ON SOME REMARKABLE INSTANCES OF CROOKES’S
LAYERS, OR COMPRESSED STRATA OF POLARIZED
GAS, AT ORDINARY ATMOSPHERIC TENSIONS.

BY
GEORGE JOHNSTONE STONEY, o.a., F.R.s.
[Read November 19th, 1877. ]

1. In a communication which I had the honour to lay before
the Royal Dublin Society at its last scientific meeting, I gave
some instances of Crookes’s layers at ordinary atmospheric ten-
sions,* and among them described one which accounts for the
great mobility that may be imparted to a light powder by heating
it in a metal capsule. It is shown that in this case the powder
floats on a stratum of air which it compresses by its weight, at
the same time that it maintains the requisite polarized condition
of the layer by radiating away its own heat so freely as to keep
itself cooler than the capsule.

2. In exactly the same way we may explain a very curious
phenomenon which has been recorded by travellers in Arabia, and
to which Professor Barrett has directed my attention. There is in
Arabia a mountain called Jebel Nagus, or Gong Mountain, which
produces sounds resembling the booming of the Nagus, or wooden
gong, used in Eastern churches instead of bells. The mountain
consists of a white friable sandstone, which produces to the south-
westward a great slope of very fine drift sand, and another smaller
one to the north. The large one is 115 metres high, 70 metres
wide at the base, and tapers towards the top. It is so steep,
being inclined to the horizon at an angle of nearly 30°, and con-
sists of such fine sand, that its surface can be easily set in motion
by scraping away a portion from its base or by disturbing it

* The theory of unequal stresses in polarized gas has thus fulfilled an anticipation which
Mr. Crookes entertained so long ago as 1873, that whatever theory would account for
the motion of radiometers would, probably, also explain the spheroidal state of liquids, and
the mobility of finely divided precipitates in heated capsules; for he enumerates these.
among phenomena, probably due, at least in part, to the same ‘“‘ repulsive action of radiation”
as is manifested in radiometers. (See Philosophical Transactions, vol. 164, p. 526). I

have only become acquainted with this passage since writing the present paper, or, if I had
seen it before, I had forgotten it, otherwise I should have referred to it in my last paper.

54 Mr. G. JOHNSTONE STONEY,

elsewhere. If this is done after the surface has been for a long
time exposed to the sun—

“The sand rolls down with a sluggish viscous motion and the sound

begins, at first a low vibrating moan but gradually swelling out into a.
roar like thunder, and as gradually dying aay, (Palmer’s “ Desert ‘of

the Exodus,” vol. 1, p. 218).

That heat contributes largely to thaw effect was proved by the
valuable observations made by Captain Palmer, for it was found—

“That the heated surface was much more sensitive to sound than the
cooler layers beneath, and that those parts of the slope which had lain
long undisturbed produced a much louder and more ee sound than
those which had recently been set in motion.”

Moreover, when the experiments were repeated on the ona!
talus, which faced towards the North, and part of which was in’

perpetual shade, it was found—

That the sand on the cool shaded portion, at a temperature of aos

I

produced but a very faint sound when set in motion, while that on the-
more exposed parts, at a temperature of 40°, gave forth a loud and even -

startling noise.”

. These observations were made in winter. They clearly indicate:
that heat renders the surface of the slope more mobile by polariz-.

ing the air between the hotter and cooler particles of the sand.

The more intense the sunshine, the more powerful must the
Crookes’s layers be, and the more widespread will be the effect of
any accidental disturbance. And if under the fierce glare of the
tropical sun the strength of the Crookes’s layers becomes sufficient’
to lift the uppermost grains of sand, the sliding motion, with its.
humming, booming, and thundering noise, will spring up without:
visible cause—a phenomenon that sometimes occurs and has

naturally occasioned much speculation.

Mr. Howard Grubb has directed my attention to another natural
phenomenon which admits of being explained by the mechanical
properties of polarized layers of gas. In certain states of the
weather large grains of sand, flat pieces of shell, and even

flakes of stone of quite a considerable size may be seen floating on

the tide as it flows in. I saw this phenomenon myself whena
boy, but unfortunately did not make a careful examination of the —
attendant circumstances. It is, however, easy to see the conditions
which would be most favourable to its production. They area

- =

”

On Crookes’s Layers, at Atmospheric Tensions. 55

very powerful sun to heat the stones and to maintain their tem-
perature sufficiently high after they are set floating ; calm air
that no breeze may cool them; a cold sea to increase as much as
possible the difference in temperature between the flakes of stone
and the water, and the absence of waves that the heavy little
barges may escape shipwreck.

I think it fortunate that I had written out the foregoing state-
ment of the conditions indicated by the theory, before I saw the
following record of observations upon this phenomenon made by
Professor Hennessy. (See Proceedings of the Royal Irish Academy,
Vol. L, Series 2) :—

“On the 26th July, 1868, when approaching the strand at the river
below the village of N ewport, county Mayo, I noticed what appeared to
be extensive streaks of scum floating on the surface of the water * * *
until I stood on the edge of the strand, and I then perceived that what
was apparently scum seen from a distance, consisted of innumerable
particles of sand, flat flakes of broken shells, and the other small débris
which formed the surface of the gently sloping shore of the river. The
sand varied from the smallest size visible to the eye, up to little pebbles
nearly as broad and a little thicker than a fourpenny piece, Hundreds
of such little pebbles were afloat around me. ‘The air during the whole
morning was perfectly calm, and the sky cloudless, so that although it
was only half-past nine, the sun had been shining brightly on the exposed
beach. The upper a of each of the little pebbles was perfectly dry;
and the groups which they formed were slightly depressed. in curved
hollows of the liquid. The tide was rapidly rising, and owing to the
narrowness of the channel at the point where I made my observations
the sheets of floating sand were swiftly drifting farther up the river into
brackish and fresh water. On closely watching the rising tide at the
edge of the strand, I noticed that the particles of sand, shells, and small
flat pebbles, which had become perfectly dry and sensibly warm under
the rays of the sun, were gently uplifted by the calm are es rising
water, and then floated as readily as chips or straws.”

The calm air, tranquil water, hot sun, and warm stones, predicted
from the theory, are all recorded in these observations,

This rare phenomenon must not be confounded with the familiar
one in which patches of fine sand float upon water in con-
sequence of its surface tension. The surface tension of water in
contact with air will not support flakes of stone of above a certain
size, and those described by Professor Hennessy are at or beyond
the limit of size* that could even if separate be floated by surface

* Taking the surface tension of water in contact with air as 8:25 grammes per metre
as determined at 20° C. by M. Quincke, and assuming 2°5 as the “ee gravity of the

F2

56 Mr. G. JOHNSTONE STONEY,

tension. Hence they could not be supported by that agency in
the groups which he describes. We are therefore forced to look

elsewhere for the cause of the support of these groups; the

thermal and mechanical properties of Crookes’s layers show that
they will suffice: and we have seen that all the conditions were
present which would call Crookes’s layers into existence.

Mr. George F. Fitzgerald has pointed out another very striking
example. A piece of cold iron may be made to float on melted
east iron, and will even float high like cork on water. Here
the difference between the temperature of the glowing mass
of molten metal and the cold piece of iron is so considerable
that the stresses that are developed are able to support the
weight of the piece of iron while it is still at such a distance
from the fiery liquid that it seems to float high upon it.
What it floats on is in reality a bath of polarized air, the
stresses within which both support its weight and foree down
the surface of the molten metal. This air-bath keeps it out of
contact with the glowing mass; and, accordingly, it receives heat
from below only by diffusion and radiation, in quantities far
short of what it would receive from actual contact, and as it loses
much heat by radiation upwards, it may be able for a considerable
time to maintain a sufficiently low temperature to continue
floating.

On the same principles we are to explain the safety of expla
that are occasionally performed, viz—The licking of a white hot
poker, the dipping of the fingers into molten metal, and the plung-
ing of the hand into boiling water. In all these cases the
Crookes’s layers that intervene prevent that contact which would
cause a dangerous scald or burn. ii .

It is usual before performing these two latter experiments, to
moisten the hand with soapy water, ether, turpentine, or liquid
ammonia. All of these would have the useful effect of lowering
the surface-tension of the hot liquid, and thus diminishing the
extent to which it would compress the Crookes’s layer.

_ But the most splendid example I have yet seen of a Creve
layer is one which was first noticed by M. Boutigny, and which

stone, it follows that a circular disk, 16 m.m. in diameter and 0°85 of a m.m. in thickness —
would be the extreme theoretic limit that could be supported by surface tension, Thisis —

about the size of a fourpenny bit. ~

On Crookes’s Layers at Atmospheric Tensions. 57

was shown by Professor Barrett, at the Brighton meeting of the
British Association, with the improvement of adding soap to
the water, an addition which seems essential to the full success
of the experiment. A copper ball, some six cm. in diameter,
furnished with a staple by which it can be lifted, was brought to
a bright red heat, and while glowing was lowered into a large
beaker of soapy water. As the ball approaches the cold surface
of the water heat passes from the ball to the water by conduction
or penetration* as well as by radiation ; accordingly the interven-
ing air becomes intensely polarzied, and the Crookes’s stress that
accompanies the polarization makes a hollow in the surface of the
water. Let the ball be lowered till it is half submerged, the de-
pression in the water is now nearly hemispherical, but not quite
so, since the interposed layer of polarized gas will. be thinnest at
the bottom, where, to withstand the pressure of the water, it must
exert most force. The stresses at any point of this polarized
layer consist of a constant stress P nearly equal to the tension of
the open atmosphere, acting equally in all directions, along with
a variable Crookes’s stress p, acting for the most part nearly in
the direction of a radius of the ball; the most marked deviation
from this direction being close to Ane horizontal surface of the
water, where the action of the upper hemisphere of the ball gives
an inclined direction to the Crookes’s stresses, and helps to round
off the surface of the water. The amount of the Crookes’s
pressure acting on the water will vary with the depth, being such
at each point that it gives a component equal and opposite to
the resultant of the pressure of the water at that depth, and of
the surface tensions round the point. Whenever the Crookes’s
force is not quite in the direction of this resultant, there will be
a free tangential component, and this must produce surface cur-
rents in the water. These, however, cannot be observed in the
present experiment because they are of small amount, and too
much mixed up with convection currents arising from the heat
that reaches the water by radiation and diffusion.

When the ball is lowered until it is quite submerged it will be
surrounded on all sides by its envelope of polarized air, thinnest at

_ * The heat which diffuses across a layer of gas passes under what are known as the
laws of conduction if the number of gaseous molecules present is sufficiently large. If
fewer molecules are present the heat passes under other laws, which may be distinguished:
from the laws of conduction by calling them the laws of penetration.

58 Mr. G. JoHNSTONE STONEY, |

the bottom, where the pressure of the water is greatest, thickest
above. So long as there is any communication between the
polarized layer and the atmosphere, the lateral stresses within
the layer will be equal to P, while those in the direction in which
the heat penetrates will be P+; but both of these will suffer
an increase if the ball is plunged deeper after the communication
with the atmosphere has been cut off. No one can see this splendid
experiment for the first time without a feeling of astonishment.

- A Crookes’s layer formed in the same way, but without the
exquisite beauty which it has in this experiment, may be seen
any day in a smith’s forge, whenever the smith has occasion to
quench white-hot iron in water.

A phenomenon closely resembling the experiment with the
glowing ball was witnessed lately by my brother and two
other friends while out walking. There was a shower when they
reached some rather deep water. The afternoon had become
chilly, and the phenomenon that presented itself shows that the
water must have retained a temperature higher than that of the
air. As the rain-drops fell into the water, some of them
(estimated at one in twenty) became spheroidal drops floating on
the water, and of these some (estimated at one in six) were
visibly submerged before floating about as spheroidal drops.
They sank, perhaps about half a centimetre before they rose to
the surface, and while under water looked like silvered pills,
owing to the total reflection from the boundary between the
water and the film of polarized air which enveloped each drop.
~ Several times, in the course of this communication, I have had
occasion to speak of the feebleness of conduction or penetration,
compared with the rapid outpour of heat which takes place on
direct contact between a very hot and a cold body. This is well
illustrated ee an experiment of M. Boutigny, in which a
spheroidal drop of water is formed inside a hot copper bottle, and
the neck of the bottle partially stopped by a cork through which
a thin tube passes. So long as the drop continues in the
spheroidal state, a mixture of air and vapour slowly escapes

through the tube in the cork, but the instant the spheroidal state
ceases, and the water comes into contact with the copper, a suffi-
cient portion of the water flashes off so suddenly into steam er

the cork is driven out with explosive violence.

On Crookes’s Layers at Atmospheric Tensions, 59

A still more instructive illustration of these facts is afforded by
the familiar experiment, known to every smith, that an explosion
will occur if a little water is dropped on an anvil, if a white-hot
strap of iron is laid over the drop, and if the iron is then given a
tap with the sledge-hammer. In this experiment the hot iron,
when laid on the anvil, does not fit it accurately, but comes into
contact only at a few points, and leaves a chink elsewhere. While
the iron is descending towards the drop of water, a Crookes’s
layer of polarized air is formed between it and the cold water,
which-exerts a sufficient pressure upon the drop, both to flatten it
out, and to keep it from coming into contact with the glowing
iron, At this stage of the experiment the lower portion of the
chink is occupied by water, and the upper portion by polarized
air. The stratum of air moderates the flow of heat towards the
water, so that the water is able to continue liquid by parting
with as much heat downwards to the cold anvil as it receives from
above, before it is itself warmed beyond the boiling point. But when
the sledge-hammer descends, the soft iron yields, the chink is
obliterated with a force greater than that which the Crookes’s layer
can support, and the glowing mass comes, in many places, into
direct contact with the water. The vastly augmented flow of
heat which is consequent upon this direct contact, rushes across
the film of water with a speed equal to the velocity of sound in
water, which will carry it across a film the seventh ofa millimetre
in thickness in the ten-millionth of a second. Within this brief
period of time the greater part of the water is raised to a very
high temperature, and its sudden conversion into red-hot steam
causes the explosion.

Before concluding this communication I wish to take the
opportunity of publicly thanking my scientific friends for their
kindness in bringing such remarkable instances of Crookes’s ~
layers at ordinary atmospheric tensions to my notice and giving
me permission to publish an account of them.

ON THE CHEMICAL COMPOSITION OF THE COAL DIS-
COVERED BY THE ARCTIC EXPEDITION OF 1875-6.
BY
RICHARD J. MOSS, F.C.S.,

Keeper of the Minerals, Museum of Science and Art.

