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PROCEEDINGS

OF THE

AMERICAN ACADEMY

OF

ARTS AND SCIENCES.

Vol. LVII.

FROM MAY 1921, TO MAY 1922.

BOSTON:
PUBLISHED BY THE ACADEMY.

1922.

The Cosmos Press
cambridge. mass.

CONTENTS.

Page.

I. The Grid Structure in Echelon Spectrum Lines. By N. A. Kent

AND L. B. Taylor 1

II. The General Conditions of Validity of the Principle of Le Chatelier.

By a. J. LoTKA 19

III. The Effect of Tension on the Electrical Resistance of Certain Ab-

normal Metals. By P. W. Bridgman 39

IV. Notes on the Early Evolution of the Reflector. By Louis Bell . . 67

V. The Effect of Pressure on the Thermal Conductivity of Metals. By

P. W. Bridgman 75

VI. The Failure of Ohm's Law in Gold and Silver at High Current

Densities. By P. W. Bridgman 129

VII. A Table and Method of Computation of Electric Wave Propagation,
Transmission Line Phenomena, Optical Refraction, and Inverse
Hyperbolic Functions of a Comple.v Variable. By G. W.
Pierce 173

VIII. Artificial Electric Lines with Mutual Inductance between Adjacent

Series Elements. By G. W. Pierce 193

IX. The Parasitic Worms of the Animals of Bermuda. I. Trematodes.

By F. D. Barker 213

X. Additions to the Hydroid Fauna of the Bermudas. By Rudolf

Bennitt 239

XI. Some H ymenopterou^ Parasites of Lignicolou^ Itonididae. By

C. T. Brues 261

XII. A Revision of the Endogoneae. By Roland Thaxteu .... 289

XIII. The Echinoderms of the Challenger Bank, Bermuda. By H. L.

Clark 351

XIV. Atmospheric Attenuation of Ultra-Violet Light. By E. R.

Schaeffer 363

XV. The Ratio of the Calorie at 73° to that at 20°. By Arnold Rom-
berg 375

XVI. Studies on I Jisect Spermatogenesis. IV. The Phenomenon of Poly-
megaly in the Sperm Cells of the Family Pentatomidce. By R.
H. BowEN 388

CONTENTS. IV

XVII. Note on Two Remarkable Ascomycetes. By Roland Thaxter. 423

XVIII. Records of Meetings 437

Biographical Notices 470

Officers and Committees for 1922-23 623

List of Fellows and Foreign Honorary Members 525

Statutes and Standing Votes 545

RuMFORD Premium 561

Index .... 563

57-1

Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 1, — December, 1921.

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.

By Norton A. Kent and Lucien B. Taylor.

Investigations on Ligbt and Heat made and publishgd with aid from the

RuMFOBD Fund.

(Continued from page 3 of cover.)

VOLUME 57.

1. Kent, Norton A. and Taylor, Ltjcien B. — The Grid Structure in Echelon Spectrum
Lines, pp. 1-18. December, 1921. $.75.

Proceedings of the American Academy of Arts and Sciences.
Vol. 57. No. 1. — December, 1921.

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.

By Norton A. Kent and Lucien B. Taylor.

Investigations on Light and Heat made and published with aid from the

RuMFORD Fund.

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.
Norton A. Kent and Lucien B. Taylor.

Received July 7, 1921. Presented October 19, 1921.

Some years ago Nutting ^ noted a peculiar, complex structure,
termed by him the "fluting" or "grid," which appeared in many
echelon spectrum lines, and consisted of several fine components of
different and often changing intensity. Later one of us ^ independ-
ently noted this structure. Nutting crossed the 12" Lummer plate
of the Bureau of Standards with his echelon and was apparently
forced to the conclusion that the structure was real — that is, that it
indicated an actual discontinuity of emission in the source.

Proceeding on the assumption of reality, the writers attempted a
solution of the problem using LiX 6104 which, although known to be a
spectroscopic doublet, offered peculiar advantages in that the grid
was extremely brilliant, well-marked and persistent.

Apparatus.

The apparatus used consisted of: —

Two echelons: No. 1, made by Porter, 30 plates, each 14.76 mm.
thick, step 1 mm., aperture 31.0 by 33.0 mm.; No. 2, made by Petit-
didier, 30 plates, each 23.29 mm. thick, step 1 mm., aperture 31.0 by
35.5 mm.

The Bureau of Standards 12" Lummer plate kindly loaned by Dr.
Stratton.

A Hilger Lummer plate — length 131 mm., width 14.5 mm., depth
4.827 mm.

A Hilger constant deviation prism spectroscope combined with an
echelon as in Figure la; also a separate Hilger spectroscope with
another echelon spectroscope as in Figure lb. The achromatic lenses
of both echelon spectroscopes are of about 50 cm. focal length and 5 cm.

1 Astrophys. Jour. 23, pp. 64 and 220. 1906.

2 Kent, Proc. Am. Acad. XLVIII, No. 5. Aug. 1912.

KENT AND TAYLOR.

aperture; each echelon bed rotates on an axis at its center; the Hilger
micrometer is fitted with one fixed and two movable cross-hairs as
shown in Figure 2.

^J7>

Fig. lb.

Figures la and lb. S, slit; L, L, lenses; E, echelon; P, prism;
O, ocular.

Figure 2. SS', fixed crosshair; MM', MM' movable system;
LL', spectrum line.

A Littrow mount spectroscope consisting of a Petitdidier
achromat — focal length 30 feet, aperture 6"; and an An-
derson grating — aperture 3f " vertical by 5" horizontal,
15,000 lines per inch, used in the third order.

A 5 K. W. transformer, 1 10 to 30,000 volts ratio of trans-
formation, fed by a 60 cycle Holtzer-Cabot 4.5 K. W. gen-
erator. Various large induction coils capable of giving 6"
sparks and operated by a rotary mercury break and an
electrolytic interrupter, had proven insufficient.

A vacuum arc of construction as indicated in Figure 3.

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.

Figures. One fourth original size. D, D, fibre disks; O, O, water outlet;
P, P, fibre plugs; A, A, asbestos; J, water jacket; W, W, W, windows;
I, I, I, water inlet.

6

KENT AND TAYLOR.

This was also adapted to pressures of several atmospheres as the glass
windows and fibre plugs were held in place by threaded rings.

Quartz vacuum tubes — even pyrex glass having proven unsuit-

Water infahe
i

^^

2;z^

ry

7Z2L

I

To vacuum pump
\

Wafer ouiki

"Wafer /'ntaKe

I

i

-rrj

« ••:•■•'•■-:

■v_

1

Waier ouilet

Figure 4. C, C, cork stoppers; R, 11, rubber sponges; T, T, terminals.

T

To vacuum
pumps

Tc H, generaior
and
dryino apparatus

Figure 5. T, tube; M, manometer; B, bulb.

able — of various forms, the most successful of which, for salts such as
lithium chloride, proved to be that shown in Figure 4 in which fine
brass wire, often in helical form, was fitted into brass caps, 6 mm. in

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES. 7

diameter, and sealed in with De Khotinsky cement, each joint being
cooled by a water jacket. The salt is shoved into the capillary by a
wire and the tube will run many hours without refilling. It may be
used end on as well as side on. The capillaries varied from 2 to 0.5
mm.

Auxiliary apparatus as shown schematically in Figure 5. The bulb
B, prevented too rapid changes in pressure. The system was washed
out with hydrogen from a Kipp generator, dried by sulphuric acid and
a calcium chloride tower. The mercury manometer, IVI, indicated the
pressure — generally from 8 cm. to a fraction of a millimeter.

Procedure and Certain Results.

Both Lummer plates were each in succession crossed with echelon
No. 1. In each case, with a carbon arc soaked with lithium chloride,
both at atmospheric pressure and in a moderate vacuum, there
appeared a pattern which, at this stage of the investigation, seemed
to indicate that the grid was real. The following facts, (1) to (6), are,
however, clearly not in accord with this conclusion, and prove con-
clusively that this curious structure is due to the phenomenon of
"secondary maxima" observed by Stansfield ^ and resulting from
successive reflections from the surfaces of the echelon plates, producing
a Fabry and Perot system in the region of the primary light of the
echelon. (1) to (3) deal with some of the criteria of echelon secondary
maxima given by Stansfield. These criteria are, in essence, indicated
below by italics.

(1) The width of LiX 6104, given by an open carbon arc at atmos-
pheric pressure, as seen in the Littrow grating, using a narrow slit,
was found to be about 0.25 t. m. when echelon No. 2 showed the grid
plainly. The suspicion, therefore, was confirmed that the line was
too wide for the echelon, the difference between the adjacent orders
being about 0.26 t. m. In the case of Janicki's observation * of
Hg. X 5461, Nutting's work on lines of many elements, and the work
of one of us on the zinc lines as given by arc and spark, the indications
are that with all lines for which the echelon shows the grid, their
breadth is so great that the use of this instrument is not at all justifi-
able.

The writers then proceeded to study the structure from this new

3 Phil. Mag. (6) 18. .383. 1909.

* An. der Phys. Vol. XIX, p. 36. 1906.

8 KENT AND TAYLOR.

standpoint, considering the primary line of width approximately
0.25 t. m., and not as formerly, one of the grid components itself.

These componcnis are indeed, in this sense, each narrower thari the
primary maximum — 0.25 t. m. — the grid components, all of them
now regarded as secondary maxima, being only about 0.05 t. m. in
width in echelon No. 2.

(2) The curvature of one of the mercury yellow lines was compared
with that of a^ grid component in X6104. By stopping down the
echelon spectroscope slit, a line of definite length was observed, and
by setting the stationary cross-hair of the filar micrometer upon
the ends of the image, and the movable system upon its center, the
horizontal distance, d. Figure 2, from the ends of each line to its
center were measured. It was found that the curvature of the com-
ponent is about 25% greater than that of the primary line.

(3) With a small mirror, set at 45°, over the lower half of the echelon
spectroscope slit an argon vacuum tube and the lithium arc were
observed at the same time. The relative motion of the grid compo-
nents in X6104 and a nearby argon line were then studied as the
echelon was rotated. The primary argon line moves about one-half as
fast as the grid components.

Quantitative measurements of the relative displacements were later
made with Zn X4810. A quartz vacuum tube was fitted with coiled
brass wire leads and brass terminals, exhausted, filled with hydrogen
to 10 or more cm. pressure and then gradually exhausted to 1 mm. or
less. The zinc lines given by the brass wire leads appeared very
sharp, steady and brilliant. With X4810, as thus produced, was com-
pared the "gridded" line of a cored carbon arc at atmospheric pres-
sure, in which small pieces of zinc had been placed, the small mirror
arrangement allowing simultaneous observation of both sources.
Upon rotation of the echelon the grid components rushed by the
narrow tube line. To measure the relative speed a plane mirror was
attached to a side of the echelon case. The image of an illuminated
slit in a piece of cardboard was formed by a lens upon a distant scale
after reflection from the mirror. The echelon was set near the ^ = 0
position. A reading of the position of the slit image on the scale was
taken when the tube line lay upon the fixed hair of the filar micrometer.
The echelon was then rotated until the slit image moved about 2 cm.
The displacement of the tube line was then measured by the movable
cross-hair system. A similar series was then taken with a grid line.
The ratio of the displacements was 3.6 : 6.4 or about 1 : 2.

(4) The echelon was removed and the ocular focussed on the prism

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.

9

image of a line. Replacing the echelon shortened the focus for a true
narrow echelon image by about 0.6 mm. The focus for the grid com-
ponents of the same line was 0.7 mm. shorter yet — the light forming
the grid had traversed the echelon plates more than once.

(5) Although the grid components are generally very well defined
(the minimum being " deep"), it is a difficult matter, with a fluctuating
source such as an open arc, to obtain accurate measurements. The
grid spacings appear to vary slightly at different stages. When the
grid is complete the spacing is regular and, within the limits of error of
measurement is equal to one fifth the distance between the orders.
This was proven as follows : — A quartz tube having merely coils of
fine brass wire as terminals gave extremely fine zinc lines. Echelon
No. 2 was set in double order condition and Ao, the difference between
the two orders, measured for X4S10 (see Table I). Then the grid was
measured as given by a 3 ampere open carbon arc. Three distinct
series of readings were taken. Then the tube was again used. The
accuracy of an individual setting was about 0.2% in Ao and about 5%
in Ag. It thus appears that in this region, at least within 2%, Ao =
5Ag. The focus of the instrument was, of course, not changed, the
dift'erence between that for primary and secondary maxima being so
slight that distances between the components of the grid are not
appreciably affected.

TABLE I.

Distances are measured in divisions of the|micrometer head. Each Ao dis-
tance given is the mean as calculated from four settings; each Ag f rom two.
Settings were made on the six centrally situated grid components.

Ao for Zn X 4810

Ag for six grid components.

22.60

22.50

Mean

22.58

1-2

2-3

3-4

4-5

5-6

Mean

Mean

of
Means

4.6

4.3
4.8
4.3

4.8
4.4
5.0

4.6
4.6
5.0

4.8
4.8
4.3

4.7
4.1
4.7

4.6
4.5
4.6

22 58 -^ 4 . 6 = 4 . 9 or Ao = 4 . 9 Ag

A similar series for Zn X6362 gave Ao = 27.65 and Ag = 5.6, 5.9,
5.5, 5.6, 5.4: mean = 5.5. Hence Ao = 5.0jAg.

10

KENT AND TAYLOR.

(6) The structure given by both echelons is the same. That is,
there are five secondary maxima for every primary maximum. Ag for
Hydrogen X6563 is 0.061 t. m. for instrument No. 2, while for No. 1
it is about 0.09G t. m., which again is another fact fatally inconsistent
with the existence of a definite discontinuous emission in the source.

With this evidence at hand the writers then attempted to clear up
the results of the crossed dispersions. The source previously used was
hardly adequate. By removing the soft core of the lower carbon it
was possible to feed copiously into the arc a strong LiCl solution.
Greater brilliancy and steadiness were obtained. The results were
unmistakably in accord with the facts given in (1) to (6) above.
Figures 6a and 6b indicate the structure observed. These will be

y

8'

o

\

<■■'

yp

P V

Fig. 6a.

Fig. 6b.

Figure 6a. Li X6104 with crossed Lummer plate and echelon. Grid not
indicated. Xi and X2 in sing;le and double order condition respectively.
i Figure 6b. Li X6104 as in Fig. 6a. Grid shown. Xi and X2 both between
isingle and double order condition.

discussed in full below (see page 16). When one component of the
spectroscopic doublet is in double and the other in single order condi-
tion three lines appear; when both are in a condition between single

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES. 11

and double order there are four lines. It is probable that these four
lines, under conditions of inferior illumination, were interpreted as
four separate and true lines. It is unfortunate that at first the only
line available for study was a doublet. With this latter and better
source a zinc chloride solution gave X4810 sufficiently strong. The
crossed dispersions prove it to be a simple, though broad, single line
when the echelon alone shows the grid.

Further Results: Characteristics of the Grid.

(a) From numerous observations upon Li X6104 and Zn X4810, as
developed by various sources, such as vacuum tubes and arcs (on 110
and 220 volt D.C. circuits and from 1 to 20 amperes) under high,
normal and low pressure, in which the cross-hairs of the filar micro-
meter were set successively upon the true, narrow, lines given by the
tube and the grid components given by the arc, it is quite certain that
the grid is built up approximately as follows: — Suppose that in a
hypothetical grating of resolving power and dispersion equal to that
of the echelon, a line which is at first very narrow, e.g., 0.025 t. m.,
gradually becomes less monochromatic, owing to changing conditions
in the source, and appears as represented diagrammatically by the
small letters a to e, Figure 7. Four cases must be discussed as shown
in Figures 7 to 10, respectively.

Case I: — The echelon in double order condition gives successively
images A to E. When the line is very narrow the echelon shows it as
such, in A. Similarly for a line of width, Ag — the width of a grid
component or an intergrid distance — it is shown as in B. When of
width 3Ag, the echelon shows no change, C appearing as B; for, at m,
the primary and secondary action together give a decided minimum.
When the line has a width, as in d, the echelon shows a triplet, D, and
when of width as in c, or greater, the grid is complete — five grid
maxima, 1 to 5 and 6 to 10, for each maximum, such as 3 and 8, which
a narrow line would give; four maxima, 4 to 7, between the double
order positions, 3 and 8, of such a narrow line. For a given position
of the echelon these grid components do not, in forming, move very
much, if at all: they come up in situ. There exists an apparent
motion, in and out, which is probably due to the changing width of
the primary line, which may not at all times be such as to complete
the entire width of a grid component.

Case II: — When the position of the echelon, its temperature and
the wave length of the line observed, result in the central grid minimum

12

KENT AND TAYLOR.

I

a

A

^.. 1

n ^^

b

B

in '%

i

C

-JAX- 1

E ^
$:

8

' 1

1

D

^7AS— 1

^ ^

^

e ^
%

1

H

!■

/ 2 3 V 5

6 7 3 5/0

Fig. 8.

Fig. 9.

Fig. 7.

Figure 7. Case I: Echelon in double order
condition and a grid maximum coincident with
the primary maximum.

Figure 8. Case II: Echelon in double order
condition and a grid minimum coincident with the
primary maximum.

Figure 9. Case III: Echelon in single order
condition and a grid maximum coincident with
the primary maximum. ,

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.

13

occurring in the position of the narrow tube line, as in Figure 8, for a
double order condition of the echelon, there are nine or even eleven
components when the grid is strong. Note that the grid components
2, 3, 7, 8, which at first are very brilliant when the grid is "young,"
grow weaker, 2 and 8 often being so faint that it is difficult to make
accurate micrometer settings upon them.

Case III: — The treatment is the same for a single order condition
of the echelon, as in Figure 9 which shows a triplet, quintuplet, or,
with neighboring parts of adjacent orders, even as many as eleven
components.

Case IV: — Here a grid minimum coincides
with the primary maximum and the grid com-
ponents are as shown in Figure 10.

The above statements explain why an origi-
nally narrow line, as its width increases, may ap-
pear, as it actually does, a triplet or quintuplet, as
in Figures 7 and 9, or may, as it were, "reverse"
and then quadruple, as in Figures 8 and 10. Actual
reversal as shown by the grating probably occurs
much later in the historv of the line. (See page

15.)

Further, if a line be intrinsically unsymmetri-
cal, shading off to the red for instance, the sec-
ondary action masks an early stage of broadening,
and the left grid line, 2, forms as in A, Figure 11.
Line 3, as in A', then comes up as 2 strengthens.

(b) The grid begins to disappear and the line
gradually becomes broad and structureless when
the primary line exceeds 2Ao in width, Ao being
the distance between two adjacent orders. This

was determined as follows : — Using

as narrow a slit as possible, a low

power ocular and a mm. scale, an

eye estimate was made of the

breadths of various portions of an

arc line shown by the grating.

These were reduced to t. m. The

same source was viewed simultane-

Fic. 10.

Figure 10. Case IV: Echelon in single order condition and
a grid minimum coincident witii the primary maximum.

14 KENT AND TAYLOR.

ously by echelon No. 2. For Zn X4810 three components of the grid
exist when the grating shows a line 0.12 t. m. broad. Ao for X4810 =
0.155 t. m. f X 0.155 = 0.09 t. m. which compares favorably with 0.12
t. m. The complete grid exists when the line is 0.3 t. m. or 2Ao
broad and the image begins to pass into a structureless line at 3Ao.
Similarly for Li X6104 a full and well-marked grid exists at a line
width about 0.2 to 0.5 t. m. or Ao to 2Ao (as here Ao = 0.25 t. m.).
The grid is poorly marked above about 2Ao and is gone at 3Ao.

(c) Numerous lines in the spectra of Na, Hg, Fe, Mg, Cd, Ca, Sn,
Pb, and Bi, developed by an open carbon arc, show the grid whenever
the line is sufficiently broad — rendered so by introducing more of
the substance or increasing the current; also by increasing the capac-
ity in the case of a spark.

\d) LiXXG708 and 6104, Zn XX4810, 4722 and 4680, also HgX5461
(mercury being fed into the lower cored carbon) show by their behavior
that a line which is too broad will appear structureless in the echelon,
that the center of the core of an arc may show the grid complete while
light from the wings of the image gives a simple structure of but one
to three components. With a sufficient amount of vapor the com-
plete grid may be obtained even at low pressure.

(e) A study of Zn X4810, from an arc in the vacuum or pressure tank,
at pressures from 2 cm. of mercury to about three atmospheres,
showed that moderate changes of pressure do not produce measurable
displacements in the grid components, but merely alter somewhat
their relative intensities, shifting the maximum over one or two com-
ponents or even bringing up new ones. This of course means that,
as long as a grid exists, the components do not change appreciably
their position with changes of wavelength as small as 0.015 or 0.020
t. m.^ Their position is affected more strongly by the position of the
echelon and its temperature. Similarly, the grid components of the
spectroscopic doublets Li XX6708 and 6104 developed in vacuum tubes
show intensity shifts with changes of pressure over the range of one
atmosphere.

(f) The " end on " position of a vacuum tube will generally show a
more complete grid than that "side on."

(g) If a line broaden unsymmetrically with increase of current the
maximum of intensity will shift. Those components which are just
being formed show an apparent motion outward as the number of

5 According to Humphrey's and Mohler's results for Zn, the pressure shift
reduced to X 4000 is 0.057 t. m. for twelve atmospheres.

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES.

15

components increases, the first step resembling a narrow reversal as
in Figures 8 and 10 or a central fixed line with two moving wings as in
Figures 7 and 9. But the writers feel that this apparent motion is
due to the fact that each grid component is not formed in ioio at once:
the part which lies nearest the center of the system is formed first.
Certain it is that this apparent motion ceases abruptly when the
component has reached a position which is one grid distance from
its neighbor. If the source be an arc, many rapid fluctuations in
intensity occur.

(h) Although the resolving power of the grating (225,000 in the third
order) is far below that of the echelon (about 750,000 for X6100 for
echelon No. 2) it is hard to reconcile the images given by the two
instruments on any other assumption than that the grid is due to
secondary action.

To throw further light on the problem, Li X6104, given by a vertical
carbon arc soaked with LiCl, was viewed simultaneously by echelon
and grating. Table II gives a summary obtained from various ar-
rangements.

TABLE II.

1 1 1 1 indicates the grid; ■ a broad structureless line; | a narrow unreversed
line, or one very slightly reversed; || a broad and strongly reversed line.

Arrangement

Sign of
upper pole

IVile soaked
with solution

Echelon shows

Grating shows

1

+

+

At + pole nil

« _ « H

II

2

+

" + " nil

" - " ■

II

3

—

" - " ■

" + " nil

II

4

+

« _ « B

" + " nil

II

1

Therefore which pole is soaked makes no difference, nor does it
matter which pole is above. The region near the + pole generally
shows the grid in the echelon, that near the — pole a broad structure-
less line. The grating always gives a narrow unreversed line or one
very slightly reversed where the echelon shows the grid, and a strongly
reversed line where the echelon shows no structure. Thus the grid
does not result from conditions which produce a reversed grating line.

16 KENT AND TAYLOR.

With Li X6708, which usually appears widely reversed in the grat-
ing, the grid is more difficult to obtain in the echelon, while with
Na X4972 — given as an unreversed line by the grating at either edge
or centre of the arc image — the echelon shows the grid at both edge
and centre.

(i) We are now in a position to discuss jn detail Figures 6a and 6b.
These were obtained with the 131 mm. Lummer plate set between the
collimator and prism of Figure lb and crossed with echelon No. 2.
The source was that described on page 10: the arc current being from
10 to 25 amps. The plate dispersed vertically, the echelon horizon-
tally. Both figures are drawings based on visual filar micrometer
measurements, a single cross hair being moved successively along the
axes, vv' (vertical), hh' (horizontal), aa' (across the structure) pp'
(parallel to it), as shown below the two figures.

Two Lummer plate orders are shown in each figure, the primes
distinguishing these. The numerals indicate the two components of
the spectroscopic doublet, the breadth along axis aa' their approximate
relative intensity. Xi is the weaker line, Xo the stronger in both
figures — X2 being the component of longer wavelength.

In Figure 6a X2 is in double order condition; in 6b both Xi and X2
are between double and single order. The echelon grid structure is not
indicated in Figure 6a: in 6b its approximate position is shown. It
was difficult to observe at the ends of the lines and so is not there
indicated: it is slanted at an angle of about 2.4° (see gg' in Figure 6b)
with the vertical. The slant of the lines themselves as well as that of
the grid changes with the positions of both plate and echelon: further,
the grid slant is not due to the curvature of the echelon image. This
may throw some 'light on the disappearance of the grid at a breadth
of line greater than 2Ao. For, as the echelon action alone is given by
the projection, on the pp' axis, of the grids of the lines Xi and X2, it is
evident that lack of coincidence owing to slant would tend to obliter-
ate the grid altogether, this indicating that two broad lines, the centers
of which lie as far as 0.1 t. m. apart (the AX of the two components of
Li X6104), may not give coincident grid structures; or, in other words,
the grid maxima do not (for any one position and temperature of the
echelon) necessarily fall together. This is not inconsistent with shift
of intensity for small changes of wavelength (0.015 to 0.020 t. m.) as
noted on page 14. Shift of intensity and position probably both enter
with change of wavelength of the center of gravity of a primary echelon
image.

These two figures show that the grid is unquestionably a secondary

THE GRID STRUCTURE IN ECHELON SPECTRUM LINES. 17

echelon action. Otherwise the regions between hnes 1 and 2 would
have been filled in with a structure along axis aa' similar to that
along pp'.

With an echelon alone we have obtained only the weaker component
of Li X6104 as a single narrow line. We plan to cool the tube with
liquid air, thus sharpening the stronger component so that it will
no longer suffer the secondary action, to which the small satellite is
probably due.

(j) We have no record of having observed in either echelon any
ungridded line of width greater than Ag. Either there exists (1) a
very narrow line, (2) an irregular series of such, as, for instance, in the
yellow mercury lines, (3) a line of width Ag, (4) a series of such (the
grid more or less complete) or (5) a broad, structureless image cover-
ing between one and two orders. And it appears extremely probable
that the "reversal" of the main component of HgX5461, noted under
certain conditions by several observers and often noticed by us, may
be modified by the entrance of secondary action due to the excessive
breadth of this component.

(k) The retardation producing the primary maxima of a narrow line

is proportional to 7i — l, while that of the light undergoing secondary

action is proportional to 3w — 1. Thus the difference in retardation

in case of the two actions bears the ratio to the retardation of the

2n . . 2w

primary of ;, which is a function of n alone. The value of r

n— 1 n — I

varies from 5.50 for X6563 to 5.37 for X4341 in echelon No. 2; and from

5.48 to 5.35 respectively in No. 1. Since echelons are generally made of

substantially the same kind of glass, any two having equal separation

of primary orders will have equal separation of secondary maxima,

because this separation is the same fractional part of the separation of

the orders; but the values of Ag in t. m., varying with the dispersion,

will, of course, differ in different instruments.

We cannot state just why Ao = 5Ag. The measurements given
above indicate that this is so within the limits of experimental error
for both the violet and red regions.

It would be interesting to assemble an echelon under water, press
the plates together and allow the superfluous water to drain off. This
process might vastly reduce the secondary action. If successful
Canada balsam might be substituted for water thus producing a
more permanent instrument. We plan to try this experiment shortly.

18 KENT AND TAYLOR.

Conclusion.

Summarizing the above results, we may state that the evidence is
entirely against the existence of a discontinuity of emission in the
source. The grid is due to a secondary action of the echelon which
enters when the line under investigation is not sufficiently monochro-
matic. This means that the previous work of one of us ^ must be
considered as of small value and also that ^n explanation of the
apparent complexity of structure obtained by Nutting ^ can be
found in secondar}^ action.

The results obtained emphasize the fact that when an echelon is
used to measure small wavelength differences, great care must be taken
to obtain the lines so narrow that their width is less than i Ao, else
secondary action may enter to cut off an edge of a line and thus give
a false intensity-maximum position.

We must record our appreciation of the help rendered by various
student assistants, especially Alessrs. Greenleaf and Risga. We are
also indebted to Dr. Lucy Wilson for her skilful aid during part of this
research and to our assistants. Miss Pearson for mathematical work
in connection with the calculation of the constants of the echelons,
and Mr. Gilman for making the sketches accompanying this article.

We wish also to thank sincerely the Rumford Committee of the
American Academy for numerous grants which made possible the
purchase of the main pieces of apparatus used in this investigation.

6 Proc. Am. Acad., Vol. XLVIII, No. 5. Aug. 1912.

7 Astrophys. Jour., XXIII, pp. 64 and 220. 1906.

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57- 2

Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 2.— Januaby, 1922.

THE GENERAL CONDITIONS OF VALIDITY OF THE
PRINCIPLE OF LE CHATELIER.

By Alfred J. Lotka.

(Continued from page 3 of cover.)

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 2.— .January, 1922.

THE GENERAL CONDITIONS OF VALIDITY OF THE
PRINCIPLE OF LE CHATELIER.

By Alfred J. Lotka.

THE GENERAL CONDITIONS OF VALIDITY OF THE
PRINCIPLE OF LE CHATELIER.^

By Alfred J. Lotka.
Received May 20, 1921. Presented by Raymond Pearl.

The derivation of the principle of Le Chatelier from the laws of
thermodynamics is familiar.

We may approach a converse problem. What, in the broadest
terms, are the conditions which a system must satisfy in order that the
principle shall apply to it? The interest of this problem arises from
the fact that we have reason to suspect these conditions may prove
broader than the domain within which the laws of thermodynamics
are conveniently applicable.^ We may therefore expect that a satis-
factory solution of the converse problem may enable us to make
rigorous application of the principle to systems to which, from lack of
sufficient data it may be impossible, or from other causes it may be
inconvenient to apply thermodynamic methods.

Consider a system whose state is defined in terms of a variable x
and a paramenter G. The system is one of that class, the history of
which follows a law

I = /(^^ G) (1)

(For example, it may consist of a mixture of {A\— 2x) mols H2O
vapor, (yl2+ 2a-) mols of hydrogen, and (^3+ x) mols of oxygen at
2000 deg. C. in a rigid enclosure of volume G; A\, A-i, A3 being con-
stants, namel}^ initial masses). It is understood that other para-
meters besides G may enter into the function /, but it is unnecessary
to set them forth explicitly, since in the reflections which follow only

1 Papers from the Department of Biometry and Vital Statistics, School of
Hygiene and Public Health, Johns Hopkins University, No. 37.

2 See Ehrenfest, Zeitschr. fiir phys. Chem. 1911, vol. 77, pp. 227, 244;
Wolchonsky, Jl. Russ. Phys. Chem. Soc, 1912, vol. 44, pp. 305, 310; Chwol-
son, Lehrbuch der Physik, 1909, vol. 3, p. 547; Bancroft, Jl. Am. Chem. Soc,
1911, p. 92; Fournier d'Albe, Contemporary Chemistry, 1911, p. 38; Lowy,
Kosmos, 1911, p. 331; Le Dantec, La Stabilite de la Vie, 1910, p. 25; L.
Fredericq, Arch, de Zool. Exp. et Gen., ser. 2, vol. 3, 1885, p. XXV; Spencer,
First Principles, chapter 22, section 173, Burt's Edition, p. 433. For further
historical and bibliographic notes see Duhem, Traite d'Energetique, 1911,
vol. 1, pp. 523, 524.

dx^"-'

+

I--

5Xy

5G '

= -

df /df

~ do/ dx

22 LOTKA.

changes in x and in one parameter G at a time will be considered, the
other paramenters being constant.

According to (1) a stationary state (which need not be a true
equilibrium in the thermodynamic sense) is defined by

dx

0 = ^ = f{xr, G) ' (2)

where Xi denotes the equilibrium value of x.

If the parameter G is altered by a small increment 8G, the corre-
sponding increment 8xi in the equilibrium value xi of x is, in view of
(2), given by

(3)
(4)

1. Stable State.

If the stationary state defined by (2) is stable, we must have in the
neighborhood of that state ^

dx

We can then distinguish two cases:

fif
a.) 7, > 0. This means that the parameter G is one whose in-

crease accelerates the transformation the progress of which is meas-

dxi
ured by x. In this case it follows immediately from (4) that tt; > 0.

oh

In other words, if the s^\stem is stable in the stationary state defined
by (2), then increasing a parameter which accelerates the transforma-
tion will shift the position of the stationary state in the direction of
increased transformation. From this alone, however, it does not
necessarily follow that the new stationary state will actually become

df

3 Condition (5) states that the velocity f = — 5x i.s alwavs opposite in

dx

sign to the (small) displacement 5x from equilibrium. This is evidently

necessary for stability of equilibrium.

VALIDITY OF THE PRINCIPLE OF LE CHATELIER.' 23

established. But, starting from the stationary state, at which

dx

— = f = 0, increase in G leads to a positive value of /. That is to
dt

say, a change actually takes place with a velocity directed towards the
new stationary state, i,e. increased oc.

b.) — :; < 0; i.e. increase in the paramenter G retards the trans-
dG

formation. Here it follows by similar reasoning that increase in G
shifts the position of the stationary state towards diminished trans-
formation. Furthermore, in this case the increment 56' initiates a
retrograde change, i.e. a change toward the new stationary state.

In both cases, (La) and (l.b), therefore, a change 8G in the para-
meter G is followed by a transformation 8xi towards the new sta-
tionary state, in the direction of the influence of the parameter G
upon tl^ie velocity of transformation.

5, Unstable State.

df
Consider now the case in which — > 0. The stationary state de-

dx

fined by (2) is then unstable. A train of reasoning precisely analogous

to that set forth above leads, in this case, to the conclusions:

(1) A change 8G in the parameter G determines a shift of the
stationary state in the direction opposed to the influence of the para-
meter G upon the transformation.

(2) The system, disturbed from existing stationary state by a
change 56', moves, not towards, but away from the new stationary
position.

Application to Influence of Initial Masses. Consider a transforma-
tion

Sl+ ^2+ ...+ SrZ S'l-\- S'o+ . . . + S\ (6)

Let ^1, ^2, . .^r be the masses (expressed in mols) at time t of the
components Si, S2 . .Sr', similarly let ^'1, ^'2 -^'s be the masses of

S 1, S 2- ■ ■ S s

Let X measure the progress of the transformation from left to right,
and let pi x be the amount . (in mols) of S, transformed from time
t = 0 to time t = t.

Let Ai be the initial value of the mass (in mols) of some component

24 LOTKA.

Si which disappears in the transformation when x increases, and let
A'j be the initial value of some component <S', which appears in the
same transformation.

We have, according to (4),

Sx^ ^ _ dl /dl '

dAi dAil dx ^ '

If we are dealing with a system of constant mass, we have an equa-
tion of constraint

mi^i+ 1712^2+ . . . == ^1^:4- m2^2+ ... (8)

where mi, mo, . . . are the molecular weights of the substances Si, S2, . . .
From (8) we find by differentiation

so that we may write, instead of (7),

5a; 1
8Ai

(10)

From (10) it is seen that — - and ~ are always of the same sign

oAi d^i

df . . . .

provided — is negative, i.e., provided that the system is stable in the

equilibrium defined by / = 0. That is to say, if the system is stable,
and if adding a quantity of a component disappearing in the trans-
formation increases the velocity of the transformation (at the previous
equilibrium), then such addition will shift the equilibrium in the
direction of increased transformation. In this case, then, the principle
of Le Chatelier holds good.

On the contrary, by similar reasoning, it is found that if the addition
of a quantity of a particular substance disappearing in the transforma-
tion retards the transformation, the principle does not hold as regards
that substance.

Again, by similar reasoning, it is found that the principle holds or
does not hold, according as the addition of a substance *S", appearing
in the transformation retards or hastens the transformation. We
may therefore summarize the facts as follows:

VALIDITY OF THE PRINCIPLE OF LE CHATELIER. 25

1. Given that the system, at equiUbrium, is stable with regard to
changes in .r, and that there is a relation of the type (8), an "equation
of constraint " connecting the masses ^ and their initial values A,
then the condition which must be satisfied in order that the Le Chate-
lier Principle may hold with regard to the effect of a change in the
initial mass of some one component, is that the addition of such com-
ponent shall accelerate or retard the transformation (at equilibrium),
according as such component disappears or appears in such trans-
formation.

2. Given that the conditions for the validity of the Le Chatelier
Principle stated under (1) are satisfied for each and every component,
then it is easily shown that the system is necessarily stable with
regard to changes in .r, so that the condition of such stability with
regard to changes in x is automatically satisfied and does not need to

be expressly stated. For, if —j- > 0 for every component which dis-

df
appears in the transformation, and if z~Tr < 0 for every component

oA ]

which appears, then, in view of (9), the same is true of -rr and ttt .

But

dii = -pidx (11)

d^'i = + p'idx (12)

where p», p', are positive numbers, and

dx~ ^ d^i dx ^ ^ a^y dx ^^^^

= - i:§Pi+ zSv'i (14)

which is necessarily a negative quantity if

,-^>0, ^-i<0 (15)

3. It should be noted that the argument by which our conclusions
Lave been drawn depends on the existence of equations of constraint,
relations such as (8), connecting the ^'s and the A's. In the absence

26 LOTKA.

of such constraints we are in no wise assured that the principle holds.*
This must be clearly borne in mind in seeking to apply the Le Chate-
lier principle, for example, to biological systems. Thus, for instance,
the malaria equilibrium under the conditions contemplated by Sir
Ronald Ross,^ is independent of the initial amount of malaria in the
system (provided only this is not zero). This state of affairs arises
out of the fact that there is no equation of constraint of type (8), in
this case, connecting the initial amount of malaria with its status at
any subsequent epoch.

Case of more than one variable. A somewhat more complicated case
arises if the system under consideration is susceptible of several con-
current transformations, so that its state at any instant requires for
its definition not one variable x, but a number of such variables.

It will suffice if we consider here the ca.se for two variables x, y, as,
for example, the case of a pair of consecutive reversible reactions

In this case we have

dx

n't ~

/i (•'•-

y,o)

dy
dt

h (x,

y,G)

and equilibrium is

defined by

/i

= h=

-- 0

AZ ^^Z (' (16)

(18)

(19)

(20)

Differentiating, in a manner analogous to that followed in the case of
a single variable .r, we have

^U a/i dfr

- P)U du a/o

~ 6a-, + t^ 6?/i + Jf, 6 6' = 0 (22)

dx dy dU

4 For there is then no necessary relation between $ and A, so that the

r)f Hf

derivative -^ is no longer equal to ^, but is indeterminate or meaningless.

5 "The Prevention of Malaria," Second English Edition, John Murray,
London, 1911, p. 679; Lotka, Nature, Feb. 1912, p. 497.

VALIDITY OF THE PRINCIPLE OF LE CHATELIER.

27

5.ri 5//1

a system of linear equations, which we solve for — , ^y; and obtain

dh

5/1

dG

dy

dh

a/2

8xi

dG

dy

8G

5/1

dfi

dx

dy

dJ2
dx

dy

(23)

8yi
and a similar expression for 777 .

Condition of Stability. A general solution of (18), (19) can be
written ^ in the form of exponential series

x= Poi- Pie"'' + Poj''^' + Pne^^'' +

where Xi X2 are the roots of

(24)

(25)

A(X)

,6x
dx

- X

^df,
\dy

dJ^
dy

-X

0

(26)

The condition for stability "^ of the equilibrium is that the real parts
of all the roots X are negative. This in turn demands that the abso-
lute term A(0) be positive. But this absolute term is, evidently,

A(0)

dfi

dfi

dx

dy

dh

df2

dx

dy

(27)

6 A. J. Lotka, Proc. Am. Ac, 1920, p. 139.

7 Idem, loc. cit., p. 144; Hurwitz, Math. Ann., 1875, vol. 46, p. 521 ; Blondel,
Jl. de Physique, 1919, pp. 117, 153.

28

LOTKA.

SO that we must have, for stability,

5/1

5/1

d.r

dy

dfo

a/2

dx

dy

>0

(28)

In consequence, given stability of equilibrium, the sign of

dxi

dG

will be the same as that of the numerator in (23), i.e., that of the
expression "

dG dy dG dy

(29)

Example. Consecutive Reactions. By the way of example we may
apply these results to the case of a pair of consecutive reversible
reactions.

Si+ S2+ . . . + SC S'i+S'2+ . . . + S'C «"!+ ^"2+ . . . + S"t (30)

Let X denote the progress of the first reaction from left to right (so
that, for example, a quantity, -piX of the substance S» has been trans-
formed at time t); and let y similarly denote the progress of the
second reaction, from left to right.

Let us consider the effect upon x\, the equilibrium value of x, of an
increment bA" k in the initial amount of substance S" k appearing as
product of the second reaction.

We have, according to (23)

dh

a/i

dA"u

dy

dh

a/2

bxx

dA'\

dy

bA'\

dfi

a/i

dx

dy

a/2

a/2

dx

dy

(31)

We shall assume stability, so that the denominator is positive.
In the numerator, evidently ^

8 If we exclude any possible catalytic influence.

VALIDITY OF THE PRINCIPLE OF LE CHATELIER. 29

so that this numerator reduces to

= 0 . (32)

Stability demands

dA"k dy

f > 0 .(34)

On the other hand the principle of Le Chatelier would make

This, by (31), in view of (32), (33), (34), will be true or not according as

S^ > 0 (36)

Hence the principle of Le Chatelier holds good or not, as applied to
the effect of A"k upon xi, according as

af-J" (3^)

From this point on the discussion would follow essentially similar
lines as in the case of a single dependent variable; it is therefore un-
necessary to carry this out in further detail.

Influence of External Factors. We have hitherto tacitly assumed
that (1), or (18), (19) are the only conditions for equilibrium, or, that,
if there are any other conditions to be satisfied, these are in some way
automatically taken care of.

In point of fact, in general, in addition to a condition of the form

Jt = ^^'' ^^ ^^^

there will be further conditions of the form

H= H, (38)

where H is a, parameter entering into the function /, while //« is a
parameter defining certain "external conditions." For example, H
may be the pressure exerted by a gaseous mixture against an enclosure,
and He may be the external pressure applied to a movable piston

30 LOTKA.

forming part of that enclosure. Here it is not enough, for complete
equilibrium, that (1) be satisfied, but (38) also must hold.

Furthermore, the conditions (1) and (38) define equilibrium, but
are insufficient to determine its stability, since they give us no in-
formation regarding the behavior of the system when H + He, i.e.
when not in equilibrium with the external parameter H e-

In order to settle this point we must have some further data. We
are here interested in systems in which such additional data are
furnished in the following manner:

In the case of these systems it is found that, in relation to the
parameter G a certain parameter H ha\nng certain peculiar properties,
can be defined by a relation.

ip (^1, ^2, G,H) ^ constant (39)

or its equivalent

-^ {x, Ai, A^,. .G,H) = constant (40)

The peculiar propert\' of G referred to above is as follows

dG>_ >

—-. 0 according as // — //« ^=0 (41)

dt < ^ <

It will perhaps be well, before proceeding any farther, to illustrate
this by a concrete example. Consider the system

2 //2O ^ 2 H2-\- O2 (42)

If ^1 is the mass of II 2O expressed in mols, ^'1 the mass of Ho and ^'2
the mass of O2 similarly expressed; if I' is the volume (parameter 6-')
and if P is the pressure (parameter H) exerted upon the enclosure,
then the equation (39) here takes the form

py = (^1+ ^1+ r^) Re (43)

where 6 is the absolute temperature and R the general gas constant.
Or, if ^1, A'l, A'2 are the initial masses of H^O, Ih and O2 respectively,
(expressed in mols), and x measures the progress of the reaction, as,
for example, by the number of O2 mols formed, then evidently

(44)
(45)
(46)

.^1 =

Ar

—

2x

l'l=

A'

1+

2x

^2 =

A'

2+

X

VALIDITY OF THE -^PRINCIPLE OF LE CHATELIER. 31

SO that (40) takes the form

PV = { Ui- 2x) + (.l'i+ 2x) + {A'o-\- x) Rd ..^.

= \{x + A,+ A\+A'^^Re ^^^'

In this case it is quite evident that the parameters P, V (correspond-
ing to //, G of the general case) have the property defiiifd by (41),
which here appears as the characteristic property of the intensity
factor and the capacity factor of an energy.

But for our present purposes we are not concerned with the question
whetjier or not the parameters G, H defined for a given system are or
are not factors of an energy. We must be prepared to deal with cases
where this is either uncertain or actually known not to be true. All
we need to know, for our purpose, is that the parameters G, H have
the property defined by (41). An example may serve to illustrate the
fact that this property may be shared by physical quantities not
obviously related to energy.

Among the parameters on which the rate of increase of a human
population depends is the area a occupied by them, since this deter-
mines the population density, which in turn influences the death rate
in well-known mann^r,^ and. presumably, in some degree the birth
rate also.

Now there is an obvious relation between population density and
ground rent. Regulation is effected about as follows: There is a
certain demand for space, a desire for expansion, which may be
measured by the rent // per unit area that the individual is willing to
pay. On the other hand there is a certain market price He which
must be paid to obtain accommodatioji. Now \i H > II e, i.e. if, on
an average, an individual is willing to pay more than the market price,
the population will spread over a greater area by renting more ground.
If, on the other hand // < II e the individual is not willing to pay the
market price, he will retrench, he will move from a six room apart-
ment to a five room apartment say, and the area occupied by the
population will contract. The parameter He functions, in fact, much
like a "surface pressure," tending to compress the population into a
smaller area. The most striking exhibition of this " surface-pressure "
is seen in a great metropolis such as New York, where the population, a
naturally two-dimensional structure spread like a film over the earth's
surface, has been thrown into great creases towering 700 feet and more,
50 layers deep, above the street level.

9 See, for example, Newsholme, Vital Statistics, 1899, p. 154.

32 LOTKA.

It will be seen that in this case the internal parameter H and the
corresponding external parameter He so determine changes in the
area a that

da> , >

— -: 0 according as H — He~ 0 (48)

that is to say, the parameters //, a and He are related to each other
and determine the course of events in a manner analogous to the
intensity factor, the capacity factor of an energy, and the "applied
force." But it is quite unnecessary to suppose that H and a actually
are such factors of an energy in the example cited (population-spread) ;
on the contrary, the writer is opposed to this view, which he has taken
occasion elsewhere to discuss. ^° For our purposes it is quite immaterial
whether P and a are factors of an energy. All we need know is that
they enter into the condition (41) as there set forth.

Condition for Stability toward External Factor. Consider a system
for which the condition for equilibrium with the environment is
given by

H = He

(p (G, H) = constant

dG > ,. „ rr >

—r = 0 aceordmg as H — He = 0
at < <

(49)

Let

<p (G, H) = const., i.e. // = x {G) (50)

be plotted as ordinates in a rectangular system in which G is plotted
as abscissae. Then it is easily shown that the condition for stability
of equilibrium is that the curve H = x (G) must slope downwards
from left to right.

For, suppose it sloped upwards. Let the system be in equilibrium
at a point Ai (Fig. 1), where

H = ^^1= He \ fr.\

G=G, ] ^^^^

Suppose the system is in any way displaced to the point A^ where

H2 > Hi (52)

> He (53)

10 "Economic Conversion Factors of Energy," to appear in a forthcoming
issue of Proc. Nat. Ac.

VALIDITY OF THE PRINCIPLE OF LE CHATELIER.

33

Th

en

dG
dt

>0

(54)

Hence the point moves along the curve in the direction Ai A2, i.e. still
farther away from equilibrium.

On the other hand, the same reasoning applied to a curve sloping
downward from left to right shows that the system after displacement
returns to its equilibrium position.

So, for example, the curves representing the relation between pres-

G

Figure 1.

sure and volume of a gas necessarily slope downward from left to
right; the same is true of the demand and supply curves of economics.
If it were true, as sometimes stated, that the more a man has, the more
he wants, economic equilibrium would be an unstable condition.

External Stability and the Principle of Le Chatelier. Consider now
a system which obeys the condition

^ {x, G, Hy= 0

^- = 0 according as H — He^O
at < <

(55)

(56)

34 LOTK.^^.

Let the system be stable towards He both when x is held constant
and also when a- is at the equilibrium value a-i defined by

J^=f (^-1, 0) = 0 (57)

This means that all the curves " of constant composition "

if {x, G, H) =0 j (58)

X = constant j

and also the curve " of equilibrium composition "

cp (xi, G, II) = 0 (59)

slope from left to right downwards.

Now consider two neighboring curves of type (58) (curves of con-
stant composition), which we will suppose solved for H and write

7/„=^a(6'. a-„) (60)

H,==-^b{G,x,) (61)

SUppose we start with the system in the state represented by the
point Q, in internal equilil)riuni and also in equilibrium with an ex-
ternal parameter He (see Fig. 2).

Let x be changed at constant G, so as to increase H according to
(55) until X = Xb, so that the representative point strikes the second
curve of constant composition at R.

Since at the start of this operation

// = //^= //^ (62)

and at the end

H = Hbi
>

H, \ f63)

therefore the system is not in equilibrium with the external pressure
He in the state represented by the point R, but equilibrium (for
X = Xb) occurs at some other point T which must lie to the right of R
along the curve of constant composition RT, since, whenever

// >He

G increases, in accordance with (56).

Furthermore, drawing a horizontal QS, T must lie below S, since the
line of equilibrium composition QT must slope from right to left
downwards.

VALIDITY OF THE PRINCIPLE OF LE CHATELIER.

35

It is clear therefore that lines of constant composition are steeper
than lines of equilibrium composition.

It follows at once that if G be increased while the system is kept in
equilibrium, so that the representative point travels along QT, then
the change in x from Xato Xb is that which at constant G increases H,
or at constant // increases G.

But this is the principle of Le Chatelier. This principle therefore
Jiolds whenever the conditions (55) (56) are satisfied, and the system

H

G

Figure 2.

is stable towards Hg both when x — constant and when x = xi (i.e.
when x has its equilibrium value).

Similarly, it can be shown that if the conditions (55), (56) are re-
placed b^- . - ,

<p {x, G,H) = Q

dG<_ . >_

-77 — 0 according a,s H — He — 0
dt > ^ <

36 LOTKA.

while at the same time the system is stable towards H both when
a- = constant and also when x = xi, then the Le Chatelier principle
holds. In this case the curves <p {x, G, H) — 0 (x constant)

and ^ (a-i, G, II) = 0

both slope from left to right upwards, and the curves of constant
composition are again steeper than the equilibrium curves. An
example of this type is that in which // is temperature and G is heat
absorbed by the system (when // < He, G increases).

Finally, be it remarked that the results here deduced depend solely
on ki7idic stahility, i.e. on the fact that the system when displaced
from equilibrium has a velocity (rate of change of displacement)
towards that equilibrium. The conclusions reached are therefore
wholly independent of energetic (thermodynamic) consideration, since
no reference whatever has been made to forces or energies or in any
way whatsoever to the physical dimensions of the parameters involved.

This completes the present enquiry into the conditions of validity
of the principle of Le Chatelier. It remains now only to point out the
place which this communication occupies in the general plan of the
series of investigations of which it forms part. This series of investi-
gations has for its object the study of material systems evolving in
accordance with a system of differential equations

^ = I\{X„ X,, ...Xn; A; P;Q) (65)

in which the symbols A' denote the masses of certain components S
of the system, the symbol A has been written to denote collectively
the initial values of the masses of certain components, the P's are
parameters defining the state of the system (extension-in-space,
topography, climatic conditions, etc.); and the Q's are parameters
defining the character of the components S.

In a previous communication the kinetics of such a system were
studied for the case in which the ^'s, P's and Q's are constant. This
left open for discussion the effect of changes in these parameters.
One phase of this subject has been dealt with by the writer elsewhere, ^^
namely the 'eft'ect of slow changes in these parameters. The present
communication now extends the field of enquiry to the effect of

<

11 "Note on Moving Equilibria"; to appear in a forthcoming issue of the
Proc. Nat. Ac.

VALIDITY OF THE PRINCIPLE OF LE CHATELIER. 37

changes of any kind in the parameters .1 or P, with this restriction,
it is true, that we have, following Le Chatelier, interested ourselves
solely in the ultimate effect upon eciuilihrium, leaving entirely out of
consideration the path by which such equilibrium is reached. In
many cases such partial information is of value, the equilibrium being
the matter of chief interest, the path of the change of lesser practical
importance. Herein lies the utility of such general principles as that
of Le Chatelier, of Maupertuis, Lenz and others whose names have
become linked with one or other form of reciprocal relations between
the parameters defining a state of ecjuilibrium. Since the application
of such principles to biological systems has been essayed by various
authors, without, however, any rigorous foundation upon which to
build, it has appeared to the writer essential, for further progress in
this field, to make a critical examination of the basis underlying these
principles.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 3.— April, 1922.

THE EFFECT OF TENSION ON THE ELECTRICAL RESIST-
ANCE OF CERTAIN ABNORMAL METALS.

By p. W. Bridgman.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 3.— April, 1922.

THE EFFECT OF TENSION ON THE ELECTRICAL RESIST-
ANCE OF CERTAIN ABNORMAL METALS.

By p. W. Bridgman.

NEW YOkIC

BOTANICAk

(JAKUt:!'<»

THE EFFECT OF TENSION ON THE ELECTRICAL RESIST-
ANCE OF CERTAIN ABNORMAL METALS.

By p. W. Bridgman.

Received October 7, 1921. Presented October 19, 1921.

TABLE OF CONTENTS.

Page.

Introduction 41

Description of Apparatus and Method 42

Detailed Data 44

Lithium 44

Calcium 46

Strontium 47

Antimony 48

Bismuth 50

Nickel 52

Cobalt 53

Manganin 53

Therlo 56

Discussion of Results, excepting Nickel 57

Discussion of the Effect in Nickel 63

Summary 06

Introduction.

Under hydrostatic pressure the electrical resistance of most metals
decreases. On the other hand the resistance of these metals increases
under tension. There are, however, a few metals which are abnormal
in that their resistance increases under pressure. It has been known
for some years that bismuth is such a metal, and I have recently added
to the number lithium, calcium, strontium, and antimony. It seemed
to me of considerable interest to determine the effect of tension on the
resistance of these metals. These data are presented in this paper.
"When I started this work, such measurements had not been published
for any of these metals. During the course of my work, however,
data were published in Italy for the effect of tension on the resistance
of bismuth.^ The resistance of this was found to decrease under
tension, so that this metal is abnormal with respect to both tension
and pressure. I have verified this result. I find that strontium is
the only one of the remaining four which is also abnormal with respect

1 E. Zavattiero, Rend. Accad. Lincei, 29 (1) 48-54, 1920.

42 BRIDGMAN.

to tension ; the resistance of lithium, calcium, and antimony increases,
as is normal, under tension.

When I started these measurements, only one metal was known
which was abnormal with respect to tension; this was nickel. The
measurements were made by Tomlinson ^ in 1876, on nickel which
presumably had several per cent of impurity. Since it was my good
fortune to obtain through the kindness of the Leeds and Northrup Co.
some nickel of exceptionally high purity, I repeated the measurements
of Tomlinson, and also extended them to find the effect of temperature
and cyclic changes of tension. I have verified the sign of the effect
found by Tomlinson, although there is not close numerical agreement,
as was to be expected.

Since cobalt is in many respects closely related to nickel, I also
determined the effect of tension on the resistance of it. The effects
are entirely normal.

In addition to the five abnormal pure metals mentioned above, the
alloys manganin and therlo are also abnormal with respect to their
pressure coefficients. I have determined the tension coefficients of
these also, and find them to be normal in sign, but to be very small.

My previous measurements of the pressure coefficient of resistance
have suggested certain views as to the nature of the conduction
mechanism.^ In the following I shall discuss how far these new facts
are in accord with these views.

This discussion demands a knowledge of Young's modulus. I have
determined this for most of these metals.

Description of Method and Apparatus.

The apparatus and method were very simple, and for the most part
were similar to those already adopted for the measurement of the effect
of pressure.

The resistance was measured by a potentiometer method, the drop
of potential between two potential terminals attached to the specimen
being balanced against the drop due to the same current flowing
through an appropriate combination of known resistances. The
details of the apparatus were the same as those previously used in
measuring the pressure coefficient, and have been fully described

2 H. Tomlinson, Trans. Roy. Soc. 174, 1-172, 1883.

3 P. W. Bridgman, Phys. Rev. 9, 269-289, 1917, and 17, 161-194, 1921.

EFFECT OF TENSION ON CEKTAIN ABNORMAL METALS. 43

elsewhere.* The wire under tension merely replaces the wire under
pressure of the previous experiments.

The wires used were small, and a load of a few kilograms was suffi-
cient in all cases. The wire was mounted vertically, and attached at
the upper end to one arm of an equal arm balance, to the other arm of
which known weights could be applied. For most metals it was most
convenient to use the ordinary solid weights, but if there were hystere-
sis effects, as in the case of nickel, it was necessary to apply and remove
the weight continuously; to accomplish this a water weight was used.
In the case of antimony, because of its excessive fragility, a special
arrangement was necessary which will be described in detail later.

The lower end of the wire was attached to a bracket, supported from
above. This bracket, with the wire, dipped into an oil reservoir about
12 inches high and two inches diameter. The top and bottom of the
reservoir, were connected through side tubes with a turbine stirrer,
by means of which a continuous stream of oil was maintained past the
specimen. The wire itself was about 6 inches between potential
terminals. In most cases the measurements were made at room
temperature only, and the stirrer adequately maintained approximate
equality of temperature. A correction could be easily determined
and applied for the change in resistance due to drift of temperature of
the oil bath. In a few cases, however, when more careful regulation
of temperature was necessary, a large bath of water, maintained at
constant temperature thermostatically, was raised around the oil
bath. The walls of the latter were of thin brass, and exchange of heat
between the oil and the water was sufficiently rapid to maintain con-
stancy of temperature in the oil.

The magnitude of the tension applied was usually considerably less
than the elastic limit. The behavior of the resistance gives a sensitive
test of the perfect elasticity under the applied tension. The wire
was usually seasoned by a number of applications of a tension higher
than that of the final measurements. The behavior of the resistance
beyond the elastic limit is complicated, and would make an interest-
ing study on its own account. I felt this to be beyond the scope of
the present work. I have, however, in nearly all cases determined at
least the sign of the permanent change of resistance produced by
exceeding the elastic limit, and in some cases have examined the
phenomena a little more in detail. It appears that in all cases the
permanent change of resistance beyond the elastic limit is an increase.

4 P. W. Bridgman, Proc. Amer. Acad. 52, 571-646, 1917.

44 BRIDGMAN.

For the theoretical considerations suggested by these measurements
it is necessary to know the mechanical deformation produced by the
tension, that is, to know Young's modulus. I have determined this
for most of the metals. The metals were in most cases too soft to
allow a direct determination by hanging a weight on the wire and
observing the change of length, so that an indirect method was neces-
sary. The method I used was that of flexure. A horizontal wire of
known length and section was bent by a weight hung on the free end,
and the amount of the flexure of the free end determined. From this
Young's modulus can be calculated. The calculation assumes the
perfect isotropy of the wire. It is probable that this condition is not
always satisfied to as high a degree of approximation as would be
desirable, but under the conditions it seemed the best that I could do.
The modulus for manganin and therlo was determined directly.

The difficulties of the resistance measurements vary greatly for the
different metals. The effect is in any event small, and for those
metals which are soft and have a low elastic limit, the magnitude of
the maximum effect is sometimes not greatly in excess of the order of
magnitude of the accidental errors. An additional difficulty for the
metals Li, Sr, and Ca is that of making electrical connections. These
metals cannot be soldered, and mechanical spring clamps had to be
used. The resistance at the contact would sometimes vary sufficiently
to produce perceptible fluctuations in the main current, and also the
potential terminals were sometimes subject to slight displacements
under the stirring by the oil. The details of these difficulties will be
described under the metals separately.

I am indebted to the skill of my assistant, Mr. J. C. Slater, for
practically all the actual readings.

Here follows a description of the details for each metal.

Detailed Data for Individual Metals.

Lithium. The material was from Merck, for which I have no
analysis. It was apparently entirely free from inclusions of slag, and
mechanically homogeneous. Metal from the same lot was used in
previous determinations of the pressure coefficient of resistance.^ It
was formed into wire of about 0.032 inches diameter by cold extrusion,
in the usual way. The surface of the wire so formed is bright, and it

5 P. W. Bridgman, Phys. Rev. 56, 59-154, 1921.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 45

remained bright throughout the course of the experiment. The oil of
the bath, a neutral heavy white petroleum which is used for medicinal
purposes, was without perceptible chemical action, at least at room
temperature. The current and potential connections were main-
tained by mechanical contact, the potential connections by small
spring clamps of special design.

The measurements of lithium were the most difficult of any, be-
cause of the extreme softness of the metal. Four sets of runs were
made in all. The first two, made without the thermostat, established
the sign of the effect and its probable magnitude. The last two runs,
with the thermostat at 30°, were somewhat more satisfactory. The
elastic limit is so low that I could not determine the linearity of the
effect within the elastic range. There was permanent stretch under
a load of 40 gm., and there were also irregular initial effects under the
first few grams of load, which may have been due to straightening of
the wire. All the best measurements were made between a load of
15 gm. as zero and 35 gm. The change of resistance under this maxi-
mum increase of load of 20 gm. is an increase of only 0.02%. The
extreme variation of the individual determinations for the best speci-
men was in the ratio from 7 to 20. Twelve determinations were made.
The probable error of the mean, calculated by least squares, was 6.7%.

The tension coefficient of resistance, that is the proportional change
of resistance under a tension of 1 kg/cm^ was -|-4.9 X 10~^ for the
best specimen; the other run with the thermostat gave 4.6 X 10~^,
and the only one of the preliminary specimens which was worth com-
puting gave 4.7 X 10"^. In the following I shall assume for the most
probable coefficient +4.8 X 10~^.

Young's modulus was determined from the bending of three speci-
mens, of the diameter given above and approximately 7 cm. long.
The maximum load applied to these specimens was 0.066 gm. Within
the limits of error the displacement was proportional to the load.
The values obtained for Young's modulus were respectively 4.72,
5.26, and 4.93 X 10^° Abs. C.G.S. units. Take as the most probable
mean 4.9 X lOi" C.G.S. or 5.0 X 10^ in kg/cm\

The cubic compressibility of lithium has been found by Richards ^
to be 9.0 X 10~^^ pressure expressed in Abs. C.G.S. units. This may
be combined with Young's modulus by the formula of elasticity

to find Poisson's ratio. The formula gives 0.42. The
6 T. W. Richards, Jour. Amer. Chem. Soc. 37, 1643-1656, 1915.

46 BRIDGMAN.

high value is in line with our other experience that a comparatively
soft metal has a Poisson's ratio near 0.5.

Calcium. This material I owe to the kindness of the Research
Laboratory of the General Electric Company. It was from a different
batch than that whose pressure coefficient of resistance I have previ-
ously measured.^ So far as any chemical analysis can detect, all the
calcium of the General Electric Co. contains no impurity, but in my
previous discussion I remarked on the fact that there was nevertheless
some difference between different batches. Some of the material can
be extruded easily, while the extrusion of other is difficult. The wire
which I previously used was extruded with difficulty, and was inclined
to be brittle. The present wire was extruded easily, and could be
readily bent into a comparatively short radius. The wire as supplied
by the General Electric Co. had been extruded to a diameter of about
0.055 inches. In order to better adapt it to the magnitude of the
tension which I could readily apply, I drew it down through steel dies
from this size to 0.030 inches, first scraping the surface bright under
oil. I did not attempt to anneal it after this drawing. Another
piece, whose behavior beyond the elastic limit was specially examined,
was drawn to 0.019 inches. The breaking load was at the rate of
1200 kg/cm-; it was the same for the two sizes of wire. The break
takes place with very little elongation or reduction of area.

Measurements were made of the elastic rate of change of resistance
on two different samples. The range of tension was not more than one
fifth of the breaking load. The effect with this metal is large enough
to allow good readings. Within the limits of error the change of
resistance is linear with tension up to the stresses mentioned above.
Readings were made at eight or ten different loads. The maximum
departure of any single observation from a straight line was 5% of the
maximum change for one of the specimens, and 4% for the other.
The maximum change of resistance was 0.14% of the initial value.

The tension coefficient of resistance was + 8.24 X 10~^ for one
specimen, and 8.50 X 10~®, tension in kg/cm^ for the other. Take as
the most probable value the mean + 8.37 X 10~^.

Young's modulus was determined from the bending of two samples,
whose dimensions were of the same order as those of lithium. The
maximum load applied was 0.24 gm. Within the limits of error the
bending was proportional to the load. One specimen gave for
Young's modulus 2.080 X 10", and the other 2.065 X 10l^ in Abs.

7 Reference 5, p. 91.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 47

C. G. S. units. Take as the average 2.07 X lO^i C. G. S., or
2.11 X 10^, tension in kg/cm-. Richards ® has found for the cubic
compressibility 5.7 X 10~^- Abs. C. G. S. Combined with Young's
moduhis by the formula of elasticity gives for Poisson's ratio the
value 0.303.

There is a very considerable range of tension above that of perfect
elastic behavior and below the breaking point where there are de-
partures from linearity and hysteresis. The immediate effect of
exceeding the elastic limit is to permanently increase the resistance.
The wire may be seasoned for any particular range of tension
beyond the elastic limit by repeated application and removal of the
load. After seasoning, the resistance, as a function of tension, de-
scribed hysteresis loops exactly similar in appearance to the familiar
hysteresis loops of the relation between tension and elongation. The
width of the loop in the extreme case of a tension just below the break-
ing point may amount to one third of the maximum change. This
maximum change of resistance was 1.73% for one specimen, and 2.43%
for the other. The average coefficient of resistance for the extreme
hysteresis loop was 20.5 X 10~^ for one specimen, and 15.2 X 10~^
for the other, against a coefficient in the elastic range of 8.4 X 10"^.

Stroiitium. This material was from the same lot as the specimen
whose pressure coefficient of resistance was previously determined.
I am indebted for it to Dr. B. L. Glascock. The probable purity, and
some of its properties have been already discussed.^ The metal was
formed into wire by extrusion in the manner already described. Two
sizes were used, 0.035 and 0.019 inches in diameter.

Two samples were used; the first was not geometrically perfect
and did not give as good results as the second. Two series of measure-
ments were made on the second. The diameter of this was 0.019
inches. The wire breaks without much preliminary yield at a load of
about 800 gm. At a load of 700 gm. there was a very small perma-
nent increase of resistance. The tension coefficient of resistance was
determined through a range of 400 gm., readings being made at eight
different loads within this range. The effect of tension is to decrease
the resistance. Within the limits of error the relation between tension
and decrease of resistance is linear. The maximum departure from
the straight line of any single observed point was 7% of the maximum
change. The maxifnum change of resistance was 0.14% of the initial
resistance.

8 Reference 5, p. 96.

48 BRIDGMAN.

The tension coefficient of resistance given by the two runs on the
better specimen was —8.2 and^— 8.4 X 10~® respectively for a tension
of 1 kg/cm^. The other specimen, which was very much more un-
certain in its indications, gave a coefficient of —10.5 X 10~^. Take as
the best mean —8.3 X lO"".

Young's modulus was determined from the bending of two samples.
Measurements were also made on the sample of the imperfect resist-
ance measurements, but these were discarded because of the uncer-
tainty introduced by failure of geometrical regularity. The dimen-
sions were approximately the same as for lithium. The maximum
load was 0.0(36 gm. and within the limits of error the relation between
bending and load was linear. The first specimen gave for Young's
modulus 1.24 X lO^^, and the second 1.36 X lO^^ Abs. C.G.S. units.
Take as the best value 1.30 X 10^\ or 1.33 X 10^ when tension is
expressed in kg/cm-. The compressibility of strontium has never
been determined experimentally so far as I am aware. A probable
value for it may be found by interpolating in Richard's chart ^ giving
the compressibility as a periodic function of the atomic weight. The
value which I have assumed for the compressibility is 6.5 X 10~^^
Abs. C.G.S. The value of Poisson's ratio computed with these values
for Young's modulus and compressibility is 0.359. An error of 1% in
the compressibility changes Poisson's ratio by 0.5%.

The behavior of the resistance beyond the elastic limit was not
investigated, except to establish that there is a permanent increase
in resistance on exceeding the limit. The permanent change is there-
fore of the opposite sign from the elastic change.

Antimony. So-called chemically pure antimony from the J. T.
Baker chemical company was used. It was extruded into wire in the
way previously described. ^° This wire is not from the same source as
that whose pressure coefficient of resistance was previously measured,
which was from Eimer and Amend. The present material has also
been used in a determination of the effect of pressure on thermal
conductivity, and the data will be given elsewhere.

Great difficulty was experienced with antimony because of its
extreme brittleness, and a special procedure was adopted. At the
suggestion of Mr. Slater, who made the measurements, the vertical
position of the other metals was replaced by a horizontal position for
antimony. The wire was placed in an oil bath, without a stirrer,
resting on a massive bar of copper. Tension was applied by a spring

9 Reference 6, p. 1649.
10 P. W. Bridgman, Phys. Rev. 9, 138-141, 1917.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 49

balance connected to the antimony by a wire passing through a stuffing
box in the side of the oil bath. This stuffing box was very loose, and
was without appreciable friction. The current and potential termi-
nals were soldered to the antimony wire. It is very difficult to make
a soldered connection to this brittle material which shall be sufficiently
in axial alignment to permit the application of an appreciable
tension. The wires by which the tension was applied were cemented
to the antimony wire by DeKhotinski cement.

Readings were made on three different samples; those on the first
were the best. The diameter of the wire was 0.0146 inches. Three
runs were made on it; the first two were rough in character and agreed
within the limits of error with the third run. Within the limits of
error the effect is linear with tension, and is positive, the resistance
increasing with increasing tension. The maximum load applied to this
specimen without rupture was 80 gm.; it broke at 90 gm. Readings
were made at eight loads. The greatest departure from the straight
line of any single observation was 8% of the maximum effect, which
was a change of resistance of 0.025 %. The tension coefficient of this
sample was +4.5 X 10~'' for 1 kg/cm^ tension.

The second sample was extruded at a different time, and was ex-
cessively fragile. Its diameter was 0.024 inches, and it broke at a
load of 20 gm. Only two readings were made; not enough to estab-
lish the linearity of the effect or to eliminate chance errors. The
tension coefficient which would correspond to the mean of the readings
with this sample was + 20.0 X lO-'^.

The third sample was 0.0295 inches diameter. It was much stronger
mechanically than the second sample, and allowed loads beyond the
elastic limit to be applied. The results were much less regular than
for the first sample, however. Within the limits of error the effect is
linear with tension up to a load of 140 gm. Ten readings were made;
the worst of these departed from the smooth curve by 33% of the
maximum effect. The tension coefficient shown by this sample was
+ 7.5 X 10~^ for a tension of 1 kg/cm-.

In estimating the most probable coefficient, the first sample must be
given considerably more weight; I take as the most probable coeffi-
cient +5.0 X 10-«.

I have previously determined Young's modulus for antimony ;^''
The value 7.8 X 10^^ Abs. C. G. S. units was found. It was possible
to definitely establish that the wire was not homogeneous, because the
rigidity bears an impossible relation to Young's modulus. It is there-
fore not allowable to apply the formula of elasticity to compute

50 BRIDGMAN.

Poisson's ratio. The above Young's modulus, combined with Rich-
ard's value for the compressibility, 2.4 X 10~^- C. G. S.,® would give
0.18 for Poisson's ratio, which is improbably low. I shall in the fol-
lowing use 0.30, which is an average value for many metals, as more
probably correct.

The third of the specimens above allowed some examination of the
behavior beyond the elastic limit. Permanent increases of resistance
were produced by loads in excess of 140 gm. ; rupture took place at 270
gm. The phenomena were somewhat unusual in that there were no
time effects. The permanent change of resistance under a given load
assumed at once its final value, and there was no creep, as is usually
the case. This does not seem very surprising in so brittle a material.

Bismuth. Measurements were made on three different grades of
material, of three different grades of purity. The first was ordinary
commercial metal, which has about 3% impurity. The second was
electrolytic bismuth, for which I am indebted to the kindness of the
United States Metals Refining Co. x\nalysis showed only 0.03%
impurity of silver, and only traces of anything else. In spite of this
very small impurity, however, the temperature coefficient of resistance
is only about one half normal; apparently the silver exerts some very
large specific effect. The third sample was electrolytic bismuth of my
own preparation, which I had made several years ago for a determina-
tion of the pressure coefficient of resistance. ^^ I have no chemical
analysis, but spectroscopic analysis by Professor F. A. Saunders shows
less impurity of silver than the other electrolytic bismuth. I was not
able to repeat the preparation of this material, and had only a small
quantity available. I verified the high temperature coefficient on the
special piece used in this work. The question of the curious behavior
caused by the small quantity of silver is more fully discussed in my
paper on the effect of pressure on thermal conductivity.

Tension decreased the resistance of all the samples of bismuth. The
effect is comparatively large, and with little care it was possible to
obtain very good sets of readings, with deviations from the smooth
curves by individual points of not more than 1%. The effects beyond
the elastic limit are complicated. There is a very considerable initial
range, however, within which the eft'ect is linear, and there is no evi-
dence for departure from the usual relations of perfect elasticity. The
coefficients quoted in the following were determined within this range.

Three determinations were made on commercial bismuth at room

11 Reference 4, p. 624.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 51

temperature. The diameter of the wire was 0.028 inches, and the
range of tension 300 gm. The coefficients found were —4.65, —4.54,
and —4.78 X 10-^ respectively, the unit of tension being 1 kg/cm^.

jSIeasurements were made on one sample of the commercial electro-
lytic bismuth at two different temperatures. The dimensions of the
wire, and the range of tension were the same as for the commercial
material. At 31.1° the tension coefficient is —4.27 X 10-^ and at
0.0° 5.20 X 10-^. It is perhaps surprising that the coefficient should
be lower at the higher temperature, but this is also the case with the
pressure coefficient of resistance.

One set of measurements was made on my own pure electrolytic
bismuth at 30°. The diameter of the wire was 0.0207 inches, and the
range of tension 100 gm. Within this range the effect is perfectly
linear, and no reading departs from the straight line by as much as 1%.
The total change of resistance under this load was 0.13%. The ten-
sion coefficient of this sample was —2.92 X 10-^. This is considerably
less than the coefficients of the other samples, but will be accepted in
the following as the best value for pure bismuth.

Young's modulus of my pure electrolytic bismuth was determined
in the regular way by the bending experiments on two samples. The
diameter was as above, and the length about 6.5 cm. The maximum
load was 0.10 gm. The bending is linear with load within this range.
The two samples gave for Young's modulus 2.29 and 2.45 X 10^^ Abs.
C. G. S. units respectively. This is much less than the value given in
Kaye and Laby's tables, which is 3.19 X 10^^. It is of course possible
that this wire is not homogeneous, like antimony. Richards ^ has
found the compressibility to be 2.8 X 10-^-. Combined with my value
for Young's modulus this gives for Poisson's ratio 0.39; combined with
Kaye and Laby's value it gives 0.35.

The phenomena beyond the elastic limit are complicated and would
be worth study for their own sake. In the first place, the resistance
increases beyond the elastic limit, and hence the change is in the same
direction as for other metals which are normal with respect to the elas-
tic effect of tension. The time effects are very large, and may con-
tinue for many days under loads which are much below the breaking
load and so small as to produce no marked change in the geometrical
dimensions. Under a fixed constant load, the resistance increases at a
time rate gradually becoming less, according to some law which I did
not attempt to discover. Commercial electrolytic bismuth showed
creep for two days under a load of 350 gm. whereas at 300 gm. the
effects were still elastic. In these two davs the initial rate of creep

52 BRIDGMAN.

had dropped to one quarter of its initial value, which was at the rate
of an increase of resistance of |% per hour. After the removal of a
load which has exceeded the elastic limit there are also time effects,
not nearly so large in magnitude as the effects on applying load, but
in the same direction; the resistance continues to increase for some
time after the removal of load. In this particular the effect is like
an ordinary elastic after effect.

Nickel. The sign of the pressure coefficient of this metal is normal;
I have already mentioned in the introduction my reasons for repeating
the measurements of Tomlinson. The metal was provided by the
Research Laboratory of the Leeds and Northrup Co. in the form of
bars approximately 6 cm. long, L5 cm. wide, and 3 mm. thick. I cut
from this bar a piece of suitable dimensions, and drew it down in steel
dies to 0.0101 inches. It was annealed after drawing by heating to
redness.

The temperature coefficient of resistance between 0° and 100° was
found to be 0.00634. This is higher than the highest previous value
with which I am accjuainted, 0.00G18 by Fleming, and is evidence of
the unusual purity.

Tomlinson had found that nickel is abnormal in two particulars. In
the first place the resistance decreases under tension, and in the second
place the decrease is not linear with tension, but passes through a
minimum, so that at a tension of the order of two thirds of the elastic
limit the resistance begins to increase with increasing tension.

I verified both these particulars of behavior, and made a few addi-
tional observations. If instead of increasing the tension steadily to
the elastic limit, measuring the resistance as a function of tension on
the way, as Tomlinson did, the wire is subjected to a seasoning for
some fixed load by a number of applications and removals of the same
load, and then a cycle of resistance measurements is made, it will be
found that the decreasing measurements do not follow the increasing
measurements, but an open hysteresis loop is described. This loop
differs in one important particular from ordinary hysteresis loops.
By hysteresis we usually mean an effect that for some reason lags
behind. In this case, this would mean that with decreasing tension
the resistances correspond to some greater tension on the increasing
run. The curious fact here is that at the initial stages of the decreas-
ing limb of the loop the resistance may be lower than that correspond-
ing to any value of the tension on the increasing run. The mechanism
of the loop must be something quite different from the ordinary hyster-
esis effects.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS.

53

The range of tension through which the wire has been accommodated
has a sHght effect on the character of the loop; the tension of the
minimum increases somewhat as the range is increased.

200

400 600

Tension in Grams

Nickel

1000

FiGTTRE 1. The decrease of resistance of Nickel in arbitrary units plotted
against the tension in grams at three different temi)eratures. In each case the
higher curve of the loop is that obtained with decreasing tension. One arbi-
trary unit of resistance corresponds to a decrease of 0.0345 per cent. The
cross section of the wire was such that a load of 1000 gm. means 1900 km/cm^

There is a very hirge effect of temperature on the sliape of the loop.
I made measurements at 0°, 30°, and 95°. The minimum becomes

54 BRIDGMAN.

much flatter and moves in toward smaller tensions at higher tempera-
tures. The initial magnitude of the change, for small alterations of
tension, becomes larger at the lower temperatures. Here again we
find a temperature coefficient with a sign the reverse of what we
would expect.

The changes of resistance as a function of tension are reproduced
in Figure 1. The range of tension is the same at the three tempera-
tures, namely 1 kg., which corresponds to about 1900 kg/cm-. This is
not far below the elastic limit.

Cobalt. An examination of the behavior of cobalt was of interest
because of its close relationship to nickel, and the abnormal behavior
of nickel.

There was available a piece of the same cobalt wire, 0.0030 inches
diameter, as that on which the previous determinations of the pressure
coefficient of resistance were made. ^^ It was annealed by heating to
redness. Measurements were made to a maximum load of 100 gm.;
the breaking load is about ISO gm. Within the range of 100 gm. the
effect is normal with respect to sign, and the relation is perfectly linear
within errors of the single readings of not more than 2 or 3%. There
is no trace of the abnormal behavior shown by nickel.

The tension coefficient is +9-94 X 10"'^ at 30°, the tension being
measured in kg/cm-.

Young modulus was not determined for this wire; because of the
small diameter a special procedure would have been necessary. I
shall in the following computations assume that it is the same as for
iron and nickel, namely 2.0 X 10^- C. G. S. I shall also assume that
Poisson's ratio is 0.30.

Manganin. The interest of this alloy lies in the fact that its pres-
sure coefficient of resistance is abnormal in being positive. ^^

Determinations of the tension coefficient were made on samples from
the same spool as that from which the pressure coefficient samples were
obtained and from which the pressure gauges used in all my work were
cut. Measurements were made on the wire in both the hard drawn
and the annealed condition.

Thre^runs were made on the hard drawn specimen. The wire was
0.0054 inches in diameter. The breaking load was about 900 gm.
The maximum load applied before the measurements was only 300 gm.,
and the runs themselves reached a maximum of only 250 gm. The
wire was seasoned for this range of tension by a number of applica-

12 Reference 4, p. 607.

13 P. W. Bridgman, Proc. Amer. Acad. 53, p. 370, 1918.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. ' 55

tions and removals of 250 gm. The effect was found to be normal in
sign, the resistance increasing under tension. The effect is smaller
than for some of the pure metals, and accordingly was not so regular.
The maximum departure of any of the observed points from a smooth
curve was 4.5% of the maximum change. The relation between
tension and change of resistance is very nearly linear, but there are
nevertheless consistent small departures from linearity greater than
the errors of measurement; the change becomes proportionally
greater at the greater tensions. The average tension coefficient over
the entire range of tension is not more than one or two per cent greater
than the initial coefficient.

The three runs on the hard drawn sample gave the following values
for the initial coefficient respectively: +5.78, 5.72, and 5.63 X 10"''
for a tension of 1 kg/cm^. The average, +5.71 X 10~^, is taken as
the most probably correct coefficient.

A length of wire contiguous to the hard drawn specimen was
annealed by heating to redness. Measurements were made on the
first application of tension. 250 gm. was distinctly beyond the elastic
limit. The specimen was seasoned by several applications of 250 gm.,
and then by a number of applications of 200 gm., until finally the
changes of resistance had become steady. The initial coefficient of
the annealed wire was +5.88 X 10~^. After accommodation to the
range of 200 gm. the coefficient had increased to 6.75 X 10~^. This
latter is the average coefficient over the range of tension. i\.fter
accommodation the relation between resistance and tension is not
linear or single valued, but the relation involves hysteresis of the
usual character, the maximum width of the hysteresis loop being about
10% of the maximum effect.

Young's modulus of this wire was determined directly from the
increase of length under a given load. A piece about 3.5 m. in length
was hung in an elevator shaft, and observations made on fiducial
marks at the top and bottom with microscopes. The supports of the
microscope were entirely independent of the supports of the wire, so
they could not be affected by the load applied to the wire. The hard
drawn wire was used for this determination. It was seasoned by a
number of applications of 500 gm. ; the maximum load for the determi-
nation of the modulus was 400 gm. There was a slight amount of
hysteresis, but there were no perceptible time effects. The maximum
width of the hysteresis loop was 5% of the maximum extension. The
mean of points with increasing and decreasing tension lie on a straight
line within the limits of error, which were not more than 0.3%.

56 BRIDGMAN.

The value found for Young's modulus was 1.35 X 10^- Abs, C. G. S.
or 1.39 X 10® when the unit of tension is 1 kg/cm^. Neither the
coefficient of cubic compressibility nor any other of the elastic con-
stants of manganin seem to have been determined. I shall assume
in the following that a probable value of Poisson's ratio is ^.

Therlo. This alloy is made by the Driver Harris Co., and is much
like manganin in its properties. Its pressure coefficient of resistance
is also positive/* and is very close numerically to that of manganin.

Measurements were made on both hard drawn and annealed wire,
as for manganin. Two samples of hard drawn wire were used. The
range of tension was 250 gm. The diameter of the wire was 0.005
inches. Within this range the relation between change of resistance
and tension is sensibly linear; the departure from linearity shown by
the manganin was not in evidence here. One run was made on the
first sample; the coefficient found for it was + 4.32 X 10~^ for a
tension of 1 kg/cm^. Three runs were made on the second sample,
giving 5.19, 4.80, and 4.84 for the coefficient. I take as the most
probable value for the coefficient + 4.8 X 10~^.

A piece was annealed by heating to redness. Readings were made
of the resistance during a long series of applications of tension, through
a maximum range of 320 gm. The breaking load of the annealed
wire is about 350 gm.; that of the hard drawn is over 1 kg. The
initial coefficient for small loads immediately after annealing was
4.22 X 10~^. After seasoning as above, this coefficient had risen to
4.60 X 10~^. There seemed to be considerably less hysteresis in the
relation between tension and resistance than in the case of annealed
manganin.

Young's modulus was measured in the same way as that of man-
ganin. There was considerably greater departure from linearity and
more hysteresis than was shown by manganin, and much more of
both than was shown by the resistance measurements. Seasoning
was by the application and removal of 500 gm., and the modulus was
measured over a cycle of 400 gm.

The hysteresis loop for this range of tension had an extreme width of
12% of the extreme extension. If w^e take the initial slope of this loop
as giving Young's modulus, we find 1.41 X 10^- Abs. C. G. S., or 1.46X
10® in kg/cm-. As in the case of manganin, I shall assume that
Poisson's ratio is ^.

The behavior of the resistance beyond the elastic limit is compli-

14 Reference 5, p. 135.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS.

57

cated, but there seems to be nothing essentially unusual about it.
The permanent effect is an increase of resistance. There are also slow
changes with time, both on applying and removing the load, as is
normal.

Discussion of Results, excepting Nickel.

The results obtained above are collected into Table I, in which is
given the tension coefficient of observed resistance, the pressure coeffi-
cient of observed resistance, the cubic compressibility, the reciprocal
of Young's modulus, that is, the extension under unit load, Poisson's

TABLE I.

Metal

Tension
Coefficient
of Observed
Resistance

Pressure
Coefflcient
of Observed
Resistance

Cubic
Compressi-
bility

Reciprocal

of Young's

Modulus

Poisson's
Ratio

Tension
Coetlicient
of Specific
Resistance

Li

+ 4S.X10-^

+ 6.8X10"^

9.2X10-^

20.x 10-^

0.42

+ii.xio-«

Ca

+S.37

+ 10.1

5.8

4.75

0.30

+0.8

Sr

-8.3

+48. 0

6.4

7.5

0.36

-21.2

Sh

+5.0

+ 11.0

2.4

1.25

0.30(?)

+3.0

Bi

-29.2

+ 15.5

2.8

4.2

0.37

-3.65

]Mang.

+0.59

+2.31

0.7(?)

0.72

0.33

-0.60

Therlo

+0.42

+2.37

0.7(?)

0.69

0.33

-0.73

Co

+0.994

-0.90

0.6(?)

0.5

0,30

+0.19

ratio, and the tension coefficient of specific resistance. The unit of
stress, whether of tension or pressure, for which the various coefficients
is given is the kg/cm-. By the coefficient of "observed resistance" is
meant the change of resistance, per kg. per cm-, of the wire as actually
measured in the experiments, with fixed electrodes. Such a wire
increases in length and decreases in cross section under tension, and
decreases both in length and section under pressure. The coefficient
of " observed resistance," when corrected for the changes of dimensions,
gives the coefficient of specific resistance, that is the change of resist-
ance of a unit cube. The tension coefficient of specific resistance is
obtained by subtracting (1 + 2g)/E from the coefficient of observed
resistance.

Since the mechanism of conduction is an affair of atoms and elec-
trons, and since the number of atoms and electrons in a unit cube both
change when the material is subject to tension or pressure, it does not

r>S hkuh;ma\.

soom lo luo ihat tluMV is a j;ivat doal of vsigiiifioancv in iho '" oooilioiont
of spooitio irsisiauiv." Howovor, it is of intorost lo noio in ilic tahlc
that tho changvs of diuieiisioiis of maiiijaniti ami tluM'lo aiv so iaruo
v'oiu[>aivil witli tho tonsimi oooHioiom of obsorxod rosistamv tliat tho
toiision v'oothoiont of spooitic rosistaiioo is iiogativo, wlioroas tho tonsioti
iwlUoioiu of obsorvo«i rosistanoo is positivo. For tho othor inoials tho
ciM'rtvtiotv for ohaiijjo of figiuv is not larj^o oiiongh to ohango tho sign
of tho a>othoiont of obsorvoii n\sistaiioo.

It is ill tho first phioo to ho romarkotl front tho tahlo that of tho sovon
substattcvs whioh aro ahtiornial wiih rospoot to tho siirn of tho prossttro
ivotlioiont. only two, bismuth and strontimn. aiv abnormal with
n\spoor to tho sign of tho tonsion cH>otticiont. This would soom to
indioaio somo ossontial dilVoronoo botweon tho oondtiotion moohanism
of thoso two stibstamvs and that of tho othoi-s. Lot ns disonss what
this ditVotxMtcv may bo in tho light of tho thtvry of motallio oondnotiott
whioh 1 ha\o ptvvionsly do\olopod.

1 havo thought of ciwduotion as duo to a froo path mtx'hanism;
tho olassioal thtx^ry was a frtv path ihoory. Tho ditVortnicos oomparod
with .tho olassioal tlu\M"y aro those. In tho first place, tlie free paths
aro thotight of as loitg, booanso tho frtv olootivns an^ fow in ntimbor.
In normal motals. tho paths of tho oUvtn.>ns aro to bo thought of as
tlnxnigh tho snbstancv of tho atoms thomsolvos. The path may bo
terminattHi w hon tho eleotUMi makes the jnmp frtun one atom to the
next. Tho ohanct* of termination on making the jump will depend
both on the amplitude of atomic vibration and tho distantx^ apart of
tho atoms. Now if tho distamv apart of the atoms varies little com-
patwl w ith tho ohangi^s of amplitude, the variation of ft\x^ path may be
calcnlatoii in terms of the variation of amplitude only. The changes
of amplitude, nogkvting the ort'eots dne to changes of dimensions, may
be calcnlatoii for changes of prt^s^nre and tomperatnre, and so the
ehangi^ of path, and hoiuv tho changt^s of rosistamx^ may also be cal-
cnlaiixl. It is in ihrc»wing the entire bunion of tho variations on the
free p<ith. and in the method of computing the changes of the free
path, that my thixiry differs matJiematically frtim the classical thoor\-.
Now as a matter of faet, the changt^s of dimensions imder changt^s of
temperature an^ very small ctMuparoii with tlie changt^s of amplitude,
and the caloulattxi ehanges of rt^sistanct^ agree well witli the observed
ohangvs. Under ehanges of pressure the changt^s of dimensions are
several foUi larger, but still are so small compareti with the changes
of amplitude tltat an iiujx)rtant part of the pressure coelhcient
may bo (.vmpucoii. There is left an outstanding effect depending on

EFFECT OF TEN'SIOX ON CERTAIN ABNORilAL METALS. 59

the changes of dimensions. The precise value of this effect cannot be
computed without a more detailed picture of the entire mechanism
than we have at present, hut we can at least see what its sign is; as
the atoms are compressed more closely together there will be less
difficulty for the electrons to make the leap, and the mean free path,
and so the conductivity, will increase.

So much for the mechanism in the case of normal metals. This
picture would lead us to expect a decrease of resistance with increasing
pressure, as is normal. To explain the behavior of those abnormal
metals whose resistance increa.ses under pressure I believed that there
might be two possibilities. In the first place there might be such
abnormalities in the law of force between the atoms that the amplitude
of vibration increases as the atoms are brought closer together, instead
of flecreasing as normal. I thought that this was probably the case
with bismuth, and suggested that the same abnormality would explain
the increase of volume on freezing. For such a metal the paths of the
electrons are still to be thought of as through the substance of the
atoms, and the interference with the free path to take place on making
the jump from one atom to the next. A second possibility I thought to
explain the behavior of liihiurn. Here the electrons occupy spaces in a
lattice between the atoms, and conduction consists in motion of the
electron lattice through the atomic lattice. This is similar to the view
of Wien ^^ and Lindemann ^^ as to the general character of conduction;
I believe that this can be the mechanism only in exceptional cases.
The effect of pressure on such a mechanism is to constrict the channels
between the atoms through which the electrons pa.ss. A simple cal-
culation will show that the constriction of the channels due to change
of distance between atomic centers is much more than the opening of
the channels due to decreased amplitude of atomic vibration. Hence
the pressure coefficient of resistance of such a substance would be
expected to be positive, as it actually is. With regard to the other
abnormal metals,^^ I did not have any positive basis for deciding to
which type calcium and strontium belong, although I expressed my
belief that probably calcium belonged to the lithium type, and I
believed that antimony belonged with bismuth on the basis of its
expansion on freezing.

Since publishing my pressure data, the crystalline structure of cal-

ls W. Wien, Columbia Lectures, 1913, 20-48.

16 F. A. Lindemann, Phil. Mag. 29, 127-140, 1915.

17 Reference 3, p. 183.

60 BRIDGMAN.

cium has been determined, ^^ and this gives very strong probabihty to
the view that its mechanism is also of the hthium type. It has been
found that in metalhc calcium the atoms of Ca occupy almost exactly
the same positions as the Ca atoms in Ca F2, the F atoms have merely
dropped out of the structure. The inference is strongly suggested
that the F atoms have been replaced by electrons, which do not give
an X-ray photograph because of their small mass, and that therefore
metallic calcium consists of interpenetrating lattices of atoms and
electrons.

Let us now consider what these pictures of the mechanism lead us
to expect for the tension coefficient. It is in the first place evident
that we would expect the resistance of normal metals to increase in
the direction of stretch, both because the distance between the atoms
increases in this direction and because the amplitude of vibration in
this direction increases to compensate for the decrease in period due
to the weakening of the restoring force on the atoms due to their
increased distance apart. A detailed working out of the theory must
recognize in addition that changes in the positions of the atoms trans-
versely may affect the period longitudinally. Now of course it is a
fact that the resistance of normal metals increases in the direction of a
tension. The same reasoning would lead us to expect a decrease of
resistance in a direction transverse to the tension, and this also agrees
with the facts in the few cases known.

Consider now bismuth. As tension is applied, the distance between
the atoms increases longitudinally. The same abnormality in the
force that compels an increase of amplitude when pressure is applied
now compels a decrease of amplitude, and just as in the case of pressure
the increase of amplitude causes a greater increase of resistance than
can be overbalanced by the decrease due to the approach of the atoms,
so now the decrease of resistance due to decreasing amplitude more
than overbalances the increase due to the increasing separation of the
atoms. The outstanding effect will be a decrease of resistance, which
is actually the case.

It is otherwise, however, for metals of the lithium type. The
resistance is here determined by the channels between the atoms.
When a tension is applied, the channels are made narrower, because of
the lateral contraction, just as they are made narrower when a hydro-
static pressure is applied, and we should expect an increase of resist-
ance. This is actually the case for lithium.

The fact that the resistance of calcium increases under tension

18 A. W. Hull, Phys. Rev. 17, 42-44, 1921.

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 61

hence means that its mechanism is the same kind as that of Hthium,
and verifies the evidence from crystalline structure. The positive
coefficient of antimony indicates the same thing. In this regard it
may be said that recent work has cast considerable doubt on the
reality of the supposed expansion when antimony freezes/^ so that my
former expectation would now lose its chief ground for support. Also
against my former argument I may mention that there is a polymor-
phic transition of antimony at 135°, which I had previously failed to
take into account. Even if the relations are abnormal for the modifica-
tion which is stable up to the melting point, there seems no reason why
we should expect the same abnormalities in the other modification,
which is stable at room temperatures.

Strontium seems to require special consideration. Its tension
coefficient is not abnormally high numerically; it is nearly the same
as that of calcium, and much less than that of lithium or bismuth.
On the other hand its pressure coefficient is unique in being at least
three fold greater than that of any other abnormal metal. It seems
reasonable to suggest that the mechanism of conduction in strontium
may be a combination of both types. These would conspire to give
an abnormally high pressure coeflficient, and oppose each other, giving
by difference a relatively small tension coefficient, of a sign which
could not be predicted without further evidence.

These views of the conduction mechanism receive support from a
numerical discussion. We confine ourselves to changes of resistance
at constant temperature, that is to the changes under pressure and the
longitudinal changes under tension. We assume that the change of
resistance may be written down in terms of the changes of dimensions.
The transverse and longitudinal changes of dimensions will affect the
resistance in different ways, which are different for the two different
types of mechanism. We write the equation

1 A8i A8r

where k^ denotes the change of resistance per unit strain transverse to
the direction of the current, ki denotes the change of resistance per
unit strain longitudinally, and A8r and A8i are the change in the trans-
verse and longitudinal distance of separation of the atoms. Now if
the strains are produced by tension, we have

A5i_A7; A8r_ <r
8i~ E' 8r ~ £

19 M. Toepler, Wied. Ann. 53, 343-378, 1894.

62

BRIDGMAN.

where AT is the tension; and if the strains are produced by pressure
we have

M _ A5^ _ 1 1 /dv^
8i 8r S V \dp/

Substituting these expressions for the strains gives

A^j

' 1 1 /dv\ „

and Kt = T^ [^'z — o'^^vl

where Kr is the tension coefficient of resistance tabulated above, and
Kp is the pressure coefficient of resistance above. But since these two
coefficients are known experimentally, we have two equations to
determine the two unknowns ki and Av- I have made the calculations
and tabulated the results in Table II.

