| either the Citron, or the Green; but it has another difficulty to contend against
there, of this nature,—
| When the pressure of the CH gas is small, it is so very easily decomposed
| by the electric spark, that Hydrogen low-temperature lines are set free; and
_ being nowhere stronger and more multitudinous than over the Orange region,
| they completely mask any residual traces that may remain of Orange CH, and
| much of the Citron CH, band, as well. But, as I have been finding with tubes
| specially prepared to that end, the decomposition becomes less and less with
increasing density of the filling, until at several whole inches, instead of
| hundredths of an inch as with the old tubes,—Hydrogen lines nearly disappear,
and CH bands like the blow-pipe’s bands, so far as their range extends, are
| almost the only existences visible.

To get the CH Orange band, however, quite clear of those obstructions, is
particularly difficult. Thus with coal-gas at 5 inches pressure, last year, every
_ blow-pipe band was well seen, except the unfortunate Orange one; and so it
| was also this year with a fine tube of Olefiant gas prepared by Mr CasELLa at
| 2 inches pressure. But with another tube he had prepared at the same making,
| at 4 inches pressure,—such is the superiority of Olefiant, to Coal, gas for
| this purpose,—the long desired cynosure was reached at last.. For in that
| tube’s spectrum, while not a single low-temperature H line appeared, there was
“the Orange CH band as perfect in its symmetry of lines and linelets as any-
| thing could well be imagined, and as I have never seen it written yet.

There were to be counted in it 5 leading lines very bright and distinct and
perhaps a sixth, all at successively smaller intervals in proceeding towards the
violet : while between every pair of them, and in the interval beyond of greater
refrangibility, were the linelets, in infinite thinness, sharpness, and definition ;
| at first, or towards the red side, very close set, but continually increasing their
| distances apart, and preserving their inimitable Liliputian visibility, right up to
| the very beginning of the Citron band. This being a glorious extension of the
| vanishing side of the Orange band, far beyond anything ever seen with the
blow-pipe, or even with tubes, when coal-gas is the filling medium.

Next, turning to the Citron band of CH (in the same 4 inch pressure
Olefiant gas tube) its leading lines were vividly bright; its linelets also un-
precedentedly clear, and never ceasing for a moment until, although continually

430 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

widening their distances from each other, and paling and thinning their light,
but not losing their definition, they at last came right up to the Green band.
The Green band as a matter of course began with its “‘Green-giant ” line in
magnificent cue ; then came closely packed, but well separated, sharply defined
linelets ; then the second leading line, and wider linelets, then the third leading
line and after that the long expanding series of sharp linelets, which continued
on, and on, and on, until the beginning of the distant Blue band was reached.
But shortly before that point was arrived at, a broad, faint, grey haze-cloud
was passed. I had never seen anything like it, in that spectrum place before.
What could it possibly be ?
It turned out to be Glaucous Hydrogen. Not in the shape of the sharp
and vividly bright line that it always shows in tubes at smaller pressures, but a
mere amorphous bundle of Nebular haze.
Turning back then to the Red end of the spectrum, there, in the place of
the usual Red Hydrogen line, was another broad cloud of faint haze, but of
course red in colour.
This therefore was the reason why even the Orange band of CH, with its
ultra thin and sharp linelets, was, for once, not sensibly interfered with by low-
temperature H lines. For at that grand pressure of four mercurial inches on
the Olefiant gas,—mere nascent Hydrogen could only exist, even with its
strongest lines, as a sort of faint vapour, floating like a ghost over certain 7
spectrum places ; and all low temperature H lines being vastly fainter than its —
two just mentioned high temperature lines (Red, and Glaucous)—their resolu-
tion into similarly broad clouds, depressed their intensity of light to beneath —
the minimum visibile of any eye.
I spent perhaps half an hour noting these circumstances in the testing
spectroscope which has 12° Dispersion A to H, and was planning how I would —
_ arrange the great spectroscope of 60° Dispersion, to take advantage of such an
unprecedented view of the Orange band of CH,—when I fancied I saw a
double line where lately there were only linelets; then a stronger line appeared —
between two of that band’s leading lines: then another, and another. To my
horror they began to look amazingly like low-temperature Hydrogen lines.
Turning therefore to the places of the late nebulous clouds of Red H and
Glaucous H,I actually saw them slowly gathering themselves together, and
settling down as lines into their ancient places. While in half an hour more,
ted H and Glaucous H were narrow and vivid exceedingly ; while the whole
band of lines and linelets of this poor, persecuted Orange CH was now hidden.
in a positive jungle of intrusive low-temperature H lines, of a most provoking
degree of strength, brilliancy and number. .
My hope then of presenting the Society with a large map of Orange CH,
out of that tube, was gone for ever. Because, when decomposition, by spark

GASEOUS SPECTRA UNDER HIGH DISPERSION. 431

illumination, once begins in a CH. tube, it never stops until all the H has
freed itself from the trammels of connection with C (Carbon); and that
element either falls inert, or if it can find any O, combines with that, and
appears as CO, to the still further confusion of all CH bands.

At the same making where these two Olefiant gas tubes at 2’°0 and 4”:0
pressure were prepared, Mr CasELLA made for me another tube at only 0"1
pressure. There was no O nor CO visible there, nor any CH either ; nothing
but the most brilliant set of lines of pure and simple H that were ever beheld,
I should suppose, by mortal eye. In fact, at that low pressure, the first spark
had decomposed the whole of that faint charge of Olefiant gas; its C was
nowhere visible, but its H atoms were vibrating everywhere: and the only
consolation I had for seeing nothing of the expected CH was, the apposite
illustration that the whole case offered of a favourite idea of the late excellent
Sir WILLIAM SIEMENS, whose loss we all deplore. His idea being, that the
gases which, by combining under 800 inches pressure on the surface of the
Sun, give out light and heat,—may, when excessively rarefied by removal into
outer space, become decomposed or separated from each other under even the
weakest physical influences ; but are made ready in that way, on their return

to the Sun, to give out light and heat by renewed combination under pressure,
over again.

BLUE AND VIOLET CH Banps,

Of the Blue band of CH, I have little to say beyond what my readers will
find out for themselves, on referring to Plate LIV., to my Index Map (Plate
LXXVII.), and also to MM. Ancsrrom and THALEN’s Index Map, which mutatis
mutandis is fairly enough compatible therewith.

But in the case of the Violet band, so large and bulky with me, so

thin, small, and vanishing with them, there is a huge difference to be ex-
plained. :
_ Now TI should have already indicated that an exactly opposite difference in
the case of the Orange band, seemed to be attributable there to the Swedish
observations being made on gases at far greater pressure (probably the full
atmospheric) than the densest fillings of any of my tubes; and the same reason,
though with opposite effects, is apparently the acting cause at the opposite, or
violet, end of the spectrum, of what we may note there. For with my own
| tubes, the denser the filling, the nearer did the Orange band come to the
| larger Swedish development of it,—yet the nearer also did the Violet band
come to the Swedish depreciation of 2. In fact in my densest tubes I have
not only found the Violet band (the furthest visible one of the Coal-gas
| Blow-pipe series) an almost vanishing quantity,—but have proved an entire
| absence of a still more beautiful and powerful band beyond it—and which
VOL. XXXII. PART III. 4A

432 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

ought otherwise (as well as another band between the blue and the violet) to
be always seen at electric temperature, viz.,

THE MArRSH-VIOLET CH BAnp.

This band was so-called, from Professor ALEXANDER HERSCHEL first finding
it during some of these experiments in one of my tubes of Marsh gas; but it
was already known to older spectroscopists who have used pure Oxygen, in
place of atmospheric air, in their blow-pipes.

With stronger sparks too than my earlier ones, I have latterly found the
band developed to more or less extent in every kind of CH gas ;—and capable
of coming out with far more force and picturesque luminosity that the previous
Violet, or the ante-previous Indigo, band.

In short with its very pronounced leading lines, and then the expanding
linelets after each of them, in such regular series,—this last and latest “ Marsh
Violet” CH band may be considered a most typical example of a CH band.
It would also probably make a still more magnificent appearance in
photography ;—for, it is so far within the ultra violet of the spectrum range, as
not to exhibit its full glories to the human eye, but is by just so much within
the sphere of the impressibility of bromo-iodide of silver, focussed on by quartz
lenses and prisms. My own plate of it therefore (No. LIV.) must be looked on |
as its ¢nterim presentation only.

OF THE CHEMICAL INTERPRETATION OF THIS CH Spectrum.

Through all the variations I have been describing of this CH spectrum, ©
however much more or less may have been visible at its one end, or the other,
by reason of accompanying circumstances just explained,—no one known and
recognised band in it, when tested by its sharp leading lines has been moved
out of its spectrum place by the smallest, recognisable quantity. Hence it is
one and the same spectrum throughout all the above intensity variations, and
one so continually met with in this world, and in astronomy is so characteristic
of the self-luminosity of comets, that it is most important to know what
chemical science says as to its origination and nature.

I have been, thus far in the present paper, calling it the CH, or Carbo-
Hydrogen, spectrum; but in London among the magnates of Chemistry and
Spectroscopy, it has been declared to be the spectrum of C, or pure
Carbon alone.

So, too, it was evidently very firmly held to be by them, a few years ago.
For when I sent a paper on Auroral Spectroscopy to the Royal Astronomic
Society in 1871 making use of the Candle-spectrum as a reference, and attri
buting it to CH in general, and Acetylene, or C,H, in particular,—I have bee

GASEOUS SPECTRA UNDER HIGH DISPERSION. 433

told, informally of course, where a secret meeting is concerned,—that a Royal
Society Fellow on the Council of the R. A. S. informed that body that my
chemistry was entirely wrong, and my paper was consequently rejected.

Now Carbon has long been known to be one of the most refractory
substances under the Sun; though when exposed to the most terrible
temperatures of Condensed Induction Electric sparks, it is forced at last,
in the unanimous consent of all men, into incandescent vapour, and then gives
out a totally different spectrum, to anything we have been describing, viz., one
of a few isolated lines merely, see No. 3, Part I. of my Index Map (Plate
LXXVII.). This therefore was termed by the London men, “ Carbon spectrum
No. 1;” while the spectrum we have been discussing, and which may be seen
in the base of the weak flame of any little candle whose temperature is low
indeed by comparison, was, with them, Carbon spectrum No. 2, or 3, or 4; on
the then new presumption that a Chemical Element, instead of being confined
to cone spectrum alone, may have several.

The history of the origin, and metropolitan establishment, of this very
contradictory conclusion for Carbon, is, that Dr AtTrrreLp of London in 1862,
presented a paper to the Royal Society there, which that body accepted and
printed ;—wherein he claimed to have seen the banded spectrum of the Blow-
pipe flame of Coal-gas and air in every possible compound of Carbon with either
H or any other gas; whence he decided, that the spectrum must be that of
pure Carbon alone ; however different it might be from the English Carbon spec-
trum No.1. This decision therefore having been given forth under the auspices
of the Royal Society, London, has remained the rule ever since in that region,
however violently it conflicts with the Natural Philosophy of the case, and the
Chemistry of Carbon in general.

Outside the London circle some very different ideas prevailed; but were
ignored by the grand central authority there, until at last the progress of
knowledge raised an earthquake in their midst, with effects which would have
been far less disastrous, had the London magnates been previously only a little
less exclusive. For thus, with a charming naiveté of confession, explains the
British Association’s Report of 1880,—

“ On the whole it may be said that, from the publication of ATTFIELD’s paper
(1862) until the year 1875, every spectroscopist, whether he was a chemist o1
physicist, who’had set to work to decide the question, came to the conclusion
that the Candle-spectrum was a true spectrum of Carbon (2.¢., of C., not CH),
and the question appeared to be settled.”

Now I was not original in having, on the other hand, during that interval,
upheld the Candie-spectrum to be one of CH, not of C; for I had learned it
previously from my friend Professor Swan, who, with his paper on the subject
to this Society in 1856, is an older authority by many years on the Candle-

434 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

spectrum than any of the London gentlemen,—and yet, with myself, was pushed —
out of the pale of recognition through all that long period from 1862 to 1875
But, what occurred in that latter year ?

In 1875 was published the grand Memoir of MM. Anestrom and THALEN,
wherein a very polite denial is given to the correctness of one of the most
important of Dr ATTFIELD’s assertions, viz., that the candle-spectrum was an
invariable accompaniment of a CO flame burning in the open air.*

Imperfect niethods of preparing CO (Carbonic Oxide), argued M. THatEn,
may easily allow CH gas to be present and give its spectrum ;—but pure CO
does not give it. So also I have found with my tube experiments,—for while
some of M. D&miIcHEL’s very carefully prepared tubes of CO did not reveal a
particle of any of the bands of the CH Blow-pipe flame,—certain other
examples of CO by a London maker exhibited so much of the said bands, not
too as a mere residual accidental impurity in the tubes, but as a something
introduced part passu by an erroneous chemistry in making the gas, for it
increased always with the pressure, that I wrote at last for the particulars of
the manufacture; and then discovered that the maker had been using a very
weak and watery example of mere commercial Sulphuric Acid, instead of the
most pure and anhydrous example that could be obtained.

The outcome therefore in 1875 of the opinions of such men as ANGSTROM
and THALEN, could not be altogether repressed and repudiated even by the Royal
Society, London. But that Society has since then had a severer trial to bear ;
for almost in the e¢ tw Brute manner of the stricken Ceesar, they have had to —
read the later essays of Professors Liveinc and DeEwar, from the Cavendish —
Laboratory at Cambridge; and find therefrom, that those distinguished —
scientists have come to precisely MM. ANnestrom and THALEN’s conclusion;
viz., that the Candle-spectrum is a CH, not a C, spectrum; and that its
uniformity through all varieties of CH chemicals, depends upon the formation
of Acetylene, C,H,, in the course of the combustion or incandescence.

In short, the mental confusion that has now overtaken those who have
ruled the London world of spectroscopy in this matter, so long,—is illustrated _
at the end of the British Association’s Report upon it ;—for it terminates with a
disjointed, unnecessary and primitively simple statement of the spectrum places
of the mere general beginning of the Orange, the Citron, and the Green bands”
of what may now be firmly called by every one, the CH spectrum.

Unnecessary was that proceeding of the Committee, because all men have

* From p. 14 of Messrs Anesrrom and Twaten’s Memoir. “Quant & Vobservation de M.
ArtrieLp que l’oxyde de carbone donne le spectre ordinaire des carbures d’hydrogéne, nous devons
remarquer que cela ne s’accorde pas bien avec nos propres expériences.

“Dans un tube de Geissler, contenant de l’oxyde de carbone ou de V’acide carbonique, on p
certainement trouver des traces des spectres des carbures d’hydrogéne, puisque le gas n’est jam i
parfaitement sec.”

GASEOUS SPECTRA UNDER HIGH DISPERSION, 435

been long since agreed on the said places, quite closely enough for identifying
the phenomenon; and the Bezonian query of “C or CH” has never yet been
attempted to be answered by referring to any doubt about exact Spectrum place.

PART III.

THE CO SpEcTRUM.

This CO spectrum should symmetrically arise in a combination of Oxygen
with Carbon; just as CH represents Hydrogen joined to the same element ;
and accordingly vacuum tubes with a trace of Carbonic Oxide (CO) give the
spectrum we have now to discuss, in a most marked manner and easily
recognisable character.

In my former paper to this Society, I regret to say that I did, though with
expressions of considerable reserve, allow for the time, with the English
spectroscopists, that this spectrum might be one of pure Carbon, at a
temperature between lamp-flame and that of the Condensed Induction spark.
But I beg now to apologise for that error, to withdraw the name of “Tube
Carbon spectrum,”—and to follow the teaching of Messrs ANcsTRoM and THALEN,
who consider it to be the spectrum of the compound gas CO, (Carbonic Oxide)
and of that alone; for even if CO, (Carbonic Acid) be also in the tube, or even
occupy it entirely, one charge of its Oxygen remains ineffective, and exactly
the same visible spectrum, as that of CO alone, appears.

Now this CO spectrum, from the materials of its origination, is one of
almost as extensive presence on the earth as CH; and has at first sight
‘something of its appearance. Yet they are two opposing and antagonising
principles at every step.

STATICAL DIFFERENCES.

In small spectroscopes the CO spectrum is so far like the CH, in that it isa
spectrum of bands; but it has many more; so that while MM. Anesrrom and
THALEN have shown in their Mesures Micrometriques two only for CH, they
show three for CO; and in their general Index Map they have represented
8 principal, 5 secondary, and some 16 very faint indications of tertiary bands,
for CO; but 5 only for CH.

The 8 principal bands of CO reinforced by 2 bright ones of the secondary,
are, from their spectrum places, of the following notable grades of colour—

(1) Red, (6) Green,

(2) Scarlet, (7) Blue,

(3) Orange, (8) Indigo,

(4) Yellow, (9) Violet, and

(5) Citron, (10) Ultra violet.

436 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

All these have their brightest, hardest edges toward the red end of the
spectrum, in so far agreeably with all the CH bands; while the Citron and
Green of the CO bands, fall so nearly on the spectrum places of the similarly
coloured Citron and Green CH bands, that beginners may sometimes confound
them; or even imagine a physical connection and community between them.

A very little increase however of Dispersive power with Definition, will
show that the CO bands have no leading lines in them, like those which are so
prominent in CH bands. The CO bands in fact are made up of nothing but
very uniform linelets, and therefore present a smoother, more enamelled
looking, surface ; and they are narrower than those of the other compound.

A far more certain difference however comes out on very highly increasing
the spectroscope’s powers; for then it will be found that every band of CO has
its every linelet of a different construction, or we might almost say material, to
any linelet of CH; and every arrangement of them is different also. This will
appear perhaps most strikingly on comparing the Green band of either; but as
we have already given that band of CH, we have only here to picture, describe
and discuss the

GREEN BAND oF CO.

In the Upsala micrometrical view this band is very short, and the linelets —
of which it is dimly indicated to be composed are coarser and wider apart
than those of CH.

The shortness of the band, as given, merely arises from the circumstance,
that at the point where it is cut off towards the violet side-—Green CH
(when that is simultaneously present, owing to faulty chemical preparation of
CO, or otherwise) comes in, and one band, after that, overlying the other
produces confusion. The Upsala philosophers therefore did well, in picturing
for green CO by itself, only that little bit of its Green band by whose small
breadth it comes out from behind the bright beginning of Green CH ; forming
in that way a tiny peninsula of perfectly pure Green CO illumination, which is
already somewhat celebrated in spectroscopic story.

A few years ago this peninsula was thought so. very narrow, or minute, a
quantity, that it was proposed as a test, much better than the Micrometer
measures of that day, to settle whether the carbonaceous spectra of Comets
belonged to CH. or CO.

In MM. Anestrom and THaten’s Index Map, the said little bit measures
0-23 of an inch broad, and the shading expended upon it does not claim to Db
anything more than engraver’s ornament.

In the larger plate of their Mesures Micrometriques the CO peninsula 0:
Green measures 1°4 inches across, and shows 14 indistinct or roundet
corrugations, or “ flutings ”” of surface.

GASEOUS SPECTRA UNDER HIGH DISPERSION. 437

In my own finally reduced plates it measures 4°3 inches across, and shows
no less than 44 distinct and positive lines.

But in the original records of my spectroscope, and which alone I would
desire to refer to now (see Plate LX XVIII.), the breadth of the peninsula is
upwards of 26:4 inches; and though it shows only the same 44 lines just
alluded to,—yet it gives them with a force, a character and an effect that can
be attained on no smaller scale ; and was the practical mean by which many of
them were first discovered to exist.

Though speaking of these 44 luminous existences as lines, yet it is to be
remembered that they are nothing but the linelets composing what appears in
smaller instruments a smooth shaded band ; and with my largest spectroscope,
it was the most extraordinary thing to contemplate the broad fields of absolute
blackness that separated each one of these vivid, hard, sharp-edged, well-defined
lines from its nearest neighbour on either side.

Nor was it less instructive to use a tube containing both CH and CO; and
then compare in the same field of view these two opposing principles, as it
were, of the Physical world. The unoxidised against the oxidised; the fuel
still to burn, against the refuse of fuel long since burnt; this latter the condition
of the whole surface of our planet, rocks and water alike, excepting only its
coal beds and a little amount of gold and other unoxidisable metals.

The green CH band comes in (as will be very clearly seen in Plate LVIIL)
just on the right of the green peninsula of pure CO; and with its doubled
Green-Giant line of CH, shines gloriously enough, but yet with a suspicion of
haziness along its edges; while its closely packed following CH linelets, though
sometimes exquisitely defined, have something of a gossamer weakness and
transparency of look. ‘They are like mere filaments of silk, or spider lines at
the best ; and if doubles are seen amongst them occasionally, it arises probably
from a process of decomposition having set in, or Hydrogen freeing itself from
all earthly contamination; a liliputian curiosity in a vacuum tube, but the chief
acting agent in the mighty red prominences of our Sun, and in the terrific
conflagrations of so called new, or temporary, stars.

With CO on the other hand, and its CO linelets, which are the best defined
and hardest of diamond-like lines in structure,—if you see them once, you see
them always; fixed like the rocks; or even growing in their places; for when
once Oxygen has got hold of any Carbon, all the further actions of the
illuminating spark seem only to enable it to go on taking an equally firm hold
of all the rest of the carbon that may be within its reach.

In fact, while the usual mode of failing for any CH tube by powerful
Sparking is to end in its showing nothing but H lines, so for tubes containing
| any compound of Oxygen, it is to finish by showing nothing but the CO
spectrum. And if it has been said, that in the event of a solar conflagration

458 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

of this world, nothing of its solid material would be left, except atoms and
molecules vibrating in the intense light and heat, we may be pretty sure that
while Hydrogen would be dancing like the fire-fiend above tbe scene of
destruction, the more stolid CO would dominate beneath.

Its NuMERICAL EXPLANATION.

But would such a reproduction of Nebular haze bring back the chaos, the
confusion, of the Greeks; or would it be an entrance into a superior realm
of law and order, in number, weight, and measure ?

Let the 44 lines in this Green peninsula of CO, now first rescued from the
very bad definition, uniform haze, and contracted views of the old observers,—
answer for themselves.

There are evidently amongst them, on the grand 26: inch scale, lines thick,
and lines thin; lines single, and double, and triple; some expanding their
distances apart in the direction of the violet, and others towards the red;
there are places of unseemly crowding together of many lines, and other
spaces which are comparatively bare,—in short, a careless viewer would
pronounce at once for confusion. But having fortunately sent one of the ori-
ginal, and raw, but large sized instrumental records to my friend Professor
ALEXANDER S. HERSCHEL,—he was enabled by his experienced study of such
phenomena to return in three days a demonstration, that each of those 44
lines was a necessary step in a remarkable system of physical numeration,
proceeding in two rows of simple arithmetical progression, one over, but slightly -
advanced upon, the other; not accidently or discordantly,—but so as to set
forth the unit, the quinary, the decimal, and even the quinquagesimal
standard of what may be now termed the CO system of linear construction. __

The success of this numerical demonstration, this extraction of scientifically
ordered simplicity out of at first sight extreme complexity, may be quickly —
judged of by reference to the large Plate No. LX XVIIL. prepared especially to
show it; but more completely still, by reading Prof. A. S. Herscuer’s letters
in Appendices Nos. I. and II. Their account is happily so complete, and so:
independent, as to leave nothing further for me to remark upon here, except:
observationally ; for theory in this case has given pretty certain indications
that 8 lines out of the 44 which I have set down as single, are really doubles;
but far closer than anything which I have yet been able to resolve. These
cases must therefore be left to future observers, a test for their instrument
to come; and a still further proof we may expect, when it does come, of the
exact geometrical foundations of the very smallest components of the ultimate
materials of Nature.

GASEOUS SPECTRA UNDER HIGH DISPERSION. 439

REMAINING BAnbs oF CO.

Of the Red, the Scarlet, the Orange, the Yellow, and the Citron bands of
CO below that Green band which we have just been discussing; and of the
Blue, the Indigo, and the Violet bands above the Green,—and which are all
pictured in the Plates Nos. LVIII. and LIX.,—their linelets seem to have
somewhat similar characteristics on the whole to those of the Green band,—
but with compound variations,—not yet fully made out by observation. Nor
| perhaps very soon likely to be much further elucidated, because
(1) The dispersion of my present Prisms below the Green is too small;

(2) Above the Green the definition is not sufficiently good ;

(3) Towards either end of the Spectrum the illumination of my existing
_ sparking apparatus is not sufficiently bright; and

| (4) It is very difficult to get those bands perfectly free from impurities of
| CH, H, and other gases.

I will therefore at present proceed to a provisional termination of the CO
subject, by means of a few words on some general characteristics of that
| compound gas in vacuum tubes.
| A small pressure of the gas, say 0°25 inch, seems to be most suitable for
| securing a maximum of brilliancy conjoined to stability. For higher pressures,
) say 1 inch, 2°5, 5:0, or 125 inches, simply show the same spectrum, but fainter
and fainter as the pressure is greater; while lower pressures, say 0°1 inch or
under that, though exceedingly brilliant for a time, are very apt to get their
tubes overheated and loosened at their electrodes with loss of illuminating
| power altogether. To prevent this catastrophe, the electrode ends of the
| tubes, whether with platinum wires as usual passing through them, or coated
only with a film of silver outside, have been made to dip into vulcanite
| insulated basins of water, and receive their electric charge from thence ; but
| the illumination was never at its best in that manner, the whole apparatus
| sometimes became inconveniently charged ; and with the silver coated tubes,
| the glass was actually perforated sooner or later. Some of the best exhibi-
tions, however, of the CO spectrum, have been the unintended ones; as of tubes
prepared with Oxygen alone; and showing at first the Oxygen spectrum,
but that changing during use into CO; and always more and more quickly or
inevitably, the weaker the pressure at which the Oxygen had been sealed in.

Whence comes the C for this transformation of O into CO?

Some persons have suggested, from the use of a coal-gas, in place of a
| hydrogen, blow-pipe in working the glass ; and an extraordinary hypothesis has
been recently started in Germany, of Si being convertible into C in vacuum tubes.*

* The following note has been furnished to me:—‘‘Herr WrssenpDonx«K prepared Siliceous gas with
most scrupulous care and purity, without being able to obtain a trace of Silica lines, only CO bands over
and over again, and more and more brilliant the purer the gas he used. Silica could never be found,

VOL. XXXII. PART IIL. 4:18

440 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

But my own idea is still, that it may be owing to the electric spark’s
power of convecting C along its wires; and then, not merely because such
wires are usually coated along their whole length with an easily melted
material so rich in C as Gutta Percha,—but because the Induction coil itself
is, throughout its chief bulk, little but a huge mass of soft C; and the rolled
up insulated wires inside it, make it a perfect ganglion for accumulating all
possible transportable atoms of that element.

Some small spectroscopic evidence in this direction too, is already in print;
as thus, plate i. of M. Lecocg DE BorsspAupRAn’s admirable book Spectres
Lumineux gives two pictures of the electric spark in open air; one near
the positive, and the other near the negative, Pole. They both of them
exhibit chiefly the well-known low-temperature Nitrogen bands; but the
latter, or Negative Pole’s end, has a glorious distinction from the Positive’s,
in this, that it has also a very strong violet line, the a, or chief of the whole

— display, which does not belong to the simple Nitrogen’s or to the Air’s low-
temperature spectrum at all; nor to their high-temperature spectrum either.

To what then does it belong ?

According to my earlier and perfectly mdependent “gaseous Spence
paper to this Society in 1880, it is the characteristic line of Cyanogen, or
Carbon combined with Nitrogen, the chief constituent of our atmospheric
air. Carbon vapour then added to the spark which is producing the Nitrogen —
spectrum in the open air, can hardly but produce this Cyanogen leading
line; and such Carbon can be obtained by the electric current from nothing
so readily as the gutta-percha, vulcanite, and waxed, or resined-paper
interstitions, which form so notable a portion of every Induction coil.

But as I had an opportunity of setting forth something of this view in

- Nature journal last year, assisted by a woodcut of the spectra,—I here close
this part of the present paper on the two compound and opposed gases, CH
and CO; in order to proceed to the next part treating of the three elemental
gases H, O, and N.

PARTLY,
THE THREE ELEMENTAL GASES, H, O, anp N.

SuBJECT 1.—H or HyYpDROGEN.

There is little trouble in procuring good H tubes; and they are such
excellent illuminators as to get the better of all ordinary impurities, espe-

in any quantity to speak of ; so it could not have come out of the glass. SiH, and Sif, were used
(very easily prepared pure) CO was the only result he could possibly obtain. That,
always that.”

GASEOUS SPECTRA UNDER HIGH DISPERSION. 441

cially with time and use; and show at last nothing but the Hydrogen tube-
spectrum with brilliancy and certainty at any pressures between 01 and 0°5
inch.

One particular impurity, however, has to be guarded against; for its lines
though few, are strong, viz., Mercury,—whose vapour always has a chance of
entering, in connection with the Sprengel air-pumps now so generally used in
the exhausting operations. To this end therefore some tubes specially contain-
ing Mercury have been made for me in Edinburgh by Mr W. H. Suarp (of
Kemp & Co.), and have furnished the Mercury low-temperature spectrum
which appears as No. 13 in the second division of my Index Map; and will
enable any one with great ease to eliminate Mercury, from the H, lines ; espe-
cially if they try it at various lamp temperatures.

But not a great deal has yet been written on the tube, or “low electric
temperature,” H spectrum, though every one knows about the 4 grand lines in
its high-temperature spectrum, and which reappear in the tubes, together with
all their low-temperature lines. MM. Ancstrom and THALEN, for instance,
are silent on the subject in 1875; and still more remarkably Hydrogen does
not figure in the otherwise very comprehensive list of gaseous spectra treated
of by the British Association’s Committee’s Report of 1880.

Fortunately these low-temperature Hydrogen lines attracted the attention
several years ago of the savants of the Imperial Central Observatory of Russia
at Pulkowa; and Dr HassevzereG, their chief spectroscopist (a former pupil
too of M. Anesrrom), entered into the subject with intense enthusiasm. He
had begun with other gases, but soon alighted, as I had done in my paper of
1880, on the existence of low-temperature lines, as an addition to the well-known
high temperature spectrum of 4 lines only for Hydrogen. He found them
too so invariably in any and every mode of preparing Hydrogen gas, that he
concluded they must belong to it alone, and under such impression prepared
a map of them about 18 inches long, with three of the four great lines intro-
duced amongst them.

But that size of map he afterwards considered did by no means do
justice to the richness of this H spectrum, wherefore he laboured again with
new prisms; and in the course of last year, published with the Imperial
Academy of St Petersburg, a new map of Hydrogen “tube” lines by simple
electric spark, or the many low-temperature + the few high-temperature lines ;
the map having a length altogether of nearly 90 inches from the Red to near
the Violet line.

This last map of Dr HassELBerc’s is a very grand work as compared to
anything yet published, either on the H, or indeed any other, gaseous
Spectrum; and it will doubtless be long regarded as a high authority for the
absolute spectrum place of the lines which it contains.

442 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

Hardly so, however, for either the number or minute physiognomy of most
of its lines; for whereas the Doctor begins the low-temperature H lines far
within, or above, the great Red Hydrogen or C line of the Sun,—I have found
them commence far without, or below, Red Hydrogen ; continually increasing
too in brightness as they pass that line, and at length join on to Dr HasseEz-
BERG'S earliest lines, which are with me very bright. And then again, his scale
of 90 inches must necessarily fall lamentably short of a 480 inch spectrum,
when it is a question of detecting a close, double, or triple, hitherto recorded
as single only.

This indeed by itself might have been got over, or apologised for; but
unhappily the laborious author has allowed his engraver to exert his own taste
in doubling and frebling the chief part of his principal lines, and even making
a banded group out of the grandly single line Red H, in a manner, and to a
degree which must entirely mislead the spectroscopic searcher after micro-
metrical truth.

Now my own original measures of this spectrum, though they cannot
pretend to compete with his for accuracy of absolute-spectrum place, are on
such a scale that from the earliest Red to the Hydrogen, Violet occupies as I
have already mentioned, a continued length of 120 feet. So that if, in this
grand hall, you imagine the spectrum strip to begin over the President’s Chair,
and extend thence continually towards the right, the red and scarlet would
reach the end of that wall, the orange would cross that end of the room, the
yellow, the citron, the green and the glaucous would occupy all the other long —
side of the room, the blue would cross its further end, and the indigo, the
violet, and the ultra violet would come back and overlap very nearly the
beginning of the spectrum’s scroll right over the President’s head.

Along with that immense length, truly immense considering it is merely a
magnification of a slit about 3,5 of an inch wide,—you would see nothing of
bands of CO with their orderly, closely set regiments of linelets, nothing of the
leading lines and fainter linelets of CH,—but only lines and lines and lines
again, free, easy and distinct of H. There are some 1625 of them absolutely
recorded at the instrument; generally they are brilliant, well-defined, showy
lines; nowhere very closely packed, but forming all the way along an-
independent kind of open groups, which have perhaps a certain kind of
family resemblance among themselves, but with never any precise repetition
between one group and another, either of its strongest single lines, or the
occasionally exquisite doubles or trebles which try all the powers of the best
spectroscopes yet made to resolve them. In short Hydrogen, in between the
positions of its four grand high temperature lines, shows in these almost
endless low temperature lines of the tubes, nothing but a saltatory sort 0
movement, such as an ariel sprite might indulge in, and such as does typify the

GASEOUS SPECTRA UNDER HIGH DISPERSION. 445

taste or the instinct of Hydrogen to shake itself loose from all terrestrial
matter, and rise above all the other elements the lightest and most ethereal of
them all.

But my apparatus is still so far from describing all that Hydrogen has to
show, and which future observers may discover,—one does not know how
soon,—that I make no attempt in the present state of the question to try to
develop the kind of order on which its arrangements are founded ;—but would
beg leave to call attention; by its means, to a general feature touching definition in
all bright-lines pectra, viz., excepting some of the fainter lines in the ultra
Red, the definition of Hydrogen lines is inimitably fine and sharp through the
red, scarlet, orange, yellow, citron, and green until we come near the blue,
where a little falling off sensibly occurs. In the further Blue and the Indigo
the defalcation increases ; and in the Violet becomes unbearably offensive ; so
that what should be a sharp line of light, becomes more like a dull, broadened,
or diffuse woollen cord or hazy band.

Is this change which thus supervenes on approaching the Violet end of the
spectrum, a fault of the instrument ; or a quality of Nature ; or a failure of the
human eye ?

Not a fault of the particular instrument built up by me in rather rough and
economical fashion, because I have met the same principle of effect in every
spectroscope I have looked through,—even including that charming instrument,
the Cooke-Monckhoven spectroscope of Professor Tart’s Natural Philosophy
Laboratory,—a spectroscope whose every adjustment is carried out to perfec-
tion, and where nothing seems to have been omitted or neglected.

Nor is it a necessary, and innate quality of Nature; for exquisitely defined
spectrum lines in both the Violet and ultra Violet regions are said to be
obtainable, and have I believe often been obtained, though not by me, in the
medium of Photography.

Then the failure must arise in the eye. Yes, in.the human eye and its
total inability to distinguish between Violet as it is in the spectrum, and every
Other so-called Violet colour under the Sun. For these, so far as I have yet
‘examined, whether in chemical solids, or fluids, flowers or stained glass, are
jnothing but a mixture of blue and red; and are allocated to a totally
| different mean spectrum place than that of violet, by the more than man’s dis-
criminating power of either the prism, or a diffraction grating.

In fact, except for the purpose of establishing a sort of border neutral
, territory, where eye-results may be compared with the blackened imprints on
| bromo-iodide of silver, so extra sensitive to violet light,—no eye observations
|should be trusted for minute features and full effects, much beyond Glaucous
| Hydrogen,—for there Photography can be brought in with advantage, and
probably will be, before long for everything, by those eminent scientists who

444 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

have of late employed that method in their own special researches, but usually
on a far too miniature scale to satisfy present requirements.

SuBJECT 2.—O oR OXGYEN.

With this gas comes in a change; a relief perhaps to many persons after
the growing complexities of other spectra.

So far at least as the O spectrum has yet been seen and published in
vacuum tubes, it is simplicity itself; and though called “the compound-line”
Spectrum of Oxygen, that name was given to it merely in deference to a
theoretrical idea, in accordance with which the lines owght to have been
compound; or at all events totally dissimilar to what has been termed, by way —
of pre-eminence, ‘the line” spectrum of Oxygen ;—because that is what
results from the high temperature of the jar, or condensed discharge of
induction sparks,—in contradistinction to the low temperature, or direct
discharge, of the simple spark, which we are now dealing with.

Of this low temperature, “called” compound-line, Spectrum of Oxygen then
it is, that the British Association’s Report speaks, when it declares it to consist
of four lines only; one in the Red (or Orange rather), two in the Green (or
rather one in the Citron and one in the Green), and one in the Blue (or rather —
between the Indigo and the Violet); but the spectrum places of all four have
been accurately measured in Wave-lengths, so that they can be easily identified
by any one. |

A. gaseous emission spectrum then, consisting of four widely apart lines
only, must surely be as simple as any one could desire;. and the statement is
founded on very high authority, viz.,.a paper by one of the British Association’s
Committee, printed by the Royal Society, London, in 1879. The author of it too,
—being one who not only “ fills his own gas-vacuum tubes,” but who launched
the depreciating accusation against me that I did not perform that operation for
myself (pp. 11 and 12),—I shall hardly be allowed, by either of those two great
English Associations to put forth any accounts of more lines than their four;
and yet, if my mode of arriving at more than four had been dependent on my
filling my own tubes,—would there not have been a chance of my being com-
pared to that publie lecturer who, about half a century ago, in London, under-
took, in defiance of the doctors, to drink off half an ounce of Prussic Acid, ot
deadly strength according to the Pharmacopeia, but stipulated that he must
prepare the fluid himself! | :

Before relating however what I have found, and how ; viz., by open methods
which should bring out the same result in whatever part of the world they are
performed, and have brought out the same in the hands of both French and
English workers ;—there is something more to be precisionised in the Royal

GASEOUS SPECTRA UNDER HIGH DISPERSION. 445

Society’s printed paper alluded to. The letterpress thereof certainly speaks of
four lines only, and gives the places only of 4, in figures; but in the map
accompanying them they are made into 8; viz., each line of the four is made a
double line; two, much more distinctly so than the other two. It is not for me
to pronounce on the accomplished fact of the Society’s thus doubling the
number of lines in a very scantily furnished spectrum; and making the original
single lines of observation conform more nearly to the theory they publish, by
representing them ‘‘ compound” to the extent of doubling each one,—but it is
absolutely necessary for truth’s sake to warn all into whose hands the Philo-
sophical Transactions may come, of the absolute falsity of the (London) Royal
Society's Oxygen spectrum plate, in that respect.

The talented author of the paper, moreover, has never claimed to have
seen more than four single lines, placed as described; has made an immense
number of most admirable experiments to assure himself that they belong to
pure Oxygen, and not to any accompanying impurity,—and that there is
nothing else in the O spectrum of equal visibility. That degree of visibility
however, being something very small; for Oxygen gas is what is generally
known, as a bad illuminator, in all vacuum tubes.

There then, with only jour truly observed lines, the tube spectrum of
Oxygen might have remained, had I not in 1879, independently of the late
energetic Dr VAN MonckHoveEN, both struck, and worked out, the idea of using
vacuum tubes end-on, in place of transversely to their capillary part, as others
seem to have done universally before that time; some of those earlier observers
even using the tube’s upright line of light, in place of the slit of a spectroscope
proper. But with the new end-on vacuum tubes, and equally when they were
made for me in Paris, or in London, I immediately, through the greater bright-
ness of their light, saw the presence of many fainter features constant in, or
evidently belonging to, the O Spectrum of the four lines.

First, for instance, I found that three, out of the four, primitive lines were,
each of them, a triple. Each triple a long way from its nearest neighbour, but
of precisely similar build; and I have since then discovered three other such

| triples, one of them further away towards the Red, than the longer known

ee ae >

Orange one; and two others further towards the Blue, than the older Green
one.

They make moreover a remarkably connected, though wide apart, and only
faintly luminous system altogether, extending through so great a range of the
Spectrum as from Red to Glaucous; for the six triples are arranged in three
pairs, whereof the mean place of the third pair is from the mean place of
the second pair, close on half the distance that the mean place of the second

| is from the mean place of the first; while at the same time the much smaller

distance apart of the sixth triple from the fifth is just about half that of the

446 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

fourth triple from the third; and that is again about half that of the
second triple from the first. And finally, to carry the principle still further
into details, but these details supposed to be more nearly eternal than worlds, —
and suns, and stars,—in each of the six triples the third line is about half
the brightness of the second, and at half the distance from it, that the second
line is from the first line.

Indeed the characteristics of an Oxygen triplet are so peculiar, and so
closely adhered to in every instance, that I have been able in some tubes
swarming with lines of impurities to pick out an Oxygen triplet, as easily as
one would distinguish in a crowd of civilians, a soldier with cross-belts and —
scarlet coat.

Although then there is so little show of general light in a pure Oxygen
tube, geometrical order is preserved there amongst such lines as it does show,
most rigidly. So that while Hydrogen, with its multitudinous, brilliant, varied
lines dancing or vibrating through the whole length of the spectrum, may be
likened to a big, curly-haired, Newfoundland dog, bounding about and barking
at its own free will,—Oxygen is a Bull dog which, without any show, runs
straight to his quarry and holds him fast with an iron grip.

This view, moreover, trifling as it may appear, comes out more notably still,
when we attend to the many single lines which there are, after all, in the
Oxygen spectrum, and are shown both in my Index Map, and the larger plates,
Nos. LXVI., LX VIL, LX VIII, and LXIX. For, in spite of its faintness of
light, Oxygen in the spectrum actually outflanks every other gas. That is to
say, it begins with a very well marked and sharply defined line, further away
into the ultra-red than any line, band, or haze of any known elemental gas.
This same lowest line too of the O tubes appears to be identical with the most
red-ward line in the jar-discharge in the open air, as described in my recent
paper to this Society on BrewstTEr’s Solar line Y.

SuBsecT 3.—N or NITROGEN.

This is the last gas I have observed on the present occasion, and its
spectrum is in many respects the most mysterious, and most multitudinously
lined of all, when seen with great dispersive power; for otherwise, it is an affair
of hazy bands alone.

Just as it was with O, so here, mutatis mutandis is it with N, that a
condensed induction spark, or jar-discharge, discloses the high-temperature,
line, spectrum of the gas; and if the two gases be mixed together as they are
in the atmosphere, the same discharge shows the line spectra of both gases
overlying or multiplying each other; as may be seen in the upper portions ol
of the Index Map; forming hazy lines when in a dense, sharper lines im 4

=
B.- F

GASEOUS SPECTRA UNDER HIGH DISPERSION. 447

rarefied, medium; but evidently the same linear spectrum in each case, and of
but a few, say a score or two, lines even at brightest.*

With the simple or direct spark on the contrary in the open air, those two
spectra vanish, and are replaced by other two, perfectly different; whereof, as
just described, that of O is barely visible to moderate power, even in its isolated
compound triples or the stronger of its single lines lately discovered; while N
is heavily conspicuous all along the spectrum in the shape of a closely packed
arrangement of numerous, narrow bands. In a vacuum tube of N alone this
arrangement is still more brilliant, is generally known as “the band spectrum
of N,” and “is one of the most beautiful,” says the British Association Report,
“which can be observed.”

The best map of it I have yet seen is that in ANGsTROm and THALEN’s paper
of 1875; a map about 27 inches long, and exquisitely engraved; i.¢., so far as
engraver’s work alone is concerned, for the vertical limes wherewith the bands
are shaded are engraver’s ornament only, and have no pretension to represent-
ing lines seen by the observer. But with this reservation accepted, the map
effectively reproduces all that was known of the spectrum until 1880; when
Prof. Avex. 8S. HerscHEL communicated to this Society some notable exten-
sions of the spectrum into the ultra red, which he had just then made with my
Spectroscope as it then was, or merely in a pretty good condition.

His whole conclusion I believe was, that he could identify many more of
the narrow bands of N, in that lower region, far beyond or outside the place
where the first of THALEN’s pictured bands begin. And he could even trace
them up to a place where a triplet.of sharp lines shot up, and seemed to form
a sort of fountain head, whence had flowed down the continued stream of
Nitrogen cross-bands all through the Red, the Orange, the Yellow; and the
Green of that spectrum. .

With my present improved instrument, and several new and exquisitely pure
tubes of N prepared for me by both M. Demicuet in Paris, and Mr CaseLLa in
London, at various pressures between 1:0” and 2°5”,—I have been enabled
somewhat to modify the above view, as thus,—

(1) The band spectrum of Nitrogen, even in those brilliant colour regions
Just cited, is by no means one uninterrupted series of similar bands,—but is a
succession of four large groups of bands; each group bringing in with it slight
variations on the preceding one, and separated from its neighbour group on
| either side, by a tolerably distinct breadth of 2 or 3 bands of weaker action.

(2) THALEN’s first band, though no longer to ‘be regarded as the first band
or beginning of the N spectrum, is yet the first band of its own, or the Red,
p group; which we may therefore worthily denominate THALEN’S group.

* The manner in which the Red Hydrogen line comes into that Spectrum, is very striking, and I
have not yet seen a good reason given for it.

VOL. XXXII. PART III. 4c

448 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

(3) Outside and far away into the ultra-red, more N bands do extend, as
Prof. HERSCHEL saw; but they form a group of their own, beginning in faintness
far beyond Prof. HERScHEL’s triplet of lines, or anything that he saw; rismg in —
intensity of light and markedness of physiognomy as they pass that triple of —
his, and finally subsiding again very materially before they join, but
unsymmetrically, the first band of the THALEN group; for which features
please to examine, first the Index Map, and afterwards Plates Nos. LXX. and
LXXL
(4) Prof. Herscuet’s triplet of lines is however a very interesting
existency, with nothing else like it through all the rest of the N spectrum,
and with these two following features in addition,—

(a) It is shown only, so far as I can make out, in N tubes at very small
pressures, say under 0°1”; for brighter tubes as to the bands but at greater
pressures, say 0°5” to 2°5” show nothing of it.

(b) This triplet of lines, so anamolous in the tube, and unsymmetrically
placed as to the bands of the ultra-red group which pass in front of it,—is
nevertheless owing to the N gas; for it appears to be identical with the triplet
of lines which I discovered last summer in the jar discharge in the open air.
The one line seen on that occasion outside the triple, has since then been —
identified with Oxygen; but the triple having no resemblance to anything in
that spectrum, can hardly be of any other than N material, and may be
deservedly noted as HerscueE’s N triple.

If the large Plates of the N spectrum, Nos. LX XI., LX XII, and LX XIII,
as observed by myself be now examined, it will be seen that THaLen’s Red
series of bands opens a more brilliant portion of this spectrum; and one
which, in and after its third band, effloresces into almost an infinity of the
closest and most exquisitely defined lines and linelets that were ever packed
into a telescopic field of view. Nor were they all revealed even then, for
amongst them seemed to be doubles, or other multiples so exceedingly close
that they passed the power of my spectroscope, even at the best, to resolve
with certainty; and how many degrees further their intricate refinements of
structure extend through the residual haze, of which a little still appears,—it
is dangerous to speculate.

Had it not been for the method I elaborated of recording any number of
micrometrical places of lines consecutively, and without taking the eye away
from the eye-piece,—the attempt to note the exact place of each and every one
of such legions of lines in the usual micrometrical manner, would have been
hopeless ; for at the average rate of closeness of those which I could separate,
there are probably 4000 in the first half of the N spectrum alone.

The brightest example of the N tubes, viz., one at 0:1” pressure, brok
down, I regret to say, early in the work, or when I was using it near the -

GASEOUS SPECTRA UNDER HIGH DISPERSION. 449

region; the rest was therefore recorded by means of a 0°5” pressure tube,
compared occasionally with 1:0” and 2:5” pressure tubes.

Of the gradual swellings and subsidences of brightness in each of the four
long groups of bands (the red, the orange, the yellow, and the green), and the
minute variations introduced into the composition and settings of the linelets
forming all the several bands of one group, compared with all those of another
group,—the Plates Nos. LX XI. to LX XIV. will give a better and quicker idea
than verbal description. And they will also indicate well the immense change
which comes on in the Glaucous region, making the rest of the Nitrogen
spectrum, through the Blue and Violet an utter contrast to its earlier appear-
ance from ultra Red to Green.

This difference is marked strongly in ANGSTROM and THALEN’S map, in so
far as those classic authors represent the Blue and Violet bands much broader
than the Red and Yellow. But they have wholly missed the club-like, or
fascicular, groups of lines with which each such Blue or Violet band com-
mences.

I have had therefore to alter my Index Map considerably from theirs, in
order to represent this most innate and valuable distinction, as it appears to
me, of blue N, from blue CO, bands when in close neighbourhood. And the
minuter construction of these clubs of lines may be made out pretty well in
the larger plates of N, as Plates LXXV. and LXXVL., notwithstanding the
characteristic bad definition of any and all spectral lines in the Blue and Violet.

There is another peculiarity, however, well worthy of note in these more
refrangible and very broad bands; viz., that there is another class of bands
with sharper beginnings mixed up with them; and these additional, or smaller
featured bands (unnoticed I believe as yet by other spectroscopists), are more
constantly and certainly seen in tubes prepared for N, than those prepared for
N,O, or Nitrous Oxide. Or, in other words, the N,O Spectrum is simpler
than that of N; though the chemical notation as it stands now, is more
complicated.

But I have no maps of the Nitrous Oxide spectrum to show, on account of
all the N,O tubes, after a preliminary eye survey had been taken, having gone
wrong spontaneously, while I was observing those of N; and I had no more
funds for further tube making.

My present task therefore is finished, save a few words, or perhaps mere
conjectures respecting the possible chemical origin of the spectra just described
for
THe THREE ELEMENTAL Gases, H, O, anv N.

450 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

PART V.

ConcLupInc Notes ON THE ELEMENTAL Gases, H, O, ann N.

If in the earlier part of this paper, we found it expedient to admit that the —
two separate spectra there described were the spectra in each case of a
compound Gas, viz.; the one of CH and the other of CO; and to some degree
because the high-temperature or jar discharge gave a totally different spectrum
to C alone; is there not something rather similar to be said touching the
spectra we have just been describing for H, O, and N, though they are simple
and elementary gases according to the Chemists ? .

There is at least in so far, that if we try said reputed simple gases, not
with the weak direct spark which we have been using all along, but with the
intensified or jar discharge, there is introduced for each of them a totally
different spectrum from that which we have been describing. But why, in
that case, are our tube spectra of those gases not ascribed to compounds of
each of them with some other, in place of being confined to the one gas alone ?

Partly, I imagine, because no one knows at present what the other
component may be. And partly because there is a very conveniently
classifying theory for use in the meantime, which sets forth how one, simple,
elemental gas may have two or more different spectra under different
temperature circumstances; granting always that it exists as a gas at those
temperatures, and is not, like Carbon, inert and solid at all but one of them.

M. THALEN has controverted the multiple view for gases in general, not
only on the grounds that his deceased, revered, and loved friend M. Anastrom
held that each chemica] element cowld have only one spectrum under any, or
all, circumstances (though how proved is not stated)—but considers he has
demonstrated that the low temperature or “ Band-spectrum” of Nitrogen, is
the spectrum of the bi-oxide of that gas, and not of that gas by itself.

In 1872 (Proc. R. Soc., xx. p. 482) Dr Scuusrer, the able writer of the
Report for the British Association Committee in 1880, held a similar view.
But in 1880 he repudiates the idea, and states that no emission, or bright,
spectrum has yet been found that can with certainty be referred to a compound
of Nitrogen and Oxygen; so that he restores the “ gorgeous Band-spectrum” to
Nitrogen alone ; its /ine spectrum at higher temperature notwithstanding.

Dr ScuustTer is also the hero for claiming the particular Oxygen spectrum
we have been describing, viz., the spectrum of minute triplets and a few thin
lines, for Oxygen alone; calling it the compound-line, or low-temperature, or
simple-spark, spectrum of that gas; but without invalidating in any degree its
claim to the strong Line-spectrum which it shows at high electric temperature,

GASEOUS SPECTRA UNDER HIGH DISPERSION. 451

And Dr HAssELBerG seems to perform a somewhat similar part for
Hydrogen, excepting that there, the high-temperature lines are seen simultane-
ously, or together, with those of the low-temperature spectrum.

Of these three elemental gases, all of them equally and similarly disputed
upon, the case of Oxygen is perhaps the most advanced and instructive.

_ With simple, direct, uncondensed induction sparks, passing through an

Oxygen vacuum tube, every one allows, or will allow I hope after reading this
paper, and severely experimenting, that he does, as he should, get that spectrum
of minute triplets which I have been describing here at length. And every one
also allows, and has allowed it for many years past, that if you send a suffi-
ciently condensed, intensified, jar discharge of induction electricity through the
same tube, the spectrum immediately changes to something perfectly different,
viz., the high-temperature, or line-spectrum of Oxygen, as set forth on strips
Nos. 7 and 8 of our Index Map, Plate LX X VII.

The facts therefore are allowed, and it is only the interpretation of them
which is different with different parties. One side insisting on a different
vibration of the same particles of Oxygen, under the two kinds of electric
sparks, being the only reason of the two totally different spectra; and the
other declaring that with the milder spark, the Oxygen must have entered into
momentary chemical combination with something else that was already in the
tube, but unperceived by, and totally unknown to, its owner.

There is little doubt too that there may be many more infinitesimally small
things in a tube, or extractible out of its sides by electric discharge, than
chemical philosophy is at present aware of. While even with so gross a
matter, as CH in sufficient quantity to give strong spectral bands,—we have
seen London scientists going on for years preparing CO, and quite unconscious
that they were at the same time manufacturing CH with it, even pari passu.
Some particular kinds of gaseous impurity that may be in a tube, adhering to

its sides or otherwise,—I have shown in this paper may be easily submerged by
| greater density of another gas thrown into it. But if that gas be contaminated
at its birth with some other, either not yet recognised by Chemistry, or in too
small proportions to be detected by any existing chemical method,—who shall
help! There may have to be a new chemistry elaborated, dealing with infinite-
simally small combining quantities. But that is something so hazardous to
count upon, that we may well in the meantime accept the varying temperature
vibration theory, as a mere method of classification; and then we shall find that
there is an immense deal yet to be done, in order to collect even the plain and
practical facts of the spectra of the best known gases, in such degree of purity
as they can be prepared in, at present. For with every elemental and permanent
gas, 7.¢., gaseous at all known temperatures and moderate pressures,—there
seem to be three different temperatures under which its spectrum in some

452 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

shape may appear, viz., the temperature of the condensed spark, the simple
spark and the atmospheric or auroral.

With compound gases, there are only the two latter temperature stages, viz.,
the simple spark and the cold auroral; for the high-temperature condensed
spark resolves them instantly into their known chemical components, which
then give out their own elemental spectra. While with Carbon, and every other
similar solid, there is only one temperature stage; viz., that highest one at
which alone it can be volatilized.

To return then to the elemental and permanent gases, as the commplente
system, how little do we know yet of all three varieties of spectra belonging
to any one of them;—not to say anything of each variety, in order to be fully
understood, requiring to be made to appear /i7'st as an emission spectrum with
bright lines in a dark field, and second, as an absorption spectrum, with the
same set of lines but dark in a bright field.

Suppose we take Oxygen again as an example.

1. Its emission spectrum of bright lines in the condensed spark, or jar
discharge has been grandly studied by Kircuorr, THALEN, Plucker, and
Hucerns in long past years, with a most satisfactory cataloguing of Wave-
length places again and again,—and yet it was left for me to discover the
earliest of its ultra red lines last summer. But no one has yet seen either that
line, or I suppose most of the others, as dark, or absorption, lines; though
Professors Liveinc and DEwAR are now working at that subject, and towards
that end very magnificently in the Cavendish Laboratory at Cambridge.

2. Oxygen’s emission spectrum in the simple spark, viz., the spectrum of
minute triplets and a few thin lines, has been set forth in this paper at some
length, though elsewhere, and particularly in London, only 4 lines of it have
been recognised ; but none of them have yet been seen by any one as a dark
absorption spectrum, so far as I am aware.*

3. At the atmospheric, the cold, or auroral, temperature no one has ever
yet seen any bright, or emission, spectrum of Oxygen. But two persons are
said to have recently seen its dark, or absorption lines connected with that very
low, or non-fiery, temperature; and it came about in this manner.

After I had for years and years besought, but in vain, the rich London
Societies, or the Government to make the enormous experiments which are
necessary for the purpose,—these have recently been made in St Petersburg!
There, in connection with the University of that city, M. Ecororr, with his.
friend M. KHAMANTOFF,—so far as we can trust the rather too scanty informa-
tion yet given out,—established a horizontal tube 66 feet long with glaze

*T thought, on the first discovery of 3 of these triplets, that they could be recognised i
Anestrom’s Normal Solar Map as dark Fraunhofer lines, but I delay now either affirming or refuti
that idea, until I have made more satisfactory and exact observations on the Solar Spectrum itself.

GASEOUS SPECTRA UNDER HIGH DISPERSION. 453

ends; filled the tube with pure Oxygen gas at several atmospheres pressure,
looked into it at the near end with a powerful spectroscope, while an incandes-
cent lime-light was placed outside the other end ;—and then, pictured on the
bright continuous spectrum of that light,—they inform us they saw and
measured certain most distinctive bands and groups of dark absorption lines.
These were totally different in both arrangement and spectrum place from any
of the bright lines of either the high-temperature, or low-temperature, spark-
ings already described for Oxygen,—but they were held, nevertheless, to be
Oxygen lines, because they were only seen when that one particular gas, in

'immense excess, was introduced into the tube ; while there was quite lowering

enough of temperature between the simple induction-spark and atmospheric
temperatures, to permit of another kind of gaseous vibration being set up, if
that was already allowed to be possible, between the simple, and the compound,
spark, by reason of the latter’s superiority therein.

The special interest, however, of the St Petersburg experiment, if confirmed,

| depends still further, and more pointedly, on this other observational fact; viz.,

that the dark absorption groups which MM. Ecororr and KHAMANTOFF saw
in their Oxygen tube they declare to be identical in build, and spectrum place,

| with the powerful groups of similar dark absorption lines, telluric chiefly, but

perhaps partly Solar, or extra-Solar,—seen by all the world constantly in the

|} spectrum of the Sun’s light, and so well known there as FRAUNHOFER’s great
| A and great B. While still more recently M. Cornu in Paris, by an exceedingly

elegant method of his own, having lately succeeded in eliminating from the
a (Alpha) band of the same Solar spectrum, both the Solar metallic and the
terrestrial water-vapour lines, found the residual markings so exactly the

| counterparts of the now thoroughly understood geometrical construction of
the preliminary bands of great A and great B,—that he can pronounce with

the utmost certainty for their being all three born of one and the same kind of

| gas ; though whether, after all, that gas be really Oxygen, the world will be

better instructed when other physicists have repeated the bizarre experiments
of the Russian capital, and vouched for the purity of the gas introduced there
into the long tube.

Even concerning Oxygen then, our knowledge is but rudimentary, and in
fragments; while of Hydrogen, and Nitrogen, how very little have we yet seen
of one, possibly two, of the three double phases which the temperature theory

| indicates must belong to every one of such permanent gases ; and all of whose

phases too, our observations in this paper promise will be found replete with
the most exact Natural writing, whenever they be efficiently and sufficiently
interrogated by man.

454 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF >

He eg agp gt 8 a aaa

PROF, ALEX. 8. HERSCHEL’S LETTER ON THE GREEN BAND OF CO, AND ITS
EXPLICATIONS (EVENTUALLY CONDENSED INTO PLATE LXXVIIL).

Dated November 20th, 1883 ; College of Science, Newcastle-on- Tyne.

The chart of the green band’s lines* is beautiful; it is quite a page of the spectrum itself
much more clearly laid down, I am sure, than I have ever seen the tribe of linelets, and I’m
astonished how you can have both discovered and plotted so many perfectly !

You have far surpassed the sight you gave me last, I find, of the CO band, by dividing
“broad” and plenty of the fine lines too, into pairs and triplets. This is a real triumph, that
I couldn’t well believe possible, when i discovered it by trying to recognise your new map in
the drawing and measures that I took of SALLERON’s CO tube’s green band (with five Sulphide
of Carbon prisms) in December Jast; and couldn’t make them fit immediately, until I found
that you had duplicated and triplicated numbers of the lines that I recorded “ broad,” “ winged,”
“united pair,” &c., only, so that there is a profusion of new dissections of the band that you
have managed now to supply for its anatomy! And then Ilo TrIUMPHE! in searching over
the spaces of my “readings” to identify your lines with, I lighted luckily on the key of the
construction, which is simplicity itself, and couldn’t well be exceeded in the exactness with
which your new map reveals it! Lux in tenebris, what a happy and glorious release you have
disclosed to all our uncertainties !

a_i a a a
I grounded first on this palpable feature of themeasures [| * | ise | [ile | [\ |,

that while the “leaders,” and twin-cub followers open out regularly all down the range, it is.
not so between the twin-cubs and the leader neat following them, so that the distances a remal n
constant, varying from 0159 revns. to 0172 revns. in my readings without any symptoms of
expanding, as far as my list went; so that these “leaders” are simply accompanied on the pre-
ceding side by a companion pair that is at an invariable distance from them! In other words,
the “leaders” form a scale-in-chief by themselves, and a little distance preceding it is just such
another scale of fainter twins, overlying the former scale.

How will this relationship, I asked myself, be borne out 7m the thronged part of the band
between its front edge and the “ crossing ” point, beyond which point as far as the “ green giant,”
it is as plain as the alphabet ?—The answer was to take up the constant distance a between any

* This was merely the raw record-slip taken at the Instrument, in the manner which I specially arranged for all the
Spectra described in this paper.—C. P. S. ;

GASEOUS SPECTRA UNDER HIGH DISPERSION. 455

leader-line and its precursor shadow-pair from any good specimen conjunction of them on your
rap, and to apply it successively to all the leader lines from near the “green giant” backwards
across the crossing-point and on into the thick of the mélée that precedes it, right up to the first
edge of the band. The result was, to my joyful surprise that it accownts instantly, and in toto for
every single line of the band laid down on your map! The band is simply two exactly similar
single-rank line progressions laid over each other displacing one of them slightly on the other;
and while one consists of single strong lines, the other is formed of fainter, closely double ones.
You will see this by the enclosed card strips* along the top edge of one of which your map of the
band is exactly copied, while under it the members that compose the close double, or fainter series
are prolonged so as to produce a linelet progression by themselves. On another card the rest of
the band’s linelets are figured, also in a single-ray progression of (in red ink) strong single lines ; by
applying this card with its left hand leader at No. 5 line of the natural delineation, you will
see that it includes all the lines not prolonged downwards or abstracted from that stripe to
form the partial stripe of duplex lines; and by then shifting it leftwards till its beginning
coincides with No. 1 line of the natural band, you will see too that it then exactly covers all
the duplex line series of the natural band.

Besides the two constituent bands’ precise resemblance to each other, there is also this
link of connection between them, that the ruler of the following band is not placed anywhere,
| but on Wo. 5 line of the foremost one. And again there is this simplicity about the single-
| rank or partial bands themselves, that their intervals are quite distinctly an arithmetical
| progression of spaces denoted by the series of natural numbers 1, 2, 3,4, &. I have plotted
| in, under each (singular and duplex) portion of the band a ¢rue simple progression of this kind,
| so that the eye can judge how nearly each of the two tributary bands satisfies it, and there is
no question, I think that it is, with some very slight disturbances here and there, the simple
tule of formation of them both? Instead of being, therefore, a linelet band of the most
curiously involved compleaity, as it at first sight looks by its “ crossing” lines and close pack of
crowded lines near the front edge, the ruled CO green band is really the very simplest in its
| mode of construction that I think has yet been met with in Spectroscopy! The way in which
| your sharp resolution of the two “crossings” lines themselves into a minute triplet and a
_ minute doublet respectively agrees with the conjunction is by itself a wonderful corroboration
of the structure. But without the clear and precise resolution of all ats lines throughout with
the most accurate autographic measurement that you have effected, it would evidently have
been quite impossible to recognise and establish it in its microscopic mixture! A good
example of the powerful discrimination that you have used upon the band occurs in its very
first line, which I had noted “ BROAD,” only, in my little sketch of measurement, but which you
| have mapped as a pair Nos. 1 and 2 of the band, just as accurately placed as the other equi-
vocal looking linelets of the band are all clearly and exactly broken up and divided into their
proper places in the dual band.

The displacement between the band’s two parts is 10 (1+2+3+4), unit spaces of the
structure, which is neither an indifferent interval nor an indifferent number of unit-intervals of
its structure; so that the two parts can’t be described as two independent overlying bands
belonging possibly to two different gases. But yet the duality is singular, as if either sever-

* These very ingenious card strips of Prof. HnrscHEL’s, being unsuited to beok-illustration, —it occurred to me, to
prepare Plate ‘LXXVIIL, including them both and the manner of working them, but in one statical view. This Plate
afterwards had his rapoovel. though with a proviso touching ideal accuracy, which he has touched on in Appendix II.
page 43.—C. P. S.

VOL. XXXII. PART III. 4D

456 C, PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

ance into constituents physical, or constituents chemical, of the CO, was accomplished by the
spark ; and the tetravalence of Carbon wnsatiated by the bivalence of Oxygen, or in other words
the propriety that chemists admit (our chemical Professor, Dr Bepson, just now suggests to
me) of regarding Carbon as sometimes divalent like Oxygen in forming neutral combinations

such as CO, may be the origin of ( y O- =e ¢O- =-O° \ the double structure
Tetravalent Carbon, Divalent Carbon.

of this CO linelet band. At any rate it will interest me very much to see if I can make

better sense now, and trace some similar evidence, of duality perhaps in other “ Carbon ” records

of the CO citron, and Blow-pipe-green Band-lines that I have, distinctly enough measured I~

daresay to tell the same tale if they are carefully interrogated.

A. S. H.

GASEOUS SPECTRA UNDER HIGH DISPERSION. 457

ee NX

PROF. ALEX. 8S. HERSCHEL’S LATER REMARKS ON PLATE LXXVIII, AND AN
IMPROVABLE POINT IN ITS SCALE OF REPRESENTATION.—May, 1884.

| Two distinct “spectra closely resembling each other, together form the Green band of
| Carbonic oxide figured in the Plate LXXVIII.; one of which consists of single linelets, and
| the other of slowly opening double ones, or of linelets coupled together in close pairs. If the
| whole unilinear spectrum is shifted together to the left until its first line coincides with the
| leading one at the band’s least refrangible edge, all its lines fall nearly into coincidence either
| with the middle place, or else with one or other side-line of the several linelet pairs of which
the remaining bilinear portion of the spectrum is composed.

An ideal spectrum is placed for comparison above and below the two component spectra
| of the band, forming an arithmetical series of micrometer-revolution, or of sensible dispersion
| intervals, representing with a suitable scale-unit of measurement, the series of natural numbers
11, 2,3,4,&c. The necessary data for replacing this array of gradually increasing micrometrical
intervals by a similar, more scientific arithmetrical progression having a wave-number unit
| instead of a micrometrical dispersion one for prime measure of its successive terms or intervals,
| was not exactly procurable in the state of the instrument’s adjustment; but the small regular
| differences which are noticeable in the Plate between the two observed spectra and the
| arithmetical comparison series of micrometrical line intervals, are, it may be remarked, of
| exactly the description in direction and in varying magnitude which the provisional substitution
in the Plate of a micrometrical for a wave-number series of successive intervals would
| correspond to, and serves sufficiently to account for. Were such a replacement of the
provisional array by a corresponding wave-number one made with perfect certainty and
| correctness, it would seem to bea safely legitimate assumption to conclude, that the small
visible departures of the ideal from the observed spectra which their comparison together
exhibits on the Plate, would all, then, be quite satisfactorily obliterated and removed.

AQIS. ae

To which I, as the Observer, may probably be allowed to add,—not “ quite removed.” For
wherever there is numerical observation aiming at exactness, there will always be errors of the
observer to some extent. But I must confess I have been well pleased to see the smaller
amount of the apparent errors of observation, when one Natural System of spectral lines is
compared with another, as in the lowest compartment of Plate ;—than when either one of them
is contrasted with the artificial screw-unit scale, as shown /irst at the top of the plate, and then
near the bottom of it; viz., Plate LXXVIII.—C. P. S.

458 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF

APPENDIX ITI.

MR CHARLES F. CASELLA’S LETTERS ON THE PREPARATION AND
PURIFICATION OF SOME OF HIS LATER VACUUM TUBES:

147 Hoizorn, Lonpon, E.C.,

31st August 1883.
To Professor C, Piazzi Smyth, F.R.S.E,

15 Royal Terrace, Edinburgh.

DeEaR Sir,—I am in due receipt of your favour of the 30th inst., and I must thank you
for the kind expressions that you make use of with regard to my Father, as well as for your
kindness in communicating with me on the subject of the Tubes.

By train to-day I have great pleasure in sending you three tubes, viz., the 4th CO+C02
Tube at 0:2” pressure, and the CO+CO? Tube at 0:3’ pressure, also the N tube at 12:5”
pressure—all of which I trust will be entirely to your satisfaction.

This now completes all the Tubes I have had to do for you, and I now beg to give you a
formal note of how the gases in the above tubes have been made, the various processes being
as follows.

Hydrogen, by electrolysis of water. Oxygen I tried as above, but the manufacture of the
gas was so dreadfully slow, that I had to resort to a chemical process, viz., by heating chlorate
of Potass, which I think is the most satisfactory way of obtaining Oxygen.

Nitrogen, by boiling Ammonium Nitrate; of course the preliminary bubblings yielding
impure Nitrogen, were allowed to escape, and only the subsequent bubbles of gas collected.
Carbonic Acid, by heating ferro-cyanide of Potassium with eight times its weight of
sulphuric acid.

Coal-gas simply by connecting the gas jet with the gas receiver connected to the Pump.

CO+CO? prepared by heating crystallised oxalic acid with concentrated sulphuric acid.

All the above gases were prepared in glass retorts, then passed through water into glass
receiver, which latter was connected with the Pump by glass tubes, and a very delicate small
steel tap; the various drying tubes used were—next to the end-on tube a Caustic Potass tube;
immediately next to which was an Anhydrous Phosphoric acid tube: then came a four-foot
pummice-stone tube saturated with concentrated sulphuric acid; next to which was a small
chloride of Calcium tube, and then came the small steel tap separating the Pump from the gas
receiver. Before making each gas the trough, receiver, and everything were thoroughly
cleaned, and fresh water and new drying tubes used each time; a new Phosphoric Acid tube
being used for each tube.

I trust I have made myself clear in all the above details, but if I have not, pray do not
hesitate to ask me for further particulars.

Assuring you of best attention at all times, and hoping that at some time I may have the
honour of being specially mentioned in connection with the preparation of these tubes, which

, |

GASEOUS SPECTRA UNDER HIGH DISPERSION. 459

I confess require the greatest personal thought and attention—lI am, dear Sir, yours very
truly, CHARLES F, CASELLA.

P.S.—Your note of the 31st just to hand. I will carry out your suggestion by using
naked copper wires instead of gutta-percha covered ones, which already are suspended across
my laboratory with a pair of leads coming down to each Pump.

Before doing so, however, may I have your opinion on the following suggestion in
opposition to yours, namely, the various strong and damp fumes the naked wires would be
subjected to, would create a strong oxidation on them, and would not therefore the current,
instead of conveying one gas into the tubes, which gas we already are acquainted with, carry a
variety of “gaseous” all sorts into our tubes.

This is a mere hypothesis of mine, and therefore please take it for what it is worth.

Crag.

Lonbovn, E.C., 13th Nov. 1883.

Dear Sir,—Your favour of the 9th inst. has duly reached me, and I have now much
pleasure in telling you that I am back again in office, having returned last week.

Before being able to say that I am ready to commence vacuum tube work again, I must
tell you that my pump room or laboratory-is without pumps, they having all become spoilt and
broken by wear and tear.

To make fresh ones will take about two or three weeks, they being very elaborate but
exquisite instruments,

Please state how many olefiant and acetylene tubes and at what pressure you would like.

I will note all my chemical proceedings, and also let you have an account of those last
sent, which is as follows, viz.:—Action of Nitric Acid on pure copper filings (turnings), gas
collected in a receiver in water, and communication from receiver to pump, the gas first
passing through four drying tubes as follows, viz.—(1) Chloride Calcium, (2) Anhydride
Phosphoric Acid, (3) Anhydride Phosphoric Acid, (4) Caustic Potash. Minor details, &c.,
were conducted as before, but with the same care in every respect.—Yours truly,

CHARLES F, CaSELLA.

Previous to these chemical operations of Mr C. F. CaseLa, his father, Mr Louis P.
CASELLA, had had some curious experiences with the wires forming the electrodes of his vacuum
tubes.

Platinum wires usually blacked the inside of the bulbs; wherefore he then tried gold,—
the following recommendation of that metal in the Proceedings of the Royal Society, London
(and subsequently reprinted in the Philosophical Transactions, Part I, for 1884, page 51),
having been brought to his notice :—

“Of all metals affording materials for electrodes, gold appears to be the best; its spectrum
is a weak one, containing comparatively few lines; it is an excellent conductor of electricity,
and it is not attacked by solutions of metallic chlorides.”

No sooner, however, did he try this highly commended material than the insides of his
tubes were brilliantly, opakely, and utterly gilt by 7¢, combined with the six-inch induction
sparks employed. He had, therefore, to fall back on aluminium wire and to use that very

thick, or between ;1, and +1, inch in diameter. CaP. 8.
VOL. XXXII. PART III. 45

“7

460 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES.

APPENDIX IV.

SEE THE THIRTY-ONE PLATES, FOLLOWING AFTER THE
PRINTED MATTER.

Viz. 29 Plates, each opening to 18x11 inches, and showing what they contain on a 40
foot spectrum length from A to H;

1 Plate, folding out to 42x11 inches, giving approximate and contracted views only, of
whole spectra, 26 inches long from A to H ;

And 1 Plate, folding out also to 42x11 inches; but showing what it contains on a
spectrum length of 220 feet from A to H; a length erroneously printed in earlier pages herein
as 120 feet only.

APPENDIX \V.

ON THE NUMERICAL “ WAVE-NUMBER” SPECTRUM SCALE
OF ALL THE PLATES.

The regularly altering number of theoretical Waves of Light at each part of the spectrum,
contained ina certain constant unit of length, and called for shortness “ Wave-number,” has been
adopted here, rather than the successive lengths of each of such waves, or “ Wave-length,” as a
practical scale for each of our spectrum pictures—because it gives a most desirable mean between
the oppositely exaggerated views of Prisms on one side, and Gratings on the other. And the Inch
was at the same time employed as the unit of absolute length referred to, because it is not
only British, but nearly Earth-commensurable in the best way; viz., as the 500 millionth of
the length of the Earth’s Axis of Rotation ; and it furnishes also a convenient series of numbers
for the memory.

The method is, moreover, in the direction of its increase of figures, combined with the
universal European mode of writing from left to right,—exactly suitable to Fraunhofer’s now

nexpugnable order of lettering the chief lines of the Solar spectrum from Red A as the beginning,
to Violet H as the end; or from lowest to highest, or Earthly ordinary, to Solar transcendental,
temperatures. Hence “ Wave-number” always goes conformably from Fraunhofer’s A to his
B, C, &e., and from his so-called b* to his 0%, b3, &. While the “Wave-length” method,
with its reversed numbers, leads the Spectroscopists who adopt it—whether in terms of .
French or English measures of length-——to do despite to the memory of their great predecessor
by going backwards with his letters, while forwards with their own numbers; or by beginning
the visible spectrum with H and ending it with A, in a manner so confusing to the rest of
the world, accustomed loug since to invariable procedure from A to H; and also from b! to b4,

in place of the opposite arrangement so recently introduced by the French metricalists.
C. Bas

ERRAT A,
P. 416, line 29; p. 420, line 19 ; p. 420, line 12 ab imo; p. 421, line 20; p. 442, line 19; and back of Plate
Ixxvi. line 4 ab imo, for 120, read 220, foot spectrum length passim.
P, 442, line 12, for frebling vead trebling.
P. 443, line 9, for bright-lines pectra, read bright-line spectra.
P. 443, line 21, for spectrescope read spectroscope.
P, 447, footnote, erase the latter half,

asa @

WiTGe AGE TO THE PLATES OF

MICROMETRICAL MEASURES OF GASEOUS SPECTRA

GENERAL RULES FOR THE METHOD OF REPRESENTATION

ADOPTED IN THESE PLATES.

(1) The Method is Negative, in that Light is represented by
Black, and Darkness by White.

i.

(2) Every straight Vertical Line, whether thick or thin, and
whether close to another or not, within the limits of
eaeh horizontal Spectrum Strip, always stands for a
veritable and measured Spectroscopic Line, or monochro-

matic image of the Slit; and nothing else.

3) Lines in any other direction than Vertical, i.e, whether
a worizonial or slanting, and from either side, or both
sides at once as in crossed lines, also wavy /lines,—are
to be interpreted as Nebulous Shade only, in vertical

bars or bands of corresponding width at the place.

4

(4) Greater or less Height or Depth, either of Lines or Bands,—
is intended, in connection with the amount of ink bye
pended upon them, to typify greater or less intensity

and visibility of such Lines or Bands.

(5) Cones of shade arranged on a vertical central axis, indicate
nebulous bands of pale light, shaded off towards either

side very gradually and delicately.
CoP a 8:

F del T_ A. Ritchie ¢ Son, Photo-lith. 1884

Trans. Roy. Soc. Edin.

|
er)
x
ia
&

PE RE BE IY AOD) | PS || 17 | | |e pee

-- Nat fic ; - |

7

Ht

be RA:

fd

ol

2

S P27 et

record

o
2,
» RSE

Fre

Lets

e

VO
SRL

C

J883.

AL more

7

=

#)

July 3/

(Cont

2

Dor Solar and Terrestrial Gall: Chloride of Sodtunr or Na.) deal

BAND

v
ee
BOC

ORANGE BAND, «
SaR008
ORANGE

ORANGE BAND
i BB OI

RORY

ROOT

BAND.

‘<

CITRON

y2

Suty 28/889. Prismatic Disperstow < 4

*f

J

CPS. obs. ¢ del

Tin eben

Vol XXXII PI.XLVII

MOA
+
orate

Anaxy

and

Slrong 27 than ri Orange. Cand,

x
N

/

fer

breadth and conf lee xt feertness of faze.

i

i

Sete, hat LOD
: Ee Xe | PoeSeSSosos es
Kl ae SOK

Cw very

Vt

The

and lnelets fer clearer

H..
Ways tnerensing ow

1%

Trans. Roy. Soc. Edin. “a

o

CITRON. BAND, Cone2y

eee eM

GREEN BAND,(Gut, “eneledts , Gut falls o f Very Fe

CPS. obs. ¢ del. /

Vol. XXX 4: -PE. XLIX

eee

UE MUMS

HLL THUL

HES LDR

Trans. Roy. Soc. Edin.

ON

CH IN Be

OOY
SX O5 50505

oO

» SSA)

(Cott) Desferseonm = B78

BAND,

BLUE BAND, @entyy Cut they are-all very fated «a

CPS. obs. del]

lene
es
Ci Haely

Vol. XXXII

ae

rot ttr
x PS

L
es:

jealeafa esha}
Lré

ap the Gre

Beae

Low oO

5)
S
N
SS H

echt

llog ether beyond the reg

mao Ee BAND

rd
4 Ml

2

if Trans. Roy. Soc. Edin.

2 82 } ease
OPon | eae Se
a

oo
o +
s oo j =
+ th fy i a 1a cect behets

VIOLET BAND. August 2 , /883.

—_

oT

SL

S25

VIOLET BAND, (Cows

Ver notable band La fee tlm c

age.
Em a
Seteeh as ves

LL

\

Flees

Vol. XXXII

atin,

Wore uneerlea

flere

es

w

LT he: dele

{

.

0

9,

XK

\
OX)

SK

FI ¥
»
RX ‘
Uh
x)
YOOO
SONOS

yA of arte form ol

950

%
xS
RS

SRC
Orese SRR

SS 5
SOR
OR Qo

GYR HAE OD)

D and D oF Sopium. or Na..VAPoUR
AS THEY APPEAR IN DIFFERENT SUCCESSIVE METHODS OF INCANDESCENSE.

Pe eee
ee

_preponder ates

CVS <P i AME.

va TARUENTUNUANOD NANDA

and gucking ty lemunous heat.
oe CONDENSED. SPARK.
Lai f/0

aa
wedesesee

Sharp, solid , bright, clear in absolutely black field |
IN VACUUM “TUBE.

SPS, obs. & del. 7. L. Hi. del. 2.

rans. Roy. soc. Edin.

CITRON BAND. June 18, 1883. Casetat 5 bressure Co

ie a
iy
a o
U +
B
E

Te

Sa)
Task.

CITRON BAND

R 4ug. 18, 1883. Casetlas 5” pressure
00

y a ———— :
49\000 os 4100 =
@:02 8 ¢ | ©. 6. co © 4) oS o-on °
S585 15663 | =a ©
96 6 | 9 6 | = =
BUNCE aS ++ fr LI { attr ioe

CH

mnoc-4

GREEN BAND 2 Aug 70, (883 .Caseltas Crat-gas tube at ;

CPS. obs. ¢ del. / A. Ritch

WOr,AAASIT TI. LI.

Disperston ia A tH Nag nufy ing power yo Quantity
46 |600 46\|700 vole
3 iS) | ° o = (o}

eee | ical sa ro a a ee
_UE SR EERE SEER Baas cH cH nee falcata tet oes PEDEEES fi i fae

850

5 5 8

ee tt ot bchchrtet

wv : Prof Rowlands Grating. Se order., Wuantily Trimary . Abh's Gal

a

rans. Roy. Soc. Edin.

920
930.
+0

Piri!
Oabosh«)

|
wRaeuharah

anf
1) LEGER

710
720
730

i
|

CH

em A

moc

4 Me 4, /8 83.

¢')°

VIOLET BAND.

60 000 a 60 eee

o Oo
on

o 9°
o oO

°o
wo 8
°o

GE

ee TH babstaranate

| B ;
= MARSH VIOLET BAND. 4 October //, 1993. "Vad
| | Alcohol tube and Casetlas soverat

Vol. XXXII PI.LIV.

n
Ue a
SSeS ial lelete sain

34300

a2 9 ([omme)
oO oOo ot AQ
i) to 7

Aan Sanna

HO ATS D.

Trans. Roy. Soc. Edin.

oe

3)000 ——ael200. ee
#28 ees gegs|eese2
99 ° a NN NN oO mM © 9
PTELLE cane Lit aa Pht Ee

¢ Deptt 1883. Sees o.'5 Press. CO Che.

b
4440

— =
— —
— a
— —
— —d
— —
7 a

bb absolute Alauce , theugh perhaps arheps fecr ee differences .
RED BAND, (Contd),

7.0|000 a Zoi100 200
ceeeels Spies 2g
fae east i el eae
|_| a = arty beteectet ee) nt ag em ee eae teense ca

~ —— a eens — = - a

SCARLET BAND, ano ORANGE BAND. Soat-/Sana 20, (868

- l

Vol. XXXII PI. LV,

ee 707. aise pScade tn error as

oo
on
ee)

oo
o on
a n

: U at Di and 25° Pressure, also Dermichels CO elalee Ade: are

Dy LOL ee,

Trans. Roy. Soc. Edin.

Leaderd. CH Orange band comes tr

(Cort)

2)

,5ANp ORANGE BAND

SCARLET BAND

| !

Sudphueree accd, contains 3

Sune neee eeuceeareseea

te

a

ar ve

ORANGE BAND, ALONE, (G22)

YELLOW BAND.

% Sept. 12, 1883

4h 506

but impure

YELLOW BAND, (Gnt2)

Prismatic Des pe

with CH.

Vol. XXXII PI.

ORANGE BAND OF

Cas elias CO , preporedl with weak,

42800 421900 j =e

950

SS
an Dn
(4
edt ess in

PUNTA

frrisheh with Cusettas COtube at O'S Press.

:

BUOSDODESM OR IDI

very bréeght
£5\S00

oo) Oo
Oo a

(i BSS Wnduction Cok
TH: del?

—~

45)000

01 Gye

The previous. parluon refi

O°
=)
-
st

06s

rans. Roy. Soc. Edin.

cs
OC)

[ieee

Drtrrary

YELLOW BAND. (Conta

|

i)

|

CO Citron band prepa

CH Caron band impurity.

“

O:'s- Press.

v

cs

Casetd

CITRON BAND.

2 Soot. 21, 1883.

very fine CO tite ts now Wackened t

CITRON BAND, (Cont#).

XXXII Pd. LVI

45/900 ue
2°

oO fe) te)
oa t+ on
@o Oo oO a on

980

Es. Il eel Ho ai | Hy

= aie

CO+ BO: tube at Prass. O2. and noarly free of CH impurity yseeege
— 46\600 46\700

Oo

w

ww
LI

TE SMM CL Ae.

Trans. Roy. Soc. Edin.

“Green Gtunt!

.