[Read November 19th, 1877. ]

Durine the late Arctic Expedition an extensive seam of coal was
discovered in Grinnell Land, close to. the winter quarters of
H.MS. Discovery, 81° 43’ N.L., 64° 4° W.L. Dr. Moss, late of
H.MS. Alert, presented a large specimen of the coal to this
Society. It is now deposited in the Museum of Science and Art.
The specimen was taken by Dr. Moss from the seam at about
fifteen feet from its upper surface, the estimated thickness of the
seam being about twenty-five feet. The coal possesses the lustre,
fracture, and other external characters of bituminous coal of good
quality, notwithstanding that the shale which overlies it is rich
in fossil remains of a flora of the Miocene period. The coal cakes
when heated, and leaves sixty-one per cent. of a coherent coke.
Its specific gravity is 13. The following are the results of my
analysis, every precaution having been taken to insure that the
sample analyzed was a fair average of the entire specimen :—

Carbon, . : ane ‘ 75°49
Hydrogen, . : . 5°60
Oxygen and Ni trogen, : : 9°89
Sulphur, *. ° . 0-52
Ash, “ : : ; 6:49
Water, : : : 2:01

100-00

The composition of the coal, excluding water, sulphur, and
ash, 18 :—

Carbon, . " : . 82:97
Hydrogen, : : 6°16
Oxygen and Nitr ogen, : : 10°87

100-00

* Including Sulphur in the form of iron pyrites, 0°36 per cent.

62 Mr. R. J. Moss, F.C.S. On Arctic Coal.

I have analyzed the ash and found that it consists of ——-

Silica, . ; ; : 5 34-69

Alumina, : : ; LT Oe
Tron Sesquioxide, d : 5 6-72
Lime, . ie eee ee ; 7:79
Magnesia, : : : : 1:83
Potash, . ; ; pase ei 7:58
Soda, . ‘ . nA 0:10
Sulphuric Anhydride, ‘ A 4 13:79

Phosphoric ee : : : trace

; eplenisie; : A pa) irabe:ra-
Sis) 80

The quantity of potash in the ash is unusually large. On
comparing the composition of the coal with that of other
coals of various geological ages it will be found that the Aretic
coal most closely resembles those of the true carboniferous period.
Coal from the great seam in the Bay of Fundy, Nova Scotia,*
possesses a chemical composition almost identical with that of
the Arctic coal. On the other hand some lignites of the Miocene
period bear a close chemical resemblance to the Arctic coal, if the
composition, exclusive of water, sulphur, and ash, be compared.
For example, a lignite from the Jaland. of Sardinia possesses the
following .compositiont :—

Carbon, 3 ; ‘ 4 82°26

Hydrogen, . REE ee Re uy 6°52
Oxygen and Nitrogen, . ; - 11-22
100-00

It has been shown = Tinea that it is impossible to deter-
mine the geological age of coal from its chemical composition ; of ”
this fact the Arctic coal affords a good ulustration.
; * Percy’s Metallurgy, Fuel, &e., p. 836.

ft Ibid. 313.
-- { Die*Physiographie der Braunkohle.

NOTES ON THE SKELETON OF AN ABORIGINAL
AUSTRALIAN. |
BY
A. MACALISTER, M.D.,
Professor of Comparative Anatomy, University of Dublin.
| [Read November 19th, 1877. ]

THE Museum of the Dublin University has recently received a
fine skeleton of an aboriginal Australian, which is a valuable
addition to its ethnological department. I am indebted to Dr.
R. Tuthill Massy; of Brighton, for. this- interesting donation, and
have made a careful series of measurements and observations on
it, the results of which I have embodied in this paper.

_ The stature was small, 5’ 12”, which is about the average for

Australian natives; though I am informed by Dr. J ohnston, of
this city, who has fad extensive experiences of these races, that
in some tribes, much taller individuals are common; and that on
one occasion he met with an encampment of natives on the Murray
river, many of whom were six feet high. Such are, however,
exceptional, for the general consensus of opinion is that “ very
few could be said to be tall and still fewer to-be eel eae
(Collins’ Account, p. 356.)
_ The skeleton is that of a male, known and eit as & mes-
senger, and who had been known to travel seventy miles in a
day. The proportions are as follows compared with the standard
in a Professor Humphry’ 8 Works —

rs i. as

Height. Spine. Humerus. Radius. Femur. Tibia.
- Australian,. 1-00 - 205°. SLD 286 226

‘Trishmen, . 1:00 -340 194 154 270 ~— 295
Negroes, . 1:00 ‘311 195 -151 274 +939
Bushmen, . 100 314 “20 “153. 277 2389.
Bushwoman, 100 333 182 131 +264 2108

To represent more accurately the relationships of the inter-
membral lengths, I append the following three tables :-—

64 PROFESSOR MACALISTER,

. TABLE IT.
RELATIVE Proportion of FoREARM to HuMERUs in length.
Humerus. Forearm.
Australian, . : 1:00 T4
Bushman, . ‘ 1:00 “80 -
Negro, . : : 1:00 ‘76
European, . : 1:00 6)

The decimal obtained in this table or antebrachial index is in-
teresting, as it shows that this individual had a greater propor-:
tional length of forearm than the average of Europeans, a pithecoid
character.

TABLE III.
RELATIVE PROPORTION of FEMUR to TIBIA.
, Femur. Tibia.
Australian, . : 1:00 80
European, . : 1:00 85
Negro, . : ‘ 1:00 “89
Bushman, . 2 1:00 78

- From this table it appears that the crural index is rather
shorter than usual..

TABLE IV.
RELATIVE PROPORTION of FoREARM and Arm to THIGH and LEG.
Lower. Upper.
Australian, . 5 1:00 69
Bushman, . : 1:00 “ON
European, . : 1:00 ‘70

This intermembral index shows that in this Australian the
proportion of the arm to the leg is smaller even than the European.

The three methods of measurement adopted above are, I think,
calculated to give us more definite results as to the relative
regional developments of extremities than any other plans hither-
to used. With many of the most interesting aboriginal tribes it —
is impossible to get whole skeletons, and when got, the spinal
unit, so important a factor in Professor Humphry’s whole
number, is rather a vague one, on account of the varying thick-
nesses of intervertebral substance, unless-the observer has obtaine
the skeleton while fresh. Limb bones, on the other hand, 4
easily obtained, and by a series of measurements like those given
above and carried out on an extensive scale, we can easily formu-
late in the simplest possible manner, the relative developments of

On the Skeleton of an Aboriginal Australian. 65

the portions of the limbs. One set, like that given here, tells us
comparatively little of ethnological importance, as the original
may have been a Rob Roy among his tribe, or else brachybrachial,
but an extensive series of such measurements would, doubtless,
be of value.

The vertebral column showed no appearances of note. The
third cervical had a trifid spine, as is not uncommonly the case.
The spine of the sixth cervical was bifid, and the transverse pro-
_eess of the seventh perforated at each side. The sacral laminze
were mesially ununited, and the spinal curvatures were smaller
than usual. The sacrum measured 3# inches in length, and 46
inches in breadth, the average male European sacrum being 3°9
inches by 5 inches.

‘The os innominatum is small, not unduly elongated, with no
pre-auricular groove (Zaaijer), but with well-marked muscular
impressions. The thigh bone has a small carina, and its neck
forms a large angle (123°) with the shaft. The anterior inter-
trochanteric and the ectogluteal ridges are strong and rough.

The tibia has a tuberous external condyloid eminence for the
attachment of the ligamentum iliotibiale (Maissiat and Merkel),
a structure which I have always found to be of proportional
strength in all persons, with great powers of endurance in their legs.

The skull presents the usual Australian dolichocephaly, and is
of the usual small size, with narrow frontal region. The sutures
are open and are comparatively simple, the lachrymo-planal being
reduced to a very short space 0°2" in length. There is a distinct
double temporal crest (Hyrtl.), a double supra-orbital hole on the
right side, the inner opening being for the supra-trochlear nerve.
The spheno-parietal suture measures 0°4” on the left, 0°35” on the
right. The occiput has two rough splenial ridges and a short
fissure exists behind each. The tympanic is separated from the
periotic by a distinct deficiency, and the post-glenoid process is
separated from the tympanic bone by a fissure continuous with
the glaserian. <A strong supra-mastoid ridge exists, and strong
stylohyals; a narrow transverse glenoid cavity, and a vertical
anterior edge of the squamosal. The spine of the sphenoid has a
double styloid process, one external and one internal to the
foramen spinosum. The left lachrymal bone has an inferior
hamulus, and the chin process is small,

‘ viened

Saar

a ;
ot ey RB

ea

a 3

fo oe re >
sitahieee Oe 44

a b 9 ge yy ie
RENNES: Lh end pala

yeony pie
Ae eS a5 8

ep apt e

ED

egreetr a bs
th raed thes ad eed Si

”
!

ia, ae vd pagal rts i090 Ne
aaryd all Latiled edetng

wo a ") = fr + >
+ ee OM ut? ry he os a ! ry WHS : F

a

eh aid mork b

ibaa ad dainet Deed? “U

re coe hi we a) TH, B

as eed |
TAD Kiderewae on
j

ie Ae
rhe ret
a a

ae a

A FRAGMENT OF HUMAN SKELETON FROM
NORTH LATITUDE 81° 42’,

BY

DR. EDWARD IL. MOSS.
Late Surgeon H.M.S. Alert.

[Read November 19, 1877.]

At the time the Arctic Expedition of 1875, left England, all that

was known of the migrations of the Eskimo appeared to warrant

the hope expressed in the manual supplied to the expedition by

the Royal Geographical Society that Ethnological results of
interest might be obtained. That hope was based upon the con-.
sideration that the route chosen for the expedition lay through’
an altogether exceptional region, exceptional in that it afforded
the only ascertained. gap in the northern frontier line bounding

the geographical distribution of man.

In every other part of the circumpolar regions Hae fi
had penetrated either to lands, such as Spitzbergen or Franz
Joseph Land, that bore no trace of an indigenous people, or to a
barrier of eastward drifting perennial floes, impassable alike by
Eskimo or European, and which if their full import had been.
appreciated might have saved much speculation as to the possi-
bility of an inhabited Polynia in the middle of the Polar ice-cap.

But on the eastern side of the Parry group, and along both.
shores of Greenland, land spread continuously to the northward,
and though each successive explorer had forced his way to a
latitude never before reached on land, all had been obliged to
confess that at their turning point the soos of their un-
civilized predecessors still lead Poleward.

When our ships started, the most northern known traces of
man, were those found by Dr, Bessels, of the U.S.S. Polaris,
at Cape Lupton. There, within a day’s march of the furthest
point on land reached by his expedition, rings of stones that.
had been used to fasten down the edges of tents, marked the.
temporary camp of some travelling Eskimo,

68 ; Dr. EpwarD L. Moss,

It was from this latitude that our continuous search along the
coast-lines began. South of this point our visits to the shore on
both the outward and homeward voyages were of the most
flying character. Every movement of the ice had to be taken
advantage of, and our naturalists had often less than twenty
minutes to bundle together their specimens, Botanical, Zoological,
and Geological; and yet abundant evidences of man were found
on every beach, till Lady Franklin Sound intersected the coast-
line. The Discovery wintered in a bay inside Bellot Island,
on the north shore of Lady Franklin Sound, and in the same
latitude as Cape Lupton, and the shores to the north instead of
being merely visited at intervals, were traversed over and over
again by our sledge parties.

Lady Franklin Sound had not interrupted the Gee passage
of the Eskimo. Tempted doubtless by the reindeer and musk-oxen,
on Bellot Island and the neighbouring main-land, their hunters
had crossed the sound, and several hearths, where splinters of
burnt drift wood and bits of scorched bone lay amongst the
blackened stones, where found on a long low spit of Bellot Jsland.
On a little rocky island within a stone’s throw of the main-land :
similar marks of summer hunting parties were discovered. For
seventeen miles to the north-eastward the shore still affords a
practicable path; but at Cape Beechey, the steep cliffs of Robeson
Channel rise abruptly from the tumbling stream of Polar ice,
that pours through the strait, under these cliffs and at the very
end of the practicable coast, Captain Feilden discovered a broken
sledge and a broken lamp. From this point northward our sledges
followed the coast for 100 miles to the north-east, and for 250
miles to the north-west and found no further trace. |

All the likely parts of the coast were traversed dozens of times
both before and after the disappearance of the snow, and no spot
where Eskimo had ever camped or cooked could possibly have
escaped us. I feel quite confident that all who have travelled
over the respective coasts will indorse the opinion already pub-
lished by Captain Feilden,* that “the men whose tracks we
followed to the 82° parallel never got round Cape Union, and
that it is impossible for any Eskimo to have rounded the northern
shores of Greenland.” iS

* “ Naturalist,” Aug. and Sept., 1877.

On a Fragment of Human Skeleton. 69

The frontier line of known migration is therefore complete.
Henceforward any hypothesis that inhabited lands exist in the
unknown North must be based only on the vague traditions of
the tribes on both sides of Behring Strait that ee from
their shores have reached Kellett’s Land.

_ But the traces we have hitherto spoken of do not include any
vestige of man himself.

- Even at Norman Lockyer Island, where we found the remains
of a whole city of not only tent circles but “yourts,” meant for
winter habitations, we failed after hours of careful search to find
anything like a burial place. When Captain Feilden discovered
the lamp and sledge, the way in which the lamp was broken—so
like the broken vessels left on the Indian graves of the far west—
and the valuable pieces of wood that had been left lying beside it
suggested the possibility at least that they had been left for the
future use of their buried owner, but I could find no heap of stones
or anything else like a tomb in the neighbourhood.

But seventeen miles backward, along the coast on the northern
shore of Lady Franklin Strait, and at the most southern point
overlooking Kennedy Channel, the fragment of human femur
which I exhibit this evening was picked up. I am not aware
that any human bone has been found in a higher latitude than
the Etah burial-ground at Port Foulke, and this fragment lay
200 miles beyond that spot. The spot where it was found was
eighty feet above the beach, and 100 yards inland, opposite the
spit of Bellot Island, and about three-quarters of a mile eastward
from the marks of camps on “ Dutch ” Island—the rock already
spoken of. It was embedded in the side of one of those little
polygonal hillocks into which the frost splits clayey ground. Both
ends of the bone are broken off, the one through the neck and
trochanters, the other about two inches and a quarter from the
lowest point of the articulating surface. It has been gnawed by
either wolf or fox, though I think the jaws of the little arctic
fox are hardly strong enough to break the ends off so strong a
bone. Like every other trace of man found at high latitudes in
Smith’s Sound it is very old; the tongue adheres to its surface,
it is spotted with lichen, and a moss has found root in the can-
cellous structure of its upper end. The fragment measures eleven

G

70 Dr. Epwarp L. Moss,

and a half inches in length, and by comparing it with femora
from old Eskimo graves on an island near Egedesminde, I esti-

mate its restored length at sixteen inches. When its front is
placed on a level surface the antero-posterior curve deviates a quar-
ter of an inch from the horizontal at either end. As may be seen:
from the annexed section it is as carinate as most platycnemic

femora. There are two nutritious foramina three and three-

quarters and three inches below the lesser trochanter. Its mini-

mum circumference is three inches below the lesser trochanter,
and measures 3'43.inches. This with the estimated length gives
a perimetral index of 214.