TABLE II.

Metal

kr

kl

Li

-3.2

+ 1.0

Ca

-5.4

+0.16

Sr

-15.8

-6.7

Sb

-13.6

-0.1

Bi

-7.0

-9.6

ISIang.

-7.3

-1.6

Therlo

-8.1

-2.1

Co

+ 1.92

+2.6

Let us now consider what sort of numerical values our theory would
lead us to expect. For a normal metal we expect ki to be positive, and
greater than unity, since in addition to the increase of resistance
brought about by increasing the distance apart of the atoms, there
is an increase due to the simultaneous increase of amplitude. Since
most of the electron paths have a transverse as well as a longitudinal
component, the same reasoning would lead us to expect that kr would
also be positive and less than ki, but of the same order of magnitude,
there being two transverse degrees of freedom against one longitudinal.
In the same way, we would expect that for bismuth, Avhere the effect of

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 63

amplitude is abnormal in sign, and more than counterbalances the
effect of changing distance between atoms, A7 and k., should both be
negative, and k^ less numerically than ki. On the other hand, for
those metals whose conduction mechanism is by the passage of elec-
trons in channels between the atoms, we expect k^ to be negative, since
increasing the transverse separation of the atoms decreases the
resistance, and ki to be relatively small. For strontium, which has
a combination of both types of mechanism, we expect both ki and kr
to be negative, kr being numerically larger than ki.

An inspection of the table shows that in every case these anticipa-
tions are strikingly verified, and the probable essential correctness
of the theory receives strong support.

The values of the coefficients found for manganin and therlo indi-
cate that for these the mechanism is for the most part like that of
lithium, calcium, and antimony, but that there is in addition a small
contribution by a mechanism of the bismuth type. Of course the
phenomena for alloy's are most complicated and varied in their types
of behavior, but it is not difficult to picture to oneself that under some
conditions when two different kinds of atoms crystallize side by side
into the same space lattice that there should be channels left between
the atoms for the passage of conduction electrons, or that the law of
force between atoms of different kinds should show the same sort of
abnormality that the atoms of bismuth show.

So far as I know there has been no previous attempt to make con-
nection between any theory of conduction and the tension effects.
In the light of the success of the above for abnormal metals it would
now be of much interest to accurateh'' determine the tension coeffi-
cients of the normal metals. If in addition the coefficient of trans-
verse resistance could be determined, a most valuable check would be
obtained, for we would then have three independent experimental
coefficients, which must be expressible in terms of the two quantities
ki and kj.

Discussion of the Effect in Nickel.

The peculiar nature of the phenomena for nickel makes it evident
that there must be some unusual mechanism involved. It seems to
me that there is probably an intimate connection with the poly-
morphic transition at 360°. Under a tension the transition tempera-
ture will be displaced by an amount proportional to the square of the
tension, and if a certain function of the compressibilit^' and Young's
modulus has the right sign, the transition temperature will be

64 BRIDGMAN.

depressed. (The compressibility and Young's modulus which enter
this relation have not been determined experimentally.) To explain
the failure of a single sharp transition point, we invoke the same sort
of mechanism that we suppose to be responsible for elastic hysteresis.
Modern theories of the structure of metals explain elastic after effects
and hysteresis by the fact that the microscopic crystalline grains are
unequally exposed to changes of stress. Certain grains are unfavor-
ably situated, and the elastic limit of these is exceeded before that of
the average. Just these grains would first reach the transition point
under an increase of tension, and other grains not until later. Thus
the transition and also the change of resistance would not be expected
to take place discontinuously at a single tension, but to be spread over
a range instead. If now the resistance of the new phase is less than
that of the original phase, we have a reason for the sign of the observed
effect. The minimum of resistance with increasing tension is reached
at that point where the rate at which new grains are being trans-
formed has been so decreased by exhaustion that the decrease of resist-
ance brought about by the transition is equalled by the increase of
resistance due to the normal tension effect on the transformed grains.
This view of the phenomenon demands in the first place that the
effect of tension be normal on that phase which is stable above 360°.
So far as I know this effect has never been measured, but it would be
going out of one's way to assume that it is abnormal. It is also
demanded that the resistance of the high temperature phase when sub-
cooled into the low temperature region be less than that of the low
temperature phase, at least under the tensions which are found inside
the grains. This again is subject for further experimental investiga-
tion. So far as I know, no measurements have been made on nickel of
high purity. The measurements of Werner ^° are the only ones which
I know with respect to the behavior of resistance through the transi-
tion point. I find from his data that the temperature coefficient of
his hard drawn wire between 31° and 110° was 0.0041 of its value at
0°, and for soft wire the corresponding coefficient between 18° and 111°
was 0.0054. The pusest nickel should give under the same conditions
a coefficient of about 0.0062. Werner finds no discontinuity in the
resistance at the transition point, but does find a change in the direc-
tion of the curve with temperature. It is highly probable that there
was actually a discontinuity, which was masked by the effect of
impurity. It has almost always turned out that a phenomenon which

20 M. Werner, ZS. Anorg. Chem. 83, 275-321, 1913.

I

EFFECT OF TENSION ON CERTAIN ABNORMAL METALS. 65

was at first thought to be continuous through a transition point is
found, on increasing the purity, to be really discontinuous. It is true
that the direction of the difference of temperature coefficients found
by Werner is the reverse of that demanded by the above explanation,
but in view of the extreme sensitiveness of the temperature coefficient
to small impurities, I do not believe that a great deal of importance
should be attached to this.

In support of the suggested explanation is in the first place the fact
that neither iron nor cobalt show similar effects. These metals and
nickel are similar in many respects, but are unlike in regard to their
transitions. Cobalt does not have any polymorphic transitions, and
the first transition of iron is at so much a higher temperature than that
of nickel that it may well be without effect. The decrease of the
tension of the minimum resistance of nickel with increasing tempera-
ture is also in accord with this view; at a higher temperature a smaller
tension is necessary to make the transition take place. It is of course
not possible to make any very exact numerical comparisons in view
of the flatness of the minimum of the curves, but the data are at least
not inconsistent with a depression of the transition point of a single
homogeneous crystal by an amount proportional to the square of the
tension. My explanation also demands that the resistance of the high
temperature phase when it is subcooled be less than that of the low
temperature phase. In view of Werner's failure to find a large dis-
continuity in the transition poinj;, this probably means that the tem-
perature coefficient of the high temperature phase is greater than that
of the low temperature phase, and this is in accord with the fact that
the initial rate of decrease of resistance with tension is less at high
temperature than at low.

The abnormal character of the hysteresis loop on the falling branch
is to be explained as follows. The primary effect of a tension is to
force a transition from one phase to another. This transition would be
expected to show hysteresis on reversing the direction of the change of
tension. On the other hand, the sum of the pure tension effect in all
the individual grains shows no hysteresis, because this is determined by
the average tension, which is equal to the applied tension itself.
Hence on decreasing the direction of the change of tension, the abnor-
mal effects are decreased in magnitude, whereas the normal effects are
unaltered. An application of this analysis to the upper end of the
loop beyond the minimum of resistance (maximum on the diagrams)
shows that on release of tension the resistance may drop to less than
under any increasing tension.

66 BRIDGMAN.

Before this explanation can be finally accepted, experimental con-
firmation in several respects is required. Temperature measurements
should be made on the high temperature phase above the temperature
of transition. The resistance relations should be carefully studied in
the neighborhood of the transition point for nickel of high purity.
Finally it ought to be possible to recrystallize a wire by proper heat
treatment so as to make it into a single large crystal. Under these
conditions the character of the phenomena should entirely change.
The initial effect of tension should be normal, and should continue
so until a tension is reached so high as to force the transition to take
place, when there should be a discontinuous drop of resistance greater
in amount than the previous increase. Of course it is not obvious or
necessary that the tension of this discontinuity be less than the elastic
limit, and hence it may not be possible to realize it.

Summary.

The tension coefficient of resistance of lithium, calcium, strontium,
antimony, bismuth, manganin, and therlo has been determined.
These substances are all abnormal in that their pressure coefficients
of resistance are positive. Young's modulus for these metals has also
been determined. The tension coefficient for bismuth and strontium
is found to be negative, but positive for the other five. In the dis-
cussion I have shown that these coefficients are in accord with my
theory of resistance. The conduction mechanism of lithium, calcium,
antimony, manganin, and therlo is on the whole " transverse," that of
bismuth is longitudinal, and that of strontium is a combination.

The negative tension coefficient found by Tomlinson for nickel
has been verified for nickel of high purity, and in addition the hystere-
sis effects and the effect of changes of temperature has been studied.
Cobalt, on the other hand, is found to be entirely normal. It is sug-
gested that the explanation of the abnormal behavior of nickel may
be found in a depression by tension of the transition point normally
at 360°.

The Jefferson Physical Laboratory,
Harvard University, Cambridge, Mass.

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Vol. 57. No. 4.— February, 1922.

NOTES ON THE EARLY EVOLUTION OF THE

REFLECTOR.

By Lons Bell.

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Proceedings of the American Academy of Arts and Sciences.
Vol. 57. No. 4.— February, 1922.

NOTES ON THE EARLY EVOLUTION OF THE
* REFLECTOR.

By Louis Bell.

^EW YORK

BtnANlCAt

NOTES ON THE EARLY EVOLUTION OF THE REFLECTOR.

By Louis Bell.

Received November 11, 1921. Presented November 9, 1921.

There is some tradition of reflecting telescopes in classical times,
probably groundless save as the ancients had concave mirrors and
these, if of fairly long focus, would present to the eye an enlarged
image of a distant object.

The first suggestion that a mirror might be used instead of an
objective seemed to have come from Mersenne about the middle of the
seventeenth century in a letter to Descartes. The idea did not
appeal to the latter and the matter was dropped. The first actual
reflecting telescope was designed by James Gregory, who published an
account of it in his "Optica Promota" in 1663. In this he described
the rather elegant construction which still bears his name, a perforated
parabolic mirror with an elliptical concave mirror placed beyond its
focus and returning an erect image to the ocular through the perfora-
tion.

The next year Gregory started Reive, a well known London optician,
at making a 6 foot telescope. This failed on account of inability to
get the necessary figufe, largely owing to the fact that Reive tried to
polish his mirrors on cloth, never a satisfactory material for accurate
figuring. It is possible that Gregory had better luck later, for there
is a well defined tradition that he died from a stroke of apoplexy in
1675 while showing to a group of students Jupiter's moons through
one of his own telescopes. Certainly Robert Hooke presented a
passable example to the Royal Society at its meeting February 5,
1673^.

Now enters upon the scene the biggest figure of the period in science,
Isaac Newton, then a young man who had just discovered the dis-
persion of light. A great speculative philosopher and mathematician,
he was neither a practical astronomer nor a particularly good experi-
menter, and failed to discover the dift'erence of relative dispersion in
refractive media by the inexcusable blunder of raising the refraction
of the water with which he was comparing glass by loading it with
sugar of lead, and then jumping at the conclusion that all substances
varied equally both in refraction and dispersion.

70 BELL,

In other words he assumed without real investigation that the quan-
tity which we now know as v was a constant for all substances.

Just how this singularly maladroit piece of experimentation leaked
out is unknown, although the fact is stated in the most positive manner
both by Sir David Brewster, Newton's admiring biographer, and by
Sir John Herschel. It is not unlikely that the fact got abroad at
Cambridge in Newton's later years, and was passed along to Sir
William Herschel. Certainly, as one of Newton's later apologists
naively suggests, the fact was not recorded in Newton's "Opticks."

Be that as it may, it was the kind of thing for which a second-year
student in physics would get a wigging which would linger long in his
memory, but a blunder with a great name behind it carries far, and in
this case it put off for a couple of generations the discovery of the
principle of achromatism.

Following his error, Newton gave up all idea of an achromatic lens,
and turned his attention to reflectors, apparently being unacquainted
with, or entirely disregarding, what James Gregory had done before
him. Newton had taken to the country on account of the plague, and
only about 1670 did he apparently begin to revolve in his mind a re-
flecting telescope. It was 1672, January 11th, when he presented to
the Royal Society a small model of his preferred form of reflector,
which is still in the possession of the Society.

This little model had an aperture of about 1" and focal length of
about 6", and magnified some 38 diameters. Newton was able, he
says, to detect with it the moons of Jupiter and the horns of Venus,
both feats which can be accomplished with the very slightest of
optical aid, providing the magnification is anywhere near that which
Newton used. But here again Newton gave notable evidence of his
unpractical experimenting, clever though he was.

He had firmly fixed in his mind the entirely erroneous idea that a
spherical mirror was quite good enough for the purpose, even when an
aperture of F/6 or F/8 was used, believing that the trouble with the
long telescopes of the day was almost entirely their chromatic aber-
ration. This was partly true, but the spherical aberrations would
have been equally bad save for the very narrow aperture employed.

This error would certainly have brought Newton to grief had he
attempted a telescope of any perceptible size and in fact there is some
evidence that this actually happened. On January 25th, just two
weeks after his model was displayed, the minutes of the Royal Society
note that: "There was produced a reflecting telescope 4 feet long of
Mr. Newton's invention which though the metaline concave was not

NOTES ON THE EARLY EVOLUTION OF THE REFLECTOR. 71

duly polished yet did pretty well, but was under charged. It was
ordered to be perfected against the next meeting."

At the next meeting the following: — " The 4 foot telescope of Mr.
Newton's invention was produced again, being improved since the last
meeting. It was recommended to Mr. Hooke to see it perfected as
far as it was capable of being." So far as the annals record it never
again appeared on the scene.

While it was not definitely stated by whom this telescope was made
an entry of March 1st of the same year in the Journal de S^avans
definitely ascribes this 4 foot telescope to Newton, although the ac-
count is rather vague. It would look therefore as though Newton
himself or some of his friends had tried out his invention on a larger
scale, and had fallen into exactly the trouble that might have been
expected*

Perhaps Newton's aversion to the paraboloid, of which he knew
perfectly well the properties, may have been partly due to the fact,
as stated in one of his letters, that there is no strictly geometrical
method of grinding it. About the same time Hooke proposed to stamp
up the specula out of silver and before the end of the year he was
working on a 15 inch mould for a speculum of 10 feet focal length, of
which nothing has since been heard.

Meanwhile enters upon the scene the personage known in the
histories of science as " Cassegrain, a Frenchman." A communication
from M. DeBerce to the Royal Society describes his invention and
gives a very rough sketch of it. This was a translation of a letter sent
by DeBerce to the Academy of Sciences from Chartres, and read at the
seance of April 16, 1672. DeBerce says that this invention had been
communicated by Cassegrain to him some three months previously,
and how much before this time Cassegrain had been working on the
problem will probably never be discovered. At all events the Casse-
grainian telescope was disclosed to others than the inventor at sub-
stantially the same time as Newton's and was certainly an independent
invention, although one letter to the Royal Society vigorously berates
the Frenchman for stealing "Our Newton's" thunder, and explains
how an ingenious friend of the writer is making a still further im-
provement on Cassegrain's form by using a flat secondary speculum.

Newton's comment on DeBerce's letter plainly shows that he did
not enjoy a rival in the field, for it is somewhat discouraging in tone
and incidentally his specific criticisms were consistently wrong, as for
instance he had the erroneous idea that speculum metal reflects much
better at 45° incidence than at normal incidence, whereas in fact the

72 BELL.

difference is too small for even its sign to be distinguished with
certainty. It is the irony of time that the Cassegrainian form is the
one which has survived in the greatest instruments of the present time.

The writer is glad to be able to drag "Cassegrain, a Frenchman,"
from something of the obscurity in which he has been veiled, intro-
ducing then, Sieur Guillaume Cassegrain, sculptor in the service of his
glorious Majesty Louis Quatorze, modeller and founder of statues for
the decoration of the king's gardens at Versailles.

In 1666 he cast a bust of the King, after Bertin's model, for which he
received 1200 livres, and for the next twenty years or thereabouts
made also many replicas from the antique, including groups like the
Laocoon receiving payments from the Royal Treasury for his artistic
services well into the year 1684, at which time we lose sight of him.
He is believed to have died in the period between 1684 and 1686.
Cassegrain like his friend DeBerce was of Chartres, a city long con-
secrated to the art of sculpture. At about the same time that
DeBerce sent to the Academy of Sciences the little note on Casse-
grain's telescope, Cassegrain himself wrote a long letter to the Academy
concerning the speaking trumpet lately invented by Sir Samuel
Morland.

It was in this letter that the writer got the first clew to Cassegrain's
identity, since in it he displays beautiful draughtsmanship, as shown in
the accompanying copper plate, in striking contrast with his friend's
rough sketch, and also a notable familiarity with the art of bell found-
ing, which very likely may have been practiced in his own atelier. In
fact he writes like an educated and experienced artist, and was obvi-
ously regarded as a person of some consequence, for this letter formed
the piece de resistance at the meeting of the Academy of Sciences on
the 2nd of May 1672. When and where Cassegrain was born one can-
not tell with any certainty, although it is not unlikely to have been
somewhere about 1630 to 1635, quite possibly in Chartres. At all
events his profession and facilities were such as would very readily
have led him toward a reflecting telescope if a hint of Mersenne's sug-
gestion to Descartes, or of James Gregory's theory, had come to his
notice.

Note that in the account of Newton's telescope in the Journal de
S9avans the word is used in its modern English sense instead of being,
as now, confined in French to reflectors, while the Cassegrainian
instrument is spoken of as a little "lunette d'approche." One does
not generally suggest dimensions for a thing non-existent. Whether
Cassegrain actually made and experimented with telescopes nobody

NOTES ON THE EARLY EVOLUTION OF THE REFLECTOR. 73

actually knows, but ds a founder, familiar with bronze and bell metal,
it is not unlikely that he tried it.

It was bell metal, by the way, which was the basis of Newton's
speculum metal. He merely whitened it a little with arsenic, as the
alchemists had done before him, thinking the alloy one stage in the
transmutation of copper to silver. Bell metal ranged in early times
from one part tin to four of copper, to one part tin to two of copper.
Newton's was very likely between the two, since he recommends one
of tin to three of copper, a material which works and polishes well,
but tarnishes with great rapidity, as Sir William Herschel found to his
cost many years later.

Exit now the reflector, for more than about half a century. Newton
made one more try at it, working on a 4 inch glass speculum to be
silvered on the back after the plan early proposed by Gregory. The
instrument was apparently never completed.

Another item often ascribed to Newton was the discovery of pitch
polishing. That he found the process to work well is undeniable, but
he did not disclose it for more than thirty years after his little telescope
had been laid on the shelf of the Royal Society, in fact not until several
3'ears after there had been published, subsequent to Huygens' death,
the fact that he had been in the habit of polishing his true tools for
lens grinding in exactly this manner.

It was not until Newton was a venerable invalid, a half century after
his telescope had been put away and forgotten, that the reflecting
instrument was finally put upon the stage by John Hadley, the in-
ventor of the reflecting octant.

Hadley knew enough to make his own speculum metal and in his
struggles with it derived very little information from Newton's ex-
perimentation. He realized the importance of parabolizing his main
mirror and of giving a hyperbolic figure to his small mirror. He
polished them both not directly upon pitch, but upon pitch over-laid
with the finest silk fabric, which apparently helped in distributing and
holding the abrasive, and in 1722 presented to the Royal Society the
first veritable reflecting telescope.

This instrument was of about 6 inches aperture and of about 5 feet
focal length and proved on test to be better than the telescope of 123
feet focus belonging to the Royal Society and made by Huygens. The
tests of the telescope show that it had a pretty good figure, and in fact
Hadley hit upon the method of testing for figure used for many years
thereafter, by examining the speculum at the centre of curvature and
judging of the parabolic figure by the default of the image from the
characteristics of a spherical mirror.

74 BELL.

John Hadley in fact was the real inventor of the reflector in quite
the same sense that Mr. Edison invented the incandescent lamp;
from grasping the true principles of the matter and carrying them out
to success while the only previous attempts had ended in dismal
failure.

It was Hadley who taught the art to Molyneux and others and to
whom James Short, the most celebrated of eighteenth century artists
until the time of Herschel, was undoubtedly indebted for the start
upon his brilliant career.

Short, however, worked to the Gregorian principle with success,
doubtless since because this telescope rectifies the image, it is avail-
able both for terrestrial and celestial use. He made instruments from
all accounts of beautiful figure, some of them up to 8 or 10 inches diam-
eter, and of a speculum metal so nicely compounded and polished that
some of his specula were still serviceable well toward the end of the
nineteenth century.

There is good reason to suspect that Short may have been the in-
ventor of the system of distributed grooves given to the tools, upon
which successful figuring so much depends, since, dying, he ordered
the destruction of his whole equipment, a quite needless precaution
against the success of posterity had there not been very radical im-
provements, easily detected. James Short, too, was the first con-
structor of genuine equatorial mountings of which he executed several
about the middle of the eighteenth century. He died leaving the
methods which led him to success a mystery unsolved, for Herschel
and his successors to puzzle over. The only change in the situation
after Herschel 's day was the independent invention of Steinheil and
Foucault which gave to silver-on-glass its present supremacy. The
earliest examples of Foucault's work show how little, otherwise than
in the material and figuring of the speculum, the art of telescope con-
struction had progressed since Hadley and Short were working a
century before.

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57-5

Proceedings of the American Academy of Arts and Sciences.
Vol. 57. No. 5.— April, 1922.

THE EFFECT OF PRESSURE ON THE THERMAL
CONDUCTIVITY OF METALS.

By p. W. Bridgman.

Investigations on Light and Heat made and published with aid fbom the

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(Continued from page 3 of cover.)

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 5 — April, 1922.

THE EFFECT OF PRESSURE ON THE THERMAL
CONDUCTIVITY OF METALS.

By p. W. Bridgman.

Investigations on Light and Heat made and published with aid from the

RuMFOHD Fund.

NEW YORK

BOTANICAL

UAKUtJil

THE EFFECT OF PRESSURE ON THE THERMAL
CONDUCTIVITY OF ISIETALS.

By p. W. Bridgman.

Received Oct. 7, 1921. Presented Oct. 19, 1921.

TABLE OF CONTENTS.

Page.

Introduction 77

Description of Apparatus and Method 78

Experimental Procedure 98

Detailed Data 100

Lead 100 Silver 110

Tin 103 Nickel 110

Cadmium 106 Platinum 113

Zinc 107 Bismuth 114

Iron 107 Antimony 116

Copper 109 Petroleum Ether 119

General Comment on Lussana's Results 122

Discussion 123

Summary 126

IXTRODUCTION.

It is known that there is an intimate connection between the
electrical and thermal conductivities of metals. This connection
finds expression in the constant value of the Wiedemann-Franz ratio
for different metals; the meaning of this is supposed to be that the
largest part of the heat transfer in metals is accomplished by the same
electrons which transfer the electricity in current conduction. I have
already measured the effect of pressure on the electrical resistance of a
large number of metals, and have drawn certain conclusions from the
results as to the mechanism of electrical conduction.^ It seemed that
it would be no less interesting to measure the effect of pressure on
thermal conductivity. This paper contains the results of measure-
ments of the effect of pressures to 12000 kg/cm^ on the thermal con-
ductivity of lead, tin, cadmium, zinc, iron, copper, silver, nickel,
platinum, bismuth, and antimony at 30° C.

At the time that I undertook these measurements this was an en-
tirely untouched field; not even the sign to be expected for the effect
was known. Since starting this work, measurements have been
published by Lussana ^ on the effect of pressures to 3000 atmospheres

78 BRIDGMAN.

on the thermal conductivity of eight metals and four alloys. Except
for two of the alloys, he finds that the thermal conductivity always
increases under pressure, and the change is of such a magnitude that
the Wiedemann-Franz ratio remains nearly constant. The classical
conception of the mechanism of conduction would prepare one to
expect this result. I have not been able to verify the results of Lus-
sana, but find that the conductivity of more than half my metals
decreases instead of increases under pressure. This is perhaps a result
not to be expected, and must have considerable significance for our
picture of the mechanism. With regard to the differences between
Lussana's results and my own, I think that Lussana's work is open to
serious criticism in several particulars, and I have gone into this in
detail later.

Measurements of thermal conductivity are known to be among the
most difficult in physics (witness the disagreement among different
observers as to the sign of the temperature coefficient of thermal
conductivity), and I was accordingly prepared for considerable diffi-
culty in measuring changes, which might be expected to be of the order
of a few per cent, in a quantity which is itself so hard to measure. The
difficulties were of course enhanced by the technical necessity of mak-
ing the apparatus so small that it could be enclosed in a pressure
chamber. The anticipated difficulties were encountered; these
measurements are by far the most difficult of any that I have at-
tempted under pressure. The accuracy is accordingly much less than
that possible in such measurements as of electrical resistance under
pressure, for example. Certainly not more than two significant
figures can be claimed for the pressure coefficient of thermal conduc-
tivity. If the work were to be repeated now it would be possible to
improve considerably on the accuracy, or at least the presentability,
of much of it. But I believe that the results which follow are essen-
tially correct in their large features, and that the use which can at
present be made of such data does not justify the expenditure of more
time.

Description of Apparatus and Method.

The choice of methods was much restricted by the limitations of
space imposed b}' the necessity of getting the specimen and all the*
attachments into a pressure cylinder, and by the necessity of using
only four electrical leads to the heating element and thermo-couples.
Two methods were used ; these were both of the same general character

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 79

in that they carry the determination of thermal conductivity back to
the definition. A known steady supply of heat was put into the speci-
men, and by means of a thermo-couple the difference of temperature
was measured between two points when equilibrium was reached.
In terms of the geometry of the configuration the temperature gradient
and the rate of heat flow across unit area can be immediately found,
and hence the thermal conductivity may be found from its definition.
The first method was in theory the simplest, as there were practically
no corrections to be applied. This was a radial flow method. The
specimen was in the form of a massive cylinder, almost filling the bore
of the pressure cylinder. Along the axis of the cylinder was a linear
source of heat, and the difference of temperature was measured be-
tween two points at different radial distances from the axis. The
formula for thermal conductivity in this case is

Q r.

where h is the conductivity, Q is the heat input per unit length of the
axis, ri and r-i are the radial distances of the two junctions of the
thermo-couple, and ^i and 6^ are the temperatures of these two junc-
tions.

The flow of heat under these conditions is radial, except at points
near the ends of the cylinder. By locating the thermo-couple midway
between the ends of the specimen any end effect may be avoided.
The method is therefore unusual in that there is no correction for heat
leak. Further there is no correction for the change of dimensions of
the specimen under pressure, for it is only the ratio of the two radial
distances that enters the formula, and this is not changed by a hydro-
static pressure which uniformly changes the dimensions in every
direction. There is a correction in the heat input due to the change of
length of the heating unit under pressure, but this correction is equal
to the linear compressibility, and is so small as to be almost negligible.
The heating element was made of nichrome. Assuming the com-
pressibility of nichrome to be calculable by the law of mixtures from
that of nickel and chromium, its two constituents, the magnitude of
this effect is 0.2% under 12000 kg/ cm-. The correction is an addition
to the observed pressure effect. There is also to be considered the
change of resistance of the heating unit under pressure, but by a
suitable arrangement of the circuits this may be made to eliminate
itself, as will be seen later.

I designed this method of radial flow to meet the needs of the high

80 " BRIDGMAN.

pressure measurements, and found only later that it had been previ-
ously proposed by Niven ^ in 1905, particularly for measuring the
conductivity of comparatively poor conductors.

The method was used with many modifications, as will be described
later. Its essential weakness is that it demands that the specimen be
perfectly homogeneous ; this is difficult to obtain in sufficient perfection
in a casting, or even in commercial drawn metal. The method worked
best for lead, which is fairly easy to cast, is a comparatively poor
conductor, and is not crystalline, so that inhomogeneities due to
crystallization during cooling were not important. The method
failed for copper and nickel.

The second method was a longitudinal flow^ method. Heat is put
into the end of a rod, the other end of which is connected with a mas-
sive copper block in intimate contact with the pressure cylinder, so
that we have essentially a rod with a source at one end and a sink at
the other. The difference of temperature between two points on the
axis of the rod is measured with a thermo-couple. In contradistinc-
tion to the other method there is here an important correction due to
the lateral loss of heat to the fluid by which pressure is transmitted.
An elementary discussion shows that in order to reduce this correction
to the smallest value it is necessary that the dimensions of the specimen
be very small. The specimens actually used were only \ inch in
diameter, a little over 1 cm. long, and the two thermal junctions were
2 mm. apart. The correction for lateral loss is evidently smallest for
those metals with the greatest conductivity, so that this method
supplements the other, working best for those metals for which the
first method gave the poorest results. The magnitude of the correc-
tion for lateral loss may vary from 20% of the total effect for bismuth,
to about 1% for copper and silver. The most disagreeable feature of
this correction is that it changes with pressure because of the change
of conductivit;\' of the transmitting medium under pressure. This
effect is large and has to be independently determined. The thermal
conductivity of petroleum ether, which was the medium used in all
the later part of this work, increases 2.2 fold under 12000 kg/cm^.
The determination of the pressure effect on petroleum ether will be
described in detail later.

Discussion of further details of these two metliods is reserved until
later.

The electrical measurements involved in either method were es-
sentially the same in character, and could be made with the same
apparatus. The measurements necessary were of heat input, which

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 81

involved a knowledge of current and resistance, and of temperature
difference, which demanded a measurement of the electrO-motive
force of a thermo-couple. Since it was necessary to find only the
relative changes in thermal conductivity, a source of heat of unknown
magnitude would have been sufficient, provided that it remained
perfectly constant. The arrangement of the circuits, to be described
in the next paragraph, ensured approximate constancy of the heat
input, so that the measurements of the heating current degenerated
to check readings from which a small correction was determined. The
measurements of both heating current and e.m.f. were made on the
same potentiometer as was used in previous measurements of the
effect of pressure on thermo-electromotive force.'* This apparatus
has already been described in sufficient detail. By an arrangement
of suitably protected switches either the thermo-couple or a small
potential tap from the heating circuit could be connected in place of
the couple as previously used. The tap in the heating circuit was
constructed of heavy manganin wire of a resistance of approximately
1/13000 ohm.

Correction for the change of resistance of the heating element with
pressure was avoided by using a similar heating element in shunt with
the one exposed to pressure. The shunt unit was mounted in the
same thermostated bath as the pressure cylinder, but was not exposed
to pressure, so that its resistance remained constant during changes of
pressure. By writing down the equations for the divided circuit, one
can see in an instant that if the total input of current into the two
heating elements in parallel is maintained constant, the rate of genera-
tion of heat in that one of the two elements which is exposed to small
fluctuations of resistance remains constant. The total input of cur-
rent was maintained approximately constant by using for the source
of supply a storage battery in series with a ballast lamp (iron filament
in an atmosphere of hydrogen) obtained through the courtesy of the
General Electric Company. The total fluctuation of resistance in
series with the lamp due to changes of pressure was only 0.08%, and
wath constant e.m.f. the lamp reduces the fluctuations of current due
to this to negligible proportions. However, the battery itself was not
always sufficiently constant, and in order to determine the small
correction due to its fluctuations, the total current delivered by the
battery was measured by determining the current in the two branches
of the shunt. This was done with the potentiometer and a low re-
sistance tap, precisely as for the heating circuit. The total corrections
due to fluctuations in the heat input were always a small fraction of 1%.

82 BRIDGMAN.

A correction also had to be applied for the change in thermal e.m.f.
of the couple under pressure. The couple was of copper-constantan,
and the corrections due to pressure may be taken from data already
published.* The total correction at 12000 kg. due to this effect is
0.8%; the correction is to be subtracted from the apparent thermal
conductivity.

It will be noticed that this method differs from those previously
used in determining the effect of pressure on electrical conductivity
or thermal e.m.f. in that it is not a differential method, but is direct.
A number proportional to the total thermal conductivity is determined
at different pressures, and from these data the effect of pressure is
computed. As originally planned I had intended to make the method
differential, measuring the difference of thermal conductivity between
one sample exposed to the pressure and a similar one not exposed.
This can be simply done by opposing the two thermo-couples of the
two specimens. It soon appeared, however, that the regularit}- of the
results was not sufficient to justify this refinement, and the simpler
direct method was used. The direct method demands somewhat
greater accuracy in the resistances and the comparison standard cell,
which, however, was easy to attain.

Since the primary interest of these measurements was in the pro-
portional changes of thermal conductivity produced by pressure, a
highly accurate knowledge of some of the absolute data was not
essential. For instance, it is much easier to compare within 0.1% the
two potential taps for the heating unit and its shunt than to measure
the resistance of either accurately to 10~^ ohms, which would have
been demanded by 0.1% on the absolute resistance.

We return now to a discussion of the details of the two different
methods. First the radial flow method will be described.

The difficulties were chiefly mechanical, involved in getting the
specimen into proper shape, and ensuring the right boundary condi-
tions. The method demands not only that the heat input take place
accurately on the axis, but most of all that the exterior surface of the
specimen be maintained at constant temperature. The difficulty of
this last requirement can be seen when it is considered that the thermal
conductivity of copper, for example, is 3000 times greater than that
of the petroleum ether by means of which pressure is transmitted to
the specimen. There must of necessity be some crack between the
walls of the pressure cylinder and the specimen; even if this crack is
made vanishingly small at atmospheric pressure, it assumes quite
appreciable proportions under 12000 kg. owing to the elastic deforma-

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 83

tion of the cylinder under internal pressure. If the specimen does not
remain accurately centered in the cylinder at all times the flow of
hekt becomes unsymmetrical and the method is yitiated. Originally
I endeayored to meet this condition by surrounding the specimen with
a massiye cylindrical sheath of copper, approximately | inch thick.
The specimen itself was f inch in diameter and 2.5 inches long, and the
interior diameter of the pressure cylinder was about | inch. The
crack between specimen and pressure cylinder was of the order of
0.005 inch initially, and it might increase by double under the extreme
pressure. The use of the copper sheath is applicable only to those
substances with low conductiyity compared with copper. It might
be expected to work best for lead and bismuth, and to work less well
for tin and zinc.

Many yariations were tried on this method. The chief difficulty
proyed to be that of getting good thermal contact between the speci-
men and the copper sheath. I at first tried to cast the easily fusible
metals into the sheath. Unexpected difficulties were encountered in
getting good enough contact. Casting into the bright sheath in air
always introduced a film of oxide. Casting into the sheath in yacuum
was tried, and also casting after making a preliminary coating of the
interior of the sheath with solder or tin or the particular metal in
question or silyer plating, both in yacuum and a protecting atmosphere
of illuminating gas. Satisfactory results were not obtained with any
metal except lead. It was a surprise that it was so difficult to make
good contact with tin.

A difficulty anticipated with this method because of the unequal
compressibility of the copper of the sheath and the metal of the core
did not turn out to be formidable; this difficulty could be turned by
drilling the sheath with a number of fine holes so as to allow direct
access of the pressure to the interior.

The deyice was tried of splitting the sheath into two pieces at a plane
passing through the axis. In this way the inside of the sheath could
be thoroughly tinned, as also the outside of the specimen, and by
squeezing the specimen between the two halyes of the sheath while
still hot, good thermal contact could be secured initially. But with
this arrangement the unequal compressibility of sheath and core was
prohibitiye; there was a progressiye change with each application of
pressure, the two halyes of the sheath separating and working loose
from each other. AYith tin, for example, a progressiye change in the
apparent effect of pressure on the thermal conductiyity of three fold
was produced by three applications of pressure.

84 BRIDGMAN.

The attempt to maintain the external surface at constant tempera-
ture by using a sheath was finally abandoned, and the specimen was
maintained concentric in the pressure cylinder by an arrangement of
springs. The specimen was made larger than when the sheath was
used, being now only 0.02 inch smaller than the internal diameter of
the pressure cylinder. Between the surface of the specimen and the
walls of the pressure chamber were placed six longitudinal strips of
german silver 0.002 inch thick, and about 0.42 inch wide. A sectional
view through the specimen and the pressure cylinder is shown in
Figure 1. The strips are shown bent to a nearly circular figure be-

FiGURE 1. Section through the pressure cylinder and the radial flow speci-
men, showing the method of keeping the specimen concentric by springs.

tween the walls of the cylinder and the specimen. It is obvious that
these springs will take up any stretch in the internal diameter of the
cylinder, and maintain the specimen concentric at all pressures. The
springs are so thin, and the thermal conductivity of german silver is so
low that any error due to flow of heat away from the specimen through
the springs is small, and need not be expected to change greatly with
pressure. But as a precaution against any error from this effect the
specimen was wrapped with a layer of paper between the springs and
itself, thus minimizing any irregularity due to unequal heat loss at
different parts of the surface of the specimen arising from inequalities
in thermal contact between spring and specimen because of geometrical
imperfections.

As far as I can judge, this method of maintaining the outer surface
of the specimen as constant temperature was successful, but there
were numerous other sources of irregularity. The chief outstanding
mechanical problem now was that of getting the holes into the speci-

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 85

men for the heating element and the thermo-couple. The heating
element must be of fine wire in order to have the requisite resistance,
and the conditions of the problem demand that there be a cyHndrical
surface somewhere surrounding the heating element which is at con-
stant temperature. That is, a surface at constant temperature is
demanded both external and internal. I attempted to satisfy the
requirement at the inner surface in the same way as at the outer sur-
face by enclosing the heating element in a copper tube. The tube
was small, usually about 0.040 inch outside diameter and 0.020 inch
inside diameter. The outer surface of the tube was originally tinned
and the specimen cast around it. I soon found the same difficulty in
making good thermal contact as at the outer surface. If the speci-
men were melted after use and the copper tube examined it was very
seldom that the surface was found completely wet with the metal of
the specimen. But bad thermal contact at the center was not so
serious as at the outer surface, because of the much smaller dimensions.
Considerable improvement was made by using a tube of silver instead
of copper. The difficulty here is due to the exceptional affinity be-
tween the silver and the metal of the specimen. If the mold is pre-
heated, as is necessary to get a coherent casting, the alloying action
between the metal and the silver is in many cases so great as to result
in complete eating away of the silver tube. This effect was avoided
by an arrangement of the mold by which the silver tube was drawn up
into it from below after it was already filled with the molten metal,
and the metal immediately chilled from the bottom up, so as to avoid
the formation of blowholes. Specimens were made in this way and
measured of lead, tin, and cadmium, but the method did not work
with bismuth, the alloying here being so rapid that the silver was eaten
away before the mold could be chilled.

The attempt to maintain internal equality of temperature by a tube
of highly conducting material was finally abandoned, as it had been at
the outer surface, and the heating element was placed directly in an
axial hole made by casting the metal around a tungsten wire stretched
along the axis during casting. The diameter of the nichrome heating
element was 0.005 inch; this Was enamelled, bringing the diameter to
O.OOG, and the diameter of the hole was 0.007, so that only a small
amount of play was possible; furthermore the wire was always kept
from direct contact with the specimen by at least the thickness of the
enamel. This method of making the center hole could be used for all
the metals that could be cast, including lead, tin, cadmium, zinc,
bismuth, and antimony. With other metals of higher melting point

86 BRIDGMAN.

which were used in the form of cylinders the heating element has to be
put in an axial copper tube. In these cases the axial hole was 0.040
inch in diameter, drilled through the specimen, which was then turned
concentric with the hole, and the copper tube, which was not less than
0.039 inch in outside diameter, was then sweated into place. After
some practise it was possible to get fairly good sweated contact. Since
the pressure penetrates the interior of the tube, error from unequal
compressibility of the two metals at the interior surface must be small.
It is obvious that the use of an axial copper tube to contain the heating
element can be unobjectionable only for those metals whose thermal
conductivity is small compared with that of copper. The method
cannot be expected to give good results for copper itself, for example.

The thermo-couples as well as the heating element were at first
placed in two copper tubes cast into the cylinder, but this was later
abandoned for a hole cast into the metal itself. In making the hole
for the thermo-couple there are two opposing tendencies that must
be guarded against. In the first place the wire of the couple must be
so good a fit for the hole in which it is placed that the thermal conduc-
tion from the ends of the cylinder along the wires of the couple can be
neglected. In the second place, if the fit is too close, pressure is not
transmitted freely throughout the interior of the hole when pressure
is high and the transmitting medium has acquired a certain amount of
viscosity. Such viscosity results in the introduction of stresses into
the wire, with an effective change in its thermo-electric constants, so
that readings of temperature difference are no longer reliable. The
attempt was made to meet these two opposing conditions by making
the hole larger at the two ends with a narrow neck in the middle where
the junction is situated. The cylindrical specimen itself was 2.5
inches long. The narrow part of the hole to receive the junction was
0.014 inch diameter and 0.5 inch in length. The larger part of the
hole at each end was 0.040 inch diameter, and joined to the smaller
part by a conical part 0.25 inch long, thus leaving the 0.040
part at each end 0.75 inch long. The diameter of the wire of the
thermo-couple was 0.010 inch, and this was brought to 0.012 by the
enamel. An approximate calculation shows that these dimensions
are amply sufficient to prevent any appreciable flow of heat along the
thermo-couple wire to the region of the junction, even with the metal
of lowest conductivity. The hole was cast in the shape required by
filing down a wire to a neck of the dimensions given at the middle,
and holding this stretched through the mold in the required location.
After the casting had been made, the wire was removed by pulling

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 87

out, the wire breaking at the narrow part, and allowing the two pieces
to be pulled out separately from either end.

This method of casting the thermo-couple holes was of course not
applicable to the metals with high melting points, and for these copper
tubes sweated into place were used exactly as for the central heating
element. The inside diameter of these tubes as used for this purpose
was 0.016 inch. The junction of the couple was wrapped with fine
wire in order to bring its diameter nearly up to the internal diameter
of the tube, thereby preventing play in the \ube and ensuring better
thermal contact at the junction. In this case also the dimensions
were such that any error due to flow of heat along the thermo-couple
wire from one junction to the other was negligible. The results
obtained with specimens made in this way are subject to a correction
not easy to calculate for the disturbing effect of the copper tubes on
the flow of heat. This correction should not be large because the

Figure 2. The radial flow specimen attached, with the electrical con-
nections, to the insulating plug, ready to screw into the pressure cylinder.

copper tubes are comparatively small. The centers of the thermo-
couple tubes were 0.098 and 0.201 inches respectively from the center
of the specimen.

The electrical connections were got into the cylinder by means of a
three-terminal plug of the same design as that used previously in
determining the effect of pressure on electrical resistance by the
potentiometer method. The only difference is that this plug could be
made somewhat larger, because of the larger bore of the pressure
cylinder, | against | inch. There is an advantage in this in that the
thermo-couple leads can be got a greater distance from the heating
element leads, and so there is less danger of heat leaking into the
thermo-couple.

The manner of attaching the specimen to the plug ready for mount-
ing in the cylinder is shown in Figure 2. The plug and specimen were
attached together, and all electrical connections made before assem-
bling so that the whole combination could be screwed into the cylinder
as one self-contained unit. Attachments were made to the specimen

88 BRIDGM.^A.

itself by three steel pillars 0.062 inch in diameter at either end. These
pillars passed through washers of transparent bakelite at either end.
At the lower end the bakelite washer was in turn attached to a thin
steel sleeve, which was attached by screws to the three terminal plug.
The screws connecting the bakelite washer to the steel sleeve were
made a loose fit in order to allow sufficient freedom for the german
silver springs to keep the specimen concentric in the cylinder. The
german silver springs were soldered to thin discs of german silver
drilled to slip over the three steel pillars at either end and held in
position by the same nuts which held the bakelite washers. The steel
sleeve was cut away on two sides, allowing the ends of the thermo-
couple and the heating unit to be brought through the bakelite washer
and soldered to the three terminal plug. As an additional precaution
against leakage of heat from the heating element into the thermo-
couple, two massive pieces of copper in the form of a double wall
were placed entirely across the pressure cylinder between the terminals
of the plug connecting the thermo-couple and those connecting to the
heating element.

Two forms of heating element were used for these cylindrical
specimens, according to whether there was an axial tube, or the
heating element was mounted in a fine hole cast along the axis of the
specimen. ^Yhen the tube was used, the heating element was in the
form of a hairpin of 0.005 inch nichrome wire. By means of a jig the
wire was made accurately 5 inches long when straightened out, so
that it would exactly occupy the length of the tube when bent double.
It was silver soldered at either end to a half-round piece of copper
filed from a | inch copper wire. The whole arrangement was covered
with five or six coats of insulating enamel baked on, having a thickness
of about 0.0008 inch. After enamelling, the wire was bent double
into the hairpin form, thus bringing together the two halves of the
copper wire so as to form a single completely round piece | inch in
diameter. As an additional precaution the two halves of copper were
frequently insulated from each other by a thin layer of mica. The
two halves were then bound together into a single piece by wrapping
with fine silk thread. The resistance of the copper terminal pieces is
so much less than that of the nichrome element itself that there is only
a very small error introduced by any generation of heat outside the
element. The massive copper pieces were attached to the terminals
of the three terminal plug by a short length of flexible conductor
twisted out of many fine strands of copper. The total resistance of
the heating elements made in this way was nearly 10 ohms.

EFFECT OF PRESSURE ON CONDUCTIVITY OF INIETALS. 89

If the specimen were one of those with a small hole cast along the
axis the heating element was a single length of 0.0035 inch nichrome
wire, coated with enamel as the hairpin unit, silver soldered at one end
to a massive copper wire, and grounded at the other to the specimen
itself by soldering to a piece of fine german silver sheet, which was in
turn soldered to the specimen. By using an intermediate member of
fine german silver sheet the difficulty of attaching the fine wire to the
massive specimen at exactly the required point was obviated, and it
was easy to make the heating element the same length as the specimen
itself, at least within 0.002 inch, which was close enough. The speci-
men itself, which was grounded to the pressure cylinder, was used as
the return connection for the heating element. In order to eliminate
any danger of bad contact between the specimen and the cylinder, a
connection was soldered to one of the steel pillars and the ground
connection of the three terminal plug.

The thermo-couple, as already mentioned, was constructed of copper-
constantan. Each couple was made of three pieces of wire, first a
length of copper, then one of constantan, and then one of copper, of
the same length as the first. This was bent into a hairpin form, and
the two legs of the pin slid through the two thermo-couple holes. The
dimensions were so chosen as to bring the two junctions copper-
constantan midway between the ends of the specimen. The two
copper ends of the couple were attached by solder to the two copper
thermo-couple terminals of the three terminal plug. It is thus seen
that the e.m.f. of the couple is determined by the temperature
difference of the two copper-constantan junctions.

The wires of which the couple were made were 0.010 inch diameter.
It is essential that the junctions be absolutely smooth butt joints. It
is a little trick to successfully make these, but the following procedure
finally gave satisfactory results. The ends of the wires to be united
were first coated thinly with silver solder and borax, precisely as
ordinary objects are "tinned" for soft soldering, by dipping into a
drop of molten silver solder covered with a little borax. The drop of
silver solder was maintained molten at the desired temperature in a
miniature electric furnace made by winding nichrome wire around a
core (of course insulated from it) of j inch nichrome rod, in the end
of which was drilled a shallow depression to hold the drop of molten
solder. After coating the ends of the wires, they were brought into
exact axial alignment in a clamp with three adjustments. The wires
were held in pieces of quartz tubing drawn down to the proper size,
and projected perhaps | inch or less from the tube. The solder on

90 BRIDGMAN. '

the ends of the wires was then melted and the wires fused together by
a small blue gas flame. A flame of the required size may be obtained
from a jet issuing from a piece of drawn out glass tubing. The gas to
give the blue flame is supplied from a gasometer, which may be im-
provised from a couple of old tin cans, filled with a mixture in the
right proportions of illuminating gas and air. The joint so formed is
very strong mechanically. If the wires are not in satisfactory align-
ment they may be made so by hammering. The method is consider-
ably superior to any simple electrical method of welding with which I
am familiar. Of course there is no objection to smoothing the junc-
tion with a little fine emery paper; by this means a joint can be made
that cannot be detected by the sense of touch, or of sight, after the
wires are enamelled. The wires used were all cut to standard lengths
by jigs, so that after enamelling the joints could be located by measure-
ments. I have used this same method to make junctions as small as
0.004 inch, which are considerably more than two and one half times
as hard to make by the ordinary method.

A great many measurements were made with specimens of the
cylindrical form described above, and every effort was made to make
the method give good results. The measurements with any one speci-
men were usually regular, and would repeat, and were apparently as
good as could be asked. The trouble was that the numerical results
obtained with different specimens of the same metal did not agree.
The lack of agreement was much worse for some metals than others.
I finallv came to the conclusion that the method is essentiallv limited
by the demands for homogeneity which it imposes on the specimen.
Any slight flaw in the casting, resulting in cracks whose dimensions
would change with pressure, must change the direction of the lines of
flow with pressure. Further, any large scale crystal structure would
give different results for different castings.

The second method was designed to obviate as much as possible
the effect of inhomogeneity in the sample. As already mentioned,
this is a longitudinal flow method, there being a source and a sink at
the ends of the specimen, and the difference of temperature at two
fixed points is measured. Since the heat input must cross each section
of the specimen, any distortion of the flow by local inhomogeneities
must have less effect than in the case of the cylinder, where as an
extreme case it is possible that a flaw properly situated might force
all the heat input to flow out of the cylinder at one side only. The
much smaller dimensions of the longitudinal flow specimens would
also seem to reduce the chance of errors from flaws.

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS.

91

A scale drawing of the longitudinal specimen mounted in the
massive copper block ready for assembly in the pressure cylinder is
shown in Figure 3.

The sink at one end of the specimen was formed by soldering it into
a massive copper block of a diameter nearly the same as the interior
of the pressure cylinder. Good thermal contact between the copper
block and the cylinder was ensured by a centering arrangement of
springs of strip metal, exactly as in the case of the cylindrical speci-
mens, except that now the strips were made of heavy copper instead
of thin german silver. In order to reduce mechanical distortion due
to unequal compression of the specimen and the copper of the block,
the bottom of the hole in the block into which the specimen was

Figure 3. Longitudinal section of the pressure cjdinder with the longi-
tudinal flow specimen attached to the three terminal plug and in place.

soldered was brought into connection with the pressure transmitting
medium by a small drilled hole.

The source of heat at the other end of the specimen was provided
by a small coil of nichrome wire 0.005 inch diameter and exactly 1
inch long, silver soldered to copper,leads of the same diameter. The
resistance was of the order of two ohms. This wire was wound into a
coil of small dimensions on a core of a fine piece of glass tubing, and
was placed in a small copper capsule in the form of a square bottomed
cup about 2.5 mm. deep. One end of the heating coil was grounded
to the cup with solder, and the other end was connected to a lead
from the three terminal plug. The copper capsule was let into a hole
of the proper dimensions drilled in the end of the specimen. By the
use of the capsule I hoped to more nearly realize a uniform heat input
over the entire cross section of the specimen. To further realize these

92 BRIDGMAN.

conditions, and obviate irregularity due to poor thermal conduction
of any transmitting medium which might get into the cracks between
specimen and capsule, the capsule was cemented into the specimen with
deKhotinski cement, which has a considerably higher thermal conduc-
tivity than the liquid.

It will be noticed that the method of connection described above
amounts essentially to grounding one end of the heating element on
the sample itself, there being effectively a junction between the metal
of the specimen and copper. When a heating ciu'rent is passed there
will be a generation of Peltier heat at the junction in addition to the
Joulean heat in the element itself. This effect reverses in sign when
the direction of the heating current reverses and so may be eliminated.
However in the experiment as actually performed the independence of
the reading of the thermo-couple of the direction of the heating cur-
rent was used as a criterion for absence of electrical leakage between
the heating and the thermal current circuit, so that elimination of the
Peltier heat by reversal of the heating current was not desirable. For
most of the metals the effect is very small and may be neglected, but
for antimony and bismuth the effect becomes inconveniently large,
rising to a change in the apparent magnitude of the thermal conduc-
tivity of 25% with reversal of heating current. For these two metals
the ground to the capsule was discarded, and two independent leads
to the heating element were used.

The thermo-couple was constructed in the same way as those for
the cylindrical specimen ; a length of copper, then a piece of constantan
1 inch long, and then copper again. This was bent into the form of a
hairpin, whose two legs were thrust through two diametral holes 2 mm.
apart in the specimen. The junctions were located on the axis of the
specimen. Aft^r wrapping the wires around the specimen, as will be
described in a later paragraph, the two copper ends of the hairpin
were then soldered to the two copper thermo-couple terminals of the
three terminal plug. The thermo-e.m.f. of the couple obviously gives
the difference of temperature of the two junctions points.

In order to avoid error from heat leak along the wires of the couple
it was necessary to make these of much smaller wire than in the case
of the cylindrical specimens. The wire used was 0.004 inch diameter,
and the hole in which the couple was placed was 0.007 inch. The
couples were brought to a diameter of 0.005 inch by the coating of
enamel. There is an outstanding possible play of the couples in the
holes of 0.002 inch, which might lead to maximum errors in the ap-
parent thermal conductivity of 5%. This is probably the chief source

EFFECT OF PRESSURE ON CONDUCTIVITY OF ?iIETALS. 93

of error in this method, and it will be seen later that the results are
consistent with this explanation. In some of the later measurements
the attempt was made to cut down the motion possible in the thermo-
couple b}' threading into the hole along with the couple a wire 0.002
inch diameter. In some cases this seemed to produce good effects,
and in others apparently not. There is danger that too close a fit
may introduce tensions into the thermo-couple, and so change its
constants. It did not seem feasible to try for a much closer fit be-
tween the couple and the hole because of the difficulty of getting a
perfectly smooth coating of enamel on the wire of the couple.

The specimens of the two soft metals lead and tin were cast, and the
holes for the thermo-couple were cast with the specimens, using a
0.007 inch -wire for the core, held in a proper position in the mold.
For all the other metals the holes were drilled. A small jig was made
and the holes were drilled in a jeweller's lathe. In spite of the use of
the jig it was not possible to make all the specimens exactly alike, and
the distance apart of the holes was independently measured in every
specimen with a microscope. The extreme variation in their distance
apart was from 0.190 to 0.210 cm. I found that a very convenient
drill may be made of a piece of tungsten wire, pointed so as to form the
conventional flat drill. The advantage of this over steel is that it is so
tough that it is almost impossible to twist oflf, which may very easily
happen to a steel drill in a clinging metal like gold, for example.
While not as hard as steel, tungsten is hard enough to drill all the
metals used here, which included iron, nickel, and platinum, all in the
annealed condition.

Because the hole containing the couple is comparatively short,
there is greater danger of error from heat leakage along the thermo-
couple wire than in the first method. To eliminate this source of
error, the wire of the couple was bent sharply at the entrance of the
hole, at either end, and was wrapped once, or in some cases twice,
about the specimen, and held in close contact with the external sur-
face by a wrapping of fine silk thread. This ensures that the wire for
some distance from each junction shall have the same temperature as
the specimen at the junction, and so should eliminate error from leak.
As an additional control with regard to heat leakage along the wire,
the experiment was tried with two specimens of first using a couple
constructed as above (constantan between two lengths of copper) and
then a couple constructed of constantan between two lengths of
"therlo." "Therlo" is an alloy made by the Driver Harris Co. with
very nearly the same e.m.f. against constantan as copper, btit with

94 . BRIDGMAN.

a thermal conductivity at least fifteen times less. The error from
heat leak along the wires of the couple should therefore be very much
less with the therlo couple. As a matter of fact, the same results
were obtained with both couples, establishing freedom from heat leak.

A central band of one or two coats of enamel (thickness not over
0.0001 inch) was usually baked on the outside of the specimen. This
was to avoid danger of short circuit where the thermo-couple wires
were wrapped about the cylinder. Baking on this band of enamel,
which required about 210° C, .served the additional purpose of anneal-
ing the specimen. All the specimens were further heated to 150° or
so when soldered into the massive copper l)lock.

As already explained, the dimensions were forced by compromise
between various opposing tendencies. If it were not for lateral loss,
the specimens would have been made much longer, and the source and
sink would have been situated further from the couple. This would
have allowed the lines of flow to more completely straighten out in the
vicinity of the couple. It is possible by a rough calculation to get an
approximate idea of the extent of the failure of the lines of flow to be
entirely straight. The actual distribution of temperature over the
section at the source end cannot of course be accurately determined,
but it seems fair to assume that the temperature is higher at the center
of the rod than at the outside surface. A solution corresponding to
this state of affairs may be obtained by assuming a distribution of
temperature according to a Bessel's function over the source end. I
carried through an approximate examination in this way, and con-
vinced myself that any errors from this effect were not important.

The largest correction to be applied in the longitudinal flow method
is for the lateral loss of heat through the transmitting medium. The
lateral loss is a small part of the total input, so that we may assume
the distribution of temperature approximately linear along the speci-
men. The temperature gradient at the mean point between the two
junctions is the difference of temperature divided by the distance
between the junctions. The total flow of heat long the rod at this
point under this gradient is not the total input, because there has been
some lateral loss between the source and the junction. This loss takes
place partly from the lateral curved surface, and partly from the end.
The loss from the lateral curved surface of the bar was computed on
the basis of the formulas for the radial flow of heat through a cylinder
between inner and outer surfaces maintained at constant difference of
temperature. The temperature of the inner surface, that is, the
temperature of the bar, varies along the axis. The total lateral loss

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 95

was taken as the integral of the losses of short elepientary cylinders.
The loss from the upper end was calculated from the formula for the
flow between two concentric hemispheres, one having the radius of the
specimen, and the other the internal radius of the pressure cylinder.
The value obtained in this way is obviously too large, as most of the
pressure cylinder is situated further from the end of the specimen than
its internal radius. The lateral flow and the flow from the ends as
computed in this way involve the difference of temperature between
the source end of the specimen and the outer cylinder. This tempera-
ture difference may be expressed approximately in terms of the heat
input into the rod and the thermal conductivity of the rod. The
temperature difference may ndw be eliminated, giving a result in
terms of heat input and the conductivities of the liquid, /l2, and the
metal of the bar, ki. For the lateral loss of heat I obtained the formula

11.7 ~Q, and for the loss from the end 12. — Q (this last is too high).
ki ki

As an approximate value for the total loss through the transmitting
medium the value 20 — Q was used in the computations.

The value of /1-2, the thermal conductivity of petroleum ether, was
determined by direct experiment, as will be described later. At
atmospheric pressure the value found was 0.0004. At a pressure of
12000 kg/cm^ the conductivity has increased 2.2 fold. The change in
the value of the lateral flow correction with pressure determines the
correction that must be applied to the apparent change of conductivity
of the metal under pressure in order to obtain the true change. The
magnitude of this correction evidently changes greatly with the metal
used. The details with regard to this correction will be discussed
under the different metals separately.

In the longitudinal flow method there is no correction to be applied
for the change in dimensions of the heating element, as there was in
the radial flow method. The same arrangement of a shunt circuit
which eliminated the necessity for a correction for the changing re-
sistance of the heating element with the radial flow method was used
here also. There is a correction to be applied here, not necessary in
the radial flow method, for the change of dimensions of the specimen
under pressure. Under pressure the cross section becomes less and
the distance between the thermal junctions also becomes less, the first
b\' twice the linear compressibility and the second by the linear com-
pressibility. The sum of the two effects is a correction equal to the

96 BRIDGMAN.

linear compressibility in the direction of an increase to the apparent,
conductivity. In the absence of direct determinations of compressi-
bility at high pressures, the corrections applied in the following were
then taken from Richard's determinations at low pressures, neglecting
the changes of compressibility with pressure. The correction is in
any case small; the value for bismuth is a maximum at 1.2%. In
addition to these corrections there was an effect not present appreciably
with the radial flow method due to loss of heat along the leads to the
heating element. The leads were of copper and the heating element
was of nichrome. The thermal conductivity of copper is about 30
times and the electrical conductivity about 50 times that of nichrome.
Hence most of the heat input is confined to the nichrome and there
cannot be much heat conduction out along the leads; any cooling of
the copper leads can affect only the extreme ends of the nichrome coil.
The correction for this effect must be small, but may affect the abso-
lute conductivity. Only the change of this correction with pressure
can affect the final results, and I have neglected it.

There is one source of error that might be anticipated to be serious
with the longitudinal flow method, namely convection effects in the
liquid. In any event the convection effects may be expected to
vanish at high pressures because of the known large increase of vis-
cosity of the transmitting medium. I did expect the elfect to be
appreciable at atmospheric pressure, however, and at first made no
reading at atmospheric pressure, but used 2000 kg. as the zero. It
later appeared, however, that points obtained at atmospheric pressure
lay on a smooth curve with those at higher pressures, so that no error
from this effect is to be expected. It is in any event to be remarked
that the error from convection may be made vanishingly small by
cutting down the heat input. Assuming that the convection loss is
only a small part of the conduction loss, we see that if the heat input
is halved the temperature differences in the liquid are halved, the rate
of convective flow of the liquid is halved, and the rate of heat flow into
the liquid is halved, so that the total heat carried away convectively
is quartereil. (Of course the loss of heat by conduction to the liquid
is only halved). In the actual experiment the magnitude of the heat-
ing current was so chosen that the temperature of the source end of the
specimen was about 5° higher than ihat of the pressure cylinder. In
one or two cases parallel runs under pressure were made with changes
in the heat input by a factor of 2, with no change in the results. Also
at atmospheric pressure I verified that the temperature difference
measured on the thermo-couple was proportional to the square of the

EFFECT OF PRESSURE OX CONDUCTIVITY OF METALS. 97

heating current. Both of these checks prove freedom from convective
effects.

The longitudinal flow method showed itself a great improvement
over the radial flow method with regard to the agreement of the
results obtained with different specimens of the same metal. The
individual readings for a single specimen, however, were very much
more irregular, and until the interpretation of the irregularities was
found, I was in doubt whether this method was actually any improve-
ment over the previous one or not. After readings had been made on
a number of specimens, it appeared that in almost all cases the read-
ings for a single specimen would lie on three or perhaps four straight
lines. The extreme separation of these lines amounted to a difference
of not more than o% in the total thermal conductivity. It has already
been mentioned that this is the variation which might be caused by a
shift of position of the thermo-couples in their holes. The natural
interpretation is that the couple may take one of two extreme posi-
tions, like the bottom of an oil squirt, bent so as to touch either the
top or the bottom of the hole. The couple may change from one to
the other of these positions with change of pressure. The two couples
together can thus occupy any one of three different positions, so that
the readings will lie on one of three lines. If the initial curvature of
the wires of the couples is such that one of the positions of equilibrium
is not exactly at the top or bottom of the hole, then there will be four
relative positions of the couples, and the results will lie on four lines,
two of them comparatively close together. Figure 9, given later in
the detailed discussion of the data for nickel, is a good example of the
tendency to lie on discrete lines.

After the reason for the irregularities had been found it was possible
to a considerable extent to control the location of the readings on one
or the other of the possible lines. It was found, as might be expected,
that rapid changes of pressure were favorable to a jump of the readings
from one line to another, but that by changing the pressure very
slowly it was in many cases possible to obtain long successions of
points on a single straight line. It is easy to see that the nature of the
irregularity is such that it was quite possible, before its true nature
was recognized, to obtain results which might be erroneous even as
to the sign of the effect. Suppose for example that the true effect
gives points lying on a falling curve, but that as pressure increases the
thermo-couples snap over in the holes in such a way as to pass from
the low lying to the high lying curves. If only a few readings are
taken, and if the snapping about of the couples is a fairly regular

98 BRIDGMAN.

matter, as it often is, it can be seen that a regular succession of points
may be obtained apparently lying on a rising curve. To avoid error
from this effect each individual set-up demanded individual study, as
the way in which the wires snap about is an individual matter. The
true curve can be found by taking a larger number of readings than at
first I thought necessary, and by studying the possibilities of obtaining
successions of points on single straight lines under very slow changes
of pressure. In one or two cases, after the effect had been recognized,
it was found that the results originally obtained were in fact of the
wrong sign, and that on setting up the specimen again and carefully
analyzing the situation the correct result indubitably appeared of the
opposite sign. Examples of this will be mentioned later.

Experimental Procedure.

The procedure for either the radial or the longitudinal flow method
was essentially the same. The specimen was first attached to the
three terminal plug, connections to the interior end of the plug being
made with solder. The plug with the specimen in place was then
screwed into the pressure cylinder, and connections made to the outer
end of the plug by soldering. The temperature bath was then put in
place, and temperature adjusted to 30°, which was the universal
temperature of these experiments. (The accuracy was not great
enough to justify an attempt to determine the temperature coefficient
of the pressure coefficient, such as had been possible in the case of the
measurements of electrical resistance, for example.)

The heating current was now turned on and equilibrium waited for,
as shown by the constancy of readings of the thermo-couple. An
interval of 20 or 30 minutes was necessary to reach initial equilibrium
after adjusting the temperature bath. This time was nearly all con-
sumed in acquiring equilibrium throughout the interior of the pressure
cylinder, and particularly between the outer and inner ends of the
three-terminal plug. The leads through the plug were of necessity of
steel in order to obtain sufficient strength, whereas the metal at either
end of the plug was copper. Hence any temperature inequality be-
tween different parts of the plug introduces spurious e.m.f.'s into the
circuit, so that it is essential to wait for complete equilibrium. As far
as the specimen itself and the heat flow through it from the heating
element is concerned, equilibrium was attained very quickly. If the
heating current was turned on or off after the bath and cylinder had

EFFECT OF PRESSURE OX COXDUCTIVITY OF METALS. 99

reached equilibrium, the thermo-couple reached equilibrium in a
fraction of a minute in the radial flow method, and in at most two or
three minutes in the longitudinal flow method.

While the bath was coming to temperature equilibrium, I usually
made a preliminary application of 12000 kg. to be sure that the joints
were tight, and that the electrical insulation resistance between the
heating element and the thermo-couple circuit was sufficiently high.
The insulation resistance was measured independently of the potentio-
meter, and had in all cases to be as high as 100 megohms if satisfactory
results were to be obtained. The pressure transmitting medium in all
these experiments was petroleum ether. The use of this was neces-
sary to avoid stresses in the couples introduced by viscosity effects.
The mechanical difficulties of retaining this liquid under pressure
without leak are very materially greater than for the mixture of ether
and kerosene which I had used before. Slight mechanical imperfec-
tions in the bearing surfaces become much more important, so that the
preliminary test for leak on the whole saved time. There did not
seem to be any seasoning effect proper produced in the specimen itself
by the initial application of pressure, as indeed there ought not to be
if the specimen is homogeneous and well annealed. In a number of
cases when the radial flow method was used and the specimen was
mounted in a copper sheath, the specimen was seasoned by several
applications of the maximum pressure before any of the electrical
connections were made. Seasoning in this case was necessary because
of unequal compressibility of the specimen and the copper of the
sheath.

After reaching equilibrium at atmospheric pressure, the pressure
zero was read. The magnitude of the current in the heating element
and its shunt was then read on the potentiometer, both for the direct
and the reversed direction of the heating current. The reversal of the
heating current was accomplished with a double pole double throw
switch and took place so quickly that there was no appreciable inter-
ruption in the heat input. The mean of readings with du-ect and
reverse heating current eliminates the effect of any parasitic thermal
e.m.f.'s in the heating circuit. The final reading made was that of
temperature difference on the thermo-couple. This reading was also
made with both direct and reverse direction of the heating current.
Any error from electrical leakage from the heating circuit (in which
the current is of the order of 0.5 amperes) into the thermo-couple
circuit (in which the e.m.f. is of the order of a few microvolts) because
of defective insulation, is thereby eliminated. The reversal of [the

100 BRIDGMAN.

heating current does not eliminate the effect of spurious e.m.f.'s in the
thermo-couple circuit. There were no such spurious e.m.f.'s of de-
tectible magnitude in the circuit in the absence of the heating current,
as could be checked by the complete vanishing of the thermal e.m.f.
on breaking the heating current. The only assurance against spurious
e.m.f.'s introduced by the heating current itself was in the careful
design of the apparatus. T could think of no way of making a direct
check of this point without being able to introduce a cooling equal to
the heating. In addition to the measurements above, as a rough
check, the total current output from the storage battery into the
ballast lamp was read on a commercial ammeter.

The pressure was then changed, usually by a step of 2000 kg., and
after attaining equilibrium, the same succession of readings was again
made. An interval of about 15 minutes was usually sufficient for
equilibrium. This time is required to dissipate the heat of com-
pression in the liquid and to again attain complete equality of tempera-
ture at the outer and inner ends of the three terminal plug. The
usual routine consisted of two complete sets of readings to 12000 kg.
and back. The results were plotted roughly as soon as obtained,
making correction for any slight changes in the heating current and
for fluctuation in the temperature of the copper coils of the potentio-
meter. This last correction was usually not necessary. When using
the longitudinal flow method, after the cause of the irregularity of the
readings was discovered, the plotted results were used to best direct
the subsequent changes of pressure. The final computation of the
results and the application of the other corrections which have been
described above was made later.

The detailed data for the different metals follows.

Detailed Data.

Lead. More readings were made on this metal than on any other,
and in general the results are better and the final result is probably
more accurate than for any other. Nearly all the readings were made
by the radial flow method, to which this metal is best adapted, be-
cause of its comparatively low conductivit3^

Three grades of metal were used. A first rough trial was made with
ordinary commercial lead. Several of the early measurements, in
which a copper sheath was used, were made with so-called test lead
from Eimer and Amend. The majority of the measurements, how-

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS.

101

ever, were made on lead of unusually high purity provided by the
Bureau of Standards for the calibration of thermo-couples by the
melting point. The analysis of this lead was as follows:

Ag .0002 - .0003%, Sb .0019 - .0028%, Sn .0008 - .0011%,
Cu .0003 - .0004%, Fe. .0004 - .0006%, As, Bi, Zn, Co, Ni, trace,
Cd, Mn, none; Lead (by difference) 99.9948 + %•

The melting point according to the certificate of the Bureau was 327°. 3.
The accidental errors in the measurements were greater than differ-
ences due to slight amount of impurity, since all varieties of metal
gave essentially the same results. The results are summarized in the
following table.

TABLE I.

Summary of Results for Lead.

Description of Specimen

Percentage Change

of Conductivity for

12000 kg/cm2

Solid Cu sheath, 3 copper tubes, commercial

" " " " " " " test "

21.5

f20.2

\l9.2

23 . fi

" " « central Cu tube, " test " '

Split Cu sheath, central Ag tube, Bur. Stds

Large cylinder, no sheath, central Ag tube, Bur. Stds

" 0.007" central hole, Bur. Stds. . .

11 11 11 U U 11 11 l( 11

Longitudinal flow, Bur. Stds. holes cast in specimen

11 11 a 11 11 11 11 11

Average

<

f23.6

|20.2

J21.8

\23.S

' 19.7

20.2

,(12.1)

flS.7

\20.0

16.5

20.9

(8.1)

20.7

In the above table, those specimens for which the nature of the
central tube only is specified had the thermo-couple holes cast in the
body of the metal in the isthmus shape already described. The

102

BRIDGMAN.

figures in parentheses in the table were omitted in taking the average,
as evidently they are affected by some large error.

Of these measurements the best was the second run with the first
specimen with the 0.007" central hole. It is indeed to be expected
that this manner of mounting the specimen would give the best re-
sults. The individual readings of this run are reproduced in Figure 4.

4 5 6 7 8 9

Pressure. Kg. / Cm/ X 10'

Lead

Figure 4. Lead. Thermal conductivity on an arbitrary scale against
pressure in thousands of kg/cm-. These results were obtained with a radial
flow specimen.

The first of the two sets by the longitudinal flow method comes next in
order of consistency, the individual poihts of this run lying even
more nearly on a smooth curve than those shown in Figure 4, except
for the initial point at atmospheric pressure, which lay off the curve
by a large amount. The readings on the second longitudinal sample
were not good for some unknown reason; possibly there may have

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 103

been flaws in the casting, as was indeed found to be the case one or
two other times when the longitudinal specimen was cast. For lead,
the correction to be applied to readings on the longitudinal specimens
for the lateral flow through the transmitting medium was unusually
large, reducing the observed efl^ect from 30% to 20%.

The readings on the two best samples were sufficiently good to show
a departure from linearity with pressure, the slope becoming less at
the higher pressures. This is as would be expected. Part of the
departure from linearity is without doubt to be ascribed to the effect
of the transmitting medium, and since for most of the other metals
the accuracy was not great enough to show this departure from
linearity, it did not seem worth while to attempt to establish it more
exactly for lead.

It will be seen that the two best runs agree pretty closely with
each other and with the mean of all the measurements, so that con-
siderable confidence may be given to the average value, 20.7%, as
the most probable effect of 12000 kg. It is to be remarked that this
change of thermal conductivity is markedly greater than that of
electrical conductivity under the same pressure, which is only 14.6%.

The average pressure coefficient of thermal conductivity per kg.
change of pressure is 0.0000173. Lussana ^ found as the average
coefficient between atmospheric pressure and 2600 kg., 0.0000134.
His initial coeflficient was 0.0000164, and the final O.O4II6, showing
departure from linearity in the same direction as I found, but much
greater in amount. His results do not show, however, any departure
from linearity in this range in the relation between pressure and
electrical conductivity.

Tin. A few preliminary measurements were made on tin with
"chemically pure" metal from Eimer and Amend, but all the results
of any value were obtained with Bureau of Standards tin, prepared
for the calibration of thermo-couples by means of the melting point.
The analysis of the tin was as follows: Pb .007%, Cu .003%, Fe .002%;
As, S trace; Sb, none; Tin (by difference) 99.988%, and the melting
point given by the Bureau's certificate was 231°. 9.

Twelve different samples of tin were used, ten by the radial and two
by the longitudinal flow method. None of those specimens in which
a copper sheath was used gave results of any value whatever. The
reason for this has already been discussed; the effect is due to lack
of good thermal contact between the tin and the sheath. Neither was
it found possible to get any results of value with those specimens in
which the heating element was enclosed in a central silver tube. For

104

BEIDGMAN.

some reason it was not possible to make such good contact between
silver and tin as between siher and lead. It may be that the greater
ease of alloying between silver and tin resulted in inhomogeneity of
the casting in the neighborhood of the central tube. Fairly consistent
results were obtained, however, from those castings in which the
heating element was placed in an axial hole 0.007 inch in diameter
cast with the specimen. The results with the poor specimens which
were discarded varied from 9 to 45% (the latter was for the split
sheath which showed a progressive change with successive applica-
tions of pressure). The results with the better specimens are shown
in the table.

TABLE II.
Summary of Results for Tix.

Description of Specimen

Effect of 12000
kg/cm2

Large cylinder, no sheath, 0.007" central hole

15.47c
fl4.2
113.6
jl8.4
\lS.l

11.1

11.9

u u u a a it a

u u u u u » u

Longitudinal flow, all holes cast in specimen

(( « U U U 11 u

Average

14.7

It is to be noticed that the results with the longitudinal flow speci-
mens are lower than those for the radial flow specimens. The indi-
vidual readings were not so good by the longitudinal method. It
would perhaps have been bettcF to have used a piece of extruded tin
wire rather than the casting, in order that the specimen might be more
homogeneous. The correction for lateral flow in the longitudinal
method was 4.3 %, about a quarter of the total eifect as measured. It
is further to be noticed that the readings on the radial flow specimens
which were repeated agree with each other more closely than they do
with the mean, so that apparently the difl^erences between the speci-
mens are real. This may perhaps be partly ascribed to the effect of
crystalline structure. Tin does not crystallize in the regular system,
and is distinctly more crystalline in character than lead, for example,
so that it is not surprising that there should be differences.

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS.

105

The best results were obtained with the first of the radial flow speci-
mens listed above. The results with this specimen are reproduced
in Figure 5. The same departure from linearity Avhich was shown by
lead is shown here also.

The average of the results listed above gives a mean pressure
coefficient to 12000 kg. of thermal conductivity of + O.O4I22 per
kg/cm-. The corresponding coefficient of electrical conductivity is
+ 0.0o929.

820 tii
0

I

3

0

12

4 5 6 7 8 9

Pressure, Kg. /Cm.' X 10'

Tin

Figure 5. Tin. Thermal conductivity on an arbitrary scale against pres-
sure in thousands of kg/cm^. Results obtained with a radial flow specimen.

Lussana ^ found for the average coefficient of thermal conductivity
to 2600 atmospheres O.OsTlO (pressure expressed in kg/cm'-). Lus-
sana's relation was not linear, but there was a falling off of the coeffi-
cient of 19% between 0 and 2600 atmospheres. Up to 2600 atmo-
spheres Lussana found the relation between pressure and the electrical
resistance of tin to be linear, and the value of the coefficient O.O582O.
In my prcA'ious work I have found the relation to be sensibly not
linear, and the initial value of the coefficient to be O.O4IO05.

106 BRIDGMAN.

Cadmium. The material used for the experiments was " chemically
pure" cadmium from Eimer and Amend. I have no analysis. In all,
eight sets of readings were made, four by the radial flow method, and
four hy the longitudinal flow. In general the results were not good.
A number of smooth curves were obtained by the radial flow method,
but the numerical values for the difl'erent specimens varied greatly,
the extremes being 5.0 and 31.5%. One of the radial flow specimens
had a central silver tube to contain the heating element; the results
with this were very irregular. The three other specimens had a
0.007 inch central hole, and the results with them were not so irregular.
The best mean values with the four radial flow specimens were re-
spectively 5.8, 26.7, 4.2, and 14.8%. The mean of these is 12.9%,
or discarding the highest as differing too much from the others, the
mean of the three remaining is 8.3%. Doubtless much of the irregu-
larity in the resuks by the radial flow method was due to imperfections
in the castings.

The individual readings for any one specimen by the longitudinal
flow method were widely scattered, and would not give much confi-
dence in the correctness of the result if it were not for the fact that the
different specimens gave results in agreement. The longitudinal flow
specimens were two of them cast and two extruded. One of the
castings was annealed at 130° for 30 minutes, the other not. The
extruded specimens were seasoned by a preliminary application of
12000 kg. These differences in treatment seemed not to affect the
results. The last of the longitudinal flow specimens did not give
results of value; the other three specimens gave changes under 12000
kg. of 9.0, 8.7, and 8.7% respectively. The magnitude of the correc-
tion for the pressure effect on the petroleum ether was 3.8%. The
best mean coefficient from these measurements is taken to be 8.9%.

The pressure coefficient of thermal conductivity given by the
above mean value is +0.0574. For the mean pressure coefficient of
electrical resistance between 0 and 12000 kg. I found 0.05932. The
results for the effect of pressure on thermal conductivity were not
sufficiently accurate to establish any departure from linearity with
pressure. The effect of pressure on electrical resistance becomes less
at the higher pressures; I found the initial coefficient to be O.O4IO85,
and the mean O.O5912. These results may be compared with those of
Lussana. Up to 3000 he found the effect of pressure on both thermal
and electrical conductivity to be linear; the coefficient of thermal
conductivity he found to be O.O4I22, and of electrical conductivity
O.O592. The first is higher than my value, and the second lower.
Lussana's value for the pressure coefficient of thermal conductivity

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 107

would be lowered by about 5% if my correction for the effect of pressure
on the thermo-couple is applied. Lussana applied no such correction.

Zinc. Runs were made on three samples by the radial flow method,
and two by the longitudinal method. The radial flow results were
valueless; there is considerable difficulty in making homogeneous
castings. The longitudinal flow specimens were extruded hot, and
should be sufficiently homogeneous. The material was obtained from
the Bureau of Standards, one of their melting point samples, and had
the following analysis: Fe .005%, Pb .0004%, Cd .0018%o, As, S
trace; Sb, Sn none; Zinc (by difference) 99.993%. Melting point
419°. 4. The results obtained with the two longitudinal samples were
scattering, the points lying on several distinct lines, as already ex-
plained, but the correct slope could be picked out with some assurance.
The change produced by 12000 kg. was 2.4% for one sample, and 2.7%
for the other. Take as the mean 2.5%. The correction for the pres-
sure effect on the transmitting medium was 3.0%, reducing a directly
observed effect of 5.5% to 2.5%.

The pressure coefficient of thermal conductivity given by the
above is -)-0.0521. I had previously found the pressure coefficient of
electrical resistance for a pressure range of 12000 kg. to be —0.05463.
Lussana, over a pressure range of 2600 atmospheres, found the effect
of pressure on thermal conductivity to fall off slightly from linearity,
and the mean coefficient to be O.O54I. The pressure coefficient of
electrical resistance he found to be — O.O56O2; this relation he found
to be sensibly linear.

Iro7i. Two samples were made for the radial flow method, and four
for the longitudinal. The radial flow results were unsatisfactory.
The thermo-couples and heating element were placed in copper tubes
sweated into larger holes drilled in the specimen. The results were
irregular, and the irregularities repeated themselves, showing that the
effect is real, and denotes some defect in the specimen, not in the
accuracy of the measurements.

Two of the longitudinal flow specimens were made from American
Ingot Iron, from the same piece as the wires whose pressure coefficient
of resistance and thermal e.m.f. have been previously measured.*
The total impurity in this iron was not over 0.03%. The other two
samples were made from a small sample of electrolytic iron of high
purity for which I am indebted to the Bureau of Standards. The
analysis of this iron is as follows:

Carbon 0.005 per cent.
Silicon 0.007 "
Sulfur 0.011 "

108

BRIDGMAX.

For some unknown reason the readings on one of these four samples
were not satisfactory. The readings on the other three were quite
typical of the results by this method, lying on one of several discrete
lines. The results obtained with one of these are reproduced in
Figure 6. The observed effect for iron is an increase of apparent
conductivity of between 5 and 6% under 12000 kg., but the correction
for the effect of pressure on the transmitting medium is so large, 5.3%,
as to wipe out nearly all the observed effect. The results obtained

4100

4000

>

o

^
o
z
o
o

<

3900

3600

3700

4 5 6 7 8

Pressure. Kg./Cm.'X 10^'

Iron

10

li

12

Figure 6. Iron. Thermal conductivity on an arbitrary scale against
pressure in thousands of kg/cm-. Results obtained with a longitudinal flow
specimen. The points he on several hnes of the same slope; the reason for
this is explained in the text.

with the three good samples, after applying all corrections, were
—0.6, —0.2, and —0.2% respectively. The discarded data were not
inconsistent with these values. We take as the mean —0.3%.

The pressure coefficient of thermal conductivit}" given by the above
results is — O.OeS. I found for the pressure coefficient of electrical
conductivity between 0 and 12000 kg. +0.0o229. Iron is not one of
the metals measured by Lussana, so there are no previous values for
comparison.

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS.

109

Copper. Two specimens were made for the radial flow method, and
four for the longitudinal. As in the case of iron, the thermo-couples
and heating element of the radial flow specimens were placed in
copper tubes sweated into place, and the results were not at all satis-
factory. The points were not regular, and the irregularities repeated,
showing some real effect. Furthermore, the two radial flow specimens
were made from contiguous lengths from the same piece of commercial
drawn rod, and the irregularities were much the same in character for
each specimen, showing a real effect of inhomogeneities in the metal.

The four longitudinal specimens were made from electrolytic copper
wdiich I obtained a number of years ago from the Bureau of Standards.

3 4 5 6 7 8

Pressure. Kg. / Cm/ X 10'
Copper

Figure 7. Copper. Thermal conductivitj^ on an arbitrary scale against
pressure in thousands of kg/cm-. Results obtained with a longitudinal flow
specimen.

Their analysis is as follows : Cu 99.995 per cent, trace S, no x\g, CU2O,
As, or Sb. It is to be noticed that the purity is unusually high.

Measurements were made on some of these samples in the annealed
condition, and others not; there seemed to be no difference in the
results.

These four samples gave fairly good results, the points lying on
discrete lines, as usual. The least scattering of these is reproduced
in Figure 7. The effect is seen to be fairly large, and negative, the
mean effects shown by the four samples were —9.7, —8.2, —8.3, and
— 7.5% change respectively under 12000 kg/cm^. The mean is
—8.4%, but we will take as the best result —9.0% instead, because

110 BRIDGMAN.

the best of the specimens gave the higher results. Because of the
high conductivity of copper, the correction for the transmitting
medium is small, being only 1.2%.

The pressure coefficient of thermal conductivity deduced from the
data above is — 0.0o75. No departure from linearity could be de-
tected. I have found for the effect of pressure on electrical con-
ductivity over this range the mean value +O.O5I8I. Lussana's
results for copper run only to 1000 kg. He found the effect to be
linear, and the conductivity to increase under pressure, the opposite
sign from my results. His coefficient is +O.O5IO. The relation be-
tween pressure and electrical resistance he also found to be linear, and
the coefficient to be O.O5212.

Silver. Only the longitudinal flow method was used on this metal.
The material was obtained from Baker, and was said to be of high
purity, but I have no analysis. Three different samples were used.
The two runs made on the first two samples apparently indicated an
increase of conductivity- under pressure. The reason for this has been
discussed in detail previously; not enough readings were taken, and
there was a tendency for the points to shift from a lower lying to a
higher lying curve with increase of pressure, thus simulating a false
effect. IMore readings were made on the third sample, and an effort
made to control the position of the points on one or another of the
possible lines. The results with this sample are reproduced in Figure
8. The tendency of the points to lie on one or another of three dis-
tinct lines is obvious, as also the fact that the effect is negative, the
conductivity decreasing with increasing pressure, instead of increasing,
as was indicated by the results first obtained. The two first samples
were now set up again, and the measurements repeated, with the
precautions which had been gained from the intervening experience.
The results shown by these two samples were now also unmistakably
negative, and of nearly the same numerical value as shown by the
third sample. The numerical magnitude of the total decrease of
conductivity under 12000 kg/cm^ shown by the three samples was
4.1, 4.4, and 4.6% respectively. The correction for the pressure
effect on the transmitting medium was 1%.

The pressure coefficient of thermal conductivity given by the above
data is —O.O^Sl. The average pressure coefficient of electrical
conductivity between 0 and 12000 kg. I have found to be +0.05334.
This metal was not investigated by Lussana, so there are no previous
results for comparison as to the thermal conductivity.

Nickel. Both methods were used for this metal, and material from

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS.

Ill

two different sources. I am indebted to the International Nickel Co.
for a piece of | inch round rod of high commercial purity (99%).
From this two samples were made for the radial flow method, large
cylinders without the sheath. The thermo-couples and heating ele-
ment were placed in fine copper tubes sweated into place. The re-
sults obtained with these samples were very irregular, and it was
evident that the thermal contact between the copper and the nickel
was not sufficiently good. These measurements did little more than
establish a strong probability that the effect was negative. After
the radial flow measurements had been made, two small pieces were

0 12 3 4 5 6 7 8 9

Pressure, Kg. / Cm.' X 10'
Silver

«

FiGTTRE 8. Silver. Thermal conductivity on an arbitrary scale against
pressure in thousands of kg/cm-. Results obtained with a longitudinal flow
specimen. The points lie on several lines of the same slope; the reason for
this is explained in the text.

cut from one of the cylinders for longitudinal flow specimens, and a
few readings were made with them. This was before the explanation
of the scattering of the points by this method had been found. The
results were very scattering, and repetition would have been necessary
to make sure of even the sign of the effect.

After completing the measurements on commercial nickel I was
fortunate enough to obtain through the kindness of Mr. I. B. Smith
of the Research Laboratory of the Leeds and Northrup Co. several
samples of exceedingly pure nickel. I have no analysis of the nickel,
but its high purity is vouched. for by the unusually high value of the
temperature coefficient of electrical resistance, which between 0° and

112

BRIDGMAJSr.

100° was 0.00634, against 0.0049 for commercial nickel over the same
range. Two longitudinal flow samples were made from this pure
material.

The first of these samples gave points lying on tliree different lines
separated by the usual 5%. The slope corresponded to a decrease of
conductivity of 13.5% for 12000 kg. In setting up the second sample
I made the attempt to prevent motion of the thermo-couple wires in
the holes with a piece of 0.002 inch wire laid beside them, as has been

>-

>

a

z
o
o

<

i

llJ

X

1900

1850

1800

1750

1700^

4 3 6 7 8

Pressure. Kg./Cm.'X 10'

10

II

12

Figure 9. Nickel. Thermal conductivity in arbitrary units against
pressure in thousands of kg/cm^. Results obtained with a longitudinal flow
specimen. The points lie on several lines of the same slope; the reason for
this is explained in the text.

mentioned in the description of the method. This was the first
attempt, and as often happens, succeeded better than subsequent
attempts. For some reason I was fortunate enough to get the wire
into place without introducing strains into the thermo-couples, and
the results showed a gratifying regularity. The results of the final
run with this second specimen are shown in Figure 9. It is seen that
the readings still lie on three different lines, but these lines are now

E^ECT OF PRESSURE ON CONDUCTIVITY OF METALS. 113

separated by much less than 5%, as is to be expected. A partial
run with this same specimen, which had to be discontinued because
of leak and also because of short circuit in the three-terminal plug,
gave exactly the same slope for those readings which could be obtained
as the final run. The change shown by this second sample was a
decrease of conductivity of 14.5% for 12000 kg., agreeing fairly well
with the first sample. Since the second sample gave somewhat more
regular results, it is given greater weight in the mean, which I take as
14.1%. The total correction for the effect of pressure on the trans-
mitting medium was 5% of the total conductivity, amounting to
about 33% of the observed change under 12000 kg.

The results found above give for the pressure coefficient of thermal
conductivity — O.O4I2. There are no previous results for comparison.

An incidental result obtained from the measurements with com-
mercial and pure nickel was a comparison of the absolute thermal
conductivities. The longitudinal flow method is not well adapted to
give the absolute conductivity because of the uncertainty in the cor-
rections for loss through the leads, etc. (the absolute conductivities
directly calculated average about 5% higher than the values of Jaeger
and Diesselhorst), but the comparative values of absolute conductivity
of different materials should be nearly correct. The thermal conduc-
tivity of the two samples of pure nickel was found to be 37% higher
than that of the two samples of commercial nickel. Considerable
confidence may be put in these values, as the individual readings were
very consistent; the two samples of pure nickel gave results differing
by less than 0.5%, and the results on the two samples of commercial
nickel were identical to three significant figures.

Platinum. Measurements were made on two different samples by
the longitudinal flow method. The material was obtained from
Baker, the purest which they could supply. I have no analysis, but
have the statement of Baker that the impurity is guaranteed to be
less than 0.1% and is probably not greater than 0.01%.

The measurements on platinum were scattered on three lines of a
maximum separation of about 5%, as is usual with this method.
The two specimens gave identical results, a decrease of conductivity
of 1.9% for a pressure change of 12000 kg/cm^. The observed effect
was positive, but the correction for the effect of the transmitting
medium is so large, 5.2%, as to alter the sign of the result.

The pressure coefficient of thermal conductivity as given by the
above measurements is — O.O5I6. The pressure coefficient of electrical
conductivity at 30° between 0° and 12000 kg. is +O.O5I86.

114 BRIDGMAN.

Bismuth. An attempt was made to obtain measurements on this
metal by the radial flow method, but without success. It did not
prove possible to get sufficiently good thermal contact with the fine
copper tubing, and I have already mentioned that the attempt to use
silver tubing failed because of the extremely rapid alloying action
between silver and bismuth. Measurements were finally made on
three different specimens by the longitudinal flow method.

A great deal of time was spent in the endeavor to obtain pure
material. In my previous work on the effect of pressure on electrical
resistance I had purified the metal by electrolysis. I now endeavored
to repeat this, but without success; I could not make the bismuth
form a coherent deposit. The procedure of the previous work was
exactly repeated as far as I could tell. Previously the hydrosilico-
fluoric acid had been obtained from a German source; this was no
longer available and acid from the J. T. Baker Chemical Co. was used
instead. The acid was of high purity as indicated by the analysis on
the label, but there is a possibility that some impurity not covered by
the analysis might have been responsible. I then obtained some
bismuth from the U. S. S. JNIetals Refining Co. I have to thank them
for supplying me with six pounds of the metal, in two lots. Their
product is prepared electrolytically, in distinction from the ordinary
commercial product, and is guaranteed b\' them to have less than
0.1% impurity. Ordinary commercial bismuth has about 3% im-
purity. My test for purity has been the temperature coefficient of
electrical resistance. This electrolytic bismuth showed a very low
coefficient, only 0.0022 between 0° and 30°. Ordinary commercial
bismuth is higher. Professor F. A. Saunders was kind enough to
make a spectroscopic analysis; he found a very strong silver line,
which seemed to indicate a rather considerable impurity. I con-
sulted the U. S. S. Metals Refining Co. again, and they were so kind
as to send me a second sample, which they had submitted to chemical
analysis, and found to contain only silver in detectible quantity, and
this was less than 0.06%. But the temperature coefficient of this
new sample was again very low. I attempted a purification by slow
crystallization from the melt, with the result of bringing the coefficient
up to only 0.0025. Ordinary commercial material, purified in the
same manner, showed a coefficient of 0.0034. Professor Saunders
was again kind enough to make a spectroscopic analysis and found
again the strong silver line, which seemed to him could only arise from
a rather large amount of impurity. He found traces of Cu and Pb,
and no traces of Sn, Cd, Zn, Li, As, or Sb. Professor G. P. Baxter

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 115

was now so kind as to make a quantitative determination of the silver,
and found 0.03%, confirming the conservative estimate of the U. S. S.
Metals Refining Co. I now succeeded in finding a small residue of
my original electrolytic bismuth, and Professor Saunders made a
spectroscopic analysis of this. He could find only traces of Cu and
Pb, the Cu being stronger than in the commercial electrolytic bismuth,
and some silver, evidently considerably less than in the commercial.
The conclusion seems forced that a quantity of silver as small as
0.03% can depress the temperature coefficient to half the normal
value, thus exerting an effect very much greater than such impurities
as Pb and Sn, which are present in ordinary commercial bismuth.
That difficulty would be expected in removing the silver by recrystalli-
zation is evident on an inspection of the mixed crystals diagram for
these two metals. This would also be indicated by the energetic
alloying of silver and bismuth, which made impossible the preparation
of the radial flow specimens.

Under the circumstances it seemed that the best thing to do was to
use the commercial electrolytic bismuth, with its known analysis of
0.03% of silver, in the expectation that the effect of this small impurity
is abnormally high on the temperature coefficient of resistance. I
had previously found that the effect of impurity on the pressure
coefficient of resistance is much less than on the temperature coefficient
of resistance.

The samples were made from | inch wire which had been formed
by hot extrusion in the regular way. One advantage of forming the
specimen by extrusion is that the crystalline structure is very much
finer than when the specimen is cast, and so the results are much more
likely to give the average for all the directions of a single crystal.

The thermo-couple holes were drilled in these specimens in the
regular way, but a modification was necessary in mounting the heating
element. Previously the heating element was mounted in a copper
capsule, which was cemented into a hole drilled in the end of the
specimen. This was no longer possible, because the capsule was so
large that it was not possible to drill a hole to receive it without
breaking out the walls in so brittle a material as bismuth. The
heating element was accordingly placed in a smaller hole drilled
directly in the end of the specimen. This has the disadvantage that
the terminal conditions of temperature are not so accurately defined
as with the other metals, and the motion of the heating element in
its receptacle may produce other irregularities. This was indeed the
fact; the points were more scattered than with the other metals, and

116 BRIDGM.^N.

the width of the band of scattering was greater than the 5% usually
found. The magnitude of the scattering varied with the specimen,
as it might be expected to.

In setting up the first sample, the ground of the heating element
was made to the sample itself. It has been previously exphiined that
this introduced an effect due to the Peltier heat, which is unusuallv
large for this metal. The mean of readings with two directions of the
heating current should eliminate this effect. With the other two
samples an independent ground was used, and the eft'ect disappeared.

It is to be expected that if there is any error due to heat leak along
the thermo-couple wires that it will be especially large for this metal,
whose own thermal conductivity is so small. In order to test this
point, duplicate runs were made on the third sample, first with the
ordinary copper-constantan couple, and then with a couple of " therlo"
constantan. Very nearly the same results were found, showing the
adequacy of the precautions taken to prevent leak along the couple
wires.

The third sample gave the most regular results; probably some
accidental twist or bend in the wires made them less likely to be
displaced under pressure than those of the other samples. The
results with this sample are reproduced in Figure 10.

The results found with the different samples are as follows:^!,
-38.8% for 12000 kg.; ^2, -38.8%; #3 (copper-constantan couple)
—37.3%, and ^'3, (therlo-constantan couple) — 35.5%. Mean
—37.8 %. Because of the low conductivity of bismuth the correction
for the transmitting medium is large, amounting to 13.8%, and is in
the direction to make the true effect more negative than the observed
effect.