Green CO intruded ivito by ae

Bei We B

| BLUE BAN D,“(Cxe4)

CPS. obs. & del

— primary.

Vol. XXXI1 Pl. LVI,

-der of Spectrum . Mag, porver = geey:

Bess COGihe

soi

Tytlins :

— ae

Mex p-

21, Defiriction supayb.

H

60 Ab

ersto PV

Bids matic Disp. =

Prismatic Disp

frere -

XB

erilérs

flue band of CH bonp ur ely

OI MAGLI,

Trans. Roy. Soc. Edin.

ll

INDIGO BAND. R Seat 29, 71883 Casetlas O'% Press

5 bah bed i
ae RIM LAY
eB ety”

Definction of violet lines camnot Ge b
VIOLET BAND. R Soft, 7 1883. Denuchels CO tube, also Cosel co

Definttion a “ttle betler at beginning , cut fm
VIOLET BAND. © October 1, 1883, Above reheated with same ~

a a —_

Vol. XXXII PI. LIX.

Dispersion = 48° AtH, Maz Jonr-2/.Lines difficutt and becomming |

: vr) : 5
[i a FG a i oe a Po Ff Fai Fes aw Fs fa ei fo
|
I

> platés in Battery, oh Sharks trecreased from 2% 3 long. Definition distressinyubad

CO

ips CHEN so:

Trans. Roy. Soc. Edin.

BSRGESRERe

h 0b. 20° 78835

POUR Wana.

150
°
©
Banas

BD

R

PE

obs

4 del. /

CPS

><
a)
a
>
“
3<
rr)
>

AEH.

60°

—_
—

Ay dro JL.

swmatu QD espers tory

$1700

le

2"
Red

We ty tree ee =

=

1853 .

Ohiber

164

o

NISCARLET ro ORANGE.

TH. del. 2.

Trans. Roy. Soc. Edin.

4/\100

050

tebe .

°

> ‘a F /
fe) 13) =
4 Le} S x ar
x al Fa WwW
N : < :| >
or hc hh - °
J s O 3 L
S ‘1 Oo

ache

| YELLOW ro CIT

42/300

mite Lisperstow

250

Z)
(Cont).

Les

(Cond

be es a Me

);

ah

ORANGE

Press,

ry 2.
1 (Cont

|

PI. LXI,

Vol. XXXII

one

gacenaade

lercuyy |.

“V Mlow

CO begins hore.

is

ORANGE

at (OWL. Pressure.

Casellas H tite

or 2S, 1883 .

SMR LALA

Trans. Roy. Soc. Edin.

wi
hy

E

SSERRERERSESRSERRSSROGEs

‘To © Octiber 29, 7883.
Za 000 0

r

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CPS. obs. $¢ del]

TIN ALEL, 2,

Vol. XXXII] PI. LXIL

a
\

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S Nov,
150
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7
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GLAU CO.Us

& del

TO
7 |000

GREEN

obs

Trans. Roy. Soc. Edin.

ofS.

ee a

|

LXIll,

Vol. XXXII PI.

ay, power

Me

A a oF,

48

Ie =

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Vol. XXXII PI.LXIV,

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a) n eo

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+

Dispersiow = 48°

Trans. Roy. Soc. Edin.

ie j age a
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mates Ecatabtatsttctstte

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INDIGO re VIOLET, sae

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CPS. obs. ¢ del. 1

Vol. XXXI]_ Pl. LXV,

(ey G)
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8|700 5|800 58/900
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G oO
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fi | eee 8 Peporen ies sales es |eaas | sees

ZH. del. 2.

Trans. Roy. Soc. Edin.

December 1883, and January 185% The 18 and

adl ae 050 me 150 2me08 250 aD 350
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wa Pe 7 =e RED H , por reference onty . a
|} December /9, 1883. Sallerons © tube at 01 Pras COMM

CPS. obs. ¢ del. 1

Vol. XXXII PI. LXVI,

Week R Ay “BOE BD
I4- G25 W. NV. Place, Were measured

DEEP

SCARE. ©.

Msi l (LAL, SZ,

Trans. Roy. Soc. Edin.

a sae Bist

Satine eae O.
G Dec./7, 1883, ( GntZ)

1

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© December 17, 1883, Coritinead.

—_——

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\ Decernber 17,4883 CordinueA
cf S.

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Vol. XXXII Pl. LXVIL

24.

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© Dec. 4),

Trans. Roy. Soc. Edin.

SD Dec. 78, 1883, (Cont %)

- 350

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LXVIIl,

Vol. XXXII PI.

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LXIX,

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Vol. XXXII

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LS ee
Trans. Roy. Soc. Edin.

isla any 2130

(=) oo;o | oo = oo oo oo
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= nu nxn NN Om m eae Ve
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CPS. obs. & del er

Vol. XXXII Pl. LXX,

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x Eartiest VY band or light Jercecevadble.
era Spectro scope. ULTRA-RE D.
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RED

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4

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Trans. Roy. Soc. Edin.

=a oe
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MEV, (LOA

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Vol. XXXII Pl. LXXL

RED Group begins.

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Trans. Roy. Soc. Edin.

Vol! XXXII Pl. LXXII,

Ro : mates et
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LXXIII,

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Vol. XXXII

950

the bands

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Trans. Roy. Soc. Edin.

© 4 Fab .

1884, (Conte.

COLOUR:

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Peter

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4 Feb. sh, (88h.

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LIST OF ALL THE PLATES CONTAINED HEREIN, —
ViZ, 29 DOUBLE-PAGE PLATES, AND 2 LONG FOLDING PLATES, AS BELOW. —

RK Sums THIS

VOLUME PAPER’S GENERAL SUBJECT. PARTICULAR DETAILS.
a NUMBER. |. NUMBMBY asi ee Eee 26S eee eee
XLVIII. 1 C i Orange band, and Citron band.
XLIX. 2 IN BLOW-PIPE FL AME; Citron band continued, and Green band.
Li. 3 on a 40 foot Green band continued, and Blue band.
Li. 4 Spectrum lensth. Violet band at the end thereof.

Characteristics of several methods of Gaseous-Incandescence. A single-

page Representation.

CH again, but in
Vacuum Tubes, and
by Electric Spark.

Citron band and Green hard
Green, Blue, Violet and Marsh Vi. bands.

LV. 8 CO Red band and Scarlet band. —
LVI. 9 a ee hues Orange band and Yellow band.
LVI. 10 ID GHC Yellow band and Citron band.
LVIII. a 40 foot Spectrum Green band and Blue band.
LIX. ‘2 length. Indigo band and Violet band.

x Early Red, Red, and Scarlet, regions.
LXl. ar Orange, Yellow and Citron regions.
LXIl. J Citron to Green, region, :
LXIII in Vacuum Tubes, Green, Glaucous, and Blue regions.
LXIV on same Scale. Blue and Indigo regions.
LXV. Violet region.
LXVI. Ultra Red, Red and Scarlet regions,
LXVII. O Orange and Yellow regions.
LXVIII. ] Citron to Green, region. ~:
LXIX Pa Vines ne Glaucous to Violet, region. WN.B.—The Glawcou
coloured Oxygen triplets at 50,630 and 5.
on same Seale. W.N. Pl. respectively, should be decreased a
what in intensity and size. 4
LXX. Ultra Red region.
LXXI. N Red and Scarlet, regions.
LXXII. 5 Yellow and Citron, regions.
LXXIIh. in Vacuum Tubes, Citron and Green, regions.
LXIV. Glaucous and Blue, regions,
LXV. on same Scale. Blue and Indigo, regions.
LXVI. Violet regions.
Long, folding, Index Map, on a very small Spectrum scale, of all the
LXXVII above, and some other, Gases, at both high, and low, Electric
; temperatures; intended to serve as a Frontispiece and useful Key,
to the whole.
Long, folding Plate of Green CO’s extra CH’s green, portion. Full size 0
original instrumental record, viz. on a 120 foot Spectrum length (cl b
LXXVII. 31 H of Fraunhofer) ; with explication of its remarkable double Art

metical Series of construction, by Professor Alex. S. Herschel, « d.
College of Science, Newcastle-on-Tyne.

PLATE LXXVII.

or 30
TRANSACTIONS R.S.E.

rom Angstroms
CoH LHR ERS AdUinS by co

Silex Hep,

RED.

Stlooo

PTET Li reedel

VOL XXXII. ae
=Dpee
0 BS Bee ee ee ee ee eee eee eee eee eee eee eee ees
{
rn =e
< <=
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> o
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. ae s SZ DROGEN; from
[-4
o OO o = a Of Angstrom, Thaler, o.
” 8 fo So yy,
= TS i ERCURY, from
5 > = z4 a A, Thaten, Plucheor, te.
‘a 2S f= Zz o Jer AC Wetts.
Ary B S: ITROGEN from
> IP S33 ee 25 Thaten , Plucher, ¥.
5 ° a Sor IL por MM. batts
F =n)
as
Ww, =% = Y Oxy cen from
Avpr ia © Thaler .
Cae e (a,
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Zo a a
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| 3 = 2 cwa I. on CO.
a, Sameer (7
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zo 5 YDROGEN,
x ese 52 H
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>) 7
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faa) = 2 Mercury,
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_ =)
Bk pve BORER os N,
Our Si ie posscl
t+ 5 Bio xIDE or een
« 1
° OXYGEN,
; on O,
Sovar Guioe. 12 SCARLET i YeLLow —CiTRON
i} _

j

i : 3 ¥

BLUISH- KY=6

coe

ee

a)

PP Viouer. os] Lavences.

zy [vou

62|oe om S| 63/00

6/| G00

BuiuisH,

Skv-Bive, DCE

}
iH
L

$8|o0e Splece
a

62Jooo | 63)00

#

fie

rem Angstroms Setar Map,

OLAR GUIDE.

Z
Air,

AIR, fom as
. per Df. Watts.

CARBON,
prom Thaler .

HyDROGEN, AX
Angstrom, Thaten, Ke:

MERCURY, fom
Thaten, Plucker, %.
Ber I. Watts .

NITROGEN, mac
Thalen, Plucker,
MN. Wate .

oueen » from XQ

Thalon.

SW jtbe) 2) alts

(a2-uvuHosita

Oxyeen, prom
Schuster .

Guibe.

SOLAR

uve)
a35N44N09 wo

fsguntvuadw3at H!IH

HAuvwds

~ “T

9

CARBO -HyYDROGEN}
or CH.

O
CarBo-OxyceEn,

on CO.

CYANOGEN,
on CN.

CTPTTT TTT

7]
Hyprocen,

on H.

° 6zlace 6s|oc0
Cor

Soar

Mercury, 7]

On Hg.

NITROGEN, on NN&
possibly

Biox10E or NITROGEN,

OXxVGEN, &|

on O

"“S3E94NL NANIVA Ni

VulId3ads

SorarR GuIDe.

31dwis vo
Mo

“yYuwds

‘JUNLVYSI WIL

—-——— 4]

PLATE LXXVIL.

oR 30
TRANSACTIONS R.S.E.
VOL. XXXII.

za
° io)
oO Mm
br x
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58 =.
oN
Sy 2 ©
zm 2
oe
4 >
i)
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THe Green CO | Bano’s Becinnince, on tHe Scate-ror Size emp! coven py M.M. Anestrom anv THALEN, IN

PLATE LXXVIIL ss :
anal THEIR Mesures Micrometriques” 7 &753 But TRANSLATED HERE FROM THE

TRANSACT! ace

yo. XXXII. PosiTive, To THe NEGATIVE, MANNER, AS REGARDS LIGHT AND Snape.

eC ee |
THE SAme | GREEN Band's BEGINNING , RESOLVED IN EDINBURGH BY C)

EXPLICATED AS TIWO SERIES IN ARITHMETICAL PROGR LE

| Sums. — = q
TweoRETICAL ARITHM., PROGRESSION, | mxe-l]2| >]

t
rr

===
a
me
35
5-

ae
Se

SPLIT-LINE OPECTRUM PRODUCED UPWARDS.

OBSERVATIONAL, |
YZ NERY Na

IN NEGATIVE REPRESENTATION
EXACTLY AS MEASURED,

Fut Size OF THE INSTRUMENTAL RECorRD. |

MAIN-LINE SPECTRUM PRODUCED DOWNWARDS.

=

¥
| ‘ice
THEORETICAL ARITHM. PROGRESSION AGAIN, [| 5 6
BEGINNING on 5” Line of First SERIES. ‘ 2
PUTT) TU EEE
SPECTRUM-PLACE iw WaAVE-NUMBER een BR.INCH, ‘18 il |

£8,950 44,000

APPROXIMATELY ONLY: |

1 Serit— Se uM ITH
COMPARISON OF it— Line ECTR Ww |

| ERS. obs adel. Main-Line -Speotrum Set /O units’ sack.

— : a, aeameii | ia ti “Tl

See “Recherches sur l (es Spectres des Métalloides, par A.J. Angstrim et
( Ext rait des Wova Acta Reg. Soc. Upsal. ,Ser. Ill, Vol. IX.)
Up sal, Fd. Berling, Imprimeur de l'Université. 1875.

f4goo goo hy,0e0 | Meg Joe Ufjtoe

WAVE N2 SPECTRUM-PLACE , APPROX.
W. N24” Bret. Inch -

PLATE LXXVIII,
or 31
TRANSACTIONS R.S.E.
VOL. XXXII.

T.R.Thalen,

eT CT NE OS A WO A ROR ET: STS

AZZ |

SMYTH

INTO

nS

COMPO NENT LINES,

JNIND) Wee SIE

ESSION BY PROFESSOR ALEXANDER S.H ERSCHEL , Morr 7883.

16

Z

EET
10 /20

49,/00

ETT
90

Oo

POO
130 14.0

49,050

| THEORETICAL

THEORETICAL ARITH. PROGRESSION.

SH LZABSAGA SHERI +I H9H/IOFM +12 +13 +14 + 1S +16 +17 + BH,

SPLIT-LINE SPECTRUM PRODUCED UPWARDS.

ea VA VON,

<= Every LINE,
REPRESEN TATION,

IN NEGATIVE

IMG WIE WANS WIE AS WIR TE, 1D),

Fury Size oF THE INSTRUMENTAL REcorD.

MAIN-LINE SPECTRUM PRODUCED DOWNWARDS.

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XXV.—On Bipartite Functions. By THomas Muir, LL.D.

(Read 16th February 1885.)

1. If a row of elements be taken, and closely following this array, but
separated by a bar from it, we write nm rows of n elements each; and closely
ing either outside column of this square array, but separated by a bar
it, we write » columns of n elements each; and closely following an
de row of this second square array, but separated by a bar from it, we
n rows of n elements each; and so on, passing from the rows or columns
me array to the columns or rows of the next, and ending not with a square
wy, but, as we began, with a single line of elements, we have the matrix
sentation of a bipartite function.

For example, when n»=3 and the number of square arrays is 4, the repre-

2. The ordinary algebraical expression of the function is obtained from the
ata ix representation by forming every possible term containing as a factor
, and only one, element from each array, subject to the condition that
element to be taken from any one array must be in the same row or
column with the element taken from the preceding array, and in the same
column or row with the element taken from the following array; and then
connecting, by means of plus signs, the terms thus formed.
- VOL. XXXII. PART III. 4¥

462 THOMAS MUIR ON BIPARTITE FUNCTIONS.

For example,

b
- d\g i = acgk +acil + achk + aejl + bdgk + bdil + bfhk + bff ;
k
and
ab. (Cdd gti e pat ben
oF hl Se

H(abedtefgh).

3. If the number of elements in a row or column be x, the bipartite is said
to be of the n™ order: if the number of arrays, square or not, be m, it is
evidently of the m'™ degree; and combining these we may speak of such a
bipartite as being of the deg-order (m, 7).

4. The number of terms in the final expansion of a bipartite of deg-order
(jm, 7) is n™™.

For the deg-order (2, x) the number is evidently , 7.¢.,n°~*: for the deg-
order (3, 2) there must be one term, and one only, for every element in the
square array, and therefore in all n? terms, 7.¢, n°’; and if the number of
terms in a bipartite of deg-order (p, 7) be n’~', it is readily made evident that
the number in the bipartite of deg-order (p+1, 7) is n”: hence the statement
is established.

5. Each element of any one of the square arrays of a bipartite of deg-order
(m, n) occurs n”™~'+ n?, 7.2. n”~* times in the final expansion; and each element —
of either of the other arrays occurs n”~'+n, 7.e., n”~* times.

For, one of the former, and only one, must occur in each term, and there are
nw” of them; and one of the latter, and only one, must occur in each term, and
there are 2 of them.

6. The elements of the square arrays may therefore be called secondary
elements, and the others primary.

7. The two lines of primary elements may be distinguished as initial and
Jinal. Strictly speaking, however, either is at the beginning, and the other at
the end; for the definition shows that the order of writing the arrays may be
reversed without affecting the final expansion. Thus

ab phat io 2
CO Gs C= Th Pe
eflh 7 4g\d¢

kl Bite a

THOMAS MUIR ON BIPARTITE FUNCTIONS. 468

8. Also, it may be remarked, the law of formation of the terms would give
the same result if the initial row of any bipartite were made into a column, and
at the same time all the other rows and columns altered accordingly. Thus
the bipartite of § 7 may also be written

ale e agit

bid f aa ghi\k
gh\k alc e
a Jl bld f

if on any occasion there be convenience in so doing.

9. If any two rows or two columns of a square array be interchanged, and,
at the same time, the two collinear rows or columns in one of the adjacent
arrays, the bipartite is in substance unaltered.

Thus

m nq m n\q
a bik Cp 2a b\k 1 |p
Coes ee @ EL, gl

Cay Ge a @ aig 4
k L |p
ia bm n\ ¢
Mia tal gue 2

Ce feet yg

10. A bipartite is multiplied by any quantity if each of the elements of any
one of its arrays be multiplied by that quantity.

11. A bipartite having every element of one of its square arrays a sum of
p terms may be expressed as the sum of p bipartites, the first of which is got
from the original by deleting all the terms of each of the p-termed elements
except the first term, the second by deleting all the terms of each of the
p-termed elements except the second term, and so on.

12. The cofactor of any one of the principal elements of a bipartite of
deg-order (m, 2) is expressible as a bipartite of deg-order (m—1, m), which is
obtained from the original bipartite by deleting, first, the line to which the said
principal element belongs, and then the elements of the adjacent square array
which are not collinear with the said principal element.

464 THOMAS MUIR ON BIPARTITE FUNCTIONS.

Thus in

aS

Ms a/hy hy
Cy |e & e
d\f, te Ss
cs ds|\% Jo Js

So oO
so

we

the cofactor of a, is

and the cofactor of h, is
Gy lig de
b, & ad, | 4,
bp tp delhi
bs ¢s Ag}.

13. A bipartite of deg-order (mm, 2) is thus expressible as a sum of » products
of two factors each, the first factors being elements taken either all from the
initial line or all from the final line, and the second factors being bipartites of
deg-order (m—1, 7).

Thus

hy, he, 0, hh | hy, ky ky

7 he, ene ie Gee a Ue. dy |e, ee,
be Sf Io Ss Gg ji ty Is dy A So Ss

bs! Yo Ys (3191 Go Is 43191 Go Ys

This recurrent law of formation of a bipartite might of course have been
adopted as the definition.

14. The cofactor of any one of the secondary elements belonging to the p™
array of a bipartite of deg-order (m, m) is expressible as the product of two
bipartites, one of deg-order (p—1, m) and the other of deg-order (n—p, n),
the first being got from the first p—1 arrays by deleting from the (p—1)"
array all the elements not collinear with the element in question, and the
second being got from the last »—yp arrays in the same way.

THOMAS MUIR ON BIPARTITE FUNCTIONS. 465

Thus in
hs ky 15| Py Po Ps
hig olen, “Uy| My Ma Me
a, a, M,| hy hk, 1,| m, m, m,
b CY ay Q 6 Og) Ty Sy UW]
bo Cy del|fi So Ja|%2 82 Wel
bz C3 d3\91 92 9s\T3 $3 Us! %
the cofactor of /, is
a, M, Ms M1 My Ms
by Cy d, Cy Ty Sy Uy, | @,
by Co dy h Up) Sq Uy | Yy
bs Cy ds | Jo 73 Sz Ug | % ,

and the cofactor of f, is

or

A, o 4, le Is |a, yy 2

6G, ay My Mh, Py % Te. Tr;
My Ne Po|S, S_ $3

Ms Nz Pz|Uy Uz Us

15. A bipartite of deg-order (m, 2) is thus expressible as a sum of n’ products
of three factors each, the first factors being elements all taken from any one of
the square arrays, the p™ say, the second factors being minor bipartites of deg-
order (p—1, m), and the third factors being minors of deg-order (n—p, n).

Thus
So In| hy Fe |

van | hy

5 ee A hy [Pr
bh a4 jd, a, | Gye Hf | My, Me
bp Oy | 0, lg yg | ye

_ if we decide on taking the elements of its fourth array, is equal to

oS CE aha) ee a a
eral Te fe | Bt Ws Cae raluct. em eid ae 0s
by Cy | ty Jo | = Me by Cp | & ty Ja |M Me

(a)
of. ‘s a» hy ky Oi Gh Pg a hy key hh
1 4/4 CT se HE al aig LS) by | de Bey Sa i erty
by Cy | % fg |My Me by Cg | @ tz Jo | My

466 THOMAS MUIR ON BIPARTITE FUNCTIONS.

or, if we decide on taking the elements of its 3rd array, is equal to

S| k ky
Bes eee Aj! : Pine as ey a ee ho| Py
b ty Gy Fe | Wa te Caos re ei ee
re ps Mae Rs tg Jog |M% Me
B
I2 ky Key | I2 ky ky
a pre hy hy Py by gees Cy Ti Sel eo A, hel Py h .
6G, 4, jy |™m m, US eGo 4 Jy | my ™M,
1% Jo |My My tq Jo |My My

16. Since a bipartite function is linear with respect to the elements of any
one of its arrays, the cofactor of any of the elements (which has been shown
above to be expressible as a minor bipartite or as a product of minors) is
expressible also as the first differential coefficient of the function with respect
to the element in question.

Hence, B denoting the bipartite whose initial line is a@,, a, a3, ...., Qs
the theorem of § 18 may be alternatively stated in symbols thus—

oB
B=2a,5- (r=1, 2, ..., m)

and the elements of any square array of B being the elements of the deter-
minant |q@,,,|, the theorem of § 15 is
B=2an5,- Ce ant ot)

17. A bipartite of deg-order (m, 2) is expressible as the sum of » products
of two factors each, viz., a minor bipartite of any degree less than m, say of
the degree p, and a minor of the degree m—vp, the former being obtained from
the first p arrays by deleting all the lines of the p” array except one, and the
latter being obtained from the last »—~p arrays by deleting all the lines of the
(x—p)™ array except the line collinear with that formerly undeleted in the
p™ array from the beginning.

This theorem is deduced from the theorem of § 15 by combining those
terms of the development there obtained which have a common factor. Thus,
taking the first development of

Jn Ga \ hy he
a, a\f er ge te hy he Giles hte
bn oe da, d,\t jf, |m, m,

Ba Cy dey lg ty ie, WE eS

THOMAS MUIR ON BIPARTITE FUNCTIONS. 467

en as an example in § 15, viz.—

a a ' hy he Pit We Oy sy ; Ay him HM
"by Gd fy} mm mM, ms b 4 fd, 4 fy | Im mM,
b, Cy fal ty Ja |My Me by Cy | ly tg fg | MMe
Pie 8s ky keg | Py G Lie it ee? kK kelp om
Der G, Pay, — ty. gy lay mn, J2* Be ld tie fu ey, aig 2
by Cy |@ ty Jo |™ Me b, Ca |} % Jo | Me

f Gr es re G, a,

a +100 1

bh Gg | dy bh 864 |] a,
Boitasatgel €; Gy) Ott. ee

qh al nH
5, 6 | dy dy
De. Og | Op Oy

| rly, the cofactor of the factor common to the last two terms is seen

Gy O2\ fo Go 4
bh 4) ad, a,
Don lelen beg Yeo

hy A,| Pr % ae EG TED An byl, Bh G2 | helm Y (a)
do\% fy jm mM, & G |a, dg | fj mm & & |d dy % J, | Mm Mm,
| % Jo | M My dy Ole Cy ty fg |My My dy Cp |e by tg Jn | 1 My

Jo Ga|\ hy hy ori kp go) ky ky
lh, | hy hol Pr GH _ % Si\ ty he| Pi He, % Ge K| My he) Pr %
me al am. B Fe a a a b pe —— | — = .
GA Ay(% Jy | Mm My 1% | % y Jy | Mm M, 1 % | % WH fi | mM, My,

72 10 ly} % Jo | Mg dg 6} e [4 Jy | Mg dy Cy | tg Jo |My Ne

‘

468 THOMAS MUIR ON BIPARTITE FUNCTIONS.

Again, by combining the first and third terms of the second development in
§ 15, we should have the case where the one factor is of the second degree, and
the other of the sixth, viz.—

Sr g2| hy to Go| By Ie | So Go| hy he
dy Ms I Ni | hy hel Pr Hh 2 ty % A K\ Ay ho| Pr H era % AN hy hg Po
b, & | dy dal gf) |p mm, b,c, a, dy By an my bh eee ieee
Dy Cy} Cy) %_ Jo | Me (Uy Jo | Ny Ny ty Jo |M My

The case where the one factor is of the Ist degree and the other of the 7th
falls under the theorem of § 13, which may thus be looked on as a particular
case of the present theorem.

18. Two minors such as those of each term of the development in the
preceding paragraph—that is to say, minors which, when multiplied, give terms
that are all terms of the parent bipartite—may be called complementary minors.

19. A bipartite of deg-order (m, n) is expressible as a sum of x” products of
three factors each, the first being an element of the initial line, the second an
element of the final line, and the third the minor bipartite of deg-order (m— 2, m),
which is obtained from the original by deleting the initial and final lines, and —
those lines of the first and last square arrays which are not collinear with one
of the said pair of elements.

Thus
a ay Sas 9

Bee Sty ilad, a5
Oy Mes Me, ie,

2

bi, 205 Oe, . C,
+ gy rey + afi d, & <i “91d ey
This of course is but the result of a double application of the theorem of § 13.

20. A bipartite function may be expressed as a bipartite of lower degree,
in which elements occur that are themselves bipartites, and to which, on that
account, the name compound bipartite may be given.

21. The theorem of § 17 is the case of this where the compound bipartite is
of the second degree. Thus the identity (a) there given may be written also in
the form

By aN Ty ay Oy Mel So Go

| fo Jah fe | 6b 6G |d, a, bh | |dq ad,
ye | A yg | PU a a Ls
b, Fea ahr ae 4 hi hy hy Ys. Tis ae ee :
by Cy |€, yp | ty Ig JM = My dy - Jy | My Ms; 4, jy | Me
tg Jy |My ty Jz |M Me

and so of the others.

THOMAS MUIR ON BIPARTITE FUNCTIONS. 469

22. The theorem of § 15 is the case where the compound bipartite is of the
third degree, and its square array is a square array of the original bipartite. Thus
the identity (a) there given may be written also in the form

So Ga | hy Ig

Ai fa hy byl H _ aE Q:

| d, daft fy | mM M fy 91K,
OM ML) Si #1 '%,

i a
bye,

where sal Vest ton pe
— b) i ?
7 lee caine Ser ba Per |
b, Cy | OA” 1€3.| 6
pee ky (5 A, helm
‘ Ty ay, My a lee My
My fa |M Ne a tot Rak | es

23. The theorem of § 19 is the rather important case where the compound
bipartite is again of the third degree, but having for its initial and final lines
the initial and final lines of the original bipartite.

Thus
So G92\* he
h 1h, Aly bein 4 G& &
b, C, d, dy a, vk m, M, U, 1. P;
bp lg |G ha Fy fg | = My Ve Yel %
where
Jo Go| hye} Jo Go| hy fy
U.=+— th hey ho Ban A i h, he yoo
Cyl Oy lity | yp | a? OTe,

b,|é, | 4, pn Co! 6, ly |p Ja | My

So Io ky ky Jo = % ky ke
V.=— AW hy hy hs oe i EI: hy hy \adieby
by} d, dy|% fy | Me SG | ay dg} fy | Me
by} ey | ty Jg | Me Cy} @ | %, Jo | Me

24. There are, however, other modes of expressing a bipartite of a degree
higher than the third as a compound bipartite of the third degree. These we
obtain by making use of both § 15 and § 17.

For example, by § 17 (or § 13) we have

te Jo | hy he | fo Go| hr Be) Jo Go| he
& a, in 91 hry he 12 it ie Gy | hy hg | Pi fi a, A Wn hy hy Py hh (a)
Reid, dl j ia m, bay dai J, | my, Ms = Tel Ge Gaia Filmy, a,
by Cy ca €o G Je | nN, No b, é} €5 Lg Je ny No Co Cy C2 tp a5 Ny No

VOL. XXXII. PART ITI. 4G

‘ai
’

470 THOMAS MUIR ON BIPARTITE FUNCTIONS.

and by § 15 the cofactor of a, is equal to

Jo nh So Gx | he
eo ees Ay ; Pin el beh [Ry : Py Hh (B:)
b,\/¢@, 4d, 4,|m, Mm, " b,\d, ade ji| mm, x
Bi |e noah dk ig|M Neg Da te, wens Fo tye
and the cofactor of a, is equal to
Jo 92 \* Sr 92 | he
An Ay : | elie a hy ‘ Pi hh (B,)
¢,/d, dy %,| My Ms |ad, dy, Ji| M, Mg ;
C16, 1,.|2,A Np C,{ ey. Jo|%y Me
Hence
Jo 9o\hy he
ay Oe |fi_ ily hel P, % _ % %
Oe de tn |, in, ge Ste Gee eliely
b, 2] le | Mm fg | My = Me Q, N,!S,
where
Jo 92| Jo Ja | hy
= 1 L| Ay A an |h =
oe 4 a Ppa Cy is re a Vide PE a, = a
b, | & G\e, tg| M,N
Jo 92 | ke Jo 92 | *e
ape ee A hy = Tae a fa ee Bi is
Dil ty. ee ae eae cae APS Fee
bole ee eatin 22 Jo| My Mg

It will be observed that, in using § 15 the second time here, it is necessary —
to do so in such a way that each term of (f,) shall have a factor common to the
corresponding term of (,).

25. When we note that in using the theorem of § 17 in the preceding para-
graph, several other identities might have been got in place of (a), and that in
using the theorem of § 15 we might have chosen several other pairs of identities
in place of (8,)(B,), it is clear that we have not by any means exhausted the
possible ways of expressing the given bipartite as a compound bipartite of the
3rd degree.

There is little difficulty in seeing what the theorem is which includes these
different forms in the same way as theorems of § 17 and § 15 include all the
forms of §§ 21, 22; but the formulating of it would at the present stage be
troublesome | see § 42].

26. The expression of a bipartite of a degree higher than the 4th as a
compound bipartite of the 4th degree, and generally the expression of a bipar-

THOMAS MUIR ON BIPARTITE FUNCTIONS. 471

tite of a degree higher than the m' as a compound bipartite of the m™ degree,
can be obtained in a manner similar to that of § 24 by repeated use of the
theorems of §§ 15, 17.

27. A more expeditious and more instructive method, however, is to make
use of the already obtained transformations into compound bipartites of the
2nd and 3rd degrees.

Suppose, for example, that it is required to express the bipartite of the 6th
degree—

hy Ky ls \ 0, Te Te
h, hy 12) My Nz
l

Oh bs | Ceol dreds Mm, Ms. ™

om NS ME LTR Bs say,
by c dy |e, & |e Y %

b & G1f, Sa Ss

bs ¢, G3 |9, Go Qs

as a compound bipartite of the 4th degree. A probable form for the latter
would be that in which the initial and final lines were the same as those of the
original, and the elements of both its square arrays bipartites of the 2nd degree.
Let us denote this form by

a, A, As yy &

P, Q, RS; 8, 8,

P, Q, R/T, TT, B:-

P, Q; Rk, U, U;, U;,

Then, changing both 8, and B, into bipartites of the 3rd degree by means of
the theorem of § 23, we obtain on comparison of the two results—
BPs Ps 6 6) 05 lan, ry, Oy 05 8, | my My 7; aay
STU, 4h Hl mAs A» Ae Ue?
ey Se Ir hy ky k,
6s Jz Jal ly fs
Py PoP. _. b, by bg | my My 1,
22 U, ‘ As A;

and seven other similar equations. But by the theorem of § 21 these may be
transformed into

2 Le
ae CW eae ae cas Gs

7

iP
Si, Ve UF ™, Ny rT Mm, nN, rT; My, Ny Y%
RE eRe! «L, Ugs b

3
On 0, bs By 05 05 Oy OF 6,
eo So Gs és ts Ys

iP
S., T,, Us Ms Ny To My Ny Te M,N, Te
Re PIE Tha, Tet ty cil

472 THOMAS MUIR ON BIPARTITE FUNCTIONS.

which are evidently all satisfied by

b 0. inn tox [y) (oe la, 13)
Py at Ss Me) Sp ey ee ee
: ah n ; Co Jo Yo es ts Is

See a
ahn

The problem is thus solved. .
28. Of compound bipartites, some interest attaches to that special form,
each of whose elements is the cofactor of the corresponding element in another
bipartite, and which, in reference to an analogue in the theory of determinants,
we may term the bipartite adjugate to the parent bipartite.

29. The bipartite adjugate to a bipartite of the m' degree is equal to the
(i — 1)" power of the latter. The bipartite adjugate to

Pm Cennes

Ss GHA

is gia a e or De
A, A, ae
hence evidently
B=, e
The bipartite adjugate to
a, Uy A
bo dy | ey
by Co del fi or Bs ’
bs ¢, d3| 95
is
A; A, A,

Aye, Ape, a, | H, B
AS, If, J, | F, om 3?
UJ, UJ, %9, |Gy,

if the capital letters be used to denote the cofactors of the corresponding small
letters in B,. Now (§ 13)

B3= MA; +dpAg+agAg ,
and

Be=GE, +AFi+mGi ;

and multiplying together the two dexter members we obtain nine terms, which
are exactly the nine terms of B,. Hence

B,=63. a

THOMAS MUIR ON BIPARTITE FUNCTIONS. 473

Thirdly, denoting the bipartite adjugate to
ly

Is

a, d,|h, k
& d)& €

or
C d\f, to Ss Bs,
c; as 19. Go 9s»

1

ry

wn

SS SS

wo

by

-
| =
es
ia
Nise

We el >
&

D
SiG. Dip} Bo Bey iM
Ba GD bGe Ga Ckc 4

and, proceeding on the same lines as in the foregoing case, we have

(§ 13) By=4,A,+ a,A,+4;A; ,
(§ 13) Be=hH,+4,K,4+41, .
Also, by an extension of the same theorem (§ 17),
= dh, M% a ih ih | op Ue a, Hii by abe Bs an ci Be adie aids

7h % a & & bs bo Op dg fi te Ss b, cs dy 9, Jo Js
Multiplying together the three dexter members of these equations we obtain an

expression of twenty-seven terms which are exactly the twenty-seven terms of
B,. Hence B, = Bt

The same mode of demonstration is evidently applicable when the bipartites
are of any higher degree.

30. If the bipartite adjugate to a given bipartite be formed, any minor of it
of the 7» degree is equal to the product obtained by multiplying the cofactor
of the corresponding minor in the original bipartite by the (*—1)™ power
of the latter.

For example, in the third case of the preceding paragraph, the minor

ee ae ae at as
a, —————- » a, =—> —> >> A=. —
DD; Dee Boy ee Si te ts 91 Go Ys
EB, BG, y, 1m 7 Go 4» % Ge %
pacman we oon a" Be a,
Gy, d, dy|hy bh | ;
= hy Bi Wey ey. € es
bp Cy d, i Dae
by ¢; d3!f, Go Ys
= Ash: (a)r 3
and a;h, is the cofactor of that minor of 8, which corresponds with the minor
DI
iD, Be or B;.

‘= F, G

1

474 THOMAS MUIR ON BIPARTITE FUNCTIONS.

31. To every general theorem which takes the form of an identical relation
between a number of the minors of a bipartite or between the bipartite itself
and a number of its minors, there corresponds another theorem derivable from
the former by merely substituting for every minor its cofactor in the bipartite,
and then multiplying any term by such a power of the bipartite as will make
all the terms of the same degree.

This is the important Law of Complementaries already known to hold good
in regard to Determinants and Pfaffians. Any class, indeed, of algebraical com
binatory functions, concerning which we can assert the truth of two theorems -
like those of §§ 29, 30, is ruled by the Law of Complementaries. The mode of
establishing the law is literally the same for all. (See my Theory of Deter-
minants, pp. 141, 142.)

32. If all the rows or all the columns of any square array of a bipartite be
identical the bipartite is resolvable into two factors.

For by the theorem of § 17 the bipartite is expressible as a sum of products
of pairs of factors, and all these products by the datum have one factor in
common. Thus

Gi, ‘whi =) % 4% % , % My ty a, ad,
a: re Er — Mtb ee ad, b, G; dy 110, Mere
by 6, Gy| Gj. 6, 96 ‘
b, ¢, d,|€; € ¢s x 212% ;
An bth Ain | hy
Jo 92 hg} l, Jo Gn Ne]
Jz 93 hm, Ss 93 hg! my
33. Any power of a bipartite of the second degree may be expressed as a
bipartite.
For example—
(OLN NE a> 'b) Ye =( a)
ax ay aZ\ «x ZY 2) ax Coe me ee 28) sted
bu by bz\y ae) | by
CL CY One GY — vn
and Ge by Oy 2 bY tae Oy by ners eg The
ax ay az\ax bu ce 2 | ae abe ace *
z
Z

x
be by bz ay by cy x
ce Cy Cz az bz @ it

THOMAS MUIR ON BIPARTITE FUNCTIONS. 475

34, The product of two bipartites of the third degree may be expressed

as a bipartite of the third degree.

For example—

’
a a 4s GQ, Ay G3 Be). Why 97 ah Nn 4A Hn
b dale > 5
meet. 81 | By 8} 4 He ats ave a, A, as
161 LE) 36)
b, 6, de|f, By 2 82} dy Br 8
mee, d,\ 9; B 6, | ¥ Gy Gy. @
fr Bs me 8! Xs ry ag gp
e Yo
A a.
NX eX) AsX, |——_2— 5
B, Y3 8s

The law of formation of the product is the same for all orders.

35. The product of a bipartite of deg-order (3, m) by the (1 —2)™ power of

the determinant of its square array is expressible as a determinant of the
(n+ 1)” order.

Thus denoting the determinant |), c,d;e@| by A, and its adjugate by

|B, C, D, E,|, we have

Wy Wy A, & a a, a a
Beds «| nity, b, a d, @ _ A dA a aA wt
i\%, % dy N\A A dA eA
h,\ bs; ¢3 ds ¢, POL Meg Vd, K eA
Kyi by Cy dy % kibA «4A GA &A
ay a, he hy
~ Fi) \C.D Bal o—|.BD.E,| |B,C;E,| —|B,C;D,|
9, |—|C,D3E,| |B,D,E,| —| B,C,E,| | ByC.D 5
A,| |C,D.E,| —| B,D,E, | B,C, E, | —|B,C,D,
k |\—|C,D,E,; | |B,D,E,| —| B,C,E, | | B,C,D,
_ _|9 @ mW a a
Fi Bie DE,
mn B GQ dD, E,
hy Be (Cy Ds EB,
Ey Bb, Cyr,” E,

36. § 22 makes it evident that the foregoing theorem is quite generally true

—that is to say, is true when the bipartite is of deg-order (m, 2) (m being of
‘course greater than 3), and when the determinant she is the determinant of
any one of the square arrays of the bipartite.

37. A very much wider definition of a bipartite may be given than that

with which we started. The arrays lying between the initial and final lines,

-F

476 THOMAS MUIR ON BIPARTITE FUNCTIONS.

instead of being squares, may be merely rectangles, the length of the first
rectangle being the same as that of the initial line, the length of the second the
same as the breadth of the first, the length of the third the same as the breadth
of the second, and so on. ‘Thus, starting with a line of m elements, we draw
the separating bar and write » rows of m elements each, then 7 columns of
n elements each, then s rows of 7 elements each, and end with a line of
s elements. The case of this where m=2, n=3, r=4, s=1 is represented by

My, A,
b, 4 |d, dy ad, a,
Da Gs | Bi Ne Gok ea
bs Cs | fi _h debude
mn & & | | m,

38. A little consideration serves to show that almost every theorem we
have given can be extended so as to hold true of bipartites with rectangular
arrays whose length and breadth are different. Indeed, this extended defini-
tion was not adopted from the first, only because it was seen that by doing so
the difficulties of exposition would have been considerably increased.

39. Of course any bipartite with arrays that are merely rectangular may be
expressed as a bipartite with square arrays by the introduction of a sufficient
number of zero elements; and in this way what we have called the more
' general form of bipartite may also be looked upon as a degeneration of the
particular form. Thus the square-arrayed bipartite

8
S\8

Oia, as sd, “a,
Oia) ey) 1B. €
0
0

aS
i)

Q
wo

Se Is Ss
he Go Gein 1G
i. te, 14

S
r)
SS
re)
(Si Mes y tak (iit
|

oO
So

1 m 1

is evidently equal to the merely rectangular bipartite

Aye
b ¢ |d, dg dy
Bs "Oy iy “ey te
Os Cy. Ju. Ja TR ve
h 1 my

1

and has only 2'3:4 terms instead of 4:4°4. Fewer zeros than twelve, be it
also remarked, would make it assume the latter form; for, in a square-arrayed
bipartite, if any line of any square array be a line of zeros, the line collinear
with it in one of the adjacent squares may be made a line of zeros also.

THOMAS MUIR ON BIPARTITE FUNCTIONS. 477

40. A few examples will now be given of the occurrence of bipartite func-
sin mathematical investigations. These will partially indicate the bearing

. The elements of the determinant which is the product of m determinants
1e 2" order are bipartites of the degree-order (m, 7). |

hus
{ | 3
| | fai MOR el Bin Wis Mel a &,
ay tly as a, a, a, 1 2 3 . 1 2 3 ' 2 3
ge Bn a Bo 2 a, Bs Ys
b b b af |b, b, 7b, b, by b5 6; b,8 65) |
1 Bee Cael | Pe see Pal = eee B : B
| | | er B, Wil 2. Po Y2 3, P3 V3
; Oe Oca 6 (hy ol a ae ees Cn" |
: 1. Wo: Ss ee oop 1 %
1¢ ¢ Cc % Yo Y Sea eS Se
1 2 8 1 2 3 , D |
a By wal a Po Qe B, Ys |
@ GM, a, .G, 4a, ity Ly Me

dh, Wy Os hy Oy Ms @, A, as
a By y% a, a By y1 |2, a, By V1 ie
dp Bo ¥2i~i ta Ba Yo [Yo ta Bo Yo \Ys
‘ay Bs Ys % az By Ys |% ay Bs Ys 23
b, by bg by 0, D, bbs 0,
HB n1% UB a Bi |%
ay By YoY; dy Bo Yo Yo tn Ba ‘V2 |Ys
az By y3 as Ps Y3 % az Bs Ye |%

‘a CeeGo G5 O15 So hs Cyto es
HA m|% UB |e% 1, |e,
ay By ¥2|%1 ae By Yo /Yo 42 Bo Y2 |¥s
Gg Bz Ys }%4 az Bs V3 |% ag By Ys *31>

[@y by es} > [4 Bo %g| > [@1 Yo %| * [My ho 4s
has for its first element

&, Ge A|h, k, lL,

a By y1 | & Ly We

ay Bo Y2 ‘Yn Yo Ys

a Bx Ys % & %.

478 THOMAS MUIR ON BIPARTITE FUNCTIONS.

_ The truth of any individual case of this follows at once from the preceding
case by use of § 13.

42. The existence of a notation for the elements of a determinantal product
and a knowledge of the properties of the elements facilitate very much the in-
vestigation of the laws of repeated determinantal multiplication. Some results
of an investigation of this kind are intended to form the subject of a future
paper: the matter is therefore not now entered on. Suffice it merely to
draw attention to the fact that, when using the notation of bipartites, the jirst —
element of a determinantal product is all that need be given. For example, the
last instance of § 41 is quite fully stated when we write

| @, by ¢,| + | a, Bo ¥s oP Yy 2g) |My ep le a, G, 4 hy ky ly
a; By Yi | % % Ly”
dy By 2/41 Yo Ys
a, Bs Ys % % %

The element given on the right hand side is the element of the place (1, 1), and
the element of the place (7, s) is got by substituting for the Ist row a, dg, a,
the 7 row of the same determinant, and for the 1st column /,, 4,, 1, the s™
column of the same determinant.

43. This relation between bipartites and determinants is of considerable
importance to the bipartite theory itself. Thus, we have seen (§ 23) that

Ue

We

My N, 7; LM
@, % d3/a,8,y, P, Py P,|s,
b, b, 05 | a2 Bo Yo Q, Q2 Qs | s,
C, Cy Cz | as Bs Ye R, R, R, | s
@, By By | Sy
My Yo Ys | S2
Ac ap Meg Reg

where

= iy. Bot Dy Bae Bg __ & Ly 2s

¥ Ay 3 ay By ¥1 |e”
by ay By Yo [os

Cy az Bs 3 5

8 Pe
a By y, | a Bi Ys
ay By yo 2, ay By Yo
as Bs Y_!% as Bs Ys

Py

y.
= My Y2 8 &e.
Ta By ¥1 | %
7) Bo Y2 b
As Bs ¥3 %

But these bipartites are in order the elements of the determinant which is the

THOMAS MUIR ON BIPARTITE FUNCTIONS. 479

product of

|, Yo %| » [41 Bo ¥g| > [4 5g | 5
hence, putting

|@, 65 3] =Ay, |¢; Bo ¥3|=Ao» |%1 Yo %3| =As»

we may write the above identity in the form

mM, Ny ry EG Ny r,
A, | Dy a | $1
eee TA AA. 3,
8p | | 53
83

and the like holds when there 1s ay number of square arrays A,, Az, Az,
Z

As another instance, the theorem of § 27 may be taken, which may now
stand thus—

ly As

AG | Ae | 4 9, 2, 4. By A, | Ag A,

|
A, | Ay __ & My Mg | BY, %

Al

but in the case of every theorem we have given regarding the condensation of
bipartites a like simplification of expression is possible. The only points
requiring attention are—(1) that, in forming the determinant of any square array,
we must take for the first row that line of the square array which is contiguous
with the bar separating it from the previous square array; (2) the initial and
final lines of a bipartite are to be looked on as lines of a determinant whose
other elements are all zeros.

44, @uantics are expressible as bipartites. Thus the binary cubic
(abcde vy) is

and the ternary quadric

ax + by? + cz + Qday + Zen + 2fyz
is

45. A notable characteristic of the bipartite expression for a quadric is that
it brings into evidence the discriminant of the quadric—the discriminant, in
fact, being the determinant of the square array of the bipartite. This suggests

480 THOMAS MUIR ON BIPARTITE FUNCTIONS.

for examination how the matter of the invariance of the discriminant will look
from the new point of view. ;

Instead of the special symmetric form which represents a quadric, let us
rather take the quite general bipartite of the third degree

calling the determinant of it its square array A, and perform the two sets of
substitutions

&
|

Bié at Poy + Bog
z= nF + yon t+ yh

NS
ll

== Ba + Ba + a

Y = ME + Ngy! +246

“= M,€ +My + “|
z# =7& +7 +726

calling the determinant of the first substitution A, and of the second A,.
The mere substitution changes the bipartite into

ai dG a Bu Bz Bs OAR

OE IES Seek te

which

>
oe
sae
Faery
oS
es ass

THOMAS MUIR ON BIPARTITE FUNCTIONS. 481

If, now, in this generalisation we make A axisymmetric, put & », C=&’, 1’, (,
and consequently put A,= Ax, we have the theorem that the discriminant of
the quadric resulting from a linear substitution performed on a given quadric is
equal to the discriminant of the original multiplied by the square of the
modulus of substitution.*

* After the theory of this new class of functions had been worked out under a temporary designa-
tion of my own, I got the Philosophical Transactions for 1858, in consequence of a communication on
another matter from Professor Tait, in order to read Professor CayLny’s Memoir on Matrices ; and there
found, immediately following the said memoir, another, “On the Automorphic Linear Transformation of
a Bipartite Quadric Function.” This quadric function I saw at the first glance was a member of the
class I had been dealing with—viz., that of the third degree. This led me to discard the name I had
been employing, and to adopt bipartite instead. Professor Cayuny gives the above extension of the
theorem regarding the invariance of the discriminant of a quadric, but without proof, and not as if
looking at it from that point of view. I think, however, I am correct in saying that this is the only
point in which my paper has been anticipated. Professor CayLey’s notation for the bipartite we have
used above is

(ad, % a, §eyeta yz )
Dt ibaa ibe |
Cy Co Cg |}
which does not, I think, bear on the face of it the exact nature of the two-sidedness of a bipartite of
the third degree ; that is to say, it does not imply, as

Si Oe
dy, Gy |

does, that the function is equal to

(aye' + by’ + ez/)e (yx + Any + gz) a0’
either < +(agx’ + byy’ + cg2’)y or < + (0+ bay + bg2)y'
+ (ager' + Bgy’ + C52')e + (6% + Coy + Cg2)2’ .

It may be of interest, as another evidence of the usefulness of bipartites, to remark here that the
“ Memoir on Matrices” came opportunely for another reason. The new instrument I had got hold of
seemed as if specially devised for dealing with matrices, and I immediately succeeded in proving
Car.zy’s great theorem that, if m be a matrix, the equation—

a-M b é
d e-M if =)
g h k-™
is satisfied by
@ @ @))
M= id e #
- Gy te AN.

This proof, with its accessories, has been communicated to the Mathematical Society of London.

VOL. XXXII. PART III. 41

-

482 THOMAS MUIR ON BIPARTITE FUNCTIONS.

46. A continuant is expressible as a bipartite.

Thus
Peres sp?
1
aoe 7 POE ae Maslin SR eet
1 —1 gi oil
=—L- |,
i
Phe inn alt
ama a bis ie hc Meat
ari oi) a = a
i MS ie
and more generally
pl a
Pole toe ete
1 , SLE Gin “Gh
aaa le eg
—-1l is

This mode of expression seems more natural than the determinant form, a
continuant consisting essentially of positive terms, if the elements be positive. —

All the known theorems regarding continuants- flow with the utmost
readiness from the properties of bipartites.

(i4s8°4)

>

XXVI.—The 364 Unifilar Knots of Ten Crossings, Enumerated and Described.
By Rev. THomas P. Krrxman, M.A., F.R.S.

(Read July 20, 1885.)

1. The 119 subsolids (marked ss) and the 244 unsolids (marked ws), of these
unifilars are here arranged in lists according to their flaps. F, is the num-
ber of flaps of ¢ loops upon a knot; and the headings of the lists, as, e.g. I,
F,=1, F,=8, describe so far all the knots in the lists. Thus in ,,I each has
one 2-ple flap and three single ones. After the number in the list comes always
the base on which the knot is constructed by the rules of my paper, XVII. in
vol. xxxii. part ul. of the Trans. R. S. EF. ; and the reader who has that paper
before him will find it easy to draw any knot on its base, nearly always there
figured, by the first given flap, which is the leading one of the knot described ;
thus in ,,J the first written flap is the double one, and in ,,P, F,;=1, F, =2, it
is the triple one. ‘The leading flap of a subsolid is always followed by a colon.

It will be seen that no two subsolids nor unsolids have the same description.
A flap AB, CD is generally given by its collaterals AB only ; but the coverticals
CD are added when required for distinguishing the knots from each other.

To me it appears that this tabulation of these knots will be more useful
than the engraving of the figures; for the student who draws a 10-fold unifilar
will hereby more readily satisfy himself that it-is found or not found in my
census, than if he had 364 knots projected before him, in the manner of the
plates of my former paper. One solid knot makes up 364 unifilars.

2. I am indebted to Professor Tarr for the detection of several bifilars which
Thad passed as unifilars, and for the addition of four to my list of unifilars, —
namely, ,,B.21 ; ,.D,17; 1,30; and ,,I4,8; and I may obtain from him farther
contributions before he has performed on the figures all his surprising feats of
twisting, which add a charm of conjuring to this curious and difficult inquiry.

The abbreviations which mark the symmetry are those used and explained
in my paper above mentioned. My linear drawings of these unifilars of ten, as
well as the more numerous figures of the unifilars of eleven crossings, will be
found in the archives of the Royal Society of Edinburgh.

I have to acknowledge two omissions in my census of the knots of nine
crossings. One is that of the bifilar ,Az? referred to as a base under ,,J. This
ought to have been formed in art. 55 by drawing from the point ¢ the flap 63,44.

The other knot omitted is a unifilar (,Av?) which should have been formed

VOL. XXXII. PART III. AK

484 REV. T. P. KIRKMAN ON

by drawing in art. 53, in the base under 7, the flap 35,44. But no unifilar of
ten crossings can be made on this ,A7”.

3. As Professor Tair excludes all compound knots, 2.¢., all that can be cut by
a closed curve in two mid-edges only, the name of a fixed flap ought to be given
to every flap whose deletion lays bare such a compound, @¢., such a section
through two edges only. As the deletion of such a flap is forbidden, so must
be the drawing of it; and it cannot compete for the leadership with a flap
drawn or about to be drawn.

A correction is to be made also in (2) of art. 27, which ought to stand
thus :—

(2) If neither e nor ¢ be zoned polar, but be () one zoneless polar and the
other epizonal, or (b) one zoneless polar and the other zonal, or (c) one epizonal
and the other zonal, only one resulting configuration is possible: in all other
cases, When neither « nor é’ is zoned polar, and not both are asymmetric, two
and only two configurations can and must be made by the above variation of -
posture of the charge.

In my plates in volume xxxii. part i. a few errors require correction.
In Pl. XLI, for ,H; 8,10; read ,H; 4,4,10: im Pl. XLIL, for ,By, 18; read
oBy ; 8,10: for Db; 4, 14; read ,Db, 4,4,10: for ,Ch, 18; read ,Ch; 4,14:
for »Dk, asym. ; read Ds, Moz: after ,D/ and after ,Dm write 18. In Pl. XLIIL
under ,G/, for asym. write 2z0. Mox. Het.

Postscript, July 13, 1885.—This day I see for the first time that when the
problem is to construct, not all the knots of ” crossings, but only the non-
compound unifilars, in which the tape passes over and under itself alternately
at successive crossings, there is no need to discuss at all marginal dissections,
nor marginal charges, nor any use of bifilar bases. This is shown as follows :—

Let K,, be any non-compound unifilar of 2 crossings alternately under and
over all through the circuit. Going round the circle, plant at every mid-edge
between two crossings a (lot on the right of the thread.

Every flap will have two dots, both inside, or both outside, or one inside
and the other outside of it. In the last case call the flap odd; in the others,
even,

The following theorems are easily proved :—

Theorem A.—If K,, above defined has an even single flap (of one loop
only), it can be reduced to an unifilar, solid or unsolid, of 7-1 crossings by
shrinking up that flap to a point.

Theorem B.—If K,, has an odd single flap, it can be reduced to an unifilar,
solid or unsolid, of n-2 crossings by effacing the two edges and the two
summits of that flap.

Theorem C.—If K has a double flap, of two loops, the two terminal con-

UNIFILAR KNOTS OF TEN CROSSINGS. 485

tiguous loops of a (2+7)-ple flap (¢>0), the knot can be reduced to an unifilar,
solid or unsolid, of 2-2 crossings by shrinking up those two loops to a point.

It is evident that, if any clear definition of a leading flap and of a fixed
flap be made and stuck to, the constructing converses (easily defined) of these
three theorems must completely solve the fcllowing problem :—

The non-compound unifilars of 2-1 and of n-2 crossings, alternately over
and under, being given, to construct all the unifilars K, above defined of
m crossings, without risk of repeating a result in any posture, or of making a
plurifil knot.

All that we have to do in reducing K, is to do that at a leading or co-leading
“flap. All that we have to do in constructing K,, on a base, is to see that we
do it by drawing or completing a flap which shall be the leader, or a co-leader
on K,. And we shall of course define that a plural flap leads any single one.

Thus, by theorem A, ,A (vide Pl. XL. vol. xxxii. Trans. R. S. EH.) reduces
to ;A, on which it is regularly built by its even flap.

By theorem B, ,A reduces to ,A, on which ,A is properly constructed by
its odd flap.

By theorem C, ,F and ,G reduce to ,A, on which by a double flap either is
correctly formed.

By these little examples the constructing converses are plainly suggested.

This appears to make an end of the puzzle of unifilar knots whose crossings
are all through alternately under and over, so far as their construction upon
lower non-compound unifilars is desired, as a preparation for the curious
transformations and reductions by twisting of Listine and Tair.

I fear that my distinction of subsolids and unsolids is of little value, as a
subsolid can often be twisted into an unsolid, and vice versd.

I have had theorems B and C for nearly a year. Had I obtained theorem A
earlier, my tasks on the unifilars of 8, 9, 10, and 11 crossings would have been
much easier, and under less risk of error.

The simplicity of the three theorems is provoking enough, as usual, after
the labour spent with clumsier tools, which looked so much more learned.

ioe 3. ss. .C; 63,43: 43; asym.
p= 4 03,88: p ;
J. » ” 54,438: 3 ”
ee: ses 6, , 5843: 2p. Mox. Het.
2. ss. gAg; 55,33 2z0. Mox. Het. 7 43.53:
3. ss. ,Ap; 43,54: asym. goes ADE 53,53: 43; asym.
sin One <5 OA Oo 55
ae 10 ele Gta ch: A
a 11. , , 4348: 2p. Mox. Het.
He ss. A; 63,63 : 2p. Mox. Het. ley ps, Os OES -

2
Bees, 60,04: 53%; asym. 13. ,, ,M; 4448: 2zo. Mox. Het.

486 REV. T. P. KIRKMAN ON

14. ss. QU; 54,33: 44; asym. 20, ss. .G; 54,43: 44; 43; asym.
15. ,, gW; 43,54: 43; ns Bhoce to yyip, GODpO Le, Doenoe
16.0 34 3. aado see ade . 22: 5° gl gb4: 545,53.
LT cbgiiced St ieee 2p. Mox. Het. 23: ies Lp DOL eon EA orion é
IS. 45 3" oa esbees Moz. 24, ,, P; 54,53: 44; 43;
1D; ew pe ae 2p. Mox. Het. 25. 5, g@; 53: 53; 43,54;
20% og” ere i! 26. ,, gh; 55,43: 64,43); 53.44; |
DY Oreipe haa Moz. Zi? yo ype ODsUOR MOO Oe Moz.
aoe 14, gates6ae Moz. 28)", 11495408 HGR E Bae -
23. us. ,A; 53,63; 33; asym. 29. , 4 5453: 535 535.) sya
24: 5, eB; AL; 33; s 30... > 5, 68,40); 63:5 55 ee ee
QDs iN ag Geo. os © 31. -,, V5, 63,582 :63.5 Aas Moz.
2G. Se Rotor oor ys BQ. 5) — a» Oastog bon aan
Zils 4, 6D, 405 p05 i 2p. Mox. Het.
20-5 gl; 10s oo; \ Bas, 55) yy Os Oona asym.
Zo: 74, gk oes oor i 34, ,, X: 53,54: 538 Aa oee es
OU 5 (eA Wog ous Moz. 30. , 4 63,44: 48; 435 _
S15) 4h AS. OBE 13385 r. S620qur ing 638,047 Sais
D2. 4), CsG3>) Das asym. a7. 4, 4 63,44: 48; 43; 5
Dos he teenth IO aL Ps 38. , ,, 5444: 44; 43; ,
Oki” 36% DEbo 433 ne 39. 5, Aa; 541-545 43°obeeee
DD ei eNO ata = 40. ,, Ae; 64,435.65; 4am =
36. 5, aA; 585 53; 2p. Mox. Het: Al. ,, jAd; 64437635 4355 =
AO. 4! ly) 44S 1S i ee
be! 43, ,, gAe: 74335) 733 He E
t 44. ,, gAd; 65,33: 63 53a
ae AB. hy) yg BBA 5S 4Seuee
ss. ,A; 63,64: 64; 63; asym. 46. 3/0 gAjf;00;83:; 53 5-435 ee
ia poy OS,04-0055 boc 4 47: 4, Af; 6438: 635 438; -:
pie ent OO peo ie gh AS... SAG: 73 t tose oe Moz.
ie od, DDO. oe oe + 49; ape, DOA? Domoer
3 6p OSU: oasou: uae 2p. Mox. Het.
» » 40,64: 64; 43; 3 50.- ,, Ah; 68,54: 63; 58; asymn
5 VDE Bajb0 25353" if DIF 4 4 Ad Seetoor a
yy yy JOB DA RSS IoS:: F 52.) a8, (Ei; Tos eeu roas asym.
» - ») wets sb4: AB; 4 53. ss. gAt; 55,43: 54,33; 53,44 ,,
9 Oaspet DOs Adda 9 54, ,, gAw; 54 54; 48.44; ,
» 43,54: e 55. , gAv; 6433: 65; 465
» gl; 60,400-ba5 Dos < 56. , Ba; 64: 64; 43; 5
, 68: 54; 53; 3 57. us, ,E; 63,53; 54; 335 aay
» ». eiot 00. pos ; 58. , gi; Gog at4 37: F
; 63,58: 53; 43; a DO, 4, ~O: bade 456 Ba5 Fe
» » OOm aes 3 60. 4, gh; Daiaos 30. 6
3: 64; 43; bs 61, |, ., Soh verses: 4
8. , , 58: 44; 43; 3 62. 05, 9 35385 435 Sa ”
(9. 4 44: bo 43. z 63. , .Q;-445 43; 33; .

ONO oR oN

eo
oR AN ESS

——

OU
oo

Se

a
Sar
ot

gts fo5, Fos ool; Moz.
Pa) As ok ook asym.
3 (go; 69; 53; 335 ,
Ds (035 635339 2p. Mox: Het.
» gU; 63,43 54; 33; asym.

Py a sO OB. Soars ¥
ee PGACHOD = be $30.5 x
Py; 025.63 5°43 ; ¥
Pape o4 3°50. 5a: x
Pee, 64;°535'43: ¥
aia (83 te, 43; ,
mee “Op O04 5°53: F
Peete pies ae,
» gh; 68; 44; 43; f
Bee 100; a0. dos 220, Mox. Het.

Sia; Goe G4 54. 53:

UNIFILAR KNOTS OF TEN CROSSINGS. 487

gA; 53; 44; 43;

”»

10D.
F=4.

asym.
» D4: 54; 54; 54:

2p. Mox. Het.
s<G; 63: O4; 53; 44; asym.
mPdos o> 5a Oo" 3
mp os 00ero4, abo 53k,
gl; 638: 63; 54; 54; ¥
f +Go:Ge" 55; 53: x
» 04542545553: 53;

2p. Mox. Het.
gb; 63: 64; 55; 53; asym.
pe oae- Oe bo AAs
mp u0e. Gay of: 45:

3s; 53: 53; 44; 44; 2p, Mox. Het.

, 03: 54; 44; 43; asym.
EV bo 5 60 Ode 5S 5 -
;, 63: 655 04; 43; :
» Ode 05:43; 33; ,

. gb; 5d: 54; 53; 48;

g¥ ; 54:54; 53; 48; Z
gAb; 65: 64; 53; 43; .
74: 74; 73; 43; :
PAC OO? Lon 4e -
He 00 200 * 0a Ads F
sAe; 64: 64; 63; 63;
2p. Mox, Bet.

bo bo bo
OU

oom

b> bo bo

2 C
V0.

42,

st

bo

oN)

bo

4,

an

Ss.

us.

us.

sAf; 64: 63; 55; 53;
gAls 64:64:63; 63; 2,,
gAv; 63: 66; 63; 44;
2p. Mox. Het.
e thectocl ton 445 SNioz.
» Joos 00% 533. asym.
xOGGor, 45 :-) a,
gAws bbs OF: 54 43.5 15
ie (4s 535 TF
wae Oo +555 55% 53 :
2p. Mox. Het.
» 04:54;48;43; Moz.
sBf; 65: 64; 53; 53; asym.
387; 55:55;55;44; Moz.
3B; 55: 54; 54; 44;
2p. Mox. Het.

. gsAw; 75,43; 74; 43; 33; asym.

eae: Wey 40 38 | a
gAz; 65,33; 64; 43; 33;
», 00,384; 64; 43; 33; ,,
3By; 76; 76; 43; 33;
plmlGGr Oar 0o 5 44. f
Sek hoa Log 44.5 3
go ; 66; 66; 33; 33;

2zo0. Mox. Het.
guyoo; DO donee: Lay,
gAj; 64: 63; 54; 43; asym.
» . 00,44: 54553543; ,,

1
An; 55:65 68; 43; 48;
2p. Mox. Het.
eRe: bo? 6D “6b; 55; 58> Moz,

Ri gb! 62 i160 3445 Sor,

REV. T. P. KIRKMAN ON

us. Ac; 54; 54,33; asym. 33. us. Bk; 66; 65; 65; Moz.
» gAp; 54; 54,35; 5 on, . 9bl; Go: 65° 54. asym,
i gbF 3 lage: b 55 30, 4, poms 75; Yes 7de © sao
» 44;63; 3. 36, 3; GBP; Gos oe oon 7

iP pbs; Baas £ OT: 4) tl” Rote aoe oak
>i op Abeaoe 3 38. 5 gbgs 166: bo oe ¥

x gy Aas 35 Moz. 30. 5)) Gbes O&= as ape asym,
5 /GbRS5y 5 40: 5 tp Se bose ™

9Ck; 64; 43; asym. Aly gts 16. ao gae
pls Was as : is 42, , gbv; 44; 54: 53:

See saree ee Se

eS et pe
Le ae)

Aa. 3; Gee GOs) Ga so. .
oH. Ae MS? Seated Sas e
45. 5 bw; 44: 54: 43- i

Py=1; F=2. 46, ,, -) 8528 ee

us. .M;54;55;53; asym, 47. ,, Bue; 55; 54; 33; -

» » 65;63; 53; ss 48. Cd; 44; 65; 43; ;

gNG (2; Woo Moz. 49. 3, » (6A8: 43-233)

y glvs De noo. OOF asym. DO. 5) ay) eee rOoe eae s

y » O04. 63543; f Ol. 4 9Ces 10335 40" Bor s

» 99; 64; 53; 44; . 52. , , 44; 65; 48; :

ol ; 64,44; 63; 43; - De: yee ih" Dee Gor aepe P

Fie seit Seesyoito pp Moz. " 54 ,,. 9Cm; TA; 7833-44" Moz,

» oV; 64; 54; 43; asyn). DOL / T4; 78,Ad ee

DO. SO ee eor ip 06. ,, On; 64,44; 53; 44; f

11. |, 4 Wsobsbas 43: - 57. yo yt vbaghe be, ame is

12. , 4. 54,64;5454;43: , 58. ,, jCps b4e6S- 53: asym.

13. ,, 9X;55; 44; 44; ‘ D9, |) Wb; 44.7555 .50- 5 aaa

14. ,, ,Aa; 54,54; 54,44; 43; ,, 60. 38 Gye (66255o-"33 2. ae
1D. 9 | ago ba aBe aw G1" 5 SDR SEreoe sae asym.
16, ,, Ac; 54;64; 63; = 02905) gDms T4276 bas a
ie 3) Spe ee As eM

18. 4, gid $747 742750, (4s n mf

TOS OS: “ly, © 64364 (65 es ; <i

20. ,, gAf'; 64; 64; 53; ; F=1; F=3.

21. ,, Ag; 65; 64; 44,54; » us. oli; 64; 65; 53; 53; asym:
22, 4 55; 545°54; Moz, » Ah; 65; 63; 54; 44; |
3d. , gAn; 64; 44; 43; asyl. » » 803; 55; 68; <u
24, ,, Ar; 64; 64; 43; s » gAt; 65; 64; 58; 5onuem
25, ,, As; 74; 74; 43; » » » 84; 55; 54; 500mm
26 ,, At; 64; 65; 43; i » glk; 75; 74. 48. 43am
27. gAu; 74574; 53,73; pAl; ‘75; 74; 68; 537mm
28. ,, oAv; 64; 65; 53; » pAw; 66363; 63; 54am
29, Ba; 55; 54; 54; 9 , » 64;65; 54; 53,54: ar
30, 9Ba; 65; 64; 44,34; —, 10. ,, ,, 64; 65; 54; 53,58; 4
31, ,, Be; 66; 645 44.63° ‘. 11. ,, ,Aw; 74; 74; 78; 54,44; ,,
32. , » ‘(503 ba? 64; Moz. 12), 6» )| 14s T4378: Soe

Pe CNS

DO OMIAR SM

Su cog tar

CISD

UNIFILAR KNOTS OF TEN CROSSINGS. 489

ieeus, ,Ax; 75; 73; 73; 54; asym. Loss. ,Y 3 bossa 53 _ Moz.

mie, ,A7; 6b; 65; 435 43; _,, 17, eZ; 54; 44; 53; és

mm , , 14:55; 54:43: ,, 18). 4) 62464583 2970. Mow Ect.

Mme, ty 005-645 43: 43: ,, 19. , ,Aa@; 65; 44; 55; Moz,

Me, be; 55; 55; 54; 53; 20). 5, gAc; 76; 44; 73; asym.

mer, , 65; 63; 54; 54: ,, . Clee 0) (4544s Toe

mato, ,, Bf; 54; 54; 65; 63; _,,

eee, 5 055 535 6D; 63s. ; L

eee bg; G5; 60; 53: 53; ,

ee) 4. Obs G4: 53% 53%. ,, Peary == 2).

meee 6, «= 642 163: 55> 543 » ,.

Pe «Cf; 74; 75; 44; 33; _,, ‘ :

emi sees > 2, , JK; 65; 64; oe :

Pome, » 95; 65; 63; 33; _,, epee gs

27. ,, Ch; 15; 76; 65; 93; , NS i al ee

ceme, (07, 425 76; 765° 735) | ,, A ieeet ce beakes- rj ‘

Pome, »,. 91;.87; 835 33; ,, Pak Ia ile Eas Pate

30, Ave; 54; 65;°63; 43; , epee Hee,
» g¥ 365; 54; 55; 65; asym.

Se hos tasoo7 45:
gAn; 77; 44; 77; 33; Moz.
gl; 73; 74; 54; 53; asym.

1. us. J; 55; 55; 54; 54;

-

o

i
oS eX

us. ,A; 64; 64; 2p. Mox. Het.
a é . MI.
» gC; 64; 54; asym.
» gD; 54; 54; 2p. Mox. Het. Kop) EO,
4. ,, X; 54; 44; asym.

ho

1, us. ,E; 75; 74; 54; asym.
» 7; 65; 65; 54; Moz.

bo

F,=2; Fy=1. oN.

us. .E; 74; 74; 44; asym, F3=1; F,=1.
me! Oo: 64: 65.65; ,,
Pee, 005, 6463.63 _,,
Peg! 7 O45. a0 5 Od, :
sG; 65; 54; 43,63; __,,
meow Op wos: 43655. ,,
Pe Ot; 545 54; i
» gl; 65; 64; 53; :
» of; 54; 54; 58; Moz or:
» gM; 95; 54; 43; asym. eee GE 8
aR; 85; 84; 83; ; Se ae Poe
Bo (Ost; Go; .
io, ,U; 64; 55; 65; z
re 00.’ GO 63;
Peek (Als OF: i

us. .B; 66; 44; asym.

ge LOSE |

g gh 095 935" ,,

gO CFs | 5,

eAm ; 55; 33; 2z0. Mox. Het.

eae

ibe
=
=

Cota AR oN
ol

Se ee
SS

us, gE; 75; 73,45; 54; asym.
Be iy ch Loon OA es
DT LMG Das be 4 3
tee eiOGH oor sor Moz.

po
i
POON RE

—
oo

490 REV. T. P. KIRKMAN ON

5. us. ,.F; 755 73; 44; asym. gel
6. , gG; 76; 43; 438; -
Te 5% ot OOD bas DAM Aa ye
8. | (65,085 54543; 1. us. ,A; 65; 65; 2p. Mox. Het.
9. 4, —Q; 66; 43; 43; 2p. Mox. Het.

10.~,, 2! Goeads4se asym.

1, gp Gb osneos Moz to We

12. 4,“ ODS wor aa * Rynig \aeesis

P= 2)

1S. 4 - gets ae 33 -
14. 5 gf@3Sbn Shee asym, 1. us. ,C; 86; 83; asym.
Ld. 3, (ee aes Oe : Zc, AAO ore.

O°

UG. oy se DOOD s 6h 7G ; 66; 53; Moz.
0Q- 10 W.
Kylee RyS32 =i) B=

TS. alg Orga sone too « asym.
a ges Oe is

us. ,E; 87; 83; 43; asym.
ya, TOS DAS G eae
es Tiles de Aa se
“J ; 66; 55; 33; Moz.

oe hob

: ”
oR.

ioe ie (0,
3 2 1 1.8

1. us. ,C; 85; 84; asym. , ;
2 » »D ; 65; 54; ” ; el Est
By a5 Gg TOG AA Fit, 1. us. ,A;'76; 54; asym.
ws: ie'¢

F;=1; F,=1; F=1. dye B=: shea
1, us, ,E; 76; 54; 73; asym. 1. us. ,B; 77; 54; 53; Moz,
% » mo; 8b5aay me OPE thes) te capa
2 ay EE, Bi on gly Oa OpoUee ue
A 5. nh ODEO EEOSr= 7.
5Y rT yes 7637 o2A35% »”
6. .od8 oy SBS URRb4ia PG
Tey 5 T7144 38) Moz, :
B.. i gy 00 Aeon e. 2) Fy=1; Fj=1.

1, us. A; 96; 95; Moz.
ol:

Fo=Ls) dese =O 0A

1. us. .B; 75; 74; 55; Moz, Fy=1; F,=1.

2. , C377; 76; 76; 220, Mox. Het, 1, us. ,A; 87; 43;asym,

UNIFILAR KNOTS OF TEN CROSSINGS. 491

109: oe
F,=1; F,=1. ora Bai; Fei.
us. ,A; 97; 94°; Moz. . ius. ,A; 98; 93; Moz:
0 ®-
Bt; Fo). jes 61a
1. us. ,A; 77; 55; 2z0. Mox. Het. T. ys. ,A; 99; 33; 220, Mox. Het.

Finally, there is one solid unifilar knot, the ,B described in art. 68 of my
ir above referred to. In that article the quadrifilar (4466) ,,A is
ly designated a zoned triaxine; that ,A is a 4-zoned monarchaxine

XXVII.—On Knots. Part III. By Professor Tair. (Plates LXXIX.,
LXXX., and LXXXT.)
(Chapter I. read June Ist, Chapter II. July 20th, 1885. One change, small but important, was made during printing.
It is described at the end of the paper.)

The following additional remarks are the outcome of my study of the
polyhedral data for tenfold knottiness, which I received from Mr Kirkman
on the 26th of last January. My main object was, as in the first chapter of
Part II., to determine the number of different types; as well as the number
of essentially different forms which each type can assume, as distinguished
from mere deformations due to the mode of projection.

This study has been a somewhat protracted one, in consequence (1) of the
great number of tenfold knots; (2) of the very considerable number of dis-
tortions of several of the types, many of which are essentially distinct while
others present themselves in pairs differing by mere reversion; and especially
(3) of the fact that the polyhedral method often presents some of the distinct
forms of one and the same type projected from essentially different points of
view (of which, in the present case, there are sometimes twelve in all). Reason
(3) depends on the fact that Kirkman’s method occasionally builds up various
forms of one type on different bases of a lower order, and it really involves
additional labour only ; but great care is requisite to avoid confusion as regards
(2), and in consequence I may not have fully reduced the final number of
distinct types. [At the end of this paper I shall give a simple illustration of
the nature of this special difficulty. |

The fact that I was dealing with knottiness of an even order induced me to
commence the testing of the materials at my command by picking out the
Amphicheirals. This led to some new considerations of a very singular nature,
which are treated in the first of the following chapters. The second deals
with the tenfolds as a whole.

I. Various Orders and Classes of Amphicheirals.

1. As one form of check on Kirkman’s results, I sought for an independent
method of forming all the amphicheirals of a given order. But, as will be
seen below, we must be careful in this matter, which is not so simple as I first
thought. I therefore commence by recalling the original definition of an
amphicheiral.

VOL. XXXII. PART III. 4M

494 PROFESSOR TAIT ON KNOTS.

In § 17 of my first paper I introduced it thus :—

An amphicheiral knot is one which can be deformed into its own perversion.

The word ‘“‘ deformed” was here used in the sense of alteration of form by
mere change of point of view, or mode of projection; a process which leaves
the number of corners in each mesh, and the relative positions of the various
meshes, unchanged. This definition implies that the right and left handed
meshes are similar in pairs and similarly situated in congruent groups; and
it will be adhered to for the present, though we shall afterwards find that there
are at least three other senses in which a knot may be called amphicheiral, and
shall thus be led to speak of different orders and classes of amphicheirals. The
above definition will then be considered to belong to amphicheirals of the First
Order and First Class.

2. Suppose an amphicheiral knot to be constructed in cord, and extended
over the surface of a sphere which swells out when necessary so as to keep the
cord tight like the netting on a gazogene. Let its various laps be displaced
until the several corresponding pairs of right and left handed meshes are made
equal as well as similar. Trace its position on the sphere. Now suppose it
to become rigid, and move it about on the surface of the sphere. We can
again bring it to coincide with its former trace, but in such a way that each
left-handed compartment now stands where the corresponding right-handed
one was, and each right-handed where its corresponding left-handed was.
Now such a displacement, as we know, can always be effected by a finite
rotation about a diameter of the sphere as axis.

This axis, of course, cannot terminate (at either end) inside a mesh, else
that compartment could not be shifted by the rotation to the original position
of the corresponding one of the other kind. Hence either end of the axis
must be at a crossing, or midway on the lap of cord passing through two
adjoining crossings. A little consideration shows that if one end be at a
crossing the other also must be at a crossing, and the whole must be a link.
This is easily seen from the fact that, if one end of the axis be at a crossing, the
four meshes which meet there must each exactly fit that next it when the
whole is turned through a right angle; and the series which immediately
surrounds these must possess a similar property, &c., &c. Thus the whole
spherical surface must be covered with a pattern which consists of four equal
and similar parts, each of which takes the place of the preceding one at every
quarter of a rotation about the axis. And four laps of the string must there-
fore proceed all in the same way from one end of the axis to the other;
since, if we can trace one lap of the string continuously from one crossing to
the other, exactly the same must be true of the other three. [Of course, if the
string cannot be traced from one crossing to the other, there must be two
separate strings at least. |

PROFESSOR TAIT ON KNOTS. 495

Hence, for a true knot, both ends of the axis must be the middle points
of laps ; and therefore—

There must be two laps, at least, in every amphicheiral knot, each of which as
common to a pair of corresponding right and left handed meshes; and when the
whole is symmetrically stretched over a sphere the middle points of these laps are
at opposite ends of a diameter.

3. With regard to the middle point of either of these laps, the various
pairs of corresponding right and left handed meshes are situated at equal
arcual distances measured in opposite directions on the same great circle.
Hence if the whole be opened up at the middle point of either of these laps
and projected on a plane symmetrically about the middle point of the other,
the halves into which the plane figure is divided by any straight line passing
through the latter point are congruent figures applied on opposite sides of
that line as base; the point being, as it were, a centie. There are, thus, at
least two ways of opening up any amphicheiral knot so as to exhibit this
species of quasi-symmetry.

What precedes is on the supposition that the system of right, or of left,
handed meshes can be applied to itself zm one way only. If there be, as
happens in some specially symmetrical cases, more than one way of doing this,
there is a corresponding increase in the number of pairs of common laps, as
defined in the preceding section.

It has also been assumed above that, on the sphere, the systems of right
and left handed meshes are not only similar but congruent. The question of
the possible existence of knots in which the system of right hand meshes
shall be the reversion of the left hand system will be considered later.

4. Wenow obtain a perfectly general, though of course in one sense tentative,
method of constructing amphicheirals of any order. Think of the result of § 3
as to the congruency of the halves of the knot when opened at either of the pair
of corresponding laps. Asa continuous line necessarily cuts the projection of a
complete knot in an even number of points, the half figure which is to be
drawn on one side of the common base must meet it in an odd number of
points because one lap has been opened. Let these be called, in order, A, B,
C, &c. Then, to form the half figure, these points must be joined in pairs,
the odd one forming one end of the line whose other terminal is at the broken
lap. These joining lines, and that with the free end, must be made to inter-
sect one another in a number of points equal to ha/f the knottiness of the
amphicheirals sought. Every mode of doing this gives a figure which, when
its congruent has been applied on the other side of the base, possesses the
amphicheiral quasi-symmetry above described.

5. To ensure that the figure shall be a knot, and not a link ora set of
detached figures, the following precautions are necessary. If A’, B’, C’, &.,

496 PROFESSOR TAIT ON KNOTS.

in the congruent figure correspond to A, B, C, &c., in the original, they will be
adjusted to one another as follows. (The case of five is taken as being suft-
cient to show the general principle.)

ABCDE
E/ D’ C’B A’

Now if B be joined with D, however the joining line be linked with the others,
B’ will be joined to D’; and these parts will form, together, one closed circuit,
so that the figure is not a knot. Similarly if A and E be joined. Similarly
if A be joined to B, and also D to E. If C be the terminal of the free
lap, so will C’; and again we have a figure consisting of more than one
string.

It will be observed that the common characteristic of these excepted cases
is that each possesses at least partial symmetry in the mode in which points
to be joined are selected from the group. Hence the rule for selection is
simply to avoid every trace of symmetry.

Even when this is done the final result may be a composite knot, 2.e., two
or more separate knots on the same string. These can be detected and
removed at once, so that it is not necessary to lay down rules for preventing
their occurrence.

Repetitions of the same form from different points of view form the only
really troublesome part of this process. These are inevitable, as we see at
once from the fact that there may be several essentially different ways of
cutting the complete quasi-symmétrical figure into congruent halves by lines
meeting it in the same odd number of points. But it may also often be cut by
one such line in one odd number of points and by another in a different odd
number.

Still, with all these inherent drawbacks, the method is applicable without
much labour to the tenfold amphicheirals ; and it fully answered my purpose,

6. I had proceeded but a short way with the application of this method
when I found that there may be more than one distinct amphicheiral belonging
to the same type.

One example of this had been already given in § 48 of Part I. while I was
dealing with amphicheirals, and again in Part II. in my census of eightfolds
(Type V.), but I had carelessly passed it over as a special peculiarity probably
due to the fact that the knot in question, though not composite, was constructed
of portions each of which possessed, all but complete, the outline of the four-
fold amphicheiral. From the point of view taken in § 4 above, however, the
reason of the property is evident. For if the half knot, when the extremities
of the strings are all held fixed, be capable of a distortion which shall change
the relative positions of some of its meshes or the numbers of their corners,

PROFESSOR TAIT ON KNOTS. 497

the same can of course be done with the congruent half. ‘The whole pre-
serves its type, and is still amphicheiral, but it becomes an essentially distinct
form. 7

It will be seen that there is one type of tenfolds which has four different
amphicheiral forms ; another contains three ; while there are four types each
with two forms. The remaining seven amphicheiral types are either unique
forms or have no amphicheiral distortion.

7. We are now prepared for one extension of the definition of an amphi-
cheiral given in § 1 above. But we prefer to establish a new and independent
definition :—thus

An amphicheiral knot of the First Order and Second Class is one which can
be distorted into its own perversion.

Under this definition every distortion of an amphicheiral knot is included,
even although it be such that its right and left handed meshes do not corre-
spond to one another in pairs. For, whatever be the distortion, and whatever
parts of the knot be affected by it, an exactly similar distortion might have
been applied to the congruent parts of the original amphicheiral. These two
distorted forms are, of course, capable of being distorted one into the other :—
and that other is its perversion.

Every amphicheiral knot of the first order and second class corresponds to,
and can be distorted into, at least one of the first class :—but the converse is
not necessarily true.

8. Whether there are other classes of amphicheirals of the first order besides
these I do not yet know. I have made attempts to construct a specimen of a
supposed Third Class which should have the property of being changed into its
own perversion by the twisting of a s¢ng/e, limited, portion, while the result could
not be obtained by any simpler method. Such forms, if they exist, must in
general be incapable of distortion into amphicheirals of either the first or the
second class. This search has been fruitless. Among the requirements which
it introduces, is the necessity for an ordinary amphicheiral in which two pairs
of corresponding right and left hand meshes shall have one common corner ; a
condition which does not seem to be satisfied except by the simplest (amphi-
cheiral) link, in which indeed it must be satisfied, as there are but four com-
partments in all. But this gives no satisfactory solution.

9. We may now take up the curious question raised in the last paragraph
of § 3 above.

A simple method of producing arrangements in which the group of left-
handed meshes is similar to, but not congruent with, that of the right-handed
follows at once from the fact that, if one end of a diameter of a sphere trace a
figure of any kind, the other end traces a similar and equal but (except in
Special cases of symmetry) non-congruent figure. These figures can, if we

498 PROFESSOR TAIT ON KNOTS.

choose, be taken so as together to form one closed curve; and this, along with
a great circle of the sphere, forms a link of two cords possessing the required —
property. On the plane we can carry out this construction by describing any
- figure within a circle, along with its inverse as regards the circle but on the
opposite side of the centre; and arranging so that these may join into a con-
tinuous curve linked with the circle. But this arrangement vemains a link
when we unite the new curve with the circle by so introducing new meshes as
to leave the whole possessed of the required property.