If its index were taken at the English average, 1.€., 194, its
restored length would be 17°68 inches, but the bone is evidently
shorter than an average English femur, and the former estimate.

is probably the more accurate.

If Aeby’s statement that races do not materially differ in the
relative proportions of their limbs is correct, we may roughly.
estimate the stature of the man who owned this bone. The pro-
portionate measurements of the skeleton given by Pruner Bey:
make the femur 27°29 in 100 of total height. Humphry’s average
is slightly greater, but calculating by either of them the man when
living must have stood a little over 5 feet.

A careful search was made round the spot where this bone ia
The ground was very uneven. Some vertebree and the skull of a
young musk-ox were found within 200 yards,

- It seemed probable that a longer search would have led tes
we discovery of some dilapidated cairn or cyst, for if the bone
had been recent when first exposed to the attacks of carnvora,
the medullary cavity would certainly have been broken into. © -

But no other vestige of man or trace of anything like a burial-
place could be discovered before movements of the ice between
our boat and the ship put a peremptory stop to our proceedings,
The Alert and Discovery were then only waiting for an opening
across the ice of Lady Franklin Strait to begin their return
voyage, and our visit to the spot was never repeated.

On a Fragment of Human Skeleton.

Section through the centre of
the Bone, natural size.

ee

rad
*
”
s

mfr

ON THE ELECTRIC TELEPHONE.
BY
W. F. BARRETT, F.nr.s.%
{Read November 19th, 1877. |

The following paper does not lay claim to any originality. It
is simply a brief description of an instrument which will probably
play an important part in the future of the human race;
together with an historical note of what had been accomplished
by Reis fifteen years ago.

The various attempts to communicate audible speech by means
of electricity have culminated in the recent discovery by Professor
Graham Bell of the articulating telephone. The discovery was
not the result of chance but of long and patient endeavour.
Every sound of the human voice is communicated from the
speaker to the listener by means of aerial vibrations of a definite
character. For the same sound the same wave-form is always
reproduced. Starting from this fundamental axiom, Professor
Bell’s first efforts were made with the view of visibly recording
speech. A model of the human ear was constructed, to the
tympanum of which a delicate style was attached, the movements
of which recorded themselves on a moving slip of smoked glass.
Thus the vowel sounds and a few simple words were readily
recorded by this phonautograph ; which, however, differed but
little from similar instruments previously constructed. These
experiments revealed to Professor Bell the important point that
the transmission of speech by electricity could onlybe accomplished
by using what may be termed an undulatory current: that is to
say, one that merely varied in strength without the occurrence of
any actual interruptions which would give rise to a discontinuous
or intermittent current. It is this principle of an unbroken
current which distinguishes Bell’s telephone from all preceding
efforts. The electric currents in this telephone are in simple
proportion to the motions of the air produced by the voice, and
further the electric waves sent to the distant extremity are (by
a receiving arrangement precisely similar to the transmitting
instrument), caused to reproduce motions of the air identically
the same in character as those that gave birth to the currents.
Thus not only is articulation heard perfectly, but moreover, the

74 PROFESSOR BARRETT,

different qualities of different voices are heard, so that at 50 or
100 miles distance the individuality of the speaker is transmitted
as well as his ideas.

A section of the present form of this important instrument is
shown in figure 1. A diagrammatic representation of the essential
parts is given in figure 2: a permanent bar magnet (N.S.) (about
four inches long), has a coil of fine wire (b) wound at one extremity,
in front of the coil a disc (a) of thin sheet iron is fixed. The
transmitting and receiving instruments are precisely alike, and no

On the Telephone. 75
the to and fro motion of the iron disc. On speaking into the
Instrument vibrations of the disc are set up which give rise to
magneto-electric currents in the coil of wire, one end of which is
attached to the line wire. These electric pulsations produce
corresponding changes in the intensity of the magnetic field at
the receiving instrument, and hence give rise to motions of the
iron disc analogous to those at the other end.

The extraordinary feature of this instrument is its extreme
sensitiveness, The amplitude of the vibrations of the transmitting
dise must be wonderfully small, and yet every inflexion of the
voice is faithfully transmitted. At the receiving end the ampli-
tude of the vibrations of the iron disc is so small as to be
immeasurable, nevertheless not a syllable is lost, and in the larger
instruments the voice is heard at a distance of some feet from the
instrument. |

The question arises, is the sound due to a molar or a molecular
motion of the disc? Jron when magnetized and demagnetized
gives rise to a peculiar click due to molecular changes, to which
reference will be made in the sequel. No motion of the iron
would be apparent in this case, but if the sound sprung from any
motion of the disc as a whole, such as would arise from currents
of sensible strength fluctuating through the coil beneath, then
the motion of the disc might be capable of detection. Attaching
a mirror to the disc and reflecting therefrom a ray of light, no
motion of this reflected ray was visible on speaking through the
instrument. Other arrangements were tried by the author of the -
present paper to test this question. A sensitive flame is an ex-
tremely delicate acoustic re-agent. Removing the wooden mouth-
piece of the telephone, a small metal chamber was substituted,into
this chamber coal gas at high pressure was sent, and burnt from an
orifice furnished with a suitable jet. The gas thus traversed the
iron dise within two inches of which it issued as a sensitive flame,
so that any sensible motion of the disc would be detected by a dis-
turbance of the flame. Although a flame of extreme sensitive-
ness was obtained, no effect was produced on the flame by any
sounds shouted or hissed into the distant and electrically-joined
telephone. These results confirm an experiment of Professor Bell’s,
who glued the iron disc to a thick block of wood, and in this way
spoke through and heard by the telephone. Here any molar

76 PROFESSOR BARRETT,

motion would seem impossible. But if it be a molecular motion
one would expect the sound to be of a peculiar quality, the mole-
cular motions of solids having a crepitating character.

The solution of the difficulty seems to be this: Lord Rayleigh
has shown (Nature, vol. 16, p. 114) that sonorous vibrations may be
heard although the amplitude of the waves generating them be
of transcendent smallness, an amplitude of one ten-millionth of
a centimetre, Lord Rayleigh states is perfectly audible. Hence it
is probable that the varied motions set up in the iron disc are
motions of the disc as a whole, but of surpassing minuteness, and
if so the telephone has directly confirmed Lord Rayleigh’s edie
tions, and added to the wonders of our organs of hearing.

The greatest obstacle to the practical introduction of the tele-
phone is at present the disturbing noises produced by induction
from powerful battery currents traversing neighbouring wires. —
Apart from this it would appear that conversation can easily be
carried on two or three hundred miles apart, and breathing has
been heard by Professor Bell at 150 miles distance. By employing
a return wire instead of an earth connexion much of the inductive
disturbance can be neutralized. In the trials of the telephone at
the Royal Dublin Society, a loud ticking was heard every second .
which much interfered with telephonic conversation. This
ticking was not due to any neighbouring clocks, but was found to
arise from the general electric clock system of the town. Instead
of a return wire connexion was made with the gas-pipes of the
. building; this “earth” happened to be the same as is employed
in the electric clocks, and hence the disturbance. Substituting a
second wire the disturbance was removed.

Another obstacle at present before the telephone is the difficulty
of its use in long submarine lines. This arises from the well-
known cause termed “inductive embarrassment,’ the line with
its insulating sheath and the sea around acting as a condenser,
and thus preventing the rapid delivery of electric pulsations.
Nevertheless, conversation has very successfully been carried on
between Dover and Calais and Holyhead and Dublin. The mere
resistance of along line but little impedes telephonic conversation.
The author of this paper has spoken with great ease through an
actual line of some thirty miles, with an added resistance exceed-
ing that of the Atlantic cable. The addition of the artificial

On the Telephone. 77

resistance simply renders the sound of the voice of the distant
speaker fainter, as if he had gone further off, but in no way
alters the quality of the sounds heard. Professor Bell has even
spoken through a resistance of 60,000 ohms (the resistance of
the Atlantic cable is equal to 7,000 ohms).

Various practical] applications of the telephone at once suggest
themselves. It is already largely in use in the United States for
commercial purposes. It has been successfully tried in diving
and mining operations in this country. In physical research it
promises to be the starting point of new investigations, and as a_
delicate phonoscope, or sound test, it will doubtless be most
useful both in the lecture-room and physical laboratory. The
telephone also reveals the existence of very feeble electric currents
by the audible vibration of its iron disc. So prompt and sensitive
is it to the slightest fluctuation in the strength of the current
traversing its coil that it is not unlikely it may be of use in searching
out rapid and feeble variations in a current that may escape
detection by a galvanometer, owing to the inertia of even a light
magnetic needle. Information as to the duration and character —
of rapidly intermittent currents is needed in medical science and
not improbably the telephone may be able to furnish this infor-
mation, when associated with a chronograph.

The first attempt to transmit sounds by electricity is due to
Philip Reis, teacher of natural history in a grammar school at
Freidrichsdorf near Homburg. A brief reference to what Reis .
accomplished may here be of interest. I am indebted to Dr.
Messel, a name well-known to chemists, who was a former pupil
of Reis and eye-witness of his early experiments, for the following
interesting letter on this subject :— |

* Reis’ first experiments date as far back as about 1852. But at that
time ended in failure, and were not resumed as far as I know till 1860.
The first publication about Reis’ telephone appeared in a daily paper of
Frankfort-on-Main, which however I have not succeeded in procuring.
Reis gave his first public lecture on October 26th, 1861, when he showed
his telephone before the Physikalische Verein (Physical Society) of
Frankfort-on-Main, and I send you herewith a copy of his paper.

‘<The original telephone was of a most primitive nature. The trans-
mitting instrument was a bung of a beer barrel hollowed out, and a cone
formed in this way was closed with the skin of a German sausage which
did service as a membrane. To this was fixed with a drop of sealing

78 PROFESSOR BARRETT,

wax a little strip of platinum, corresponding to the hammer of the ear,
and which closed or opened the electric circuit, precisely as in the instru-
ments of a later date. The receiving instrument was a knitting needle
surrounded with a coil of wire and placed on a violin to serve as a sound-
ing board. It astonished everyone quite as much as the more perfect
instruments of Bell now do. |

‘ “The instrument I have described has now passed into the hands of
the Telegraph Department of the German Government.”

The paper referred to in the foregoing letter is contained in the
annual report of the Physical Society of Frankfort-on-Main for
the year 1861. It is entitled “Telephony by means of electric
currents” for the word telephone is first suggested by Reis in
this paper as the name of his instrument. The transmitter is
shown in fig. 3, instead of a cork a cubical wooden block is used
with a conical orifice closed at the smaller end by a membrane.

- The accompanying diagram, fig. 4, shows the principle of Reis’s

Fic. 3.

On the Telephone. 79

telephone ; b is a box or small resonant cavity into which the
operator sings through the mouthpiece a; a diaphragm of
bladder or paper ¢ covers the upper part of the box. This is
thrown into vibration by the voice, and comes into contact with
the platinum point d. The centre of the diaphragm is furnished
with a fragment of platinum foil whereby contact is made and
broken with the battery e. The «intermittent currents thus
transmitted through the line arrive at the receiver f, which is
simply a straight iron wire, surrounded by the coil through which
the current passes. The rapid magnetizations and demagnetiza-
tions of the iron wire by the current give rise to a musical note
emitted by the iron, the pitch of the note corresponding to that
sung into the receiver. |

The discovery that a sound was produced in iron by magnetiza-
tion is due to an American page in 1837. It was explained by
De la Rive, of Geneva, in 1843, who showed that it was caused by
the slight elongation of the iron which accompanies the act of
magnetization, a fact discovered by Joule in 1842. The author
of this paper has found that the magnetic metals nickel and
cobalt also yield a corresponding sound on magnetization .
with cobalt the note is clearer and more metallic. The author
has also corroborated the fact noticed by De la Rive, that stretch-
ing the iron wire diminishes the sound, because it diminishes the
elongation by magnetization, and further at a certain tension the
sound ceases, the elongation here ceasing. At a still greater
tension iron shortens by magnetization, and the author has found
that here too, as we might expect, the sound again is produced,
and shortly before the breaking strain of the wire is reached the
loudness of the “ magnetic tick” is almost. as great as with the
unstretched wire. By attaching the iron wire, surrounded by its
coil, to a monochord, and using a rapidly interrupted current, the
rise and fall and extinction of the sounds by varying the tension
of the wire can be easily heard throughout a very large theatre.

After his first success Reis improved both his transmitting
and receiving instruments. In a report on Reis’s telephone by
Legat, Inspector of Telegraphs in Cassel, &c., published in 1862 in
the journal of the East-German Telegraph Company and reprinted

80 PROFESSOR BARRETT,

Fie. 5.

Reis’s improved Transmitter.

Fia. 6.

Reis’s Electro-magnet Receiver.

On the Telephone. 81

in 1863 in Dinglei’s Polytechnisches journal Vol. 169, p. 29, the
following sentence occurs. “Melodies can be reproduced with
astonishing certainty, whilst single words, in reading speaking, &c.,
were less distinct, although the peculiar modulations of the voice
in speaking, calling, interrogation, surprise or command were
clearly marked.”

The instrument described in this report is somewhat different
from the earlier form. The diaphragm was a collodion film and
the contact-breaker behind it was lighter and constructed in form
of an S shaped lever, the longer arm of which was in contact with
the membrane while the shorter made and broke the circuit (Fig 5.)
There was no metal disc on the membrane but the circuit was
completed by means of the arm on which the lever delicately
moved. The receiver, moreover, was a small horse shoe electro-
magnet, fixed horizontally to a sounding-board. (Fig. 6.) Here
the movement ofa light keeper adjusted by a spring before the
poles of the magnet reproduced the original sounds.

In a paper on Reis’s improved telephone published in Béttgers
Polytechnisches Notizblatt No. 15, 1863, it is stated “ Particularly
distinct was the reproduction of the scale. The experimenters
could even communicate to each other words; only such however
as they had already heard frequently.” In confirmation of this
may be added the following extract from a recent letter of Dr.
Messel to the present writer. “There is not a shadow of doubt
about Reis having achieved imperfect articulation, I personally,
remember this very distinctly and could find you many other
ear-witnesses of the same fact.”