The pressure coefficient of thermal conductivity to be deduced
from the above measurements is — O.O43I. It is to be noticed that
this is negative, and also that it is abnormally high. The abnormal
sign agrees with the pressure effect on electrical conductivity, which
also decreases under pressure. I found at 30° the average pressure
coefficient of electrical resistance up to 12000 kg. to be — O.O4212.
Bismuth was not among the metals measured by Lussana, so there
are no previous results for comparison.

Antimony. IVIeasurements were made on four samples, all by the
longitudinal flow method. The material was obtained from the J. T.
Baker Chemical Co. It was supposed to be especially pure, although
I have no analysis. Antimony from the same source was formerly
used by the Bureau of Standards to give a fixed melting point, but

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 117

their experience was that although the chemical analysis might show
very little impurity, there was nevertheless present in all antimony
from American sources some slight impurity which was sufficient to
displace the melting point by several degrees. Presumably my anti-
mony suffered from the same impurity.

Two of my samples were made from cast antimony and two from
extruded metal. The metal was cast by pouring it into a groove in a
massive iron block to a thickness of a trifle over | inch. The chilling
was hence very rapid, and the crystalline structure very fine. From

1500

0

10

12 3 4 5 6 7 8

Pressure, Kg. / Cm.' X 10

Bismuth

Figure 10. Bismuth. Thermal conductivity in arbitrary units against
pressure in thousands of kg/cm^. Results obtained with a longitudinal flow
specimen.

this casting two pieces were machined for the longitudinal flow
method. The metal is so brittle that it was not possible to cut it with
the tool in the ordinary way, but the machining had to be by grinding.
Even then extreme caution was necessary, and there were many fail-
ures before success was attained. The wire for the other two speci-
mens was extruded at a red heat through a high speed steel die of the
required dimensions. Some little practice was needed before the
proper manipulation was found. It is possible to extrude antimony
at a considerably lower than a red heat, but with a wire as large as |

118

BRIDGMAN.

inch the product is Hkely to be very brittle, or break spontaneously
into small pieces. If the temperature is raised very close to the melt-
ing point, however, it is possible to get by extrusion a uniform straight
wire with no apparent flaws, and not as brittle as the casting.

The thermo-couple holes were drilled in the four pieces in the
regular way. The heating elements, as in the case of bismuth, were
mounted directly in small holes drilled in the ends, it not being feasible
to drill so large a hole as the use of the copper capsule would have
demanded. This manner of attaching the heating element was
responsible for the greater irregularity of the points, as also in the case
of bismuth. In one case the scattering was such and the accidental

0

I 2 3 4 3 0 7 ■-)

Pressure. Kg./Cm.'X 10'

Antimony

Figure 11. Antimony- Thermal conductivity in arbitrary units against
pressure in thousands of kg/cm-. Results obtained with a longitudinal flow
specimen.

distril)ution such that a positive sign for the effect might have been
suspected.

The readings obtained with the first of the cast specimens were the
most regular; these are reproduced in Figure 11. The thermo-couple
used with the second of the extruded specimens was therlo-constantan,
instead of copper-constantan. The readings with this were essentially
the same as with the others, thus again showing freedom from heat
leak along the wires of the couple.

The thermal conducti\dty decreases with rising pressure; the two
cast specimens gave respectively —23.9 and —26.3%, and the two
extruded specimens —24.8 and —23.9%. The mean of all four is

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 119

—24.7%. It is to be noticed that within the limits of error no differ-
ence is to be detected between the cast and the extruded specimens.

The pressure correction for the transmitting medium was 15.3% on
the total conductivity; this means that the final corrected result was
three times as large as the observed pressure effect.

The above results give for the pressure coefficient of thermal con-
ductivity — O.O42I, larger than for any other metal except bismuth.
I have previously found that the electrical conductivity of antimony
also decreases with rising pressure, and at 30° the average coefficient
to 12000 kg. is -O.O4IO8.

Lussana has also measured the effect of pressure on the electrical
and thermal conductivity of antimony, and his results are in precise
disagreement with mine. He finds that the electrical conductivity
increases under pressure, as it does for normal metals. At 25° his
coefficient, presumably to 3000 atmospheres, is O.O5874. There must
be something vitally wrong here; measurement of electrical resistance
under pressure should offer none of the difficulties of thermal conduc-
tivity, and there should be no reason for a disagreement as to sign
between different observers. The relation between pressure and
thermal conductivity Lussana finds to be distinctly not linear. The
initial change is at a rate corresponding to a coefficient of O.O525I, and
at 3000 the rate corresponds to a coefficient of only O.O5I64. So large
a departure from linearity in a metal with as high a melting point as
antimony is without precedent. It does not seem improbable that
the sign that Lussana found for the coefficients of both electrical and
thermal conductivities may be due to a closing of minute fissures
between the crystalline grains under pressure, such as Borelius and
Lindh found for bismuth.^ The departure of his thermal conductivity
from linearity is in accord with this suggestion.

Petroleum Ether. It has already been explained that it was neces-
sary to determine the absolute conductivity and pressure coefficient
of this substance in order to obtain the correction due to the effect of
pressure on the transmitting medium in the longitudinal flow method.
The method adopted for determining these constants for petroleum
ether was a radial flow method, and demanded very little change in
the apparatus already used for metals. The apparatus is shown in
Figure 12. It consists of an inner cylinder of copper held concen-
trically within an outer hollow cylinder, which in turn fits closely
inside the pressure cylinder, and is maintained concentric with it by
the same spring device that was used for the metals. The petroleum
ether fills the annular space between the two copper cylinders. The

120 BRIDGMAN.

axis of the central cylinder contains a linear source of heat, that is a
wire carrying a current, precisely as for the metals. The difference of
temperature between the outer surface of the inner cylinder and the
inner surface of the outer cylinder is measured by thermo-couples.
These were of the same construction as for the metals, and were
mounted in fine copper tubes, which were sweated into small holes
drilled lengthwise of the cylinders. Of course with this construction
the couples could not be located exactly on the surface of either
cylinder, but the thermal conductivity of the copper is so much higher
than that of the petroleum ether that practically all the temperature
drop takes place across the annular space of the liquid, and a rough
computation shows that with the dimensions used any error from this
cause is negligible. As a precaution against failure of perfect geometri-

inn\unnnumn\vnHi«i»\\muuun»\H\nu»nunuu\u\u\»n

IMwmwwuwwwwvwwwwwwwwwwwwuwwwwTOwnwmuwuwn

Figure 12. Longitudinal section of the apparatus for measuring the
thermal conductivity of petroleum ether. The liquid is showTi shaded between
copper cylinders, with a central heating unit and two sets of thermal junctions
bridging the liquid.

cal centering of the inner cylinder in the outer one, three couples
instead of one were used, spaced at even angular intervals around the
cylinders, and these were connected in parallel, so that the reading
obtained gave the mean of the temperature differences around the
cylinder, and any geometrical imperfection is eliminated. The annu-
lar space between the cylinders was only 1.3 mm. wide. This is so
narrow as to remove any error from convection in the liquid, even at
atmospheric pressure, and it has already been explained that such
error vanishes at higher pressures because of the rapidly increasing
viscosity. No effects were found in the measurements to suggest
error from such a source.

Because of the substantial equality of temperature throughout the
copper cylinders, it is to be expected that errors from slight changes in
position of the thermo-couples, which played so large a part in the
measurements of the metals, would vanish. This is indeed the fact,
and the measurements showed a high degree of regularity, much
beyond that obtained for any metal.

In making the readings, the entire interior of the apparatus was

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS.

121

filled with petroleum ether. The same method would serve for any
other liquid which does not absorb impurity, or become conducting
under pressure. Unfortunately most of the liquids whose other
properties are best known, and which it would be most interesting to
measure, such as the alcohols, are not of this kind. To determine the
thermal conductivity of these under pressure it will be necessary to so
modify the apparatus that the liquid can be insolated from the electri-
cal leads.

I 2 3 4 5 6 7 8 9 10 II 12

Pressure, Kg. /Cm.' X 10'
Petroleum Ether

Figure 13. Petroleum Ether. Thermal conductivity in arbitrary units
against pressure in thousands of kg/cm-. Results were obtained with the
apparatus of Figure 12.

The observed results with petroleum ether are shown in Figure 13.
The greater regularity of th'fe results as compared with the metals is
manifest. The lowest pressure of these readings was 500 kg. The
reason for not going to atmospheric pressure was not error from con-
vection currents, but because at this pressure the heating effect would
have been sufficient to vaporize the ether, and so introduce error.

122 BRIDGMAN.

The effect of pressure is seen to be a large increase of conductivity,
amounting at 12000 kg. to an increase of 2.22 fold. The increase is
not linear with pressure, but there is a departure from linearity in the
normal direction, in that the change becomes proportionally less at
the higher pressures.

The initial rate corresponds to an increase of conductivity of about
20% per thousand kg. So far as order of magnitude goes, this agrees
with Lussana, who found the correction for his transmitting medium
to be at the rate of 30% per thousand kg. He did not find a departure
from linearity. Of course there is no reason to expect more than
agreement as to order of magnitude, because his transmitting medium
was a comparatively heavy oil, quite different in properties from mine.

The measurements of the effect of pressure on the thermal conduc-
tivity of liquid is a thing worth doing for its own sake, and I hope to
get the chance to make measurements on a number of others. In fact
I already have results for two alcohols and kerosene. Suffice it here
to mention that there seems to be an intimate connection between the
pressure effect on thermal conductivity and the pressure effect on the
velocity' of propagation of sound.

General Comment on Lussana's Results.

The only previous measurements of the effect of pressure on thermal
conductivity are those of Lussana. Since his results often differ
essentially from mine, even as to sign, and since this is a master of
considerable importance for theoretical considerations, some critical
survey of his results seems called for. In general, Lussana finds that
the thermal conductivity of all metals increases under pressure, and
this increase is nearly the same as that of the electrical conductivity,
so that the Wiedemann-Franz ratio remains nearly constant under
changes of pressure.

Lussana's method was an adaptation to high pressures of one origi-
nally due to Depretz and Biot. A long bar of metal has a source of
heat at one end and is immersed in a medium through which the heat
may flow away laterally. The temperature of the bar, which is as-
sumed constant across the section, is measured at three equi-distant
points along it, and in terms of the two differences of temperature thus
obtained, a relation can be found between a certain geometrical factor
and the ratio between the thermal conductivity and the lateral con-
ductivity into the surrounding medium. The essential difference
between this method and mine is that in mine there is a source at one
end of the bar and a sink at the other, so that nearly all the heat input

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 123

flows through the bar and out at the other end, and only a compara-
tively small part is lost laterally to the surroundings; whereas with
Lussana all the heat input flows out laterally. In Lussana's method
the correction for the efl^ect of pressure on the transmitting medium
affects directly the entire heat input, whereas in my method the pres-
sure correction is to be applied only to that part of the heat input
which escapes laterally.

My most serious criticism of Lussana's method concerns this cor-
rection for the transmitting medium. The magnitude of the correc-
tion is about 30% per thousand kg., whereas the order of magnitude of
the changes of thermal conductivity of the metals is at most only 3%,
or one tenth of this. This demands that the effect of pressure on the
transmitting medium be known ten times well as the final result for
the metal. Nevertheless, Lussana determined the correction for the
liquid to only one significant figure; as a matter of fact there is a mis-
print in his paper, which made the correction appear to be at the rate
of 300% for one thousand kg. I inquired about this in a letter to
Lussana, and he told me that the decimal point had been displaced one
figure, and that the correct result was 30%, agreeing with my own
results as far as order of magnitude goes. Having determined the
correction to one significant figure, not even noticing the departure of
the effect from linearity with pressure, Lussana gives his coefficient for
metals to three significant figures. Three significant figures for the
metal would have demanded at least four significant figures in the
correction.

Lussana states that his results were computed from the observa-
tions by the method of least squares ; he does not anywhere reproduce
a single set of observations, nor does he state the probable error of his
results, sui'ely a significant omission considering the method of
computation. There is no clue in his paper to the accuracy to be
attached to his results.

There seems to be almost no correlation between Lussana's results
and my own. In only one case, that of zinc, do we find the same sign
for the change produced by pressure in the Wiedemann-Franz ratio.
It seems to me that for the present we are justified in assuming that
there are large errors in Lussana's results.

Discussion.

Probabl}' the most significant theoretical conclusions from the
aljove data may be derived from the pressure coefficient of the Wiede-
mann-Franz ratio. The classical electron theory would lead us to
expect that the coefficient would be zero, since the ratio is the same for

124

BRIDGMAN.

all metals at the same temperature, and the same metal under different
pressures at the same temperature is merely a special case of two
different metals. As a matter of fact the ratio is not constant, but
may either increase or decrease with increasing pressure; in the ma-
jority of cases it decreases. The average values of the coefficient
between 0 and 12000 kg. are shown in Table III.

TABLE III.

Metal

C'ocllicicril of

W iedciiiaiin-Frunz

Hatio

Pb

+O.O56

Sn

+0.063

Cd

-O.O5I7

Zn

-0.062.1

Fe

-O.O52O

Pt

-0.063.5

Ag

-O.OsTO

Cu

-0.0693

Ni

-o.oa3

Sb

-O.O4IO

Bi

-O.OiK)

My own theory of electrical conduction attempted to explain the |
Wiedemann-Franz ratio,® and to do this, I imagined the .same sort of
mechanism of conduction as the classical theory. I still can see no
reason to suppose that the most important part of heat conduction is
not as imagined by the classical theory; the success of the theory in
accounting for the numerical value of the ratio, which is approximately
constant for the different metals, (it may vary from 6.38 X 10^" for
aluminum to 9.14 X 10'" for bismuth), is too striking to be put aside \
with no substitute. At the same time it is evident that the account
given by the classical theory cannot be complete; no account has been
taken of the conduction by the atoms, and the agreement of the
theoretical with the experimental value is not as close as we must '
demand of a finished theory.

It is natural to look to the still unexplained part of thermal con-
ductivity to account for the departures from constancy of the ^Yiede-
mann Franz ratio under pressure. The part of the conductivity

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 125

which is due to the electrons would be expected to have the same
pressure coefficient as the electrical resistance (except for a possibil-
ity to be mentioned later); the remaining part must be capable of
either positive or negative variation under pressure, and must be of
the right order of magnitude.

In the first place, let us consider the possible magnitude of the
non-electronic part of heat conduction. The first deduction of the
theoretical value of the Wiedemann-Franz ratio, given by Drude, was
an elementary one, in which certain simplifying assumptions were
made, particularly that the velocities of all the electrons were the
same. Later Lorentz gave a more exact discussion, taking account of
the ^Maxwell distribution of velocities among the electrons, and ob-
tained a value for the ratio only two thirds of that of Drude. The
discussion of Lorentz has later been verified by Bohr and others. The
elementary value for the ratio is much closer to the experimental
values than the more rigorous one, but still lies somewhat low. The
failure of the more exact value to agree more closely with the facts
has been regarded by some as a blot on the classical theory, but by
others is regarded rather as to the credit of the theory, because the
Wiedemann-Franz ratio as calculated by the elementary theory was
felt to be too close to the experimental value to sufficiently allow for
the atomic part of the conduction.

I shall take this latter point of view, and consider that the value for
the Wiedemann-Franz ratio calculated by Lorentz represents the part
due to electronic conduction, and that the dift'erence between this
theoretical value and the actual value represents the part of the heat
conduction that must be accounted for in other ways. This point of
view at once imposes certain numerical limits on the changes under
pressure that it should be possible to obtain experimentally. For the
total change of thermal conductivity under any pressure must never
be so great as to more than wipe out the part of the conductivity which
was initially ascribed to the non-electronic part. This means that the
total decrease of thermal conductivity, after allowing for a change
equal to the change of electrical conductivity, must not be greater
than the difference between the total initial thermal conductivity, and
the part given by Lorentz's expression. In practise this imposes a
restriction only when the thermal conductivity increases under pres-
sure less rapidly than the electrical conductivity. An examination of
the results obtained in this paper will show that this condition is met
in all cases. The condition imposed is most restrictive in the case of
nickel. Under 12000 kg. its thermal conductivity decreases by 14.5%,

126 BRIDGMAN.

and the electrical conductivity increases by 1.8%. The sum of these,
16.3%, is an upper limit which the fractional part of the total con-
ductivity due to the non-electronic part must not exceed. Now the
theoretical value for the Wiedemann-Franz ratio is 4.3 X 10^'' (Lo-
rentz's value), and the experimental value for nickel is 6.99 X lO^**.
This allows the possibility of 39% of the thermal conductivity initially
being of non-electronic origin, which is more than twice the extreme
set experimentally. It would seem that under these conditions, when
so comparatively large a part of the atomic conductivity has been
wiped out by pressure, that the relation between conductivity and
pressure must depart from linearity. The experimental accuracy
was not great enough, however, to show such a departure.

Further consideration of the theoretical significance of these results
is reserved for a forthcoming paper in the Physical Review.

Summary.

Two methods are described for measuring the thermal conductivity
of metals under pressure. The first of these is a radial flow method,
which has many theoretical points of advantage, but is of limited
applicability in practise because of the difficulty of getting metals in a
condition of sufficient homogeneity. The second is a longitudinal
flow method, the essential of which is the small size of the specimen.
The irregularities of the individual readings by the second method are
greater than by the first metliod, but the eft'ect of inhomogeneities is
less and different specimens of the same metal will give the same result.

Measurements of the effect of pressures to 12000 kg/cm^ on the
thermal conductivity of 11 metals have been made by one or the other
of these methods. The effect may be either positive or negative, and
is more often negative than positive. In only two cases, lead and tin,
does the Wiedemann-Franz ratio increase under pressure; for the
other metals it decreases, and sometimes by large amounts. In addi-
tion to the metals, the pressure coefficient of thermal conductivity of
petroleum ether has been measured. The conductivity increases by a
factor of about 2.2.

The only previous measurements have been by Lussana, who ob-
tained results entirely different from those found here. His method is
criticised in some detail, chiefly on the basis of the uncertain correc-
tion for the lateral loss of heat to the pressure transmitting medium.

These results indicate that a fairly large part of thermal conduction

EFFECT OF PRESSURE ON CONDUCTIVITY OF METALS. 127

in a metal is performed by the atoms. Theoretical reasons are given
for estimating the atomic contribution to the thermal conductivity as
50 per cent of the electronic contribution.

I am much indebted to the skill of my assistant Mr. J. C. Slater,
who made a large number of the readings. It is also a pleasure to
acknowledge my indebtedness to the Rumford Fund of the American
Academy of Arts and Sciences for a grant with which a part of the
expenses were defrayed.

1 P. W. Bridgman, Proc. Amer. Acad. 52, 571-646, 1917, and 56, 59-154,
1921. Phys. Rev. 9, 269-289, 1917, and 17, 161-194, 1921.

2 S. Lussana, Nuo. Cim. 15, 130-170, 1918.

3 C. Niven, Proc. Roy. Soc. 76, 34-48, 1905.

4 P. W. Bridgman, Proc. Amer. Acad. 53, 267-286, 1918.

5 G. Borelius und A. E. Lindh, Ann. d. Phys. 51, 607-620, 1916.

6 Reference 1, fourth paper.

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57-6

Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 6 — April, 1922.

THE FAILURE OF OHM'S LAW IN GOLD AND SILVER
AT HIGH CURRENT DENSITIES.

By p. W. Bridgman.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 6.— April, 1922.

THE Fx\ILURE OF OHM'S LAW IN GOLD AND SILVER
AT HIGH CURRENT DENSITIES.

By p. W. Bridgman.

NEW YORK

SOTANJCAS,

THE FAILURE OF OHM'S LAW IN GOLD AND SILVER AT
HIGH CURRENT DENSITIES.

By p. W. Bridgman.

Received October 7, 1921. Presented October 19, 1921.

TABLE OF CONTENTS.

Page.

Introduction 1^1

Historical Survey ]^^

Outline of Method 1^5

Experimental Details |42

Dimensional Discussion of the Cooling Process 149

Various Experimental Checks and Precautions 153

Experimental Procedure and Data 159

Other Possible Explanations of the Effect 164

Computation of the Departure from Ohm's Law 166

Theoretical Discussion 168

Summary ^'^

Introduction.

It is to be expected that at high current densities the usual Hnear
relation between current and E.M.F. in a metal will break down,
that is, that Ohm's law will fail. J. J. Thomson,^ for instance, has
shown that on the basis of the classical free electron theory of metallic
conduction the current will eventually increase only as the square root
of the E.M.F. at very high values, which means that the resistance will
increase at high current densities. On the usual assumptions the
current densities at which this effect will become important are of the
order of 10'^ amp/cm^. Many attempts have been made to detect
the existence of this effect experimentally, but hitherto without suc-
cess. The chief obstacle to success is that the changes of resistance
due to heating by the heavy current are sufficient to mask the changes
of resistance due to a possible departure from Ohm's law.

By the employment of a new method of attack, which avoids errors
due to temperature rise, I have, I believe, not only succeeded in
establishing the existence of the effect, but in measuring the departures
from Ohm's law with some exactness in gold and silver. These
results are described in the following paper. I find a departure from
Ohm's law in the direction of an increase of resistance at high current
densities, the maximum effect being of the order of 1% at a current
density of 5 X 10*' amp/cm-.

132 BRIDGMAN,

Historical Survey.

A few attempts were made to detect the existence of the effect
before Maxwell, but we may pass these over as not approaching in
sensitiveness the method of ^laxwell.^ ^Maxwell was the chairman
of a committee, the other members of which were J. D. Everett and
A. Schuster, appointed by the British Association in 1876, to investi-
gate the accuracy of Ohm's law. Two experimental methods were
used, both apparently proposed by Maxwell; the experiments were
performed by Chrystal.

The first was a substitution method, by which the resistances of
five similar coils were compared in various combinations of two in
parallel and two in series against a single one. The current density
in the single coil was thus double that in the multiple arrangement,
and if there is an effect of the kind sought, the resistances should be
different. A small positive result was found, but was ascribed to
errors in view of the fact that the second method, which was much
more delicate, gave negative results.

The current densities employed in the first method were so low as
not to cause apprecial)le heating of the wires. The second method
was such that currents large enough to heat the wires to incandescence
could be used. A heavy and weaker current were passed alternately
in rapid succession through a fine wire, which was made one of the
arms of an ordinary bridge. The period of alternation was so high
that there were no appreciable cooling effects. Observations were
made with a galvanometer of period long compared with that of the
alternations. The apparent resistance was read first with the large
and the small currents flowing in the same direction, and then with the
small current reversed. Let us suppose that there is an effect of the
kind sought, which means that the resistance for the large and the
small current is not the same. If the galvanometer indicates balance,
it must be because it is really off balance for both currents, to the one
side for the large current, and to the other side for the small current.
If now the small current is reversed the galvanometer will be off balance
to the same side for both currents, and there will be a steady deflection.
Hence if there is an effect, the balance will be altered by changing the
direction of the small current. There were difficulties in the method.
The period of alternation had to be chosen as high as 60 per second in
order to avoid appreciable cooling effects in the short intervals of time
when the small current replaces the larger one. There were consid-
erable mechanical difficulties in designing an alternator of the requisite

I

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 133

constancy, for it is obvious that the durations of the large and the
small currents must be absolutely constant. A platinum contact
dipping into a mercury cup and driven by a tuning fork was used, but
always gave trouble, and the limits of accuracy were set by this part
of the apparatus.

The conclusion as usually quoted which was drawn from these
experiments was that any deviation from Ohm's law must be less
than one part in 10^^. This statement needs some expansion; it is
obvious that no measurements can be made directly to this degree of
accuracy. For one thing, changes of temperature of the surroundings
absolutely preclude the direct attainment of any such accuracy as this.
The meaning of the statement is as follows. Maxwell remarked that
any departure from Ohm's law must involve only even powers of the
current ; it is obvious that the first power cannot enter, for if so there
will be a dependence of resistance on the direction of the current, which
cannot be the case in an isotropic material. The initial departures
from the law may be supposed to be proportional to the square of the
current density. The maximum current density employed by Max-
well was 5.6 X lO"* amp/cm^. At this density the resistance was found
to have changed by not as much as 0.3%. Assuming the square law,
this means that at a current density of 1 amp/cm- the departure from
Ohm's law cannot be more than 1 part in 10^^. The original paper
contains the careful statement of the conclusion in this form.

The metals used by Maxwell were cylindrical wires of platinum
(0.042 mm. diameter), German silver (0.051 mm.) and iron (0.14 mm.).
The maximum current densities were respectively 3.4, 1.2, and 5.6 X
10* amp/cm2.

Recently Wenner ^ of the Bureau of Standards has objected to the
second form of Maxwell's experiment. He has repeated a modifica-
tion of the first method with very much higher accuracy, and finds no
deviation of as much as 3 parts in 10^. His objection to the second
experiment is that negative results might be obtained even if there is a
departure from Ohm's law. Thus if the potential difference across
each arm of the bridge is proportional to the square of the current
flowing through it, negative results will be obtained, because the
bridge will stay in balance for any current, large or small. More
generally, negative results will be found if the potential difference
across each arm is the same function of the current for each arm. It
is to be noticed, however, that this is not the manner of departure
from Ohm's law which is to be expected. The departure sought for is
not a function of the total current flowing through the resistance, but

134 BRIDGMAX.

is a function of the current density. Furthermore, this function is
known to be nearly independent of current density for low values.
Doubling the total current in a conductor of small section will produce
a much greater departure from Ohm's law than doubling the same
current in a conductor of larger section. This is the only sort of
departure from Ohm's law which we are looking for, or indeed which
seems at all likely, and in my opinion Maxwell's experiment is entirely
competent to answer this question up to its limits of error. As regards
the other sorts of departures from Ohm's law, I believe that Wenner's
position is sound.

Since ^Maxwell, very few attempts have been made to detect the
effect, probably because of the appalling sensitiveness of ^Maxsvell's
experiment as usually quoted. Lecher * in 1906 made measurements
on platinum and silver wires. He attempted to correct for the tem-
perature effect in the platinum by observing the thermal expansion
of the wire when carrying a very heavy current, and comparing the
resistance to this heav\' current with the resistance to a feeble current
passing through the wire when heated artificially to have the same
thermal expansion as when carrying the heavy current. The diameter
of the wire was 1 mm., and the current density was 3.8 X 10^ amp/cm-;
there was no effect greater than 0.1%. The silver wire was 0.03 mm.
in diameter. It was placed in a rapid stream of water, and the
resistance measured under a current increasing until it fused. No
temperature correction was applied. The apparent temperature when
the wire burned out, using the ordinary temperature coefficient of
resistance, and assuming that Ohm's law is true, was 130°. It is to
be expected that this temperature would be somewhere between 100°
and the melting point of silver. Hence within limits of error which
may be several hundred percent, the experiment is consistent with
Ohm's law. The accuracy is very much less than that of Maxwell;
but on the other hand, the current density is ver\- much higher,
reaching a maximum of 1.4 X 10^ amp/ cm'-, 25 fold greater.

H. Rausch von Traubenberg ^ has attempted to avoid the tempera-
ture difficulty by employing a condenser discharge of very short
duration. The current densities that may be reached are higher than
previously realized, attaining in one case a maximum of 10^ amp/cm"-.
But the measurements of potential are inaccurate, being estimated
by the break-down of a spark gap in air, and there are other sources of
error arising from distributed capacities and inductances and the
necessity of a long range extrapolation. I estimate that the error may
certainly be as high as 10 or 15%. Within these limits, no effect was

FAILURE OF OHM S LAW AT HIGH CURRENT DENSITIES.

13;

found. The material used was constantan, of a diameter of 0.1 mm.
The maximum current density reached produced a potential gradient
in the wire of 400 volts per cm. With "Kruppin" wire, a gradient
of 1500 volts/cm. was reached, although with not so high a current
density. In spite of the very considerable error, these experiments
have pushed the boundary of the validity of Ohm's law considerably
farther back than the previous limit. "With regard to the materials
used, it should be said that the maximum departure from the law is
to be expected in those materials which, other things being equal, have
a long free electronic path, and which are presumably the best con-
ductors. From this point of view the most promising place to look
for the effect is in silver, copper, and gold. Of course, on the other
hand, it is to be said that in poor conductors it is possible to reach
much higher potential gradients for the same current density, so that
this advantage may outweigh the disadvantage.

Outline of Method.

In the method which I have used, the specimen exposed to the high
current density is made one arm of a bridge, and its resistance is meas-

FiGURE 1. Skeleton of the bridge
connections.

ured simultaneously for a heavy
direct current and a small superposed
sinusoidal current of acoustical fre-
quency. If there is a deviation from
Ohm's law the resistances to the two
currents will not be the same. The
following considerations show why
this is. It must in the first place be
remembered that a bridge is an instrument for testing the equality
of potential of two points in a net work. In Figure 1, x denotes
the arm of the bridge which contains the fine wire in which the

Figure 2. Hypothetical re-
lation between current (I) and
e.m.f. (E) not satisfying Ohm's
law.

136 BKIDGMAN.

current density is to be high. In this branch we suppose that
Ohm's law does not hold, but the relation between current and E.M.F.
is given by a curve of the form shown in Figure 2. The other arms of
the bridge, Ro, R3, and Ri are made of larger wire, in which the current
density is always small, and hence their resistance is ohmic. Assume
for the moment that it is possible to balance the bridge simultaneously
for D.C. and A.C. Now let a heavy direct current h flow through z
and Ro and a direct current I3 through R3 and Ri. Also let a small
alternating current h sin w/ flow through x and R2 and is sin w< flow
through R3 and Ri. The difference of potential between the ends of
X is

Ii tan 6 + ?'i tan 6' sin wt

The potential difference across the galvanometer is

(/i tan 6 + i\ tan 6' sin ut) — {I3 + is sin oi)t) R3.

Since the extremities of Ro and Ri join, their potentials are equal, or

/i (tan 0 + i?2) + h (tan 6' + R.2) sin o^t = {1 3 + (3 sin w^ {R3 + ^4).

This splits into two equations

7i tan 6+ hR2= I3 (i?3 + Ri) (1)

ii tan d' + h /?2 = is (Rs + Ri) (2)

Now if the galvanometer is balanced for D.C. the constant part of
the potential difference across its terminals must vanish, or

7i tan 0 - /a i?3 = 0.

Combined with (1) above we get

h R2 - hRi= 0,
or, dividing

tan d R3

Ro Ri

(3)

In the same way, if the bridge is balanced for A.C. the alternating
part of the potential difference across the galvanometer vanishes, or

ii tan 6' = is R3

Combined with (2)

ll XL2 ^ I3 Ri

and dividing

tan e' R3

XV2 Ri

(4)

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 137

' Now conditions (3) and (4) are incompatible unless tan 6' = tan 6.
Except for singular points, this means that the relation between
current and E.M.F. in the arm x must be linear, or Ohm's law is satis-
fied. Conversely if Ohm's law is not satisfied, the setting for balance
will not be the same for D.C. and small A.C., tan 6 may be called the
direct current resistance, and tan 6' the alternating resistance. They
may both be determined by the ordinary bridge formulas by first
adjusting i?3 and Ri for D.C. balance, and then readjusting them for
A.C. balance. The departure from Ohm's law at a given current
density, which I denote by D, is the fractional dift'erence between
tan 6 and tan ^o, the tangent to the curve at the origin, that is, the re-
sistance under small currents. This definition gives the equation for D :

tan 6 — tan ^o
tan ^0

It is now obvious that if we measure 6 and 6' at all points of the curve
we can find the curve itself by an integration, hence the tangent at
the origin, and so the departure from Ohm's law at any given current
density. The mathematical details of this deduction will be given
later.

It is evident that the method in simple outline, as given above,
avoids the difficulty of the unknown temperature correction because
both currents are fiowing simultaneously, and hence the temperature of
the wire is the same to both. There is, however, a temperature effect
of a different kind from that usually met in this sort of experiment
which arises as follows. The total rate of heat input under the cur-
rent is proportional to the square of the total current, that is to
(/i + ii sin oj/)-. The 27i ii sin cot term in this expression denotes
an alternate heating and cooling, so that superposed on the large
steady temperature increase there is a small sinusoidal fluctuation of
temperature whose average is zero. But this small fluctuation of
temperature produces a small fluctuation of resistance, and a heavy
current flowing through a fluctuating resistance gives rise to a fluctu-
ating difference of potential at the terminals of the resistance. There
is, therefore, effectively introduced into the .r arm of the bridge a
spurious additional sinusoidal E.M.F. which changes the A.C. balance.
The action is similar to that of a microphone.

We now discuss mathematically this spurious E.M.F. and the experi-
mental means taken to eliminate its effects. We are for the present
concerned solely with this effect, and in the following treat the resist-
ance as ohmic. Any residual effect left after the elimination of this

138 BRIDGMAN.

"microphone action" constitutes the departure from Ohm's law for
which we are searching. Various tacit assumptions will be made in
the course of this discussion which will be justified later.

Return to Figure 1 for the bridge, and consider the heating effect
in the arm x, treating its resistance as ohmic. The heat input is pro-
portional to (/i + ^1 cos caty, where ii is small compared with 7i.
Expanding this, neglecting the term in ij^ the rate of heat input is
proportional to /i^ + 2/i ii cos cot, that is, there is a constant input
proportional to 7i^, independent of the presence of the A.C., and there
is a sinusoidal heating and cooling of the same period as the A.C.
which is proportional in intensity to both the D.C. and the A.C.
Under this heat input the conductor experiences a change of tem-
perature, which may be analyzed into a constant change dependent
only on the D.C, and a small alternating rise and fall, of the same
period as the A.C, but not necessarily in phase wath it. The factor of
proportionality which determines the amplitude of the alternating part
is not the same as that which determines the amplitude of the steady
part, but is a function of the period, becoming less for higher fre-
quencies. Let us call the stead^^ change of temperature to, the ampli-
tude of the in-phase part of the alternating part ri, and that of the
out-of-phase part to. If the heat input is removed rapidly, t^ will be
small compared with ri. The increase of temperature above that of
the surroundings is therefore to + n cos cot -\- t2 sin cot. Now if Rq
is the initial resistance at the temperature of the surroundings, a the
temperature coefficient of resistance, and R the actual resistance
when the current is passing, we have

R = i?o [l + a (to + Ti cos cot + T2 sin wt)].

The potential difference across the terminals of x is

R{li + ii cosoj^).

Expanding this by substituting the value of R above, and using the
relations

cos^ 0 = i (1 + cos 26), 2 sin 6 cos 6= sin 2d,
we get :

Potential difference = i?o( A(l + arc) + I hcxTi}

-f RolhaTi + fi(l + q:to)} COS wt
+ Ro{liaT2} sin cot
+ i?ol| ^i«Ti| cos 2cof
+ Ro\^ iiocTo} sin 2cot.

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 139

Using the same notation as before for the current in the other arms of
the bridge, we have at D.C. balance

and

Roh il-\-aTo-\-^aTij

hRo = hRi.

= ^3 ^3,

Dividing to ehminate the currents, we obtain

i?fl

hi

1 + ocTo + lari - r

= jRo

Rs

This shows that in general, even neglecting the cos^ term in the
heat input as we have above, the D.C. balance will depend on the A.C.
But this effect is doubly small, since ri is small compared with to and ii
small compared with /i, and hence the effect may be neglected.
The correctness of this assumption was checked experimentally.

\Yith regard to the A.C, the expression above shows that there
cannot be complete balance. There will always be higher harmonics,
and there will be an out-of-phase component (in sin co<). These terms
are small, as examination of the coefficients shows, but may neverthe-
less be perceptible. The ear can set on the fundamental alone, and so
eliminate the higher harmonics. The out-of-phase component gives
rise to a smearing out of the sharpness of the minimum. This can be
corrected by introducing another out-of-phase component to neutral-
ize it by a variable mutual inductance between input and detecting
circuits.

The equilibrium conditions for the in-phase component are

Roil
and

Eliminating the current,

R,

= is Rs

i\Ri — iz Ri-

h'

1 + a I To + n T
V '^1

i?2

Rz
Rd

The condition for A.C. balance is therefore different from that for
D.C. balance, the large term Ii/ii occurring in the expression for A.C.
balance against the small term ii/Ii in the expression for D.C. balance.

As the experiment was actually performed, Ro was kept constant,
and Rs and Rt were varied. R3 and Ri consisted of extension coils

140

BRIDGMAN,

connected to a bridfje wire, wliich was tapped by a moving slider.
Hence adjustment was made by adding to R3 an appropriate resistance,
and at the same time subtracting the same resistance from Ri.

Let us call the initial resistance for balance with no heating effect
(small D.C. or A.C. only) R^ and Ri. To maintain balance under the
heavy D.C. with no A.C, R3 must be increased by AR and Ri dimin-
ished by AR. A.C. balance with the heavy D.C. flowing is now main-
tained by an additional increase of AR' to R3 and decrease of Ri by
AR'. The conditions for balance under these three states of current
flow are:

Ro = R2 ^ (5)

lU

U.

R. I + a

= R-2

Rs + AR
Ri-AR

Ro\l+a(

To + n

'1/

R-2

R3 + AR + AR'
Ri - AR - AR'

(6)

(7)

Subtracting (6) from (7) and discarding squares and products of AR
and AR' gives

RoCtTi

1} _ 1 II

Ri

AR'iRs + Ri)

/?4- - Ri {^AR + AR')

Also neglecting hii/h compared with Ij/ii, and substituting for Ro
its value from (5) gives

Ri^

"^' /i Ri- (AR' -\-2ARy
which gives again approximately

From (6), for the D.C. setting, we get approximately

Hence finallv we have

a-

'0 —

AR

ik

1
^ R.

r\

ii

AR'

To

—

h

AR'

(8)

(9)

(10)

FAILURE OF OHM'.S LAW AT HIGH CURRENT DENSITIES. 141

If now the alternations are slow, so that at every moment the wire
is approximately in thermal equilibrium, the factor of proportionality
connecting ri with the alternating heat input is the same as that con-
necting To with the steady heat input, so that we would have

To = const Ii~ R }
Ti = const 2/iti R )

which gives, substituting above in (10),

AR'

AR

= 2.

That is, for slow alternations, the difference between A.C. and D.C.
settings due to the microphone action alone is twice the D.C. shift due
to temperature rise under the steady current, and this relation holds
no matter how feeble the alternating current. Since the steady rise of
temperature is high, because the current density has to be pushed to
the limit that the conductor will carry without burning out, it is
obvious that at slow alternations the microphone action will entirely
mask any sought for deviation from Ohm's law. The acoustical
frequencies used in these experiments were not low enough to reach
the extreme value 2 for the ratio AR' /AR. At the lowest frequency,
320 cycles, the ratio had reached about 1.2.

At rapid rates of alternation, however, the conditions of heat
transfer change. At low frequencies the thermal conductivity of the
surroundings alone determines the equililjrium; at higher frequencies
part of the heat input is used in raising the temperature of the sur-
roundings and a term enters proportional to the .specific heat, and at
still higher frequencies this term preponderates, and the factor of
proportionality between amplitude of rate of heat input and amplitude
of temperature alternation becomes proportional to the specific heat
and inversely proportional to the frequency. We shall later apply
a dimensional analysis to obtain more information about to and n,
but for the present we may write, for any frequency

and as before
This now gives

n = const /(oj) 21 ill R,
To = const I^ R.
AR'

AR

2/(a,).

142 BRIDGMAN.

At high frequencies /(w) o^ — , so that at high frequencies the micro-

co

phone effect is proportional to the reciprocal of the frequency, and it

may be eHminated by proceeding to infinite frequencies (or zero

reciprocal frequency).

The procedure suggested by this analysis was that followed in the
experiment. For a fixed D.C. the difference between the settings at
D.C. and A.C. balance (that is AR') was observed over a range of
frequencies, AR' was plotted against the reciprocal of frequency, and
extrapolated to zero. The residual, if there is one, is the effect due
to deviation from Ohm's law at the particular D.C. density in question.

This procedure was repeated for a number of currents, and so the
departure from Ohm's law obtained as a function of current density.

Before proceeding further with the theoretical discussion it will
pay now to describe the experimental details, in order that we may
have an idea of the order of magnitude of the quantities involved.

Experimental Details.

The bridge was an ordinary four gap alternating current bridge, so
constructed that inductive and capacity effects in the bridge were
negligible. The resistance Ro, which was kept constant during the
measurements on any single specimen, was a coil of heavy manganin
wire immersed in an oil bath to carry away the Joulean heat. This
resistance was approximately ec^ual in magnitude to the resistance x
which carried the high current density. The resistances R3 and Ri
consisted of heavy manganin coils connected by a slide wire, which
was tapped by a slider. The wire was about 1 meter long, with a total
resistance of about 3 ohms. The resistance of the extension coils was
five or ten times greater than that of the specimen x, and the genera-
tion of heat in them was so small that it w as not necessary to immerse
them in an oil bath.

The method of connecting the D.C. and the A.C. sources and of
tapping across with the detectors for D.C. and A.C. balance is shown
in Figure 3. The direct and alternating current sources are connected
to the same terminals of the bridge, with a large inductance L in the
D.C. line to prevent the A.C. backing into the battery, and a large
condenser C in the A.C. line to prevent the D.C. backing into the
A.C. source. D.C. balance was shown by a Leeds and Northrup high
sensitivity galvanometer of about 8 ohms internal resistance connected

FAILURE OF OHM S LAW AT HIGH CURRENT DENSITIES.

143

as shown with a high resistance i?7 in series and another small resist-
ance in shunt to cut down the sensitivity. In the latter part of this
work this galvanometer was replaced by another of less sensitiveness.
The A.C. detector was a telephone tapped between the same points
as the D.C. detector, but with a large condenser in series to prevent
D.C. getting into the telephone circuit. The telephone was tapped
across a transformer placed in this circuit. In this circuit is also one
of the coils of a mutual inductance, M, the other coil of which is in
series with the A.C. source, and is not shown. This makes possible

FiGUEE 3. Details of the bridge connections.

the elimination of the out-of-phase component by suitable adjustment.
The A.C. was prevented from entering the galvanometer circuit by
the high resistance in series with it, and by an open key when the
galvanometer was not in use. The condenser in the telephone circuit
proved an unnecessary precaution, the resistance of the transformer
and mutual inductance being sufficient to prevent enough diversion of
the D.C. into the telephone line to introduce appreciable error. The
condenser was used in most of the work, but in some of the later read-
ings it was omitted. The telephone was one of 1100 ohms resistance,
made by the Western Electric Co., type 509 W. The transformer was
one of the small ones of the General Radio Co. made for this purpose,
type 166.

In Figure 3, the resistances R5 and Re which are connected to the
same points as the sources of the current constitute an auxiliary bridge.

144 BRIDGMAX.

The intermediate point was put to ground. This is the regular method
of avoiding capacity effects in the telephone. i?5 and Re were so large
that there was no serious diversion of current from the bridge.

The D.C. source was a storage battery connected in series with
a General Electric Co. ballast lamp (iron filament in hydrogen) of
1.4 amp. capacity. In series with the lamp was a commercial ammeter
with which the constancy of the input current was checked. Any
desired fraction of the output of the battery could be diverted from the
bridge by a variable shunt between the lamp and the bridge. The
actual current into the bridge or through the sample was not measured
directly, but was computed from the ammeter reading, and the resist-
ances, which were measured with the requisite accuracy. If a heavier
current than 1.4 amp. were needed, two ballast lamps could be used
in parallel. The dimensions of the sample were such that in almost
all cases the maximum current that it could carry without burning
out was not over 1 amp.

The source of A.C. was a vacuum tube oscillator. The methods of
connecting this were the canonical methods, and need not be gone into
here. I am much indebted to Professor L. E. Chaffee and Mr. S.
Ballantine for assistance and advice in setting up this circuit. For
the first readings a Western Electric Co., hot lime transmitting tube
Type VT2 was used, but this soon was burned out, and for most of
the work a G. E. transmitting tube, type T Pliotron, was used.

Not only does the present differ from preceding attempts in the
method of measurement, but also in the form and dimensions given
to the metallic resistance carrying the high current density. In all
preceding work the metal has been in the form of a fine wire, of
diameter of the order of 0.001 inch or more. An elementary discus-
sion will show that a wire of these dimensions will carry only a limited
current of the order of lO'' amp/cm- in the most favorable case. The
limit is reached at a rate of heat input so high that the interior of the
wire is at the melting point while the outer surface is at 0°, the thermal
conductivity of the metal just sufficing to carry off the heat input
under the temperature gradient so produced. It is possible to gain
somewhat by rolling the wire flat as a galvanometer suspension, but
not a great deal. An elementary dimensional discussion will show
that the only way to gain on the upper limit of current density is by
decreasing the thickness of the specimen, so that a given difference of
temperature between interior and exterior will give a larger tempera-
ture gradient, and therefore a greater heat dissipation. The thinnest
metal that can be obtained is in the form of beaten leaf, and it was

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 145

with gold and silver leaf that I made the measurements. I was afraid
to try films deposited by cathode spattering because it did not seem
to me that the condition of the metal was sufficiently like that of
ordinary metals, whereas the leaf may be supposed to be more like
the massive aggregates of metal of ordinary dimensions. However,
a few experiments at the end with spattered films of gold gave the
same results as beaten leaf of the same thickness, and my fears are
probably ill founded. The next work that suggests itself in this
connection is an extension of the results found here for silver and gold
to other metals, using spattered films.

The thickness of the gold and silver leaf was determined by weighing
a known area, assuming in the calculation that the density is the same
as that of ordinary metal. The thickness of the silver leaf was 2.0 X
10~^ cm. Three thicknesses of gold were used, 8 X 10~®, 1.67 X 10"^
and 5 X 10-^.

It was with some difficultv that I obtained the intermediate thick-
ness of gold. Gold is beaten out in comparatively large quantities
at a time in books of gold beaters skin, a great many thicknesses
together. The last stage of the beating reduces the thickness by a
factor of 6, from 5 X 10~^ to 8 X 10~^, and only these thicknesses can
be obtained commercially. I am indebted to ISIr. Drew of Province
Court, Boston, for his kindness in interrupting the last stage of the
beating, and at some trouble removing a few of the partially beaten
leaves from a large book. The sheets so obtained from the partially
completed process were not nearly as perfect as those from the nor-
mally completed beating.

The state of the metal in a thin film differs in some unknown
respects from that in larger masses. It has long been known that the
specific resistance of spattered films is several times higher than that
of the massive metal. ^ The specific resistance of gold films has been
shown to be very high for very small thicknesses, to decrease rapidly
as the thickness increases up to a certain point where the resistance
is about five times normal, from here on to remain nearly constant
over a range of thickness of about 20 fold, and beyond this point to
decrease to the normal value. The temperature coefficient of resist-
ance of spattered films has been frequently observed to be negative.
The films of leaf metal used in this work did not show such great
abnormalities as the usual spattered films, but nevertheless the
resistance was very different from that of the massive metal. The
temperature coefficient of my gold leaf was about 0.0015 between 0°
and 30°, and was the same for the two thicknesses with which most of

146 BRIDGMAN.

the measurements were made, namely 8 X 10"® and 1.67 X 10~^ cm.
The temperature coefficient of the silver was much more nearly normal,
and was 0.0032, its thickness being 2.0 X 10"^. The specific resistance
of these metals was much higher than normal. That of the thinnest
gold varied from 8.4 to 19.7 X 10"^ ohms per cm. cube, average 11.6.
The spattered films of the same thickness varied from 15.4 to 2.3.8 X
10~^ average 19.2. The normal value for massive gold is 2.42 X 10~®.
The thicker gold had a higher resistance than the thinner, varying
from 9.75 to 18.5, average 13.3 X 10~^. The cause of the high specific
resistance of the spattered gold is doubtless to be found partly in the
lack of crystalline structure and perfect coherence, due to its manner of
formation. The high resistance of the leaf metal, on the other hand,
is doubtless in large part due to mechanical imperfections. Examina-
tion of the thinnest leaf under a microscope shows a large number of
folds and creases; it is practically impossible to spread the leaf on a
surface so that it will lie smoothly in a single unwrinkled layer. The
mechanical imperfections in the thicker gold were even greater than in
the thinner, as already mentioned, doubtless partly due to the inter-
ruption of the beating process at a disadvantageous stage. Two
samples of gold 5 X 10"^ thick had resistances of 15.0 and 10.0 X 10~^
not essentially different from the other pieces.

The specific resistance of the silver leaf varied from 3.5 to 5.1 X
10-^ average 4.1 X lO"*'. The normal value for silver is 1.63 X 10-^
It is seen that silver lies much closer to the normal than does gold.
Under the microscope it too was full or minute imperfections, but of a
different character from the gold. There were no folds, but a number
of minute round perforations through the leaf. |

It would doubtless have been most desirable if these experiments
could have been performed on more massive samples with the normal
electric constants, but the necessity of conducting away the heat seems
absolutely to preclude such a possibility.

The resistance has to be artificially cooled if current densities high
enough to obtain an appreciable effect are to be reached, and the
problem of mechanical support had to be solved. For this purpose
the leaf metal was mounted on a piece of glass. The glass was covered
with a very thin coat of insulating enamel by dipping it in a very dilute
solution of the enamel in chloroform, the leaf metal was blown or
otherwise spread over the surface, and was then baked at 210° until
the enamel was hard. Gold or silver leaf so attached to the surface
of glass is full of minute flaws, but by a search under the microscope
parts can usually be found of sufficient homogeneity. The leaf was

FAILURE OF OHm's LAW AT HIGH CURRENT DENSITIES. 147

cut SO as to leave a narrow isthmus of the shape shown in Figure 4.
It is the isthmus that carries the high current density. Connection
to the leaf on either side of the isthmus was by means of fine leads of
copper caught to the leaf with a touch of solder. A special tool had
to be made for cutting the isthmus. The point of a very fine needle
Avas made to travel in any desired direction across the surface of the
foil, scratching through to the glass, by an arrangement of two screws

Figure 4. The isthmus form of the specimen.

at right angles to each other. With this device, under the lens of a
microscope, the isthmus could be cut to a high degree of precision.
The dimensions of the isthmus varied somewhat from specimen to
specimen, but the length was of the order of 1 mm. and the width of
the order of 0.1 nun. The dimensions of each specimen were measured
with a microscope.

The specimen was cooled by a stream of water flowing across the
isthmus at right angles to its length. This water was delivered from
a small glass nozzle suitably held and directed. At first kerosene was
used as a cooling liquid, in order to avoid danger of short circuit, but
the cooling was not sufficiently rapid and the desired current densities
could not be reached. I also tried currents of compressed air and
hydrogen, with results very much inferior to those even for kerosene.
In order to protect the specimen from the short circuiting action of
the water, it was covered on the upper surface, except over the isthmus
itself, with an additional coating of enamel. Any enamel on the
isthmus itself is fatal. At first I used tap water, but this was too
conducting. Ordinary distilled water, however, proved to be suffi-
ciently insulating so that no short circuiting effects from it could be
detected. After the distilled water hatl been used for some time
slight irregularities began to appear due to increasing conductivity
from miscellaneous impurities picked up from the air of the room;
these irregularities could be made to disappear by replacing the water
with fresh.

It is necessary that the velocity of the cooling water be maintained
constant. For small streams, a syphon arrangement was satisfactory,
but for more rapid delivery the proper head was maintained by air

148 BRIDGMAN.

pressure obtained from a large compressed air bottle, and was regulated
to any desired value with a safety valve of special construction.

In addition to the gold and silver leaf, I made attempts to detect
the effect in manganin wire 0.001 inch thick rolled flat, and with
Wollaston wire of platinum about 0.00006 inch thick. The attempt
with manganin failed because the heating effects were too large, due
to the dimension of the specimen. The attempt with platinum failed
because of mechanical difficulties in mounting the wire and su)>jecting
it to a stream of water. It is possible that with more pains it might
be feasible to obtain results with platinum in this way.

The thickness of the leaf metals used in this experiment was more
than sufficiently small to ensure conduction of the Joulean heat
developed by the heavy current without excessive rise of temperature.
To illustrate the order of magnitudes involved let us consider an
example. One specimen of silver that gave good results had the fol-
lowing dimensions: Length 0.536 mm., width 0.072 mm., and thick-
ness 2 X lO"'' cm. The maximum current before the specimen burned
out was 0.745 amp., and the initial resistance was 1.30 ohms. The
heat input into this specimen was therefore:

rr . (.745)2X1.30 ,

Heat input = -tTo S^^ cal/sec.

4.18

= 0.173 gm cal/sec.

This heat flows out through the area of one face, which is 0.0536 X
0.0072 = 3.87 X 10-* cm^. The heat outflow per unit area is therefore
(0.173)7(3.87 X 10^) = 4.5 X 10- cal/sec cnr. Since the thermal
conductivity of silver is approximately unity, the temperature gradi-
ent required to drive this thermal stream is 4.5 X 10- degrees per cm.
But the total thickness of the film is 2 X 10"^, so that the extreme
temperatiu'e difference in the specimen between front and back face
is 4.5 X 10-' X 2 X 10-» = 0.009°.

It is of interest to compare the heat input with the heat capacity of
the specimen. Its volume is 3.87 X IQ-^ X 2 X 10"^ = 7.8 X IQ-^cml
Taking for the specific heat of silver 0.056, and the density as
10.5, we find the heat capacity to be 10.5 X 0.056 X 7.8 X 10-^ =
4.6 X 10"^. If there were no heat outflow the temperature would rise
at the rate of (0.173)/(4.6 X 10-^) = 0.038 X 10^ = 38,000,000
degrees per second.

The magnitude of the steady temperature rise actually observed in
this specimen was about 50°, or 5000 times more than the mean rise
of temperature required to procure conduction of the heat input out of
the metal itself. It is ol)vious, therefore, that practically all the

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 149

r
resistance to heat out flow is in the thin layer of cooHng water immedi-
ately in contact with the surface of the metal. Our previous estimate
of the maximum current density that a wire can carry must be cut
down many fold. A 0.001 inch wire cannot carry 10'^ amp/cm^ under
practical conditions. It still remains true under these new conditions,
however, that the only change of dimensions of the specimen which
will increase the maximum obtainable density is a decrease of diameter.
Our numerical example shows that the body of the metal can be
regarded as approximately at a single constant temperature, both for
the steady rise of temperature and for the alternating fluctuations.
In the mathematical discussion above it was assumed that the tem-
perature of the metal could be specified by a single number; the
numerical discussion just given constitutes the justification of this.

Dimensional Discussion of the Cooling Process.

In order to get further in our understanding of the phenomena we
must now consider in some detail the steady and alternating changes
of temperature ro and ri, remembering that practically all the resist-
ance to heat outflow is in the cooling water. It is of course not possible
to give an exact solution; the best that we can do is to give a dimen-
sional discussion. Let us consider in the first place the ecjuations of
heat transfer in a fluid that is in motion. The equations may be
obtained by a slight generalization of the process by which the equa-
tion of heat transfer is deduced for a medium at rest. Let us suppose
that the medium is homogeneous except for temperature differences,
that its specific heat per unit volume is c and its velocity of motion at
any point v. Consider a small closed surface S at any point in the
liquid. The rate of rise of temperature of the matter within this
surface is the total heat input divided by the heat capacity. The heat
input consists of two parts. The first is the ordinary conduction

across the boundary, and is I I k — dS, where k is the thermal con-
ductivity. This assumes that the velocity v is so small compared with
the velocities of molecular motion within the liquid that the ordinary
process of conduction takes place independent of the motion. The
second part of the heat input is that which is convected, and is
— f/cTPndS. From these two expressions we get the equation

150 BRIDGMAN.

Applying Green's theorem to the surface S, transforming the surface
to vokime integrals, using the condition that Div v = 0 because the
liquid is to be considered as incompressible, and removing the integral
sign, gives for the differential equation of heat transfer

dr k ^ ^ ,

— - = - v-T — V • Grad r .
dt c

This equation applies at points inside the liquid. There will also be
an equation to fix the boundary conditions. This equation is of the
ordinary type, independent of the motion of the liquid, and is merely
the statement that the heat input across the boundary is equal to the
conductivity of the fluid multiplied by the normal temperature
gradient.

Apply these equations now to the present problem. If the motion
of the liquid is not turbulent, and if the lines of flow are not altered l)y
the heat input, then at the surface of the metal the liquid flows in
planes parallel to the surface, the velocity increasing from the surface.
The determination of the velocity distribution is a problem of hydro-
dynamics, and involves the viscosity of the liquid and the variables
which describe the mechanical roughness of the surface, but as far as
we are interested in the problem the elements which enter our heat
equations are determined if we can specify the velocity gradient at the
surface. The other elements which enter the equation of heat trans-
fer are the thermal conductivity of the liquid and its specific heat per
unit volume.

Subject now to the restrictions mentioned, we may make a dimen-
sional analysis of the situation. Notice in the first place that since
the flow of water is transverse to the specimen the rise of temperature
etc. is independent of the length, provided only that the specimen is
long enough for us to neglect end effects.

We now enumerate the elements with which we are concerned and
their dimensions.

Name of Quantity Symbol Dimensional Formula

Average rise of temperature

Rate of heat input per unit length

Velocity gradient in liquid

Thermal conductivity of liquid

Specific heat of liquid per unit volume

Breadth of specimen

Frequency' of impressed heat input

T

T

Q

// L-1 r-i

9

f-i

k

HL'^ r-i T-i

c

HL-' r-1

b

L

CO

r-i

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 151

Consistently with our numerical discussion we have not tabulated
the thermal properties nor the thickness of the specimen itself, since
the effect of these is vanishingly small.

We have now two cases to consider; first the steady temperature
rise. The period of the impressed heat input does not enter, and we
have to find all the dimensionless products of the first six quantities of
the list above. Since there are four fundamental kinds of quantity
(instead of unit quantity of heat H, we might have expressed heat in
mechanical units, thus replacing // by M, with no change in the final
result), and hence two dimensionless products. Inspection shows
these products to be kr/Q and k/gch-. Hence the relation which we
want may be expressed as

urn

where / is some unknown arbitrary function. This relation can be
tested by experiment, and so some idea obtained of the correctness of
the assumptions underlying the discussion. For instance, at constant
rate of flow of cooling water, the above equation shows that the steady
temperature rise should be proportional to the rate of heat input, or
to /-. We can obtain an additional check for low rates of flow. For
low rates, but not too low, it seems natural to assume that an impor-
tant part of the rise of temperature is inversely proportional to the rate
of flow, or inversely as g. This means that in / there is an important
term which is the reciprocal of its argument, and we obtain as a partial
expression

• T = Const Q/gclr'.

Some experimental information may be obtained here by varying
the breadth of the sample at approximately equal rates of flow. That
the average rise of temperature should be less for the greater breadth
seems somewhat paradoxical, and affords a more drastic test than the
proportionality of temperature rise to the rate of heat input.

Now let us consider the alternating fluctuations of temperature.
To distinguish from the steady case, and consistently with the previous
notation, we denote the amplitude of the alternating heat input by Qi,
and the amplitude of the alternating temperature change by n. We
now have seven quantities, and hence three dimensionless products.
The additional product, beside the two already obtained, is gr/co. The
relation between the variables now takes the form

152 BRIDGMAN.

where <p is an arbitrary unknown function of its two arguments. For
high frequencies g/oi is a small quantity. It is obvious in the first
place that at high frequencies the temperature amplitude cannot
approach a constant value, but must vanish. Hence developing the
function ip for small values of the argument g/w, putting the constant
term zero, and retaining only the first order terms, we have for high
frequencies the approximate relation

If now we make the further assumption that the conductivity cannot
enter at high frequencies, the effect being determined by the specific
heat alone, we get the approximate relation

Ti = Const — —'

The striking thing about this relation is that the velocity of flow has
disappeared, the amplitude of temperature fluctuation being propor-
tional to the heat input, and inversely as the frequency. This again
is a result that can be tested by experiment, and its verification would
go far toward making probable the assumptions underlying the dis-
cussion.

These values which we have found by dimensional analysis for the
steady and alternating changes of temperature may now be substi-
tuted back in the relation ti/tq = iiAR'/liAR which we obtained from
the equations for the bridge. The rate of heat input entering the
dimensional formulas for to and ti may be written down at once in
terms of the currents, namely

Q = Pi R'
Qi=2IAR',

where R' is the resistance per unit length. Substituting these values
in the dimensional formulas for tq and ri, and these again in the value
of ti/to above, gives

/cgP_ g\
AR' ^V k ' J

AR

= 9

i

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 153

We now discuss the various experimental checks wliich were made
of the adequacy of the apparatus and the correctness of the assump-
tions underl\ing the mathematical discussion. One may perhaps
feel that I have gone too much into detail here, but in view of the
importance of the result, and the feeling of disquiet which must be
produced by the fact- that the final result has to be obtained by an
extrapolation I do not believe that multiplication of precaution is
superfluous.

Various Experimental Checks and Precautions.

Relative Magnitude of B.C. and A.C. A fundamental requirement
of the experiment has been that the A.C. be small compared with the
D.C. If it is not, the cos- term in the heat input becomes appreciable,
and the steady temperature rise is different when the A.C. is flowing
than when it is absent. This is easy to check experimentally. If the
A.C. is sufficiently small, the D.C. setting should be the same whether
the A.C. is flowing or not. This condition was checked repeatedly.
Before the experiments were begun the constants of the oscillating
circuit were so chosen for the different frequencies that the condition
should be met. In general the accuracy of setting for D.C. zero was
much greater than for A.C. zero. The latter could not usually be
set much closer than 0.5 mm. of bridge wire, whereas the D.C. balance
could be determined to 0.1 mm. Sometimes at the lower frequencies
there was a displacement of the D.C. balancing point by an appreci-
able amount when the A.C. was turned on, but less than the error in
the A.C. reading. Error at low frequencies does not affect the extra-
polation. At the high frequencies, however, any shift of D.C. balance
in the presence of the A.C. was less than 0.1 mm. An error of 0.1 mm.
in the slider setting means on the average an error of 1/20000 in the
resistance.

An additional check was afforded by the requirement that the
difference between A.C. and D.C. settings (that is AR') should be
independent of the A.C. intensity over a considerable range of A.C.
intensity in the neighborhood of that used in the measurements.
This requirement is shown at once by the formula on page 152. At
constant D.C, i.e. constant AR, AR' is independent of the alternating
current. This requirement obviously continues to be demanded if
part of the AR' is due to a departure from Ohm's law of the kind for
which we are searching, for this departure depends only on the D.C.
density and not on the small A.C. This again was checked over the

154 BEIDGMAN.

range of frequencies, with particular care at the three highest fre-
quencies, as error here will affect the extrapolation. The check is not
as good as that above because of the greater error of the A.C. readings,
but the requirements were met within the errors of reading, which
were 0.5 mm. The A.C. intensity was varied over a range of 10 or
20 fold, and its intensity determined by means of a thermo-couple.
At the greater intensities of this range, the difference. between A.C. arid
D.C. settings might be of the order of 1 cm.

For the actual measurements the A.C. was made as large as possible
in conformity with these requirements, in order that the sensitiveness
might be as high as possible. The requisite intensity varied somewhat
at the different frequencies, (there was resonance at about 1000 cycles
in the telephone) but as a rough average was about 0.02 amp. This
is of the order of l/30 of the D.C. current near its maximum, so that
the COS" term, which must be negligible, is of the order of 5 X 10~^
of the steady heating term. The D.C. shift of zero near the maximum
was of the order of 15 cm. of bridge wire. 5 X 10~* X 15 is 0.075 mm.,
which is thus beyond the possibility of detection or error.

Equality of A.C. and D.C. Zeroes. If the bridge is properly set up
and free from capacity and inductive effects, the D.C. zero for small
direct currents and the A.C. zero (that is, the A.C. setting in the
absence of D.C.) should be the same. This condition was satisfied
within the limits of reading at the three highest frequencies. The
settings could be made and read to 0.1 mm. for both A.C. and D.C.
It was only when the A.C. settings were made in the presence of D.C.
that there was room for as much uncertainty as 0.5 mm. At the lower
frequencies the two zeroes might sometimes differ by as much as sev-
eral tenths of a mm., but this does not affect the extrapolation or the
final results.

Indepcndejice of Rate of Cooling. If the extrapolated difference
between A.C. and D.C. readings is due to a real departure from Ohm's
law, and is not in some way connected with the microphone action,
which depends on the heating, then for a fixed D.C. density the extra-
polated difference of readings must be independent of the steady rise
of temperature, which may be made to vary by changing the speed
of the cooling water. That this condition is satisfied is shown in
Figure 5, in which the difference between D.C. and A.C. settings is
plotted against the reciprocal of the frequency. The D.C. heating
current was the same for the two curves, but the rate of flow of the
cooling water was different, the steady rise of temperature of the
upper curve being 1.4 times as great as that of the lower.

FAILURE OF OHM S LAW AT HIGH CURRENT DENSITIES.

155

Effect of Speed of Cooling IVatcr on Steady Temperature Rise. For
low speeds of cooling water with a constant D.C. the rise of tempera-
ture decreases rapidly with increase of speed. At higher rates of flow,
however, the effect becomes much less, until above a certain point
there is very little dependence of steady temperature rise on the rate
of flow. In the actual experiments the speed was chosen high enough
to be within this insensitive range. This ensures that conditions on
different days with different samples were rather closely the same.
There were slight outstanding dift'erences in the cooling conditions

J0005 .001 .0015 .002

Figure 5. Results obtained with gold 8X10"" cm. thick. The abscissae
are reciprocals of the frequency and the ordinates difference between A.C.
and D.C. settings in cm. of bridge wire. The two curves were obtained with
the same D.C. but with different heating effects, produced by varying the
rate of flow of the cooling water. The two curves should extrapolate to the
same point if there is a genuine departure from Ohm's law.

of the different samples, however, due to slight-changes in the position
of the sample in the holder, changes in the angle of presentation of the
nozzle of the cooling stream, etc.

Dependence of Stcadij Temperature Rise on Rate of Heat Input. Our
dimensional analysis, subject to the restrictions assumed for the
manner of flow of the cooling water, has" shown that the steady rise of
temperature does not depend on the metal, but only on its breadth, the
rate of heat input, and several other factors which do not change if
the cooling fluid is always water, and its velocity is in the range where
it does not much affect the cooling. Now the rate of heat input is
proportional to the square of the D.C. and may be computed in terms
of the resistance and the dimensions of the specimen. This computa-
tion was made, and the results plotted for a dozen specimens, com-
prising gold of the three thicknesses and silver.

In the first place the steady temperature rise for all these specimens

156 BRIDGMAN.

is a linear function of the rate of heat input up to rates which are near
the burning out point. When this point is approached there is a break
in the curve, and the temperature rise increases more rapidly than the
heat input. The probable explanation is that the lines of flow of the
cooling water are changed, it not being unlikely that there are localities
where the water is even vaporized. The general magnitude of the
temperature rise observed is consistent with this idea.

In the second place, the steady temperature rise shows no corre-
lation whatever with the thickness of the sample or its material, but
the rise for the thickest and the thinnest gold or for the silver is
approximately the same for the same breadth of sample. This estab-
lishes the correctness of the assumption that the dissipation takes
place in the layer of water in contact with the specimen, and does not
depend at all on the properties of the metal, always provided of course,
that the metal is sufficiently thin. The rise of temperature for speci-
mens of dift'erent breadths is less at the same input per cm- of surface
for the wider specimens. The total variation was by a factor of 2, the
rise of temperature of the narrowest specimen per unit heat input per
cm^ being about twice that of the widest. The breadths varied from
0.007 to 0.022 cm. At the same time it was a matter of experiment
that it was possible to reach higher current densities in the narrow
samples without burning out than in the wider ones. The reason for
this is that the break in the curve at which the linear relation between
temperature rise and heat input ceases is reached much sooner for the
wide than for the narrow samples.

Effect of Breadth of Sample on Heating. In order to test more
exactly the precise dependence of rise of temperature on breadth, a
series of runs was made on the same piece of gold, cutting down the
breadth after each run so as to make it successively narrower. The
sample was initially 1.18 mm. broad and 1.33 mm. long. End effects
are important at these dimensions, and agreement with the results of
the dimensional analysis is to be expected only for the narrower
samples. Readings were made at six breadths. In the first place,
as the breadth became less the heating effect became continually
greater for the same current. Now if p is the two dimensional resist-
ance of the thin metal film, and b its breadth, its resistance per unit
length is p/b, and the heat input Q per unit length is Pp/b. Our
dimensional analysis shows that

P P Jcgb'^\
'= Ic'b-ni^ -

FAILURE OF OHm's LAW AT HIGH CURRENT DENSITIES. 157

Now / cat one extreme, for very slow rates of flow, contains an impor-
tant term which is the reciprocal of its argument, whereas at high rates
of flow we have seen that experiment suggests that it tends to become
constant. Hence, keeping all the other arguments constant except
b, the variation of r may be expected to be between l/b and l/b^.

Experimentally the three narrowest breadths were 0.090, 0.155,
and 0.305 mm. The shift of D.C. setting (proportional to temperature
rise) for 0.2 amp. was respectively 8.5, 3.4, and 0.2 cm. Variation
as 1/P would have given 8.5, 1.7, 0.3; as l/b\ 8.5, 2.9, 0.9; and as
l/b, 8.5, 5.0, and 2.7. The variation is within the limits set and proba-
bly nearly as 1/6^, within the limits of error.

This check is very rough, but does,bear out the paradoxical variation
with b given by the dimensional argument. The difficulties of the
experiment are great, it l)eing impossible to exactl^,• reproduce the
conditions of flow when the sample is removed from position, its
breadth cut down, and then replaced. In the actual measurements
of the departures from Ohm's law, this source of irregularity was of
course not present, a complete series of measurements at different
D.C. strengths being made on the sample unchanged in position and
with the same flow.

These measurements also showed the same fact as that mentioned in
the preceding section, namely that the relation of proportionality
between heat input and temperature rise ceases at high rates of heat
input, and the point of break in the linear relation comes at lower
values of heat input per unifarea for the large than the small breadths.
This set of measurements with changing breadth of the same sample
showed that the current at the point of break is roughly proportional
to the square root of the width, which means that the break occurs
when the generation of heat per unit length reaches a fixed value,
independent of the breadth.

Dependence of Results on Position of Electrodes. There is another
sort of check of entirely different character which may be made by
changing the position of the electrodes on the sheet of metal leaf.
There is an essential dift'erence between the resistance of a two and a
three dimensional mass of conducting material. If two electrodes are
immersed in a three dimensional conducting medium, and the distance
between them is increased indefinitely, the resistances between them
will approach a finite value, the sum of the so-called electrode resist-
ances. On the other hand in a two dimensional medium, the total
resistance between electrodes of definite shape increases indefinitely
as the distance between the electrodes is increased indefinitely. One

158

BRIDGMAN.

cannot speak of the electrode resistance of a tAvo dimensional conductor.
Applied to the present case, this means that if the electrodes are not
situated near to each other on opposite sides of the isthmus, the total
resistance will not be merely the resistance of the isthmus and practi-
cally nothing else, but the rest of the sheet will make a finite con-
tribution. But the rest of the sheet will not make a finite contribu-
tion to the departure from Ohm's law, since the departure increases
very rapidly with increasing current density, and it is only in the
isthmus that the density is high.

The experiment was tried of making a specimen with two sets of
electrodes, one pair close to the isthmus, and the other pair much

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Figure 6. Results obtained with gold 8X10~® cm. thick. Abscissae,
current density in 10* amp/cm^, ordinates, e.xtrapolated difference between
A.C. and D.C. settings in cm. of bridge wire. The two sets of points were
obtained with the same specimen, but with different positions of the electrodes.
The points shown by the crosses are the observed points corrected by the
ratio of the total resistance to the resistance of the isthmus. If the effect
measured is a genuine departure from Ohm's law, the corrected points should
faU on the same curve with the others.

more remote. The total resistance between the second pair of elec-
trodes was 1.27 times that between the first. Now if the effect found
is genuine, the extrapolated value of AT?' for the same value of the
current density in the isthmus should have the same absolute value
irrespective of the position of the electrodes, and should not merely
be the same fraction of the total resistance between electrodes. That
this demand is met is shown in Figure 6. The points for the two posi-
tions of the electrodes lie on the same smooth curve within the errors
of the measurements, and this error is evidentlv much less than a
factor of 1.27.

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 159

Experimental Procedure and Data.

After the preparation of the sample, and measurement of its dimen-
sions, it was adjusted in the holder, the fine copper wires which were
soldered to the metal leaf were in turn attached to heavier leads,
and these were connected to the proper gap in the bridge, and the
nozzle for the cooling water was adjusted to give the most efficient
stream over the specimen. As already mentioned, the cooling water
was distilled water. This was contained in one of two large carboys,
which were at the temperature of the room. On starting the water,
there was no change in the zero due to change of temperature of the
specimen. Because of the limited capacity of the carboys, it was
necessary several times in the course of the experiment to interrupt
the readings to turn water from one carboy into the other.

Readings were bcgim at some small value of the direct current,
obtained l)y insertion of the proper shunt in the feeding circuit.
An initial reading was made of the A.C. zero, with no D.C. flowing.
Readings were now made of the D.C. balancing point with A.C. flow-
ing, and the A.C. balancing point with D.C. flowing, and the two
readings were repeated with D.C. reversed. This set of four readings
was repeated for each of several frequencies, beginning at the lowest.
The frequencies used were 320, 460, 680, 1140, 1530, 2450, and 3750.
The frequencies were calibrated with tuning forks. At each frequency
the mutual inductance was readjusted to give the sharpest setting.

Originally more readings were taken. These were the balancing
point for small D.C, A.C. zero with no D.C, D.C. balancing point for
large D.C. with no A.C. flowing, balancing point for large D.C with
A.C. flowing, and balancing point for A.C. with large D.C. flowing.
After a number of runs had been made, taking all these readings, I was
satisfied that these precautions were not necessary, and the readings
mentioned above proved sufficient.

The A.C. zero, which gives the actual resistance of the specimen
itself, may change slightly during a run at a single D.C. intensity
and a series of frequencies. This may be due to some mechanical
change in the specimen, because of friction by the cooling water, or
at high current densities may be due to incipient burning out. Any
such change during a run was always small however, and could be
disregarded in the computations.

The series of readings at different frequencies was now repeated at
some higher value of D.C, and the series continued until so high a

160 BRIDGMAN.

D.C. was reached that the specimen burned out. It was usual to make
readings at five to seven different D.C. intensities.

The difference between D.C. and A.C. settings for each constant
D.C. were now plotted against the reciprocal of the frequency, and
the results extrapolated to zero (that is, infinite frequency). Of
course the chief point of the experiment is this extrapolation. It is
in the first place to be remarked that the extrapolation is not a wide
one, the observed frequencies covering a range of ten fold, so that the
distance of extrapolation is only one tenth of the distance covered
by the readings. It is in the second place to be noticed that we have
theoretical evidence as to the form of the curve in the neighborhood of
zero. The part of the plotted difference which involves the heating
effect, and which we are trying to eliminate varies linearly as the
reciprocal of the frequency. The remainder, which is the departure
from Ohm's law, is constant, independent of the frequency. The
curves therefore extrapolate as straight lines, their curvature disap-
pearing as they approach the axis. Given this condition, the extra-
polation can be made with very little uncertainty. The curve is
already so nearly straight at the last two or three frequencies that in
most cases a straight line could be drawn through these points with-
out error. However, this is not quite satisfactory. In the early part
of the work I made the extrapolation by plotting the results on a large
scale, and drawing free hand the curve which seemed to best satisfy
the conditions. Later, however, in order to make the process of
extrapolation more mechanical and less subject to error by personal
bias, I adopted the following mechanical device. A steel spring was
made to conform as closely as possible to the observed points by
imposing on it three restrictions. It was made to go through, or
near, the observed point at the lowest frequency, another point near
the middle of the frequency range, and it was made to go through
such a point on the axis that it coincided as closely as possible with the
points at the upper end of the frequency range. This process will be
more fully described in the next paragraph.

Three typical sets of readings, giving differences between A.C. and
D.C. settings in terms of cm. of bridge wire plotted against reciprocal
of frequency, are shown in Figures 7, 8, and 9. These figures are for
the two thicknesses of gold and the one of silver. It will be seen that
there can be little doubt about the extrapolation. The fact that the
extrapolated curve does not pass through the origin, but strikes the
axis at a point higher up, constitutes the evidence for the departure
from Ohm's law. The mechanical extrapolation was made as follows.

18

16

14

12

10

8

6

4

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Figure 7. Results obtained with one specimen of gold SXlO"" cm. thick.
Abscissae, reciprocal of the frequency; ordinates, difference between A.C.
and D.C. settings in cm. of bridge wire.

Figure 8. Results obtained with one specimen of gold 1 .67 X 10~^ cm. thick.
Abscissae, reciprocal of the frequency; ordinates, difference between A.C.
and D.C. settings in cm. of bridge wire.

Figure 9. Results obtained witli one specimen of silver 2X10"^ cm. thick.
Abscissae, reciprocal of the frequency; ordinates, difference between -V.C.
and D.C. settings in cm. of bridge wire.

162 BRIDGMAN.

Consider the upper curve in Figure 8. A needle was stuck rhrougli
the paper at the point .1 and another at B. The spring was passed
under A and over B, and under a third needle C which was moved
up and down the axis of ordinates at the same time that slight trial
readjustments were made in the positions of A and B until that com-
bination was found at which the spring coincided most closely with
the observed points, particularly at the high frequencies. It will
be seen that under these conditions the spring crosses the axis in a
straight line, which is one of the demands. The spring also passes
through ^ as a straight line, which it theoretically should not do.
Any error due to this cannot have a perceptible effect on the extra-
polated value. A number of times I made independent extrapolations
by the free hand method and by the use of the spring, with essentially
the same results.

Additional evidence of the correctness of the extrapolations is the
fact that these were all made independently. The extrapolations
were first made, and then afterwards the factors were computed by
which the extrapolated differences in cm. of bridge wire were reduced
to fractional parts of resistance, ^^hen the extrapolations were made
I had no knowledge of whether the results would conform to the
results with other specimens or not.

Successful results were obtained with gold S X 10~* and l.()7 X 10"^
cm. thick, and with silver 2 X 10"^ thick.

The collected results for the eleven samples of 8 X 10"" gold (that
is, extrapolated difference between A.C. and D.C. settings as frac-
tional parts of the initial resistance plotted against current density)
are shown in Figure 10. The breadth of these samples varied from
0.066 to 0.226 mm., and both gold leaf and spattered gold are included
in the results. If the effect is genuine, there should of course be no
relation with the breadth. We have seen that there is a striking
dependence of heating effects on the breadth, but it is evident that
there is no such correlation here, and that within the limits of error
points for all samples lie on the same curve. This, I lielieve, consti-
tutes rather telling evidence for the genuineness of the effect. With
regard to the magnitude of the experimental error, it is true that the
points are perhaps more scattered than one could wish, but when we
consider that we are dealing with an effect whose exiscence even has
not hitherto been established, although much sought for, I do not
believe that the scattering is more than one might expect.

The collected results for gold 1.67 X 10"^ thick are shown in Figure
11. This comprises results on four different samples. The results

FAILURE OF OHM S LAW AT HIGH CURRENT DENSITIES.

163

are much more irregular, and the limits of error are greater for the
thicker than the thinner gold. The extrapolation is more uncertain
because perceptible curvature continues to higher frequencies than for
the thinner gold. It was not possible to reach such high current densi-

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Figure 10. Collected results for gold 8 X 10"" cm. thick. Abscissae, current
density in 10'' amp/cm-, ordinates, extrapolated difference between A.C. and
D.C. resistance in per cent of D.C. resistance. The numbers in the body of
the diagram show the breadth of the various samples in mm.

0 I

Figure 11. Collected results for gold 1.67X10"^ cm. thick. Abscissae,
current density in 10'' amp/cm'^; ordinates, extrapolated difference between
A.C. and D.C. resistance in per cent of D.C. resistance. The numbers in
the body of the diagram show the breadth of the various samples in mm.

164 * BRIDGMAN.

ties without the specimen burning out. If the maximum current
density without burning out is fixed by the amount of heat that can be
carried away by the cooHng water, and if this is independent of thick-
ness, as we have seen it is approximately, then the maximum current
density for a piece of twice the thickness should be inversely as V2.
This relation is approximately satisfied. It is to be noticed that the
effect is greater for the thicker gold; this would be expected from
theoretical reasons.

In addition to these two thicknesses of gold, I ^tried several
samples of the next size gold that I could obtain in the market, namely
5 X 10"^. Results with this were unsatisfactory. The curvature of
the relation between A.C. and D.C. difference and reciprocal frequency
continues to much higher frequencies than for the thinner specimens,
and in fact is quite marked over the entire frequency range, so that
it was not possible to extrapolate. It can be seen at once that the
inequalities of temperature in a leaf of five times the thickness are
twenty-five times as great for the same current density.

The results for silver 2 X 10~^ cm. thick are shown in Figure 12.
Measurements were made on five different samples, of widths varying
from 0.072 to 0.165 mm. The results are more scattered than for the
thin gold, but again there can be no question of the existence of the
effect, and the fact that there is no correlation with the breadth.

In addition to these measurements on gold and silver I attempted
to measure the effect in aluminum. The thinnest aluminum leaf that
can be obtained in the market is 5 X 10~^ cm. thick, and I found the
same trouble with it that I did with the thickest gold, namely that the
curvature persists to such high frequencies that the extrapolation
cannot be made with any assurance.

Other Possible Explanations of the Effect.

Skin Effect. It is natural to search for explanations of these
results other than a departure from Ohm's law. One of the first
that suggests itself is the "skin effect." The resistance of a con-
ductor is higher to alternating than direct currents because the
alternating current tends to collect in the surface layers, not having
time to soak into the interior of the conductor. This effect is very
important at wireless frequencies with conductors of the ordinary
dimensions. It increases rapidly with increase of frequency, and is
greater in large than in small conductors. An upper limit for the
conductor used in these experiments may be found by applying

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES.

165

Rayleigh's formula for a conductor of circular section to a conductor
of the same area of section as that of the specimens actually used.
At the upper limit of frequencies used here the skin effect for such a
circular conductor is only one part in 10^-, and is hence absolutely
not to be considered.

The Electrosiriction. Effect. The pinch effectMs well known in con-
ductors carrying heavy currents, and it might be expected that under
the high current densities of these experiments there might be mechani-

FiGtJRE 12. Collected results for silver 2X10~' c^. thick. Abscissae,
current density in 10** amp/cm^; ordinates, extrapolated difference between
A.C. and D.C. resistance in per cent of D.C. resistance. The numbers in
the body of the diagram show the breadth of the various samples in mm.

cal strains set up in virtue of the magnetic action of the current ele-
ments on each other which would alter the resistance. But it is to be
noticed that the pinch effect depends on the total current carried by
the conductor and not on its density. The currents carried here are
only of the order of 1 ampere, and numerical calculation shows that
any such effect is beyond the possibility of detection.

Variation of Resistance with Frequency. The electron theory pre-
dicts a change of resistance at high frequencies independent of the skin

166 BKIDGMAN.

effect. It is usually considered that this effect is important only at
optical frequencies, but it is worth our while to consider it here. The
formula may be found on page 432 of Richardson's book on Electron
Theory of Matter, and is

(To

1 + F

9 o

Here o-p is the conductivity at the frequency in cjuestion, ao the con-
ductivity at zero frequency, j^ the angular velocity corresponding to
the frequency, m the mass of the electron, e the charge on the electron,
and N the number of electrons per cm^. The only quantity in this
formula which we do not know definitely is N. Let us assume for the
moment that N is equal to the number of atoms. If now we sub-
stitute numerical values for silver we find that cTp differs from co by
5.3 X 10~^^. (I have used for p = 27r X 10^, which is more than twice
the highest experimental value). But now according to my theory
of conduction, the number of electrons must be very considerably less
than the number of atoms, and this will increase the difference between
(Tp and ctq. If we assume as an extreme value that the number of
electrons is 10~^ as great as the number of atoms, we find that o-p still
differs from^o by 5.3 X lO-^" at 10,000 cycles. Evidently this effect
is not a factor under our conditions.

Computation of the Departure from Ohm's Law.

Referring again to Figure 2, we have defined the departure from
Ohm's law as (tan d — tan 0o)/tan ^o- What we have actually meas-
ured and plotted in Figures 10, 11, and 12 is (tan 6' — tan ^o)/tan do.
Given this as a function of current, we require to find the departure
from Ohm's law as a function of current. For convenience replace
E by y, and / by x. Let the required curve be represented by y = f{x).
Experimentally we determined

(Jjl _ y

dx X

= ^(.r),

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 167

where ^ is a known function. Without essential restriction we may
put

M X - 0

The sohition is

= 1. We now have to solve

dy

dx X

y

^(.v)

y

f fJo

<p

(.r) d.

+ const. \ ■

Figure 13. Final results, showing the departure from Ohm's law in per
cent (ordinates) against current density (abscissae) in 10^ amp/cm^. Curve 1
is for silver 2X10"* cm. thick, curve 2 for gold 8X10"^ cm. thick, and curve 3
for gold 1.67X10-5 cm. thick.

The value of the constant is unity in order to satisfy the condition

/dy\ . y

-;- I ^ = 1. Now the departure from Ohm's law is - — 1, or
\d.v/x = 0 X

f

^(.r) dx

X

This may be determined graphically from the experimental curve for
(p. The departure from Ohm's law has been computed from the
graphs according to this formula for the two thicknesses of gold and for
silver, and is reproduced in Figure 13.

168 BRIDGMAN.

Theoretical Discussion. •

I have already mentioned that J. J. Thomson has suggested that
at extreme current densities the current will increase as the square
root of the E.M.F., instead of linearly. As far as I know, no theoreti-
cal discussion has ever been given of the magnitude of the effect to
be expected at lower current densities, where departures are jugt
beginning to be perceptible. Swann ^ has discussed the resistance of
thin films from the standpoint of the classical electron theory of con-
ductivity, and has retained the second order terms, subject to the
assumption of the classical theory that after every collision of elec-
tron with atom all vestige of the effect of the electric force acting on
the electron before the collision is wiped out. Under these assump-
tions he obtains a departure from Ohm's law in the opposite direction
from that found experimentally above, or given by Thomson's theory.
Subject to the same assumption I have also carried through an exami-
nation from the classical point of view, retaining the second and third
order terms in the expressions for the velocity imparted to the free
electron by the applied force during its free path, and arrive at a result
similar to Swann's, that is, a departure from Ohm's law in the drection
of a decrease of resistance with high E.M.F.'s. The first term in the
departure involves the square of the 'E.M.F., as considerations of
symmetry show that it must. This simple analysis must be incorrect,
however. It is not likely that the trend at very high E.M.F.'s found
by Thomson is reversed at lower E.M.F.'s, and it is also exceedingly
probable that the assumptions at the basis of the classical theory are
not exact. One would certainly expect an effect of higher order on
the velocity distribution by the applied force, even if there is no effect
of zero order.

I have not been able to make the modifications in the classical analy-
sis which would be necessary to take account of terms of higher order
in the velocity distribution. I believe that it must involve the
details of atomic and crystal structure.

Not being able to give the exact analysis that we could desire, we
may fall back on a dimensional analysis. If the mechanism of con-
duction is a free path mechanism, as is supposed in the classical
theory, and as I think most likely, we see that the departure from
Ohm's law is going to depend only on the kinematics of the motion of
an electron moving with a certain normal velocity in a free path when
acceleration is impressed by an additional force from without. This
assumes that the number of free electrons is not changed by the exter-

FAILURE OF OHm's LAW AT HIGH CURRENT DENSITIES. 169

nal force. The efemeWts that enter our analysis are the acceleration of

the electron (a), its mean free path (/), and its normal velocity in the

absence of the external impressed force (r). The departure from

Ohm's law is to be expressed in terms of these. As we have defined

it, the departure from Ohm's law, D, is a ratio of similar quantities,

and is hence dimensionless. The only dimensionless combination of a,

. al ^
I, and I' is -^. Hence we have

Considerations of sj'mmetry show that the unknown function must be
an even function of its argument, since reversing the direction of the
acceleration leaves the resistance unaltered. Also the acceleration
of the electron is determined by its charge, mass, and the applied force
by the equation

Ee
a = — .
m

Hence finally we have the result

D = even function — : I .

\mv-/

Maxwell assumed, as was perfectly natural, that the function was
algebraic, and hence that the first term was proportional to E"^, it
being an experimental fact that the constant term vanishes. In the
light of the experiments above, however, it is exceedingly question-
able whether this assumption is justified. It seems to me that the
curve hugs the axis at the origin much more closely than an algebraic
curve, and in fact may have contact of an infinitely high order, like
an exponential curve. I have not succeeded in satisfactorily repro-
ducing the course of the curve with two or three terms, although this
may be done with a fair degree of approximation. I found this signi-
ficant thing in trying to fit an algebraic curve to the experimental
results. If the first term, that is the square term, corresponds to
anything real physically, then its magnitude in a three constant
formula should not be very different from its value in a two constant
formula, the terms of higher order constituting merely correction
terms. This is not the case. The square term in a three constant
formula fitting the results for 8 X 10~^ gold was only about one fifth
as large as in a two constant formula. It seems to be likely, therefore,
both from the appearance of the curve and this evidence from com-

170 BRIDGMAN.

putation that the correct form of the curve is not algebraic, or at any
rate that the first term is not a square term.

However, merely in order to afford a basis for comparison with
previous results, let us assume for the moment that at compara-
tively small values of the current the most important term is the
square term. My results for 8 X 10"*^ gold show that at a current
density of 10^ ftmp/cm- the departure from Ohm's law is certainly not
any greater than U)~^. Assuming, in lack of anything better, that the
coefficient of the square term is unity, and assuming the square law,
this would mean that at a current density of 1 amp/cm^ the departure
from Ohm's law is not greater than 10"^^. Maxwell stated the limit
as one part in 10^" for the same current density. The law is probably
actually much closer than 10~^^ at 1 amp/cm^.

Another argument against the probability of the square law is the
very high values that it would mean for the free path. Let us assume
again that the coefficient of the sc^uare term is unity, and substitute
numerical values. We have to put

/Eeiy
— =10-^,

where E is the electric field at a current of 10^ amp/cm^. In accord-
ance with the usual assumption of classical theory, which I have
attempted to show elsewhere is very probably true,^ we put the
energy of the electron equal to the energy of a gas molecule at
the same temperature (300" Abs.). We may simplify by writing
mv" = 2kT, where k is the gas constant and r absolute temperature.
We have to solve the above equation for I, the only unknown. The
specific resistance of gold is 2.4 X 10~^. To drive 10^ amp/cm- takes
2.4 volts/cm which is 0.08 Abs. E. S. U. Substituting these values
gives .

/ = 4.5 X 10-4 cm.

It would appear on this basis, therefore, that the free path is of the
order of 5 X 10"^ cm. long. This is in the direction that I would like
to find the path to differ from the previous results of the classical
theory, which gave something of the order of 10~^ cm., for my theory
demands a long path and few electrons,^ but I believe that the number
above goes rather too far in the desired direction. It is, however,
perhaps not impossible that the path should be of the order of 10-^ cm.
In default of a better theory, my measurements do not afford the basis
for a better calculation. It would be necessary to refine on the meas-

FAILURE OF OHM's LAW AT HIGH CURRENT DENSITIES. 171

urements at current densities less than 10^ in order to pick out the
square term (provided that it exists), or to improve on the theory.
I do not believe that the latter will be possible without taking into
account the detailed structure of the atom. At the same time, I
believe that the existence of the effect at current densities so much lower
than would be expected on the basis of a free path of the order of 10~^
cm. is at least presumptive evidence that this value of the path is too
low.

The appearance of the v- term in the formula above suggests an
essential observation. The measurements, and the results computed
from them, do not refer to metal at the same temperature at the differ-
ent current densities, but the observations at the higher densities are
for the metal at higher temperatures, because of the heating effect.
This of course was not eliminated by extrapolating to infinite fre-
quency. The change of temperature at the maximum current density
was in the neighborhood of 50° for all specimens. If the form of the
function were known, it would have been possible to correct for this
temperature effect, but in the absence of the knowledge, I thought it
better to give the results as obtained without attempting any correc-
tion. If conduction is by a free path mechanism, then at higher
velocities the departures from Ohm's law are less than at lower ones,
(that is, lower temperatures) so that if the corrections had been
applied a deviation from Ohm's law even greater than that shown
would have been found at the higher current densities.

We have noticed that the deviations are gi-eater for the thick than
for the thin gold- Although the results are not as accurate for the
thicker as the thinner leaf, there seems to be no possibility that all the
difference can be accounted for by errors of observation. If the free
path is long, as I have supposed, an effect in precisely this direction
would be expected. For the leaf is considerably less in thickness than
the length of the normal path, so that increasing the thickness would
have the effect of increasing the average path, and so increasing the
departure from Ohm's law.

The departure is considerably less in silver than in gold of the same
thickness. This would mean a shorter path in silver than in gold.
In view of the greater conductivity of silver this may mean that the
number of free electrons is greater in silver than in gold. It is, how-
ever, perhaps dangerous to drive the comparison too far between the
different metals, because the much closer approach to normal of both
the specific resistance and the temperature coefficient of resistance of
silver suggests that the internal conditions may not be comparable.

172 »uuih;m.\n.

Mmmakv

l\v (ho omploN u\on( of a now motho^l, by whioli tho rosistaiuv is
luoasimHl sintultniuHHisly for a hoavy dinvt oiirivnt aiul a small supor-
{Hv^oil aUornatiui: ounvut of a«.\nis(ioal frtHiuouoy. iloviatious from
Ohin'vS law at hijjh ounvnt donsitios havo boon dotivt^nl and nioav^^urtnl
in loaf i::v>Kl and silvor. Tho uiaximum ounvi\t donsitios woro about
r> \ 10" «'up ^''^^'' '*''^^ *^^^' doviations fwm (.'•hni's law woiv of tho
onlor of ono por ivi\t. If (l»o nuvhanism of c\Muluotion is a froo path
mivhai\ism. thoso ri^sults prv^bably moan that tho froo patli is nmoh
U^n^^T than snppvv*tHl on tho olassioal oUvti\>n thix»ry.

It is a ploasnrt^ to aoki\owK\lct' nty indobtixlnoss to my assistant
Mr. «1. C Slator for n\akinv: noarly all tho rt\»dinj::s.

1 J. .1. ri»oT\tsvM\. Tho iVrpusovUtjr Thtvrv vM Mattor. l^H^T. p. oo.

a iMork MawvoU, .1, H, Kvon^tt. A. Sohvistor. Brit Asi:oo. Kop. 1S70. otH>3.

S F. Wonuor. rUvj*. Kov. oJ^ lo. :>;ii >>;vj. UV.XV

4 K. l.<vhor. Sitjlvr. Wion. Akad. IU»-'* I, 4«MV. UXK.

5 H. K, Yv>n IVtuilvnlvrs:. rh\->!- Z8. IS. To-TS. H)17.
e J. r.Httorv\>n. Phil. M,s»i. 4. tv\2-<>7S, UXVJ.

: W. R Ot. 8\vann. ^hil.^l;^>i. JS. U>: 4VHv 1914.

^ r W". l^rivi^iitnan. rivv^ Kov, i>. Jl^iWJSi). 1917, and 17. UU-liM. 1921.

H.srN~>;rvi ruivorsitv, 0;uubrids?\ Mas?,

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A TABLE AND METHOD OF COMPUTATION OF ELECTRIC
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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 7. — April, 1922.

A TABLE AND METHOD OF COMPUTATION OF ELECTRIC
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t •

A TABLE AND METHOD OF COMPUTATION OF ELECTRIC
WAVE PROPAGATION, TRANSMISSION LINE PHE-
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PERBOLIC FUNCTIONS OF A COMPLEX VARIABLE.

By George W. Pierce.

Received Jan. 13. 1922. Presented Jan. 11, 1922.

1. Table I. — Table I appended contains values of /(/?) and g{h)
for various numerical values of h, where /(/«) and (j{li) are defined by
the following equations

/(/O = + V -^ -i-^/r^l^ ^^

1+

Vl + A2

+ 1

/+

V 1 + /,2

- 1

g{}i) = + \/ ^ ^^" i- (2)

The solution of a number of physical problems involves these
functions in a manner to render the table serviceable for computation.
It will be noticed that /(A) and g{h) have the following properties

if(/os— i^(/or- 1, . (3)

2/(/0 g(h) = h. (4)

2. To Extract the Square Root of 1 + jh, where h is Real and
Positive, andy = V^i.

Let Vl+j/i = A+jB,

then

A'- F-= 1,

2AB = I // 1 .