Or, we may trace any curve on a hemisphere, and its image (in the common
base) on the other hemisphere. These, together with the great circle separat-
ing the hemispheres, give another link solution.

It is clear, from the essentially limited nature of the spherical surface, that —
these two methods give the only possible solutions of the problem :—.e., when
the corresponding right and left handed meshes required by the conditions are
made equal in pairs, the lines joining similarly situated points in them must
either meet in one point (which, of course, must be the centre of the sphere),
or they must be parallel.

10. As I did not at once see how to obtain solutions corresponding to
unijilar knots by means of either of these methods, I asked Mr Kirkman
whether he knew of a polyhedron which possessed the requisite property. The
first he suggested to me corresponded, as I easily found, to a trifilar which
belongs to the results of the first method above :—z.e¢., one of its cords being
taken as the circle, the other two were inverses of one another with regard to
it. But, as soon as he mentioned to me that the polyhedron, corresponding to
a composite knot consisting of two separate once-beknotted 5-folds on the
same string, satisfies the special conditions of the present question (though
inadmissible on other grounds), I saw why I had failed in obtaining unifilars
by the first of the two methods above. For the purpose of avoiding trifilars
from the first I had always made the curve traced by either end of the moving
diameter (in the process of § 9 above) cross the great circle wherever it met it,
so as to join that traced by the other end. No insertions of new meshes could
then reduce the whole to a unifilar without depriving it of the property for
which it was sought.

11. But if we make the closed curve traced by one end of the moving
diameter touch the great circle in one point, the point of contact must of course
be regarded as a crossing, while the circle and the closed curve necessarily fuse
into one continuous line. The same happens with the curve traced by the
opposite end of the diameter. Thus we may obtain with the greatest ease any
number of unifilars satisfying the conditions. And it is clear that, by a slight
extension of the definition above, all such knots will be brought under the
general term amphicheiral. To make them true knots, 7.¢., not composites, th

PROFESSOR TAIT ON KNOTS. 499

curves traced by the ends of the diameter must intersect one another, which
implies that they must each cut the great circle in two points at least besides
touching it at one or more. Hence the lowest knottiness in which they can
possibly occur is 10-fold; 7@¢., 2 points of contact with the great circle, 4
intersections with it, and 4 intersections of the two branches.

This process fails when applied in connection with the second method of
§ 9, for it brings in triple points which cannot be opened up into three double
ones without depriving the whole figure of the desired property.

12. The 10-fold, whose genesis is described in last section, has the form
shown in Plate LX XIX. fig. D, where the great circle is made prominent. It
is easily recognised as the ordinary amphicheiral, fig. 31, of Plate LX XX.
The reason why it figures in both categories is that the arrangement of the
right or left handed meshes, being symmetrical, is not changed by reversion.
Thus every ordinary amphicheiral, which is in this sense symmetrical, belongs
also to the new kind of amphicheirals with which we are now dealing.

Plate LX XIX. fig. A shows a 12-fold knot, which is its own inverse with
regard to the part drawn as nearly circular, and which is not amphicheiral
in the ordinary sense.

Equal distortions of two corresponding parts give it the new form fig. B,
which is also its own inverse with regard to the circular part.

But if, as in fig. C, we perform one of these distortions alone, the form is no
longer its own inverse. But it is certainly amphicheiral, in the sense that it
can be distorted into its own perversion. ‘Thisis effected, of course, by undoing
the single distortion which produced C from A, and inflicting the other of the
pair of distortions which, together, produced B from A.

13. Thus there are at least four different senses in which a knot may be
amphicheiral.

A(a) Those in which the systems of right and left hand meshes are similar
and congruent.

A(f) Unsymmetrical distortions of any of the preceding, when such exist.
| When the distortion is symmetrical the knot remains one of A(c). |

B(a) Those in which the systems of right and left hand meshes are similar
but not congruent.

B(@) Unsymmetrical distortions of any of the preceding. [When the
distortion is symmetrical the knot remains one of B(c). |

A and B may be spoken of as different Orders, the First and Second; a and
B as Classes, First and Second. As already stated, the knot of fig. D belongs
to both orders. But no knot can belong either to both classes of one order,
or to the first of one order and the second of the other.

14. In fig. (D) the 10-fold (fig. 31) of § 11 is drawn so as to exhibit its
symmetry. And we thus see at a glance that there are at least two ways

500 PROFESSOR TAIT ON KNOTS.

(indicated by heavier lines, one continuous, the other dotted) in which we can
choose the laps which are to form the circle with regard to which it is its own
inverse.

Fig. 38 of the 10-folds, which by reason of its symmetry belongs to both
orders of amphicheirals, can have its circles shown as in figs. (E) and (F).

15. But if we take a non-symmetrical knot of the kind B(a), such as fig. A
above treated, we obtain some still more striking results as to the number of
ways in which we can choose the laps which form the circular portion. In
this figure corresponding right and left handed meshes are marked with the
same letter.

Thus, if we throw out the right hand mesh, d, from the contents of the
circle and take in the left hand d instead, the figure (drawn to show the new
circle) becomes fig. G.

If we throw out 7 and take the amplexum instead, we obtain fig. H.

' But, if we throw out from the circle g, c, and e, and take instead of them
the corresponding external meshes, the figure takes the curious form K. Here
the full line is the new boundary between the two halves of the figure. This
new boundary, as well as the entire figure, is easily seen to be its own inverse
with regard to the part bounded by the heavier portion of the full line. This,
however, is only one of four ways in which it might be selected from the full
line alone. Such modifications are very curious as well as numerous, but we
cannot pursue them here.

16. In the upper rows of Plate LX XIX. I have given the amphicheirals
of the first class, up to the tenfolds inclusive. They are drawn on the principle
of § 4 above, and the first form in which each presented itself has been
preserved. A comparison of these, with the corresponding figures as drawn
in Plate LX XX. directly from Kirxmay’s results, is very instructive.

[ Added, Oct. 19, 1885.—Though the general statement in § 11 above is
true from the point of view there taken, there is a possibility of evading it.
Thus, if we draw a figure like E, Plate LX XIX., but with a four-pointed star
inside, we get vil. of the 8-folds; which is thus shown to be an amphicheiral
of the Second, as well as of the First, Order. But, if we try a three-pointed
star, we get the simp'est trifilar locking ; as in Part I. § 42 (1), and Part II. § 8.]

PROFESSOR TAIT ON KNOTS. 501

II. Census of Tenfold Knottiness.

17. Omitting composites, the number of separate types of 10 fold knottiness
is, as shown in Plates LXXX., LXXXI., 123. Of these 48 are unique, while
the remaining 74 give 315 distinct forms, 364 individuals in all. The largest
number of distinct forms for one type is 12; and there are two such groups.
One type which furnishes a group of 10, has 4 of them amphicheirals of the
first order and first class, the remainder of the second class.

Each of the figures is drawn in the special deformation in which it is
presented by the polyhedral method; and, for reference, the corresponding
designation of the knot in KirxMan’s list is appended to it.

18. Of the 107 partitions of 20, under the limits imposed by the nature of a
knot, 52 only are utilised; the rest belonging to links, composites, &c. These
are as below; each being followed by a distinctive letter, which will presently
be employed (for brevity) in place of it. ;

For knots with 6 right-handed and 6 left-handed meshes :—

ErratumM.—Page 501, par. 17, line 2, for 48, read 49.
a
1B
‘y
ne)
(4452 € 55532 q 4433222 ¢
74333 f 50442 r 4333322 €
66422 g 55433 s 3333332 y

66332 h 54443 ¢

65522 k 44444 yw

For 4 of one and 8 of the other :—

8732 a 7652 f 43322222 0
8633 b 7643 ¢ 33332222 k

8552 ¢ 7544 h

8543 d 6653 k

7742 e 6554 1

And for 3 of one and 9 of the other :-—

992 p 965 5 332222222 Xr

983 q 875 t

974 r 776 u

19. In Part II. of this series I arranged the types of each degree of knotti-
ness in the order in which their respective deformations first appeared in Mr
VOL. XXXII. PART III. 4N

502 PROFESSOR TAIT ON KNOTS.

KirkMan’s lists. This had the disadvantage of mixing up together types
with very different relative numbers of right and left handed meshes. On the —
present occasion I have taken in the first rank the knots which have an equal
number of meshes (six) of each kind, next those which have respectively 5 and
7,4 and 8, &c. This will considerably simplify the process of seeking for any
particular ten-fold in so long a list. The arrangement of the various types in
each rank, however, follows somewhat closely the order of their earliest —
appearance in the first list which I got from Mr Kirkman, that upon which I-
commenced the present work.

To identify any 10 fold, all that is necessary is to count the numbers of
corners in the respective right and left handed meshes, look out the contracted
expressions for the corresponding partitions of 20 in § 18, and then search below —
for the symbol, or pair of letters so obtained. Their order, of course, is imma-
terial, as it can be altered by a mere change of mode of projection. If the
symbol occur more than once, a closer examination must be made, account —
being now taken of the way in which the right, ov the left handed, meshes
are coupled together. This is easily done as in § 20 of my first paper.

20. The number of distinct forms which I detected as not contained in Mr —
KirkMan’s first list of 10 folds bears a far smaller ratio to the whole than was
the case with the ninefolds. I consider that this is due not to my remissness,
but to Mr KirkMman’s improvements in his methods, ¢@.¢., rather to the non-
existence than to the non-detection of omissions ; and I think it is improbable
that any distinct variety of a recognised type has escaped detection. Thus in
the present census some types may be omitted (this is more likely to be true
of unique types than of others); and I may have, as already indicated,
grouped in two or more smaller detachments the varieties of one and the
same type. But the possibility of either defect is due to the somewhat
tentative nature of the methods employed.

The guarded way in which I spoke (Part II., § 1) of the completeness of the
Census has been justified by a recent observation made by Mr Kirxmavy, viz.,
a9 fold not included either in his list or in mine. Fortunately this knot,
figured as fig. L, Pl. LX XIX., is not a new type but a distinct form of type
VI. of the 9 folds as shown in the Plate attached to Part II. My methods
ought to have supplied this additional member of a group, of which some
forms had been furnished by Kirkman; but I had not, at the time, much
readiness in applying them. The labour of the 10 folds has made me much ~
more skilful than before in this matter,

21. In the following list, the order is the same as in the plates. The symbols
for each knot are so written that the second, in all cases, corresponds to the
group of meshes to which (as the figure happens to be drawn) the amplex
belongs.

PROFESSOR TAIT ON KNOTS. 5038

The various Types of Tenfolds with their distinct Forms.

Six right and six left hand meshes ; 24 non-unique types, 14 unique; 133
individual distinct forms in all. Amphicheirals of the first order and first class
are marked by a bar over the symbol instead of a repetition.

BeaCeCO,.GGlI0G, KC KG, GiGK, K .., 2. HC, GF, GF, GF.

. HB, LB, BC, GB, BG, KB, HF, FC, FG, LF, GF, FK.

hGH, KE GE, GE, BK, GB, GB, KB, BG, GB, EK, EG.

/ EF KB, FB, BF, FF,FK. 6. GE, LE, KE.

Sib bC PB BB, EG, BE FE FG, FB. 8. EK,KF 9. F.FF.F. 10. GF KF.
weene Ke, BB, Gr, KG, GB, EF, KB, BE. 12 L¥,LF,FH. 13. KG,K, G.
i]s §.G, EB, BG,EG. 15. A,EA,E, 16. BB, FB, KB, KF, FB, FF.

a Gt Gr 18. FD;DB,KD. 19. FA, KA, FA. GA, GA, EA.

worBA, KA, KA, AF 2 GA,GA,AF,BA. 22. FB,B,F 23. DB, FD.

iW A Ady 25. KG. .26:.G. Drab ae Celine 292K | 30s LG.
2 EE 633. WE 34, BE 35..D. ~ 86. AD. . 37.A, .38. 0,

STIo Ff ©

Five meshes of one kind, seven of the other. Forty-three non-unique
types, twenty-one unique—200 distinct forms in all.

39. €5, €S, EP, YP, SY, SY- 40. em, em, ef. Al. el, ec, yl, ye, ne, nl, Sl, Se, ef, If.

42. &, yl, el, ya, €g, &. 43. ef, em, ep, €s, yf, ym, ys, yp, PS s& Em, Ef. 44, se, te.
45. &d, th, ch, ch, ed, ed, hf, dé. 46. &, &, ml. AT. kr, ek, nk, &.

48. eh, ed, em, h3, mB, dB. A9. &, &, ne, ye, &, ec. 50. gy, eg, &9, Sg.

DI. 66, 6b, fb, be, yb. 52. Bb, cb, HB, ch, eh, ed. 53. er, Br, el, el, Bl, 1B. 54. ve, fe.
55. sB, (8, mB, sB, pP, sB. 56. Of, dp, os. 57. my, yn, en, en.

58. Gr, ry, €¢, ye, &, er. 59. Ol, 89. 60. ee, ey, ly, el, &, &.

61. ee, el, et, 8, eB, IP. 62. ¢8, pB, IB, él, ep, ee. 63. ek, ky, Ch. 64. Bl, Ba, 8.
65. rf, ec, er, Be. 66. &b, Bb, eb. 67. dB, mB, Bl. 68. dB, Bl, sf.

69. eg, gy. 70. dd, 06. TL. Br, g8, eB: 72. (Bor 8. 73. pa, ta, la, ra.

74. ec, 7B, re, cf. 75. ek, Bk. 76. Be, ec. 77. ea, ea, a8. 78. dB, LG.

wo: Be; ec. 80. ra, ac. 81. ha, ab. 82. fu. 83. se. 84. et. 85. &
86. &. 87. 78. 88. pF. 89. er. 90. fn. 91. eg. 92. re. oc
meme 95.¢e. 96.d Mile 98 cl 99. ch, 100.6% 101.46. 102. aa,

_ Four meshes of one kind, eight of the other. Seven non-unique types and
eight unique—twenty-five distinct forms in all.

103. «f, Of. 104. «a, «a, Oa. 105. «d, «ge, dd, gé. 106. «ce, Oc. 107. 6d, 10.
108. Ob, g@. 109. 61, Oh. 110. «k. jE iat M3 112, xh. 113. xg.
114, 6k. 1 GeO 116. Oe. ag)

Three meshes of one kind, nine of the other. Six unique types.

Meme) 119) xg, 128) Ap, 104, re.. 122 rr 128, at.

504 PROFESSOR TAIT ON KNOTS.

22. The nature of the special difficulty hinted at in the beginning of the
paper will be easily seen from the simple case illustrated by the four figures M,
Plate LX XIX. They denote various forms of the type 40 of Plate LX XX.

It will be noticed that the crossings A, B, C may, one, two, or all, be
changed from one lap of the string to the other, as shown in the second figure.
Also D may be transferred to a position between A and B, or between A and C.
There are thus two positions for each of A, B, and C; and three positions for
D; giving 24 combinations in all. But it is clear that we need not shift D at
all, so far as the outline of the figure is concerned; for a mere rotation of the
whole in its own plane (as A, B, and C are similar to one another) will effect
this. Then a change of B will merely give the reverse of the figure obtained by
changing C. Again, by inverting the first figure about a point in the inner
mesh, we get the second. If we had changed C, and then inverted, we should
have got the same figure as by changing simultaneously A and B. By changing
C alone in the first, we get the third; but by shifting D in the first we get the
fourth ; and these two are obviously each the reverse of the other. Thus the
24 figures reduce to the three shown in Plate LX XX. As another example,
take the third form of the third type of 10 folds as given in Plate LXXX., —
Two of thecrossings on its external boundary can be shifted, but each to one
other place only. The form itself, and the same with one or both of these
crossings shifted, give a set of four; each of which can take five new forms by
the shifting of other crossings. But it will be found that the 24 forms thus
obtained are identical in pairs ;—thus reducing to the 12 given in the Plate.

23. Mr Kirxman informs me that he has nearly completed the enumeration
and description of the polyhedra corresponding to the unifilar 11 folds. I
hope, therefore, at some future time to lay before the Society the census of
11 fold knottiness. This was the limit to which I ventured to aspire nearly
two years ago, in a paper* which, I am happy to think, directed Mr Kirxman’s
attention to the subject.

24. It must be remembered that, so far as these instalments of the census
have gone, we have proceeded on the supposition that in each form the crossings —
have been taken over and under alternately. But, as was shown in § 13 of —
Part I., as soon as we come to 8 folds we have some knots which may preserve
their knottiness even when this condition is not fulfilled. These ought, there-
fore, to be regarded as proper knots and to be included in the census as new
and distinct types. This is a difficulty of a very formidable order. It depends
upon the property which I have called Knotfulness (Part I. § 35; IL. § 6),
for whose treatment I have not yet managed to devise any but tentative
methods.

To show, by a single case (even though not thoroughly worked out) of how

* Listing’s Topologie, § 22, Phil. Mag., Jan. 1884,

PROFESSOR TAIT ON KNOTS. 505

great importance is this consideration, I have appended to Plate LX XIX. the
five figures N ; with the nature of each crossing indicated. The numbers affixed
show the positions they occupied in the census of 8 folds, when the crossings
were alternately over and under. Then they were all unique knots, incapable
of any change of form. Now they are capable of being changed into one
another. The linked trefoils in N, xiv. are perversions of one another. But we
may have them of the same kind, and the link such that there shall be
continuations of sign. This was briefly treated in Part I. § 42,1. How many
new types may by this process be added to the census, I have not yet made
out with certainty even for the 8 folds.

P.S.—I may introduce here, as a note on Part I. of this series of papers, a
remark or two with reference to the three-ply plaits treated there; in § 27 as
fully knotted, and in § 42, 1 as fully beknotted. First, it is obvious that the 4
fold, as first drawn in § 17, should have been repeated in Plate XV., at the head
of the series of figures 15, 16,17, &c. Itis the case of 3n+1 of § 27, with n=1.
Secondly, with its crossings arranged as in fig. P, Plate LX XIX. of the
present paper, it should have come in before figs. 24 and 25 of Plate XVI
Part I., in a form reducible to the ordinary trefoil. Fig. 25 of that Plate
puzzled me much at the time when I drew it, for I could not account for the
production of a 3 fold and a 5 fold (linked) from a figure possessing a peculiar
kind of (cyclonic ?) symmetry round an axis. The figure is accurate, but I now
see that it gives an erroneous impression of the true nature of the knotfulness.
The correct idea is at once obtained from Plate LX XIX., fig. Q, of the present
paper. The knot is an irreducible trefoil, with a second of the same character
tied twice through one of its three-cornered meshes.

(Added, September 3, 1885.)

Three days ago I received from Mr Lockyer a copy of a most interesting
pamphlet ‘“ On Knots, with a Census for Order Ten,” a reprint from the Trans
Connecticut Acad., vol. vii., 1885. The author, Prof. Lirrte of the State Uni-
versity, Nebraska, has made an independent census of 10 fold knots ; employ-
ing the partition method, with some new special rules analogous to those in
Mr Kirxman’s recent paper. So far as I can judge from a first hasty compari-
son of the mere number of types and forms in each class, there are important
discrepancies between this census and my own. One of these, at least, is due
to a slip on my part; and, as my paper was not printed off when I detected
it, I have taken the opportunity of correcting it both in the text and in the
corresponding Plate. I had failed to notice that the two forms which now
appear under No. 109 really belong to one type. Hence I have had to

VOL. XXXII. PART III. 40

506 PROFESSOR TAIT ON KNOTS.

reduce by one the number of the distinct 10 fold types which was originally
given in my paper. I hope in time to make a full comparison of the two
versions of the census. Meanwhile I may note that there is one omission,
and also one duplicate, in Class VI. of Mr Lirrte’s version. This duplicate
has led him to insert one type too many.

More than a month ago I received from Mr Kirkman the full polyhedral
data for the census of 11 folds, which I hope soon to undertake. The number
of forms is so great, and the time I can spare for the work so limited, that I
cannot promise it at an early date.

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( 507 )

XXVIIIL—A New Graphic Analysis of the Kinematics of Mechanisms. By
Professor Roserr H. Smiru, Mason College, Birmingham. (Plate
LXXXII)

(Read 19th January 1885.)

A mechanism may be defined as a combination of plates, bars, or flexible
- members jointed together, so that, while the parts may move relatively to each
other, the relative positions of all the different parts are determinate for each
given possible relative position of any two parts.

It follows immediately that the simultaneous relative displacements,
velocities, and accelerations of velocity of all parts are also strictly determinate.

This determination, by accurate graphic means, forms the subject of this
paper. In it those mechanisms alone are considered that are composed of
rigid members, the motions of whose parts are all continually parallel to one
plane, the constancy of the plane being defined relatively to one of the members
of the mechanism itself.

The different rigid members of mechanisms will be termed “bars.” That
bar relatively to which the displacements, velocities, and velocity-accelerations
are measured, will be termed the base-plate or bed-plate. The displacement,
velocity, and velocity-acceleration of the base-plate remain, of course, always
zero.

To avoid repetition of the cumbersome phrase “ relatively to,” this phrase is
discarded for the shorter expressions ‘‘ through,” “past,” “ over,” or ‘“ round.”
Every possible motion or other vector is through some field in which positions
and directions may be defined in a determinate manner. It is improper to
speak of the motion of one point past another, without mention of the parti-
cular field through which the motion is measured, because two points alone are
inadequate to define a field in which vectors may be measured. In what follows,
when the field of reference is not mentioned, it is to be understood that the
vectors are taken through the “ field of the base-plate,” 2.¢., through the space
surrounding and defined with reference to the base-plate. On the other hand,
it is perfectly definite to speak of the motion of a point or of a bar over, past,
or round another bar, the motion being understood, without further mention, to
be measured through the field of the bar round which it takes place.

The graphic determination of the simultaneous positions of the various bars
of most commonly used mechanisms is easy and well understood. When
difficulties occur, as in various engine reversing link-motions, the special
methods here explained enable them to be readily overcome. The /oci of the
successive positions of the various parts may be called the “motion curves” or

VOL. XXXII. PART III, 4P

508 PROFESSOR R. H. SMITH ON A NEW GRAPHIC

more simply the “paths” of these parts. These paths are drawn in on the ~
“mechanism diagram.”

From these “paths” the displacements from any assumed initial configuiaai”
can be directly measured. It may, however, be often advantageous to have a
separate “displacement diagram,” consisting of a series of curves, showing the
successive simultaneous displacements of all important points of the mechanism
as vector-radii from one and the same pole. These curves in the “ displace- —
ment diagram” are, of course, exact copies of the “paths” in the “mechanism —
diagram.”

Let ABC and BDE be two bars linked together at the joint B. Let P’ be
the pole of the displacement diagram, and let the curves A’A’, B’B’, D’D’ be |
the displacement curves of the three points ABD. All these curves, of course,
pass through the pole P’. P’A;, P’B;, and P’D), being simultaneous displace-.
ments of AB and D, draw on A;B; and B,D; as bases, the triangles A,B,C; and
B,D,E; similar to the triangles ABC and BDE in the mechanism. It can
easily be shown that P’C; and P’E; are the simultaneous displacements of C
and H, By joining all the points C’ and E’ found by such constructions, the
displacement curves of C and E can be drawn in. Numerous simultaneous
points on the various displacement curves should be marked, and numbered 1,
2,3, 4, &e.

The advantage of such a displacement diagram over the set of “paths”
dispersed over the mechanism diagram, consists in the greater facility of com-
parison between the displacements of the various parts of the mechanism that
it affords. Thus, comparing simultaneous points A’ and C’ belonging to the
same bar, the vector A’C’ is the displacement of C’ past (or relatively to) A in
the base-plate field. The same holds for points in different bars; thus, D’C’ is
the displacement of C past D in the base-plate field. As a useful fact of -
assistance in drawing these diagrams, it may be noted that any line, such as
A’C’ belonging to one bar, is perpendicular to the line bisecting the angle
between the simultaneous and “initial” positions of the line AC in the-
mechanism. This does not, however, apply to a line, such as E’C’, joining
points belonging to different bars.

The method of obtaining the velocities by taking the small differences of the
displacements, which method is the basis of kinematic analysis developed by
means of the differential calculus, has often been adopted as a graphic process
for the solution of specially complicated problems. After constructing the
velocity hodographs, the same method may be followed to find the velocity
accelerations. As a graphic process, however, this method is capable of no
accuracy ; it is, in fact, practically useless.

Professor RevLeavx’s method of centroids, more properly called axoids, has
now become famous; but, although the writer has constructed the axoids of

ANALYSIS OF THE KINEMATICS OF MECHANISMS. 509

many mechanisms, he has so far failed to discover any practical use to which
these axoids can be applied. They are very tedious of construction, and when
constructed furnish no direct means of measurement of any useful quantities.

The method now proposed furnishes velocity and acceleration diagrams,
somewhat similar im appearance to stress diagrams, which show the true
directions and magnitudes to scale of the velocities and velocity accelerations
of all points in the mechanism; there being one pole only for each diagram
from which all vectors radiate, so that the velocities or accelerations of all parts
and at all times of the complete cyclic period can be compared with maximum
facility.

Fig. 1.—Let ABCD be a rigid bar. Suppose the velocity of A over the
base-plate P to be known. Choose any pole p, and draw pa parallel to the
velocity of A, and of a length to represent its magnitude to any scale considered
convenient for the velocity diagram. If now the angular velocity w of the bar
be also known, ab may be plotted perpendicular to AB, and equal in length to

«AB to the above velocity scale. Then, pb is the velocity of B over the base-
plate. If, instead of w being known, we know the velocity of B as well as that
of A, then pb may be plotted directly, and joining ab the angular velocity may,
if desired, be calculated by dividing ab by AB. Since the (relative) velocity of
C round A is perpendicular to AC, and its relative velocity round B is perpen-
dicular to BC; if ac and be are drawn perpendicular to AC and BC, their
intersection c gives pc the velocity of C through the base-plate field. Similarly,
pd is found to measure the velocity of D. The diagram gives not only the
velocities over the base-plate P, but also all the velocities of pairs of points
relative to each other. For instance, bd is that of D round B, and db is that of
B round D, these relative velocities being through the field of the base-
plate P.

It is clear that the figure abcd forms a diagram of the bar ABCD to a
diminished scale and turned through a right angle in the direction of .*
Further, on this new diagram of the bar, altered in scale and rotated through
90°, the pole p represents the position of the instantaneous axis of rotation,
Theoretically, the original diagram ABCD, with the position P of the instan-
taneous axis added, would serve equally well as a diagram of velocities, the
scale being chosen suitably, so that PA would represent the velocity of A.
But for practical graphic construction it cannot be so used, for several reasons.
Firstly, the usual variation of the position of the instantaneous axis is extremely
inconvenient, and in almost all mechanisms this axis periodically recedes to an
infinite distance. Secondly, the scale to which it could represent the velocities

*Tn an abstract of this paper written for the engineering journals, the late Professor Fiemmine
JENKIN very expressively called abed the “image” of ABCD. In the acceleration diagram another

“image” a'b’c'd’ appears.

510 PROFESSOR R. H. SMITH ON_A NEW GRAPHIC

is always varying throughout the periodic motion of the mechanism; it is
always necessarily an awkward scale to measure to, and it periodically becomes
in most cases an impossible scale by becoming infinitely large. Thirdly, the
various bars of a mechanism have all different instantaneous axes, and the scales
of the velocities would be entirely different for the different bars. As will be
shown presently, in the method explained in this paper, the velocity diagrams
of all the bars of even the most complicated mechanisms are all grouped
together so as allto radiate from one pole, and so as to be to the same scale for
all the bars and at all times throughout the periodic motion of the mechanism.
A similar construction is applicable to accelerations of velocity. In fig. 2 —
let ABCD be one rigid bar. Let the acceleration of velocity of point A through
the field of the base-plate be known, and represented in direction and magni-
tude by p’a’ drawn from any convenient pole p’ to any convenient accelera-
tion scale. The acceleration of B can be obtained by adding to the vector p’d’
the vector acceleration of B in its relative motion round A. If be the
angular velocity of the bar in the base-plate field, and if ’ be the acceleration
of angular velocity, the radial or centripetal component of velocity acceleration
is w AB and the tangential component is »*AB. The whole acceleration of —
relative velocity is therefore, AB:,/o'+”, and its direction is inclined to BA

by the angle tan™! a This angle is the same for every pair of points in the

same rigid bar ; and, since the magnitude of the acceleration of one point round
any other is proportionate to the distance between them, therefore, if w’b’ be

drawn inclined to BA at the angle tan“! # and of length AB,/o*+@”, and if
a

2
the figure a’b’c'd’ be made similar to that of the bar ABCD, then p’'0’, pc’, pd,
will be the accelerations of the points BCD in the base-plate field. Further
a’c’, for instance, is the acceleration of C round A. In the graphic construction
it is simplest to plot aB’=AB‘o’, and parallel to BA (not AB), and
Bb’ = AB-o’ perpendicular to AB and in the direction given by the sign of o’.
The radial component is usually obtainable from the already constructed
velocity diagram, where the velocity of B round A is called ad, and the radial

acceleration is therefore oe Fig. 3 gives the two most ready graphic con-

structions for calculating oe In figs. (1) and (2) the velocity ab is plotted —
along BA from B to 8 towards A in (1); and away from A in (2). From Bas
centre with B@ as radius, a circular arc is struck intersecting in 8, any other

radius from A. From £ is drawn Bf’ parallel to that other radius, and
intersecting BB, in B’. Then Bf’ is the radial acceleration fae In (8) (ab) is

plotted from B as B£ perpendicular to AB, and a circular are with centre in

ANALYSIS OF THE KINEMATICS OF MECHANISMS. 511

BA is struck through A and 8. This arc cuts the diameter AB in f’ giving
B£’ the desired radial acceleration.

If the bar be plotted to the scale m’=1”, m being a fraction ; and if the
velocity be plotted to the scale m’=1 inch/second ; then such constructions

give the acceleration to the scale (") inch =1 inch/second.?

It is evident that the figure a’b’c'd’ of the acceleration diagram is simply a
reproduction of the figure ABCD of the bar altered in scale and rotated through

an angle | 180°—tan™ “| in the direction of » where in tan“ Ws the sign of
we

w is to be taken positive or negative according as it is in the same or the
opposite direction to that of w. In this altered diagram p’ is the point of the
bar if the bar extends so far, or of its field if it does not extend so far, which
suffers no acceleration or is moving uniformly in a straight line. This point does
not in general coincide with the instantaneous axis of rotation. If the velocity
diagram were rotated and altered in scale, and placed on top of the acceleration
diagram so that ab’c'd’ coincided with abcd, then p’p would represent in
direction and magnitude the acceleration of that line in the bar or in the field
of the bar which is at any time the instantaneous axis.*

If G be the centre of inertia of the bar and the similar points g and g’ be
plotted in the velocity and acceleration diagrams, then the products of the
bar-mass by pg and p’g’ are respectively the integral momentum and the
integral acceleration of momentum of the whole bar.

In what follows the capital P will denote the base-plate through whose
field the velocities, &c., are reckoned.

The pole of the velocity diagram will be called p. The pole of the accelera-
tion diagram will be called p’.

Points in the mechanism will be named by capital letters ABC, &c.

The corresponding points in the velocity diagram will be named by the
same letters in small type, abc, &c.; so that pe will denote the velocity of C
over the base-plate and bc the velocity of C round B, and cb that of B
round C.

The corresponding points in the acceleration diagram will be named by
accented small letters ; this being in accordance with the common mathematical

convention, whereby x’ represents 2
a

In finding, for instance, the point 0, it is sometimes necessary to find other
points which are not afterwards required in the completed diagram. When
such construction points require to be named, they will be called A,, B., &c.,

* The acceleration “image” of a bar moving without rotation reduces to a point. The velocity
“image” of a bar moving without rotation reduces to a point.

512 PROFESSOR R. H. SMITH ON A NEW GRAPHIC

if used to find b in the velocity diagram, and @; 83, &c., if used to find 0’ in the
acceleration diagram.

In the displacement diagrams described above, the accented capitals
A’BC’ &c., are suitable.

The simplest mechanism is that with four bars and with two joints, P,P,
in the base-plate, and two joints AB coupling the other three bars together.
An example is shown in fig. 4, the calculations being made for five different
phases of the periodic motion.

The velocity of the crank-pin A is supposed known at each phase. From
any pole p, and to any convenient scale this velocity pa is plotted perpendicularly
to P,A. From p a line is drawn perpendicularly to P,B. Evidently the —
extremity b of bp, the velocity of B, must lie in this line. But also pb pa
plus a velocity perpendicular to AB. Therefore from @ a line is drawn
perpendicular to AB to meet the above line in 4. Thus pb is determined. In
the example pa is taken of the same magnitude at all the five phases.

To obtain the acceleration diagram we assume the acceleration of A. This

2 . e . .
is constant in magnitude he on the supposition that pa is also constant in
1

magnitude and is wholly radial, since pa is taken as constant.
From any pole p’ this acceleration oars pa is plotted parallel to AP,
1

(not to P,A).
The calculation of the magnitude is performed by the graphic construction

previously explained. By the same construction the magnitudes oF and
_ of the radial components of the accelerations of B round P, and round A
are found and plotted off from p’ (as p’B’) and from a’ (a’f’) parallel to BP, and
to BA. From these two points 6’ thus obtained, lines are drawn perpendicular —
to BP, and to BA. The point 0’ sought for must lie on both of these last lines,
and is, therefore, at their intersection. The acceleration p’b’ of the joint B
through the field of P is thus obtained for the five different phases of the ©
motion. The method of procedure is plain. Each joint of the mechanism is a
point in two different bars, and therefore the calculation for that joint may be
approached, as it were, from two different sides. In each of the two calcula-
tions there is one element missing, and the last stage of the calculation cannot
be completed directly ; for example, approaching the calculation of the accelera-
tion of B through A, we can calculate the radial component (parallel to BA) of
the acceleration that has to be added to that of A, but of the tangential com-
ponent the direction only is known, but this gives a line in which the desired point —
must lie.* Another conditioning line being similarly found by approaching the cal-
culation in another way, the point is found at the intersection of these two lines.

ANALYSIS OF THE KINEMATICS OF MECHANISMS. 513

In the ordinary steam-engine with guide bars, the radius bar BP, swinging
in the base-plate-bearing at P, is replaced by the cross-head sliding in straight
guides which form part of the base-plate. The effect is the same as if BP, were
infinitely long. On account of the cross-head joint being guided in a straight
line, passing through the crank journal centre, a symmetry is given to the
motion which materially lightens the labour of drawing complete velocity and
acceleration diagrams. Fig. 5 illustrates this.

Here the four positions 1, 2, 3, and 4 of the crankpin A are taken equi-
distant from the dead-points O and O’. Therefore the two cross-head positions
B, and B, coincide, as doalso B, and B;. Therefore also the four velocities pa,
po, pds, and pa, are equally inclined to the velocity line pb, and the four points
Mh, Ge, M3, d, are equidistant from the line pb. Also at 1 and 2 the connecting
rod has the same inclination to the centre line, which inclination is equal and
opposite to that at 3 and 4. Thus the lines a,b, and a,b,, and a,b, and aszbs,
are equally inclined to pb; and, therefore, the velocities pb, and pb, have equal
magnitudes, as also have pb; and pb,. Therefore also the radial accelerations
Mi, 85, 383, 048; have equal magnitudes, and are equally inclined to pv’;
while also the tangential accelerations, 6,b;, &c., are equally inclined to the
same line, and are of the same length, because ai, a3, a3, and a, are equidistant
from pb. Therefore, finally, b{ coincides with b;, and 6; with b;. The four
accelerations a’b’ have equal magnitudes, but p’b;=’b; differs in magnitude as
well as direction from p’bi=p' bi.

This symmetry is, of course, destroyed by want of uniformity in the rotation
of the crank.

The joint lines of the bars of a mechanism, the velocity lines, and the
acceleration lines need be drawn in full for one position only. The results for
the other positions are indicated by numbered points on the three set of curves,
which are the loci of the corresponding points or extremities of lines. The first
" set of curves are the paths of motion of the joints. The second series of curves
are the hodographs of the velocities of these same joints. The third series are
the /oci of the extremities of the lines representing the velocity accelerations.

Six-bar motion is nearly equally easy to deal with by this method.

The first example given in fig. 6 is quite simple, because the velocity pa of
the joint A is assumed as known, the bar P,A being one of the quadrilateral
P,ABP,. The determination of the velocity pb is, therefore, the same as that
given already. Thus, pb and ab are drawn perpendicular to P,B and AB, and
their intersection gives b. Then the triangle abc is made similar to ABC. pd
is then drawn perpendicular to P;D, and cd to CD, the intersection giving pd
the velocity of D. To find the velocity of E, there are drawn pe and de per-
pendicular to P;E and DE. The construction of the acceleration diagram here
offers no special difficulty.

514 PROFESSOR R. H. SMITH ON A NEW GRAPHIC

The solution of the next example in fig. 7 is not quite so direct, because
here the velocity assumed as known, namely, pa that of A, is that of a joint in
the pentagon P,ABCP,. First, pa is drawn of the known magnitude and
perpendicular to P,A ; and then a8 of indefinite length perpendicular to AB.
Then, pd and pe are drawn of indefinite length perpendicular to P;D and P,C,
that is, in the directions of the velocities of D and C. The points b and d now
sought for are known to lie on the lines a8 and 6, and also it is known that
the line joining 6 and d is perpendicular to BD. Any point 8 on @@ is chosen,
and from it 8d drawn perpendicular to BD; and then the triangle @dy is con-
structed similar to BDC, corresponding sides being perpendicular. The triangle
bde that is sought for must evidently be similarly placed to Bdy between the
the lines pd and af. Therefore, y is joined with the intersection of pd and af,
and this line is produced to intersect pc, drawn from p perpendicular to P,C.
This gives the true position of c, and the triangle dcb is then completed by —
drawing cd and cb perpendicular to CD and CB to meet pd and af. The
point e is obtained by drawing pe and de perpendicular to P,E and DE.

The acceleration diagram has, in this case, to be constructed according to a
similar indirect method, The acceleration of A being supposed known can be —
plotted at once. Then the radial components of the accelerations of B round
A, of C round P,, and of D round P;, are calculated and plotted off in their

* 1 7 4 4 7 7 1 b ? (pe)? (p Ss
roper directions from a’ and P; their magnitudes being ay) ——
So 8 BA’ P Ca PD

From the three points so obtained, three lines, which we may call £, y, and 8,
are drawn of indefinite length perpendicular to BA, P,C, and P,;D. The
tangential components of the above three accelerations lie along these lines,
which, therefore, contain the three points b’, c’, and d’ sought for. On the
line 6, any two points, 8, and 6,, are chosen, and from each the centripetal

acceleration Lee of C round D is plotted parallel to CD; and from the two

points thus obtained are drawn two lines perpendicular to CD, to meet the
line y in two points, say y, andy On the two bases, Sy, and 8:7, are con-
structed two triangles similar to DCB, whose two vertices may be called 6, and
B,. Neither of these points, 8,, 6, will be found to lie on the line 8, and their
distances from this line may be taken as measures of the errors involved in the
two guesses, 6,, 6, at the position of d. The error thus found in the resulting
position of £, is a linear function of the error in the guessed position of 6; and,
therefore, the interpolation between these two errors in order to reduce them j
to zero is to be performed by simple proportion. This linear interpolation is at —
once effected graphically by drawing a line through A, and £,, and producing it
until it meets the line 8. The intersection thus found will be the true position
of b.. Or, otherwise, the two error-distances of 8, and £, from the line 8 may
be plotted off from the points 8, and 8, perpendicularly to the line 6 (or both in

ANALYSIS OF THE KINEMATICS OF MECHANISMS. 515

any one direction inclined to 8), and through the two points thus obtained a
straight line is drawn to cut the line 6 in the true position of d’, From a’ or
b’ thus determined, the other points are constructed as usual.

This indirect method of ‘two trials and two errors,” and linear interpolation
between them, is adopted in drawing the velocity and acceleration diagrams for
the ordinary steam-engine reversing link motion. These diagrams could not be
obtained except by this method. It may be mentioned that this is frequently
the only practicable method by which stress-diagrams of immovable linkworks
can be completed.

In the common steam-engine mechanism we have already had a case of one
bar sliding on another, namely, the cross-head sliding in the guide-bars of the
bed-plate. A circular slot in which sliding takes place may, of course, be
looked upon as simply an incomplete pin joint of large size, the radius of the
pin becoming infinite when the slot is straight. But when the radius of the
slot is large, this manner of regarding the joint is not practically useful. A
more direct application of the present graphic method to sliding joints is
effected thus: If B be a bar sliding over the bar. A, the difference of the
velocities of any two touching points in B and A is a velocity parallel to the
slide-surface, or “ guide-surface.”

Thus, the velocity of the bar A being known, the velocity of any point in B
can be obtained by adding to the velocity of any touching point in A a velocity
parallel to the guide-surface, and further adding a velocity perpendicular to the
line joining this touching point with the point in B whose velocity is to be
found.

This last added component is that due to the rotation of B in the field of
the base-plate. If the touching surface of B has the same shape as that of A,
so that B always “fits” on to all parts of A into contact with which it comes,
and if during the sliding these fitting surfaces are forced always to le close
together, then the angular velocity of B is always the same as that of A. In
this case, if the velocity of A be completely known, the linear velocity of any
point in B can be calculated by adding to the velocity, which the point would
have if B were rigidly attached to A, a velocity parallel to the guide-surface.

In the illustration (fig. 8), the velocity of point A round P, is supposed to be
known, and it is plotted as pa. Then p@ and af are drawn perpendicular to
P,Band AB. This gives p@ the velocity that point B would have if the cross-
head were rigidly attached to the guide-bars, and if 8b be drawn parallel to the
slot, the point 6 must lie in this last line. But B is guided by the radius rod
P,B. Therefore pbis drawn perpendicular to P,B to meet 8b in b; then pb is
the velocity of B in the P fieid, and 8b is the velocity of sliding in the slot.

If a block C (see fig. 9) slide in two slotted bars A and B, the first of which
has a translatory velocity pa, and the second a translatory velocity pb,

VOL. XXXII. PART III. 4Q

516 PROFESSOR’ R. H. SMITH ON A NEW GRAPHIC

evidently the method of finding the velocity pe of the block is to draw from a
and b two lines parallel to the two slots in A and B. If these lines meet in «,
then pe is the velocity required. :

If the slotted bars have rotational instead of purely translatory velocities,
then precisely the same construction is to be followed, making pa and pb the
linear velocities of the touching points of the guide-surfaces in A and B. Now,
however, it is evident that one and the same block cannot constantly fit close
to both slotted guide-surfaces. But if two fitting blocks, one fitting the one
slot and the other the other, be pinned together, then the above construction
may be applied to find the velocity of the centre of the joing pin, and from
the velocity of this centre it is easy to deduce by methods already explained —
the velocities of all other points in the two sliding blocks.

These last graphic methods have been applied to the calculation of velocity
and acceleration diagrams for Player’s pneumatic forging hammer, in which a
combination of oscillating sleeves, through which slide levers, makes the com-
plexity of the mechanism such as to be incapable of algebraic treatment in a
manner that is at once accurate and yet not impracticably cumbersome.

The following application (see fig. 10) of the construction for sliding motion
to toothed wheel gear well illustrates the complete generality of the method,
and owes its interest not chiefly to its technical character.

The sketch represents four wheels, P,A, P;B,, P;B, and P.C, pinned to the
base-plate at P,, Py, and Pe. The point A of the first touches the point B, in
the second, the two surfaces having here a common tangent to which the
line (AB,)T,, is drawn normal. The third wheel being mounted on the same
shaft as the second, these two are to be looked upon as forming, along with the
shaft, one bar of the mechanism. The third and fourth wheels touch at the
common point (B,C), and the line (B,C)Tx¢ is drawn normal to the common
touching surface. The points T,, and Ty, are in the centre lines P,Ps
and Treo

The velocity of the wheel A, and therefore of its touching point A, is
supposed known, and this velocity is marked off as pa from any pole p, the
the line pa being drawn perpendicular to P,A. Then ph, and ab, intersecting
in 6, are drawn perpendicular to P,B, and to B,T,,. This gives pd, the velocity
of B, and ad, the velocity of sliding of one tooth over the other.

Then ph, and 6,b, intersecting in b, are drawn perpendicular to P,B, and to
B,B,; pb, is the velocity of the point B,. Finally, pe and 0,c intersecting in ¢
are drawn perpendicular to P.C and to the normal CTyc. This gives pe the
velocity of C, and b,c the sliding velocity of this second pair of teeth over each
other. The process may be carried on indefinitely through a whole train of
wheel work, however complicated, As a method of finding the velocities
throughout such a train, however, it is not a practically useful one, because the

ANALYSIS OF THE KINEMATICS OF MECHANISMS. 517

directions of the normals to the touching surfaces cannot be very accurately
obtained on the drawing unless the “ pitch points” T,;, Tc, &c., are known, and
if these are known to start with, the various velocities can most simply be
determined from them directly without reference to the touching points.

The point T,, may be looked on as indicating two points, one in the first
wheel, which may be called T,, and the other in the second, which will
be called T;. To obtain the velocity of T, the triangle pat, is constructed
similar to the triangle P,AT,. In this triangle az, coincides with the line ab,,
and pt, is perpendicular to P,P3;. Making a similar construction for the
velocity of the point T;, we find that the point 7, coincides with the point @.
Thus the points T, and T, in the two wheels have the same velocity pt», and
the point T,, is therefore called the “pitch point.” The angular velocities of
the two wheels are therefore inversely as the distances P,T, and P,Ts, this
being a familiar theorem proved in the ordinary treatment of toothed gearing.
Similarly, if pt,, be drawn perpendicular to the centre line P,P, to its inter-
section with b,c, this pt,, is the velocity of the pitch point Ty, of the pair of
wheels (BC). If the teeth be so shaped as to give constant angular velocity
ratios between the wheels, the points Ty;, Tc, &c., in the diagram of the
mechanism and the points t., ¢,,, &c., in the velocity diagram remain fixed
throughout the periodic motion of the train. It may also be noticed that since
bt, _ B,Ts

: tab ANI 12 qt P Ab

ee and —— = 1-8 th Ma pli & = Joe Big

es 9 , — pyr Mere ae te, ~ Pals’ Bs ~ Pal,’
Ata 3 :

so that ; = also measures the ratio of the angular velocity of wheel A to that
it

of wheel B. The condition that the angular velocity ratio should remain
constant may thus also be expressed by the condition that the line ab in the
velocity diagram, representing the velocity of sliding of tooth over tooth, should
be divided in a constant ratio by the fixed-point ¢,. [This point ¢,, is only
fixed if the angular velocities themselves, as well as their ratio remain constant,
the magnitudes of these angular velocities being proportional to pt,.| Whether
this proposition can be utilised in simplifying the practical drawing out of the
teeth-profiles, so as to secure a constant velocity ratio, the author has not yet
had time to investigate.

Velocity and acceleration diagrams have been completely worked out for the
Joy’s valve gears used by Mr F. W. Wess on his compound locomotive engines,
the gear being differently arranged for the high and low pressure cylinders.
These mechanisms are too complicated to be treated without very inaccurate
approximation by any other graphic or algebraic process known to the
author.

Velocity

Diagram

Acceleration Diegram

en
Vol. XXXI. Plate 12

Mechanism
Diafram

Velocity
Diagram

Acceleration
Diagram

GRAPHIC ANALYSIS OF THE KINEMATICS
= UN CARTALIOS,

or MECHANISMS

Tivariane berskine Ine

( 519 )

XXIX.—The Visual, Grating and Glass-lens, Solar Spectrum (in 1884).
By C. Prazzi Smyrtu, F.R.S.E., and Astronomer-Royal for Scotland.
(Plates LX X XIII.-CXLITIL.)

CONTENTS.
PAGES

Part I. The Observations ; their objects, and the mode of pee nase them, F : 519-524
Meteorological Appendix to the Same, c . c : 524-526
Part II. Reduction of the Instrumental, to a Wave- Reber pcale) 5 x : 526-528
Part III. Graphical representation, in place of printed numbers alone, * . a, 3 529-531
Part IV. Indexing by Colour, ; : 531-532
Parr V. Variations of Temaperaniize and giier Crane sources of Mesa Distutbaries, 3 532-537
Parr VI. Appearancesand Disappearances of Terrestrial Water-Gas lines in the Solar Spectrum, 537-539
Part VII. Some of the results arrived at touching true Solar lines in the year 1884, Q 539-541

Parr VIII. Testimony of Successive Gaseous Groups as to the most practical of Natural
Spectrum Seales, . : : 541-543

Part IX. The Map in 60 Plates and with an index Plate, LXXXIIL _OXLIIL

Part ].—THE OBSERVATIONS ; THEIR OBJECTS, AND THE MODE OF
COMPASSING THEM.

Throughout the year 1884 the sun was seen over most countries under
peculiar atmospheric circumstances; and these, instead of being confined to
low altitudes, were never more conspicuous than during the summer of the
year, and noon-tide of each day, and in the clear air on mountain heights of
every country, whenever the sky was more or less free of actual clouds.

On such occasions then, the usual phenomenon to be noticed by the eye,
was, that nothing like blue sky could be witnessed near the sun. But in

place of that, there was a broad glare of whitish light extending for several

degrees around the luminary; and beyond that range, or over 20 degrees
distant from him, there spread a wide reddish haze, passing into purple, and at
greater distances into blue, but nowhere a very decided and deep blue sky.

That the medium producing this appearance was terrestrial rather than
Solar, was indicated by similar effects being seen about the full moon. But
that its locality must have been far higher than the ordinary clouds was still
more conspicuously proved by the said clouds always appearing in front of, or
backed by, the peculiar reddish glare; and then showing their own cloud-
tints, greenish-white on their illuminated edges, and blue-gray on their shaded
sides, in most pronounced chromatic relief.

The upper air, to produce any such effect, must at the very least have
been filled with far more than the average amount of those minute dust
particles, which are always floating about there in greater or less quantity far
above the level of all ordinary massive clouds of watery vapour. And though
some of the extra amount of this higher dust may have been derived from
several other sources, yet the general opinion of most men of science in

VOL. XXXII. PART III. 4k

520 . CG. PIAZZI SMYTH ON. THE

most nations appears now to be, that by far the greater part of it must have been
supplied by the widely extended volcanic eruptions of 1883, in Australia, in
Alaska, but chiefly at Krakatao in the Indian seas.

In each of those three cases, clouds of matter went up, and mud, stones,
and coarse dust came down, both speedily and within such immediate
proximity of each volcanic vent as to testify unmistakably to their parentage,
But in the Krakatao case, if not in the others also, a far finer kind of dust
went up very much higher; so high indeed as to be left behind by the earth —
in its axial rotation; and thus to be seen successively by every terrestrial
meridian in the course of 24 to 35 hours; and was recognised to be spread-
ing out sideways widely and rapidly at the height attained.

One of these resultant cases, I believe that I saw from the Calton Hill in
December 1883 when, after sunset, a brilliantly illuminated display of broad,
thin, and nearly uniform cirrus cloud, stretching at one moment apparently
through the whole heavens from south, through the zenith to north,—went —
down with remarkable speed, and in one piece, towards the west, as though it —
had been a curved shutter of the outer sky, pivoting in the south and north
points of the horizon, turning rapidly upon them as an axis, and leaving
ordinary clouds hanging about in the lower air, amenable only to petty winds —
blowing this way and that, near the low-down surface of the solid earth.

That any great portion of a volcanic eruption is ever got rid of by being
reduced to impalpable powder, projected upwards far above the clouds, and
eventually sprinkled in homceopathic dust-rain over all the surface of the globe,
seas and continents alike, and found in rain-gauges—was evidently beyond the
ideas of geologists in 1850. For then after a valuable paper read before the
Royal Society, Edinburgh, by one of its most respected Fellows, on the volcanic
features of the Alban Hills near Rome,—wherein the learned author enlarged
on the terrific intensity of the ancient explosions which had blown out the
once stupendous rock-contents of their now deep, hollow craters, a gray-headed
geologist present inquired with painful care, what had become of that mass of ©
ejected rock? Was it to be found close outside the craters, or at what distance
therefrom, and in what sizes and shapes of blocks? Whereupon the really able
author of the paper became confused, admitted he had made a mistake, and
ought to have said that the supposed blown-out rock-masses had really fallen
in; and that was the reason why they were not to be found lying about in big,
recognisable portions outside.

But with the ultimate Krakatao volcanic ejection which went up, it is said, |

as a mighty dust cloud, formed of half the mountain’s bulk, to a height of forty _
miles, and under such compelling force as to carry its electrical charge, as due —
to the interior of the earth with it, and thereby became endued in its every atom
with a power of floating perhaps for years above the terrestrial planet,—did

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 521

any gaseous matter, and if so, of what kind and in what quantity—accompany
the ultra triturated dust of material shot up from earth’s furnaces far beneath the
sea?. In the red prominence explosions of the sun, which are far more like the
gigantic Krakatao upshoot, than are any of the cannon-ball experiments at Wool-
wich, gaseous matter is conspicuous enough. But in the case of any earthly
voleanoe, such a conjectured material has never yet been proved for its superior
manifestations. For though many persons may—like the elder Pliny when he
ventured too near Mount Vesuvius at its classic eruption in A.D. 79,—may, I
repeat, have perished from noxious gases exuding out of the lower flanks of
the mountain,—those cases do not seem to have excited much curiosity as to
whether such volcanic gases are chemically different from those already known
to exist in the atmosphere, and are ever ejected in such quantity and with such
force as to form a notable part of the explosion in the higher regions of the air.

The spectroscope however is, with the assistance of transmitted light, an
infallible test as to whether any particular medium in the upper air, dense
enough to colour the rays of the sun when shining through it,—is formed of
solid insoluble particles only, or is composed of a true but strange gas, unnatural
to our atmosphere. For in the former case the solar spectrum will be merely,
but continuously dulled from one end to the other,—while in the latter some
remarkable localised spaces or transverse lines of absorption, in addition to
all those already known as Fraunhofer lines, whether of solar or terrestrial
origination, may be expected to be met with.

Hence a solar spectroscoping in 1884, besides its own proper uses for
cosmical knowledge, might be expected to have some further special interest
connected with our own earth, 7.¢., if conducted with sufficient dispersive and
magnifying power; and unprecedented power of the former kind has been
lately given to many scientists by the magnificent diffraction gratings prepared
by Professor Rowianp of Johns Hopkins University, Baltimore, on his novel and
admirable ruling engine.

I was among the happy number to receive one of those gratings, with a
surface ruled at the rate of 14,438 lines to the inch, over an area of 3°5 x 5:0
inches ; but had intended to confine its use to vacuum tube spectra,—until I
learned that the mysterious attractions of the invisible, over the visible,
especially when brought out by the hasty, labour-saving method of photography,
—were leading most of the other donated observers to neglect the visual portion
of the solar spectrum, in spite of its beauty, its central character, and the
wonderful organs by which the Creator has enabled man to enjoy it.

Without giving up therefore my own eventual hopes and intentions on
artificial spectra, or interfering in the slightest degree with the recondite
proceedings of the greater physicists on the invisible extensions at either end

of the solar visible spectrum,—I proceeded through the autumn, winter, and

522 C. PIAZZI SMYTH ON THE

spring of 1883-4, with the valuable aid of Messrs T. Cooxe & Sons, of York,
to adapt my example of a Rowland’s grating for use in a large wood and metal
apparatus. This was of somewhat unusual form, carried object glasses 4 inches
in diameter, employed a magnifying power of 67 times linear on the inspecting
telescope, and was specially adapted for securing differentially, but with
remarkable rapidity, a highly magnified record of the whole visual solar
spectrum, whatever that might prove to be at the epoch.

Something however still more than one single record of such a spectrum
appeared due to the science of our time ; for such science has established most
profoundly, that there is no scientific subject of numerical mensuration whatever,
wherein any man, or any number of men, can do more, when they aim at
exactitude, than arrive within certain limits of probable error as to what the
truth may be. As these limits too may be very various for the different lines
of the spectrum, of which there are several thousands,—I determined, if I
could observe one spectrum well, to follow it up by a second, and even third
time of going through the whole of it; with the view of eventually bringing
the three records together in such a manner as to facilitate their comparison,
and rather provoke, than silence, criticism on every line.

But could three such extensive spectra be successively, as well as com-
pletely, observed micrometrically by the eye and hand of one observer in the
course of two months only of an ordinary North-British summer season ?

Not unhappily in Edinburgh ; where, over and above the general cloudiness
of the summers, the fearful increase of coal smoke in the air, during these
latter years of unexampled growth of its happy population in numbers, wealth,
and abundant burning of coal without consuming the smoke thereof,—has
vitiated the city’s atmosphere to a degree quite prohibitive at last of any of the
nicer observations of Astronomical Physics.

Could, however, the desired end be obtained by visiting the South of
England, profiting by itsusually sunnier summers, the absence of coal fields, and
avoiding the larger cities ?

That was what I proposed to try; and after some deliberation pitched on
Winchester. Once indeed the ancient metropolis of England under her Saxon
Kings; but now is it so shrunk within its former magnificent bounds, and so lowly
withal, that with the exception of its Cathedral, St Mary’s College, and a new
town-hall by GitBert Scort—the rest of its generally diminutive, flint-walled
houses might almost all be packed away, even hid, within our George Street.
Eminently neat and decorous however is modern Winchester ; with no manu-
factories to speak of, save a few small ones for brewing beer, or preparing
Hampshire bacon and flower honey. A useful country town evidently for farmer's
supplies, and yet grandly historic. Surrounded by healthy, open, undulating
chalk downs, with umbrageous trees and charming gardens in their hollows;

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 523

sky-larks and wood-peckers the principal birds. Noble landscapes of English
kind on every side, teeming with well preserved objects of even higher than
Saxon antiquity. Roman roads shooting straight over hill and dale. and tumuli
of aboriginal Britons far older still, While the primeval soil itself, wherever
opened, shows virgin white ; and nothing gets smirched in that fair champaign
with either smut, or soot, or any appreciable coal smoke.

In the largest upper chamber therefore, of a new country house, by name
“Kurn Hattin” (for every house there, even in the town streets seems to have
a name) and about two miles North of Winchester, which my Wife and I engaged
for the time, the rather unwieldy spectroscope was set up, with its heliostat
looking out of a window towards the South-east ; and where, when clouds
permitted, the sun could be conveniently commanded at the summer solstice
from 10 a.m. to 1 P.M, at an average altitude say of 45°. Suitable therefore
for both solar originated lines, and those produced by the higher telluric
atmosphere whether natural or adventitious.

Seldom however, through the two months of observation, June and July,
did the far too frequent clouds permit of anything being seen except themselves ;
and little would have been accomplished unless by utilising every moment of
occasional or even partial break ; and sometimes even by observing through the
thinner clouds, though that was very untoward for securing the fainter lines.
At the same time the heliostat, employed for bringing the solar rays whenever
they were visible, to the grating, being only the same rude, hand-worked affair
I had taken before to Lisbon and Madeira, required the services of an assistant
in rapid observation. Well too had I been assisted therein at both those foreign
stations, by my Wife’s patient enthusiasm, and enduring skill. But through
almost the whole of our stay at Kurn Hattin she was unfortunately laid up
with severe, even dangerous illness ; and the observing conditions would have
gone too heavily against me, but for a circumstance as unexpected, as it proved
appropriate, grateful, and effective.

This was,—that the country-house next to us, was occupied by Colonel
Kyicut, an officer recently retired after a long and honourable period of active
service in tropical climates. But now he was prosecuting to his heart’s content
Meteorology of the most careful and conscientious kind,—while he rejoiced also
in the possession of an Astronomical Observatory built by himself, furnished
with both Transit Instrument and magnificent Equatorial by Cooke, and was
both F.R.A.S. and F.R.MLS.

This gentleman then most obligingly gave me the utmost aid in working the
heliostat. For whenever there was the slightest chance of seeing the sun, he
would come over to Kurn Hattin, sit out the most perverse clouds until sun-
shine broke at length ; and then he would keep any solar image visible at all,—
and more particularly the same colour region in the preliminary spectrum

524 C. PIAZZI SMYTH ON THE

which he knew I was working at in the subsequent spectrum,—steadily on the..
collimator’s slit, for as long as I could make effective use of it.

This important assistance so greatly increased my powers for work, as to
enable me after all just to accomplish the three spectra, pack up the instrument,
and return to Edinburgh within a day of the date required.

METEOROLOGICAL APPENDIX TO PART I.

The originals of the following Meteorological observations, so important as a guide to
water-gas lines, and their varying manifestations from day to day, though telluric, in the
Solar Spectrum, have been kindly handed to me by Col. KNIGHT; and were taken by himself
at his Observatory, within a few yards of Kurn Hattin, Harestock, Winchester,—in

Latitude =51° 4’ 434 N.

Longitude = 0" 5™ 21°53 W.

Height of cistern of barometer above mean sea-level==316 feet 7 inches.
The daily time of observation being 9" a.M., and the means referring always to that hour
except in the case of self-registering instruments; whence,
in June, Mean Barometric Pressure, reduced to sea-level and Temperature 68°, = 307145 inches

1884, Mean Temperature of Air in shade, , ; , A : . =08 anes
Mean of Self-registering Maximum Thermometer, . ; ; - - =Ope ORE:
Mean of Self-registering Minimum Thermometer, . : : . =—43™ia
Mean Semi-daily Range of Temperature in shade, . : ; < = Fe ome
Mean Depression of Wet-bulb temperature in shade, .. : . SS"
Water-gas in a cubic foot of Air, computed, . : ; : . = 40 grains
Mean Relative Humidity (Saturation =100), computed, . ; . S7o0
Water-gas still required to saturate a cubic foot of Air, computed, . =1°5 grains
Total Sunshine, by Recorder, in A.M. hours, . : 2 . =80 hours 45 minutes
Total Sunshine, by Recorder, in P.M. hours, . : . . =92 hours 14 minutes
Wind, Measured mean miles per hour, . ; , . =6°74

Wind, Direction E. to W. as 3 to 6; and S. to N. as a to 16, . =N. by W. nearly

and in July, Mean Barometric Pressure, reduced to sea-leveland Temperature 68° F., = 30-064 inches

1884, Mean Temperature of Air in shade, . ; ; é ; . “= '62°25RF
Mean of Self-registering Maximum Thermometer, t . = 68°-60R,
Mean of Self-registering Minimum Thermometer, 5 ‘ . =62°>E:
Mean Semi-daily range of Temperature in shade, , ‘ . = 8:0,
Mean Depression of Wet-bulb Temperature in shade, . : . = £3
Water-gas in a cubic foot of Air, computed, 5 , . = 46 grains
Mean Relative Humidity (Saturation=100), ae ay : . =760
Water-gas still required to saturate a cubic foot of Air, computed, = 1°6 grains
Total Sunshine, by Recorder, in A.M. hours, ; 4 . =60 hours 38 minutes
Total Sunshine, by Recorder, in P.M. hours, ( - . =84 hours 37 minutes —
Wind, Mean measured miles per hour, : : . =8:24

Wind, Direction, E. to W. as 2 to10; andS. to N. as 14 to 3,=S.58.W. nearly.*
* From observations taken by my friend, Mr Ranp Caproy, F.R.A.S., at Guildoun, Guildford,

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 525

THE DAILY OBSERVATIONS ARE AS FOLLOWS :—

Sofia 4 geile eR eee
esl = o | & Festi eased. | a
Date. oe ro Fe | Sz @o |s8 = Re Sun-shine Recorder. Wind.

ss. 2 © ‘og e< 2) Se) Ee

Ree Er se Wee 8 nbs |s

B28 Se | 98 | 22. | Sa ees | as

25s £o iy || Gh) Rett || celal) Sie

ES aa | £6 | Se | ee | 822) 37 niles ee

1884. Hour. ge & Sa | 3 Za | s3 | g AM. P.M. Hoe, Direction.
an & A 2 =
A.M. Inches. Grains, Grains. H. MIN. H. MIN
June 1. © 9 30103 54-2 6°7 2°8 60° 1-9 (On 2 45 584 |S.S

ne 2. se 29-736 573 5°8 3°4 65° 1°8 See 2 34 3 38 8°87 S
ng 3. 6 29625 55°8 5°0 3°5 70° ic) 0°03 0 00 0 00 9°63 N.E
a 4, % 29-870 50°2 iY oD 87° 0°6 20 0 00 0 38 7°58 N.
sty Den aL 29°931 53°4 2°4 3°8 83° 0°8 06 0 00 Lt 24. 6:72. N.W.
ae Gs >2 29°872 55°0 46 3°5 72° 14 95 1 14 2 29 7°59 | W.N.W.
ay ie Dp 29°632 46°7 13 3°4 92° 0°83 03 0 00 2! 10°51 | N.N.E.
ag 8. © 29:908 52°4 3°2 3°5 79° 0:9 20 0 44 0 05 11:05 | N.N. W.
An os te 29°9938 50°3 3°77 3'0 15" 11 0 08 0 32 7°85 | N.N.W.
36 10. 6 30°199 54-2 4°8 353 69° 14 if bl 1 09 7°69 | N.N.W.
ey Mes 30°296 54°3 0 4°4 93° 0°3 0 00 0 00 4:26 Ss. W.
pin 12. 4 30°413 62°0 orf 4°6 79° 14 4 57 6 49 6°64 N.
eels. 9S 30°399 66°6 6°7 4°8 65° 2°5 6 04 4 59 2°58 S.W
oF 14. h 30°347 58°9 3°8 4°3 76° 1°3 2 46 6 42 8°22 N.
x6 15. © 30°414 55°3 4-7 3°5 72 14 2 26 38 10°09 N.
15 16. ¢ 30°321 52°4 27 3°5 81° 0'9 WPA 2 59 7°84 |N.N.W.
ae WG Ws 30°279 54°6 3°3 3°9 80° 1:0 00 0 20 7°96 N.W.
an ih) 30°293 59°3 4°8 4°0 fats 16 1 52 0 09 4.93 N.W.
AB OL = 2) 30°341 60°1 56 4:0 68° 1°9 3 09 4 00 3°66 | N.N.W
an 20. @ 30°299 62°6 4-9 4°6 2 1°8 sit 5 34 A bil 3°80 | N.N.E
An 21. h 30°306 60°0 4:2 4°4 76° 14 02 3 59 WBS} 5°06 N.E
59 22. © 30°262 63-4 Ue 4:0 63° 2°4 ‘Ol 5 25 1 05 5:07 N. W.
AS 23. ¢ 30°171 60°7 5-6 4:2 70° Uh) e 5 108 6 08 7°59 N.E
“9 24. 6 30°105 62°2 8:2 3°6 58° 2°6 4 15 0 18 4°69 | N.N.W
Ap 25. 9% 30124 61°1 2:2 52 88° 0°8 1 952 6 43 7°89 N.W.
» 26. 1 30:283 || 65:8 | 9:8 | 8:7 | 52° | 3:3 6 56 6 39 4-76 | S.W.
> 2. 9 30°236 68°4 WB) 5'0 63° 225) 6 12 6 41 4°64 S.S.E.
» 28 kh SOA || BEI O87 |) Ze) |) ase 7B || 1 Bi) 6 38 | 4:59 | S.E.
An 29. © 30°105 56°9 0°8 4:9 94° 03 ‘ 1 24 6 13 7°29 E.
os 30. ¢ 30°209 61°8 4°8 4-4 (PX 1°8 4 23 4 38 1°22, W.

Surrey,—projected in graphical curves on compendious table-forms, and then photographed by himself,—
it would appear that these two months, June and July of 1884, were peculiarly unfortunate for
sunshine. For not only was the preceding month of May bright with frequent sun, but the following
month of August was the brightest and sunniest month of that, or any name which had occurred in the
South of England for years.

And yet it would have proved dangerous to trust to that precedent for another campaign, as in
the very next year (1885), it was the month of July that proved to be the most admirably sunny ; and
to a degree far beyond both May and June on one side of it, and August and September on the other.
—Subsequent Note. C.P.S.

526 C. PIAZZI SMYTH ON THE

AND FOR JULY—
on : ; =
SE B/E Se Bibel eens
Date. oe mee | eget mer (lesa ates Sun-shine Recorder. Wind.
Bee | 82 | 28 | £2 | os |gas| 12
522 ea aH Be £5 | hee) ad
23° 5a Zo ma) SE | ag €
ES a= za gs g3 225 a= Miles per
1884. Hour, E 3 5 z2 iS 24 |S22| 2 AM. P.M, suk. | Direction.
fo)
A.M. Inches. Grains. Grains, H. MIN. H. MIN
July 1. ¢ 9 30°310 62°1 4:0 4°7 HOP 15 1 44 6 21 6°81 | S.W.
Pr 2.3 ; 30°280 64:7 6°4 4°5 66° 2.3 4 58 6 48 4°72 | S.E.
9 3. 1 80°115 70°7 7:0 5:4 Gor 2°9 6 45 4 21 2°33 | S.S.E
55 ce 29°998 70°3 7:0 5-2 65° 2°8 a 8 40 6 08 2°96 NS)
s be Th 30°021 65°9 6°0 4°8 68° 2°2 07 0 00 2 04 5°96 iS)
re 6. © 30°054 61°6 3°4 4°9 ie 1°3 03 3 06 2 08 511] SW
5 Une 30080 64°2 55 4°6 67° 2°0 01 3) 14 6 47 10°88 s.
< 8. 6 30°005 63°9 4°5 5:0 74° 1°6 oe 3 02 5 04 6°62 | N.E.
33 9. 8 29935 65°6 37 56 79° 1°4 02 0 18 3 32 5°94 S
oy LOL Ml 29°737 62°9 3°4 5:0 79° 1°4 13 0 36 0 Ol 4°72 | S.S.W.
Be valle GO 29°856 62°'4 67 3°9 62° 2°3 87 3 450 0 28 10:36 | S.W.
a 2. 29°956 60°4 1°4 5°3 91° | 05 19 0 45 iy ae 10°06 | S.S.W.
a les FO 29962 721 8:2 5:3 61° 32 ‘01 4 58 5a 8:09 8.E.
yp ea? WG 30063 61°3 2°5 5°0 84° 1:0 =al7/ 1 27 By aly/ 13°54 | S.W.
a LD. as 30°034 60°5 0°6 58 96° 0:2 24 0 00 0 41 14°35 | S.W.
ae) 29°797 59°4 sy 50 90° 0°6 0 02 6 34 14°40 | S.W.
Sete altima! 29°858 62'2 3°8 4-7 we 1°5 01 27, 4 47 14°33 | S.W.
5p aq 8: RO 30°155 60°5 67 3°8 64° 2°2 3) hl 0 00 11°61 W.
55 te lO a 80'245 58°9 7:0 3°5 61° 21 4 02 5 36 7°94 | "N.W.
2058S 30°214 58°7 3°3 4°5 80° Wal 1 52 iL 57} 4°49 S.E.
ay add. RG 30°055 60°3 |% 3°3 4°6 80° 12 0 00 2 32 3°43 | S.W.
A EP eS 30°135 62°9 4:0 4:9 Tift 15 04 0 45 Oo 14 10°73 | W.S. W.
Hy Bs 19) 29°996 59°6 0:9 54 94° 0°4 05 0 12 0 02 12°14 | S.W.
a3 ek 29°862 LOA I ayes} 3°8 68° 1°8 ‘13 2 35 2 O1 10°12 W.
rae 7a Ak: 80°042 58°3 4-9 3°8 (le 1°6 08 Bf 3 59 9°38 NE
5p) eos. ip 30°254 53°4 3°8 34 ow ila 15 0 15 0 12 5:87 | W.
oo he 1S 29°925 58°4 32 4°5 81° 11 1 58 2129 13°82 | W.S.W.
Pn eae aC 30°245 59°0 7°8 3°2 57° 2°4 07 Lt 50 0 O1 7:97 N.
aay eee: ae 30°164 64°6 37 5°4 80°} | 14 £ 0 Ws 0 03 7°22 |W.N.W.
eg CLUES 8, 30°302 65°9 4:2 bya) 78° 15 0 10 0 47 3°71) S.W.
i wo 30°318 57°6 01 one 99° 00 1h yy 2 38 3°81 | S.S.E.

Part IJ.—REDUCTION oF THE INSTRUMENTAL, TO A WAVE-NuMBER, SCALE.

The shape in which the Winchester Spectrum work was brought to Edin-
burgh on July 30th, consisted in three packets of seven lengths of paper each ;
every such length containing 19 to 20 parallel, but consecutive revolution strips,
and each strip, 14 inches long, holding on an average the recording marks for
about 50 Fraunhofer lines. So that each of the three spectra might be formed
into a continued length of nearly 160 feet of paper, holding something between —
6 and 7,000 symbolic notings in its course, to indicate various characteristics
besides the very important one of angular place, by micrometric screw
measure, of as many solar, spectral, “fixed” lines.

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 527

The first step in reduction consisted in transferring with ruling pen and
square all these fiducial markings at their several distances apart, to large
engraved sheets, furnished with scales of nearly equal length to that of the
Micrometric apparatus, but with much more space above and below whereon to
develop the condensed symbology of the original pencillings, and introduce
dates and notes for every day’s work. Each of the three spectra was thus
treated in perfect independence of the others, and the third one had further still
been observed in a very different manner to the first and second. For while
they had the benefit of a collimator 70 inches long, the collimator used for the
third, though with the same diameter of objective, was only 35 inches long ;
while the cone of rays from the preliminary condensing lens of the heliostat was
now still further condensed and shortened by a supplementary lens.

Greater brightness of spectrum was hoped for by this concentration of Sun-
light on the slit, but was not obtained ; and in place of it only a third spectrum
very like the first and second ;—no one of them being perfect ; and the mean of
the three, probably better than any one taken by itself alone.

The amounts of such residual failings in each set of measures, though very
small in themselves and hardly to be perceived in most spectrum work, was
nevertheless, on the grand scale here attempted, quite sufficient to prevent the
records, though derived from a Diffraction Grating, bemg always read off
implicitly as a continuous scale of wave-lengths. 1 determined therefore to look
upon them as varying differential measures, to be trusted only for short micro-
metric runs ; while an absolute scale was prepared for them all, by referring the
places of their chief lines to Ancsrrom’s celebrated Normal Solar Spectrum
Map,—assisted where necessary by the numbers recorded in the much later
works of MM. VoGEL, Cornu, Fievrez, THOLLON, and Professor Younc, U.S. Am.

Their scales however being for Wave-lengths in terms of the French
Metre,—I had to reduce their figures to Wave-number per British Inch, for
the reasons stated in my paper lately printed by the Royal Society, Edinburgh,
entitled “Micrometrical measures of Gaseous Spectra.” While finally I
entered tlie leading divisions of such a scale, to the number of 600 for each
spectrum, upon the sheets of pen and ink work,—after having obtained the
rates of variation by the usual method of projecting the places of known lines
on paper ruled transversely with the Micrometer scale, and drawing curves,
through the points of intersection. The insertion of nine marks of nearly equal
subdivision between every pair of the original 600 then followed, and gave each
spectrum by itself a Wave-number scale with as many as 6000 fiducial steps
marked and numbered; but on a continually contracting, or conical, scale in
passing from Red to Violet: as well as totally different when, for some parts of
the spectrum,—as the very earliest of the Red,—the first order of the Grating
was substituted for the second order, or that usually observed upon.

VOL. XXXII. PART III. 4S

528 C. PIAZZI SMYTH ON THE

These 6000 fiducial steps had, of course, next to be transferred to sheets
representing a Wave Number Scale of equal parts; and in order that the
ultimate comparison of different authorities might be as instant as possible,
these latter sheets must be of a collective character and contain all the
authorities, at each point, one under the other.

To this end, 60 plate forms of a long or double quarto size were prepared,
each carrying 500 units of Wave-number scale, as adapted to a spectrum now
of only 80 feet in length, and in strips one under the other five times repeated.
In the three lower strips the three Winchester spectra were entered by
measure ; and in the two upper, the standard tests and critical references.

The topmost of these two reference strips, excepting for the three first
sheets of the series, wherein Kircnorr’s celebrated spectrum was followed, could
not but be devoted to ANcstrom’s Normal solar Spectrum ; not only on account
of the accuracy of his absolute places, and his long priority—but for his, and
his friend M. THALEN’s invaluable chemical equivalents of solar lines; and as
they were now stretched out on these new sheets to about ten times the length
they occupied in the original Upsala Atlas,—I was much pleased to find that a
certain amount of microscopic confusion which has been complained of by some
persons there, was completely corrected.

The second however of the reference strips was confined both to solar lines
and to the most advanced maps of them by any of the later observers, as
Professor VoceL, M. Firvez, M. Cornu, M. THoiion, Professor Youne of
Princeton, and Professor Row .anp, Baltimore, U.S.,—duly naming each of
those great authorities whenever cited.

But it is now time that I should render due thanks, and give proper praise
to Mr Tuomas Hearn, First Assist. Astron. R. Obs. Edin., for the very great
help he has afforded me in this section of the work. For not only has he, in
the long conical sheets of the three Winchester spectra, inserted the nine sub-
dividing lines and their numbers between each pair of my 600 preliminary
points thrice repeated; but he has had the whole responsibility of copying,
introducing, and greatly enlarging at the same time ANcstTRom’s celebrated
Normal Solar Spectrum with all its chemical references in clearer guise, into
the topmost horizontal strip of each of the final and collective plates ;—besides
doing the same for all the consecutive selections of various spectra introduced
into the second reference strip,—where too the various depths of lithographic
tints employed by some of the authorities, could not have been reproduced
certainly and satisfactorily in printable form, except by such admirable and
clear-lined penmanship as Mr HEAtu’s.

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 529

Part IJI.—GRAPHICAL REPRESENTATION IN PLACE OF PRINTED
NUMBERS ALONE.

The final step, that of transferring into the three lower strips of each of the
60 plate forms above alluded to, every line of each of the Winchester Spectra
from the long sheets with the conical scales—had of course to be carried out
rigidly by myself; and as it has also been done on a partly symbolic plan of
my own, intended to secure greater trustworthiness in spectrum drawings for
the future,—I may as well say a few words upon it at this point.

For the middle of the Spectrum, the ordinary method of representing all
the stronger Fraunhofer lines, as vertical and parallel black lines ruled of more
or less thickness, but of equal height on a horizontal strip of white paper,—
such a method, I say, is just about as good a one as can be desired; for
excepting colour, which has been hitherto tabooed in all high class Solar
Spectrum Maps, the white paper stands expressively enough for the brilliant
continuous part of the Spectrum of the Sun, and black ink lines also well
represent the darkness of sharply-defined Fraunhofer lines seen thereon.

But when exactly the same method is carried out to each end of the
Spectrum, where of course the continuous spectral lhght of the hitherto
lumimous back-ground in Nature at last vanishes in darkness, and no black
lines can be seen clearly, in a quite, or even an almost, dark field,—such
method I would beg to point out, misleads these who use such maps,
grievously. For they are led to believe that there is just as much continuous
spectrum light between, or as it almost looks behind, the lines of the pre-
liminary band of Great A, as there is between those of Great B, or of the
Alpha band ; and such reading students may form very erroneous estimates of
the probable error attending on the observations of place for the first named
lines, or on the distribution of lines, their thickness and the degrees of definition
prevailing among them.

To meet this imperfection in previous maps, I have introduced into mine,
towards each end of the spectrum, a black shade running along the lower side
of the otherwise white horizontal strip, and gradually rising in it as the
spectral light fails ; until, when that ceases any longer to be visible, the black
shade has risen to the top of the horizontal white strip, and eclipses it from
that place onwards. Hence at any intervening point between the full height
of the white strip near the middle of the spectrum, and its final extinction at
either end, readers may judge of the degradation of the light, by the com-
parative heights of the black shade below and the white paper above it; or
they may imagine the sort of gray that would be produced over the full height
of the strip, by smearing upwards, though but approximately, the amount of
black contained in that part which is so coloured by the shade below.

530 . PIAZZI SMYTH ON THE

So much then for the strength of the illumination of the back-ground of
continuous spectrum light, whereby alone any Fraunhofer lines can be
distinguished at all. But amongst Fraunhofer lines themselves, there are very
ereat differences ; and while there is nothing so easily imitated or represented
by merely drawing a sharp, simple line with a ruling pen and black ink
on white paper, as a strong, well-defined, Fraunhofer line,—there are all sorts
of deviations from such an ideal in the course of the Solar Spectrum. For
there, every experienced observer knows so abundantly, that besides lines
thick and lines thin, there are lines of various degrees of paleness, and of
various degrees of sharpness, as welias sometimes of even extravagant haziness ;
and all these are physical facts which should be expressed to some extent,—
though minute accuracy does not stand with them on the same high level of
importance as with accuracy of place in the horizontal scale.

_ Hence with those two great ‘“ Dioscuri” leaders of modern Spectroscopy,
KircHorF and ANGSTROM, the former’s map is not so popular now as it once was,
—and partly because the method he adopted of indicating both paleness and
thinness of some lines, by printing them in from pale tint stones amongst black
lines previously printed from another stone, both sacrificed accuracy of place,
and produced very ultra ideas of colour as well as paleness. While Angstrom’s
map, which printed every line from one stone, with one inking, and sought to
give thinness and paleness by exquisitely fine engraving only,—still holds its
own among Spectroscopists with remarkable power and tenacity.

Yet his is not a perfect method, for it cannot show such an undoubted
existence as is occasionally met with, in the shape of a broad Fraunhofer line
of pale material. While partly to make up for that graphical weakness as well
as some others, the plan of pure engraving has been made the parent of a most:
widely followed, yet distinctly vicious, system of representing shade, especially
pale shade, in the spectrum by thin, close, vertical and parallel lines.

Now some shady, nebulous bands to inferior spectroscopes, do undoubtedly
resolve themselves into thin lines in a better instrument, but some of them do
not, and ought not, in any spectroscope whatever; and even with those that do,
the question of importance is to determine, into how many lines, and at what
distances apart? Wherefore for an observer who has seen nothing whatever
but a hazy, nebulous shade, to represent that in his map by clean, distinct lines
of his own invention, drawn just as they would, or ought to, have been drawn,
if he had seen veritable Fraunhofer lines in that place, is a species of wilful,
scientific misleading which should be tolerated no longer.

I have had no scruple therefore in my own maps, and also in my copies of
anything really important from other men’s maps, in adopting as a governing
principle for representing both paleness, and degrees of haziness in the spectrum,
a symbolic method, not only easy of execution but perfectly impossible to be

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 531

confounded with any genuine Fraunhofer, or spectroscopic line proper,—and
have called attention to the fact, and the principles on which it is based, at the
foot of every one of the 60 plates now presented.

These plates are further, though only half the size * of the original records,
yet still on so very large a scale, that the places of any lines thereon, despite
much roughness in the drawing, may yet be read off to such an accuracy, as
not to require any columns of printed numbers to follow. There only remains
therefore the propriety, when the plates are so numerous, to devise some easy
and effective Index to them and their chief contents.

Part ITV.—INDEXING BY COLOUR.

The want of something of that kind becomes most evident, when some one
line has to be looked for among actual thousands of others, without its exact
Wave-Number place being perhaps known beforehand ; and not known most
prebably on account of the Scientist or Student having been accustomed to use
some other Spectrum scale, as either French Wave Lengths, or Kircuorr’s
private Prism numbers, or the devices of some optician.

But no matter what strange, artificial and human devised spectrum scale any
one may have been using,—he must also, if an observer, bave had Nature’s
inimitably beautiful, and effective general indexing of spectrum place by Colour,
before his eyes again and again; till those colours must, if he has a soul, have
been impressed involuntarily and indelibly, on the tablets of his heart in thankful
admiration of God’s glorious Creation. Wherefore such a person’s search for
any particular lines, guided otherwise by merely the one remaining, self-
evident feature, viz., their configuration in black and white,—a configuration
which may repeat itself very nearly, and therefore deceptively, many times in
the course of the whole spectrum,—will be enormously aided, expedited and
rendered more agreeable too, if, knowing beforehand that the group he wants
is in the Gireen,—he finds 6 out of the 60 sheets coloured Green, and the rest
of them steeped in colours as easily distinguishable from Green as they can
well be.

The manner however of introducing this colour into the Winchester work,
is again partly symbolic ; in so far as, instead of one colour blending insensibly
into another, each is inserted in a flat tint, perfectly uniform from beginning to
end; but for that very reason, by so much the more easy to be separated by the
eye, from either the preceding or the following colour. Nor need this be
considered much of a violation of the more important laws of the Natural
Spectrum ; because, as I have shown several years ago in the Transactions of

* This note of size refers to the drawings for the plates. The actual prints, for economy’s sake, are
only one-third the size.

532 C. PIAZZI SMYTH ON THE

the R. Soc. Edin. (vol. xxviii.)—the spectrum colours, unlike the Fraunhofer, or
“fixed” lines in the solar spectrum, are not fixed and unalterable in spectrum —
place; but are positively locomotive therein through certain limits, according
to the colour and the strength of the light. Hence Colour, though gloriously
powerful, can only be, under any method of representation, an approximate
indicator of exact spectrum position ; and will be most useful, when we employ
it on that clear understanding alone.