In 1865 a modification in Reis’ transmitter was made by Mr.
Yeates of Dublin which might have led to important results had
it been followed up at the time. A drop of water was introduced
between the contact breaker of the transmitter. By this means the
current was to some extent rendered a continuous one, the essential
feature in a perfect articulating telephone, where gradual variations
of the current strength are necessary and not sudden interruptions.
Mr. Yeates also independently adopted the electro-magnet form of
receiver that Reis had introduced in his later form of telephone.
The instrument as modified by Mr. Yeates was shown at a meeting
of the Philosophical Society in Dublin in 1865 and the articulation
of several words was distinctly heard. But even in this and in

82 PROFESSOR BARRETT, On the Telephone.

Reis’s latest form of telephone there is no comparison between the
feeble attempts at articulation and the almost perfect articulation
that is obtainable in Professor Graham Bell’s simple and beauti-
ful instrument: almost perfect, but not quite, for there is a peculi-
arity in the sibilants which render them extremely difficult of
transmission, the letter S sounds as F to the listener at the receiv-
ing instrument and M sounds as P; so that whim becomes
whip or even hip: strength turns into something like creap or
creace, &c. |

In Professor Bell’s telephone the voice itself generates magneto-
electric currents and hence the reproduced sounds are very faint
and slight electric disturbances are frequently fatal to the effective
working of this instrument. The telephone of the future will
doubtless employ the voice of the speaker to modulate the strength
of an electric current generated by independent means. Hence
the discovery of a more perfect and pliable means of varying the
resistance in a circuit by the act of speaking is one of the chief
objects to be attained at present in the new art of electric-
telephony.

NOTE ON THE SPHEROIDAL STATE.
BY
W. F. BARRETT, r.rs.F.

[Read December 17th, 1877.]

AT the last meeting of this Society, Mr G. Johnstone Stoney gave
a new and beautiful explanation of the so-called spheroidal state »
of liquids, wherein he showed that the force detected by Mr.
Crookes, and which is the cause of the motion of radiometers, was
also competent to explain the phenomena of the spheroidal state.
A liquid drop is said to be in the spheroidal state when falling
upon a hot body it does not come into contact with the surface
but rolls over it as a flattened spheroid. A mobile elastic spring
evidently buoys up the drop until such times as the hot body
cools, when, with a sudden rise of temperature and generation of
steam, the drop comes into contact with the surface below it,
spreads out into a film, and rapidly disappears into vapour.
Hitherto this phenomenon has been regarded as due to the
fact that the proximity of the hot surface converts a portion ‘of
the liquid into vapour, the elastic force of which sustains the
drop. There are, however, several phenomena, allied to the
spheroidal condition, to which this generally received explanation
gives no solution. Such, for example, as the mobility of light
powders in a hot crucible, or the formation of globules on
the surface of water and other liquids, Mr. Stoney’s explana-
tion, on the other hand, embraces the whole of these outstanding
and hitherto enigmatical phenomena. Briefly stated this theory
is based on the fact that whenever two bodies at different
temperatures are brought sufficiently near each other a modifica-
tion takes place in the molecular structure of the layer of gas or
vapour between them, giving rise to the so-called ‘Crookes’ force,’
wherein there is an excess of pressure in the direction joining the
hot and cold surfaces over the pressure in transverse directions.
Now this excess of pressure depends partly on the quantity of
heat making its way across the intervening layer of gas or

S4 PROFESSOR BARRETT,

vapour, and partly on the proximity of the two surfaces. A
proximity not to be estimated absolutely, but with reference to
the length to which a molecule of the gas will travel in the
intervals between its encounters with other molecules. Hence
there are obviously three modes whereby the excess of pressure,
this Crookes’ force, may be developed or augmented :—

1st. Bylengthening the paths of the molecules between the warm.

and cool surfaces, accomplished by attenuating the gas.
2nd. By bringing the hot and cold surfaces very near together.
3rd. By increasing the difference of temperature between the
two surfaces. | ,

Now if the support of the spheroidal drop be due to this

Crookes’ force a difference of temperature must exist between the
drop and the surface over which it stands, and the greater this
difference of temperature the larger the drop that ought to be
supported, and the more persistent the phenomenon. Mr. Moss
has shown (Proc. R. D.S., Dec. 1877) that by securing a continual

difference of temperature a globule of ether may be supported on

the surface of its own liquid for upwards of an hour, until in
fact some accidental derangement occurs. The conditions of the
two theories being thus defined, it is easy to see that several
crucial experiments might be devised which should help to
decide the question at issue.

The following experiment the author has made with this object.

in view. Upon the surface of the ordinary petroleum of commerce,
liquid globules of transient duration can readily be formed, simply

by removing a small quantity of the liquid in a pipette and care-

fully depositing a drop on the surface of the liquid. These drops
are clearly in the spheroidal condition, and they are easily and
abundantly formed by dipping a vibrating tuning fork into the
liquid, or by drawing a fiddle bow over the edge of the vessel
containing the liquid. According to the ordinary explanation
the drops are supported by the elastic force of the vapour of the
liquid, which would, of course, be greater the higher the tempera-
ture of both liquid and drops. According to Mr. Stoney’s theory
the drops are supported by the Crookes’ force, generated by the
proximity of the drop and liquid, and by the fact that they are
at different temperatures. Evaporation rapidly cools the drops
jerked up from the liquid, and thusa slight difference of tempera-

vo

Note on the Spheroidal State. 85

ture instantly comes into play. If, however, Mr. Stoney’s theory
be true, then a drop of cool petroleum would be more easily and
longer sustained on a surface of warm petroleum, or vice versd,
than a drop taken from the mass of liquid below it, where only a
slight temperature difference is created.

Two beakers were filled with petroleum from a common source,
one (A) at the temperature of the air, the other (B) at a tempera-
ture of 100° F. With a pipette some liquid was taken up from
A and a drop carefully deposited on its own surface, a globule was
formed, floated for a fraction of a second and then disappeared.
The same occurred with a drop from B placed upon B. A drop of
B was now removed and deposited on A, a large globule was easily
formed on the surface, floated about from 10 to 20 seconds and
then disappeared. <A drop of A was now placed on R, the same
thing occurred, but the duration of the drop was not quite so
great, owing to the greater density of the cool drop tending to
sink it below the surface of the warm liquid, thus rupturing the
Crookes’ layer and destroying the difference of temperature.

There is no doubt or uncertainty whatever about this experi-
ment, and it shows that, if the ordinary explanation be correct
the second case, where B rests on B, should give the best result,
whereas the reverse isthe case. Further, the experiment wherein ~
the best result is obtained, is such as best fulfils the condition of
Mr. Stoney’s theory.

The limit of formation of these spheroids, when the liquid is
uniformly dropped through a gradually increasing height, may be
employed to test the relative degrees of force which sustain the
globule, and careful experiments made by the author in this
direction still further corroborated the truth of Mr. Stoney’s
views.

i

ON THE SPHEROIDAL STATE.
BY

RICHARD J. MOSS, F.C.8.
(Read December 17, 1877.)

IN a paper on “The Penetration of Heat across Layers of Gas”
read at a recent meeting of the Society, Mr. Stoney* includes
Leidenfrost’s phenomenon, or as M. Boutignyt calls it, the spher-
oidal state of volatile liquids, as an instance of the action of the
peculiar form of pressure which is exerted between hot and
cold surfaces when they are within a certain distance from one
another, depending on the length of the free path of the mole-
cules of the gas enclosed between the hot and the cold surfaces,
and on the difference of temperature of these latter. This
explanation of the spheroidal state places the phenomenon in an
entirely new light. It has hitherto been supposed that a volatile
liquid in this condition was sustained, and prevented from
touching the adjacent hot body by a rapid disengagement of
vapour from its surface. The explanation that was generally
accepted is very clearly expressed by Dr. Tyndall in his “ Heat
as a mode of Motion,” p. 154, where, referring to a spheroid of
water in a hot metallic basin, he seys :—“ The drop rolls about on
its own vapour—that is to say, it is sustained by the recoil of the
molecular projectiles discharged from its under surface. I with-
draw the lamp, and allow the basin to cool, until it is no longer
able to produce vapour strong enough to support the drop.
The liquid then touches the metal; the instant it does so violent
ebullition sets in.”

It has, however, been regarded as a remarkable circumstance
that a quantity of vapour sufficient to produce the effect could
be given off by the liquid under the circumstances, for, as M.
Boutigny has shown, the spheroidal drop is always at a tempera-
ture below its boiling point, a condition that is not favourable

* Transactions of the Royal Dublin Society, vol. 1 (new series), p. 13.
t Proceedings of the?Royal Institution of Great Britain, vol. 1, p. 179.
H 2

88 Mr. R. J. Moss,

to the maximum production of vapour. Mr. Stoney’s explana-
tion not only removes this anomaly, but demands the compara-
tively low temperature of the spheroid as an essential condition
of the phenomenon, since the existence of the layer of polarized
air or vapour by which the spheroid is supported, requires the
proximity of a cool surface, in order that the velocity of the
gaseous molecules moving from this surface may be much less
than that of the molcules which move towards it from the adja-
cent hot surface.

Mr. Stoney suggested to me the possibility of maintaining
spheroids on liquid surfaces of the same substance by ensuring
that the floating drop shall continue cooler than the liquid under-
neath, and by otherwise removing the causes which occasion its
shipwreck. Commercial ether readily adapts itself to the re-
quired conditions. After a series of experiments I have adopted
the arrangement shown in the figure as one which successfully
accomplishes the desired objects.

A thin glass tube about 15 mm. in diameter and 12 cm. long ;
having a spout-like limb about 7 mm, in diameter and 7 em, in

On the Spheroidal State. 89

length attached 4 cm. from one end, is contracted at the other
end, and attached to a narrow tube bent twice at right angles,
so that the two tubes are parallel. The narrow tube termi-
nates in a small funnel. This apparatus, held vertically in a
clip, is immersed in a beaker of water, so that the surface of the |
water is about a centimetre below the attached end of the spout-
like limb, the other end of which extends beyond the edge of the
beaker. By means of the funnel ether is poured into the nar-
row tube until it rises in the larger tube to the level of the water
in the beaker, or a millimetre or two above it. The beaker
stands on an iron plate which can be heated in any convenient
way until the temperature of the water in which a thermo-
meter is placed reaches 30°-32° C. If a narrow pippette with a
very small opening be now immersed to the depth of 1 or 2 cm.
in the ether in the large tube and quickly withdrawn to a short
distance, the drops which fall from it being rapidly cooled by
evaporation, readily assume the spheroidal state, and often con-
tinue to float on the warm ether for a long time. The evapora-
tion from the spheroid is so very slight that some time must
elapse before any alteration in its size can be detected. On the
other hand, the warm ether on which the spheroid floats evapo-
rates very quickly, and its heavy vapour flows out through
the spout at the side mixed with air which is drawn in at the
mouth of the large tube. This cool air passing over the surface of
the spheroid enables it to part with the heat which it is constantly
receiving from the warm ether by radiation, by the passage of
_ heat through the Crookes’s layer on which it is supported, and by
the precipitation of ether vapour. The ether lost by evaporation
is replaced from time to time by pouring ether i in at the funnel.
By means of this arrangement I have kept a ” spheroid about
5 mm. in its longest diameter, floating for more than an hour
and a half.

In the progress of this experiment the sustaining medium
becomes ether vapour alone; it may, however, be experi-
mentally demonstrated that the presence of a gaseous medium
other than that derived from evaporation produces the same
effect. For this purpose it is desirable that the substance em-
ployed should not be very volatile. It is also important that it
should be specifically light, as the heavier the spheroid the more

90 Mr. R. J. Moss, a

force has to be exerted to keep it afloat, or in other words, the
greater must be the disparity of the velocities of the molecules
of the intervening medium; and to produce this disparity there
must be a considerable difference of temperature between
the spheroid and the liquid on which it floats. In the case of light
liquids there is less force to be exerted, and therefore a slight
difference of temperature suffices. I find melted paraffin supplies
all the requirements of the case. It is light, its sp. gr. at 15° ¢,
being 0°86, while in the liquid state it is much lighter. On
placing ordinary paraffin in a shallow silver basin and melting it
I found that drops in the spheroidal state were easily obtained
at temperatures not greatly exceeding the melting point of the
paraffin, They are very easily obtained at 80°-90° C, and by
directing a current of cool air over the surface of the liquid
they may be kept in existence for a-considerable time. I have
kept them afloat for more than twenty minutes without any
special attention to the temperature of the paraffin or the strength
of the current of air employed to keep the drops cool, and I have
no doubt that with care their existence might be indefinitely
prolonged. I have devised a method for performing the experi-
ment in a closed flask in which any gas may be contained, and
at any desired tension; my experiments with this apparatus are,
however, not yet completed.

For the purpose of ascertaining whether there was any appre- .
ciable evaporation from melted paraffin at a temperature favour-
able to the existence of spheroids, I placed three porcelain cap-
sules containing paraffin on an iron plate, and heated them until
a thermometer placed in one of them rose to 90° C. One of the
capsules was then allowed to cool, and weighed, after which it
was replaced on the hot plate and kept there for two hours,
during which time I occasionally produced spheroids on the
paraffin in the third capsule, some of these lasting a considerable
time. When the weighed capsule was allowed to cool and again
weighed I found a very slight increase had taken place. On
repeating the experiment twice similar results were obtained, I
therefore decided upon performing the experiment an vacuo for
which purpose 5°5 grammes of the paraffin that had been re-
peatedly heated in one of the capsules was transferred to a
small flask which was attached to an air pump and exhausted.

On the Spheroidal State. 91

The paraffin was melted by immersing the flask in boiling water.
After half an hour the flask was allowed to cool in vacuo and
weighed. This operation was now repeated, the paraffin being
heated for an hour by enclosing the entire flask and part of the
tube communicating with the pump ina metallic vessel which
was immersed in boiling water. The paraffin having been
allowed to cool wm vacuo was found on again weighing the flask
to be precisely the same weight as it was originally. I-could
have detected a loss of 0:00005 gramme or 574555 of the weight
of the paraffin if it had taken place, and considering that the
temperature employed was 10-20° higher than that at which
spheroids of paraffin are readily produced, I think one may reason-
ably conclude that paraffin is not appreciably volatilized at a
temperature which admits of the existence of a spheroid on its
surface. And since the spheroid must in this case be at a lower
temperature than the liquid on which it floats, it is even less
likely to produce vapour suflicient to keep it floating. In confir-
mation of this conclusion I may mention that I have been unable
to detect the slightest diminution in the size of paraffin spheroids,
though I was occasionally much puzzled by the appearance of
small spheroids in the place of large ones which I had left
floating a short time before, until I detected one of these large
drops disappearing with a slight splash which called into existence
a new spheroidmuch smaller than its predecessor. These experi-
ments in all their details are in accordance with Mr. Stoney’s
explanation of the phenomenon, and they demonstrate that the
previously accepted theory is untenable.