These results compared with (3) and (4) show that

Vl^jJ, =.± i /(/,)+. />(/,) }. (5)

Likewise, for h positive.

Vl -jh= ± {f{h)-jg{h)}. (6)

176 PIERCE.

3. To Extract the Square Root of P -\- jU, where P and U
are any Real Quantities. — Factoring out the square root of P,
we have by (5) and (6)

VP+jU = ± Vp Ifih) -hjg(h)}, if U/P is positive,

= ± VP {fig) - j g{h)}, if U/P is negative, (7)

where

h = U/P.

4. To Find sinh-^ (P + jU) where P and U are Both Positive
and Real. —

Let

smh-' {P +jU) = A+jB, (8)

then

P + jU = sinh A cos B -\- j cosh A sin B,
whence

P = sinh A cos P, (9)

U = cosh yl sin B. (10)

Regarding signs, in accordance with the caption, we see that, since
cosh A is always positive, sin B is positive and sinh A and cos B are
both positive or both negative.

Taking the sura of the squares of (9) and (10), we have

P2-I- u^= sinh^ A cos2 B + cosh^ A sin^ B

= sinh2 A cos2 P + (1 + sinh^ A) (1 - cos- B)
= 1 - cos^P + sinh2.4,

whence by using (9), we have

P2

OS' P + , „ , and

COS" P

(11)

P2

ii-ii-t'' 1

(13)

'"^^^^ ~ Sinh-^P-

1 - P2- f72

Letting

V = V^^' (14)

and solving (11) and (12) as quadratics, we obtain

cos-p = r ± \/p2+ V%

sinh^.l = - !'■ ± \/P-+ r^.

TABLE FOR TRANSMISSION LINE PHENOMENA. 177

Using the proper signs before the radicals to make the expressions
positive as demanded by their left hand equivalents, extracting the
square roots and employing (1) and (2), we obtain the following
results

If V>0, sinh .4 = ± V2Vg{h), cos 5 = ± VWjQi),

if r<0, sinh A = ± V- 2Vf{h), cos 5 = ± V- 2V g{h),
where h = P/V.

Having regard to the rule of signs enunciated under (10), we may
WTite

sinh-i (P + jU) = X + i (?/ + 2Trn) and - .r + i (tt - y + 27rw), (15)

where

if V >0, X = sinh-i { + V2F g{h) ],y= cos-i { +VWf{h) \ , (16)

if F<0, X = sinh-i {+ V-2Vf{h)], y = cos-^+V- 2V g{h)],{ll)

with h = P/V. (18)

Equation {15) gives the value of sin-^ (P -\- jU), xohere P and U are
real, positive quantities, in terms of x and y defined by {16) and {17).
The value of V is given by {14). The signs in {15) are so chosen that the
value of y in the first quadrant is to be employed.

5. To Find sinh-i (P - jU), where P and U are Positive,
Real Quantities. — This differs from the preceding problem only in
the fact that sin B is negative, whence

s\nh-\P-jV) = x-j {y+2Trn) and -.r+j (i/+7r+27r70, (19)

with y in the first quadrant and with x and y defined as in (16), (17)
and (18).

6. To Find sinh-^ {-P-jU) and sinh-i (-P + yC/), where P
and U are Positive, Real Quantities. — These results may be had
directly from Sections 4 and 5 by use of the facts that

and

sinh-i (-P - jU) = - sinh-i (P + jU), (20)

sinh-i (- P + jV) = - sinh-i (P - jU). (21)

178 PIERCE.

7. To Find cosh-i (P + jU), where P and U are Positive and
Real. —

Let

cosh-HP -\-jU) = A -{-jB, (22)

then

P + jU = cosh A cos B -\- j sinh A sin jB,

whence

P = cosh /I cos B, (23)

[7 = sinh A sin 5. (24)

The sum of the squares of these two equations gives

P2 -j- u^= cosh2 J cos2 B + sinh2 .4 sin- B
= 1 + sinh- A — sin^ B,

whence by substitution from (24) and by solution of the resulting
quadratic equations we obtain

sinhM = - r ±Vr2+ V\ and
sin2 5= r±VL^2_|_pr2,

These give, with choices of signs to make A and B real and satisfy
(24)

if V >0, sinh A = ^V2Vg(h), sin B = ^V2V f{h), h = U/V,

if F<0, sinh .4 = ±V'-2r/(/0,sin5 = ^V~^2V g{h), h = U/V.

In accordance with (23) and (24), in each line the sinh A and sin B
have the same sign before their radicals, and the angle B must be so
determined that cos B is positive. Whence

cosh-i (P + jU) = ± {a + j {cp + 27rn), (25)

where
if F>0, a = sinh-M+V2r^(/0}, <p = sin-M+v'2r7(/0}, (26)

if V<0, a = sinh-M+V-2F/(/0}, ^ = sin-H -\- V -2V g(h)} , (27)

with h = U/V. (28)

Equation {25) gives the value of cosh~i (P + jU), where P and U are
real, positive quantities, in terms of a and (p defined by {26), {27) and {28).
(p is in the first quadrani. V is defined by {14)-

TABLE FOR TRANSMISSION LINE PHENOMENA. 179

8. To Find cosh^ (P — jU), where P and U are Positive and

Real. — This case differs from the preceding only in that, by (24),
sinh A and sin B have opposite signs, so that

cosh-i (P - jU) = ± \a -j{<p + 27r/0, (29)

Where a and (p have the values given by (26) and (27).

9. To Find cosh-^ (— P + jV), where P and U are Positive

and Real. — This case differs from that of Section 7 only in that cos B
is negative, so that

cosh-i (- P + jU) = ± {« + i (tt - ^ + 27r«)}, (.30)

where a and (p have the values given in (26) and (27).

10. To Find coshi ( — P — jU), where P and U are Positive

and Real. — This case differs from that of Section 9 in that sinh A
and sin B have opposite signs, whence

cosh-i (- P - jV) = ± {a + i (tt + ^ + 27rw)), (31)

where a and ip have the values given in (26) and (27).

11. Attenuation Constant, Retardation Angle, and Surge
Impedance of a Smooth Electric Transmission Line Without
Leakage. — If

r, c, and I = respectively resistance, capacity, and inductance per
loop unit of length of a smooth line,
CO = angular velocity of impressed e.m.f. in radians per

second,
a = real attenuation constant of current per unit of length

of line,
j3 = retardation angle per unit of length of line,
Zi= surge impedance of the line,
Ri and Xi= respectively surge resistance and surge reactance of
the line,
then 1 _

a = Wic g{h), (32)

IS = Wkfih), (33)

1 These equations are obtained by introducing the g- and /-functions into
familiar equations. Compare Pierce: Electric Oscillatioris and Electric Waves,
pp. 327 and 329, McGraw-Hill Book Co., 1920.

180 PIERCE.

Ri= Vj/^fih), (34)

Xi= - VJ/^gih), (35)

where

h = r/I<o. (36)

12. Constants of a Leaky Line. — If to the list of quantities
defined in Section 11, we add

g = leakage conductance per loop unit of length of the line,
then^

I. lilc<jy^>rg,

a = Vlcc^^— rg g{h), /3 = V/cco- - rgfih), (37)

rcco + gloi
where h = - — - — ' — •

Icco-— rg

II. Ulcc^'<rg,

a = Vrg - lcoo^f{h), j3 = Vrg - Ico:^ g{h), (38)

rcco + gico

where * h = T^V-

rg — lew

III. If ^/> re,

^.■=\'^^^l/W+i^(/OK (39)

glw — row

where h = ^^ , — - — ~.

rg -\- lew

IV. ligKrc

^i = \' '•'^' o'T \m - j g{h) } , (40)

rcco — gl(j}

where h = — ; — -.

rg + lew

1 Obtained by introducing the /- and g- functions into familiar equations.
Compare Kennelly: Applications of Hyperbolic Functions, pp. 70 and 125.
University of London Press.

TABLE FOR TRANSMISSION LINE PHENOMENA.

181

13. Constants of an Artificial Electric Line. — If

2i = complex impedance of the series elements of an artificial

line,
22 = complex impedance of the shunt elements,
M = mutual inductance (if any) between adjacent series

elements,
(p = retardation angle of current per section of line,
a — real attenuation constant per section of line, and if

w

/e let

and

P+jU =

V =

2l+ 2So

1 - r— r-

(41)
(42)

where P and U are real quantities, then ^

I. IfV>0, _ _

a = sinh-V2F g{h), <p = sinh-i { ± V2V f{h) }
with h = U/V.

II. IfV<0,

(43)

(44)

a = smh-W-2Vf{}i), <p = sin-i {^V-2Vg{h)\

with h = U/V.

These equations are to be employed subject to the following rule
regarding the cjuadrant of (p.

Rule Regarding ip.

sign of

quadrant of <p

P

U

+
+

+
+

first
second

third
fourth

1 Compare Pierce: Electric Oscillations and Electric Waves, p. 296, on which
the present results are based.

182 PIERCE.

As to surge impedance of the artificial line, its value depends upon
the arrangement of elements by which transition is effected from the
terminal apparatus to the line. For a line provided at each end with
a series element of half the impedance of the internal series elements
of the line the complex surge impedance is

- (zo- ./3/co). (45)

«

The real and imaginary parts of this expression may be readily
obtained in a numerical case by the method of Section 3.

14. Index of Refraction and Extinction Coefficient for
Electric Waves in an Absorbing Medium. — As another example
of the utility of the functions here presented attention is called to the
following equations from optics and electric wave theory' applied to
an absorbing medium.

If

7 = specific conductivity in absolute c.g.s. electrostatic units.

€ = dielectric constant of the medium,

/u = its permeability,

n = its index of refraction for waves of period T seconds,

K = extinction coefficient for waves of the period T,

then (see p. 413 Electric OsciUalions and Electric Waves), using the
functions / and g, we may write

n = V7^f{h), (46)

K = VeiJ.g{h) (47)

wi th

h = 27 T/e.

15. Note on a Relation of /(/») and g{h) to Hyperbolic Func-
tions Giving an Easy Method of Computing the Table of/ and
g. — Having given some illustrations of the utility of the table, we
next call attention to a simple relation employed in computing the
table.

If we let

h = sinh X, then VI + /;- = cosh .r,

TABLE FOR TRANSMISSION LINE PHENOMENA. 183

SO that it is seen that

/(/.) = V^^^llZ+1 = eosh (i sinh-. /,), (46)

and Hkewise

</(/0 = sinh (J sinh-i /H. (47)

Eqviations (46) and (47) were used in computing many of the values
of the table by referring to values of hyperbolic functions given in the

Smithsouicui Institute Tables.

16. Extension of Table to Larger Values of h. — By expansion

in series it is easily shown that

Cruft Laboratory,

Harvard University, Cambridge, Mass.

184

PIERCE.

TABLE I.

^ = 0 to .286

h

f{h)

g(h)

h

fih)

g{h)

h

nh)

gih)

h

f{h)

g{h)

.000

1.000

.0000

.072

1.001

.0360

.144

1.003

.0718

.216

1.006

.1074

.002

1.000

.0010

.074

1.001

.0370

.146

1.003

.0728

.218

1.006

. 1084

.004

1.000

.0020

.076

1.001

.0380

.148

1.003

.0738

.220

1.006

.1094

.006

1.000

.0030

.078

1.001

.0390

.150

1.003

.0748

.222

1.006

.1104

.008

1.000

.0040

.080

1.001

.0400

.152

1.003

.0758

.224

1.006

.1114

.010

1 . 000

.0050

.082

1.001

.0410

.154

1.003

.0768

.226

1.006

.1124

.012

1.000

.0060

.084

1.001

.0420

■ . 156

1.003

.0778

.228

1.006

.1133

.014

1.000

.0070

.086

1.001

.0430

.158

1.003

.0788

.230

1.007

.1143

.016

i.opo

.0080

.088

1.001

.0440

.160

1.003

.0798

.232

1.007

.1153

.018

1.000

.0090

.090

1.001

.0450

.162

1.003

.0807

.234

1.007

.1163

.020

1.000

.0100

.092

1.001

.0460

.164

1.003

.0817

.236

1.007

.1172

.022

1.001

.0110

.094

1.001

.0470

.166

1.003

.0827

.238

1.007

.1182

.024

1.001

.0120

.096

1.001

.0480

.168

1.004

.0837

.240

1.007

.1192

.026

1.001

.0130

.098

1.001

.0490

.170

1.004

.0847

.242

1.007

. 1202

.028

1.001

.0140

.100

1.001

.0499

.172

1.004

.0857

.244

1.007

.1211

.030

1.001

.0150

.102

1.001

.0509

.174

1.004

.0867

.246

1.007

.1221

.032

1.001

.0160

.104

1.001

.0519

.176

1.004

.0877

.248

1.007

. 1230

.034

1.001

.0170

.106

1.001

.0529

.178

1.004

.0887

.250

1.008

.1240

.036

1.001

.0180

.108

1.001

.0539

.180

1.004

.0896

.252

1.008

.1250

.038

1.001

.0190

.110

1.002

.0549

.182

1.004

.0906

.254

1.008

.1260

.040

1.001

.0200

.112

1.002

.0559

.184

1.004

.0916

.256

1.008

.1270

.042

1.001

.0210

.114

1.002

.0569

.186

1.004

.0926

.258

1.008

.1280

.044

1.001

.0220

.116

1.002

.0579

.188

1.004

.0936

.260

1.008

. 1289

^046

1.001

.0230

.118

1.002

.0589

.190

1.004

.0946

.262

1.008

.1299

.048

1.001

.0240

.120

1.002

.0599

.192

1.005

.0956

.264

1.008

. 1309

.050

1.001

.0250

.122

1.002

.0609

.194

1.005

.0966

.266

1.009

.1319

.052

1.001

.0260

.124

1.002

.0619

.196

1.005

.0975

.268

1.009

. 1329

.054

1.001

.0270

.126

1.002

.0629

.198

1.005

.0985

.270

1.009

.1338

.056

1.001

.0280

.128

1.002

.0639

.200

1.005

.0995

.272

1.009

.1348

.058

1.001

.0290

.130

1.002

.0649

.202

1.005

. 1005

.274

1.009

. 1358

.060

1.001

.0300

.132

1.002

.0659

.204

1.005

. 1015

.276

1.009

. 1368

.062

1.001

.0310

.134

1.002

.0669

.206

1.005

.1025

.278

1.009

.1377

.064

1.001

.0320

.136

1.002

.0679

.208

1.005

.1035

.280

1.010

. 1387

.066

1.001

.0330

.138

1.002

.0689

.210

1.005

.1044

.282

1.010

. 1397

.068

1.001

.0340

.140

1.002

.0698

.212

1.006

.1054

.284

1.010

.1406

.070

1.001

.0350

.142

1.003

.0708

.214

1.006

.1064

.286

1.010

.1416

TABLE FOR TRANSMISSION LINE PHENOMENA.

185

TABLE I.

h = .286 to .572

h

Kh)

g{h)

h

f{h)

g{h)

h

f{h)

g{h)

h

/(/»)

g{h)

.286

1.010

.1416

.358

1.015

.1762

.430

1.022

.2104

.502

1.029

.2438

.288

1.010

.1426

.360

1.016

.1772

.432

1.022

.2114

.504

1.029

.2447

.290

1.010

. 1435

.362

1.016

.1782

.434

1.022

.2123

.506

1.030

.2456

.292

1.010

.1445

.364

1.016

.1792

.436

1.022

.2132

.508

1.030

.2465

.294

1.011

.1455

.366

1.016

.1801

.438

1.023

.2141

.510

1.030

.2475

.296

1.011

.1464

.368

1.016

.1811

.440

1.023

.2150

.512

1.030

.2484

.298

1.011

.1474

.370

1.016

. 1820

.442

1.023

.2159

.514

1.031

.2493

.300

1.011

.1484

.372

1.017

.1829

.444

1.023

.2168

.519*

1.031

.2.502

.302

1.011

.1494

.374

1.017

. 1839

.446

1.023

.2177

.518

1.031

.2510

.304

1.011

. 1503

.376

1.017

.1848

.448

1.024

.2186

.520

1.031

.2520

.306

1.011

. 1513

.378

1.017

. 1858

.450

1.024

.2197

.522

1.031

.2529

.308

1.011

.1522

.380

1.017

.1867

.452

1.024

.2207

.524

1.032

.2.538

.310

1.012

.1532

-.382

1.017

.1877

.454

1.024

.2216

.526

1.032

.2547

.312

1.012

.1541

.384

1.018

.1886

.456

1.024

.2225

.528

1.032

.25.56

.314

1.012

.1551

.386

1.018

.1896

.458

1.025

.22.34

..530

1.032

.2566

.316

1.012

. 1561

.388

1.018

.1905

.460

1.025

.2244

.532

1.033

.2575

.318

1 012

1570

.390

1.018

.1915

.462

1.025

.2253

.534

1.033

.2584

.320

1.012

.1580

.392

1.018

.1924

.464

1.025

.2262

.536

1.033

.2593

.322

1.013

. 1590

.394

1.018

.1934

.466

1.025

.2271

.538

1.033

.2602

.324

1.013

.1600

.396

1.019

.1943

.468

1.026

.2281

.540

1.034

.2612

.326

1.013

.1609

.398

1.019

. 1953

.470

1.026

.2290

.542

1.034

.2621

.328

1.013

.1619

.400

1.019

.1962

.472

1.026

.2300

.544

1.034

.2630

.330

1.013

.1629

.402

1.019

.1972

.474

1.026

.2309

.546

1.034

.2639

.332

1.013

. 1638

.404

1.019

.1981

.476

1.026

.2318

.548

1.034

.2648

.334

1.013

.1648

.406

1.020

.1991

.478

1.027

.2327

.550

1.035

.2658

.336

1.014

.1658

.408

1.020

.2001

.480

1.027

.2337

.552

1.035

.2667

.338

1.014

.1667

.410

1.020

.2010

.482

1.027

.2346

.554

1.035

.2676

.340

1.014

.1677

.412

1.020

.2020

.484

1.027

.2355

.556

1.035

.2685

.342

1.014

.1686

.414

1.020

.2029

.486

1.028

.2364

.558

1.036

.2694

.344

1.014

.1696

.416

1.020

.2038

.488

1.028

.2372

.560

1.036

.2703

.346

1.014

. 1705

.418

1.021

.2048

.490

1.028

.2383

.562

1.036

.2712

.348

1.015

.1715

.420

1.021

.2057

.492

1.028

.2.392

.564

1.036

.2721

.350

1.015

.1724

.422

1.021

.2067

.494

1.028

.2401

.566

1.036

.2730

.352

1.015

.1734

.424

1.021

.2076

.496

1.029

.2411

.568

1.037

.2739

.354

1.015

.1743

.426

1.022

.2085

.498

1.029

.2420

.570

1.037

.2748

.356

1 .015

.1753

.428

1.022

.2095

.500

1.029

.2429

.572

1.037

.2757

186

PIERCE.

TABLE I.

h

= .572

to 3.18

k

f(h)

9{h}

h

f(h)

g(h)

h

/(/»)

9(.h)

h

/(A)

g{h)

.572

1.0.37

.2757

1.04

1 . 106

.4702

1.76

1.230

.715

2.48

1.3.56

.915

.574

1.038

.2766

1.06

1 . 109

.4779

1.78

1.233

.722

2.50

1.359

.920

.576

1.038

.2775

1.08

1.113

.4852

1.80

1.237

.728

2.52

1.362

.925

.578

1.038

.2784

1.10

1.116

.4933

1.82

1.241

.733

2.54

1.366

.930

.580

1.038

.2793

1.12

1.119

.5005

1.84

1.244

.740

2.56

1.369

.935

.582

1.039

.2802

1.14

1.122

.5080

1.86

1.248

.745

2.58

1.373

.939

.584

1.039

.2811

1.16

1.126

.5151

1.88

1.251

.751

2.60

1.376

.945

.586

1.039

.2820

1.18

1.129

.5225

1.90

1.255

.757

2.62

1.379

.9.50

.588

1.039

.2829

1.20

1.132

.530

1.92

1.258

.763

2.64

1.383

.9.55

.590

1.040

.2838

1.22

1.135

.538

1.94

1.262

.769

2.66

1.386

.960

.592

1.040

.2847

1.24

1 . 139

.544

1.96

1.265

.775

2.68

1.390

.964

.594

1.040

.28.56

1.26

1.142

.552

1.98

1.269

.780

2.70

1.393

.969

.596

1.040

.2865

1.28

1.146

.559

2.00

1.272

.786

2.72

1.396

.974

.598

1.041

.2874

1.30

1.149

.565

2.02

1.275

.792

2.74

1.400

.97!)

.60

1.041

.2882

1.32

1 . 1.53

..572

2.04

1.279

.798

2.76

1.403

.984

.02

1.044

.2969

1.34

1.156

.580

2.06

1.283

.803

2.78

1.407

.989

.64

1.046

.3059

1.36

1.160

.586

2.08

1.286

.809

2.80

1.410

.993

.66

1.049

.3146

1.38

1 . 163

.593

2.10

1.290

.814

2.82

1.413

.998

.68

1.051

..3235

1.40

1.167

.600

2.12

1.293

.820

2.84

1.416

1.003

.70

1.054

.3321

1.42

1.170

.607

2.14

1.297

.825

2.86

1.420

1.007

.72

1.057

.3406

1.44

1.174

.613

2.16

1.300

.831

2.88

1.423

1.012

.74

1.060

.3491

1.46

1.178

.620

2.18

1.304

.836

2.90

1.426

1.017

.76

1.062

.3578

1.48

1.181

.627

2.20

1.307

.842

2.92

1.429

1.022

.7S

1.065

.3662

1.50

1.184

.634

2.22

1.310

.847

2.94

1.433

1.026

.80

1.068

.3745

1.52

1.188

.640

2.24

1.314

.852

2.96

1.436

1.031

.82

1.071

.3828

1.54

1.191

.647

2.26

1.317

.858

2.98

1.440

1.035

.84

1.074

.3911

1.56

1.195

.653

2.28

1.321

.863

3.00

1.443

1.040

.86

1.077

.3993

1.58

1.198

.659

2.30

1.324

.869

3.02

1.446

1.044

.88

l.OSO

.4074

1.60

1.202

.666

2.32

1.328

.874

3.04

1.449

1.049

.90

1.083

.4155

1.62

1.205

.672

2.34

1.331

.879

3.06

1.4.53

1.053

.92

1.086

.4236

1.64

1.209

.678

2.36

1.335

.884

3.08

1.456

1.05S

.94

1.089

.4316

1.66

1.212

.685

2.38

1.338

.889

3.10

1.459

1.062

.96

1.093

.4392

1.68

1.216

.691

2.40

1..342

.894

3.12

1.462

1.067

.98

1.096

.4471

1.70

1.219

.697

2.42

1.345

.900

3.14

1.465

1.072

1.0

1.099

. 4552

1.72

1.223

.703

2.44

1.349

.904

3.16

1.469

1.076

1.02

1.102

. 4028

1.74

1.226

.710

2.46

1..3.52

.910

3.18

1.472

1 . 080

TABLE FOR TRANSMISSION LINE PHENOMENA.

187

TABLE I.

h = 3.18 to 6.04

h

f(h)

g(h)

h

f{h)

g{h)

h

f{h)

9{h)

h

Rh)

9(h)

;; . 18

1 . 472

1.080

3.90

1.585

1.230

4.62

1.692

1.365

5.34

1.794

1.490

3.20

1 . 475

1.085

3.92

1.588

1.234

4.64

1.695

1.369

5.36

1.797

1 . 493

3.22

1.478

1.089

3.94

1.591

1.238

4.66

1.698

1.372

5.38

1.800

1.497

3.24

1.482

1.093

3.96

1.595

1.241

4.68

1.701

1.376

5.40

1.802

1.499

3.26

1.4,85

1.098

3.98

1.598

1.245

4.70

1.704

1.379

5.42

1.804

1 . 502

3 . 28

1 . 489

1.102

4.00

1.601

1.249

4.72

1.706

1.383

5.44

1.807

1..506

3.30

1.492

1.106

4.02

1.604

1.2.53

4.74

1.709

1.3S7

5.46

1.810

1 . 509

3.32

1.495

1.110

4.04

1.607

1.257

4.76

1.712

1.390

5.48

1.813

1.513

:; . 34

1.498

1.115

4.06

1.610

1 . 261

4.78

1.715

1.394

5.50

1.815

1.515

3.36

1.502

1.119

4.08

1.613

1.265

4.80

1.718

1.397

5.52

1.818

1.518

3.38

1..505

1.123

4.10

1.616

1.269

4.82

1.721

1.400

5.. 54

1.821

1..522

3.40

1 . .508

1.127

4.12

1.619

1 . 273

4.84

1.723

1 . 403

5.56

1.824

1.526

3.42

1.511

1 . 132

4.14

1.622

1.276

4.86

1.726

1.407

5.58

1.827

1..529

3.44

1.514

1 . 136

4.16

1.625

1.280

4.88

1.729

1.411

5.60

1.829

1.531

3 . 46

1.517

1.140

4.18

1.628

1.284

4.90

1.732

1.415

5.62

1.831

1.535

3.48

1.520

1 . 145

4.20

1.631

1.288

4.92

1.735

1.418

5.64

1.834

1.537

3.50

1.523

1.149

4.22

1.634

1.291

4.94

1.738

1.422

5.66

1.837

1.540

3 . 52

1 . 526

1 . 1.53

4.24

1 . 637

1.295

4.96

1.741

1 . 425

5.68

1.840

1.546

3.54

1..529

1 . 1.58

4.26

1.640

1.299

4.98

1.743

1.429

5.70

1.842

1.548

3.56

1.533

1.161

4.28

1.642

1.303

5.00

1.746

1.4.32

5.72

1.844

1.5.50

3.58

1.536

1 . 165

4.. 30

1.645

1.307

5.02

1.749

1.435

5.74

1.847

1 . 5.53

3.60

1..5.39

1.170

4.. 32

1.648

1.310

5.04

1.752

1.439

5.76

1.8.50

1 . 557

3.62

1.542

1.174

4.34

1.651

1.314

5.06

1.755

1.442

5.78

1.853

1.560

3.64

1.545

1.178

4.36

1.6.54

1.318

5.08

1.758

1.445

5.80

1.855

1 . 562

3.66

1..549

1.181

4.38

1.657

1.322

5.10

1.760

1.449

5.82

1.8.57

1.564

3.68

1.5.52

1.186

4.40

1.660

1.325

5.12

1 . 763

1.452

5.84

1.860

1.568

3.70

1..555

1 . 190

4.42

1.663

1.328

5.14

1.766

1.455

5.86

1.863

1..571

3.72

1.5.58

1.194

4.44

1.666

1.3.32

5.16

1.769

1.4.59

5.88

1.866

1..575

3.74

1.561

1 . 198

4.46

1.669

1.336

5.18

1.772

1.463

5.90

1.868

1.577

3.76

1.564

1.202

4.48

1.672

1..340

5.20

1.774

1.465

5.92

1.871

1.581

3.78

1.567

1.206

4.50

1.675

1.343

5.22

1.777

1.468

5.94

1.874

1.584

3.80

1..570

1.210

4.52

1.678

1.346

5.24

1.780

1.473

5.96

1.877

1..588

3 . 82

1..573

1.214

4.. 54

1.681

1 . 350

5.26

1.783

1.477

5.98

1.880

1..592

3.84

1.576

1.218

4.. 56

1.684

1.354

5.28

1.786

1.480

6.00

1.882

1 . 594

3 . 86

1.579

1.222

4.58

1.686

1.358

5.30

1.788

1.482

6.02

1.885

1.598

3.88 1.582

1.226

4.60

1.689

1.362

5 . 32

1.791

1 . 486

6.04

1 . 888

1 . 602

188

PIERCE.

TABLE I.

h

=

6.04 to 8.90

h

/(/«)

9(.h)

h

/(/I)

g(.h)

h

fih)

g(h)

h

fih)

g{h)

6.04

1.888

1.602

6.76

1.979

1.708

7.48

2.066

1.808

8.20

2.151

1.904

6.06

1.890

1.604

6.78

1.981

1.710

7.50

2.069

1.811

8.22

2

153

1.906

6.08

1 . 892

1.606

6.80

1.984

1.713

7.52

2.071

1.813

8.24

2

156

1.909

6.10

1.895

1.609

6.82

1.986

1.716

7.54

2.074

1.816

8.26

2

158

1.912

6.12

1.898

1.613

6.84

1.989

15719

7.56

2.076

1.819

8.28

2

160

1.915

6.14

1.900

1.616

6.86

1.991

1.722

7.58

2.078

1.822

8.30

2

163

1.918

6.16

1.903

1.619

6.88

1.994

1.725

7.60

2.081

1.825

8.32

2

165

1.920

6.18

1.905

1.621

6.90

1.996

1.727

7.62

2.083

1.828

8.34

2

167

1.923

6.20

1.908

1.625

6.92

1.999

1.730

7.64

2.086

1.830

8.36

2

170

1.926

6.22

1.911

1.628

6.94

2.001

1.733

7.66

2.088

1.833

8.38

2

172

1.92S

6.24

1.913

1.630

6.96

2.004

1 . 736

7.68

2.090

1.836

8.40

2

174

1.930

6.26

1.916

1.633

6.98

2.006

1.739

7.70

2.093

1.838

8.42

2

176

1.933

6.28

1.918

1.636

7.00

2.009

1.743

7.72

2.095

1.841

8.44

2

179

1.935

6.30

1.921

1.639

7.02

2.011

1.745

7.74

2.097

1.844

8.46

2

181

1.93S

6.32"

1.924

1.641

7.04

2.014

1.748

7.76

2.100

1.847

8.48

2

183

1.941

6.34

1.926

1.645

7.06

2.016

1.751

7.78

2.102

1.850

8.50

2

186

1.944

6.36

1.929

1.649

7.08

2.019

1.754

7.80

2.104

1.852

8.52

2

188

1.946

6.38

1.931

1.652

7.10

2.021

1.756

7.82

2.106

1.854

8.54

2

190

1.949

6.40

1.934

1.655

7.12

2.023

1.758

7.84

2.109

1.857

8.56

2

193

1.952

6.42

1.936

1.657

7.14

2.026

1.761

7.86

2.112

1.860

8.58

2

195

1.954

6.44

1.939

1.661

7.16

2.028

1.764

7.88

2.114

1.863

8.60

2

197

1.956

6.46

1.941

1.664

7.18

2.030

1.767

7.90

2.117

1.866

8.62

2

199

1.9.59

6.48

1.944

1.667

7.20

2.033

1.770

7.92

2.119

1.868

8.64

2

202

1.962

6.50

1.946

1.669

7.22

2.035

1.772

7.94

2.122

1.871

8.66

2

204

1.965

6.52

1.949

1.672

7.24

2.038

1.775

7.96

2.124

1.873

8.68

2

207

1.967

6.54

1.951

1.675

7.26

2.040

1.778

7.98

2.126

1.876

8.70

2

209

1.970

6.56

1.954

1.678

7.28

2.042

1.781

8.00

2.128

1.878

8.72

2

211

1.972

6.58

1.956

1.6S0

7.30

2.045

1.784

8.02

2.130

1.881

8.74

2

214

1.975

6.60

1.959

1.684

7.32

2.047

1.786

8.04

2.133

1.884

8.76

2

216

1.977

6.62

1.962

1.689

7.34

2.050

1.789

8.06

2 . 135

1.886

8.78

2

218

1.980

6.64

1.961

1.690

7.36

2.052

1.792

8. OS

2.138

1.889

8.80

2

220

1.982

6.66

1.966

1 . 692

7.38

2.054

1.795

8.10

2.140

1.892

8.82

2

222

1.984

6.68

1.969

1.696

7.40

2.057

1.798

8.12

2.142

1.894

8.84

2

225

1.987

6.70

1.971

1.698

7.42

2.059

1.800

8.14

2.144

1.897

8.86

2

227

1.989

6.72

1.974

1 . 702

7.44

2.062

1.803

8.16

2.147

1.900

8.88

2

229

1.992

6.74

1.976

1 . 705

7.46

2.064

1.805

8.18

2.149

1.902

8.90

2

231

1.994

TABLE FOR TRANSMISSION LINE PHENOMENA.

189

TABLE I.

S.90 to 22.4

h

f{h)

y(h)

h

/(/")

aUi)

h

nh)

9(h)

h

fih)

g{h)

8.90

2.231

1.994

9.7

2.319

2.092

13.3

2.678

2.484

16.9

2.995

2.823

S.92

2.233

1.997

9.8

2.329

2.104

13.4

2.687

2.494

17.0

3.003

2.832

8.94

2 . 236

2.000

9.9

2.340

2.116

13.5

2.696

2.503

17.1

3.011

2.841

8.96

2.238

2.002

10.0

2.351

2.128

13.6

2.705

2.513

17.2

3.019

2.8.50

S.98

2.240

2.005

10.1

2.362

2.140

13.7

2.714

2 . 523

17.3

3.027

2.859

9.00

2 . 242

2.007

10.2

2.372

2 . 151

13.8

2.723

2.533

17.4

3.035

2.868

9.02

2.244

2.009

10.3

2.382

2.162

13.9

2 . 732

2.. 543

17.5

3.044

2.876

9.04

2.247

2.012

10.4

2.392

2.173

14.0

2.741

2.-5,53

17.6

3.052

2.885

9.06

2 . 249

2.014

10.5

2 . 403

2.185

14.1

2.7.50

2.. 563

17.7

3.060

2.894

9.08

2.251

2.016

10.6

2.413

2.196

14.2

2.759

2.573

17.8

3.068

2.903

9 . 10

2.2.53

2.019

10.7

2.423

2.207

14.3

2.768

2.582

17.9

3.076

2.910

9.12

2.2.55

2.021

10.8

2.4.33

2.218

14.4

2.777

2.592

18.0

3.084

2.919

9.14

2.2.58

2.024

10.9

2.443

2.221

14.5

2.787

2.602

18.1

3.093

2.928

9 . 16

2.260

2.026

11.0

2.454

2.242

14.6

2.796

2.612

18.2

3.101

2.937

9 . 18

2.262

2.029

11.1

2.465

2.253

14.7

2.805

2.621

18.3

3 . 109

2.945

9 . 20

2.264

2.031

11.2

2.475

2.264

14.8

2.814

2.631

18.4

3.117

2.952

9.22

2.266

2.034

11.3

2.484

2.274

14.9

2.823

2.640

18.6

3 . 1.33

2.969

9.24

2.269

2.0.36

11.4

2.494

2.285

15.0

2.832

2.649

18.8

3 . 148

2.986

9.26

2.271

2.039

11.5

2.504

2.296

15.1

2.841

2.659

19.0

3.164

3.002

9.28

2 . 273

2.042

11.6

2.514

2.307

15.2

2.850

2.669

19.2

3.180

3.019

9.30

2.275

2.044

11.7

2.524

2.318

15.3

2.859

2.678

19.4

3 . 196

3.035

9.32

2.277

2.046

11.8

2.534

2.329

15.4

2.867

2.688

19.6

3.227

3.0.52

9.34

2.280

2.049

11.9

2.544

2.340

15.5

2.876

2.697

19.8

3.231

3.068

9.36

2.282

2.051

12.0

2.554

2.350

15.6

2.885

2.706

20.0

3.243

3.085

9.38

2.284

2.053

12.1

2.563

2.360

15.7

2.894

2.715

20.2

3.258

3.101

9.40

2.286

2.056

12.2

2.573

2.370

15.8

2.903

2.724

20.4

3.273

3.117

9.42

2 . 288

2.0.58

12.3

2,. 582

2.. 381

15.9

2.911

2.733

20.6

3.288

3 . 132

9.44

2.291

2.061

12.4

2.592

2.392

16.0

2.919

2.742

20.8

3.303

3.148

9.46

2.293

2.063

12.5

2.601

2.401

16.1

2.928

2.751

21.0

3.318

3 . 164

9.48

2.295

2.065

12.6

2.610

2.411

16.2

2.936

2.760

21.2

3.333

3.179

9.50

2.297

2.067

12.7

2.620

2.421

16.3

2.945

2.769

21.4

3.348

3 . 195

9 . .52

2.299

2.069

12.8

2.630

2.432

16.4

2.953

2.778

21.6

3.362

3.210

9.. 54

2.302

2.072

12.9

2.640

2.443

16.5

2.961

2.787

21.8

3.377

3.226

9. 56

2.. 304

2.075

13.0

2.650

2.454

16.6

2.970

2.796

22.0

3.392

3.241

9.. 58

2.306

2.077

13.1

2.660

2.465

16.7

2.979

2.805

22.2

3.401

3.256

9.60

2 . 308

2.080

13.2

2 . 669

2.475

16.8

2.987

2.814

22.4

3.421

3.272

190

PIERCE.

TABLE I.

h

= 22.4 to 107

h

Kh)

g{h)

h

Kh)

3 (ft)

h

J{h)

g(h)

h

f{h)

g{h)

22.4

3.421

3.272

29.6

3.912

3.782

36.8

4.348

4.232

72

6.042

5.9.59

22.6

3.436

3.287

29.8

3.924

3 . 795

37

4.359

4.243

73

6.084

6.001

22.8

3.450

3.303

30.0

3.937

3.808

38

4.417

4.302

74

6.123

6.041

23.0

3.465

3.318

30.2

3.950

3.821

39

4.473

4.360

75

6.166

6.084

23.2

3.480

3.333

30.4

3.963

3.835

40

4.528

4.416

76

6.205

6.124

23.4

3.494

3.348

30.6

3.-976

3.848

41

4.584

4.473

77

6.245

6.168

23.6

3.509

3.. 363

30.8

3.989

3.862

42

4.6.3S

4.. 528

78

6.285

6.205

23.8

3.. 523

3. 378

31.0

3.002

3.875

43

4.692

4.. 584

79

6.326

6.246

24.0

3.538

3.393

31.2

4.014

3.888

44

4.743

4.6.36

SO

6.364

6.284

24.2

3.551

3 . 407

31.4

4.026

3.900

45

4.797

4.691

81

6.405

6.326

24.4

3.563

3.423

31.6

4.039

3.913

46

4.848

4.744

82

6.443

6.364

24.6

3.577

3.437

31.8

4.051

3.925

47

4.899

4.795

83

6.481

6.403

24.8

3.590

3.452

32.0

4.063

3.938

48

4.952

4.850

84-

6.519

6.442

25.0

3.603

3.467

32.2

4.075

3.951

49

5.000

4.898

85

6.558

6.481

25.2

3.618

3.481

32.4

4. 087

3.963

50

5.050

4.9.50

86

6.. 597

6.. 521

25.4

3.632

3.495

32.6

4.100

3.976

51

5.099

5.000

87

6.633

6.557

25.6

3.647

3.509

32.8

4.112

3.988

52

5.147

5.049

88

6.669

6.593

25.8

3.661

3.524

33.0

4.124

4.001

53

5.198

5.101

89

6.706

6.637

26.0

3.676

3.538

33.2

4.136

4.014

54

5.244

5.148

90

6.746

6.671

26.2

3.689

3.552

33.4

4.148

4.026

55

5.293

5.198

91

6.782

6.708

26.4

3.702

3.565

33.6

4.161

4.039

56

5.. 341

5.246

92

6.819

6.744

26.6

3.716

3.579

33.8

4.173

4.051

57

5.. 387

5.294

93

6.8.57

6.783

26.8

3.729

3.592

34.0

4.185

4.064

58

5.433

5.. 340

94

6.894

6.821

27.0

3.742

3.606

34.2

4.197

4.076

59

5.478

5.386

95

6.928

6.8.59

27.2

3.756

3.620

34.4

4.209

4.088

60

5.524

5.433

96

6.966

6.894

27.4

3.769

3.634

34.6

4.220

4.100

61

5 . 568

5.477

97

7.001

6.929

27.6

3.783

3.648

34.8

4.232

4.112

62

5.612

5 . 522

98

7.035

6.964

27.8

3.796

3.662

35.0

4.244

4.124

63

5 . 656

5.567

99

7.056

6.985

28.0

3.810

3.676

35.2

4.2.56

4.136

64

5.701

5.613

100

7 . 105

7.035

28.2

3.823

3.689

35.4

4,267

4.148

65

5.746

5.6.58

101

7.141

7.070

28.4

3.836

3.703

35.6

4.279

4.160

66

5.789

5.712

102

7.176

7.106

28.6

3.848

3.716

35.8

4.290

4.172

67

5.832

5.745

103

7.212

7.142

28.8

3.861

3.730

36.0

4.302

4. 184

68

5.875

5.788

104

7.247

7 . 178

29.0

3.874

3 . 743

36.2

4.314

4.196

69

5.916

5.830

105

7.279

7.211

29.2

3.887

3.756

36.4

4.325

4.208

70

5.959

5 . 875

106

7.321

7 . 244

29.4

3.899

3.769

.36.6

4.336

4.219

71

6.000

5.917

107

7.349

7.280

TABLE FOR TRANSMISSION LINE PHENOMENA.

191

TABLE I.

^ = 107 to 250

h

Kh)

9(h)

h

/(/»)

gi.h)

h

Kh)

9{h)

h

f(h)

9(h)

107

7.349

7.280

143

8.459

8.453

179

9.463

9.4.58

215

10.371

10.. 366

lOS

7.381

7.313

144

8.488

8.482

180

9.489

9 . 482

216

10.395

10.390

109

7.414

7 . 347

145

8.518

8.512

181

9.516

9.511

217

10.419

10.414

110

7.440

7.. 380

146

8.. 547

8.541

182

9.542

9.. 537

218

10.443

10.438

111

7 . 485

7.417

147

8.576

8.580

183

9.568

9.563

219

10.467

10.462

112

7.518

7.451

148

8.605

8.599

184

9.. 594

9 . 589

220

10.491

10.480

113

7.552

7.485

149

8.634

8.628

185

9.620

9.615

221

10.514

10.510

114

7.. 582

7.515

1.50

8.663

8.6.57

186

9.646

9.641

222

10. 5.38

10.. 533

11.-)

7.0 10

7 . 550

15i

8.692

8.686

187

9.672

9.667

223

10.. 562

10.. 557

110

7.050

7.584

1.52

8.721

8.715

188

9.698

9.693

224

10.. 585

10.581

117

7.680

7.615

1.53

8 . 749

8.744

189

9.724

9.719

225

10.609

10.604

lis

7.714

7.649

1.54

8.778

8.772

190

9.749

9.744

226

10.633

10.628

119

7 . 745

7.680

155

8.806

8.804

191

9 . 775

9.770

227

10.6.56

10.651

120

7 . 780

7.715

156

8.835

8.829

192

9.800

9 . 796

228

10.679

10.675

121

7.811

7.746

157

8.863

8.8.57

193

9.826

9.821

229

10.703

10.698

122

7.842

7.778

158

8.891

8.885

194

9.851

9.846

230

10.726

10.722

123

7.S72

7.809

1.59

8.919

8.914

195

9.877

9.872

231

10.749

10.745

124

7.908

7 . 844

1()0

8.947

8.942

196

9.902

9.897

232

10.773

10.768

125

7.939

7.876

161

8.975

8.969

197

9.927

9.922

233

10.796

10.791

12(;

7.941

7.934

162

9.003

8.997

198

9.9.52

9.947

234

10.819

10.814

127

7.972

7.960

163

9.031

9.025

199

9.978

9.973

235

10.842

10.838

128

8.003

7.997

164

9.0.58

9.053

200

10.003

9.993

236

10.865

10.861

129

8.034

8.028

165

9.086

9.080

201

10.028

10.023

237

10 . 888

10.8S4

13i)

8.005

8.0.59

166

9.113

9.108

202

10.052

10.047

238

10.911

10.906

131

8.090

8.090

167

9.141

9 . 135

203

10.077

10.072

239

10.9.34

10.929

132

8.127

8.121

168

9.168

9 . 163

204

10.102

10.097

240

10.957

10.9.53

133

8.158

8.152

169

9 . 195

9 . 190

205

10.127

10.122

241

10.980

10.975

134

8.189

8.182

170

9.222

9.217

206

10.151

10.146

242

11.002

10.998

135

8.219

8.213

171

9.249

9.244

207

10.176

10.171

243

11.025

11.020

130

8.249

8.243

172

9.276

9.271

208

10.201

10.196

244

11.048

11.043

137

8.280

8.274

173

9.303

9.298

209

10.225

10.220

245

11.070

11.066

138

8.310

8.304

174

9., 330

9.. 325

210

10.249

10.245

246

11.093

11.088

139

8.340

8.. 334

175

9 . 357

9.351

211

10.274

10.269

247

11.115

11.111

140

8.370

8.364

176

9.384

9.389

212

10.298

10.293

248

11.136

11.133

141

8.399

8.393

177

9.410

9.405

213

10.322

10.308

249

11.158

11.1.56

142

8.429

8.423

178

9.437

9.431

214

10.347

10.342

250

11.180

11.178

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 8.— May, 1922.

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUC-
TANXE BETWEEN ADJACENT SERIES ELEMENTS.

By George W. Pierce.

f Continued frotn page 3 of cover.)

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ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUC-
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By George W. Pierce.

ARTIFICIAL ELECTRIC LINES ^^TTH MUTUAL INDUC-
TANCE BETWEEN ADJACENT SERIES ELEMENTS.

By George AY. Pierce.

Received Jan. 13, 1922. Presented Jan. 11, 1922.

L Gexer.^l Principles.

1. Introduction. — So far as I have been able to ascertain, the
artificial lines with lumped sections heretofore employed have been
generally devoid of appreciable mutual inductance between adjacent
elements.

In artificial line construction the inductive elements are placed
mutually at right angles to each other or are wound in toroidal form
so as to reduce to a minimum the mutual inductance caused by
magnetic leakage from one inductive element to the next.

In my Text Electric OsciUatiotis and Electric Waves,^ Chapter XVI,
I have treated theoretically artificial lines in which mutual inductance
exists between adjacent series elements.

It is proposed here to show, ^vith the aid of the general treatment in
my text, that such mutual inductance, if properly chosen, has a de-
cidedly beneficial eft'ect in the following two types of apparatus:

A. An Electric Compensator designed to introduce into circuits a
time lag substantially independent of the frequency of impressed
e.m.f. ;

B. An Artificial Line designed to simulate an actual smooth line.^

2. General Type of Line. — Let us direct our attention to the
general type of artificial line shown in Figure L

The shunt elements of complex impedance Z2 may be of any charac-
ter. The series elements of complex impedance 21 may likewise be of
any character, and have between such of these elements as are adja-

1 Pierce: Electric Oscillations and Electric Waves, McGraw-Hill Book Co.,
New York, 1920. (See also corrected reprint in press 1921.)

2 Since sending this paper to press I have been informed by Mr. K. S.
Johnson that application of the present device in Case B has been in use for
.several years at the Western Electric Company, but has not been described in
publications.

196

PIERCE.

cent a mutual inductance M, which may be set equal to zero in case
results without M are required. The mutual inductance between
non-adjacent elements is supposed to be negligible in all cases.

The line is supposed to terminate at both ends in a series half-
element of complex impedance Zi/2 so constructed as to have also
mutual inductance M with its neighboring series section.

?t

in-,

MM

« z, — 5.

< — ^— ^

6'

Figure 1. General type of artificial line containing mutual inductance
between adjacent series elements.

The line is shown connected to an input terminal apparatus of
complex e.m.f. e and complex impedance 20 and connected to an out-
put apparatus of complex impedance Zf.

The artificial line here shown may be regarded as consisting of n-1
loops and two terminal series half elements, or it may be considered
to consist of n sections, known as T-sections, each of the character
shown in Figure 2.

Figure 2. A T-section.

It may be noted that the treatment of other general types of lines
(for example, lines of 7r-sections) are deducible from the treatment of
the line of Figure 1 by postulating certain changes in the terminal
conditions.

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE. 197

3. General Definitions. —

2^ = complex impedance of the series elements.

So = complex impedance of the shunt elements.

M= imdual inductance between adjacent series elements, esti-
mated positive when the coils are wound in the same sense.

(p = retardation angle of current per section of the line = the
angle of lag of steady-state current in any section behind
the current in the preceding section.

T = time lag of current in seconds per section.

a = real attenuation constant of current per section of the line
= the exponent in the factor e-", by which factor the
steady-state current-amplitude in any series element of
an infinite or non-reflective line must be multiplied to
give the current-amplitude in the next series element.

Zj = complex surge impedance of the line = complex impedance
of a line of an infinite number of sections or a line with
non-reflective output impedance.

CO = angular velocity of impressed sinusoidal e.m.f. in radians
per second.

4. Abbreviations and Subsidiary Notation. — The following
notation taken from Electric Oscillations and Electric Waves with slight
augmentation will be employed.

p+ir. = ^^i±^ (1)

where P and V are real quantities;

1 _ IJi — p2

v-'-^, ; (2)

h = U/V; (3)

2 2

Other notation will be introduced below in Section 10.

5. Equations for a and (/? for Steady-State Current. — It is
proved in Electric Oscillations and Electric Waves, equations (49) and
(50), p. 29G, that, for the steady-state current under the action of an

198

PIERCE.

impressed sinusoidal e.m.f. of constant amplitude and frequency, a
and (f are given by expressions which factored may be written

n = sinh-i ] + V' - ^' \ '^^ 1 + h-

<P = sm- I ^ \' ^ ^' V - . - - J

-1 J

(5)

+

V JV 1 + h^ =^ 1 - ,

in which T' and h have the value given in (2) and (3), and in which the
upper signs or the lower signs are to be tised together in each case and are
to be chosen so as to make a and <p both real quantities. For definitions
of a and ip see §3.

6. Modified Form of Equations for a and (p. — Using the/- and
(/-functions given in (4), we may write (5) as follows:

I. If r > 0,

a = sinh"^ V2f' dW^ ^ — sin

h = U/V.

-1 i

V2vm}

(6)

with

II. ifr<o,

a = sinh-i V-2VfUi), ^ = sin-^ !± V- 2V 5'W}

with h = U/V.

These equations are to be employed subject to the following rule
regarding the quadrant of cp:

Rule Regarding (p.

sign of

quadrant of <p

P

U

+ 11 +

1 1 + +

first
second
third
fourth

Equations (6) are the general expressions for the real attenuation con-
stant a and the real retardation angle (p per section in terms of U, V, f{h),

I

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE. 199

and g(k), which are defined in equations (1), {2), (3), and (4). These
equations apphi to the f/nirral ti/pc of line given in Figure 1 .

In a paper now in press ^ entitled A Table and M et hod of Computation
of Electric Wave Propagation, Transmission Line Phenovieiia, Optical
Refraction , and Inrrr.sc Ili/jjcrholie Functions of a Coinplrx Variable
I luive given a table of the I'linetions /(/;) and g{h) for various values
of //, so as to render very simple the eoniputations of a and (p of
equations (6).

7. General Equation for Surge Impedance Zi. — Before passing
to a further discussion of a and ip, we shall introduce the general ex-
pression for surge impedance Zi, taken from Electric Oscillations and
Electric ]\'aves, Ecjuation (34), p. 292, as follows:

., = * ^(Ii±^ _ (J, .„ _ ^.^,, (7)

In Equation (7) the sign before the radical must he chosen to make the
real jxtrt positive.

It may be noted that this equation also permits of easy computation
by the method of the paper referred to in Section 6.

8. Time Lag per Section. —

Let

T = time lag in seconds per section of the line introduced

into the current by the line,
oj = angular velocity in radians per seconfl of the impressed

e.m.f.

In the steady state, the current will also have the angular velocity oj
and the time lag per section will be given by

T = <p/i,. (8)

The steady-state time lag in seconds per section is the retardation angle
per section in radians divided -by the angular velocity in radians per
second.

1 These Proceedings: Vol. 57, No. 7.

200 PIERCE.

II. The Electric Compensator.

Improvement Introduced by Proper Mutual Induction between

Series Sections.

9. Brief Description. — In the determination of the direction
of submarine sovmd signals and in giving to submarine sound appa-
ratus directive qualities so as to permit discrimination of certain sounds
from other sounds coming from a different direction, Professor Max
Mason ^ of Wisconsin University has made use of two or more sound
detectors (rubber nipples in the water) communicating with the ear
of the observer through paths (air pipes) capable of adjustment as to
time of travel (by adjusting pipe lengths), so that, when the detectors
are struck, one after the other, by a sound-wave front, the impulses
set up in the transmission paths connected to the several receivers
may all be brought to the ear together by a suitable adjustment of
retardation by the paths (compensation). In this way the setting of
the apparatus (a compensator) to give a maximum of sovmd will, when
the apparatus is properly calibrated, give a direct reading of the
direction of the incident sound. Sounds coming from other directions
(as, for example, noises from the listener's boat) will in general not be
compensated to give a maximum of intensity and will be discriminated
against by the apparatus.

Professor Mason developed this apparatus in a form known as the
Accoustical System employing rubber nipples on the ends of tubes as
sound detectors, and introducing compensation by varying the lengths
of air colums through which the resulting sound waves in the air
columns were transmitted to the ear of the observer. The Mason
system gives excellent results in practice.

It readily occurred to those who knew of Mason's Device that some
advantage might result by using microphones, or other electrical
detectors, in the place of the rubber nipples, provided electrical
methods could be employed to produce the required retardations of
currents set up at the microphones.

An apparatus for this purpose was devised by me at the Naval
Experimental Station at New London, and is called an Electric Com-
yensator.

An Electric compensator is a device for giving electrically to an electric

1 See H. C. Hayes, Detection of Submarines, Proc. Am. Phil. Soc, Vol. 59,
pp. 1-47, 1920: and U.S. Navy MV-T ype of Hydro-phone as an Aid and Safeguard
to Navigation, Ibid., Vol. 59, pp. 371-40-4; Max Mason: Submarine Detection
by Multiple Unit Hydrophones, Wisconsin Engineer (1921).

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE.

201

current any desired time-retardation substantially independent of the
frequency over a significant range of frequencies.

An artificial line consisting of inductances in series and capacities
in shunt and provided with suitable switching devices is an electric
compensator. To have practical application the attenuation of the
compensator must be low and the steps must be made small enough
in inductance and capacity values to obviate filtering effects, and the
dimensions of the coils must be chosen in a manner to diminish dis-
persion and other distortions. The principles governing the design of
such a compensator are given in my book Electric Oscillatwns and
Electric Wares, pp. 285-323.

It is proposed here to show how improvements result from the use
of suitable mutual inductance between the neighboring series induc-
tances of the electric compensator.

10. Proof that Introduction between neighboring sections
of Mutual Inductance Approximately Equal to One-Tenth of
the Self Inductance of the Series Elements Greatly Reduces
Dispersion in an Electric Compensator. — It is proposed to prove

LJ^

M

Li

l-i

T-i

M

t-ilz

^W^^^T^^SWA^V^^^^^^^

Q

Figure 3.

that mutual inductance between adjacent series inductive sections
of the value specified in the caption reduces dispersion; that is, that
it makes T, the time retardation per section, less dependent on the
frequency of the impressed e.m.f.

The line to be employed has inductive elements in aeries and capa-
city elements in shunt, as is shown in Figure 3. The series elements
have an inductance L\ and resistance R\ per loop, and the shunt
elements have each a capacity C\. Let there be mutual inductance
M between the inductances of each two adjacent loops, and let there
be zero mutual inductance between inductances not adjacent.

202 PIERCE.

We shall then have (compare El. Osc. and El. Waves, p. 316)

21 = i?i + jIiOJ, (9)

22 = - J/C2CC, (10)

These values substituted into (1) give

U = vQ/2, (11)

Q { Q )

T^ = ||l-f (1+T)|, (12)

in which the following abbreviations are employed

i = Li + 2M, R - /?!, (13)

,= /?/Lc., and Q=^^rtRj~^- (14)

As a further abbreviation, let us write

^ = 1 - I (1 + rf), (15)

SO that equation (12) becomes

T' = QA/2. (16)

Then by the general equations (6), we have for tp the Aalue

if ^'>0, ^=sin-i /^ /^/l+^ + l- (17)

This equation is the equivalent of (142), p. 317, of Electrical Oscilla-
tions and Electric Wares. \Ye now proceed to develop the subject
further.

Confining our attention to this case in which V is greater than zero
(that is, A positive), and expanding the inner radical in (17), we obtain,
after transposition and squaring,

sinV=<?j|l + ^-j|^ + ...j (18)

If now we consider the resistance per section to be so small in com-
parison with the inductive reactance per section that

ri- <<\ and y]' < < 4.4^ (19)

ARTIFICIAL ELECTRIC LINES WITH iMUTUAL INDUCTANCE. 203

we have

sinV = QA = Q- Q'/4:. (20)

Let us now expand the two sides of (20) in series, obtaining

T2/7 2 4

- ^ (1 - 2J/Coco2 + UPC'?u^^ ). (21)

4

By reference to (8) it will be seen that to make T, the time retarda-
tion per section, independent of the frequency, we shall require ^- to
be proportional to or. This requirement will be consistent with (21)
provided we can so choose M that

<p- = LC;i/-, (22)

and

(23)

are both satisfied.

Equations (22) and (23) are equations from which to determine M.
Instead of an exact determination of M we shall content ourselves by
an approximate determination of M by substituting (22) into (23)
and equating separately terms of the same power of co, obtaining

^^V^- = LMC-ro^\ and (24)

12

45 2

Equation (24) gives

M = L/12, (26)

which substituted into (25) gives

iV45 = LV41. (27)

Equation (27) is not true, but since terms in which U enters are of a
higher order than terms in L and U, we may consider the difference
between the two sides of equation (27) as negligible, and employ (26)
as the approximate condition required.

204 PIERCE.

By the use of (13), this condition (26) becomes

M = Xi/10, (28)

and by (8) and (28) equation (22) gives

T = VlC2 = Vl.2L,C2- (29)

Equation (28) gives the value of the Mutual Inductance M to be intro-
duced between the adjacent series coils of Self Inductance Li {and of
negligible resistance) in order to make the time-retardation T per section
be as nearly as possible independent of the frequency and to have over a
xvide range of frequencies approximately the value given in (29).

// the resistance of the coils is not negligible it is possible to modify the
relation {28) slightly in a manner that will enhance slightly the constancy
of T over a given range of frequencies, but in practice, where a reasonable
effort is made to keep resistances small, the relation {28) is sufficiently
accurate.

In any case the exact value of T can be calculated by the use of {17) and
(8).

11. Computed Table and Curves Showing the Performance
of a Line with Mutual Inductance Equal to One Tenth of Self
Inductance in Comparison with a Line of Zero Mutual In-
ductance.— Table I of which four columns were computed from
the exact Equation (17) with the use of (8), gives the values of

T jy/LCi for different values of my/LCi.

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE. 205

TABLE I.

Values of T/V LC^ for Various Values of ioV LC^ for the Case
of R/Ro =0 and the Case of R/ Ro = .1, with M = 0 and M = .1 Li
in each case.

a, VLC,

R/R

0=0

R/R

0= .1

M =0
L = U

M = .ILi
L = 1.2L,

M = 0
L = Li

M = . ILi
L = 1.2Li

M = 0
L = U

M = .ILi
L = 1.2Li

T/ ^LC2

r/ VLC2

T/ VLC2

T/ ^LC2

a

a

.00

1.0000

1.0000

00

00

.00000

.00000

.01

1.0000

1.0000

2.347

2.347

.02131

.02131

.02

1 . 0000

1.0000

1.745

1.745

.0287

.0286

.03

1.0000

1.0000

1.497

1.497

.0334

.0334

,05

1.0000

1.0000

1.272

1 , 270

.0394

.0394

.10

1 . 0007

1.0000

1.099

1.098

.0456

.0456

.15

1.0017

1.0000

1.050

1.049

.0479

.0478

.20

1 . 002

1.000

1.030

1,029

.0489

.0487

.25

1.003

1.000

1.022

1 , 019

.0495

.0494

.30

1.004

1.000

1.017

1.013

.0500

.0498

.35

1.005

1.000

1.016

1,009

.0503

.0499

.40

1.007

1.000

1.015

1,007

.0507

.0503

.50

1.011

1.000

1.016

1.005

.0514

.0508

.60

1.016

1,000

1.018

1.004

.0523

.0514

.70

1.022

1,001

1.023

1.002

.0532

.0521

.80

1.032

1.001

1.031

1.003

.0545

.0528

1.00

1.050

1.002

1.046

1.004

.0577

.0547

1.20

1.075

1.004

1.072

1.007

.0624

.0574

1.40

1,121

1.009

1.109

1.010

.0700

.0605

1.60

1.156

1.019

1.160

1.016

. 0834

.0659

1.80

1 , 239

1,027

1.241

1.026

.1142

.0736

2.00

1.570

1 . 047

1.044

.0862

2.20

1.0S2

1.079

.1129

2.40

1,172

1.144

OJOO

206

PIERCE.

The last two columns contain corresponding values of the attenua-
tion constant a computed by the use of the exact equation (6), for the
case of R/Ro= .1. For R = 0 the value of a is zero throughout the
range of the table.

In the table the values of R are specified by specifying values of

R/Ro, where Ro= V Z/CV Only two values of R/Ro (namely, zero
and .1) were employed in computing the tables. The case in which
the ratio is zero is a case of zero attenuation, while the case with the
ratio . 1 is a case of much higher attenuation than would arise with
coils built with a reasonable effort to keep the ratio of resistance to
inductance small, so that the table gives extreme ^'alues.

Curves of the data of the table are presented in Figures 4, 5 and 6.

.4

.e /. 0 tZ 14

Figure 4.

/-6 1.8 ^0 X'l «'/

12. Comparison of Line of Mutual Inductance equal to One
Tenth of Self Inductance with Line of Zero Mutual. — By refer-
ence to the curves of Figures 4 and 5 it is seen that the range of values
of CO for which the time retardation T per section is within a given
percentage of constant is much larger in the case M = . IXi than in
the case M = 0. With M = .\L\ the range of frequencies over which
T is within one percent of constant is three times as great as when no

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE.

207

lAC
1.36
13Z
1.E8
1.24
1.20
1,16

^1.08
1.04
1.00

0 .2 .4r ,6 .S 1.0 1.2 1.4 1.6 1,8 ZO 2.2 2.4
Figure 5.

.2 0

.16

.12

.08

.04

1

^

J

R/Ro='l

^^

.

— ■=

^^

■ ■

/

.00'

0 .2 .4- .6 .8 l.O I.Z /.4 /.e fS Z.O Z.Z ^.4

Figure 6.

mutual inductance is introduced between the series coils. Reference
to Figure G shows that the attenuation constant a is also slightly
smaller with the mutual inductance than without it.

If air-core coils are to be used it requires less space and is much

208 ' PIERCE.

easier to supply the required mutual inductance than it is to leave it
out, so that b}' using the mutual inductance between sections we can
increase the frequency range for a specified constancy of time retarda-
tion to three times the range without the mutual inductance, and this
can be done with a better space 'factor and with a significant diminu-
tion of cost.

13. Constancy of Surge Impedance also Somewhat Improved
by Introducing Mutual Inductance = .1L> between Series Sec-
tions of a Low Resistance Line. — Equation (7) is the general ex-
pression for surge impedance of the line of Figure 1. When the series
impedances are inductances and the shunt impedances are capacities,
as in Figure 3, 2i and 22 take on the values given in (9) and (10).
These substituted into (7) give

1

SvEt'- '"

Equation {30Y is the general expression for surge impedance of a line
of the type shown in Figure 3. In this equation L = L\-\- 2M, and

Ro= VL/C'2.

It is seen that, if the resistance of the line is low, the imaginary
term in (30) is small, and the real term tends to approach independ-
ence of CO as 4il/ approaches L. Making M = .lZi= L/12, as is
required in order to make T less dependent on frequency, has the
effect of cutting the real term containing or by about ^ and hence the
introduction of M = .iLi reduces the dependence of surge impedance
on frequency for low resistance lines.

1 The corresponding equation (142) p. 317 of EI. Osc. and Wares has in the
first printing of the book an error, that has been corrected in the Second Im-
pression of 1921.

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE 209

III. An Artificial Line to Simulate an Actual Smooth Line.

Improvement as to Attenuation and Surge Impedance brought
ABOUT BY Proper Mutual Induction between Series Sections.

14. Constants for Actual Smooth Line. — In the case of an
actual smooth line, let

r, I, c = respectively the resistance, self-inductance, and capa-
city per loop unit of length;
a = real attenuation constant per unit of length;
13 = angle of lag of current per unit of length ;
Zi= surge impedance of the line;

then

a = CO

(3 = CO

l\

0

C /CO

(31)

(32)

(33)

These equations are the familiar expressions. See, for example
El. Osc. and El. Waves, pp. 329 and 330.

15. To Design an Artificial Line with Lumped Sections that
Will Simulate the Smooth Line as to Surge Impedance. — For

this purpose we shall postulate a line of the type shown in Figure 3,
and shall determine what value of M brings the surge impedance of
this line, as is given in (30), most nearly into the form of (33) in so far
as dependence of s,- on co is concerned. Since the real part of (30)
is generally much larger than the imaginary part, it is seen by inspec-
tion that a good approximation to this result is made by making

M = L/4.; (34)

which bv (13) means >

M = Li/2. (35)

210 PIERCE.

By making M have the vakie given in (34) equation (30), in view of
the fact that

^0 = Vl/C., (36)

becomes

(37)

Equation {37) gives the surge impedance of a lumpy artificial line with
31 = Li/3. Since the imaginary term in the surge impedance of a
smooth-line {equation {33)) is generally small over practical ranges of
frequency, it is seen that {37) is essentially of the form of {30) in so far as
concerns dependence of surge impedance on frequency}

16. To Determine the Mutual Inductance between Series
Section in a Lumpy Artificial Line to Bring it into Close Simi-
larity with A Smooth Line as to Attenuation Constant.^
Postulating a line of the type of Figure 3, and substituting (9), (10),
(13), (14) and (15) into the value of a given in (5) we obtain

If F>0,

\~i i I r

(38)

Equation {38) is the general equation for attenuation constant for a line
of the type of Figure 3, tinder the condition T' > 0.

Equation (38) expanded with neglect of higher powers of rf'/A^ gives

smha=,^\j ^1-— +-- + •••• f (39)

A corresponding expansion of (31) gives approximately for the
smooth line

« = fVfc.|l-f +■■•[, (40)

1 This fact was called to my attention by Mr. Phillip Machanik, who based
his observation in an examination of the equations in Electric Oscillations and
Electric Waves.
\

ARTIFICIAL ELECTRIC LINES WITH MUTUAL INDUCTANCE. 211

where

770 = r/Zio. (41)

Since the second terms in (40) and (39) are usually small, and since
a is also sufficiently small to make sinh a essentially equal to a, the
two equations reduce to nearly the same form in respect to co if

Q/A = iCaco^. (42)

Replacing A in (42) by its value from (14) with neglect of 77- in (15)
w^e obtain

^ " 1 + i>cwy4'

which compared with (14) shows that (42) is approximately satisfied
when

M = L/4: = ii/2. (42)

A substitution of this value of M into the exact equation (38) gives
in a careful approximation

sinh a = I Via, CO I 1 - f + ^ (iCoV + I U~C,w) I . (43)

If now w^e expand the hyperbolic sine into

sinh a = a -\- a^/6,
and replace the a in a^ by the first term of (43), we obtain

a = IVLC, CO I 1 - 3 + ^ (lC^co^ + I UC.}u:) \ ■ (44)

The approximation of equation (44) shows that even when rj. is as large
as . 5 and ivith LCoui^ as large as 1 the introduction of a mutual inductance
of the value given in {4'2) makes the attenuation constant of the artificial
lumpy line of the same form as the attenuation constant a of the smooth
line, and that the two attenuation constants can be thus made to agree
over a wide range of frequencies.

212 PIERCE.

IV. Conclusions.

The following results, believed to be novel, for artificial line con-
struction have been here derived.

1. To obtain a minimum dependence of time lag per section on
frequency of an electric artificial line of low resistance, the line should
be constructed with mutual inductance between neighboring series
inductive elements equal to one-tenth of the self inductance of each
series inductive element.

2. To most closely simulate a real smooth electric line as to attenu-
ation constant and surge impedance by the use of an artificial electric
line with lumpy sections, there should be in the artificial line a
mutual inductance between adjacent loops equal to one-half of the
series self inductance per loop.

3. Details for calculating the performance of lines constructed
according to 1 . and 2 . are given.

Cruft Laboratory,

Harvard University, Cambridge, Mass.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 9.— May, 1922.

CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION

FOR RESEARCH. No. 135.

THE PARASITIC WORMS OF THE ANIMALS OF BERMUDA.

I. TREMATODES.

By Franklin D. Barker.

With Thbee Plates.

( Continued from page 3 of cover. )

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 9 — -May, 1922.

CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION

FOR RESEARCH. No. 135.

THE PARASITIC W0R:MS OF THE ANIMALS OF BERMUDA.

I. TREMATODES.

By Franklin D. Barker.

With Three Plates.

CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION

FOR RESEARCH. NO. 135.

THE PARASITIC \YORMS OF THE ANIMALS OF BERISIUDA.

I. TREMATODES.
Franklin D. Barker.

Received Feb. 12, 1922. Presented by E. L. Mark, March 8, 1922.

Introduction.

Through the courtesy and generous assistance of Professor E. L.
Mark, Director of the Bermuda Biological Station, and of the National
Academy of Science, it has been my pri\dlege to spend two seasons at
the Bermuda Station, collecting and studying the parasitic fauna.
The following paper is the first of a series which will embody the results
of these investigations.

The two forms here described were found in the stomach of a Hawk's-
bill Turtle, ChcJonia imbricata (Linn.), at the Bermuda Biological
Station.

Pachypsolus brachus, n. sp.
(Pis. I and II, Figs. 1-8, 12).

1 . Morphology.

General Appearance. — The description of the following species is
based on the study of 27 preserved specimens, 1 1 of which were killed
and fixed in 2% formol and 16 in vom Rath's osmio-sublimate mixture.
Little difference can be seen as a result of the different killing reagents
other than in color. Specimens fixed in formol are grayish-yellow,
those fixed in vom Rath's fluid black. A detailed study has been made
of specimens in toto, both unmounted and mounted, and of series of
frontal and sagittal sections.

The body is oval and plump (PI. II, Fig. 8), being one half as thick
as wide. The length varies from 3jnm. to 3.7 mm., the mode being
3 mm., which is the length of 50 per cent of the individuals. The
width varies from 1.5 to 1.9 mm., the mode being 1.7 mm., which is
the width attained by 60 per cent. The ends are bluntly rounded,

216 BARKER.

the anterior end slightly more tapering than the posterior. In the
median line at the posterior end is a well defined terminal invagina-
tion, which marks the position of the excretory pore. The dorsal
surface of the body is strongly arched, the ventral surface slightly
cupped. The sides are nearly parallel with the exception of a wide,
shallow constriction midway between the ends at the level of the
acetabulum. Spines or scales were not found anywhere on the body.

In the preserved specimens, the anterior third of the body shows a
marked and constant tendency to flex ventrad, which gives rise to a
well defined and rather deep ventral cup between the oral and ventral
suckers. This cup-like depression persists in compressed specimens
and possibly functions as a secondary holdfast (PL II, Fig. 8).

The oral sucker is comparatively large, well defined, nearly circular
in outline and ventral in position, with its dorso-ventral axis at right
angles to the chief axis of the body. In compressed specimens the
oral sucker is 0.80 mm. to 0.82 mm. wide by 0.66 mm. to 0.82 mm.
long. In frontal sections it measures 0.82 mm. wide by 0.82 mm. long.
The ventral sucker, or acetabulum, lies in the median area at the
posterior margin of the anterior half of the body and faces obliquely
cephalad. It is of approximately the same size and shape as the oral
sucker. It measures 0.60 mm. to 0.74 mm. in length by 0.70 mm. to
0.74 mm. in width in compressed specimens and 0.72 mm. by 0.80 mm.
in frontal sections.

The genital pore is not salient and lies in the median line, at the
anterior margin of the acetabulum, or else slightly to the left of, and
just anterior to the acetabulum.

In the middle quarters of the body (PI. I, Fig. 2), along the sides,
and extending well toward the median line on the dorsal surface, can
be seen the characteristic dark colored, convoluted tubular and finely
granular vitelline glands in moss-like patches. The uterus appears
as a dark coiled mass nearly filling the \entral field of the posterior
third of the body.

Digestive System. — The transversely oval mouth leads into the
triangular lumen of the oral sucker, which is 0.90 mm. deep in sagittal
sections with thick muscular walls. A thick walled, large and power-
ful cup-shape pharynx follows immediately (PL II, Fig. 12). The
pharynx measures 0.58 mm. long by 0.52 mm. wide by 0.44 mm. deep
in sagittal sections. Eight longitudinal muscular ridges or folds
project from the inner' wall of the anterior two thirds of the pharynx
into its lumen. Of the four larger or primary ridges, one is dorsal,
one ventral, and two lateral; alternating with these are four smaller

PAKASITIC WORMS BERMUDA. I. TREMATODES. 217

or secondary ridges. An oesophagus is not present, the common
transverse caecum following immediately behind the pharynx. On
each side of the pharynx a single well defined diverticulum extends
cephalad from the transverse caecum lateral, or dorso-lateral, to the
oral sucker to a height of one half the sucker's depth. These diver-
ticula may or may not bifurcate at their terminations. The lateral
caeca are broad and deep and they extend in an undulating course to
the posterior end of the body, where they end blindly, giving off in
their course numerous small lateral and deep ventral diverticula.
The caeca are deeper than wide and lie in a plane mid-way between
the dorsal and ventral surfaces in the lateral fields of the body (PI. II,
Fig. 12).

Male genitals. — The two testes (PI. I, Figs. 1, 5), of medium and
nearly equal size, irregular in shape and with undulating to slightly
lobed margins, are situated in the same transverse plane midway
between the anterior and posterior ends of the body. The testes vary
in size from O.oS mm. to 0.68 mm. by 0.34 mm. to 0.54 mm. The
right one is slightly behind the posterior margin of the acetabulum
and its left end projects beyond the median plane into the left half of
the body. The bulk of the left testis is farther from the median plane
than is the left margin of the acetalnilum, and its anterior end extends
a little farther forward than the posterior margin of the acetabulum.
From the antero-dorsal margin of each testis a small vas efferens
passes obliquely forward and toward the median plane. These unite
just cephalad and dorsad to the OA'ary to constitute the vas deferens
(PI. I, Fig. 3); this continues in the median area to the base of the
cirrus pouch, which it enters. The cirrus pouch, though compara-
tively short, is an elongated pear shaped organ situated immediately
anterior to the acetabulum, with its long axis nearly perpendicular to
the frontal plane of the body. It is 0.96 mm. long and from 0.24 mm.
to 0.2S mm. in diameter, I)eing a little longer than the acetabulum is
deep, so that its base lies slightly dorsad and cephalad to the acetab-
ulum. It is so short that it does not bend around the acetabulum.
The vas deferens upon entering the base of the cirrus pouch vmites
with the enlarged transversely coiled seminal vesicle, which fills the
basal third of the pouch. The seminal vesicle connects, in turn, with
a comparatively wide prostatic duct, which has an undulating course
and tapers toward the distal end of the pouch, where it merges into
the ejaculatory duct of the short cirrus.

The cells forming the prostate gland (PI. I, Fig. 3) occupy the
peripheral portion of the pouch and extend from the seminal vesicle

218 BARKER.

nearly to the distal end of the pouch. Fine ducts leading from the
prostate cells occupy the medullary portion of the pouch and enter the
prostatic duct. The lumen of the cirrus is lined with cuticula, while the
lumen of the prostatic duct is covered with high filamentous papillae.

The Avail of the cirrus pouch possesses a heavy outer sheet of longi-
tudinal muscle fibers and a thin inner one of circular fibers. The
cirrus, which is approximately one-fifth the length of the cirrus pouch,
has an outer and an inner muscular component. The outer compo-
nent comprises an outer sheet of longitudinal muscle fibers and a
heavier inner sheet of circular fibers. The inner muscular component
immediately surrounds the lumen of the cirrus and the prostatic duct
and is likewise composed of an inner sheet of circular muscle fibers
and an outer sheet of longitudinal fibers. The cirrus pouch is anchored
and possibly controlled by a pair of oblique muscles which are attached
respectively to the cephalic and caudal faces of its base.

The cirrus opens into a common genital atrium, which has its out-
let in the genital pore lying in, or a little to the left of, the median line
and slightly anterior to, or just under, the anterior margin of the
acetabulum.

Female genitals. — -The ovary (PI. I, Figs. 1, 5, 6, PI. II, Fig. 7) lies
near the middle of the body, in the median area, dorsal to the posterior
portion of the acetabulum and is from one-half to two-thirds the bulk
of one of the testes, globular in general form with undulating or
slightly lobed outline. In the specimen figured (Fig. 5) it measured
0.38 mm. by 0.38 mm.

The oviduct leaves the ovary from the middle of its anterior margin
and at once turns sharply mediad; after making several loops it passes
caudad in descending transverse coils, lying a little to the right of the
median plane, to the end of the body, where, turning, it winds cepha-
lad, a little to the left of the median plane, in ascending transverse
coils; the terminal portion passes between the testes and thence to
the left and dorsally over the acetabulum ; finally it turns to the right
and crosses obliquely the distal third of the cirrus pouch (PI. I, Fig. 3),
where it enters a well defined metraterm or vagina. The base of the
metraterm is enlarged and lies across the left side of the terminal
portion of the cirrus pouch, but the neck parallels the pouch and ter-
minates anteriorly and to the left of the pouch in the common genital
atrium. The wall of the metraterm is thickened and supplied with an
inner sheet of circular muscle fibers and an outer sheet of longitudinal
fibers. An invagination of the cuticula appears to form the lining of
its lumen, the wall of which is transversely ridged.

PARASITIC WORMS BERMUDA. I. TREMATODES. 219

A diffuse, but well defined, shell-gland (PI. I, Fig. 6), or gland of
Mehlis, lies dorsal, and for the most part anterior, to the ovary. Its
posterior portion covers the anterior third of the ovary. The oviduct
penetrates the mass of shell-gland cells, which are connected with the
oviduct by numerous minute ducts.

A globular compact receptaculum seminis (PI. I, Figs. 1, 5, 6), one-
third the bulk of the ovary, lies dorsal to the shell-gland and the
anterior half of the ovary. A small duct leaves its anterior margin
and turning mediad joins the oviduct soon after it leaves the ovary.

At the junction of the receptaculum duct with the oviduct a tubular
Laurer's canal (Fig. 6) originates and in a slightly undulating course
makes its way dorsad and opens on the dorsal surface of the body
dorsal to the ovary and the posterior part of the acetabulum and
slightly to the right of the median line.

The vitellarium (PI. I, Figs. 1, 2, 5) is rather striking in appearance
and is composed of two masses of convoluted tubules grouped in moss-
like patches, which lie in the lateral and latero-dorsal fields in the
middle three-fifths of the body. The patches are fairly definite and
constant in number, three patches being present on the right and four
on the left side. They extend forward of the anterior margin of the
acetabulum a distance approximately half of the diameter of that
organ, the posterior limit being about mid-way between the testes and
the posterior end of the body. The latero-dorsal patches are dorsal
to the testes and uterine coils. A fine vitelline duct (PI. I, Fig. 6)
connects with each other the patches or groups of each side and a
larger vitelline duct leaves the central group of each side and passes
transversely mediad to unite with the one from the opposite side to
form a small, but distinct, vitelline reservoir, which lies dorsal to the
left margin of the ovary. From the reservoir a small duct leads
cephalad and joins the oviduct a short distance beyond the union of
the receptaculum duct with the oviduct.

The eggs (PI. I, Fig. 4) are numerous, spindle shaped, light brown in
color, with thick shell. A comparatively large, well-defined and easily
separated operculum is present, and a slight opercular rim can be
detected. The opercular pole is the more pointed. The eggs measure
0.0375 mm. to 0.0450 mm. in length by 0.015 mm. to 0.020 mm. in
width. The older eggs contain a well developed embryo, but many
appear empty, which probably indicates a non-fertile condition.

Excretory System. — The excretory system (PI. II, Fig. 7) is volumi-
nous and consists of an enormous median dorsal reservoir, with a pair
of anterior prolongations. The reservoir is one-fourth the width and

220 BARKER.

one-half the depth of the body, and extends from the posterior end of
the body to the posterior margin of the ovary, where it bifurcates, one
arm passing to the left and one to the right of the ovary; the arms
extend cephalad around the oral sucker to the anterior end of the
body. The reservoir and arms give off numerous long lateral and
deep ventral diverticula, but these do not anastomose. The reservoir
terminates behind in a short narrow median canal at the posterior end
of the body, which ends in a well-defined excretory pore, terminal in
position and nearer the ventral than the dorsal surface. The short
excretory canal appears to be lined with cuticula. The entire excre-
tory system is filled with a mass of fine globular, gray and golden,
glistening particles among which are numerous larger globular bodies
which stain a bright blue with methylen blue.

2. Taxonomy.

Braun (1901, p. 36) described under the name of Distownvi irrora-
iuvi R. a trematode found in the intestine of a sea turtle, ThaJassoch-
elys caretta, from New Guinea, which has a number of characters
similar to the trematode described in this paper. Looss (1901, p. 558)
described a similar trematode found in the stomach of a sea turtle,
Thalassochelys corticata, from Triest, which he named Pachypsolus
lunatvs. In a later paper Looss (1902, p. 485), after a careful com-
parative study of new adult specimens, as well as the forms described
by Braun and by himself, reached the conclusion that all were speci-
mens of Distowvm irrondum Rudolphi, those described by Braim and
by himself in his earlier paper being young forms, while those studied
bv himself later were mature. He accordinglv classified all of them
as Pachypsolus irroratvs (R.). *

Looss (1902, p. 503) gives the following characters for the genus
Pachypsolus, "Mittelgrosse Distomen mit sehr kraftigem, dickem,
vorn und hinten abgerundetem, auf dem Querschnitte kurz ovalem
Korper. Saugnjipfe gross und kriiftig, Haut besonders im Vorder-
korper mit scheinbaren Biindelen feiner stabchenartiger Stacheln
bewaifnet. Darm mit starkem Pharynx, ganz kurzem Oesophagus
und Darmschenkeln, die bis auf einige von ihren Angfangstheilen nach
vorn abgehende Blindsacke einfach sind. Excretionsblase Y formig,
mit bis zum Keimstock reichendem Stamme und bis ins Kopfende
sich erstreckenden Schenkeln. Stamm und Schenkel mit massig
zahlreichen, weiten und zum Theil wieder gespaltenen Seitenzweigen,
die nach der Bauchseite hinabsteigen mit Ausnahme des vordersten

PARASITIC WORMS BERMUDA. I. TREMATODES. | 221

Paares, welches uber clem ]Mun(lsaiignapfe eine einfache Querana-
stomose der Schenkel bildet. Genitalporus etwas Hnksseitig von dera
Bauchsaiignapfe, Copulationsorgane vorhanden. Cirnisbeutel cy-
lindrisch, von betraehtlicher Ltingc, in seinem Innern eine mehrfach
gewunden, sehlanke Sanienblase, lange, cylindrische Pars prostatica
und dicker Penis, der sich im ausgestiilpten Zustande nach seiner
Spitze zu merklich verjilngt. Hodeii stark seitlich hinter dem
Bauchsaiignapfe. Keimstock seitlich vor ihnen; Laurer'scher Canal
und Receptaculum seminis vorhanden. Dotterstocke in den Seiten
und unter der Riickenflache, aus in der Jugend deutlich sternformigen
FoUikelgruppen zusammengesetzt, Uterusschlingen hauptsachlich
hinter den Hoden die ganze Breite des Korpers ausfiillend und nur
die Enden der Darmschenkel freilassend. Eier zahlreich, klein, mit
zugespitztem Deckelpol und dickerm Hinterende, zwischen 0,04 und
0,05 mm. lang. Bewohner des Tvlagens von Seeschildkroten. Typus:
P. irroratns (R.)."

The trematode from ChcJonia imbricata which I have described has,
in general, the characters of the genus Pachypsolus, and I do not
hesitate to place it in that genus. When compared with the trema-
todes described by Braun and Looss under the name Irwratus several
essential differences are e\'ident. Externally the following may be
noted. The absence of spines, or scales, which may, however, have
been lost, the very large and more nearly equal size of the suckers, the
ventral cup-like depression and the non-salient genital pore. In-
ternally, the position of the testes and ovary nearer the acetabulum
and the less diiTuse arrangement of the vitelline masses, which are
more nearly like those described by Braun, may be noted. The most
striking and essential difference, however, is the size and position of
the cirrus pouch, which in Pachypsolus irwratus (PI. II, Fig. 11) bends
around the acetabulum, its posterior end extending to the level of,
or posterior to, the ovary, while in the form here described (PI. I,
Fig. 3) the cirrus pouch is much shorter, parallel with the dorso-
ventral axis of the body and entirely anterior to the acetabulum.

Linton (1910, p. 24) has described a new species, Pachypsolns
omlis, found in large numbers in the intestine of a Loggerhead Turtle
{Caretta caretia) from the Tortugas. A third species, Pachypsolus
tcrtius, has been described by Pratt (1914, p. 416) from the small
intestine of the same host and of the same locality. The species
described by Linton and by Pratt differ from P. irroratvs in minor
points and distinctively in the position and extent of the cirrus pouch.
Pratt (1914, p. 418) describes the cirrus sac in P. tcrtius (PI. II, Fig. 9)

"222 J BARKER.

as "a long cylindrical structure, extending from the genital pore
around the dorsal side of the acetabulum to the vicinity of the ovary
and the shell-gland, and in some cases to the anterior border of the
testes." According to Linton (1910, p. 25) the cirrus pouch in P.
ovalis (PI. II, Fig. 10) is " relatively short, reaching barely to the
posterior edge of the acetabulum." Both Linton and Pratt consider
the differences in the extent of the cirrus pouch, together A\ath other
minor differences, to be of specific rank. It is evident that the form
which we have described resembles P. ovalis Linton more than it does
P. tertius Pratt or P. irrorahis (R.) Looss; l)ut it differs from P. ovalis
Linton in minor characters and distinctively in the position and
lesser extent of the cirrus pouch. The difference in the length of the
cirrus pouch in P. ovalis Linton and in the trematode here described
is greater than that between P. ovalis and P. tertius Pratt and decidedly
greater than that between P. tcrtivs Pratt and P. irroratiis (R.) Looss.
We agree with Pratt that the "actual position is undoubtedly de-
pendent upon the condition of contraction," but it seems improbable
that this constant and marked difference could be due entirely to the
contraction of the acetabulum or the body.

We feel warranted in ascribing to this difference in the position and
extent of the cirrus pouch, taken together with the minor differences
noted, a specific value, and therefore class this trematode as a new
species in the genus Pachi/psolus, designating it as Pachy psoitis hrachus}

In the four species of Pachypsolus now recorded we find, in addition
to differences of secondary importance, a striking gradation in the
position and size of the cirrus pouch, which is the distinctive specific
character. The old question, raised by Looss, arises as to specific
differences and the specific effects of different hosts on the same
species.

From the standpoint of geographical distribution, it is of interest to
find in the Hawk's-bill Turtle from the Bermudas a different species
of Pachypsolus from that found in the Loggerhead Turtles of New
Guinea and the Mediterranean and from those found in the Logger-
head Turtles of the Tortugas.

1 ..Jpaxi's, short, having reference to the cirrus pouch.

PARASITIC WORMS BERMUDA. I. TREMATODES. 223

Synechorchis megas, n. g. et n. sp.
(PI. Ill, Figs. 13-22).

1. Morphology.

General Appearance. — Twenty-four specimens of this trematode
were studied, twelve of which were fixed in 2% formol and twelve in
vom Rath's osmio-sublimate mixture. In general the body is boat- or
cradle-shaped, the dorsal surface being strongly convex both longi-
tudinally and transversely and the ventral surface correspondingly
strongly concave. The body tapers slightly toward the anterior end
making the posterior end the broader and more bluntly rounded. In
unmounted specimens the length varies from 4.2 mm. to 9 mm. and
the width from 2.2 mm. to 3.2 mm. The thickness of the body is

1.04 mm. with slight variations. No cuticular spines or scales were
found.

At the anterior end of the body is a well defined terminal cephalic
hood or collar (PI. Ill, Figs. 18, 19), 1.50 mm. to 1.65 mm. wide and

1.05 mm. to 1.17 mm. long. The dorsal margin of the hood is unbroken
but the ventral margin is indented by a wide shallow notch or hilus
(Fig. 17). The whole hood has the general appearance of a cocked
hat; its ventral face is slightly concave, with the lappets not promi-
nent, giving the whole somewhat the shape of a kidney. A well
defined muscular oral sucker lies in the ventral cupped face of the hood,
but an acetabulum is not present (Figs. 17, 18, 22).

At the posterior end of the body, on the dorsal surface, in the
median line is a funnel-shaped opening, which marks the termination
of the excretory system. The male and female genital pores are
separate and salient; they lie on the medial side of the left intestinal
caecum (Figs. 17, 22) at the level of the posterior margin of the
anterior fourth of the body. The large cirrus was extruded in several
of the specimens examined (Fig. 17).

Digestive System. — The oral sucker, having a fairly well developed
musculature, opens directly into the oesophagus. It measured 0.66
mm. wide by 0.60 mm. long. A pharynx is not present. The length
of the oesophagus varies much; in some specimens it appears to be
wanting, in others it may reach a length of 0.50 mm. The wide
intestinal caeca occupy a lateral and dorsal position in the body and
extend from the oral sucker in an undulating course to near the end
of the body, where they end blindly. The caeca throughout their

224 BARKER.

course are folded or pleated, which gives rise to distinct but irregular
pockets along their course.

Male genitals. — One of the most characteristic features of this tre-
matode is the testes (Fig. 22), twelve in number, arranged in two
groups of six each. They are small, irregular, lobed bodies situated in
the posterior third of the worm lying on each side of the body immedi-
ately ventral to the terminal portions of the intestinal caeca. Taken,
together the testes have the shape of a horseshoe, with its open end
directed cephalad and extending from the level of the ovary and
vitelline glands caudad to the ends of the intestinal caeca. The testes
may be separated from, or may overlap, one another. A small duct
connects all the testes comprising each group and a larger duct, the
vas efferens, passes mediad from the anterior testis of each group. The
vas efferens from the left side passes transversely across the body and
unites with the short vas efferens from the right side. The vasa effer-
entia vmiting from a short vas deferens, which passes cephalad in the
right mediolateral field and joins a long tubular convoluted seminal
vesicle, which runs anteriorly, mediad to the right intestinal caecum,
and enters the cirrus pouch (Fig. 22). The seminal vesicle is lined
with a high columnar epithelium.

The cirrus pouch (Figs. 22, 20) is a very muscular elongated sac
lying between the intestinal caeca at the level of the posterior margin
of the anterior fourth of the body. It extends obliquely across the
body from right-dorsal to left-ventral and enters the male genital pore.
It is provided with an outer thick sheet of strong longitudinal muscle
fibers and an inner (toward its lumen) thin sheet of circular muscle
fibers. Parenchymal tissue fills the space between these muscle sheets.
The seminal vesicle enters the base of the cirrus pouch, where it
enlarges to form a short tubular pars prostatica, which is surrounded
by the prostate cells. The pars prostatica enters a cone-shaped
cavity, the ductus ejaculatorius, which is one-fourth of the length of
the pouch and is lined with high columnar epithelial cells having the
appearance of coarse cilia. The ductus ejaculatoris is followed by a
narrow canal which forms the lumen of the cirrus (Fig. 20).

The cirrus is strongly developed and consists of two distinct regions,
both of which are protrusile. The basal proximal portion is bulbous
and in one specimen measured 0.33 mm. long by 0.25 mm. in diameter;
the distal portion is more slender and tapering and in the same speci-
men measured 0.50 mm. long bv 0.125 mm. in diameter. The distal
portion can be retracted into the bulbous portion. The entire
extruded cirrus may be 0.85 mm. long. The cirrus is covered with a

PARASITIC WORMS BERMUDA. I. TREMATODES. 225

cuticula in which, on the distal portion, are lightly embedded minute
spinelets. It is supplied with an outer sheet of circular muscle fibers
and an inner thicker sheet of longitudinal muscle fibers. Its lumen is
lined with cuticula. The external opening of the cirrus pouch is
separate from that of the metraterm, or vagina, and lies mesad to it
and to the left intestinal caecum.

Female gcniiah. — The OA'ary (Figs. 13, 22) is a little larger than a
single testis and is irregular in outline with a lobed margin. It lies
at the right of the median plane, posterior to the uterus and at the level
of the most anterior testes. A short oviduct leaves the dorso-medial
portion of the ovary and, proceeding obliquely dorsad and to the left,
is joined by the Laurer's canal, whence it turns posteriad and mediad
across the dorsal surface of the shell-gland (gland of Mehlis) and is
joined in the central area of the shell-gland, by a duct from the yolk
reservoir. The common duct now enters the shell-gland and enlarges,
forming the ootype, which receives numerous small ducts froni the
shell-gland, after which it passes ventrad and posteriad through the
shell-gland to its posterior margin, whence, after making several
coils, it turns cephalad along the left side of the shell-gland and con-
tinues as the uterus. The uterus makes its way cephalad, in the
median area, in wide compact transverse folds, which may extend
laterally as far as the outer edge of the intestinal caeca and \'itelline
glands. The uterus terminates in a well defined metraterm, or
vagina, which opens to the exterior through a separate female genital
pore (Figs. 17, 20, 22) at the left of the male genital pore and central
to the left intestinal caecum. The metraterm is an elongated slightly
convoluted tubular organ, approximately as long as the cirrus pouch,
and lies caudad, and almost parallel, to the pouch. Its wall is strik-
ingly thick and muscular, being provided with a thick outer layer of
longitudinal muscle fibers and a thick inner (toward the lumen) layer
of circular fibers. Its lumen is lined with a thick layer of cuticula,
which is raised into longitudinal ridges.

A compact, irregularly shaped, shell gland, or gland of INIehlis
(Figs. 13, 22), as large as the ovary, lies in the median field at the left
of, and more dorsal than, the ovary. A receptaculum seminis is not
present. A short Laurer's canal lea\'es the oviduct near the ovary
and proceeds dorsad and cephalad opening on the dorsal surface at
the right of the median line and slightly anterior to the shell-gland.

The ^■itellarium (Fig. 22) is composed of two groups of vitelline
glands lying in the lateral fields of the third fourth of the body, ventral
to the intestinal caeca. Each group is made up of from seven to ten

226 BARKER.

compact coarsely granular glands, which are so arranged as to simu-
late an anterior prolongation of the free ends of the testicular horse-
shoe; they extend cephalad to approximately the same level on the
two sides of the body. A small Aitelline duct connects the successive
glands of each group ; a larger one leaves the posterior gland of either
side and, passing caudad and mediad, unites with its mate to form a
yolk reservoir (Fig. 13), which lies dorsal to the anterior portion of the
shell gland. A small yolk duct leads from this reservoir and joins the
oviduct in the central area of the shell gland.

Excretory System. — Two lateral canals, one on each side of the body,
arise at the level of the oesophagus. They parallel the sides of the
body and lie slightly external and ventral to the intestinal caeca. At
the level of the anterior testes their course becomes obliquely caudo-
mediad and they unite just posterior to the shell-gland to form the
excretory bladder, which lies in the median plane at about the level
of the more posterior testes and ventral to the intestinal caeca. The
bladder extends backward in a straight course from the shell gland
and terminates in the excretory funnel near the posterior end of the
body. The funnel itself runs dorso-caudad and opens through an
excretory pore on the dorsal surface in the median line 0.15 to 0.30 mm.
from the posterior margin of the body. According to Looss (1902 : 593)
this excretory funnel (Figs. 14-17, 22) is characteristic of the Prono-
cephalidae; it is lined by cuticula raised into 7 to 9 longitudinal ridges.
Cilia were not observed in the funnel, the inner end of which is sur-
rounded by numerous gland cells.