Dependent then in part on what the chromo-lithographer can accomplish,
and what I shall be able to pay for—as the Society is not to be put to the
expense of colour,——I have turned to the chromatic plate in my book “‘ Madeira
Spectroscopic,” and have extracted thence ten well separated and easily dis-
tinguishable colours,—extending by equal spaces of 3000 W.N. Units on 6 plates
each, through all the visual spectrum depicted as here from 33,000 to 63,000
W. Number place. And I have also described, as well as exhibited, each of
those 10 colours, together with an ultra-region at the beginning and end
of them in a single collective plate, which I trust will be found all the title-
page and index, which the whole mass of the following plates requires.

These plates are numbered, not 1 to 60, but 2 to 61; for the reason, that
the No. 1 plate after being finished in MS., was found to contain only one line,
and that of no very pronounced character. In the spectrum itself too, it is
exceedingly difficult to see, and therefore not capable of much accuracy of
measure, so the plate carrying it has been omitted for economy’s sake. While
finally, at the suggestion of the Secretary R. 8. Ed., I have added throughout, to
the two upper strips, the scale points of ‘“‘ Wave lengths” in modern French
metric terms, adopted by ANcstrrom in the latter years of his life, vice the
“inches” of his renowned and heroic Scandinavian forefathers.

Part V.—OF VARIATIONS OF TEMPERATURE AND OTHER PROBABLE
Sources oF MINUTE DISTURBANCE.

On comparing the three Winchester Spectra carefully together, after they
were entered, reduced to Wave-number scale, on the final 60 sheets,—I was
rather disappointed to find that they did not agree more closely and minutely
at every point—whether as regarded (a) the exact places and appearances of
strong and well-known lines; or (/) the existence or non-existence, as well as
the exact places, of very thin lines not hitherto generally known of, or
recognised amongst most observers.

In matter (a) the anomalies were found, not only in the absolute Wave-
number places of the sheets of reduction, but in the original instrumental
records ; so that the simple intervening distances there, in three several cases
of certain well-identified lines between great A and great C,—measured, in

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 533

mere inches of the paper micrometric record, with these decidedly too broad
limits of variation :—

5°90 5°95 6.16
88°24 89-02 88°34
56°76 56°37 56:27

Still, however, being facts of observation, unexplained and unexpected,—I
have never scrupled to give the anomalies in place thence resulting to any of the
spectral lines, exactly as they came out, through all the finished Plates. But
in the inferior matter of intensities of lines, and where my method of recording
was confessedly weak,—I have often used considerable licence in making each
of the three records, if certainly of the same line, approximate from their
individual, to their mean, value as to strength. This proceeding will enable
every reader to identify the same lines much more easily, in spite of not
exactly coinciding places. And though this latter kind of discordance is
undoubtedly a blemish, yet its full and intrepid insertion may perhaps prove in
the end a valuable aid in deducing the limits of probable error for the place
of any line, as given in either a single spectrum representation or in the mean
of the three.

But in matter (5) the immense variations that appear both for place and
even existence among the thinnest and faintest orders of Fraunhofer lines are
truly surprising and need inquiry before going further.

Some portions of the uncertainties of place, generally, and for all kinds of
lines, thick and thin together, are due to the effects of varying temperature on
the grating. Not indeed of the absolute temperature, when settled down
to something like permanence ;—for that should have been eliminated by the
method of reduction and its appeal to M. Awnastrom’s standard places.
But quick changes of temperature, and sudden springings of the apparatus
during a rise or fall of temperature are much more difficult to guard against,
and are only too likely to occur from the very nature of the case. That is
to say, from the direct heating influence of the Sun, condensed by the heliostat
on the slit, and thence passed on to the Grating itself ;—but acting there, as
dependent on the clouds from minute to minute, sometimes for an hour
together, sometimes for only five seconds during several hours.

Some of the errors of place in special localities of the spectrum were
Owing to the want of correctly fixed standards of reference in regions where,
until lately, nothing was known to exist. And some again are due to the
fragmentary character of the observation opportunities afforded by the too
frequent clouds, whereby the time interval between noting two successive and
neighbouring lines, may have been prolonged from a second, to an hour, or a
day, or even a week; and a spectrum run which should have been con-

534 ©. PIAZZI SMYTH ON THE

tinuously as well as speedily obtained at one temperature, may have been a
slowly accumulated piece of patchwork at several temperatures.

Other portions again have been suggested to be owing to the natural dis-
placement of lines by the rotation of the Sun, when taken from either East or
West limb, instead of from the centre of the visible disc. But these effects
could only have been exceedingly small; for I had much difficulty in realising
anything of that kind to be measurable, when I actually tried the experiment
with the apparatus arranged as employed through the whole of these observa- —
tions ; ¢7z., with an anterior separating prism to confine the grating’s view to
one colour region, or nearly so, of the spectrum at a time. And that again
reduced to a minimum the chance of occasionally mistaking intruding lines —
from an overlapping order of spectrum, for those of the order intentionally
in the field of view,—-a source of error to which Gratings are peculiarly
liable.

A ruder but more powerful source of occasionally possible error, existed in.
an imperfect action of the inspecting telescope, combined with the peculiarities
of vision through a narrow vertical slit. For though when the focal position
of the eye-piece was too far out, that fact was easily shown, and as it should be
by a haziness in the image of a line, yet when it was too far 77, every line in the
field of view split immediately and sharply into two: and these separated
further and further from each other, as the error of the focus increased.
Wherefore the appearance of close and similar double lines had to be jealously
watched whenever the observer’s telescope, by passing from green to violet of
the spectrum, was innately growing in focal length. On the other hand, when
the definition of the atmosphere was bad, the members of a really double line
would throw out fringes of haze towards each other, and conceal thereby their
real duplicity, if very close. While all the time alteration of focus had to be
very sparingly employed, as it was only too apt to spoil the nicety of bisection.

Something also of the highest accuracy may have been lost, in exchange for
the greater speed at which the observations both were, and imperatively
required to be, secured whenever the sunshine was continuous. In _his
authoritative little work, Studies in Spectrum Analysis, Mr Norman Lockyer
has rightfully stigmatised the slowness of the ordinary hand and eye micro-
meter observation, as only enabling a careful observer “to lay down ten lines
an hour.” But with the peculiar method,—utilising both hands and the eye,—
which I arranged for this spectroscope, I was enabled on Thursday, June 26,
1884, to lay down permanently 1865 lines in three hours.

Yet where so many opposing difficulties are concerned, I cannot perhaps d
better than conform at once to the General Secretary’s suggestion to give
further details as to the chief apparatus, and the daily circumstances unde
which the three several spectra were measured.

Now these latter were thus :——

First WINCHESTER SOLAR SPECTRUM, 1884.

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM.

535

VOL, XXXII. PART III.

Hours of
. Order of L - Max.Shade| Water-gas| Forenoon
Portions of Ain Nes Coloured Glass ~ é a _ = :
x Day of Grating’s . | Temp. in | in Cubic | Sun-shine :
Spectrum in . Ss loyed ee rig ‘ Notes at the time.
WN. Place, | OPeYation, Spectrum | UW tront oF Si | Ou Fe ats Pe
Recorder.
°F. Grains. H. M.
33,000-35,000| 8% June 25 1st two blue 70°0 5-2 a2: Between openings of
clouds only.
35,000-36,500| S$ June 24 1st 1 blue + 1 red 67:0 3°6 4 15 Violet lines of 2nd order
intrude.
36,000-39,700 | ¢ June 23 and 1 red 68°3 4:2 i) Xs) Blue lines of 8rd order
intrude.
39,700-43,050| 3 June 24 2nd None 67:0 36 4 15 Definition exquisite, no
coloured glasses.
43,050-46,830| &% June 12 2nd 68°0 46 4 57
46,830-48,150| h June 14 2nd 69°7 4:3 2 46
48,150-49,630| @ June 16 2nd 62°5 3°5 i Pal
49,630-50,000| % June 18 2nd 64°5 4:0 iy
50,000-55,850 | Y% June 19 and 66°4 40 3) 19 Focus of Collimator thus
far untouched.
55,850-58,950} ?@ June 20 2nd 1 blue 67:0 4°6 5 84 Afterwards moved simi-
larly to telescope’s focal
adjustment, but to half
the amount only, and
58,950-60,600] h June 21 2nd 1 blue 66:0 4°4 8 59 at frequent intervals.
60,600-62,950| @¢ June 23 2nd 1 blue 683 4°2 bf
SECOND WINCHESTER SOLAR SPECTRUM, 1884.
‘, é = eens of
Portions of rder of Coloured Glass ES bade VEMOIEEES) guenoon
os Day of Grating’s an: Temp. in | in Cubic | Sun-shine :
Spect é s loyed Ds ‘ Notes at the time.
Bm Pisce. | Observation: | Spectrum | “font of Slit. | Observing [Footof Ain) by Col. ee ee
Recorder.
2355 Grains. H. M.
33,000-34,400| 2 June 27 Ist 2 blue+1 red 73°4 5-0 6 12
34,400-43,050| h June 28’ and 1 blue+1 red 76:0 4°9 yi) The last part of the way,
43,050-47,700| 9 June 13 2nd None 73°0 4°8 6 4 1 red-glass only.
47,700-58,900| 4% June 26 2nd None 72:0 on 6 56 A marvellous three days
for nearly continuous
sun-shine, viz., W, ¢
and kh. Says Col.
58,900-62,900| ¢ June 27 2nd 1 blue 73°4 5:0 6 12 Knicut, “It cannot
last !” And it did not..
THIRD WINCHESTER SOLAR SPECTRUM, 1884.
Hours of
7 Order of Max. Shade} Water-gas| Forenoon
Portions of eer Coloured Glass 5 : " oe 4
. Day of Grating’s A P Temp. in | in Cubic | Sun-shine Notes at the time.
Spect : , Sereens employed in : .
Bieice, | Oberration, | Ses | front of Sit, | Bom SF omatde. | “Kalght's
Recorder.
eyitts Grains. H. M. ; ita
33,000-36,500| 4 July 3 Ist 2 blue + 1 red 73:0 54 6 45 ee ‘¢a” in immense
orce.
36,000-41,750| 4% July 3 2nd 1 red 73:0 54 6 45
41,750-44,650| 9 July 4 2nd 1 orange 73°5 5:2 3 40 All between clouds.
44,650-50,000| « July 7 2nd 1 green 68°5 4°6 3 14
50,000-55,320| 3 July 8 2nd 1 blue 71°8 50 8
55,320-56,000| % July 9 2nd 1 blue 70°5 56 0 18 Through clouds.
56,000-58,100} 2% July 17 2nd 1 blue 66°8 4°7 1 27 euuen clouds more or
ess.
58,100-60,700} @ July 18 2nd 1 blue 66°4 3°8 3 31 Den clouds more or
ess,
60,700-,63000| h July 19 2nd 1 blue 66:0 3°5 4 2 Between clouds, and with

lower eye-piece.

4T

536 C. PIAZZI SMYTH ON THE

To the above numerical particulars, the following details of focus, taken on —
h June 21 may be usefully added. _

The Collimator being kept at a fixed focus, the telescope’s focus tried
on the Solar lines of the Grating’s spectrum with an eye-piece magnifying
67 times, was found to be at the following successive distances in inches
from its objective :—

At Solar Lines. Ist Order of Spectrum. 2nd Order of Spectrum. 3rd Order of Spectrum.
Great A (68°55) ? Mixture of Spectra. | Mixture of Spectra,
Little “a” 68:43 shown by red and
B 68°39 B= 6357 blue lines inter-
C 68°36 C'= "68°50 mingled.
D 68°31 D = 68°43 D = 6846
E 68°34 E = 68-43 E = 68:46
F 68°39 F = 68°46 F = 68:52
F to G 68°47 F to G = 68°55 Mixture of Spectra
G 68°59 G = 68-702" again, red and blue
H (68°72) ? Mixture of Spectra. lines intermingled.

These numbers show that Messrs Cooxke’s form of achromaticity of
objectives, gives a more nearly uniform focus throughout the spectrum than is
generally met with. Yet that very excellence rather conduces sometimes to
the mistaking of intermingled lines of two adjacent orders of the Grating’s
spectra.

Such intermingling was probably less on this occasion than it often is, by
reason of the employment of a large anterior prism, which never allowed
a white image of the.Sun to fall on the Slit, from the Heliostat’s condenser lens
(6 inches in diameter and 90 inches focus); but spread it out sideways as a
short spectrum-coloured smear. Of very “impure” spectrum-character 10
doubt, yet enabling the greater mass of each individual colour to be thrown
separately on the slit at will.

The Prism was of moderately good Flint glass, of 38° Refracting Angle, and
with the faces enclosing that angle, measuring 5 by 5 inches. It was inserted
transversely into the cone of Solar rays coming from the Heliostat lens,
65 inches before they arrived at a focus; and the large spectroscope table,
carrying collimator, grating and telescope on its surface, rotated horizontally
round a vertical axis under the centre of the prism; and could afterwards be
adjusted slowly or definitely fixed by a grand screw motion in tangential
direction at the outer end of the whole and on the floor level,—when the colli-
mator had been placed by trial in the line of minimum deviation for the prism
at the part of the Spectrum under observation with the Grating.

In the third Winchester Spectrum, more use was made of coloured glasse

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 537

than in the first two; with the effect of spoiling the purity and beauty of
spectrum colour, but of blackening the lines, without I hope disturbing their
position for differential measures such as mine. }

Part VI.—APPEARANCES AND DISAPPEARANCES OF TERRESTRIAL WATER-
GAS LINES IN THE SOLAR SPECTRUM.

But the most powerful cause of all, for altering the very physiognomy of
some districts of the spectrum, is due to the invisible vapour, or gas, of water
dissolved in the lower strata of the atmosphere; and thickening or thinning
certain lines, or making new ones, according to its varying amount from day to
day, from season to season, and from one country to another. In the dry
climate of Portugal in June, and near Noon-day, I could only see a few
mediocre lines occupying the spectrum place of “little a” and its preliminary
band—hboth of them due to water-gas. So likewise was it in Edinburgh during
the early days of May, in the present year 1885, when the air was both cold
and dry; or with a temperature of 46°, and grains of water-gas in a cubic foot
of air=2°6 only. But in Madeira, that “ Ocean-flower” fed by perpetual
exhalations from the warm currents around it, with a July temperature of
72°°9, and grains of water-gas=6'49,—both those constellations of spectral
water-vapour lines, even in a high Sun, were rich exceedingly in thick, black
groups inimitably defined on brilliant red light, so as to form quite an inspirit-
ing sight to have beheld once in one’s life.

And at Winchester, in both June and J uly, Iam bound to confess that the
said constellations put on a most respectable appearance, under the usual
impregnation of the air in that locality and at that season to the extent of 4°5
and even 5°0 grains of water-gas to the cubic foot; chiefly thickening lines
already known both to exist, and to represent water vapour.

The puzzling manner however in which the thinnest class of Fraunhofer
lines, if of water-gas, may either appear, or entirely disappear in the spectrum,
in places where they might have been entirely unexpected by the observer,—
was first and well described by Professor Jostan P. Cooke, of Cambridge,
Mass., U.S., in a contribution to the American Journal of Science in November
1865. For, confining himself there, to the narrow space between the two Solar
and therefore permanent and steady D lines in the Yellow,--he showed how
the number of thin interstitial lines increased, just as the weight of water-gas
in the cubic foot of air gradually enlarged from 0°81 to 6°57 grains.

Professor Cooke further reasoned well on the Annual Maximum of such
lines occurring in the American autumn, when the weight of such transparent
water-gas dissolved in the air, but not forming clouds, or interfering with the
brightness of the Sun, comes also to its maximum.

Now this weight of water-gas in the air, is quite a different matter to the

538 C. PIAZZI SMYTH ON THE

usual term of “Humidity” among Meteorologists, but which is in reality
“ Relative Humidity” only; and means nothing for spectroscopic purposes, nor
for absolute chemical composition either, unless accompanied by a statement of
the temperature at the time. This may be well illustrated by the exceilent
annual account of New York Meteorology published by Dr DAnteL DRaAPrr, at
the Central Park New York Observatory for 1884. For, while his annual list
of monthly means of “ Elastic force of Vapour” numbers (which are but
another form of “Grains of water-gas in a cubic foot of air”) shows a grand —
curve through the year, having its mmimum in January, and Maximum in
August or September,—agreeably with Professor Cooxe’s observed growth of
“ Aqueous lines between D* and D?”—yet the New York “Relative
Humidity,” runs up to its terrible maximum of 96, not in August or
September, but in January! On referring however to the Doctor's Tempera-
ture return for the same month, and same hour, it is found to be only
21°42° F. Wherefore the amount of water-gas in each cubic foot of air at that
time could only have been 1°3 grains ; under which scarcity, all thin water-gas
lines would have been practically imvisible.

Even at Edinburgh, in the present month of May, looking with the identical
Winchester grating spectroscope—it was almost startling to find hardly
anything except the one Nickel line, by contrast most pronounced in the middle
of an apparently waste, empty space between the two D’s ; the water-gas amount-
ing in this case to 2°6 grains per cubic foot of air. While at Winchester, when
assisted by double that weight, I seldom looked at the D lines without seeing
eleven or more finer, and evidently water-gas lines between them, besides
the solar Nickel line ; and some of the former were almost as strong as that.

Although therefore definite and constant lines of water-gas have only
hitherto been much noticed towards the red end of the Spectrum, where
they are undoubtedly strongest, and most easy to see, yet in warm, moist
weather we may expect to find them elsewhere also. And there is a narrow,
but positive band of them, noticed by ANGsTRoM as “ strong in summer,” so far
away as in the further Green, or beyond little b. This band too, from the
interesting manner in which it has lately been independently rediscovered, and
even utilised in Jamaica as a Rain indicator, has been proposed to be named
“ Maxwell Hall’s Jamaica Rain-band.”

Besides which, Spectroscopists should be warned, that as the whole violet
end of the spectrum is sensibly dulled by water-vapour when in abundance,
there is most probably a formation over the whole of that region of infinitely —
fine linelets. And though these have not yet been distinctly resolved to view
by any one,—still with every increase in the power of new spectroscopes
we may expect to fall across some cases of them made visible; especially if
we look under the most powerful of the appropriate Meteorological conditions.

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 539

Such for instance would be those, if true, recently described in the
Newspapers, as being much complained of by our army at Suakin on the
Red Sea; viz., a temperature in the shade of 110°, and a depression of the
Wet bulb of 4° or 5° only; which implies no less than 20 grains of water-gas to
every cubic foot of air; and would present a subject of observation to any
earnest spectroscopist of perfectly phenomenal attraction,—if Government would
only condescend to make it possible to him, by granting commissariat facilities
of transit to, and lodging at, the place.

Part VII.—RESULTS ARRIVED AT TOUCHING TRUE SOLAR LINES IN
THE YEAR 1884.

It is now time, however, to return to our own more immediate subject ;
viz., the hard and fast lines of Solar origin in the Solar spectrum. Lines which
every one, in every country and in all varieties of climate sees, or should see, as
constant as the Sun itself. And yet some anomalies occasionally will, and do,
occur, when even such lines have to be observed and tabulated by human
agency. ‘So that an important business before us now, is to ascertain by fact,
whether the method here adopted, of publishing three successive and indepen-
dent spectra in final juxta-position with each other, and with two previous
authorities, has any real advantage in clearing up some of those otherwise
doubtful, perhaps inscrutable cases, which will now and then happen among
even the latest and most carefully taken observations.

Thus at 44,620 W. N. Place, or on Plate 25, a strong line, far outside any
water-gas variation effect, and represented both by M. Frevez’s, and the 2nd and
3rd Winchester, Spectra, is not contained in the Ist Winchester Spectrum. So
that had that view alone been published by me, it might have led to time-
Wasting discussions on a supposed lost line of the Solar Spectrum, vanished
between 1882 and 1884; when the simpler, and I believe the true, explanation
is, that the omission was merely an accidental slip on my part of one line in
6000, occurring at the first, but not on the two succeeding occasions.

On Plate 43, however, we find in M. Fievez’s spectrum no symptom
whatever of a very strong line, also far above water-gas variation limits in that
part of the spectrum (viz., 53,673 W. N. Place), although it is conspicuously
and solidly recorded on each of the three Winchester spectra.

Wherefore, if the Belgian Astronomer maintains the truth of his negation
of that strong line’s existence when he observed in 1882; and if neither he, nor
any one else can disprove that there must have been such a line there when I
observed in 1884; and, without any prepossession in favour of such a thing did
on three independent occasions, separated from each other by two or three
weeks,——always record a nearly first class line, whose position was subsequently

540 C. PIAZZI SMYTH-ON THE

ascertained to be in the very middle of a blank region of M. Firvez’s
Solar Spectrum map,—-why this is, in so far, just the kind of result that would
be given either by the Krakatao volcanic explosion having caused a transmis-
sion of some new and strange gas to the upper regions of the atmosphere,—
or by something still more extraordinary having happened in the Sun, And
yet I do hope M. Fievez will forgive me, if I am more inclined at present to
attribute the ominous-looking blank in his work to the imperfections necessarily
inherent in any single-drawn spectrum map (which is by its nature positive on
everything, but may be mistaken on anything likewise), than to any new gas
having appeared within the last two years in either the Earth’s atmosphere or
the Sun’s surrounding.

But when we come to the question of a possible recent increase in opaque
dust effects, or a general dulling of the whole Solar and Telluric spectrum,—
such indications in the Winchester work, and equally in all three of its
spectra, are vast and undeniable. These dust effects, however, are more easily
recognised towards each end of the Spectrum; for there, the “continuous”
light, elsewhere in blinding excess, fades away into utter darkness, and
increases thereby the sensitiveness of the photometric scale.

Compared then with what I was enabled to observe of the Solar Spectrum
in Portugal in the years 1877—78,—-each Winchester spectrum is deficient at the
Red-end by the whole of what precedes great A; and deficient at the Violet-end
by all that follows little “h,” including therefore those notable spectrum mile-
stones—so grand when the air is pure and clear, viz., great H, and great K.

But the Winchester Spectrum was observed on a grating, while prisms were
used at Lisbon; and some gratings are very limited in the length of spectrum
they are capable of reflecting at any time. I proceeded therefore, on returning
to Edinburgh last July, to arrange a prismatic Solar spectroscope very like that
employed in Portugal, though furnished with a stronger preliminary condenser
for the Solar rays, and armed with very transparent simple glass prisms, in
place of rather dark compound ones,—so as to make up, in Edinburgh, for the
want of the clearer air, and brighter Sun, of Lisbon.

With the Edinburgh arrangement then in 1884, and during many trials there
in August of that year,—I could not only see the middle of the spectrum, but
also as far towards the Red as great B, rather better than I used to do at
Lisbon in 1877-78. But great A, further towards the Red-end, not so well;
Brewster's Z still further that way and always faint in the middle of the day,
not at all; his great Y line and accompanying bands, by no means so well; and
his great X line, with its distant companions, not in the least degree,—though
they were abundantly clear at the southern station in 1877.

Heuce an extra-dulling of the Red end of the spectrum in 1884 is established
with much certainty.

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 541

Again, on trying in a similar manner with the Violet end—great G, and
some distance beyond it, were, with the better. apparatus, seen better in Edin-
burgh in 1884, than at Lisbon in 1878. But every trace of light died out in
the Edinburgh spectrum long before arriving at great H or great K, though
they were grandiose spectral existences on the earlier occasion in Lisbon.
Wherefore the whole result of this prismatic appendix to the Winchester
grating observations evidently is, that the Violet end, joined testimony with the
Red, in illustrating that there actually must have been just such a dulling of the
Solar Spectrum in 1884, as should arise from the upper air being at that
time over-charged with opaque, dusty particles—whether from the Krakatao
explosion, or any other source.

Leaving that matter, however, of location of the dust’s origin, to geologists
to pursue further,—I will beg leave to terminate this paper with a few words
on the subject of Spectrum Scales.

Part VIII.—TESTIMONY OF SUCCESSIVE GASEOUS GROUPS TO THE
MOST PRACTICAL OF NATURAL SPECTRUM SCALES.

_ In 1878 the British Association for the Advancement of Science, published
in their Dublin volume, an admirably extensive exhibition (in 52 printed pages)
of the numbers for a Solar Spectrum, compiled from both M. Anestrom and
Professor Krrcuorr, with the chemical origin of the chief lines, and the places
of all, given throughout in terms of “ Oscillation ereeency: ” This being,
4 _ however, in practice, only “Inverse Wave Lengths;” or the “ Wave-number”
here employed, though in terms of a French, instead of a British, standard of
_ of linear measure.
In their volume for 1881 (at York) the Association ale further “strongly
recommended” their method of “Oscillation-frequency,” as against “ Wave-
Lengths”; and led its Members to expect a speedy publication of lists also of
the lines in Chemical elemental spectra, expressed in the terms they so much
‘approved of. They had also in 1878 promised to distribute to the Members,
at the Sheffield meeting in 1879, a map of the Solar Spectrum in terms of the
‘same “Oscillation Frequencies.” This promise, however, I have just ascer-
tained from the Secretary, they never fulfilled ; and now in their volume for
1884, where the lists of metallic elemental lines are given at last, and to the
noble extent of 95 pages,—the Members, and the outside world too, will be
much amazed to find, that without a word of explanation or apology, the
places are all expressed in terms of Wave-Lengths.

Such a breaking of its previous promises, inferences, and example, on
the part of a great Association, supposed by many to have necessarily more
continuity, and less vacillation in its opinions from year to year, than any

542 C. PIAZZI SMYTH ON THE

single human being—is rather disturbing to private workers in science. And
I cannot but think the change to be a mistake, wherever at least Spectrum —
maps are concerned, for this amongst other reasons derived from the
Winchester records.

Viz., there are divers practical cases known, where the same chemical
element repeats a certain constellation group of lines of its own, at several
successive places in the length of the Spectrum. And evidently, if only for
recognition purposes by means of measure, it would be of advantage to every
one researching these matters, that the scale of a spectrum map should be
such, that each of these repetitions of a recondite natural phenomenon should
be presented of the same size,—in whatever successive colour of the spectrum
it may reappear.

Now the grandest example throughout the whole Solar Spectrum, of such
a_repetition-form, is without doubt set forth in those three most striking linear
constellations of great A, great B, and the Alpha band; all of them now
considered to be due to absorption by cold Oxygen in telluric, and super-—
telluric, position.

Much of the peculiar arrangement of the lines in great B and its pre-
liminary band, has been known for a long time past, from ANGsTROM and_
THALEN* downwards. But that the arrangement in great A is exactly similar,
even down to the doubling of every line but one, in its preliminary band,—was
only discovered with the powerful assistance of one of Mr RuTHERForD’s best
gratings so lately as 1878, by Professor LANGLEY of the Allegheny Observatory,
_U.S.; and that a similar arrangement prevails in the Alpha band, was the very
recent and neat discovery of M. Cornu in Paris, in 1883.

Whoever too has had the privilege of repeating these observations with
sufficient diffraction, or dispersion, power—must have been struck with the
extraordinary perfection of the series. In the preliminary bands for at least
ten couples and one single line, the emplacement is exact; and in the subse-
quent line groups very nearly, though not quite, or simply so; for they are

* Tt seems by a recent publication from Upsala, that M. TaaLen with prisms, saw the clear
duplicity of the linelets of Great B’s preliminary band much better than did M. Anestrom with a
small grating, mounted on a theodolite stand. In fact the latter did not see them to complete identi-
fication ; and in his extreme anxiety not to pass beyond the modesty of observation and the truth of
nature, disputed long before he would allow his friend M. THatEn to draw these linelets double, as he —
saw them without any doubt, on the manuscript for the immortal “ Normal Solar Spectrum.” They —
were however so drawn at last by M. Tarun, and were so engraved by the lithographer; but on his
sending a proof of his work for correction to M. Anesrrom, then on his death-bed, the dying
philosopher, in his over conscientious desire not to exaggerate what he had really seen, took a pencil
and filled in therewith the narrow spaces between the double members of each linelet; the engraver
imitated the granular pencil markings ; and that is the origin of the shading by dots, quite anomalous
in spectroscopy, to be seen now on the finally engraved and published Atlas of the Normal Solar
Spectrum, in its particular plate representing that preliminary band of the great B line. F

VISUAL, GRATING AND GLASS-LENS, SOLAR SPECTRUM. 543

fraught with a further degree of close set lines and linelets; following,
apparently, in each of the three cases, certain harmonic variations of one
fundamental idea; and that not of the uniformity of an iron railing and its
mere equal spaces, but with a delicate rise and fall of proportions most
intensely admired by those of artistic mind. Wherefore every good observer,
can hardly but regard with almost solemn awe, this surpassing and esthetic
symmetry of elemental matter, which is obeyed so perfectly by every vibrating
atom of a given element, but remains at present beyond all human mathematical
theory to equal or explain.

Now if we measure these groups on a Wave-length scale they give, as on
my original instrumental records,—

Great A = 23°86 inches,

Great B = 18-40 inches, and

Alpha band= 14°98 inches ;
or with most violent variations of size and a converging tendency, threatening
compression amounting to practical extinction and invisibility in the much
further blue, and violet, regions of the Spectrum. Regions too where every
observer knows so well, that more map space than what the “ Wave-length ”
can give, is so imperatively required to do simple justice to the increased
number of lines that appear there, as compared with the Orange and Yellow
domains.

But if we now measure the three Oxygen repetitions on a Wave-number
scale (or practically the same as the Oscillation frequencies, so long advo-
cated, but now at the last moment rejected, by the British Association), they
come out thus, on the final plates herewith presented to the Royal Society,
Edinburgh, viz. :—

Great A = 9-24 inches,
Great B = 9-00 inches,
Alpha band = 9:20 inches.

So that, as a natural representation, and in accord with the latest dis-
coveries of both Solar and chemical spectra, there is not at present known any
better scale than that which has been employed, for already published good
physical reasons, throughout the 60 plates of this paper on “The Solar (grating
and glass-lens) visual Spectrum in 1884.” And these plates themselves now
follow,—with their naturally expanded room for Blue, Violet and Ultra-violet,
lines,—to aid quick and easy examination of their multitudinous natural features,
which consist as often in the grouping of many close lines, as in the absolute
place of one standing solitary by itself.

Part [X.—TuHe Map In 60 PLATES, AND WITH AN INDEX PLATE.
VOL. XXXII. PART III. 4U

VoU. XXX. Pl. LXXXH.

ce. Edin.

ZX TO THE WINCHESTER VISUAL SOLAR SPECTRUM IN 1884.

TRUM COLOUR
AT PLACE.

JOURS NAME.

3ERS OF THE PLaTEs

Sa 10,000...33,000. 33,000....., 36,000. 36,000...... 39,000. 39,000 ..... 2,000.
IOLUDED THEREIN.
Great X = 29,680.
para Toms camury mann | Suu ATS tg] game B=389H8 | sta tnd soe
Great Z = 31, 900.

§ INCLUDED THEREIN.

ee Pisces | 2,5400...7697. WOO Acces 7056. 7056......6513, 6518...... a. |

[LARLY INCLUDED.

Great Y = 8231. Lille Go85. ees Alpha band = 6278.
Great Z= 7962.

a
ss
|

26 to 31. 32 to 37. 38 to 43.

fees. f 45,000......48,000. 48,000......51,000. 51,000......54,000.

AURORA’S Great E = 48,205. Inttle c=51,242.
ee Inne = 45,550. Iittle 6=49,005. Great F = 52, 255.

ee. ; , eee | = ae > jaeo. 97 4704.

Aurora’s Great E= 5269. Little c= 4957.
Chief Line = 5576. Tittle b = 5183. Great F= {86/.

SPECTRUM COLOUR
AT PLACE.

La DEEP BLUE. VIOLET. ULTRA-VIOLET. | COLOUR’S NAME.
P
— 50 wo 6 56 1 61, ee eee
Wave NuMBER PLACES

bese 57,000. 57,000...... 60,000. 60,000...... 63,000. 63,000...100,000. ein Naot
D6 509 To REE Little g= 60,100. | Gnear H=64,012. Sranparp Lines
: : ; Great bie 58, 967. Tittle h= 61, 933. Great K = 64, "582. ALSO INCLUDED THEREIN.
7, 4 AOE Bi WavE Sao. PLACES
0. Be cad 4456. VHA Omapoce 4233, PES racoece 4082, KOSS gorcon 2540. CLARE INGE:
latile e= 4404. Little g = 4226. Great H = 3968. SranparD Lines IN W. A.:

Inttle h = 4101. Great K = 3933. Anastrom’s Norm. Sot. Sp.

Little f= 4383.
W. & AK Johnston, Edinburfh, t& London

Great G = 4307.

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XX X.—Observations on the Recent Calcareous Formations of the Solomon Group
made during 1882-84. By H. B. Guppy, M.B., F.G.S., Surgeon H.MLS.
“Lark.” Communicated by Joun Murray, Esq. (Plates CXLIV.,

CXLV.)
(Read 15th June 1885.)

PRELIMINARY REMARKS.

On account of the treacherous character of the natives of the Solomon
Group, no extensive geological observations have ever been made in these
islands since the period of their discovery by the Spaniards three centuries
ago. For this reason my excursions in these regions were not free from
personal risks; in many places they were considerably curtailed, and in some
places they had to be abandoned altogether. Fortunately, however, I was
able to make a detailed examination of several of the smaller islands, the
natives of which had been first conciliated by the ki dly tact of Lieut.-Com-
mander C, F. OLDHAM, to whom I am indebted tor much assistance in
my pursuits. But from the circumstances in which I was placed, both on
_ board and on shore, it was necessary, in order to accomplish much, to dare
| alittle.

This archipelago includes seven or eight large islands, some of which are
from 70 to 80 miles in length, and the highest from 8000 to 10,000 feet in
height. Besides these, there are a great number of smaller islands and islets,
some of volcanic and others of recent calcareous formations. Restricting my
' remarks to those islands which are wholly or in part composed of these cal-
careous rocks, I may observe that, although only able to become acquainted with
' a small portion of the Solomon Group, the islands which I examined represent
| the different types of islands that there exist. The larger islands, composed in
mass of ancient volcanic rocks flanked on the lower slopes of their sea-borders by
| more recent calcareous formations, are represented by St Christoval. Among
| the smaller islands, the following types occur :—in the first place, there are
| those which are made up in bulk of a soft Foraminiferous deposit encrusted
only by coral limestone, as in the island of Ugi. ‘Then there are those which
| are composed in great part of these soft deposits and coral limestones, but
partly also of volcanic rocks, as in the Shortland Islands. In the next place,
| there are islands, usually small and of no great height, which are entirely of
| coral rock, as in the case of Stirling Island. Santa Anna represents probably
/an uncommon type of island, being an upraised atoll with its foundations
/™ VOL. XXXIL ‘PART II. AX

546 H. B. GUPPY ON THE RECENT

exposed. The numerous islets formed on the coral reefs at the present sea-
level do not come within the province of this paper.*

The methods employed by Mr Murray in the examination of these recent
rocks are similar to those which he employed in examining the deep-sea
deposits obtained in the ‘‘ Challenger” and other Expeditions. The Carbonate
of Calcium was determined by estimating the carbonic acid, weak and cold
hydrochloric acid being used for this purpose. The part insoluble in the acid
is designated ‘‘ Residue,” which by washing and decantation is separated, on
account of the different densities of its constituents, into three parts—(q)
Minerals, the contraction m. di. indicating their mean diameter in millimetres ;
(b) Stliceous Organisms, including also the glauconitic casts of Foraminifera and
of other calcareous organisms ; (c) Mine Washings, including those particles
which, resting in suspension, pass with the first decantation. The numbers in
brackets indicate the percentage in the whole deposit In addition to the
foregoing method, sections of many of the rocks were employed in their ex-
amination.

Tue IstAnp oF UGI.

The island of Ugi, which is six miles in length and between two and two
and a half miles in breadth, rises to an elevation of about 500 feet above the
sea. From some points of view it has the profile of a broad-brimmed hat, due
to a pause in the elevating movement when the land was 200 feet lower than
it is at present; but more commonly, losing its hat-shape, it appears as a level
topped island rising gently from the sea. Fringing reefs skirt the greater por-
tion of its coast.

Its geological structure may be briefly described as composed in mass of a
soft earthy bedded deposit, resembling the “ volcanic muds” of the “Chal
lenger” soundings, containing numerous Foraminifera, and encrusted near the
coast by coral limestone which almost disappears in the higher regions.

The Coral Limestone.—Referring for a moment to the low-lying sea border
of this island, which, elevated between 2 and 8 feet above the sea, is com-
posed of calcareous sand, shells, and coral débris imperfectly mixed with soil,
I pass on to the description of the coral limestone crust. This rock is
occasionally exposed at the coast in cliffs not exceeding 16 or 18 feet high.
In the northern part of the island I found an eminence of this coral rock rising

* In the examination of these calcareous rocks, as well as in the preparation of this paper, I have
been assisted by Mr Jonn Murray, to whom, as well as to the Appi Renarp, I have to express my
indebtedness. I also desire to express my thanks to Mr Murray’s assistants in the “Challenger”
Office, Mr Frep Prearcry and Mr James Cuumury.

+ For further information on this subject vide a paper on “The Nomenclature, Origin, and Dis:

tribution of Deep-Sea Deposits,” by Joun Murray and A. Renarp, in the Proceedings of the Lo al
Society of Edinburgh, 1883-1884, pp. 504-506.

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 547

to between 90 and 100 feet above the low-lying land at its base, and removed
inland a few hundred yards from the coast. Its interior has been excavated
into a suite of caverns known as the Waupa Caves. This was the greatest
thickness of coral rock that I saw exposed in the island of Ugi; and I doubt
if it anywhere much exceeds a hundred feet. As one ascends the slopes of
the island this formation thins away, and only occasional fragments occur in
the red argillaceous soil. The greatest elevation at which I found the coral
rock was about 425 feet above the sea.

The Soft Foraminiferous Deposit.—This rock, which is exposed in the ravines
and gorges excavated by the streams, forms the mass of the island. Closely
resembling the prevailing formation of Treasury Island, described in another
portion of this paper, it presents itself in the fresh condition as a chocolate-
coloured argillaceous and somewhat friable deposit, in which Foraminiferous
tests may be usually observed. It is often stained reddish-brown near the
surface through the hydration of its iron oxides. Specimens of this rock, after
being kept some time, become more friable and of a lighter colour. Subjoined
I have given the characters of this deposit with the list of the Foraminifera,
as determined by Mr Murray :—

A friable rock of a greenish-blue colour showing minute organisms imbedded.
Its characters are those of the “volcanic muds” found in the “ Challenger”
Expedition around volcanic islands. It seems to have been formed in com-
paratively shallow water, although not sufficiently near to the surface to permit
the reef corals to grow.

Carbonate of Calcium (13°93 per cent.) consists of Coccoliths, Rhabdoliths,
Gasteropod and Lamellibranchiate shells, Echinoderm fragments, calcareous
Alge, and many pelagic and bottom forms of Foraminifera, (vide List).

Residue (86°07) of a slate colour, consists of—

(a) Minerals (50°00) m. di. 0°3 mm. a few larger ; felspar, magnetite
(abundant), hornblende, augite ; many fragments of volcanic rocks
with pumice and glassy materials.

(b) Siliceous Organisms (1:00) ; a few Sponge spicules.

(c) Fine Washings (35:07), argillaceous matter, and many fine mineral

particles.
List of Foraminifera.

Planispirina celata (few). Globigerina rubra (common).
Bolivina costata (rare). ae dubia (few).
Textularia quadrilatera (rare). Pe inflata (few).
Bulimina sp. (many). FA conglobata (few).
Sagrina columellaris (common). Spheroidina dehiscens (few).

» Striata (common). Pullenia obliquiloculata (few).

5, virgula (common). Pulvinulina menardii (many).
Uvigerina asperula (few). is 5, var. tumida (many).
Globigerina bulloides (rare). Nonionina umbilicatula (rare),

” » var. triloba (common). Polystomella craticulata (rare).

548 H. B. GUPPY ON THE RECENT

Additional List (relative frequency not ascertained).

Cassidulina crassa. | Pulvinulina elegans.
Bulimina marginata. | a4 canariensis,
Uvigerina pygmeza. | iH menardii var. fimbriata.

Nodosaria soluta. | i repanda,
Globigerina sacculifera. Truncatulina sp.

This formation displays regular bedding, the beds being in some localities.
separated by thin bands, one to two inches thick, of a loose coarser-grained deposit
of the same nature.* Having explored most of the principal streams, which are
mostly confined to the west side of the island, I have shown the main results in
the accompanying plan of Ugi (Plate CXLIV. fig. 1); whilst the ideal section
(Plate CX LIV. fig. 2), which actually represents a section through the south por- —
tion of the island, will serve to illustrate the structural features, more particularly
the curvature of the beds and the comparative thinness of the crust of coral rock.
The tortuosity of the streams, with other circumstances, combined to hinder
my efforts to arrive at a satisfactory explanation of the lie of the beds; and
it was only after repeated tedious examinations of these stream-courses that I
was able to reduce my observations to order. The dip varies usually between —
10° and 15°, but it may rise to as muchas 35°. In the higher parts of the island,
near the sources of the streams, the beds are generally horizontal or very gently
inclined. By referring to the plan of the island, where the arrows indicate the
direction of the dip, it will be seen that the prevailing trend of the folds is
N.E. to S.W. ; but in the northern part of the island they run more N.W. to
S.E. Although the series of curves into which these beds have been thrown
are generally regular, yet the occasional sudden increase of the dip and the
occurrence of local contortions are circumstances which afford evidence of the
minor disturbances to which these beds have been subjected. The natural
sections displayed in the sides of the ravines and gorges vary considerably in
different streams, and in different parts of the same stream ; most frequently,
however, the stream appeared to have run along the crest of an anticlinal
ridge. I should here allude to a common feature of these stream-courses,
as well as of those of Treasury Island, viz., the extensive deposits of cal-
careous tufa which frequently encrust the sides of the gorges and constitute
a series of step-like terraces over which the water flows in the higher parts of
some of the streams ; leaves, twigs, and shells are often thus imbedded.

I carefully searched these beds for enclosed organic remains in addition to
the minute organisms there imbedded. Entire shells are rarely found, those
referred to in the description of the composition of these rocks being the fine
fragments of Lamellibranchiate and Gasteropod shells, I only came upon five

* Tn a limited locality in the south part of the island the rock was a very fine grained calcareous
tuffa, containing a few siliceous marine organisms,

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 349:

specimens of a small bivalve, which from its delicacy was often difficult to
obtain in anything like a perfect condition. Dark patches, where the Foramini-
ferous tests occur in increased numbers, stain these deposits; and there are
imbedded numerous small rounded masses of a concretionary nature, contain-
ing much peroxide of iron and a little peroxide of manganese. The upper
surfaces of these beds are frequently marked by cracks, which have been filled
with a material that projects above the surface of the rock on account of its
greater durability ; but from the moist and semi-consolidated state of the rock,
these shrinkage-cracks must be viewed as of modern origin.

It is noteworthy that I did not find any volcanic rock in situ in this
island.

In concluding my description of Ugi, I may refer to the pauses in the
movement of upheaval which have left their marks behind them. On the
north-west coast, I found in the faces of the cliffs of a small sheltered cove two
lines of ancient erosion, the lower indicating an elevation of 4} to 5 feet as the
most recent change in level, and the upper line indicating a previous upheaval
of 6 to 7 feet. In the interior there is evidence of a long pause in the elevatory
movement, when the island was about 200 feet lower than it is at present, which,
as already stated, has given Ugi from some points of view the profile of a broad-
brimmed hat. In the quiet waters of Selwyn Bay on the west coast, we find
testimony of an upheaval still in progress. Reefs have been elevated in mass
so that points of coral rock project between 1 and 2 feet above the high-water
level. Mr STEPHENS, a resident trader at Selwyn Bay, tells me that during
the past eight years the greater projection of these points of the reef has been
a matter of observation to him ; and that within that period the high-tide mark
has receded between 12 and 15 feet, so that some cocoa-nut palms, which
eight years since were within reach of the waves at high-water, are now only
reached by the spray.

In the description of Treasury (page 555), I have referred to the two most
recent lines of ancient erosion as corresponding with the two most recent up-

| heavals of Ugi. In bothislands there is evidence of a recent upheaval of about
| 5 feet, and of anterior upheaval of about 6 or 7 feet. Such coincidences in two
_ islands situated towards opposite ends of the group, and lying about 400 miles
_ apart, would appear to indicate the general character of the movement of
| elevation in the whole of the Solomon group.

Tue ISLAND OF TREASURY.

The island of Treasury is of an oval shape, with a breadth of 53 miles, a
| length of 9 miles, and an elevation of 1150 feet above the sea. Viewed from

552 H. B. GUPPY ON THE RECENT

(c) Fine Washings (32°26), argillaceous matter and many fine mineral

particles.

List of the Foraminifera contained in a Specimen of the Soft Foraminiferous
Rock above described.

Miliolina oblonga (rare),
Textularia turris (few).

* concava (few).
Gaudryina rugosa (few).
Clavulina communis (few).
Vaginulina bruckenthali (rare).
Bolivina punctata (many).

» hbanktkeniana (many).

», subangularis (few).
Bulimina inflata (rare).

As affinis (many).
Nodosaria filiformis (rare).
Frondicularia ineequalis (rare).

: 53 interrupta (rare).
Cristellaria articulata (rare).

A crassa (several).

5 calcar (several).

i latifrons (several).

- aculeata (several).
Uvigerina pygmeea (rare).

3; schwageri (many).

In some localities this deposit becomes highly fossiliferous, when it generally
assumes the character of a compact mottled grey limestone, and displays to the
eye fragments of corals with Pteropod and Lamellibranchiate shells, &c. Inter-
bedded with the softer rock, and offering a greater resistance to the action of
water, its position is often marked by waterfalls in the stream-courses ; but it
is absent from the higher parts of the streams and from the central districts of
the island. The following are the characters of this harder rock :—

A compact fossiliferous limestone, containing a good deal of volcanic débris,
and probably formed in shallower water than the friable rock just described.

Carbonate of Calcium.—About 60 per cent., consists of fragments of
Lamellibranchiate shells, coral, calcareous Algee ; and the following Foramini- —
fera :—Carpenteria, Globigerina bulloides, Polytrema rubra, Truncatulina,
Lagena, Nummulina, and Cristellaria.

Residue, 40 per cent., consists of—

(a) Minerals (15 per cent.), felspar, magnetite, augite, hornblende, and

glassy fragments.

(b) Siliceous Organisms, none noticed.
(c) Fine Washings (25 per cent.), consisting of argillaceous matter and
fine mineral particles.
The softer friable deposit is alone found in the elevated interior of the
island, where it is exposed in a line of inland cliffs 300 feet in height, lying

Sagrina columellaris (many).
» vVirgula (many).
», Striata (many).
Truncatulina lobatula (many).
35 rostrata (very common).
3 haidingeii (few).
Globigerina bulloides (many).

S », var, triloba (common).

i rubra (many),

¥ dubia (few).

= zquilateralis (few).

43 (orbulina) universa (few).
Pullenia spheeroides (rare).
Planorbulina larvata (rare).
Pulvinulina menardii (many).

3 repanda (few).

Me elegans (few).

Rotalia soldanii (few).
Amphistegina lessonii (rare).
Nonionina umbilicatula (rare).

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 553

near the centre of the island and entirely composed of this formation. This
was the greatest thickness that I saw exposed of this soft Foraminiferal deposit ;
and since this line of cliffs represented a natural section of the summit, I may
safely conclude that the elevated interior of the island is entirely of this forma-
tion, a conclusion which is supported by the existence of other sections almost
as extensive in that region, and one which has an important bearing on the
past history of Treasury Island. The beds in this line of inland cliffs dip west-
ward 12° to 15°; the vertical faces of the cliff being preserved by the scaling off
of large slabs of rock along the lines of joint which correspond with the strike
of the beds.* On the level summit, wherever a small rivulet exists, this soft
Foraminiferous deposit is exposed. I now append the description of specimens
of this rock obtained from the inland cliffs above referred to.

A very friable rock, of a greenish-grey colour, containing from 3 to 10 per
cent. of carbonate of lime, which consists of a few Coccoliths, and the following
Foraminifera :—Cassidulina crassa (rare), Uvigerina asperula (few), Truncatulina
lobatula (rare), Rotalia soldani (rare), Pulvinulina elegans (rare), and fragments
of Globigerine.

Minerals, about 60 per cent., consisting of mica, quartz, magnetite, horn-
blende, augite, felspars, many glassy fragments, scorie, and green fragments—
glauconite ?

Fine Washings, about 30 per cent., consisting of argillaceous matter, fine
mineral particles, glassy fragments, and fragments of scorie.

Note.—This rock seems to have been formed in comparatively shallow water,
as it is made up chiefly of the débris of volcanic rocks washed down from the
land, and afterwards mixed with the remains of minute organisms which live
near the coast.

Deposits yet more recent than those which compose the mass of the island,
I found exposed in the banks of the lower parts of the streams opening
on the south coast. Here is displayed a bluish calcareous loam-rock con-
taining Foraminifera and numerous Molluscan shells. The following are its
characters :—

A very friable rock.

Carbonate of Calcium (6°52 per cent.), consists of a few Coccoliths ; frag-
ments of Echinoderm, Lamellibranchiate, Pteropod, and Ostracode shells ;
a few Alcyonium spicules ; and some Foraminifera (vide List).

Residue (93°48 per cent.), greenish-brown in colour, consists of—

(a) Minerals (50:00) m. di. 03 mm. A great quantity of magnetite,

* At the foot of these cliffs a rich red ochre-clay has accumulated, probably as washings from the
cliffs above. It contains only 15 to 20 per cent. of mineral particles, and exhibits but a very slight

| effervescence with dilute acid.

VOL. XXXII. PART III. 4yY

554 H. B. GUPPY ON THE RECENT

felspar, hornblende, augite, many glassy fragments, and fragments
of black organic matter. |
(b) Siliceous Organisms (2:00), a few glauconitic-like casts. ;

(c) Fine Washings (41°48), argillaceous matter, fine mineral particles,
many glassy fragments, and a greenish organic-like matter. -
Foraminifera.—Globigerina bulloides, and var. triloba; G'. (Orbulina) universa,
G. dubia, G. wquilateralis, Pulvinulina menardii and P. elegans, Sagrina,
Bolivina, Nonionina, Polystomella, and Biloculina. All these Foraminifera
are in a dwarfed stage.
Molluses.—Nassa, Cylichna, Tellen, and another bivalve (in numbers), asi
Conus, Natica, Turritella, Melania, Monodonta, Dentalium, Bulla, Leda, Arca,
&c.: Pteropods represented by Creseis (in numbers), and Hyalwa (a few).
Lichinoderms.—A. species, probably of Spatangus, in numbers.
Miscellaneous.—Partially carbonised stems of plants; fragments of branch-
ing corals and volcanic rocks, 2 to 3 inches in diameter and under. Frequently
penetrated by small tubular cavities, filled with coarse sand and minute shell
being the burrows probably of some annelid or crustacean.
This deposit displays a rudely laminated structure, the layers between 1
and 3 inches in thickness being steeply inclined 70° towards the coast. It
forms the level ground on which the village of Saveki stands, removed 10 to
20 feet above the beach; and may be shortly described as formed from the
washings of Treasury Island previous to its last upheaval. A very similar
deposit is now in process of formation in the deeper parts of the harbour in
depths below the coral zone, evidently derived in great part from the large
amount of sediment brought down by the streams during the rains. Probably
the above loam-rock was formed in a similar manner and at similar depths
(20 to 50 fathoms), and the dwarfed condition of its Foraminifera may be
attributed to the injurious effect of the fresh-water of the streams. ;
Hard Foraminiferal Limestone.—I have included under this name rocks

the nucleus of volcanic rock around and over which have been formed the
Foraminiferous muds and overlying coral-reef formations that have been
described in detail. The only locality where the volcanic rock is exposed

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 555

view is near the south side of the island. The large stream that opens into
the harbour close to the village of Saveki, cuts through, at a distance of some
300 yards in a straight line from the coast, an amygdaloidal dolerite. This
rock, which is here exposed in mass, is often porphyritic in structure. Up
the adjoining slope of the hill-spur on the right side of the stream, fragments
of this and other volcanic rocks may be found on the surface. At the height
of 300 feet it is exposed im situ; and at intervals on the hill slopes above
small fragments of volcanic rocks of somewhat varying characters* may be
observed, even up to 900 feet above the sea. I have little doubt therefore but
that the mass of the spur, overlooking the village of Saveki on the west, is of
volcanic formation, being merely encrusted by the recent Foraminiferous muds
and coral rocks.

History of the Formation of the Island.—By a reference to the section of
Treasury Island (Pl. CXLIV. fig. 4), its structural history will be readily under-
stood. An ancient submerged volcanic peak, having been covered by a thick-
ness of several hundred feet of deposits, for the most part resembling the
muds now being formed around oceanic volcanic islands, has finally been
encrusted with coral reefs and been elevated above the sea to a height of
nearly 1200 feet. How far beneath the surface of the sea this volcanic peak
may have been originally submerged, it is difficult to say. But as bearing
on this question I may here quote from Mr Murray’s description of a hard
Foraminiferal limestone, which was found at the surface. “The organisms in
this rock, as well as the minerals, are,’ he writes, ‘‘ similar to those found
in deposits of modern seas in depths from 500 to 800 fathoms, near volcanic
islands.” The class of hard Foraminiferal limestones has already been referred
to in connection with Treasury Island (p. 554).

That there have been pauses in the elevatory movement, there can be no
doubt ; but only the latest have left their marks behind at the present day.
Thus, the broad ledge of coral rock which forms the sea-border was the work
of a lengthened interval, since which there has been an upheaval of from 50 to
100 feet. At that time (vide Plan and Section Pl. CXLIV. figs. 3 and 4) Stirling
Island appeared at the surface as a line of barrier-reef off the weather coast of
Treasury Island, from which it was separated by a deep lagoon-channel between
50 and 60 fathoms in depth—the present harbour. The islets of coral rock,
that lie inside Stirling Island, may possibly mark the position of other
volcanic peaks. We have, however, in the coasts of the harbour and in the
cliffs of Stirling Island, evidence preserved of yet more recent pauses in the
elevation. An old sea-level is indicated in several places, since which there
has been an upheaval of some 10 or 12 feet. But the most modern upheaval
is shown in the margin of recently elevated and often well-preserved corals,

* Augite-andesite and porphyritic felsite, &e.

556 H. B. GUPPY/ON- THE RECENT

exposed about a foot at high tide, which fringes the shores of the harbour.
Allowing for the rise and fall of the tide in this region, I estimate this most
recent elevation at not less than 5 feet. It is of importance to note, as indicat-
ing the coincidences in the elevatory movements in this region of the Pacific,
_ that in the islands of Ugi and Santa Anna, which lie over 400 miles distant at
the opposite end of the Solomon group, there have been modern upheavals of
the same limited extent (vide page 549).

The first page in the history of Treasury Island, as an island, began when
the submarine volcanic peak had been brought up to within the depths at
which reef corals thrive, by the constant piling up of sediment assisted by the
upheaving movements. During these movements, the barrier-reef, now repre-
sented by Stirling Island, was formed by the outward growth of the reef. Coral —
reefs, however, have played but a secondary part in the actual building up of
the island of Treasury as a whole.

THE ISLAND OF SANTA ANNA.

The small island of Santa Anna, at the eastern extremity of the Solomon
group, presents an example of a raised atoll. Having a nearly circular form
with a length and breadth of 24 and 2 miles respectively, this island consists
of a central basin surrounded by an elevated rim which is wanting at the
middle of the west or lee side. The bottom of the basin, which extends
downwards to about 100 feet below the sea-level, is occupied by two fresh-
water lakes (vide Plan and Section of this island Plate CXLIV. figs. 5 and 6).

The elevated rim has a broad level summit, varying between a quarter and
one-third of a mile in width, and elevated 200 feet above the sea, except on
the south and south-west sides of the island, where it has only half this
elevation. From the middle of this raised margin, on the east or weather side,
there rises an elevated mass to a height of about 470 feet above the sea, which
gives to the island, when viewed either from the eastward or the westward,
a profile resembling a broad-brimmed low-crowned hat. On the flat summit
of this elevated mass, there is a basin-shaped hollow between 100 and 150
yards across and 35 or 40 feet in depth (vide Section Plate CXLIV. fig. 5).

The central depression may be described as a somewhat symmetrically shaped
hollow, the bottom of which, lying about 100 feet below the sea-level, is
occupied by two fresh-water lakes, the waters of which are not affected by the
rise and fall of the tide, although lying at or about the mean tide-level. ‘The
iuterior of this island is, in fact, a closed basin, which is completely cut off from:
the sea; and it may be aptly compared to a bowl of fresh water floating on sea:
water. But so low is the barrier that shuts out the waters of the ocean—a
barrier which is composed for the most part of coral detritus, calcareous sand,
and shells—that a depression of about 25 feet would admit the sea into the

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 557

lakes, and a continuation of the downward movement to the same extent
would transform the interior of the island into a large salt-water lagoon. In
my traverses across this basin-shaped interior I found evidences of the sea
having very recently occupied its lower levels. In the marshy ground in the
vicinity of the lakes I occasionally came upon the coral rock exposed in flat
surfaces resembling those of the ordinary reef-flat, whilst in the drier regions
the soil was mixed with calcareous sand and shell “ débris;” and numbers of
sea shells, of ancient appearance from prolonged exposure, lay on the surface
or were buried an inch or two beneath the soil. Many of these shells,
belonging to the Ostreide, Cardiadee, Neritide, &c., were encrusted on their
inner surfaces by a dried calcareous mud. On opening one bivalve shell, with
the two valves in apposition, the ligament having decayed, I found its interior
to a great extent filled by this dried calcareous mud, which, from the impression
that it retained of the soft parts of the Mollusc, afforded proof that the shell-
cavity had become filled with this material before decomposition had set in.

The lakes, I should have added, do not occupy the centre of the basin but
lie towards the western side of the island, the centre being marked by an
eminence of coral limestone, the level summit of which is elevated about 160
feet above the sea. In concluding my description of the interior of this island,
I will refer to the basin of Port Mary Harbour which lies opposite the break in
the elevated rim on the west coast. The shore-reefs, which skirt the circum-
ference of Santa Anna, here enclose a remarkable circular lagoon 700 to 800
yards in width, which, entered by a narrow passage, affords a snug anchorage
for ships during the S.E. trade. Its depth is about 100 feet (16 to 17 fathoms),
thus corresponding with the depth of the basin in the interior of the island,
from which it is separated by a barrier of coral detritus, calcareous sand, and
shells, that a depression of about 25 feet would, as above observed, completely -
submerge.

It was only by a detailed examination of this island that I was enabled to
learn its true structure. Contrary to my expectations I found that, instead of
being composed in mass of coral rock, this upraised atoll had been formed
around a submerged volcanic peak which had been first invested, in great part,
by a deposit of calcareous mud on which the reef-corals had commenced to
grow. :

The most interesting locality for the examination of the structure of the
island is situated on the north coast. A mass of crystalline granular volcanic
rock, an altered dolerite, here protrudes in situ 6 to 8 feet above the level of the
reef-flat, forming a conspicuous object on the shore, and covering a space
of 10 yards in horizontal extent. This ancient peak, if I may so term it, has
evidently: been denuded by the waves at the present sea-level ; and in places
most exposed to the action of the sea its surface is formed of water-worn frag-

558 H. B. GUPPY ON THE RECENT

ments of its own substance joined together in a calcareous cement.* My
interest was engaged in a further degree in this locality, on observing that in
the vicinity of the protruding mass of volcanic rock the flat was composed in
places, not of the ordinary reef-rock, but of a soft argillaceous light-coloured
rock that effervesced with an acid. Walking in a few yards from the beach I
clambered up a slippery slope t between huge masses of coral limestone that
had been detached from a line of cliffs above; and ina few minutes I became
aware that I had made a discovery of some importance. <A vertical precipice
of coral limestone, about 80 feet in height, here rested on a friable argillaceous
rock, light brown in colour and sparingly Foraminiferous (ede diagram of this
locality, Pl. CXLIV. fig. 7). Appended is the description of this rock which
Mr Murray has given to me :— set
A friable earthy rock of a yellowish-brown colour, which, from the small
size of the minerals, the absence of Foraminifera that inhabit the bottom, an i
the scarcity of pelagic forms, resembles somewhat a deep-sea clay; and dis-
plays a thin coating of manganese peroxide between the small layers or folds
of the rock. A detached concretionary block of manganese peroxide, one or
two cubic feet in size, was observed by Lieut. Matan on the reef-flat on th
north coast of this island, not far from the locality where the clay above
described was met with. The typical fragment which was brought home is,
Mr Murray says, quite similar to smaller masses dredged by the “ Challenger”
and Blake.
Carbonate of Calcium (20°79 per cent.) consists of Coccoliths, Globigerina
bulloides, G'. (Orbulina) universa, G. conglobata, Pulvinulina menardii, and a few
small fragments of Echinoderms.
Residue (79°21) reddish-brown in colour, consists of— f
(a) Minerals (35:00) m. di. 0:08 mm., felspar, hornblende, one or two frag-
ments of magnetite, with a few glassy fragments. c
(b) Stliceous Organisms (1:00), fragment of a sponge spicule noticed.
(c) Fine Washings (43°21), argillaceous matter, very fine mineral particles
and some glassy fragments.
Such being the characters of the deposit underlying the coral limestone, as
exposed in this natural section, I now come to the consideration of the coral
limestone itself, which is a hard compact rock resting abruptly on the soft
underlying deposit. Imbedded in the base of this cliff of coral limestone were
two dome-shaped masses of Astreean corals of different species, one of them

* A small patch of massive coral, which still adheres to its surface, probably found attachment during
the most recent upheaval of the island (vide posted). = ’
+ This slippery slope, which is of the argillaceous rock to be immediately referred to, is in part
encrusted by calcareous tufa, containing, at an elevation of 15 feet above the sea, a few small angular
fragments of volcanic rocks, These fragments would appear to indicate the vicinity of the parent mass
further in from the reef-flat. '

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 599

being apparently an ‘“ Orbicella” (Dana). The larger mass measured 4 feet
across; and both were in the position of growth. These imbedded corals
were elevated about 40 feet above the sea, and from their position in the base
of the cliff they must have been buried beneath not less than 80 feet of coral
rock ; whilst below them, on which in fact they almost rested, was the friable
earthy deposit, or in other words, the partially consolidated ooze on which the
reef began to grow, or over which it extended by lateral expansion. A coat-
| ing of calcareous tufa concealed from view the upper portion of the face of
the cliff, and thus prevented my examining its structure. It was evident
that the undermining action of water which found its way between the base of
the cliff and its soft foundation, assisted by the earthquake-shocks to which
this region is liable, had caused large masses of the cliff to become detached,
thus exposing the foundation of these upraised coral reefs. Another locality
in this island in which I was able to find the rock subjacent to the coral
limestone was on the western slope of the summit at an elevation of 200 feet
above the sea. Here I found a stream issuing from the line of junction of the
coral rock and an underlying earthy friable rock. On the south shore of Port-
Mary I found masses of red ochre, protruding above the reef-flat.

Before drawing any inferences as to the thickness of the coral limestone in
this island, I will refer briefly to the elevated eastern portion of the rim (vide
Plan and Section Pl. CXLIV. figs. 5and6). Near the summit, and at an eleva-
tion of 400 feet above the sea, I found a volcanic rock (a hornblende trachyte)
exposed i situ in the bed of a rivulet. Small fragments of this and of one or
two other volcanic rocks (mostly gabbros) occur mingled with masses of coral
rock on the summit, and are frequent in the small basin-shaped hollow there
situated. With these exceptions, coral limestone forms the surface of the most
elevated portion of the island, sometimes displaying faces 25 feet in thickness
even at the lip of the summit. The occurrence, however, of a rubbly conglomerate
of various volcanic rocks (for the most part gabbros), cemented together by a
calcareous material, at the foot of the eastern slope of the island affords sufficient
evidence of the proximity of the parent rocks, some of the blocks being from a
quarter to half a ton in weight. In accordance with the greater age of the
eastern side of the island as dry land, we should have expected to find it almost
stripped of its calcareous coverings.

From the foregoing remarks, the following conclusions may be drawn as to
the history of the formation of this island. A submerged volcanic peak,
having been covered by the accumulation of a deposit resembling a deep-sea
mud, became the base of a coral-atoll, which has been subsequently upheared
together with its foundations, to a height of nearly 500 feet above the sea. The
thickness of the coral crust probably does not exceed 150 feet, thus corre-
sponding with the limit of depth at which reef corals are supposed to thrive.

560 H. B. GUPPY ON THE RECENT

An inspection of the diagram referring to the north coast of Santa Anna will
show that probably the underlying soft deposit is not much over 30 feet in |
thickness in that locality.

The various stages in the movement of elevation which this island ha .
passed through since it first appeared at the surface of the sea are worthy of
notice. There was a time in its history when the present summit alone
appeared at the surface of the sea as a tiny atoll encrusting a submerged
volcanic peak, the remains of which still exist in the shallow basin on the
summit before referred to. Then succeeded a period of upheaval, during which,
without any lengthened pause, this tiny atoll was raised to a height of from 250
to 300 feet above the sea. This was followed by a prolonged interval of rest
during which the main atoll was formed, differing however from the typical
atoll in that a pinnacle-islet rose up abruptly to a height of nearly 300 feet —
from the middle of the east side of the reef. Then commenced another long
period of elevation, prolonged to the present time, during which the rim of the —
atoll has been raised 200 feet above the sea, the waters of which have been ~
excluded altogether. There were pauses during this stage of elevation, the
most marked being midway in the stage when that portion of the rim on the
south side, which is only 100 feet above the sea, was formed. But in the lower
levels, wherever the land descends by a gentle slope to the coast, the retro-
cession of the sea may be traced in the successive linear heaps of coral masses,
1 to 2 feet in height, which mark slight pauses in the elevation. The most
recent upheaval] is shown in an ancient line of erosion removed usually from 5
to 8 feet above the present line of wave-action. Where the coast is cliff-bound,
the present and ancient lines of erosion are displayed in the faces of the cliffs ; _
but where the coast is low, the old sea-level is to be found in a line of erosion,
often worn back into caves, displayed in the base of a line of inland cliffs which
are removed at distances varying froma few paces to a hundred yards from the
beach, a low strip of recently elevated land supporting cocoa-nut palms and —
other vegetation intervening.

In concluding this reference to Santa Anna, I will make a few observatidil
on the small adjacent island of Santa Catalina, which from its profile has
evidently experienced the same stages in the upheaving movement, which Santa
Anna has undergone during its last elevation of 200 feet. Santa Catalina is a
low level-topped island elevated about 180 feet above the sea. Here, we have
another ancient and originally submerged volcanic peak, which, having become
encrusted by coral reefs, has been upheaved toa height of nearly 200 feet above
the sea. Although the coral rock apparently forms the whole island, it is in’
reality but an outer crust, investing as a nucleus some ancient peak once sub-
merged. In the beds of two small streams on the summit, I found exposed in—
mass a breccio-conglomerate formed of fragments of various volcanic and

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 561

calcareous rocks imbedded in an earthy calcareous matrix, together with
another dark coloured rock of doubtful volcanic origin. It is therefore
apparent that this small island of Santa Catalina existed as a patch of coral
reef contemporary with the existence of Santa Anna as an atoll; and that the
breccio-conglomerate was formed when the submerged peak, on which the
patch of coral reef had based itself, came within the limit of breaker-action.

THE SHORTLAND ISLANDS.

This small group of islands consists of one principal island, named Alu,
with a number of smaller off-lying islands and islets. Alu Island, which has a
breadth of eleven or twelve miles and an elevation of about 500 feet, is composed
in its N.W. portion of old and originally deep-seated volcanic rocks (mostly
quartz diorites); while the greater part of it, together with the off-lying lesser
islands and islets, may be described as made up of more recent calcareous
formations.

The accompanying section of Alu (Pl. CXLIV. fig. 8) will explain the struc-
ture of this island and will show the relation to each other of the volcanic rocks,
the coral limestones (so called), and the soft Pteropod and Foraminiferous
deposit which apparently makes up the mass of the island. The two off-lying
islets, shown in this section, are two broken lines of barrier-reefs which skirt the
weather or S.E. coast of Alu Island. The innermost (marked B) is an ancient
reef which has experienced an elevation of about 200 feet above the sea; while
the outer reef (marked C) has been in great part formed at the present sea-level,
having in no part been upheaved more than 20 feet above the sea. Both lines
of reef have within them a lagoon-channel, which in the case of the inner or
ancient line of barrier-reef is shoaling and evidently filling up.

The Shortland Islands have been upheaved along an extensive line of
barrier-reef that skirts the eastern extremity of the adjacent large island of
Bougainville at a distance of about 15 miles from the coast ; and a conception
may be obtained of the history of their formation by referring to the section
before alluded to. Here we have the original land of volcanic rock in the
N.W. portion of the group, from which, as from a nucleus, line after line of
barrier-reef has been advanced in a south-easterly direction based on a foundation
| of Pteropod and Foraminiferous muds, and forming ultimately as the upheaving
| movement continued the large island of Alu, which yet preserves in the ridges
| of its interior these ancient barrier-reefs now removed far from the coast and
elevated some hundreds of feet above the present sea-level. If we may judge
| from the existence off the weather coast of the double line of barrier-reef, before
| referred to, the island of Alu is still extending itself in the same direction.

The Soft Pteropod and Foraminiferous Deposit.—This deposit, which in all
VOL. XXXII. PART III. AZ

562 H. B. GUPPY ON THE RECENT

its characters resembles the formation of Choiseul Bay, subsequently to be
described, apparently composes the bulk of the island of Alu. It is exposed in
the banks of the streams that open on the S.E. coast ; and may be followed up
in the higher parts of their courses in the interior, being also exposed in the
lower slopes of the inland ridges at an elevation of 200 feet above the sea.
Bedding is rarely well displayed on account of the limited character of the
natural sections, the beds displayed having, however, a gentle inclination. In
the mass it has the appearance of an argillaceous, earthy, moist rock, containing
the shells of Pteropods in abundance, such as Hyalea, Diacria, Cleodora,
Creseis, together with numbers of Gasteropod and Lamellibranchiate shells,
such as Murex, Nassa, Hemicassis, Mitra, Natica, Dentalium. Foraminiferous
tests are present in profusion, the large tests of such as Cristellaria cultrata
and C. rotulata can be picked out by the fingers. The otoliths of fish are also
abundant. In addition, I found some simple corals referable to the deep-sea
genera, Odontotrochus, Flabellum, Bathyactis (symmetrica?), portions of the
shells of a sessile Cirriped; and occasional leaves with their venation in a —
condition of fair preservation. The Pteropods, bivalves, otoliths, and Foramini- —
fera, are from their numbers most characteristic of this deposit.

Mr Murray thus describes the characters and composition of specimens
of this deposit :—

A very friable rock, chiefly composed of volcanic ashes with great numbers
of minute imbedded organisms, and resembling the “volcanic muds” in~
character. . F

Carbonate of Calcium (33°67 per cent.), consists of Coccoliths, Otoliths,
Gasteropod and Lamellibranchiate shells, Pteropod and Heteropod shells,
Polyzoa, Serpule tubes, Ostracode shells, Echinoderm fragments, and many
pelagic and bottom-living Foraminifera. (See list below.)

Residue (66°33), brown, consists of—

(z) Minerals (40:00), m. di. 0°5 mm., some particles 1:0 mm. ; felspar,
magnetite, augite, hornblende, mica, quartz, &c.; and a great many
glauconitic-like casts of Foraminifera.

(b) Siliceous Organisms.—None noticed.

(c) Fine Washings (26°33), argillaceous matter with fine mineral particles, —
and black fragments of organic matter.

List of Foraminifera.

Miliolina seminulum (rare). Cristellaria cultrata (few).
Biloculina depressa : x calcar -
Reophax pilulifera (very few). 5 aculeata ,,
Bulimina marginata (rare). 9 italica ,,
Pleurostomella alternans (few). An echinata ,,
Chilostomella ovoidea (many). vortex ,,

”
Cristellaria rotulata (few). Uvigerina tenuistriata (common).

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 563

Uvigerina pygmea (rare). Globigerina cquilateralis (many).
Nodosaria hispida (few). = inflata (few).

i papillosa ,, ‘ orbulina (universa) (many).

FA raphanus ,, Spheeroidina dehiscens (many).

5 filiformis (rare). Ramulina globulifera (rare).
Sagrina virgula (common). Truncatulina pracincta (few).

» columellaris (very common). 5 lobatula __,,
Lagena hispida (few). 5 haidingerii ,,

5, desmophora (few). Pulvinulina menardii (common).

Globigerina bulloides (common). bs » var. tumida,,

x », var. triloba ,, “ elegans (few).

3 conglobata _,, “A micheliniana ,,

Fe dubia 95 Xf procera i

‘ sacculifera _,, Pullenia obliquiloculata (few).

es rubra (many). »» Spheroides -

The Coral Limestone—This rock is found capping the inland ridges (as
shown in the section) where it does not attain a greater thickness than 30 to 40
feet, being usually much less. It displays considerable variety in its characters ;
and had I not satisfied myself of its true relation to the underlying soft deposit
previously described, I should hesitate in coming to the conclusion that all the
varieties belonged to an ancient barrier-reef. By striking the inland ridge
(marked A in the section) where it approaches the coast and following along
its crest for some three or four miles, one first finds capping the ridge and
overlying the soft deposit a hard compact yellowish-white coral limestone con-
taining many Amphisteginc. Further along, as the ridge gradually rises from
150 to 200 feet above the sea, this coral rock displays itself as a chalky lime-
stone capping the ridge and exposed in huge masses, with vertical faces 30 to
40 feet high, on its slopes. These large masses resembled much in their position
and appearance ancient reefs still occupying the sites they originally held
beneath the sea. ‘The superficial position of this chalky coral limestone and its
relation to the underlying soft Foraminiferous deposit are points of some
interest.* Appended is the description given by Mr Murray :—

A compact chalk-like coral limestone of a cream colour, showing no
definite structure, and resembling in section the Lower Chalk of Kent, if the
corals are not taken into consideration.

Carbonate of Calcium (95°76 per cent.) consists of Lamellibranchiate shells,
Polyzoa, Echinoderm fragments, corals, calcareous Algz, and Foraminifera
as Nummulina.

* [ found a similar chalk-like coral rock in the small island of Biu which lies off the north end of
Ugi Island. This island is only 14 miles in length and about a hundred feet in height in its centre
where this rock was found. It may be briefly described as a patch of coral reef which has been elevated
about a hundred feet. In the southern island of the Three Sisters, which are adjacent to Biu, I
obtained from the elevated central portion hand-specimens of coral rock which were in part chalky.
This island, like Biu, is simply a patch of coral reef which has been upheaved 60 or 70 feet above the
sea. The present reefs which skirt the more elevated portion have a rude atoll form.

564 H. B. GUPPY ON THE RECENT

Residue (4:24), yellowish-red in colour, consists of—

(a) Minerals (2:00) m.-di. 0°1 mm.; magnetite, felspar, hornblende, augite,
afew casts of small Gasteropod and Lamellibranchiate shells, and
many little spheres.

(b) Siliceous Organisms, none noticed.

(c) Fine Washings (2°24), a reddish argillaceous and flocculent material
and fine mineral particles.

Another sample of this chalky coral limestone, which was made up chiefly
of decomposed coral and calcareous Algee and held 99:23 per cent. of car-
bonate of calcium, approaches to a magnesian limestone, on account of the
considerable amount of magnesia which it contains.* In a third sample the
only recognisable organisms are calcareous Algz.

As one proceeds further inland along the crest of the ridge, which pursues
a very uniform direction, the chalk-like coral limestone is left behind; and
rising gradually with the ridge crest to from 300 to 350 feet above the sea, one
finds a yellowish-brown Foraminiferous limestone taking its place, both capping
the ridge and overlying the soft deposit. The following are its characters :—

A hard compact Foraminiferal limestone, of a yellowish-brown colour. A
few simple corals are imbedded in this rock, but the bulk of it is made up of
pelagic and bottom-living Foraminifera.

Carbonate of Calcium (76°69 per cent.) consists of Echinoderm fragments,
Pteropod shells, and Foraminifera, as follows -—Globigerina bulloides, G.
hirsuta, G. Orbulina (universa), Pulvinulina menardii, Carpenteria, Nodosaria,
and Amphistegina.

Residue (23°31), consists of—

(a) Minerals (6:00) m. di. 0°-4 mm.; mica, a few perfect crystals of quartz,
felspar, augite, and glassy fragments.

(6) Siliceous Organisms (10:00), perfect casts of the Foraminifera of a
reddish colour.

(c) Fine Washings (7°31), broken down parts of casts of Foraminifera and
a few fine mineral particles.

In the elevated barrier-reef through which the section passes, somewhat
similar rocks are displayed. In this islet (marked B in the section), which

* Dr Leonarp Dossin, who determined for Mr Murray the carbonate of lime in the rock samples,
writes :—‘I would draw your attention to the result obtained in the case of the sample ‘Shortland
Island, No. 587,’ where the usual calculation, from the observed weight of carbonic acid, seems to
indicate an almost theoretical composition of calcium carbonate. As our method could not give such a
result with pure calcium carbonate (the results being in every case at least 2 per cent. too low), I tried
to find out the cause of this rather anomalous result. ‘The first and most likely explanation was that
the specimen contained considerable quantities of magnesium carbonate, and I find that is the correet
explanation, as I found on examining it that a good deal of magnesia is present. I may add that the

carbonic acid is not liberated from this specimen with anything like the rapidity with which it is
liberated from the other specimens.”

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 565

is named “ Poperang” and has a height of 200 feet, the soft deposit is rarely,
if ever, exposed, on account probably of the small érosive power of the streams.
Here we find the chalky limestone containing 95 per cent. of calcium car-
bonate and composed of fragments of Molluscan shells and of Echinoderms,
with calcareous Algee, and the following Foraminifera :—Globigerina, Polytrema,
Carpenteria, and many Amphisteginw. On the slopes also is exposed a hard
Foraminiferal limestone, chiefly made up of the tests of pelagic and bottom-
living Foraminifera, and containing 82 per cent. of calcium carbonate. The
Foraminifera found in specimens of this rock had crystals of calcspar in their
cavities ; they include the following :—G'lobigerina bulloides and other species,
G. Orbulina (universa), Pulvinulina menardii and micheliniana, Pullenia obliqui-
loculata, Planorbulina, Polytrema, Rotalia, Calcarina, &c.

But the bulk of this islet of “Poperang” is of a unique formation,
which may be termed the Rhynconella limestone on account of the number of
Brachiopod shells of that genus that are there imbedded. This limestone may
be briefly described as a hard grey rock containing numbers of Brachiopod,
Gasteropod, and Lamellibranchiate shells,
with many simple corals of deep-sea
genera, imbedded in a calcareous matrix
largely composed of the tests of Fora-
minifera. I did not observe bedding in
this limestone. Further details of the
imbedded organic remains and of the
composition of the rock are subjoined.

The Brachiopod shells all belong to
the same species of Rhynconella. Mr
Davinson, to whom they were submitted 1, 2, cee i ee
for examination, is mclined to look upon
them as belonging to Rhynconella Grayii, a species represented hitherto
by a single specimen discovered in the British Museum amongst other
natural history objects from the Fii Islands (?) collected by Mr J.
M‘Gitivray. This unique specimen was described by Mr S. P. Woop-
warp and figured by Mr Davipson, in the Annals and Magazine of
Natural History as far back as 1855 (vol. xvi. p. 444, plate 10, fig. 16).
Since that time no other recent specimen has been discovered. Hence
has arisen the difficulty in pronouncing as to the identity of species since the
comparison of a number of fossil specimens with a single recent living one
| does not afford sufficient material for exact determination.* I am indebted

* The appearance of this solitary specimen of Rhynconella Grayii, which is contained in the
| British Museum collection, might suggest its having been washed out of some recent deposit. I am
| informed, however, by Mr Davipnson that portions of the mantle, peduncle, and some muscular fibres
| were still attached to the shell.

566 H. B. GUPPY ON THE RECENT

to Mr Davipson for the accompanying figures of the fossil and living speci-
mens. The Gasteropod and Lamellibranchiate shells are such as live in the
shallow waters at the present day. A few Pteropod shells occur in the rock
belonging to Hyalea; and some Serpula tubes are also found. The Simple
Corals belong to the deep-sea genera, Leptocyathus, Stephanophyllia, Odonto-
cyathus, Flabellum, &c.; but since the shells with which they are associated
are of shallow-water habit, as Iam informed by Mr E. Smiru, this limestone
would appear to be a comparatively shallow-water deposit. The Foraminifera
forming largely the matrix of the rock include the following pelagic
species :—-Pullenia obliquiloculata, Globigerina hirsuta, G. cequilateralis, G.
Orbulina (universa), Pulvinulina menardii and micheliniana, &c.

The composition of this limestone is as given below :— .

Carbonate of Calcium (75:23 per cent.) consists chiefly of Foraminiferous
tests of pelagic species with fragments of Echinoderms, Gasteropods, Lamelli-
branchs, and Brachiopods.

Residue (24°77) consists of— |

(a) Minerals (10°00); felspars, augite, hornblende, and glassy fragments ;
often surrounded by a red coating, apparently a silicate.

() Siliceous Organisms (11:77), a very large number of casts of the
Foraminifera of a red colour.

(c) Fine Washings (3°00), broken parts of Foraminiferous casts.

Such then are the characters of this limestone rock. The occurrence in it
of aspecies of Rhynconella closely allied to, if not identical with, a species that
is represented only by a solitary specimen which was described thirty years
ago, is one of the more noticeable features in connection with this rock.
Another feature is the imbedding of corals belonging to deep-sea genera in a
comparatively shallow-water deposit.

Coming now to the outer line of barrier-reef (marked C in the section) it
will be sufficient to describe it as formed in great part at the present sea-level.
The elevated portion, which has been raised some twenty feet above the sea,
is formed in many places of massive reef-corals imbedded in the position of
growth.

CHOISEUL Bay.

The large island of Choiseul, as viewed in profile from the islands of
Bougainville Straits, has the appearance of a level-topped ridge destitute of
peaks, and not elevated more than from 1500 to 2000 feet above the sea. A
line of barrier-reef skirts the west end of the island and encloses Choiseul Bay
which receives the waters of three large streams that flow through wide belts
of mangrove swamps in the lower parts of their courses. About half a mile

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 567

from its mouth one of these streams, in cutting across the extremity of an out-
lying spur of the neighbouring hills, exposed a soft earthy rock bedded with a
gentle inclination of 2° to 3°, and abounding with organic remains. This rock
resembles the prevailing formation of Alu, the principal island of the adjacent
Shortland Islands already described. Further up the stream, the same deposit
was exposed in the banks, until I reached a narrow gorge rather over a mile
direct from the coast, the sides of which were of a chalky coral limestone.
This limestone I traced up the slopes of an adjoining cluster of hills to an
elevation of about 120 feet above the sea. A grained limestone* then
appeared at the surface, and composed the summit of the hill, which was
elevated about 200 feet above the sea.

Subsequently I ascended another stream which opened into the bay. After
following its course through the mangrove belt for about two-thirds of a mile,
I struck off on foot through the swamp, and came upon a mound about 35 feet
high—an outlier of the neighbouring hills—which rose up like an island from
the midst of the swamp, and was formed of the same deposit, similarly laden
with organic remains, as that which I had observed during my ascent of the
neighbouring stream. Ascending one of the outlying hills to a height of about
a hundred feet above the sea, I found the same deposit, but not sufficiently
exposed, however, to display bedding.

Unfortunately the uncertain reputation of the natives restricted my field of
observation. I was, however, able to satisfy myself that the mass of the low-
lying land near the coast was of this soft earthy deposit, the characters of
which will be now described.

When in the mass, it has the appearance of an argillaceous earthy rock,
somewhat moist and effervescing with an acid; and displaying to the eye
numerous Pteropod shells of the genera Hyalewa, Diacria, &c., Lamellibranchiate
and Gasteropod shells, the tubes of Dentalium being especially noticeable ;
otoliths of fish; macroscopic tests of such Foraminifera as Cristellaria
cultrata, Nodosaria soluta, &c., together with numbers of shells of the more
microscopic kinds; and, lastly, often fragments of leaves. Subjoined is the
description given by Mr Murray of samples of this deposit :—

A very friable rock, of a greenish-grey colour, having the composition of a
Foraminiferous ooze mixed with much volcanic débris (it resembles the Short-
land deposits in all its characters).

Carbonate of Calcium (33:14 per cent.) consists of otoliths of fish, Pteropod
and Heteropod shells, Gasteropod and Lamellibranchiate shells; Serpula
tubes, Ostracode valves, Echinoderm fragments, with many pelagic and
bottom-living Foraminifera (vide List).

* This grained limestone has not been examined by Mr Murray. It, however, closely resembles
in appearance the Foraminiferal limestones of Alu, and is probably of the same character.