It is noteworthy that in 1874 Mr. Crookes* suggested that “The
phenomenon of the spheroidal state is probably due in some
measure to a repulsive force exerted between closely approxi-
mated bodies, one of which is at a very high temperature.” And
although the true nature of “ the repulsive action of radiation,” to
which Mr. Crookes considered the phenomenon attributable was at
this time unknown, he ventured to anticipate “that a condition
similar to the spheroidal state will be found to obtain between
non-volatile bodies.”

* Philosophical Transactions of the Royal Society ef London, vol. clxiv., part 2.

$

Ag eee
. Le

z

‘ vi

mea:

+

NOTE ON THE MICROSCOPIC STRUCTURE OF THE
SCALE OF AMIA CALVA.

BY

H. W. MACKINTOSH, B.A.,
Senior Moderator in Natural Science, Trinity College, Dublin.

[ Read December 17th, 1877.]

Axout four years ago Professor Macalister, Director of the Museum
of Comparative Anatomy and Zoology in the University of
Dublin, obtained a fine specimen of the North American Ganoid
Amia calva, and before sealing it up and placing it in the
- Museum, kindly gave me one of the scales for microscopic ex-
amination. Pressure of other matters prevented me at the time
from bestowing upon it more than a cursory glance, and it has
lain mounted in my cabinet almost forgotten till a few months
ago, when, having occasion to demonstrate some points in the
structure of the scales of fishes, I was led to give it a more careful
study, which brought to my notice a peculiar form of lacune
which does not seem to have been hitherto described, and which
may be of interest to the members of this Society.

Amia is commonly described as a ganoid with overlapping
cycloid scales. I submit that in the face of figs. 1 and 2,
the term cycloid must be abandoned and replaced by ctenoid.
The mistake has probably arisen from the fact that the teeth
on the free edge are too fine to be noticed by the unaided eye,
whilst the ridges of which the teeth are the terminations give
a circularly striated appearance to the whole scale, a decep-
tion which is aided by the deposit of thickening layers on the
proximal parts of the scale, leaving thinner and therefore more
transparent spaces between them. In reality the ridges run in a
sinuously longitudinal direction, with a certain tendency to
confluence along a line (a, 8, fig. 1) transverse to the scale, and
placed at a short distance from its fixed (anterior) edge. They
are apparently compound, separated from each other by a very

94 Mr. H. W. MackrinTosuH,

narrow groove (a, 4, d, fig. 2), and bearing on their upper surface
a broad flat elevation, the middle of which is again raised up
into a sharp narrow ridge. The lacunze whose form I wish
specially to call attention to are grouped together in the middle
line near the anterior edge of the scale, and appear as minute
black dots visible to the unassisted eye on careful scrutiny.
They are placed immediately beneath the superficial layer of
ganoin which clothes the whole surface of the scale, and apparently
makes up the entire of the posterior thin part, which is altogether
devoid of lacunz of any sort. When examined under a low
power (180 diams.) they are seen (fig. 3) to consist of a central
axis which for the most part has a decidedly fusiform shape,
but which sometimes (a, fig. 8) is simply linear. From this
central axis arise a number of very short canaliculi, which are
mostly linear and end abruptly, but sometimes taper rapidly to
a very fine point. Starting from these, in some cases, and super-
posed on them in others, are other canaliculi, which lying thickly
together often give the lacuna to which they belong a wonder-
fully confused appearance (0, fig. 3), and may even render it a
matter of some difficulty to trace the central axis. It must be
understood, however, that in many cases like ), fig. 3, the apparent
canaliculi are really small independent lacunez, not connected at
all with the central lacuna but merely overlying it. Asa rule
there is not much tendency to communication amongst the
different lacunze ; sometimes (c, d, fig. 3) we find a small lacuna
or a system of passa in slight connexion with a larger one, though
I have not been able to satisfy myself that this e always a true
anastomotic union. Employing a higher power (260 diams., fig. 4)
we bring out more clearly the fusiform shape of the main lacuna,
and the usually abrupt termination of the canaliculi, Very otten
(d, fig. 3; a, b, fig. 4) these are placed with singular regularity,
forming a series of crosses with the points of intersection at the
lacuna, giving the entire system an appearance which is unique’
so far as I can ascertain. These are the only lacunz found at
the centre of the scale, but as we go out towards the margin we
find others making their appearance, more in accordance with the
usual form. Thus in fig. 4, which represents a group occurring
mm the same field of view, whilst a, b, and ¢ are eminently

On the Microscopic Structure of the Scale of Amia Calva. 95

characteristic and unlike ordinary lacunze, d with its elongate and
more tapering form and fewer canaliculi is assuming a more
normal appearance, and is still more normal, having altogether
lost its short abrupt lateral branches, and only presenting very
fine and tapering terminal ones. At the margin of the scale we
find lacunze of this kind alone (fig. 5), differing from each other
only in respect of their length, number and extent of canaliculi,
&c., and reminding us of the well known lacune of the allied
Lepidosteus osseus (fig. 6) which are figured in most books
on microscopy. They differ from them, however, in being much
larger, less globular, and having much wider canaliculi which do
not anastomose to the same extent; whilst the scale itself does
not exhibit any of the canals running in from the surface which
seem to be constant in the scales of Lepidosteus. There do not
appear to be any lacune in the posterior part of the scale from
about cd backwards, in front of this line they begin as small
simple forms like e, fig. 4, and a, fig. 5.

EXPLANATION OF THE PLATES.

Fig. 1. Entire scale of Amia calva magnified 5 diameters, showing the finely toothed
posterior edge, the general direction of the ridges, and the position of the characteristie
lacunez. The line a 6 indicates the place where the ridges tend to run into each other,
cd the level behind which no lacunz are found.

Fig. 2. A portion of the posterior part of the scale showing the nature of the ridges
and the toothed border, x90. The arrows show the direction in which the light came,
oblique illumination having been used.

Fig. 3. Lacunz from the central part of the scale, 180. At ais seen one in which
the central lacuna is linear; 5 is one of the highly complex forms; c and d have smaller
lacunar systems connected with them.

Fig. 4. Lacune occurring in the same field of view, X260. Taken from a part of the
scale about half way between the centre and the margin; a, b,c, are of the characteristic
complex form, d and e are simple.

Fig. 5. Lacune from the marginal part of the scale, x260. Atais seen one of the
simplest forms.

Fig. 6. Lacune from the scale of Lepidosteus osseus, x 260 showing the small size of
the lacunsz, their globular shape and very fine canaliculi.

The drawings were all made under a Wollaston camera lucida.

etre

{
f
5
|
a
x
,
'
;

: Py Li 3 vay te

+ oa f ait
fete Mri we WE) ‘
apa et 18. aid : ae

uly

ou ,
ae

< KK

he Uheat

_ nhett!

rh
HW14

rom

at
~~

in

at

PUBLICATIONS OF THE ROYAL DUBLIN SOCTETY.

TRANSACTIONS: Quarto, in parts, stitched.

al. I. (raw series), [Already published.] — uy | :

Part 1.+—On Great Telescopes of the Future. By Howarp Gruse,
F.R.A.S. (November, 1877.) - / ‘

Part 2.—On the | Penetration of Heat across Layers of Gas. By:
G. J. Stonny, M.A., F.R.S. (November, 1877.) |

Part 3.—On the Satellites of Mars. By Werntwortn Ercx,
LL.D. (May, 1878.) ; ee

Part 4.—On the Mechanical Theory of Crookes’s, or Polarization

‘Stress in Gases. By G. J. Stonny, M.A., F.R.8. (October, 1878.)

Part 5.—On the Mechanical Theory of Crookes’ s Force. By G.
F. Firzcrraup, M.A., F.T.C.D. (October, 1878.)

Part 6.—Notes on the Physical Appearance of the Planet Mars.
By J. L. E. Dreyer, M.A. Plates 1 and 2. (October, 1878.)

Part 7. —Section 1. ——On the Nature and Origin of the Beds of
Chert in the Upper Carboniferous Limestone of Ir eland. By
Epwarp Hutt, M.A., F.R.S. With Plate 3. Section II.—On the
Chemical Compageece of Chert, and on the Chemistry of the Process
_ by which it is formed. By HbWARD HARDMAN, F.C.8. (November,

eh

PROCEEDINGS: 8vo., in parts, stitched.

Vol. I. (new series). [Already published.]

Part 1.—Pages 1 to 52. (November, 1877.)
2,—Pages 53 to 132. (May, 1878.)

5 %&—Concluding Volume I. With Title age and Table of
Contents. (November, 1878.) Stee

7)

Vol. II. (new series.) cant |
Part 1.—Pages 1 to 120. (October, 1878.)
_ Part 2 will be published in January, 1879. .

sae

oe sas
; aa

ON THE VARDOUS FORMS OF APPARATUS USED
FOR POLISHING SPECULA FOR REFLECTING TELE-
SCOPES.

BY

SAMUEL HUNTER, F.R.A.3.
[Read 17th December, 1877. ]

WE owe the reflecting telescope to Sir Isaac Newton,* and the
idea was presented to his mind through a remarkable mistake he
made in believing that retracting telescopes as then made were
incapable offurther improvement. In a paper presented to the
Royal Society in February, 1672, he writes :—“ In the beginning
of 1666 (at which time I applied myself to the grinding of optical
glasses of other figures than spherical) I procured me a triangular
prisme to try therewith the celebrated phenomenon of colours,’
which “was at first a very pleasing divertissement.” Starting
from this “divertissement” he found that the colours observed in
the telescopes, as then constructed with object-glasses consisting of
a single lens, were due to the nature of light. He writes—* When
I understood this I left off my aforesaid glass works, for I saw that
the perfection of telescopes was hitherto limited—not so much for
want of glasses truly figured—as because that light itself is a
heterogeneous mixture of differently refrangible rays; so that
were a glass so exactly figured as to collect any one sort of rays
into one point, it could not collect those also into the same point
which, having the same incidence upon the same medium, are apt
to suffer a different refraction.” That is, he discovered that rays of
light falling on a single lens at AA’ become decomposed into
the colours of the spectrum on leaving it at B B’, the red rays
coming to a focus at 7, the violet at v, and the other colours
at intermediate points. Sir Isaac failedt to discover that with
different kinds of glass the distance vr, varies (i.e. their dis-
persion) and hence did not see that by combining glasses of

* Gregory described his form of reflecting telescope in 1663, and had one constructed in

1664, but failed in obtaining a satisfactory result.
t Query—Did this arise from his having used only one kind of glass in his prisms ?

98 ; Mr. SAMUEL HUNTER,

- We 2.

Fig. 1.

different dispersive powers an achromatic telescope could be
formed. .

“This made me,” he writes, “ take reflexions into consideration,
and finding them regular, so that the angle of reflexion of all
sorts of rays was equal to their angle of incidence, I understood
that by their mediation optick instruments might be brought to
any degree of perfection imaginable, provided [1] a reflecting
substance which would polish as finely as glass, and [2] reflect as
much light as glass transmits, and [3] the art of communicating
to ita parabolic figure be also attained.” Here Sir Isaac gives us
the three requisites to a good reflecting telescope, but it is with
the last alone we have to do at present. ;

Let us first see why the figure must be parabolic. Suppose
the rays A and A’, B and B’ fall on a segment of a sphere, A and
A’ being more remote from the axis than B and B’, C being the
centre of curvature, Sir Isaac found that the angle of inci-
dence AAC was equal the angle of reflection DAC. So also the
angle BBC=EBC. Hence parallel rays falling on a true
spherical surface come to a focus at different points, accord-
ing to their distance from the axis of curvature DC. Now
if the curve at A could be flattened a little, as indicated by
the dotted line, it is clear that the angle of incidence, AAO,
could be made=the angle EAC and all the rays would come to a
focus at the same point E. The curve of which that holds good
is called a parabola. The difference between these two curves

On Apparatus for Polishing Specula for Reflecting Telescopes. 99

is so small that at the margin A of a telescope 4 feet in diameter
and 40 feet focus, their distance apart is less than the sis of an
inch (zz}53). You will observe that the parabolic figure is
best suited for parallel rays, such as come from the heavenly
bodies ; for viewing terrestrial objects the spherical form is just
as good, and for near objects, much better.

After two years’ interruption, caused by the Great Plague, Sir
Isaac Newton, to use his own words, had then “thought on a
tender way of. polishing proper for metal,” and set to work.
After a time he succeeded in making the first reflecting telescope
of thirteen inches radius, by which he was able to see Jupiter’s
four concomitants, as he calls them. And strange to say, since
_ then we have simply been following in his track; he indicated
the metals still used in the construction of the speculum, and the
mode of operation we owe to him in a great measure; we have
only improved in the details.

The production of a spherical surface is comparatively easy, for
the mutual rubbing of two bodies naturally tends to produce that
form, but it is otherwise with the parabolic.

We will first describe in detail the hand process of polishing
specula used up to the time of Sir Wm. Herschel, who first con-
structed a machine for this purpose. ,

A tool made of iron, pewter, or some such material, was cast
and turned to a radius of twice the intended focal length. Some
had this tool of a greater diameter than the speculum, some of
the same diameter ; this was fastened on an upright post, with
the face upwards, emery and water was applied, and the operator,
holding the speculum by a wooden handle cemented to its back,
walked round the post, pushing the speculum to and fro in
straight, elliptic, or circular strokes, supplying emery from time
to time, until every part of the speculum was acted on equally by
the emery. The tool was then examined to see if the curvature
had altered, if so it was turned again to the proper radius, and
the grinding proceeded as before. When the speculum was
equally acted on by the emery, and the tool found to be of the
proper curve, finer emery was applied, and finally using only the
sediment obtained from water in which flour of emery had
been stirred up and allowed to stand for ten seconds, thirty
seconds, and up to four minutes before being poured off.

100 Mr. SAMUEL HUNTER,

If proper care were taken, the surface was now free from
scratches, capable of reflecting a considerable amount of light,
and of a spherical form. The polishing now commenced, the
object of which is not only to make the surface reflect the greatest
amount of light, but also to give the parabolic figure, and in this
consists the great difficulty.

Speculum metal is very porous; a moderate magnifying power
will show the surface full of little holes, so that if we used an
elastic cushion of any kind to carry the polishing powder, the
result would be that the powder would be forced into these pores,
whose edges would be worn away, and the entire surface would
thus be full of little pits, so that a true figure or good reflecting
surface would be impossible.