The uterus is packed with numberless eggs; those from different
parts of the uterus were studied. In mass the eggs appear dark
brown, but individual eggs are light brown or golden yellow. In
shape (Fig. 21) they vary from short or long oval to ovoid, and every
egg bears a tuft of filaments at each pole. The body of the egg in
glycerine preparations varies from 0.0287 to 0.0387 mm. in length,
and from 0.0162 to 0.0187 mm. in width. The shell is thick and has at
the more pointed end a definite flattened operculum, but mthout an
opercular rim. Six to ten coarse filaments, which may attain a length
of 7 times that of the egg proper, occur at the opercular pole and there
are at the opposite end 12 to 20 coarse very long filaments, 15 times as
long as the egg proper, wath an equal number of short finer filaments.
The diameter of the coarser filaments is about one-half the thickness
of the egg shell and they appear to be composed of the same material.
The intertwining of these filaments causes a characteristic massing of
the eggs, and makes it difficult to separate them.

PARASITIC WORMS BERMUDA. I. TREMATODES. 227

2. Taxonomy.

The presence of the single sucker, the cephalic hood, and the peculiar
funnel-shaped depression which is associated with the excretory pore
undoubtedly place this trematode in the Family Pronocephalidae as
characterized by Looss (1902, p. 611). It cannot, however, be placed
in the genus Charaxicephalus of Looss on account of the difference in
the number, arrangement and position of the testes and other, though
minor, differences.

It has many of the characters given by Braun (1901, p. 48) for
Mo7iostomwn pandum, which he describes as follows: "Mir liegt nur
ein einziges, wohl erhaltenes Exemplar vor, das folgende Verhaltnisse
aufweist: es ist 11 mm. lang, kahnformig gekriimmt, verbal tnismassig
platt, der Riicken gewolbt, die Bauchflache konkav; weder der
Hinterrand noch die SeitenrJinder sind wie bei Mon. trigonocephalum
bauchwarts eingebogen: am Hinterrande keine Spur von irgend
welchen Anhangen. Das Kopfende tragt ein nierenformiges, dem
Halskragen der Echinostomen ahnliches Schild (2 mm. breit), aus dem
sich ein niedriger, an der Spitze die Mundoflfnung tragender Kegel
erhebt: offenbar entspricht dieses Schild dem Kopfwulst der bisher
besprochenen Monostomen aus Seeschildkroten, der demnach auf der
Ventralflache nur schwach gebogen und nicht winklig ausgeschnitten
ist wie bei Mon. trigonocephalum Rud. Die Breite des Korpers
betragt in der Hohe der Genitalpori 2.7, am Beginn der Dotterstocke
3.5, und in der Hohe des Keimstockes 4 mm.; sie nimmt also ganz all-
mahlich von vorn nach hinten zu.

Der Saugnapf ist 0.625 mm. lang und 0.729 mm. breit; vom Oesoph-
agus kann ich etwas bestimmtes nicht angeben, da ich ihn nicht sehe,
allem Anschein nach ist er kurz, denn die beiden Darmschenkel sind
bei genligend starker Vergrdsserung sowohl auf der Riicken- wie
Bauchflache dicht hinter dem Kopf schild bereits erkennbar: sie
Ziehen, die Endteile der Geschlechtsgange zwischen sich fassend nach
hinten und sind zwischen den Dotterstocken und dem Uterus bis an
die Hoden zu verfolgen; ihr weiterer Verlauf ist nicht mit Sicherheit
zu erkennen, sie scheinen dorsal iiber den Hoden und der Mittellinie
etwas mehr genahert bis an den Hinterrand der Hoden sich zu ers-
trecken. Soweit ich sie deutlich erkenne, sind sie nach aussen wie
nach innen mit kurzen Blindsiickchen besetzt.

Vom Exkretionsapparat sind nur die beiden weiten Sammel-rohren
aussen von den Dotterstocken erkennbar.

Wie haufig bei Monostomidcn, findet sich auch hier je eine Aus-

'228 BARKER.

miindungsstelle fiir mannliche und weibliche Organe; dieselben liegen
dicht neben einander, hinter der Gabelstelle des Darms auf der linken
Seite, die Uterusmiindung seitlich von der Cirrusmiindung. Ganz im
Hinterende liegen symmetrisch die beiden grossen (bis 3 mm. langen)
vielf ach gelappten Hoden ; sie beriihren sich hinten mit ihren medianen
Flachen, A-orn weichen sie auseinander. Vom Leitungsweg bemerkt
man reehts die gewundene Vesicula seminalis, die durch einen graden
Kanal in den langgestreckten und dickwandigen Cirrusbeutel miindet ;
seine Lange betragt iiber 2 mm.

In dem von den vorderen Enden der Hoden freigelassenen Raume
liegt reehts der vierstrahlige Keimstock, neben und etwas hinter
diesem in der ISIittellinie die Schalendriise. Hier beginnt der Uterus,
auch fliessen an dieser Stelle die queren Dottergange zusammen.
Die Dotterstocke Hegen wie gewohnhch seitHch im Korper und
erstrecken sich vom Vorderende der Hoden bis vor die Korpermitte;
sie bestehen aus zahh-eichen, eine traubige Gruppierung aufweisenden
FoUikeln.

Die UterusschHngen breiten sich, c^uere Richtung einhaltend, in
dem Raum zwischen den Dotterstocken und vor den Geschlechts-
driisen aus; das neben dem Cirrusbeutel liegende Metraterm ist kurz
vor seiner Ausmiindung von einer kompakten Driisenmasse umgeben.
Die Eier scheinen Polfiiden nicht zu besitzen; sie liegen allerdings so
dicht im Uterus, dass sich Filamente den Blicken leicht entziehen
konnten, andererseits wiirde aber, wenn Filamente vorhanden waren,
kaum eine sehr dichte Lagerung der Eier moglich sein ; Messungen an
jungen, sicher der Anhange entbehrenden Eieren aus dem Anfangsteil
des Uterus ergaben 0.035 mm. Lange und 0.01 mm. Breite."

It is evident that the trematode which I have described differs from
M. imndum not only in minor dfetails but more especially in the larger
number of testes.

Pratt (1914, p. 411) has described a monostome trematode, Wilderia
cUiptica, found in the Loggerhead Turtle from the Tortugas, which
has many characters in common with both M. pandum and the form
here described, but differs from both of them in the absence of a
cephalic collar or hood. On the ground of the absence of a collar and
the presence of several testes Pratt has created the new genus and new
species Wilderia eUiptica. The trematode described in this paper
cannot be classed as M. pandum, on account of the several testes, nor
as Wilderia elliptica, on account of the presence of a definite cephalic
hood or collar.

If, as Pratt (1914, p. 416) suggests, Braun's description of the testes

PARASITIC WORMS BERMUDA. I. TREMATODES. 229

in M. panel um is incorrect and " they are as a matter of fact made up
of successive pairs of distinct organs," then the trematode which I
ha\'e described may be identical with Monosfomum pandum. Also,
if Pratt is in error regarding " the slightest indication of the collar-like
cephalic ridge at the forward end of the body " being absent in Wildcria
elliptica, his species is probably identical with the trematode which I
ha^'e described and with Monostomuvi pandum. Until these points
are determined, it seems advisable to create a new genus and a new
species for this trematode, which I accordingly designate as Syne-
chorchis mcc/as, making it the type species of a new genus, Syncchorchis,^
designed to include those monostome trematodes which have a con-
tinuous cephalic collar, and numerous testes placed laterally in the
posterior part of the body.

The material, on which these descriptions are based, was collected
and sent to me by Prof. E. L. Mark, Director, and Dr. W. J. Crozier,
Resident Naturalist, of the Bermuda Biological Station. To both of
them I wish to acknowledge my appreciation and indebtedness.

To Mr. Hiram O. Studley, one of my students, I desire to express
my appreciation for his assistance in making a preliminary study and
drawings of the second form described in this paper.

^ Swexvs, continuous line, and opxi-s, testicle.

k

230 BARKER.

Papers Cited.

Braun, M.

1901. Trematoden der Chelonier. Mitth. zool. Mus. Berlin,
Bd. 2, 58 pp., 2 Taf.
Linton, E.

1910. Helminth Fauna of the Dry Tortugas. II. Trematodes.
Carnegie Institution of Washington, Publication No.
133, pp. 11-98, 28 pis.
Looss, A.

1901. Notizen zur Helrninthologie Egyptens. IV. Ueber Tre-

matoden aus Seesehildkroten der egyptischen Kiisten.
Centralbl. f. Bakt., Abt. 1, Bd. 30, pp. 555-569.
Looss, A.

1902. Ueber neue und bekannte Trematoden aus Seesehild-

kroten. Zool. Jahrb., Abt. f. Syst., Bd. 16, pp. 411-
894, Taf. 21-32.
Pratt, H. S.

1914. Trematodes of the Loggerhead Turtle (Caretta caretta)
of the Gulf of Mexico. Arch, de Parasitol., tom. 16,
pp. 411-427.

EXPLANATION OF PLATES.

All drawings were made with the aid of a camera lucida except Figures 10,
11 and 12.

act.

Acetabulum

o'typ.

Ootype

cae. in.

Intestinal caeca

phx.

Pharynx

can. exc.

Excretory canal

po. exc.

Excretory pore

can. L.

Laurer's canal

po. gen.

Genital pore

cir.

Cirrus

po. gen.'

Male genital pore

coll.

Collar

po. gen."

Female genital pore

cstr. vt.

Yolk reservoir

poc. V.

Ventral cup

di. vt.

Yolk duct

rep. sem.

Recaptaculum seminis

fil. pol.

Polar filament

sac. cir.

Cirrus pouch

gl. cnch.

Shell gland

sue. or.

Oral sucker

gl. prost.

Prostate gland

t€.

Testis

gl. vt.

Vitelline glands

Ul.

Uterus

oa.

Ovary

va. df.

Vas deferens

oes.

Oesophagus

vg.

Vagina

o'dt.

Oviduct

vs. exc.

Excretory vesicle

op.

Operculum

vsl. sem.

Vesicula seminalis

232

BARKER.

PLATE I.

Pachypsolus brachus.

Figure I.
Figure 2.
Figure 3.

Figure 4.
Figure 5.
Figure 6.

Ventral view. X 40. Scale line, at the margin, represents 1 mm.
Dorsal view of unmounted specimen. X 40. Scale line 1 mm.
Cirrus pouch, vagina, acetabulum, etc. Composite view ob-
tained by superposing several successive para-sagittal sections.
X80.

Eggs with and without lid. X 110. Scale line 0.1 mm.
Dorsal view. X 40. Scale line 1 mm.

Reconstruction of female genitals, based on frontal and
sagittal sections. X 60.

Barker. — Bermuda Trematodes.

Plaie I.

Ml-'-ft^

^^JTS.oU.

Fig. 5

Proc. Amer. Acad. Arts and Sciences. Vol. LVII.

234 BARKER.

PLATE II.

Figure 7. Reconstruction of excretory system of Pachypsolus brachus

based on frontal sections. X 50.
Figure 8. Ventral view of unmounted specimen of Pachypsolus brachus.

X 30.
Figure 9. Cirrus pouch etc. of Pachypsolus tertius, after Pratt 1914,

Figure 2. X 64.
Figure 10. Cirrus Pouch etc. of Pachypsolus ovalis, after Linton 1910,

Figure 7. X 60.
Figure 11. Cirrus pouch etc. of Pachypsolus irroratus, after Looss 1902,

Figure 169. X 38.
Figure 12. Reconstruction of digestive tract of P. brachus based on frontal

and sagittal sections. X 50.

Barker. — Bermuda Trematodes.

Plate II.

Proc. Amer. Acad. Arts and Sciences. Vol. LVII.

236

BARKER.

PLATE III.

Synechorchis megas.

Figure 13.

Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.

Figure 21.
Figure 22.

Reconstruction of female genitals, dorsal aspect, based on

frontal and sagittal sections. X 220. Scale line, below the

figure, represents 0.1 mm.

Sagittal section of excretory funnel. X 250.

Cross section of excretory funnel near surface level. X 250.

Cross section of excretory funnel at deeper level. X 250.

Ventral view of unmounted specimen. X 23.

Ventral view" of cephalic region of unmounted specimen. X 68.

Sagittal section of cephalic hood. X 75.

Details of male and female copulatory organs. X 90. Scale

line 0.5 mm.

Egg. X 500.

Ventral view of mounted compressed specimen. X 33. Scale

line 1 mm.

Barker. — Bermuda Trematooes.

Plate III.

Fig. 17

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By Rudolf Bennitt.

i

CONTRIBUTIONS FROM THE BERMUDA BIOLOGICAL STATION

FOR RESEARCH. No. 136.

ADDITIONS TO THE HYDROID FAUNA OF THE
» BERMUDAS.

By Rudolf Bennitt.

Received February 15, 1922. Presented by E. L. Mark.

The hydroids which have been studied in the preparation of this
paper are from two sources, namely, the collection made by the writer
during the summer of 1921, and those made at various times since 1903
by Dr. E. L. Mark and others in attendance at the Bermuda Biological
Station. I am greatly indebted to Dr. Mark, both for having made
my stay at Bermuda possible and for having given me the opportunity
of examining for hydroid material his miscellaneous collections.

The only papers hitherto written on the Bermuda hydroids are by
Congdon (1907) and Ritchie (1909). Congdon described 19 species,
of which five (Eudendrimn hargitti, Clytiafragilis, Sertularella speciosa,
Scrhdaria humilis, and Thyroscyphus intcrmcdius) are new. Several
others, described by him as new, have been shown by later writers,
notably Nutting and Fraser, to belong to already established species,
Ritchie discusses the synonymy of one of the Bermuda campanula-
rians, and extends the range of two "Challenger" hydroids from the
West Indies to the Bermudas.

Fraser's paper (1912) on the hydroids of Beaufort, N. C, is also a
valuable aid in the study of the Bermuda hydroids, since 21 species of
the latter, or over half of the Bermuda forms, occur also in the Beau-
fort region. The strong affiliation of the hydroid fauna of the Ber-
mudas with that of the West Indian region, already suggested by
Congdon, is still more strikingly demonstrated by the species now
reported from Bermuda; in all, 29 species are common to the two
regions.

The distribution of the individual species found in Bermuda is
shown in the following table: —

242

BENNITT.

Bimeria humilis

Eudendrium hargitti ....

Eudendrium ramosum . . .

Pennaria tiarella

Halecium bermudense . . .

Halecium nanum .......

*Halecium tenellum

Campanularia niarginata

'Campanularia raridentata

'Clytia bicophora

'Clytia cylindrica

Clytia fragilis

'Clytia johnstoni

Clytia noliformis

'Obelia geniculata

Obelia hyalina

Lafoea venusia

Hebella calcarata

Sertularella speciosa

*Sertularella tenella

Sertularia brevicyathus . .
*Sertularia cornicina

Sertularia aestuaria

Sertularia stookeyi

Sertularia versluysi

Thyroscyphus intermedius

Aglaophenia cylindrata . .

Aglaophenia lophocarpa. .

Aglaophenia minuta

'Antennularia pinnata ....

'Lytocarpus clarkei

Lytocarpus philippinus. .
*Monotheca margaretta . .

Plumularia diaphana ....

Plumularia corrugata. . . .

*Plumularia inermis

*Plumularia setacea

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_

* The first record of these species from Bermuda is contained in the present
paper.

HYDROID FAUNA OF THE BERMUDAS, 243

This paper records 37 species, including all the hydroids reported
from Bermuda up to the present. Where both trophosome and gono-
some have been adequately described elsewhere in readily available
papers, as is nearly always the case, I have attempted no taxonomic
discussion. References are given to the text and plates of the original
description, and also to the standard works dealing with the hydroids
of the American shores of the Atlantic, in many of which a more com-
plete bibliography may be found. Similar references are given for the
species which I have not seen, but which have been reported from
Bermuda by Congdon and others.

Family BOUGAINVILLIDAE.
Genus Bimeria.

Bimeria humilis Allman.

Allman, 1877, p. 8, pi. 5, figs. 3-4.
Congdon, 1907, p. 467, fig. 6.

Family PENNARIDAE.
Genus Pennaria.

Pennaria tiarella McCrady.

McCrady, 1857, p. 51.
Hargitt, 1900, p. 387, 4 pis.
Hargitt, 1901, p. 311, figs. 8, 9.
Nutting, 1901, p. 337, fig. 14.
Congdon, 1907, p. 464.
Fraser, 1912, p. 355, fig. 12.

Pennaria tiarella is common on the buoys and reefs about Hamilton
Harbor and Great Sound, and on the flats outside. Specimens exam-
ined showed as many as 17 filiform tentacles, confirming Congdon's
belief that P. symmetrica (Clarke, 1879) of Cuba, which has 18 filiform
tentacles, is identical with P. tiarella.

Stoloniferous reproduction was here observed for the first time in the
family, and, so far as I am aware, for the first time in the whole group
of Gymnoblastea. ^Yell-marked stolons extend from the distal ends

244 BENNITT.

of the stem and branches (Fig. 1) ; they are considerably larger than
the parts from which they arise, anastomose freely, and have the same
appearance, even to the exact color, as the normal hydrorhiza of Pen-
naria. The free ends of the stolons are somewhat knobbed, and along
their course appear broken stumps, precisely like the base of the origi-
nal stem. This colony was growing in a horizontal position on the
under side of a floating buoy, and the stolons had grown along the
bottom of the buoy, there to give rise to new colonies.

Figure 1. Pennaria tiarella. Colony showing stolon-formation. X If.

Family EUDENDRIDAE.

Genus Eudendrium.

Eudendrium hargitti Congdon.

Congdon, 1907, p. 465, figs. 1-5.

Besides being extremely abundant in Hungry Bay, the shallow inlet
on the south shore where it was found by Congdon, E. hargitti is gen-
erally distributed on buoys, timbers, ledges, and eel-grass all over
Hamilton Harbor and Great Sound, just below low-tide mark. Cong-
don's specimens were 20-50 mm. high, and had 35-45 tentacles. Spec-

HYDROID FAUNA OF THE BERMUDAS. 245

imens in my collection from Fairyland Creek reached a height of 80
mm., and the number of tentacles varied from 35 to 60. The distal
hydranths are usually larger than the proximal.

Eudendrium ramosum (Linnaeus).

Tubniaria ramosa, Linnaeus, 1767, p. 1302.
Eudendrium ramosum, Hargitt, 1901, p. 309, figs. 5, 6.
Eudendrium ramosum, Nutting, 1901, p. 332, fig. 7.
Eudendrium ramosum, Congdon, 1907, p. 464.
Eudendrium ramosum, Fraser, 1912, p. 349, fig. 8.

A few colonies, 50-75 mm. high, were found on a floating buoy in
Hamilton Harbor.

Family HALECIDAE.
Genus Halecium.

Halecium bermudense Congdon.

Congdon, 1907, p. 472, figs. 16-20.
Fraser, 1912, p. 367, fig. 28.
Stechow, 1914, p. 134.
Stechow, 1919, p. 33.

This is one of the most abundant species in Bermuda, growing on a
great variety of structures in almost every locality where hydroids are
to be found. My specimens attained a height of 75 mm., Congdon's
25-35 mm.

Halecium nanum Alder.

Halecium nanum. Alder, 1859, p. 355.
Halecium marki, Congdon, 1907, p. 474, figs. 21-23.
Halecium nanum, Fraser, 1912, p. 367, fig. 29.
Halecium nanum, Stechow, 1914, p. 135.
Halecium nanum, Stechow, 1919, p. 36.

This minute species was often found on floating Sargassum ; a few
colonies were also found with //. bermudense on Pennaria from Cow-
Ground Flat. The colonies reached a maximum height of 8 mm.;
Congdon's specimens were l|-3 mm. high.

Halecium nanum appears to have two modes of growth; the resulting

I

246 BENNITT.

forms are shown to belong to the same species by the presence of the
characteristic female gonosome on both. One form is short and
scrubby, the other longer and with a few irregular branches coming
off just below the hydrophores. The trophosome of the latter variety
agrees so well with what Fraser (1912, p. 368, fig. 30) doubtfully
called H. repens Jaderholm, that I believe the two are identical, and
that he observed this straggling variety of H. nanum.

Halecium tenellum Hincks.

Hincks, 1861, p. 252, pi. 6, figs. 1-4.
Hincks, 1868, p. 226, pi. 45, fig. 1.
Nutting, 1901, p. 357, fig. 52.
Fraser, 1912, p. 369, fig. 31.
Stechow, 1919, p. 41.

A few colonies were found, in all stages of growth, on Sargassum at
Somerset Bridge, the hydrorhiza forming an extensive network over
an alga. The gonosome, essential for a satisfactory determination
of the species, which Fraser failed to find in his Beaufort specimens,
was present in the Bermuda material.

Family CAIViPANULARIDAE.

Genus Campanulaeia,

Campanularia marginata (Allman).

Obelia marginata, Allman, 1877, p. 9, pi. 6, figs. 1, 2.
Campanularia insignis, Congdon, 1907, p. 469, figs. 10, 12.
Leptoscyphus insignis, Ritchie, 1909, p. 3.
Campanularia marginata, Nutting, 1915, p. 44, pi. 6, figs. 5-7.

Campanularia raridentata x\lder.

Alder, 1862, p. 315, pi. 14, fig. 5.
Fraser, 1912, p. 357, fig. 14.
Nutting, 1915, p. 39, pi. 4, fig. 1.

A single small colony of two or three individuals was found on float-
ing Sargassum. Identification is somewhat doubtful, owing to the
absence of the gonosome, but the trophosome agrees in every way
with Nutting's description. The ten pointed teeth, the 3-5 annula-

HYDROID FAUNA OF THE BERMUDAS. 247

tions at the ends of the pedicel, the tubular hydrotheca, and the con-
siderable variation in the height of the pedicel, together seem sufficient
to place the Bermuda specimen in this species.

Genus Clytia.

Clytia bicophora Agassiz.

Agassiz, L., 1862, p. 304, pi. 29, figs. 6-9.
Nutting, 1901, p. 343, fig. 21.
Nutting, 1915, p. 56, pi. 12, figs. 1-3.

Fraser and many other writers consider Clytia hicophora identical
witli C. johnsioni (Alder). Nutting, with some hesitation, regards it as
a separate species, on the basis of the following points: 1) the tenuity
of the hydro thecal wall; 2) the smaller size of the hydrotheca; 3) the
presence of a simple instead of a complex diaphragm. IMy specimens
of C. hicophora, found growing on Pcimaria from Cow-Ground Flat,
have hydrothecae which are distinctly smaller than those of C. john-
sioni, and show many cases of the collapsed hydrothecal wall. They
also have only 12 marginal teeth, and there are annulations in the middle
of the pedicels, which are sometimes annulated throughout. None of
my specimens of C. johnstoni show these features, and I have found no
stages intermediate between the two; this seems sufficient to establish
C. bicophora as a separate species.

Clytia cylindrica Agassiz.

Agassiz, L., 1862, p. 306, pi. 27, figs. 8, 9.
Nutting, 1901, p. 342.
Fraser, 1912, p. 358, fig. 16.
Nutting, 1915, p. 58, pi. 12, figs. 6, 7.

A few colonies were found on Sargassum at Agar's Island, and on
floating Sargassum oft' the north shore.

Clytia fragilis C'ongdon.

Congdon, 1907, p. 471, fig. 13.
Nutting, 1915, p. 62, pi. 15, fig. 1.

A number of colonies, 10-12 mm. high, were found on Sargassum
at Somerset Bridge. The gonosome was absent, but the trophosome is
quite characteristic in this species.

k

248 BENNITT.

Clytia johnstoni (Alder),

Campanularia johnstoni, Alder, 1857, p. 36.

Clytia johnstoni, Hincks, 1868, p. 143, pi. 24, fig. 1.

Clytia grayi, Nutting, 1901, p. 344, fig. 23.

Clytia johnstoni, Fraser, 1912, p. 358, fig. 17.

Clytia grayi, Stechow, 1914, p. 128, fig. 5.

Clytia johnstoni, Nutting, 1915, p. 54, pi. 11, fig.s. 1-6.

Clytia johnstoni, Stechow, 1919, p. 43.

This was one of the commonest species on floating Sargassum. The
characteristic annulated gonangia were extremely numerous in the
specimens collected. In one colony a stolon twice as long as the pedi-
cel extended out from the middle of the pedicel, establishing connec-
tion with the substratum. This is the first case of stolon-formation
that I have seen in the genus Clytia. There were never less than 14
marginal teeth, and I found no cases of the collapsed hydro thecal wall;
these points, with the greater size of the colonies, made them readily
distinguishable from C. bicophora.

Clytia noliformis (McCrady).

Campanularia noliformis, McCrady, 1858, p. 92.
Clytia noliformis, Nutting, 1901, p. 343, fig. 22.
Clytia simplex, Congdon, 1907, p. 472, figs. 14, 15.
Clytia noliformis, Fraser, 1912, p. 359, fig. 19.
Clytia noliformis, Nutting, 1915, p. 57, pi. 11, figs. 7-10.

Colonies of Clytia noliformis are very numerous on floating Sar-
gassum. My specimens showed many intergradations between
C. simplex as described by Congdon and C. noliformis as described by
Nutting.

Genus Obelia.

Obelia geniculata (Linnaeus).

Sertularia geniculata, Linnaeus, 1758, p. 812.
Obelia geniculata, Nutting, 1901, p. 351, fig. 38.
Obelia geniculata, Fraser, 1912, p. 362, fig. 23.
Obelia geniculata. Nutting, 1915, p. 73, pi. 18, figs. 1-5.

A few colonies were found on floating Sargassum.

HYDROID FAUNA OF THE BERMUDAS. 249

Obelia hyalina Clarke.

Obelia hyalina, Clarke, 1879, p. 241, pi. 4, fig. 21.
Obelia hyalina, Congdon, 1907, p. 468, figs. 7-9.
Obelia congdoni, Hargitt, 1909, p. 375.
Obelia hyalina, Fraser, 1912, p. 363, fig. 24.
Obelia hyalina. Nutting, 1915, p. 76, pi. 18, figs. 6, 7.

This is one of the hydroids found most often on the floating Sar-
gassum, and a number of colonies 2-3 cm. high were found on a fish-car
at Agar's Island. There were many cases of stolon-formation from the
ends of the branches, and in one case these stolons were thickly inter-
twined with similar stolons of Aglaophenia minuta. Obelia hyalina
often grows far out on colonies of Sertularia stookeyi no larger than
itself.

Family LAFOEIDAE.
Genus Lafoea.

Lafoea venusta Allman.

Allman, 1877, p. 11, pi. 6, figs. 3-4.
Ritchie, 1909, p. 260.

Specimens of Lafoea venusta were dredged by the " Challenger" " off
the Bermudas, 30 fathoms."

Family HEBELLIDAE.
Genus Hebella.

Hebella calcarata (A. Agassiz).

Lafoea calcarata, A. Agassiz, 1865, p. 122.
Lafoea calcarata, Hargitt, 1901, p. 387, fig. 24.
Hebella calcarata. Nutting, 1901, p. 353, fig. 56.
Lafoea calcarata, Congdon, 1907, p. 467.
Hebella calcarata, Fraser, 1912, p. 371, fig. 34.

250 BENNITT.

Family SERTULARIDAE.
Genus Sertularella,
Sertularella speciosa Congdon.
Congdon, 1907, p. 476, figs. 24-28.

Sertularella tenella Alder.

Alder, 1857, p. 23.

Hartlaub, 1901, p. 63, Taf. 5, figs. 21-24, Taf. 6, figs. 2, 4, 7, 9, 10.

Nutting, 1904, p. 83, pi. 18, figs. 1, 2.

A large number of colonies, about 9 mm. high (Nutting's specimens
were 12.5 mm. high), were found among branching Bryozoa in a col-
lection made in 1903 by Dr. A. W. ^Yeysse. The trophosome agrees in
every way with that described by Nutting and by Hartlaub; occa-
sional branches are given off at right angles to the stem, and the hydro-
thecal walls may be nearly smooth or may have six or seven well-
marked annulations. The gonangia are one and a half to two times
the length of the hydrothecae.

Genus Sertularia.
Sertularia brevicyathus (Versluys).

Desmoscyphus brevicyathus, Versluj^s, 1899, p. 40, figs. 9, 10.
Sertularia brevicyathus, Nutting, 1904, p. 60, pi. 6, figs. 1, 2.
Sertularia brevicyathus, Congdon, 1907, p. 481.

Numerous colonies of this little Sertularia were found on a gorgo-
nian stem and on algae dredged in 1903 at four stations on the Challen-
ger Bank, about 15 miles southwest of Bermuda, in 31-70 fathoms.
Others were collected on Sargassum near Agar's Island.

Sertularia cornicina (McCrady).

Dynamena cornicina, McCrady, 1858, p. 102.
Sertularia complexa, Nutting, 1901, p. 360, fig. 57.
Sertularia cornicina. Nutting, 1901, p. 359, fig. 56.
Sertularia cornicina, Nutting, 1904, p. 58, pi. 4, figs. 1-5.
Sertularia cornicina, Fraser, 1912, p. 374, fig. 38.

HYDROID FAUNA OF THE BERMUDAS. 251

Sertularia cornicina was found on the ledges and on Sargassum at both
Agar's Island and Somerset Bridge, also on a gorgonian dredged in 32
fathoms on Challenger Bank. The latter specimens showed the for-
mation of unusually long stolons from the tip of the colony back to the
hydrorhiza. No sign of the often epizoic Hebella calcarata was seen.

Sertularia aestuaria Stechow.

Sertularia humilis, Congdon, 1907, p. 479, figs. 29-32.
Sertularia aestuaria, Stechow, 1919, p. 157.

This very common sertularian frequently formed thick mats over
the ledges at about the low-tide mark in practically all the locali-
ties visited. The specific name humilis was used in 1879 by Arm-
strong (Jour. As. Soc. Bengal, vol. 48, p. 101, tab. 9) for Desmoscyphus
humilis of the Indian Ocean, and Stechow has suggested for Congdon's
S. humilis the name 8. aestuaria, descriptive of its habitat at tide-level.

Sertularia stookeyi Nutting.

Nutting, 1904, p. 59, pi. 5, figs. 6, 7.
Fraser, 1912, p. 375, fig. 39.

A large number of colonies, with gonangia, were taken on floating
Sargassum both off the north shore and in Hamilton Harbor. In
many cases there was profuse growth of stolons from the extremities.

Sertularia versluysi Nutting.

Desmoscyphus gracilis, Allman, 1888, p. 71.
Desmoscyphus inflatus, Versluys, 1899, p. 42.
Sertularia versluysi, Nutting, 1904, p. 53, pi. 1, figs. 4-9.
Sertularia versluysi, Congdon, 1907, p. 481.
Sertularia versluysi, Fraser, 1912, p. 375, fig. 40.

Genus Thyroscyphus.

Thyroscyphus intermedius Congdon.
Congdon, 1907, p. 482, figs. 33-36.

252 BENNITT.

Family PLUMULARIDAE.
Genus Aglaophenia.

Aglaophenia cylindrata Versluys.

Versluys, 1899, p. 49, figs. 19-21.
Ritchie, 1909, p. 261.

Specimens of Aglaophenia cylindrata were dredged by the "Chal-
lenger" " off the Bermudas, 30 fathoms." The species is very similar
to A. rhyncocarpa Allman, being separated from it by differences in the
corbulae.

Aglaophenia lophocarpa Allman.

AUman, 1877, p. 41, pi. 24, figs. 1-4.
Nutting, 1900, p. 92, pi. 18, figs. 6-8.

Several immature colonies, about 25 mm. high, were found on the
stem of a large colony of Lytocarpus clarkei, dredged in 32 fathoms
on Challenger Bank. The gonosome was absent, but the complex
trophosome is sufficient for identification.

Aglaophenia minuta Fewkes.

Fewkes, 1881, p. 132.

Nutting, 1900, p. 96, pi. 31, figs. 1-3.

Congdon, 1907, p. 483.

Fraser, 1912, p. 378, fig. 43.

There is a dense growth of this little plumularian on many pieces
of floating Sargassum; specimens have also been found at Agar's
Island and among material dredged in 32 fathoms on Challenger Bank.
The two nematophores noted by Congdon in the axil of each hydro-
cladium are mentioned in Nutting's description, though Congdon
must in some way have overlooked this statement. No gonosome was
found.

Genus Antennularia.

Antennularia pinnata Nutting.

Nutting, 1900, p. 71, pi. 5, figs. 5, 6.

Growing among encrusting Bryozoa on a floating buoy in Hamilton
Harbor and reaching a height of 37 mm., were a large number of col-

HYDROID FAUNA OF THE BERMUDAS.

253

onies of this hydroid, whose canaHculated coenosarc and unprotected
gonangia place it in the genus Anicnnularia. The trophosome agrees
with that described by Nutting for A. pinnata, except that I was able
to find only one nematophore, instead of two, in the axil of each hydro-
cladium, and none at all on the stem, although Nutting states that
they are "scattered over the stem."^ There is also considerable dis-
parity in size between my specimens and his, but this is not conclusive
evidence of specific difference. Some of the colonies are sparsely
branched, and the arrangement of the hydrocladiu is invariably alter-
nate or subalternate.

Figure 2. Antennularia pinnata.
female gonangia. X 12.

Portion of colony bearing male and

The gonangia (Fig. 2) are unprotected, oblong-ovate, coarsely and
irregularly annulated, about 20 times as long as the hydrothecae, with
strictly terminal apertures, and are borne singly on short processes
from the stem opposite the hydrocladia. Both male and female
gonangia are found in the same colony. The female blastostyle bears
usually a single gonophore, which is situated on one side. The male
blastostyle is entirely surrounded by the mass of male reproductive
cells. The position of the gonangia, their annulated walls, their

1 Professor Nutting has kindly corroborated my identification of this species
and of Plumularia inermis.

254 BENNITT.

terminal apertures, and their comparatively large size, make this gono-
some, previously undescribed, distinct from that of any other American
species of Antennularia.

Genus Lytocarpus.

Lytocarpus clarkei Nutting,

Nutting, 1900, p. 124, pi. 32, figs. 5-7.

Large colonies of Lytocarpus clarkei, measuring from 100 to 300 mm.
in length, were dredged at five stations on Challenger Bank, in 31-70
fathoms. The gonosome is absent, but the trophosome agrees com-
pletely with that described by Nutting. The color of the perisarc in
the preserved specimens varied from light brown to deep chocolate-
brown.

Lytocarpus philippinus (Kirchenpauer).

Aglaophenia philippina, Ivirchenpauer, 1872, Pt. 1, p. 45, Taf. 1, 2, Taf. 7,

fig. 26.
Lytocarpus phiUppinus, Nutting, 1900, p. 122, pi. 31, figs. 4-7.
Lytocarpus philippinus, Congdon, 1907, p. 484, fig. 37.
Lytocarpus philippinus, Fraser, 1912, p. 379, fig. 45.
Lytocarpus philippinus, Stechow, 1919, p. 132.

An immature colony, about 25 mm. high, was taken on Sargassum
at Somerset Bridge. The gonosome was absent.

Genus Monotheca.

Monotheca margaretta Nutting.

Nutting, 1900, p. 72, pi. 11, figs. 1-3.
Fraser, 1912, p. 380, fig. 47.

Several colonies in good condition, 6-12 mm. high, were found on
floating Sargassum. The gonosome is unknown; the trophosome
agrees in detail with that described by Nutting.

Genus Plumularia.

Plumularia diaphana (Heller).

Anisocalyx diaphanus, Heller, 1868, p. 42, tab. 2, fig. 5.
Plumularia alternata, Nutting, 1900, p. 62, pi. 4, figs. 1, 2.

HYDROID FAUNA OF THE BERMUDAS. 255

Schizotricha tenella, Nutting, 1900, p. 80, pi. 4, figs. 4, 5.
Schizotricha tenella, Nutting, 1901, p. 365, fig. 70.
Plumularia alternata, Congdon, 1907, p. 484.
Plumularia alternata, Fraser, 1912, p. 381, fig. 48.
Schizotricha tenella, Fraser, 1912, p. 383, fig. 52.
Plumularia diaphana, Bedot, 1914, ]). 89, tab. 5, figs. 14-16.
Plumularia diaphana, Stechow, 1919, i). 114.

Plumularia diaphana is rather common on floating Sargassura.
Branches were observed in a few cases, though the colonies are nearly
always unbranched. Stechow noticed that in many colonies the
proximal three or four hydrocladia were paired instead of alternate;
I find this to be almost universally the case in Bermuda specimens.
The gonosome is unknown.

Plumularia corrugata Nutting.

Nutting, 1900, p. 64, pi. 6, figs. 1-3.

A few colonies, 10-12 mm. high, were found on floating Sargassum.
The gonosome was absent. The colonies were unbranched, and the
stem showed a pair of internal ridges at both the proximal and distal;
end of each internode.

Plumularia inermis Nutting.

Nutting, 1900, p. 62, pi. 5, figs. 1, 2, 2a.
Fraser, 1912, p. 382, fig. 50.

This delicate hydroid covered thickly a large area of eel-grass in
the shallow water of Fairyland Creek; the colonies attained a height
of 18 mm. The trophosome agrees with Nutting's description, except
that the intermediate internodes are much more numerous than one
would infer from his reference to their "occasional appearance," and
there are often one or two short intermediate internodes between the
proximal hydrotheca and the stem. The hydrocladia rarely bear more
than three hydrothecae, and are often prolonged into stolons.

The gonosome, heretofore unknown, was found in abundance. The
gonangia (Figs. 3, 4) are 20-30 times as long as the hydrothecae, unpro-
tected, oblong-ovate, decidedly annulated throughout, and differing
from those of all other American species of Plumularia in springing
directly from the hydrorhiza. The colonies are dioecious; the female

256

BENNITT.

blastostyle (Fig. 3) shows the thick, rounded "Deekenplatte" of
ectodermal cells about the terminal orifice, and bears usually a single
gonophore on one side; the male blastostyle (Fig. 4) is surrounded
by a solid mass of sperm-producing cells.

Figure 3. Phimularia inermis. Female gonangium. X 11.
Figure 4. Phimularia inermis. Male gonangium and portion of colony,
showing stolon-formation. X 11.

Plumularia setacea (Ellis).

Corallina setacea, Ellis, 1755, p. 19, pi. 11.

Plumularia setacea, Nutting, 1900, p. 56, pi. 1, figs. 1-4.

Several colonies of Plumularia setacea were found on Sargassum;
in one group of colonies stolon-formation was extensive.

A

k

HYDROID FAUNA OF THE BERMUDAS. 257

BIBLIOGRAPHY.

Agassiz, A.

1865. North American Acalephae. Illustr. Cat. Mus. Comp.
Zool. Harvard Coll., no. 2. viii + 234 p.
Agassiz, L.

1862. Contributions to the natural history of the United States,
vol. 4, 372 p., 35 pis.
Alder, J.

1857. A catalogue of the zoophytes of Northumberland and
Durham. Trans. Tyneside Nat. Field Club, vol. 3, pp.
1-70.
1859. Description of three new sertularian zoophytes. Ann. and

Mag. Nat. Hist., (3), vol. 3, pp. 353-355.
1862. Description of some rare zoophytes found on the coast of
Northumberland. Ann. and Mag. Nat. Hist. ,.(3), vol. 9,
pp. 311-316.
Allman, G. J.

1871. A monograph of the gymnoblastic or tubularian hydroids.
Ray Society, London, vol. I, xxiv + 450 p. ; vol. II, 23 pis.
1877. Report of the Hydroida collected during the exploration
of the Gulf Stream by L. F. de Pourtales. Mem. Mus.
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during the years 1873-1876. Part II. Report Chal-
lenger Exped., Zool., vol. 23 (pt. 70), 90 p., 39 pis., 1 map.
Bedot, M.

1914. Nouvelles notes sur les hydroides de Roscoff. Arch. Zool.
Exper., tom. 54, pp. 79-98, tab. 5.
Clarke, S. F.

1879. Report on the Hydroida collected during the exploration of
the Gulf Stream and the Gulf of Mexico by Alexander
Agassiz, 1877-1878. Bull. Mus. Comp. Zool. Harvard
Coll., vol. 5, pp. 239-252, 5 pis.
Congdon, E. D.

1907. The hydroids of Bermuda. Proc. Amer. Acad. Arts and
Sci., vol. 42, no. 18, pp. 463-485.
Ellis, J.

1755. An essay towards a natural history of the corallines.
London. 103 p., 40 pis.

258 BENNITT.

Fewkes, J. W.

1881. Report on the Acalephae, etc. Bull. Mus. Comp. Zool.
Harvard Coll., vol. 8, pp. 127-140, 4 pis.
Fraser, CM.

1912. Some hydroids of Beaufort, N. C. Bull. U. S. Bur. Fish.,
vol. 30, pp. 337-387.
Hargitt, C. W.

1900. A contribution to the natural history and development of
Pennaria tiarella. Amer. Nat., vol. 34 (401), pp. 387-406.

1901. The hydromedusae. Amer. Nat., vol. 35, (412), pp. 301-
315; (413), pp. 379-395; (415), pp. 575-595.

1909. New and little-known hydroids of Woods Hole. Biol.
Bull., vol. 17, (6), pp. 369-385.
Hartlaub, C.

1901. Revision der Sertularella-Arten. x\bhandl. a. d. Geb.
Naturwiss., Bd. 16, 143 p., 6 Taf.
Heller, K.

1868. Die Zoophyten und Echinodermen des adriatischen
Meeres. Wien. 88 p., 3 Taf.
Hincks, T.

1861. A catalogue of the zoophytes of South Devon and South
Cornwall. Ann. and Mag. Nat. Hist., (3) vol. 8, pp. 152-
161, 251-262, 290-297.
1868. A history of the British hydroid zoophytes. London,
vol. I, Ixviii -j- 338 p.; vol. H, 67 pis.
Jaderholm, E.

1907. Leber einige nordische Hydroiden. Zool. Anz., Bd. 32,
pp. 371-376.
Kirchenpauer, G. H.

1872. Ueber die Hydroidenfamilie Plumularidae. Abhandl.
a. d. Geb. Naturwiss., Bd. 6, 52 p., 8 Taf.
Linnaeus, C.

1758. Systema naturae, 10th ed. Holmiae. vol. I, 1384 p.
1767. Systema naturae, 12th ed. Holmiae. vol. I, pt. 2, 1327 p.
McCrady, J.

1858. Gymnophthalmata of Charleston Harbor. Proc. Elliott
Soc. Nat. Hist., vol. 1, pp. 1-119, pis. 8-12.
Nutting, C. C.

1900. American hydroids. Part I. Plumularidae. Spec. Bull.
U. S. Nat. Mus., 135 p., 34 pis.

1901. Hydroids of the Woods Hole region. Bull. U. S. Bur.
Fish., vol. 19, pp. 325-386.

HYDROID FAUNA OF THE BERMUDAS. 259

1904. American hydroids. Part II. Sertularidae. Spec. Bull.
U. S. Nat. ilus., 151 p., 41 pis.

1915. American hydroids. Part III. Campanularidae and
Bonneviellidae. Spec. Bull. U. S. Nat. Mus., 118 p., 27
pis.
Ritchie, J.

1909. Two unrecorded " Challenger " hydroids from the Ber-
mudas, with a note on the synonymy of Campanularia
insignis. Zoologist, (4), vol. 13, pp. 260-263.
Stechow, E.

1914. Zur Kenntnis neuer oder seltener Hydroidpolypen, meist
Campanulariden, aus Amerika und Norwegen. Zool.
Anz., Bd. 45, pp. 120-136.

1919. Zur Kenntnis der Hydroidenfauna des Mittelmeeres,
Amerikas, und anderer Gebiete. Zool. Jahrb., Abt. f.
Syst., Bd. 42, pp. 1-172.
Versluys, J., Jr.

1899. Hydraires calyptoblastiques recuellis dans la mer des
Antilles pendant I'une des croisieres accomplies par le
comte R. de Dalmas sur son yacht " Chazalie." Mem.
Soc. Zool. France, tom. 12, pt. 1, pp. 29-58.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 11. — Mat, 1922.

SOME HYMENOPTEROUS PARASITES OF LIGNICOLOUS

ITONIDID.E.

By Charles T. Brues.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 11. — M.\y, 1922.

SOME HYMENOPTEROUS PARASITES OF LIGNICOLOUS

ITONIDID^.

By Charles T. Brues.

SOME HYMEXOPTEROUS PARASITES OF LIGNICOLOUS

ITOXIDII)^. 1

By Charles T. Brues.

Received Jan. 18, 1922. Presented Jan. 11, 1922.

TiiE interesting material which led to the preparation of the present
paper was obtained by Professor W. M. Wheeler during the summer of
1920, when he visited the Tropical Research Station maintained by
the New York Zoological Society under the direction of Mr. William
Beebe at Kartabo, British Guiana. While exploring the forest in the
vicinity of the laboratory he found upon the surface of some freshly cut
stumps of trees, numbers of a minute species of gall-midge, the females
of which were ovipositing in the lumen of exposed vessels of the wood.
The larvse of these midges undoubtedly feed within the vessels and
their presence attracts swarms of very small Hymenopterous parasites
of the family Platygastridse, which are seen scattered over the moist,
freshly cut surface depositing their eggs within the bodies of the midge
lar^•ui upon which they are parasitic. Professor Wheeler secured speci-
mens of the midges and a large series of the parasites which he very
kindly turned over to me, thinking that they would prove of interest
on account of the extremely long abdomen possessed by some of the
parasites, whereby they are enabled to deposit their eggs in the host
larvae within the vessels, well below the surface of the wood. The
midges are similarly modified for this purpose as the apical abdominal
segments are very slender and form an extrusible tubular ovipositor
which can also be inserted into the interstices of the woody tissue.
Dr. E. P. Felt has been so good as to examine the midges and informs
me that they are probably referable to the genus Janetiella Kieffer,
although a knowledge of the male might show them to represent a new
genus. Felt ('18) lists a number of North American .species of Jane-
tiella that produce galls on very diverse plants (Pinaceae, Vitacese and
Myricacese) and one that occurs under decaying bark of chestnut, but
cites no zoophagous forms. Janetiella occurs in Europe and both
North and South America.

The parasites proved to be of much greater interest than had been

1 Contribution from the Entomological Laboratory of the Bussey Institu-
tion, Harvard University, No. 196.

264 BKUES.

anticipated, due not only to theii- strangely modified egg-laying
apparatus but on account of a type of variation which they exhibit
that appears to be c^uite different from any hitherto reported among
the females of insects.

Previous to a careful examination it appeared probable that two
species were represented in the series, one with the abdomen lengthened
to a varying degree in different individuals and a second with the
abdomen short like that of most genera of Platygastridse. Closer
study has shown, however, that no less than six species, distributed in
as many genera, are included, in addition to some males which I
cannot associate with the females of any of the species in the lot.

These forms from Kartabo, described on a later page, are as follows :

Polymecus (Dolichotrypes) minor sp. nov.
Synopeas meridionalis sp. nov.
Gastrotrypes spatulatus gen. et sp. nov.
Polygnotus simplex sp. nov.
Platygaster tubulosa sp. nov.
Isostasius crassus sp. nov.

Three of them, Dolichotriy^pes, Gastrotrypes and Platygaster have the
apical portion of the abdomen, the ovipositor, or both, lengthened and
modified to reach their hosts within the wood, while the others are
apparently in no way specially adapted to the habits of the host. The
latter must, therefore, be able to parasitize only host larvse which are
feeding very close to the surface of the wood unless they may have
active first-stage larvje, but this does not seem probable, since no
planidium forms or other free-living larvse are known to occur within
the family. ^

In 1911 Crawford and Bradley ('11) described the genus Dolicho-
trypes in which they placed a single North American species, D.
hopkinsi. This remarkable insect had been first collected in West
Virginia by Dr. Hopkins who found the females supposedly o\'ipositing
in the bodies of dipterous larvfe living in a stump. Later, in 1897,
Professor J. H. Comstock found the same species near Ithaca, New
York. He noted them in large numbers, the " females busily inserting
the long part of the abdomen into the intercellular spaces of the wood
near the bark. They were confined to the outer two inches of the

1 The larvse of some other species of Polygnotus, Platygaster and Synopeas
which have been observed are cyclopoid when first hatched, cf. Marchal, '04,
Marchal '06, Richardson '14.

HITVIENOPTEROUS PARASITES. 265

wood." That the insect occurs generally about Ithaca is evident as
it was again taken by Prof. C. R. Crosby in 1910. INIy own first
acquaintance with Dolichotrypes was during the summer of 1911
when ]Mr. W. F. Fiske, then director of the Gipsy-moth Laborator^^ at
IMelrose, j\Iass., gave me several vials containing numerous specimens
of minute Platygastridse that he had collected upon freshly cut stumps
not far from his laboratory. He was quite certain that the females
were ovipositing in objects concealed within the wood, and from the
known habits of numerous related genera, surmised that Dolichotrypes
attacks the larva? of some Itonidid midge. ^

At the time I noticed that there was a great Variation in the size and
appearance of jNIr. Fiske's specimens and on having them mounted,
found that more than one species was represented. This material
received no further study, however, till Professor Wheeler showed me
the series of similar insects obtained at Kartabo. A re-examination of
my New England material then showed the presence of not only
Dolichotrypes, but also of two of the other genera found at Kartabo.
]\Ir. Fiske's material then, includes the following:

Polymecus (Dolichotrypes) hopkinsi Bradley & Crawford.
Synopeas sp. (perhaps S. cornicola Ashm.).
Gastrotrypes caudatus sp. nov.

I found no males, and there appears to be considerable doubt also,
whether the males of Dolichotrypes described and figured by Bradley
and Crawford ('11) are really such. This is a minor matter, however,
in the present connection, as the interesting points here dealt with
relate to the females.

If one examines a large series of Dolichotrypes minor under the micro-
scope it is at once evident that the individuals vary greatly in length,
and that this variation is confined almost entirely to the apical seg-
ments of the abdomen. The head, thorax and the first three abdominal
segments which form the gaster are uniform in conformation and equal
in size, apart from the small differences which are always exhibited
even by tlie least variable insects. Among the Platygastridie in
particular, \-ariations in body size are usually well marked as the spe-
cies are parasites of the larvae of Diptera, and they reflect not only the
intraspecific variability of the host, but also to some extent, its change

1 Since then the genus Dohchotrypes has been found in Australia by Dodd
who described ('16) a species from Queensland. The single female known was
taken on foliage of sugar-cane.

266

BRUES.

in size due to age at the time of parasitization. Such variation is
always more pronounced among the parasites of insect larvte than is
the case with egg-parasites where the food supply of each individual
parasite is more evenly apportioned {e.g., in the related family
Scelionidse).

As can be seen from the diagrammatic sketches shown in Figure 1,
the variability in size of the gaster is quite noticeable, but notexcessive.
The following segments (four to six) show enormous differences not

Figure 1. Polymecus (DoHchotrypes) minor sp. nov. Diagrammatic views
in profile of the abdomen of a selected series of females.

only in actual length but also in proportionate length in any selected
series. Of these, segments four, five and six are black and heavily
chitinized, while the seventh or apical one is membranous and almost
hyaline. Beyond it, extends the ovipositor and its two sheaths which
may be exserted to great length or very nearly concealed within the
body. Taken together, these elongated segments resemble the tele-
scopic arrangement of parts seen in many insects and other animals.
In fact the abdomen of all insects is built upon this principle as its

HYMEXOPTEROUS PARASITES. 267

extension and retraction depends upon slight telescopic movements of
the sclerites permitted by the infolded membranes which connect their
adjacent edges. In a greatly exaggerated form this type of construc-
tion is by no means rare; it occurs in the apical part of the abdomen of
the higher Diptera, in the midge upon which Dolichotrypes is parasitic,
in the Serphoid Scorpioteleia, referred to on a later page, and quite
frequently in association with the ovipositor of various insects.

Careful dissections of the abdomen of Dolichotrypes show, however,
that only the membranous apical segment is extrusible and retractile in
response to muscular impulsion. The basal tubular segments (4, 5
and 6) are of a fixed length in each individual insect although one seg-
ment may be eight or ten times as long in one specimen as the corre-
sponding one in another example. Furthermore, it is impossible to
segregate a large series of indi\dduals into classes, based on length of
segments as the proportionate lengths are not constant, although there
is a well-marked tendency for all to be either long, short, of medium
length, etc.

The reasons for believing that the lengths of the chitinized segments
cannot be changed by muscular action are very clear. The individuals
do not show any segments in which the chitinized basal end is tele-
scoped within the apex of the preceding segment, nor do any of them
show an elongation of the intersegmental membranes. In all cases the
exposed portions are black and thickly chitinized, but no hardened
portions remain concealed. It is evident, therefore, that the seg-
mental lengths of adults are fixed and that they have been determined
previous to the hardening of the exoskeleton which occurs soon after
the insects have undergone their last ecdysis from pupa to imago.
AVhether it occurs at the time of pupation cannot be stated definitely as
no puppe have been observed, but as the form of such parts is usually
determined at that time there is no reason to believe otherwise in this
case. It seems probable, therefore, that the ultimate form of the
abdomen is determined when the pupa is first formed, after which
pigmentation and chitinization develop slowly.

It is noticeable in specimens with extremely long fourth segment
that this segment is just long enough, if it could be retracted within
the body, to reach to the anterior region of the thorax as is the case
with the ovipositor in Inostemma. ^ Such is also true in most of the
long-tailed individuals with regard to the length of the membranous
scA'enth segment which when exserted equals approximately the sum

1 The condition of the ovipositor in this genus is discussed on a later
page (p. 280).

268 BRUES.

of the lengths of the more anterior parts of the abdomen and the thorax.
In other genera {e.g., Scorpioteleia, p. 279) with similar parasitic habits,
the apical portion of the abdomen consists of long tubular slender
segments which telescope one within another, but remain movable
during life. In Dolichotrypes a precocious extrusion of the segments
at the time of pupation would lead to their chitinization and fixation
at whatever length they happened to have been protruded. I am
therefore inclined to believe that the polymorphic conformation of the
abdomen of the imago is actually determined by the individual insect
at the time it pupates and that the process is by no means an entirely
passive one.

Nevertheless, the condition of the abdomen in Dolichotrypes recalls
the high and low males of other insects {e.g., certain Dermaptera and
lamellicorn beetles) well known to entomologists and subjected to
statistical study by Bateson, '92). That this dimorphism may be due
to Sporozoan parasites was suggested by Giard ('94), but however
plausible and attractive this hypothesis may appear, it seems, at least
in the case of the earwigs, to be disproved by the findings of Brindley
and Potts ('10) and of Brindley ('18) as these authors found no such
correlation between gregarine parasites and the high and low males of
Forficula auricularia. So far as Dolichotrypes is concerned such an
explanation undoubtedly cannot apply. I have been unable to find
any Protozoan or bacterial parasites in them and, moreover, as such
endoparasitic species do not have extensive opportunity to acquire
microorganisms they are never generally supplied with them, and stand
in marked contrast to the free living earwigs, termites, lamellicorn
beetles, et al.

As already indicated, one of the species of Dolichotr^^jes and most
of those belonging to the other genera are new to science so that it has
been necessary to include a taxonomic account of these. This is given
below.

Polymecus (Dolichotrypes) minor sp. nov.

9 . Length 0.8 mm., exclusive of the 4th, 5th and 6th abdominal
segments; these together fully exserted 3 mm., and fully retracted
0.4 mm.; the hyaline 7th segment extrusible to 1.5 mm., rarely to 2.5
mm., filaments of ovipositor extrusible to 2 mm., rarely a little more.
Black, with the basal half of the scape, the coxae, and the legs, except
the thickened parts of the tibiae and femora, brownish yellow. Wings
entirely hyaline. Head, oval, fully twice as wide as thick, the occiput
more convex than the front; ocelli in a curved line, the lateral ones
one-half as far from the eye-margin as from the median one. Head

HYMENOPTEROUS PARASITES. 269

shagreened, more densely so above. Eyes bare; malar space half as
long as the eye, without furrow. Antennse 10-jointed; scape half as
long as the pedicel and flagellum together, much thickened apically;
pedicel narrow at base, twice as long as thick; four funicle joints much
more slender than the pedicel, the first and fourth short, quadrate,
and the second and third considerably longer than thick; club 4-
jointed, joints of about equal length, as broad as long. Mesonotum
shining, very delicately shagreened, distinctly longer than wide;
parapsidal furrows obsolete, indicated only by a depressed spot on the
hind margin of the mesonotum; basal scutellar groove narrow, but
deep. Scutellum highly convex, with a short, slightly curved and
upturned thorn at apex. Pro- and mesopleurse smooth and shining;
metapleura punctate and densely hairy, as is also the first abdominal
segment; lateral angle of propodeum with a long, straight, backwardly
and outwardly directed slender spine. Second segment of abdomen
almost as broad and as long as the thorax, polished, with scattered,
short, white bristles; broadest just before the middle; third minutely
punctured, narrowed apically, the tip only one-fourth as wide as the
base of the second. In fully extruded specimens the following seg-
ments are very slender, and proportioned as follows, fourth as long as
the remainder of the body, the fifth and sixth each as long as the body,
including the third segment. In retracted specimens the fourth seg-
ment may be only half as long as the second and the fifth and sixth
each not over one-half to two-thirds as long as the second. The ovi-
positor is rarely extruded to any extent, except in otherwise greatly
extended examples. Fourth to sixth segments shining, but under high
magnification, distinctly scabrous ; on these segments the sharp lateral
edge is visible, but becomes obsolete on the second, except at the
extreme base. Fore wing with only very minute marginal cilia; disc
hairy, the hairs large and sparse, forming indistinct lines; basal third
with minute hairs. Hind wing with two frenulum hooks.

Type and numerous paratypes from Kartabo, British Guiana,
August 20 and 21, 1920, ovipositing as previously described in a cvit
stump, containing larvae of the Itonidid, Janetiella sp.

This species differs from D. hopkinsi Crawford and Bradley- ('11) by
its much smaller size, almost entirely obsolete parapsidal furrows and
somewhat different color. The club of the antenna and the fifth and
sixth segments ^ of the abdomen are entirely black, not brown as in
the North American species.

1 Not the fourth and fifth as stated by Crawford and Bradley; the third is
short and narrow and so closely attached to the second that tliej' have con-
sidered it as a part of the latter.

270

BRUES.

Polymecus (Dolichotrypes) hopkinsi Crawford & Bradlev

('11, p. 124).

Mr. W. F. Fiske obtained numerous females of this species on May
19 near Boston, on cut stumps, behaving as described by Crawford and
Bradley. From some of his specimens which he kindly gave me at the
time, I have been able to compare the South and the North American
species.

The genus Dolichotrypes is probably not distinct from Polymecus
according to Mr. Fonts who has given much time to taxonomic studies
in this family. I have retained it above in subgeneric form to include
the two species here dealt with. Other species of Polymecus have the
apical prolongation of the abdomen to a lesser degree as do also some
species in other genera such as Sactogaster. In addition to the " tail,"
the females of the latter genus possesses a sac-like enlargement of the
venter probably associated with the egg-laying apparatus. A Euro-
pean species was bred more than half a century ago by Winnertz
('53) from Contarinia (Cecidomyia) pisi, but further observations on
this interesting genus do not appear to have been made.

In two other Serphoid families there is a somewhat similar ventral
swelling of the second segment which extends forwards ; the Diapriid
Cardiopria Dodd and the Belytids Acanosema Kieffer and Cardio-
spilus Kieffer are thus modified.

Gastrotrypes, gen, nov.

Antennre 9-jointed, with a minute hyaline joint-like connection in
addition, between the pedicel and first flagellar joint. Maxillary palpi
consisting of two equal, elongate joints; labial palpi one-jointed, elon-
gate. Head about twice as broad as thick, a little wider than the
thorax. Ocelli in a broad triangle, the lateral ones much closer to the
eye than to the median ocellus. Parapsidal furrows wanting. Scutel-
lum highly convex, without spine, not deeply separated from the
mesonotum which bears a large shallow impression at each side behind ;
pubescent, especially at the sides apically. Abdomen with the first
four segments forming an oval mass; second segment quadrate; third
and fourth short, much narrowed; fifth very narrow, sometimes very
much elongated; sixth segment membranous, very slender, capable
of being greatly extruded. Wings veinless, with very weak discal
hairs; with prominent marginal cilia apically behind.

Type species: G. spatulatus sp. nov.; other included species: G.
caiidains sp. nov.

HYMENOPTEROUS PARASITES. 271

Gastrotrypes spatulatus sp. nov.

9 . Length 0.8-1.20 mm., exclusive of the very slender hyaline
apical portion of the abdomen which may be entirely withdrawn or
extruded to a length of slightly more than that of the body; true ovi-
positor very short, never extruded for more than a very short distance
beyond the hyaline tube which comprises the sixth and seventh seg-
ments, although in many specimens it appears to consist of only a
single segment, the sixth. Black; antenna! scape honey-yellow,
except more or less at apex; legs honey-yellow, hind coxse sometimes
darker; hind femora and tibipe infuscated apically, also sometimes the
femora and tibire of the other legs. Head, seen from above oval,
slightly, but distinctly more than twice as broad as thick. Ocelli large,
the lateral ones removed by somewhat less than their own diameter
from the eye-margin, surface of head shining, the vertex and sides of
the front shagreened, but the front almost entirely smooth medially;
head behind and cheeks, smooth; malar space rather long, more than
half the width of the eye, smooth and polished, without furrow.
Antennae nine-jointed, not taking into account a minute hyaline con-
nection between the pedicel and first flagellar joint; scape about half
as long as the remaining joints together; pedicel short, one-half longer
than wide; first flagellar joint slightly longer than the second, nearly
twice as long as thick; third very small, half as long and half as thick
as the second; club 4-jointed, rather stout, the joints as long as broad,,
except the last which is more elongate. Mesonotum shining, sparsely
clothed with pale appressed hairs laterally; without parapsidal fur-
rows; much narrowed anteriorly, with the pleurse largely visible from
above. Scutellum not separated by a basal groove, but with a large
pubescent fovea at each side; strongly convex, the posterior portion
obliquely sloping, almost truncate; entire surface densely hairy and
apparently closely punctate beneath the hairs. First four abdominal
segments smooth, forming an oval mass as long as the thorax; first
segment short, campanulate, with a deep fovea at each side, densely
pubescent, except above; medially with a median groove which
receives a corresponding ridge on the propodeum when the abdomen
is bent upwards; second segment as long as wide, broadest behind,
one half longer than the third and fourth together; third and fourth
sharply narrowed, of equal length; fifth segment longitudinally
aciculate, slightly longer than the fourth, only one-fifth as wide as the
second segment, its sides parallel, except on the narrowed apical half;
from its apex projects the hyaline sixth segment which is scarcely

272 BRUES.

thicker than the posterior tarsi. Pleuree smooth, the metapleurse
behind densely clothed with backwardly directed pale hairs. Wings
hyaline, with a well-developed marginal fringe apically below; disc
with very minute hairs ; hind wing with two frenulum hooks.

Type and numerous paratypes from Kartabo, British Guiana
(W. M. Wheeler).

The color of the legs in this species varies as in Synopeas meridionalis,
but the variation is continuous and no color forms are distinguishable.

Gastrotrypes caudatus sp. nov.

9 . Length 2.5 mm., including the long stylate apical segment of
the abdomen which is nearly as long as the remainder of the body.
Black, the wings hyaline, the antennse and legs, including coxse,
brownish yellow; upperside of antennae, especially' the apex of scape
and the club and the thickened parts of the femora infuscated. Head
seen from above twice as wide as thick, shining and almost smooth,
the occiput faintly transversely striate and separated from the vertex
by a distinct, very fine, raised line; lateral ocelli twice as far from the
median one as from the eye margin. Antennae 9-jointed, the scape
rather slender, more than half the length of the flagellum; pedicel
small, narrower and one-third shorter than the first flagellar joint;
first flagellar twice as long as thick, considerably longer than the third;
fourth minute, narrowed at base, about as long as wide; club 4-jointed,
first joint longest, twice as long as thick, following subequal, each
shorter and somewhat thicker than the first; malar space nearly as
long as the width of the eye. jNIesonotum smooth and shining, with a
band of sparse appressed pale hairs on each side of the middle; parap-
sidal furrows entirely absent; behind with a transverse impression on
each side at the base of the scutellum, densely clothed with pale hairs.
Scutellum highly convex at the middle, obliquely sloped behind and
finely, densely punctate beneath a mat of woolly hair. Pro- and
mesopleurse smooth and highly polished, metapleura with backwardly
directed pale hairs. Propodeum angularly produced laterally and
medially with a tubercle which corresponds to a central impression on
the dorsal surface of the first abdominal segment. Body of abdomen
ovate, nearly as long as the head and thorax together, consisting of
four segments; first segment about as wide as long, much narrowed
basally, its posterior edge set into the base of the second; medially
with a quadrate impression and woolly laterally; second segment as
long as wide, broadest behind the middle; its basal margin produced

HYMENOPTEROUS PARASITES. 273

forward at the sides and also medially, so that it is bisinuate, on each
side of the middle basally with about five fine longitudinal strife that
extend nearly half way to apex; third and fourth segments evenly
narrowed to the base of the stylate fifth; third twice i^s wide as long;
fourth triangular, as long as broad; fifth of even widtli throughout,
ten or twelve times as long as broad; apical segments membranous,
very slender, usually retracted but in one specimen exserted to a
length equally the entire length of the body; filaments of ovipositor
not much extruded. Fore wings without marginal cilia; hind wing
with two frenulum hooks.

Type and numerous paratypes obtained by Mr. W. F. Fiske on
stumps of freshly cut trees in the environs of Boston, Mass., on May
19, 1911.

This species is very much larger than the preceding South American
G. spatidatus described on a previous page, the fifth abdominal seg-
ment is much longer and more slender and the sculpture of the second
segment is quite diiferent. The length of the fifth segment gives it
quite a difl^erent appearance, but as most of the important structural
characters are similar in the two forms, I believe that they should be
considered to be congeneric.

This species was found associated with Dolichotrypes by Mr. Fiske,
but does not seem to have been represented in the material examined
bv Crawford and Bradlev when thev described the latter ('11).

Synopeas meridionalis sp. nov.

9 . Length 0.7-0.8 mm.; occasional specimens from 0.6-0.9 mm.
Black; with the basal half of scape, trochanters base of femora and
tibise deep yellow; front and middle tarsi whitish, posterior ones in-
fuscated; thickened apical parts of femora and tibiae piceous; coxse
piceous, the hind ones somewhat lighter; wings hyaline. Head, seen
from above, broadly oval, twice as broad as thick; shagreened above,
less distinctly so and more shining on the front; lateral ocelli twice as
far from the median one as from the eye margin; malar space as long
as half the width of the eye; cheeks and back of head distinctly
shagreened. Antennae 10-jointed; scape nearly half as long as the
remaining joints together, strongly thickened apically; pedicel as
long as the width of the scape, nearly twice as long as thick; basal
four joints of flagellum slender, the first and fourth but little longer
than tliick, second and third longer, but less than twice as long as
thick; four club-joints broad, each about as long as thick, oblique.

274 BKUES,

Mesothorax as broad as long; the mesonotum strongly convex, shining,
faintly shagreened, with only very slight traces of parapsidal furrows
anteriorly; scutellum triangular in outline, highly convex and sepa-
rated from the mesonotum by a deep, narrow groove, terminated by
a short spine or thorn at the apex. This thorn is straight or slightly
curved downward at tip and projects horizontally in the plane of the
upper surface of the thorax; below it near the upper edge of the
propodeum on each side is another backwardly projecting spine of
very slender form which is more or less concealed in dried specimens
by the dense white backwardly directed hairs that cover the propo-
deum; upper surface of thorax sparsely covered by short sparse white
oppressed hairs. Pro- and mesopleurje smooth and highly polished,
bare. Abdomen short, ovate, no longer than the thorax, highly
polished, with a few minute appressed white hairs; lateral carina
distinct; first segment densely white woolly pubescent on the sides,
but bare medially above; second segment one-third longer than the
remaining ones together, widest just before apex, almost as wide as
long; remaining segments very rapidly narrower; third and fourth
extremely short, fifth noticeably longer; sixth triangular, as long as
the three preceding. Ovipositor very short, never exserted for more
than one-third the length of the abdomen; third, fourth and fifth
segments occasionally exserted to twice the extent described above.
Wings with only extremely minute marginal cilia; disc with rather
sparse strong hairs which form very irregular lines; base with very
minute hairs; anterior and posterior margins bare near the middle of
the wing. Frenulum consisting of two hooks.

Type and numerous paratypes from Kartabo, British Guiana
(W. M. Wheeler).

Synopeas meridionalis var. clara var. nov.

9 . Length the same as the typical form. Differs by the entirely
yellow antennal scape and yellow coxse and legs, with only the thick-
ened part of the hind femora and the hind tarsi, infuscated. Rarely
the hind femora are slightly darkened at tips, but there are no inter-
grades in the many specimens of both forms before me.

The typical form and the pale variety are about equally numerous
in the series and the variety averages a trifle larger in size.

This species differs from the North American form with similar
habits, perhaps S. cornicola Ashm., mentioned on a later page in the
following characters: it is considerably smaller, the lateral ocelli are
closer to the eye-margin, and the parapsidal furrows are not complete.

/

HYMENOPTEROUS PARASTIES, 275

Synopeas (?) cornicola Ashm. ('93, p. 288).

With Dolichotrypes and Gastrotrypes, Mr. Fiske took several
specimens which apparently belong to this species, so far as Ash-
mead's original description is concerned. His types of S. cornicola
were reared from an Itonidid gall on Cornus iMniculaia, however,
which suggests that the present form is probably distinct. These
specimens are very much like the species from British Guiana (S.
meridionalis) but considerably larger and otherwise specifically dis-
tinct.

Polygnotus simplex sp. nov.

9 . Length O.S-0.9 mm. Black; antennal scape honey-yellow,
darkened toward apex; legs honey-yellow, the coxre piceous and the
femora, especially the hind ones inf uscated ; hind tibiee and sometimes
the other tibiae also, darkened at tips. Head very much flattened,
seen from above nearly three times as broad as long; lateral ocelli
nearly as close to the median one as to the eye-margin; head behind
the ocelli transversely aciculate; front smooth and polished; malar
space long, fully half the width of the eye, faintly shagreened as is also
the head behind the eyes. Antennae 10-jointed; scape stout, not much
thickened apically, half the length of the remaining joints together;
pedicel elongate, nearly twice as long as thick; first flagellar joint
small, pale colored; half as long and half as thick as the pedicel;
second and third larger, nearly equal, each a little longer than thick;
remaining five forming a rather slender club of which the basal joint
is smaller and the last longer than the intermediate n;pre or less quad-
rate ones. Mesonotum convex, smooth, without furrows, thinly
clothed with appressed pale hairs. Scutellum very highly convex,
separated at base by a narrow groove, with a large oval impression at
each side; its surface finely and shallowly punctate-reticulate. Abdo-
men elongate ovate, widest near the apex of the second segment.
First segment quadrate, as long as the scutellum, coarsely longi-
tudinally fluted; second considerably longer than wide, twice as long
as the following segments together, with several short grooves medially
at base and a large cuneate basal impression near each side at base;
third and fourth equal, each very short; fifth small, triangular, but
longer than the fourth; terminal segments not exserted, ovipositor
very short. Pro- and mesopleurte smooth and shining; metapleura?
clothed with rather sparse backwardly directed pale hairs. Lateral

276 BRUES.

carina of abdomen sharply defined. Femora, especially the hind ones,
very strongly clavate. Wings with a well developed marginal fringe
apically, especially near the lower outer angle; disc with very minute
hairs, almost bare, except on apical third of wing where the hairs are
large and strong; basal third also somewhat more noticeably furnished
with minute hairs. Hind wing with two frenulum hooks.

Type and a number of paratvpes from Kartabo, British Guiana
(W. M. Wheeler).

This species is not very abundantly represented in the collection;
a careful sorting has disclosed only about thirty specimens.

Platygaster tubulosa sp. nov.

9 . Length to tip of third abdominal segment 1.0-1.2 mm. Black;
scape of antenna? yellowish brown basally; coxre, thickened portions
of femora and of middle and hind tibia? piceous; trochanters and
anterior tibijie pale yellow; tarsi pale, with the last joint infuscated;
wings hyaline; third segment of abdomen brown, the apical ones not
always extruded, hyaline, with the tips brownish. Head rather flat,
more than twice as broad as long when seen from above; ocelli rather
large, the lateral ones almost as far from the eye-margin as from the
median one; vertex and occiput fineh- shagreened; front shining,
practically smooth; malar space nearly half as long as the eye-width,
smooth, as is also the head behind the eyes. Antennse apparently
9-jointed, but really with ten joints, counting the small joint just
beyond the pedicel; scape considerably more than half as long as the
remaining joints together, slender, much narrowed basally; pedicel
one half longer than thick; first flagellar joint almost as long as the
pedicel, with a short, indistinctly separated ring-joint attached to its
base; second and third joints slightly shorter, about quadrate; re-
maining four joints forming a slightly thickened, but not very distinct
club, the joints of which are slightly longer than wide. Mesonotum
with finely impressed, but complete and distinct parapsidal furrows,
shining, clothed with sparse appressed hairs. Scutellum large, con-
vex, longer than wide and gently sloping downwards behind, its base
without foveje and separated only by a thin, shallow impressed line.
Propodeum with a strongly raised longitudinal ridge toward each side,
enclosing a deep quadrate median impression. Pro- and mesopleurse
shining, faintly punctate; metapleura thinly pale pubescent. Abdo-
men elongate, lanceolate; first segment broader than long, coarsely
longitudinally striated; second segment three times as long as broad

HYMENOPTEROUS PARASITES. 277

tapered from middle toward base and apex, more strongly so behind;
base medially with some short fine longitudinal striee and toward each
side with a larger and deeply impressed groove that extends to the
basal fourth; third segment one-third as long as the second, very
narrow and evenly contracted to the more or less blunt apex; fourth,
fifth and sixth segments tubular capable of being entirely retracted;
the fourth nearly as wide as the tip of the third, but the other two very
slender; ovipositor never extending much beyond the sixth segment.
In the most fully extruded example the fourth to sixth segments
together measure 1.5 mm., or distinctly more than the length of the
remainder of the abdomen. Wings absolutely hyaline, without dis-
tinct marginal fringe, except for some almost transparent hairs api-
cally; disc bare. Hind wing with two delicate frenulum hooks.

Type and eight paratype specimens from Kartabo, British Guiana
(W. M. Wheeler).

This species is represented by fewer specimens in the collection than
any of the others.

Isostasius crassus sp. nov.

9 . Length 1.0 mm. Black; coxae piceous, the trochanters, base
of femora and tibiae and tarsi, except last joint pale yellowish; re-
mainder of legs dark brown or piceous. Wings hyaline, the vein
fuscous. Head considerably broader than the thorax, flattened, more
than twice as wide as long when seen from above. Ocelli large, close
together, the lateral ones as far from the eye-margin as from the median
one; vertex and occiput shagreened, subshining; face shagreened,
but more shining; lower margin of face elevated at the insertion of the
antennae; makir space indistinctly transversely striated, more than
half as long as the width of the nearly round eyes; head behind eyes
shagreened, with a faint trace of striae curving upwards across the
cheeks. Antennae 10-jointed, less than half as long as the remaining
joints together, rather stout, more slender basally; pedicel large,
almost as broad as the scape, one-half longer than wide; funicle, con-
sisting of the first four flagellar joints, short, the joints very small, of
about equal length and quadrate, except for the broader and dis-
tinctly transverse fourth joint, club large, first joint narrower than the
others; second and third very broad, nearly twice as wide as long, last
elongate, triangular, narrower than the preceding one. Thorax broad,
the mesonotum as broad as long and the pleurae only slightly visible
from above; mesonotum shagreened; rather dull, sparsely clothed

278 BRUES.

with fine appressed hairs like the remainder of the thorax and the head;
parapsidal furrows deHcate, quite distinct behind, but obsolete in
front. Scutellum strongly convex medially, noticeably elevated above
the level of the mesonotum, separated at the base by a narrow impres-
sion, wider at the sides; posterior margin defined by a semicircular
raised margin inside of which is a deep submarginal groove. Propo-
deum trilobed behind, woolly on the sides and with a pair of longi-
tudinal ridges on its central portion. Abdomen short, ovate, barely
longer than the thorax; first segment short, more than twice as broad
as long, slightly woolly and longitudinally fluted; second segment
shining, very convex, twice as long as v/ide, broadest at the middle,
and forming the entire gaster except for the small, elongate-triangular
third segment; second finely longitudinally striate at its extreme base,
with a larger and deeper groove at each side of the base; third segment
punctulate, with sparse pale hairs. Venter highly convex, the lateral
carina not very distinct. Propleurse shagreened ; mesopleura broadly
impressed medially and behind, obliquely striate near its posterior
border; metapleura thinly clothed with short pale hairs. Ovipositor
only slightly projecting, curved downwards. Legs rather slender, the
femora strongly clavate, the tibiae more weakly so. ^Ying with a short,
but distinct marginal fringe, the disc bearing strong and rather large
hairs except at the base; vein capitate, one-third as long as the wing.

Type and 12 paratype specimens from Kartabo, British Guiana
(W. M. Wheeler).

As may be gleaned from the taxonomic description (p. 270) of Gastro-
trypes, both species have the abdomen lengthened as in Dolichotrypes,
but the stylate fifth segment is not of variable length so that, exclusive
of the greatly elongated apical membranous segments, all individuals
are of approximately equal length. The membranous parts naay be
entirely retracted or extruded to a length equalling that of the entire
remainder of the abdomen. ^^

Similarly in Platygaster tuhulosa the apical abdominal segments (in
this case the fourth and following) are tubular and capable of complete
retraction or of extrusion to a length somewhat greater than the re-
mainder of the abdomen.

The foregoing observations on Dolichotr;v^es and the Gastrotrypes
and Platygaster associated with it in British Guiana, suggested an
examination of several other Serphoid Hymenoptera. A brief account
of these is given below.

A similar elongation of the terminal portion of the abdomen occurs
in females of members of the genus Serphus (Prodotrypes), but here the

HYMENOPTEROUS -PARASITES. 279

anatomical structure is ciuite different. The fifth apparent (possibly
really the sixth) segment is contracted to the tip from which issues a
stylet-shaped piece, often curved or hooked at the apex and varying in
length from a slight projection to a piece nearly as long as the remainder
of the abdomen. The stylus is heavily chitinized and appears to be
the terminal abdominal segment. Dissection shows, however, that
it is composed of the paired sheaths of the ovipositor. These are
crescentic in cross-section and fit closely together along the median
line above and to form a hollow tube through which the ovipositor
extends. The latter can be only slightly extruded as it is enlarged
into a bulb at the base which lies within the last segment and is sup-
ported by a chitinous strut ventrally. This apparatus is evidently
suited for puncturing cjuite resistant tissues.

' In Scorpioteleia of the related family Belytidse an elongation of the
terminal abdominal segments occurs, very similar to that sho\)'n by
the species of Gastrotrypes and by Platygaster tubulosa. This re-
markable genus was first described by Ashmead ('97) from Eastern
Canada and later recorded by the present writer ('09) from Wisconsin
and the state of Washington. Several other species are known from
Europe, which Kieffer ('10) regards as congeneric with Cinetus be-
lieving that the modified abdomen of the female is not a good generic
character. In the type species, S. mirabilis Ashm., I find upon re-

FiGURE 2. Scorpiotelia mirabilis Ashm. Abdomen of female in profile.

examination that the apical prolongation of the abdomen is undoubt-
edly retractile as it is not chitinized except toward the apices of the
segments and the proportionate lengths of the extruded parts of the
latter vary considerably in different individuals. The third, fourth,
and fifth segments are tubular, successively smaller, but the sixth and
last is of much greater diameter, enlarged at the base, then constricted
and then turned upward at the pointed tip. Althougli the curve is
reversed in position, the resemblance to the sting of a scorpion is very
striking and suggested the appropriate name of Scorpioteleia. Dis-
section shows the last segment to consist of a ventral valve and two
dorsal ones, one overlapping the other. The basal piece extends

280 BRUES.

halfway to the tip and the apical one to the tip where it meets the tip
of the ventral one. Between these the ovipositor issues. It is very
short and its basal attachment lies well within the last segment. Its
valves are heavy and lie one on each side, meeting on the median line
above and below. Many Belytids are parasitic on dipterous larvse in
fungi and quite probably the Scorpiotelei is modified to reach its host
in some tube-bearing fungus such as Boletus or Polyporus. ^ In cer-
tain other Belytids, e.g., Miota, the tip of the abdomen is upturned and
more or less plowshare-shaped, but does not exhibit such excessive
elongation.

The Platygastrid genus Inostemma is characterized by a most
remarkable projection which arises from the dorsum of the first
abdominal segment and extends forward over the thorax with its tip
over the anterior ocellus. The curvature of this horn corresponds
closely to that of the mesonotum, above the surface of which it is
raised, and the vertex of the head bears a median depression to allow
free motion of the head without interference by the tip of the horn.
This rigid process is present only in the female and although several
entomologists had suggested that it received the ovipositor, its func-
tion remained in doubt till Marchal ('06) showed that in the European
Inostemma piricola, it really serves to receive the basal portion of the
ovipositor which is much longer than the abdomen, so that when not
extruded the base lies in the anterior part of the horn. The Inostemma
studied by Marchal deposits its eggs in a Cecidomyiid larva which
feeds within the small developing fruits of the pear. An examination
of the North American Inostemma liorni Ashm. shows that, as might
be expected, the mechanism of the oviposition is entirely similar to
that of the European species. Marchal was at a loss to account for
the apparent origin of the ovipositor within the basal tergite of the
abdomen. Unfortunately the only specimens available have been
mounted dry for a number of years, but dissections of these which I
have made show that the ovipositor appears actually to arise within a
n^embranous apical segment which has been invaginated so as to
occupy the cavity of the process on the first segment. As there are
six visible chitinized segments, this membranous tube is no doubt the
seventh, or seventh and eighth abdominal segments and it must
furnish the muscular apparatus for the manipulation of the ovipositor.
The horn is therefore only secondarily a housing for the ovipositor.

1 The Australian genus Stylaclista Dodd ('15) is evidently very similar to
Scorpioteleia, having the third to sixth abdominal segments produced into a
long fleshy stylus.

HYMENOPTEROUS PARASITES. 281

The genus Brachinostemma and several genera (e.g. Baryconus,
Probary conns, Ceratoteleia, Caloteleia, Ceratobseus, etc.) of the
closely allied family Scelionidre show a tubercle or very short horn
arising from the dorsum of the first abdominal segment, but in no case
does this ever attain a dcA-elopment approaching that seen in Ino-
stemma. From the apparently rudimentary development of what is
seemingly homologous to the horn in Inostemma, one might readily
conclude that these genera show it in an incipient stage. From the
standpoint of function this does not seem possible, however, as the
projection is often so short that it does not serve to lengthen the space
within the abdomen. Possibly the tubercle or horn may have been
developed for some other reason and later served for the accommoda-
tion of the ovipositor. The long horn appears to be unique, however,
and no one has so far been able to attribute to it any other function.
^Ye may readily suppose that its ontogenesis is in direct response to
pressure produced by the base of the developing ovipositor. It seems
impossible that its length, at least in the incipient stage could be of
any selective value, since most Hymenoptera provided with length-
ened ovipositor have developed no structures or devices of any kind
to permit of extensive retraction of this organ. After what has been
said of the conditions prevailing in Dolichotrypes which have been
considered at some length, it is evident that a more extensive knowl-
edge of these minute Hymenoptera may lead to interesting conclusions
concerning the relation between the morphology of the body and the
function of oviposition.

At the same time, it must be borne in mind that the horn of Ino-
stemma does not vary to any excessive degree and that its form and
size are at present as definite and clearly fixed in each species as are
the other parts of the body, and that they are not variable like the
abdominal segments of Dolichotrypes which have not yet attained
fixed dimensions.

282 BRUES.

Literature Cited.

Ashmead, W. H.

'93. A Monograph of the North American Proctotrypidte. Bull.

U. S. Nat. Mus., No. 45, pp. 463, pis. 18.
'97. Descriptions of Some New Genera and Species of Canadian
Proctotrypoidea. Canadian Entom., vol. 29, pp. 53-56.
Bateson, W.

'92. On Some Cases of Variation in Secondary Sexual Characters,
Statistically examined. Proc. Zool. Soc. London, 1892, p. 585.
Brues, C. T.

'09. A Preliminary List of the Proctotrypoid Hymenoptera of
Washington. Bull. Wisconsin Nat. Hist. Soc, vol. 7, pp.
111-122.
Brindley, H. H.

'18. Notes on Certain Parasites, Food and Capture by Birds of the
Common Earwig {Forficula auricular ia). Proc. Cambridge
Philos. Soc, vol. 19, pp. 167-177.
Brindley, H. H. and F. A. Potts.

'10, The Effect of Parasitic Castration in Insects. Science, n.s.
vol. 32, p. 836.
Crawford, J. C, and J. C. Bradley.

'11. A New Pelecinus-like Genus and Species of Platygastridse.
Proc Ent. Soc. Washington, vol. 13, pp. 124-125, pi. 1.
Dodd, A. P.

'15. Australian Proctotrypoidea, no. 3, Trans. Roy Acad. So.

Australia, vol. 39, pp. 384-405.
'16. Australian Proctotrypoidea, no. 4, ibid., vol. 40, pp. 9-32.
Felt, E. P.

'18. Key to American Insect Galls. Bull. New York State Mus.,
no. 200, 310 pp.
Giard, A.

'94. Sur certains cas de dedoublement des courbes de Galton. CR.
Soc. Biol., 1894 and Biologic Generale, pp. 335-338. Paris,
1911.
KiefEer, J. J.

'10. Family Belytidse. In Gen. Insect., fasc. 107, pp. 45.
'16. Beitrag zur Kenntnis der Platygasterinse und ihrer Lebens-
weise. Centralbl. f. Bakt., vol. 46, pp. 547-592.

HYMENOPTEROUS PARASITES. 283

Marchal, P.

'04. Recherches sur la biologic et developpment des Hymenop-
teres parasites. Arch. Zool. Exper. et Gen., vol. pp. 257-335,
4 pis.
'06. Recherches sur la biologic et le developpement des Hymenop-
teres parasites. II, les Platygasters. Arch. Zool. Exper.
Ser. 4, No. 6, pp. 485-640, pis. 8.
Richardson, C, H.

'14. Studies on the Habits and Development of a Hymenopterous
Parasite, Spalangia muscidarum Richardson. Journ. Mor-
phol. vol. 24, pp. 513-557, 4 pis.
Winnertz, J.

'53. Beitrag zu einer Monographic der Gallmucken. Linn.
Entom., vol. 8, pp. 154-322.

EXPLANATION OF THE PLATES.

286

BRUES.

PLATE I.

1. Antennae of Polymecus (Dolichotrypes) minor sp. nov. 9

2. Antennae of Synopeas meridionalis sp. nov. 9 .

3. Antennae of Gastrotrypes spatulatus Gen. et sp. nov. 9 .

4. Antennae of Polygnotus simplex sp. nov. 9 .

5. Antennae of Platygaster tubulosa sp. nov. 9 .

6. Antennae of Tsdstasius crassus sp. nov. 9 .

#

Brues. — Hymenopterous Parasites.

Plate I.

^^^^ ^„.,---^^

v/

Proc. Amer. Acad. Arts and Sciences. Vol. 57.

288 BRUES.

PLATE II.

7. Wing of Polyrnecus (Dolichotrypes) minor sp. nov. 9 .

8. Wing of Synopeas meridionalis sp. nov. 9 .

9. Wing of Gastrotrypes spatulatus gen. et sp. nov. 9 .

10. Wing of Polygnotus simplex sp. nov. 9 .

11. Wing of Isostasius crassus sp. nov. 9 .

12. Wing of cf not associated definitely with any of the foregoing species.

13. Polyrnecus (Dolichotrypes) hopkinsi, 9 . (After Crawford and Bradley.)

14. Inostemma piricola Kieffer, 9 . (After Marchal).

Brues. — Hymenopterous Parasites.

Plate II.

Ji^

N» ^

>

=5

\ /

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LXXXIX. A REVISION OF THE ENDOGONEAE.

By Rol.vnd Thaxter.
Received March 17. 1922. Presented April 12, 1922.

In preparing the present Contribution concerning the Endogoneae
it has not been my intention to consider the subject in all its aspects,
phylogenetic, cytological and other; and this revision has been under-
taken chiefly with a view to the improvement of the systematic status
of the family. For although relatively small, it has not escaped the
taxonomic confusions and uncertainties which so frequently beset the
path of the systematic mycologist, and it has seemed worth while to
make at least an attempt to clear up some of the moot points relating
to it, and at the same time to add such new information as I have been
able to accumulate from personal observation or otherwise. I have
therefore endeavored to obtain authentic information in regard to as
many of the known forms as possible, and personally to examine as
complete a representation of the type-material as could be assembled.
Such value as this account possesses is therefore largely due to the
courtesy of correspondents who have been so kind as to assist me in
accomplishing these objects; and in this connection I desire to express
my great obligation to Professor Abrams, of Leland Stanford, who has
allowed me to examine all the Harkness types of Endogone in the
University Herbarium: to the Abbe Bresadola, who has sent me a
specimen of his E. reniformis collected by Rick in Brazil: to Dr. C. W.
Dodge for Californian material collected by himself and by IVIr. H. E.
Parks: to Professor E. C. Jeffrey for a very interesting collection from
Little Metis, Quebec, given to me many years ago: to Professor G.
Lindau for the privilege of examining portions of all the types of
Hennings and Bresadola in the Berlin JMuseum; to IMr. C. G. Lloyd
for a portion of his Endogone tuberculosa and other interesting forms;
to Professor O. Mattirolo who has sent me for examination specimens
of all his material of Endogone, including the types of E. Pamyaloniana
and E. Tozziana; to M. N. Patouillard for confirming my determina-
tion of his E. lignicola and for portions of the types of Acker mannia

292

THAXTER.

Dussii and A. coccogcna; to Professor Carlos Spegazziiii for communi-
cating the types of Endogone juegiana and E. argcutiua; and to jNIiss
E. A. Wakefield for opportunity to see Berkeley's types of Endogone
ansirolis and GlazicUa vesiculosa.

Index.

Ackermannia

coccogena 333

Dussii 329, 333

Endogone

arenacea 317

argentina 321, 324

australis 312, 313

borealis 318

canadensis . . . 317, 310, 318
fasciculata . . . 308, 309, 311
fulva 312, 317, 319, 320, 322, 326
fuegiana . . 303, 304, 309, 310
incrassata . 305, 293, 304, 316

lactiflua

306, 304, 308, 310, 312-314

lanata 306

lignicola 319

Ludwigii 298, 301

macrocarpa 312, 307, 315, 321, 326
malleola . . 323, 297, 322, 324
microcarpa 315, 297, 307, 323, 326

Moelleri 319, 320

multiplex 301, 304, 307, 317, 331
Pampaloniana . . . . 314, 313

pisiformis

298, 295-297, 304, 323, 327-8

pulvinata 319, 321

radiata 316, 305

reniformis 321

sphagnophila .... 299, 301

tenebriosa 314, 326

Torrendii 323, 324

Tozziana 326, 291

tuberculosa

293, 302, 303, 305, 311, 331

vesiculifera 309, 331

Endogone xylogena . . . 301, 300

Endogonella borneensis . . . 334
Glaziella

abnormis ....... 338

aurantiaca 334

ceramichroa 338

splendens 338

sulphurea 338

vesiculosa 334

Glomus

macrocarpus 312

microcarpus 315

Hypomyces alboluteus .... 334

Paurocotylis fulva 319

Protomyces xylogenus .... 300
Sclerocystis

coccogena 333

coremioides . . . 328, 331, 332

Dussii 329, 328

pubescens 326

Sphaerocreas

pubescens 326, 301

javanicum . . . 328, 327, 329

Dussii 329

coccogena 333

Stigmatella pubescens .... 326

Xenomyces ochraceus . . 328, 329
Xylaria

aurantiaca 334

splendens 338

The fungi which are grouped in this assemblage of somewhat
diverse forms are, in general, rather infrequently met with; owing in
part to their apparent rarity, and partly to the fact that certain of the
species, at least, are truly hypogaeous, and may develop at a depth of
several inches below the ground, or beneath thick mats of Sp hagna or
other mosses. While types of this sort are thus usually encountered
by accident, or through the acquisition of what may be called a
"hypogaeous instinct" which may enable one, after experience, to
judge by various indications what situations are the most promising

REVISION OF ENDOGONEAE. 293

for the collection of these and other fungi hypogaei, the recognition of
others is surrounded by no such difficulty, since their fructifications
may be developed free to the air, on mosses, rotten wood, leaves, dung
or other substances above the leaf co\'er, or emerging from it.

It seems not improbable that the vegetative hyphae of all the
Endogoneae are at first continuous. In a majority of cases, however,
the hyphae of sporulating conditions show at least occasional septa,
which, in highly developed sporocarps like that of Glaziella, become
very abundant. The spores developed from these hyphae are either
zygospores, thick-walled acrogenous chlamydospores or thin walled
spores formed endogenously in sporangia.

The true relationships of the group to other families of fungi have
long been a matter of conjecture, as is evident from the terms — asci,
sporangia, cysts, vesicles etc. — which have been applied by various
authors to the chlamydospores alone. But although the admirable
researches of Bucholtz, who first (1912) published an account of its
sexual reproduction, have thrown much needed light on its affinities,
the group as a whole has been assumed to include forms of considerable
diversity.

The inclusion in a single genus of the zygosporic and chlamydo-
sporic types, has hitherto been based entirely on a general resemblance
in habit and habitat, and a similarity in the appearance of the two
types of spore, and there has been no evidence which would indicate
that the two were ever produced simultaneously in the same sporo-
carp, or were closely associated in their natural habitats. This as-
sumption proves, however, to have been justified; since in a single
instance, among the northern forms collected by Professor Jeffrey and
herewith described, zygospores and chlamydospores are so intimately
associated in the same spore mass, that there can hardly be any
question as to their specific identity.

Although the zygosporic or chlamydosporic nature of these spores
is usually manifest, except in very old material, it is not always easy
in cases where they are surrounded by densely compacted hyphal
tissue, to determine whether their origin is sexual or not, the elements
involved being so compressed and distorted that conjugating processes,
unless very conspicuously differentiated, might well escape notice.
This is true for example in Endogone incrassata, Figures 17-19, or E.
tuberculosa. There seems, however, at least in the genus Endogone,
to be a rather fundamental difference between the two types. In the
zygospores, which are usually surrounded by a more or less definite
hyplial envelope, an outer wall is present, within which a continuous

294 THAXTEK.

endospore is laid down, so that the contents is completely separated
from the cavity of the origins. The contents is also more fatty and
dense, often composed of distinct elements which may be very regular
in size and shape (Fig. 9) and might even be mistaken for endospores.

The chlamydospores, on the other hand, although' they may closely
resemble the zygospores, do not appear, as far as I have seen, to pro-
duce a continuous endospore; unless the otherwise anomalous Glaziella
in which such an endospore is clearly distinguished (Fig. 91) proves to
be an exception. For this reason, in a majority of species, the proto-
plasm of the chlamydospore and that of the sporophore are continuous,
being connected by a protoplasmic isthmus which may remain un-
broken even in mature spores (Fig. 46), or may be finally pinched off
in the middle by the gradual thickening of the lateral walls. In a
smaller number of instances, the separation between the cavities of
the spore and sporophore is accomplished at an early stage through the
formation of an independent septum, Figures 52-59 and Figure 85.
Spores of the latter type have, for the most part, much thinner walls
than those of the former, and were regarded by Bucholtz as perhaps
young sporangia. An examination of various species and copious
material, however, has convinced me that they are homologous with
chlamydospores of the first mentioned type.

The so-called sporangia which have been above alluded to. Figures
60-78, which have been associated only with the genus Endogone, are
quite unlike the other types of reproduction; and although I have
followed previous writers by including them in this genus, there is no
evidence beyond a certain resemblance between the sporangiocarp in
the one case and the sporocarp in the other, which would tend to
confirm the correctness of this reference. These sporangia are termi-
nal vesicles, formed in a solid mass at the extremities of branching
sparingly septate filaments which radiate more or less definitely from
a cushion-like base. The spores which they contain are variable in
size, form and number, thin-walled, with dense or fatty contents, and
result from a total cleavage of the sporangial protoplasm. They are
so characteristic that it would be quite impossible to mistake them for
the spore-like masses above mentioned which may occur in zygospores
or sometimes even in chlamydospores.