568 H. B. GUPPY ON THE RECENT

Residue (66°86), of a dark green colour, consists of :—
(a) Minerals (40°00) m. di. 0°3, some fragments 1:0 to 2°0 mm.; mica,
quartz, felspar, hornblende, magnetite, augite; many glassy frag-
ments. A few beautifully formed quartz crystals were found in

this rock.

(b) Siliceous Organisms.—None noticed.

(c) Fine Washings (26°86).—Green organic-like substance with argillaceous q
matter and fine mineral and glassy fragments.

Many glauconitic-like casts of most of the organisms mentioned above were
also obtained in this rock.

List of Foraminifera.

Biloculina ringens (rare). Cristellaria compressa (rare).
Miliolina seminulum (several). - dentata (rare).
Reophax pilulifera (few). 3 italica (few).

Textularia sagittula (rare). Globigerina bulloides (common).
Bulimina marginata (rare). 5 », var, triloba (common).
Nodosaria soluta (several). e sacculifera (common).

», Yaphanus (rare). (fe dubia (many).
Rhabdogonium tricarinatum (rare). nr equilateralis (few).
Virgulina subsquamosa (few). Orbulina (universa) (many),

”
Uvigerina tenuistriata (many). Spheroidina dehiscens (many).
Sagrina virgula (common). Pullenia obliquiloculata (rare),

», columellaris (common). Cymbalopora poeyi? (few).

», striata (few). ’ Truncatulina lobatula (rare).
Frondicularia alata (rare). 4 rostrata (many). :
Cristellaria cultrata (few). » preecincta (many).

is papillosa (few). Ramulina globulifera (rare).

i calcar (few). Pulvinulina menardii (common).

Ps aculeata (few). nf », var, tumida (common).

ey articulata (few). yy elegans (few).

The chalky coral limestone, before referred to as forming the sides of a
gorge in the higher part of one of the streams, presents most of the characters”
of true chalk. It was exposed in faces 20 feet in thickness; but I was
unable to ascertain its position relative to the soft Foraminiferous deposi
exposed in the sides of the stream lower down. However, a similar chalk-like
limestone in the Shortland Islands overlies the softer deposit, as noticed in the
description of those islands.

Mr Murray describes the characters of specimens of this interesting rock
which I sent to him, as follows :— ¢

A friable chalky coral limestone rock, of a light creamy colour, showing
no definite structure.

Carbonate of Calcium (94:19 per cent.) consists of Lamellibranchiate shells,

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 569

. coral, Serpula tubes, Echinoderm fragments, Alcyonium spicules, and Foramini-
fera, as Globigerina, Polytrema, Rotalia, and Nummulina.

Residue (5°81) of a light brown colour, consists of—

(a) Minerals (2:00), m. di. 0'1 mm.; felspar, augite, hornblende, magnetite,
and a few glassy fragments.

(b) Siliceous Organisms (1:00) ; a few fragmentary sponge spicules.

(c) Fine Washings (2°81), consisting of a flocculent substance.

Sections of this rock show specimens of all the organisms mentioned above,
together with calcareous Algze and Carpenteria.

In concluding these observations on this locality, I may remark on the
probable geological character of the elevated interior of this portion of Choiseul
Island. Judging from my partial examination of the lower slopes, and from
the significant profile of the high land behind, I think it probable that the
western portion of this large island will be found, on examination, to exhibit the
same geological structure as that which characterises the islands of Treasury,
Ugi, and other islands in the Solomon group.

St CHRISTOVAL.

The large island of St Christoval, which is rather over 70 miles in length
and about 4100 feet in elevation, may be taken as probably representative,
respecting its raised calcareous formations, of the larger islands of the Solomon
group. My examination of the island was considerably curtailed on account
of the uncertain disposition of the natives. I was able, however, to obtain a
general acquaintance with the north coast and its vicinity, together with such
knowledge of the interior of the island as a traverse across its breadth from
Wano to Makira and various ascents, never exceeding 1400 feet, could afford me.

The north coast is skirted by a margin of low-lying land of varying breadth,
which in its turn is fringed by shore-reefs along a large portion of its extent.
This low-lying margin is either of calcareous sand, shells, and coral detritus,
imperfectly mixed with humus, when it is raised from 2 to 4 feet above
the sea; or it is of coral rock elevated 5 or 6 feet at the sea-coast, and rising
to some 15 or 20 feet as one proceeds inland.

The general character of the mountainous interior is that of a parallel series
of long level-topped and gently rounded ridges, separated by deep valleys from
each other, and composed, as far as my limited field of observation enables me
to judge, of ancient volcanic rocks. From the elevated interior several lofty
spurs descend with a gentle slope and even profile to the north coast, where
they protrude as bold headlands that often retain an elevation of 800 or
1000 feet. My observations have shown that the masses of these headlands
| are of old basic rocks ; whilst more recent calcareous formations encrust their
| VOL. XXXII. PART III. DA

570 H. B. GUPPY ON THE RECENT

lower slopes. Such is without doubt the geological structure of Cape
Keibeck, which has an elevation of over 1100 feet at the coast. I traced the
coral limestone as high as 500 feet above the sea when examining this cape, —
this being the greatest elevation at which the coral rock came under my
observation in St Christoval. In many parts of the coast a fawn-coloured
crystalline limestone, with homogeneous texture, in which sometimes reef
débris can be observed, in fact just such a rock as might arise from the
consolidation of the white ooze of coral reefs, takes the place of the coral rock.
I followed it up to about 500 feet above the sea. It is probably of no great
thickness, its relation to the underlying volcanic rocks being often displayed in
the courses of the smaller streams.

I will here relate my experience in the case of a hill that lies on the east
side of Wano Bay, since it is very typical of my experiences in other parts of
this coast. During two different ascents, in which I purposely avoided the
courses of the streams, J traced the coral rock on the surface to a height of 150
feet above the sea, and at the summit, 400 feet up, I found the fawn-coloured
limestone before alluded to. In no place during these ascents did I find a
fragment of volcanic rock at the surface; but when, taking advantage of the
deep gulleys that had been worn by the streams into the mass of the hill, I
availed myself of the rude sections of the hill’s substance there displayed, I
found in position the old volcanic rocks (altered dolerites).

These volcanic rocks are not uncommonly exposed protruding in mass above
the flats of coral formation which skirt the coast. Doleritic rocks project
through the coral rock on the point east of Wano Bay; whilst in the vicinity —
of Cape Keibeck, a dolerite, from which the coral rock that originally invested
it has been but partially removed, protrudes in mass to a height of 10 or 12 feet
above the reef-flat. Pebbles and small blocks of volcanic rocks are frequently
to be observed in the reef-rock all along this north coast of St Christoval.

With reference to the estimation of the thickness of these encrusting
calcareous deposits, I have no certain data. The fawn-coloured limestone, as
has been remarked above, can be of no great thickness ; whilst the coral
limestone, which I rarely saw exposed in faces exceeding 20 feet in height,
probably constitutes a thinner crust than I have found in other parts of the
group. Without doubt these calcareous envelopes originally extended to far
higher levels, from which they have been stripped by the agency of subaerial
denudation, which in these regions of great rainfall must be very rapid. From
my observations of the rainfall in this archipelago, I am inclined to estimate
the annual amount at usually not much under 150 inches.* Of the rapid

* This estimate refers only to the coast. In the elevated interiors of the larger islands the annual
fall is probably twice as much ; whilst on the lofty summits of Bongainville and Guadalcanar the rain-
fall is still greater.

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 571

degradation of the surface which these calcareous districts undergo during a
heavy fall of rain, of as much as 2 to 3 inches in the same number of
hours, I have been a frequent witness. In a few minutes the whole hill-slope
discharges a continuous sheet of muddy water, the rivulets swell to turbid
streams, and the water rushes down the permanent courses with the roar of a
mountain torrent. After the rain-storm has passed away, the band of muddy
water that fringes the whole length of coast, to a distance of one-quarter or
one-third of a mile from the shore, indicates the loss of material which the land
surface has sustained.

The bedded Foraminiferous deposit that forms the mass of the neighbouring
island of Ugi is rarely represented among the coast formations of St
Christoval. I came upon it only once in position exposed in the banks of a
stream near the coast.* The coral rock and the fawn-coloured limestone here
appear as a rule to rest directly on the volcanic rock. Occasionally in different
parts of the coast I found a coarsely grained deposit composed of the water-
worn débris of volcanic and coral rocks with a few shells imbedded.

THE FLoripa SuB-GROUP.

From the few traverses which I made in this sub-group I learned that the
western islands are more of volcanic formation, whilst the large island on the
east side of the narrow passage which bisects the main mass of land is composed
on the surface largely of recent calcareous formations. It is to this eastern
island that I will restrict my remarks. Traversing it in a S.W. direction from
the vicinity of Mboli Harbour to the village of Gaeta, I found an argillite and
a dark trap-rock scantily exposed in the lower hill-slopes. At a height of 500
feet a grained limestone associated with a limestone conglomerate appeared
at the surface. The coral limestone occurred at an elevation of 600 feet above
the sea, and formed the surface up to rather over 900 feet—the greatest
elevation I attained. In one locality it displayed a joint-structure. Descending
on the other side of the range, the grained limestone occurred at the same
height, and I traced these calcareous formations down to about 200 feet above
the sea. In the vicinity of the village of Gaeta, which is elevated rather over
100 feet, a volcanic rock appeared at the surface and was exposed in the bed
of a neighbouring stream.

I subsequently made an excursion into the interior of the island for a
distance of between two and three miles N.N.E. from Gaeta. I traversed a
region of coral limestone gradually rising until an elevation of about 350 feet

* A similar rock, but sparingly Foraminiferous, occurs on the slopes of Cape Keibeck at an eleva-
| tion of 500 feet above the sea,

572 H. B. GUPPY ON THE RECENT

was attained, when I descended into a deep valley and followed up the bed of
a large stream, which finally emerged from a cavern of considerable dimensions
in the face of a hill of coral limestone. This cavern was first visited by the |
Rey. Mr Penny of the Melanesian Mission, and was subsequently explored
by Bishop SELwyn, to whom I was indebted for the opportunity of examining
it. The interior, the entrance to which is between 60 and 70 feet in height,
presents the usual features of these subterranean cavities. A series of lofty
chambers, connected by narrow passages and containing numerous stalactitic
and stalagmitic columns in all stages of formation, some of them between
1 and 2 feet in diameter—such is the character of this cavern which Bishop —
Srtwyn found to be about 750 yards in length. I emerged from the farthest —
mouth into the bottom of a deep valley, across which the coral limestone hill
lies as a dam through which the stream has found its way. In the bed of the ©
stream, as it follows its subterranean course, there are numerous blocks and
pebbles of a dark crystalline volcanic rock and of a marley rock, of which I
was unable to find the parent rocks in the valley above. They are probably
traversed by the stream in its passage through the hill, where they would be
concealed from view by the stalagmitic and stalactitic deposits. The marl
presumably represents the immediate foundation of the limestone, and will be
found to cover the crystalline volcanic rock. From the presence of these rocks —
in the bed of the stream as it flows through the caverns, I suspect that these
subterranean passages traverse the base of the limestone ; and on this supposi-
tion the thickness of this coral limestone would be not greater than the height
of the hill which is pierced by the stream, #.¢., about 150 feet. .

The general conclusion that I formed of the structure of this eastern island —
of the Florida Sub-group was, that the calcareous rocks were merely superficial —
formations encrusting a nucleus of volcanic rocks which has been occasionally
exposed to view by the denuding forces.

THE CLASSIFICATION OF THE SOLOMON ISLAND RECENT FORMATIONS.

These rocks may be grouped into two chief classes, according to the pro-
portion of volcanic débris they contain.

The First Class comprises those rocks which, being largely composed of
such volcanic débris mixed with the tests of Foraminifera, Pteropods, and
other Molluscs, have a composition very similar to that of the volcanic muds
at present forming around oceanic volcanic islands in the Pacific. These rocks
contain both pelagic and bottom forms of Foraminifera, lists of which have
been given in the, previous pages. The soft rock, resembling a deep-sea clay,
which underlies the elevated reef-mass at Santa Anna, may be referred to this
principal division of the rocks; but, as shown in the description on page 558,

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 573

it differs essentially from all the other deposits of the class. Four prevailing
kinds of these rocks may be distinguished.

(1) A friable rock, containing from 5 to 20 per cent. of carbonate of
lime, and displaying to the eye only the white specks of minute
Foraminiferous tests with a few of macroscopic size, such as C7vs-
tellaria cultrata and Nodosaria soluta, Molluscan shells being rarely
observed. Rocks of this character form the masses of Treasury and
Ugi Islands ; and their composition is described in detail in the
sections treating of those islands (vide pages 547, 551, 552).

(2) Avery friable rock, containing from 30 to 35 per cent. of carbonate of
lime, and inclosing in great numbers the shells of Pteropods,
Gasteropods, Lamellibranchs, together with otoliths of fish, simple
corals, and numbers of Foraminiferous tests, many of them
macroscopic. Rocks of this character largely compose Alu, the
principal island of the Shortlands, and are exposed in the low hills
in the rear of Choiseul Bay (for the detailed descriptions, see
pages 562, 567).

(3) A hard grey fossiliferous limestone, containing usually about 60 per
cent. of carbonate of lime, and much volcanic débris. It is chiefly
composed of the broken down fragments of corals and Lamelli-
branchiate shells, with calcareous Algee, and a few Foraminifera.
This rock is exposed in the lower courses of the Treasury Island
streams, where it gives rise to water-falls on account of its greater
hardness. Its further description is given on page 552.

(4) Coarse rocks, composed of the fragments of volcanic and coral rocks
in rounded grains. Occasionally larger fragments, together with
shells, are imbedded. These rocks occur on the northern slopes of
St Christoval, near the coast.

The Second Class includes those rocks which are largely composed of coral,
Molluscan shells, Foraminiferous tests, and calcareous Alge, with but a small
proportion of volcanic débris. The share that each of these four principal
| constituents takes in the building up of the rock differs widely ; and on this
| basis the following groups have been made. Yet to the great majority of these
| rocks, if not to all, the term of coral limestone is quite applicable in its widest
| sense. Probably, however, the term “coral-reef formation” would be
_ preferable, as including the variously composed rocks that are being formed in
| connection with coral-reefs. Whether the rock is formed by the upward
| growth of successive tiers of large masses of reef-corals, or whether it is
| formed from the fragments of such corals broken off by the waves and mixed
_ with shells and other organisms in varying proportions, such as must be form-
_ ing on the outer slopes of reefs, it has the same coral origin. For the same

574 H. B. GUPPY ON THE RECENT

reason, the calcareous muds and sands found at the bottom of the lagoons are
of coral origin, representing as they do the final stages of the process of
degradation. The variety in character exhibited in the followimg groups of
coral limestones may be thus in a great measure explained :—
(1) Coral rocks, properly so called, which are merely the massive reef-
corals in different stages of fossilisation. The porous and small-

celled corals, as the Poritida, are the first to lose their characteristic

structure, usually passing through a drusy stage, when they present

a saccharine appearance, and finally, by the continued percolation of

water charged with calcium carbonate, assuming a compact texture
exhibiting no coral structure to the eye. Such coral rocks are best

observed at the coast.

Here I may refer to a peculiar variety of coral rock which is not

uncommon on the south side of Treasury Island on the higher slopes

of the hills, as high as 750 feet above the sea. It is a hard, compact,

partly crystalline greyish rock, chiefly made up of a coral belonging to

the Fungidee, which Mr J. J. QuELcH, to whom fragmentary specimens —

were submitted for examination, has identified as being with very

little doubt Leptoseris striatus (Kent), a species founded for the

reception ofa rare coral collected by Capt. Sir E. BeLcuEr at Borneo,

(the only other recorded specimen being from Madagascar (?). This

coral is not included amongst my collection of reef-corals in the

Solomon Islands. It may probably, however, occur in the deeper

water.*

(2) Coral rocks, which are chiefly made up of calcareous Alge,t fragments

of Molluscan shells, corals, and Echinoderms, the interstices being

filled up by the tests of Foraminifera and other small calcareous
organisms. In the composition of such rocks, coral fragments take

only a secondary part. The majority of coral limestones that I found

in the Solomon Islands may be referred to this division. They are

usually white in colour, but often reddish or yellowish brown, being

hard, compact, and sometimes partly crystalline in texture, and often
displaying a fragmental structure. The percentage of calcium

* In one of the islands of the Pelew Group, Professor Srmprr observed that the base of the coral
cliffs was formed entirely of species of Lophoseris mixed with other deep-sea forms, the higher portion
of the cliffs containing Astrwide, Poritide, Madreporide, &e. Lophoseris and Leptoseris belong to the
same sub-family of the Fungide. See The Natural Conditions of Existence, &e., p. 275, London, 188].
I am inclined to consider this variety of rock in Treasury Island as representing the hae of the elevated
reef-masses, since it only occurs on the higher and more denuded slopes.

+ Some specimens of coral rock which I obtained at Santa Anna were entirely formed of the joints
of a calcareous Alga, resembling apparently the genus Halimeda, which are found commonly in the sound:
ings off the outer edge of the present coral reefs.

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 575

carbonate in this group varies between 90 and 95, the resedue con-
sisting of the minerals named in the subjoined analysis, of
Foraminiferous casts, and argillaceous matter.
The Composition of a Typical Sample.
Carbonate of Calcium (94:47 per cent.), consisting of the various
materials mentioned above.
Residue (5°53), consisting of—
(a) Minerals (1:00) m. di. 02 mm.; augite, hornblende, felspar,
magnetite, and a few glassy fragments.
(b) Siliceous Organisms (2°00), casts of Foraminifera, &c., of a
red colour.
(c) Fine Washings (2°53), broken down parts of casts of
Foraminifera, fine mineral particles, argillaceous matter,
and a red material—probably oxide of iron.

(3) Compact fawn-coloured crystalline limestones of a homogeneous
texture, apparently formed by the consolidation of the ooze found
at the bottom of the lagoons inside coral-reefs. These rocks are of
common occurrence on the lower slopes of the large island of St
Christoval, where they overlie the volcanic rocks of the district.
They are sometimes coarse-grained.

(4) Chalk-like coral limestones, which contain about 95 per cent. of
calcium carbonate, and are chiefly composed of the fragments of
Molluscan shells, Echinoderms, corals, calcareous Algee, and Fora-
minifera. These rocks, therefore, in their general composition
resemble the rocks of the second group of coral limestone
differ conspicuously in their chalk-like appearance and in being
more friable. ‘They occupy, however, the usual surface position of
other coral rocks (as shown in the description of the Shortland
Islands, page 563), although being by no means of common occurrence.
They may sometimes be found in the central elevated portions of
islands like Biu, which have been formed by the partial upheaval of
coral reefs. I found them only on four occasions in the Solomon
eroup, viz.,at Alu, Choiseul Bay, the Three Sisters, and Biu Island
Their composition is described at length in pages 563, 568.

(5) The Foraminiferal limestones, which are grey or yellowish-brown in
colour, hard and compact in texture, and are chiefly made up of the
tests of pelagic and bottom-living Foraminifera. They contain
generally from 75 to 85 per cent. of calcium carbonate, their typical

* White men resident in the group tell me that chalk-like rocks are found in the island of Ulaua,
which lies near the Three Sisters.

576 H. B. GUPPY ON THE RECENT

composition being described on page 564. They usually, like the coral
limestones, are found at the surface; and in the island of Alu they
overlie the soft Pteropod deposits, as described on page 564. In
‘Treasury Island they occur on the tops of the lower hills.
In the island of Treasury, however, I found exposed in a stream-
course a Foraminiferal limestone of somewhat different character,
and occupying the usual surface position of the coral limestones,
Appended is the description of this rock. |
A hard, compact, grey, Foraminiferal limestone, showing a —
simple coral imbedded, the whole rock chiefly composed of pelagic
Foraminifera. |
Carbonate of Calcium (66°26 per cent.) consists of the following
Foraminifera—Globigerina bulloides hirsuta, G. (Orbulina) universa,
Pullenia obliquiloculata, Pulvinulina menardiu, Amphistegina.
Residue (33°74), brown colour, consists of—

(a) Minerals (20:00) m. di. 0 mm.; felspar, hornblende,
augite, magnetite, mica, and many glassy fragments.

(b) Siliceous Organisms (3°00), casts of Foraminifera.

(c) Fine Washings (10°74), argillaceous matter and fine mineral
particles. q

The organisms in this rock, together with the minerals, are
similar to those found in deposits of modern seas near volcanic
islands at depths of from 500 to 800 fathoms. The Foraminifera are
identical with those found in the surface waters of the tropics at the
present day.
(6) The Rhynconella limestone, which was only found in one locality,
viz., in the islet of Poperang in the Shortland Islands, may be briefly
ret as composed of a large number of Brachiopod, Lamelli-
branchiate, and Gasteropod shells, together with many simple corals
of deep-sea genera imbedded in a matrix largely formed of pela
Foraminiferous tests. A detailed description of this limestone is
given on pages 565 and 566.

THE OCCURRENCE OF FLINTS. 7

This paper would be incomplete without a reference to the occurrence of
flints in these islands. They are usually found where the soil has been
disturbed for purposes of cultivation; and I was never successful in fi ding
their source. They occur, however, together with a chalky rock, on the
beaches of the island of Ulaua. Having been unable to visit this island, |
would recommend future visitors who may land there to pay attention to his

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 577

point, which was one constantly before my mind during my examination of the
calcareous formations of these islands. The explanation of their origin held by
many natives is that they have fallen from the sky; and since many of these
flints have all the characters of flint implements of the paleeolithic type, we are
thus reminded of a similar superstition prevalent amongst the agricultural
classes of some of the English counties as to the source of the polished stone
implements named “celts.” (For further information on this subject vide
some notes of my own read by Professor LiversIpGE before the Royal Society
of New South Wales [| Journal for 1883, vol. xvii. p. 223. |)

CoNCLUSION.
[Added December 16, 1885. |

From the general character of these calcareous formations it may be safely
inferred that they will be found wherever there has been elevation during the
recent period in regions where coral reefs are flourishing. Amongst other
| localities we may look to the West Indies, the Indian Archipelago, New
Guinea (more particularly the south coast), New Britain, New Ireland, the
| Santa Cruz Group, the New Hebrides, the Loyalty Islands, New Caledonia, and
_ the Fiji and Tonga Groups, as likely to possess at the sea- border formations of
| a similar character.

I have thought it best to add to the completeness of this paper by making
a few general remarks on the general bearing of these observations.

In this, the largest of the Pacific groups, I not only found existing fringing-
reefs, barrier-reefs, and atolls, but I discovered pre-existing reefs of these three
| chief classes, which have been recently elevated to a height sometimes of
several hundred feet above the sea. My observations on these recently ele-
vated reefs and their foundations have enabled me to approach the problem of
_ the formation of coral reefs by the inductive rather than by the a priorz method,
| for it is evident that in passing from the consideration of a probable cause of
| the formation of existing reefs to the examination of ancient reefs that have

been raised with their foundations above the sea, we enter a domain
| of greater certainty. I will begin by briefly restating the principal points
_ of this paper.
In the first place, there are numerous small islands and islets less than a
hundred feet in height, which are composed entirely of coral limestone. Then
| there are islands of larger size, which are composed in bulk of partially con-
, solidated volcanic muds, such as are at present forming around oceanic volcanic
islands. Coral limestones encrust the lower slopes of these islands, and do not
| attain a greater thickness than 150 feet. In the next place, we have islands of

|similar structure, but possessing in their centre some ancient volcanic peak
VOL. XXXII. PART III. 5B

578 H. B. GUPPY ON THE RECENT

that was once submerged. Then there are islands in which the volcanic peak
has become an eccentric nucleus, from which line after line of barrier-reef has
been {advanced overlying the volcanic muds, islands in which I did not find
the coral limestone of a thickness of 100 feet. Then we have the
upraised atoll, such as Santa Anna, which, within the small compass of a
height of 470 feet, displays the several stages of its growth,—first, the
originally submerged volcanic peak, then the investing soft deposit, and over
all the ring of coral limestone that cannot far exceed 150 feet in thickness ;
lastly, we come to the mountainous islands formed of old volcanic rocks,
such as St Christoval, which, although over 4000 feet in height, showed
to me no calcareous envelopes at a greater height than 500 feet above the
sea, the coral limestone crust being even thinner than in the smaller and more
recent islands.

I purpose now to draw four limited inferences from these facts of observa-
tion, without reference to any particular view that may be held on the subject
of the formation of coral reefs, and to compare such inferences with the prevail-
ing views on that subject.

(1) That these upraised reef-masses, whether atoll, barrier-reef, or fringing-
reef, were formed in a region of elevation.—This is self-evident. The last upheaval
that occurred, of which I found proofs in different parts of the group, was to
the extent of about 5 feet, but at the present day there are signs of this move-
ment being still in operation; and for the purposes of future observation I have |
established datum-marks in different islands. This, therefore, being a reign of
elevation, it is apparent that that portion of Mr Darwuy’s theory of coral reefs,
which ascribes the formation of atolls and barrier-reefs to a movement of sub-
sidence, cannot be applied to the islands of the Solomon Group, since we here
find upraised atolls and barrier-reefs associated with existing reefs of the same
description. This conclusion accords with the results obtained by Professor
SEMPER in the case of the Pelew Islands, and by Professor A. AGassiz in the
case of the Florida reefs.

(2) That such upraised reefs are of moderate thickness, their virtual measure-
ment not exceeding the limit of the depth of the reef-coral zone.—Amongst
the numerous islands which I examined I never found one that exhibited
a greater thickness of coral limestone than 150 feet, or at the very outside 200 —
feet. One of the corollaries of the theory of subsidence is concerned with
the great thickness of atolls and barrier-reefs. My observations in this region,
and it is such regions that can alone afford such evidence, show that atolls and
barrier-reefs can be formed with no greater thickness than they would possess
in accordance with the depths in which reef-corals thrive, the vertical thickness
of the reef not exceeding the depth of the reef-coral zone... . . The only
objection worthy of attention that has been advanced against the atoll-theory

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 579

of Mr Darwin was, in the opinion of Sir CuarLes LYELL,* the circumstance that,
as far as was known, no bed or formation of coral of any thickness had been
discovered. This objection, which was proposed by Mr Mac aren in 1842,
derives additional force at the present day in the light of my observations in
the Solomon Islands.

(3) That these upraised reef-masses in the majority of islands rest on a partially
consolidated deposit which possesses characters of the “ volcanic muds,” which were
Jound during the “ Challenger” Hapedition to be at present forming around
volcanic islands.

(4) That this deposit envelops anciently submerged volcanic peaks.

These two latter conclusions corroborate in a remarkable manner the views,
based on the observations of the “‘ Challenger ” Expedition, which Mr Murray
has advanced. I will cite the structures of two islands to illustrate these
views. In the small island of Santa Catalina I found that the elevated reef
was based on volcanic rock with the intervention of a thin brecciated
conglomerate. In the island of Treasury I found the volcanic rock covered by
a soft partially consolidated volcanic mud, which attained the thickness of some
300 or 400 feet, and was itself encrusted on the lower slopes of the island by
the elevated reef-mass. In the one island the volcanic peak had been first
exposed to breaker-action before the reef-corals established themselves. In
the other island the submerged volcanic peak was first brought within the reef-
coral zone by the deposition of layers of volcanic mud, assisted by the move-
ment of elevation.

With reference to my own bias on this subject, I may here add that during
the first eighteen months I passed in the Solomon Islands I was only
acquainted with the theory of subsidence ; and that after having failed to make
my observations harmonise with the theory of Mr Darwin, I collected my
facts with a very confused idea of the direction towards which they were
tending. It was therefore a cause of great satisfaction to myself when I first
became acquainted with the views of Mr Murray.

I will close this paper with a few remarks on the amount of elevation that
has occurred in this region in recent times. It is, however, difficult to gauge it.
So great has been the subeerial denudation in these islands, that although the
elevatory movements have brought up to our view a deep-sea clay with its con-
cretions of manganese and a Foraminiferal limestone that was probably formed
in a depth of from 500 to 800 fathoms, two rocks which occur in islands
at opposite ends of the group, yet, notwithstanding this great upheaval, the
calcareous envelopes usually disappear from the slopes of the large volcanic
islands at heights of 500 or 600 feet above the sea, and never came under
my observation in such islands at greater elevations than 900 feet. In the

* Principles of Geology, 12th edit., vol. ii. p. 612.

580 H. B. GUPPY ON THE RECENT

calcareous islands the greatest height at which the soft deposits occurred
was 1150 feet, which was the greatest elevation at which I found any of the
recent calcareous formations in this group. They probably occur in the western
end of Choiseul at an elevation of 1500 feet and over.

EXPLANATION OF PLATES CXLIV., CXLV.

Heights in feet ; depths in fathoms. Arrows indicate the dip; horizontal beds
shown by a cross, thus +.

Pate CXLIV.

Fig. 1. Plan of Ugi Island, } inch to a mile.

Fig. 2. Ideal section of Ugi Island, intended to illustrate the relative thinness of the coral
limestone,

. Plan of Treasury Island, 4 inch to a mile.

Ideal section of Treasury Island, adapted to show its principal structural features.

Plan of Santa Anna Island, 4 inch to a mile.

. Section of Santa Anna Island, drawn on a true scale of 2 inches to a mile.

. Diagram showing the relative position of the raised coral rock and its foundation to the mass
of volcanic rock in situ on the reef flat ; north coast of Santa Anna Island.

Fig. 8. Ideal section of Alu Island, showing the relation to each other of the coral limestone, the soft —

Pteropod and Foraminiferous deposit, and the volcanic rock.

aa
ag

Puate CXLY.

Fig. 1. Section of a compact grey Globigerina limestone from Treasury Island (see page 576), The
rock contains 66:26 per cent. of carbonate of lime, consisting chiefly of species of pelagic
Foraminifera, such as Globigerina bulloides, G. hirsuta, G. (Orbulina) universa, Pullenia
obliquiloculata, and Pulvinulina menardii ; Amphistegina, and one or two other bottom —
living Foraminifera. The organisms are cemented by carbonate of lime, sometimes
erystallised in rather large grains (d). The mineral particles consist of (1) plagioclase-
felspar, presenting the extinctions of labradorite; sometimes these crystals are twinned
following the albitic law (c); sometimes they are twinned following the law of pericline.
The crystal (e) shows a plagioclastic section, exhibiting at the same time the twinning, —
following the law of albite and pericline; (2) fragments of hornblende; one of these (a) is
cut perpendicular to the crystallographic axis, and presents the hexagonal contours, aud the
cleavage lines crossing at an angle of 124°; (3) fragments of augite; the section () of this
mineral presents two individuals grouped with their axes parallel; the section is octagonal,
and crossed by the cleavages at right angles; (4) fragments of magnetite and biotite.

Fig. 2. Section of a tufa of an augite-andesite, from the central region of Treasury Island (see page
551). The rock contains 7:74 per cent. of carbonate of lime, which consists of a few
coccoliths, several species of Globigerina, and fragments of Echinoderms. The ground-
mass is composed of particles of volcanic glass, magnetic particles, and small decompose:
mineral fragments. The larger minerals are lamelle of plagioclase (@), twinned following
the albite law, with the extinction of labradorite; also twinned, following the law ot
Baveno (a); sections of augite (») more or less parallel to the axis, with a twinning follow
the orthopinakoid ; and crystals of augite (c) with a black glass particle attached, pro
that the crystal was not formed in situ; also some hornblende. The presence of the Gl
gerine and Echinoderm particles show that the tufa was formed under water in which the
surface organisms lived.

CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 581

Fig. 3. Section of a compact coral limestome from N.E. side of Treasury Island, consisting almost
entirely of crystallised carbonate of lime, and fragments of the following organisms :—
Gasteropod and Lamellibranch shells, Echinoderms, corals, calcareous Algze, Serpula tubes,
and Foraminifera of the genera Curpenteria, Polytrema, Tinoporus, Gypsina, Calcarina,
Aimphistegina, Cycloclypeus, Nummulites, Globigerina, and Pulvinulina.

Fig. 4. Section of a compact Rhynconella or Foraminiferal limestone, from Poperang Island (see
pages 565 and 566), containing 75:23 per cent. of carbonate of lime, which consists chiefly of
pelagic and other Foraminifera, shells of Rhynconella, and fragments of Gasteropods,
Lamellibranchs, and Echinoderms. A considerable quantity of the carbonate of lime is
crystallised with a rhombohedral cleavage (c). The interior of the Foraminifera shells is
frequently filled with a reddish substance. The mineral particles are—(1) fragments of
plagioclase very much altered, with the twinning of albite and pericline (d); (2) hornblende,
often zonary (a), with inclusions of apatite (the little white spot in the section) or twinned
(b); and (3) black mica (e).

VOL. XXXII. PART III. 50

rans. Roy. Soc. Edin’ Vol. XXXII, Plate CXLIV

100 ’
ans vce fere Pk TREASURY ISLAND.
9 The arrows indicate the dip. Horizontal beds shown by +
N
NI ii
Qu NW AS na SAE W. E
NS “ Mn

ia Mii: xii fe 5

eat?
wi HAN Wy,

Heights in feet. Depths in fathoms.
0 1

iss 2 3
Oe

Scale of Miles.

N

aint,
Ay

Nyy

Uy
Y

570 foel®

iv"

Fig. 1.
: . REEF FLAT aim eee eee .
: TX A Coral limestone cliff—80 feet high—with massive corals (marked +
; ae Ase la ‘ UGI ISLAND.
aN B Detached masses from the clifi face. ° i 2 j
: C Underlaying soft argillaceous and calcareous rock. %
ae fm D Volcanic Rock ‘‘in situ” protruding above the reef flat. Scale of Miles.

Diagram showing the relative position of the raised Coral Rock
and its foundation to the mass of Voleanic Rock “‘in situ” on the
reef flat (north coast of Santa Anna).

_ SANTA ANNA.
ay _/ Heights in feet. Depths in fathoms.
ot ar) met 2 3) ae

Scale of Miles.

Section of SANTA ANNA (W.W. W.-E.S.£.) to the 100 Fathom Line.
Drawn on a True Scale of 2 inches to the Mile.

—s Soft Pteropod and
Foramintferous deposit.

<a A Coral limestone.
Fig. 2. SE
Ideal Section of UG! ISLAND, ‘intended to illustrate the relative thinness cf the Coral Limestone.
3 ES Pelee ie: aise
Coral limestone.
Fig. 4, STE Z f NU Volcanic rock.
ee ae HARBOUR UN igen
} Votecante nucleus
Ideal Section of TREASURY ISLAND, drawn on a purposely exaggerated scale, and adapted to
show the principal structural features of the island.
| ww A B Cc SE.
| : Elevated
Fig. 8. A Barrier-reef Barrier-reef
LEVEL eee ee eee dee eee oe nde ee ee - eee A eae 2 ey TO ON
LAGOON LAGOON
Ideal Section of ALU, the principal island of the Shortland Islands, showing the relution to each other CH ee fal
Koraminiferous deposit.

of the Coral Limestone, the soft Pteropod and Foraminiferous deposit, and the Volcanic Rock. (UM Voccanic rock

M‘Farlane &Erskine, Lith"! Edin™

gis. Roy. Soc. Edin‘ Vol. XXXII, Pl. CXLV.

¥ Huth, Lith* Ddin*

| CALCAREOUS ROCKS OF THE SOLOMON ISLANDS.

( 583 )

XXX I.—Observations on Atmospheric Electricity. By C. Micurz Smiru.
(PL .CXEVE)

(Read June 1st, 1885.)

The following observations on atmospheric electricity were made on the top
of Dodabetta, between 3rd and 12th January 1885. The position of the
electrometer, when not otherwise stated, was at a height of about 5 feet above
what remains of the walls of the bungalow formerly used as a meteorological
observatory. Dodabetta is the highest hill in the Neilgherries, and the bunga-
low was built exactly on the top, which is in latitude 11° 24’ 5”-40 N., longitude
76° 46’ 4439 E., and at a height of 8642 feet above mean sea-level. The top
is free from trees, and my tents were slightly below, and at a sufficient distance
off to prevent them interfering in any way with the accuracy of the readings.

The rainfall at the end of 1884 was unusually heavy, and continued till near
the end of December, so that mists were very frequent in the afternoons and
evenings. These mists usually collected over the hollow in which Coonoor and
Wellington are situated, and gradually spread round Dodabetta from about E.
by N. to W., and at times remained for hours as a sea of mist, with a nearly
horizontal, though of course wavy, upper surface, which reached to within a
few hundred feet of the top of the mountain. At times portions would be
blown off from the surface of this sea, and would reach the hill-top; but usually,
during the day, any mist that reached the top dissolved almost instantly on
reaching the warmer air rising up the north-west face of the hill from the valley
in which Ootacamund lies. Occasionally, however, the top was completely
enveloped in mist, and it was impossible to judge with certainty whether it was
a condensing or a dissipating one. Unfortunately I had no hygrometer with me;
for, knowing the difficulty of making any satisfactory shade, I thought there was
no use of taking one. It is, however, worth noticing that the mists after sunset
were, as a rule, very wetting, and were therefore probably condensing.

Turning now to the observations, these are interesting in two ways. First,
as regards the daily range and period of maximum strength; and, second, as
regards the influence of mist. As it was impossible to carry on observations
all night without an assistant, I confined myself to an attempt to get a fairly
complete series of readings between 7” and 20" (Madras mean time, reckoned
from midnight). On half the days readings were taken up to 22", and on
one night to 24. From 6th to 12th January the readings were, with
two exceptions, taken hourly from 7" to 20°, and a number of intermediate
readings were taken, when, owing to the presence of mist or from other cir-
cumstances, it seemed likely that they would be of value. Im all, above 150
observations were made. The morning readings from 7" to 13" were little dis-
turbed by mists, except on the 8th, and the readings for these hours agree

VOL. XXXII. PART III. j 5 D

584 C. MICHIE SMITH ON

remarkably well with each other, so that the diurnal curve for the forenoon
may be considered to represent the true curve very fairly; but this cannot be
said for the part for the afternoon hours, for on four days out of the nine the
readings have almost no value for determining the normal variation. I have ©
thought it well, however, to give a curve (No, 2, Pl. CX LVI.) showing the mean
of all the observations, indicating the number of disturbed readings in each case by
a corresponding number of marks on the small circle surrounding the point mark-
ingthe mean. The curve is drawn from the following means of the readings:—

Hours, . 5 ‘ |) ZN SEY SY Wty yy ati 12/13 14 15 | 16 17 | 18 | 19

98 | 82

Readings, . ; : . | 44 | 49 | 64 | 71 | 84 | 91 | 95 | 99 | 102 | 98 | 114

95 | 75 | 59

The other curve (No. 1) shows the means of the two hourly observations on the
4th, 5th, 6th, 7th, and 9th, which are nearly free from the effects of mists.
The following table gives the actual observations on these days :—

Hours, : a ae Pe I Oe EY aay |p Mee Wy abay |G © aly, 18 | 19 | 20 | 21 } 22 | 23) 24 )—

January 4, . em Niecemll Zi oe All Osteen te OF rect am O ORM er. Mi\ielO-2i0|\-toi |G Ace earn (Roe | Jee
By POs. 2) Uirese nt DU Seen dal) meek bh Meeen Heelies aOR ts. 2in) SON Nal eee Om moM
ee Ore as . |... | 60 | 65 | 60 | 74 | 78) 84 | 78 | 68 | 74 | 70 | 75 | 49 | 68

40 | 62 | 66 | 74 |[91]| 76 75 | 92 | 3 | 79 | 64 | 54 | 52 |[85] [95]| 58

(Oe SS
~
~
~
bo
~w
ins)
_
[—)
lor)
©
~I

115 |[142]|[110)| [871 | [84] |[124] |[106]

111| 109 | 129 | 125 | 120 | 98 | 60

(fe)
~
NN
~
No)
for)
Or
~w
~“I
co
lor)

Mean
en scenes eel BB cohen Gio iloxee alt 98st co pilose ulPas se ven68

NV. B.—Those readings within brackets were taken in mist.

If we take this curve as most nearly the true one, we see that there is a
well-marked maximum about 14" M.M.T., and that the curve is fairly sym-
metrical on the two sides of this maximum for at least four hours; and there is
some evidence, though it is by no means conclusive, that the maximum normal
readings are obtained at the time of maximum temperature. The observations
made do not fix the time of minimum satisfactorily ; but probably there are”
two minima—one early in the morning and another about 19", with a small
secondary maximum two or three hours afterwards. This diurnal curve differs’

OBSERVATIONS ON ATMOSPHERIC ELECTRICITY. 585

far as my observations went, I never obtained indications of negative electri-
city either in the clouds or round them; but on some occasions I found the
positive charge very small, and I was irresistibly led to the conclusion that, on
the edge of a dissolving mist, the potential was lower than the normal, while in
a condensing mist it was higher than the normal. The following table shows
the chief readings that were made in mists :—

No. Date. | Hour. Reading. Remarks.
1 | Jan. 3 Berso= 90 Thin driving mist.
2 Bee, 114 oT Thin mist all round.
3 hee 205 85 | Thin driving mist.
4 : 214 95 Do. do.
5 F 8 he 202 AT On edge of dissolving mist.
6 we 45 125 115 Mist all gone.
ul ee Wh! 142 Heavy mist near.
PNAS { 50 ) Mist passing in small quantities, and dissolving
8 » | 13" 10 P va i over brow of hill.
t e37
46
9 rj, 135 30™ to Tn hollow below tents, more mist.
27
10 ae 134 40™ 75 At post pretty thick mist.
11 mrs, 135 50™ 22 In hollow mist not so soon dissipated,
12 Pe hiss 14h 110 Post—pretty thick mist.
13 5s 145 20™ 29 Thick mist all round.
14 Per 45; 155 87 Mist all round at a little distance.
15 Ties) Lo" 84 Clear all round below, cloudy above.
16 55 he 124 Mist all round, and a little driving over the top.
Li sadah iss 18 ~ 106 Clear. Thin mist below.
18 ; 19= 74 Clear.
foie S| 16h 120 Mist in distance.
20 ot ED 165 40™ 49 In hollow—umist drifting past and dissolving.
21 es 165 45™ 70 6 Do. oe all past.
22 10 LSE 73 vercast.
23 : 5 155 45™ 136 At post thin mist driving past from N.E.
66
24 a 155 55™ } to On ridge to N.E. thin mist ; just on edge of cloud.
59
25 — ;, 165 73 Very constant—little mist.
160
26 ee ies to ( Mist all round.
128 |
133,
27 ees 7 30™ to Tn pretty thick mist.
145
28 Bee | 18 153 In thick mist.
29 — IG) 100 Clear. Clouds on horizon, and a little sheet light-
30 ba de es 285 82 \ ning on clouds below.
31 me © G5 165 150 Thick mist all round, and drifting over the top.
32 meres 165 20™ 137 Still thick mist.
SESE) sie Se aaa ares erie
: 0 r st.
Bee Pi) Panga 166 Mist on again.
155
36 eh ua’ 18 to Thick mist.
162
37 tee 3 Wee 109 Mist.
38 eg 205 149 Dense mist.

586 C. MICHIE SMITH ON

Before discussing these it is necessary to note that when the observations
were not made at the “post” they were made at places where I found that in
fine weather I got readings very nearly the same as those got at the post. It
is not necessary to go over the whole table. A few of the more marked cases
will sufficiently illustrate the main features.

No. 6 at 11" 20™ the reading on the edge of a dissolving mist was 47, while
the average for that hour is about 87.

No. 8 shows small quantities of mist passing and dissolving, and the
readings varying from 50 to 97. The normal reading for this time being
about 90.

No. 9. This reading was taken at some distance from the post as the mist
was drifting up a ravine to the west, and I stood so as to be just in the mist.
The readings were very low—46 to 27.

No. 11, taken at the same place as No. 9, gave a reading of 22. The mist
was then thicker, and so went farther before it was completely dissipated, but
it was clearly a dissolving mist.

No. 13 is a doubtful case, as the mist was all round, but as it cleared off
soon after it was probably even then dissolving.

Nos. 20 and 24 are very clear cases.

No. 26. Here the readings are from 160 to 128 when the normal was about —
93. This mist was a very wetting one. |

Nos. 27 and 28 are also far above the average. :

Nos. 31 to 38 were all in thick condensing mists, and in each case the
readings are far above the average. I may add that I purposely avoided —
examining the observations in detail at the time, and simply recorded as many
as possible. It should be noted, too, that in heavy wet mists the readings may
at times be too low, as the ebonite which insulates the wire in communication —
with the inside of the electrometer is apt to get moist in spite of the umbrella.
This difficulty is got over by using a match which burns quickly, and by seeing —
that the ebonite is quite dry before each observation. With a slow burning
match I found the results quite untrustworthy.

The observations detailed above are by no means conclusive evidence of the
theory that I have ventured to draw from them, but they are sufficient to show
the importance of a much more careful examination of the electrical state of
condensing and dissipating mists. Such observations would be of great value
in connection with the discussion of the cause of thunderstorms, and if my
results are confirmed by more extended observations strong support will be
given to the theory which looks on the condensation of a number of slightly
charged particles into large drops as the cause of the high potential indicated
by disruptive discharges. It has been suggested as an explanation of some of
my observations that every cloud is surrounded by a zone at a lower potential

OBSERVATIONS ON ATMOSPHERIC ELECTRICITY. 587

than the cloud, but a careful study of the observations will show that this is
not quite an accurate statement of the case, as some of the observations show
a high potential outside, but near a thick mist. Of course most clouds are
dissipating at the outside, so that a low potential will, if I am right, be usually
found there.

It seems worth pointing out that, if we neglect the readings made in mist,
the highest were got on the 5th, when it was almost perfectly calm and there
was a thin but very decided haze. The temperatures during the day were also
above the average.

The electrometer used throughout my observations was Thomson’s small
portable electrometer, No. 43, which gives a reading of about 24 divisions
for 100 Daniell cells, when tested at a temperature of about 90° F. I find,
however, that there is a large temperature effect on the zero readings, and I
have not been able to test whether or not this affects the value of the scale
readings. In Madras the leakage is so great and the temperature range so
small that I could never be quite sure of the effect of temperature on the zero
reading, but it was different in the comparatively dry atmosphere of Dodabetta,
where the instrument retained its charge well and where it was used in
temperatures varying from about 38° to 69° in the shade, but really with a
much wider range since the day observations were made in the sun, in which a
black bulb thermometer rose to from 125° to 188°. The accompanying curve
(Pl. CXLVI.) shows the changes in the zero readings during four days, and an
approximate curve for the shade temperatures during the same period. The
temperatures are only a very rough approximation, as during the time that the
sun was above the horizon they were taken between the outer and inner walls
of the tent near the door, on the side away from the sun, no better shade being
available; at night the thermometer was placed outside 4 feet from the
ground.* It will be seen from these curves that on the 8th the zero rose from
1202 at 14" to 1261 at 23" a rise of nearly 5 per cent. At first this large
temperature change gave me considerable trouble, as I found that the earth
readings before and after the air reading differed considerably from each other,
but this difficulty was reduced to a minimum by leaving the electrometer on
the observing post for a few minutes before making the observation. It will be

* The minimum thermometer gave readings varying from 32°°5 on the 7th to 40° on the 5th and
6th, with an average of 36°. It is interesting to compare this with the reading made in the Dodabetta
observatory, and I have accordingly taken the observations for the five years from 1848 to 1852 for the
corresponding days of January. I find the lowest recorded temperature is 40°:4, while the average is
45°-1, or 9° higher than the average which I got. Only a small part of this difference can be ascribed
to the unknown error of the thermometer used then, and it is equally improbable that the present year
was so much colder than any of the years during which the observations were made. The only remain-
ing explanation is that, as popularly believed, the observer took his thermometers inside the hut that
so he might escape the necessity of going out into the cold mist-laden air after nightfall.

_ VOL, XXXII. PART III. oO:

588 . C. MICHIE SMITH ON ATMOSPHERIC ELECTRICITY.

noticed that the. temperature error is in the opposite direction to that us
found in these instruments, though Sir Wi1t1AM Tuomson has found *
(White, No. 18) which showed an error in the same direction.

The above observations were rendered possible by the kindness of
Excellency the Right Honourable M. E. Grant Durr, who placed tents ai
disposal, and of Mr L. R. Burrows and Mr D. Hooper, who gave me a
assistance.

* Flectrostatics and Magnetism, p. 301.

Manras, 22nd April 1885.

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XXXII.—Note on Ectocarpus. By Joun Ratrray, M.A., B.Sc., Scottish
Marine Station, Granton, Edinburgh. Communicated by Jonn Murray,
Esq., Ph.D. (Plates CXLVII., CXLVIILI.)

(Read 2nd February 1885.)

The group of the Phaeosporex was first recognised by THurET* in 1850. It
includes alge that vary greatly in size, habit, external appearance, and mode of
branching, some possessing a flat thalloid appearance with or without a long
stalk (¢.g., Laminarie), others being filamentous and much branched (e¢.g., Ecto-
carpus, Sphacelaria, Chordaria, &c.). The great majority of the genera
included in the group are marine or brackish water forms, but recently E.
FLAHAULTt has described, under the name of Lithoderma fontanum, a fresh
water species from the neighbourhood of Montpellier.

All the forms included under the genus Ectocarpus are filamentous, and
usually much branched, EF. crinitus being one of the simplest types, and £.
siliculosus one of the most complex. The primary branches again may be
straight or present gentle undulations (¢.g., E£. si/iculosus), or may exhibit well-
marked geniculations at the points of origin of the ramuli (¢.g., #. distortws and
EL. Landsburgii). In some the central filament is of greater diameter than the
secondary branches, and so remains a prominent feature in the plant, but in
others this occurs to a much less degree, both being of approximately equal size
(e.g., E. crinitus, &c.).

The particular zone in which the Ectocarpi flourish is that extending from
high to low water mark, some being found over the whole bathymetrical extent
of this belt (¢.g., #. brachiatus, E. tomentosus, E. littoralis, E. siliculosus, E.. sphero-
phorus), others occurring chietly at the level of half tide (e.g., #. crinitus), while
yet others are especially obtained near that of low water (e.g., EF. fasciculatus).
Their mode of attachment, too, varies very greatly. They are to be found
adhering to mud-covered rocks aud stones in the shade (¢.g., #. crinitus) or in
exposed situations (¢.g., EL. littoralis), as well as epiphytically on other algee in
shaded pools (¢.g., HL. brachiatus), or in open places (¢.g., £. spherophorus).

The great majority of the species of this genus are found to grow epiphyti-
cally on other seaweeds, some being apparently confined to a limited number
of host plants, others being less restricted in this respect. Thus #. brachiatus is
only found associated with Rhodymenia palmata, just as Polysiphonia fastigiata
Imost exclusively occurs on Ascophyllum nodosum, while LE. fasciculatus and E.

* Thuret, “ Recherches sur les zoospores des Algues,” Ann. des Sct. Nat., series ili. vol. xiv. 1850.
+ Comptes Rendus, xcviii. (1884), pp. 1389-91.

VOL, XXXII. PART III. 5 F

590 MR JOHN RATTRAY ON ECTOCARPUS.

tesselatus chiefly occur on Laminaria digitata and L. saccharina. On the other
hand, the host plants of £. Uttoralis and £. siliculosus are very numerous, the
latter, up to the present time, having been found on Cladophora rupestris,
Corallina officinalis, Chorda lomentaria, Chordaria flagelliformis, Ceramium
Deslongchampsti, Asperococcus echinatus, Halidrys siliquosa, Polysiphonia elon-
gata, P. urceolata, Myriotrichia claveformis, and Rhodymenia palmata, in the —
Firth of Forth.* Next to £. siliculosus and £. littoralis, E. sphwrophorus is —
that which is least restricted in its range of host plants, being chiefly found
associated with Rhodosperms (e.g., Callithamnia and Ptilote). From this —
peculiar habit the entire genus might be conveniently divided into two groups
—a smaller containing the non-epiphytic species, and a larger including all those
found growing on other alge.
Ectocarpus siliculusus (Lyngb.), upon which my present observations are
founded, is an annual plant occurring chiefly from May to September, or,
according to Harvey,t from “spring to autumn.” As already indicated, this”
species is found between the highest and lowest limits of the tide, and even
extends to depths varying froin three to four fathoms.
In general habit H. siliculosus is most closely allied to Z. littoralis, but may
be distinguished from the latter by its more slender and somewhat softer
growth, and by the fact that its ramuli, which may be either alternate or subse-—
cund, are never opposite—an arrangement which may occur in young branches
of £. littoralis: The multilocular sporangia, moreover, of the two species may
be readily distinguished, those of £. littoralis being placed in the middle of the
ramuli, while those of #. szdiculosus are lanceolate aud terminal.
In addition to the ordinary multilocular sporangia (= Trichosporangia, Nob.)
upon whose true reproductive significance all observers are agreed, various
species of Ectocarpus have from time to time been found to possess so-called
“ unilocular sporangia” (=Oosporangia, Nob.) with regard to which there has
not been the same consensus of opinion among algologists.
Tuvret, { when discussing the fructification of the Pheeosporeze, says :—“ La
seule fructification que l’on signale dans ces plantes consiste en sporanges
ovoides (Oosporangia, Nob.), qui ont d’ailleurs été toujours décrits comme des
spores simples, quoique en réalité ils soient remplis de nombreux zoospores.
Cet organe est le plus visible, et c’est ce qui explique pourquoi il a surtout
attiré l’attention des observateurs. L’autre forme de sporanges consiste en
filaments cloisonnés.
“(Trichosporangia, Nob.), fort étroits et généralement assez courts, composés:
d’une séries de petites cellules, dans chacune desquelles est renferné un zoospore.

a

* Traill, Monograph of the Algae of the Firth of Forth, 1885.
+ Harvey, Phycologia Britannica.
t Thuret, loc. cit., pp. 235-236.

MR JOHN RATTRAY ON ECTOCARPUS. 591

Ces filaments sont tres nombreux, et occupent la méme place que les sporanges
ovoides, quils accompagnent parfois: plus ordinairement néanmoins, on ne
trouve 4 la méme époque que l'une ou I’autre forme de fructification sur le méme
individu. Les zoospores issus de ces deux organes offrent une parfaite ressem-
blance. Seulement ceux qui proviennent des sporanges filamenteux sont un
peu plus grands que ceux qui s’echappent des sporanges ovoides. J’ai vu
dailleurs germer les uns el les autres, ce qui prouve suffisament leur compléte
identité.”

J. E. Arescnoue” finds “ Oosporangia” and Trichosporangia in Ectocarpus
littoralis, Harv., and in £. fasciculatus, Harv.

J. G. AcaArput describes the fruits of Ectocarpus as consisting of (1)
spherical or ovate sessile spore or sporidia, enclosed within a hyaline peris-
porium, and (2) of motile sporidia—the sporidia being spherical or ovato-
ellipsoidal capsules. He also describes pod-like propagula,

Kitzine { figures in Ectocarpus fasciculatus unilocular forms of fruit as
“ spores,’ and multilocular as ‘“‘ spermatoidia,” the latter, according to Professor
PERCEVAL WRIGHT, being very like parasitic Chytridial growths. He also repre-
sents, according to Professor Macnus, Chytridial parasites as ‘“ intercellular
spores” of various Callithamnia.

C. Goxr§ figures ‘‘Oosporangia” and Trichosporangia in Lctocarpus
approximatus v. balticus, Kiitz.

W. G. Fartow || notes that the so-called “ oosporangial” fruit of Ectocarpus
has not hitherto been observed in America, although the trichosporangial form
is well known.

Harvey,{ as pointed out by Professor WricuT, represents the round or
elliptical sessile “ utricles ” or “spores,” which have been recognised as “ oospor-
angia,” as outgrowths of cells in Ketocarpus crinitus, HE. pusillus, E. granulosus,
and EL. spherophorus.

PrinesHEr,** while figuring (Taf. ix. fig. 7) the terminal portion of a branch
of Sphacelaria olivacea v. cespitosa, Dillw., which has become invaded by
parasitic Chytridial cells, also represents (Taf. ix. fig. 9,c) certain cells which
have enlarged into a rounded ball-shaped form, which he calls “ Brutzelle,” but
the exact interpretation of these structures he leaves undecided. ‘‘ Die sonder-

* J. E. Areschoug, Algae Scandinavice exsiccate, serei nove, Feb. 4, 1862.

+ J. G. Agardh, Species, Genera, et Ordines Fucoidearum, Lunde, 1848, p. 14.

{ Kiitzing, Tab. Phyc., vol. v. pl. 50, i.

§ C. Gobi, “Die Brauntange des Finnischen Meerbusens,” Mem. de Acad. Imp. des Set. de
Petersbourg, sept. serie, tome xxi. No. 9, 1874.

|| W. G. Farlow, “List of the Marine Algze of the United States,” in Proc. Amer. Acad. of Arts
and Sciences, vol. x. 2nd series, p. 351, 1875.

@ Harvey, loc. cit.

** Pringsheim, “Ueber den Gang der morphologischen Differenzirung in der Sphacelarien-Reihe.,”
Abhandl. d, Konigl. Akad. der Wiss. zu Berlin, 1873.

592 MR JOHN RATTRAY ON ECTOCARPUS.

bare Umwandlung ihres Inhaltes, die sich von der der endstiindigen Sphacelen
wesentlich unterscheidet, gestattet noch keine sichere Deutung. Entschiedene
Parasiten sind mir in ihnen nicht aufgefallen. Es ist mir nicht fraglich, dass
es diese Bildungen sind, welche einige iiltere Algologen als sitzende Sporen
beschrieben und abgelildet haben.”

The parasitic or non-parasitic nature of the much swollen club-shaped cells
represented in plate ix. fig. 9, d, and in plate x. figs. 5, 6, and 7, the contents of
which escape as free swimming ciliated swarmspores, a more or less definitely —
defined network of the mother cell walls being left behind, this author also
leaves undecided, remarking—“Ich habe diese Bildung, die sich, wenn sie
nicht in den Entwickelungsgang der Pflanze selbst gehért, an keine bekanntere
Parasitenform anschliesst, bisher nur an der Sphacelaria olivacea von Helgoland
aufgefunden ; an anderen Sphacelarien ist sie mir nicht aufgestossen. Sie ver-
langt eine weitere, eingehende Beriicksichtigung.”

Coun,” in 1867, drew attention to the fact that Chytridial parasitic organisms
had often been represented as part of the tissue proper of the host plants, @.g.,
by Sorter and DeErs&s,t in the case of Aglaophylluin ocellatum, while Maenus
refers the ‘abnormally swollen up apical cells in Ceramium spiniferum, Kiitz.,
figured by Cramer, to a new species of Chytridium—Olpidium tumefaciens,
Mag.,{ which is figured by Harvey§ as probably the antheridia of Callitham-
nion dispar, Harv.; he also believes that the “abortive spore mother cells,”
figured by NAGELI|| in Callithamnion cruciatum, are referable to the parasitic
Chytridium plumule, Cohn. .

Professor E. P. Wricut{ maintains that Grunow** has taken parasiti¢
Chytridia for true spores in Callithamnion, and possibly in Leda capensis (Grun.),
&e.

In Ectocarpus granulosus, Professor Wricut ‘has watched through all its
stages, save that of germination, the Chytridial form which has been mistaken
for an oosporangium,” and while satisfying himself that the parasite is the “only
fruit known” in Ectocarpus crinitus, he believes that in E. spherophorus the
oval cells, although they may not be foreign bodies, are “‘ most suspiciously like
some Chytridial growth.”

* F. Cohn, “ Beitrige zur Physiologie der Florideen,” Max Schultze’s Archiv fiir Mikroskopische
Anatomie, Bd. iii. s. 41, 1867.

+ Capt. Solier and Dr Derbés, Memoire sur la Physiologie des Algques, p. 67, pl. xxi. figs. 10-12.

t¢ Magnus, in Jahrbericht der Commission zur wissenschaftlichen Untersuchung der deutschen Meere
in Keil, fur die Jahre 1872-73, Berlin, 1875.

§ Harvey’s Phycologia Australica, vol. vi. 1862,

|| Nageli, Die newern Algensystem, Zurich, 1847, p. 202, Tab. vi. fig. 1, 8, s; 4, s, 8.

{| Prof. E. P. Wright “On a Species of Rhizophydium parasitic on Species of Ectocarpus, de.” Tra
Roy. Irish. Acad., vol, xxvi. August 1877.

** Grunow, Reise S. M. F. Novara um die Erde. Botanik, Th. i. Algen, Tab. vi.

MR JOHN RATTRAY ON ECTOCARPUS. 593

The genus Rhizophydium was established by ScHEeNnxK for Chytridiaceous
parasites, whose spores escape by one or more apertures. The globular and
unicellular Rhizophydium Dicksonii has hitherto only been noted on Ectocarpus
granulosus gathered at Howth, near Dublin, during the winters of 1876 and 1877.
I, however, gathered specimens of Ectocarpus siliculosus which were affected
with this parasite on December 4, 1884, about 10.30 a.m. The host plant was
found growing epiphytically on a fragment of Polysiphonia fibrillosa, which was
obtained about the level of ?-tide in the old Granton Quarry. <A small part of
the shale on which the Polysiphonia grew was removed at the same time, so that
the epiphyte and its parasite were disturbed as little as possible. The tempera-
ture of the water at the time of removal was 41°°2 Fahr. Some of the speci-
mens of Ectocarpus thus obtained were placed in a small glass vessel containing
sea water, and kept for some days in the microscopic room of the “ Ark,” the
floating laboratory connected with this station. This material was repeatedly
examined to determine when rupture of the cells would be likely to take place:
and this occurred about 1.30 p.m. on December 7, when specimens were at once
mounted in weak acetic acid. The temperature of the water in the vessel in
which rupture occurred was 51°°8 Fahr.

The parasitic Rhizophydial cells were found to be widely disposed over the
penultimate, but sometimes occurred on the ultimate ramuli of their host plant
(Pl. CXLVII.). In the former they were not confined to any definite region, but
were found scattered at irregular intervals along their entire length. They usually
occurred singly, but at other times were found in pairs (Pl. CX LVIIL. fig. 8), while
in a few cases three contiguous host cells were attacked (Pl. CXLVIII. fig. 3).

The parasitic cells enter the cells of the host plant at a very early stage of their
existence, and gradually develop at the expense of the highly organised proto-
plasmic contents of the latter. In Pl. CXLVIIL fig. 2, two adjoining host cells
have been penetrated by the Rhizophydial cells, which have arrived at different
stages of development; PI. CXLVIIL fig. 2, a, represents the earliest stage which
I have observed. The parasite presents the appearance of a nucleus, and is
surrounded by a thin but definite cell wall. In figs. 1, 4, and 5 of the same Plate
| somewhat more advanced stages of development are represented, and while in
_ figs. land 5 the Rhizophydium has assumed an almost perfectly ellipsoidal form,
| in fig. 4 it exhibits a tendency to expand laterally, being even slightly involuted
/ at one end, on account of the greater resistance to which it is exposed in this
| region. At this stage the presence of the parasite is, in ordinary circumstances,
_ revealed by the slightly globular form assumed at a very early period by the
host cell containing it. Sometimes, however, as in the case represented in
| fig. 2, b, the parasitic cell may grow to a moderate size without producing
| the ovoid bulging of its containing host cell, and without itself retaining the
normal globular or ellipsoidal outline. This is probably attributable to the

594 MR JOHN RATTRAY ON ECTOCARPUS.

fact that it has entered a cell which is not very rich in organic contents, in
which it is enabled to develop without producing so great internal pressure
as must necessarily be exerted when the latter is tensely filled with fluid cell
sap and other protoplasmic substances, or derivatives from these.

A still more remarkable appearance is that represented in fig. 6. Here the
host cell has become distinctly globular, and contains a well-defined parasitic
Rhizophydium, around which a more or less hyaline area is found, in which the.
chlorophyll granules show manifest pathological changes. Instead of being
absolutely round, this parasite has a well-defined and moderately deep indenta-
tion on one margin, around which its cell wall passes without interruption. It —
is not easy to give a satisfactory reason for the existence of this fold, although
two possible explanations may be offered, namely, it may be due to the exist-—
ence of a greater internal pressure existing in the host cell at this point, a slight —
divergence from the perfect equilibrium being sufficient to cause a sinuosity in
the thin and pliant cell membrane, or if this parasite should ultimately be found
to possess this indentation in its earlier stages, it may point to a specific
distinction between it and the perfectly ovoid or globular type. As only a
single instance of this peculiar phenomenon was observed, it is not unlikely
that the former explanation is the more trustworthy.

At the moment of rupture the cells containing the mature Rhizophydia
present in most cases a distinctly ovoid appearance. That the internal tension
in these cells is at this time great is proved at once by their external form, by
the fact that they bulge into adjoining cells of the host plant which are not
so affected, and by the existence of creases which may not uncommonly be
observed just after the rupture (fig. 12). It is also to be noted, that as soon as
relief from this tension is obtained, the adjoining cells of the thallus of the host
plant at once become convex on the side of the ruptured cell in virtue of their
own elasticity, and so tend to cause a more violent rupture, and to facilitate the
dissemination of the swarmspores of the parasite. a

In cases where three adjoining cells contain parasites (fig. 3, a, 0, ¢), the
middle cell, which is unable to indent the walls of the adjoining tense cells,
expands usually in a somewhat lateral direction, and always towards that side
on which the resistance is least when this tendency is first manifested.

After rupture takes place the appearances presented by the affected cell
areas are sometimes of a very fantastic kind. The cell wall of the parasite, as
soon as the wall of the host cell opens, suddenly swells up, owing to the pressure
exerted by the contents against its inner surface, in many cases to twice it a
former dimensions (figs. 7, 10, 11, &c.). At first the parasitic cell membrane is
entire (fig. 10), but it soon opens to the exterior, sometimes by a single pore
(fig. 9), which may be directed either towards the base of the filament, or
towards its apex, or at right angles to its longitudinal axis, sometimes by two

MR JOHN RATTRAY ON ECTOCARPUS. 595

pores, the one being directed towards the base of the filament, the other towards
its apex (fig. 8, a), or both being placed approximately at right angles to its axis,
either on opposite sides (fig. 8, ¢), or on the same side, at other times by three
apertures arranged in various ways (figs. 11, @, and 12). It should here be
noted that these apertures in the cell wall of the parasite often lie in different
planes, and that it is not always possible to see all of them without a change of
focus under the microscope.

Although two or three openings are of frequent occurrence in the cell
membrane of the parasite, the cell wall of the host plant invariably opens only
at one point, and in many cases it is possible to see clearly the margins of the
ruptured wall (figs. 7, 9,10, and 11). It may also be observed, that this ovoid
wall is no longer able to recover its original form after rupture, inasmuch
as the limit of its elasticity has in most cases been passed, so that a perfect
rebound is not possible, while the long continued internal tension has con-
_ tributed to it a certain fixity of form which its remaining elasticity is not able
to reverse.

In some cases (fig. 9) one meets with a remarkable involution of the wall of
the host cell after rupture has occurred. This fold, which usually occupies a

position approximately diametrically opposite to the place of rupture, may have
| resulted either from the fact that the cellulose wall burst before the limit of its
elasticity was passed, so that a sudden and sharp recoil became possible, or
| from the impact of some foreign body which, by striking against the involuted
| region, at once caused that fold, and affected a rupture of the wall at the
| diametrically opposite point. The occurrence of such a fold is, however, un-
/ usual. ;

After rupture the swollen cell membrane of the parasite, which invariably
remains very thin and pliable, exhibits numerous creases, which become especi-
ally manifest when examined under a water immersion high power lens (fig. 7).
| These fine irregular folds point to the presence of a certain amount of rigidity
in this membrane, which may be partly induced by direct contact with the
| water of the surrounding medium. That the immense surface which the intact
| but swollen host-cell membrane offers to the waves must tend powerfully to bring
_ about the complete destruction of the host plant by inducing or effecting complete
| breakages of the thallus at these already weakened regions is at once obvious.
| When the parasitic cells have just opened, relief from internal tension is at

first experienced in the neighbourhood of the orifice or orifices, and it is often
| possible to observe that the young swarmspores, into which the protoplasm has
| divided, and which lie toward the opposite side of the cell, have, at this time, an
jangulated or polyhedral outline. This, however, is of a transitory character, and
|is due to the mutual pressure resulting from their continued growth (fig. 11, a).
A peculiar and interesting disposition of the swarmspores is to be observed

596 MR JOHN RATTRAY ON ECTOCARPUS.

in fig. 10. Here the host cell wall has ruptured, and the membrane of the
parasitic cell has swollen so much that a complete relief from internal pressure
has occurred without rupturing the latter. The result is that the smarmspores
are arranged in a retiform manner, forming meshes by adhering to each other
along certain lines. That this is a transitory stage is at once manifest, but that
it may be the final appearance, presented by the swarmspores generally just
before the rupture of their bounding cell membrane takes place, is not unlikely.
It indicates that, although the protoplasm contained in the parent Rhizophydium
divides by a simultaneous process into numerous spores, a final separation
is not effected at the same moment throughout the entire mass, but rather
along certain lines whose direction is in all probability determined by the lines
along which the force or forces that determine rupture act.

Various causes operate in bringing about the rupture of the cell wall of the
host plant, as well as of the thinner and more elastic membrane of the endo-
parasite. These may be regarded as being (@) intrinsic and (4) extrinsic. Of —
intrinsic causes there may be noted (1) internal tension, and (2) weakness
resulting from pathological changes. The former of these factors is no doubt
that of the greater significance. It originates in the developmental changes that
take place inside the endo-parasite. The volume of the latter is being slowly
increased, and while a certain amount of nutritive material must be removed from
the host cell to produce this result, so that tension strain would thus so far be
antagonised, the growth of the parasite that follows more than counterbalances”
the changes effected, while at the same time a certain amount of carbonic acid —
gas, resulting from protoplasmic oxidation, given out by the parasite, will tend
still further to increase the pressure. As already noted, that pressure causes,
first a bulging of the host cell to the surrounding medium chiefly, but also
partly into adjoining cells of the thallus when these are not similarly affected,
and finally it results in producing rupture at their weakest point. The ultimate
expansion and rupture of the parasitic cell wall are due to a similar tension
exerted by the ever-increasing swarmspores.

(2) The weakness resulting from pathological changes, operates, though ina
less degree,in accelerating the bursting of the host cell wall. The full complement
of nutritive material no longer reaches this wall from its normal channel, viz., .
its own cell protoplasm, so that the supply of new food molecules, to maintain —
the oxidation consequent on vital activity, is partially checked. This may
result in pathological molecular transformations in the wall, producing areas of
weakness, where rupture becomes possible by the operation of internal pressure
and the other extrinsic causes. In confirmation of this view, it is to be
remarked that the host cell is not usually found to rupture at or towards an
angle of the cell,* but, in most cases, opposite the middle of the cell lumen.

* If rupture occurs here, it is attributable to the action of extrinsic and purely accidental causes,

MR JOHN RATTRAY ON ECTOCARPUS. 597

This is explicable on the supposition that the parts of the cell wall adjoining
other cells continue to receive relays of food molecules from the latter, when
they are no longer able to procure them from the protoplasmic material which
occupies the lumen of the cell which they themselves bound, so that devitalising
changes are retarded most, just in the immediate vicinity of these adjoining
cells, but less and less as we advance from that point, and least of all opposite
the middle of the cell lumen where rupture is effected.

Among the extrinsic causes that induce rupture, there may be noted (1) the
pressure exerted by the contents of adjoining cells which are not similarly
affected with the parasite. The operation of this cause becomes plain when it
is remembered that the bulging of the affected cell causes the cell walls, bound-
ing adjoining cells, to become concave on the side next itself. This sets up an
elastic pressure in the contents of these adjoining cells, which in turn acts on
cells next them, and so on. When rupture of the ovoid host cell takes place,
the hitherto concave walls of the neighbouring cells become convex, and so
bulge into the ruptured cell, thereby causing a wider dissemination of its con-
tents than would otherwise be the case.

(2) The impact of ripples or foreign bodies against the swollen host cells,
the former of which especially occurs when the tide just reaches the level at
which the plant grows, have obviously a similar tendency.

Negative heliotropism of the swarmspores of Rhizophydium.—After a large
number of the swarmspores of Rhizophydium had escaped into the watch-glass
in which the host plants lay, the glass was surrounded, to the level of its brim,
with black paper, so that no light could penetrate into it from beneath. The
surface was then covered as closely as possible to the level of the water with a
similar piece of black paper. Before being covered on the surface, the water
in the glass was stirred gently with a needle, so that the swarmspores were
equally diffused through it. The cover when adjusted was allowed to remain

' for several hours, and it was so arranged as to conceal the surface of fully
three-fourths of the glass. On re-examination of the water by removing two
samples of it simultaneously with two very small dipping tubes, and placing them
| under microscopes, it was found that while the water which had been exposed
_ to the daylight contained a few swarmspores, the greater number of the spores,
| which were still in active motion, had congregated on the dark edge of the glass.
| Their general tendency must, accordingly, be regarded as negatively helio-
| tropic.

| In connection with this subject, it may at this point be noted, that in the
| same gathering of Ectocarpus siliculosus, many specimens were obtained which
| bore the ordinary multilocular fruit figured by Harvey.* The biciliate swarm-
| spores that escaped were observed for some hours under the microscope. The
| * Harvey, Phyc. Brit.

VOL. XXXII. PART III. DG

598 MR JOHN RATTRAY ON ECTOCARPUS.

light was so adjusted, by means of the mirror, that about two-thirds of the
field was dark, while the remaining third was illuminated with diffuse daylight, .
and it was observed that the true reproductive swarmspores of this species had _
similar negative heliotropic tendencies, as they congregated on the dark part of
the field.* In a genus closely allied to Ectocarpus, viz., Sphacelaria plumigera,
I am informed by Mr Trariu that Mr EH. M. Hotes, F.L.8., has recorded
similar heliophobic movements of the swarmspores. It may be added, by
way of contrast, that, according to Borz1,t the zoogonidia of Ulva are posi-
tively heliotropic, while the conjugated zoospores have opposite or heliophobic
tendencies.

The significance of such movements, in relation to the light, may be of im-
portance as affording an early indication of the habit of the plants. Thus many
marine algee avoid exposed sunny places, and delight in dark rocky crannies,
where the rocks, from their softer nature, have become eroded by wave action,
aided by the denudatory effects of the impact of hail, snow, rain, &c. That —
such seaweeds tend to accelerate marine erosion cannot be doubted, when it is
remembered that their rhizoids, in many cases, become entangled among minute
particles of shale or other soft rock, and that the plants possess a certain
buoyant power which tends to lift the fragments, to which these rhizoids are
fixed, from their place. This buoyant power, moreover, is often largely in-
creased by the passage of waves which play against the thallus, and so increase -
its pull upon the rock to which it is fixed.

Although swarmspores, that are thus heliophobic, tend in the first instance —
to settle down upon shaded water-worn spots, it does not follow that round
mammillated or exposed rocks are never covered by algae, whose spores exhibit
such a tendency. It is to be borne in mind, on the contrary, that a heliophobic —
spore may often find enough of shade among the rhizoids of other pre-existing
weeds, while its rhizoids will in turn form a suitable nidus for another similarly
disposed spore, so that finally a round exposed protuberance may be entirely
covered with algze whose spores are negatively heliotropic.

In connection with what has been stated above, with regard to the escape of
the multilocular swarmspores of Ectocarpus siliculosus, it is of interest to record
that the period during which spores may escape in that species can no longer be
limited to the summer season, as has hitherto been done in the basin of the
Firth of Forth, but must be extended to December. It is, however, to be borne
in mind, that the unusual mildness of the season, combined with the sheltered
locality in which the specimens were found, may have largely contributed to
this result. It is also worthy of remark, that a rise of temperature has a direc
influence in hastening the escape of the swarmspores, inasmuch as specimens

* In this case direct rays of light were carefully excluded from the stage of the microscope.
} Bora, Studi algologici, 117 pp. (9 pl.). Messina, 1883.

MR JOHN RATTRAY ON ECTOCARPUS. 599

from the same gathering, which were kept in a somewhat colder part of the
“ Ark,” did not discharge them so soon as others which were placed in the micro-
scopic room, which was kept at a higher temperature.

It is, moreover, interesting to observe, that although the septa across the
multilocular sporangia of Hctocarpus siliculosus usually persist, yet it sometimes
happens that these septa disappear before maturation of the spores, in which
case the sporangium becomes ultimately unilocular.

This observation corroborates the statements made by PriInGsHEIM™* with
regard to Ectocarpus siliculosus and E. granulosus, whose general conclusion
is stated as follows :—‘‘ Diese Beobachtungen fiihren zu dem Schlusse, dass
die Differenz der beiden Sporangienformen der Pheeosporien, die sich in der
fehlenden oder vorhandenen Facherung ausspricht, keme absolute ist, sondern
nur einen verschiedenen Grad der Ausbildiing und Persistenz oder Resorption
des transitorischen Mutterzellgewebes der Schwirmsporen ausdriickt. Bei den
Oosporangien geht dasselbe der Regel nach schon gleichzeitig mit der Reife
der Zoosporen zu Grunde und persistirt nun in einzelnen Fallen; bei den
Trichosporangien bleibt mindestens der altere Theil des Mutterzellgewebes
gewohnlich stehen, waihrend die jiingeren Generationen—ob immer ?—zu
Grunde gehen; aber in einzelnen Fallen wird auch hier das ganz Mutterzell-
gewebe resorbirt und dann erscheinen die Trichosporangia wie uniloculare
Organe.”

Although conjugation between the escaped swarmspores of the multilocular
sporangia was carefully looked for, no instance of it was detected. GoEBEL,t
however, has already pointed out that such swarmspores conjugate during
summer, when two neighbouring sporangia burst simultaneously. Probably
the inertness induced by the lower temperature of the watery medium in
December was enough in itself to check any such reproductive process.

Although in most cases specimens of Hcetocurpus siliculosus which were
affected with parasites did not bear true normal reproductive organs of any
kind, I have, in one case, seen young multilocular sporangia and parasitic
Rhizophydia on the same plant, but in no instance have I found these sporangia
to be mature.

In conclusion, it would appear that the effect of the presence of Rhizo-
phydium in Ectocarpus cells is to produce results analogous to those found in
animal tissues that have become invaded by Bacterial germs of disease. That
there is primarily the same stimulation, which, however, does not advance so far
as to induce rapid cell divisions, as happens in the case of Bacteria, is manifested
| by the fact that the parasite containing cells are usually of a somewhat larger

* Pringsheim, Joc. cct., p. 169, 170.
+ Goebel, Bot. Zett., 22nd March 1878.

600 MR JOHN RATTRAY ON ECTOCARPUS.

absolute size than the other cells of the thallus. This stimulation is no doubt
caused by the waste products evolved by the parasite as well as by the very
presence of the latter inside the host cell. Moreover, in both cases, there is”
the same final result, namely, complete devitalisation of the organic substance,
and the ultimate death of the host. q
All the figs. on Plate CXLVIII. have been drawn by the aid of Abbe’s
camera: fig. 7, under Leitz’s microscope Oc, 1, Ob. No. 10 Hartnack (water
immersion) ; the other figures under Zeiss’s microscope Oc. 3, Ob. CC.

EXPLANATION OF PLATES CXLVIL, CXLVIIL..

Plate CXLVIL represents a specimen of Lctocarpus siliculosus richly covered with the parasitic Rhizo-
phydium Dicksonii. The latter occurs in various stages of development on the ultimate and penultimate
ramuli of the host which bears none of the ordinary fructification.

On Plate CXLVIII. various conditions of the parasite may be observed.

Fig. 1 shows a host cell enlarged, rounded, and containing a Rhizophydium of considerable size, and —
bounded by a faint though distinct cell wall.

Fig. 2, a, represents the earliest stage of the parasite that has been observed, while the adjoining cell
(fig. 2, b), contains a large reniform Rhizophydium, which, however, has not caused the usual bulging
of the host cell wall.

Fig. 3 shows a condition in which three adjoining host cells have been attacked.

Fig, 4. Here the host cell is slightly swollen, and the parasite, instead of being perfectly round, has —
expanded somewhat in a lateral direction, and shows slight involutions on two opposite sides.

Fig. 5 represents a perfectly elliptical Rhizophydium lying in a somewhat swollen host cell,

Fig. 6 shows a parasite which possesses a remarkable indentation on one of its margins. The host
cell is very much enlarged and rounded.

Fig. 7 is a very much enlarged representation of a parasite which has just ruptured. The broken
margins of the host cell wall are well seen, as also the creases of the cell wall of the parasite.

Figs 8a, 8), and 8c show the positions of the points of rupture of the cell wall of the parasite, with
reference to the direction of the axis of the filaments of the host plant.

Fig. 9 shows a remarkable involution of the cell wall of the host plant, rupture having taken place
at the diametrically opposite point.

Fig. 10 shows a peculiar reticulation of the spores of the parasite, which occurs just before rupture
of its cell wall.

Fig. 11, a, represents the angulated condition in which the spores exist at and before the period of
rupture. This is the result of mutual pressure caused by the continued growth. In fig. 11, 0, a very
much enlarged cell is seen, which is also obviously affected by the presence of a parasite. .

In fig. 12 the angulation of the parasitic spores, the creasing of the cell wall, and the positions of
rupture of the parasite, may be studied.

WU. Lit: Vor XXAL] Plate CXLV

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XXXITI.—Anatomy and Physiology of Patella vulgata. Part I. Anatomy.
By R. J. Harvey Gipson, M.A. Communicated by Professor HErp-
MAN, D.Sc. (Plates CXLIX.-CLIIL)

(Read 5th January and 20th July 1885.)

CONTENTS.

PAGE PAGE
INTRODUCTION, . ; : : é . 601 3. Circulatory System, . ‘ ; 2) Gls
Historican Account, . ‘ : é =) 60 4, Purificatory Systems, : 614

MorpHo.oey : 5. Muscular, Connective reese and
1. External Form—General Arrangement Epidermal Systems, . . 620
of Viscera, . : : : . 603 6. Nervous System and Sense Gone . 626
2. Alimentary System, . : : - 605 7. Reproductive System, ‘ P . 633

INTRODUCTION.

The following research was undertaken chiefly with the object of furnishing
a complete memoir on the morphology and physiology of Patella vulgata. A
number of isolated observations on various organs are recorded, but no
systematic account has as yet been written, so far as the writer is aware. He
has endeavoured to incorporate these observations in such a general account,
having first convinced himself of their accuracy so far as lay in his power.

The paper is divided into two sections. Part I. deals solely with Anatomy
and Histology; Part II. will contain an account of the Physiology of the
systems described in Part I. An attempt will be made to give a description
of the as yet uninvestigated development of Patella. These observations will
doubtless afford material for certain conclusions bearing on the phylogeny of
the Patellide.

All the observations described in Part I. were made on specimens obtained
from Granton, the Gareloch, Loch Goil, and Firth of Clyde, fresh or preserved
in spirit, or a saturated solution of picric acid.

The research was conducted in the Zoological Laboratory of University
College, Liverpool ; and the author is indebted to his friend Professor HErp-
MAN, D.Sc., not only for permission to make these observations in his labora-
tory, but also for constant advice during the prosecution of the work. His
best thanks are also due to Dr Murit, F.L.S., for the great assistance rendered
by him in the bibliography of the subject.

HIsToRICAL ACCOUNT.

As indicated above, the investigations into the minute anatomy of the
limpet are not numerous, and with few exceptions exceedingly fragmentary
and contradictory. Dat, in a recent paper, afterwards to be referred to,

~

VOL. XXXII. PART III. oH

602 R. J. HARVEY GIBSON ON THE

expresses a hope that the anatomy and development of this form may be taken
up by some one; and although it is to be regretted that the task had not fallen
into more competent hands than the present writer’s, yet he hopes that he has, —
in the following research, done something towards dispelling the prevailing
uncertainty in regard to many questions, which have too long demanded inves-
tigation. The desideratum at present in the natural history, more especially of
the Mollusca, is a series of complete accounts of all the more common types ;
and it seems to the author that much more might be made with regard to
interesting problems of Phylogeny, if, instead of elaborating a number of small
detached papers on special points, some naturalists were, for a few years at
least, to devote themselves to the working out of complete monographs of the
most important forms belonging to each group.

A considerable amount of work has been done in the way of naming and
identifying the numerous species of the Patellide; although, owing to their
identification being based on unimportant external features, e.g., the form and
colour of the shell and exposed parts, many forms have received several —
synonyms, and have consequently been described several times. :

In this summary of research, the author desires rather to indicate the
leading papers on which our knowledge of Patella is based, than to give any
detailed account of these papers themselves, which he prefers to postpone until
the different organs with which they deal come to be discussed.

The limpet is mentioned first, of course, by the all-observant ARISTOTLE,
who gives a brief account of some of its more obvious characters and habits,—
referring especially to its moving from place to place and returning after each
forage to its old roosting place. General descriptions have been given by
Linnaus, Born, ADANSON, and various other naturalists of the last century;
and we are generally able to identify the species described by them with those
now inhabiting our coasts. Similar accounts are given by later conchologists,
more especially by REEVE, HANLEY, GwyN JEFFREYS, GRAY, and WooDWARD.