On the other hand, if we used a hard unyielding substance, we
could only produce a spherical surface, as it is by the mutual
adaptation of the two surfaces that we are enabled to obtain the
parabolic.

Fortunately, in pitch we have an almost inelastic body Het.
of adapting itself to any surface with which it is in contact, and
yet being a solid. Ice is the only other solid that I know of
which possesses this latter property. The tool used in grinding,
or another made to the same curvature, usually a little larger
than the speculum, was now covered with pitch to a depth
varying from the thickness of a half-crown to half an inch ;
grooves were cut in this to allow it to expand equally in a
lateral direction, and thus become more quickly adapted to the
speculum. Some made the polisher smaller than the speculum,
and others used an oval polisher.

The Rev. Mr. Edwardes, writing in 1787, recommends that the
longest diameter be to the shortest as 10:9, the latter being
equal to that of the speculum, and seems to be the first who used
the oval polisher. Sir John Herschel speaks highly of the oval
form, as also Messrs. Delarue and Nasmyth.

The consistency of the pitch should be such that a sovereign
resting on its edge for one minute should leave clear impressions
of three of the millings on its edge (Lassell’s test) ; if softer than
this it will not produce a good figure, if harder an inferior polish
will be the result. The pitch can be made harder by boiling or
softer by the addition of oil of turpentine. .

On Apparatus for Polishing Specula for leflecting Telescopes. 101

The polisher being now prepared the speculum was laid on it,
being first gently warmed to about 80°, and moved about on the
polisher gently until it was found that the pitch touched it at all
points. Rouge and water was then applied and polishing com-
menced, the operator proceeding as in grinding, carefully observing
that the polishing proceeded equally.

Tripoli was at first used, but is now entirely superseded by the
sesquioxide of iron or Jewellers’ rouge, by which name it is sold
inthe shops. __

Mr. Mudge polished the speculum to a true spherical surface
and then ended by a few large circular strokes upon the round
polisher so as to increase the radius of curvature near the margin.
I hope you will not consider that I have gone too much into
detail, but as the machines used only change the mode of using
the power, I shall not have to recur to these processes again.

The disadvantages of hand polishing are, the unequal pressure,
the inability to exactly control the length and direction of the
stroke, theirregular increase oftemperaturefrom friction, and finally
the inability to work specula larger than eight or nine inches in
diameter.

As already stated, Sir William Herschel was the first who used
a machine in polishing, although it is not many years since a
description of it was first published. —

We shall now proceed to describe it.

Sir William Herschel’s Machine.

The ring RS G surrounded the speculum which rested on the
polisher face downwards; within this ring loosely fitting, and
held in position by three pins above and below, there was a thin
flat rmg T K L, on which was screwed a ratchet ring; this
annulus also carried three cocks at T, K, and L, which rest upon
the speculum, with flanges projecting downwards, covered
with felt, and capable of being adjusted so as to hold the speculum
concentric, yet without being pinched; RCS is a claw attached
to the ring by two pivots at R and §, and with an eye at C, to
connect it by a pin to the lever A B, which pivots on B, the
power being applied at A. D K and D L are two arms fastened

I

102 Mr. SaMveL HuntzR,

Fig. 3.

to the lever at D, and kept pressed by springs at K and L against
the ratchet ring, D K ending in a hook, so that when the lever
A Bis pushed towards the speculum this hook seizes the ratchet
ring and causes the speculum to turn a little, because the motion
at D is less than at C; for the same reason, when the motion is
reversed D L pushes against the ratchet ring and causes another
little turn.

I N isa similar arm, causing at each pull the ratchet wheel
M N to turn; this wheel carries an arm, O M, attached to the
lever Q H, H being attached to the projection G; Q H pivots on
F. By regulating the length of O M or F H or both, the amount
of side motion is adjusted. The arms attached to the lever at
E caused the polisher to revolve when a circular one was used.
But Sir John Herschel states, that with a speculum of 18? inches
diameter by using a fixed oval polisher of 1:12 and 0:97 diameters
(the speculum being 1), with grooves at an angle of 45° to the
stroke, he obtained most satisfactory results without using any
side motion, H being then fixed in position and the arm I N
detached. When the speculum and polisher are caused to
revolve, with the side motion in action, the speculum will describe
curves somewhat similar to those of Lord Rosse’s polisher, but
the shock given to the speculum at the commencement of each
push and pull must be injurious. In Lord Rosse’s machine this
shock is not felt, the stroke being given by a crank motion. The
length of stroke used on a round polisher without side motion
was 0°47, and with side motion 0°29, the total side motion being
0°19, the speculum as before being 1,

On Apparatus for Polishing Specula for Reflectung Telescopes. 103

Lord Rosse’s Machine.

Fig. 4,

In this machine the speculum is worked face upwards, both
- grinder and polisher being grooved so that an even distribution of
the emery used in grinding is obtained as well as of the rouge in
polishing. The polisher fits loosely but accurately in the ring, so
that it revolves with the speculum, but at a different rate, partly
from being carried round with it by friction at the end of each
stroke, and partly from the change of direction given to the stroke
each time by the revolution of the eccentric.

The power is applied by means of the spindle A, which drives the
spindle P, carrying the eccentric B ; this eccentric gives the length
of stroke, equal about one-third the diameter of speculum. P again
drives O, which latter drives N and R; on N rests the speculum
H I, while R carries the back eccentric G, which controls the side
motion, usually about one-fifth of the diameter (measured on the
side of the speculum). ‘The diameters of the various pulleys, as
now used for polishing the three feet speculum, are approximately
as follows :—Those on the spindle P, 30 and 7 (inches); O, 18, 9,
and 18; N 36, and R 30; G performs a revolution in about five
strokes of the eccentric B, and the speculum once in about eleven ;
D is a fixed guide, DG being rigidly attached to the ring KL,
carrying the polisher. This bar and polishing ring is supported
at D, and by the fork at G, which latter is free to revolve in its
socket. The polisher is counterpoised, leaving a weight of about
10 lbs. pressing on the speculum, M being a circular disc attached
to one end of the lever by its centre, but by six hooks in its
circumference to the polisher.

The curve actually described by the centre of the polisher in
the model of Lord Rosse’s machine which you see before you, of

I2

104 Mr. SAMUEL HUNTER,

one-third the dimensions, and on which I have frequently worked
to an excellent figure a 9-inch speculum, is given in figure 5, —
where you have the result of 94 strokes, 2} revolutions of
eccentric G, and 1 revolution of the speculum, the stroke, &.,
being adjusted to a 9-inch speculum.

Mr. Lassells Machine.

The power is applied in this machine to the pully I I, which
drives the worm spindle H K, this drives the wheel L of 77
teeth, and by means of the band G, a similar wheel C, on which
the speculum rests. The spindle M turns with L, carrying the
arm S P; the wheel O is fixed to the frame N, so that as the arm
S P is carried round the pinion Q of 16 teeth works in O of 72;
R of 72 revolves with Q, working in the pinion T of 16 ; T carries
with it the eccentric V; T and V can be adjusted by means of
the slots as shown in the figure. A pin at V carries round the -
polisher J.

On Apparatus for Polishing Specula for Reflecting Telescopes. 105

IF aS
base Hil

iil a

W Vi) =

1 HII!
(i re CD

106 Mr. SAMUEL HUNTER,

For a 2-feet speculum H K revolves about 132 times per
minute ; the eccentric S 1°7 times; V 347. The speculum A,
0-46, T Satine 1-7 inches from its ae to centre of spindles, My,
and V being 1:4 inches from centre of T. The curve described
by the centre of the polisher in these conditions is shown in
figure 7. An exactly similar curve would be obtained if S did
not revolve at all (the revolutions of T being unaltered), and the
speculum at a speed of 1°7-+0°46, the sum of their velocities,
equivalent to 1 turn of speculum to about 16 of V. The dotted
line in figure 7 shows the path of the centre of T, the centre
of the speculum being at C. It was found by Mr. Lassell that
the polishing was apt to proceed in rings to the detriment of the
figure, he caused the speculum to rest on a sliding bed instead of
directly on the wheel C, which being acted on by a roller fastened
to the wall plate, received a thrust of about one and a-half inches
on two opposite sides. Delarue made a further improvement by
causing the speculum slowly to revolve on this, so that the thrust
did not always occur across the same diameter.

Mr. Grubb’s First Machine.

Fig. 8.

This machine gives Lassell’s curves, and is capable also of —
approximating closely to Lord Rosse’s.
fis a worm-shaft driving the wheel 6 of 90 teeth ; c also of 90

On Apparatus for Polishing Specula for Reflecting Telescopes. 107

revolves with b and works a wheel of 52 attached to the lower
surface of the cam d; in the groove of this works a pin fastened
to the cam-lever e, which is thus made to oscillate ; this is linked
to the sliding-plate B, which thus by the rotation of the cam is
made to vibrate with a uniform motion. The plate B carries a
spindle h, on which vibrates the arm?. The link will either hold
this arm in position or cause it to vibrate with the eccentric /,
which is driven by a shaft at the back. The variable crank m can
be driven either quickly by the pully %, or slowly by the worm-
wheel 0. The pin in ™ drives the polisher.

To give Lord Rosse’s motion the pin of m is set central, and l is
set in motion, this gives the stroke, the side motion being given by
the sliding plate B. To give Mr. Lassell’s, J is stopped and fixed in
position, so that the pivot of ni is equal the distance of the centre
of the pinion T (fig. 6) from the centre of the speculum, the arm >
2 being held firm by the link /; the pin of m is then set to the dis-
tance V T (fig. 6), and by the vibration of B, Mr. Lassell’s eccentric
motion can be given.

This machine Mr. Grubb has superseded by one of great
simplicity of construction.

Mr. Grubb’s Second Machine.

In figure 9 you have an isometric perspective view of the
machine with which the great Melbourne telescope was ground
and polished.

A is the speculum in its box revolving on a vertical spindle, B
the polisher, a portion of the weight of which is counterpoised by
a lever attached to the bar a. The horizontal bars b,b’ are
attached to a atc; these are moved by the cranks at dd’, which
receive their motion (by means of bevelled wheels) from a hori-
zontal bar connected with the driving pully D. By the adjust-
ment of the length of the arms 6 0’, or of the cranks at dd’, a great
variety of curves can be given to the bar a, carrying the polisher.

By means of the handle at e the speculum was made to turn
on its edge so as to view a distant artificial star, and thus to test
the figure—thus a great saving of time was effected and the
risk of accident diminished.

108 | Mr. SAMUEL HUNTER,

Fig. 9.

A curve produced from a similarly constructed machine set at
random is given in fig. 10.

Fig. 10

It is unnecessary to speak of Foucault’s process of hand abrad-
ing or the American system of local polishers, as these require
highly skilled artificers to be successfully used.

The choice of machines evidently les between that of Lord
Rosse’s and that of Mr. Grubb’s No. 2. The latter is so compact
and admits of such a variety in the curves which the polisher

On Apparatus for Polishing Specula for Reflecting Telescopes. 109

may be caused to describe, that it probably deserves the pre-
ference. On the other hand, on looking at figure No. 5, and
observing the variety of continuously varying curves described
by the polisher in Lord Rosse’s machine, one has little doubt that
with it there will be less liability to polish the surface in rings
than with a machine which gives a uniform curve of whatever
description.

The objection that the polisher is kept too long over the edge
by the eccentric (G, figure 4), is obviated by making the pully by
which it is driven oval as in the machine for Lord Rosse’s 6-feet
speculum.

It is certain, however, that both machines have produced good
results in the hands of their inventors.

Note.—In Mr. Grubb’s Machine No. 2, one revolution of the speculum coincides
with 14 strokes of the eccentrics, of which there were 33 per minute in the rough
grinding, and 24 in fine grinding and polishing.

ON BABBAGE’S SYSTEM OF MECHANICAL NOTATION AS
APPLIED TO AUTOMATIC MACHINERY,
BY
HOWARD GRUBB, C.E., F.R.A.S.
Read December 17th, 1877.

In the year 1826, the celebrated mathematician, Mr. Charles
Babbage, presented a paper to the Royal Society of London, on
a method of expressing by signs the action of machinery.

The ingenious and elegant system Mr. Babbage describes in
this paper appears to have been paid but little attention to by
engineers, and I can only find one mechanical author, and that
of old date, treating of Mr. Babbage’s system.

The fact of this (as it seems to me), most useful system of
notation, having been apparently buried in oblivion, has induced
me to bring the matter under the notice of this Society in the
hope that it may prove as useful to many others as it has been
tome. I may also say that I am further induced to notice this
matter, from the fact that my father, who made considerable use
of this system in planning his automatic printing, and other
machinery, found the system capable of extension in directions,
certainly not recorded, and perhaps never contemplated, by Mr.
Babbage.

I shall first endeavour to explain the object which Mr. Babbage
had in planning this notation, then the principle of the system,
and lastly the uses to which it may be applied.

Firstly. The object Mr. Babbage aimed at was to supply a
serious want which he felt existed in graphically representing an
elaborate piece of machinery. He desired to devise such a
method of graphical representation as would present to the
mind of the mechanic a true representation, not so much
of the general form and disposition of the small parts, for that
can be done by ordinary draughtsmanship, but of the quantity
and nature of the different movements, the time each movement
occupies, and the sequence of such movements, &c. Such a re-
presentation could no doubt be made by a series of drawings of

112 Mr. HowarD GRUBB,

each part, showing the machine in every possible position, but
this would require enormous labour, and numerous sets of draw-
ings for each individual position of the machine, and such, even
if accomplished, would not fulfil the required conditions, for it
would be almost impossible for any person to properly follow the
various motions through these elaborate drawings, and carry in
his mind the true nature of the movements.

Mr. Babbage’s system, however, enables a person who has a
slight mechanical knowledge, and a very little practice, to per-
fectly understand the complicated movements of a piece of
machinery like this automatic numbering machine,* from a few
minutes study of a single chart, on which all its motions are
laid down according to his system.

Secondly. The principle of this system of notation may
be thus described :—The various movements of the machine are
classified, and named, and placed, one under the other in the first
column of the sheet. Opposite them is a portion ruled into small
vertical columns, which in its total horizontal dimensions is sup-
posed to represent a certain space of time, in fact the time
occupied by the machine in completing one period or cycle of its
duty. This may be divided into any convenient number of parts.
In the present case as the machine completes a cycle in about
six seconds, I have divided the space into six parts, and each of
these again into ten, representing tenths of seconds.

The vertical distances represent, on various empirical scales,
“spaces” travelled over by that particular part of the machine
specified in the first column.