Baccarini (1903) was of the opinion that these sporangial types
should be removed from the Endogoneae and placed in the Mortierel-
leae; the sporangium in both cases being separated from the sporangio-
phore by a simple septum. As Bucholtz remarks, this disposition
appears to be somewhat premature. It must be confessed, however.

REVISION OF ENDOGONEAE. 295

that if these sporangial forms are rightly inchided in the Endogoneae,
it seems very probable that the two families should be regarded as very
closely related, at least; since they are similar in two other important
characters; namely, through the production of specialized zygosporic
envelopes, and the presence of highly specialized acrogenous chlamydo-
spores.

As far as I am aware, there has as yet been no successful attempt to
germinate the spores of any of these fungi, or to grow them under
artificial conditions; and in my own experience I have been unable,
after repeated attempts, to induce the zygospores of Endogone pisi-
formis Lk. {sphagnophila Atk.) to germinate; or to procure any
characteristic growth when uncontaminated spore-masses have been
transferred to agar nutrients. The spore-masses of this species, when
wintered over out of doors, have also failed to develop further. When
placed on fresh sphagnum in a moist chamber for a protracted period
during the summer, they usually l>ecome covered by a thin white
coating of nondescript hyphae: but although various peculiar Zygo-
mycetes, to which reference has been made in a former paper, (Thaxter
(1897) p. 12) have at times been observed in such cultures, there is no
reason to believe, even though, as in some instances, they seemed to
grow from the masses themselves, that the association was other than
an accidental one. It seems very probable that the thick-walled
spores of the Endogoneae, as in various other instances, germinate
as a rule only after special preparation, or under special conditions,
and that in Nature they are eaten by various animals; continuing
their development after being voided. This is suggested by the fact
that I have myself observed uninjured spores of species of Endogone
in the stomach-contents of shrews and of myriopods. Until successful
cultures have been made, and the development of the three spore
types has been successfully followed, or at least until more careful and
extended field observations have given some evidence of their actual
connection it cannot be assumed that they should all three be included
within the limits of a single genus.

The literature of the Endogoneae, since the type species of the
genus Endogone was described by Link in 1809, has been scattered
and not very voluminous. With the exception of the paper by Buc-
holtz, above mentioned, and the enumerations in the Kryptogamen-
flora of Rabenhorst and of Cohn and the Pflanzenfamilien, there has,
I think, been no general summary even of this genus. Von Holinel in
his Fragmenta, Nos. VI, X and XV, discusses the synonymy and
relationships of the genera Endogone, Endogonella, Sclerocystis,

296 THAXTER.

Xenomyces, Ackermannia and Sphaerocreas ; and numerous other
references to the genus Endogone, or descriptions of new species, are
to be found here and there in various other pubhcations. In the
appended list of literature, however, only such titles are included as
are in some measure essential, and those which have reference merely
to records of occurrence have been omitted.

Turning first to the genus Endogone, and following the conception
of the genus which has been adopted by Bucholtz and all recent
writers, one is forced to include in it all the three categories of spore-
forms above enumerated, namely, zygospores, sporangia and chlamy-
dospores. In order to avoid new names and combinations I have
adopted this procedure as a provisional solution. It may be well to
repeat, however, that although the sporangial forms arise in general
from a similar vegetative body, and are associated in somewhat similar
aggregations in similar habitats, their connection with the other types
has not been definitely indicated, even by close association in nature,
and their inclusion in the same genus is based on a pure assumption.
Whether it may prove desirable to retain the name Endogone for the
sexual and chlamydosporic forms and to apply a different name to
those which form sporangia is not as yet clear. It may further be
pointed out that the presence of isogamy and of heterogamy, of
specialized spore envelopes or their absence, as well as of simple and
multiple aggregations of the zygospore masses, may similarly lead to a
subdi^■ision of the sexual forms themselves, under more than one
designation. The desirability or the reverse of either of these pro-
cedures will, however, doubtless become more clear as the lacunae in
our knowledge of the group are gradually filled.

The reasons which have determined the selection of the sexual forms
as the true representatives of the genus, as originally founded, are
based on an examination of the original figures and description given
by Link (1808), of the type-species, Endogone pisiformis, on p. 33 of
the apparently rare publication in which his paper is contained. The
exact wording of this description is as follows :

"38. Endogone. Sporangium subglobosum, extus floccosum, intus
grumosum sporangiola minuta,globosa, membranacea,sporidiis repleta.

"Praecedenti generi affine, (Tuber), supra terram in muscis crescit
hypothallo radiciformi. ISIembrana externa sporangii tenuis floccosa.
Contextus caeterum vesiculosus, microscopio simplici inspectus
grumosus, at compositi ope conspiciuntur sporangiola, ut in prae-
cedenti genere, dispersas inter vesiculos multo minores. Sporidia
minuta, globosa, sporangiolis inclusa. Unica species.

J

REVISION OF ENDOGOXEAE. 297

"E. pisiformis, irregulariter glohosum, lutescens membrana floccosa
inductum. IMagnitudine pisi. Fil)rillis panels muscis adnascitur in
silvis abietinis. jMenil)rana floccosa inducta tenuissiina, sporangium
intus colore lutescente Tuberis, at non venosum, sed grumoso granu-
losum. Segmenti transversalis particulam, V. fig. 52a, sporangiola
cum sporidiis ibid. lit. b."

The figure " a " referred to, shows a portion of the spore-mass covered
by a radiating sterile tomentum (membrana floccosa tenuissima) of
tapering filaments, evidently more or less diagrammatically repre-
sented. The spores, which are shown embedded in the general mass
(sporangium), are not subspherical, but more nearly elliptical, with
the exception of those which may be assumed to be viewed end on.
Figure " b" shows several of these spores (sporangiola) which have been
forcibly and irregularly broken, as is evident from the rent through
which the contents is represented as emerging. This contents is made
up of granules indicated by single black dots, the "sporidia rninuta"
of the description, which bear no resemblance to resting spores and
could not by any stretch of the imagination be regarded as intended to
represent the large thin-walled spores of the sporangial type. This
description is sufficiently clear, although, like most descriptions, in-
complete, and taken in connection with the figures, which are not bad
for the period, afford a reasonably satisfactory basis for determination.

Since K. jyisiformis is the generic type, it is a matter of much im-
portance to determine with some approach to accuracy, to which of
the European forms now recognized it may be assumed to corre-
spond.

Bucholtz, who may have seen transcriptions, only, of the original
paper, and may have been misled by the confusing use of the terms
sporangia sporangiola and sporidia, has assumed that- the classic
specimen collected near Naples by Vittadini and distributed in the
Fungi Europaei No. 2516 under the name Endogonc microcarpa, was
to be regarded as the true pisiformis. It seems cjuite impossible,
however, to reconcile the characters of the Mttadini form, which is the
Endogonc mallcola of Harkness, with the account given by Link whose
figures alone are sufficient to preclude the possibility of such a con-
clusion.

The more important points brought out by Link's account indicate
that he was dealing with the type of sporocarp usually found in Endo-
gonc, consisting of yellow ellipsoid thick walled spores with coarsely
granular contents, associated with smaller vesicular structures, and
irregularly disposed in a solid compact rounded mass surrounded by

298 THAXTER.

a rather conspicuous "thin floccose membrane," and developed above
ground on mosses.

If one compares with this account the characters of the other known
European types, none seem to correspond so closely as E. Ludwigii
Bucholtz (E. sphagnojMla Atk.) No other species is found, as far as
I am aware, growing on mosses above the surface of the ground, while
its yellow ellipsoid spores with uniform coarse granular contents, and
its conspicuous thin white superficial tomentum further distinguish it.
The vesicular swellings of its hyphae, which are sometimes conspicuous
among the larger spores, may further correspond to the "vesiculae
multo minores" of Link.

Since for the reasons above indicated the reference by Bucholtz of
E. maUeola Hark, to E. pisiformis Link cannot be regarded as a possi-
ble solution of the difficulty, and since it is quite necessary to form
some reasonably plausible opinion as to what constitutes the Type of
the genus, I have felt it desirable to follow Krieger (1902) and the
earlier opinion of Bucholtz, in referring to E. pisiformis Link the spe-
cies more recently named by the latter (1912) Endogone Ludwigii.

ENDOGONE Lk.

Link (1809), p. 33.
Ghmus Tulasne (1845), p. 63.

Hypogaeous or epigaeous: producing thick-walled isogamous or
heterogamous zygospores with or without specialized envelopes:
thick walled acrogenous non sexual chlamydospores: or thin-walled
sporangia. The three types, as a rule, produced separately in com-
pact groups, which may be single or associated in a common mass,
naked or surrounded by a variably developed pseudoperidium or
tomentum, and may form either a definite sporocarp or an indefinite
loosely coherent spore-mass.

Type Species.

Endogone pisiformis Link.

(Figs. 1-7.)

Link (1809), p. 33, Taf. II, fig. 52, a & b. Bucholtz (1902), p. 81, Tab. II,

fig. 13 and V, fig. 4.
Krieger (1902), Fungi Saxonici, No. 1651.

REVISION OF ENDOGONEAE. 299

Endogone Lmlwigu Bucholtz (1911), p. 194, Taf. IX, figs. 77-87.
E. sphagnophila Atkinson (1918), p. 16.

E. xylogena Schroeter (1887), p. 260, nee. Saccardo (1877), p. 1-4, sub Proto-
myces. Thaxter (1897), p. 12.

Spore-masses waxy when fresh, horny when dry, pale to golden
yellow, becoming somewhat orange yellow, subspherical to reniform,
or lobed, less often convolute, flattened, umbilicate below: covered by
a thin tomentum, clear white when dry, formed by characteristic,
thick-walled hyphae 4-6- m in diameter with numerous free, projecting,
distally attenuated branches. The substance of the spore mass con-
sisting of an irregular plexus of stout branching non-septate filaments,
showing numerous irregular vesicular enlargements, becoming more
or less obliterated as the irregularly crowded, broadly ellipsoid to
ovoid, thick-walled, pale orange yellow zygospores mature. Spore-
masses (dry) 2-7 X 1-2 mm. thick. Zygospores, 35-60 X 30-45 fx,
the wall subhyaline 3-5.5 jj. thick. Peridial hyphae X 3-8 fx.

Usually above, rarely below the leaf cover; on mosses, especially
near the tip of Sphagnum; on leaves, twigs, dung, rotten logS; etc., in
moist situations, especially in coniferous woods. Tempei'ate Europe
and North America.

This species is without doubt very generally distributed in temper-
ate America; since it is already known to occur in Maine, New Hamp-
shire, Connecticut and eastern Tennessee (Thaxter); West Virginia
(Sturgis); New York and Maryland (Atkinson), and in Michigan
(Kauffman). In my own experience it has proved not at all uncom-
mon, and was first met with at Kittery Point, Maine, in 1886, when
young conditions, showing the early stages of conjugation were ob-
tained. Although it is found most frequently at or near the tips of
Sphagnum, especially in moist coniferous woods, and is conspicuous
in this position from its bright color, it bears no definite relation to
this substratum as a host; since it occurs also, as above indicated, on
various other substances. Its waxy consistency, when fresh is, as
noted by Schroeter, characteristic; as is the hard almost horny char-
acter of the dry spore mass, which loses its bright color, becoming
dirty yellowish; the variably developed superficial tomentum assum-
ing a more noticeable clear white appearance, owing probably to the
refractive character of the thick walled filaments which compose it.
The size and form of the spore-mass varies considerably from nearly
round to flattened and somewhat convolute. The largest individual
seen measures 7 mm. in width when dry.

The early conditions of development are much more difficult to

300 THAXTER.

detect, from their small size and much paler color. The process of
conjugation is not progressive in the developing mass; but occurs
almost simultaneously throughout it, the rather rapid enlargement of
the whole being due to the simultaneous increase in size of the indi-
vidual zygospores. The gametes are subequal, and do not differ from
one another more than is frequently the case in other isogamous types.
They are subcylindrical and lie parallel to one another, distinguished
by a clean cut septum at some distance below their adherent tips.
Figure 1. The developing zygospore rises from this point of contact,
above and between the extremities of the gametes, Figures 2-6. The
successive stages in this process are not unlike those figured by \ an
Tieghem (1873), PI. Ill, figs. 88-93, in Synccphalis cornu.

Before full maturity, the hyphal elements of the mass are con-
spicuous, and rather characteristic from their large size, their branching
and the development of vesicular swellings which I have assumed to
be the "vesiculi multo minores" mentioned by Link, and which are
referred to by Bucholtz as " stellenweise verbreiterungen." As the
zygospores mature, these elements become compressed between them,
and may be hardly recognizable, their flattened remnants forming,
in many cases, an irregular envelope about the individual spores.

The branching terminations of the filaments which form the super-
ficial tomentum are well figured by Bucholtz (1911), fig. 77, and
possess great individuality, Figure 7, but are not always conspicuous
in older individuals. The prominence of this tomentum varies greatly
in different individual masses, and under different conditions. It
seldom seems to be so copiously developed as is represented in the
figure of Link, which is evidently somewhat diagrammatic, and in
older specimens may appear to form a rather even covering of appar-
ently nearly uniform elements.

The description given by Schroeter of Endogone xylogcna corre-
sponds so closely to this species, that I have included it as a synonym.
It seems quite improbable that the plant which he examined could
have been the Protomyccs xyhgenns of Saccardo; since the latter is
without hyphae, and corresponds in all respects to the sclerotium-
condition, "Phylloedia," of some myxomycete: its habitat, buried in
soft rotten wood and exposed only by the weathering of the latter;
its yellow color, and the general appearance of its spores, being the
same. The figures given by Saccardo (1877) in the Fungi Italici,
fig. 104, show the somewhat irregular outline and the characteris-
tically thickened, but ill defined, walls of this well-known condition of
the myxomycete plasmodium.

REVISION OF ENDOGONEAE. 301

With reference to the occurrence of this species in Europe, it may be
mentioned that the single specimen collected by Bucholtz in Livonia
was found " in einem nadelwald unterirdisch," and was associated with
insect-remains, which suggests that it may have grown on the dung of
some small animal, a habitat which I have myself observed. The
apparently copious material collected in Thuringia by Ludwig, which
forms the basis of the account given by Bucholtz, was found on the
dung of Liparis caterpillars. The specimens distributed by Krieger
were found "Auf Moos, faulenden Bliittern, Aestchen, unter Strau-
chern von Vaccinium myrtilus auf dem Fichtelberge in Erzgebirge."

With regard to mutual identities in connection with this species, it
should perhaps be clearly stated that while the use of the name E,
pisiformis and the inclusion of E. xylogena as a synonym represent
merely my personal conclusions. Professors Atkinson and Bucholtz
have both examined the material on which the present account is
based, and have pronounced it identical with E. sphacjnopkUa in the
one case, and E. Liidwigii in the other. It may further be mentioned
that one of the specimens distributed by Krieger, has been examined
by me personally, and is also identical; although a second specimen in
the same copy of this set, the gross appearance of which is very similar,
proves to be Sphacrocreas pubesccns. As it is stated that the fungus
was found " sehr selten," it may be assumed that the distribution is a
miscellaneous one, accumulated from more than one gathering. The
possible relation between Sphacrocreas pubesccns and Endogone pisi-
formis will be further alluded to under the former species.

For convenient comparison, the description of E. xylogena given by
Schroeter (1. c.) may be here appended.

"Endogone xylogena (Saccardo (1877): Protomyces x.). Fruiting
bodies irregularly rounded, flattened, 3-4 mm. broad, 1-2 mm. thick,
waxy when fresh, horny when dry, reddish yellow. Peridium thin,
formed from 3-5 yu thick, strongly refractive hyphae, smooth. Gleba
homogeneous, consisting of closely woven hyphae between which the
spores are disposed. Spores spherical to elliptical or ovoid, 35-50 X
26-40 fx, the wall 6 fi thick, nearly hyaline, contents clear orange
yellow.

Endogone multiplex nov. sp.

(Figs. 8-10.)

Fruiting body about 15 X 12 mm., dirty whitish, turning yellowish
brown in alcohol; somewhat lobed, the surface rough from the pro-
jecting contours of the very numerous small, more or less firmly

302 THAXTER.

coherent, rounded or somewhat irregular spore-aggregates, of which
the mass as a whole is composed, and throughout which a large amount
of finely divided humus material is incorporated. Individual spore-
groups more or less rounded, or somewhat irregular, mutually coherent,
or readily separable, 350-700 jj. in diameter, and including from ten to
fifty spores each, more or less; each group surrounded by an envelope
of hyphae among which a considerable amount of humus material is
incorporated; the hyphae variable in diameter, 4-18 /x, thick-walled,
rather brittle, freely branched, three or sometimes four branches often
radiating from subtriangular or angular enlargements, especially in
the larger ones, which are rather conspicuously distinguished, though
scanty. Zygospores yellow, spherical, oblong to ovoid or piriform,
often irregularly subangular from pressure, 80-90 X 60-84 ^t; the
endospore clearly defined, slightly yellowish, about 5 yu; the exospore
hyaline and, when freed, swelling to 8-10 n; the contents rather bright
yellow, composed of nearly spherical fatty bodies 4-8 /x in diameter
which completely fill the cavity. The attachments of the suspensors
clearly defined, sometimes approximated, more often distant: the
spore surrounded by a clearly defined, relatively thick, separable
envelope, 8-12 p. thick, of closely felted hyphae.

Growing beneath the leaf cover beside a path in mixed deciduous
woods (oak and hickory) on Cutts Island, Kittery Point, Maine:
September 15, 1902.

This species is most nearly related to E. tuberculosa, but differs in
various essential points. The individual spore-masses are, as a rule,
very readily separable, so that a small fragment of the fruiting body,
when teased or rubbed under the cover glass, separates to a mass of
rather uniform coarse granules, which represent the individual spore-
groups. Figure 10: the envelopes of which are composed largely of
humus particles which often wholly conceal the spores within.

The material is unfortunately fully matured, and it is thus impossible
to determine the exact nature of the process of conjugation, and even
the suspensors are for the most part disorganized to such an extent
that their form and limits can no longer be made out. The relation
and attachment of the latter to the spore are very characteristic.
They are always quite distinct. Figures 8-9, sometimes close together,
but usually separated by a considerable interval; in this respect re-
calling the similar relation so often seen in the zygospores of Choane-
phora. On treatment with potash, the separable exospore and the
surrounding filaments become considerably swollen and gelatinous, so
that their limits are determined with difficulty.

REVISION OF ENDOGONEAE. 303

The peculiar characters of this species illustrate the culmination of
the tendency toward a definite grouping of the spores within the gleba,
which is present to a less marked degree in E. tuberculosa and E.
fuegiana. The sexual nature of the spore-origin is unquestionable
from the two distinct origins are present in all spores. The alterna-
tive that they may be intercalary and represent a lateral bulging, so
to speak, in the continuity of the hypha, is an explanation which is
rendered quite improbable by our knowledge of spore-formation in all
the chlamydosporic types. The conjugation is evidently somewhat
peculiar, as is evidenced by the often remote origins, and it is to be
regretted that, owing to the fact that the whole spore-mass is hardly
distinguishable from a slightly coherent mass of earth, the younger
stages are not likely to be found, unless by accident.

Endogone tuberculosa Lloyd.
(Figs. 11-16.)
Lloyd (1918), p. 799; fig. 1239.

This species has been described and its gross appearance well illus-
trated by Lloyd, to whom the writer is indebted for a small portion of
the type material on which the following notes are based. It was col-
lected in New South Wales by Mr J. B. Cleland, who states that it
was found just at the surface of the ground, apparently partly buried
in it, if one may judge by the coating of earth which completely
envelopes it. Its gross characters are peculiar from the fact that the
gleba is not a continuous and undifferentiated spore-mass, but is in a
sense compound.

The sporogenous area, which is only visible in sections. Figure 11, is
very irregular in outline, pushing indeterminate lobes or extensions
outward into the surrounding covering of earth, which thus varies
greatly in thickness, and appears to be held together by a scanty
penetrating mycelium. It is possible, after slightly moistening the
cut surface, to determine that the golden yellow spores are arranged in
rounded masses of variable size and shape, or are associated in larger
somewhat less definite areas. In either case they are often, though
not always, separated by intruding layers of the earthy matrix, the
presence of which is indicated by its darker color, and which may be
even more intimately incorporated in the general mass, although none
appears to occur within the individual spore-groups.

In these spore-groups, or areas, the more clearly defined of which

304 THAXTER.

may be from 350-1000 fi in diameter, more or less, the bright yellow
spores are closely packed and coherent, each surrounded by a thin,
but as a rule clearly defined, envelope of closely matted finer hyphae.
Penetrating the larger groups or areas, or separating the smaller ones,
vein-like wefts of coarser filaments, forming an irregular pseudo-
parenchyma, may be present. Figure 12, so that the general appear-
ance of the cut surface is not unlike that of one of the Tuberaceae.

The individual spores. Figures 12-16, are often irregular from pres-
sure, and very variable in size and outline; subspherical or more often
longer than broad, elliptical, subpiriform or often elongate, 50 X 42-
150 X 90 fjL, the average about 90 X 65 ^t; the exospores about 5-6 fx,
becoming very thick, even 15 ju; t^e endospore comparatively thin,
about 1-2 fjL. The yellow contents consists of not always dense,
granular fatty protoplasm, usually associated with larger fatty masses
or globules; but in certain fully mature individuals, it appears to have
lost its color, becoming hyaline; while the exospore is greatly thick-
ened, Figure 14, intruding irregularly, somewhat as in E. incrassata,
and throwing the endospore into irregular folds.

Although, owing to the mature condition of the specimen, the spore-
origins are for the most part shriveled or destroyed when freed from
the tenaciously adherent spore-envelopes, a sufficient number have
been isolated to satisfy me that two hyphal elements are involved in
spore-production, which are associated and differentiated much as in
E. lactiflua; although relatively smaller and less conspicuously difPer-
ent, one from the other, than in this species. In one instance, only,
Figure 13, has it been possible to determine with some exactness the
more normal appearance and relation of the two conjugating elements,
although many have been observed in which the remains of corre-
sponding structures were clearly traceable.

In the type figured by Lloyd, the surface of the specimen is con-
siderably and irregularly roughened, pitted or lobed, the roughness
having apparently suggested the specific name. This tuberculate
habit does not, however, appear to be related to the presence of the
characteristic spore-groups, and is merely a modification of the earthy
covering.

The species is more like E. pisiformis in the form and color of its
spores, but resembles E. lactiflua in its type of conjugation. In the
grouping of its spores and its yellow color it recalls E. viuUiplex, which
is nevertheless readily distinguished by the two discrete suspensor-
insertions which characterize this species. The grouping of the
spores is similar to that found in E. fuegiana, which, however, forms

REVISION OF ENDOGONEAE. 305

a compact continuous spore-mass, without incorporated foreign
material, and in which the origin of the spores and spore-groups is
quite different and apparently non-sexual.

Endogone incrassata nov. sp.
(Figs. 17-19.)

Fruiting body even or somewhat lobed, yellowish, with a whitish
scaly or reticulate crust variably developed, about 2-5 mm. in diame-
ter when dry. Gleba firm and compact, yellowish; the hyphae thin-
walled and vesicular, or running in strands or bundles between the
spores; the thin peridial region of more slender thick-walled filaments.
Spores scattered thickly, without definite arrangement, throughout
the mass of the gleba, which contains no foreign matter; more nearly
isodiametric, somewhat irregular in outline, subspherical to broadly
oblong, at first filled with rather uniform yellow subspherical fatty
granules, about 3-5 /j., the continuous endospore clearly defined,
thinner than the exospore; the two about 8 /x thick; the exospore
becoming much thickened, 16-20 /jl, intruded toward the center and
pushing the endospore into folds, the contents losing its color and
granular character. The spores 66 X 64-75 X 85 /x.

Under spruce, about two inches below the surface of the cover;
with a distinct aUiaceous odor. Gerrish Island, Kittery Point, Maine;
August, 1896.

Three specimens of this species were found associated, and close by a
single individual of E. radiata, of which it may possibly prove the
sexual form. The gleba is so dense, and its elements surrounding the
spores so vesicular, that it has been impossible to make out with cer-
tainty the character of the gametes which are evidently small, not
clearly distinguished and almost obliterated by the enlargement of the
spores and the consequent pressure. In a few instances, appearances
have been seen such as are represented in Figures 18-19; but, in the
dense pseudotissue about the spore, it is quite possible that the appar-
ent conjugating spore-origin may be in reality due to an accidental
juxtaposition of gleba elements, bearing a superficial resemblance to
conjugating structures.

The spores when fully matured. Figure 19, resemble those of E.
tuberculosa, Figure 14, although the wall of the exospore becomes rela-
tively thicker and the endospore is thrown into deeper and more
complicated folds by its intrusion. In this condition it is quite hya-

306 THAXTER.

line and impenetrable by stains, the contents losing its granular char-
acter entirely. The spore-envelope is thin and not clearly differ-
entiated. The scaly or flecked appearance of the surface of the
sporocarp is due to patches of loose hyphae which project from the
peridium, and in section appear as flat tufts.

Endogone lactiflua Berkeley (1846).
(Fig. 20.)

Berkeley (1846), p. 81. Tulasne (1862), p. 183. Bucholtz (1912), p. 155,

figs. 1-61.
Endogone lanata Harkness (1899), p. 280.

This species has become for the first time thoroughly well known
through the researches of Bucholtz, who was not only the first to see
and to describe the sexual origin of its spores, but to figure clearly the
remarkable envelope which surrounds them at maturity, formed from
labyrinthine filaments which eventually become thickened and modi-
fied to form what he has called a "flammenkrone," which is firmly
adherent to the exospore. Both the envelope and the flammenkrone,
however, vary, as is mentioned by Bucholtz, (1912), p. 165, in different
individuals, apparently according to the age of the spore-mass, and in
some of the Hesse specimens in the Farlow Herbarium neither are
striking or easily recognized; while in others they are apparent at a
glance. The same is true of material which the wTiter has collected
at various times and in various localities in New England; at South
Billerica, Mass.; at Kittery Point, Maine, where seven different
gatherings were made; and at Intervale, New Hampshire. In all
these gatherings, which were mostly of single specimens, the gross size
is smaller and the spores themselves larger than in the Hesse speci-
mens; and while in some the labyrinthine envelope-filaments (Buc-
holtz, fig. 50), though finer, are quite as distinct and the fiammen-
krone clearly distinguished, in a majority of cases these structures are
not clearly visible, except that a well developed hyphal sheath is
always present. Entirely similar conditions are, however, seen in
some of the Hesse specimens, so that it seems probable that their
distinctness may be a matter of age or some of the circumstances
associated with their growth. Although in the Hesse material the
spores are usually only 100 /x in diameter, while in the American they

REVISION OF ENDOGONEAE. 307

are 120-125 fi, specimens received from Hesse by Ed. Fischer are
reported to be 115-125 X 70-90 i^l, and in the large number of cases
reported by Bucholtz, the range of variation is 68-160 X 60-104 fj..
The discrepancy is thus not so great as it might at first appear; al
though further examination may indicate that more than one specific
form is represented in this series.

Although the occurrence of this species in America has not been
hitherto recorded, it appears to have been collected several times by
Harkness in California. Through the courtesy of Professor Abrams
of the Leland Stanford Herbarium, I have had an opportunity to
examine all the material of Endogone referred to by Harkness, (1899),
in his paper on Californian Hypogaeous Fungi, including " E. lanata"
sp. nov., " E. microcarpa" Tul. and " E. viacrocarpa" Tul. The
portions of these specimens communicated are similar in color and
appearance, and it would be impossible to distinguish either of them
by their microscopic characters from the eastern material above re-
ferred to. In all, the conjugating processes are clearly defined, and
the spore-envelope well developed. In the specimen marked " E.
macrocarpa" this is especially true, the flammenkrone, though not
as striking as in the best developed Hesse specimens, being clearly
present. The size of the spores in these Californian specimens is also
similar, the longer axis varying from 125 ^t or less to 160 /z: a range
similar to that reported for the European types.

In a single specimen found at Kittery under beech trees, the gleba
is dark blackish brown, the color being apparently due to the fact that
a large amount of finely divided humus material is incorporated
throughout its substance, a condition seen elsewhere in E. multiplex
and a few other species. The zygospores differ somewhat in possess-
ing a somewhat roughened, smoky brown exospore, distinctly unlike
the yellowish wall of the ordinary type. It has not seemed desirable
to separate this form specifically, however, on the basis of a single
specimen.

For further details in regard to E. lactiflua, the admirable and very
complete account of Bucholtz should be consulted. The possibility
should be borne in mind that the very variable series of forms now
included under this name may prove to represent more then one
species, when they become more thoroughly known, and their life-
histories have been traced. In the present state of our knowledge,
however, the use of a single nanje to designate them seems in every
way desirable.

308 THAXTER.

Endogone fasciculata nov. sp.

(Figs. 21-28.)

Spore-masses spongy, loosely coherent, rather thin and irregularly
lobed, somewhat amorphous, 10-14 X 4-5 mm., but very variable,
incorporating more or less of the substratum (Sphagnum) and other
foreign matter. Chlamydospores in rounded or somewhat elongate
or irregular coherent groups, associated with less definitely distin-
guished masses of readily separable zygospores; pale yellowish or
faintly brownish, mostly spherical or somewhat longer than broad,
60 X 60-85 X 70 fx, the wall becoming relatively very thick, 6-10 fx.
Zygospores immature, irregularly spherical, colorless, about 50 n,
arising from the larger of two unequal gametes.

In Sphagnum. Little Metis, P.Q. E. C. Jeffrey.

This species is in some respects the most interesting member of the
genus, since it is not only peculiar from the grouping of its spores, but
presents the only instance in which zygospores and chlamydospores
have been found intimately associated in the same spore-mass. It
thus furnishes the first indubitable eA'idence that the zygosporic and
chlamydosporic types have been rightly included in a single genus.

None of the zygospores examined are mature, but there is no indi-
cation that any special envelope is developed about them, as in E.
ladiflua and some other sexual forms; although the process of forma-
tion. Figures 23-26, is very similar to that which occurs in the last
mentioned species. The hyphae with which they are associated are
thin-walled, scanty and evanescent; so that even in the youngest
stages of conjugation, the exact origin and relation of the progametes
is not clearly evident. Although this cannot be regarded as deter-
mined beyond question, examination of young stages under an immer-
sion seems to show that the type of conjugation is homothallic, and
that the progametes arise in proximity to one another from the same
filament. The gametes are distinguished much as in E. ladiflua, one
being larger than the other, and bearing the zygospore, which bulges
upward; both remaining attached, with slightly thickened walls and
septa. The groups of zygospores are more irregular and undifferen-
tiated than those of the chlamydospores, among which they are
irregularly distributed in continuous masses.

The chlamydospores arise from a plexus of clearly defined, thick-
walled, variously bent and interlaced branching hyphae, which form a
core from which short irregular sporiferous branches grow radially

REVISION OF ENDOGONEAE. 309

outward. The chlamydospores are thus at first rather firmly asso-
ciated in grape-like clusters, which may be of definite rounded outline,
Figure 21, or longer or more irregular. This definite relation seems to
be more or less obscured in older specimens in which the hyphae tend
to break up, as in other species of the genus. It should be mentioned
that zygospores do not seem to be invariably associated with the
chlamydosporic form. The chlamydospores themseh'es are rather
uniform, commonly more or less spherical or but slightly longer than
broad, and when fully mature possess a relatively very thick wall,
surrounding a coarsely fatty contents.

The species is most nearly related to E. vcsicuUfcra, which seems
very clearly distinguished by the peculiar clavate empty vesicles
which are associated with the chlamydospores. In the grouping of its
spores it also bears some resemblance to E. fuegiana, which is at once
distinguished by its hard continuous gleba.

Endogone vesiculifera nov. sp.

(Figs. 29-32.)

Spore-mass loose in texture and without definite form, about 5-8 X

4 mm., incorporating more or less of the substratum (Sphagnum) and
some other foreign matter. Chlamydospores arising in groups,
rounded or more elongate, often nor clearly defined; pale yellowish,
spherical or slightly longer than broad, rather uniform, about 65 X

05 (JL, the larger 80 X 70 yu: arising from fascicles of intricately woven,
branching, thick walled hyphae, and borne terminally on short radiat-
ing branches; associated with broadly clavate vesicular cells, 100-125
X 50-64 jj., which extend outward beyond them.

In Sphagnum, Little Metis, P.Q.' E. C. Jeffrey.

The material of this form is somewhat scanty, although sections of
three different individuals are preserved. It resembles E. fascicvlata
very closel}', the chlamydospores being very similar in size and shape
and similarly grouped about a core of thick-walled hyphae. It is
readily distinguished, however, by the presence of numerous pear-
shaped or broadly clavate, nearly empty, thin-walled, sterile vesicular
structures which arise in company with the chlamydospores from
slender short branchlets. These bodies are very characteristic, and
although their origin is the same, are by no means ordinary chlamydo-
spores which have failed to develop. They arc no doubt the homo-
logues of spores, but cannot be directly compared with the numerous

310 THAXTER.

empty abortive vesicle-like spores which are conspicuous, for example
in E. canadensis. In many cases their broad projecting terminations
form a continuous margin about the spore-groups. Those of the latter
which are peripheral, may be further enveloped externally by a closely
woven layer of fine, thin-walled, hyphae, which may penetrate inward
to some extent, between the vesicles and spore-groups, entering the
spores themselves and filling them more or less completely. This
parasite seems similar to that which attacks E. lactifliia, E. fuegiana
and other species.

Endogone fuegiana Spegazzini.
(Figs. 33-34.)

Spegazzini (1887a), p. 6, No. 5; (1887b), p. 120.

Through the courtesy of Professor Spegazzini I have had an op-
portunity to examine the type of this species collected on Staten
Island, Straits of Magellan. In its present condition the type does
not show all the characters mentioned in the original description which,
since the publication in which it appeared is rare, should perhaps be
quoted in extenso.

"Globoso vel elliptico repanda, extus alba, levis vel vix sub lente
valida flocculosa, parvula (2-5 mm. diam.), inferne saepius umbilicata
vel depresso-rugulosa centroque nodulosa vel subcicatricosa, uda
compactiuscula tenacella; sicca dura, fere cornea: cutis carne arete
adnata persistens; caro sordide alba sub sectione fulvo-maculata, ob
punctulos rufos dense congestos: puncti 7-8 cellulares, globoso sub-
polygoni (180 ^i diam.), carne innati, nunquam confluentes: cellulae
punctulorum sphaeroideae e mutuo pressione saepius ovoideae (80 X
65 fx) laeves, crasse tunicatae ad verticem precipue, inferne subapicu-
latae ac nodulo majusculo obscuriore donatae, fulvae vel subtestaceae.
Inodora, insipida."

Found under moss on Staten and Clarence Islands, Straits of
Magellan.

There has been some question as to the true position of this species,
owing to the characteristic arrangement of its spores, the "cellulae"
of the above description, which are more or less definitely and com-
pactly associated in small groups of six or usually more, Figure 33,
separated by variably distinct strands of compact parallel hyphae, an
arrangement which gives an irregular and rather faintly areolate
appearance to sections of the gleba. This has led to the suggestion
that the plant might be an immature condition of some tuberaceous

»

REVISION OF ENDOGONEAE. 311

form. The species Is, however, a well defined Endogone. The spore-
groups -are smaller and more clearly defined than those of E. tubercu-
losa. Spegazzini remarks that the spore-groups are never confluent;
but a section from the dried material shows that they are not always
distinguished with great clearness, and are at least often in close
contact.

The spores, unlike those of E. tuberculosa, are reddish brown, con-
siderably smaller and more nearly spherical, though usually irregular
from mutual pressure. Their greatest diameter seldom exceeds SO /x,
while that of E. tuberculosa is often as much as 125 m- The gleba is a
dirty brownish yellow with a reddish tinge, horny when dry, the
strand which separates the spore-groups, which are not always clearly
marked, having a darker brownish color. The gleba, unlike that of
E. tuberculosa, is continuous in the sense that, as far as I have seen, it
contains no incorporated foreign matter.

The origin of the spore-groups is quite remarkable, and I have had
some difficulty in making it out, owing to the scantiness of the material
which it was essential to injure as little as possible. Their origin
seems unassociated with any sexual process, and careful examination
of a section shows that the spores, which are practically sessile, origi-
nate by budding in all directions from an enlarged hyphal termination.
In the fully mature condition which characterizes the type, this
termination is very thick-walled and irregular in outline. At points
where a spore-group has been cut nearly through the middle, one may
see sections of these thick-walled terminations with one or more
definitely related spores in situ, as indicated in Figure 34:. Each
termination appears to produce as many spores as can be crowded
around it, and when the group is viewed from without, it is quite
impossible to see any indication of their mode of origin. Although a
multiple origin of zygospores from a single conjugation is not neces-
sarily excluded as a possibility in this instance, and might find a cer-
tain analogy among the Entomophthorales where two distinct zygo-
spores may be produced in this manner, it may be assumed that the
process in this instance is purely asexual and that it is merely a more
specialized manifestation of that which occurs in E. fasciculata, in
which, owing to the loose texture of the general mass, the spores,
although arising in crowded groups, are produced in a more nearly
normal fashion. This conclusion is further supported by the structure
of the individual spores which lack a continuous endospore. A
majority of the spores are attacked by a sterile parasite similar to
that mentioned in the preceding species and shown in the spore at the
right in Figure 34.

312 THAXTER.

Endogone macrocaepa Tul.

Tulasne (1851), p. 182, PL XX, fig. 1. Bucholtz (1912), p. 184, figs. 62-74.

Nee Harkness (1889), p. 279.
Glomits macrocarpus Tul. (1845), p. 63.
Endogone australis Berk. (1860), p. 270.

Bucholtz (1912) gives an extended summary of the occurrence and
spore-variation in this species, which indicates that it is perhaps the
most frequently observed and variable member of the genus. The
only records of its occurrence in America are that of Lloyd (1908), who
reports it somewhat doubtfully from the Bahamas; and that of
Harkness (1899) Avho speaks of finding it under Libocedrus at Towles,
in the Sierra Nevada Mountains, California. Mr. Lloyd informs me
that the Bahama specimen, which was doubtful, and may have been
E. fulra, has been lost; so that this record must remain very
dubious. The California form, which I have examined, proves, as
above stated, to be E. lactifiua and is identical with what I have called
by this name from the East. The spores are clearly zygospores, and
the hyphal envelope is well developed, although the "flammenkrone"
are not so strikingly differentiated as in some of the Hesse specimens,
in the Farlow Herbarium.

In New England I first encountered what I have regarded as this
species, growing on earth in greenhouse pots at the Botanic Garden
in Cambridge, in company with Hymcnogastcr Khischii and Ilydnan-
ghnn carneum, a habitat and association which has also been noticed
in Europe. Of this material, one gathering made in the winter of
1891-92, has spores seldom exceeding 100 jj. in greatest diameter, while
a second gathering made two years later from the same pots, has spore-
masses in which the larger spores measure from 170-200 ix in greatest
diameter. In neither of these was any definite peridium developed,
possibly owing to the fact that both grew on the surface and were
subjected to constant watering.

In addition to these two gatherings, seven others have been made at
Kittery Point, Maine. In these instances the fungus was found in
moist coniferous and deciduous woods, usually just below the leaf cover
rarely on the surface; the spore-masses usually solitary, or but two
or three together. This material also shows a considerable range of
variation in the size of the spores; although a majority correspond in
this respect to the first gathering above mentioned. The larger spores
are in general 80-100 /x in greatest diameter. This average maximum

REVISION OF ENDOGONEAE. 313

is considerably below that given by Bucholtz in his summary of the
spore measurements of twenty-seven European gatherings; which
includes no case in which the maximum is below 100 fj.. When one
considers, however, that he gives a variation of the maximum diameter
in this summary between 112 ^t and 230 //, the smaller maximum of the
American material does not appear significant.

The structure and character of the gleba is also subject to variation
which bears no evident relation to the size of the spores. The hyphal
matrix is thus quite loose in some individuals, and the spore origins
correspondingly conspicuous ; while in others it is as densely compacted
as in E. laciiflua, so that clearly recognizable spore-origins, though
readily made out, have to be sought for. Although Baccarini (1903)
has made this difference a basis for the separation of his E. Pampalo-
mana (vide infra), it hardly seems a sufficient specific distinction.

Through the kindness of Dr. Dodge, I have had an opportunity to
examine three gatherings made by Mr. H. E. Parks in California:
No. 348 at Saratoga, No. 312 at Aldercroft Creek, and the third at
Guadalupe. All of these are unusually well developed. The largest
measures 15 mm. dry: the peridium is unusually thick, yellowish
white, with adherent humus material. The gleba is firm and dull
yello\A'ish in the dry material, although dark brown in the alcoholic
specimens. The nearly spherical spores often reach the maximum of
230 fjL mentioned by Bucholtz, and the wall, which may reach a thick-
ness of 18 fjL, is traversed by radial canals (?) which, although they are
much less strikingly developed in a few other specimens examined in
which the walls are unusually thick, are here very numerous and
conspicuous, and appear to be associated directly with flattened
masses of oily material which adhere to the inner surface, and from
the middle point of which they seem to spring. In the absence of
intermediate conditions, this California form would be specifically
separated from the Eastern ones without question. It seems prefer-
able, however, as in the case of E. lactiflna, of which they may prove
to be the chlamydosporic condition, to include them under one name
until we know more about them. It must be acknowledged, never-
theless, that the variations above enumerated may prove too great to
justify this procedure, and it is possible that, as in the case of E.
lactiflna, in the light of further information, more than one species may
emerge from this rather too comprehensive assortment.

I am indebted to Miss Wakefield of the Kew Herbarium for an
opportunity to examine a portion of the type of E. australis Berkeley,
from Tasmania. The spores are like those of E. macrocarpa, the

314 THAXTER.

maximum diameter observed being 170 /x. In all its characteristics it
comes well within the variations of the present species, and there
seems to be no reason for maintaining it as a distinct form.

Endogone pampaloniana Baccarini (1903), p. 90, has been examined,
through the courtesy of Professor Mattirolo, who has kindly communi-
cated a slide of microtome sections from the type of this species.
Like most sections of this nature, they are of little use for the pur-
poses of specific determination, and it is difficult to decide from them
what the distinctive characters, if such exist, really are. Baccarini
based the species on the fact that the hyphae between the spores are
more copiously developed and compactly woven than in the usual
types of E. macrocarpa, in which he conceives the spores, "ampolla,"
to be simply gregarious, while in E. yampaloniana they form a
"cumulo," which he regards as a transitional condition between the
loose heap formed in E. macrocarpa, and the more definite sporocarp
of E. lactiflua. The different origin of the spores in E. lactiflua would,
however, destroy any significance in such a series. The spores corre-
spond in size to those of E. macrocarpa, 120-140 n, but have much
thinner walls, owing perhaps to the immature condition of the speci-
men. As has been mentioned above, similar conditions have been
found in New England, although the compact " gleba" is characterized
by the usual thick-walled spores, and the same is true of Californian
material. Until we have much more information concerning the
variations of E. macrocarpa it seems desirable to regard E. pampalon-
iana as at best no more than a variety of this species.

Endogone tenebrosa nov. sp.

(Fig. 46.)

Spore-mass spongy, easily disintegrating, blackish. Hyphae loose
and friable, 8-40 /x in diameter. Chlamydospores spherical or sub-
spherical, 200-270 IX, the largest 260 X 275 ix, brownish yellow, be-
coming quite opaque at maturity, the reddish brown wall becoming
15-20 II thick and finally invisible; surrounded by a thin hyaline
exospore.

In Sphagnum. Little Metis, P. Q. E. C. Jeffrey.

The material of this species is so broken up in the fluid in which it
is preserved that it is difficult to determine what was the original form
of the irregular spongy masses. The huge spores are readily visible
with the naked eye, and become absolutely opaque from the darkening

REVISION OF ENDOGONEAE. 315

of the contents, and finally of the thick endospore, which, at maturity,
is invisible even with bright illumination, and is surrounded by a very
thin hyaline exospore. Though sometimes slightly irregular, or
slightly longer than broad, they are as a rule rather uniformly and
evenly spherical. In structure and development they correspond to
those of E. viacrocarpa: but are even more closely comparable with
those of the species referred to below, which was found in the stomach
of a shrew.

Endogone microcarpa Tul.
(Figs. 35-37.)

Tulasne (1851), p. 182, Plate XX, fig. 2. Bucholtz (1912), p. 192, figs. 75-76.
nee Rabh. Fungi Europaei No. 2516.

Glomus microcarpus Tulasne (1845), p. 63.

This species has been recorded from America only on the authority
of Harkness (1899), who collected what he regarded as this form in the
forest at ISIill Valley, California, No. 237. The description which he
gives does not make at all clear what he had before him ; but the corre-
sponding number from the Harkness Collection, which has been kindly
sent me for examination b}' the Stanford University Herbarium,
proves to correspond to some of the forms of E. lactifiua, the spores
being clearly zygospores.

A form, however, identical in all respects with the figures and de-
scription of Tulasne, has been kindly communicated to me by Dr. C.
W. Dodge; who collected it in June, at Aldercroft Creek, Los Gatos,
California. The spore-masses are well formed, though rather small,
firm and similar to those of E. macrocarpa in form and color. The
spores are nearly spherical, 40-48 /x, and very thick-walled.

Although there have been various records of this species in Europe,
it does not appear, from published accounts, that it has been recog-
nized with certainty since the original records of Tulasne, by whom it
was found in Italy and France; and it seems to have been confused
with smaller types of E. macrocarpa. Some of the latter from America
serve in a measure to bridge the gap between the two species, but E.
microcarpa, with a rather constant maximum spore diameter of 48 fx,
seems clearly distinguished. The accounts of Tulasne and of Buc-
holtz, who reexamined the original types, should be consulted for
further information in regard to this species.

316 THAXTER.

Endogone radiata nov. sp.
(Figs. 47-51.)

Fruiting body variously lobed, whitish, becoming yellowish brown
in alcohol, about 10 X 5 mm., the dried specimen about 5 mm.
Gleba tough, dense, nearly homogeneous, the closely coherent rather
slender elements hardly distinguishable, yellowish with a fibrous
appearance; the peridial layer rather thin, darker brow^nish, the
superficial hyphae usually producing terminal and intercalary vesicu-
lar enlargements with distinguishing septa. Spores scattered, some-
times rather distant, sometimes wdth a slight tendency to grouping,
rarely spherical, usually with the longitudinal axis considerably
greater than the transverse, oblong, elliptical or subpiriform, often
irregular from pressure, the long axis more or less coincident with the
radius of the fruiting body, 68 X 38-85 X 50 ju, borne terminally on
often clearly recognizable simple hyphae, somewhat stouter than
those which compose the substance of the gleba. The spore-wall
shows no visible distinction between exospore and endospore and is
from 4-5 /x thick: the contents rather finely granular, pale brownish
yellow.

Under the leaf cover in spruce woods; Gerrish Island, Kittery
Point, Maine; Intervale, N. H. ; August, 1896 and 1901 : in Sphagnum,
Little Metis, P. Q. E. C. Jeffrey.

This species was first taken for E. microcarxM : but is certainly
distinct. Its spores are rarely spherical although they appear to be so
when cut transversely; the wall is comparatively thin, and is not
\'isibly double. The radiate arrangement of the spores, which are
firmly embedded in a dense fibrous matrix, seems to be characteristic;
but is lost as soon as the section deviates from the radial direction.
In the specimens from Kittery and Little Metis, the surface of the
peridium shows numerous short projecting filaments with swollen
terminations, and intercalary vesicular cells of no great size. At
Kittery Point this species was found in company with E. incrassata
which was supposed, at the time, to be the same. It is thus not now
possible to say whether it had the same alliaceous odor. None was
noticed in the Intervale rnaterial. Among the rather numerous
individuals collected by Professor Jeft'rey, there are no individuals of
E. incrassata, as far as has been ascertained. x\ny connection be-
tween the two is thus problematical.

REVISION OF ENDOGONEAE. 317

Endogone arenacea nov. sp.

(Figs. 38-40.)

Spores associated in an indefinite mass through which the material
of the substratum (sand) is uniformly and copiously distributed, the
whole bound together in an irregular crust-like aggregation, by a
loose white mycelium of occasionally septate hyphae. Spores,
chlamydospores, rather uniformly spherical, thick-walled, brownish
yellow, about 70 fx in diameter (65-75 fj.): the walls 5.5-6.5 /x; with

koH, S M.

Near margin of brook, Maraval Valley, Port of Spain, Trinidad,
B. \Y. I., in sand under trash.

This species was found at no great distance from the gathering of
E. fulva, hereafter mentioned, from the same locality. The spore-
mass has the appearance of a bit of caked sand, about 16 X 15 mm.
and about 4 mm. thick when dry. The rather scanty mycelium is
visible with a lens over the surface, but it would be unlikely to attract
attention, and was preserved and examined almost by accident. The
mass is less characteristic and more amorphous than that of any other
species, unless it be E. vudtiplcx. The spores, although they show
occasional variations in outline and slight differences in size, are
exceptionally uniform in these respects as compared with other
chlamydosporic types, and are usually quite spherical. The very
thick endospore is not continuous, and no septum is present : the thin,
often hardly distinguishable, exospore is usually externally roughened
by adherent more or less granular disorganized material. The hyphae
are much bent and tangled between the spores and sand grains, and
the spores often arise from a very short branch. Their non-sexual
origin is, however, unquestionable. When treated with potash a
rather characteristic smoky stain appears about their insertion.
Figure 40. The fatty contents is apt to develop acicular fat crystals,
Figures 38, 40. The hyphae show the usual irregularities seen in
other species of the genus, and are very rarely septate.

Endogone canadensis nov. sp.

(Figs. 52-55.)

Sporocarp subspherical or irreguhirly lobed; soft, but rather firmly
coherent, with a rather well defined whitish (?) peridial layer: gleba
dark brown. Spores distinguished by a septum, ovoid to ellipsoid, or

318 THAXTER.

somewhat asymmetrical, 70-80 X 54-58 /x very rarely 100 X 65 ^t;
the wall hyaline or pale yellowish, 4 ^t thick. Hyphae 8-14 ^i, of the
usual type, with occasional clearly defined septa; the sporophores
characteristically slender, 5-6 ix.

In Sphagnum, Little Metis, P. Q. E. C. Jeffrey.

The spore-mass in the material examined, which is all alcoholic, is
similar to that of E. radiata. The gleba, however, does not consist of
a firm dense matrix in which the spores are firmly held, but is formed
of a loose mesh of friable mycelium, of the usual type, in which the
spores are free, and are associated with numerous vesicular mostly
spherical abortive spores of variable size which eventually shrivel and
turn brownish.

The species is most nearly related to E. fulva, but is distinguished
by its decidedly smaller and more regularly ovoid spores, which are
borne on characteristically slender sporophores, and separated by a
septum. The nearly hyaline wall of the spore is relatively distinctly
thicker; the exospore thin, but rather clearly defined. The fatty
coarsely granular contents is at first hyaline, becoming brownish.

Endogone borealis nov. sp.
(Figs. 44-45.)

Spore-mass irregular, coherent, spongy, dark, almost chocolate
brown, about seven to eight mm. in greatest diameter. Gleba of
loosely woven hyphae, 10-25 /x in diameter, among which much
foreign matter and many abortive spores are incorporated. Spores
reddish brown, broadly and rather symmetrically elliptical, about
125 X 100 M, the larger 145 X 110 ijl: the thick red-brown walls
about 8/x: borne on rather slender hyphae and frequently subtended
by a septum.

In Sphagnum, Little Metis, P. Q. E. C. Jeffrey.

This species seems clearly distinguished by the form and color of its
thick-walled spores, the contents of which, in the alcoholic material
examined, forms a rather finely granular more or less fibrous proto-
plasmic network. It does not seem nearly related to other known
species unless it be E. canadensis, from which it is distinguished by the
peculiar color and broadly and symmetrically elliptical outline of its
large thick-walled spores. The endospore is not continuous when ex-
amined under brilliant illumination although the isthmus is a very
narrow one and a small septum appears to be present.

REVISION OF ENDOGONEAE. 319

EndogoNe pulvinata Henn.

(Figs. 41-43.)

Hennings (1897), p. 212: nee Lloyd (1918), p. 800, fig. 1240.

Dr. Lindau has very kindly allowed me to see a fragment of the
type of this species, collected by Gollmer, and found growing on the
ground at Caracas, Venezuela. The specimen, which is not in the
best condition, resembles E. fulva in general appearance and color.
The spores, however, although they have thin walls like E. fulva and
are similarly separated from the hypha by a septum, are distinctly
different in general appearance, being more nearly spherical, often
asymmetrical, and seldom showing the considerable difference l)etween
the two diameters that is so characteristic in the last mentioned
species. The larger spores are 85 X 85 /i or 75 X 85 ix, according as
the axes tend to vary slightly : the average being about 75 X 75 m or
75 X 70 fjL, with considerable variation below these dimensions, and
no little variation in outline. The walls are 2-4 jjl thick, as in E. fulva,
and the hyphae which, in the specimen seen, are for the most part
disorganized, appear to be entirely similar and loosely woven.

Endogone fulva (Berk.) Pat.

(Figs. 56-59.)

Paurocotylis fulva Berkeley (1873), p. 137.

Endogone Moelleri Hennings (1897), p. 211.

Endogone lignicola Patouillard (1902), p. 183. Bucholtz (1912), p. 199, figs.

97-99.
Endogone fulva Patouillard (1903), p. 341; Bucholtz (1912), p. 200, figs. 97-99.
Endogone pulvinata Lloyd (1918), p. 800, fig. 1240, nee E. pulvinata Henn.,

(1897), p. 212.

Patouillard first called attention to the fact that Paurocotylis fulva
belonged to the genus Endogone and that it was unrelated to P. pila
Berk, which is the type of the genus. From the data and figures
given by Bucholtz, who has examined the original material in both
instances, the identity which he suggests between E. fulva and E.
lignicola seems almost certain. The fact that they occur in widely
separated regions, the one in Ceylon, the other in the West Indies, is
shown to be of little significance; since other species, like E. malleola
may have, as will be seen, an equally wide distribution.

320 THAXTER.

I have collected this species in abundance in the Maraval Valley
near Port of Spain, Trinidad, growing subgregariously along the
Maraval brook in moist bamboo trash, fruiting within this material
and running out to produce its fructifications on the surrounding sand
and pebbles. A single specimen was also found under the leaf cover
in the forest about the Grand Etang, Grenada; and I obtained
several typical specimens growing exposed on rotten logs in Boggs'
Hammock, a short distance south of Cocoanut Grove, Florida.

Dr. Lindau has been so kind as to send me a fragment of the type of
E. Moelleri, described by Hennings from Brazil. This material is, as
above indicated, identical with the Trinidad form, which has been
submitted to M. Patouillard and is pronounced by him in all respects
the same as his E. lignicola. The spores of the Brazilian form have
the darker color which seems to be more characteristic of individuals
which have developed in humus, without exposure to the light and air,
and are, as in the Grenada gathering, sometimes almost opaque when
first mounted.

Mr. Lloyd has also been so kind as to send me a portion of the
Jamaica material figured by him (1. c.) as E. pidvinata Hennings, as
well as a second specimen collected by Mr. Brace in the Bahamas.
These gatherings also correspond in all respects to the Trinidad form,
and must be regarded as typical E. fulva. I have further received from
Professor Mattirolo for examination, a specimen collected by Rick in
Brazil, which also has all the essential characters of the present spe-
cies, although the spores are not turgescent: and from Professor
Spegazzini a gathering from La Boca, Buenos Aires, doubtfully de-
termined as A. argentina, which seems quite typical of this species,
although not in very good condition.

The spore-masses of E. fulva vary from 1^ cm. to a few mm. in
diameter when dry, and are usually umbilicate below, subspherical to
flattened and irregularly lobed; and even in the same gathering there
may be great variation in color. The peridium, which is usually well
developed, although in some specimens it may be absent to a greater
or less extent, exposing the naked spore-mass, is at first pure white and
floccose in young fresh individuals, turning brownish with age, or
when handled, the color deepening from ochraceous tawny to chestnut
brown.

The hyphae are of the usual type, rather stout, 8-12 (x in diameter,
more or less, often nodulose or irregular, showing occasional septa,
which are more frequent than in most other species, and are in some
cases quite loosely interwoven.

REVISION OF ENDOGONEAE. 321

The spores vary considerably in color, even in the same indi\'i(hial;
and although sometimes nearly opaque, "atro olivaceis vel atris,"
ma}', when produced free to the light and air, have a decidedly pale,
yellowish color. Their outline is characteristically oblong, elliptical
to oval or even subpiriform, rarely nearly circular in outline, except
when viewed end on. They may be more than twice as long as broad,
e.g. 125 X 55 /i, and ordinarily show a decided difference between
the long and short diameter; the average variation being from 50-
125 X 45-70 fjL. The wall, although thin as compared with some
forms of E. macrocarpa, for example, is thick, 2-4 n, in contrast to the
walls of the sporangial types. Bucholtz makes a separate category, a
fourth subdivision of the genus, to include this somewhat thinner
walled type of spore, and speaks of them as possible sporangia. Hav-
ing examined a large series of specimens in all stages of development,
and from widely separated localities, it seems evident that they are
certainly nothing more than chlamydospores, having somewhat thinner
walls than those of the more familiar species, and being distinguished
by a septum. The attachment of the spore is often sublateral, as is
indicated in figure 97 of Bucholtz, and the sporogenous hypha is
often, though by no means invariably, somewhat narrower just below
the point of attachment. ,

The contents of the spores may be rather dense and uniformly
granular, or is often somewhat stringy in appearance apparently from
the presence of fatty crystalline structures. The species is most
nearly related to E. puhinata and the other forms in which the spore
is distinguished by a basal septum.

Endogone reniformis Bres.

(Figs. 60-71.)

Bresadola (1896), p. 297.

Endogone ? argentina Spegazzini (1899), p. 300.

Through the kindness of Professors Lindau and Spegazzini I have
been able to examine the type material of E. reniformis Bres. collected
by Moller in Brazil and of E. argentina collected at Santa Catalina,
Llavallol, Argentina. The Abbe Bresadola has also sent me a third
specimen collected by Rick in Brazil, and I myself found apparently
the same form in the antarctic forest at Punta Arenas, Magellanes,
Chile.

322 THAXTER.

A comparison of these four gatherings indicates tliat, although the
spores of the Magelhm specimen are distinctly larger, the other three
are not separable, and correspond in all essentials. Bresadola, in his
description, spealvs of monosporic asci in which the spore is clearly
distinguished, but was probably misled by the appearance of young
sporangia in which the contents was still continuous, not having yet
divided into spores.

The sporangiocarps of this species which occur on or just under the
leaf cover, are subspherical to reniform, umbilicate, yellowish when
dry, nearly white when fresh, 4-10 mm. in diameter, sometimes 20 mm.
according to Spegazzini, and arise from a ropy mycelium which may
form a more or less distinct stalk as in E. mallcola. In the specimens
examined there is no peridial layer distinguishable, the surface being
composed of sporangia and slightly projecting scanty hyphal elements.
The fertile liyphae are sparingly septate and branched, bearing the
sporangia terminally and diverging from a cushion-like basal region
associated with the umbilicus. The sj)orangia are more commonly
spherical, but, as in E. inalhola may show variations in length and
breadth and may be asymmetrical in outline (Figs. 61-62). At
maturity the sporangium wall collapses about the spores and follows
their irregular contour. The average diameter is about 35-40 fx, but
may reach 60 ju or over. The spores, which are evidently formed by
cleavage of the whole contents in these sporangia, vary in number from
four to a dozen or even more, although Spegazzini mentions eight,
only, and are rather variable in size and irregular in shape from mutual
pressure. In the Brazilian and Argentine material. Figures 04-71,
they are 12-30 X 12-25 fi the average about 18 X 20 n, but in the
Magellan material. Figures 60-63, they are for the most part distinctly
larger, 20-38 X 14-34 fx. The number present in a single sporangium
varies from four to a dozen or more; although, as stated by Spegazzini,
there are often not more than eight. This number is, however, by no
means constant or even characteristic. On the rupture of the spor-
angium wall they are readily set free, although when fully mature,
Figures 67-68, they appear to be held by the collapsed sporangial
wall and rather firmly coherent. They are quite hyaline and con-
tain, as a rule, one or more large oil globules or coarse dense granules.

A second Argentine collection from La Plata sent me by Spegazzini
doubtfully determined as this species, proves to heE.fulva, as already
mentioned.

REVISION OF ENDOGONEAE. 323

Endogone malleola Harkn.
(Figs. 72-78.)
Harkness (1899), p. 280, Plate XLIV, figs. 22 a & b.

Endogone microcarpa Fischer pro parte (1897), p. 121, figs. 4-5. Rahenhorst

Fungi Europei, No. 2516, nee Tulasne (1851).
Endogone pisiformis Bucholtz (1912), p. 196, figs. 88-96; nee Link (1809).
E. Torrendii Bresadola. In Torrend (191.3), p. 101: (1920), p. 55. Torrend

(1913), Fungi Selecti Exsiccati, No. 1.59.

This species seems to have been responsible for much of the con-
fusion with which the genus has been afflicted, since, although it is
fundamentally unlike the majority of the other types which have been
included in Endogone, it bears certain resemblances to them which
have led to a misconstruction of appearances that are frequently
found in the spores of the other two sections of the genus. This mis-
conception has led to the opinion that the chlamydospores, for ex-
ample, were to be regarded as sporangia, or at least that they might
become directly transformed into sporangia. This conclusion, how-
ever, seems to have no better basis than the fact that, in many cases,
the contents of these spores is so modified, that they become filled
with large granules or fatty bodies, often so uniform in size and form
that their spore-like character has been assumed. Thus Bucholtz in
his Beitrage, influenced probably by the use of the terms sporangium
and sporangiolum in Link's description, has assumed that the present
form may be regarded as the true E. -pisiformis, and is thus the type
of the genus. The reasons for belie\'ing that this reference can hardly
be correct, have already been mentioned. In E. malleola, however,
the large spherical or somewhat irregular bodies which form the
fructifying mass are filled with numerous relatively large, separable,
walled spores; quite different in appearance from any differentiation
such as has been above referred to.

The references to this species which occur in the literature, are for
the most part based on the material collected by Vittadini in the vicin-
ity of Naples and distributed in the Fungi Europaei under E. micro-
carpa. Fischer (1896) assuming that the determination was correct,
and that the material showed a condition of this species in which the
chlam\dospores had become transformed into sporangia, regarded it as
a demonstration of the sporangial or hemiascoid nature of the spores
of Endogone in general.

324 THAXTER.

The significance of this condition has been variously discussed, and
the terms ascus and sporangium variously applied to it. Its re-
semblance to the sporangium of the ]Mortierelleae was first pointed
out by Baccarini (1903), who believed that it should be excluded from
the Endogoneae for this reason. The researches of Bucholtz who
demonstrated the sexual origin of the spores in certain species, and the
necessity of their inclusion among the IMucorales, gave further support
to this suggestion of Baccarini, and, assuming that the three sections
herewith distinguished actually represent conditions of a single generic
type, the view that the members of the family are close relatives, at
least, of the Mortierelleae, is, as has been already pointed out, strongly
supported by the fact that in this family alone among the Mucorales,
does one find zygospores ha^^ng specialized envelopes, associated with
highly developed acrogenous chlamydospores; and sporangia sepa-
rated from the sporangiophore by a simple septum. It should be
remembered, however, that although the two may be provisionally
thus associated, the apparent parallelism is not necessarily more than
a coincidence.

The second record of this species is that of Harkness (1899) who first
described it under the name E. malleola from material, collected on
Mt. Tamalpais in California, which I have had the privilege of ex-
amining, and which differs in no essential from the Naples material,
although the maximum diameters of the latter are often greater
(Figs. 72-74).

The form was not again reported till specimens collected in Portugal
were described as E. Torrendii Bresadola, Figures 75-76, in an enumer-
ation by Torrend (1913) of the second century of his Fungi Selecti
Exsiccati, published in Broteria. Quite recently this description has
been republished by Bresadola (1920) among his Selecta Mycologica,
where, however, the fact of its distribution by Torrend is not men-
tioned.

Its range has been further extended by its discovery in New Zea-
land where material, having dimensions somewhat greater than those
of the Naples gathering, has been collected by jNIr. James Mitchell,
and very kindly communicated to me by Mr. Lloyd (Figs. 77-78).

If one compares these different gatherings, although there is a
general agreement in the form, structure and color of the fruiting
masses, which are very similar to those of E. arcjcntina, the average
size of the sporangia and the number of spores which they contain is
subject to considerable variation. Treatment with potash, slight
pressure of the coverglass, and degrees of maturity, have to be con-
sidered in such a comparison; but quite apart from these, there is a

REVISION OF ENDOGONEAE. 325

marked difference observable even between ^^di^•iduals of the same
gathering. Thus of two individuals from the Torrend distribution,
one shows sporangia with an average diameter of 55-GO /x, while those
of the other average from 70-75 jx or slightly over, the latter dimen-
sions corresponding to the Californian and Naples gatherings. Al-
though Bucholtz reports a maximum diameter of 116 // for the latter,
I have not seen any above 100 // in the specimen examined. The New
Zealand form, on the other hand, is distinctly larger, the maximum
diameter being 120 /x, diameters of 100 ju being common and the
average being 80-85 n.

The form of the sporangia is normally subspherical, but may be
irregular, longer than broad, or even broader than long, or subangular
from mutual pressure. The wall usually appears thin, and tends to
follow the contour of the contained spores; but, especially when
treated with potash, may form a clear gelatinous envelope around the
spores, 4-5 jj. thick. The spores are somewhat variable in size, sub-
angular from pressure, but often become spherical when free, and
possess a distinct thin wall. None have been seen, even in the Tor-
rend material, which closely approach the measurements given by
Bresadola, 15-28 X 15-17 ju. Measured in the sporangium they
rarely seem to exceed 14-15 ix, and usually average from 8-12 fi:
although when set free and treated with potash they may reach 20 n
occasionally. They form a rather viscous^ mass, and when the
sporangium is violently broken, are apt to escape in more or less
coherent groups. The filaments, on which the sporangia are borne
terminally, are branched and usually rather copiously septate, even
submoniliform; the contents above the upper septum, which is often
a short distance below the sporangium, being often divided into
several superposed spores.

From its general characters this form could probably be cultivated
with ease by anyone who was fortunate enough to find it in a fresh
condition, and a thorough examination of its development in pure
cultures is very much to be desired.

Doubtful or Excluded Species of Endogone.

Reference has been made above to the occurrence of spores of En-
dogone in the digestive tract of animals, and in this connection it may
be mentioned that in one of these instances spores and mycelium were
found in the stomach of a shrew, sent me by Mr. Judd from the
vicinity of Washington, D.C. In this material, scanty but typical
Endogone filaments bear a few very large spores, some of them 240 /x

326 THAXTER.

in diameter, similar to those of E. macrocarpa, when young, but be-
coming quite opaque as they mature, owing to a blackening of the
exospore. This cannot apparently be referred to any of the described
species, although it is very similar to E. tenehrosa. The opacity of the
spore, however, seems due rather to the formation of a black encrusta-
tion than to a gradual darkening of the contents such as takes place in
E. tenehrosa.

A second type found in the digestive tract of a m\Tiopod collected
in Eastern Tennessee, appears also to belong to an undescribed En-
dogone. The hyphae and spores are typical of this genus, the latter
browTiish yellow, mostly longer than broad, the greater diameter about
38-45 At, the walls not greatly thickened, peculiar from its slightly one-
sided insertion on the sporiferous hyphae. Its size is very near that of
E. microcarpa, but it differs in its much thinner wall, asymmetrical
insertion and more elongate outline. On the other hand it differs from
E. fulva in its smaller spores with relatively thicker walls.

A third form, which approaches more nearly to some of the varia-
tions of E. viacrocarpa, was observed by Dr. ^Yeston while working
with water moulds in the Harvard Laboratory. It produced a rather
scanty groT\i;h, consisting of a single subdichotomously branching
hypha having all the characteristics of those peculiar to the genus.
This grew in water about a fly, attacked by Saprolegniae, and pro-
duced abundant spores rather thin-walled, subspherical, pale brownish
yellow, the larger 85-100 ix in diameter. It is quite probable that this
represents a form of E. macrocarpa, modified by its growth under
unnatural conditions.

E. Tozziana Sacc. & Cav. has been referred to Leucogaster, a dispo-
sition which is confirmed by an examination of a portion of the type.

SPHAEROCREAS Sacc. & Ell.

Type species

Sphaerocreas pubescens Sacc. & Ellis.

(Figs. 79-82.)

Saccardo & Ellis (1882), p. 582.

Stigmatella pvhescens Saccardo (1886), p. 680.
Sderocystis pvbescens von Hohnel (1910), p. 399.

This species was based on rather scanty material collected on leaves
and sticks at Newfield, New Jersey, by Ellis; a portion of which has

REVISION OF ENDOGONEAE. 327

been examined in the Farlow Herbarium. For some inexplicable
reason it was later associated in the fourth volume of the Sylloge, in
the genus Stigmatella, with a second form, Stigmatella aurantiaca B. &
C, a wholly different organism belonging to the Myxobacteriaceae, as
I have formerly pointed out (Thaxter (1892), p. 402), where the close
relationship of S. pubcsccns to Endogone is also referred to. Von
Hohnel (1909), p. 127, includes in this genus his own <S. javanicum, as
well as the two species included in Ackermannia by Patouillard; al-
though in a later paper (1910), p. 399, he transfers all of these to
Sclerocystis B. & Br., reducing his own species, S. javanicum, to a
synonym of S. corcmioidcs B. & Br. Although this disposition seems
correct, in so far as the others are concerned, it is certainly not justified
in the case of the present species which has no characters which would
indicate a near relationship to Sclerocystis.

Sphaerocrcas pubescens is by no means an uncommon fungus, and is
probably widely distributed. It has been repeatedly collected in
moist woods and maple swamps at Kittery Point, Maine, and its
vicinity, and has been also found at Intervale, N.H. by myself and at
Chocorua by Dr. Farlow. It usually produces its fructification on
dead leaves or twigs on the leaf cover, or on rotting branches, and in
one instance was found in some quantity about old carrion. Less
often it has been found on Sphagnum, like E. pisiformis, which it
resembles very closely in general appearance; although it is usually
much smaller, .2-2 mm., subgregarious, and paler in color when fresh,
with a much more conspicuous external tomentum. The resemblance
is so close, however, that Krieger appears to have included specimens
of both in the miscellaneous gatherings which he has distributed in the
Fungi Saxonici under Endogone pisijorviis, No. 1651. In the Harvard
copy at least, one of the two individuals examined proved to be S.
pubescens, which, as far as I am informed, is the first European record
of its occurrence; while the other was typical E. pisiformis, as I have
interpreted it. It is at once distinguishable, however, from the small
size of the subspherical, or broadly elliptical spores, Figures 81-82,
which are IS X 15-25 X 22 fx, rarely larger, although Saccardo men-
tions a maximum of 30 /x. The spore-walls are relatively thick,
1.5-2.5 n, and distinctly yellowish, while the contents appears to be
hyaline or nearly so; usually with one or more large oil globules,
associated with a variable number of small granules, but seldom uni-
formly and densely granular. They are produced acrogenously on
very fine branching thick walled, refractive hyphae, 2 jjl or less in
diameter, with few if any visible septa, and are distributed indis-

328 THAXTER.

criminately throughout the compact mass, which becomes very hard
on drying. On the surface of the spore-mass, which is subspherical,
sHghtly umbiHcate, and rather firmly attached to the substratum
which it may partly envelope (Fig. 79), the hyphae gather in rather
regularly disposed, compact, attenuated, radiate, discrete bundles.
Figure 80, 60-100 ^^ in length and 12-30 ix at the base, while the apex
may be less than 2 /x. The hyphal elements which form these bundles
are so firmly and closely coherent that the individual filaments which
compose them can only be distinguished with a high magnification or
by crushing them apart. They form the conspicuous superficial
tomentum which, although it may be less evident in older specimens,
is very striking in younger individuals (Fig. 79).

Although the peculiarities of the hyphae and spores above referred
to, might not be regarded as very convincing evidence for the separa-
tion of this species from Endogone, I have preferred to keep it dis-
tinct provisionally. The indiscriminate distribution of its spores in a
solid mass would certainly forbid its inclusion in Sclerocystis, as repre-
sented by S. coremioidcs and S. Dnssii, in both of which they are dis-
posed "en une seule zone radiale," about a central columella.

The rather close resemblance between the general appearance of
this species and that of Endogone pisiforinis, above alluded to, might
suggest that they were possibly stages in the cycle of a single fungus ;
S. puhcsccns representing the chlamydosporic condition of the zygo-
sporic type. The character of the hyphae appears to be so different
in the two cases, however, that such a connection seems very improba-
ble, and although their habitats are similar, I have never seen them
closely associated in Nature.

SCLEROCYSTIS B. & Br.

Berkeley & Broome (1873), p. 137.

Xenomyces, Cesati (1879), p. 26.
Ackerinannia, Patouillard, (1902), p. 180.

Type Species ,

Sclerocystis coremioides B. & Br.

Berkeley & Broome (1873), p. 137, Plate X, fig. 56.

Xenomyces ochraceus Cesati (1879), p. 26.

Sphaerocreas Javanicum von Hohnel (1908), p. 30, fig. 1.

REVISION OF ENDOGONEAE. 329

Von Hohnel, who examined the original types, vouches for the
identity of his Sphacrocrccis Javanicum and of Xcnomi/ccs ochraccns
Ces., with Sclcrocystis coremioidcs B. & Br., and an examination of the
type material of Ackermannia which M. Patouillard has very kindly
communicated seems to bear out his conclusion that this genus must
also be regarded as a synonym. It appears to belong in the Endog-
oneae, the characters of its spores and hyphae being in general similar
to those of Endogone. The three species seem to conform to a well
marked generic type, and are distinguished from Endogone in produc-
ing numerous small sclerotium-like sporocarps in which a well defined
sporogenous layer is very characteristic, the large spores lying side by
side with their long axes directed radially from a central columella-like
region.

Von Hohnel states that the sporocarps in his material, which was
found in the Buitenzorg garden growing on bits of wood and sticks,
were "zu einer festen porosen IVIaase verwachsen." They are repre-
sented as short-stalked, 500-600 yu broad, hard, dull yellow to grey-
green, sometimes becoming superposed through distal proliferation.
The closely woven hyphae are said to be septate, those of the short
stalk 8 M in diameter, those which occupy the central portion of the
sporocarp about 4 fx, as are those which form a well defined outer layer;
their free terminations showing no indication of special or charac-
teristic modification. The spores as represented are placed side by
side, as already described, immediately beneath this outer layer, and
are long oval to long elliptical or even clavate, 60-90 X 20-50 jjl.
Their walls appear to be thin, and the contents is either finely granular
or wholly lacking.

The type material of Berkeley and Broome in the Kew Herbarium
was found in Ceylon and was regarded by Fetch (1908) p. 116, as a
sclerotium. Later, however, (1912) p. 282, he confirms the statement
of von Hohnel as to its identity. The type of Cesati, now in the
Herbarium of the Royal Gardens at Rome, was collected by Beccari
in Borneo.

ScLEROCYSTis Dussii (Pat.) von H.

(Figs. 83-85.)

von Hohnel (1910), p. 390.

Ackermannia Dussii Patouillard (1902), p. 181, figs. a-g.
Sphaerocreas Dussii von Hohnel (1909), p. 401.

This species, which was collected by Ackermann in Martinique and
by Duss near Basse-Terre, corresponds very closely in general charac-

330 THAXTER.

ters to the preceding species. It is said to form a superficial, golden
yellow, more or less reddish "stroma," forming a crust or cushion, and
covered with yellow giant cells 260-400 X 50-100 ^i. The individual
stromata are rounded or ovoid, solitary and scattered, or contiguous
and confluent; each containing a "perithecium" (sporocarp), or two
to three superposed, about one third of a millimeter in diameter, com-
pletely surrounded (entoures) by the stroma. The spores, (theques)
are rounded ovoid, brownish yellow, 70-130 X 35-lOO^iu, the walls
thick; the sporogenous filaments 12-16 /x in diameter: they form a
single radial zone lying side by side in a single layer with the long axis
radially directed. The sporocarps ("perithecia") are hard and
sclerotium-like, whitish, formed from interwoven hyphae which are
thick-walled, colorless and 4-5 ix in diameter, surrounding the sporo-
genous layer, those on the surface terminating in characteristically
modified broadly fusiform swollen extremities, or by a series of two or
three such enlargements.

M. Patouillard has been so obliging as to send me two fragments of
the type, one of which is comparatively young. From an examination
of these specimens it would appear that the fungus arises in yellowish
patches which may become variously confluent. This mycelial layer,
crust or stroma, is made up of two distinct elements: relatively slender
and thick-walled, branching, interlaced, aseptate hyphae extending
radially and giving rise to the sporocarps: and large septate hyphae,
the swollen segments of which are thin-walled and usually closely
coherent, forming the covering of giant cells mentioned by Patouillard,
as well as a rather scantily developed lysigenous matrix about the
sporocarps, which appear to become completely free through its
ultimate disappearance. On the surface of the crust or stroma, these
cells, which appear very irregular in outline, though radially elongate,
form a yellow pseudotissue. Figures 83-84; the whole at first con-
tinuous, but later, and on drying, becoming cracked and broken into
irregular areas, with uneven elevations of the surface which corre-
spond in a general way to the sporocarps lying immediately below
them. Beneath this crust, the sporocarps are crowded, at maturity,
in a loose dry mass, and may be supposed to be scattered separately
when freed by its disintegration.

The younger specimen examined shows the sporocarp-origins still in
process of formation immediately beneath the surface of the crust, as
well as the more or less clearly defined relation of superposition which
the older sporocarps continue for a time to bear to one another. Their
temporary coherence is due to connecting wefts of smaller, relatively

REVISION OF ENDOGONEAE. 331

thick-walled, slender, intricately interwoven aseptate hyphae above
mentioned, which form the second element of the mycehal crust, or
stroma. How these wefts at first originate, it is not possible to de-
termine from the material; but as they develop, a distal portion is
distinguished from a basal, which forms a very short stout stalk,
usually broader than long, but variably developed in different cases;
and the broadening distal portion organizes the sporocarp proper.
In this process the latter becomes differentiated into a central region,
or columella, continuous with the stalk, and surrounded by a sporo-
genous layer from which the long oval to somewhat wedge-shaped or
subclavate thick-walled brownish yellow spores diverge radially;
lying side by side in a single layer which completely surrounds the
columella, except in the basal region, where it remains continuous with
the stalk (Fig. 83). A section of the sporocarp in this condition sug-
gests a mushroom "button" in general outline.

The sporogenous layer, which occupies the surface of the columella,
is thin and somewhat more dense. The spores, which radiate from it
with great regularity, are rather uniform, with somewhat flattened
extremities, and are attached by a pointed base, which is usually
distinguished by a small well defined septum from its origin in the
sporogenous layer (Fig, 85). Owing to the confused structure of the
branching, densely woven elements which form the sporogenous layer,
it has not been possible to determine the exact nature of these origins.
Even in thin sections, I have been unable to determine satisfactorily
such a simple and continuous relation, between the spores and the
hyphae of the columella, as is shown by the figure of Patouillard in
this species; or in that of <S. coremioides drawn by Weese, in von
Hohnel's Fragmenta, No. 174, fig. 1; which appears to be some-
what diagrammatic. Although it is not impossible that some form of
conjugation may occur in this layer, which is hidden by the confusion
of cut ends, loops and convoluted branches, I have seen nothing in the
dried material that could be thus interpreted. The thin-walled spores
with their basal septum suggest a resemblance to the corresponding
t^'pe in Endogone illustrated by E. fulva. It may be said in this con-
nection that the extraordinary definiteness of the spore-relations is not
such as one would expect in a chlamydosporic type; but might possi-
bly be interpreted as a higher development of the tendency to segre-
gate somewhat specialized spore-groups, which has been above de-
scribed in certain sexual species of Endogone, like E. multiplex or E.
tuberculosa, and in the chlamydospores of E. vesiculifera and E.fascicu-
lata.

332 THAXTER.

The intersporal spaces are traversed by hypliae which grow radially
from the columella and form, outside the spores, a laj'er about 40 fi
thick of intricately woven filaments, which are also continuous ex-
ternally with the similar hyphae of the stalk. After a given sporo-
carp has developed, this outer la} er proceeds to organizeone or more
new wefts of hyphae, which may be terminal or sublateral or both, and
these wefts in turn organize new sporocarps in a manner similar to that
which has been just described (Fig. 84). The successively formed
sporocarps may thus be arranged in series corresponding to the suc-
cessive origins of these wefts; either in simple rows, or in a more
complicated fashion, owing to divergence from the long or radial axis.

The stalk-portion which is often but slightly developed, shrivels and
separates from its point of origin, as the maturing sporocarp becomes
hard and sclerotic, and persists as an inconspicuous tuft of shriveled
filaments; the lysigenous elements above referred to having also
disappeared and freed the sporocarps from their lateral attachments.

After examining a number of sporocarps w^th some care, I have
been unable to detect either in young or in more mature conditions
the peculiar subfusiform superficial hyphal terminations figured and
described by Patouillard, as above indicated. When fully mature
and freed from its attachments, the hard sclerotic sporocarp is ex-
ternally furfuraceous from the numerous broken projecting ends of
the filaments which cover it. Were the peculiarly swollen termina-
tions seen by Patouillard normally recognizable, their presence should
readily separate this species from S. coreviioides, but since it seems
certain that they are not always present, it is possible that the two
species are not specifically distinct, even though the presence of the
large celled evanescent pseudotissue is not mentioned in descriptions
of the East Indian form. The spore-measurements, as given by von
Hohnel, are somewhat smaller, 60-90 X 20-50 ju; the average dimen-
sions in the West Indian form, as I have determined them, being 95-
115 X 20-50 (x; the extremes 60-120 X 34-55 ju, the shorter diameter
being that of the distal end of the spore. The sporocarp measure-
ments, on the other hand, as given for S. coremioides, are 500-600 n,
while those of S. Dussii which I have measured are 350-450 X 300-
460 fx. Although the spores of the East Indian form are thus some-
what smaller and the sporocarps somewhat larger than in the W'est
Indian species, the discrepancy does not appear to be very great, as
compared with other instances of variation in the group.

REVISION OF ENDOGONEAE. 333

ScLEROCYSTis coccoGENA (Pat.) von H.

(Figs. 86-87.)
von Hohnel (1910), p. 390.

Ackermannia coccogena Patouillard (1902), p. 183, figs. h-j.
Sphaerocreas coccogena von Hohnel (1909), p. 401. ,

I am indebted to M. Patouillard for a very small fragment of this
species, which was collected by Ackermann in company with Endogone
lignicola Pat., growing on rotten wood, the locality being the Plateau
des Rivieres, Martinique, and the date of collection June, 1901. This
fragment shows a small portion of the crust or covering which sur-
rounds the sporocarps, and three or four of the latter, which are fully
mature, but still attached to it.

Judging from the original figures and description, the "stroma" of
this species is more definitely circumscribed and thicker (6-8 mm. by
4 mm. thick) than that of S. Dussii, resembling closely the spore-mass
of some Endogone, and covered by a more even and clearly differ-
entiated pseudoperidial layer. The small fragment of this layer which
I have examined, is composed of rather loose coarse septate hyphae,
the segments of which are irregular and do not form a coherent pseudo-
tissue of giant cells as in the preceding species.

The sporocarps are similar in form and appearance to those of S.
Dussii, but somewhat larger, 400-675 /jl in greatest diameter. The
spores, which are similar in their origin and arrangement, are some-
what smaller, their average dimensions being about 100 X 40-50 fx.
The sporocarps themselves are at once distinguished, however, by the
presence of numerous small spherical chlamydospores. Figure 87,
similar to those of Endogone, which are formed terminally in the
tomentum which covers the intricately woven superfical layer
(Fig. 86).

In its thicker and more clearly circumscribed stroma, and more
definite pseudoperidium, in its larger sporocarps and the production
on their surface of spherical chlamydospores, and in the apparent
absence of a lysigenous pseudotissue of large thin-walled hyphal
segments, this species seems to be clearly distinguished.

334 THAXTEK.

GLAZIELLA Berk.

Berkeley (1879-80), p. 31, No. 852^
EndogoneUa von Hohnel (1913), p. 294.

Type Species

Glaziella vesiculosa Berk,

(Figs. 88-94.)

Berkeley (1879-80), p. 31.

Xylaria aurantiaca Berkeley & Curtis (1868), p. 382, d.
Glaziella aurantiaca Cooke (1883), p. 83: Lloyd (1919), p. 30, fig. 1460.
Hypomyces alholutevs ElUs & Everhart (1893), p. 262 and 285.
EndogoneUa horneensis von Hohnel (1913), p. 41, figs. 4-5.

Owing to its large size and conspicuous orange yellow color, this
species has been repeatedly observed in the American tropics, but the
early misinterpretation of its characters has led to much confusion
as to its probable position. It was first collected in Brazil by Glaziou,
No. 8526, this type, of which through the courtesy of Miss Wakefield
I have been able to examine a portion, being still in the Kew Her-
barium. Later, material collected by Wright in Cuba, a portion of
which has been examined in the Curtis Herbarium at Harvard, was
redescribed as Xylaria aurantiaca by Berkeley and Curtis, it being
assumed in both instances that it was an immature ascomycete, and
that its peculiarly developed spores were young perithecia. In a
similar fashion a gathering from Jamaica, communicated by Cockerell
was subsequently described by Ellis as a new but sterile Hypomyces,
which he named H. albolideus E. & E. Still more recenth' it has again
been described under a new generic name by von Hohnel, as Endo-
goneUa horneensis n. g. et n. sp., this being the first record of its
occurrence in the Eastern Hemisphere.

This plant occurs in the form of a bladder-like, variably lobed, or
even convolute, soon unattached sporocarp. Figure 88, 2 to 4 cm. long
by 2 to 3 cm. broad and 1.5 to 3 cm. thick, more or less, when chy;
much larger when fresh. The tough gelatinous wall 700-900 (j.
thick, is perforate below% the perforation entering a central cavity
which is quite empty. On drying it becomes hard and brittle and
loses much of its color, fading and becoming brownish with age, and
exposure. The outer surface is more even, with a slight bloom, the
inner pale yellowdsh and somewhat uneven. A section of the wall cut

EEVISION OF ENDOGONEAE. 335

radially, Figures 89-90, shows a rather clearly defined distinction
between an outer thicker, and an inner thinner dense layer and a
looser broader sporogenous region which lies between them, but is not
separated by any clean cut line of demarkation.

Although the fungus is usually described as immature or sterile, I
have myself seen no specimens which are not fertile and but two that
were even moderately young. Of these the youngest was found in
1891, near Kingston, Jamaica, partly buried in a very soft rotten log.
The sporocarp was completely enveloped by a thin white separable
universal membrane within which it was already free and perforate
below. The hyphae composing this membrane are slender, thick-
walled and septate. In this unexpanded condition, which was thick
and somewhat flattened, the spores, although for the most part
nearly mature. Figure 90, were crowded in an irregularly double layer,
and the plant was set aside as a species of Endogone.

As the sporocarp matures and enlarges this crowded condition dis-
appears, and the outer and inner layers, especially, evidently take an
important part in the tangential increase, so that the crowded spores
become more and more discrete as the wall stretches itself, so to speak,
and eventually assume a more or less definite arrangement in a single
layer. The hyphal elements which take part in this process are thick-
walled with rather frequent septa, densely compacted in the two walls
and somewhat looser in the middle region (Fig. 94). As the sporocarp
increases in size the septa become very numerous a^d the filaments
greatly enlarged, so that the inner and especially the outer layers ap-
pear to be made up of dense thin-walled parenchyma which gradually
passes into the looser lacunose middle region, the hyphae of which are
also thin-walled for the most part and submoniliform. Figure 93,
with large interhyphal spaces.

Unfortunately no information is available as to the earlier stages in
the formation of the sporocarp, or the initial processes of spore-
formation. The sporogenous zone is evidently traversed at intervals
by radial wefts of finer, closely septate hyphae, which are dense and
have a dark granular appearance (Figs. 90-91). These wefts are the
sporogenous centres above referred to, and conceal the spore-origins
which traverse them. The spore-initials emerge from them as shown
in Figure 91, a tangential section, in the form of long clavate structures,
terminating apparently aseptate filaments which, although it has not
been possible to trace them to their origin, appear to grow radially
from the inner margin of the inner dense layer of the sporocarp. The
tips of these clavate structures become greatly enlarged and the walls

336 . THAXTER.

enormously thickened; the hnnen being sometimes ahiiost obhter-
ated. These swollen terminations push out into the interhyphal
spaces of the middle zone, cur\ang outward or backward, and are
transformed to the mature spores. Sporulation seems to be more or
less simultaneous at a rather early stage of development, and the
enlargement of the orange sporocarp, after this has taken place, seems,
under favorable conditions, to be a relatively rapid process.

The mature spores are very large, 200 X 200-415 X 380 n, spherical
to broadly ellipsoid, a thinner gelatinous exospore about 10 ^u thick and
continuous with the wall of the sporogenous filament, being at first
clearly distinguished from the very thick, continuous, laminated,
20-30 // thick (to 38 /x with KOH) endospore. The contents is rather
dense and finely granular, or jelly like in appearance, with larger oily
bodies here and there. The sporogenous filaments which can some-
times be traced a short distance even from mature spores, seem to be
simple and show no signs of any structure which might be regarded as
possibly conjugating elements; although it is by no means certain that
such organs might not possibly be recognizable in much earlier stages
then those which have been examined. Owing to secondary tangen-
tial growth of the sporocarp, the spores, as above mentioned, not only
tend to become discrete, and to arrange themselves in a single layer;
but the spaces in which they lie may become considerably enlarged,
so that they may lie in a loculus of considerable size, quite free, or
suspended by a Jew adherent radiating filaments, Figure 92.

The spores, when they have been seen at all, have been variously
referred to as asci, perithecia, vesicles or even glands. In very well
matured individuals which have been slightly shrunken by alcohol,
the position of the spores may be indicated externally, even to the
naked eye, by slight corresponding ele\ations, which have very much
the appearance of perithecial ostioles; and it is therefore liqt so sur-
prising that, in the original description of the type, they shoiHd have
been spoken of as "pale perithecia filled with hyaline gelatine."

Von Hohnel in his description, gives the first indication which has
been found in the literature, of what appears to be their true nature,
and includes what he regarded to be the new genus Endogonella among
the chlamydosporic types of the Endogoneae. Apart from the fact,
however, that the plant is described and represented upsidedowTi, it
answers in all particulars to GlazicUa vcsicjtlosa Berk. There is also
absolutelv no difference which I have been able to discover, between
Xylaria aurantiaca B. & C. collected by Wright in Cuba, and Berke-
ley's type collected in Brazil by Glaziou. It seems quite remarkable,

KEVISION OF ENDOGONEAE. 337

however, that there appear to be no other synonyms, and that, al-
though several other species of Glaziella have been listed, the genus
remains monotypic.

A final opinion with regard to its true relationships can hardly be
formed until the nature of the primary vegetative and sporogenous
hyphae is known. It seems not impossible that, like Sclerocystis, it
possesses two distinct sets of hyphal elements, the one concerned in
sporulation and without septa, the other copiously septate. Although
in Sclerocystis the septate elements seem to be lysigenous, and are
designed to free and scatter the sporocarps and spores; and in the
present genus, on the contrary, their object appears to be to hold them
firmly in a coherent mass which they render esculent and make con-
spicuous by raising it above the substratum through a mechanism
remotely comparable to that of some phalloids, their ultimate function,
namely an effective dispersal of the spores, may be assumed to be the
same.

In both genera, the fact that one element in their structure does not
conform to the ordinary phycomycetous type, since it is composed of
copiously septate filaments, may be explained by their specialization
for a definite purpose other than sporulation. In Sclerocystis at
least, the sporogenous element corresponds in structure to that of the
Mucorales, since its hyphae are more strictly continuous even than in
Endogone. Whether this is also the case in Glaziella cannot be
determined till very young material is available for study. The
presence of an independent and continuous endospore, Figure 91, like
that of the zygospores in Endogone, points to a further possibility of
their sexual origin.

In any case Sclerocystis and Glaziella may be assumed to illustrate
the highest degree of differentiation which is reached in the family, so
far as it is known; and their structure and development is the more
remarkable, when it is contrasted with the relatively simple condi-
tions which obtain in other forms. They do not seem, however, to be
nearly related, although, if the above suggestion as to the sporogenous
element in Glaziella is correct, the dual nature of the elements which
compose them and the definite segregation of the sporulating regions
are characters in common. The wefts of finer filaments which in
Glaziella are associated with spore-origins which might be regarded
as corresponding to the sporocarp initials of Sclerocystis, do not, how-
ever, seem comparable; since the fine filaments which compose them
become closely septate, and seem to arise directly from the inner layer.

It should be mentioned that all other fungi which have been in-

338 THAXTER.

eluded in Glaziella appear to belong among the ascomycetes: simi-
larity in color, sterility, and gelatinous consistency having apparently
been the only reasons for their inclusion in it. Among these forms
the most important is Glaziella splendens Cooke (1882), p. 83, de-
scribed by Berkeley & Curtis (1868) as Xylaria splendens, which, like
" Xylaria" aurantiaca, was also collected in Cuba by Wright, is repre-
sented in the Curtis collection by one half of the type, the other half,
which is figured by Lloyd (1919), p. 29, being in the Kew Herbarium.
The Curtis half has been examined and sectioned with some care, and
is certainly in no way related to Glaziella. Its characters are entirely
similar to those of Entonema liquescens Moller (1901), p. 247 with
figure, and it seems very probable that it may be the sterile condition
which appears sometimes to be associated with this species, or at the
least an immature stage. It is not hollow, has the same bright granu-
lar superficial crust and an inner gelatinous region composed of color-
less hyphae with thick soft gelatinous walls, which is subtended by a
contrasting black zone or line. There are absolutely no signs of spores
or of developing perithecia, and one is inclined to agree with Moller
that descriptions of sterile forms of this nature should be disregarded
by mycologists.

Glaziella sidphurca Patouillard (1903), p. 292, judging from the
description, is certainly not a Glaziella, and appears also to correspond
very closely with the sterile condition of Entonema liquescens.

Glaziella ceramichroa (Berk. & Broome) Cooke (1882) is very surely
not of this genus. Mr. Fetch assures me that his reference (1910),
p. 427, No. 61, of the species to Hypocrella is correct.

Glaziella abnormis (Berk.) Cooke (1882), in which asei and asco-
spores are described, must evidently be excluded; since it also appears
to be very near to, if not identical with, Entonema liquescens.

REVISION OF ENDOGONEAE. 339

List of Literature and Exsiccati cited.

Baccarini, P.
1900. Sopra i carrateri di qualcue Endogone. Nuovo Giornale
Bot. Ital., II Ser., Vol. X, p. 79.
Berkeley, M. J.

1860. In Hooker, J.: Botany of Antarctic Voyage. Part III,

Vol. II, p. 270, Fungi in " Flora Tasmaniae."
1868. Journal Linnaean Soc, Vol. X, p. 382.
1879. No. 8526 in Warming: Symbolae ad Floram Braziliae
centralis cognoscendam. Videnskabelige Meddeleser
Naturh. Foren. Kjobenhaven, p. 31.
Berkeley and Broome.

1873. Fungi of Ceylon. Journal Linnaean Soc. Vol. XIV, p. 137.
Bresadola, Abbe J.

1896. Fungi Brazilienses lecti a clar. Dr. Alfred Moller. Hed-

wigia, XXXV, p. 297.
1913. See sub Torrend.

1920. Selecta Mycologica. Annales Mycologici, XVIII.
Bucholtz, Fedor.

1902. Beitr. z. Morphol. etc. der Hypogaeen. Naturhist. Mus.
der Grafin K. P. Scheremetjeff, Moskau, I. Riga.

1911. Ueber die Befruchtung von Endogone lactiflua Berk.

Annales Mycologici, Vol. IX, p. 329.

1912. Beitrage zur Kenntnis der Gattung Endogone Link. Bei-

hefte zum Botanischen Centralblatt. Vol. XXXIX,
Abt. 2, p. 147-224, Plates 3-10.
Cooke, M. C.

1882. Notes on Hypocreaceae. Grevillea, Vol. XI, p. 83.
Ellis, J. B.

1893. Hypomyces alboluteus E. & E. n.s. Journal Institute of
Jamaica, Vol. I, p. 2(32; and Note on Glaziella, p. 265.
Fischer, Edward.