The first attempt at giving a complete account of the anatomy of Patella is
that of Cuvier in his Memoires, where the species is described with tolerable
fulness. Gray, and later Datt, have described and figured the radula, the
mechanism of which has been lately fully investigated by GEppxEs. The renal
organs have come in for a good deal of attention from LANKESTER, DALL, and
CUNNINGHAM, and are perhaps the most thoroughly investigated portions of the
whole animal. The respiratory organs have not been so fortunate, having bee
examined, in allied forms only, by WiLL1AMs (whose paper the writer has not
been able to see). Some remarks on the respiratory organs by BLAINVILLE ali
ADANSON are mainly contradictory of each other. The nervous system has been
investigated by Branpt and by SPENGEL; and their admirable work leaves little
to be done in that system, save to make a few remarks on histology. SPENGEL

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 603

also gives an account of the olfactory organ; and Fraisse describes and figures
the eye of an allied species, Lacaze Duruigrs has investigated the auditory
organs. With regard to the reproductive system there is great uncertainty,
the existence of oviducts and of vasa differentia being asserted and denied
repeatedly. Cuvier asserts the presence of an oviduct ; DALt in one research
thinks that he has seen it, and in another he denies that it exists. LANKESTER
describes two so-called “ capitopedal orifices,” which he took to be the openings
of oviducts, but which he now believes are the rudiments of true gills; DAL
denies their existence altogether. Gray mentions the presence of reproductive
glands, but gives no details.

Many authors have made observations on the habits of the limpet, and
some few notes on its development have been published by FiscuEer; these
researches, however, do not fall to be discussed in this part, since they are
rather physiological than anatomical in their nature.

MorpPHOLOGY.

1. External Form.—In size, Patella vulgata varies from 4 inch to 23 inches in
maximum antero-posterior diameter. The maximum transverse diameter is
about 2 to ¢ of the maximum antero-posterior diameter.

In a typical moderately large specimen, say 2 inches long, the short
diameter is about 13 inch, the height of the dome about ,% inch; but in no
case are the relations of the measurements perfectly constant.

Before removal of the shell, such a specimen is seen to be dome-shaped, the
apex being rounded. The marginal outline of the shell is oval, the narrow end
corresponding to the head end of the animal; the apex of the dome is nearer
the anterior end. The rim of the shell is sharp and irregularly notched; it is
also bevelled, the bevelled side being inner. Two series of markings are
visible, one series running from the apex to the edge of the shell, 2.¢., radial, the
other concentric with the edge. Internally, bands of colour of varying tint
replace the radiating lines. The radial lines, externally, are usually
tuberculate.

The body is surrounded by the mantie skirt, which in specimens preserved
in spirit extends beyond the ventral surface of the foot, owing to contraction
of the muscle of that organ, but which naturally reaches a point midway down
the side of the body. The mantle skirt is notched or wrinkled and pigmented.
It usually retreats ‘somewhat from the shell, its extreme edge forming a
thickened rim.

From the inner surface of the skirt, throughout its entire circumference,
_ there depends a series of lamellee, the functional gills. These occupy a grove, or
_ valley formed by the mantle on one side, and the concave side of the muscular

604 R. J. HARVEY GIBSON ON THE

foot and of the circular muscle which attaches the foot to the shell on the
other. This band of muscle is discontinued at the anterior end for a space
equal to about ith of the circumference ; which space is occupied by the head.
The mantle and gill processes are, however, continued round the anterior end,
and depend in front of the head.

The head is distinct, and a slight narrowing indicates a rudimentary neck
region. The oral disc (Pl. CXLIX. fig. 1), in the centre of which is the oral —
aperture, is corrugated and kidney-shaped in outline, the hilus being ventral.
On either side of the head there is situated a epee more or less pigmented
tentacle (the ‘‘nuchal” tentacle), usually from 4 to 4 of an inch long in its con-
tracted condition, but, when extended, in large fienplots as much as # to an inch
in length. On either side of the neck there may be seen an oval yellowish
body, the rudimentary gills or ctenidia. They are usually about twice their
own length from the circular muscle. They vary in length according to the size
of the animal, from 7; to 24 of an inch (Pl, CXLIX. fig. 3).* Over the right —
shoulder may be seen the anal papilla, and the right and left renal papilla, one
on either side of it. Ventrally the muscular foot is seen widening as it passes
downward, and having a thin rim as its ventral edge.

On removal of the shell, the visceral dome is exposed, and found to be
covered by a deeply pigmented membrane. The colours are deep indigo,
streaked with dull yellow. The yellow tinge being due mainly to the subjacent
viscera shining through the visceral integument. The superficial dark pigment
layer is easily scraped off (Pl. CX LIX. fig. 2). 7

The muscle connecting the foot and the shell is now visible, on surface view,
as a ring, incomplete in front, of uniform width, save at its anterior extremities,
which are rather wider and rounded off. The superficial pigment is most
abundant near the muscle band. '

The eyes may be made out as minute black specks, one on either nuchal
tentacle, on a slight prominence on their outer aspect, near the base.

General Arrangement of the Viscera.—The general arrangement of the
viscera may be made out on remoyal of the shell, and after the superficial
pigment layer of the visceral integument has been scraped off. If the imtegu-
ment itself be removed, the relation of the viscera may be still better defined
(Pl. CXLIX. fig. 3). The integument must be removed with care, as it is
intimately related in some parts to the subjacent tissues. The free edge of the
mantle over the cephalic region being also removed, the visceral mass is seen to
be bounded anteriorly by a ridge, from which project forwards on the right hand
side the anal and renal papille. From the anal papilla, the rectum passes _
backwards transversely for a certain distance, and then passes circularly round

* In the figure they are represented as too near the middle line and too near the base of the tentacle.

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 605

the visceral mass. Posteriorly to the rectum, and supporting it, lies the genital
organ (male or female), which at certain seasons is very large, and forms a
erescentic mass, on surface view, enclosing and supporting the other organs.
It is wedge-shaped, and extends along the floor of the visceral cavity, its thick
edge forming the crescent above mentioned.

Between the rectum and the genital gland, and spreading round the former
and sending projections over the latter so as to enclose it, is the posterior
portion of the right nephridium. It may be traced as a dark brown mass pass-
ing up the right side. It is very variable in form, sometimes scarcely apparent
on surface view, at other times ramifying extensively over the dorsal surface.
It varies in colour from a brown yellow toa deep burnt umber. On the extreme
right may occasionally be seen-a portion of the lingual ribbon inits sheath. The
right nephridium usually extends for 4 of the circumference of the visceral mass.

The centre of the visceral dome is occupied by the liver, a granular villous
mass of yellowish-green colour. It is enclosed by a coil of intestine, which
springs from and ends at the right side, and which separates it from the right
nephridium. Between the anterior bend of this coil and the rectum lies a branch
of the right nephridium.

Anterior to the rectum, and between it and the anterior boundary ridge,
there is a quadrilateral region, which is divided into two by a fibrous septum.
That part, usually more or less triangular in outline, lying nearer to the anal
end of the intestine, is entirely occupied by a light brown body, the left
nephridium. The rest of the space is white and fibrous in appearance, and
forms the dorsal wall of the pericardium. The visceral integument is free from

the viscera, save where it lies upon the nephridia and pericardium, with both of
_ which it is intimately connected.

Born and REeEve, among the older naturalists, give the fullest accounts of
the external features, the former in his Testacea Mus. Ces. Vind., the latter in
his Conchologica Iconica. CuviER gives a short description of the soft parts
visible without dissection (Mémoires pour servier a UVhistorie et Canatomie des
Mollusques). Gwyn Jerrreys (British Conchology) gives the most complete
recent account, but errs in saying that the shell is opaque. None of the shells
examined by the writer were altogether opaque ; the majority were translucent,
though some were less so at the apex than elsewhere.

2. Alimentary System.—The alimentary system is very complicated, and
has not hitherto been investigated in any detail. The following account does
not profess to be perfectly complete, either macroscopically or microscopically ;
and the difficulties in the way of a thorough and accurate examination of all
the parts are such that it cannot profess to be final either. Many points yet
require a more detailed investigation, which the writer means to undertake in

606 R. J. HARVEY GIBSON ON THE

connection with the physiological section of this research. With that intention
he has omitted certain histological details, more especially into the minute
structure of the crop, the openings of the bile ducts, &c., with regard to which
it may be possible to obtain some information when the physiology of these
parts comes to be investigated.
Considering the alimentary canal first of all macroscopically. The buccal —
cavity is entered by an oval or kidney-shaped opening on the oval dise.
Immediately within the circular puckered outer lip which guards the opening —
is a shallow cavity, which is closed posteriorly by a pair of inner lips. These
inner lips are two stout flaps of muscle which rise vertically from the floor of
the buccal cavity, and project almost to the roof. They leave between them a
narrow vertical slit, through which the odontophore may be seen (Pl CLIL.
fig. 54, a). Within these lips a large irregular chamber is found, which may be
termed the pharyngeal chamber. Its form may best be understood by following
the reflections and foldings of the pharyngeal mucous membrane (Pl. CLI.
fig. 62). Ventrally the mucous membrane, starting from the inner aspect of the
inner lips, runs along the floor of the chamber for a short distance until it has
reached the middle of the odontophore. There it bends anteriorly, and is
reflected up over the anterior part of the odontophore. Laterally the mucous —
membrane follows a similar course, being there reflected over the sides of the
odontophore. The mucous membrane then passes beneath the radula, forming
the subradular membrane. Ata short distance from the centre of the dorsa
surface of the odontophore the membrane unites above the radula,—forms in
this way a bag for its reception. Indeed, the radula is an epidermic modifica-
tion of the pharyngeal mucous membrane. The radula lies folded in this bag,
from the wall of which it is developed. The bag is suspended among the
viscera, usually to the left side, sometimes, however, on the right, more rarely
still in a spiral coil on the floor of the visceral cavity.
Returning to the pharyngeal mucous membrane, dorsally it springs from
the palate, and when it has become free from the body or neckwall, and uniting
with the lateral portions of itself, passes backwards over the dorsal surface of the
odontophore. After passing the origin of the radular sheath, it unites with
the ventral portion, and becomes the pharynx proper.
On the palate and on the floor of the pharyngeal chamber, there are two
structures which require mention. These are two plates which protect the
subjacent tissues from injury from the teeth of the radula. The palatal plate
(Pl. CL. fig. 17, and Pl. CLIII. figs. 63 and 64) is sunk in the tissue of the
palate, and like the radula and the ventral plate, is a development of the
pharyngeal mucous membrane. Looked at from below, it presents a central
triangular area, which is of a brown colour, and from which posteriorly (apex) —
project two large almost colourless flaps; from the (base) anterior end also_

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 607

project two smaller wings. These wings are sunk in the tissue, the triangular
central piece being that against which the radula works. The anterior smaller
wings are seen to be flaps of a collar which is formed by the turning back of
the plate. In other words, the anterior flaps are on a higher plane than the
posterior flaps. The palate is slightly depressed where the anterior margin
appears ; and the plate itself is curved, the concavity being ventral, and being
the groove in which the radula slides. Since the radula passes over the
anterior end of the odontophore, the teeth are therefore brought into contact
with the floor of the buccal cavity. There accordingly is found another plate
(Pl. CLII. figs. 55, 56), which has not hitherto attracted the attention of de-
scribers of the hard parts of the limpet. It is not so large nor so distinct as
the other, but that it affords protection to the tissues at that point, is shown
by the fact that the surface of the plate is furrowed by the radular teeth. The
entire plate (as described below) is simply a thickened cuticle. The pharynx,
behind the palatal plate, becomes distinct above. It has very thin and delicate
walls. It may be seen to be 3-chambered, or rather to have two very evident
folds running down one on either side (Pl. CLIIT. figs. 61, 62). The wall of
either lateral division has a very manifest thickening of a yellowish colour,
where the salivary ducts enter. The roof also of the pharynx has posteriorly
a large number of mucous glands in it, which give it a white appearance, as
contrasted with the more transparent anterior portion.

The buccal mass now falls to be described. And, first of all, having theo-
retically stripped off the pharyngeal mucous membrane, the radula must be
noticed as distinct from the odontophore and its muscles. The radula is a
narrow belt usually about (in a moderately-sized limpet) ;4,th of an inch broad,
and about twice the length of the animal in length. Anteriorly it widens out
into a flat plate, in the centre of which is the radula proper. The plate and
radula is merely a modified cuticle. The plate is bent over the front end of the
buccal mass. It is fastened to the mass beneath, whilst, superficially and pos-
teriorly, it sinks beneath the level of the muscles of the buccal mass, and runs
into its sheath as already described. ‘Towards the posterior end the teeth
gradually disappear, and ultimately it ends in a soft hammer-shaped knob. Its
minute structure will be described under the histology of the alimentary system.
The odontophore itself is composed of muscles and cartilages. The buccal
mass (Pl. CLIII. fig. 65), deprived of its covering and radula, is ovoid, and
divided almost into two hemispheres by a furrow, which runs vertically from
before backward. Anteriorly the furrow widens and becomes shallow, and has
a prominence in its centre, over which the radula was bent. Either hemisphere
is composed, therefore, superficially of a mass of muscle whose fibres run out-
wards and from before backwards, and are the muscles of the radular mem-
brane. Beneath these muscles lie the cartilages. The cartilages are six in

608 R. J. HARVEY GIBSON ON THE

number—two anterior, two posterior, and two lateral. The anterior cartilages
are the largest ; they are pointed and slightly curved upwards in front, and are
arranged like the legs of the letter V, with the apex pointing towards the mouth
(Pl. CLIIL. fig. 66). At the bases of the legs lie the posterior cartilages, and
closely attached to them. The posterior cartilages are square blocks with
corners rounded off. The lateral cartilages lie alongside the anterior cartilages,
and towards their anterior ends. They are triangular in shape, having the base
of the triangle anterior. These various cartilages are bound to one another (a)
by connnective tissue, and (b) by muscles. (a) Distinct bands of connective
tissue bind the posterior cartilages to the anterior, and also the lateral to the
anterior. (b) There are also a number of muscles which connect the various
cartilages to each other; a band uniting the anterior and lateral cartilages on
either side, dorsally ; two bands or sheets uniting the two anterior cartilages,
ventrally ; the upper of these being the broader and larger, and being separated
from the under narrower band by two bands of muscle passing from the infra-
radular membrane to the base of the posterior cartilage on either side ; and,
lastly, a band uniting the anterior and lateral cartilages on either side, ventrally.
All these muscles may be termed intrinsic. There are, however, in addition
several extrinsic muscles connecting the buccal mass with the neck wall.
Firstly, two broad plates attached posteriorly, one on either side to the posterior
cartilage, anteriorly to the floor of the neck cavity. These may be termed the
ventral protractor fibres (Pl. CL. fig. 17, v.pr.). Also attached to the posterior
cartilage on either side is a lateral protractor, which is attached anteriorly to
the roof of the neck cavity. Finally, attached laterally to the anterior cartilage,
on either side, is a vertical band of muscle, attached at its upper end to the
roof of the neck cavity. Many delicate muscular fibres also pass from the
pharynx to the walls of the neck cavity.

Returning now to the pharynx, it is found, as already stated, to be more or
less divided externally by two longitudinal furrows into three parts, a central
and two lateral. These several parts are in complete communication with each
other, the division being rather apparent than real. Anteriorly the wall of the
pharynx is thickened by the development of two oval yellowish-brown masses,
one on either of the lateral divisions. Into these masses the four very evident
salivary ducts open, two into either mass (Pl. CLIII. fig. 61). The ducts are long ~
isolated, slightly twisted, yellowish-brown tubes which run from thence back-
wards, the two inner lying in the furrows of the pharynx, but easily detachable
therefrom, the two outer running alongside the odontophore. The two inner
enter the salivary glands about the middle; the two outer are attached to the
glands at their extreme edges (Pl. CLIIL fig. 61). The glands themselves vary
somewhat in size and colour. They are usually large orange-coloured masses
closely united together, lying over the shoulders, beneath the pericardium on one

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 609

side, and the renal and anal papillee on the other. The pharynx widens consider-
ably after becoming free from the buccal mass, and two deep pouches, the
continuations of the lateral divisions of the pharynx, lie on either side of the
neck in front of the salivary glands. The so-called “crop” (the name is very
inappropriate) is a long thick-walled sac continuous on the one side with the
pharynx, on the other with the cesophagus. The folds in the pharynx are con-
tinued to the crop, which has other transverse folds of its own. The interior has
been justly likened to the maniplies of a sheep’s stomach. Round the “crop”
and the true stomach, which lies above it, is the liver, an irregular yellowish
mass which fills up all the intervening space between the “crop,” stomach, and
coils of intestine soon to be mentioned. It is a compound tubular gland,
supported by a framework of connective tissue. The biliary secretions appear
to be poured into the crop at many points; more accurate information must be
obtained, however, with reference to that point. The cesophagus is of small
and uniform diameter; it makes one short coil on the floor of the visceral
cavity and then widens into a long stomach, which is doubled on itself, and lies
across the centre of the body (when not displaced by the greater size than
usual of the genital gland), the blunt or folded end lying behind the peri-
cardium, but usually separated from that by one or two folds of intestine. The
two halves of the stomach are closely applied. From the pyloric end of the
stomach the intestine springs, and maintains throughout its entire length a
constant diameter, viz., about equal to that of the cesophagus. The intestine
immediately after leaving the stomach bends sharply back and runs beneath the
folded end of the stomach round to the head, passes in front of the cardiac
portion of the stomach, over the buccal mass, and, on reaching the extreme
edge of the visceral sac on the left side, bends sharply upwards, and coils over
a subsequent loop of intestine. It then forms a superficial loop on the dorsal
surface, over the top of the stomach, passes again back to the point at which it
bends upwards, and there bends downwards. The ascending and descending
portions touch one another at that point. The intestine then travels along the
floor of the visceral sac, and, after making a complete circuit of the sac, passes
forward, and, curving backward once more, forms that portion of the intestine
which is looped over by the ascending and descending parts above mentioned.
It makes one more complete circuit of the visceral sac, and then ends at the
anal papilla on the right shoulder.

The columnar epithelium of the exterior epiderm is continued into the
interior of the alimentary canal. The pharynx is lined with columnar epi-
| thelium resting on a layer of connective tissue and muscle. Over the roof of
| the pharynx, both in the central and in the lateral divisions, there are many
| convoluted compound tubular mucous glands. The secretion of these glands,
| which is poured into the buccal cavity, is thick and viscous, and contains many
| VOL. XXXII. PART IIL. bE

610 R. J. HARVEY GIBSON ON THE

~

cast-off epithelial cells. At the palatal plate, and also at the ventral plate, the
epithelium becomes many layers deep (elsewhere it is in a single layer, save in
the glands), and the superficial cells secrete a very thick cuticle which becomes
modified into the distinct and separable palatal plate in the one case, but in the
other remains attached to the cells (Pl. CLIT. fig. 56). Beneath the edges of
the ventral plate the connective tissue forms two soft pads.

The radula, which lies in a long sac formed by an out-pushing of the
pharynx, from the wall of which it is developed, is a ribbon, expanded at the
anterior end into a flat plate, which is wrapped round the anterior cartilages,
and is continuous with the pharyngeal mucous membrane, viz., with that —
reflection of it which covers the under surface of the buccal mass. Posteriorly
the ribbon is bent on itself in its sac and ends in a soft clubbed end. The teeth
are not developed in the latter part of the ribbon, though their general position
is mapped out on the membrane. The various ridges are then strengthened
and developed by deposition of particles of chitinous matter with which the
sac is plentifully supplied. When completely formed (Pl. CLII. fig. 60) the
radula is seen to be composed of a tough chitinous band, from which spring a
number of teeth. The teeth are arranged in curved rows, the concavity of the
row being anterior. The radula tends to tear in that way. Each row consists
of ten teeth. The four central teeth (4, 5, 5, 4) are similar in shape, although —
the middle two are slightly smaller than the exterior two. Each is composed
of a yellowish root and neck, succeeded by a brown band or collar, and
terminated by a black crown, which is in shape like a bird’s claw, the claw
having its convexity directed: towards the mouth. Next to the four central
teeth, and placed a little in advance of them, is, on either side, a tooth slightly
larger than any of the central teeth, but similar to them in structure, save that
it has three claws instead of one (3.3). Most external of all, there is a pair of
teeth on either side which are flat, faintly yellow in colour, without claws; the
ends are, however, slightly curved upwards and backwards. ‘These teeth are
also slightly in advance of the last mentioned, and the outer of the two is
slightly beneath and in advance of the inner. The form and relationships of the
teeth will be much better understood by reference to the figure (Pl. CLI.
fig. 60).

The cartilages of the odontophore are composed of the usual elements. The
cells are large, and the matrix (cell walls) small in amount, so that the cartilage
is spongy in texture. The cells are smaller as they approach the perichondrium.
The muscle fibres of the odontophore are nucleated, and are similar to tho
fibres found in the heart (q.7.).

The salivary glands are compound tubular glands. The walls of the tubule
are composed of cubical epithelium with yellow granules in the cells. The
outlines of the cells are difficult to make out. The salivary ducts likewise are

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA, 611

lined by cubical epithelium. Both tubules and ducts are supported by a base-
ment layer of connective tissue. The ducts enter the pharynx towards its
anterior end, and where they do so there is a large mucous gland, the cells of
which, however, are largely supplied with the yellow granules found in the
salivary glands. The pharynx is a very complicated structure, and its fuller
investigation is left to the physiological part of this research. In the anterior
part there are two distinct folds from the dorsal wall; the lateral chambers
are continued into a pouch over either shoulder. These folds, along with others
on the ventral wall, are continued into the crop. The entire pharynx is lined
with columnar epithelium.

The crop is thick-walled, but in reality the thickness is due to the presence
of an enormous number of long compound tubular follicles, much resembling
those found in the large intestine of a mammal. There are two very distinct
longitudinal folds running from one end of the crop to the other on the ventral
wall, and also one pretty definite fold on the dorsal surface. Each of these
folds has secondary longitudinal folds on itself. Further, the wall generally is
thrown into transverse folds, which are arranged like a series of leaflets across
the intervening spaces. On these folds are developed the follicles above-
mentioned. The follicles are lined by elongated cubical or columnar cells, two
or three layers deep. The superficial layer is composed of pear-shaped cells,
which are filled with granular protoplasm. The larger cells contain rounded
granular masses of a highly refractile nature. These masses are often placed in
a vacuole, and are apparently shed into the lumen of the follicle. The cells
spring from a basement membrane of connective tissue cells, and there is a
lymph space between every two follicles. These spaces communicate with the
spaces in the connective tissue surrounding the glandular stomach, and con-
sequently with the circulatory system.

The liver, as already stated, is a compound saccular gland, irregular in
form, and filling up generally the spaces between the glandular stomach, the
true stomach, and the various coils of intestine. It consists of a framework of
connective tissue, covered by secreting epithelium. The epithelium is one
layer deep, and is extremely difficult to make out, so full is the whole tissue of
biliary secretion. When the débris is washed away, usually the epithelium is
also removed. When found, it is seen to be composed of delicate columnar
or cubical cells, without evident cel] wall, and filled with the minute droplets
or granules of which the biliary secretion is composed. The cells are not
unlike goblet cells in form. There are usually to be seen some minute cells
between the bases of these larger cells, which probably replace the larger cells
when destroyed. The bile is apparently poured into the glandular stomach by
a number of ducts. A fortunate section may show the opening of one of
these ducts (Pl. CLIIL. fig. 71). The ducts open between the bases of the two

612 R. J. HARVEY GIBSON ON THE

follicles, and is lined by nucleated squames. Apparently the liver tubules open
into a single lobular duct, which passes between the irregular lobes into which
the liver is divided. There does not appear to be a common bile duct.

The stomach proper is a large sac, with a very thin non-glandular wall. The
epithelium is often ridged, but the arrangement of the ridges is not constant.
The epithelium is very beautiful columnar, ciliated two or three layers deep,
The wall is composed of the usual muscle (non-striated) and connective tissue.
There are abundant blood spaces in the gastric wall.

The entire alimentary canal is lined throughout by columnar ciliated
epithelium one layer deep, but with young cells inserted between the bases of
the superficial large cells. The alimentary canal has, in various parts, the
power of secreting in its interior a whitish rod. The nature of that structure
will be discussed in the physiological section, with the subject of secretion
generally.

Tlie rectum is often ridged and papillose, in a manner similar to the rectal —
papilla. The muscle is circularly arranged, and the faeces escape in masses
more or less like strings of beads. The cilia of the alimentary canal must be
eminently useful in preventing obstruction in the course of a canal of such
length.

The rectal papilla, which projects a variable distance from the anterior
edge of the visceral mass on the right shoulder, is composed of a thick layer of
circularly-arranged muscle fibres, thrown internally into ridges and papilla,
the whole interior being covered by columnar ciliated epithelium. The cilia
are very long, and the cells very distinct and perfect. They are arranged ina
single layer. The papillae are in most cases compound, and they, assisted by
the cilia, no doubt prevent the entrance of infusoria and other small creatures
into the rectum.

The alimentary canal and its connected glands have received less attention
than any other part of the animal. With the exception of Cuvier (/oc. cit.) no
one has done anything towards unravelling the apparently endless coils in
which the intestine lies. The dissection is attended with great difficulty, not
only on account of the extreme tenderness of the intestinal walls, but also on
account of the intricate way in which the coils are intertwined, and the inti-
mate connection subsisting between them and the liver, right kidney, and con-
nective tissue supporting these organs. Out of over a score of limpets, which
the author dissected with a view to the untwining of the alimentary canal, he
was successful in only one case ; and it measured over 14 inches in length, the
antero-posterior diameter of the animal itself being 21 inches. Cuvier’s figure
errs in showing far fewer coils than there really are; he excuses himself by
saying that the directions in which it twists are “assez inutiles & décrire!”
The stomach also is inaccurately drawn. The buccal mass, its cartilages and

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 613

muscles, are described and figured by Geppss (7rans. Zool. Soc., x. 485). TLaAn-
KESTER (Ann. and Mag. Nat. Hist., 1867) confirms Cuvier’s discovery of a crop
of salivary glands, and says they (the salivary glands) open into the buccal
cavity by four ducts. Datu (Amer. Jour. Conch., 1871) figures and describes
the radula ; as does also Gray (Sys. Distrib. of Mollusca in Brit. Mus.).

3. Circulatory System.—The circulatory system consists of a branchial vein
and veinlets, a heart, and two efferent vessels.

The branchial vein is easily seen in fresh specimen as a large clear belt
beneath (ventral) the circle of gill lamelle, when examined in section. It
cannot be distinguished from a large lacuna. No special lining of epithelium
is visible; its walls are composed of connective tissue. Crossing it at reeular
intervals can be seen clear veinlets, which however do not open into the
branchial vein. These veinlets spring from the mantle skirt beyond the bran-
chial vein,—.¢., nearer its edge,—and open into lacune at the origin of the
gill lamelle. From the gills again arise veinlets (Pl. CLI. fig. 38, ¢), which
open into the branchial vein (Pl. CL. fig. 28). The branchial vein sur-
rounds the entire mantle skirt, and the ends unite to form one vessel, which
passes over the left shoulder to enter the pericardium at its extreme left
corner. The vessel, as it passes--round the pillar-like termination of the
circular muscle, becomes surrounded by fibres of muscular tissue, which are
continuous with the fibres of the auricle into which the vessel immediately
opens (Pl. CLI. figs. 41 and 43).

The pericardium, which is continuous with the visceral integument, but
thicker, is composed of very tough connective tissue, to which muscle fibres
are attached on its inner aspect for the support of the heart. It is lined
internally with squamous epithelium, often scarcely visible owing to its thinness.

The heart consists of two chambers, an auricle and a ventricle. The
| auricle is large, and very thin-walled. It is attached to the pericardium at
_ some points, especially in front. The attachment at that point is extensive,
_ and the writer has not been able to convince himself that no communication
_ exists between the auricle and the very vascular cephalic portion of the mantle.
| He has not been able to force any injection into the auricle from the lacune,
| nor has any injection passed into the lacunz from the heart, so far as he can
_ make out. It is possible, however, that further injection experiments, which he
| purposes trying, may lead to different results. [These experiments the author
has since made, with the result that he feels convinced that the mantle in the
| head region acts as an accessory respiratory organ, and that the blood from
| that area enters the auricle by openings in the “attachment” referred to. ]
|The auricle is very distendible. It opens into the ventricle, which lies be-
i neath it, by a slit which is guarded by muscle fibres rather curiously placed.
|The fibres are continuous with others which form a network inside the

614 R. J. HARVEY GIBSON ON THE

ventricle, rendering it more or less of a sponge. From the arrangement of
the muscle fibres round the auriculo-ventricular opening, contraction of the —
ventricle must bring about contraction of these muscle fibres, and cause —
occlusion of the opening, thus preventing regurgitation (Pl. CLI. fig. 44).

The ventricle is practically a sponge of muscle fibres. It is oval, and
more or less pointed in shape at the ends, where it opens into two aorte.
The long axis of the ventricle runs transversely,—that is, from right to left.
The left aorta, or efferent vessel, passes into and supplies the circular muscle.
The right, after passing out of the pericardium at the posterior right-hand
corner, breaks up and opens into a very perfect system of lacune. Although
the writer has made many injections with carmine gelatine in fresh specimens, —
he has never been able to trace the vessels beyond a very short distance,
The right efferent vessel runs beneath the rectum. ;

The wall of the auricle is composed of diagonally arranged belts of
musclé which are held together by single nucleated muscle and connective
tissue cells. The fibres seem embedded or covered by a connecting mem-
brane with small nuclei scattered in it, which may represent squamous
epithelium (Pl. CLI. fig. 39). The ventricle has a similar structure, but—
the muscle fibres cross and recross in the interior of the ventricle.

The muscle fibre of both auricle and ventricle is composed—the auricle
partly, the ventricle wholly—of a species of striped fibre common enough in
invertebrate hearts. The transverse striation is not very distinct, and it gives
the individual fibres rather a granular appearance. Bundles of fibres are
enclosed or wrapped round by nucleated connective tissue cells (Pl. CLI. figs.
39 and 45.

The blood corpuscles (Pl. CLI. fig. 42) are colourless and ameeboid. —
They appear something like spiny balls; though here and there flatter, more
irregular corpuscles are visible. Each contains one or more nuclei, and
is composed of granular protoplasm. When a coagulum is formed, the pseudo-
podial processes anastomose, and the clot under the microscope resembles
a plasmodium of Monobia.

With the exception of Cuvirr’s (loc. cit.) brief remarks on, and rather
meagre drawing of, the heart, and WiLLIAms’ reference to the structure of the
blood corpuscles (quoted by Datu in his paper on “ Limpets” in the Amer.
Jour. of Conchology, 1871), the writer has been unable to find any observation
of importance on the circulatory system. LAnKeEstTEr (art. ‘“ Mollusca,” ney.
Brit., 9th ed.) makes a brief reference to it, but does not enter into any detail. —

4, Purificatory System.—(a) Respiratory System.—The functional gills are in
the form of lamella, arranged round the inside of the skirt of the mantle. They
are morphologically processes of the mantle. They are attached to the mantle
in an oblique manner, so that a transverse (7.¢., vertical) section may cut through

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 615

two or more lamellz. Under the low power they appear as flattened pockets
more or less triangular in form, with a base attached to the mantle, and with the
apices projecting into the valley between the mantle and the foot (Pl. CLI.
fig. 38).

The structure of the mantle and of the gills is so similar, and since, as shall
be afterwards shown, the mantle is also respiratory in function, it may be best
to describe them together.

Under the low power (Pl. CL. fig. 24) a vertical section shows the mantle
to be attached to the circular muscle just where it springs from the shell, and
to extend as a plate thickened in its outer third, and having certain processes
springing from its ventral surface, which are vertical sections of gill lamelle.
The entire surface of the mantle is covered by epithelium, which is in many
places greatly wrinkled. The mass or body of the mantle consists of connective
tissue and muscle, with large and small lacunar spaces. The lamelle are also
hollow, and their opposite walls are connected by transverse bands of tissue.

When the epithelium is examined under a high power, it is found to be
columnar, but presenting variations in structure at different parts.

The epithelium over the dorsal surface of the mantle is low columnar, with
large nuclei. Towards the attachment of the circular muscle it becomes
squamous, which again becomes continuous with the dense epithelium covering
the surface of the circular muscle. Outwards, the cells become longer and
more tapering. They are arranged in fan-shaped masses owing to the corruga-
tion of the surface. The tapering ends (Pl. CL. fig. 25) are individually
attached to the fine ends of transverse muscular fibres, while the free ends,
which are more granular than the bodies of the cells, are covered with a
continuous homogeneous cuticle. Just beneath the epithelium, and separat-
ing the fine tapering extremities of the cells from one another, lies a layer
of muscle which runs in a circular manner round the mantle edge, 2.¢., in
vertical section the ends of these fibres are cut across. These fibres are
extremely close to the epithelium, and are not separated from it by any base-
ment membrane or connective tissue. Beneath this layer, and closely applied
to it, is another layer, which is arranged vertically, ¢.¢., parallel with the long
axis of the section, in which they are seen as strands. The transverse fibres
run between these fibres, crossing them at right angles, to be attached to the
tapering ends of the epithelial cells. Beneath that layer there is a quantity
of connective tissue of loose texture, which is succeeded by another but much
thicker layer of vertical muscle fibres, which is prolonged downwards to the
very edge of the mantle skirt.

At the edge of the mantle the epithelium becomes low and cubical, and is
frequently pigmented, the pigment being deposited chiefly as a band in the
centre of the cells. There are frequent indentations on the dorsal surface of
the edge of the mantle, the cells lining which are pigmented.

616 R. J. HARVEY GIBSON ON THE

. The under surface of the mantle differs in many respects from the upper
surface, and resembles the structure of the gills so markedly that no doubt it is
to be looked upon as functionally a respiratory organ, just as the gill lamellee
are to be considered as morphologically processes of the mantle. The epithelium
covering the under surface of the mantle and the lamelle is also columnar ;
at the tip it is regular and low; over the thicker part of the mantle the cells
are very small and crushed, and the columnar structure is not always evident.
Their outlines on surface view are ragged, and their free ends are embedded in a
homogeneous membrane. Their inner ends are also ragged, the processes being
sunk in the subepithelial connective tissue (PI. CL. fig. 26).

Where the mantle again thins, and where the gills rise, the cells become
regular columnar, as on the dorsal surface, and spring from a muscular layer
similar to but thicker than the most superficial layer mentioned, as underlying
the epithelium ofthe dorsal surface. The fibres are, however, frequently oblique.
Above the origin of the gill lamelle the epithelium is also columnar, and is
covered by a very distinct cuticle. The muscle in this part of the mantle is

arranged in a thin radial layer separated by connective tissue from the epithelium —

(Pl, CL fig./27);
The body of the mantle in its upper half is divided by transverse muscular
bands into a series of quadrilateral‘compartments, which are lacunar blood spaces.
The thicker ventral or outer part of the mantle is composed in the main of
connective tissue and muscle with scattered nerves, forming a dense network
in which, however, there are lacunze—one large one, which is the branchial vein,

and several of smaller size. The whole mantle is well supplied with nerves,

There are usually five or six branches, which run at uniform distances round the
mantle skirt. Each is enclosed in a connective tissue sheath, and each divides
up into fibres and fibrillz, which are distributed to the muscular fibres.

Occasionally a specimen is found in-which the branchial vein is enormously
swollen. In such cases, the tissue of which the mantle is composed can be
studied to much better advantage (Pl. CL. fig. 28). The connective tissue
corpuscles are specially well developed (Pl. CL. fig. 29).

The free part of the mantle skirt over the head is similar in structure to
that just described. The membranous portion has a structure like that of the
visceral integument. It is composed of three layers—a superficial pigmented
layer composed of cubical cells, a middle layer of connective tissue and a few

muscle fibres, and a deep layer of cubical cells similar to those of the visceral
integument (q.v.). The middle layer contains many lacunar blood spaces

(Pl. CL. fig. 20).

Each gill lamella is composed of two flattened plates of connective tissue,
with a few muscular fibres connected by transverse bands of connective tissue
‘Pl. CL. fig. 30). A single layer of columnar epithelium covers over each

-

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 617

side of the lamella. These cells have large nuclei, and a comparatively thick
cuticle. The cells are relatively far apart, the spaces between the cells being
filled probably with intercellular substance, possibly with sea water. The pro-
toplasm of the cells is clearer, but with larger granules in the superficial than
in the basal portion. The nucleus lies in the basal portion. Towards the free
extremity of the lamella the cells are more flattened and more vacuolated,
and the cuticle is not so distinct. All parts of the lamella and the ventral
face of the mantle not occupied by the muscle and connective tissue frame-
work above indicated are filled by a network of delicate fibres and films, the
cavities in which are lacunar blood spaces, and are filled with blood corpuscles, &c.
In the basal portion of the lamella the muscle which underlies the epithelium
may be seen to be continuous with the muscle of the mantle.

At intervals along the mantle edge there are to be found papille, probable
tactile in function, sunk beneath the surface. The papille are on an average
about °35 mm. long, and about half that in breadth. They are conical in
shape (Pl. CLI. fig. 31), and spring from a broadened base. They lie in pits,
which are sunk beneath the surface about half a mm. The pits are slightly
broader than the papillz, and have a narrow outlet to the exterior. In some
sections the papillee can be seen cut tangentially when it is seen to be completely
surrounded by the mantle tissue. The walls of the pit and of the papille itself
are covered with epithelium, which is continuous with the epithelium lining the
dorsal and ventral surface of the mantle. In Patella vulgata they are about 100
in number, arranged apparently in a single row.

The epithelium of the dorsal wall of the mantle, just before it bends in-
wards to form the pit, is very regularly columnar. The cells are widely separated
by cement substance (Pl. CLI. fig. 32), which spreads out over the surface
to form a cuticle, with which the free ends of the epithelial cells are fused.
The nuclei are oblong. The epithelium covering the pit walls and the papilla
is very irregular. The cells are widely separate and irregularly columnar. The
surface of the papilla is much corrugated, and the epithelium is thus thrown
into folds which run circularly round the papilla. The epithelial cells are
attached by fine processes to the subjacent tissue (Pl. CLI. fig. 33). The
centre of the papilla is composed of muscular fibres running longitudinally in
the papilla, and spreading in a fan-like manner, so as to unite with the
epithelium with their ultimate fibrille. The muscle fibres are continuous with
those of the mantle. The very centre is occupied by a large nerve. There is
a nerve plexus, more or less distinct at the root of the papilla.

The papilla lies nearer the ventral side of the mantle, and the inside wall of
the pit on that side is lined by squamous epithelium.

(6) Renal System.—The kidneys (nephridia) are two in number, right and
left. Their position and relationship have been more fully worked out than

VOL, XXXII. PART III. aK

618 R. J. HARVEY GIBSON ON THE

most other parts. There are, however, points in their anatomy and histology
which do not appear to have received sufficient attention. x

The left nephridium is by far the smialler of the two, and occupies the
triangular space between the pericardium and the terminal portion of the
rectum. It is bounded above by the visceral integument, and beneath by the
dorsal wall of the subanal portion of the left nephridium; to the right it is
bounded by the wall of the rectum. (

The left nephridium communicates with the pericardium by a minute canal.
On laying open the pericardium, the opening of this canal may, in specially
large limpets, be seen (Pl. CLI. fig. 36). The one from which the figure is
taken was about 24 inches long with the shell removed. A split bristle was
inserted into the aperture, and on dissection was found to have penetrated into
the cavity of the left nephridium. The pericardial opening was situated just
beneath the attachment of the auricle, and very near the front wall of the
pericardium. It lay almost in front of the much larger opening of the right
nephridium. The left nephridium communicates also with the exterior by a
papilla which lies to the left of the anal papilla. The left nephridium itself
consists of a sac whose walls are folded and ridged to an enormous extent, , $0
that the central cavity is broken up into a series of diverticula. The central
cavity remains continuous with the duct into the pericardium on one side and
to the exterior on the other. The canal leading from the pericardium to
left kidney is lined by squamous epithelium continuous with the epithelium
lining the pericardium. ‘Towards the cavity of the kidney itself the squamous
epithelium becomes cubical and then ciliated, and contains granular concretions.
The cilia are exceedingly difficult to preserve, and only a cell here and there
showed the cilia at all satisfactorily. |

The author has not been able to see the “triangular piece of tissue,” de-
scribed by CUNNINGHAM as functioning as a valve at the opening into the kidney
but his sections may not have been in this respect so favourable. The canal is
surrounded by a quantity of connective tissue and nonstriped muscle, by the
contraction of which it may be possible to occlude the canal altogether. The
valve under such circumstances seems to be rather superfluous, though the
writer is not prepared to say it does not exist. The folded wall of the ki
is composed of connective tissue containing a large quantity of nonstriped
muscular fibre. In the connective tissue there are a large number of lacunar
blood spaces; in short, as well put by Lanxesster, “the sac is practically a
series of blood-vessels covered by renal epithelium.” The renal epithelium is
in some points difficult to make out in its structure.

It has been described as consisting of ciliated nucleated columnar cells
containing small dark-coloured concretions.

So far as the author has been able to make out from a study of the

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 619

epithelium in the fresh condition and in section, the connective tissue of the
folds is covered by epithelium which is in several layers (Pl. CLI. fig. 35).
The lower cells are rounded or polygonal, and present a homogeneous protoplasm
crowded with granules of a light green or brownish tinge. A nucleus may
here and there be distinguished, but, as a rule, the density of the protoplasm,
and the manner in which it is filled with concretions, prevents it being possible
todo so. The upper cells of the epithelium are much larger (Pl. CLI. fig.
37), and present a large number of vacuoles. These cells are ciliated; and it
has been possible in some sections to make out distinctly the cilia, although
in by far the most cases they could not be made out. They are, however,
visible in the fresh condition by teasmg. As stated by Von JHERING to occur
in Tethys, and as suggested by CunnINGHAM in Patella, probably the process
of secretion is the absorption from the blood in the lacunar spaces in the walls
of the diverticula of the urinary matters, the presence of which in the cells
causes them to be vacuolated. Probably, as the lower cells become so filled,
they come to the surface, aud burst into the lumen of the gland, where they
appear as granular débris, composed partly of the remains of the epithelial cells
themselves, partly of the concretions which they contained. The writer thinks
he has been able to make out the successive stages in this process in sections
which were found to show best mounted in balsam (Pl. CLI. fig. 37). (The
subject will be referred to in detail in its proper place in Part II.) The
epithelial layer varies in thickness at different points. On surface view the
polygonal outlines of the cells could be distinctly seen, and in sections mounted
unstained in balsam the separate cells were perfectly distinguishable.

The right nephridium is of far larger size than the left nephridium. It
forms a large sac much darker in colour than the left kidney, and extending
round the viscera from almost the median line above quite to the median line
below, where it ends abruptly in a straight edge. It encircles the posterior
part of the genital gland, and rises over the coils of the alimentary canal behind.
It ends at the posterior part of the superficial coil of the intestine. In front it
is bounded by the anterior body wall, but passes in the form of a long tongue
behind the rectum, being bounded in that region behind by the anterior part of
the superficial intestinal coil. On dissection it is found to send a corresponding
tongue beneath the rectum (the “subanal tract” of LANKESTER and Bourne),
which is like the superficial tongue irregular in outline. Like the left kidney,
the right has two outlets—one to the exterior and one.to the pericardium.
The canal opening to the exterior opens at the right renal papilla situated
to the right of the anal papilla. The opening into the pericardium can be
easily made out in a large specimen from the pericardial aspect. It lies
beneath and slightly behind the opening of the left kidney, and appears when
viewed from the interior of the pericardium as a longish pear-shaped slit lying

620 R. J. HARVEY GIBSON ON THE

horizontally, the broader end being anterior. The duct connecting it with the
cavity of the kidney is comparatively short and wide, and like that of the left
kidney is lined by squamous epithelium, and surrounded by connective tissue
and muscle. The duct soon opens into the subanal tract of the right nephridium,
and then becomes lined by granular ciliated epithelium similar to that found in~
the left kidney. The histological structure of the right kidney is similar in
all respects to that of the left, but the cells are filled with granules which are
much darker in colour, though they can scarcely be said to be more numerous.

While the left nephridium partakes more of the nature of a sponge, the right
is rather a sac with plaited walls (Pl. CL. fig. 34).

With regard to the comparative structure of the two kidneys, the author is
inclined to think that the substances which the right kidney secretes from the
blood are chemically different from those secreted by the left. The degree of
solubility in certain reagents of the granular matter of the two kidneys is
different, and the granules are much darker, in addition to being more numerous
in the right than in the left. This subject will, however, be gone into in
detail in the physiological part of the work.

Cuvier (loc. cit.) asserts that the laminze dependent from the mantle are
gills. BLAINVILLE denies this, and thinks the mantle over the neck is respira-
tory in function, owing to the number of vessels found there. ADAMSON,
Mitne-Epwarps, and Gray support Cuvier’s view. As above shown, both
views are to be accepted as true. Dawn (Amer. Jour. of Conch., 1871, 268)
strangely enough, says that the cordon of gills is uninterrupted; an undoubted
interruption does take place at the point of entrance of the branchial vein over
the left shoulder (PI. CLI. fig. 38). Lanxesrer (Ann. and Mag. Nat. Hist., iii.
p. 20, 1867), showed that Patella had two distinct kidneys, one of which, he was
at that time able to show, opened into the pericardium. The opening into the
right kidney was subsequently discovered by LaNKESTER and Bourne, and the
existence of the subanal tract pointed out (Ann. and Mag. Nat. Hist., vii. 188. ).
Doubt being thrown by various observers upon certain points in LANKESTER'S
description, more especially on the connection between the left kidney and
the pericardium, the subject was reinvestigated by CunnincHAm (Quart. Jour.
Mic. Science, xxii. 369), who further described the form and structure of the
renal organs, and confirmed LANKESTER’s account. WILLIAMS’ account of the
structure of the branchie (as quoted by Dat in Amer. Jour, Conch., 1871)
the author is able to confirm and extend; the author found, however, no indi-
cation of the cilia mentioned by WitLIAMs as covering the branchiz ; nor are
they, indeed, to be expected there, since the laminz are really outpushings of
the mantle wall, and not morphologically true gills, as in the cited case of the
gill plate of Anodon.

5. Connective Tissue System.—The connective tissue of Patella does not

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 621

for special mention. It consists of the usual elements, viz., connective tissue
fibres, connective tissue cells, and elastic fibres. These last are few in number,
‘and are never so distinctly definable as in the Vertebrata. Many amceboid cells
are also found among the connective tissue fibres. These are usually larger
than the blood corpuscles, and have long branched processes.

The presence of connective tissue has been indicated, and its general features
have been pointed out under the different organs in which it occurs.

Muscular System.—The general muscular system, comprising the muscular
fibres entering into the structure of the various organs, is described under the
different sections where these organs are described.

The special muscular system includes (a) the muscle of the head and neck,
(b) the circular muscle connecting the foot and the shell, &c., and (c) the
muscle of the foot proper.

(a) The muscle of the head and neck is arranged in three layers over the
dorsal surface, from tentacle to tentacle, a superficial transverse, or circular,
layer, a middle longitudinal with numerous oblique fibres, and a deep transverse
layer. These layers are continuous with the muscle bands composing the foot
and circular muscle, and fibres from them pass up into the tentacle. On the
ventral aspect the middle layer is usually wanting, though a few strands of
oblique fibres are occasionally present. The outer and inner layers also are
much thicker. |

(6) The circular muscle at its origin from the shell is composed of a number
of plates arranged vertically, and having their long axes parallel with the
surface of the body. Their free ends where they spring from the shell are
covered with a very dense layer of epithelium, which is in direct contact with
the shell. The epithelium is cubical, and so closely packed that the general
appearance is such as to suggest that the ends of the muscle fibres are them-
selves in contact with the shell, and that the epithelium is really only the
denser terminations of the muscle fibres (Pl. CX LIX. fig. 6). If the epithelium
covering the free part of the mantle in the head region be examined, the cubical
nature of the epithelium is there clearly to be made out. The inner ends of
the cells are serrated in a manner similar to the epithelium in many other parts
(Pl. CL. fig. 18). The free ends are covered by a thin cuticle. The cells are
continuous on the one hand with the epithelium covering the dorsal surface of
the visceral integument, and on the other with that of the dorsal surface of
the mantle skirt (Pl. CL. fig. 20).

The muscle plates descend vertically, branching and spreading in a fan-
shaped manner, so as to cause the circular muscle to be twice the breadth at
its union with the foot as it is at its origin from the shell. The outer lamelle
| pass directly downwards, the inner lamellz curve round, and are continuous
| with the muscle of the foot proper. These bands of vertical muscle are separated

622 R. J. HARVEY GIBSON ON THE

by thin plates of oblique or circularly arranged muscle, which almost entirely
take the place of the vertical muscle towards the exterior of the foot (Pl. CL.
fig. 19). The fibres there are fine, and are enclosed in bundles by strands of
connective tissue.
(c) In the foot proper, towards the margin there is an open connective tissue
network, with variously arranged branching muscle fibres scattered through it,
many of which are in connection with the inner ends of epithelial cells by fine
processes. The upper portion of the foot, which forms the floor of the visceral _
sack, is composed of the horizontal or oblique plates of muscle continued from
the circular muscle. The ventral portion is composed of a network of con-
nective tissue fibres, amongst which are found a large number of horizontal,
vertical, and oblique muscle fibres. u
The connective tissue is dense on the ventral surface, especially just beneath
the layer of epithelium. The cells of the epithelium are continuous with those
of the side of the foot, but are much crushed, and often wanting in section.
There are no glands of any kind in the foot. |
In the head region, where there is no circular muscle, the muscle fibres
which sprung from the shell are continued into the free skirt of the mantle
(Pl. CL. fig. 20). _
The individual muscular fibres of which the bands of muscle are made up,
are of the nonstriped variety. ach cell is a very long fibre, often as much as
4 of an inch in length, while the breadth is about z455 of an inch. The fibres
do not branch, but are collected in fasciculi with a small amount of cement
substance between. ach fasciculus is surrounded by a small quantity
connective tissue. The fibres themselves are perfectly homogeneous or faintly
fibrillated (Pl. CL. fig. 21).
Epidermal System.—The visceral dome is entirely covered by an integuiitlll
which is easily detachable, and which is composed of two or three layers
according to the position. .
Externally (Pl. CXLIX. fig. 4) is a layer of dark pigment cells, then a
layer of connective tissue, and internally (in those parts where it covers the
nephridia) a layer of light pigment cells. :
The external pigmented cell layer consists of a single layer of tabular ot
cubical cells, each containing a round or elliptical nucleus, with one or two
nucleoli. On vertical section, the outlines of the cells can be distinctly made out,
but they are not so easily seen on surface view. In such a surface view as that
represented in Pl. CXLIX. fig. 5, the nucleus is seen to be surrounded by a
quantity of pigment in the form of rounded black granules. In other situations —
the granules do not surround the clear nucleus, but lie between it and the
upper part of the cell, which is hyaline in appearance, but possesses no cuticle.
As the edge of the dome is reached, the pigment is wanting, and there appears

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 623

over the cells a delicate homogeneous highly refractile cuticle. Just before the
circular muscle, the cells for a short distance become spindle-shaped, and lie on
their sides (Pl. CX LIX. fig. 6). The fine processes of these cells fuse with the
cuticle on one side, and with the subjacent connective tissue on the other. Over
the circular muscle the cells are cubical and densely packed, and set directly on
the ends of the muscle fibres. Over them there is a tolerably distinct cuticle.
These cells are continuous with the epithelium of the dorsal surface of the
mantle. Where the pigmented epithelium is absent, as at the top of the dome,
there is a layer of squamous epithelium forming a superficial covering to the
middle layer of connective tissue.

The second and main layer of the visceral integument consists of a feltwork
of connective tissue fibres and branched connective tissue corpuscles. A few
fibres of a more highly refractile nature may be seen which are probably elastic
in their nature. The middle layer is divisible into two chief layers, one of
which allies itself to the superficial pigmented epithelium, the other to the deep
pigmented epithelium when that layer exists. Hach layer is composed of several
finer layers separable by pressure or teasing. The fibrils of which each layer is
made up are extremely fine, and are united by a gelatinous and in some places
eranular matter into thin films. Connective tissue cells and nuclei are
scattered irregularly among the fibres.

The third layer consists of a single layer of large cubical cells which are
polygonal in outline on surface view (Pl. CX LIX. fig. 7), and contain nucleus
and nucleolus, and a large number of greenish-yellow granules. These cells
really form the superficial layer of the right nephridium, but are usually found
adherent to the visceral integument when that is removed. The author has not
been able to make out any squamous epithelium on those parts of the inner
surface of the integument not covered by this pigment layer.

The integument of the side of the foot (Pl. CXLIX. fig. 8) is composed of
cells similar to those found on the tentacle. Near the origin of the mantle the
cells are low columnar ; they increase in size as the lower edge is approached,
and on the lower half they are thrown into ridges as in the tentacle. The cells
are there very long, with nuclei near their centres, and with a cuticle externally.
The upper part of the side of the foot sometimes bears permanent ridges,
composed of outpushings of subepithelial tissue, covered by columnar cells,
much longer than those covering the side of the foot in that region. The dense
layer of connective tissue found beneath the epithelium in the tentacle is in this
situation very scanty; and beneath it is a series of vacuoles, or lacunar spaces,
between the trabecule which pass from the general muscle of the foot to be
connected with the ends of the epithelial cells.

The epithelium is continued round the edge of the foot for a short distance,
in the form of long columnar cells, which soon, however, become modified into

624 R. J. HARVEY GIBSON ON THE

a granular crushed layer, very irregular, and resting on a dense layer of con-
nective tissue. The epithelium, at least in sections, most commonly falls off,
and leaves the subjacent connective tissue exposed. ~

Over the head and neck the columnar epithelium is composed of large cells
which have distinct nuclei. The subepithelial connective tissue layer is very
evident, and fibres are seen passing through it to the epithelial cells
(Pl. CXLIX. fig. 9). On surface view the cells present a granular mosaic.

Protective System.— Under the head of protective system may be classed the
mantle, whose function in this relation is to afford protection to the functional
gills and the shell. The mantle has already been described under the respinteeias
system.

The shell, as has been already stated, is dome-shaped, and has ventrally an
oval outline (Pl. CL. fig. 22), the narrow end being anterior. The apex of —
the dome is blunted, and the outline of the sides is curved. The apex of the
dome is nearer the anterior end (Pl. CL. fig. 23).

Externally two series of lines are visible on the earns a radiating
series from the dorsal apex to the edge; () a series concentric with the
ventral edge. The lines are of various degrees of coarseness, and some are
nodulated and tuberculate. |

Internally, the radiating lines are represented by bands of blue and yellow —
of variable shade and width. These bands are crossed at intervals by con-
centric bands of dark colour more or less distinct in different individuals.

The rim of the shell is chisel-shaped, the bevelled side being inwards. The —
shell rapidly thickens from the edge, and then maintains a tolerably constant
thickness throughout. The edge is sharp and notched.

The pallial line is visible as a pale belt of variable width (usually } inch)
running in a sinuous manner along the shell about 4 inch from its edge
(Pl. CL. fig. 22).

Inside the mantle line at a short distance is the impression of the attach- —
ment of the circular muscle connecting the foot and the shell. The impression
is divided, as is the muscle itself, into more or less distinct areas. The breadth —
of the belt is tolerably constant (usually about + inch.) The most anterior
muscle impression, one each side, is larger, and rounded anteriorly. The inner
border of the belt is more irregular than the outer. id

Within the impression of the circular muscle there is a belt of irregular
breadth and outline, generally broadest posteriorly. The belt marks the
attachment of the integument of the visceral dome. The impression expands
in front, and fills up the space left vacant by the absence of the circular muscle
impression. That space is about one-sixth the entire circumference of the shell
at that level. The remainder of the concavity of the shell is not touched by
the derm of the visceral dome. It is usually white, and lacks the lustre of the

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 625

other parts of the inside of the shell. The entire shell is translucent, though
the portion round the apex tends to become opaque.

~The microscopic structure of the shell is extremely difficult to determine
accurately. If it be soaked in strong nitric acid for some time, a series of
lamine may be peeled off, each lamina being apparently made up of a net-
work, or meshwork, of very fine fibres. The superficial lamine have much
wider meshes than the deeper lamine.

A vertical section through the entire shell presents three layers, the middle
layer above extending from edge to edge (Pl. CLII. fig. 46). The inner layer
is found only beneath the dome, and, under the low power, presents itself as a
granular, more or less structureless film, occupying mainly that portion of the
shell not touched by the derm of the visceral mass. The outer layer, which also
appears granular, carious, and pigmented, extends over the entire surface, save
the extreme borders. This layer, when examined under a higher power, is found
to be perforated in every direction by minute canals (Pl. CLII. fig. 49). These
canals are not more than 79, of an inch in diameter, and branch and anasto-
mose to such an extent as to give that part of the shell the appearance of yellow
elastic cartilage, or the framework of a sponge. The canals are much more
abundant towards the surface. The canals break into one another, and thus
form larger canals varying in size according to the number of small canals which
have gone to form the larger. The small canals are long, unbranched, and
straight, and much fewer in number as the middle layer is approached. Indeed,
there can scarcely be said to exist three distinct layers; the inner and outer
layers being simply the middle layer under different conditions of growth or
decay. The middle layer itselfis composed of long, branching, polygonal “ cells”
or rods, whose long axes lie at right angles to the outer surface of the shell.
Each rod is made up of a large number of febrils, lying parallel to the long axis
of the rod, and the rod has in consequence a striated appearance. In section
the rods are polygonal, round, oval, or irregular ; they are separated from each
other by a cement substance, which forms the reticulum left after the removal
of the mineral matter by the nitric acid. This substance, which is fibrillated, is
stained yellow by the acid, and is therefore probably animal in its nature. These
rods are crossed, especially towards the border of the shell, by lines indicating
_ the successive laminz of deposition. The arrangement of the various elements

will be best understood by reference to the figures (Pl. CLII. figs. 46-49).
q The inner and middle layers are perfectly colourless ; the outer layer has
yellowish-green and brown pigment granules deposited in the canals by which
it is perforated. The bands of bluish-grey, usually seen on the inner surface of
the shell, are therefore not due to pigment, but probably to the peculiar
arrangement of the rods, and the effect of light upon them. On the inner
VOL. XXXII. PART III. OL

626 R. J. HARVEY GIBSON ON THE

surface of the dome, however, at the very apex, the inner layer becomes im-
pregnated to a slight extent by pigment granules.

It is very doubtful whether the caries on the surface layer of the shell be a
natural condition ; the author is inclined to think that it is due to a parasitic
growth, and that the pigment is foreign matter, either belonging to the parasite
or introduced from the surrounding water into the canals formed by it. This
view is supported by the fact that in some places the shell is much more
decayed than elsewhere, and that some shells, though younger, are more carious
than others which are obviously of older growth. The shells examined were of
course not fresh, and so any possible inhabitant of these tubes could not be
detected. In the physiological section of this research, the subject will be
reinvestigated. Irrespective of the possible truth of the explanation above
suggested, it will be interesting to know what conditions are necessary for the —
formation of this caries, and what are the agents and modus operandi employed.

The general appearance of the shell has been described very frequently ;
indeed, in the older accounts of Patella the shell was the only part which was
described with anything like completeness. CARPENTER, who, so far as the ©
writer is aware, alone has studied the shell microscopically, says that it consists
of three layers, inner and outer layers less compact, and a middle layer of
polygonal or prismatic cells. "

Dau. (doc. cit.) quotes WILLIAMS as saying that “the lining membrane of
the branchiz is continuous, and therefore that it is highly improbable that
water penetrates into the circulatory system, as in some other molluscs.”
With reference to that statement, it may be well to remember the nature of the
epithelium lining the branchiz, as indicated above (vid. “ Respiratory system ”).

REAUMUR mentions the existence of glands in the foot, and Born (oc. cit.) —
says there are tubercles in the same organ; and these authors affirm that from
these glands, or tubercles, there exudes a glue, by which the animal fixes itself _
to the rocks. ADANSoN also speaks of suckers on the pedal surface; and
ADAMS (Recent Mollusca, i. 465) asserts that the cavities which the limpet not
infrequently makes in some kinds of rock are made by spicula with which the ~
foot is provided. The writer has not been able to find the slightest indication
of glands, either beneath the surface or in tubercles; nor has he been able to
see anything that could be mistaken for a sucker or a spicule of any kind —
whatever, although he made a very thorough examination of the foot, not only
by superficial search, but also by many microscopical sections.

6. Nervous System.—The nervous system is exceedingly complicated, but,
with moderate care, it may be dissected out in its entirety.

There are altogether no less than eight pairs of ganglia; only three of

these, however, are of primary importance, viz., the cerebral, visceral, and
pedal (Pl. CLIT. fig. 50).

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 627

The cerebral ganglia are large irregular nervous masses, situated deep down,
just at the base of the tentacles; the visceral and pedal ganglia lie close
together just at the anterior edge of the floor of the visceral cavity. The
cerebral ganglia are found to give off (a) nerves and (2) commissures. The
nerves are four in number, on either side. (The nerves of the left cerebral
ganglia only are here described, those of the right being precisely similar.)
First, the tentacular nerve, which arises from the anterior left corner, and
passes directly into the nuchal tentacle. This nerve very soon divides, giving
off numerous branches to the muscles and skin of the tentacle. Just at its base
anteriorly arises a small nerve, the cutaneous, supplying the skin of the neck
and snout. Immediately behind the origin of the tentacular nerve is the optic
nerve, which is not a branch (as might be supposed) of the tentacular, but is an
entirely distinct nerve, going directly to the eye. The nerve divides repeatedly
ere reaching the eye, and loses itself in a nervous plexus, immediately behind
the retina. All these nerves spring from the outer aspect of the cerebral
ganglion. On its inner aspect, immediately opposite to the origin of the optic
nerve, is a small nerve supplying the muscles of the pharynx, and which may
be termed therefore the posterior lateral pharyngeal nerve. In addition to
these nerves there are a number of commissures uniting the cerebral ganglia to
the rest of the system. The anterior end of either ganglion gives off two com-
missures, one passing in front of the buccal mass, and easy to find, the other
passing vertically up the side of the same, and more or less involved in muscle
and connective tissue. The former is a large thick white commissure which
runs in front of the csophagus, far forward. It unites the two cerebral
ganglia. After leaving either ganglion the commissure is slightly swollen,
| and at that point it gives off a nerve, which, since it supplies the anterior
| - muscle of the pharynx, may be termed the anterior lateral pharyngeal nerve.
In front the commissure gives off many small nerves which supply the lips.
At the point where the anterior pharyngeal is given off a nerve loop encloses
the commissure, coming from below upwards and passing backwards. It is
not connected in any way with the commissure. Following now the second
commissure, which springs from the cerebral ganglion, we find it mounts
the side of buccal mass, and becomes united to a small ganglion lying
at the side of the pharynx and on the top of the muscles of the infraradular
sheet. This ganglion is one of four which lie at the angles of a square formed
by the commissures which unite them, 7.¢., along either side of the pharynx.
On the top of the muscles of the infraradular sheet there are two ganglia
united to each other and to their fellows on the opposite side. These ganglia
are the superior, anterior, and superior posterior buccal ganglia respectively.
To the anterior ganglion on either side is united the end of the loop spoken
of above as enclosing the cerebral commissure. The commissures uniting the

628 R. J. HARVEY GIBSON ON THE

two anterior and the two posterior ganglia to each other lie between the
pharynx and the muscles of the infraradular sheet. Tracing the loop above
mentioned round the cerebral commissure, it is found to bend suddenly back-
ward, and to unite itself with a small ganglion on a second cerebral commissure
which lies beneath the buccal mass. These two small ganglia on this second
commissure have been considered as inferior buccal ganglia; and, since
the nerves from them supply the ventral protractors of the odontophore, they
may be so named.

From the posterior part of either cerebral ganglion two slender white
commissures pass backwards along the sides of the neck—the exterior to join
the visceral ganglion, the interior to join the pedal ganglion. The pedal and —
visceral ganglia form one thick hoop of nerve matter rather than four ganglia
unitedly commissures. The visceral ganglia are, as already stated, united
to the cerebral ganglia by slender commissures, to the pedal by a thick short
band. They give off two important nerves on either side of the body,—first,
externally, the musculo-pallial nerve (which soon splits into two branches,
which go to supply the branchie and mantle and the circular muscle
respectively) ; and, internally, the splanchnic nerve. This splanchnic, soon
after it leaves the ganglion, gives off a delicate nerve which travels back along
the pharynx, and may be termed the recurrent nerve. The left splanchnic
itself mounts the left shoulder, passes beneath the salivary glands, and, cross-
ing the right splanchnic, gives off a minute branch to the right ctenidium; 22., —
the right ctenidium is supplied by the left splanchnic. The nerve then
crosses back and unites on the way with the right splanchnic. The combined —
nerve gives off a number of branches to the viscera as it goes; and finally,
crossing over to the left side once more, it supplies the left ctenidium. (We
are indebted to SPENGEL for this discovery, and for the important suggestion that
accompanies it, viz., that these ctenidia are really the rudiments of the lost true
gills.) SPENGEL describes a minute ganglion, the olfactory ganglion lying near —
the ctenidia ; that the writer has not been able, however, to see. ;

The pedal ganglia lie between the two visceral ganglia, close together and —
united by a very thick and short commisssure. They are united, as already
stated, to the cerebral ganglia by long slender commissures, one for either
ganglion. They give off into a slit in the muscle of the foot two large nerves |
each, one of which supplies the deep muscles of the foot, the other the super-
ficial muscles.

Both the pedal and musculo-pallial nerves divide ultimately into a large
number of secondary branches.

The histological structure of the nervous system is extremely simple. The
nerves are composed of fibres, each of which is a very elongated, nucleated, cell.
The cell itself is band-shaped and fibrillated, nucleus oblong, taking on a deep

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 629

stain, and exhibiting a nucleolus in its interior. These fibres are collected in
bundles, and among them, 7.¢., between the individual fibres, are a number of
bipolar spindle-shaped cells. These cells are provided with nucleus, nucleolus,
and a small quantity of granular protoplasm prolonged at either end of the
spindle into long and delicate threads (CLII. fig. 51).

Both cells and fibres are enclosed in a sheath of ordinary connective tissue,
usually one cell thick. The nuclei of the connective tissue corpuscles and
fibres are very evident, and quite distinguishable from the nuclei belonging to
the nervous elements.

The ganglia are composed of a framework of neuroglia of the ordinary
nature (a very delicate connective tissue), with a very large number of nerve
cells. The great majority of these cells are small triangular or irregular masses
of protoplasm, with short branching or unbranched processes. The cells con-
tain nuclei and nucleoli, and take on a deep stain.

The cells are usually much more abundant towards the surface of the
ganglia, and this is more especially the case with the cerebral ganglia. The
cells (round) also run up the sides of the principal nerves for a short distance
as a distinct layer beneath the sheath.

In some places, more especially in the pedal and visceral ganglia, there is
an abundant admixture of long bipolar cells. This may be owing to the almost
undifferentiated nature of the ganglia and commissures in that situation. The
author has not been able to ascertain definitely the connection between the cells
of the ganglion and fibres of the nerve.

In some positions, notably in some parts of the pedal and visceral ganglia,
and also in the buccal ganglia and their longitudinal commissures, there are
present a number of yellow or orange granules, which appear to be immediately
within the connective tissue sheath. These give to the parts where they are
present a yellowish-orange hue.

Touch.—The special organs of touch are the tentacles—two in number—
situated on the right and left sides of the neck. Each in its contracted condi-
tion is about } inch in length, but it may be extended to from four to eight
times that length. At the base they are about +4; inch in diameter, and taper
to a bluntish point. When examined with a hand lens, they appear corrugated
and pigmented, especially towards the tip. About 5 inch from the base, a
small pit can be made out, on the outer aspect of either tentacle. The pit
is filled with pigment, and has its open mouth pointing towards the tip of
the tentacle. Itis ocular in function, and is described below. The tentacle
consists essentially of a mass of connective tissue in which are embedded
longitudinal and transverse muscular bundles. In the centre are one or
more nerves. The outer surface of the tentacle is covered by epithelium,
consisting of a single layer of columnar cells (Pl. CXLIX. figs. 10 and 11).

630 R. J. HARVEY GIBSON ON THE

The cells are narrow and tapering. The nuclei are long, and usually contain
two nucleoli and granular protoplasm (Pl. CXLIX. fig. 12). The cells
are slightly swollen in the position of the neuclei. They spring from
a more or less homogeneous layer of dense connective tissue, which acts as a
basement membrane. The epithelial cells are connected to this layer by fine
processes, which give their inner ends a serrated appearance. The connection
can, however, be easily made out in their sections under a high power. The
cells are not closely arranged, but leave spaces between, filled probably with
cement substance, so that a greater degree of contraction and extension is
thus attainable in the tentacle. The outer ends of the cells are widened some-
what, and become continuous with a homogeneous and relatively thick (in the
contracted condition) cuticle, which is highly refractile, stain bright yellow with
picric acid, and is therefore probably elastic in its nature. The cuticle on its
under aspect is lined by a layer of granular protoplasm formed apparently by
the fusion of the ends of the epithelial cells. The epithelial cells become more
cubical nearer the base of the tentacle. The subepithelial connective tissue
layer is not so apparent at the tip of the tentacles, where the distinctly tapering
epithelial cells are seen to be continuous with fibres in the mass of the tentacle.
In the thicker part of the tentacle the subepithelial layer may be seen to give
off fine processes, similar to those which connect the subepithelial layer to the —

epithelial cells, to join the feltwork of connective tissue of the body of the
tentacle (Pl. CX LIX. fig. 14).

At the tip of the tentacle the connective tissue layer sehen subjacent

to the epithelial layer is pigmented, the pigment being in the form of minute

rounded granules. No pigment is found in the epithelial cells in that position.
The muscle of the tentacle is disposed in a longitudinal manner, running
from the base to the tip (Pl. CXLIX. fig. 11). The muscle fibres are arranged in —
loose irregular strands, which may be seen to branch and unite again at intervals.
There is a tolerably distinct layer of longitudinal fibres beneath the epithelial
cells, especially on the outer aspect of the tentacle, the larger fibres being
ventrally placed. There are many transverse fibres, not arranged in any definite
bundles ; also a few oblique fibres. There are no circular fibres, nor are they
required. The muscle fibres are of the type described under the muscular
system.

Connective tissue, and a reticulum of connective tissue corpuscles, fill up the
rest of the body of the tentacle. ‘The connective tissue is of the ordinary type,
a dense feltwork of homogeneous and fibrillated fibres against and among which
lie many nucleated connective tissue corpuscles. One or more nerve branches
are found occupying the centre of the tentacle. Each is made up of a bundle
of very fine wavy fibres, amidst which may be seen minute red-stained nuclei.
The nerves branch and give off fibrils to the bands of muscle.

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 651

On transverse section (Pl. CXLIX. fig. 12) the relation of the muscle to the
connective tissue can be more distinctly seen. ‘The bands of muscle underlying
the epithelium are observed as rounded areas, each surrounded and clasped by
a number of connective tissue cells. Sometimes one area only is so enclosed
occasionally many such are clasped by one cell, whose neucleus is seen as a
bulging at one point. There are a large number of trabeculee composed of
connective tissue fibres and cells which spring from the homogeneous sub-
epithelial connective tissue, and passing inwards lose themselves in the general
feltwork of the body of the tentacle. The transverse bands of muscle are
specially numerous in the distal portion of the tentacle. The wrinkles are for
the most part temporary, but there are some where the epithelium lining the
valleys differs from that covering the ridges.

Numerous very fine fibrils are seen among the connective tissue and muscle.
As they are highly refractile, they are probably elastic in their nature.

A fortunate transverse section may show the epithelial cells in surface view
(Pl. CXLIX. fig. 13). They form in such an aspect a mosaic. The outlines of the
individual cells are roughly hexagonal or polygonal. ‘Their ends are granular,
and seem embedded in a clear membrane. Probably the cuticle is a secretion
of the cells, and is therefore made up by a fusion of a number of distinct areas,
each corresponding to the end of one epithelial cell. The epithelial cells them-
selves are not close together. They do not touch, hence the spreading
appearance presented by their outer ends on longitudinal section, and their
isolated appearance on end view. The tactile papille of the mantle are
described under the respiratory system.

Sight.—The eye lies at the base of each tentacle, and consists of a small
indentation or pouch which resembles the scar of a fallen leaf. The centre of
the pouch is apparently filled with a black pigment. On longitudinal section
of the tentacle, a distinct bulge is visible in the position of the eye, with a
secondary bulge of lesser size below the large one (Pl. CXLIX. fig. 15). The
large bulge forms the thick roof of a cave which is lined on its upper (roof)
surface by pigmented epithelium. The cave is perfectly open to the exterior,
and its mouth points forward. The swelling or bulge is very vacuolated,
there being large oval and irregular spaces amongst the connective tissue (PI.
CXLIX. fig. 15). The epithelium covering the bulge is continuous with the
epithelium covering the general tentacular surface. The cells are, however,
slightly longer, and are separate from each other, save near the edge of the
cave, where they are more crowded together. As they enter the cave they
increase in length, and again become wider apart. Among the long epithelial
cells of the outer surface of the ocular swelling are to be found a few cells
which spring by many processes from the basement layer, and after swelling
out and containing at that point a large round nucleus, terminate among the

632 R. J. HARVEY GIBSON ON THE

epithelial cells in a fine-pointed end (Pl. CXLIX. fig. 14). The epithelium of the
surface is continuous with the epithelium lining the ocular pit. Just after
turning the edge of the pit the cuticle becomes thicker, and then becomes split
into two layers, which are farthest apart at the bottom of the pit, but which
are connected throughout by a series of columnar fibres which pass directly
from upper to the lower layers (Pl. CL. fig. 16). The cuticle is therefore
replaced by a latticework bounded on either side by a cuticle. The fibres are
straight and homogeneous. They vary in thickness from the finest threads
searce visible to columns about half as thick as a columnar cell. From the
outer layer of the cuticle and projecting into the cavity of the pit, are a number
of very fine fibrils of variable length. They are extremely delicate, and are |
often destroyed in the section-cutting. The inner layer of the cuticle, which is
much thinner than the outer and not so hyaline in appearance, is continuous
with the ends of long, narrow columnar cells, which are longer than those of —
the surface of the ocular swelling. Their basal extremities taper to fine fibres,
and become lost in a dense feltwork (often so dense as to appear homogeneous)
which underlies the epithelium. The upper half of these cells is pigmented,
the dark granules of pigment being arranged round the cell, not generally in —
the protoplasm (Pl. CL. fig. 16a). The nucleus occupies the lower half of the
cell, and is long and contains many granules. The general protoplasm of the
cell also is very granular.

Continuous with the subepithelial layer is a dense network of fibres and of
cells, which are probably nervous. A secondary pit in the floor of the eye
pit is usually to be seen, but it contains no pigment, and the cuticle has here
regained its single nature and uniform thickness. Beneath the ocular swelling, —
a secondary swelling is situated; a pit similar in form to that just described is
present, but neither the cuticle nor the epithelium show the differentiation
mentioned as occurring in the true ocular pit.

The connective tissue of the ocular pit and of the secondary pit is loose, and —
presents large vacuoles. (The relation of the eye to the nervous system is dis-
cussed under the Nervous system.) :

The most important researches on the nervous system are those of BRANDT, |
SPENGEL, FRAtssh, and LAcazE DuTHIERS.

Branpt (Bull. Acad. St Petersburg, 1869) gives a very full account of the
nervous system, describing in detail the system of buccal ganglia. His account
does not differ in many respects from that given above. He has, however,
fallen into error more especially with regard to the arrangement of the visceral
nerves. The recurrent nerve, also, he makes to spring from the musculo-
pallial, whereas it springs from the splanchnic. SPENGEL (Zeit. f. wissen. Zool.,
xxxy. 382) has an important statement in reference to the arrangement of the
visceral nerves, and to their relation to the ctenidia, which has already been

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 633

noted. He has also described the olfactory organs, which lie in close relation
to the ctenidia. FRratssn’s account of the eye of Patella cerulea (Zeit. f. w.
Zool., xxxv. 461) agrees generally with that given above for P. vulgata; the
chief difference seems to be that, in Patella vulgata, the “cuticularsaum” is
double. In both species the outer surface of the cuticle is provided with a
number of cilia—the ‘‘ Faserchen” of Fraisst. Lacaze DuTHIERS’ investiga-
tions into the nature of the auditory organ (Arch. Zool. Exper. i.) will be
referred to subsequently. With reference to the sense of touch, CLARK (oc.
cit.) mentions but does not describe the minute tentacles (or “ cirrhi,” as he
terms them) on the mantle edge.

7. Reproductive System.—The male and female reproductive elements are
developed in separate individuals. The glands are single, and pour their con-
tents, when ripe, into the cavity of the right kidney, from which they escape
by the right renal papilla, together with the urinary excretions.

Male.—The male generative gland is a wedge-shaped, yellowish mass, lying
on the floor of the visceral cavity, and having its thicker side towards the back
and left side of the visceral mass. It is covered by a delicate membrane com-
posed of fibres of connective tissue, covered by squamous epithelium. The
gland itself is a spongy mass, less dense towards the centre. Peripherally, it
is composed of a framework of connective tissue, which sends processes
inwards, between which trabecule, therefore, are formed a large number of
“nests” in which sperms are developed. The trabecule are covered by cubical
epithelium, many layers deep, the superficial layers of which become the future
sperms. The manner of their development and their general appearance is
extremely like that of mammalian sperms, as described by KLEIN (Adlas of
Histology). The cubical epithelium is composed of rounded or polygonal
cells, variable as to size, but usually considerably smaller than a human blood
corpuscle. The superficial cells are slightly pear-shaped, and are arranged in

| tufts or mounds. Each cell contains a nucleus and many granules, but a cell
| wall is not visible (Pl. CLIII. fig. 77).

The process of development seems to be the gradual formation of a slender
_ filament at the attached end of the cell (Pl. CLIIL figs. 78, 79) when superficial
and in its pear-shaped condition ; probably at the expense of the protoplasm of
_ the cell, the nucleus becoming the head. The appearance of the cellular tuft at
| what may be termed the second stage is that of a raspberry, with the individual
_ drupes separated slightly from each other. In the next stage the tuft assumes
| the appearance of a sheaf of barley, the “heads” of the grain corresponding to
| the heads of the sperms. The entire tuft meanwhile has been growing, so
| that ultimately any portion of the gland examined shows a series of long strands
| of fibre fringed and tufted with delicate plumes.

If a single plume be next examined, under a higher power, it is discovered
VOL. XXXII. PART IIL. oM

634 R. J. HARVEY GIBSON ON THE

to be composed of a central stalk, evidently formed by the union of the several
filaments of a number of heads, which are arranged around the stalk in an
extremely graceful manner. Very careful focussing, under a power of 800 —
diameters (after long staining), is necessary before the separate filaments can
be seen (Pl. CLIII. fig. 79).

Isolated sperms show themselves to be composed, as in the case of mam-
malian and other sperms, of a head and tail. ‘The head is oblong, about gzg
of an inch in length, and about a third of that in breadth, and apparently
structureless. It takes on a deep stain with picro-carmine. The tail is very
slender, being not more than 35.455 Of an inch in breadth by about zoo of an
inch long. It takes on scarcely any stain after an hour’s immersion in picro-
carmine ; the head, meanwhile, as already stated, becoming deeply stained of a
crimson colour (PI. CLIII. fig. 80).

Female.—In principle, the structure of the female generative organ is some-
what similar to that of the male. Like the male organ, it is more or less
wedge-shaped, and usually larger in size. It is covered by a very delicate —
membrane composed of connective tissue, and covered with squames, of which
latter the nuclei are the most evident parts. The gland itself is merely a bag,
with a fibrous wall puckered externally and covered by a cubical epithelium
many layers deep; the superficial layers of which become free, and fill the
cavity of the gland as ova. The ova are of all sizes, from that of the cubical
epithelial cells to spheres which can be perfectly easily seen with the naked
eye. The cubical epithelium is more abundant in certain spots, which, as in
the case of the testis, may be termed “ nests.”

An ovum (Pl. CLIII. fig. 76) fully developed is polygonal, or, when free,
rounded mass, about from ;3, to gg of an inch in diameter. It is covered —
externally by a stout capsule, structureless, or vertically striated and punctured.
The protoplasm is made very opaque by the presence of a very large quantity —
of yolk spherules. A nucleus containing nucleolus and endo-nucleoli is always
visible after staining or crushing. In the younger ova, however, it is easily seen.

Historically, with the exception of FiscHer’s researches on development,
very little indeed has been done towards the elucidation of the structure of the
reproductive organs. In fact, any observations made on the system have been
mainly as to whether ducts are present or not, and if so, whether or not the
“capito-pedal orifices” are the openings of these ducts. Cuvier (loc. cit.) de-
scribes and figures an oviduct, which no one since his time has been able to find,
Dat thinks he has seen a duct “from the extreme left of the gland, and open-
ing into the dendritic renal sac” (Amer. Jour. of Conch., 1871, vi. 271). In.
another later paper, however (Proc. Acad. Philad., 1876, 239), he denies all
knowledge of an oviduct ; he denies the very existence of LANKESTER’S “ capito-
pedal orifices” in the first-quoted paper, but admits in the second that they are

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 635

present in some Patelliide, but denies that they occur in P. vulgata; he more-
over thinks they are “ aquiferous pores.” The author’s experience is that they
are present, and can be seen with the greatest of ease in all limpets; that they
are, as described by SPENGEL (doc. cit.), uot “ orifices” at all (and how they could
be called or thought so is to him a mystery), but rudiments of the lost true gills.
Gray, in his British Museum Catalogue, says that the milt or roe lies on the right
side ; the author’s experience is that in the vast majority of cases it lies on the
left, although the point is of no great importance.

Rosin and Lepert (Anal. de Sc. Nat., 1846) say that the generative gland
was wanting in more than half of the specimens they examined. Without
going so far as to contradict that statement, the writer must state that, in the
examination of over 100 specimens, he never found the generative glands
entirely wanting, although in some cases they were smaller in size. The
animals examined were collected in April, July, October, and December. The
writer found no indication whatever of any duct either from the testis or
ovary, and therefore is disposed to believe that the reproductive glands must
open at certain seasons into the right renal sac, and that they do not possess
special ducts of their own.

EXPLANATION OF PLATES.

PLATE CXLIX.

Fig. 1. Patella vulgata, face view (x2). v.h., visceral hump; l7.p. and 7.r.p., left and right renal
papille ; a.p., anal papilla; c.m., circular muscle; ¢., tentacle; m., mouth; f, foot.

Fig. 2. Dorsal view, shell removed (n.s.). m.s., mantle skirt.

Fig. 3. Dorsal view, visceral integument removed (n.s.). 7., rectum ; pr., pericardium ; ct., ctenidium ;
l., liver; Z.n., left nephridium ; 7.n., right nephridium ; ¢.m., circular muscle; ra., radula ;
s.t., superficial coil of the intestine; g., genital gland.

Fig. 4. Visceral integument (x 250), a, superficial pigmented epithelium ; 6, median connective tissue
layer ; c, deep pigment layer (renal epithelium).

Fig. 5. Superficial pigment layer of visceral integument ( x 500), surface view.

Fig. 6. Epithelium over the circular muscle-band (x 250). a, ordinary cells; 0, transitional spindle-
shaped cells; d, dense epithelium over the muscle, with cuticle ; c, muscle.

Fig. 7. Deep epithelium of visceral integument, surface view ( x 500).

Fig, 8. Epithelium covering the surface of the foot ( x 350).

Fig. 9. Epithelium covering the head and neck ( x 500).

Fig. 10. Transverse section of nuchal tentacle (x 500). a, epithelium; 0, nerve fibres; c, ventral

muscle band ; d, eye.

Fig. 11. Longitudinal section of nuchal tentacle (x50). d, eye; e, pigment in subepithelial connective
tissue of tip of tentacle.

Fig. 12. Epithelium of tentacle (x 500). a, columnar cells; 6, subcuticular layer of granular
proptoplasm ; c, cuticle; d, trabecule of connective tissue passing inward from g, the
subepithelial layer of connective tissue; jf, muscle fasciculi enclosed by connective tissue
cells, e,

Fig. 13, Epithelium of tentacle on surface view (x 500).

636 R. J. HARVEY GIBSON ON THE

Fig. 14. Epithelium from the outer aspect of the ocular swelling (x 500). a, cuticle; b, columnar
cells ; c, pointed short cells ; d, subepithelial connective tissue ; e, trabecule.
Fig. 15. Longitudinal section of eye (x 250). a, ocular pit and retina,

PLATE CL.

Fig. 16. Retina (x 800). a, cuticle with two layers. 6, prisms separating them ; c, pigmented epithe-
lium; d, nerve plexus. (This figure was drawn from a preparation in which the cilia were
aaa )

Fig. 16a. Arrangement of pigment granules in the columnar cells ( x 800).

Fig. 17. fecayane section through neck behind the origin of the tentacles. ph., pharynx; s., salivary
gland; p., palate; 7., radula; m.s., muscle of infraradular sheet ; /.c., lateral cartilage ; a.c.,
anterior cartilage; U.p., lateral protractor; v.pr., ventral protractor; w.p., under plate; —
v.tr. and v’.tr’., ventral transverse muscles ; Z.m., longitudinal muscle.