As the horizontal distances represent “tome,” and the vertical
space, any portion of a machine at rest for any particular number
of seconds, or tenths of seconds, is represented by a horizontal
line, thus :—

: Ht ORE

:
nL

* An automatic numbering machine, the invention of Mr. Thomas Grubb, ¥.Rs , was
exhibited as an illustration to this paper.

On Babbage’s System of Mechanical Notation. 113

A uniform motion is represented by an inclined straight
line, inasmuch as the spaces passed over in each unit of time
‘are equal :—

A crank motion which begins gradually, attains its greatest
velocity in the centre of its half-stroke, and ends also gradually,
is represented thus :— :

In fact the space passed over in any particular unit of time, is
represented by the difference of the ordinates at beginning and
ending of that unit.

A glance therefore at the accompanying chart will show the
actual positions of all parts of the machine at any particular
tenth of a second during the whole six seconds.

Thus, for example, it will be seen in the first line that the
inking rollers roll backward and forward by a crank motion (or
motion analogous to it) six times during a cycle. In the second
line it will be seen that the inking rollers rise uniformly, and
attain their highest level in three-tenths second; then they
continue (rolling backward and forward, as the first line has
previously informed us), for 1:1 seconds; they then uniformly de-
scend and ascend again (to change position of rollers) in 0°6 second,
continue at their highest level, inking the rollers for 0°6 second,
and then uniformly descend and spend the remainder of this
time, 3°0 seconds, in taking up fresh ink.

I might go through all the lines in the same way, but as the
same principle applies, it is hardly necessary as a very little
study will render the matter quite plain.

Thirdly. The uses to which this system is capable of being
applied are numberless, and seem to continually increase as one gets

114 Mr, Howarp GRUBB,

more conversant with the principle and practical working of the
system. They may, however, be classified into three heads :—

(a). The designing of the machine.
(b). The working out of the details of construction.
(c). The putting together of the machine.

(a). Let us first consider the designing of the machine. What- —
ever difficulties there are in understanding the working of
a complicated machine from accurate drawings made after the ma-
chine is completed, or even from the machine itself, much greater
are the difficulties to be encountered in designing the machine, for
in this case the designer has neither machine nor drawings to
guide him, and the only representation of the machine lies in his
own brain; while, therefore, he mentally plans one part, he has to
keep in his mind (if he can) the relative positions and actions of
all the other parts, and frequently to go back in his work and
modify and remodify various parts in his mind’s eye, and all
this must be thought out before he puts pen to paper; for after
all, mechanical drawings represent, not the actions and motions
of the machine but the appliances (levers, wheels, cams, dc.), by
which these motions are produced. We cannot plan these appliances
before we know what is required for each part to do.

What we do want, therefore, is a means of graphically repre-
senting the various motions and actions of the machine without
reference, in the first place, to the nature of the mechanical ~
appliances by which these various motions and actions are effected.
I have said enough I think to show that this part is most ad- —
mirably tulfilled by this system of notation, for as the designer
plans motion after motion, and action after action, he represents
the nature, direction, quantity, and quality of each by these
various curved lines, and can go backwards and forwards touching
up and modifying the various actions (without taxing his brain
to carry the nature of all or any one of these acta until he
gets all to his satisfaction, and in proper sequence.

(6.) The next task of the designer is that of working out the
details of construction of the machine, and here again the system
assists him, for he can decide from the nature of the curve on his
chart (which curve he has before decided on to be the best

On Bubbage’s System of Mechanical Notation. 115

possible for that particular purpose),” what class of motion,
whether crank, link motion, wheels, or cam work, he should
adopt, and supposing he is required to adopt the more compli-
cated form of cam work, the curve on the chart will enable him
to sketch directly,and without any calculation the shape of his cam.

(c.) Now as to the putting together of the machine. I do not
mean by this, simply the reputting of the machine together after
it has been once completed, but I mean the putting together for
the first time of the various parts which have been separately
and disjointedly completed to scale drawings, the ascertaining
of the exact position in which to place each wheel, levers, and
cams, so that all may work properly, and each part fulfil its
proper duty, and at the proper time. In complicated machines,
this is the one operation in which above all others, workmen are
apt to make mistakes, for as the appliance for each motion has
to be placed and “keyed” independently, it is very difficult indeed
to say, except by a laborious tentative system of trial, whether
that particular motion tallies perfectly with all the other motions,
not only these already attached, but those to be attached.

Here again Mr. Babbage comes to our assistance, for by
attaching to the main shaft of the machine (which makes one
revolution for each cycle), a cardboard disc divided into the same
number of parts as the chart, we have in keying on any par-
ticular motion, only to bring the shaft round till the divided disc
reads such a division as corresponds to some certain action
of that particular cam, or lever—say the commencement or end
of some particular action, and then turn the cam or lever on the
shaft until that action does actually take place, and there key .
it, and so on through all the motions: so that really the work-
man might put the whole machine together, find out the position
for all the motions, key them on, and be perfectly satisfied in
his own mind, that the machine will work perfectly correctly,
even though he never tried it once. |

It may be said that a mathematician could describe and note
down the nature and quality of all these actions without reference
to a graphical representation. No doubt; but in the first place
the mathematics required even for very simple machinery would
be far higher than what we can expect mechanics to be conversant
with, and J think we need no argument to show that a mathe-

= iy

otieat explanation of oe mechanical er v

_ the requirements even of a highly educated m¢
find Mr. Babbage himself, one of the , greatest t ma
_ this century, actually engaged i in devising this sys ;
representation.

GOR DE ROR SERED ASI ROARS Cee Eee il AIBUNG Ub } ea ee ‘
HUNAN DS WUVeanananua untnvannevnvanuaneavoanalaVOa aUU04(Gl Peeeeeeeees:- mr coca tara ns

ANU HOGA AERRRAARAL
AARRTHR PVE OEE SU ARIU ec as ea cleearece LaLISUL LIAL

NOLLOW GONVH

Wann vee
qOU 9g 77a PIYSIL fT AZAZ 7, LO2°

Pa1aM? IG

Se ine AAAI? LOG

LINDT buryao TT

GIYPLOL UO YIOT

saeeee -- patted Yur ar SIILD J
LUTEAL) exzewscre aren Ped FT
TMT) orn seer
ag pesmees sesseecors asses ——— ; oe

fine UE aA A eee —
CTT sees omy Par
MTT TTT “ecm PP ger
TOTTI] etsy eter ety
TTT TTT ae ee say Beep
aq pasag poze pag pang jas aa pe a %
eR NTN ib sizing Bisap

Il 0)

NOILOW JIDVILOLOV

SUGGESTIONS FOR AN EXPERIMENT TO DEMON-
STRATE THE POLARIZED STATE OF THE GAS IN
CROOKES’S LAYER.

BY
GEORGE FRANCIS FITZGERALD, M.A., F.T.C.D.

{Read 21st January, 1878.]

I DESIRE to apologise to the Society for bringing before them only
a proposed instead of a performed experiment, but my excuse is
that it will probably be some time before Iam able to perform
the experiment myself, and as I desire to get credit for having
at least proposed it, I take this opportunity of publishing it, and
of giving my reasons for supposing it likely to be successful, by
showing that the quantities involved are quite within the reach
of our present methods of observing them.

I would first notice that, according to both Clausius and Max-
well’s theories of the conduction of heat in gases, the existence
of a force like Crookes’s depends essentially upon the distribution
of the velocities among the molecules, it being easily seen from
either of their investigations (as is also evident from many other
obvious considerations) that it is quite possible to imagine such
a distribution of velocities among the molecules as that, though
heat be propagated through the medium, yet the pressure in all
directions shall be the same. Hence, any independent method of
demonstrating a polarized state of the gas is of considerable im-
portance ; and the experiment I am about to propose is for the
purpose of doing so.

When any homogeneous transparent substance is in a state of
stress, its refractive index for light, polarized in certain planes, is
different from that for light polarized in other planes, and conse-
quently a ray of plane polarized light, when passed though such
a medium in certain directions, emerges elliptically polarized.
If the gas in a Crookes’s Layer be in the state of stress that
theory indicates, it ought to behave similarly, and a plane
polarized beam when transmitted along it should emerge ellipti-

K

118 Mr. G. F, FitzGEra.p,

cally polarized. Now, the amount of elliptic polarization, we may —
- expect, can be calculated in the following manner :—I have esti-
mated by aseries of unfortunately rather rough experiments that
when a red hot ball is plunged into cold water to a depth of half
a centimetre, the thickness of the Crookes’ Layer formed, is about
a quarter of a millimetre. This is, of course, only a rough ap-
proximation, but it will give us results which determine with
what order of quantity we are dealing. Hence, the excess of
pressure in the vertical over that in the horizontal direction that
I measured was half a gramme per sq. centimetre, which is about
the ‘0005 of the atmospheric pressure. Now, I will make an as-
sumption which is, however, only partially true, but as one object
of the experiment is to determine to what extent itis so it is legiti-
mate provisionally, and it is that we may treat the strain in the
gas as due entirely to a difference of density in different directions.
That we may do so to some extent, at least, is manifest, for, ac-
cording to theory, the number of molecules moving in the direction
of the strain is greater than the number moving in other di-
rections. To what extent this is true could only be determined
either by elaborate theoretical investigations into the state of the
gas or else by experiments such as I am proposing. Assuming
then the strain to be wholly due to a difference of density we
can proceed as follows :—The law connate the refractive in-

dices of a gas at different densities is * Ben ind oda ai so that in air
when p= 1:0002940, and in the case we are considering where
aoa 1:0005 we have p’ = 1:0002941. As there are 100,000

vibrations of light per five centimetres in vacuo there will be
100029'40 when the density is », and 100029°41 when it is py’,
and consequently a difference of phase of ‘01 of a wave length
will be introduced per five centimetres or a twentieth of a
wave length in 25 centimetres. Now, as the intensity of light
in the analyzer depends upon the square of the sine of the
difference of phase, this will give the intensity as the square
of the sine of 9°, which is ‘02 or 2th. Hence I conclude
that if a ray of cee polarized light be transmitted through 25
centimetres of a Crookes’s Layer between two surfaces, one of

On the Polarized State of the Gas im a Crookes’s Layer. 119

which is red hot, and the other below the temperature of boiling
water, and with an interval between them of a quarter of a
millimetre, then one-fiftieth of the light will be restored in an
analyzer which was so turned as to extinguish the beam before
transmission between the plates. Such an effect could be easily
observed, but asit is very unlikely that the whole of the strain
in a Crookes’s Layer is due to a difference of density of the gas in
different directions, itis very unlikely that so great an effect would
be produced. One object, however, in trying the experiment
would be to determine to what extent the strain is due to a
difference of densities.

ON THE BARYTES MINES NEAR BANTRY,

BY
EDWARD T. HARDMAN, F.C.S., of the Geological Survey of Ireland.
[Read January 21st, 1878. ]

SULPHATE of Barytes or Heavy Spar is a mineral of not very
common occurrence in Ireland, and is only met with in a few
localities in sufficient quantity to be of commercial value. In
various places in the county Cork it is found in some abundance ;
and near Bantry it has been, and I believe is at present, being
extensively worked. Having visited these mines some time ago, I
propose giving a brief description of them.

The most extensive lode is met with in the townland of Derry-
ginah, Middle, about two miles east of Bantry. It bears nearly
due east and west, N. 80° E. & S. 80° W.; cutting the strike of
the Old Red Sandstone slates, at an angle of about ten to fifteen
degrees. The lode is ten to fifteen feet thick, and has been fol-
lowed for some 200 or 300 yards, the workings extending to a
depth of about fourteen fathoms. About one-third of the lode in
the centre consists of extremely pure Barytes, but the sides of it
consist of an impure variety called cawk, which contains a quan-
tity of quartz, carbonate of lime, green carbonate of copper,
Peacock copper ore, and micaceous or specular iron. The last
is found in considerable quantity—so much so, that the manager
of the works was of opinion it might prove commercially valuable
could it be smelted.

Besides the difference in purity of the Barytes, two varieties
occur in this lode. One a crystalline glassy-looking specimen ;
the other a granular saccharoidal variety, and the last is the
kind most valued, as it is the most easily ground in the process
of preparation.

From this mine a considerable quantity of mineral has been
obtained and exported by the Bantry Barytes Mining Company,
who are now working it. When in full work they can easily
turn out twenty tons per day. But the mine is capable of yield-

122 Mr. E. T. HARDMAN,

ing a much larger quantity, being in fact so far only limited by
the amount of labour obtainable, and the state of the market.
Owing to the cost of carriage also, the price of the mineral is
necessarily rather high.

The next locality for Barytes is.a little more than a mile south-—
east of Bantry, in the townlands of Ardargh and Darreengreanagh,
and so far as I know of, has not been mentioned in any list of
localities of that mineral ; although the occurrence of the lode is
marked in the field maps of the Geological Survey. And the
mode in which it oecurs is sufficiently curious to deserve a passing
notice. |

This deposit occurs in similar grits and slates to those enclos-
ing the first named, but instead of forming a lode it consists of a
thick pipe-like mass of nearly pure Barytes. This pipe is about
thirty feet long, and fifteen wide, and it has been proved to
extend downwards for at least ninety feet, having been entirely
excavated to that depth. Atthe corners it throws off small
branches or veins, from two to five feet thick, and some of these
have been found at the surface some distance from the n main body,
but appear to thin away on every side. ! |

This great mass is almost entirely composed of the very purest
sulphate of Baryta. An analysis of it showed it to contain over
ninety-five per cent. of sulphate. The “ seconds” or “cawk”
(which forms but a very small proportion of the lode, being prin-
cipally confined to the walls), contain various copper ores, the
green carbonate, Peacock ore, and copper pyrites, as well as galena,
all in very small quantity. The walls of the lode are coated in
some places with steatite; or chlorite. The rocks =
it strike N. 80° E., with a high dip of 75° to 80°
_ This deposit a been worked for a considerable time by the
Scart Barytes Mining Company, and the principal mass of ore has.
been removed to the depth above stated—ninety feet.

There is always an amount of mystery kept up as to the uses
for which Barytes is intended, arising from the fact that it is
chiefly in demand for purposes of adulteration, its high specific
gravity being taken advantage of. Thus it is principally in re-
quest for the adulteration of white lead and other paints; and
some even say that it is employed as a commercial substitute for

~

On the Barytes Mines. 128

sugar. Such at least is the Bantry native opinion. It is besides
occasionally useful for the manufacture of glazes for porcelain*,

The mineral is worth about £1 per ton, delivered free on board
at Bantry, but when ground and prepared it fetches £4 per ton.