1897. Hemiascineae and Tuberineae in Rabenhorst, Kryptogamen-

Flora. Vol. I, Abth. v, p. 124, figures.
Harkness, H. W.

1899. July. Californian Hypogaeous Fungi. Proceedings Cali-
fornia Acad, of Sciences. Ill Series, Vol. I, No. 8, p. 279.

340 THAXTER.

Hennings, P.

1897. August. Beitrage zur Pilzflora Siidamericas, II. Hedwigia.
p. 211.
Hohnel, F. von.

1908. October. Fragnienta zur ^Mycologie, V. Sitzungsberichte

d. kaiserl Akad. der Wissenschaften in Wien. Mathem.-
naturw. Klasse, Vol. CXVII, p. 1014, figures.

1909. April, do. VI. 1. c. C XVIII, p. 401.

1910. May. do. X. 1. c. CXIX, p. 398.

1913. February, do. XV. 1. c. CXXII, p. 294, figures.
Krieger, K. W.

1902. Fungi Saxonici, No. 1651.
Link, H. Y.

1809. Observationes in Ordines Plantarum naturales. Gesell.
naturf. Freunde zu Berlin. Magazin. f . d. neuesten Ent-
deckungen in den gesammten Naturkunde. Vol. Ill, p. 33.
Lloyd, C. J.

1918. October. Mycological Notes, No. 56, p. 799, figures.

1919. July. The Large Pyrenomycetes, II. p. 29, figures.
Patouillard, N.

1899. July. Champignons de la Guadaloupe. Bulletin de la
Societe Mycologique de France, Vol, XV, p. 206.

1902. May. Champignons de la Guadaloupe, recueillis par le

R. P. Duss. Ill Series; 1. c. Vol. XVIII, pp. 180-183,
figures.

1903. December. Note sur le Genre Paurocotylis Berk. 1. c.

XIX, p. 341.

1914. September. Quelques Champignons de Congo. 1. c, Vol.

XXX, p. 346.
Petch, T.

1910. January. Revisions of Ceylon Fungi, II. Annals of the
Royal Botanic Gardens, Peradeniya. Vol. IV, Part 6,
p. 427.
1908. January. Preliminary Note on Sclerocystis coremioides B.

& Br. Annals of Botany, Vol. XXII, p. 116.
1912. August. Revis. Ceyl. Fungi, III. Ann. Roy. Bot. Gard.
Peradeniya, Vol. V, p. 282.
Rabenhorst, L.

1880. Fungi Europaei, No. 2516.
Saccardo, P.

1877. May. Fungi Italici Autographice Delineati. Fig. 104.
1877. MicheHa, Vol. I, p. 14.

REVISION OF ENDOGONEAE. 341

Saccardo, B. and Cavara, F.

1900. Funghi de Vallombrosa I. Nuovo Giornale Botanico

Italiano. Ser. II, Vol. VII, p. 296.
Schroter, J.

1887. Protomycetes in Cohn, Kryptogamen-Flora von Schlesien.

Vol. Ill, Lief. 3, p. 260.
Spegazzini, Carlos.

1887. Las Trufas iVrgentinas. Annales de la Sociedad Scientifica

Argentina, Vol. XXIX, p. 125, No. 5.
1887. Fungi Fuegiani. Boletin de la Academia Naeional de

Ciencias de Cordoba. Vol. XI, p. 120, No. 311.
1899. April. Fungi Argentini novi vel critici. Anales del

Museo Naeional de Buenos Aires. Vol. VI, p. 300,

No. 676.
Torrend, C.

1913. July. Fungi Select! Exsiccati, Choix de Champignons du

Portugal, Bresil et des Colonies. Broteria, Vol. XI, p.

101.
1913. Fungi Selecti Exsiccati, No. 159. Endogone Torrendii

Bres. '

<f

EXPLANATION OF THE PLATES.

Description of the Figures.

The figures are for the most part camera drawings which have been reduced
more than one half in reproduction. Unless otherwise stated the original com-
bination used is Zeiss obj. D and ocular 4, with table projection.

344 THAXTER.

PLATE I.

Endogone pisiformis Lk.

Figures 1-5. Successive stages in the formation of zygospores. 1-4, obj.
J, oc. 4; 5 obj. J, oc. 2.

Figure 6. Mature spores with gametes still attached.

Figure 7. Peculiarly differentiated hypha forming the superficial tomen-
tum of a young individual.

Endogone multiplex Thaxter.

Figure 8. Mature spore showing hyphal envelope.

Figure 9. Mature spore with discrete gamete attachments, treated with
KOH.

Figure 10. Larger and smaller spore-groups surrounded by envelope with
incorporated humus-material.

Endogone tuberculosa Lloyd.

Figure 11. Section of sporocarp showing disposition of sporogenous areas,
(light), with surrounding and penetrating earthy envelope (dark): magnified
about seven times as reduced.

Figure 12. Portion of gleba showing spores and pseudoparenchymatous
hyphal tissue.

Figure 13. Spore showing envelope and origin from gametes. Zeiss J,
oc. 1.

Figure 14. Fully matured spore with greatly thickened exospore.

Figures 15-16. Spores of more elongate type.

Endogone incrassata Thaxter.

Figure 17. Section of a portion of sporocarp, showing peridium and gleba
with fully mature and more immature spores.

Figure 18. Spore showing characteristic fatty contents and probably
sexual origin. Zeiss D, oc. 12.

Figure 19. Fully mature spore with greatly thickened exospore and com-
pacted surrounding hyphae.

Endogone ludiflua Berk.

Figure 20. Showing origin of zygospore from dissimilar gametes.

PROC. AM. ACAD. ARTS & SCI. VOL. LVIl

PLATE I

sr^.

TH AXTER-REVISION OF ENDOGONEAE

cc -^i^attif: n n ■i-'or:

346 THAXTER.

PLATE II.

Endogone fasciculata Thaxter.

Figure 21. Sorus of chlamydospores viewed externally. Zeiss obj. A,
oc. 4.

Figure 22. Section of sorus of chlamydospores showing, above, a few
adjacent young zygospores. Zeiss, obj. A, oc. 4.

Figures 23-26. Different stages in the formation of zygospores. Zeiss
obj. J, oc. 2.

Figures 27-28. Separated chlamydospores.

Endogone vesiculifera Thaxter.

Figure 29. Partial section of a sorus showing origins and association of
chlamydospores and thin-walled clavate vesicles. Zeiss obj. A, oc. 4.
Figure 30. Clavate vesicles and their origin.
Figures 31-32. Separated chlamydospores and their origins.

Endogone fuegiana Spegazzini.

Figure 33. Section of gleba showing discrete spore-groups. Zeiss obj. A,
oc. 4.

Figure 34. Section of single spore-group, showing spore-origins.

Endogone microcarpa Tulasne.
Figures 35-37. Chlamydospores from Californian material.

Endogone arenacea Thaxter.
Figures 38-40. Three mature chlamydospores with their origins.

Endogone pulvinata Hennings.
Figures 41-43. Three chlamydospores from the type material.

Endogone borealis Thaxter.
Figures 44—45. Two chlamydospores.

PROC. AM. ACAD. ARTS & ,SCI. VOi_. LVII

PLATE I ;

jr^:

f?"^-^.

/.'Ut''.

%\

^^fw

f

'26

21

Qi:

'/ \

,^/ .,,,,

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THAXTER-REVISIOIM OF ENDO&ONEAE

348

THAXTER.

PLATE III.

Endogone tenebrosa Thaxter.

Figure 46. Nearly mature chlamydospore, showing unbroken proto-
plasmic isthmus.

Endogone radiata Thaxter.

Figure 47. Section of sporocarp, .showing part of surface and gleba, with
radiately arranged chlamydospores. Zeiss obj. A, oc. 4.
Figures 48-51. Chlamydospores of varying form.

Endogone canadensis Thaxter.
Figures 52-55. Chlamydospores showing the slender sporophore.

Endogone fulva (Berkeley) Fatouillard.

Figure 56. Chlamydospore from the Type of E. Molleri.

Figure 57. Chlamydospore from the island of Grenada, B.W.I.

Figure 58. Chlamydospore from Florida.

Figure 59. Chlamydospore from Grenada, B.W.I.

Endogone reniformis Bresadola.

Figures 60-63. Sporangia from the Straits of Magellan.
Figures 64-66. Sporangia from Spegazzini's type of E. argentina.
Figures 67-68. Sporangia from the Berlin type of E. reniformis.
Figure 69. Single spores from the last.
Figures 70-71. Single spores from Spegazzini's type.

Figures 72-74.
Figures 75-76.
Torrendii Bres.
Figures 77-78.

Endogone malleola Harkness.

Sporangia from the calif ornian type of Harkness.
Sporangia from Torrends Fungi Selecti, No. 159, E.

Sporangia from New Zealand communicated by Lloyd.

PROC. AM. ACAD. ARTS & SCI. VOL. LVII

PLATE II

THAXTER-REVISION OF" ENDOSONEAE

350 TIIAXTER.

PLATE IV.

Sphaerocreas pubescens Saccardo & Ellis.

Figure 79. Spore mass seen in optical section seated on fragment of wood.
Zeiss obj. A. oc. 4.
Figure 80. Hypluil bundles which radiate from the spore-mass.
Figures 81-82. Six spores showing their attachment to slender hj^phae.

Sclerocystis Dussii (Patouillard) von Hohnel.

Figure 83. Sorus showing stalk arising from a second sorus below, with
central columella and external hyphal layer, above which is a portion of the
upper surface of the "stroma" showing the "giant cells." Zeiss obj. C, oc. 2.

Figure 84. Section including the surface of the stroma with its giant cells,
and showing several different sori in situ. Zeiss obj. A, oc. 2.

Figure 85. Two spores isolated and showing basal septum.

Sclerocystis coccogena (Patouillard) von Hohnel.

Figure 86. Small portion of a sorus, showing a small part of the columella,
spore zone and outer layer, the filaments of the latter producing several small
spherical chlamydospores. Zeiss obj. A, oc. 2.

Figure 87. Small chlamydospores separated from surface of sorus-
envelope.

Glaziella vesiculosa Berkeley.

Figure 88. Hollow sporocarp. A lobe cut away to show interior, the
smaller black area below being the normal inferior perforation. Partly ventral
view. Somewhat less than natural size as reduced.

Fu;URE 89. Section of the sporocarp wall from a nearly mature individual
in which the spores are becoming discrete. Zeiss obj. A, comp. oc. 3.

Figure 90. A similar section from a young individual, showing the dense
superficial layers, the (black) hyphal wefts associated with the sporogenous
filaments, and the crowded arrangement of the spores. Zeiss obj. A, comp.
oc. 3.

Figure 91. Tangential section from same individual, showing sporogen-
ous weft cut transversely, with several sporogenous hyphae emerging from it.
bearing terminal spores in several stages of development. Zeiss obj. A, oc. 2.

Figure 92. Portion of fully mature sporocarp, showing a spore suspended
by hyphae in a large chamber, a part of the lacunose middle layer shown at
left. Zeiss obj. A, oc. 2.

Figure 93. Hyphae from the middle zone of a younger individual. Leitz
water im. oc. 2.

Figure 94. Hyphae from the same region in an older individual. Same
magnification.

PROC. AM. ACAD. ARTS & .SCI. VOL. L V I I

PLATE IV

^y

\ ^.

B«3^.,'TI f "'

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THE ECHINODERMS OF THE CHALLENGER BANK,

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THE ECHINODERMS OF THE CHALLENGER BANK,

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THE ECHINODERMS OF THE CHALLENGER BANK,

BERMUDA.

By Hubert Lyman Clark.

Presented by E. L. Mark. Repeived April 8, 1922.

When H. M. S. Challenger visited Bermuda in 1873, one day
(April 23) was spent in "sounding out" the "bank" lying a few miles
southwest of the Bermuda bank itself, and as a result this shoal area,
some seven miles long and six miles wide, with a minimum depth of
24 fms. has since been known as the Challenger Bank. In August,
1903, a party from the Bermuda Biological Station, under the direction
of Professor E. L. Mark and Professor C. L. Bristol, made an excursion
to the Bank and did some dredging there.-^ One of the party, Dr.
H. B. Bigelow, has published (1905, Proc. Amer. Acad. 40, pp. 586-
591) a very interesting account of the physical characteristics of the
Bank, and of the peculiar nodules with which it is covered. So far
as I can learn, no other scientists have done any dredging on the
Challenger Bank and our knowledge of its fauna must thus be based
on the material obtained by these parties in 1873 and 1903. The
Challenger took but four species of echinoderms, one sea-star
{Chaetasfer nodosiis, recorded in the Challenger Reports as Ch.
longipes) and three brittle-stars {Ophiomi/xa flaccida, Ophiofhrix angu-
lata, Ophiothrix suenso)iii). The party from the Biological Station did
much better, as they dredged a dozen species. This collection lias,
through the kindness of Dr. Mark, recently come into the possession
of the IVIuseum of Comparative Zoology and as it proves to be of
unusual interest, the present report has been prepared.

Of the four species taken by the Challenger, the party from the
Bermuda Biological Station took all except Ophiomyxa flaccida, a

1 This expedition was made possible by the invitation of the late Captain
William E. Meyer, ship owner, of "Gliickauf", St. Georges, Bermuda, who
very generously fitted out his ocean-going tug Gladisfen for the occasion,
and with her crew personally took the whole membership of the Biological
Station, thirty-seven in number, and a few^ others for a three days' trip to the
Challenger Bank. The expedition left St. Georges on July Slst, 1903, and
returned on August 2nd. E. L. Mark.

354 CLARK.

well-known West Indian species common at Bermuda. The other
species taken by the Station party were four sea-stars, three brittle-
stars and two sea-urchins, and of these nine, one represents a species
hitherto undescribed, and three others are not known from Bermuda.
As the sea-star Chaetaster is also unknown from Bermuda itself, it
appears as though nearly half the echinoderms found on the Chal-
lenger Bank have not made their way across the three or four miles
of deep water that separate them from Bermuda.

All the Echinoderms at present known from the Challenger Bank
are referred to below but there is every reason to believe that the list
would be greatly augmented by more thorough exploration.

ASTEROIDEA: SEA-STARS.

Chaetaster nodosus.

Perrier, 1875. Arch. Zool. Exp., 5, p. 146 (330 of reprint).
Verrill, 1915. Bull. Univ. Iowa, n. s. no. 92, p. 116; pi. VIII.

The unique holotype of this species was recorded as from " Guade-
loupe. M. Duchassaing, 1870," but no specimens were taken by
either the Blake in her extensive dredgings in the West Indies, 1877-
79, or by the Albatross in 1884-87. The expedition from the Uni-
versity of Iowa took two specimens in rather deep water (140-200
fms.) off Havana, Cuba, which in size and appearance were very simi-
lar to the holotype. One of these was described and well figured by
Verrill, /. c. The Challenger took specimens of Chaetaster at her
Station 36, off Bermuda, 30 fms., but Sladen (1889, Challenger
Asteroidea, p. 399) regarded them as examples of the Mediterranean
species, longipes, although he says "a number of the examples" from
Bermuda have here and there tubercular enlargements of the paxillae"
like those characteristic of nodosus. Unfortunately he gives no infor-
mation as to the number, size or form of these specimens from the
Challenger Bank, data which would now be of veiy great value.
Verrill (1. c.) suggests that these specimens taken by the Challenger
are probably nodosus and not longipes. Examination of the six speci-
mens in the Museum of Comparative Zoology collection, all from the
Challenger Bank, shows positively that they are not longipes and
Sladen was no doubt in error in referring his Bermudan material to
that species. For longipes has well-marked series of actinal inter-
mediate plates extending far out on the arm, and even in a specimen
with R only 24 mm., one of these series is evident. These inter-

ECHINODERMS OF CHALLENGER BANK, BERMUDA. 355

mediate plates are wanting in nodosus, except on the actinal surface
of the disk, where there are a few; the lower surface of the arm is
covered chieifly by the inferomarginal plates, which abut directly on
the adambulacrals. The Bermudan specimens agree with nodosus
in this, and should, I think, be referred to that species, but it must be
admitted that they differ from both Perrier's description, and Verrill's
description and figures, of nodosum in their much smaller size and longer
and more slender rays. Perrier's type, from Guadeloupe, had R = 70
mm., while the specimens Verrill studied had R = 74 and 76 mm.
Sladen gives no measurements of his specimens from Bermuda, but
the largest of the six Museum specimens from the Challenger Bank
has R only 40 mm. These specimens have the ray only about a third
as wide at tips as at base, whils in the West Indian specimens it seems
to be as much as two-fifths. Verrill's figures show this, although his
description says the rays taper "to unusually slender tips." Perrier,
on the other hand, says the rays "termines en pointe tres-obtus."
Whether this difference in the form is constant and has any significance
can only be determined by actual comparison of specimens of the same
size.

Sladen implies, but does not directly say, that some of the Chal-
lenger specimens lacked the "tubercular enlargements" character-
istic of nodosus. Of the specimens in the Museum of Comparative
Zoology collection, the three which are dried show these enlargements
plainly; in the smallest R = 34 mm.), there are 9, in the largest
(R = 40 mm.), about 25, and in the third specimen (R = 36 mm.),
about 35. The enlarged plates are all either abactinal or rarely super-
omarginal, and are chiefly on the basal half of the rays; they are only
rarely on the disk. They vary greatly in size and grade down to
normal plates. In the alcoholic specimens, they are much less con-
spicuous than in the dried ones, although the specimens are of about
the same size, and in one individual they seem to be ciuite wanting.
It seems probable that both in number and size the enlarged plates
increase with the age of the individual.

Ophidiaster schismochilus^ sp. nov.

Plate I.

R = 113 mm.; r = 11 mm.; br = 16 mm.; R = lOr or 7br.
Disk very small and flat. Rays very unequal (113, 100, 90, 85, 55,

2 crxicMa, a cleft -j-xfi^os, a lip or margin, in reference to the numerous pedi-
cellarian clefts on the margin of the ambulacral furrows.

356 CLARK.

mm.), but only the two longest have normal tips; the next two have
the tips truncate and the shortest has the tip conspicuously regener-
ated, the new part l)eing 7 mm. long; all the rays are flattened cylindri-
cal, slightly constricted at base; only the terminal fourth tapers to
the normally pointed tip. Body surface very finely and uniformly
granular, 80 or more granules to a square millimeter in the dry con-
dition. Papulae in 8 well-marked series of large, scarcely depressed
areas, 20-50 to each area, except near base and tip of arm, and on
disk, where areas are evidently smaller; papulae of actinal areas appear
to be a little larger than those of abactinal surface; on basal part of
arm each area is very much larger than any adjoining plates, a typical
one being 2 mm. long and 4 mm. wide; series of areas fairly regular
and parallel till very near arm-tip where they converge and each area
is greatly reduced containing only one or two papulae. Marginal
plates not noticeably larger than, nor different from, al)actinal plates.
Terminal plate relatively small, not nuich more than 2 mm. across,
not granular l)ut with about. 7 fairly large tubercles. Madreporite
smooth, flat, 3 mm. across.

Pedicellariae numerous but widely scattered abactinally, not on
the plates but on the papular areas with seldom more than one to an
area; the ^'alves and sockets are straight and narrow; each \'al\'e is
about 0.3-0.4 mm. long, markedly compressed, straight, terminating
in a sharp tooth nearly at a right angle to the valve itself; below this
terminal tooth are three or four much smaller and stouter, blunter
teeth; the sides of the socket are .somewhat irregularly serrate in the
drv condition but carrv no real teeth. Actinallv there are several
pedicellariae on the interradial areas and here and there on a papular
area on the rays, but the characteristic feature of the species is the
series of pedicellariae that lie on the adambulacral plates between the
furrow spines and the subambulacral spines; these pedicellariae are
somewhat larger than those of the abactinal surface but are otherwise
like them; for the most part they lie end to end in a single almost
continuous series placed on a fleshy ridge or fold of skin close to the
subambulacral spines, but there are many scattered pedicellariae
also, usually lying at more or less of an angle to the ridge or squarely
across it, and in many places the ridge disappears or is very indistinct;
there is no ridge and there are few pedicellariae on the distal third of
the ray.

Adambulacral armature as usual in two series; furrow spines in
pairs, subequal, about three or four times as long as wide and about
once and a half as wide as thick, with slightly rounded tips, con-

ECHINODERMS OF CHALLENGER BANK, BERMUDA. 357

nected together by a thin membrane without granules on either sur-
face. Subambulacral spines conspicuous, stout, shghtly flattened,
with bhmt tips, about 2 mm. long and not quite a millimeter thick;
there are half a dozen subambulacral spines on the first half dozen
adambulacral plates, but further out there is only one such spine to
each pair of adambulacral plates, or occasionally the ratio is one to
three. Oral plates concealed; oral angles with half a dozen marginal
spines on each side, and several pedicellariae and two stout suboral
spines (one on each plate) on the surface. Color light yellowish-
brown without any markings. The specimen is now without any
trace of the color the sea-star had in life.

Holotype, M. C. Z. No. 2758. Bermuda: Challenger Bank, 303^
fms. Aug. 1, 1903.

This is one of the most clearly marked members of the genus, not
at all like the other West Indian species. The small skeletal plates
and unusually large papular areas give it a characteristic facies, while
the size, form and arrangement of the pedicellariae are also very dis-
tinctive. As no species of Ophidiaster has been found north of south-
ern Florida, not even in the Bahamas, the occurrence of this fine new
form on the Challenger Bank is of exceptional interest.

Stephanasterias gracilis.

Asterias gracilis Perrier, 1881. Bull. M. C. Z., 9, p. 4.

Stephanasterias gracilis Verrill, 1899. Trans. Conn. Acad., 10, p. 223; 1915,
Bull. Univ. Iowa: Nat. Hist., 7, p. 25; pi. IX, figs. 2-2e.

This is a very small sea-star, the largest specimen of the more than
sixty in the M. C. Z. having R only 20 mm. and the great majority
of the specimens are much smaller than that. It has been recorded
from numerous stations in the West Indian region in from 56 to
270 fms., l)ut it has never been reported from so far north as the
Bermudas nor from such shallow water as that which covers the
Challenger Bank. There are four specimens, however, in the collec-
tion made by the party of 1903, and the depth at which they were
taken is recorded as 303^^ fms. They are all very small and as usual
in the species, they show great diversity in form. The largest has
three arms with R = 9 mm. while the three on the other half of the
body has R = 5-6 mm. A second specimen has the arms 9, 8, 7, 5, 4
and 4 mm. long, the three longest opposite the three shortest. A third
specimen has three arms about 7 mm. long and on the other side,
three about 13>2 i^ini- The smallest specimen has but three arms.

358

CLARK.

each about 5 mm. long, and there is no evidence as yet of new arms
forming. Of course, these pecuharities are due to the autotomous
asexual reproduction, characteristic of the genus. There is no clue
to what the color in life mav have been.

Stolasterias tenuispina.

Asterias tenuispina Lamarck, 1816. Anim. s. Vert., 2, p. 561.
Asterias (Stolasterias) tenuispina Sladen, 1889. Challenger Asteroidea, pp.
563, 583.

This species has long been known from Bermuda, where it is de-
cidedly the most common sea-star, so its occurrence on the Chal-
lenger Bank is not surprising. It is worthy of note, however, that
the specimens collected in 1903 are all very small, the largest of the
five being only 13 mm. across its six arms. One has seven arms,
while the smallest, which is obviously the result of a recent autoto-
mous division, has but three.

Coronaster briareus.

Asterias briareus Verrill, 1882. Amer. Jour. Sci., 23, p. 220.
Coronaster briareus Verrill, 1914. Monograph of the Shallow-water Starfishes
of the North Pacific Coast, p. 49.

The occurrence of this rare sea-star on the Challenger Bank is not
surprising, as it has previously been recorded both north and south of
that latitude and has been taken at least once in quite as shallow water.
Nevertheless the specimen in the present collection is notable, for it
is not only of unusually large size but it has an extraordinarily large
number of arms. There are six arms on one side of the disk, 110-125
mm. long, while on the other side are two sets, one of five and one of
four arms, 10-16 mm. long. The inner two arms of the set of five lie
somewhat above the inner arms of the set of four, as though one series
overlapped the other. Verrill says the "rays" are "variable in num-
ber, ten to twelve in the larger specimens; one of the larger has the
radii 8 mm. and 76 mm.; ratio 1 : 9.5." (1915, Bull. Univ. Iowa: Nat.
Hist., 7, p. 31). In the present 15-rayed individual, the lesser radius
is about 8 mm. Since the greater radius is 110-125, the ratio is some-
thing like 1 : 13-16, or as it is more usually expressed R = 13-16r.
The color of the alcoholic specimen is the usual yellowish of bleached
material and there is no indication of what the color may have been
in life. Perrier's figure -of C. ixirfaiti (1894, Trav. et Tab, Stell., pi.

ECHINODERMS OF CHALLENGER BANK, BERMUDA. 359

VIII) shoAVS that species to be conspicuously red. Professor Nutting
in his Narrative of the Bahama Expedition (1895, BuU. Univ. Iowa:
Nat. Hist., 3, p. IGS) is enthusiastic over the beauty of the Coronasters
collected, but says never a word as to the color!

OPHIUROIDEA: BRITTLE-STARS.

Ophiomyxa flaccida.

Ophiura flaccida Say, 1825. Jour. Acad. Nat. Sci. Philadelphia, 5, p. 151.
Ophiomyxa flaccida Liitken, 1859. Add. ad hist. Oph., pt. 2, p. 79.

This common West Indian brittle-star is well known from several
Bermudan stations. It was taken on the Challenger Bank by the
Challenger in 32 fms. but was not met with by the party from the
Bermuda Biological Station.

Ophiactis savignyi.

Ophiolepis savignyi Miiller und Troschel, 1842. Sys. Ast., p. 95.

Ophiactis savignyi Ljungman, 1867. Ofv. Kongl. Vet.-akad., Forh., 23, p. 323.

The occurrence of this ubiquitous tropicopolitan brittle-star at the
Challenger Bank is quite natural. Indeed, it would be extraor-
dinary if it did not occur there. Yet its presence is indicated by
only a single small specimen taken in 1903.

Ophiothrix angulata.

Ophiura angulata Say, 1825. Jour. Acad. Nat. Sci. Philadelphia, 5, p. 145.
Ophiothrix angulata Ayres, 1852. Proc. Boston Soc. Nat. Hist., 4, p. 249.

This common West Indian brittle-star, which Verrill (1900, Trans.
Conn. Acad., 10, p. 585) lists as "not common" at Bermuda, was taken
at the Challenger Bank by both the Challenger party and the
one from the Bermuda Station. Lyman says nothing whatever
as to the specimens taken by the Challenger, but those taken by the
party in 1903 represent two quite distinct varieties:

Ophiothrix angulata Aar. phoinissa.

H. L. Clark, 1918. Bull. M. C. Z., 62, p. 317.

A single individual of this form was taken. It is 5 mm. across
the disk and the uniformly deep red color is perfectly evident, though

360 CLARK,

lighter in the dry specimen than it is in hfe. The variety has previ-
ously been reported only from Cuba and the Tortugas.

Ophiothrix angulata var. poecila,

H. L. Clark, 1918. Bull. M. C. Z., 62, p. 319.

There are four quite typical examples of this variety, all dry and
showing the usual variegated coloration well. A fifth and larger
specimen, 6 mm. across the disk, is in alcohol, and has lost all dis-
tinctive coloration, but the disk-covering and arm-spines and plates
are as in the smaller specimens. As there is no indication of a white
longitudinal stripe on the arm, it seems best to consider this specimen
also as poecila, although it is not at all unlikely that it represents the
red-orange form which I have called var. phlogina (1. c, p. 318).

Ophiothrix suensonii.

Liitken, 1856. Vid. med., p. 16.

This very handsome and easily recognized species was taken at the
Bank by the Challenger and again by the party from the Bermuda
Biological Station. The latter secured four specimens, of which the
largest is 7 mm. across the disk and has the arms over 50 mm. long.
Verrill (1900, Trans. Conn. Acad., 10, p. 585) reports that this species
was taken by G. Brown Goode at Bermuda, but it is more than likely
that the specimen secured by Goode was from "off shore." For
neither Verrill himself, nor the New York University parties, nor the
Bermuda Biological Station collectors (and they have been many!)
nor myself, have ever found suensonii at Bermuda.

Ophiocoma pumila.

Liitken, 1859. Add. ad Hist. Oph., pt. 2, p. 141.

A single very small 6-rayed specimen with disk about 4 mm. across
was taken in 1903. As the species is very common at Bermuda, it
would be strange indeed if it did not occur on Challenger Bank.

Ophiocoma riisei.

Lutken, 1859. Add. ad Hist. Oph., pt. 2, p. 141.

This species is also common at Bermuda and hence its occurrence
at Challenger Bank would be expected. But the only specimen as

ECHINODERMS OF CHALLENGER BANK, BERMUDA. 361

yet known from there is a very young one (disk about 3.5 mm. across)
taken by the 1903 expedition. The contrast in appearance between
this specimen and the young pumila just listed is very striking and
one finds it hard to consider them congeneric. For in pumila the
arms are rather short and stout with short, basally thickened arm-
spines and the disk has its scales pretty completely concealed under
the covering of elongated granules; whereas in riisei, the arms are
long and slender, with long, slender arm-spines, and the disk carries
no granules but is covered by a well-marked coat of scales. In both
cases, however, one is strongly reminded of the Ophiacanthidae and
it is only from the presence of evident dental papillae, and the char-
acter of the tentacle-scale, that the relationship, to the Ophiocomidae
can be deduced.

ECHINOIDEA: SEA-URCHINS.

Stylocidaris affinis.

Cidaris affinis Philippi, 1845. Arch. Naturg., Jhg. 11, 1, p. 351.
Stylocidaris affinis Mortensen, 1909. Ech. Deutsch. Stidpolar-Exp., p. 52.

The occurrence of this cidarid at Challenger Bank is of great
interest as it extends the known range of the species very considerably
to the northeast, so far at least as the western side of the Atlantic
is concerned. As affinis occurs in the Mediterranean, and probably
at the Cape Verde Islands, its occurrence near Bermuda helps to
bridge the gap between the West Indian and European areas. The
specimen taken by the party in 1903 is only 10 mm. in diameter and
has the primary spines only about 15 mm. long, but its identity seems
to be beyond cpestion.

Centrechinus antillarum.

Cidaris {Diadema) antillarum Philippi, 1845. Arch. Naturg., Jhg. 11, 1, p. 355.
Centrechi?ius antillarum H. L. Clark, 1918. Bull. Lab. Nat. Hist. Iowa, 7, no. 5,
p. 24.

Two very young individuals were taken in 1903. They are about
8 mm. in diameter with primary spines about 16 mm. long. The
general color is quite different in the two, one having the primaries
light claret red, rather indistinctly banded with whitish, while the
other has them whitish distinctly banded with pale brown.

EXPLANATION OF PLATE I.

Figure 1. View of actinal surface of Ophidiaster schismochilus sp. nov. Holo-

tjTie. Natural size.
Figure 2. View of abactinal surface of the same specimen. Natural size.

Clark — Echinoderms Challenger Bank.

Plate I

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57-14

Proceedings of the American Academy of Arts and Sciences.

Vol. 57 No. 14— Jtjne, 1922.

ATMOSPHERIC ATTENUATION OF ULTRA-VIOLET LIGHT.

By E. R. Schaeffer.

With One Pi ate.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 14.— June, 1922.

ATIVIOSPHERIC ATTENUATION OF ULTRA-VIOLET LIGHT.

By E. R. Schaeffer.

With One Plate.

Investigations on Light and Heat made and published with aid from the

RuMFOHD Fund.

ATMOSPHERIC ATTENUATION OF ULTRA-VIOLET LIGHT.

By E. R. Schaeffer.

Received March 29, 1922. Presented by Theodore Lyman.

Synopsis.

Absorption of ultra-viold light by the loiver atmosphere. — Photographs
of the spectrum of a Cd spark, in the interval X.3o00-2500 were taken
from several stations where the air path ranged from 160 to SOOO
meters. The apparent absorption for the shorter wave-lengths was
very marked as the distance between the source and the spectrograph
increased. A method of photographic photometry, similar to that
devised by Stetson to determine stellar magnitudes, was used to
measure the changes in relative intensities of the lines as the air path
was increased. The values of the relative intensities of the spectral
lines were plotted with the curve for molecular scattering computed
from the Rayleigh formula. The results agree with Strutt's work in
showing that the ozone concentration in the lower region of the
atmosphere is negligible but molecular scattering will not explain the
magnitude of the effect as has been previously supposed. The
absorption of light in this region of the spectrum by long columns of
oxygen and loss b}^ ionization of the air may account for the observed
attenuation.

Introduction. — It has long been known that the ultra-violet solar
spectrum ends c^uite abruptly near X2900. Cornu ^ found that the
limit depended upon the altitude of the sun and concluded that the
earth's atmosphere was the cause of the apparent absorption. On the
assumption that the concentration of the absorbing material did not
change with altitude, Cornu calculated the amount the spectrum
should be extended with increase in altitude. He then made observa-
tions at several stations from sea-level to a height of 2560 meters and
obtained experimental results in accord with this amount.

About the same time Hartley ^ was studying a number of gases to
get information on absorption spectra. He photographed ultra-violet
spectra after the light had been transmitted through measured quanti-
ties of gas at atmospheric pressure. The oxides of nitrogen, CO2,

1 Cornu, Journ. de Physique, 10, 1881.

2 Hartley, Journ. Chem. Soc, 39, 1881. Nature, p. 475, 1889.

366 ^ SCHAEFFER.

NH3, H0O2, and water vapor showed no appreciable absorption in this
region even in far greater quantities than occur in the atmosphere.
Ozone, when very dilute, showed an absorption band of great intensity
extending from X2S50 to X2320. The limit of transmission was finally
restricted to X3160 in presence of greater quantities of the gas. Hart-
ley concluded that ozone in the atmosphere is the absorbing factor
which accounts for the limit of the solar spectrum, since he found an
indication of ozone in free country air. He also presented some
■evidence to show that the concentration of ozone at higher altitudes is
;greater than at sea-level.

In repeating Cornu's experiments on the limit of the solar spectrum,
Miethe and Lehmann ^ found no change in the ultra-violet limit when
the altitude Avas varied by 4500 meters. ^Yigand,* taking special
precautions to prcA-ent fog on the photographic plate, took the ap-
paratus used by jMiethe and Lehmann to an altitude of 9000 meters
in a balloon. Confining his attention to the last trace of light action
recorded on the plate, he found the limit to be X2896 and the difference
in the limit at this great altitude and at Halle, near sea-level, to be
inappreciable.

In view of these conflicting results, it seemed worth while to investi-
gate the absorption of long columns of air near the earth's surface,^
for under these conditions the uncertainties as to the composition of
the absorbing layer are largely eliminated. Work was begun in 1916
but suffered several unaA'oidable delays. During the progress of the
research Strutt ^ published the results of his investigations on the same
subject; the conclusions arrived at in this paper do not materially
differ from his, but the author was able to express the magnitude of
the effect in quantitative terms and to show that molecular scattering
does not explain the observed absorption.

In the present investigation the spark spectrum of Cd was photo-
graphed through columns of air from 160 meters to 8000 meters. By
comparing the measured opacities of the plates thus obtained with the
opacities produced in the laboratory when the air path was small, the
changes in the relative intensities of the principal Cd lines in the ultra-
violet were obtained. These changes in intensities give a measure of
the absorption due to the column of air under examination. i\.s the
results did not point to the presence of ozone as the dominating factor

3 Miethe and Lehmann, Ber. Preuss. Alvad. Wissens., 8, p. 268, 1909.
4Wigand, Physik. Zeits., 14, p. 1144, 1913.

5 Lyman, Monthly Weather Review, 42, 8 August, 1914.

6 Strutt, Proc. Roy. See, London, 94A, p. 260, 1918.

Schaeffer: — Atmospheric Attenuation of Ultra-Violet Light.

Plate 1.

Tsur
issr

3i

tf

(-1

_ if = c ^ 2

b£

O

HHi^x'o.SS

-^-^ f-H

<u

<B

<D

o '^

;_

b

^

= ^

3

D

3

CG

73

M

X -'

O

o

O

P.2

X

a

X

o

6 S

_g

G

_c

^ -^

'5

r-

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<N

O
CO

CO

o

^

Proc. Amer. Acad. Arts and Sciences. Vol. 57.

ATMOSPHERIC ATTEXUATIOX OF ULTRA-VIOLET LIGETT. 367

and as the effect of scattering may well be important, these relative
intensities were plotted with the computed curves for molecular
scattering. The details of the procedure follow.

Procedure. — Over a hundred photographs of the ultra-violet spec-
trum of a Cd spark were taken between January 191G and November
1917, at varying distances from the source. Nearly all the work was
done on the clearest nights so as to avoid the long exposures caused by
haze. The spark between Cd terminals in parallel with a suitable
capacity was produced by a half kw. transformer on a 60 cycle, 110
volts circuit. The apparatus for photographing the spectra con-
sisted of an objective prism arrangement, — a box containing a large
60° quartz prism, a quartz lens about S cm. in diameter, of approxi-
mately one meter focal length, mounted directly back of the prism,
and a holder for the photographic plate. An open tube about 60 cm.
long, 10 cm. in diameter was mounted in front of the prism and
several diaphragms were inserted along the path of the light to prevent
stray radiation from reaching the photographic plate. A small
telescope was attached permanently to the box to aid in getting the
apparatus in line with the distant source. The adjustment, once
made, was not changed until a number of photographs had been taken.

The images are recorded as small spots as shown in the accompany-
ing photographs. (1) shows the spectrum of the Cd spark X3612-
X2573 through 160 meters of air obtained by a 10 seconds exposure.
(2), (3), and (4) were all taken on the same plate on an exceptionally
clear night through 2300 meters of air, the exposure being 15, 30 and
60 minutes respectively. A number of exposures were then made
through an air path of SOOO meters. On several plates of 4 hours
exposure X2573 was recorded through this long path of air but the
images were very faint. Strutt has already published photographs
of mercury vapor spectrum through about 6500 meters which show the
same result.

Although many photographs werQ. taken, only a few nights in a
year are really satisfactory for this work. A short rain followed bv a
dry Northwest wind seemed to leave the air in the best condition.

A large number of exposures were made in the laboratory also with
an air path of two or three meters. The same plate, Seed 30, emulsion
15511, and the same development were used throughout the work.
By using a diaphragm in the collimator the exposure times as well as
the opacities given in (2), (3) and (4) were approximately reproduced.
In the case of plates for the five mile air path, it was found that the less
refrangible end of the spectrum was over-exposed so badly in order to

368 SCHAEFFER.

get a record of the shorter wave-lengths, that no satisfactory measure-
ments of opacities could be made on them, except for a very limited
range of wave-lengths. The opacities in this case for X3404 were con-
siderably greater than for the same wave-length recorded through
2300 meters of air while for X2748 and X2573 the opacity was much less
than for that wave-length recorded through the shorter distance.
However, the plates for the 2300 meters distance give quite a definite
idea of the effect. These exposures were taken with the spectograph
at Jefferson Physical Laboratory and the source of light at the Chapel
at Tufts College.

The decrease in intensity for the shorter waves may be seen by
comparing the opacities of the plates for the different spectral images
obtained with a long air path, with the corresponding opacities pro-
duced when the air path between the source and the plate is negligible.
If /i is the intensity of the light which reaches the photographic plate
for a gi\'en wave-length Xi, and I-i, the same for light of shorter wave-
length Xo, then the ratio iJh for the case with a long air path is less
than the same ratio for a short air path. The ratio is different be-
cause the apparent absorption is greater for the shorter wave-lengths.
This can easily be seen by direct comparison of exposures (1) and (4).
If i? = h/Ii is the ratio of the intensities of these two lines as produced
in the laboratory when the air path is negligible, and IV = I'ljl'i is the
ratio for the long air path, then /?'//? gives the relative intensity of the
light of shorter wave-length after passing through the long column of
air, compared with the intensity of Xi. This ^alue of R' IR was de-
termined from the opacities produced on the photographic plates for
the principal lines in the ultra-violet spectrum of Cd, X3404 being used
as the standard. The absorption for light of wave-length greater
than X3404 was found to be small and this line was most suitable since
the opacity of the silver deposits for this wave-length was not too great
to be easily measured.

Photometric mctJiod. — The notation generally accepted in photo-
graphic photometry '' is used in this paper. Z) = log 0, D = K log
E and E = It^ where D is the density of silver deposit, 0 the opacity,
K a constant, E the exposure, I the intensity of the light which acts
for / seconds and j^ is a constant.

The opacities were measured with Dr. Stetson's ^ apparatus for
determining stellar magnitudes. In this apparatus the photographic

7 Sheppard and Mees, Investigations on the Theory of the Photographic
Process, (Longmans), p. 45.

8 Stetson, Astrophysical Journal, 43, p. 253, 1916.

ATMOSPHERIC ATTENUATION OF ULTRA-VIOLET LIGHT. 369

plate is placed emulsion side down over a small diaphragm, through
which light passes from a standard source. The light is then brought
to a focus on one junction of a Bi-Ag thermo-couple connected to a
sensitive galvanometer. The deflections of the galvanometer, when
the diaphragm is covered by the spectral image and when it is covered
by the clear plate near the image, give a means of eliminating the effect
of fog on the plate and of getting a quantity proportional to the ca-
pacity.

If d is the galvanometer deflection when the image is over the

diaphragm, and d' the deflection for the clear plate, then = — j, —

(-1/

is proportional to the opacity, cb = O. The density of the silver

deposit, D = log 0, is proportional to the logarithm of the exposure,

1

D = K log E. So we have (cS)'^ = E. Within certain limits we may
write E = It^ where ^j is a quantity which must be determined by
experiment, as it is a factor of the plate and over any considerable
variation of / is by no means constant. Over the range of time and of
wave-lengths used p was found to be approximately 0.92.

In order to determine the range over which the densities were pro-
portional to log time, the values of 8, from the galvanometer readings
for X3404 taken from a number of plates made in the laboratory, were
plotted against log t, where t varied from one to thirty minutes. It
was found that between 5 = 0.30 and 8 = 0.65 for this wave-length
the curve was practically a straight line, the complete curves resem-
bling the familiar D, log E curve. Similar curves were made for the
spectral images of the other Cd lines. Since 8 = 0.50 falls very near
the middle of the straight portion of each of these curves, the corre-
sponding values of log t necessary to produce this particular value of 5
for the different wave-lengths, give a means of calculating the intensi-
ties of the Cd lines. Of course the spectral sensitivity of the plate
enters into the problem here. If the time required for X3404: to regis-
ter 8 = 0.50 is taken as a standard, then the time required for X2S81
to register 8 = 0.50 must contain a factor a which depends upon the
change of sensitivity with wave-length. For the same values of 8,

since (cS)* = It^, we have for two different spectrum lines R = hj I\ =

"ry ) gives the transmission of Xo through

f 2 fl/

a long column of air compared to the transmission of Xi as a standard.
Since only ratios are desired, the factor a expressing the spectral
sensitivity of the plate drops out.

370

SCHAEFFER.

In the ratio R'/R =

, /i is the intensity of X3404

for the exposures in the laboratory where the radiation suffers no
appreciable absorption, I\ the intensity of X3404 after passing through
2300 meters of air, and h and I'2 are in turn the corresponding in-
tensities for the lines X3250, 2981, 2881, 2748, and 2573.

Molecular scaticring. — It will be shown below that ozone absorption
has little if any effect on I'l and I'l but it is known that molecular
scattering plays an important part. The problem of the scattering
of light by small particles was studied by Lord Rayleigh more than
forty years ago. If h is the initial intensity of the light, then the
intensity, i, after passing through a scattering medium of thickness x is
given by the equation i = ?o c~^^, where K is the coefficient of scatter-
ing. Rayleigh first calculated the value of K on the basis of the elastic
solid theory and found,

?,2tvHix - If

K =

ZN\'

where ^i is the index of refraction for the light of wave-length X, and A^
is the number of particles per cubic centimeter of air at N.T.P. The
same result was obtained by Rayleigh ^ later from the electromagnetic
theory, and Schuster ^° and recently King,^^ by quite different
methods, have also arrived at this result. The formula has been
tested experimentally by several investigators and found satisfactory.
The observations of Dr. C. G. Abbot ^^ on the intensities of sunlight
at Mt. ^Yilson and at Washington, D.C. agree very well with the
values calculated for molecular scattering according to the above
formula.

It is necessary then to correct the intensity of the standard after the
light has passed through a considerable layer of air. Using the
Rayleigh formula, the calculated amount of scattering for light of
wave-length X3404 is 16% in the air path under consideration. Conse-
quently, the value 0.84 is taken as the intensity of X3404 after passing
through 2300 meters of air. For instance, consider a line of shorter
wave-length whose intensity appears to be equal to the standard when
the air path is small, then if the measured opacities show this line to be

9 Rayleigh, Phil. Mag., 47, p. 375, 1899.

10 Schuster, Theory of Optics, p. 325.

11 King, Phil. Trans. Roy. Soc, London, 212A, p. 375, 1913.

12 Abbot, v. (10). Ann. Astr. Abs. Smithsonian Inst. 2, p. 113, 1908.

ATMOSPHERIC ATTENUATION OF ULTRA-VIOLET LIGHT. 371

one-half the intensity of X3404 after passing through a long column of
air, the intensity of the line of shorter wave-length is taken as one-half
of 0.84. The results obtained in this way are plotted in Figure 1 with
the computed curves for scattering.

Figure 1. The lower curve shows the effect of molecular scattering calcu-
lated from Rayleigh's formula for an air path of 8000 meters at N.T.P. — an
equivalent to the earth's total atmosphere. The upper curve shows the same
for an air path of 2300 meters at N. T. P. The points plotted between these
curves were obtained from the measured opacities of the spectral images.

The decrease in intensity for the shorter wave-lengths, as found in
my experiments, is very marked. In view of the results obtained by
Fabry and Buisson ^^ on the absorption of ozone and the recent work
by Fowler and Strutt ^* on the absorption bands in the ultra-violet
spectra of the sun and a number of stars of different spectral types,
this deviation from the scattering curve can hardly be attril)uted to
ozone absorption. The Cd lines X2748, 2573 and 2313 seem normally
to have about the same intensity. X2o73 lies very near the maximum
of the great absorption band of ozone in the ultra-violet region, — a
path of 1.2 cm. of 1% ozone suffices to absorb it completely, while
X2748 and X2313 are only slightly diminished. If atmospheric ozone
were the chief factor in the apparent absorption, indicated by a long

13 Fabrv- and Buisson, Comp. Rend., 156, p. 782, 1913. Journ. de Phy.sique,
3, p. 196, 1913.

14 Fowler and Strutt, Proc. Roy. Soc, London, 93-\, p. 577, 1917.

372 SCHAEFFER.

air path, X2313 would be shown stronger than X2573. In no case did
this occur. Photographs taken for the five mile distance agree with
the work of Strutt in showing that a concentration of ozone in the air
near sea-level greater than 10"^ is improbable. Chemical determina-
tions give results over a thousand times this amount, but the difficul-
ties of such determinations are very great and the data given by
several observers differ widely.

Evidently, the problem of the effect of our atmosphere on ultra-
violet light has been resolved into two parts. The first calls for an
explanation of the abrupt termination of the solar spectrum in the
ultra-violet, the second calls for an explanation of the deviation of the
intensity of a distant terrestrial source from the curve calculated from
a consideration of molecular scattering.

Properties of Ozone. — The limit of the solar spectrum is certainly set
by ozone absorption. From the chemical and physical properties of
ozone, there is reason to believe that there is a fair concentration of
that gas probably in the isothermal layer of our atmosphere where the
mean temperature is about —55° C and the pressure about 250 m.m.
Ozone is quite stable at this low temperature and although the sta-
bility decreases with decreasing pressure the effect is not very large
until the pressure ^^ is beloAv 100 m.m. It is also important to note
here that ozone is produced quite rapidly by light of wave-length
less than X2000, but is slowly recombined by light of longer wave-
length. Accordingly, light of waA'e-length less than X2000 coming
from the sun, forms ozone in the higher layers of our atmosphere.
This ozone should be found in higher concentration in the isothermal
layer since the conditions of temperature and pressure are the most
favorable there. ^^ Such a layer of ozone would account for all the
observed facts on the absorption of sun-light in the region above X2000.

The data collected by several observers on the ozone content at
varying altitudes ^'^ are in fair agreement in showing a gradual increase
up to 3600 meters. Pring ^^ gives average values obtained by sending
his apparatus up as high as 20,000 meters in Hydrogen balloons but
the results were hopelessly discordant. A greater percentage of the
heavier molecules as O3 should be found at the lower altitudes, but the
very rapid recombination of O3 into O2 at temperatures found near the
surface of the earth and the violent chemical action of ozone on or-
is von Bahr, Ann. d. Physik, 33, 3, p. 598, 1910.

16 Warburg, Ber. Preuss. Akad. Wissens., Berlin, 48, p. 1126, 1901.

17 Thierry, Comp. Rend., 124, p. 460, 1897.

18 Pring, Proc. Roy. Soc, London, 90A, p. 204, 1914.

ATMOSPHERIC ATTENUATION OF ULTRA-VIOLET LIGHT. 373

ganic matter would be certain to prevent an appreciable concentration
of that gas in the lower atmosphere.

Results. — The result of the present paper shows, first, that the con-
centration of ozone near the surface of the earth is negligible — as may
be expected from the properties of ozone given above; second, the
attenuation of ultra-violet light by the lower atmosphere cannot be
explained by atmospheric scattering alone. There are several other
agents which, no doubt, ha^'e some effect. The absorption by a long
path of oxygen, and the ionization of the air by the light of wave-
length under consideration deserve attention. Sulphur dioxide and
methane absorb ultra-violet light, but no data are at hand which show
the effect to be important for concentrations of these gases too small
to be detected easily by chemical means.

Little is known about the absorption of long columns of oxygen in
this region of the spectrum. The effect of oxygen on shorter wave-
lengths is well known; Kreusler ^^ found that a column of air 20 cm.
long absorbed about 9 per cent of the light at X1860, while he detected
no absorption at X1930. By compressing the gas in a tube, Liveing
and Dewar ^° extended the absorption band of oxygen into the longer
wave-lengths. In one experiment the spectra of the carbon arc and
of the iron spark were photographed through a tube 18 meters long
containing oxygen under pressure of 85 atmospheres. Under these
conditions the gas was found to be quite transparent for violet and
ultra-violet rays to about X2745. From that point, the light gradually
diminished, and beyond X2664 appeared to be wholly absorbed.

The mass of oxygen used in this experiment is approximately the
same as that traversed in a column 8000 meters long at N.T.P., but
the absorption is no doubt somewhat more at the higher pressure than
for an equal mass at a lower pressure. But the shoulder of the great
absorption band in the Schumann region may extend far enough into
the longer wave-lengths to affect the intensity of the light appreciably.

The formation of ions by the action of ultra-violet light on air may
be important. Bloch ^^ found that strong ultra-violet light of wave-
length greater than 1800 produced a certain ionization on inifiltered
air. Lenard and Ramsauer ^^ verified this, but found there was no
volume effect on the pure gases of the atmosphere and that the effect
on air containing dust depended upon the presence of moisture. No

19 Kreusler, Ann. d. Phvs., 6, p. 412, 1901.

20 Liveing and Dewar, Phil. Mag., 26, p. 286, 1888.

21 Bloch, Comp. Rend., 146, p. 892, 1908.

22 Lenard and Ramsauer, Sitz. Ber. d. Heidelberger Akad. 1910-1911.

374 SCHAEFFER.

results are at hand, however, which show the variation of such an
effect with wave-length. All that can be stated is that the photo-
electric effect on dust may cause part of the diminution of intensity
and the deviation from the scattering curve as recorded in Figure 1.

Concliusioii.—lt seems that (1) the lower atmosphere is practically
free from ozone, (2) molecular scattering alone will not account for the
attenuation of the shorter wave-lengths from distant terrestrial
sources, (3) absorption by oxygen and ionization of tiie air may ex-
plain the deviation from the curve for molecular scattering, (4) prob-
ably the isothermal layer of our atmosphere contains the ozone which
sets the limit of the solar spectrum in the ultra-violet.

My thanks are due Professor Lyman for many suggestions and for
his aid in securing suitable locations for conducting this work, and Dr.
Stetson for the use of his apparatus in measuring the opacities.

Jefferson Laboratory,

Cambridge, February, 1922.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 15.— June, 1922.

THE RATIO OF THE CALORIE AT 73° TO THAT AT 20°.

By Aknold Romberg.

Investigations on Light and Heat made and published with aid from the

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Vol. 57. No. 15.— Juxe, 1922.

THE RATIO OF THE CALORIE AT 73° TO THAT AT 20'^

By Arnold Romberg.

Investigations on Light and He^t made and published with md from the

RUMFORD Fu.ND.

THE RATIO OF THE CALORIE AT 73° TO THAT AT 20°.

By Arnold Romberg.

Received April 21, 1922.

Presented by P. W. Bridgman.

The present paper, publication of which has been deferred for
various reasons, describes an experiment designed as a crucial test of
the correctness of the temperature variation curve of the specific heat
of water. The desirability of such a test is apparent from figure 1,

which gives the results of some of the best researches on the subject,
and which shows the great discrepancies existing at the higher temper-
atures.^ The work was suggested by H. N. Davis, and carried out in

1 The task of finding from the published papers the reasons for the differ-
ences in these curves must be regarded as hopeless. In connection with the
excellent work of Barnes a possible sovu-ce of error may however be pointed out.
The heating current in Barnes's calorimeter is carried by a platinum wire
between copper terminals at which a certain amount of heat is absorbed and
liberated, respectively, due to the Peltier effect. The thermometers are
situated within these hollow terminals, and it is conceivable that an appre-
ciable error might result.

378 ROMBERG.

the Jefferson' Physical Laboratory of Harvard University, and to
Professor Davis is also due the distinctive feature of the method, as
will be pointed out below.

The method may be explained schematically by reference to the
diagram, figure 2. Hot water flows through a tube Fi containing
resistance thermometers Ti and T'l, the tube being in thermal contact
at C between these two points, with another similar system F2, in
which cold water is flowing. The two streams of water are made
equal. The thermal coupling C is variable; a device due to Professor
Davis, and of fundamental importance in giving the method its
advantage.

7;

WW

r/Q. 2.

With constant temperatures Ti, To, and flow/, readings are taken of
Ti—T\ or T'o—T2, and of (Ti— 7"i) — (T'o— T'a). This is repeated
for other values of the flow, and for other conditions of the thermal
coupling.

If there are no complications, and if Ti— T\ is small, the ratio of
the specific heats is

cj _ T'.- To
Co ~ 1\ - T\
and therefore

C2-C1 ^ iT,-T\) - jr.- To) ^ ^0
Co ~ 7'i- n ~Ai

Heat currents to and from the flowing stream at places other than C
may introduce errors in the thermometer readings. These errors may
be represented as

. ^ . _ -^JTi, T2) Depending upon the temperature variations
^ f of the water-supply.

o\ -) i — ^^^ ^^^^ ^^ cross-heat-losses proportional to the

' / temperature differences T'l — 2"i and 2^2— T'2-

i

THE 73° CALORIE. 379

3) dst = C{f, i) Due to differences in the temperature rise pro-

duced by the thermometric measuring current
in the dift'erent (resistance-) thermometers.

4) dit = ir(/) Due to the heat-equivalent of the work of

forcing the water through the tubes.

These errors will influence the quantity Ao= {Ti— T'l) — {T'2— T2)
by an amount

A + BX

dt = dif + 34 -I- ^3/ + ^4/ = -. + C + Tf'

The true value of {co— Ci)/c2 in terms of the flow and the measured
temperatures is therefore

C2- Ci _ X+ dt _ ^ 1
c-2 iAi Ai Ai

from which

'A + /iAA

Ao= {-^-^ - - ) Ai- - - 6' - W

If Ao and Ai be regarded as variables, this equation represents a
family of straight lines of slope

Co — ci B

from which (co— Ci)/c2 may be obtained by varying the parameter/.
If B is small, / need not be accurately known (in the work to be de-
scribed the B/f correction was of the order of .001). The ratio
(c2— Ci)/c2 has been assumed constant over the range of temperatures
employed. This assumption, not hazardous in the first place, is ex-
perimentally justified if the data for any one flow lie on a straight line.
That this was true within the limits of error of the data presented
below, appeared from the preliminary tests.

The temperatures Ti and T2, which are not changed, have no in-

' fluence on the changes in Ai or Ao, and are mere auxiliary temperatures.

The thermometers at these temperatures serve only to balance the

bridge, and to compensate automatically for any slight changes that

might occur in the water supply temperatures.

The measurement of the changes in Ai= Ti— T'l, or Ao= T'o— T2,
by determining the difference R\— R\, or R'2— R2 between a pair of
similar thermometers, to the required accuracy of one per cent, is not

380 ROMBERG.

difficult, and need not be discussed. The value of Aq or (Ti— T\) —
(T'o— T2) is measured as (i?i— R'l) — iR'2— R2) on a Carey Foster
bridge. The changes in Ao thus measured are in terms of a tempera-
ture scale defined by R\ and R'o in their respective temperature
regions. They may be subsequently expressed in terms of a single one
of the thermometers used, and finally reduced to the gas scale by
comparing this thermometer with one that has been tested for its
" delta." These reductions involve a determination of the differences
between the temperature coefficients of the thermometers Ti and T^,
and between one of them and T3, the thermometer whose "delta" is
known. There is no need of accurate knowledge of the resistance of
any thermometer in any unit, nor of the relative resistance of any pair
of them, nor of their temperature coefficients. Nowhere in the work
is there any need of knowledge of the heat loss, of the heat capacity
of the apparatus, or of the work of the flowing water. No absolute
precision measurement is required in the entire calorimetric work, and
but a single such measurement, that of the Callendar "delta" of one
of the thermometers, in the entire work.

The apparatus may best be described by following the course of the
water tlu-ough it. Water enters at A (see Fig. 3) from a regulating
valve from which it flows under a head of about eight inches, kept
constant by an overflow. It flows into a steam heater B, where it
boils. An arrangement not shown allows air to escape from the top
of this heater. The water is then cooled to about 80° by a cold water
circulation, and enters a coil of about 100 feet of 3/8" copper tubing
in the hot thermostat, w^here it is brought to the inflow temperature —
usually 78°. This temperature is kept constant by a regulator not
shown, which vaW be described later. From the thermostat the water
enters the thermometer tube Ti, which is lagged with wool, and is
placed in a 4" tube jacketed by the thermostat itself. It then passes
through a Dewar tube D, and a straight glass tube, into one of the
copper tubes of the thermal coupling, which consists of two tubes
coiled together in a double layer, in such a manner that the hot water
flows in alternate turns of each layer. It then passes up in tubes D'l
and r'l situated behind Di and Ti, and passes a second thermometer
inside the same jacketing tube. It then passes to the cooler, where a
tap-water circulation brings it to a temperature of about 12°. It then
traverses the cold thermostat coil, where it is brought to about 16°;
then the thermometer tube To, etc., and takes up in passing through the
second tube of the coupling a quantity of heat which may be con-
trolled by varying the amount of mercury in the bottom of the Dewar

THE 73° CALORIE.

381

flask protecting the coupling. Finally it flows out through the fourth
thermometer tube, to a pump which returns it to the constant-head
reservoir above A. Distilled water is used, and renewed from time to
time.

It was intended to choose the temperature so that the ratio of the
75° calorie to the 20° calorie might be obtained. The actual tem-
peratures chosen happened to be somewhat more easily handled with
the thermostats.

THERnOiTATi
Afl/D
CaI- CALORirrCTCR

The resistance thermometers contain about 33 ohms of No. 42
platinum wire, coiled in helixes of inside diameter .02", silver-soldered
to copper leads, which are passed in the shape of ril)bon \" wide be-
tween copper leaves of somewhat greater width, and 2\" long, from
which they are insulated l)y mica. They arc held between these leaves
by a tight winding of copper ribbon. The purpose of this arrangement
is to make certain that the leads come to the temperature of the ther-
mometer case, and to this end the copper leaves referred to are silver-

382

ROMBERG.

soldered into saw-cuts in the copper plug which joins the two parts of
the case. Compensating leads, carrying about | ohm of platinum, are
provided. Figure 4 shows the thermometer somewhat distorted, the
upper portion being drawn too short. These thermometers show
a temperature rise of .02 degrees with the measuring current of 3
milliamperes.

The thermostats, which contain about 6 cubic feet of water each,
are so lagged and heated that they would attain without automatic
regulation a temperature too low by perhaps a degree. Electric heat-
ing by bare-wire helixes with alternating current at 30 volts, controlled
by a toluol regulator, supplies the further heat needed. The tempera-
ture is thereby kept fluctuating about a mean, and the variations, of
perhaps .005°, are so smoothed out by the heat capacity and imperfect
conduction of the streams in the coils, as to keep these streams well
within .001° of the desired temperature.

- Copper teavei
Silver .5o'o/erca '"fo i'a**' ="

The regulators consist of about GO feet of \" copper tubing, closed
at one end, the other terminating in the top of a piece of half-inch iron
pipe 6" long, capped at both ends. Through this top extends also a
steel tube \" diam., to near the bottom of the pipe, where it is amal-
gamated with mercury. All joints are soldered. Mercury fills the
lower portion of the pipe; toluol the rest and all of the copper tube.
When the toluol expands, mercury is forced up the steel tube into a
glass capillary attached to its upper end, and there makes an electric
contact which operates a relay and circuit-breaker, stopping the heat-
ing current or introducing resistance. The purpose of amalgamating
the end of the steel tube is to keep the toluol from creeping. The
success of these regulators, whose task is made severe by the flow of
unthermostated water, is attributed to the close thermal contact of the
toluol with the bath, to the large quantity of toluol used, giving ample
sensitiveness, and to the generous size of the bath. No contact
difficulties were experienced, and no drifting of temperatures noticed.

Although the coils of the thermal coupling were made as symmetrical
as practicable, it was feared that when there was only a small quantity

THE 73° CALORIE.

383

of mercury present, any lack of complete symmetry might, by keeping
the mercury from taking on the true mean temperature, affect the
heat loss. A new coupling was therefore made, in which all of the
outer turns were cold. This certainly resulted in a temperature
distribution much more dependent upon the quantity of mercury
present. No influence on the data was found. A separate test
showed the heat loss from the Dewar flask to be so small that the
entire contents of the flask might have changed in temperature by five
degrees without afl^ecting the final result, the 73° calorie, by one part
in a thousand.

Two series of consecutive runs are given. A third series, tfiken
between the other two, is omitted, having been taken with a different
arrangement of the calorimeter, under unsteady conditions resulting
therefrom. Of the first series only the results are given. The last,
figures 5 to 10, is plotted in terms of the bridge readings. In this
series it was attempted to obtain readings for two flows, with two
temperature dift'erences for each flow, resulting in four groups of points.
No two points in any one group were. taken in succession. The im-
portance of this is shown especially in the data for figure 7, where the
points scatter widely. Reference to the data shows this to be due not
to erratic readings but to a gradual drift, leaving the result practically
unaffected. A is given in centimeters of bridge wire, this unit being
equivalent to about .016 degrees. The flows were 7.5 c.c./sec. and
15 c.c./sec, marked s and / respectively.

Data for figure 7.

Flow

Ao + const.

A2 cm.

s

19.93

132

s

9.77

570

f

7.33

577

f

17.85

90

f

S.29

514

s

9.90

512

s

17.14

163

s

9.24

520

f

8.66

492

f

17.61

92

s

l(i.25

169

s

8.02

529

s

16.70

176

f

17.77

100

f

S.31

503

I

i ■

ioa,-^-

Mo

--::;|||tTp

..:|-.>!5\.]-:4^.c..:' -,:^.--

THE 73° CALORIE.

385

The first column of figures gives the difference between the two read-
ings of a Carey Foster bridge. The second gives similar dift'erences
added to the small auxiliary resistances employed. These data are
plotted in figure 7, using A2 which was measured, instead of Ai.

, , A2 A2
Correction for this is made by multiplying the slopes by — = t —

Ai Ao — Ao,

which amounts to the addition of .0004 to the numerical values of the
slopes. Thus corrected, these slopes are —.0219 for the slow flow, and
— .0228 for the fast flow, giving —.0237 when the correction for 5//
has been applied. A further correction is applied to reduce this
result to the scale of a single thermometer, — it thus becomes —.0198,
the value which appears in its proper place in the table below. The
slopes have in all cases been obtained arithmetically, and may not be
in exact agreement with the plotted lines.

In the following table, a "set" consists of at least four points, —
one in each group. The first series of four runs, though comprising a
considerable number of points, is not entitled to as much consideration
as the last, because the points were not taken in regular order, and
often lie too close together. If the last six runs alone be considered,
and if they be weighted according to the number of sets in each
run, the mean is —.0201, which perhaps best represents the data.

Number of sets in

the run

(C2 — Cl) /C2

-.0191

.021

.0189

.0184

3

.0191

1

.0254

3

.0198

1

.0177

3

.0198

3

.0208

Had the previous data been included, counting each as a single set,
they would have reduced the result by two parts in ten thousand.
This figure needs but one further correction, that to the gas scale.
For this purpose use was made of Callendar's well-known formula

386 ROMBERG.

in which the quantity 5 is as yet unknown. A thermometer cali-
brated by the Bureau of Standards at ^Yashington was obtained, its 8
being given as 1.47 =t .01. By comparison of the two, the 8 of the
thermometer in whose scale these results are given was found to be
1.53. This value, when put in the Callendar formula, gives as net
corrections in the intervals of 17°-23° and 70°-76°, which were ap-
proximately the intervals used in the last series of runs, the values
—0.055° and 0.042° respectively, increasing Co— Ci/co from —0.0201
to —0.0040, whence the ratio of the specific heats Ci/co is 1.0040. In
its relation to the results of previous observers this is shown by a
circle on the 73° line of figure 1 .

The average deviation from the mean, of the last six runs weighted
as before, is 0.0007. The "probable error" is about 0.0003. The
error arising from the reduction of thermometer ?^ 5 to ^ 3 cannot well
be greater than 0.0002. A larger error might have crept in through
the 8 correction. If this be due to an error of 4% in 8, the change in
Ci/c2 would be a little less than 0.0007. In this connection it is to be
noted that the value 1.53 for 8 is within about 4% of the lowest value
ever found for platinum, and within 2% of the 5 values commonly
found. Since a decrease in 5 would result in raising the point plotted
in figure 1, no possible uncertainty in 5 could raise that point above
about 1.0047. If the "probable error," namely 0.0003, the estimated
limit of error from the thermometer comparison, namely 0.0002, and
the error due to a 2% uncertainty in 8, namely about 0.0003, be added,
the total uncertainty in Ci/co would be about O.OOOS. The root mean
square of these errors would be a little less than 0.0005.

It will be noted from figure 1 that the author's value, 1.0040, agrees
very closely with Dietrici's and fairly closely with that of Barnes,
which has been corroborated by Callendar. Bousfield's value, on the
other hand, lies close to the older work of Liidin and of Regnault, and
the formula of Jager and von Steinwehr, if extrapolated from 50° to 73°,
gives 1.0088, which happens to agree almost exactly with Bousfield.
These results fall, therefore, quite definitely into two groups, one of
which averages about half a percent higher than the other. Now it
happens that all four of the methods that led to the high results
involved the use of calorimeters containing a stationary pool of water
with a free surface,^ while of the four low values, three were obtained

2 The methods of Janke, Cotty, and BartoU and Stracciati are also of this
type, and their results also run high.

THE 73° CALORIE. 387

by continuous flow calorimetry and one by the use of water hermeti-
cally sealed in quartz capsules. This difference may be significant.
Unfortunately, however, although it suggests a number of possible
explanations of the discrepancy, no one of them, when examined
quantitatively, seems to give a correction term of the right order of
magnitude.

Sutnmary.

The work reported in this paper leads to the value

1.0040 ± 0.0005

for the ratio of the specific heat of water at 73° C. to that at 20° C.
This agrees more closely with the results of Dieterici, Barnes, and
Callendar than with those of Regnault, Liidin, Bousfield, and Jager
and von Steinwehr.

References.

Bartoli and Stracciati: Beibl. 1891, p. 761, 1893, pp. 638 and 1038.

Liidin: Diss. Zurich, 1895, Fortsch. d. Phys., v. 56, 11, 1903, p. 304.

Barnes: Phil. Trans. Roy. Soc. (A) v. 199, p. 149, 1902.

Dieterici: Ann. (4) 16, p. 593, 1905.

Janke: Diss. Rostock, 1910.

Cotty: Ann. Chim. Phys. (8) 24, p. 282.

Bousfield: Phil. Trans. Roy. Soc. (A) v. 211, p. 199.

Callendar: Phil. Trans. Roy. Soc. (A) v. 212, p. 1.

Jager and v. Steinwehr, Ann. (4) 64, 1921, p. 305.

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STUDIES ON INSECT SPERMATOGENESIS.

IV. THE PHENOMENON OF POLYMEGALY IN THE SPERM CELLS
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By Robert H. Bowen.

Fbom the Department op ZoStoav, Columbia. University.

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STUDIES ON INSECT SPERMATOGENESIS.

IV. THE PHENOMENON OF POLYMEGALY IN THE SPERM CELLS
OF THE FAJVIILY PENTATOMIDAE.

By Robert H. Bo wen.

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LIBRARY
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uaroen
STUDIES OX INSECT SPERMATOGENESIS.

IV. THE PHENOMENON OF POLYMEGALY IN THE SPERM CELLS
OF THE FAMILY PENTATOMIDAE.

By Robert H. Bowen.

From the Department of Zoology, Columbia University.

Received May 6, 1922. Presented by Edmuad B. Wilson.

Introduction.

In my preliminary "Study" on the formation of the hemipteran
sperm (Bowen '20), a summary was given of the occurrence of j^oly-
megalous spermatocytes and sperms in the Family Pcntatomidae, to-
gether wdth a brief statement of the processes by which the poly-
megalous sperms are differentiated. It is the purpose of this paper to
amplify my original account, thereby concluding the detailed descrip-
tion of hemipteran spermiogenesis which was begun in the second and
third articles of this series (Bowen '22a and b).

The material, as indicated by the title, was drawn entirely from
Hemiptera belonging to the Family Pcntatomidae. Illustrative mate-
rial has been drawn from a great variety of genera; but, as in my
second paper (Bowen '22a), the details of sperm formation were
worked out only in Murgantia histrionica Hahn, the testes of which
were fixed for one hour in strong Flemming and subsequently stained
with Fe-hamatoxylin and light green. For studying mature sperms
in their entirety, smears were made substantially in accordance with
the method of Faust ('13), osmic fumes, Gilson or Bouin being used
C^ for fixation, followed by Fe-hematoxylin, sometimes with a counter-
cj^ stain. In preparing these smears only the vas deferens was used, —
'^ a precaution which insures the exclusion of immature sperms. The
preparations examined for the occurrence of polymcgalij were fi.xed for
the most part in Flemming and stained in Fe-hematoxylin. Wherever
S^ possible, the comparisons of various cell elements were carried out on
r- such preparations, but for certain purposes it was necessary to employ
special methods which are indicated in the explanatory text accom-
panying the figures.^

1 For a more complete treatment of technical methods see Bowen, '22a.

I

392

BOWEN.

The carrying out of this study on a comparative basis was made
possible by the comprehensive collection of preparations of hemipteran
germ cells which Professor E. B. ^Yilson had accumulated during his
years of chromosome study. This entire collection he very kindly
placed at my disposal, and for its use I am greatly indebted to him.
I am further indebted to Professor Wilson for many valuable criti-
cisms, appreciation for which I wish to express in this place. I am
again indebted to Mr. H. G. Barber for the identification of much
material of my own collecting which was employed for checking and
other purposes.

Observations.

I. The Phenomena of Polymegaly.

Hemiptera of the Family Pentatomidae possess two compact testes,
presenting typically a rather oblong contour when seen in the proper
longitudinal section (Text-figs. lA and B). Each testis is enclosed in
a connective tissue sheath which is continued into the body of the
gland as septa or partitions dividing it into a number of compartments,
or, as I shall call them, lobes, arranged parallel to the long axis of
the testis. These lobes vary in number from three to seven (in the
forms examined by me, — see Table I), but for any particular species
the number is constant. The lobes are typically arranged side by
side in a single series (Text-figs. 1/1 and B), each lobe passing from
one side of the testis to the other (Text-fig. IC); but in some cases
{Perillus (= Mineus) bioculatus for example) a tendency for the lobes
of the testis to be bunched together is evident, and in Stiretrus an-
chorago, the serial arrangement is completely lost, all the lobes being
visible at one time only in cross-sections (Text-fig. IZ)). In a few
cases of this kind, some of the lobes appear to have arisen by the sub-
division of an originally single, typical lobe. In any case, the lobes
all open at one end into a common collecting chamber, from which
the efferent duct {d in the figures) of the testis is given off. In the
typical case, this duct arises laterally (Text-figs. \A and B), but in
Apatetici^s crocatus, for example, it is more nearly median, and in
Elasmostdhus cruciatus it is quite central, the testis spreading out fan-
wise like that of a coreid. Euschistus and Murgantia are good ex-
amples of the typical arrangement, and Text-figures \A and B give an
idea of the general topography as seen in longitudinal sections of the
testis of these bugs. It will be noted that the lobes differ in width,
and these differences are in general definite and specific ones, which

STUDIES ON INSECT SPERMATOGENESIS.

393

may be accompanied by still other peculiarities of constant occurrence
(see Montgomery '10). Within each lobe the cells are grouped in
cysts which are arranged as a rule in a double ^ series (as seen in
longitudinal sections like that of Text-figures I A and B) throughout
the length of the lobe, the various stages following one another in an
accurate series, beginning at the blind end of each lobe with spermato-
gonia. At any giAcn le\el the cysts of each lobe are in about the same
stage (the large spermatocyte generations introduce some discrepan-
cies) so that in a given testis it is usually possible to find in one lobe
or another every step in the spermatogenesis. When the cysts of

D

C

B

Figure 1. Structure of the pentatomid testis (xl8). Lobes numbered as
described in the text; r/, efferent duct. (Flemming;-hematoxylin). ^4, longi-
tudinal section of the testis of Euschistus scrrus; B, the same — Mtirgantia his-
trionicn; C, cross-section of the testis of Murgantia histrionica; D, the same —
Stiretnis anchorago.

completed sperms reach the open ends of the lo]:)es, the sperms are
emptied into the collecting chamber, whence they pass into the efferent
duct.

The occurrence of morphological differences between the lobes or
their contents makes some system of nomenclature desirable, whereby
reference may readily be made to any particular compartment in a
testis. For this reason I have adopted the plan ^ of numl)ering the

2 In large-celled lobes the cysts are often arranged in a single series.

3 This method of designation was used by Montgomery ('98) who appears
to have numbered the lobes quite arbitrarily, his numerical order being the

394 BOWEN.

lobes consecutively, reckoning the first on that side toward which the
efferent duct opens as lobe 1, lobe 2 the next, and so on, as indicated in
Text-figures 1/1, B and C. In certain special cases, e.g., Stiretnis
(Text-fig. ID) this plan can not be rigorously applied, and in such
cases, a more or less arbitrary numbering must, of course, be adopted.*

In 1898 Montgomery called attention for the first time to the fact
that in Evsckistus (probably tristicjmus and another species (Mont-
gomery '10), though both were referred originally to Pcntatoma and
Tropicoris) lobes 4 and 6 of the testis were characterized by the con-
stant possession of spermatocytes unusually large as contrasted to
those of lobes 1, 2, 3 and 5. In lobe 1, the spermatocytes averaged
slightly smaller than in those of lobes 2, 3 and 5, but the difference was
not considered significant. The structure of all the spermatozoa was
stated to be the same, though differences in size were inferred. This
peculiar polymorphism is not due to any of the known nuclear de-
rangem.ents, in fact the cells in all lobes are identical up to the synaptic
period. As the spermatocytes enter the growth period, however, the
nucleus and cytoplasm of those in lobes 4 and 6 increase in size very
much more than the others, resulting in characteristically "large"
generations. Nevertheless, in the reduction divisions all the chromo-
some plates are identical in composition and corresponding chromo-
somes are of exactly the same size regardless of the disproportion in the
sizes of the cells themselves. Montgomery was disposed to attribute
the greater size of the cells in lobes 4 and 6 to nutritional dift"erences
traceable to the blood supplies. He also noted some specific differ-
ences in the cytoplasmic structures to which reference will be made
elsewhere.

In 1910, ]\Iontgomery published a paper dealing in part with this
unusual "dimegaly," — as he now termed it,^ — including observations
on the mature sperm and further notes of a general nature. In this
paper he repeated his former statements as to the size relationships,
but now reported that in lobe 5 the spermatocytes were constantly
smaller ^ than in lobes 1, 2 and 3. No reference was made to his

reverse of mine. Some systematic method of orientation is, however, essen-
tial in examining many different species, and as the sperm duct is a constant
landmark 1 have found it convenient to number the lobes in relation to it. I
shall express Montgomery's findings in my own system of numbering, a fact to
be remembered in comparing with his original reports.

4 For other details of the structure of an hemipteran (Euschistus) testis,
reference may be made to Montgomery's papers, especially that of 1898.

5 I shall refer to the three sizes of cells as (1) large or unusually large, (2)
normal or small, and (3) smallest or unusually small.

STUDIES ON INSECT SPERMATOGENESIS.

395

earlier statement that a smaller generation occurred in lobe 1, an
inaccuracy due, perhaps, to a typographical error. His later descrip-
tion is certainly correct for Euschistus variolarius and E. euschistoides
and probably for all the other species of the genus as well. Mont-
gomery now considered the dimegaly as " due directly to differences of
the nurse cells of the different follicles, i.e., to degree of nutrition."

//

///

Figure 2. Outline drawings showing extent of nucleus and cytoplasm in
primary spermatocytes of the late growth period (xl450). (Flemming-
hematoxylin.) Row I, Murgantia histrionica; Row II, Euschistus variolarius;
Row III, Artelius niboptmciatus. Columns A, B, C, — cells of the smallest,
small or normal, and large generations respectively.

He also added definite proof of size differences in the heads of the
sperms, showing from sections that each of the three spermatocyte
generations gave rise to sperm the heads of which were likewise of
three sizes. That these general size differences are constant and not

396

BO'V\TN.

mere chance variations was proved by examina-
tion of 41 testes of E^ischistns sp., and 4 testes of
E. tristigmus, in all of which the conditions were
identical. Certain other pentatomids {Brochy-
mena, Perillvs, Nezara, Cosviopepla, Mormidea,
Trichoj^epla) were also examined, but in no case
did iSIontgomery find "such constant size differ-
ence," or at least it was "much less appreciable."
In his final paper on Evschishis, ISIontgomery ('11)
intimated that he had made further observations
on the phenomenon of "dimegaly" in Enschistus,
but these were never published and the subject
has not since been reexamined.

]My attention was attracted to this problem by
the discovery that in JShirgantia size differences also
occur, very much less conspicuous than in Etischis-
tvs, gi^■ing rise to cell generations of two sizes, — the
spermatocytes in lobes 1, 2 and 5 (Text-fig. IB)
being small or "normal," in lobes 3 and 4, some-
what larger. Text-figures 2-1 give an idea of these
size relations in the primary spermatocytes, which
may be compared with the corresponding cells of
Enschistus shown in Text-figures 2-II. It was
found subsequently that the expected two sizes of
sperms (Text-fig. 3) were formed by processes dif-
fering somewhat superficially, but as constant as
the dimegalous condition itself. These facts, taken
together, aroused the suspicion that this whole
phenomenon might not be so unique as ISIont-
gomery had thought, and I accordingly undertook
to make as complete a survey as possible of the
Family Pentatomidae with respect to this particular
point. Such an examination was made possible by
the fact that Professor Wilson's preparations, — re-
ferred to abo^'e, — included a large number of penta-
tomids of which the majority had received depend-
able identification. Mv results are tabulated in

Figure 3. Mature sperms from the vas deferens of
Murgantia hisirionica (x965). (Smear preparation; osmic
fumes-hematoxylin.) .4, from the small or normal gen-
J^ erations; B, from the large generations.

STTTDIES ON INSECT SPERMATOGENESIS. 397

Table I, into -w-hich some errors have doubtless crept through
insufficient material, accidents of sectioning, or doubtful s\-non\-my
of the generic titles, ^"here the material was ob\'iously insufficient
or unsatisfactory the fact is indicated by a dash, and doubtful
points are marked " ?." It should be added that, like Montgomery,
I ha\"e as a rule recorded size differences only when they were reason-
ably ob\-ious. In other words, a case like Murgantia in which the
size differences are shght, might be overlooked, especiall\- if the
material was not first class. Furthermore, I have made no special
effort to detect lobes in which the spermatoc^-tes are unusually
small. This was because the differences in this respect are by no
means striking, — in fact are often rather difficult to make out even in
Euschistus if the material is poor,— and the value of the results
seemed hardly commensurate with the labor involved.

The table gives in the first column the list of forms examined, the
nomenclature followed being that of Van Duzee ('17); in the second
column is given the number of lobes in the testis of a given species,
while the third and fourth columns give the index numbers of the lobes
in which unusually large or unusually small (where noted > cells occur,
these numbers being assigned in accordance with the plan pre\'iously
described (see Text-figs. lA and B). Comparisons were generally
made on spermatoc\tes in the late growth period, and exact observa-
tions on the mature sjjerm were usually impossible for ob^"iou5 reasons.

Examination of Table I shows at once that far from being a phe-
nomenon unique to a single genus, the spermatic polxTnegaly is widely
distributed in the Family Peniatomidae, and is in fact rather more
common than rare. ^Montgomery's original idea is therefore erroneous,
and his failure to detect differences in some of the other genera which
he examined for this point is rather puzzling. Thus in our common
species of Brochymena the difference is very striking, though Mont-
gomery reported a general equality for this genus. Possibly a clue
is to be found in the case of Stzara, in which no dimegaly occurs in
the northern sp^ecies, hilaris, but a very noticeable one in the southern
species, viridula. At the same time it is interesting to note that ^ an
Duzee ('17) has now placed these two sp)ecies in different genera,
Nezara and Acrosternum. Doubtless the form which Montgomery
examined was Acrosternuvi (= Nezara) hilaris, in which absence of
dimegalv is also indicated bv mv obser\'ations. Further, in a number
of known cases the identification of forms studied by Montgomery
('9S and '10) was not very critical, and the discrepancies may be due
in part to such errors.

398

BOWEN.

TABLE I.

To
a

•— CO

JZ 3

Classification of forms examined

s g u

* -=

(After Van Duzee '17)

La

" fc. ra

I>obes in
colls are
ally sma

Niiml
lobes i
testis

Lobes
colls a
ally 1

Fnmilv TENTATOMIDAE

Sulifainilv 77':AT.1 TOMINAE

Tiilie IIALYIM

Bruchtpnvna A-pustidata

7

4,6

Tribe PEN TAW MINI

1 'rribaht s I i ?)i bnlarius

6

0

Trichopcpla srm irittaia

7

0

Rhytidolomia saucia

6

3,5

" senilis

6

3,5

Chlorochroa uhlcri

6

3,5

Carpororis sp.

6

3?

Soluhca jmgnax

4

0

Euschisius scrnis

6

4,6

5

" euschistoides

6

4,6

5

" injlalus

6

4,6

5

" trisfi(piius

6

4,6

5?

" variolarius

6

4,6

5

" iciericus

6

4,6

5

Coenus dclius

6

4,6

5

Aelia atncrirana

7

-

Cosmopcpla biniaculaia

5

?

Tlujanta custaior

4

0

3?

" calccala

4

0

3?

" casta

6

3,5

Lnxa Jlorida

7

4,6

5

Miirgantia histrionica

5

3,4

0

" " (var. nigricans)

5

3,4

0

Nexara viridida

6

3,5

4

Acrostcrnum hilar is

6

0

Banasa dimidiata

3

0

" caha

3

0

Piezodorus guildinii

5?

0

Arrclivs alhopunctahis

6

3,5

4

Tribe EDESSINI

Edcssa bifida

5

2,4

SuUiimily AC ANTHOSOMINAE

Elastiws'ctlnis rruciatus

7

0

SuUamUy A SOPINAE

Stirrtnis anchorago

7

0

Periling bioridatiis

7

0

Enihiirhinichus Jloridanus

6

-

Apatcticvs crocaius

7

0

Podisiis uiaculivi'nfris

7

0

STUDIES ON INSECT SPERMATOGENESIS. 399

The results obtained do not appear to be susceptible of any logical
arrangement, for between species of the same genus, e.g., Thyanta,
great differences may occur. On the other hand, in Euschistvs the
differences seem to be similar (though perhaps varying somewhat in
amount) throughout the series of species examined. It is evident,
therefore, that no obvious and constant correlation exists between the
occurrence of polymegalous spermatocytes and generic relationships,
in which respect these cellular differences parallel the similar lack of
correlation between chromosome number and grouping, and external
characters which has now been observed in a number of cases. Never-
theless, it is a striking fact that among insects these particular differ-
ences occur only in this single family, so far as I know, and whatever
the cause of their origin may have been, it was doubtless the same for
all the cases. Possibly we have to deal with a case of parallel muta-
tion. In line with this apparently capricious occurrence of polymegaly
is the absence of any conspicuous regularity in the particular lobes
affected. On the other hand, there is a curious tendency for the lobes
with large cells to occur in pairs, the components of which are separated
by a third lobe which often contains the smallest generation of cells;
and, further, these large-celled lobes tend to be located on the side of
the testis opposite that from which the efferent duct takes it origin.
With respect to their comparative morphology, I have noted that the
large-celled lobes are frequently narrower than the others (see Text-
figs. IB and C), while the lobes with unusually small cells are occa-
sionally of exceptional size. There is, therefore, no direct relation
between the sizes of the lobes and the cells they contain.

One of the most interesting points brought out by this sin-vey is
that the degree of size difference may vary greatly in different genera,
so that a whole series might be arranged running in graded order from
the complete absence of this phenomenon, to very exceptional cases
of size difference. Thus in Banasa, Acrosternwn, and other genera
there seems to be no visible polymegaly; in Murgantia (Text-figs.
2-1) the difference, though small, is usually readily distinguishable,
but by no means striking; in Etischistus (Text-figs. 2-II) and
Brochymena the difference is conspicuous; while, finally, in Arvelius
(Text-figs. 2-III) it is truly extraordinary, the whole testis being
dominated by the generations of large spermatocytes beside which the
normal and smallest generations are completely dwarfed. This last
mentioned genus deserves special comment for in Arvelius the phe-
nomenon of polymegaly reaches its greatest development. In fact, the
volume of the large primary spermatocytes is something like eight

400 BO WEN.

times that of corresponding cells in the smallest generation. This
enormous difference is of special value in determining the size relations
of various cellular components and I huxe constantly taken advantage
of this unusual opportunity for critical comparisons. I should further
state that there is in Arvclins very good evidence of a fourth genera-
tion of cells occupying lobe 2, which are slightly larger than those in
lobes 1 and 0. ]\Iy insufficient material does not, however, allow a
definite statement on this point. It thus seems not improbable that
a pentatomid genus may be found in which each of the lobes would
differ from all the others in respect to the relative size of its cells. In
line with these connnents which refer particularly to the large genera-
tions, it may be added that rarely the smallest generations of cells are
distinguished by tiieir unusual size relations. Thus in Lo.ro Jlurida
the smallest cells are strikingly smaller than those of the normal and
large size.

(a) The effects of polymegaly on varioiis cellular constituents. — It
will be con\-enient here, before going on to an examination of the
size differences in the sperms, to consider in detail the possible differ-
ences in the spermatocytes and their maturation divisions which might
be dependent upon the size relationships of the cells in different lobes.

As Montgomery ('98) first showed, all the cells in all the lobes seem
to be in cAcry way identical and normal up to the period of synapsis
which directly precedes the so-called growth period of the primary
spermatocytes. The one marked difference is in the number of cells
which are in any one of these early stages. In the large-celled lobes
the cells are much less numerous than in the lobes with smaller cells
due apparently to the lack of room, the available space being much
curtailed by the larger size of the cells in later stages and by the added
fact that the large-celled lobes are often of markedly smaller volume,
as noted above. In the growth period the size differences (quickly
become apparent and the various generations of sizes become more and
more clearly marked, cAcry ^ cell being equally involved at any partic-
ular stage. The differential factor of growth seems to be one of quan-
tity only, rather than quality. It will be interesting to inquire into the
beha^'ior of the Aarious cell elements in large and small sperm cells.

6 I have not met with a single case of faihire to develop the polymegalous
inequalities customary for a given genus, and only one case (a specimen, No.
94, of Eutichistus) has been found in which all the cells were not affected to the
normal degree. In this particular case (which was also abnormal in some other
respects) scattered cysts occurred among the large generations (in both lobea
4 and G) in which the cells were all normal in size. Cysts of this kind were
found in primary spermatocyte, and spermatid stages. There was no clue to
their method of origin.

STUDIES ON INSECT SPERMATOGENESIS. 401

Respecting the general proportion between cytoplasm and nucleus
in the large- and smaller-celled generations, Montgomery was of the
opinion that the increase in size was due primarily to added cyto-
plasm and in a lesser degree to the volume of the nucleus. My own
observations, especially on Arvelius, do not bear out these conclusions
entirely, and while the nucleo-plasmic ratio seems to be slightly re-
duced in tlie large spermatocytes, I do not think that the reduction is a
particularly striking one. (Compare especially Text-figs. 2-111^1
and C and Figures 1 and 2.) More exact measurements of the nucleo-
plasmic ratios would be of interest, and they could readily be obtained
by computing the proper areas on many camera lucifla drawings by
means of a planimeter.

As to the contents of the nucleus, I agree with ]Montgomery that the
karyolymph, linin and plasmosome are increased in volume in the
large cells, but I can not corroborate his statement that, " the chroma-
tin nucleolus" (X and Y chromosomes) "is . . . larger in cells of the
large than in those of the small generation." This statement seems
to me doubtful. The plasmosome or true nucleolus is often stained
quite differently in the large and small cells, the result apparently of
differences in the rapidity of extraction (Figs. 1 and 2). With respect
to the most important constituent of the nucleus, the chromatin,
Montgomery pointed out that its amount was the same in all nuclei
regardless of size. This is indicated in part by the difference in
appearance of the large and small nuclei during the height of the growth
period, the former being relatively poorer in chromatin as indicated by
their 'clearness' (compare Figs. 1 and 2). As several workers have
shown, the diplotene threads resulting from synapsis, become spread
out in a "confused" way during the growth period, the separate chro-
mosomes being thus lost from view for a time. In the large cells this
confused state reaches a very advanced stage, while in the smallest
nuclei it scarcely gets a start. Indeed, it is possible that in such nuclei
(in Arvelius, for example) the threads could be followed through with-
out a break to the prophases of the first maturation division. The
unusual diffusion in the confused period in the large cells has brought
to light a very interesting phenomenon in connection with the be-
ha\ior of the sex chromosome nucleoli (thus far I have studied this in
Eusclmhis only) during the earlier part of this stage. These bodies,
which are usually stated to retain their definite, compact form (and
were so described by Montgomery '11), become broken up into groups
(of more or less definite individuality) of granular masses. These
may be arranged in a chain formation, or simply massed in an in-

402

BOWEN.

definite cluster. Subsequently they become reunited to form the
characteristic chromatin nucleoli of the later growth period. This
same phenomenon occurs also in the normal cells, but the tendency
toward diffusion is here less marked and the fragmentation of the
chromosome nucleoli correspondingly less conspicuous. Indeed, it
was not noted by Montgomery ('11), who merely states that the
contour of the nucleoli at this time may be "irregular." In this con-
nection Wilson's ('12) figures (figs. 100 c, d,f) of the granular structure
of the sex chromosomes (nucleoli) of Lygaeus in the growth period are
very suggestive.

Figure 4. Metaphase chromosome plates of the second maturation divi-
sion in Arvelius alhopunctatus (x3050). The hmits of the cytoplasm are indi-
cated by a simple line. (Flemming-hematoxylin.) A, from the smallest
generation; B, from the large generations.

Except for these minor differences in the extent of diffusion, the
chromatic history in all generations of primary spermatocytes is
identical, and when the maturation division figures are formed,
the chromosome plates are likewise identical. Arvelius furnishes
excellent material for the study of these stages. In this bug the be-
havior of the chromosomes is similar to that of Etischistns (see Mont-
gomery '11), the first maturation spindle having six autosomes with
separate X and Y chromosomes, while the second has a ring of six
autosomes enclosing an X-Y dyad. The latter is shown in Text-
figure 4. Not only are the chromosomes the same in number in all

STUDIES ON INSECT SPERMATOGENESIS.

403

cells, but specific ones which can be identified by reason of various
individual peculiarities can be readily recognized in both large and
small generations. Similarly, the metaphase plates are roughly alike
in area, though the chromosomes may be sometimes slightly more
spread out than at others. Such is the case in Text-figure 4A; but
other plates of the same kind are often more compact. The point of
importance is that the plates are of approximately equal extent
(absolute, not relative), so that regardless of the amount of cytoplasm
and the length of the spindle the chromosomes in the large spermato-
cytes form a metaphase plate essentially like the one they would have
formed in a cell of very much smaller volume (compare Text-figs.
4: A and B). On the other hand, the spindle lengths (measured from
centriole to centriole at metaphase) are approximately proportional
to the size of the cells. I have made a long series of measurements
(with a filar micrometer) of the spindles in Arvelius, with the results
shown in Table II. Examples from the large cells were scanty, but
sufficient to establish the general proposition beyond question. Fin-
ally, and perhaps of most interest, the sizes of corresponding chromo-
somes seem to be the same in all cells regardless of their size. It was upon
this point that Montgomery placed special emphasis. I have tried
to check his results critically in Arvelius, which is a much more favor-
able form than Enschistus for this purpose. My results failed of a
rigorous demonstration of chromosome equality, in part because of
inadequate material but chiefly because of the lack of any sufficiently
precise method of measurement. Nevertheless, disregarding the
slight and accidental dift'erences which are bound to appear in such
direct comparisons as those of Text-figures 4/1 and B, it appears that
the corresponding chromosomes are of sizes which, if not exactly
identical, certainly correspond within very small limits of difference.

TABLE IT.

Smallest

Normal

Large

1st Mat. Div.

0.9

1.0

1.8

2nd Mat. Div.

0.7

1.0

1.7

Ratio of spindle Icngtlis. The average length of the spindle in a cell from
the "normal" generation i.s taken as unity (1.0).

The enormous increase in the amount of cytoplasm in dimegaly has
already been noted and it remains now to examine the behavior of its
various formed elements. It might naturally be supposed that in a

404 BO WEN.

process affecting the cytoplasm so vitally, its several components
would develop morphological differences (other than those of mere
size or amount) of one sort or another. Such, however, is not the case,
and with the exception of a few minor differences upon some of which
I have already touched (Bowen '20), the general progress of events in
the cytoplasm is the same in all cells regardless of size. With respect
to staining reactions and the response to impregnation methods in-
volving silver nitrate there are, however, some rather definite differ-
ences between the large and small cells, but these are perhaps referable
to a physical rather than a physiological difference.

The centrioles were stated by INIontgomery ('9S) to vary in size
directly with the amount of cytoplasm, but his figures were not en-
tirely convincing. I have reexamined this point in Arvelius, in which
the facts are demonstrated with unusual clearness. The centrioles
in this form are rod-like in shape, often arranged in the primary
spermatocytes in a "V" formation recalling the condition in Lepidop-
tera. The centrioles in the large generation are strikingly larger than
in the smaller generations. (Compare Figs. 1 and 2, in both of which
the size of the centrioles has been slightly exaggerated).

The mitochondria were found by Montgomery (he at first called
the mitochondrial material an idiozome) to vary in amount with the
cytoplasm. This is easily checked by comparing the large and small
spermatids during the stage when the mitochondria are aggregated
into the compact, rather accurately spherical nebenkern. (Compare
Figs. 3 and 4).