Fig. 18. Epithelium covering the attachment of the mantle to the shell in the head region ( x 250). a,
epithelium ; 0, subepithelial layer ; c, muscle. 3

Fig. 19. Vertical section of circular muscle (x50). a, epithelium; 0, blood vessel; ¢, vertical —
muscle; d, epithelium of side of foot; e, circular muscle (deep); h, circular muscle

; (superficial); f, nerves ; g, dense connective tissue beneath the epithelium of foot.

Fig. 20. Section of the mantle (x50), (see fig. 18). a, epithelium; 0, lacunar blood spaces; ¢,
mantle muscle, “

Fig. 21. Muscular fibres of foot ( x 500). ;

Fig. 22. Shell, with muscle, &c. impressions (interior), (n.s.). m.a., mantle attachment; c.m., circular
muscle attachment ; v., visceral attachment; d., dorsum, not touched by viscera. .

Fig. 23. Shell (exterior) (n.s.).

Fig. 24. Radial section, mantle and gill processes (x 50). a, papilla; 0, nerve; c, efferent branchial
vein; d, gill lamella; e, muscle; f, afferent branchial veins.

Fig. 25. Epithelium of the dorsum of the mantle (x 500). a, epithelium; 0, circular muscle fibres; ¢,
radial muscle fibres; d, connective tissue; ¢, muscle fibres connected with epithelial cells;
Ff, deep radial muscle.

Fig. 26. Epithelium covering the under surface of the mantle (x 250). a, surface ; 2, side view.

Fig. 27. Epithelium of the mantle at the origin of gill lamelle (x 500).

Fig. 28. Mantle, radial section, with Salen branchial vein (x30). a, cavity of papilla; 0, nerve |
ganglion; c, lacune; d, efferent branchial vein; e, transverse trabecule; /, radial
muscle ; g, afferent poeta vein.

Fig. 29. Connective tissue cells of same ( x 500).

Fig. 30. Part of gill lamella ( x 100).

PLATE CLL

Fig. 31. Mantle papilla, longitudinal section (x 100). a, ganglion and nerves; 0, nerve fibres ;
c, vascular lacunz ; d, blood corpuscles.

Fig. 32. Epithelium of the dorsal wall above the pit of papilla ( x 250).

Fig. 33. Epithelium of papilla ( x 250). -

Fig. 34. Nephridia, A, left; B, right (x50). ¢, fibrous septum; a.a’, blood vessels in the walls of the
nephridia ; 2, left roel epithelium ; e, right renal epithelium ; d, cavity of right a
ridium ; f, cavity of left nephridium ; g, epithelium of nephridia on surface view.

Fig. 35. Renal epithelium, right nephridium ( x 250). i

Fig. 36. Pericardium interior, looking towards the right shoulder (x20). a, right renal papilla; },
anus ; c, left renal papilla; d, pericardium ; e, pericardial opening of the left kidney; f,
pericardial opening of right kidney; g, right aorta; h, rectum. (This figure is semi-
diagramatic, and compounded from several preparations. )

Fig. 37. Renal epithelium, left nephridium.

Fig. 38. Branchial vein and veinlets (x50). a, gill lamella; 6, circular muscle; c, common
branchial vein ; d, afferent branchial veinlets from the mantle skirt; e, efferent branchial
veinlets from the gills to branchial vein proper; f, branchial vein of right side.

Fig.

Fig.

Fig.

Fig.
Fig.

Fig.
Fig.
Fig.
Fig.
Fig. 60.

Fig. 61.

Fig. 62.

. 39.
. 40,

. Al.

. 42,
. 43.
. 44,
. 45,

. 46.
. 47.
. 48.

. 49,
ig. 50.

51.

52.

53.

54.
55.

56.
57.
58.
59.

ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA. 637

Muscular fibres of the auricle ( x 250).

Pericardium (x 250). a, superficial clear membrane; 0, subcutaneous connective tissue; ¢,
muscular fibres attaching auricle to the pericardium.

Diagramatic representation of heart and its vessels. 0.vm., branchial vein; p., circular
muscle ; b., pericardium ; 7, left renal papilla; g., anal papilla; a., auricle; v., ventricle ;
d.d'., right and left aorte ; ¢., left nephridium ; ¢., aur, vent. valve.

Blood corpuscles.

Heart and vessels, pericardium removed. (Letters as in fig. 41.)

Auriculo-ventricular valve.

Muscular fibres of ventricle.

PLATE CLII.

Diagramatic section of shell, showing the arrangement of the lamine.

Section of shell, showing the three layers and lamin.

Do. do., magnified (x 50). a, upper; b,"middle;
c, lower layers.

Superficial layer of shell.

Nervous system, semidiagramatic. ct., ctenidium; p.s.b., posterior superior buccal ganglion ;
a.s.b., anterior superior buccal ganglion; 7.0., inferior buccal ganglion; ¢.g., cerebral
ganglion ; ¢., eye; c.c., cerebral commissure ; ¢.p., cerebro-pedal commissure ; ¢.v., cerebro-
visceral commissure; v.g., visceral ganglion; p.g., pedal ganglion; p.n., pedal nerve ;
p., pallial nerve ; m., muscle nerve ; /.s., left splanchnic ; 7.s., right splanchnic ; 7., recurrent
nerve; I, tentacular; II., cutaneous; III., ocular; IV., posterior pharyngeal; V.,
anterior pharyngeal ; VI., labial nerves. The outer dotted and inner dotted lines represent
the outlines of the buccal mass and the pharynx respectively.

Nerve elements. (1) nerve—c, isolated fibre; (2) cells of a ganglion—a, rounded, 6,
bipolar.

Vertical section through the nuchal tentacle, showing separate origins of tentacular and ocular
nerves, and of the cerebral and visceral commissures from the cerebral ganglion. a, super-
ficial layer of ganglion cells; 0, visceral commissure ; c, ocular nerve; d, tentacular nerve ;
J, epithelium of tentacle ; e, the ocular mound ; g, cerebral commissure.

Semidiagramatic representation of intestinal coils. ph., pharynx; ¢r., crop; a, anus;
r., rectum ; s, and s’., stomach.

Face view of mouth. a, radula; 0, palate ; c, inner lips; d, outer lips.

Section of the lower plate. a, cuticle; 6, stratified columnar epithelium; c, connective
tissue ( x 50).

Same, magnified ( x 250).

Section of liver ( x 150), showing hepatic tubes cut in transverse section.

Liver cells, connective tissue ( x 450).

Liver cells, isolated ( x 500).

Radula, two rows of teeth. 1 and 2, lateral teeth; 3, median tridenticulate ; 5 and 4, central
unidenticulate.

PLATE CLIII.

Pharynx and salivary glands, dorsal neck wall removed. a.b, ducts of salivary gland of right
side, d ; c, pharynx ; e, buccal mass; f, lobe of pharynx ; g, intestine.

Vertical section through neck. a, inner lip; 0, upper (palatal) plate ; c, lower (ventral)
plate ; d, pharyngeal wall; e, anterior cartilage; jf, radula; g, ventral protractor muscle ;
h, superficial transverse muscle; #, longitudinal muscle; /, deep transverse muscle; m,
posterior cartilage ; m, muscles of the subradular membrane ; 9, nuchal body cavity.

Figs. 63. and 64, Dorsal and ventral views of the upper (palatal) plate.
Fig. 65. Ventral view of buccal mass. a, ventral protractor reflected; 6, terminal radular plate

reflected ; 0’, radula; c, longitudinal muscles; d and e, superficial and deep transverse
muscles.

~

VOL. XXXII. PART III. oN

638

Fig.

Fig.
Fig.
Fig.
Fig.
Fig.

. Cartilages of odontophore, horizontal section, dorsal view. a.c., anterior cartilage ; pity

. Stomach wall. The section is taken transversely through a part where the adjacent walls of.

. Transverse section of intestine near rectum,

. Glandular stomach and liver. a, follicles ; 5, liver sacs; c, bile duct.
. Cells of the intestine isolated and more highly magnified.

. One of papillze of rectal papilla wall.

. Transverse section of rectal papilla.

. Membrane covering the genital organ.

. Ova, in different stages of development.

. Development of spermatozoa.

Figs. 78 and 79. Two stages in the development of a tuft of spermatozoa.

Fig. 80. Spermatozoa isolated.

GIBSON ON ANATOMY AND PHYSIOLOGY OF PATELLA VULGATA,

posterior cartilage ; /.c., lateral cartilage ; v.t7., deep ventral transverse muscle; ., con-
nective tissue and pemeneniinces

the two divisions of the stomach touch. ’
Vertical section through the visceral dome. a, pericardium; 8, in the stomach; c.c, sections
of intestine; d, in the ee nephridium ; ¢, section of rectum; f, left nephntdiaael n
glandular Saenas, “crop”; h, genital organ ; k, liver ; l, foot.

Cells of a follicle in glandular stomach.

mis. Roy. Soc. Edin® VoPAXAW, Plate CXL

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(. 639 )

XXXIV.—Detached Theorems on Circulants. By Tuomas Muir, LL.D.

(Read 4th May 1885.)

1. [fin a circulant the places (r, s) and (p, q), owing to the cyclical permuta-
tion, be occupied by the same element, then the complementary minor of this
element in its first place is to its complementary minor in the second as

( a 1 i : ( a 1) aaa

To prove that the complementaries are as (—1)'**:(—1)’** is the same as
to prove that the cofactors are identical. And as the cofactor of an element of
a determinant is not altered by the transposition of rows and columns provided
the determinant itself is not thereby altered, it is evident that all we have to
show is that the element in the place (7, s) may by transposition of rows and
columns be made to take the place (p, q), and the determinant remain in out-
ward form the same as before. Now it is a known property of the circulant
that this can be done by first bringing the element in the place (7, s) into the
p" row by cyclical transposition of rows, and thereafter making an exact
similar set of transpositions of columns. Thus the theorem is established.

2. Ifa, b, c,... be the elements of the first row of a circulant, say of the fifth
order, and A, —B, C,—,... their complementaries, then the circulant is equal to

(a+ob+wc+o°%d+w'e)(A+o'B+a°C +w*D + wE)
where w is any fifth root of unity.

Multiplying the circulant

Ooo wer <
Qi M8
aie¢ a be) or Cia bed e),
Cote eae O
Yi, AOE OG

by 1 in the form

=
.
&
S

VOL. XXXII. PART III. 20

640 THOMAS MUIR ON DETACHED THEOREMS ON CIRCULANTS.

we have
ad+wbtwet+owid+twe 6b cc d e
e+oa+u%+a3e+o'd a b ¢ a
C(abcde)= | d+we+oatw%d+wte ¢ a 0 ¢
ctod+wet+watwd de a bd
b+wctw'd+w%etota ¢c de al,
=(a+ob+orc+o%d+o%e) | 1 6b ¢ de
Gy Gh (dy ie Gh
oO 2 uw & @
hae Oe Oe eA)
i Ga fe. Saale

= (a+b +0%e+ ord +w*e)(A+wE+o*7D+°C+o'B) ,

as was to be shown.

3. If the linear factors of a circulant, say of the fifth order, be a, B, y,...,
and the complementary minors of the elements of the first row be A,—B,C,—...,

then |
C(aByo, aBye, aBde, ayde, Byde)=5°>ABCDE.

Let us denote by p one of the zmaginary fifth roots of unity, the other roots
being p’, p’, p*, 1, and we have from § 2 ’

C(a, b, ¢, d, e)=(at+w b4+o0%+o%d+o'c) (Ato E+w2D+o°C +B),
=(4+0*%)+o'¢+o d+w°%c) (A+e’E+o4D+o C+o°B),
=(4+0%)+o c+o1d+o%) (A+0°E+oD+o'C+o°B),
=(4+0'b+o%¢+ wd+wo e) (A+o1E + w*D+o?C +o B),
=(a+ b+ c+ d+ e)(A+ E+ D+ C+ B).

From these by division there result

A+wo E+o?D+o°C+o'!B= 6yde
A+o°E+o'D+o C+o°B=ydea
A+o*E+o!D+o'C+o*B =deaB
A+oE+o°D +@°C+o'!B=caBy
A+ E+ D+ C+ B=ays).

Calling the right-hand members here @, U’, c’, d’, e’, we see readily that

a+ + + H+ =5A
w a +b’ +o%c’ +d’ +e’ =5B
wd’ +b! +oc+w%d' +e’ =5C
wt +b’ +1 +02 +e =5D
wd +o°b’ +02 +o dU +¢=57/,

THOMAS MUIR ON DETACHED THEOREMS ON CIRCULANTS. 641
and therefore by multiplication

C@, U, ¢, d’, ¢)=5°A BCDE,
as was to be proved.

4. If the elements of the first row of a circulant of the nth order be multiplied

by w, ow", ...., w respectively, the elements of the second row by #~', w', .

w, wo" respectively, the elements of the third row by °~*, wo °,...,@, @, ow"
respectively, and so on, where w is any nth root of unity, the circulant is unaltered
in value.

If we take the circulant as thus changed outwardly, and multiply all the
elements of the second row by », all the elements of the third row by ”, and so
forth, the elements of the first column will have »” for a common factor, the
elements of the second column will have w"~', the elements of the third column
w"?,and so on. We thus can strike out of the columns the very factors we
introduced into the rows (with the immaterial addition of ©", z.¢., 1), and leave
the circulant as it originally stood free of »:—which proves the theorem.

5. If we take two skew circulants, of the 5th order say, C’(ay,..-,@;), C’(d,,...,05)
and write the first in the form

ay ay tls @, Gs =|
— Oh. ty hy Gd, a, |
Ce ay hy Ag
=Uy Sly =O; ay a,
—& —U, —-A, =—A, | ;

and the other with its rows in reversed order, then the determinant whose every
element is the sum of the corresponding elements in these two determinants,
that is to say, the determinant

a, —b, ty — bz a,—b, az—b, a,—b,
—t,—b, a, — 04 ly — b, ag+b, ay+b,
—a,—b, —a,—b; a+, A,+b, d3+; |
—t3—b, —ay+b, —a3;+b, a+b; a+b, |
—dy+b, —d3+b, —a+b, —a,+b, a,4+0, |,

has for a factor

(a, +o lg +o 23+ w+ 0~*A5) (A, + @4,+ 073+ w+ w'A;)
—(- w'ba+ wb, + w*by + w-*bs) (b,+ wb, + wb, + wd, + w'b;)

where w is an imaginary fifth root of —1, the linear factor which remains being

a, —M,+a,—a,+4,+0, —b,+),—b,+6,.

642 THOMAS MUIR ON DETACHED THEOREMS ON CIRCULANTS.

This is equivalent to saying that the determinant is equal to
[2a,? +2 003 36° (ayy + Agtlg + Ugh, + Uys — Ug) + 2 COS 72° (44+ Mgty + gs — A401 — Ag,
— 3,2 —2 cos 36° (by), + Dgby +0), +04), —Dsp,) —2 008 72° (byb,-+ 0,0, +05b,—b,b —B,),) | x
[ 2a,? —2 C08 72° (yg + Ugg + Ag, + Myls — M30ly) — 2 COs 36° (4,05 + Ay + Ag, — Ug — Agi
— Zby2+2 cos 72° (b,), + 0ybg-+0,b, +040, —b;b,) +2 cos 36° (by), +b.b, +0, —0,b, — 0,1) | x
[a.— Ay +,—A,+d;+6,—b,+ b,—b, +b; ,

where the law of signs in

Ay Ay + Ugly + Ag+ Agh;— A, ANd AyMg+ M.A, + Ags — Ay — Ugly
is made clear by noting that each expression is got from two rows of
C’ (ay, Ag, 3, Uy, Az), the former being (a, cg, dg, Ay Us, 8— Ap, Uy, Up, Ug, Uy) and the
latter (— a2, —d3, —Gy, — Ag, y8— Cg, — My Ug, — Cy, Ue).

This theorem is established exactly as its analogue in ordinary circulants.
(See Messenger of Math., xi. pp. 105-108.)

6. One of the hardest problems connected with circulants is the finding of
the final expansion of the circulant of the nth order. Anything that has been
done towards a solution will be found in the following papers: GLAISHER, Quart.
Journ. of Math., xv. p. 354, xvi. p. 33; Murr, Quart. Journ. of Math., xviii.
pp. 176, 177; Forsytu, Mess. of Math., xiv. pp. 43-46.; Muir, Mess. of Math.,
Xlv. pp. 169-1735.

One plan which occurred to me of determining the law of the coefficients
was to try to hit upon a determinant of some more general form than the
circulant and having an easier law of formation for its final expansion, and then
to specialise. The determinant which seemed to offer fairest promise is

exemplified by
| @a BB cy do ce 7A
eB ay 6 ce da
dy « ade ba cB
co de 6a a by
be ca dB ey ad.-|.
It evidently degenerates into the circulant C(q, b, ¢, d, e) whena=B=y=d0=e=1,
and, what is of importance, the letters a, B, y,4,¢ are themselves introduced
in cyclical fashion, the determinant, in fact, degenerating into the circulant
C(a, B, y, 8, «) when a=b=c=d=e=1. This determinant I find equal to
(O40 +02°+d°+e)aByde
—(asbe+bica+cdb+d%ec+ ead) (a®yd+ B'de+ y*cat+ Sab +eBy)
—(aced+b3de+ cca+d*ab+e%be) (a®Bet+ Byat y*dB + Hey + ead)
+ (abd + b+ d*a + deh + ea°c) (a? By’ + B?y0? + y*de? + 8ea? + €a3”)
+ (a*he? + bcd? + cde? + dea? + ab?) (a®B°d + Bye + ya + 0°e"6 + €a"y)
— 10abedeaByde,

THOMAS MUIR ON DETACHED THEOREMS ON CIRCULANTS. 645

which, using > for cyclic swum, we may write in the form

Da’. aByde— SarheDaryd - Yared Da2Be+ Sard Ye2By? + Sa°be2D0282S
— 10 abcdeaByde.

Putting a=B=y=d=c=1, we obtain

C@ b, ¢ d,; e)= Ya? —5Sa%be —5 Sared 4+5502bd +5 Dae? \
—10 abcdeaByce ,

and it is seen how the coefficients, —5, —5, 5,5 originate. Unfortunately the
general determinant still contains a set of unsifted terms, viz., 10 abcdeaByde,
which are got, curiously enough, from the elements by a series of knight’s
moves. Though therefore the discussion of the problem may be advanced in
this way, the full solution is not yet in sight.

VOL. XXXII., PART III. 5P

( 645 )

XXXV.—On the Hessian. By Professor CurystTat.
(Read 18th May 1885.)

12) Ket

US + +42 7+....=0

be the equation to an algebraical curve of the mth degree, the co-ordinates of
any point on which in a system of linear co-ordinates are (a, y, Z), Uo, Ui; U2-+--
being homogeneous functions of « and y of degrees indicated by the attached
suffixes ; then

H=wyU,U.+2U,.U.0.,—U,,U,2—U,,U.29—U.Ue=0

is the equation to its Hessian, which is a curve of the 3(m —2)th degree.

Every one of the 3n(m—2) points of intersection of H and U is a point of
inflexion on U if it be not a multiple point on U. In this last case the inter-
section may or may not be a point of inflexion on some one of the branches of
U; but in any case where H passes through a multiple point the total number
3n(n—2) of inflexions suffers a reduction. It is therefore a problem of great
geometrical interest to calculate the number of the intersections of H and U
which are absorbed at a multiple point on the latter. This problem has never
been solved directly in any but a few simple cases. It has been shown, for
example, that at an ordinary double point on U, H has also a double point the
tangents at which are the same as the tangents at the double point on U, and

that such a point absorbs 2x2+2=6 of the intersections HU ; also that a
multiple point of order &, all of whose tangents are distinct, is a multiple point
of order 34—4 on H, & of whose tangents are tangents to U, and that such a
point absorbs 4(3k — 4) +4=6 x 44(4—1) intersections,—in other words, has the
same effect as the 44(4—1) ordinary double points to which it may be regarded
as equivalent. It has also been shown that a point which is a cusp of the
ordinary kind on U is a triple point on H, two of whose tangents coincide with

the cuspidal tangent of U; this cusp counting for 2x3+2=8 among HU.
Finally, Cay.ey has laid down that every singularity of an algebraical curve
can be regarded, for our present purpose, as equivalent to a certain number 6
of ordinary double points, and a certain number « of ordinary cusps. But the
proofs which have been given of this theory by N6rHER, ZEUTHEN, STOLZ,
Henry Sirs, and the methods given for ascertaining the indices d and «, are
of an indirect nature, and it has been doubted whether any proof of this theory
can be given by methods appropriate to co-ordinate geometry.
VOL. XXXII. PART III. 5Q

646 PROFESSOR CHRYSTAL ON THE HESSIAN.

The direct calculation of the reduction is therefore a general problem, whose
interest is quite equal to its difficulty. With a view to clear the way for a
general solution (if such be attainable) I have worked out a number of cases, _
some quite special, others of a more general character, and propose to com-
municate the solutions to the Society in the following paper.

2. In its ultimate stage the problem reduces to the following :—

To determine the number UV of the intersections of two algebraical curves
U=0, V=0, which coincide with a common point which is multiple on one or
both. |

Let us suppose that the common point is a multiple point of order 4 on U
and of order « on V. ’

So long as no one of the & tangents of U coincides with any one of the
x tangents of V, there is no difficulty; the number of intersections absorbed at
the common point is kr.

But let us suppose that / of the & tangents and A of the « tangents coincide
with «=0, then we have

U=thip +i.
Veo yp FU sae ee.

or, what is still worse, that z=0 is a multiple inflexional or undulatory tangent,
so that
US vig FO ptembOUeen os w s o

VSO ig Oe EO Yetens Hn

and the problem becomes one of some difficulty.
In many cases the solution may be obtained by the following process :—
Ex. 1.
Let us suppose
Uj U, + U9
VEe'v, +0.
Let K=a0,U — u, VE=ary tty) — U0, Up »
say, where w,, does not contain # as a factor. Then, since K passes through all
the intersections of U and V, taking VU to denote the number of those inter-
sections which coincide with 2=0 y=0 we have, since

oe \ gives u,.V=0 and .. nV}?

UK =0V +z,
.0., Uthg=UV +U0u,,

— a a,
whence UV =Uu,, —Uu;.

PROFESSOR CHRYSTAL ON THE HESSIAN. 647

Now, provided none of the linear factors of u,, occur in vu,, and none of
those of wu, in u,, we have

Uu,,=8 x 12
Gui; =wygts=10 x 5
whence finally UV =96 —50=46.
We may consider the more general case.
Ex. 2.
UO wg A+ te, M> lh
VESOUp—p +VUetp Tp;

of which Ex. 1 is a particular case; it may be shown by the above method that
OV =kxe+ru,
This obviously agrees with the result of Ex. 1, «nd also with the following.
Ex. 3.

U=x2- UV =2x1+1x1
V=az -¥ =o.

which may be looked fs

upon as the limiting
case of Fig 2

The figure corespond-
ing to this case is

Ifin Ex. 2r>p the application of the above method is not so simple, and
the result is not in all cases the same as will be shown directly.

For the sake of comparison with the results of another process shortly to be
indicated, I work out two more examples by the present method.

Ex. 4.
US13 5 +2, + U49
Vay, +230, +,,
we have
K=20,U — 4, V=3(0,u,— U,V5) + BV U9 — UV,
=u, +4». say
L=a,K —u,0=u, +, say
7 8xi7=0L— UK + Uz,
=UV+4 0u,+ Ou,
= iy, + 2 (x?u,)U,

648 PROFESSOR CHRYSTAL ON THE HESSIAN.

Ez. 5. U=8u, +aug +49
=xtv, +270, +0,
K=a0,U —u,V =2%ly+ rhyp
L= au, K—u,U Say, + Uy
M=zu,L — uy K=u9,
11x29=MK=KL42K +u,K
= KL 4 ot + tgthy
= KU+Ku, HF atiag + Ugly
=kU FBiyg t Bigg _
=UV+u,U + &e.
=UV +20, Ugly + Qiigtlyg + Bilyy
UV =319—5 —40—216—-12=46.

redundant steps, for in the three examples (1) (4) (5) the same final result, viz.,
UV =46, is obtained by extremely different developments. Yet it is obvio s,
a priori, that the same final result ought to be arrived at in all these a
since the additional terms which appear in U and V in examples (4) and (5)
are such that they do not affect the forms of U and V at the point z=0 y=0,
which alone can be supposed to affect CV.
It is at once suggested, therefore, that the problem will be simplified by
substituting for U and V the approximations to their branches at the origin
determined by the rule of Newron and Cramer. In this way we can in general
reduce the problem to a series of others, of which the following is a type.
To determine the number of intersections of
US2"—y"=0....(1) and V=0'=—y'=0.... (2)
at the point z=0 y=0.
Since imaginary branches must be considered as well as real branches,
it may be well to give a rigorous proof of the solution in this simple case.
If aja,....a, be the m roots of +1, the m values of y given by y"=a” are
a,c” 5 ae” eynuers ant” c

The eliminant of the two equations (1) and (2) with respect to y is therefore

{ +a" y} pee C: vee | eae yi =0,
utis SLSR EH PPh tee

Now, if g be the G.C.M. of » and », and n=gn’, v=g’, then the series
ai, a,....a%, simply consists of the roots of a” —1=Orepeated g times. Hence
the equation last written reduces to

pv (apin' mv _ 19 = 0), that is (w’—a™o=0.... (3),

PROFESSOR CHRYSTAL ON THE HESSIAN. 649

where from the nature of the process employed we are sure that there is no
redundant factor.
Now 2" or 2” is a factor in (3) according as wr< or >my, w.e., the number
of zero roots of (3) is the least of the two numbers yun mv.
Hence denoting for shortness the least of the two yn mv by U(un, mv), we
have the following simple theorem.
The number of intersections of #”—y"=0 and w*—y’=0 at the point
c=0 y=0, is
(un, my).
4, By means of the NEwron-CrAMER rule we can, as far as points near
x=0 y=0 are concerned, replace U and V by
U'= (aA, y") («@ —A,y”)....
VG Bg Ge By 8) a aan
where the factors in U’ will in general be all different, those in V’ all different,
and no factor common to U’ and V’.
In this case we can at once find the number UV. We have, in fact,

LEE VS

UV=UV=l(m, vy, % my) +E (Mm, ve, M Mg) ..--
+1 (Mg vy, My My) HU (MM, Vy, Ng My). ---
et ee

This result still holds when factors are repeated in U’ or in V’; but when there

are factors common to U’ and V’ there is a modification, as will be shown
presently.

5. Before proceeding farther, let us apply the above principles to one or
two examples.

Ex. 1. U= au, + 0%, +U,)=0
] Vxtu,+a%vgtv, =0.
The NeEwrTon-CraMErR diagrams for U and V show at once that (omitting
constant coefficients as irrelevant to the issue) we may write
U = u,(a?+y°) V=v (a+) ;
—~
“ UV=5x1+5x44+3x1+4+3x6=46,
the same result as before.
Ex. 2. U = au, +2ugt uo
V = atv, +20, +0,.
Here it is easily shown that we may write
US uty’) (@+y’)
V = v, (x+y);
LS
~ UV=5x1+5x4+42x14+2x6+1x1+1x6=46.
Ex. BY U == a” Un—m + Ur—r

Nie oF 6 Ug:
VOL. XXXII. PART III. 5R

650 PROFESSOR CHRYSTAL ON THE HESSIAN.

The diagrams here are both of the same character
that for U, for example, is figure 3, where AB and
CD are parallel and each full of terms ; the co- -ordina es
of D are (m, k—m); and OA=k+7, OC=kh. The two
lines CD and BD give approxmations at <=0 y=0.

We may therefore write

) C A U= w_m(e™+y"*"), VEX +yr™).
Hence

Fig.3.

OV =(b—m)c + m(e—w) +U(p-+ um, (r+-m)u}
=kk-—ma+mp +1(pm, ru)
=kk+U(pm, 7)
=kk+pm or =kk+7u,
according as pm <or> Tp.
This result includes that of Ex. 2 in § 2 as a particular case.
Ex. 4. To illustrate the particular case of Ex. 3, where mp< 7, consider

CI

U=e—-y1. V=22—7
Here m=2, k=2, r=2,
— 2 k=2, p=1;

mp=2, ur=4.
UV. = 225-9 6.

The corresponding figure is

Fig.4.

which may, in fact, be considered as the limiting case of

(Lo be continued in another Communication.)

y

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Fellows,

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1887. |

TRANSACTIONS |

OF THE

ROYAL SOCIETY OF EDINBURGH.

VOL. XXXII. PART IV.—FOR THE SESSION 1884-835.

ae | CONTENTS.
; 4 ee EE

Page
Tae Councin or THe Socisry, . , ; } ; . 654
ALPHABETICAL List oF THE ORDINARY FELLOws, ; ; : . 5 (695
List of Honorary FELLows, . : : : : 5 , : +. 668
List or Orpinary FrLitows ELEcTED DURING SxEssions 1883-85, : ; ; . 674
_ Laws or THz Sociry, . ‘ * ; : f : : 3 “S681
Tue KeitH, BrisBane, aND Neri, Prizss, , ; ; ; : : . | 688
Awarps oF THE KriTH, MacpouGAL-BriIsBANE, AND Nuit Prizes, From 1827 to 1879, , 2690)
PROCEEDINGS OF THE STaTUTORY GENERAL MEETINGS, . A : : : O93

List or Puruic Institutions AND INDIVIDUALS ENTITLED TO RECEIVE COPIES OF THE PROCEEDINGS
AND TRANSACTIONS OF THE Roya SOcrEry, : ; . ; : aol

INDEX, ; ; : ; i : i ; ; a eOT

[Issued July 9, 1887.)

APPENDIX.

TRANSACTIONS

OF THE

ROYAL SOCIETY OF EDINBURGH.

1884-8 5.

VOL, XXXII. PART IV. 58

CONTENTS.

THE COUNCIL OF THE SOCIETY,

ALPHABETICAL LIST OF THE ORDINARY FELLOWS,

LIST OF HONORARY FELLOWS,

LIST OF ORDINARY FELLOWS ELECTED DURING SESSIONS 1883-85, .
LAWS OF THE SOCIETY,

THE KEITH, BRISBANE, AND NEILL PRIZES,

AWARDS OF THE KEITH, MACDOUGAL-BRISBANE, AND NEILL PRIZES,
FROM 1827 TO 1879, ; : i : : :

PROCEEDINGS OF THE STATUTORY GENERAL MEETINGS,

LIST OF PUBLIC INSTITUTIONS AND INDIVIDUALS ENTITLED TO RECEIVE
COPIES OF THE PROCEEDINGS AND TRANSACTIONS OF THE ROYAL
SOCIETY,

INDEX,

701
707

LIST OF MEMBERS.

COUNCIL,
ALPHABETICAL LIST OF ORDINARY FELLOWS,
AND LIST OF HONORARY FELLOWS.

At November 1886,

THE COUNCIL

OF

THE ROYAL SOCIETY: OF EDINBURG

NOVEMBER 1886.

Str WILLIAM THOMSON, LL.D., F.R.S., Foreign Associate of the Institute
of France, Regius Professor of Natural Philosophy in the University of
Glasgow.

HONORARY VICE-PRESIDENTS, HAVING FILLED THE OFFICE OF PRESIDENT.

His Grace.tHE DUKE or ARGYLL, K.T., D.C.L. Oxon, F.R.S.
Tue Ricut Hon. Lorp MONCREIFF, LL.D., Lorp Justice-Cimrx.
THOMAS STEVENSON, Esq., M. Inst., C.E.

VICE-PRESIDENTS.

ALEXANDER FORBES IRVINE, of Drum, Sheriff of Argyll.

JOHN MURRAY, Ph.D., Director of the Challenger Expedition Commission.

D. MILNE HOME of Milne-Graden, LL.D.

Sir DOUGLAS MACLAGAN, M.D., President of the Royal College of Physicians,
Edin., F.R.C.S.E., and Professor of Medical Jurisprudence in the University of
Edinburgh.

Tue Hon. Lorp MACLAREN, LL.D. Edin. and Glas., F.R.A.S., one of the Senators of
the College of Justice.

Tue Rey. Proressor FLINT, D.D., Corresponding Member of the Institute of France.

GENERAL SECRETARY.

P. GUTHRIE TAIT, M.A., Professor of Natural Philosophy in the University of Edinburgh.

SECRETARIES TO ORDINARY MEETINGS.

Sir WILLIAM TURNER, M.B., F.R.C.S.E., F.R.S., Professor of Anatomy in the
University of Edinburgh.

ALEXANDER CRUM BROWN, M.D., D.Sc, F.R.C.P.E., F.R.S., Professor of
Chemistry in the University of Edinburgh.

TREASURER.

ADAM GILLIES SMITH, C.A.

CURATOR OF LIBRARY AND MUSEUM.

ALEXANDER BUCHAN, M.A, Secretary to the Scottish Meteorological Society.

COUNCILLORS.

GEORGE CHRYSTAL, M.A., Professor of | WILLIAM CARMICHAEL M‘INTOSH, M.D.,

Mathematics in the University of Edinburgh.
ALEXANDER DICKSON, M.D., Professor of
Botany in the University of Edinburgh.

J. SHIELD NICHOLSON, Professor of Political
Economy in the University of Edinburgh.

T. B. SPRAGUE, M.A.

S. H. BUTCHER, M.A., LL.D., Professor of
Greek in the University of Edinburgh.

JOHN G. M‘KENDRICK, M.D., F.R.C.P.E.,
F.R.S., Professor of the Institutes of Medicine
in the University of Glasgow.

THOMAS MUIR, M.A., LL.D., Mathematical
Master in the High School of Glasgow.

LL.D., F.R.S., F.L.8., Professor of Natural
History in the University of St Andrews.

ROBERT GRAY, Secretary to the Royal Physical
Society of Edinburgh, Member of the British
Ornithologists’ Union, Corresponding Member
of the Academy of Natural Sciences of
Philadelphia.

ARTHUR MITCHELL,C.B., M.A., M.D., LL.D.,
Commissioner in Lunacy.

STAIR A. AGNEW, Esq., C.B., M.A., Advocate,
Registrar-General.

ROBERT M. FERGUSON, Ph.D.

Date of
Election,

1879
1871
1881

1878
1875
1878

1856

1886
1874

1883
1883
1881
1867

1883
1886
1849

1885
1879
1875
1843
1879

1877

ALPHABETICAL LIST

OF

THE ORDINARY FELLOWS OF THE SOCIETY,

B.
K.
N.
12,

HP.

BP,

CORRECTED TO NOVEMBER 1886,

N.B.—Those marked * are Annual Contributors.

prefixed to a name indicates that the Fellow has received a Makdougall-Brisbane Medal.

Keith Medal.
” »”? ” Neill Medal.
cf a », contributed one or more Papers to the TRANSACTIONS.

Abernethy, Jas., Memb. Inst. C.E., Prince of Wales Terrace, Kensington
* Aonew, Stair A., C.B., M.A., Advocate, Registrar-General, 22 Buckingham Terrace
Aitchison, James Edward Tierney, C.ILE, M.D., F.RS., F.LS., Brigade-Surgeon,
Secretary to the Surgeon-General, H.M.F. Bengal, and Naturalist with the Afghan
Delimitation Commission, H.M. Bengal Army, North Bank, Simla, Punjab, India
* Aitken, Andrew Peebles, M.A., Sc.D., F.I.C., 18 Dublin Street
* Aitken, John, Darroch, Falkirk 5
Allchin, W. H., M.B. (Lond.), F.R.C.P., Physician to the Westminster Hospital, 5 Chandos
Street, Cavendish Square, London, W.
Allman, George J., M.D., F.R.S., M.R.LA., F.L.S., Emeritus Professor of Natural History,
Univ. of Edinburgh, Ardmore, Parkstone, Dorset
* Anderson, Arthur, M.D., C.b., Ex-Inspector-General of Hospitals, Pitlochry
Anderson, John, M.D., LL.D., F.R.S., Superintendent of the Indian Museum, and Professor
of Comparative Anatomy in the Medical College, Calcutta, 71 Harrington Gardens,
London, S.W.
* Anderson, Robert Rowand, LL.D., 19 St Andrew Square 10
Andrews, Thomas, F.C.S., Mem. Inst. C.E., Ravencrag, Wortley, near Sheffield
Anglin, A. Hallam, M.A., LL.B., M.R.I.A., Medmenham, Great Marlow, Buckinghamshire
* Annandale, Thomas, M.D., F.R.C.S.E.., Professor of Clinical Surgery in the University of
Edinburgh, 34 Charlotte Square
Archibald, John, M.B., C.M., Lynton House, Brixton Rise, London, 8.W.

'|* Armstrong, George Frederick, Professor of Engineering in the University of Edinburgh 15

Argyll, His Grace the Duke of, K.T., D.C.L., F.R.S. (Hon. Vicz-Prus.), Inveraray Castle

* Baildon, H. Bellyse, B.A., 73 Princes Street
* Bailey, James Lambert, Royal Bank of Scotland, Ardrossan
* Bain, Sir James, 3 Park Terrace, Glasgow
Balfour, Colonel David, of Balfour and Trenabie, Balfour Castle, Kirkwall 20
* Balfour, George W., M.D., LL.D., F.R.C.P.E., 7 Walker Street
* Balfour, I. Bayley, Sc.D., M.D., C.M., F.R.S., Sherardian Professor of Botany in the
University of Oxford

VOL. XXXII. PART IV. 5 T

656 ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY.

Date of

Election.

1870
1886
1872

1883 |

1882
1874
1878

* Balfour, Thomas A. G., M.D., F.R.C.P.E., 51 George Square
* Barclay, A. J. G., M.A., 5 Ethel Terrace
* Barclay, George, M.A., 17 Coates Crescent 25
* Barclay, G. W. W., M.A., 40 Princes Street
Barnes, Henry, M.D., M.R.C.S., 6 Portland Square, Carlisle
Barrett, William F., M.R.I.A., Professor of Physics, Royal College of Science, Dublin
Bateman, John Frederic La Trobe, Memb. Inst. C.E., F.R.S., F.G.S., F.R.G.S., 16 Great
George Street, Westminster
Batten, Edmund Chisholm, of Aigas, M.A., 16 Pelham Crescent, South Kensington,
London 30
* Bayly, General John, C.B., R.E., Ardincaple Castle, Helensburgh, Dumbartonshire
Beddard, Frank E., M.A. Oxon, Prosector to the Zoological Society of London, 9 Cleve-
land Terrace, Hyde Park, London, W.
* Bell, A. Beatson, Chairman of Prison Commissioners, 130 George Street
* Bell, Joseph, M.D., F.R.C.S.E., 2 Melville Crescent
* Belcombe, Rev. F. E., 14 Merchiston Avenue 35
Bernstein, Ludwik, M.D., Lismore, New South Wales
* Berry, Walter, Danish Consul General, 11 Atholl Crescent
* Birch, De Burgh, M.D., Professor of Physiology, University College, Leeds, 16 De Grey
Terrace, Leeds
* Black, James Tait, Gogar Park, Corstorphine
* Black, Rev. John S., 6 Oxford Terrace 40
Blackburn, Hugh, M.A., LL.D., Emeritus Professor of Mathematics in the University of
Glasgow, Roshven, Ardgour
* Blackie, John S., Emeritus Prof. of Greek in the Univer. of Edin., 9 Douglas Crescent
Blaikie, The Rev. W. Garden, M.A., D.D., LL.D., Protessor of Apologetics and Pastoral
Theology, New College, Edinburgh, 9 Palmerston Road
* Blyth, James, M.A., Professor of Natural Philosophy in Anderson’s College, Glasgow
Bond, Francis T., M.D., B.A., M.R.C.S., 1 Beaufort Buildings, Spa, Gloucester 45
* Bottomley, J. Thomson, M.A., Lecturer on Natural Philosophy in the University of Glasgow
* Bow, Robert Henry, C.E., 7 South Gray Street
* Bower, Frederick O., Regius Professor of Botany in the University of Glasgow, 45 Kerrs-
land Terrace, Hillhead, Glasgow :
Bowman, Frederick Hungerford, D.8c., F.R.A.S., F.C.S., F.G.S., F.L.S., West Mount,
Halifax, Yorkshire
* Boyd, Sir Thomas J., Chairman of the Scottish Fishery Board, 41 Moray Place 50
* Boyd, William, M.A., Peterhead
* Bramwell, Byrom, M.D., F.R.C.P.E., 23 Drumsheugh Gardens
Brittle, John Richard, Memb. Inst. C.E., Vanbrugh Hill, Blackheath, Kent
Broadrick, George, Memb. Inst. C.E., Elmfield Lodge, Doncaster

.|* Brown, Alex. Crum, M.D., D.Sc., F.R.C.P.E., F.R.S. (Srorerary), Professor of Chemistry

in the University of Edinburgh, 8 Belgrave Crescent 55
* Brown, J. A. Harvie, of Quarter, Dunipace House, Larbert, Stirlingshire
* Brown, J. Graham, M.D, C.M., F.R.C.P.E., 16 Ainslie Place
* Brown, J. Macdonald, M.B., F.R.C.S.E., 6 Atholl Place
Brown, Rev. Thomas, 16 Carlton Street
Brown, William, F'.R.C.S.E., 25 Dublin Street 60
Browne, Sir Jas. Crichton, M.D., LL.D,,7 Cumberland Terrace, Regent’s Park, London, N. W.

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY. 657

Date of
Election.

1883
1878
1867
1869

1870
1882
1883

1869

1879
1878
1874
1882
1876

1885
1866
1874

1875
1872
1880

1875
1886
1863

1875
1882

1886
1872
1863
1879
1875
1886
1873
1878
1886
1877
1884
1871
1841
1878
1885
1867

BeP:

1. P;

* Bruce, Alexander, M.A., M.B., M.R.C.P.E., 16 Alva Street
Brunlees, Sir James, Memb. Inst. C.E., 5 Victoria Street, Westminster
* Bryce, A. H., D.C.L., LL.D., 42 Moray Place
* Buchan, Alexander, M.A., Secretary to the Scottish Meteorological Society (CURATOR oF
Lrprary), 72 Northumberland Street 65
* Buchanan, John Young, M.A., 10 Moray Place
* Buchanan, T. Ryburn, M.A., M.P. for the City of Edinburgh, 10 Moray Place
* Butcher, S. H., M.A., LL.D., Professor of Greek in the University of Edinburgh, 27
Palmerston Place
* Calderwood, Rev. H., LL.D., Professor of Moral Philosophy in the University of Edin-
burgh, Napier Road, Merchiston
* Calderwood, John, F.I.C., Belmont Works, Battersea, London 70
Campbell, John Archibald, M.D., Garland’s Asylum, Carlisle
Carrington, Benjamin, M.D., Eccles, Lancashire
* Cay, W. Dyce, Memb. Inst. C.E., 107a Princes Street
Cazenove, The Rey. John Gibson, M.A., D.D., 22 Alva Street, Chancellor of St Mary’s
Cathedral
* Chambers, Robert, 10 Claremont Crescent 15
* Chalmers, David, Redhall, Slateford
* Chiene, John, M.D., F.R.C.S.E., Professor of Surgery in the University of Edinburgh,
26 Charlotte Square
* Christie, John, 19 Buckingham Terrace
Christie, Thomas B., M.D., F.R.C.P.E., Royal India Asylum, Ealing, London
* Chrystal, George, M.A., Professor of Mathematics in the University of Edinburgh, 5 Bel-
grave Crescent 80
* Clark, Robert, 7 Learmonth Terrace
* Clark, The Right Hon. Sir Thomas, Bart., Lord Provost of Edinburgh, 11 Melville Crescent
Cleghorn, Hugh F. C., of Stravithie, M.D., LL.D., F.L.S., St Andrews, United Service
Club, 13 Queen Street
* Clouston, T. S., M.D., F.R.C.P.E., Tipperlin House, Morningside
* Coats, Sir Peter, of Auchendrane, President of the Glasgow and West of Scotland Horti-
cultural Society, Auchendrane, Ayr 85
Connan, Daniel M., M.A., Education Department, Cape of Good Hope
* Constable, Archibald, 11 Thistle Street
Cowan, Charles, of Westerlea, Murrayfield
* Cox, Robert, of Gorgie, M.A., 34 Drumsheugh Gardens
* Craig, William, M.D., F.R.C.S.E., 7 Bruntsfield Place 90
* Croom, John Halliday, M.D., 25 Charlotte Square
* Crawford, Donald, M.A., Advocate, M.P., 18 Melville Street
* Cunningham, Daniel John, M.D., Professor of Anatomy in Trinity College, Dublin
* Cunningham, David, Memb. Inst. C.E., Dundee
* Cunningham, George Miller, 2 Ainslic Place 95
* Cunningham, J. T., B.A., 1 Walker Street
* Cunynghame, R. J. Blair, M.D., 6 Walker Street
Dalmahoy, James, 9 Forres Street
* Dalziel, John Grahame, 2 Melville Terrace, Pollokshields, Glasgow
* Daniell, Alfred, M.A., LL.B., D.Sc., Advocate, 3 Great King Street 100
'* Davidson, David, Somerset Lodge, Wimbledon Common, Wimbledon

658

Date of

Election.

1848
1884

1870

1876
1879
1869

1869

1884
1876
1869
1863
1885
1881
1867

1882
1866
1878
1880
1860
1863
1870
1876
1878
1859
1874

1869
1885
1875
1880
1855

1884
1863
1879

1878

1875
1866

|

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY.

Davidson, Henry, Muirhouse, Davidson’s Mains
Davy, Richard, M.B., F.R.C.S., Surgeon to the Westminster Hospital, 33 Welbeck Street,
Cavendish Square, London, W.
* Day, St John Vincent, C.E., 115 St Vincent Street, Glasgow, and 12 Rothesay Place,
Edinburgh
* Denny, Peter, Memb. Inst. C.E., Dumbarton 105
* Denny, William, Memb. Inst. C.E., Bellfield, Dumbarton
* Dewar, James, M.A., F.R.S., Jacksonian Professor of Natural and Experimental Philosophy
in the University of Cambridge, and Fullerian Professor of Chemistry at the Royal
Institution of Great Britain, London
* Dickson, Alexander, M.D., Professor of Botany in the University of Edinburgh,
11 Royal Cireus
* Dickson, Charles Scott, Advocate, 59 Northumberland Street é
* Dickson, J. D. Hamilton, M.A., Fellow and Tutor, St Peter’s College, Cambridge 110°
* Dickson, William, 38 York Place
* Dittmar, W., F.R.S., Professor of Chemistry, Anderson’s College, Glasgow
Dixon, J. M., Professor of English Literature in the University of Tokio, Japan
* Dobbin, Leonard, Ph.D., 4 Oxford Street
* Donaldson, J., M.A., LL.D., Principal of the United College of St Salvador and St Leonard,
St Andrews 115
* Dott, D. B., Memb. Pharm. Soc., 24 Castle Street
* Douglas, David, 22 Drummond Place
Drew, Samuel, M.D., D.Sc.. Chapelton, near Sheffield
* Drummond, Henry, F.G.S., Prof. of Natural History in the Free Church College, Glasgow
Dudgeon, Patrick, of Cargen, Dumfries, 27 Glencairn Crescent 120
Duncan, J. Matthews, M.A., M.D., F.R.C.P.E., LL.D., F.R.S., 71 Brook Street, London |
* Duncan, John, M.D., F.R.C.P.E., F.R.C.S.E., 8 Ainslie Place
* Duncan, James, of Benmore, Kilmun, 9 Mincing Lane, London, E.
* Duncanson, J. J. Kirk, M.D., F.R.C.P.E., 22 Drumsheugh Gardens
Duns, Rev. Professor, D.D., New College, Edinburgh, 14 Greenhill Place 125
* Durham, William, Seaforth House, Portobello

* Hider, George, Knock Castle, Wemyss Bay, Greenock
* Elgar, Francis, LL.D., The Admiralty, London
Elliot, Daniel G., New York
* Elliot, T. Armstrong, M.A., Fettes College 1
Etheridge, Robert, F.R.S., Assistant-Keeper of the Geological Department at the Briti
Museum of Natural History, 14 Carlyle Square, Chelsea, London
* Evans, William, F.F.A., 184 Morningside Park, Edinburgh
Everett, J. D., M.A., D.C.L., F.R.S., Professor of Natural Philosophy, Queen’s College, Be
* Ewart, James Cossar, M.D., F.R.C.S.E., Professor of Nat. Hist., University of Edinburgh,
3 Great Stuart Street
* Ewing, James Alfred, B.Sc., Professor of Engineering and Drawing in University Co
Dundee 135

Fairley, Thomas, Lecturer on Chemistry, 8 Newton Grove, Leeds
* Falshaw, Sir James, Bart., Assoc. Inst. C.E., 14 Belgrave Crescent

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY. 659

“Date of

Election.

1859 Fayrer, Sir Joseph, K.C.S.I1., M.D., F.R.C.P.L., F.R.C.S.L. and E., LL.D., F.R.S., Honorary
Physician to the Queen, 53 Wimpole Street, London, W.

1883 * Felkin, Robert W., M.D., F.R.G.S., Fellow of the Anthropological Society of Berlin,
20 Alva Street, Edinburgh

1868 * Ferguson, Robert M., Ph.D., 12 Moray Place 140

1874 * Ferouson, William, of Kinmundy, F.L.S., F.G.S., Deputy-Lieutenant of Aberdeenshire,
21 Manor Place, Edinburgh, and Kinmundy House, near Mintlaw

1886 Field, C. Leopold, F.C.S., Upper Marsh, Lambeth, London

1852 Fleming, Andrew, M.D., Deputy Surgeon-General, 3 Napier Road

1876 * Fleming, J. S., 16 Grosvenor Crescent

1880 * Flint, Robert, D.D., Corresponding Member of the Institute of France, Professor of Divinity
in the University of Edinburgh, Johnstone Lodge (Vicr-PresipEnt), 54 Craigmillar
Park 145

1872 *'Forbes, G., Professor, M.A., F.R.A.S., M.S.T.E. and E., 34 Great George Street, West-
minster

1859 Forlong, Major-Gen. J. G., F.R.G.S., R.A.S., Assoc. C.E., &., 11 Douglas Crescent

1828 Foster, John, Liverpool

1858 Fraser, A. Campbell, M.A., D.C.L., LL.D., Professor of Logic and Metaphysics in the

University of Edinburgh, 20 Chester Street
1867 |B. P. | * Fraser, Thomas R., M.D., F.R.C.P.E., F.R.S., Professor of Materia Medica in the University

of Edinburgh, 37 Melville Street 150
1885 * Fraser, A. Y., M.A., Secretary to the Mathematical Society of Edinb., 8 Chalmers Street
1867 Gayner, Charles, M.D., Oxford

1880 | P. |* Geddes, Patrick, Assistant to the Professor of Botany in the University of Edinburgh,
and Lecturer on Zoology at Minto House, 814 Princes Street

1861 |B. P.| Geikie, Archibald, LL.D., F.R.S., F.G.S., Director of the Geological Surveys of Great
Britain, and Head of the Geological Museum, 28 Jermyn Street, London

1871 |B. P.| * Geikie, James, LL.D., F.R.S., F.G.S., Professor of Geology in the University of Edinburgh,

10 Bright Crescent, Newington 155

1886 * Gibson, Alexander, Advocate, 12 Great King Street

1881 * Gibson, G. A., D.Sc, M.B., F.R.C.P.E., F.G.S., 1 Randolph Cliff

1877 * Gibson, John, Ph.D., 20 Warrender Park Crescent

1885 | P. |* Gibson, R. J. Harvey, M.A., Demonstrator of Zoology in University College, Liverpool

1870 * Gifford, Hon. Lord, late one of the Senators of the College of Justice, Granton House 160

1879 * Gilray, Thomas, M.A.. Professor of English Language and Literature and Modern History
in University College, Dundee

1880 * Gilruth, George Ritchie, Surgeon, 67 York Place

1850 Gosset, Major-General W. D., R.E., 70 Edith Road, West Kensington, London

1867 * Graham, Andrew, M.D., R.N., Army and Navy Club, 36 Pall Mall, London, S.W.

1880 * Graham, James, 195 Bath Street, Glasgow 165

1851 Grant, The Rev. James, D.D., D.C.L., 15 Palmerston Place

1883 * Gray, Andrew, M.A., Professor of Physics in University College, Bangor, North Wales

1875 * Gray, Robert, Secretary to the Royal Physical Society, Bank of Scotland House

SSO! | Ps Gray, Thomas, B.Sc., 17 Hayburn Crescent, Partick Hill, Glasgow

1886 * Greenfield, W. S., M.D., Professor of General Pathology in the University of Edinburgh,
7 Heriot Row 170

1872 * Grieve, David, Lockharton Gardens, Colinton Road, Slateford

660 ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY.

Date of

Klection.

1884
1886

1883

1886
1867
1867

1881

1876
1886
1869
1877

1870
1880

1875

1870
1862

1876

1884
1881
1871
1859
1879
1885

1828
1879
1881
1883
1886
1872

1864

1855

1882
1874

1886

IN. 22:

* Grieve, John, M.A., M.D., F.L.S., 212 St Vincent Street, Glasgow
* Griffiths, Arthur Bower, Ph.D., Principal and Lecturer on Chemistry in the School of Science
of the City and County of Leicester, 15 Broadgate, Lincoln
Gunning, R. H., M.D., 30 Hazlitt Road, West Kensington Park, London

* Haddington, The Right Hon. the Earl of, Tyninghame House, Haddington 175
* Haldane, D. R., M.D., F.R.C.P.E., 22 Charlotte Square
* Hallen, James H. B., F.R.C.S.E., F.R.P.S.E., Inspecting Veterinary Surgeon in H.M.
Indian Army, 1 Lauriston Gardens
* Hamilton, D. J., M.B., F.R.C.S.E., Professor of Pathological Anatomy in the University
of Aberdeen, 1a Albyn Place, Aberdeen
* Hannay, J. Ballantyne, Cove Castle, Loch Long, N.B.
* Hare, Arthur W., M.B., C.M., 21 Ainslie Place 180
Hartley, Sir Chaves A., K.C.M.G., Memb. Inst. C.E., 26 Pall Mall, London
Hartley, Walter Noel, Fr R.S., Lhe: of Coe Royal College of Science for Irelenil
Dublin
* Harvey, Thomas, M.A., LL.D., Rector of the Edinburgh Academy, 32 George Square
* Haycraft, J. Berry, M.B., B.Sc., Professor of Physiology in Sir Josiah Mason’s Science College,

Birmingham
Hawkshaw, Sir John, Memb. Inst. C.E., FERS, F.G.S., 33 Great George Street,
Westminster Te

Heathfield, W. E., F.C.S., 1 Powis Grove, Brighton
Hector, James, C.M.G., M.D., F.R.S., Director of the Geological Survey, Wellington,
New Zealand

.|* Heddle, M. Forster, M.D., Emeritus Professor of Chemistry in the University of St

Andrews
* Henderson, John, jun., 4 Crown Terrace, Dowanhill, Glasgow
* Herdman, W. A., D.Sc., Professor of Natural History in University College, Liverpool 190
Higgins, Charles Hayes, LL.D., Alfred House, Birkenhead
Hills, John, Lieut.-Colonel, Bombay Engineers, C.B., United Service Club, London
Hislop, John, Secretary to the Department of Education, Wellington, New Zealand
Hodgkinson, W. R., Ph.D., Professor of Chemistry, South Kensington Museum, 29 Pem=
broke Square, London
Home, David Milne, of Milne Graden, LL.D., F.G.S. (Vicu-PrusipEent), 10 York Place 195
* Hood, Thomas H. Cockburn, F.G.S., Walton Hall, Kelso

* Horne, John, F.G.8., Geological Survey of Scotland, 41 Southside Road, Inverness
* Hoyle, William Evans, M.A., M.R.C.S., Office of Challenger Commission, 32 Queen Street
Hunt, Rev. H. G. Bonavia, Mus. B. Oxon., F.R.A.S., F.L.S., La Belle Sauvage, London
* Hunter, Major Charles, Plis Céch, Llanfair, Anglesea, and 17 St George’s Square, London,
S.W. 200
* Hutchison, Robert (Carlowrie Castle), and 29 Chester Street

Inglis, Right Hon. John, LL.D., D.C.L., Lord Justice-General of Scotland, and Chancellor
of the University of Edinburgh, 30 Abercromby Place
* Inglis, J. W., Memb. Inst. C.E., Myrtle Bank, Trinity
* Irvine, Alex. Forbes, of Drum, Advocate, Sheriff of Argyll (Vicu-PrusipEnt), 25 Castle —
| Terrace -

‘* Irvine, Robert, Granton, Edinburgh 205

Date of
Election,

1875

1882 |

1860
1880
1865
1869
1867
1874
1877

1866
1886
1877
1880
1883
1878

1875
1880

1875
1886
1878
1885
1870

1881
1872
1872

1882 |

1883
1863
1858
1874
1870

1882
1861

1884
1849
1886

1855

1885
1883

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY. 661

i. P.

Jack, William, M,A., Professor of Mathematics in the University of Glasgow

* Jamieson, A., Assoc. Memb. Inst. C.E., Principal of College of Science and Arts, Glasgow
Jamieson, George A., 24 St Andrew Square
Japp, A. H., LL.D., The Limes, Elmstead, near Colchester

* Jenner, Charles, Easter Duddingston Lodge 210
Johnston, John Wilson, M.D., Surgeon-Major, 11 Windsor Street

* Johnston, T. B., F.R.G.S., Geographer to the Queen, 9 Claremont Crescent
Jones, Francis, Lecturer on Chemistry, Monton Place, Manchester

* Jolly, William, H.M. Inspector of Schools, F.G.S., Ardgowan, Pollokshields

* Keiller, Alexander, M.D., F.R.C.P.E., LL.D., 21 Queen Street 215

* Kidston, Robert, F.G.S., 24 Victoria Place, Stirling

* King, James, of Campsie, LL.D., 12 Claremont Terrace, Glasgow

* King, W. F., Lonend, Trinity

* Kinnear, The Hon. Lord, one of the Senators of the College of Justice, 2 Moray Place

* Kintore, The Right Hon. the Earl of, M.A. Cantab., Keith Hall, Inglismaldie Castle,
Laurencekirk, N.B. 220

* Kirkwood, Anderson, LL.D., 7 Melville Terrace, Stirling

* Knott, C. G., D.Se., Prof. of Natural Philosophy in the Imperial University of Tokio, Japan

* L’Amy, John Ramsay, of Dunkenny, Forfarshire, 107 Cromwell Road, London, 8, W.
* Laing, Rev. George, 17 Buckingham Terrace

| * Lang, P. R. Scott, M.A., B.Sc., Professor of Mathematics in the University of St Andrews 225

* Laurie, A. P., B.A., B.Sc., Nairn Lodge, Duddingston, Edinburgh
* Laurie, Simon §., M.A., Professor of Education in the University of Edinburgh, Nairn
Lodge, Duddingston
* Lawson, Robert, M.D., Deputy-Commissioner in Lunacy, 24 Mayfield Terrace
* Lee, Alexander H., C.E., Blairhoyle, Stirling
* Lee, The Hon. Lord, one of the Senators of the College of Justice, Duddingstone House,
Edinburgh 230
* Leslie, Alexander, Memb. Inst. C.E., 12 Greenhill Terrace
* Leslie George, M.B., C.M., Old Manse, Falkirk
* Leslie, Hon. G. Waldegrave, Leslie House, Leslie
Leslie, James, Memb. Inst. C.E., 2 Charlotte Square
* Letts, EK. A., Ph.D., F.LC., F.C.S., Professor of Chemistry, Queen’s College, Belfast 235
* Lister, Sir Joseph, Bart., M.D., F.R.C.S.L., F.R.C.S.E., LL.D., D.C.L., F.R.S., Professor of
Clinical Surgery, King’s College, Surgeon Extraordinary to the Queen, 12 Park Crescent,
Portland Place, London, N.W.
* Livingston, Josiah, 4 Minto Street
Lorimer, James, M.A., Advocate, Professor of Public Law in the University of Edinburgh,
1 Bruntsfield Crescent
* Low, George M., Actuary, 19 Learmonth Terrace
Lowe, W. H., M.D., F.R.C.P.E., Woodcote, Inner Park, Wimbledon 240
Lyster, George Fosbery, Memb. Inst. C.E., Gisburn House, Liverpool

Macadam, Stevenson, Ph.D., Lecturer on Chemistry, Surgeons’ Hall, Edinburgh, 11 East
Brighton Crescent, Portobello
* M‘Bride, Charles, M.D., Wigtown
* M‘Bride, P., M.D., F.R.C.P.E., 16 Chester Street

662 ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY.

Date of |
Election.

1867
1886

1886
1847
1878
1878

1885
1877
1878
1886
1880

1879
1869

1882
1873

1840
1843

1853
1869
1864
1869

1870

1876
1883
1872
1876
1884
1883 |
1858
1880
1882

1869
1864
1866

1885

1883

pe

£

* M‘Candlish, John M., W.S., 27 Drumsheugh Gardens 245
* Macdonald, The Right Hon. J. H. A., CB, Q.C., M.P., LL.D.,.M.S,T.E, and E., Lord
Advocate of Scotland, 15 Abercromby Place
* Macdonald, William J., M.A., 4 Polwarth Gardens
Macdonald, W. Macdonald, of St Martin’s, Perth
* MacDougall, Alan, M.1.C.E., Mail Building, 52 King Street West, Toronto,’Canada
Macfarlane, Alex., M.A., D.Sc., Professor of Physics in the University of the State of Texas,
Austin, Texas 250
* Macfarlane, J. M., D.Se., 15 Scotland Street
* Macfie, Robert A., Dreghorn Castle, Colinton
* M‘Gowan, George, F.I.C., Ph.D., University College of North Wales, Bangor
* MacGregor, Rev. J., D.D., 11 Cumin Place, Grange
MacGregor, J. Gordon, M.A., D.Sc., Professor of Physics in Dalhousie College, Halifax,
Nova Scotia 255
* M‘Grigor, Alexander Bennett, LL.D., 19 Woodside Terrace, Glasgow
* M‘Intosh, William Carmichael, M.D., LL.D., F.R.S., F.L.S., Professor of Natural History
in the University of St Andrews, 2 Abbotsford Crescent, St Andrews
* Mackay, John Sturgeon, M.A., Mathematical Master in the Edinburgh Academy, 69
Northumberland Street
* M‘Kendrick, John G., M.D., F.R.C.P.E., F.R.S., Professor of the Institutes of Medicine
in the University of Glasgow
Mackenzie, John, New Club, Princes Street 260
Maclagan, Sir Douglas, M.D., President of the Royal College of Physicians, Edinburgh,
and F.R.C.S.E., Professor of Medical Jurisprudence in the University of Edinburgh
(Vicz-PresipEnT), 28 Heriot Row
Maclagan, General R., Royal Engineers, 86 Lexham Gardens, London, W.
* Maclagan, R. Craig, M.D., 5 Coates Crescent
* M‘Lagan, Peter, of Pumpherston, M.P., Clifton Hall, Ratho
* M‘Laren, The Hon. Lord, LL.D. Edin. and Glase., F.R.A.S., one of the Senators of the
College of Justice (VicE-PREsIDENT), 46 Moray Place 265
* Macleod, Geo. H. B., M.D., F.R.C.S.E., Regius Prof. of Surgery in the University of Glas-
gow, and Surgeon in Ordinary to the Queen in Scotland, 10 Woodside Crescent, Glasgow
* Macleod, Rev. Norman, D.D., 7 Royal Circus
* Macleod, W. Bowman, L.D.S., 16 George Square
* Macmillan, Rev. Hugh, D.D., LL.D., Seafield, Greenock
**« Macmillan, John, M.A., B.Se., Mathematical Master, Perth Academy 270
* Macpherson, Rey. J. Gordon, M.A., D.Sc., Ruthven Manse, Meigle
* M‘Roberts, George, F.C.S., Ardeer, Stevenston, Ayrshire
Malcolm, R. B., M.D., F.R.C.P.E., 126 George Street
Marsden, R. Sydney, M.B., C.M., D.Sc. F.L.C., F.C.S., Rillington, near York.
Marshall, D. H., M.A., Professor of Physics in Queen’s University and College, Kingston,
Ontario, Canada 275
Marshall, Henry, M.D., Clifton, Bristol
* Marwick, James David, LL.D., Town-Clerk, Glasgow
* Masson, David, LL.D,, Professor of Rhetoric and English Literature in the University of
Edinburgh, 58 Great King Street
* Masson, Orme, D Sc., Professor of Chemistry in the University of Melbourne
* Matthews, James Duncan, Springhill, Aberdeen 280

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY. 663

Date of

Election.

1885 * Mill, Hugh Robt., D.Se., F.C.8., Scottish Marine Station, Granton, 3 Glenorchy Terrace,
Edinburgh

1886 * Miller, Hugh, H.M. Geological Survey, 51 Lauriston Place

1852 Miller, Thomas, M.A., LL.D., Emeritus Rector of Perth Academy, Inchbank House, Perth

1885 * Miller, William, 8.S.C., 59 George Square

1833 Milne, Admiral Sir Alexander, Bart., G.C.B., Inveresk 285

1886 * Milne, William, M.A., B.Sc., Mathematical and Science Teacher, High School, Glasgow

1866 * Mitchell, Arthur, C.B., M.A., M.D., LL.D., Commissioner in Lunacy, 34 Drummond Place

1865 * Moir, John J. A., M.D., F.R.C.P.E., 52 Castle Street

1870 * Moncreiff, The Right Hon. Lord, of Tullibole, Lord Justice-Clerk, LL.D. (Honorary Vics-
PRESIDENT), 15 Great Stuart Street

1871 * Moncrieff, Rev. Canon William Scott, of Fossaway, Christ’s Church Vicarage, Bishop-Wear-
mouth, Sunderland 290

1868 * Montgomery, Very Rev. Dean, M.A., D.D., 17 Atholl Crescent

1879 * Morrison, J. B. Brown, of Finderlie and Murie, The Old House, Harrow-on-the-Hill

1877 | P. |* Morrison, Robert Milner, D.Sc., F.1.C., Nether Liberton House

1873 * Muir, M. M. Pattison, Preelector on Chemistry, Caius College, Cambridge

1874 | K.P.|* Muir, Thomas, M.A., LL.D., Mathematical Master, High School, Glasgow, Beechcroft,
Bishopton, Glasgow 295

1870 * Munn, David, M.A., Mathematical Master, Royal High School

1857 Murray, John Ivor, M.D., F.R.C.S.E., M.R.C.P.E., 24 Huntriss Row, Scarborough

1877 | N.P.| * Murray, John, Ph.D., Director of the Challenger Expedition Commission, 32 Queen Street,
and United Service Club (Vice-PRESIDENT)

1884 Mylne, R. W., C.E., F.R.S., 7 Whitehall Place, London, S.W.

1877 * Napier, John, 23 Portman Square, London 300°

1866 * Nelson, Thomas, St Leonard’s, Dalkeith Road

1883 * Newcombe, Henry, F.R.C.S.E., 5 Dalrymple Crescent, Edinburgh

1884 * Nicholson, J. Shield, Professor of Political Economy in the University of Edinburgh

; Eden Lodge, Eden Lane, Newbattle Terrace

1880 | p, |* Nicol, W. W. J., M.A., B.Sc, Lecturer on Chemistry, Sir Josiah Mason’s College,
Birmingham

1878 Norris, Richard, M.D., Professor of Physiology, Queen’s College, Birmingham 305

1886 Oliver, James, M.B. Edin., M.R.C.P. Lond., Montague Street, Russell Square, London

1884 * Omond, Robert Traill, Superintendent of Ben Nevis Observatory, Fort-William, Inverness

1877 Panton, George A., 95 Colmore Row, Birmingham

1886 * Paton, D. Noel, M.D., B.Sc., 4 Walker Street

1881 | N.P.|* Peach, B. N., F.G.S., Acting Paleontologist of the Geological Survey of Scotland,
8 Annandale Street 310

1863 * Peddie, Alexander, M.D., F.R.C.P.E., 15 Rutland Street

1886 * Peebles, D. Bruce, Tay House, Bonnington, Edinburgh

1869 Pender, John, 18 Arlington Street, Piccadilly, London

1883 Phillips, Charles D. F., M.D., 10 Henrietta Street, Cavendish Square, London, W.

1859 | P. Playfair, The Right Hon. Sir Lyon, C.B., LL.D., F.R.S., M.P., 68 Onslow Gardens,
London 315

1877 Pole, William, Memb. Inst. C.E., F.R.S., Mus. Doc., 31 Parliament Street, Westminster, S.W.
VOL. XXXII. PART IV. dU

664 ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY.

Date of
Etection.

1886
1874
1852
1880
1875
1849
1885
1882
1885
1880

1884

1882
1885
1869
1883
1875
1872

1883
1877

1880
1872

1859
1886
1877
1881
1862
1881
1880

1852
1880
1869

1863
1864
1849

1846 |

1885
1880

1875

|B. P.

* Pollock, Charles Frederick, M.D., F.R.C.S.E., 1 Buckingham Terrace, Hillhead, Glasgow
Powell, Baden Henry Baden-, Forest Department, India
Powell, Eyre B., C.S.L, M.A., 28 Park Road, Haverstock Hill, Hampstead, London
* Prentice, Charles, C.A., Actuary, 8 St Bernard’s Crescent 320
Prevost, E. W., Ph.D., Ellesmere, Salop
Primrose, Hon. B. F., C.B., 22 Moray Place
* Pringle, James, Provost of Leith, 7 Claremont Park, Leith
* Pryde, David, M.A., LL.D., Head Master of the Ladies’ College, 19 Fettes Row, Edinburgh
* Pullar, J. F., Rosebank, Perth 325 ©
* Pullar, Robert, Tayside, Perth

Ramsay, E. Peirson, F.LS., F.R.G.S., F.G.S., Curator of Australian Museum, Sydney,
New South Wales
* Rattray, James Clerk, M.D., 61 Grange Loan
* Rattray, John, M.A., B.Sc., 15 Scotland Street
Raven, Rev. Thomas Milville, M.A., The Vicarage, Crakehall, Bedale 330
* Readman, J. B., 9 Moray Place
* Richardson, Ralph, W.S., 10 Magdala Place
Ricarde-Seaver, Major F. Ignacio, Conservative Club, St James’ Street, London, S.W.,
and 2 Rue Lafitte, Boulevard des Italiens, Paris
* Ritchie, R. Peel, M.D., F.R.C.P.E., 1 Melville Crescent
* Roberton, James, LL.D., Professor of Conveyancing in the University of Glasgow, 1 Park
Terrace East, Glasgow 335
Roberts, D. Lloyd, M.D., F.R.C.P.L., 23 St John Street, Manchester
* Robertson D. M. C. L. Argyll, M.D., F.R.C.8.E., Surgeon Oculist to the Queen for Scot-
land, and President of the Royal College of Surgeons, 18 Charlotte Square
Robertson, George, Memb. Inst. C.E., Atheneum Club, Pall Mall, London
* Robertson, J. P. B., Q.C., M.P., 19 Drumsheugh Gardens
* Robinson, George Carr, F.1I.C., Lecturer on Chemistry in the Royal Institution, Hull 340

* Rogerson, John Johnston, B.A., LL.B., Merchiston Castle Academy
Ronalds, Edmund, LL.D., Bonnington House, Bonnington Road
Rosebery, The Right Hon. the Earl of, LL.D., Dalmeny
Rowland, L. L., M.A., M.D., President of the Oregon State Medical Society, and Professor
of Physiology and Microscopy in Williamette University, Salem, Oregon
Russell, Alexander James, C.S., 9 Shandwick Place 345
* Russell, J. A., M.A., B.Sc,, M.B., F.R.C.P.E., Woodville, Canaan Lane
* Rutherford, Wm., M.D., F.R.C.P.E., F.R.S., Professor of the Institutes of Medicine in
the University of Edinburgh, 14 Douglas Crescent

* Sanderson, James, Deputy Inspector-General of Hospitals, F.R.C.S.E., 8 Manor Place
Sandford, The Right Rev. D. F., LL.D., Bishop of Tasmania
Sang, Edward, C.E., LL.D., Secretary to the Royal Scottish Society of Arts, 31 Mayfield
Road 350

Schmitz, Leonard, LL.D., 81 Linden Gardens, London, W.
Scott, Alexander, M.A., D.Sc., 4 North Bailey, Durham
Scott, J. H., M.B., C.M., M.R.C.S., Professor of Anatomy in the University of Otago,

New Zealand

| Scott, Michael, Memb. Inst. C.E., 22 Mount Ephraim, Tunbridge Wells 7

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY. 665

Date of
Election.

1864

1872
1872
1870
1871

1859

1876
1868
1882
1885
1883
1871
1855
1886
1871
- 1880
1846

1880

1882
1874
1850
1885
1886
1884
1877
1868
1848
1868
1878
1866

1873
1848
1877

1823
1870
1848

1844
1875
1885

* Sellar, W. Y., M.A., LL.D., Professor of Humanity in the University of Edinburgh,
15 Buckingham Terrace 355
* Seton, George, M.A., Advocate, 42 Greenhill Gardens
* Sibbald, John, M.D., Commissioner in Lunacy, 3 St Margaret’s Road, Whitehouse Loan
* Sime, James, M.A., South Park, Fountainhall Road
* Simpson, A. R., M.D., F.R.C.P.E., Professor of Midwifery in the University of Edinburgh,
52 Queen Street
Skene, Wm. F., W.S., LL.D., D.C.L., Historiographer-Royal for Scotland, 27 Inver-
leith Row 360
* Skinner, William, W.S., Town-Clerk of Edinburgh, 35 George Square
* Smith, Adam Gillies, C.A. (TREASURER), 64 Princes Street
Smith, C. Michie, B.Se., Professor of Physical Science, Christian College, Madras, India
* Smith, George, F.C.8., Polmont Station, N.B.
Smith, James Greig, M.A., M.B., 16 Victoria Square, Clifton 365
* Smith, John, M.D., LL.D., F.R.C.S.E., 11 Wemyss Place
Smith, Robert Mackay, 4 Bellevue Crescent
* Smith, Colonel R. Murdoch, R.E., Director of Museum of Science and Art, Edinburgh
* Smith, Rev. W. Robertson, M.A., LL.D., Librarian to the University of Cambridge
Smith, W. Robert, M.D., 74 Great Russell Street, Bloomsbury Square, London 370
Smyth, Piazzi, Professor of Practical Astronomy in the University of Edinburgh, and
Astronomer-Royal for Scotland, 15 Royal Terrace
Sollas, W. J., M.A., D.Se., late Fellow of St John’s College, Cambridge, and Professor of
Geology and Mineralogy in the University of Dublin, 4 Clyde Road, Dublin
* Sorley, James, F.F.A., C.A., 2 Dean Park Crescent
* Sprague, T. B., M.A., 29 Buckingham Terrace
Stark, James, M.D., F.R.C.P.E., of Huntfield, Underwood, Bridge of Allan 375
* Steggall, J. E. A., Prof. of Mathematics and Natural Philosophy in University Coll., Dundee
* Stevenson, C. A., B.Sc., C.E., 45 Melville Street
* Stevenson, David Alan, B.Sc., C.E., 45 Melville Street
* Stevenson, James, F.R.G.S., 4 Woodside Crescent, Glasgow
Stevenson, John J., Red House, Bayswater Hill, London, W. 380
Stevenson, Thomas, Memb. Inst. C.E., F.G.S. (Honorary Vice-PRESIDENT), 84 George Street
Stewart, Colonel J. H. M. Shaw, Royal Engineers, Madras
* Stewart, James R., M.A., 10 Salisbury Road
* Stewart, T. Grainger, M.D., F.R.C.P.E., Professor of the Practice of Physic in the
University of Edinburgh, 19 Charlotte Square
* Stewart, Walter, 22 Torphichen Street 385
Stirling, Patrick J., LL.D., Kippendavie House, Dunblane
* Stirling, William, Sc.D., M.D., Brackenbury Professor of Physiology and Histology in
Owens College and Victoria University, Manchester
Stuart, Captain T. D., H.M.LS.
* Swan, Patrick Don, Provost of Kirkcaldy
Swan, Wm., LL.D., Emeritus Professor of Natural Philosophy in the University of St
Andrews, President of the Royal Scottish Society of Arts, Ardchapel, Helensburgh 390
Swinton, A. Campbell, of Kimmerghame, LL.D., Duns
Syme, James, 9 Drumsheugh Gardens
* Symington, Johnson, M.B., F.R.C.S.E., 2 Greenhill Park

666 ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY.

Date of
Election.

1872
1861

1870
1872
1873
1885
1884

1870
1875

1880
1863
1870
1847

1882

1870
1876
1878
1874

1874
1879
1861

1877

1875

1867
1873
1886
1864
1883
1870
1866
1866
1862
1873
1840
1882
1876
1881 |

ROE

K.P.

NEE.

Die

Tait, the Rev. A., D.D., LL.D.,Canon of Tuam, Moylough Rectory, Ballinasloe, Ireland
Tait, P. Guthrie, M.A., Professor of Natural Philosophy in the University of Edinburgh —
(GENERAL SECRETARY), 38 George Square 395
* Tatlock, Robert R., City Analyst's Office, 138 Bath Street, Glasgow
* Teape, Rev. Charles R., M.A., Ph.D., 15 Findhorn Place
* Tennent, Robert, 23 Buckingham Terrace
* Thompson, D’Arcy W., Professor of Natural History in University College, Dundee
* Thoms, George Hunter, of Aberlemno, Advocate, Sheriff of the Counties of Orkney and
Zetland, 13 Charlotte Square 400
* Thomson, Rev. Andrew, D.D., 63 Northumberland Street
* Thomson, James, LL.D., F.R.S., Professor of Engineering in the University of Glasgow,
2 Florentine Gardens, Hillhead, Glasgow
Thomson, John Millar, King’s College, London :
* Thomson, Murray, M.D., Professor of Chemistry, Thomason College, Ltoorkee, India ;
* Thomson, Spencer C., Actuary, 10 Chester Street 405
Thomson, Sir William, LL.D., D.C.L., F.R.S. (Presipnnt), Regius Professor of Natural
Philosophy in the University of Glasgow, Foreign Associate of Institute of Franee,
and Member of the Prussian Order Pour le Mérite :
Thomson, William, M.A., B.Sc., Professor of Mathematics in University College, Stellen-
bosch, Cape Colony
* Thomson, Wm. Burns, F.R.C.P.E., F.R.C.S.E., 110 Newington Green Road, London, N.
Thomson, William, Royal Institution, Manchester
Thorburn, Robert Macfie, Uddevalla, Sweden 410
* Traquair, R. H., M.D., F.R.S., F.GS., Keeper of the Natural History Collections in the
Museum of Science and Art, Edinburgh, 8 Dean Park Crescent
* Tuke, J. Batty, M.D., F.R.C.P.E., 20 Charlotte Square
* Turnbull, John, of Abbey St Bathans, W.S., 49 George Square
Turner, Sir William, M.B., F.R.C.S.E., F.R.S., Professor of Anatomy in the University
of Edinburgh, and President of the Royal Physical Society (SzcrErary), 6 Eton Terrace

* Underhill, Charles E., B.A., M.B., F.R.C.P.E., F.R.C.S.E., 8 Coates Crescent 415
Vincent, Charles Wilson, Royal Institution, Albemarle Street, London

* Waddell, Peter, 5 Claremont Park, Leith
* Walker, Robert, M.A., University, Aberdeen
* Wallace, Robert, Professor of Agriculture and Rural Economy in the University of Edin.
* Wallace, William, Ph.D., City Analyst’s Office, 138 Bath Street, Glasgow 420
* Watson, Charles, Redhall, Slateford ;
* Watson, James, C.A., 45 Charlotte Square
* Watson, John K., 14 Blackford Road
* Watson, Patrick Heron, M.D., F.R.C.P.E., F.R.C.S.E., LL.D., 16 Charlotte Square
Watson, Rev. Robert Boog, B.A., Free Church Manse, Cardross, Dumbartonshire 425
Welsh, David, Major-General (Retired), R.A., 1 Barton Terrace, Dawlish
Welwood, Allan A. Maconochie, LL.D., of Meadowbank and Garvoch, Kirknewton
* Wenley, James A., Treasurer of the Bank of Scotland, 5 Drumsheugh Gardens
White, Rev. Francis Le Grix, M.A., F.G.S., Leaming-on-Ulleswater, Penrith
Whitehead, Walter, F.R.C.S.E., 202 Oxford Road, Manchester 430

ALPHABETICAL LIST OF THE ORDINARY FELLOWS OF THE SOCIETY. 667

Date of

Election.

1883 Wickham, R. H. B., F.R.C.S.E., Borough Lunatic Asylum, Newcastle-on-Tyne

1879 * Will, John Charles Ogilvie, M.D., 305 Union Street, Aberdeen

1868 * Williams, W., Principal and Professor of Veterinary Medicine and Surgery, New Veterinary
College, Leith Walk

1879 * Wilson, Andrew, Ph.D., Lecturer on Zoology and Comparative Anatomy in the Edinburgh
Medical School, 118 Gilmore Place :

1877 * Wilson, Charles E., M.A., LL.D., H.M. Senior Inspector of Schools for Scotland,
19 Palmerston Place 435

1878 * Wilson, Rev. John, M.A., Bannockburn Academy

1875 Wilson, Daniel, LL.D., President of the University of Toronto, and Professor of English
Literature in that University

1882 Wilson, George, M.A., M.D., 23 Claremont Road, Leamington

1834 Wilson, Isaac, M.D.

1847 Wilson, John, LL.D., Emeritus Professor of Agriculture in the University of Edinburgh 440

1870 Winzer, John, Chief Surveyor, Civil Service, Ceylon, 7 Dryden Place, Newington

1880 * Wise, Thos. Alex., M.D., F.R.C.P.E., F.R.A.S., Thornton, the Beulah, Upper Norwood

1886 * Woodhead, German Sims, M.D., 6 Marchhall Crescent

1884 Woods, G. A., M.R.C.S., Carlton House, 57 Houghton Street, Southport

1864 * Wyld, Robert S., LL.D , 19 Inverleith Row 445

1882 * Young, Andrew, 22 Elm Row

1882 * Young, Frank W., F.C.S., Lecturer on Natural Science, High School, Dundee, Woodmuir

Park, West Newport, Fife
1882 * Young, Thomas Graham, Durris, Aberdeenshire 448

668 APPENDIX—LIST OF HONORARY FELLOWS.

LIST OF HONORARY CEE LORS

AT NOVEMBER 1884.

His Royal Highness The PRINCE OF WEES.

FOREIGNERS (LIMITED TO THIRTY-SIX BY LAW X.).

Elected.

1884 Pierre J. van Beneden,
1864 Robert Wilhelm Bunsen,
1867 Michel Eugéne Chevreul,
1858 James D. Dana,

1877 Alphonse de Candolle,
1883 Luigi Cremona,

1879 Franz Cornelius Donders,
1877 Carl Gegenbaur,

1879 Asa Gray,

1883 Julius Hann,

1884 Charles Hermite,

Louvain.
Heidelberg.

Paris.

New Haven, Conn.
Geneva.

Rome.

Utrecht.
Heidelberg.
Harvard University.
Vienna.

Paris.

1864 Hermann Ludwig Ferdinand von Helmholtz, Berlin.

1879 Jules Janssen,

1875 August Kekulé,

1868 Gustav Robert Kirchhoff,
1875 Hermann Kolbe,

1864 Albert Kolliker,

1875 Ernst Eduard Kummer,
1876 Ferdinand de Lesseps,
1864 Rudolph Leuckart,

1881 Seven Lovén,

1876 Carl Ludwig,

1878 J. N. Madvig,

1855 Henry Milne-Edwards,
1864 Theodore Mommsen,
1881 Simon Newcomb,

1874 Louis Pasteur, |

1864 Carl Theodor von Siebold,

1881 Johannes Japetus Smith Steenstrup,

1878 Otto Wilhelm Struve,
1855 Bernard Studer,

1874 Otto Torell,

1868 Rudolph Virchow,

1874 Wilhelm Eduard Weber,

Total, 34.

Paris.
Bonn.
Berlin.
Leipzig.
Wurzburg.
Berlin.
Paris.
Leipzig.
Stockholm.
Leipzug.
Copenhagen.
Paris.
Berlin.
Washington.
Paris.
Munich.
Copenhagen.
Pulkowa.
Bern.

Lund,
Berlin.
Gottingen.

APPENDIX——-LIST OF HONORARY FELLOWS. 669

BRITISH SUBJECTS (LIMITED TO TWENTY BY LAW Xa):
Elected.
1849 John Couch Adams, LL.D., F.R.S., Corresp. Mem. Inst. France, Cambridge.

1835 Sir George Biddell Airy, K.C.B., M.A., LL.D., D.C.L., F.R.S.,

Foreign Associate Inst, France, Greenwich.
1870 Thomas Andrews, M.D., LL.D., F.R.S., Belfast.
1865 Arthur Cayley, LL.D., D.C.L., F.R.S., Corresp. Mem. Inst. France, Cambridge.
1884 Edward Frankland, D.C.L., LL.D., F.R.S., London.
1874 John Anthony Froude, LL.D., London.
1881 The Hon. Justice Sir William Robert Grove, M.A., LL.D.,

DCs EERSS:, London.