A few words on the probable mode of formation of this mineral
may not be out of place. And first I may mention that many
of the Irish localities for veins of sulphate of Barytes appear to lie
in the Old Red Sandstone. ‘Thus Portlock records its occurrence
inthe Old Red Sandstone of Ballynascreen and Desertlyn, county
Derry, and Clogher, county Tyrone. But this is merely a coinci-
dence, because is it found here as in other counties in many other
rocks, crystalline and sedimentary, and in England it occurs largely
in the Carboniferous limestone. Now it is tolerably easy to
account for the presence of veins of this mineral in limestone,
which is easily soluble and quickly worn into fissures or pipes by
ordinary atmospheric water, in which, under some circumstances,
Barytes might be deposited, but the first difficulty with which we
have to contend in this case is the solution of such rocks as sand-
stone and slate. The Derryginagh deposit can be accounted for
by a simple fissure, but this will not account for the other case, in
which the original material has been removed in the form of a
nearly square pipe, which could never have been produced solely
by fissuring. There can be no doubt but this receptacle has re-
ceivedits present form through the action of water. Doubtless such
pipes are due to fissures in the first instance which, allowing the
water to percolate freely, 2 are eaten Po bit by bit into their
present form.

Age of these Veins.— As sh dae veins run partly sibs and partly
across the strike of the strata, which lie in flexures dipping at
high angles, it follows that they must be of more recent date than
that of the upheaving and flexuring of the Old Red Sandstone
and Carboniferous rocks of the south of Ireland. Now, as Pro-
fessor Hull has shown, these flexures are due to forces acting at the
close of as and previous to the Permian Periods. It

* It appears to me that the seeaticlat varieties might, with advantage, be substituted for
alabaster, for statuary and ornamental purposes. The mineral can be obtained in large
blocks. - |!

+ Jour. Roy. Geol. Soc., Ireland, iv., pt. iii, p. 114.

124 Mr. E. T. HARDMAN, ‘

is certain therefore that these lodes, as well as the copper lodes
of the other parts of Cork as well as Kerry, are younger than the
Carboniferous period, and may be therefore about the same age
as those of Cornwall. It is, of course, impossible to determine at
what period past the Carboniferous they have been deposited, since
there are no newer strata in this part of Ireland; but however
this may be, we may suppose that the original fissures were most
likely opened during the disturbances which produced the
flexures of the Old Red Sandstone in the south-west of Ireland.
Deposition of the Barytes and associated Minerals —Barytes
being one of the most insoluble substances known, it is unlikely
that it could have been deposited from solution in cold water; on
the other hand it is so very infusible that the heat necessary to
reduce it to a plastic condition would be more than sufficient to
melt the surrounding rocks. Its deposition is therefore to be
ascribed with most probability to the action of thermal springs,
the waters of which were forced upwards into these fissures, while
the strata at present exposed were still buried under a great mass
of superincumbent rocks. The waters at first warm enough to
hold small quantities of such difficultly soluble minerals in
solution would, as it came nearer the surface, become somewhat
cooler, and these minerals would be then deposited along the sides
ot the fissure. This point, which is insisted on by Delesse, is
demurred to by Bischof, who considers that the waters of ascend-
ing hot springs cannot produce these deposits, but it is evident he
left out of consideration the cooling of the water as it rose,
Source of the Sulphate of Barytes—This is to be sought for
either in the immediately outlying or surrounding rocks, or in
masses of rock at some distance, from which some compound
of barium may be carried down into springs. Carbonate of barium
is by no means an uncommon mineral, and barium in some form
is of common occurrence in minute proportion in limestone. Sili-
cate of barium is also found occasionally in igneous rocks, and
might, therefore, also occur in parts of the Old Red Sandstone
which are derived from the debris of such rocks*. ‘Those com-

* The very small quantity of Barium compounds disseminated through rocks, is of
little moment in this consideration. As Bischof well remarks, the minimum quantities
in rocks may become the maximum quantities in odes.

On the Barytes Mines. 125

pounds of barium are to a small extent soluble in water, and
would be brought down through the strata to rise again from
deep-seated springs. Meeting now with soluble sulphates, these
salts of barium would be converted into sulphate, and as the
water cooled in rising to the surface, this would be deposited.
As a matter of fact crystals of sulphate of barium have been
found on the granite of Carlsbad, where a hot spring, con-
taining in solution traces of that substance, burst out. Chloride
of barium is sometimes noticed in spring waters, and this would
also give rise to sulphate in the manner pointed out.

In fact it is only through the medium of hot water that the
sulphate of Barytes of Bantry, and the very insoluble minerals
associated with it, can be supposed to have been deposited.

ON THE ARTIFICIAL. PRODUCTION OF MINERALS
AND PRECIOUS STONES,

BY
MM. FEIL anp FREMY.
[Read January 21st, 1878. ]

THE artificial production of minerals presents, in a scientific pomt
of view, an interest which everybody understands, It has long
afforded a wide field of research to many scientific men, among
whom may be mentioned Ebelman, Senarmont, Deville, &c.
We thought it might be interesting, even after the works of
these eminent scientific men, to publish the result of our researches
on the crystallization of alumina and of divers silicates.

If we place in a furnace, heated to a high temperature, a mix-
ture of alumina and oxide of lead, we obtain white crystals.
alumina, and, by adding a metallic oxide as colouring matter,
—either chromium for obtainmg a red colour, or cobalt for blue,—
we can produce rubies in the first case, and sapphires in the
second. It is necessary, however, in order to procure chemically
pure crystals, from the mass obtained to separate the lead
which may yet remain in combination with the vitrifiable earth
proceeding from the crucible, and which may itself have been
eombined during the fusion. We may separate these bodies
by different processes, either by the action of hydrofluoric acid
or by potash in fusion, or by prolonged ‘calcination in hydrogen,
and subsequent treatment with alkalies and acids.

The following are the properties of the rubies we obtained :—
They scratch quartz and topaz. Their density is 40041.

They lose, like natural rubies, their pink coloration when they
are strongly heated, and regain colour on cooling. They are as
hard as natural rubies. s

When submitted to optical examination—that is to say, to
the microscope of polarization of Amici—our rubies, which have
the form of hexagonal prisms, present the characteristic black
cross and coloured rings. |

The crystals we obtained, and which we had cut by a lapidary,
have not yet the requisite limpidity for commercial pur-
poses neither do they present to the lapidary favourable facets

128 MM. Fern AND FREmy.

for cleaving ; but they have the colour and the hardness, &c.,
and we have prepared large masses in which crystals have been
found which leave absolutely nothing to be desired. Besides, we
are still studying this interesting question, and without doubt
we shall soon arrive at a perfect result in every point of view.

The second part of our investigation, i.c., that on the crystallized
silicates, will serve to demonstrate the infuene of the fluorides as
crystallizing agents. By submitting to heat, during a determined
time, a mixture of fluoride of aluminum and vitrifiable earth, we —
noticed that, by the mutual reaction of the two bodies, fluoride
of silicium is evolved, and we obtain a crystallized body which
seems to be disthene—that is to say, a silicate of alumina. It
appears under the form of acicular double refracting crystals,
which extinguish the light obliquely towards their edges. These
crystals afforded on analysis the following results :—

Vitrifiable earth, * : ; ‘ “ 47°65
Alumina, ; : 5 A > 51°85
Loss, . r - : 0:50

It is about the same as for disthene, or its varieties, trebolite,
bucholzite and bamlite, and sillimanite.

By operating in a certain manner, and by heating to a high
temperature a mixture of alumina and fluoride of barium, we
obtained prismatic needles several centimetres in length. Their
analysis afforded :—

Vitrifiable earth, . ° . 4 ‘ 34:32
Baryta, - . ° 2 . 35:04
Alumina, . : : . : . 30°37

M. Jannettez has ascertained that these long prisms are often
composed of four blades with parallel faces forming the surfaces
of a hollow prism ; they extinguish the light under the microscope,
or rather they let the obscurity persist between two crossed
prisms. They may be cut at angles of 60° 42’ and 119°.

In the course of the reaction which generates the crystallized
double silicate just described, some corundum is formed. These
bodies are the results of the following changes :—

By heating the mixture of alumina and fluoride of barium,
fluoride of aluminum and barium is formed.

* This term is doubtless used as a synonym of silica.—Eds.

On the Artificial Production of Minerals and Precious Stones. 129

Having once first produced fluoride of aluminum and decom-
posed it again under the influence of steam, hydrofluoric acid is
formed and corundum is crystallized.

By acting at the same time on the vitrifiable earth of the
crucible, there is first produced some silicate of alumina, which
by uniting itself with baryta, has produced the beautiful crystals
of double silicate of aluminum and of barium which we have
presented.

Such is the theory we think rational; and it seems to result
from our experiments that fluorides are not only excellent
mineralizers in the mass, but that they can carry along with them
the most fixed bodies. As a proof of this assertion one can instance
that reraarkable formation of orthose felspar produced artificially
in the upper part of a copper furnace at Mansfeld. The use of
the fluoride of calcium in the bed of fusion, which produced that
felspar, permits us to suppose that the fluorine served here as a
transporting agent or vehicle.

Thus, we are justified in expecting that, by prosecuting our
studies, we may be able to produce crystals capable of application
in jewellery and watchmaking. The last experiments have
shown us that we are making good progress. We have already
obtained cut crystals of remarkable value. We hope they will
shortly be presented for inspection.

/ + nae’ = . : *
ee
= = r s
ate , Poet. ore
REL sascowe aisapoys Lt
-nrooah Das
i
Bh EWS O1'CO!
ioak re re
: ae ceria
ae
aie fo. cit oft Jp
#, a id £ + e
“ay w 4 r a
Se ee arene:
= OF oy .
#8 O59 i-2)3" SUUTOMLT € BOE On OW 2 FE 4
¢ ? ¢ aad 2 > :
' a San Y XO) cdi48 betes ne ys

a bos ey 9, ¥ yr % ‘ . .
Se eer ee : pe oe —— 2s en . mh, : ; Pre al: re

131

‘THE FOLLOWING PAPERS were also read and ordered to be printed
in the Transactions of the Royal Dublin Society :—

187% < --
Nov. 19th.—Wentworty Ercx, LL.D., F.R.A.S., ‘On the Satellites
of Mars.”

Dec. 17th.—Epwarp ae, F.R.S., and E. T. Harpmay, F.C.S., “On
the Nature and Origin of the Chert-beds in the Upper
- Carboniferous Limestone of Ireland.”

- 1878.

Jan. 21st.—T. Romney Roginson, D.D., F.R.S., “On the places of
1,000 stars observed at the Armagh Observatory.”

VERBAL COMMUNICATIONS were also made to the Society on the

following subjects :—
1877.
Nov. 19th.. —On Phenol-phthalein as a test of Alkalinity by Professor
_ J. Emerson Reynorps, M.D.

» » On Specimens of Crystallized Phosphorus, exhibited by
Mr. R. J. Moss, F.C.S.

» » . On the limits of Geological dime by. Rev. S. Havuenron,
M.D., :

On the ie of Science to Practical Engineering by
Rosert Mannine, C.E.

o Bec. 17 th. — On a simple form of Telephone exhibited by Professor W.
F. Barrett, F.R.S. E.

On a new form of Spectroscope, exhibited by Mr. Howarp
Gruss, M.E., F.R.A.S.

On the discovery of Brine in the Valley of the Mersey
at Warrington by Professor Hutt, F.R.S.

On Specimens of ornamental and other stones from Jypore,
India, exhibited by Professor E. Hull, F.R.S8.

On Specimens of Idocrase rock from Cumberland, exhibited
by Professor Harkness, F.R.S,

On Nests of the oven-bird (Furnarude), exhibited by Pro-
fessor MacauisTER, M.D.

= », On an Automatic Numbering Machine, exhibited by Mr.
Howarp Gruss, M.E., F.R.A.S,

aor ys 3)

2? 9

1878.
Jan, 2ist.—On M. Cailletet’s experiments on the liquefaction of
Oxygen and other gases, by Professor J. EMERSON -
| Reynoips, M.D.

x a On the Phonograph, by Professor W. F. Barrett, F.R.8.E.

Jan. 21st. 20 the relation between the electric and capillary cont .

9)

132

ties of a surface of mercury in contact with different —
liquids, by Mr. G. F. FirzcErap, F.T.C.D.

On new forms of Laboratory apparatus for obtaining heat
and light, exhibited by Mr. R. J. Moss, F.C.8.

On the Glacial phenomena of upper and lower Longh
Bray, by the Rev. M. H. Cross, M.A.

On Totanus Haughton, (Armstrong) a new species of
Greenshank from India, exhibited by Professor A.
Macatister, M.D.

On Specimens of Barytes and associated Minerals from
Bantry, exhibited by Mr. E. T. Harpman, F.C.S.

On Nests of Mason-bees from Rayal Pindi, Ladakh, ex-
hibited by Mr. J. W. Havuauron, junr.

On a series of Human Vertebre with anomalous processes,
exhibited by Professor A. Macauister, M.D.

On Nests of Trapdoor Spiders from Jamaica, exhibited by
Professor A. Macauister, M.D.

On the skull of a Fanti from West Africa, exhibited by
Professor A. Macauister, M.D.

On a new form of Tell-tale clock, exhibited by Mr. W.
HANCOCK. |

On a Gas-light improver; also on a new form of gas

engine, used with the Gramme Magneto-electric machine,
exhibited by Mr. Jonn R. WicHam,

Evening Scientific Meetings.

The Evening Scientific Meetings of the Society and of the associated
bodies (the Royal Geological Society of Ireland and the Dublin Scientific
Club) are held in Leinster House on the third Monday in each month
during the Session. The hour of meeting is 8 o’clock, p.m. The business
is conducted in the undermentioned sections.

Section I.— PHYSICAL AND EXPERIMENTAL SCIENCES.
Secretary to the Section, R. J. Moss, F.c.s.

Section TI.—-Naruran Scrmncrs (including Geology and Physical
Geography).
Secretary to the Section, R. M‘Nax, m.p.

Section I[].—Screncr APprPLieD TO THE USEFUL ARTS AND INDUSTRIES.
Secretary to the Section, Howarp GRuBB, M.E., T.C.D.

Authors desiring to read papers before any of the sections of the
Society are requested to forward their communications to the Registrar
of the Royal Dublin Society (Mr. R. J. Moss), or to one of the Sectional
Secretaries, at Jeast ten days prior to each evening meeting, as no ‘paper
can be set down for reading until examined and approved by the Science
Committee. } |

The copyright of all papers read becomes the property of the Society,
and such as are considered suitable for the purpose will be printed with
the least possible delay. Authors are requested to hand in their MS. i
a complete form and ready for transmission to the printer.

7

‘a

Ee

SMITHSONIAN INSTITUTIO

oe il il