1883 Sir Joseph Dalton Hooker, K.C.S.I., C.B., M.D., D.C.L., LL.D.,
F.R.S., F.G.S., Corresp. Mem. Inst. France, Director of the

Royal Gardens, Kew, London.
1884 William Huggins, LL.D., D.C.L., F.R.S., London.
1876 Thomas Henry Huxley, LL.D., D.C.L., P.R.S., F.LS., F.LS.,

F.G.S., Corresp. Mem. Inst. France, London.
1867 James Prescott Joule, LL.D., D.C.L., F.R.S., Corresp. Mem. Inst.

France, Manchester.
1845 Sir Richard Owen, K.C.B., M.D., LL.D., D.C.L., F.R.S., Foreign

Associate Inst, France, London.
1881 The Rev. George Salmon, D.D., LL.D., D.C.L., F.R.S., Foreign

Associate of the Institute of France, Dublin.
1884 J. S. Burdon Sanderson, M.D., LL.D., F.R.S., Oxford.
1878 Balfour Stewart, M.A., LL.D., F.R.S., Manchester.
1864 George Gabriel Stokes, M.A., LL.D., D:C.L., Sec. R.S., Corresp.

Mem. Inst. France, Cambridge.
1874 James Joseph Sylvester, M.A., LL.D., F.R.S., Corresp. Mem.

Inst. France, Oxford.
1864 The Right Hon. Lord Tennyson, D.C.L., LL.D., F.R.S., Poet

Laureate, Isle of Wight.
1883 Alexander William Williamson, LL.D., F.R.S., V.P.C.S., Corresp.

Mem. Inst. France, London.

1883 Colonel Henry Yule, C.B., LL.D., Member of the Council of India, London.
Total, 20.

670 APPENDIX—LIST OF HONORARY FELLOWS.

LIST OF HONORARY FELLOWS

AT NOVEMBER 1885.

His Royal Highness The PrINcE oF WALES.

FOREIGNERS (LIMITED TO THIRTY-SIX BY LAW X,),

Elected.

1884 Pierre J. van Beneden,
1864 Robert Wilhelm Bunsen,
1867 Michel Eugéne Chevreul,
1858 James D. Dana,

1877 Alphonse De Candolle,
1883 Luigi Cremona,

1879 Franz Cornelius Donders,
1877 Carl Gegenbaur,

1879 Asa Gray,

1883 Julius Hann,

1884 Charles Hermite,

1864 Hermann Ludwig Ferdinand von Helmholtz,

1879 Jules Janssen,

1875 August Kekulé,

1868 Gustav Robert Kirchhoff,
1875 Hermann Kolbe,

1864 Albert Kolliker,

1875 Ernst Eduard Kummer,
1876 Ferdinand de Lesseps,
1864 Rudolph Leuckart,

1881 Sven Lovén,

1876 Carl Ludwig,

1878 J. N. Madvig,

1864 Theodore Mommsen,
1881 Simon Newcomb,

1874 Louis Pasteur,

1881 Johannes Iapetus Smith Steenstrup,
1878 Otto Wilhelm Struve,
1855 Bernard Studer,

1874 Otto Torell,

1868 Rudolph Virchow,

1873 Wilhelm Eduard Weber,

Total, 32.

Louvain.
Heidelberg.

Paris.

New Haven, Conn.
Geneva.

Rome.

Utrecht.
Heidelberg.
Harvard University.
Vienna.

Paris.

Berlin.

Paris.

Bonn.

‘Berlin.

Leipzig.
Wurzburg.
Berlin.
Paris.
Leipxg.
Stockholm.
Leipzig.
Copenhagen.
Berlin.
Washington.
Paris.
Copenhagen.
Pulkowa.
Bern.

Lund.
Berlin.
Gottingen.

APPENDIX—LIST OF HONORARY FELLOWS.

BRITISH SUBJECTS (LIMITED TO TWENTY BY LAW X.).

Elected.

1849 John Couch Adams, LL.D., F.R.S., Corresp. Mem. Inst. France,

1835 Sir George Biddell Airy, K.C.B., M.A., LL.D., D.C.L., F.B.S.,
Foreign Associate Inst. France,

1870 Thomas Andrews, M.D., LL.D., F.B.S.,

1865 Arthur Cayley, LL.D., D.C.L., F.R.S., Corresp. Mem. Inst. France,

1884 Edward Frankland, D.C.L., LL.D., F.R.S.,

1874 John Anthony Froude, LL.D.,

1881 The Hon. Justice Sir William Robert Grove, M.A., LL.D.,
mC; HRS.

1883 Sir Joseph Dalton Hooker, K.C.S.1., C.B., M.D., D.C.L., LL.D.,
F.R.S., F.G.8., Corresp. Mem. Inst. France, Director of the
Royal Gardens, Kew,

1884 William Huggins, LL.D., D.C.L., F.R.S.,

1876 Thomas Henry Huxley, LL.D., D.C.L, F.RS., F.LS., F.Z.S.,
F.G.S., Corresp. Mem. Inst. France,

1867 James Prescott Joule, LL.D., D.C.L, F.R.S., Corresp. Mem.
Inst. France,

1845 Sir Richard Owen, K.C.B., M.D., LL.D., D.C.L, F.R.S., Foreign
Associate Inst. France,

1881 The Rev. George Salmon, D.D., LL.D., D.C.L, F.R.S., Foreign
Associate of the Institute of France,

1884 J. S. Burdon Sanderson, M.D., LL.D., F.B.S.,

1878 Balfour Stewart, M.A., LL.D., F.R.S.,

1864 George Gabriel Stokes, M.A., LL.D., D.C.L., Sec. R.S., Corresp.
Mem. Inst. France,

1874 James Joseph Sylvester, M.A., LL.D., F.R.S., Corresp. Mem.
Inst. France,

1864 The Right Hon. Lord Tennyson, D.C.L., LL.D., F.R.S., Poet
Laureate,

1883 Alexander William Williamson, LL.D., F.R.S., V.P.C.S., Corresp.
Mem. Inst. France,

1883 Colonel Henry Yule, C.B., LL.D., Member of the Council of India,

Total, 20.

VOL, XXXII. PART IV.

Cambridge.
Greenwich,
Belfast.
Cambridge.
London.
London.
London.
London.
London.
London.
Manchester.
London.
Dublin.
Oxford.
Manchester.
Cambridge.
Oxford.

Isle of Wight.

London.
London.

671

672 APPENDIX.—LIST OF HONORARY FELLOWS.

LIST OF HONORARY FELLOWS

AT NOVEMBER 1886.
His Royal Highness The PRINCE oF WALES,

FOREIGNERS (LIMITED TO THIRTY-SIX BY LAW x)

Elected.

1884 Pierre J. van Beneden, Louvain.

1864 Robert Wilhelm Bunsen, Heidelberg.

1867 Michel Eugéne Chevreul, Paris.

1858 James D. Dana, New Haven, Conn.
1877 Alphonse De Candolle, Geneva.

1883 Luigi Cremona, Rome.

1879 Franz Cornelius Donders, Utrecht.

1877 Carl Gegenbaur, Heidelberg

1879 Asa Gray, Harvard University.
1883 Julius Hann, Vienna.

1884 Charles Hermite Paris.

1864

1879 Jules Janssen, Paris.

1875 August Kekulé, Bonn.
1868 Gustav Robert Kirchhoff Berlin.
1875 Hermann Kolbe, Leipzig.
1864 Albert Kolliker, Wiirzburg.
1875 Ernst Eduard Kummer, Berlin.
1876 Ferdinand de Lesseps, Paris.
1864 Rudolph Leuckart, Leipzig.
1881 Sven Lovén, Stockholm.
1876 Carl Ludwig, Leipzig.
1878 J. N. Madvig, Copenhagen.
1886 Alphonse Milne-Edwards, Paris.

1864 Theodore Mommsen, Berlin.
1881 Simon Newcomb, Washington.
1886 H. A. Newton, Yale College.
1874 Louis Pasteur, Paris.

1886 L’Abbé Renard, Louvain.
1881 Johannes Iapetus Smith Steenstrup, Copenhagen.
1878 Otto Wilhelm Struve, Pulkowa.
1855 Bernard Studer, Bern.

1886 Tobias Robert Thalen, Upsala.
1874 Otto Torell, Lund,

1868 Rudolph Virchow, Berlin.
1874 Wilhelm Eduard Weber, Gottingen.

Hermann Ludwig Ferdinand von Helmholtz, Berlin.

Total, 36.

APPENDIX.—LIST OF HONORARY FELLOWS.

BRITISH SUBJECTS (LIMITED TO TWENTY BY LAW X.).

Elected.
1849 John Couch Adams, LL.D., F.R.S., Corresp. Mem. Inst. France,

1835 Sir George Biddell Airy, K.C.B., M.A., LL.D., D.C.L., F.RB.S.,
Foreign Associate Inst., France,

1865 Arthur Cayley, LL.D., D.C.L., F.R.S., Corresp. Mem. Inst. France,

1884 Edward Frankland, D.C.L., LL.D., F.B.S.,

1874 John Anthony Froude, LL.D.,

1881 The Hon. Justice Sir William Robert Grove, M.A., LL.D.,
DC. L., E.B.S.,

1883 Sir Joseph Dalton Hooker, K.C.S.I., C.B., M.D., D.C.L., LL.D.,
F.R.S., F.G.S., Corresp. Mem. Inst. France,

1884 William Huggins, LL.D., D.C.L., F.RB.S.,

1876 Thomas Henry Huxley, LL.D., D.C.L., F.RS., F.LS., F.Z.S.,
F.G.S., Corresp. Mem. Inst. France,

1867 James Prescott Joule, LL.D., D.C.L., F.R.S., Corresp. Mem.
Inst. France,

1845 Sir Richard Owen, K.C.B., M.D., LL.D., D.C.L., F.R.S., Foreign
Associate Inst. France,

1886 The Lord Rayleigh, D.C.L., LL.D., Sec. R.S.,

1881 The Rev. George Salmon, D.D., LL.D., D.C.L., F.R.S., Foreign
Associate of the Institute of France,

1884 J. S. Burdon Sanderson, M.D., LL.D., F.R.S.,

1878 Balfour Stewart, M.A., LL.D., F.R.S.,

1864 George Gabriel Stokes, M.A., LL.D., D.C.L., Pres. R.S.,
Corresp. Mem. Inst. France,

1874 James Joseph Sylvester, M.A., LL.D., F.R.S., Corresp. Mem.
Inst. France,

1864 The Right Hon. Lord Tennyson, D.C.L., LL.D., F.R.S., Poet
Laureate,

1883 Alexander William Williamson, LL.D., F.R.S., V.P.C.S., Corresp.
Mem. Inst. France,

1883 Colonel Henry Yule, C.B., LL.D., Member of the Council of India,

Total, 20.

Cambridge.
Greenwich.
Cambridge.
London.
London,

London.

London.
London.

London.
Manchester.

London.
London.

Dublin.
Oxford.
Manchester.
Cambridge.
Oxford.

Isle of Wight.

London.
London.

673

674 APPENDIX.—LIST OF MEMBERS ELECTED.

ORDINARY FELLOWS ELECTED
Durina SEssion 1883-84,

ARRANGED ACCORDING TO THE Dare or THEIR ELxcrion.

7th January 1884.

Francis T. Bonp, M.D., B.A.

4th February 1884.

Gzorcr M. Low, Actuary. Rev. J. Gorpon Macruersoy, M.A., D.Sc.
Dr Freperick HunGERFORD BowMaAN, Cuartes Scorr Dickson, Advocate.
F.R.A.S. Rosert TRAIL Omonp.
3rd March 1884.
G. A. Woops, M.R.C.S. Ricuarp Davy, M.D.

Joun Grirve, M.A., M.D.

7th April 1884.

James Tart Buack. FE. Perrson Ramsay, F.L.8.

bth May 1884.

Professor JospPH SHIELD NICHOLSON. Rey. J. S. Buack.

Joun Hernperson, Jun.

ond June 1884.

J. T. Cunnineuay, B.A.

7th July 1884.

Davin ALAN StEvENSON, B.Sc., C.F. Guorce Hunter MacTuomas Tuoms, of
R. W. Myint, C.E., F.R.S. Aberlemno, Sheriff of Caithness, Orkney,
W. Evans, F.F.A. and Zetland.

APPENDIX.—LIST OF MEMBERS ‘DECEASED, ETC. 675

FELLOWS DECEASED, RESIGNED, OR CANCELLED,

Durine Session 1883-84.

DECEASED.
Professor Joun Hutron BaLrour. C. H. Mituar of Blaircastle.
The DuKe or Bucctevucn. JOSEPH MITCHELL.
Isaac ANDERSON HeEnry. Dr Attan THOMSON.
Ex-Provost Linpsay of Leith. Dr ALEXANDER Woop.
RESIGNED.

ALEXANDER Howe, W.S.

CANCELLED.
Francis W. Mornet, M.D.

ELECTION OF HONORARY FELLOWS.

FOREIGN HONORARY FELLOWS.
16th June 1884.
M. Cuartes HERMITE, Paris.

M. Pisrre J. vaN BENEDEN, Louvain.

BRITISH HONORARY FELLOWS.
7th July 1884.

Professor E. FRanKLAND, D.C.L., LL.D., F.R.S. Wuti1am Hueerns, D.C.L., LL.D., F.R.S.
Professor Burpon Sanperson, M.D., LL.D., F.R.S.

FOREIGN HONORARY FELLOWS DECEASED.
Session 1883-84.

JEAN Baptiste Dumas. RicHarp Lepsius.
CHARLES ADOLPHE WURTZ.

676 APPENDIX.—LIST OF MEMBERS ELECTED.

ORDINARY FELLOWS ELECTED
Durine Session 1884-85,

ARRANGED ACCORDING TO THE DATE OF THEIR ELECTION.

lst December 1884.

H. Brttyse Barnpon, B.A. RoBeRT CHAMBERS.
Cuarues M‘Bripg, M.D.

2nd February 1885.

Professor W. R. Hopexrnson. JoHN Ratrray, M.A., B.Se.
Hueu Rosert Mitt, B.Sc. Witiram Miter, 8.8.C.
ALFRED DanieuL, M.A., LL.B., D.Sc.

2nd March 1885.

Professor EuGar. Orme Masson, D.Sc.
J. M. Macraruang, D.Se.

6th April 1885.
Professor J. E. A. STEGGALL. Rk. J. Harvey Grpson, M.A.
James Prince, Provost of Leith. Professor Dycr Davipson, M.D.
A. P. Lauri, B.Sc. Georce SmitH, F.C.S.

4th May 1885.

Jounson Symineton, M.B., F.R.C.S.E. Professor J. M. Drxon.
J. F. Punwar. J. Macponatp Brown, M.B., F.R.C.S.

lst June 1885.

Professor D’Arcy W, THompson. A. Y. Fraser, M.A.
ALEXANDER Scott, M.A., D.Se.

APPENDIX.—LIST OF MEMBERS DECEASED, ETC. 677

FELLOWS DECEASED OR RESIGNED

DurinG Session 1884-85.

DECEASED.
Sir James Anexanper, K.C.B. J. W. Larpuay of Seacliffe.
_W. Linpsay Atexanner, D.D. Joun Macnair.
T. C. ArcHER, Museum of Science and Art. James Napier of Partick.
Aveustus J. D. Cameron, M. Inst. C.E. Rev. Francis Reprorp, M.A.
Francis Brown Doveuas, Advocate. Major-General A. CunNINGHAM ROBERTSON.
FREDERICK Fieup, F.R.S. Professor Morrison Watson, M.D.
Principal Sir ALEXANDER Grant, Bart. Water Wetpoy, F.R.S.
Professor H. C. Fizeminc Jenxy, F.R.S. Tuomas Wricuat, M.D.
RESIGNED.

R. K. Gattoway, Esq., B.A.
Joun Dick Peppiz, Esq.

FOREIGN HONORARY FELLOWS DECEASED.
Session 1884-85.

Heyry Mitve-Epowarps. Karu THEODOR VON SIEBOLD.

678 APPENDIX.—LIST OF MEMBERS ELECTED.

ORDINARY FELLOWS ELECTED
Durine Session 1885-86,

ARRANGED ACCORDING TO THE DATE OF THEIR ELECTION.

7th December 1885.

Dr A. B. Grirritus, F.C.S., School of Davip Cunnineuay, M. Inst. C.K,
Science of the City and County of Danie, M. Connan, M.A., Education
Leicester. Department, Cape Town.

4th January 1886.
A. J. G, Barctay, M.A.

lst February 1886.

The Right Hon. J. H. A. Macponatp. Artuur W. Hare, M.B., C.M.
Professor Freprrick O. Bower. GzorcE Fossery Lystur, M. Inst. C,E.
Rosert Irvine. D. Nort Paton, M.D., B.Sc.

GERMAN Sims Woopueap, M.D. Rey. Grorcr Laine.

Wituiam J. Macponatp, M.A.

lst March 1886.

Hucu Mitime, H.M. Geological Survey. Professor GrorcE FREDERICK ARMSTRONG,
Joun Ricuarp Brirties, M. Inst. C.E. M.A., F.G.S.
The Right Hon. Sir Tuomas Cxark, Bart., ArtTuur ANDERSON, C.B., M.D.
Lord Provost. ALEXANDER Gipson, Advocate.
Professor Ropert WALLACE. Colonel R. Murpoca Smiru.

The Right Hon. the Hart or Happrineton.

5th April 1886.

A. Beatson Bett, Chairman of Prison Joun Hatuipay Croom, M.D.
Commissioners. D. Bruce Prrsies.
J. P. B. Ropertson, Q.C., M.P. C. Leopotp Frsxp, F.C.S.
Rev. J. MacGrecor, D.D.

3rd May 1886. —

Cuartes Freperick Pottock, M.D., Byrom Bramwe tt, M.D.
F.R.C.S.E. C. A. Stnvenson, B.Sc., F.R.C.P.E.
Professor GREENFIELD. Wittram Mitnp, M.A., B.Se.

7th June 1886.
James Ouiver, M.B., M.R.C.P. Lond.

5th July 1886.

Rogzert Kinston, F.G.S. Rev. H. G. Bonavia Hunt, Mus. B, Oxon.,
ERAS. FL.

APPENDIX.—LIST OF MEMBERS DECEASED, ETC.

FELLOWS DECEASED OR RESIGNED

DurinG SEsston 1885-86.

DECEASED.
Sir Jonn Anverson, LL.D. * ALEXANDER Hamitton, LL.B., W.S.
The Right Rev. Bishop Corrrrit1, D.D., Cosmo Gorpon Loain, M.D.

LL.D. Aneus Macponatp, M.D., F.R.C.P.E.
James ‘I’. Grpson-Craic, W.S. GrarEmMe Rem Mercer of Gorthie.
Professor A. Dyce Davipson, M.A., M.D. JouN MILnr.

James Dunsmury, M.D., F.R.C.S.E. JouN Mitroy of Torsonce.

W. Mitcuett Extis, Advocate. Davin Stevenson, M. Inst. C.E.

J. SAMPSON GAMGEE. Witiam TURNBULL.

Freperick Guturin, M.A., F.R.S. Tuomas Wiiamson, M.D., F.R.C.S.E.

* Died 1st January 1884. Death only intimated on 17th June 1886.

RESIGNED.

Grorce F. Barsour of Bonskeid,

BRITISH HONORARY FELLOW DECEASED.
Susston 1885-86,
Tuomas AnpREws, M.D., LL.D., F.R.S.

VOL XXXII. PART IV. 5 Y

679

LAWS

OF THE

ROYAL SOCIETY OF EDINBURGH,

AS REVISED 20TH FEBRUARY 1882.

( 683 )

bck W 5.

[ By the Charter of the Society (printed in the Transactions, Vol. VI. p. 5), the Laws cannot
be altered, except at a Meeting held one month after that at which the Motion for
alteration shall have been proposed. |

i:

THE ROYAL SOCIETY OF EDINBURGH shall consist of Ordinary and
Honorary Fellows. 7

ie

Every Ordinary Fellow, within three months after his election, shall pay Two
Guineas as the fee of admission, and Three Guineas as his contribution for the
Session in which he has been elected ; and annually at the commencement of every
Session, Three Guineas into the hands of the Treasurer. This annual contribution
shall continue for ten years after his admission, and it shall be limited to Two
Guineas for fifteen years thereafter.*

III.

All Fellows who shall have paid Twenty-five years’ annual contribution shall
be exempted from farther payment.

IV.

The fees of admission of an Ordinary Non-Resident Fellow shall be £26, 5s.,
payable on his admission ; and in case of any Non-Resident Fellow coming to
reside at any time in Scotland, he shall, during each year of his residence, pay
the usual annual contribution of £3, 3s., payable by each Resident Fellow ; but
after payment of such annual contribution for eight years, he shall be exempt

* A modification of this rule, in certain cases, was agreed to at a Meeting of the Society held on
the 8rd January 1831.

At the Meeting of the Society, on the 5th January 1857, when the reduction of the Contribu-
tions from £3, 3s. to £2, 2s., from the 11th to the 25th year of membership, was adopted, it was
resolved that the existing Members shall share in this reduction, so far as regards their future annual
Contributions.

Title.

The fees of Ordi-
nary Fellows resid-
ing in Scotland.

Payment to cease
after 25 years.

Fees of Non-Resi-
dent Ordinary
Fellows.

se of Fellows
oming Non-
sident.

faulters.

vileges of
linary Fellows.

mbers Un-
ited.

lows entitled
l'ransactions.

le of Recom-
iding Ordinary
lows. ‘

684 LAWS OF THE SOCIETY.

from any farther payment. In the case of any Resident Fellow ceasing to reside
in Scotland, and wishing to continue a Fellow of the Society, it shall be in the
power of the Council to determine on what terms, in the circumstances of each
case, the privilege of remaining a Fellow of the Society shall be continued to
such Fellow while out of Scotland.

V;

Members failing to pay their contributions for three successive years (due
application having been made to them by the Treasurer) shall be reported to
the Council, and, if they see fit, shall be declared from that period to be no
longer Fellows, and the legal means for recovering such arrears shall be
employed.

VI.

None but Ordinary Fellows shall bear any office in the Society, or vote in
the choice of Fellows or Office-Bearers, or interfere in the patrimonial interests
of the Society.

Al al

The number of Ordinary Fellows shall be unlimited.

VIII.

The Ordinary Fellows, upon producing an order from the TREASURER, shall
be entitled to receive from the Publisher, gratis, the Parts of the Society’s
Transactions which shall be published subsequent to their admission.

Lx

Candidates for admission as Ordinary Fellows shall make an application in
writing, and shall produce along with it a certificate of recommendation to the
purport below,* signed by at least /owr Ordinary Fellows, two of whom shall
certify their recommendation from personal knowledge. This recommendation
shall be delivered to the Secretary, and by him laid before the Council, and
shall afterwards be printed in the circulars for three Ordinary Meetings of
the Society, previous to the day of election, and shall lie upon the table during
that time.

* “A. B., a gentleman well versed in Science (or Polite Literature, as the case may be), being
“to our knowledge desirous of becoming a Fellow of the Royal Society of Edinburgh, we hereby
“recommend him as deserving of that honour, and as likely to prove a useful and valuable Member.

©

LAWS OF THE SOCIETY. 685

X.

Honorary Fellows shall not be subject to any contribution. This class shall
consist of persons eminently distinguished for science or literature. Its number
shall not exceed Fifty-six, of whom Twenty may be British subjects, and Thirty-
six may be subjects of foreign states.

XI.

Personages of Royal Blood may be elected Honorary Fellows, without regard
to the limitation of numbers specified in Law X.

XII.

Honorary Fellows may be proposed by the Council, or by a recommenda-
tion (in the form given below*) subscribed by three Ordinary Fellows ; and in
case the Council shall decline to bring this recommendation before the Society,
it shall be competent for the proposers to bring the same before a General
Meeting. The election shall be by ballot, after the proposal has been commu-
nicated viva voce from the Chair at one meeting, and printed in the circulars
for two ordinary meetings of the Society, previous to the day of election.

XT.

The election of Ordinary Fellows shall only take place at the first Ordinary
Meeting of each month during the Session. The election shall be by ballot,
and shall be determined by a majority of at least two-thirds of the votes, pro-
vided Twenty-four Fellows be present and vote.

XIV.

The Ordinary Meetings shall be held on the first and third Mondays of
every month from December to July inclusively ; excepting when there are
five Mondays in January, in which case the Meetings for that month shall
be held on its third and fifth Mondays. Regular Minutes shall be kept of
the proceedings, and the Secretaries shall do the duty alternately, or
according to such agreement as they may find it convenient to make.

* We hereby recommend ted eh Ea) dist) 2 Bom:
for the distinction of being made an Honorary Fellow of this Society, declaring that each of us from
our own knowledge of his services to (Literature or Science, as the case may be) believe him to be
worthy of that honour.

(To be signed by three Ordinary Fellows.)

To the President and Council of the Royal Society
of Edinburgh.

Honorary Fellows,
British and
Foreign.

Royal Personages.

Recommendation
of Honorary Fel-
lows.

Mode of Election,

Election of Ordi-
nary Fellows.

Ordinary Meet-
ings.

. Transactions.

vy Published.

> Council.

iring Council-
be

ction of Office-
wrers.

cial Meetings ;
vy called,

easurer’s Duties.

686 LAWS OF THE SOCIETY.

XV.

The Society shall from time to time publish its Transactions and Proceed-
ings. For this purpose the Council shall select and arrange the papers which
they shall deem it expedient to publish in the Z’ransactions of the Society, and
shall superintend the printing of the same.

The Council shall have power to regulate the private business of the Society.
At any Meeting of the Council the Chairman shall have a casting as well as a
deliberative vote.

XVI.

The Transactions shall be published in parts or Fasciculi at the close of
each Session, and the expense shall be defrayed by the Society.

XVII.

That there shall be formed a Council, consisting—First, of such gentlemen
as may have filled the office of President ; and Secondly, of the following to be
annually elected, viz. :—a President, Six Vice-Presidents (two at least of whom
shall be resident), Twelve Ordinary Fellows as Councillors, a General Secretary,
Two Secretaries to the Ordinary Meetings, a Treasurer, and a Curator of the
Museum and Library. | )

XVIII.

Four Councillors shall go out annually, to be taken according to the order
in which they stand on the list of the Council.

XX:

An Extraordinary Meeting for the Election of Office-Bearers shall be held
on the fourth Monday of November annually.

2.

Special Meetings of the Society may be called by the Secretary, by direction
of the Council; or on a requisition signed by six or more Ordinary Fellows.
Notice of not less than two days must be given of such Meetings.

XXI.

The Treasurer shall receive and disburse the money belonging to the Society,
granting the necessary receipts, and collecting the money when due.

He shall keep regular accounts of all the cash received and expended, which
shall be made up and balanced annually ; and at the Extraordinary Meeting in
November, he shall present the accounts for the preceding year, duly audited.

i

LAWS OF THE SOCIETY. 687

At this Meeting, the Treasurer shall also lay before the Council a list of all
arrears due above two years, and the Council shall thereupon give such direc-
tions as they may deem necessary for recovery thereof.

) ONE,

At the Extraordinary Meeting in November, a professional accountant shall Auditor.
be chosen to audit the Treasurer’s accounts for that year, and to give the neces-
sary discharge of his intromissions.

XXIII.

The General Secretary shall keep Minutes of the Extraordinary Meetings of General Secretary’s
the Society, and of the Meetings of the Council, in two distinct books. He ee
shall, under the direction of the Council, conduct the correspondence of the
Society, and superintend its publications. For these purposes he shall, when
necessary, employ a clerk, to be paid by the Society.

XXIV.

The Secretaries to the Ordinary Meetings shall keep a regular Minute-book, secretaries to
in which a full account of the proceedings of these Meetings shall be entered ; ON ee
they shall specify all the Donations received, and furnish a list of them, and of
the Donors’ names, to the Curator of the Library and Museum ; they shall like-
wise furnish the Treasurer with notes of all admissions of Ordinary Fellows.
They shall assist the General Secretary in superintending the publications, and
in his absence shall take his duty.

XXYV.

The Curator of the Museum and Library shall have the custody and charge curator of Museum
of all the Books, Manuscripts, objects of Natural History, Scientific Produc- “*'""*
tions, and other articles of a similar description belonging to the Society ; he
shall take an account of these when received, and keep a regular catalogue of
the whole, which shall lie in the Hall, for the inspection of the Fellows.

XXVI.

All Articles of the above description shall be open to the inspection of the Use of Museum
Fellows at the Hall of the Society, at such times and under such regulations, ““* “”"™"™
as the Council from time to time shall appoint.

XXVII.

A Register shall be kept, in which the names of the Fellows shall be Register Book.
enrolled at their admission, with the date.
VOL. XXXII. PART IV. 5 Z

( 688 )

THE KEITH, BRISBANE, AND NEILL PRIZES.

The above Prizes will be awarded by the Council in the following manner :—

I. KEITH PRIZE.

The Kerrn Prize, consisting of a Gold Medal and from £40 to £50 in
Money, will be awarded in the Session 1887-88 for the “best communication
on a scientific subject, communicated, in the first instance, to the Royal Society
during the Sessions 1885-86 and 1886-87.” Preference will be given to a
paper containing a discovery.

Il. MAKDOUGALL-BRISBANE PRIZE.

This Prize is to be awarded biennially by the Council of the Royal Society
of Edinburgh to such person, for such purposes, for such objects, and in such
manner as shall appear to them the most conducive to the promotion of the
interests of science; with the proviso that the Council shall not be compelled
to award the Prize unless there shall be some individual engaged in scientific
pursuit, or some paper written on a scientific subject, or some discovery in
science made during the biennial period, of sufficient merit or importance in
the opinion of the Council to be entitled to the Prize.

1. The Prize, consisting of a Gold Medal and a sum of Money, will be
awarded at the commencement of the Session 1887-88, for an Essay or Paper
having reference to any branch of scientific inquiry, whether Material or
Mental.

2. Competing Essays to be addressed to the Secretary of the Society, and
transmitted not later than 1st June 1888.

3. The Competition is open to all men of science.

APPENDIX.—KEITH, MAKDOUGALL-BRISBANE, AND NEILL PRIZES. 689

4, The Essays may be either anonymous or otherwise. In the former case,
they must be distinguished by mottoes, with corresponding sealed billets, super-
scribed with the same motto, and containing the name of the Author.

5. The Council impose no restriction as to the length of the Essays, which
may be, at the discretion of the Council, read at the Ordinary Meetings of the
Society. They wish also to leave the property and free disposal of the manu-
scripts to the Authors; a copy, however, being deposited in the Archives of
the Society, unless the paper shall be published in the Transactions.

6. In awarding the Prize, the Council will also take into consideration any
scientific papers presented to the Society during the Sessions 1887-88 and
1883-84, whether they may have been given in with a view to the prize or not.

III. NEILL PRIZE.

_ The Council of the Royal Society of Edinburgh having received the bequest
of the late Dr Patrick Nem. of the sum of £500, for the purpose of “the
interest thereof being applied in furnishing a Medal or other reward every
second or third year to any distinguished Scottish Naturalist, according as such
Medal or reward shall be voted by the Council of the said Society,” hereby
intimate,

1. The Nett Prize, consisting of a Gold Medal and a sum of Money, will
be awarded during the Session 1888-89.

2. The Prize will be given for a Paper of distinguished merit, on a subject
of Natural History, by a Scottish Naturalist, which shall have been presented
to the Society during the three years preceding the 1st May 1888,—or failing
presentation of a paper sufficiently meritorious, it will be awarded for a work
or publication by some distinguished Scottish Naturalist, on some branch of
Natural History, bearing date within five years of the time of award.

( 690 )

AWARDS OF THE KEITH, MAKDOUGALL-BRISBANE, AND NEILL PRIZES,
FROM 1827 TO 1879.

I. KEITH PRIZE.

lst Brennrat Pertop, 1827-29.—Dr Brewster, for his papers “on his Discovery of Two New Immis-
cible Fluids in the Cavities of certain Minerals,” published in
the Transactions of the Society.
2np Biennrau Periop, 1829-31.—Dr Brewster, for his paper ‘fon a New Analysis of Solar
Light,” published in the Transactions of the Society.
3RD BieNNIAL PeRiop, 1831—33.—THomas Grauam, Esq., for his paper “ on the Law of the Diffusion
of Gases,” published in the Transactions of the Society.
47H Biennial Pentop, 1833-35,—Professor J. D. Forsrs, for his paper “on the Refraction and Polari-
zation of Heat,” published in the Transactions of the Society.
5TH Brenn1aL Periop, 1835-37.—Joun Scorr RussELL, Esq.,for his Researches “on Hydrodynamics,”
published in the Transactions of the Society.
67H Brenniat Periop, 1837-39.—Mr Jonn Suaw, for his experiments “on the Development and
Growth of the Salmon,” published in the Transactions of the
Society.
77H BrenniAL Periop, 1839—41.—Not awarded.
8TH Brenntau Periop, 1841-43.—Professor James Davin Forses, for his Papers “on Glaciers,”
‘ published in the Proceedings of the Society.
97H BrenniaL Periop, 1843—45.—Not awarded.
107TH Brennrau Periop, 1845-47.—General Sir THomas Brispans, Bart., for the Makerstoun Observa-
tions on Magnetic Phenomena, made at his expense, and
published in the Transactions of the Society.
llra Brennrat Perron, 1847—49.—Not awarded.
127H BrenniaL Periop, 1849-51.—Professor Ketuanp, for his papers “on General Differentiation,
including his more recent communication on a process of the
Differential Calculus, and its application to the solution of
certain Differential Equations,” published in the Transactions
of the Society.
137m Brenniat Periop, 1851—-53.—W. J. Macquorn Rankine, Esq., for his series of papers “on the
Mechanical Action of Heat,’ published in the Transactions
of the Society.
1478 Brennrau Periop, ]853-55.—Dr Tuomas Anperson, for his papers “on the Crystalline Con-
stituents of Opium, and on the Products of the Destructive
Distillation of Animal Substances,” published in the Trans-
actions of the Society.
157H Brenniat Periop, 1855-57.—Professor Booun, for his Memoir “on the Application of the Theory
of Probabilities to Questions of the Combination of Testimonies
and Judgments,” published in the Transactions of the Society,
167TH BrenniAu Pertop, 1857—59.—Not awarded.
177H Brenniau Peron, 1859-61.—Joun Auian Broun, Esq., F.R.S., Director of the Trevandrum.
Observatory, for his papers “on the Horizontal Force of the
Earth’s Magnetism, on the Correction of the Bitilar Magnet-
ometer, and on Terrestrial Magnetism generally,” published in
the Transactions of the Society.
181m Brienniat Pertop, 1861—63.—Professor Wiit1am THomson, of the University of Glasgow, for his
Communication ‘on some Kinematical and Dynamical
Theorems.”
19rx Brenniat Periop, 1863-65.—Principal Forses, St Andrews, for his “Experimental Inquiry into
the Laws of Conduction of Heat in Iron Bars,” published in
the Transactions of the Society,

APPENDIX.—KEITH, MAKDOUGALL-BRISBANE, AND NEILL PRIZES. 691

20TH Brennian Periop, 1865—67.—Professor C. Prazzi Smyvg, for his paper “on Recent Measures at
the Great Pyramid,” published in the Transactions of the
Society.

21st Brenniau Periop, 1867—69.—Professor P. G. Tarr, for his paper “on the Rotation of a Rigid
Body about a Fixed Point,” published in the Transactions of
the Society.

22np Brenntau Periop, 1869—71.—Professor CrerkK Maxwet., for his paper “on Figures, Frames,
and Diagrams of Forces,” published in the Transactions of the
Society.

23rp Brenniau Periop, 1871—73.—Professor P. G. Tarr for his paper entitled “ First Approximation
to a Thermo-electric Diagram,” published in the Transactions
of the Society.

247H BisnniaL Periop, 1873—75.—Professor Crum Brown, for his Researches “ on the sense of Rota-
tion, and on the Anatomical Relations of the Semicircular
Canals of the Internal Ear.”

257 BrenniaL PeRioD, 1875—77.—Professor M. Forster Heppix, for his papers “on the Rhom-
bohedral Carbonates,” and “on the Felspars of Scotland,”
published in the Transactions of the Society.

26TH Brennrat Psriop, 1877—79.—Professor H. C. Firemine Jenkin, for his paper “on the Appli-
cation of Graphic Methods to the Determination of the Effi-
ciency of Machinery,” published in the Transactions of the
Society; Part IT. having appeared in the volume for 1877-78.

277H Brenntat Periop, 1879—81.—Professor Groree Curystat, for his paper “on the Differential
Telephone,” published in the Transactions of the Society.

287H Brenntat Periop, 1881—83.—Txomas Murr, Esq., LL.D., for his “ Researches into the Theory
of Determinants and Continued Fractions,” published in the
Proceedings of the Society.

297TH Biexntau Periop, 1883—-85.—Joum ArrKeEn, Esq., for his paper “on the Formation of Small
Clear Spaces in Dusty Air,” and for previous papers on
Atmospheric Phenomena, published in the Transactions of
the Society.

II. MAKDOUGALL-BRISBANE PRIZE.

Ist BrewniaL Perriop, 1859.—Sir Roprrick Impry Murcuison, on account of his Contributions to
the Geology of Scotland.
2np Brenniat Periop, 1860—62.—Wiiiam Sevier, M.D., F.R.C.P.E., for his ‘‘ Memoir of the Life
and Writings of Dr Robert Whytt,” published in the Trans-
actions of the Society.
3RD Brenniau Periop, 1862-—64.—Joun Denis Macponatp, Esq., R.N., F.R.S., Surgeon of H.M.S.
“Tearus,” for his paper “on the ‘Representative Relationships
of the Fixed and Free Tunicata, regarded as Two Sub-classes
of equivalent value; with some General Remarks on their
Morphology,” published in the Transactions of the Society.
47H BrenntaL Periop, 1864—66.—Not awarded.
57H Brennrat Periop, 1866-68.—Dr Atnxanper Crum Brown and Dr Tuomas RicHarp Fraser,
for their conjoint paper “on the Connection between
Chemical Constitution and Physiological Action,” published
in the Transactions of the Society.
67H Bienniat Periop, 1868—70.—Not awarded.
77H BreNNIAL Pertop, 1870—72.—Grorce James Auiman, M.D., F.R.S., Emeritus Professor of Natural
History, for his paper “ on the Homological Relations of the
Coelenterata,” published in the Transactions, which forms a
leading chapter of his Monograph of Gymnoblastic or Tubu-
larian Hydroids—since published.
87H Brenna Periop, 1872—74.—Professor Lister, for his paper “on the Germ Theory of Putre-
faction and the Fermentive Changes,” communicated to the
Society, 7th April 1873.

692 APPENDIX.—KEITH, MAKDOUGALL-BRISBANE, AND NEILL PRIZES,

9raH Brenniat Periop,1874—76.— Atexanper Bucuan, A.M., for his paper “on the Diurnal Oscillation

of the Barometer,” published in the Transactions of the Society.

10rH Brannrat Periop, 1876—78.—Professor ArcarBaLD Geikin, for his paper “on the Old Red
Sandstone of Western Europe,” published in the Transactions
of the Society.

llra Brenniat Periop, 1878—80.—Professor Piazz1 Smytu, Astronomer-Royal for Scotland, for his
paper ‘fon the Solar Spectrum in 1877-78, with some
Practical Idea of its probable Temperature of Origination,”
published in the Transactions of the Society.

127TH Brennrat Pertop, 1880—82.—Professor James Gurxie, for his “ Contributions to the Geology of
the North-West of Europe,” including his paper “on the
Geology of the Farées,” published in the Transactions of the
Society.

13rH Brenniat Pertop, 1882—84.—Epwarp Sane, Esq., LL.D., for his paper “on the Need of
Decimal Subdivisions in Astronomy and Navigation, and on
Tables requisite therefor,” and generally for his Recalculation
of Logarithms both of Numbers and Trigonometrical Ratios,
—the former communication being published in the Pro-
ceedings of the Society.

III. THE NEILL PRIZE.

1st Trimnn1aL Periop, 1856-59.—Dr W. Lauper Linpsay, for his paper “ on the Spermogones and
Pycnides of Filamentous, Fruticulose, and Foliaceous Lichens,”
published in the Transactions of the Society.
2npD TRIENNIAL Pertiop, 1859-—62.—Rosert Kayz Grevitiy, LL.D., for his Contributions to Scottish
Natural History, more especially in the department of Cryp-
; togamic Botany, including his recent papers on Diatomacee.
3rD TRIENNIAL Periop, 1862—-65.—Anprew Crompie Ramsay, F.R.S., Professor of Geology in the
Government School of Mines, and Local Director of the
Geological Survey of Great Britain, for his various works and
Memoirs published during the last five years, in which he
has applied the large experience acquired by him in the
Direction of the arduous work of the Geographical Survey of
Great Britain to the elucidation of important questions bear-
ing on Geological Science.
47a TRIENNIAL Pertop, 1865-68.—Dr Witt1am Carmicuart M‘Intosu, for his paper “on the Strue-
ture of the British Nemerteans, and on some New British
Annelids,” published in the Transactions of the Society.
57H TRIENNIAL Pertop, 1868—71.—Professor Witi1am Turner, for his papers “on the great Finner
Whale ; and on the Gravid Uterus, and the Arrangement of
the Foetal Membranes in the Cetacea,” published in the
Transactions of the Society.
67H TRImNNIAL Periop, 1871—74.—Cuartes Witiiam Pracg, for his Contributions to Scottish Zoology
and Geology, and for his recent contributions to Fossil Botany.
7TH TRIENNIAL Periop, 1874—-77.—Dr Ramsay H. Traquair, for his paper “on the Structure and
Affinities of T'ristichopterus alatus (Egerton), published in
the Transactions of the Society, and also for his contributions
to the Knowledge of the Structure of Recent and Fossil Fishes.
8TH TrienntAL Periop, 1877—80.—Joun Murray, for his paper “on the Structure and Origin of
Coral Reefs and Islands,” published (in abstract) in the
Proceedings of the Society.
97H TaimnNnIAL Puriop, 1880—-83.—Professor Herpman, for his papers “on the Tunicata,” published
in the Proceedings and Transactions of the Society.
107TH TrienntAL Periop, 1883-86.—B. N. Prac, Esq., for his Contributions to the Geology and
Palaeontology of Scotland, published in the Transactions of
the Society.

PROCEEDINGS

OF THE

STATUTORY GENERAL MEETINGS,

AND

LIST OF MEMBERS ELECTED AT THE ORDINARY MEETINGS

FROM NOVEMBER 1881 TO NOVEMBER 1885,

( 695 )

STATUTORY MEETINGS.

NINETY-NINTH SESSION.
Monday, 28th November 1881.

At a Statutory Meeting, Professor MacLacan, Vice-President, in the Chair, the Minutes of
last General Statutory Meeting of 22nd November 1880 were read, approved, and signed.

The Ballot for the new Council was then taken, Messrs TENNANT and MaccuLLocH being
requested to act as Scrutineers. The following Council was elected :—

The Right Hon. Lorp Moncretrr, President.
Davip Mitnz Home, LL.D.

Sir C. Wyvittze THomson, LL.D.

Professor Dovetas Macuacan, M.D.
Professor H. C. Firemine JenKiy, F.R.S.
Rev. W. Linpsay Atexanver, D.D.

J. H. Batrour, M.D., F.R.S.

Professor Tart, General Secretary.

Professor Turnmr, F.R.S.
Professor Crum Brown, F.R.S8.
Apam Giuures Suitu, C.A., Treasurer.

ALEXANDER Bucuan, M.A., Curator of Library and Museum.

Vice-Presidents.

\ Scoretaries to Ordinary Meetings.

COUNCILLORS.
Professor CAMPBELL FRASER. Professor A. Dickson.
Professor Grrxin, F.R.S. The Right Rev. Bisnop Correrixt.
Rev. Dr CazEnove, The Rey. Professor Duns.
Davin STEVENSON. Dr Ramsay Traquair, F.R.S.
Professor CHRYSTAL. JoHN Murray.
Sheriff Forsrs Irvinz, of Drum. WittraM Ferevuson, of Kinmundy.

The TREASURER’S Accounts were submitted and approved.

On the motion of Professor Tarr, seconded by Mr Maccuttocu, the Auditor was re-
appointed.

Professor CruM Brown gave notice of the following motion for alteration of a part of the
Laws, viz., To change in Law XIV. the words “ November to June” into “ December to July.”
VOL, XXXII. PART IV. 6A

696 APPENDIX.—PROCEEDINGS OF STATUTORY MEETINGS.

HUNDREDTH SESSION.
Monday, 27th November 1882.

At a Statutory Meeting, Professor MACLAGAN, Vice-President, in the Chair, the Minutes of
last General Statutory Meeting of 28th November 1881 were read, approved, and signed.

The Ballot for the new Council was then taken, Professor SWAN and Professor Dickson
being requested to act as Scrutineers. The following Council was elected :—

The Right Hon. Lorp Moncrerr, President.

Professor Dovetas Mactacan, M.D.

Professor H. C. Fiuemine JENKIN, F.R.S.

The Rev. W. Linpsay ALExanpeER, D.D. = .
Ton Bierore: Wa. Vice-Presidents.
Tuomas Stevenson, M. Inst. C.E.

Ropert Gray, Sec. Roy. Phys. Soc.

Professor Tart, M.A., General Secretary.

Professor Turner, F.R.S.
Professor Crum Brown, F.R.S.,
Apam Giuuies Situ, C.A., Treasurer.

ALEXANDER Bucuay, M.A., Curator of Library and Museum.

| Secretaries to Ordinary Meetings.

COUNCILLORS.
Professor GzorcE CurystaL, M.A. Wi1aM Fercuson, of Kinmundy.
ALEXANDER Forses Irvine, of Drum. Professor James Cossar Ewart, M.D.
Professor ALEXANDER Dickson, M.D. Professor James Grrxre, F.R.S.
The Right Rev. Bisnorp Correritt, D.D. Professor WILLIAM RoBERTSON SMITH,
The Rev. Professor Duns. LL.D.
Ramsay H. Traquair, M.D., F.R.S. Starr A. Acnew, M.A.
JouN Murray, Director of “Challenger”

Comniission.

Read Letter from the Treasurer apologising for absence on account of illness, and explain-
ing the apparent surplus shown by the Financial Statement,

The Auditor’s Report on the Treasurer’s Accounts was read and approved.

On the motion of Dr Crum Brown, the Auditor was reappointed.

APPENDIX—PROCEEDINGS OF STATUTORY MEETINGS. 697

HUNDRED AND FIRST SESSION.
Monday, 26th November 1883.

At a General Statutory Meeting, THomas STEVENSON, Esq., Vice-President, in the Chair,
the Minutes of last General Statutory Meeting of 27th November 1882 were read, approved,
and signed.

The Ballot for the new Council was then taken, Professors SwaAN and Duns bemg
requested to act as Scrutineers. The following Council was unanimously elected :—

The Right Hon. Lorp Moncreirr, President.
Professor H. C. Furemine JENKIN, F.R.S.
The Rey. W. Linpsay ALExanpeErR, D.D.
THomas Stevenson, Esq., M.Inst. C.E.
Ropert Gray, Esq., Sec. Roy. Phys. Soc.

A. Forpss Irvine, Esq. of Drum.

Epwarp Sane, LL.D.

Professor Tait, M.A., General Secretary.
Professor TuRNER, F.R.S.
Professor Crum Brown, F.R.S.
ApvaM GiLuies SmitTH, Esq., C.A., Treasurer.

ALEXANDER Bucuan, Esq., M.A., Curator of Library and Museum.

Vice-Presidents.

\ Secretaries to Ordinary Meetings.

COUNCILLORS.
The Rev. Professor Duns. The Rev. Dr W. Ropertson Situ.
Dr Ramsay Traquair. Starr AGNeEw, Esq.
Joun Murray, Esq., Director of “ Challenger ” Professor Douaetas Mactacan, M.D.
Commission. The Hon. Lorp Mactaren.
WiuiiaM Fereuson, Esq. of Kinmundy, The Rev. Professor Fiint, D.D.
Professor Cossar Ewart, M.D. Professor T. R. Fraser, M.D.

Professor JAMES GEIKIE, F.R,S.

The Treasurer’s Accounts, duly vouched, were laid on the Table.
The Auditor’s Report was read and approved.
On the motion of Professor CRuM Brown, the Auditor was reappointed.

The General Secretary presented an Agreement by the Scottish Meteorological Society,
binding that body to relieve the Royal Society from all pecuniary and other claims connected
with the Observatory Site on Ben Nevis. It was moved by Mr FeErcuson, seconded by
Sheriff Irvine, and carried unanimously, That the Secretary be empowered to sign the
Agreement on behalf of the Society.

On the motion of Mr YounG, a vote of thanks was passed to the Chairman.

698 APPENDIX—PROCEEDINGS OF STATUTORY MEETINGS.

HUNDRED AND SECOND SESSION.

Monday, 24th November 1884.

At a General Statutory Meeting, RoperT Gray, Esq., Vice-President, in the Chair, the
Minutes of last General Statutory Meeting of 26th November 1883 were read, approved, and
signed,

The Ballot for the new Council was then taken, Professors SwAN and Duns having been
nominated Scrutineers. The following Council was duly elected :—

Tuomas STEVENSON, Esq., M.Inst. C.E., President.

Rev. W. Linpsay Auexanper, D.D.

Rosert Gray, Esq. *
A. Forzes Irvine, Esq. of Drum.
Epwarp Sane, LL.D.

Daviv Mitye Homs, Esq.

Joun Murray, Esq. |

Professor Tarr, M.A., General Secretary.
Professor Turner, F.R.8.
Professor Crum Brown, F.R.S.
Apa Gixiies Situ, Esq., C.A., Treasurer.

ALEXANDER Bucuan, Esq., M.A., Curator of Library and Museum.

Vice-Presidents.

\ Secretaries to Ordinary Meetings.

COUNCILLORS.
Professor Cossar Ewart. Rev. Professor Frnt, D.D.
Professor JAMES GEIKIE. Professor T. R. Fraser, M.D.
Rey. Dr W. Ropertson Smiru. Professor CHIENE.
Srair Acnew, Esq. J. Y. Bucnanan, Esq.
Professor Doueitas Mactagan, M.D. Professor CHRYSTAL.
The Hon. Lorp Macraren. Professor Dickson.

The Treasurer’s Accounts, duly vouched, were laid on the Table.

The Auditor's Report was read, and, on the motion of Sheriff Forses IRVINE, was
unanimously approved.

On the motion of Professor Crum Brown, the Auditor was reappointed.

The Secretary and Treasurer were empowered to sign a Discharge by the Society m
favour of CHARLES THOMAS BRISBANE, Esq. of Brisbane. Sheriff THoMs was admitted a
Fellow.

A vote of thanks was, on the motion of Lord MACLAREN, given to the Chairman.

APPENDIX—PROCEEDINGS OF STATUTORY MEETINGS. 699

Monday, 5th October 1885.

At a Special General Meeting called by the Secretary, under Law XX., for the purpose
of electing a Member of the New Governing Body of George Heriot’s Hospital—THomas
STEVENSON, Esq., President, in the Chair,—

The Secretary read Letter from the Lord Provost; also some Excerpts from the Order in
Council as to Heriot’s Hospital; and explained that the Society's Council had determined
that the Election should be conducted in the same manner as that of Office-Bearers.

On the motion of the President, the Rev. Dr Grant and J. Livineston, Esq., were
requested to act as Scrutineers.

The Scrutineers having examined the Balloting Papers, announced that Dr Jonn Murray
had been unanimously elected.

HUNDRED AND THIRD SESSION.
Monday, 23rd November 1885.

At a General Statutory Meeting, JoHN Murray, Esq., Vice-President, in the Chair, the
Minutes of the last General Statutory Meeting, of 24th November 1884, also those of the
Special Meeting of 5th October 1885, were read, approved, and signed.

The Chairman requested Professor DuNS and Mr A. YounG to act as Scrutineers.

The Ballot for the New Council was then taken, and the Scrutineers reported that the
following were unanimously elected :—

THomas STEVENSON, Esq., M.Inst. C.E., President.
Ropert Gray, Esq.

A. Forses irvine, Esq., of Drum.
Davip Minne Homg, Esq.

Joun Murray, Esq.

Professor Doveitas Mactaaan.
The Hon. Lorp Mactaren.
Professor Tarr, General Secretary.
Professor Turner, F.R.S.
Professor Crum Brown, F.R.S.
Apam Gites Smiru, Esq., C.A., Treasurer.

ALEXANDER Bucuay, Esq., M.A., Curator of Library and Museum.

Vice-Presidents.

\ Secretaries to Ordinary Meetings.

700 APPENDIX—PROCEEDINGS OF STATUTORY MEETINGS,

COUNCILLORS,
Rey. Professor Fiint, D.D. Professor SHIELD NicHoLson.
Professor T. R. Fraser, M.D., F.R.S. T. B. Spracus, Esq.
Professor CHIENE. Professor BurcueEr.
J. Y. Bucnanan, Esq., M.A, Professor M‘Kernprick, F.R.S8.
Professor CHRYSTAL. Tuomas Murr, Esq., LL.D.
Professor Dickson. Professor M‘Inrosu.

The Secretary laid on the Table the Treasurer’s Accounts for the past year, duly vouched.
These were approved.

On the motion of Professor CRuM Brown, seconded by Professor MacLaGAN, the Auditor
was re-elected.

The Secretary laid on the Table proofs of the Fasciculi of Proceedings and Transactions
shortly to be issued.

A vote of thanks was, on the motion of Professor DUNS, unanimously given to the
Chairman.

Ov n0t A)

The following Public Institutions and Individuals are entitled to receive Copies of
the Transactions and Proceedings of the Royal Society of Edinburgh :—

London, British Museum.
Royal
London.
Anthropological Institute of Great Bri-
tain and Ireland, 3 Hanover Square,
London.
... British Association for the Advancement
of Science, 22 Albemarle Street,
London.

Society, Burlington House,

.. Society of Antiquaries, Burlington
House.
Royal Astronomical Society, Burlington
House.
-.. Royal Asiatic Society, 22 Albemarle
Street.
... Society of Arts, John Street, Adelphi.
... Atheneum Club.
Chemical Society, Burlington House.
Institution of Civil Engineers, 25 Great
George Street.
..- Rvyal Geographical Society, Burlington
Gardens.
... Geological Society, Burlington House.
... Royal Horticultural Society, South Ken-
sington.
... Hydrographic Office, Admiralty.
Royal Institution, Albemarle Street, W.
... Linnean Society, Burlington House.
-.. Royal Society of Literature, 4 St Mar-
tin’s Place.
Medical and Chirurgical Society, 53
Berners Street, Oxford Street.
Royal Microscopical Society, King’s
College.
Museum of Economic Geology, Jermyn
Street.
Royal Observatory, Greenwich.
Pathological Society, 53 Berners Street.
Statistical Society, 9 Adelphi Terrace,
Strand, London.
Royal College of Surgeons of England,
40 Lincoln’s Inn Fields.

London, United Service Institution, Whitehall
Yard.
University College,
London.
Zoological Society, 11 Hanover Square.
The Editor of Nature, 29 Bedford
Street, Covent Garden.
The Editor of the Electrician, 396
Strand.
Cambridge Philosophical Society.
University Library.
Historic Society of Lancashire and Cheshire.
Leeds Philosophical and Literary Society.
Manchester Literary and Philosophical Society.
Oxford, Bodleian Library.
Yorkshire Philosophical Society.

Gower Street,

SCOTLAND.
Edinburgh, Advocates Library.
University Library.
College of Physicians.
Highland and Agricultural Society,
3 George IV. Bridge.
Royal Medical Society, 7 Melbourne
Place, Edinburgh.
Royal Physical Society, 40 Castle
Street.
Royal Scottish Society of Arts, 117
George Street.
Royal Botanic
Row.
Aberdeen, University Library.
Dundee, University College Library.
Glasgow, University Library.
Philosophical Society, 207 Bath Street.
St Andrews, University Library.

Garden, Inverleith

IRELAND.
Royal Dublin Society.
Royal Irish Academy, 19 Dawson Street,
Dublin.
Library of Trinity College, Dublin.

=".

702 APPENDIX.

COLONIES, DEPENDENCIES, &e,
Bombay, Royal Asiatic Society.
... Elphinstone College.
Calcutta, Asiatic Society of Bengal.
Madras, Literary Society.
Canada, Library of Geological Survey.
Queen’s University, Kingston.
Montreal, Royal Society of Canada.
Quebec, Literary and Philosophical
Society.
Toronto, Literary and Historical Society.
+E The Canadian Institute.
Cape of Good Hope, The Observatory.
Melbourne, University Library.
Sydney, University Library.
Linnean Society of New South Wales.
Royal Society of New South Wales.
Wellington, New Zealand. Institute.

CONTINENT OF EUROPE.
Amsterdam, Koninklijke Akademie van We-
tenschappen
; Koninklijk Zoologisch Genootschap.
Athens, University Library.
Basle, Die Schweizerische Naturforschende Gesell-
schaft.
Bergen, Museum.
Berlin, Kénigliche Akademie der Wissenschaften.
Physicalische Gessellschaft.
Bern, Allgemeine Schweizerische Gesellschaft fiir
die gesammten Naturwissenschaften.
Bologna, Accademia delle Scienze dell’ Istituto.
Bordeaux, Société des Sciences Physiques et
Naturelles.
Brussels, Académie Royale des Sciences, des Let-
tres et des Beaux-arts.
Musée Royal d'Histoire Naturelle de
Belgique.
L’Observatoire Royal.
La Société Scientifique.
Bucharest, Academia Romana.
Buda, A Magyar Tudés Tarsasag—Die Ungarische
Akademie der Wissenschaften.
Konigliche Ungarische Naturwissenschaft-
lische Gesellschaft.
Catania, Accademia Gioenia di Scienze Naturali.
Christiania, University Library.
Meteorological Institute.

Coimbra, University Library.

Copenhagen, Royal Academy of Sciences,

Danzig, Naturforschende Gesellschaft.

Dorpat, University Library.

Ekatherinebourg, La Société Ouralienne d’Ama-
teurs des Sciences Naturelles.

Erlangen, University Library.

Frankfurt-am-Main, Senckenbergische Naturfor-
schende Gesellschaft.

Gand (Ghent), University Library.

Geneva, Société de Physique et d’ Histoire
Naturelle,

Genoa, Museo Civico di Storia Naturale.

Giessen, University Library.

Gottingen, Konigliche Gesellschaft der Wissen-
schaften.

Graz, Naturwissenschaftlicher Verein fiir Steier-
mark.

Haarlem, Société Hollandaise des Sciences

Exactes et Naturelles.
Musée Teyler.
Halle, Kaiserliche Leopoldino - Carolinische
deutsche Akademie der Naturforscher.
Halle, Naturforschende Gesellschaft.
Hamburg, Naturwissenschaftlicher y Verein, 6

Domstrasse.
Helsingfors, Siallskapet pro Fauna et Flora
Fennica,

Societas Scientiarum Fennica (Société
des Sciences de Finlande).
Jena, Medicinisch-Naturwissenschaftliche Gesell-
schaft.
Kasan, University Library.
Kiel, University Library.
Ministerial-Kommission zur Untersuchung
der Deutschen Meere.
Kiev, University of St Vladimir.
Konigsberg, University Library.
Leyden, Neerlandsche Dierkundige Vereenig-
ing.
The University Library.
Leipzig, Prof. Wiedemann, KGnigliche Sichsische
Akademie.
Lille, Société des Sciences,
Lisbon, Academia Real das Sciencias de Lisboa.
Sociedade de Geographia, 5 Rua Capello.
Louvain, University Library.
Lucca, M. Michelotti.

APPENDIX. 703

Lund, University Library.
Lyons, Académie des Sciences, Belles Lettres et
Arts.
Société d’Agriculture.
Madrid, Real Academia de Ciencias.
Comision del Mapa Geologico de Espaiia.

Milan, Reale Istituto Lombardo di Scienze, Lettere,
ed Arti.
Modena, Regia Accademia di Scienze, Lettere, ed
Arti.
Montpellier, Académie des Sciences et Lettres.
Moscow, Société Impériale des Naturalistes de
Moscou.

Société Impériale des Amis d’ Histoire
Naturelle, d’ Anthropologie et d’Ethno-
graphie.

Musée Politechnique.

L’ Observatoire Impérial.

Munich, Koniglich-Bayerische
Wissenschaften (2 copies).
Naples, Zoological Station, Dr Anton Dohrn.
Societa Reale di Napoli—Accademia delle
Scienze Fisiche e Matematiche.
Neufchatel, Société des Sciences Naturelles.

Akademie der

Palermo, Signor Agostino Todaro, Giardino
Botanico.
Societa di Scienze Naturali ed Econo-

miche.
Paris, Académie des Sciences de ]’Institut.

Académie des Inscriptions et Belles Lettres

de l'Institut.
... Association Scientifique de France.

Société d’ Agriculture, 18 Rue de Bellechasse.

Société Nationale des Antiquaires de
France.

Société de Biologie.

Société de Géographie, 184 Boulevard St
Germain:

Société Géologique de France, 7 Rue des
Grands Augustins.

Société d’Encouragement pour l’Industrie
Nationale.

Bureau des Longitudes.

Dépdt de la Marine.

Société Mathématique, 7 Rue des Grands
Augustins.

Ecole des Mines.

Mimistére de I’Instruction Publique.

VOL. XXXII. PART IV.

Paris, Musée Guimet, 30 Avenue du Trocadero.
Muséum d’ Histoire Naturelle, Jardin des
Plantes.
L’Observatoire.
Kcole Normale Supérieure, Rue d’Ulm.
Société Frangaise de Physique, 44 Rue de
Rennes.
Ecole Polytechnique.
Société Zoologique de France, 7 Rue des
Grands Augustins.
Revue Scientifique, et Revue Littéraire et
Politique.
Prague, Konigliche Sternwarte.
Koniglich-Béhmische Gesellschaft der
Wissenschaften.
Rome, Accademia dei Lincei.
Societa Italiana delle Scienze detta dei XL.
Societa degli Spettroscopisti Italiani.
Comitato Geologico.
Rotterdam, Bataafsch Genootschap der Proefon-
dervindelijke Wijsbegeerte.
St Petersburg, Académie Impériale des Sciences.
Commission Impérial Archéolo-
gique.
Comité Géologique.
L’Observatoire Impérial de Pul_
kowa. .
Physikalisches Central - Observa-
torium.
Physico-Chemical Society of the
University of St Petersburg.
Stockholm, Kongliga Svenska Vetenskaps-Acade-
mien.
Strasbourg, University Library.
Stuttgart, Verein fiir Vaterlindische Naturkunde
zu Wiirtemberg.
Thronddjem, Videnskabernes Selskab.
Tiibingen, University Library.
Turin, Reale Accademia delle Scienze.
Upsala, Kongliga Vetenskaps-Societeten.
Venice, Reale Istituto Veneto di Scienze, Lettere
ed Arti.
Vienna, Kaiserliche Akademie der Wissenschaften.
Novara Commission.
Oesterreichische Gesellschaft fiir Mete-
orologie, Hohe Warte, Wien.
Geologische Reichsanstalt.
Zoologisch-Botanische Gesellschaft.

6B

704 APPENDIX.

Zurich, University Library.
Commission Géologique Suisse,

ASIA.

Java, Bataviaasch Genootschap van Kunsten en
Wetenschappen.
... The Observatory.
Japan, The Imperial University of Tokio
(Teikoku-Daigaku).

UNITED STATES OF AMERICA. |

American Association for the Advancement of
Science.
Baltimore, Johns Hopkins University.
Boston, the Bowditch Library.
American Academy of Arts and Sciences,
Beacon Street, Boston.
Society of Natural History.
Cambridge, Mass., Harvard University.
Harvard College Observatory.
Chicago Observatory.
Clinton, Litchfield Observatory, Hamilton Col-
lege,
Concord, Editor of Journal of Speculative Philo-
sophy.
New York, State Library.
Philadelphia, American Philosophical Society.
Academy of Natural Sciences,
Logan Square.

Philadelphia, Geological Survey of Pennsylvania.
Salem, The Peabody Academy of Science.
St Louis, Academy of Sciences.
Washington, United States Coast Survey.
United States Fishery Commission.
United States Naval Observatory.
United States Geological Survey of
the Territories.
United States Signal Office.
The Smithsonian Institution,
Surgeon-General’s Office, United
States Army.
Wisconsin, University (Washborn Observatory),
Madison.
Yale College, Newhaven, Connecticut.

MEXICO.

Mexico, Observatorio Meteorologico Central.

SOUTH AMERICA.

Buenos Ayres, Public Museum, per Dr Bur-
meister.
Corduba, Argentine Republic, Academia Nacional
de Ciencias.
The Observatory.
Rio de Janeiro, The Astronomical Observatory.

All the Honorary and Ordinary Fellows of the Society are entitled to the Transactions and Proceedings.
See Notice at foot of page 706.

The following Institutions and Individuals receive the Proceedings only :—

SCOTLAND.
Edinburgh, Botanical Society 5 St Andrew
Square.
Geological Society, 5 St Andrew
Square.

Scottish Geographical Society.
é Mathematical Society, 8 Queen
Street.

Edinburgh, Scottish Meteorological Society, 122
George Street.
Pharmaceutical Society, 36 York
Place.
Geological Society of Glasgow, 207 Bath Street.
The Glasgow University Observatory.
Berwickshire Naturalists’ Club, Old Cambus
Cockburnspath.

APPENDIX. 705

ENGLAND.
London, Geologists’ Association, University
College.

Mathematical Society, 22 Albemarle
Street, London, W.

Institution of Mechanical Engineers,
10 Victoria Chambers, Victoria Street,
Westminster.

Meteorological Office, 116 Victoria Street.

The Meteorological Society, 25 Great
George Street, Westminster.

Nautical Almanac Office, 3 Verulam
Buildings, Gray’s Inn.

Pharmaceutical Society, 17 Bloomsbury

Square, London.

The Editor of the Illustrated Science
Monthly, 3 St Martin’s Place, Trafal-
gar Square, London,

Birmingham Philosophical Society, King Edward’s
Grammar School.
Cornwall, Geological Society.
Epping Forest and County of Essex Naturalists’
Field Club.
Halifax, Geological and Polytechnic Society of
Yorkshire.
Liverpool, Literary and Philosophical Society.
Manchester, Geological Society, 36 George Street.
Newcastle, Philosophical Society.
North of England Institute of Mining
and Mechanical Engineers.
Norfolk and Norwich Naturalists’ Society, The
Museum, Norwich.
Oxford, Ashmolean Society.
Radcliffe Observatory.
Scarborough, Philosophical Society.
Whitby, Philosophical Society.

IRELAND,
Dublin, Royal Geological Society.
Dunsink Observatory.
Belfast, Natural History and Philosophical
Society.

COLONIES, DEPENDENCIES, ETC.

Adelaide, South Australia, University Library.
Royal Society.

Bombay, Natural History Society.

Brisbane, Royal Society of Queensland.

Canada, Natural History Society of Montreal.
Melbourne, Royal Society of Victoria.
Sydney, The Australian Museum,
Halifax, Nova Scotian Institute of Natural
Science.
China Branch of the Asiatic
Society.
The Observatory.
Madras, Superintendent of Government Farms of

Hong Kong,

Madras Presidency.
Queensland, Branch of the Geographical Society.
Tasmania, Royal Society.

CONTINENT OF EUROPE.

Amsterdam, Genootschap der Mathematische
Wetenschappen.

Berlin, Deutsche Meteorologische Gesellschaft.

K. Technische Hochschule.

Bonn, Naturhistorischer Verein der Preussischen
Rheinlande und Westfalens.

Bern, Naturforschende Gesellschaft.

Bordeaux, Société de la Géographie Commer-
ciale.

Brunswick, Verein fiir Naturwissenschaft.

Bucharest, Academia Romana.

Cassel, Verein fiir Naturkunde.

Chemnitz, Naturwissenschaftliche Gesellschaft.

Cherbourg, Société Nationale des Sciences Natu-
relles.

Copenhagen, Naturhistoriske Forening.

Delft, Ecole Polytechnique.

Dijon, Académie des Sciences.

Erlangen, Physico-Medical Society.

Gratz, Chemisches Institut der K. K. Universitit.

Halle, Verein fiir Erdkunde.

Hamburg, Verein fiir Naturwissenschaftliche
Unterhaltung, 29 Steindamm, St Georg.
Lausanne, Société Vaudoise des Sciences Natu-

relles.
Leipzig, Naturforschende Gesellschaft.
Lille, Société Géologique du Nord.
Luxembourg, Société des Sciences Naturelles,
Lyons, Société Botanique.
Société Linnéenne, Place Sathonay.

Marseilles, Société Scientifique Industrielle, 61

Rue Paradis.
Milan, Societa Crittogamologica Italiana.
Modena, Societa dei Naturalisti.

706 APPENDIX.

Nijmegen, Nederlandsche Botanische Vereeniging.
Oberpfalz und Regensburg, Historischer Verein.
Odessa, New Natural History Society.
Offenbach, Verein fiir Naturkunde.
Paris, Société d’Anthropologie (4 Rue Antoine
Dubois).
Société Philomathique.
Ecole Libre des Sciences Politiques.
Bureau des Ponts et Chaussées.
Pisa, Nuovo Cimento.
St Petersburg, Imperatorskoe Russkoe Geogra-
phicheskoe Obtshéstvo.
Stockholm, Svenska Siillekapet for Anthropo-
logi och Geografi.
Tiflis, Physical Observatory.
Toulouse, Académie des Sciences.
Trieste, Societa Adriatica di Scienze Naturali.
Museo Civiso di Storia Naturale.
Tromso, The Museum.
Utrecht, Provinciaal Genootschap van Kunsten
en Wetenschappen.
Vienna, K.K. Naturhistorisches Museum.
Zurich, Naturforschende Gesellschaft.

ASIA.

China, Shanghai, North China Branch of the
Royal Asiatic Society.
Japan, Tokio, The Seismological Society.
Yokohama, Deutsche Gesellschaft fiir
Natur- und Volkerkunde Ostasiens.
Java, Batavia, Koninklijke Natuurkundije
Vereeniging,

UNITED STATES,

Annapolis, Maryland, St John’s College.
Chicago Observatory.
California, State Mining Bureau, Sacramento,
Cincinnati, Observatory.
... Society of Natural History.
Cincinnati, Ohio Mechanics’ Institute.
Colorado, Scientific Society.
Connecticut, Academy of Arts and Sciences.
Davenport, Academy of Natural Sciences.
New York, The American Museum of Natural
History.
The American Geographical and Sta-
tistical Society.
Salem, The Essex Institute.
Peabody Academy of Science.
San Francisco, The Lick Observatory.
Trenton, Natural History Society.
Washington, Philosophical Society.
American Museum of Natural His-
tory, Central Park. :
United States National Museum.
Wisconsin, Academy of Sciences, Arts, and
Letters,

SOUTH AMERICA.

Rio de Janeiro, Museu Nacional.

MEXICO.

Mexico, Observatorio Meteorologico-Magnetico
Central.
Tacubaya, Observatorio Astronomico,

NOTICE TO MEMBERS.

All Fellows of the Society who are not in Arrear in their Annual Contributions, are entitled to receive Copies of the
Transactions and Proceedings of the Socicty, provided they apply for them within Five Years of Publication.

Fellows not resident in Edinburgh must apply for their Copies either personally, or by an authorised Agent, at the

Hal of the Society, within Five Years after Publication.

my r< TO VOL. XXXL.

A

Amphicheiral Knots. See Knots.

AiTKen (JouN), F.R.S.E. On the Formation of
Small Clear Spaces in Dusty Air, 239.

AnprEws (Tuomas), Assoc.M.Inst.C.E., F.R.S.E.
On the Relative Electro-Chemical Positions of
Wrought Iron, Steels, Cast Metal, &., in Sea
Water and other Solutions, 204.

Asteroidea dredged in the Faroe Channel during the
Cruise of H.M.S. “ Triton” in 1882. By W.
Percy Stapen, F.L.S., 153.

B

Bipartite Functions, By Tuomas Murr, LL.D.,
F.R.S.E., 461.

Bracke (Professor Jonn Stuart), F.R.S.E. On
the Philosophy of Language, 343.

Brewster (Sir Davin). Note on Sir David
Brewster’s Line Y in the Infra-Red of the
Solar Spectrum. By Professor C. Piazzi
Smytu, F.R.S.E., 233.

Bright Clouds on a Dark Night Sky. By Professor
C. Prazzi Smytu, F.R.S.E., 11.

C

Calcareous Formation of the Solomon Group. By
H. B. Guppy, M.B., F.G.S., 545.

CasetLA (Mr Cuartzs F.). On the Preparation
and Purification of Vacuum Tubes, 458.

Chain-Fractions. On the Approximation to the
Roots of Cubic Equations by help of Recurring
Chain-Fractions. By Epwarp Sane, LL.D.,
E.R.S.E., 311.

Curistison (Dr Davin).
Rosert), 45.

—— (Sir Rosert), Bart., F.R.S.E., and Dr Davin
Curistison. The Annual and Monthly
Growth of Wood in Deciduous and Evergreen
Trees, 45,

See Curistison (Sir

CrysraL (Professor), F.R.S.E. On the Hessian,
645.

Circulants. Detached Theorems in Circulants.
Tuomas Muir, LL.D., F.R.S.E., 639.
Clear Spaces in Dusty Air. By Mr Joun AITKEN,

F.R.S.E., 239.

Clouds (Bright) on a Dark Night Sky. By C.
Prazzi Smytu, F.R.S.E., Astronomer-Royal for
Scotland, 11.

Cremona (Professor L.) Hon., F.R.S.E. An Ex-
ample of the Method of Deducing a Surface
from a Plane Figure, 411.

Cubic Equations. On the Approximation to the
Roots of Cubic Equations by help of Recurring
Chain-Fractions. By Epwarp Sane, LL.D.,
F.R.S.E., 311.

CunnincHaM (J. T.), B.A., F.RS.E. On Sticho-
cotyle Nephropis, a new Trematode, 273.

By

D

Dusty Air. On the Formation of Small Clear
Spaces in Dusty Air. By Mr Jounn ArrTKen,
FE.R.S.E., 239. Effects of Gravitation, 243;
of Cold, 243; of Evaporation, 246; of Heat,
246; of Centrifugal Force, 251; of Electricity,
252 ; the Lungs and Dust, 256.

E

Ectocarpus, Note on. By Joun Rattray, M.A.,
F.R.S.E., 589.
Electricity. Effect of Electricity on the Formation
of the Dark Plane in Dusty Air. See Dusty Air.
Observations on Atmospheric Electricity. By
Professor C. Micutz Smitu, F.R.S.E., 583.
—— HElectro-Lighted Gas-Vacuum Tubes, 424.
Electro-Chemical Positions of Wrought Iron, Steels,
Cast Metal, &c., in Sea Water and other Solu-
tions. By THomas AnpREws, F.R.S.E., 204.

708

F

Faroe Channel. Pycnogonida of, 1; Tunicata of,
93; Pennatulida of, 119; Asteroidea of, 153.

G

Gaseous Spectra. See under Spectrum Analysis.

Geological Structure of the Volcanic Rocks of Shet-
land. See Shetland.

Gipson (R. J. Harvey), F.R.S.E. Anatomy of
Patella vulgata, 601; Historical Account, 601;
Morphology, 603; Viscera, 604; Alimentary
System, 605; Respiratory System, 614; Renal
System, 617; Connective Tissue System, 620 ;
Muscular System, 621; Epidermal System,
622; Protective System, 624; Reproductive
System, 633.

Grating and Glass-Lens Solar Spectrum im 1884.
See under’Spectrum Analysis.

Green Sun. See under Sun.

Guppy (H. B.), F.G.S. Observations on the Recent
Caleareous Formations of the Solomon Group
made during 1882-84, 545.

H

Hay (Matruew), M.D. A Contribution to the
Chemistry of Nitroglycerine, 67.
and Orme Masson, M.A., B.Sc., F.R.S.E.

The Elementary Composition of Nitroglycerine,

87.

Herpman (W.A.), D.Sc. F.R.S.E., Professor of
Natural History in University College, Liver-
pool. Report on the Tunicata collected during
the Cruise of H.M.S. “Triton” in the summer
of 1882, 93.

Report on the Tunicata dredged during the

Cruises of H.M.SS. “ Porcupine” and “ Light-
ning” in 1868, 1869, 1870, 219.

Herscuet (Professor ALEXANDER §.).
Green Band of CO, 454.

Hessian, On the. By Professor Curystat, F.R.S.E.,
645.

Horx (Dr P. P. C.).

On the

The Pycnogonida dredged in

the Faroe Channel during the Cruise of H.M.S. |

“Triton” in August 1882, 1.

Horne (Jonny), F.R.S.E., and Pracn (B. N.),
F.R.S.E. The Old Red Sandstone Volcanic
Rocks of Shetland, 359.

Hoyts (W. E.), M.A., F.R.S.E.. On a New Species
of Pentastomum (P. protelis) from the Mesen-
tery of Proteles cristatus, with an Account of
its Anatomy, 165.

INDEX.

K

Kinematics of Mechanisms, a New Graphic Analysis
of, 507.

Kirkman (Rev. T. P.), F.R.S. The Enumeration,
Description, and Construction of Knots of
fewer than Ten Crossings, 281.

—— The 364 Unifilar Knots of Ten Crossings,
enumerated and described, 483.

Knots. Knots of fewer than Ten Crossings, 281.
The 364 Unifilar Knots of Ten Crossings,
enumerated and described. By Rev. THomas
P. Kirxmayn, F.R.S., 483.

—— By Professor Tait, Sec. R.S.E., Part II.
Census of Eightfold and Ninefold Knottiness,
327. Beknottedness, 335.

—— Part III. Various Orders and Classes of
Amphicheirals, 493. Census of Tenfold
Knottiness, 501. The various Types of
Tenfolds, with their distinct Forms, 503.

Kworr (Professor C. G.), D.Sc, F.R.S.E. On
Superposed Magnetisms in Tron and Nickel,
193.

L

Language. On the Philosophy of Language. By
Professor JoHn Stuart Buackin, F.R.S.E.,
343,

Little b Group of Lines in Solar Spectrum. See
Spectrum Analysis.

M

Magnetism. On Superposed Magnetisms in Iron
and Nickel. By Professor C. G. Kvyort,
F.R.S.E., 193.

Marsuauti (A. Miryzs), M.D., D.Sc., Professor of
Zoology in Owens College. Report on the —
Pennatulida dredged by H.M.S. ‘“ Triton,”
19.

Mechanisms. A new Graphic Analysis of the Kine-
matics of Mechanisms. By Professor Rosprrt
H. Sirs, 507.

Murr (Tomas), LL.D., F.R.S.E. On Bipartite

Functions, 461.

Detached Theorems on Circulants, 639.

N
Nitroglycerine. A Contribution to the Chemistry
of Nitroglycerine. By Marruew Hay, M.D.,
67.

—— Action of Potash, Ammonia, Alkaline Car-
bonates, Phosphate of Soda, Chloride of Sodium
Acids and Sulphides, and Water on Nitro-

INDEX.

glycerine, 75-82. Preparation and Characters
of Nitroglycerine, 83.

Nitroglycerine. The Elementary Composition of
Nitroglycerine. By Marraew Hay, M.D., and
Orme Masson, M.A., B.Sc., F.R.S.E., 87.

O

Old Red Sandstone. See under Sandstone.

Pp

Partitions. Note on a Problem in Partitions.
Professor Tait, R.S.E., 340.

Patella vulgata, Anatomy and Physiology of
Patella vulgata. Part I.—Anatomy of. By
R. J. Harvey Gipson, F.R.S.E., 601.

Psaco (B. N.), F.R.S.E., and Horne (Jonn),
F.R.S.E. The Old Red Sandstone Volcanic

Rocks of Shetland, 359.
Pennatulida. Report on the Pennatulida dredged

by H.M.S. “Triton.” By A. Minwes MarsHatt,
M.D., Professor of Zoology in Owens College,
w1g.

Pentastomum, A New Species of, from the Mesen-
tery of Proteles cristatus, with an account of
its Anatomy. By W. E. Horus, M.A.,
FE.R.S.E., 165. Body-Wall, 167. Muscular
System, 169. Digestive Tract, 174. Secretory
Organs, 177. Nervous System, 180.
tive Organs, 181.

Proteles cristatus. See Pentastomum.

Pyenogonida dredged in the Faroe Channel during
the Cruise of H.M.S. “Triton” in August
£s82- By Dr P: P..C. Hox, 1.

By

Genera-

R

Ratrray (Joun), M.A., F.R.S.E.. Note on Ecto-
carpus, 589.

S

Sandstone (Old Red) Volcanic Rocks of Shetland.
By B. N. Peacu, F.R.S.E., and Jonn Horns,
E.R.S.E., 359.

Sane (Epwarp), LL.D., F.R.S.E. On the Approxi-
mation to the Roots of Cubic Equations by
help of Recurring Chain-Fractions, 311.

Shetland. On the Old Red Sandstone Volcanic
Rocks of Shetland. By B. N. Psacu, F.R.S.E.,
and Joun Horne, F.R.S.E., 359. Contem-
poraneous Lavas and Tufis, 361. Intrusive
Igneous Rocks, 368. Microscopic Characters,
379. Chemical Analysis of Eight Specimens
of Shetland Volcanic Rocks, 359.

709

Snapen (W. Percy), F.LS., F.G.S. Asteroidea
dredged in the Faroe Channel during the
Cruise of M.H.S. “Triton” in August 1882,
153.

Smite (Professor C. Mrcuiz), F.R.S.E. Observations
on a Green Sun and associated Phenomena,
389.

—— Observations
583.

SmitH (Professor Rogperr H.). A New Graphic
Analysis of the Kinematics of Mechanisms,
507.

SmyrH (C. Prazzi), F.R.S.E., Astronomer-Royal
for Scotland. Bright Clouds on a Dark Night
Sky, 11.

—— Note on the Little b Group of Lines in the
Solar Spectrum and.the new College Spectro-
scope, 37.

—— Note on Sir David Brewster’s Line in the
Infra-Red of the Solar Spectrum, 233.

—— Micrometrical Measures of Gaseous Spectrum
under High Dispersion, 415.

—— The Visual, Grating and Glass-Lens, Solar
Spectrum in 1884, 519.

Solomon Group. Observations on the Recent Cal-
careous Formations of the Solomon Group,
made during 1882-84. By H. B. Guppy,
M.B., F.G.S., 545.

Spectroscope. The new (Edinburgh) College Spec-
troscope. By C. Prazzi Smytu, F.R.S.E.,
Astronomer-Royal for Scotland, 37.

Spectrum of Green Sun. By Professor C. MicH1E
SmitH, 393.

Spectrum Analysis.

Note on the Little b Group of Lines in the
Solar Spectrum and the new College Spectro-
scope. By C. Piazzt Smyru, F.R.S.E.,
Astronomer-Royal for Scotland, 37.

—— Note on Sir David Brewster’s Line Y in the
Infra-Red of the Solar Spectrum. By C.
Prazat SuytH, F.R.S.E., 233.

— Micrometrical Measures of Gaseous Spectra
under High Dispersion, 416 ; Candle Spectrum,
or HC Gas in Blowpipe Flame, 418; the CO
Spectrum, 435; Elementary Gases, H, 440;
O, 444; N, 446. By C. Piazzt Smyru,
E.R.S.E., 415.

—— The Visual, Grating and Glass-Lens, Solar
Spectrum in 1884. By C. Prazzi Smyru,
FE.R.S.E., 519.

Stichocotyle Nephropis, a new Trematode.

T. CunnincHam, F.R.S.E., 273.

Observations on a Green Sun and associated

on Atmospheric Electricity,

By J.

Sun.

710

Phenomena. By Professor C. Mion1e Sirs,
F.R.S.E., 389.

Surfaces. Example of the Method of deducing a
Surface from a Plane Figure. By Professor
L. Cremona, Hon. F.R.S.E., 411.

Tr

Tair (Professor), Sec. R.S.E. On Knots. Part
1G EV a

—— (Appendix). Note on a Problem of Parti-
tions, 340.
—— On Knots. Part IIL, 493.

Trees. Annual and Monthly Growth of Wood in
Deciduous and Evergreen Trees. By Sir
Rosert Caristison, Bart., and Dr Davin
Curistison, 45. Annual Increase in Girth of
Deciduous Trees, 47. Annual Increase in Girth
of Evergeeen Trees, 48. Monthly Increase in
Girth of Trees, 51-59. Influence of Weather
on the Growth of Wood, 59.

INDEX.

Tunicata collected during Cruise of H.M.S. “ Triton”
in 1882, 93. Report on the Tunicata dredged
during the Cruise of H.M.SS. “Porcupine”
and “Lightning” in 1868, 1869, 1870. By
Professor W. A. Hmrpman, 219.

U

Unifilar Knots of Ten Crossings, 364 enumerated
and described. By Rev. THomas P. Kirkman,

F.R.S., 483.
v
Visual Solar Spectrum in 1884. See under Spectrum
Analysis.
Ww

Wood. Observations on the Annnal and Monthly
Growth of Wood in Deciduous and Evergreen
Trees, By Sir Ropert Curistison, Bart., and
Dr CarIstTIson, 45.

29 JUL. 1887

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