The Golgi apparatus was not considered by IMontgomery. In its
scattered condition in the spermatocytes (see Bowen '20) comparisons
are not very satisfactory, but after the aggregation of the Golgi ele-
ments to form the acroblast in the spermatid, the large and small
generations can be readily contrasted (Figs. 7 and 8). As with the
mitochondria and the centrioles, the large cells have much the larger
amount of Golgi material. So too, the acrosome formed in connection
with the acroblast is much larger in the large cells, sometimes very
strikingly so (Figs. 9 and 10), and the cast-off acroblast (Golgi rem-
nant) varies of course in a similar way (Figs. 9 and 10).

The chromatoid body is another rather constant feature of the penta-
tomid germ cell which was not considered by Montgomery. This
structure does not lend itself easily to comparison because of its small
size, and often subdiAided condition. However, in Rhytidolomia
senilis, as discovered by Wilson ('13), the chromatoid body is very
large and distinct, and makes a fine object for comparison (Figs. 5 and

STUDIES ON INSECT SPERMATOGENESIS. 405

6). Further, in this species, the chromatoid body is shaped like a
thick disc, the periphery of which is roughly circular, a peculiar shape
which makes possible the determination of the long diameter with-
out difficulty, and I have made a series of measurements of that
dimension in both large and small cells in spermatocyte, division, and
spermatid stages. These show that the diameter of the chromatoid
body in the small cells differs from that in the large ones in the ratio
(approximately) of 1.0 to 1.2. The thickness of the disc is also in-
creased in the large cells. My observations show, therefore, that the
chromatoid body varies in size with the cell as a whole, but seem to
indicate at the same time that the increase in size is not exactly pro-
portional to that of the cytoplasm in this particular species.

It appears, therefore, that all the cytoplasmic components are in-
creased in amount (or size) in the large cells, and that the chromatin
content is accordingly the only known constituent in the entire cell
which is not affected in polymegaly. This is a point of extraordinary
interest, and, taken in connection with the fact that this condition
occurs in the germ cells, furnishes an interesting side-light to the great
mass of evidence already accumulated that the chromatin plays the
leading role in hereditary transmission. Furthermore, the increase
in the volume of the formed elements of the cytoplasm in the absence
of a corresponding increase in the volume of chromatin in the nucleus
suggests a number of interesting possibilities as to the nature of the
relation existing between the chromatin and the cytoplasmic con-
stituents. Apparently the volume of the cytoplasmic constituents
cannot be considered as a simple function of the volume of the chroma-
tin in a given cell.

(b) The effects of polymegaly on mature sperms. — As stated above,
Montgomery found in the mature (?) sperms of Euschisius three
sizes of heads varying in length according to the size of the sper-
matocyte generation from which they originated. His observa-
tions were on sections only, so that determination of the total
dimensions of the sperm were impossible. I have worked out the
"dimegalous sperm" of Murgantia in much more complete form, and
some account of their differentiation will be given later; here I wish
merely to point out that two sizes of sperms occur corresponding to the
two generations of spermatocytes. In sections, the actual origin of
the two classes of sperms can be positively traced to the two classes of
spermatocytes, and by means of smears, tlie two kinds of sperms can
be readily isolated entire. Text-figure 3 gives a general idea of the
contrast in structure. The two classes are unexpectedly of about

406

BOWEN.

A

C

equal total length, but the large sperm have a
much hea\aer tail, near the tip of which is a
characteristic swelling. The head, on the other
hand, is exceedingly long but correspondingly
decreased in diameter, so that it is scarcely
more than a tliread. Smears of Evschistus
were also made, in which the three expected
kinds of sperm were very easy to distinguish,
the large ones pro\dng of extraordinary size.
Text-figure 5 gives an idea of the comparative
sizes of the three sperm classes. In these
figures the diameter of the sperm head has
been much enlarged in each case in order to
make the heads clearly e\'ident at such low
magnification. Actually, the large sperm head
is exceedingly delicate and thread-like, and not
at all like the figures given by Montgomery
('10; figs. 24-26). According to Montgomery
the volume of the large and small sperm heads
differs markedly, and this difference was sup-
posed to depend on the fact that the chro-
matin exists in the sperm head as a peripheral
layer enclosing a quantity of karyolymph, the
latter determining the size of the head. My
observations do not corroborate these state-
ments in any particular. As will be pointed
out in a later section, and as I have showTi
previously (Bowen '22a) for the small sperm
of Mvrgantia, the head is probably a solid rod
of chromatin, and the appearance described by
Montgomery (if in mature sperms) is due to
faulty technique. As a matter of fact, in sec-
tions such as he used the heads are often made
to appear thicker than they actually are. As
indicated by smears, the volumes of the mature
sperm heads are probably very similar, allow-

FiGURE 5. Mature sperms from the vas deferens
of Evschistus eiLSchistoides (x255). (Smear prepara-
tion; osmic fumes-hematoxylin.) A, from the small-
est generation; B, from the small or normal genera-
tions; C, from the large generations (the tail has
been bent in the drawing in order to save space.)

STUDIES ON INSECT SPERMATOGENESIS. 407

ance being necessary, however, for the expanded basal end of the
head, which is probalily to be viewed as a "centrosonial middle-
piece" (see Bowen '22o).

Unlike Murgantia, in Evschistus the length of the sperms as a whole
also differs markedly, the actual length of the large ones being about
1 mm. These large sperms are not easy to find entire, as they are
usually broken or tangled up with others in making the smear, but one
can always be certain of an entire sperm by the presence of the thread-
like head and the characteristic swelling near the tip of the tail. Sniear
material from Arvclius was unfortunately not available, so that I have
been unable to determine the length of the large sperms. If they vary
in size as in Euschistus, (and sections at hand seem to indicate that
they may), the large sperms would be one of the largest animal sperms
recorded.^

These results have an unexpected bearing on the attempts made
some years ago by Zeleny and his pupils to establish quantitative
differences in the length of the sperm head referable to differences in
the volume of the sex.(X and Y) chromosomes. As a matter of fact,
their plotted measurements of sperm heads did give a liimodal curve
in many cases, and this was held to be proof of the original contention.
Without undertaking a critique of this whole conception, it may be
pointed out that differences arising from polymegaly, such as I have
here described, were not taken into account; yet they would obviously
introduce a fatal source of error. Nor is it sufficient to say that be-
cause visible differences in the spermatocytes are not readily to be
detected, therefore, none occur in the resulting sperms; for in Mur-
gantia, to cite an instance, the spermatocytes are not always easily
separable on the basis of size, and yet the spermatic differences are
very considerat)le. It is easily conceivable that a pentatomid might
be found in which polymegaly of the sperm would be distinguishable,
and yet size differences in the spermatocytes might be to all intents
and purposes lacking. Some of the forms classed in Table I as failing
to show polymegaly may, indeed, belong to just such a tA'pe. Poly-
megalous differences of a minor type may possibly he much more
common than is suspected. As a matter of fact Zeleny and Senay
('15) did measure the sperm of Euschistus variolarius, obtaining a
strikingly bimodal curve, in which, however, the ratio of difference
was verv much more than it should have been according to the

7 The largest animal sperm on record seems to be that of Notonecla, which
also happens to be an hcmipteran. Pantel and de Sinety ('06, page 89) give
its length as 12 mms. and over.

408 ' BOWEN.

theoretical calculations. The discrepancy was never satisfactorily
explained, so far as I know. The facts here given concerning the
sperm heads of Euschistus suggest the possibility^ that Zelen,y and
Senay discarded the large sperms and that the two smaller classes
were mixed to some extent producing the result which could not be
explained.

II. The Differentiation of the large Generations of Sperm. ^

As I have stated in the preceding section, the nuclear and cyto-
plasmic components of the large and small cells behave in a very
similar manner throughout the early stages of spermatogenesis and
up to the formation of the definitive spermatids. Even during the
differentiation of the sperm the cytoplasmic elements show little if
any distincti^■e differences in the large and small cells (see Bowen
'22a). The spermatid nuclei, on the other hand, in addition to
differences in size, exhibit others of a rather unique character. The
discovery of these differences early in my study of hemipteran testes,
led me to think that the differentiation of the large sperm heads
differed fundamentally from tlaat of the smaller ones. However,
intensive study of the "normal" spermiogenesis brought to light
certain features which had been previously overlooked by workers
in this field, and finally provided the data for harmonizing the appar-
ent differences. The formation of the normal sperms in Miirgantia
has been described in detail in the second of these "Studies," and it is
my purpose here to point out especially those features wherein the
development of the large sperms is different. The period of spermio-
genesis will be divided into a series of stages the exact limits of which
are given in another place (Bowen '22a).

The description is taken from Miirgantia histrionica , because in this
form tlie relati\'ely small size of the large sperms makes possilile the
obtaining of complete (or nearly so) heads in sections, — a difficult
matter when the heads become very long, as in Euschistus for example.
I have not examined the situation in other genera very thoroughly,
but so far as my observations go, the essential features seem every-
where to accompany the formation of large sperms. In one respect
the large spermatids are less satisfactory for study because a complete

8 In comparing the plates from my study on the normal sperms of Murgantia
(Bowen '22a) with those accompanying this paper, it should be noted that the
figure magnifications are somewhat different. In the first named paper the
magnification of the plates is 3000, in this paper, 2700.

STUDIES ON INSECT SPERMATOGENESIS. 409

series of stages cannot be obtained at one time in a single lobe, due
primarily to lack of available space. The unusual length of the sperm
heads is an added difficulty. The main outlines are, however, quite
clear enough for the present purpose, and the account given is drawn
largely from a single animal in which the cysts formed a fairly repre-
sentative series of stages.

Stages I and m. From the formation of the spermatid to the casting
of of the acroblast. — These stages do not differ markedly from the
corresponding ones in the large cells. The nuclei are larger and appear
clearer, the chromatic substance seeiiiing to undergo more complete
dissolution than in the normal spermatids. During the early elonga-
tion of the halves of the divided nebenkern, the centrioles, appearing
in the form of two rods in "V" formation as in the normal spermatids,
can be made out (Fig. 11), but clear cases are not frequent because of
the relation of the usual plane of section to the long axis of the
spermatid nuclei. It is clear, howe^■er, that the general history of the
centrioles is like that in the normal spermatids. The pseudoblepharo-
plast is formed in the typical way and the acrosome arises in connec-
tion with the Golgi apparatus (acroblast) which is then cast off exactly
as in the small sperm (Fig. 12). (Bowen '22a).

The aspect of the peripheral chromatin layer, which gradually
develops on the inner surface of the nuclear membrane is, however,
clearly different, and serves at once to differentiate the large from the
small generations. This layer is never thick in the large nuclei,
forming a very thin layer (Fig. 12) similar in extent to that in the small
nuclei. This thin lining is, furthermore, not at all homogeneous but
appears more or less "vacuolated," so that internall}' the contour is
often noticeably rough. In spermatids of the small generation this
layer also exhibits some unevenness when the stain is not too heavy,
but it is by no means so characteristic as in the case of the large sperma-
tids. The comparison is interesting, however, because it shows that
the conditions in both generations are essentially alike.

Stage n. From the migration of the acrosome to its definitive position
at the tip of the head, to the inauguration of the final steps in the condensa-
tion of the nuclear material. — The first part of stage n follows the same
general lines as in the small spermatids, the acrosome becoming
applied to one surface of the head and de^'eloping anteriorly a darkly
staining (with hematoxylin) granule; simultaneously the head begins
to elongate (Figs. 13 and 14). The most striking divergence from the
small sperms is again the appearance of the peripheral chromatic
layer, which is now distinctly irregular and often very uneven on its

410 BOWEH.

inner surface. In Figure 15 this irregularity can be clearly seen (in
optical section), and this uneA"enness is reflected in the surface views
in which the chromatic layer is ver}^ unevenly stained, giving the im-
pression of ^■acuoles (Fig. 15). Of rather regular occurrence at this
time is the appearance at one side of the head and about midway of
its long axis of a clump of chromatic material (Fig. 15), which will be
again referred to presently. The most striking feature, perhaps, is the
absence of any groove formation along the head, so characteristic of
the normal sperm heads (see Bowen '22fl). This groove does not
appear ever to be formed at any subsequent stage, — at least in a
fairly representative series of cross-sections I have failed to find it at
all. ^

The pseudoblepharoplast noAv disappears (Fig. 16) as in the normal
cases, but from this point on the course of events is otherwise strik-
ingly different. The chromatic layer becomes very highly 'vacuo-
lated' (Fig. 16), and a tendency is noticed toward the formation of
what appear to be two large vacuoles, one located in front of, the
other behind the mid-axial clump of chromatic material which was
forming in Figure 15. The chromatic layer is prett}^ well broken up,
though a definite zone seems to be retained along one side of the head
as shown on the anterior vacuole in Figure 16. This stage is a very
characteristic one in Mvrganiia, and is particularly striking because
of the bizarre appearance gi^-en by the chromatic arrangements.
Apparently this condition is of very short duration, for the two clear
areas soon fade out and the whole head appears stained in an indefi-
nitely irregular way except for a clear area at the base corresponding
to the same characteristic of the normal sperm. The head elongates
very rapidly especially during the latter part of this stage, and it is
during this period that the great difference in length between the large
and small sperm heads is established. The arrangement of the
chromatic material is simply the same indefinite, vacuolated condition
characteristic of the earlier stages (Fig. 17). \Yhether the chromatin
remains peripheral or becomes distributed through the cavity of the
head is not known. This peculiar arrangement of the chromatin per-
sists into the next stage and is probably directly comparable to the
vacuolation of the chromatin which I have described in the normal
sperm heads of Murgantia (Bowen '22a).

Stage o. The condensation of the chromatic material to form the
definitive sperm head. — In stage o the chromatic material undergoes
a process of condensation the result of which is to produce a sperm
head in structure essentially like that of the normal sperms. As in

STUDIES ON INSECT SPEEMATOGENESIS. 411

them (see Bowen '22a), the chromatin seems to contract toward the
mid-Hne of the nuclear cavity, and there condenses to form a single,
thread-like axis. This is subject to various peculiarities in the early
stages, and it is in respect to these that the large sperm heads seem to
differ most conspicuously from the smaller ones. In many (all?)
cases, this thread is first formed as an irregular, usually incomplete
helical thread, or at least such seems to be its shape (Fig. 18, which
does not show the tip of the head). Sometimes this seems to be merely
irregular chromatin masses, and occasionally cysts occur in which the
chromatin is more or less broken up into a series of distinct, well sep-
arated, beadlike masses. I do not know what role these may play, or,
indeed, whether they are to be considered part of the normal procedure.
The first mentioned condition is not unlikely an early stage in the
formation of the axial thread of chromatin; while the latter condi-
tion is perhaps connected with the end stages in the same process.

In any event, this irregular thread soon becomes straightened out,
probably in part by its further condensation, and the head of the
future sperm is thus produced, corresponding remarkably with the
structure of the sperm head of normal size. Through the center of
the former nuclear cavity passes a smooth core of chromatin, which is
at first enclosed in a layer of protoplasm corresponding to the limits
of the old nucleus (Fig. 19).^ I have never been able to follow this
layer over an entire sperm, for obvious reasons, but originally it
probably forms a complete mantle as in the small sperm. A charac-
teristic vacuole (perhaps two) is also formed along the head during the
final steps, as in the normal sperm, and its origin and fate is doubtless
the same, though uncertain, in both cases. During the final conden-
sation of the chromatin thread the anterior part of the head often has a
cork-screw shape, as though an originally coiled thread were just in
process of straightening out.

Stage p. The sperm completed. — Finally, the outer protoplasmic
envelope disappears as in the normal sperm, and the completed sperm
(Fig. 20) is now ready to be released into the efferent duct of the testis,
a protoplasmic mass having been already sloughed off the tail after the
manner customarily followed in normal sperm formation. In stages
o and p, the tips of the heads are so very delicate and so closely bunched
(in sections) that it is quite impossible to separate a single one from its
neighbors. I have accordingly added the anterior part of the sperm

9 Compare with Figures 168 and 174 (Bowen '22a); the Figures 51, 53, 54
and 55 of Palvdina given by Meves ('03) are also interesting in this connection.

412 BOWEN.

in Figure 20 more or less from the indications of its length given by the
bunch as a whole. Smear preparations show the actual length to be
somewhat greater.

The study of smears gives a much better idea of the mature sperm
than sections, since the former method furnishes an abundance of
complete, isolated heads. Sperm heads from smears (Fig. 21) show
one very marked difference from those in sections, the width of the
head being apparently much less. The thickness of the head in
sections is doubtless largely due to the stain, which not infrequently
makes dense chromatic structures appear larger than they really are,
especially if the extraction of the stain is not extreme. Two other
points of difference are also brought out by smears. One of these is
the exceedingly long and delicate (its width is much exaggerated in
Fig. 21) whip-like lash at the tip of the head, terminating in a minute,
slightly elongate thickening. This lash is presumably of acrosomal
origin. The other point is the definite expansion of the basal end of
the head (Fig. 21), which seems sometimes to stain more intensely
than the rest of the head. This probably corresponds to the some-
what similar portion at the base of the normal sperm heads (see Fig.
177, Bowen '22a), for which reason I believe that it probably repre-
sents the centrioles (" centrosomal middle-piece"). This would fall
in line with the fact already noted, that the centrioles in the large cells
are proportionately larger, while the available chromatic material is
constant in amount.

The structure of the sperm tail was described in my second " Study,"
but one feature of the tail of the large sperm calls for additional com-
ment. I refer to the enlargement already noted as a constant occur-
rence near the tip of the tail (Text-figs. 3B and 5C). Smears fixed
in osmic acid fumes indicate that this enlargement is due to two bleb-
like swellings on the threads, probably of mitochondrial (nebenkern)
origin, which pass along either edge of the ribbon-like tail (Fig. 22).
The meaning and fate of this swelling is unknown. Figure 22 also
shows very clearly how the marginal threads gradually narrow into
the termination of the sperm tail.

The features described in this section as accompanying the forma-
tion of large sperms, are as constant in occurrence as is the poly-
megalous condition itself. In only one case (a specimen. No. 6, of
Murgantia), have I found a departure from this rule. In this indi-
vidual, the early stages are similar to those in the normal sperm, even
including the formation of the groove along one side of the head. But
at some point in the elongation of the head, the sperm revert to the

STUDIES ON INSECT SPERMATOGENESIS. 413

usual course of events and in the characteristic stages of large sperm
formation, the appearances are normal for the large sperm. It is
possible that this exception was due to a disturbance in the customary
amount of difference between the large and small generations of sper-
matocj'tes, of which there were some slight indications.

Conclusion.

In the preceding section the cause and meaning of polymegaly have
not been considered, because thus far I have been unable to obtain
any evidence bearing on either of these points. Montgomery first
('98) concluded that the larger spermatocytes were "due to their
recei\ing a greater amount of food, . . . That is to say," they "must
be nourished by a richer blood supply." Subsequently ('10), he
modified the latter statement, stating that the nutritional differences
"are due to differences in the follicular nurse cells of the testis."
This explanation really explains nothing, for we are still in the dark
as to the reasons why certain follicular cells should become larger than
their neighbors. Indeed, it is not e\adent why the enlargement of the
nurse cells may not as well be a result as the cause of the large genera-
tions of spermatocytes. In any event, the morphological condition
of the nurse cells helps us not at all to understand the actuating
mechanism behind the whole phenomenon. Furthermore, the un-
usual case cited in the preceding section of an individual in which
cysts of cells normal in size occur together with cysts of large cells
in the same lobe, would seem to indicate that nutritional differences
are not the only factor at work.

It may be noted here that other cases of polymorphism are known
to occur in the male germ cells of several animals, and such differences
may be of more general occurrence than we suspect. The most
interesting of these cases, from the standpoint of this study, is that
described by Blackman ('05) in Scolopendra, a myriapod in which two
kinds of spermatocytes (and spermatids), differing remarkably in size,
occur. Two sizes of sperms are produced, and in general the case
reminds one strongly of 'polymegaly' in the pentatomid germ cells.
There is, however, one noteworthy difference in the arrangement of
the large and small generations, which in Scolopendra are not confined
to particular follicles or cysts, but occur side by side in all parts of the
testis. Blackman was inclined to regard the size differences as due to
differences in the supply of nutriment traceable to the spatial relations

414 BOWEN.

of the cells. The formation of two different kinds of spermatozoa
(eupyrene and apyrene) in Lepidoptera has long been known, and a
somewhat different case (eupyrene and oligopyrene sperms) in certain
(prosobranch) molluscs is equally familiar. (See especially Meves
'03.) Less well known cases have been reported by Holmgren ('01)
and Voinov ('02) in Coleoptera. According to the former, in Staph]/-
linus there are two kinds of primary spermatocytes which originally
differ greatly in volume, but at the time of maturation are of equal
size. The resulting sperms are likewise all of equal size, but according
to Holmgren, even though they resemble each other completely, on
the basis of their genetic inequality they must also be morphologically
and physiologically unequal. This case is of particular interest be-
cause, as is evident, the conditions are exactly the reverse of those in
the Hemiptera (Pentatoviidac) . According to Voinov, in Cyhister
there are two kinds of spermatogenesis giving rise to sperms of differ-
ent morphological value. The two processes in this case are distinct,
occurring at different seasons of the year. Finally, in Rana, two sizes
of cells have long been known to occur in the gonads of many of the
larvae, the larger cells having been interpreted as abortive eggs.
The large spermatocytes of Arvelius might, indeed, easily be inter-
preted in a similar way, were it not for their further history and en-
vironment. Swingle ('21) has recently suggested that the two sizes
of cells are in reality two generations of spermatocytes, an interpreta-
tion which falls in line with the other cases noted above. It is possible
that all of these cases are really only scattered instances of a wide-
spread tendency toward polymorphism in sperm cells and are perhaps
ultimately to be explained on grounds more or less remotely similar.
In any event, the phylogenetic explanation offered by Swingle seems
less probable in the light of the other facts which I have here assembled.
There is, in all these cases, the common characteristic that the
phenomena peculiar to each seem to be perfectly normal and constant
for the particular species involved. Whether the sperms thus formed
are all able to function in any of the processes of normal fertilization
is not clear. It is indeed certain that they do not in the Anura, and
probably also in the case of the apjTcne sperm of Lepidoptera in
which the nucleus is lacking. Whether the polymegalous sperms of
Hemiptera are of equal value in fertilization is not known, and the
e\'idence for their retention in the seminal receptacle of the female
after copulation is not conclusive. The matter would be well worth
settling, for it would throw a most interesting side-light on the ques-
tion of the relative value of nuclear and cytoplasmic contributions in
fertilization.

STUDIES ON INSECT SPERMATOGENESIS. 415

The points brought out in this study may be briefly summarized : —

1. Di- or poly-megalous sperms are not confined to the genus
Eitschistus, as jMontgomery beheved, but are of frequent occurrence
throughout the Family Pentatomidae.

2. As a result, generations of at least two or three (possibly more)
sizes of sperms are developed.

3. The differences in cell-size are due to increase of all the con-
stituents of the cell except the chroinatin, which is constant in amount,
at least within xery narrow limits.

4. Tlie large sperms are differentiated by a process superficially
unlike, but fundamentally similar to, that which the small sperms
undergo.

416 BOWEN.

LlTERATUHE CiTED.

Blackman, M. W.

1905. The spermatogenesis of the myriapods. III. The
spermatogenesis of Scolopendra hews. Bull. Mus. Comp.
Zo5l. Harvard College, vol. 48.

Bowen, R. H.

1920. Studies on insect spermatogenesis. I. The history of
the cytoplasmic components of the sperm in Hemiptera.
Biol. Bull., vol. 39.

1922a. Studies. II. The components of the spermatid and
their role in the formation of the sperm in Hemiptera.
Journ. Morph., vol. 36.
1922b. Studies. III. On the structure of the nebenkern in the
insect spermatid and the origin of nebenkern patterns.
Biol. Bull., vol. 42.
Faust, E. C.

1913. Size dimorphism in adult spermatozoa of Anasa tristis.
Biol. Bull., vol. 25.
Holmgren, N.

1901. Ueber den Bau der Hoden und die Spermatogenese von
Staphylinus. Anat. Anz., vol. 19.
Meves, F.

1903. Ueber oligopvTene und apyrene Spermien und ueber ihre
Entstehung nach Beobachtungen an Paludina und
Pygaera. Arch. f. mik. Anat., vol. 61.
Montgomery, T. H.

1898. The spermatogenesis of Pentatovia up to the formation
of the spermatid. Zool. Jahrb., Anat. u. Ont., vol. 12.

1910. On the dimegalous sperm and chromosomal variation of
Euschisttis, Mith reference to chromosomal continuity.
Arch. f. Zellforsch., vol. 5.

1911. The spermatogenesis of an Hemipteron, Euschistus.
Journ. Morph., vol. 22.

Pantel, J., and de Sinety, R.

1906. Les cellules de la lignee male chez le Notoneda glauca L.
La Cellule, vol. 23.

Swingle, W. W.

1921. The germ cells of anurans. I. The male sexual cycle of
Rana catesbciana larvae. Journ. Exp. Zool., vol. 32.

STUDIES ON INSECT SPERMATOGENESIS. 417

Van Duzee, E. P.

1917. Catalogue of the Hemiptera of America north of Mexico.
Univ. Calif. Pubs, in Entomology, vol. 2.
Voinov, D.-N.

1902. La spermatogenese chez le Cybister roeselii. Comptes
Rendus I'Acad. des Sci., Paris, vol. 135.
Wilson, E. B.

1912. Studies on chromosomes. VIII. Observations on the
maturation-phenomena in certain Hemiptera and other
forms, with considerations on synapsis and reduction.
Journ. Exp. Zool., vol. 13.

1913. A chromatoid body simulating an accessory chromosome
in Pentatoma. Biol. Bull., vol. 24.

Zeleny, C, and Senay, C. T.

1915. Variation in head length of spermatozoa in seven addi-
tional species of insects. Journ. Exp. Zool., vol. 19.

Explanation of Plates.

All of the figures have been outlined as far as possible with the camera
lucida at an initial enlargement of approximately 3800 diameters. At so great
an enlargement it has, of course, been necessary to correct the outhnes ex-
tensively and to add much of the finer detail free hand. In reproducing, the
figures have been reduced uniformly to an enlargement of approximately 2700
diameters. In every case the method employed in the preparation of the
original object has been indicated.

A, acrosome c, centrioles

a, acroblast G, Golgi remnant

b, chromatoid body N, nebenkern
C, chromatin nucleolus P, plasmosome

420 BOWEN.

PLATE I.

Figures 1 and 2 are from Arvelius albopundatus; Figures 3, 4, 7 and 8 are
from Euschistus euschistoides; Figures 5 and 6 are from Rhyiidolomia senilis;
Figures 9 and 10 are from Chlorochroa uhleri (= persimilis). The large and
small cells in each pair are from the same testis in every case. Figures 2, 4, 6,

8 and 10 are from cells of the large generations; the others are from cells of one
of the smaller generations.

1 and 2 Primary spermatocytes in late growth period. (Flemming-hema-

toxylin.)
3 and 4 Spermatids, stained to show the nebenkern. (Flemming without

acetic plus cone, nitric acid-hematoxylin.)
5 and 6 Spermatids, stained to show the chromatoid body. (Flemming-

hematoxylin.)
7 and 8 Spermatids, impregnated to show the Golgi apparatus. (Modified

Kopsch.)

9 and 10 Spermatids, stained to show the acrosome just after the casting off of

the acroblast. (Flemming-hematoxyUn.)

BowEN. —Studies on Insect Spermatogenesis.

Plate I.

-<: Cn

/*'

C',

^

3

rt

h

\

yV ^
4

\

a

\

P

2

•

/

O (Tb

A
G-

1^ -A

•G

9

T 8

Proc. Amer. Acad. Arts and Sciences. Vol. LVII.

10

422 BOWEN.

PLATE II.

All the figures are from cells of the large generations in Murganlia histrionica.

11 to 20 Progressive stages in the differentiation of the sperm head (nucleus).
(Flemming-hematoxyhn, — except Figure 20 which is Hermann-hema-
toxylin.)

21 Head of mature sperm from efferent duct of testis. (Smear prepa-
ration. Osmic fumes-hemato.xylin.)

22 Detail of the bleb-like swelling on the tail of the large sperms. (Smear
preparation. Osmic fumes-hematoxylin.)

BowEN. — Studies on Insect Spermatogenesis.

Plate II

11

o

12

14

i 1 O

lo

15

\

18

21

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CX)NTRIBUTION FROM THE CRYPTOGAMIC LABORATORIES OF
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NOTE OX TWO REMARKABLE ASCOMYCETES.

l'>v Roland Thaxter.

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CONTRIBUTION FROM THE CRYPTOG.IIMIC LABORATORIES OF
IL4RVARD UNIVERSITY. LXXXIX.

NOTE OX TWO REMARKABLE ASCOMYCETES.

By Roland Thaxter.

With Two Plates.

CONTRIBUTION FROM THE CRYPTOGAIMIC LABORATORIES OF
HARVARD UNIVERSITY. LXXXIX.

NOTE OX TWO RE:\rARKABLE ASCOISIYCETES.
By Roland Thaxter.

Received June 12, 1922. Presented October 11, 1922.

The first of the two striking fungi considered and illustrated in the^
present Note, is a member of the Hypocreales, belonging to the genus
Hypocreopsis. This name was first used by P. A. Karsten (1873) in
a list of corrigenda, p. 251, to replace the preoccupied Dozya which he
had used on p. 221 of the same publication; the Spharria riccioidca of
Bolton (1791) being taken as the type. According to Tode (1790),
who called it Acrospcrmum lichenoides, it was first referred to by J. A.
Scopoli (1760), p. 109, and in a later edition (1772), p. 393, where it
was given as Var. 1, under Lichen physodes. This reference is made
under "Synonyma Omissa" by Tode on p. 47 of the paper cited; but
although he doubtless had good reasons for making it, they are not
wholly apparent to one who reads the two descriptions. The matter
has, however, a merely historical interest; since, unless one of them
should be designated as a nomen conservandum, neither is likely to be
generally recognized by mycologists; although Seaver in his revision
of the Hypocreales (1910 a and b) has combined the specific name of
Tode with the generic name of Karsten. In the absence of a nomen
conservandum, still another new combination may be necessary;
sii)ce Montague, who appears to have been the first to refer to this
species after 1821, using a new specific name, called it first (183G)
Sphaeria parmclioides, and later (1856) correctly included it among
the Hypocreales under the name Ilypocrca jMrmelioides. It was
subsequently called l^y Berkeley (1860) Hypocrca riccioidca; and,
since the paper of Karsten above cited, the only recorded American
collection of it. made by ]\Iiss Susan IMinns in the Crawford Notch,
in the White ^Mountains, New Hampshire, was renamed Ilypocrca
digitata by Ellis (1885), an error corrected subsequently (1892) in his
Pyrenomycetes.

From Karsten's text, it is not possible to determine exactly what he
regarded as tlie distinguishing characters of the genus, since he gives
no separate generic diagnosis. He places it in the Dothideae for the
reason that he saw no perithecial walls, and does not compare it

426 THAXTER.

with other genera to which it might be supposed to be related. Subse-
quent ■WTiters have separated it from Hypocrea largely on the ground
that its spores do not, at maturity, separate into two distinct halves;
and von Hoehnel (1912), p. 380, remarks that it is merely a Hypocrea
with the spores of Nectria.

Seaver, in his revision of the Hypocreales (1910 a and b) has also
included under Karsten's name two species, //. suhcarnca and H.
consimilis, both with continuous spores, and also a third, H. iremeUi-
cola, a fragment of wliich he has very kindly allowed me to examine.
This species is said to grow on TremcUa albida; but there is no indica-
tion in the specimen what the nature of the substratum really is.
The perithecia are crowded in a crust like cottony stroma, and super-
ficially closel\' resemble those of Hypomyccs candicans. The spores,
however, are distinctly larger.

If one considers the characteristics of the Type of Hypocreopsis,
its peculiar and very highly developed stroma; its characteristic
centrifugal development of thick radiating subdichotomous lobes;
its restricted perithecigerous area; its saprophytic habit and typically
didymous spores would, when taken together, seem to constitute its
most striking peculiarities. If one recognizes the validity of the genus
Podostroma (Podocrea), which, except for the fact that a somewhat
differentiated perithecigerous region is raised on a more or less definite
stalk, is quite indistinguishable from Hypocrea in all other respects,
the characters of Hypocreopsis above enumerated would seem to form
an even more satisfactory basis for generic separation.

That the type is a distinctive one is clearly shown by the occurrence
of a second species, herewith described, which was first encountered
by the writer at Cullowhee during the summer of 1888, in the south-
western part of North Carolina, where a single specimen was collected
on a dead branch of Rhododendron inaximum; while somewhat later,
abundant material was found on the same host at Burbank, East
Tennessee, near the North Carolina border. In general habit, color
and appearance this fungus seemed indistinguishable from the type-
species ; but an examination of the spores showed them to be so differ-
ent that it could not even be regarded as a variety. In both species a
series of narrow thick subdichotomously branching lobes, which when
turgescent are apt to be in close lateral contact, radiate from a com-
mon center, often with great regularity, adhering firmly to the sub-
stratum, except where an occasional branch is crowded out and grows
upward or over adjacent branches. The perithecigerous region is
confined to the upper, outer surface, and is progressively developed

TWO REMARKABLE ASCOMYCETES. 427

as the lobes extend outward. This fertile region is, as indicated in
Figure 1, A, broader than the adherent base, whicli is dehmited by a
black line. The perithecia, with their well developed necks, are
closely associated in this positioft, and almost completely immersed;
becoming prominent only when the stroma is shrunken by drying or
by alcohol, the ostioles appearing as darker points.

Karsten mentions the fact that the European species is sometimes
sterile, and the specimen in the Harvard copy of his Fungi Fenniae,
No. 664, appears to be in this condition, and looks as if it might per-
haps be parasitized. A specimen in the Curtis collection, however, is
normally fertile, as are all the indi\'iduals of the new species which have
been examined.

The surface of the stroma in the Carolina form is cinnamon to clay
color or sayal brown, according to Ridgway, when dry, with a tinge of
orange when fresh; dense, firm, whitish within; a very thin layer of
looser filaments forming the surface of contact with the substratum,
and, as indicated in the figure, subtending a clear black line which is
also present in the European form. The venters of the perithecia are
subspherical or broadly flask-shaped, the immersed necks well de-
veloped and stout. Although, in his description, Karsten speaks of
the perithecia as "parietibus destituta" the structure in this respect
is like that of other stromatic Hypocreales in both species.

The sporiferous portion of the asci is cylindrical, the characteristic
termination, Figure 1, B and C, tapering rather abruptly to form a
short blunt point. The base is also relatively short and tapers rather
abruptly to its insertion. The spores are uniseriate, broadly elliptical
to subspherical, discrete, or usually one to eight firmly coherent.
Figure 1, C-E; normally once septate; the septum median, horizontal
or oblique to vertical; less often continuous, the surface often coarsely
roughened by accretions of residual protoplasm (E), the coherent,
surfaces flattened. A comparison of these spores with Figure 1, F
which represents three spores from the Curtis specimen of the European
form, will show clearly that the two are certainly distinct, and in the
new species no tendency to variation, beyond that indicated in the
figures, has been observed.

The radiating stroma, Plate I, may be orbicular or nearly so, when
growing f)n a large liml) or tnmk, and may reach a diameter of 10 cm. ;
while on smaller brandies the segifients soon meet and mingle on the
side opposite to their origin, clasping the branch and becoming more
or less confused, while those more nearly coincident with its long
axes continue to grow along it in opposite directions. As has been

428

THAXTER.

already mentioned more branches may be formed than can be ac-
commodated on the surface available, so that all do not necessarily
lie flat, and there may be a certain amount of interference. The flat
lichenoid habit, however, is usually characteristic and striking,
recalling that of Marchantia or Riccia, and may be very regular.

Figure 1. Hypocreopsis Rhododendri Thaxter. A, transverse section of a
lobe of the stroma. B, Normal ascus with spores partly discrete. C, Portion
of ascus enlarged, the spores coherent in two groups. D, Eight firmly coherent
spores from single ascus, some septate, others continuous. E, Two groups of
three and five spores respectively, the upper continuous, both showing roughen-
ing incrustation of surface. F, Three normal spores, given for comparison,
from the specimen of "Hypocrea riccioidea" in Herb. Curtis.

TWO REMARKABLE ASCOMYCETES. 429

The development of the lobe.s is progressive; and while they are ac-
tively growing, a considerable portion of their tips may show no
developed perithecia, while further back, and at the center, the latter
may be mature. The growth is, nevertheless, not unlimited; and
after reaching a certain stage of maturity, the whole upper surface is
perithecigerous to the very extremities.

In view of the characteristics above enumerated, which are common
to the two species by which it is represented, the genus Hypocreopsis
might be defined as follows:

Hypocreopsis Karsten.

Stromatibus orbicularibus, radiatim lobatis, lobis lichenoideis,
ramosis, substrato adhaerentibus: infra nigro-limitatis, supra denique
ubique perithecigeris: peritheciis in stromate denso immersis, strato
singulo dispositis, subsphericis, collis suffultis: ascis cylindraceis
octosporis: sporidiis discretis vel arete cohaerentibus, typice uni-
septatis.

Hypocreopsis Rhododendri nov. sp.

Stromatibus subaurantiacis, vel testaceo-cervinis vel cinnamomeis,
orbicularibus, latitudine usque ad 10 cm., lobis numerosis, substrato
arete cohaerentibus, repetito-subdichotomis, 2-3 mm. altitudine; infra
nigro-limitatis, 1.5-2 mm. latis; supra undique perithecigeris, 2-4 nun.
latis. Peritheciis subsphaericis, 200-220 ix diam., collis 125 ii longis
suffultis, ascis cylindricis, octosporis, 115-130 X 14 /x, apice rotun-
dato-acuminatis, sporidiis sphaericis vel late ellipticis 12 X 12-17 X
13.5 /x, continuis \(A typice medio septatis, discretis vel saepissime 2-8
arete cohaerentibus, hyalinis vel dilute luteis, levibus vel subrugulosis.

On stems and branches of Rhododcndrum maximum. North
Carolina, East Tennessee.

The second peculiar form to be considered was first noticed early in
August, 1903, on McdcoUi virginica at IMagnolia Mass., by Dr. Farlow;
who called my attention to the fact that, altliough the material was
quite sterile and merely formed, just below the leaf whorls, a sub-
fusiform distortion which was covered by the uninjured epidermis,
the tissues in this region were penetrated by a fungus mycelium com-
posed of branching septate hyphae, about 4-5 n in diameter, which
penetrated the host cells. The same form was collected by myself on

430 THAXTER.

Gerrish Island, Kittery Point, Maine, a short time later; but it was
not till the following year, during a short stay with Dr. Farlow at
Chocorua in the month of September, that I found, on the hillside
near his house, a number of specimens in which the hyphae had pene-
trated to the surface and produced their peculiar fructification. As
the hypertrophy matures, it takes on a darker brown color and be-
comes roughened, owing to the emergence, directly through the epi-
dermal cells, which remain distinguishable in situ as a somewhat
disorganized layer, of closely associated more or less parallel filaments.
This penetration of the epidermis at first takes place at various points,
forming irregular areas which soon merge to a continuous layer of
vertically developed, brownish, simple or sparingly branched, rather
irregular elements; which have a tendency to become more or less
fasciculate, and are more frequently septate near the base. These
elements, which are paraphyses, are not as a rule clavate or otherwise
definitely modified at the tips. They arise from a denser region, or
subhymenium, just above the epidermis of the host; and, owing to
their irregularities in length and tendency to become fasciculate, do
not form an even smooth hymeniimi. The asci which finally develop
in connection with these paraphyses are not abundant, and are wholly
absent, except in certain areas which may sometimes be recognized
from the fact that the;>' take on a greenish yellow color, and have a
pulverulent appearance, although they are not actually so. In such
areas the asci are scattered as is indicated in Figure 2, A. They are
clavate in form, Figure 2, C, the extremities bluntly rounded, the stalk
rather short. The spores are subdistichous, dark l)rown, somewhat
pointed at either end. Figure 2, D, asymmetrical when viewed side-
wise, and subfusiform when seen at right angles to this position, one
margin, in the first instance, being strongly convex, the other often
nearly straight: and they are further peculiar from the presence of
numerous lines, the distinctness of which has been greatly exaggerated
in Figure 2, C, which run longitudinally, and are occasionally con-
fluent. The general appearance of the spore thus recalls that of
Wynnea americaiia or Choanephora cucurbitarum.

Although the species is no doubt to be met with wherever the host
occurs, as is indicated by the fact that it has been found in three rather
widely separated localities in New England which are the only ones
where search has been made for it, I have been unable to find any
reference to it in the literature. The host, Medeola, is one which does
not appear to be subject to fungus parasites, the Phyllostida Medcolae
of Dearness and House, being the only parasite which I find recorded
on it. I have also been unable to place this very peculiar type in any

TWO REMARKABLE ASCOMYCETES.

431

described genus of Discomj-cetes, and its general position among
known genera is not clear. Despite its abundant paraphyses, it might
be mechanically disposed of under Schroeter's Protodiscineae, which
already contain two mutually quite unrelated types, the Ascocorticia-
ceae and tlie Exoascaceae, to neither of which is the present form
even remotely related. It resembles both, however, in the possession

V Ti„n.'', ?,'^

Figure 2. Medeolaria Farlowi Thaxter. A, Part of a section of host
hypertrophied by the fungus, showing host parenchyma, remains of epidermis,
subh\Tnenium and hymenium with paraphyses and asci. B, Group of para-
physes enlarged. C,"Two asci, the striation of spores e.xaggerated. D, Four
spores, seen in different positions.

of an indefinitely continuous hymenium, so indeterminate that it is
not even delimited by a ruptured epidermis. I ha\-e therefore felt
compelled to use a new generic name for its reception, based on that
of the host, and have dedicated the single species to Dr. Farlow who
was the first to observe it.

432 THAXTER,

Medeolaria nov. gen.

Fungus Discomycetum phytogenus, hospitem pro parte deformans,
mycelio intraeellulari per epidermidem integram denique emergente
stratumque superficiale indeterminatum efficiente; paraphysibus
permultis, hinc illine ascis intermixtis, subhymenio epidermidi in-
sidente, orientibus: ascis octosporis, sporidiis eontinuis, coloratis.

Type Species.

Medeolaria Farlowi nov. sp.

Hospes sub insertione foliorum subfusiforme distortus; distortio
denique brunnea; areis indeterminatis viride-luteis aspectu pulveru-
lentibus ascigeris; paraphysibus copiosissimis, dilute brunneis, infra
septatis, supra vix clavatis, parce ramosis vel simplicibus, subirregu-
laribus et subfaseiculatis, 200-210 ix longis: ascis clavatis, 150-170 X
25-30 jji, saepe sparsis vel absentibus: sporidiis brunneis longitudi-
naliter striatis, obtuse apiculatis, asymmetricis, subdistichis, 25-30 X
12-15 M-

Forming distortions just below the leaf whorls of Mcdcola virginiana
L. Magnolia, Mass.; Gerrish Island, Kittery Point, Maine; Chocorua,.
N. H.

two remarkable ascomycetes. 433

Literature Cited.
Berkeley, M. J.

1860. Outlines of British Fungology. Hypocrea riccioidea
Bolton. On ^Yillow. p. 383.
Bolton, J.

1791. Appendix (Vol. IV) to History of Funguses Growing
about Halifax, p. 1S2, pi. 182. '
Ellis, J. B., and Everhart, B. M.

1885. New P\mgi. Journal of Mycology. Vol. I, p. 42, March.
1892. The North American Pyrenomycetes. p. 87, pi. 11.
Karsten, P. A.

1873. Mycologia Fenniae. In Bidrag till Kannedom af Fin-,
lands Natur och Folk. Finska Vetenskaps-Societaten.
Tjugondetredje Haftet. pp. 221 and 251. Helsingfors.
Hbhnel, F. von.

1912. Fragmenta zur Mycologie XIV, p. 379. Sitz. der k.k.
Akad. Wiss. in Wien. For further mention of Hypo-
creopsis by this author see the same IX (1909) p. 1479
and XIII (1911), p. 451, in which the genus is compared
with Endothia, etc.
Montagne, J. F. Cam.

1836. Notices sur les Plantes Cryptogames. Ann. des Sciences.

Nat. II Ser., Vol. VI, p. 333, Plate 18, fig. 4.
1856. ."-iylloge Cryptogamarum etc. p. 210.
Saccardo, P. A.

1891, 1902. The names included by Saccardo under Hypo-,
creopsis will be found in the 9th and 16th volumes of the-
Sylloge, pages 980 and 590.
Seaver, Fred. J.

1910, a. Hypocreales of North America. Mycologia, vol. II, p. 82.
1910, b. Hypocreales in North American Flora. Ill, i, p. 45.
Scopoli, J. A.

1760. Flora Carniohca, p. 109.

1772. The same, second edition, vol. II, p. 393. Lichen Phy-.
sodes var. 1.
Tode, H. I.

1790. Fungi Mecklenburgenses Selecti. Fasciculus, p. 9.

Note. The writer desires to express his obligation to ]\Ir. George.
Nelson of the Museum of Comparative Zoology, for the admirable.
I>hotographs from which the two accompanying plates have been made,.

434 THAXTER.

PLATE I.

Hypocreopsis Rhododendri Thaxter. General habit of the fungus photo-
graphed from dried material by Mr. George Nelson. Natural size.

Thaxter. — Remarkable Ascomycetes.

Plate I.

HYPOCREOPSIS RHODODENDRI THAXTER.

Proc. Amer. Acad. Arts and Sciences. Vol. LVII

436 THAXTER.

PLATE II.

General appearance of the host, Medeola virginiana, attacked by Medeo-
laria FarJoivi Thaxter; the lower showing a single hypertrophj'; the upper, one
below each node: considerably reduced. Photographed from dried material
by Mr. George Nelson.

Thaxter. — Remarkable Ascomycetes.

Plate II.

r

MEDEOLARIA FARLOWI THAXTER.
Proc. Amer. Acao. Arts and Sciences. Vol. LVII.

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57-18

Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 18.— November, 1922.

RECORDS OF MEETINGS, 1921-22.

BIOGRAPHICAL NOTICES.

OFFICERS AND COMMITTEES FOR 1922-23.

LIST OF THE FELLOWS AND FOREIGN HONORARY

MEMBERS.
STATUTES AND STANDING VOTES.
RILAIFORD PREMIUM.
INDEX.

(Title Page and Table of Contents.)

(Continued from page 3 of cover. J

VOLUME 57.

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Proceedings of the American Academy of Arts and Sciences.

Vol. 57. No. 18.— November, 1922.

RECORDS OF MEETINGS, 1921-22.

BIOGRAPHICAL NOTICES.

OFFICERS AND COMMITTEES FOR 1922-23.

LIST OF THE FELLOWS AND FOREIGN HONORARY

MEMBERS.

«

STATUTES AND STANDING VOTES.

RUINIFORD PREMIUM.

INDEX.

(Title Page and Table of Contents.)

RECORDS OF MEETINGS.

One thousand one hundred and fifth Meeting.

October 19, 1921.— Stated Meeting.

The Academy met at its House.

The President in the Chair. The Transactions of the last two
meetings were read and approved.

There were twenty-two Fellows and one guest present:

The following letters were presented by the Corresponding
Secretary: — from C. G. Abbot, W. C. Abbott, I. Babbitt, S. J.
Barnett, J. S. Bassett, E. W. Berry, N. L. Bowen, J. C. Branner^
C. D. Buck, F. Cajori, C. M. Campbell, L. L. Campbell, R. Cole,
C. Day, W. F. Durand, R. A. Emerson, F. E. Farley, M. Farrand,
W. S. Ferguson, E. C. Franklin, P. R. Frothingham, R. G. Harri-
son, W. E. Hocking, W. H. Howell, W. J. Humphreys, E. X. L. H.
Hyvernat, F. E, Ives, C. F. Jenney, A. Keith, O. D. Kellogg, J. F.
Kemp, F. Lawton, J. G. Lipman, J. L. Lowes, C. D, Maginnis,
C. T. Main, W. J. Mayo, J. C. Merriam, E. D. Merrill, G. S.
Miller, W. Patten, F. W. Peabody, W. L. Phelps, C. V. Piper,
C. R. Post, H. N. Russell, F. Schlesinger, A. W. Scott, J. Stebbins,
C. W. Stiles, W. S. Thayer, C. H. Walker, J. Warren, David White,
Arthur Winslow, accepting Fellowship; from Hugo de Vries, G.
H. Hardy, G. A. F. Molengraaff, accepting Foreign Honorary
Membership; from A. W. Whitcher, presenting a framed photo-
graph of Gainsborough's portrait of Sir Benjamin Thompson, re-
cently bequeathed to Harvard College; from Miss Susanna
Willard, presenting a silhouette of Rev. Joseph Willard, Vice-
President and Corresponding Secretary of the Academy from
1780-1804; from the University of Virginia, presenting a medal
commemorating its 100th anniversary; from the Wisconsin
Academy of Sciences, presenting a medal commemorating its 50th
anniversary; from the Rumford Historical Association thanking

440 PROCEEDINGS OF THE AMERICAN ACADEMY.

the Academy for a replica of the first Riimford medal ; from the
Reale Universita di Padova announcing the celebration of its
700th anniversary; from R. S. Woodward giving an account of
the centennial of the University of Virginia.

The Chair announced the death of the following Fellows : Joel
Asaph Allen, Class II., Section 3: Charles Pickering Bowditch,
Class III., Section 2: Eliot Channing Clarke, Class I., Section 4:
Hiram Francis Mills, Class I., Section 4; and of the Foreign
Honorary Member Julius von Hann, Class II., Section 1.

A biographical notice of Edward Charles Pickering, by J. II.
Metcalf was presented by the Corresponding Secretary.

The President stated that a Conference of Orientalists was held
at the invitation of Class III., Section 2, of the Academy, in the
House of the Academy, on October 5th. ^

The following communication was presented: Professor C. B.
Gulick, ''The Greek Novel."

The following papers were presented by title:

"The General Conditions of Validity of the Principle of Le
Chatelier," by Alfred J. Lotka. Presented by Irving Fisher.

"The Grid Structure in Echelon Spectrum Lines," by Norton
A. Kent and Lucien B. Taylor.

"Effect of Tension upon Resistance of Abnormal Metals," by
P. W. Bridgman.

"Effect of Pressure on Thermal Conductivity," by P. W. Bridg-
man.

"The Failure of Ohm's Law in Gold and Silver at High Current
Densities," by P. W. Bridgman.

" Waverley Researches in the Pathology of the Feeble-Minded,"
by W. E. Fernald, E. E. Southard, M. M. Canavan, O. J. Raeder,
and A. E. Taft.

"The Early Evolution of the Reflecting Telescope," by Louis
Bell.

The meeting was then dissolved.

1 For the record of this meeting see p. 460.

RECORDS OF MEETINGS. 441

One thousand one hundred and sixth Meeting.

November 9, 1921. — Stated Meeting.

The Academy met at its House.

The President in the Chair.

The Transactions of the last meeting were read and approved.

There were thirty Fellows and two guests present:

The following communications were presented:

Louis Bell, "The Early Evolution of the Reflecting Telescope."

Discussion followed by A. G. Webster, E. Thomson, H. Gush-
ing, W. S. Bigelow, and others.

Desmond FitzGerald, "On a great Collection of Skeletons of
Animals from Prehistoric Times at the Rancho la Brea, near Los
Angeles, California."

Discussion followed by W. M. Davis.

A. G. Webster, "Hermann von Helmholtz and his Significance
for a Century of Science."

C. R. Lanman exhibited specimens of Helmholtz's autograph.

The Meeting was then dissolved.

One thousand one hundred and seventh Meeting.

December 14, 1921. — Stated Meeting.

The Academy met at its House.

The President in the Chair.

The Transactions of the last meeting were read and approved.

There were thirty-nine Fellows and two guests present :

The Corresponding Secretary reported acceptances of Fellow-
ship from :

F. S. Converse, A. P. Davis, William Emerson, C. M. T. Loeffler,
H. A. Pilsbry, A. A. Young, and a resignation of Fellowship from
R. A. Cram.

The President announced the death of Charles Robert Cross,
Class L, Section 2; Chairman of the Rumford Committee since
1898.

The Librarian reported the gift to the Library from Admiral

442 PROCEEDINGS OF THE AMERICAN ACADEMY.

F. T. Bowles of a set of the Transactions of the Institution of
Naval Architects (London), and a set of the Transactions of the
Society of Naval Architects and Marine Engineers (New York),
with the offer to continue during his lifetime the gift of the volumes
of these sets as they appear.

The following communications were presented :

Edward P. Warner, Professor of Aeronautical Engineering in the
Massachusetts Institute of Technology, " Recent Developments in
Aeronautical Science." (With lantern slide illustrations.)

Robert DeC. Ward, "Some Meteorological Phenomena in Rela-
tion to Flight."

Alexander McAdie, "Aerography." (With lantern slide illus-
trations.)

The Meeting was then dissolved.

One thousand one hundred and eighth Meeting.

January 7, 1922. — Open Meeting.

An Open Meeting was held at the House of the Academy from
four to six o'clock.

The President in the Chair.

There were about two hundred and twenty-five Fellows and
guests, including ladies, present.

Mr. Harlow Shapley, Director of the Harvard University
Observatory, spoke on "The Galaxy: Its Content and Dimen-
sions," with lantern slide illustrations.

Tea was served in the Reception Room on the third floor.

One thousand one hundred and ninth Meeting.

January 11, 1922. — Stated Meeting.

The Academy met at its House, on a night made formidable by
cold and storm.
The President in the Chair.

RECORDS OF MEETINGS. 443

The Transactions of the last Meeting were read and approved.

There were fifteen Fellows present:

The Corresponding Secretary presented a letter of resignation
of Fellowship from W. T, Councilman.

The following proposed amendment to the Statutes was referred
to a Committee consisting of the Corresponding and Recording
Secretaries :

Chapter III, Article 2, second and last paragraphs, strike out
after the word Fellow, "having the right to vote."

On the recommendation of the Council it was

Voted, To make the following appropriation from the income of
the General Fund:

$300 for General Expenses.

$300 for House Expenses.

The following communication was presented :

G. A. Reisner, " Archeological Methods Used by the Harvard-
Boston Expedition." (With lantern slide illustrations.)

The following papers were presented by title:

"Some Hymenopterous Parasites of Lignicolous Itonididse,"
by C. T. Brues.

" A Table and Method of Computation of Electric Wave Propa-
gation and Transmission Line Phenomena," by G. W. Pierce.

"Artificial Electric Lines With Mutual Inductance Between
Adjacent Series Elements," by G. W. Pierce.

"The Dioptrics of the Eye As Related to Pictorial Art," by
Adelbert Ames, Jr., presented by Louis Bell.

The Meeting was then dissolved.

One thousand one hundred and tenth MeetiniT.

February 8, 1922. — Stated Meeting.

The Academy met at its House.
The President in the Chair.

The Transactions of the two last Meetings were read and
approved.
There were twenty-seven Fellows present :

444 PROCEEDINGS OF THE AMERICAN ACADEMY.

The Corresponding Secretary announced the receipt of the
following biographical notices:

Charles Pickering Bowditch, by A, M. Tozzer.

Barrett Wendell, by Robert Grant.

The President announced the death of James Bryce, Viscount
Bryce, Foreign Honorary IMember, Class III., Section 3.

The President announced that an invitation had been received
from the Academic Royale de Belgique, inviting the Academy to
take part in the celebration of its 150th anniversary on May 24,
1922.

It was

Voted, To ratify the vote taken at the last meeting, no quorum
being then present, appropriating SGOO from the General Fund,
to be applied, $300 to General Expenses and $300 to House ex-
penses.

The special Committee for an amendment to the Statutes,
Chapter HI., Ai't. 2, second and last paragraphs, to strike out after
the word Fellow the words "having the right to vote," reported,
recommending that the amendment be adopted; and, a ballot
having been taken, it appeared that the amendment was adopted,
twenty votes being cast in the affirmative, and none in the nega-
tive.

The President stated that he had appointed E. H. Hall a mem-
ber of the Committee on Biographical Notices.

The following communication was presented :

W. B. Cannon, "New Evidence for Nervous Control of Some
Internal Secretions." (With lantern slide illustrations.)

The following paper was presented by title :

"Atmospheric Attenuation of Ultra-Violet Light," by E. L.
Schaeffer, presented by Theodore Lyman.

The ISIeeting was then dissolved.

One thousand one hundred and eleventh Meeting.

March 8, 1922. — Stated Meeting.

The Academy met at its House.

The President in the Chair.

The Transactions of the last Meeting were read and approved.

RECORDS OF MEETINGS. 445

There were forty-three Fellows and several guests present:
The Corresponding Secretary announced the receipt of an
invitation from the Royal University of Padua inviting the Acad-
emy to take part in the VII centenary of its foundation, May
14-17, 1922; and an invitation from the Societe Asiatique de
Paris to send delegates to take part in the 100th anniversary of its
founding, July 10-13, 1922.

The Corresponding Secretary announced the receipt of the
following biographical notices:

John Wallace Baird, by R. M. Yerkes.
William Gilson Farlow, bv C. L. Jackson.

The President announced the death of Charles Leonard Bouton,
Class I., Section 1.

On recommendation of the Council, the following appropriations
were made for the ensuing year:

From the income of the General Fund, 88,300.65, to be used
as follows:

for General and Meeting expenses $1,300.00

for Library expenses 3,000 . 00

for Books, periodicals and binding 1,100.00

for House expenses 2,300 . 00

for Treasurer's expenses GOO . 00

From the income of the PubHcation Fund, $3,951 .95, to be used
for publication.

From the income of theRumford Fund, $6269.65, to be used
as follows:

for Research $1,000.00

for Purchase and binding of books and periodicals 200 . 00
for Publication 600.00

for use at the discretion of the Committee 4,469 . 65

P'rom the income of the C. M. Warren Fund, $1,842.44, to be
used at the discretion of the Committee.

E. B. Wilson reported for the Committee on INIembership, pro-
posing amendments to the Statutes as follow:

(1) to amend Chapter II., Art. 2, by substituting "Two hundred
and ten" for "Two hundred" in the third line.

(2) to amend Chapter IX., Art. 1, third paragraph, by omitting
the words "of the same Class."

446 PROCEEDINGS OF THE AMERICAN ACADEMY.

The President appointed the Nominating Committee for officers
for the ensuing year, 1922-23, as follows:

G. D. Birkhoff, of Class I.

C. H. Warren, of Class II,

Frederic Dodge, of Class III.

The following communication was presented:

Adelbert Ames, Jr., "The Physiology of Vision and the Tech-
nique of Art."

The following papers were presented by title:

"Additions to the Hydroid Fauna of the Bermudas," by Rudolf
Bennitt, presented by E. L. Mark.

"The Parasitic Worms of the Animals of Bermuda: I. Trema-
todes," by F. D. Barker, presented by E. L. Mark.

The Meeting was then dissolved.

One thousand one hundred and twelfth Meeting.

March 11, 1922.— Open Meeting.

An Open INIeeting was held at the House of the Academy from
four to six o'clock.

The President in the Chair.

There were about one hundred Fellows and guests, including
ladies, present..

Professor George Grafton Wilson, of Harvard University, spoke
on "The Recent Conference on the Reduction of Armaments."

Tea was served in the Reception Room on the third floor.

One thousand one hundred and thirteenth Meeting.

April 8, 1922.— Special Meeting.

A special meeting of the Academy was held at its House on
Saturday, April 8, at four o'clock in the afternoon to receive Pro-
fessor Hendrik Antoon Lorentz of the University of Leiden, a
Foreign Honorary Member of the Academy.

RECORDS OF MEETINGS. 447

A number of Fellows, and guests upon their invitation, were
present.

The President introduced Professor Lorentz who spoke on some
features in the work of the late Josiah Willard Gibbs, Professor of
Mathematical Physics in Yale College, and Fellow of the Academy.

At the close of the address an hour was spent socially in the
upper room where tea was served.

One thousand one hundred and fourteenth Meeting.

April 12, 1922. — Stated Meeting.

The Academy met at its House at 8.15 p.m.

The President in the Chair.

There were thirty-six Fellows present:

The Transactions of the meetings of March 8 and April 8 were
read and approved.

The President announced the death of John Wilkes Hammond,
Fellow in Class HI., Section 1.

The Corresponding Secretary reported the receipt of a bio-
graphical notice of William Thompson Sedgwick by Edmund B.
Wilson.

The President announced the appointment of C. H. Haskins and
A. E. Kennelly to represent the Academy at the 150th anniversary
of Academic Royale de Belgique, on May 24th; and of C. H.
Haskins and C. H. Moore at the 700th anniversary of the Uni-
versity of Padua.

The following amendments to the Statutes were adopted:

Chapter H., Article 2, last line, add the words "and ten" so as
to read " nor shall there be more than Two hundred and ten in any
one Class."

Chapter IX., Article 1, paragraph 3, strike out the words "of
the same Class."

The following Communications were presented ; —

Mr. Elihu Thomson. "Laboratory Products."

]\Ir. John L. Lowes. "A Neglected Note Book of Coleridge."

The following papers were presented by title : —

448 PROCEEDINGS OF THE AMERICAN ACADEMY.

"A Revision of the Endogoneae." By Roland Thaxter,

" The Echinoderms of the Challenger Bank, Bermuda." By-
Hubert L. Clark. Presented by E. L. Mark.

"The Heat of Vaporization of Mercury." By F. W. Loomis.
Presented by P. W. Bridgman.

"The Joule-Thomson Effect in Air." By P. H. Royster. Pre-
sented by P. W. Bridgman.

"The Ratio of the Calorie at 73° to that at 20°." By Arnold
Romberg. Presented by P. W. Bridgman.

The Meeting was then dissolved.

One thousand one hundred and fifteenth Meeting.

May 10, 1922. — x\nnual Meeting.

The Academy met at its House at 8.15 p.m.

The President in the Chair.

Thirty-seven Fellows were present.

The Transactions of the Meeting of April 12 were read and
approved.

Professor J. R. Jewett was appointed a delegate to represent the
Academy at the celebration of the 100th anniversary of the Societe
Asiatique de Paris, July 10-13, 1922.

The Corresponding Secretary reported that the Council had
transferred William Emerson, with his consent, from Class I.,
Section 4 to Class HI., Section 4.

The Corresponding Secretary presented the following biographi-
cal notices: — Joel Asaph Allen, by H. C. Bumpus; Eliot Channing
Clarke, by G. F. Swain; Henry Lee Higginson, by M. A. DeW.
Howe; Franklin Paine Mall, by W. T. Councilman; John Elliot
Pillsbury, by W. H. Dall; Elmer Ernest Southard, by C. M.
Campbell; Andrew Dickson White, by W\ D. Bancroft; Edward
James Young, by W'. W. Fenn.

The following report of the Council was presented: —

Since the last report of the Council, there have been reported the
deaths of seven Fellows: Joel Asaph Allen, Charles Leonard
Bouton, Charles Pickering Bowditch, Eliot Channing Clarke,

RECORDS OF MEETINGS. 449

Charles Robert Cross, John ^Yilkes Hammond, Hiram Francis
IMills; and two Foreign Honorary IMembers: Viscount Bryce,
JiiUus von Hann.

Sixty-one Fellows and three Foreign Honorary Members were
elected by the Council and announced to the Academy in May
1921. Two Fellows have resigned.

The roll now includes 569 Fellows and 67 Foreign Honorary
IMembers (not including those elected in April 1922),

The annual report of the Treasiu-er, Henry H. Edes, was read,
of which the following is an abstract:

General Fund.

Receipts.

Balance, April 1, 1921 $8,495.29

Investments 4,691.00

Assessments 3,480.00

Admissions 100.00

Sundries ' 257.65 $17,023.94

Expenditures.

Expense of Library $4,815.44

Expense of House 2,386.91

Treasurer 505.96

Assistant Treasurer 250 . 00

General Expense of Society 1,596.61

President's Expenses 64 . 25

Income transferred to principal 367 . 23 $9,986 . 40

Balance, April 1, 1922 7,037.54

$17,023.94

RuMFORD Fund

Receipts.

Balance, April 1, 1921 $3,938.64

Investments 4,110.92

Sale of Publications 49.90 $8,099.46

450 PROCEEDINGS OF THE AMERICAN ACADEMY.

Expenditures.

Research 1,200.00

Books, periodicals and binding 317.27

Publications 392.58

Sundries 73.50

Income transferred to principal 186.89 $2,170.24

Balance, April 1, 1922 5,929.22

$8,099.46
C. M. Warren Fund.

Receipts.

Balance, April 1, 1921 $4,226.62

Investments 1,205.55 $5,432.17

Expenditures.

Research ' . . . . $2,975.00

Vault Rent, part 3 . 00

Income transferred to principal 52.11 $3,030.11

Balance, April 1, 1922 2,402.06

$5,432.17

Publication Fund.

Receipts.

Balance, April 1, 1921 $4,470.01

Appleton Fund investments 1,843.68

Centennial Fund investments 2,441 . 28

Authors' Reprints 73.87

Sale of Publications 227.34 $9,056.18

Expenditures .

Publications $3,738.73

Vault Rent, Part 10.00

RECORDS OF MEETINGS. 451

Income transferred to principal S187.32 $3,936.05

Balance April!, 1922 5,120.13

$9,056.18

Francis Amory Fund
Receipts.
Investments $1,533.75

Expenditures.

Publishing statement $55 . 60

Interest on bonds bought 44 . 00

Income transferred to principal 1,434.15 $1,533.75

The following Reports were also presented : —

Report of the Library Committee.

The Librarian begs to report for the year 1921-22, as follows:
During the year, 87 books have been borrowed by 19 persons, in-
eluding 13 Fellows and 2 libraries. Many books have been consulted
and used at the Library. All books taken out have been returned or
satisfactorily accounted for, except three.

The number of books on the shelves at the time of the last report was
37,543. 868 volumes have been added, making the number now on
the shelves 38,411. This includes 170 purchased from the income of
the General Fund, 54 from that of the Rumford Fund, and 644 re-
ceived by gift or exchange.

The expenses charged to the Library during the financial year are:

Salaries $2,970.25

Binding: —

General Fund 1,055.10

Rumford Fund 123.21

760.93

221

.62

2,

.10

452 PROCEEDINGS OF THE AMERICAN ACADEMY.

Purchase of periodicals and books : —

General Fund

Rumford Fund

Miscellaneous

$5,313.21

Arthur G. Webster, Librarian.
May 10, 1922.

Report of the Ruimford Committee.

The Committee met on October 19, 1921. Professor Charles R.
Cross expressed himself as unwilling to be a candidate for re-election
to the Chairmanship, the matter of organization was therefore post-
poned.

Professor Cross died on November 16, 1921.

At a meeting held December 14, 1921, Theodore Lyman was elected
Chairman and Arthur G. Webster, Secretary.

The following grants in aid of researches in light or heat have been
made during the academic year 1921-22:

October 19, 1921. To Professor Norton A. Kent, of Boston
University, for the purchase of a Lummer Plate; Additional to
former appropriation (235) $500

To Professor Harvey N. Davis, of Harvard University, in aid
of his researches on the Improvement of the Design of Liquid
Air Machinery (236) 300

April 12, 1922. To Professor Percy W. Bridgman, of Har-
vard University, for the continuation of his researches on the
Thermal and Optical Properties of Matter under High Pres-
sure; Additional to former appropriation (237) 500

To Professor Frederick A. Saunders, of Harvard University,
in aid of his Spectroscopic Researches; Additional to former
appropriation (238) 150

To Professor William Duane, Harvard University, for an
Investigation on the Heat Energy of Electrons (239) . . . 300

Reports of progress in their respective researches have been received
from the following persons: R. T. Birge, P. W. Bridgman, W. W.

RECORDS OF MEETINGS. 453

Campbell, A. L. Clark, F. Daniels, P. F. Gaehr, R. C. Gibbs, H. L.
Howes, L. R. Ingersoll, N. A. Kent, F. G. Keyes, C. A. Kraus, C. L.
Norton, F. Palmer, Jr., J. A. Parkhurst, H. M. Randall, T. W.
Richards, F. A. Saunders, W. O. Sawtelle, B. J. Spence, L. S. E.
Thompson, O. Tugman, F. W. Very, A. G. Webster, D. L. Webster.

The following papers in the Proceedings have been published with
aid from the Rumford Fund since the presentation of the last Report:

Awards of the Premium and Grants for Research in Light and Heat.
Charles R. Cross, Vol. 56, No. 10.

The Grid Structure in Echelon Spectrum Lines. Norton A. Kent
and Lucien B. Taylor, Vol. 57, No. 1.

The Efifect of Pressure on the Thermal Conductivity of Metals.
P. W. Bridgman, Vol. 57, No.^5.

The following papers have been approved for publication :

The Atmospheric Attenuation of Ultra-Violet Light, Dr. E. L.
Schaeffer.

On the Ratio of the Calorie at 73° to that at 20°, Professor Arnold
Romberg.

The Heat of Vaporization of Mercury, Professor F. W. Loomis.

The Joule-Thomson Effect in Air, P. H. Royster.

For nearly twenty-five years Professor Charles R. Cross acted as
Chairman of the Rumford Committee. The members of the Com-
mittee wish to express their appreciation of his untiring devotion and
to record their deep regret at his loss.

Theodore Lyman, Chairman.
May 10, 1922.

Report of the C. M. Warren Committee.

The Committee had at its disposal at the end of the fiscal year in
March 1921, $4,501.03. During the year ending March 31, 1922,
grants to the amount of $2,875 were made. The balance on that date
was $1,626.03.

Since the last annual report awards have been made as follows:
To Professor Henry Fay, Massachusetts Institute of Technology,
$200 was granted June 1, 1921, for a research on the influence of nitro-
gen upon the case hardening of steels and the study of the heat treat-
ment of beta-brasses.

454 PROCEEDINGS OF THE AMERICAN ACADEMY.

To Professor H. H. Willard, University of Michigan, $300 was
granted June 1, 1921, for the study of an electrometric method of de-
termining the endpoint in volumetric analysis.

To Professor R. L. Datta, Calcutta, India, $400 was granted June 1,
1921, for a research on the determination of the temperature of ex-
plosion of endothermic substances.

To Professor D. A. Maclnnes, Massachusetts Institute of Tech-
nology, $100 was granted June 15, 1921, for work on liquid junction
potentials.

To Professor L. J. Desha, Washington and Lee University, $200 was
granted September 23, 1921, for a study of the fluorescence of organic
compounds.

To Professor V. K. Krieble, Jarvis Chemical Laboratory, Trinity
College, $100 was granted February 21, 1922, for a study of asphalts.

To Professor F. R. Brunei, Bryn Mawr College, $200 was granted
February 21, 1922, for work on the addition of halogen hydrides to
unsaturated compounds.

To Professor C. James, New Hampshire College, $500 was granted
May 4, 1922, to be applied toward an investigation on the ytterbium
earths.

To Professor Charles A. Kraus, Clark LTniversity, $500 was granted
May 4, 1922, to continue his work on the constitution of metallic
substances.

Reports of progress have been received from Professors Brunei,
Kraus, Conant, James, Fay, and Maclnnes. The other recipients of
grants have been asked to submit reports of their work.

The Chairman of the Committee is attempting to get as complete a
collection as possible of reprints of the papers describing the work
which has been assisted by grants from the Warren Fund in the past.

James F. Norris, Chairman.
May 10, 1922.

Report of the Publication Committee.

During the twelve months since the presentation of the last annual
report, from April 1, 1921 to March 31, 1922, there have been pub-
lished No. 3 of Vol. 14 of the Memoirs, Nos. 5-11, inclusive, of Vol. 56

RECORDS OF MEETINGS. 455

of the Proceedings, and Nos. 1 to 10, inclusive, of Vol. 57. Costs of
printing, happily, show a slight falling off from the excessive prices of
preceding years, which is partly offset by the increased use of plates
and line engravings in the published papers. The financial statement
is as follows :

Receipts.

Balance, April 1, 1921 $5,882.10

Appropriation 3,559.11

Sales of publications 226.18

Received for authors' reprints 75.03 $9,742.42

Expenses.

Engraving, printing, and binding .... $3,450 . 92

Cartage and mailing 277.97

Committee's expenses 9 . 84 $3,738 . 73

Balance, April 1, 1922 $6,003.69

The above figures do not include the sum of $382 . 58 received from
the Rumford Committee for publication of Rumford papers.

Respectfully submitted,

Louis Derr, Chairman.
May 10, 1922.

Report of the House Committee.

The House Committee submits the following report for 1921-22.

With the balance of $12.35 left from last year, an appropriation of
$2,500, and $145 received from other societies for the use of the rooms,
the Committee has had at its disposal the sum of $2,057.35. The total
expenditure has been $2,531.91, leaving an unexpended balance on
April 1, 1922, of $125.44. The expenditure has been as follows: —

Janitor $925.00

A. Light 169.53

Electricitv ^ ^^ t^ or nf\

B. Power 86 00

456 PROCEEDINGS OF THE AMERICAN ACADEMY.

Furnace 953.21

^^ I Water Heater 30.50

Care of Elevator 71.45

Gas 62.29

Water 8.80

Telephone 78.18

Janitor's Materials 10.78

Upkeep . 106.47

Ash Tickets 29.70

Total Expenditure $2,531.91

The amount $145 contributed by other societies for the use of the
building leaves the net expense of the House $2,386.91.
Meetings have been held as follows : —
The Academy

Stated meetings 8

Open meetings 3

Special meetings 4

American Antiquarian Society 1

Archaeological Institute 1

Colonial Dames • . 1

Colonial Society 4

Geological Club of Boston 2

Harvard-Technology Chemical Club 7

31

The rooms on the first floor have been used for Academy Council
and Committee meetings and also by the Trustees of the Children's
Museum.

Respectfully submitted,

John Osborne Sumner, Chairman.
May 10, 1922.

On the recommendation of the Treasurer, it was
Voted, That the Annual Assessment be $10.00.

RECORDS OF MEETINGS.

457

The animal election resulted in the choice of the following
officers and committees:

George F. Moore, President.
Elihu Thomson, Vice-President for Class I.
Harvey Gushing, Vice-President for Class 11.
Arthur P. Rugg, Vice-President for Class III.
Harry W. Tyler, Corresponding Secretary.
Charles B. Gulick, Recording Secretary.
^ Henry H. Edes, Treasurer.
Arthur G. ^YEBSTER, Librarian.

Councillors for Four Years.

Edward V. Huntington, of Class I.
Charles Palache, of Class II.
William C. Wait, of Class III.
KiRSOPP Lake, of Class III.

Finance Committee.

Henry P. Walcott, John Trowbridge,

Harold jNIurdock.

Rumford Committee.

Theodore Lyman, Louis Bell,

Arthur G. Webster, Percy W. Bridgman,

Elihu Thomson, Harry M. Goodwin,

Charles L. Norton.

C. M. Warren Committee.

James F. Norris, Walter L. Jennings,

Henry P. Talbot, Arthur D. Little,

Gregory P. Baxter, Lawrence J. Henderson,

Frederick G. Keyes.

1 Died October 13, 1922.

458 PROCEEDINGS OF THE AMERICAN ACADEMY.

Publication Committee.

Louis Deer, of Class I.
Herbert V. Neal, of Class II.
Albert A. Howard, of Class III.

Library Committee.

Harry M. Goodwin, of Class I.
Thomas Barbour, of Class II.
William C. Lane, of Class III.

House Committee.

John O. Sumner,
Wm. Sturgis Bigelow, Robert P, Bigelow.

Committee on Meetings.

The President, George H. Parker,

The Recording Secretary, Edwin B. Wilson,

Edward K. Rand.

Auditing Committee.
George R. Agassiz, John E. Thayer.

The Council reported that the following gentlemen were elected
members of the Academy : —

Class L, Section 1 (Mathematics and Astronomy):

Walter Sydney Adams, of Pasadena, California, as Fellow.

Arthur Stanley Eddington, of Cambridge, as Foreign Honorary
Member.
Class I., Section 2 (Physics) :

Edwin Crawford Kemble, of Cambridge, as Fellow.
Class L, Section 3 (Chemistry) :

Richard Chase Tolman, of Washington, as Fellow.

RECORDS OF MEETINGS. 459

Class I., Section 4 (Technology and Engineering) :

Gano Dunn, of New York, as Fellow.

Thomas Alva Edison, of New Jersey, as Fellow.
Class II., Section 1 (Geology, Mineralogy, and Physics of the Globe) :

Emmanuel de Margerie, of Paris, as P^oreign Honorary Member.

Austin Flint Rogers, of Palo Alto, as Fellow.
Class II., Section 2 (Botany):

William Henry ^Yeston, Jr., of Cambridge, as Fellow.
Class IL, Section 3 (Zoology and Physiology) :

Nathan Banks, of Cambridge, as Fellow.

Thorne ^Martin Carpenter, of Boston, as Fellow.

Alfred Clarence Redfield, of Boston, as Fellow.
Class II., Section 4 (]Medicine and Surgery):

Sir Thomas Clifford Allbutt, of Cambridge, as Foreign Honorary
Member.

Stanley Cobb, of Ponkapoag, as Fellow.

Joseph Lincoln Goodale, of Boston, as Fellow.

Robert Williamson Lovett, of Boston, as Fellow.
Class III., Section 1 (Philosophy and Jurisprudence):

William McDougall, of Cambridge, as Fellow.
Class III., Section 3 (Political Economy and History):

Edward Channing, of Cambridge, as Fellow.

George La Plana, of Cambridge, as Fellow.

Henri Pirenne, of Ghent, as Foreign Honorary Member.
Class III., Section 4 (Literature and Fine Arts):

Arthur Kingsley Porter, of Cambridge, as Fellow.

Paul Joseph Sachs, of Cambridge, as Fellow,

Charles Henry Conrad Wright, of Cambridge, as Fellow.

Monsieur J. Cavalier, Professor in the School of Science of
the University of Toulouse and Rector of the University, ad-
dressed the Academy.

The following paper was presented by title: " The Phenomena of
Polymegaly in the Sperm-Cells of the Family Pentatoraidae."
By Robert H. Bowen. Presented by Edmund B. Wilson.

The Meeting was then dissolved.

460 PROCEEDINGS OF THE AMERICAN ACADEMY.

October 5 and 6 and 7, 1921.— Special Meeting of

Orientalists.

A Special Meeting was held at the House of the Academy,
beginning on Wednesday morning, the 5th of October, at ten
o'clock, when the Academy received the Delegates from the
Societe Asiatique of Paris and the Royal Asiatic Society of Lon-
don, deputed to confer with the members of Class III of the
Academy upon matters concerning the promotion of Oriental
studies.

A series of joint meetings of Orientalists was begun at I>ondon
in 1919, and continued at Paris in 1920. This meeting of 1921 was
held as a continuation of that series. In July, 1922, the French
Society will celebrate the centenary of its foundation, and in 1923
the British Society will follow suit. Not until 1924 would another
opportunity recur for holding such a meeting in America.

Accordingly, pursuant to a vote of the Council of the American
Academy, an invitation was sent on April 13, 1921 to the Societe
Asiatique, the Royal Asiatic Society, and the Societa Asiatica
Italiana, to meet with the members of Class III of the Academy, on
the 24th of June, 1921, or at such later time as might appear more
convenient, and at the House of the Academy, in the city of Boston.

The invitation was authorized by the Council of the Academy
at the instance of several gentlemen, — Americans, Orientalists,
friends of the Orient and of Oriental learning, — whose names
follow: Dr. William Sturgis Bigelow, of Boston ; Professor James
H. Breasted, of the University of Chicago; Mr. Charles Dana
Burrage, of Boston; Professors Albert T. Clay and Charles C.
Torrey, of Yale University; Dr. Arthur Fairbanks, of the Museum
of Fine Arts, Boston; Professors James R. Jewett, Charles R.
Lanman, George Foot IMoore, and James H. Woods, of Harvard
Universitv; Professor Duncan B. ^lacdonald, of Hartford Theo-
logical Seminary.

The invitation was most cordially and promptly accepted, — on
behalf of the French Society, by its President, Mr. Emile Senart,
Member of the Academy of Inscriptions and Belles-Lettres of the
Institute of France, and on behalf of the English Society, by its

RECORDS OF MEETINGS. 461

President, Lord Reay (deceased August 1, 1921), of the British
Academy. For the Itahan Society, its President, Professor Pavo-
Hni of Florence, wrote that the Ministry held out hopes that the
sending of a Delegate might be sanctioned. Unfortunately, these
hopes were not realized.

The French Society's Delegates were: Paul Pelliot, Member of
the Academy of Inscriptions and Belles-Lettres of the Institute of
France, Professor of Chinese at the College de France; Alexandre
Moret, Director of Studies at the Ecole Pratique des Hautes
Etudes, Conservator of the Musee Guimet in Paris.

The Delegates of the English Society were: Dr. Arthur Ernest
Cowley, Fellow of Magdalen College, Oxford, Librarian of the
Bodleian Library; Dr. Stephen Langdon, Professor of Assyriology
at Oxford; Herbert ^Yeld-Blundell, Esq., of London (Queen's
College, Oxford) ; Mr. Henry Lee Shuttleworth, of Delhi, of the
Indian Civil Service.

Upon the Academy's invitation, the American Oriental Society
sent the following Delegates: its President, Reverend James
Buchanan Nies, of Brooklyn Heights, New York; Dr. William
Sturgis Bigelow, of Boston; Professor James H. Breasted, of the
University of Chicago; Charles Dana Burrage, Esq., of Boston;
Professor Albert T. Clay and Professor Edward Washburn Hop-
kins, of Yale; Professor A. V. Williams Jackson, of Columbia
University; Professor Charles Cutler Torrey, of Yale.

All these were present, except Professor Clay.

The non-resident Delegates, during their stay, were the guests
of The Omar Khayyam Club of America. With two or three
exceptions, they were lodged and entertained by the Omar Club
at the House of the Harvard Club of Boston.

The Delegates were received by the following Fellows of the
Academy; the President of the Academy, Professor George Foot
Moore; his immediate predecessor. Professor Theodore William
Richards; the Corresponding Secretary of the Academy, Professor
Harry W. Tyler; the Recording Secretary of the Academy, Pro-
fessor James Hardy Ropes; President Lowell of Harvard; ]\Ir.
John Ellerton Lodge, of the Boston Museum of Fine Arts; Mr.
Edward Sylvester Morse, of the Peabody Museum, Salem; Dr.
Francis H. Williams, of Boston; Professors James Richard Jewett,

462 PROCEEDINGS OF THE AMERICAN ACADEMY.

Kirsopp Lake, Ephraim Emerton, Charles R. Lanman, David G.
Lyon, Clifford Herschel INIoore, George Andrew Reisner, and James
Haughton Woods, of Harvard.

Sessions of Wednesday, October 5, 192L

President Moore opened the sessions by welcoming to the
Academy the Delegates of the Oriental Societies, and spoke briefly
of the purpose and spirit of the joint meeting.

Professor Pelliot responded on behalf of the visitors. Moreover,
as bearer of an official message to the Academy, he read a letter
addressed to President Moore by M. Senart, of the Institute of
France, as President of the Societe Asiatique. The letter tells of
the satisfaction of the Society at the establishment of relations of
sympathy and cooperation with the Academy, and of its hope for
long and fruitful maintenance of these relations. In particular,
it tells of the proposed celebration in the early days of July, 1922,
of the hundredth anniversary of the founding of the French
Asiatic Society, and expresses the hope that the Academy will
take part on that occasion.

Professor Hopkins, of Yale, in response to a call from the Chair,
gave a brief account of the recent progress of American studies in
the literature of India.

Professor Torrey, of Yale, in like manner, spoke of the progress
of Semitic studies, with some account of the collections of Semitic
antiquities in the Museums at Philadelphia, Yale, Harvard,
Princeton, and New York (collection of J. Pierpont IMorgan).

Professor Reisner, of Harvard, reviewed the work of American
philologists and archaeologists in the Egyptian field, and mentioned
the notable collections of Egyptian antiquities in American
Museums.

Professor Lyon, of Harvard, finally, gave some account of the
Harvard Semitic Museum, and of the Harvard Excavations at
Samaria.

The assembled company then proceeded in motor-cars to the
Boston Museum of Fine Arts. The Director, Dr. Arthur Fair-
banks, being detained at home by illness, the visitors were received

RECORDS OF MEETINGS. 463

by the Acting-Director, Mr. Hawes. They were the guests of the
Museum at hnicheon. In the afternoon, they were conducted,
some through the Egyptian Rooms by Dr. Reisner, and others
through the Japanese Rooms by Mr. John Ellerton Lodge. The
Delegates and their hosts dined together at the Harvard Chib.

During the afternoon, Dr. Reisner gave an account of his twenty-
two years of archfeological research in Egypt, ilhistrated by the
objects now on exhibition, of which the most notable are: 1.
Eleven sculptin-es in the round of Chej)hren, ]\Iycerinus, Shepse-
skaf , and other members of the royal family of the Foui'th Dynasty ;
2. Two sculptures in the round of prime importance, and many
lesser statues and reliefs of the Old Empire; 3. The statue of the
Lady Sennuwy, and the painted wooden coffin of the monarch
Dehuti-nekht, both of the Middle Ethiopian IMonarchy (900-300
B.C.), the other half of which is in Khartum.

Sessions of Thursday, October 6, 192L

President ]\Ioore called the assembly to order at ten o'clock.

Dr. Arthur Ernest Cowley, of Oxford, Librarian of the Bodleian
Library, spoke upon the Hittite hieroglyphic inscriptions. He be-
lieves that they belong to the ninth and eighth centuries B.C.,
and that their language is connected with that of the inscriptions
of ^"an, the ancient Armenian tongue.

Dr. Cowley laid stress on the distinction between these and the
earlier cuneiform Hittite texts. We cannot assume without proof
that the language of the Carchemish inscriptions is the same as
that of the cuneiform tablets of Boghaz-keui. Nor can we even
be sure that the signs always have the same values and conceal
the same language at Tyana and Marash, for instance, as at Car-
chemish. Still we mav continue to call the inscriptions Hittite,
since the Assyrians spoke of the king of Carchemish as Sar mat
Hatti, and since the king of Carchemish also called himself by a
similar title. Lord of Hana, ruler of Hattina, according to Dr.
Cowley's decipherment. Hana, at the confluence of the Habur
with the Eui)hrates, and Hattina, the district to the west of
Carchemish, are mentioned together in the Cappadocian texts just

464 PROCEEDINGS OF THE AMERICAN ACADEMY.

published by Mr. Sidney Smith for the British Museum. These
places were on the caravan route to Babylon, and Carchemish was
bound to keep possession of them.

In the inscriptions of Carchemish three successive kings are
named, and the last inscription mentions a name which is deci-
phered as Sarduris. This must be Sarduris II of Van, who had
various dealings with the Hittites, as is known from the Vannic
inscriptions. His date, and therefore the date of the last of the
three kings of the Carchemish inscriptions, is about 750 B.C.
Other indications corroborate this conclusion, so that the dates of
this group of texts may be taken to fall between 850 and 750 B.C.
They are thus contemporary with the inscriptions of the neighbor-
ing kingdom of Van, with which also there seems to be some lin-
guistic connexion. Several comparisons were made with Vannic
grammar and vocabulary.

Mr. Alexandre Moret, of Paris, Conservateur of the Musee
Guimet, speaking in French, then followed. The title of his
paper was: L'acces de la plebe aux droits religieux et politiques
en Egypte.

A visit to the splendid Egyptian galleries of the Boston Museum
of Fine Arts shows what a contrast there is between the funerary
monuments of the Old Empire and those of the Middle Empire.
Among the former, the superb statues of king Mycerinus and his
family are most notable; among the latter, the magnificent coffins
of private individuals. This change implies nothing less than
a religious and social revolution. Under the Old Empire (3000 to
about 2600 B.C.), the king admits to religious and administrative
functions only his relatives, friends, courtiers. And to them alone
he accords participation in the funerary rites which assure survival
in the other world. In Egypt, as in Greece and Rome, religious
rights blend with political rights. To play a role in society, one
must take some part in the religious rites of which the king, son
of the gods, god himself, is the sole dispenser among men.

Beginning with the Middle Empire, about 2000 B.C., all is
changed. The funerary monuments, by their character and
increasing number, make it evident that every man has meantime
gained access to the much-valued religious and funerary rites.
Every man, no matter whether he be a plebeian or of the royal

RECORDS OF MEETINGS. 465

family, whether favored by the king or not, may now possess a
tomb, a coffin, a stele, may have the attributes of a king in the
other world, and may claim as such to bear a sceptre and to wear a
crown and the royal apparel. These things are depicted upon the
sides of the coffins of common people. The sacred rites which were
formerly known only to the king are now known to all. From a
religious point of view, society has become quite democratized.

Political and civil rights also have in the meantime been won by
the common people. This appears from the steles and from the
papyrus-texts of administrative and literary contents. These
show that the royal administration now concedes to every man the
right to enter upon a public career, to hold land for burial-places,
and to use and dispose of royal lands (subject to the king's right
of eminent domain), and the right to independent commercial
and industrial activity (not, for instance, in the royal workshops
alone), and to have recourse to the royal tribunals of justice by
right of petition, formerly accorded only to the higher classes.
Society has been levelled under a monarchy which, although of
divine right, has become democratized.

This rise of the common people, in the period between the Old
and the INIiddle Empires (say from 2800 to 2000 B.C.), was not
brought about without violent crises, which, as in Greece and
Rome, wear the aspect of a social revolution. A description of
these changes may be found in the texts which Professor James
H. Breasted has commented upon and coordinated in the seventh
chapter of his Development of Religion and TJwught in Ancient
Egypt. The beautiful coffins of the time of the ^Jiddle Empire
attest the results of the social and political struggles involved.

Dr. Stephen Langdon, Professor of Assyriology at Oxford, pre-
sented the results of his studies upon the Babylonian Poem of the
Righteous Suft'erer. His reconstruction of the poem upon the
basis of tablets from Niniveh and Sippur and Assur shows striking
resemblances to the Hebrew Book of Job.

Dr. Langdon announced the recovery of several new texts which
supply missing sections of the Babylonian poem. It now appears
that the poem consisted of four books, each of about 120 lines,
WTitten in strophes of ten lines each. The book was written by
an orthodox poet of the ninth century B.C., as an apology or

466 PROCEEDINGS OF THE AMERICAN ACADEMY.

defence of traditional theology against the current pessimism and
skepticism of the time. This legend of a righteous and orthodox
man unjustly afflicted with poverty and disease, originated in
Sumer, and was known as early as the twenty-fifth century.

The Righteous Sufferer was a resident of Nippur, named Lalur
elimma, "Good is the protection of Enlil." The Semitic poem, as
now reconstructed from texts of the late period, utilizes some old
Sumerian legend which has not been recovered. The poem con-
tains a detailed statement of the pessimism of the day, and the
orthodox reply thereto. The Righteous Sufferer challenges the
justice of God and the ways of providence. The good suffer and
the wicked prosper. Strict observance of the rituals availed not.
The priests of the mysteries and divination failed to avert the
afflictions sent by the gods. This righteous man had committed
no sin, and yet he was daily visited by divine punishment. Death
is therefore preferal)le to life, and labor in the service of religion is
futile.

After a long account of the current pessimism as illustrated by
Lalur elimma 's bitter complaint, the poet refers to the orthodox
theory of rewards and punishments. Affliction is a certain indi-
cation of sin. If the sufferer has committed no offense against
God, then his ancestors must have done so. The orthodox theory
of original sin is expounded, and emphasis is laid on man's igno-
rance and God's impenetrable wisdom. x\cross the gulf between
God and man, only prayer and ritual elicit a reply. Faith in the
orthodox rituals finally triumphs over skepticism, and the Right-
eous Sufferer receives a revelation bv divination, and sees that his
virtue will soon receive its reward. He is restored to health and
prosperity, and the poem ends with a long hymn of praise to
IMarduk, god of Babylon, who intervened and delivered the be-
liever. This later element of the poem shows that the work was
finally issued from the school of the priesthood at Babylon, who
redacted all the older poems in like manner to glorify their patron
deity INIarduk.

The Poe7n of the Righteous Sufferer forms one section of Mr.
Langdon's volume, Babylonian ]]'isdom. This will contain also
the recently recovered Dialogue of Pessimism and the Books of
Proverbs.

RECORDS OF MEETINGS.

467

On behalf of The Omar Khayyam Club of America, its President,
INIr. Lanman, presented to each one of the Delegates a copy of
Mr. Biirrage's three volumes, to wit: 1 . his "Twenty Years of The
Omar Khayyam Club of America," (Boston, 1921); 2. his "Exact
Facsimile of the rare and famous first edition of Edward Fitz-
Gerald's Rubaiyat of Omar Khayyam, the Astronomer-poet of
Persia. Translated into English verse. London: Bernard Qua-
ritch, Castle Street, Leicester Square, 1859"; and 3. his miniature
edition of "The Rubaiyat of Omar Khayyam of Naishapur." ^
In presenting these gifts, the speaker said, for substance, somewhat
as follows:

It would indeed be a doubtful compliment to give to you, in
the House of this venerable Academy, the works of a sot and a
materialist. Such a one, as Mr. Burrage observes,^ many people
suppose that Omar was. This belief is far from the truth. Like
Demokritos of Abdera, Omar was one of the most learned men of
his day, and with that learning went a deep religious conviction and
feeling which we may not lightly deny. If any incline to doubt it,
we may well ask them, Why did Co well, who was the Professor of
Sanskrit at Cambridge and Edward FitzGerald's teacher and
friend, — Why did Cowell urge his pupil to the work of translating
the Quatrains and aid him in the doing? For Cowell was one of
the most devout Christians that ever combined learning with
unaffected piety.

You, gentlemen, who, representing the Asiatic Societies, are
today here present as duly accredited Delegates to the American
Academy, are the guests of the Omar Club. It would ill comport
w'ith the dignitv of the Academv if she should turn you over to the
hospitality of a Club organized for mere conviviality. Happily,
such is not the case. Its members do indeed set store by good-
fellowship; but they have endeavored, — notably through the

1 This last is about 1 inch by 2 f in size, and is an edition of twenty copies
bound in full blue morocco, hand-tooled in gold, with inlays of red and green
morocco, with jade jewel inset, and put in a case, and privately printed by the
Rosemary Press for the Omar Club. A leaf following the title reads: "Dedi-
cated by The Omar Khayyam Club of America to its guests, the Delegates of
the Societe Asiatique, Royal Asiatic Society, Societa Asiatica Italiana, and
American Oriental Society, as a souvenir of their Joint-meeting with the Ameri-
can Academy of Arts and Sciences at Boston, in October, 1921."

2 "Twenty Years," page 17.

468 PROCEEDINGS OF THE AMERICAN ACADEMY.

labors of Eben Francis Thompson,^ the founder of the Club, —
to earn the respect and gratitude of scholars and men of letters,
by making possible a right estimate of Omar as mathematician
and teacher and poet, and by setting in a true light the relations of
FitzGerald's consummate poetry to its Persian original.

In his "Quatrains from the Greek," Walter Leaf speaks of "the
pathos of human life, its vanity and vexation, its brevity and un-
certainty, with the background of ' the veil through which we can-
not see' and the recurrent refrain, 'Let us eat and drink, for to-
morrow we die.'" He adds that "the genius of FitzGerald has
given us . . . what is, for our own day, a classical form for this
poignant theme."

FitzGerald himself, in his once despised first edition (page xiii),
says of Omar's poetry. "Any way, the Result is sad enough: sad-
dest perhaps when most ostentatiously merry: any way, fitter
to move Sorrow than Anger toward the old Tentmaker, who, after
vainly endeavouring to unshackle his Steps from Destiny, and to
catch some authentic Glimpse of Tomorrow, fell back upon Today
as the only Ground he got to stand upon." FitzGerald's presen-
tation of what seemed to him the essential features of Omar's
philosophy of life has attained (as witness the editions and trans-
lations — for number, they pass belief) a popularity in which some
would see a sign of the decadence of the age. Rather, let us look
at Omar, — as that man ^ would have us do of whose loving labors
and of whose gladness in gladdening others these books are the
fruit, — let us look at Omar as one who would teach us the lessons
of courage and hope and contentment and self-reliance, as one
whose lessons, superimposed upon "the will to believe," shall
teach us to make the most of the present through love of home
and of country and of God.

At the close of the Session, the company took luncheon at
Young's Hotel, and spent the afternoon visiting places of historic
interest in the environs of Boston, such as Lexington and Concord.
In the evening, it met again, informally, in Cambridge, at the
house of Professor James R. Jewett of Harvard University.

1 In his "Quatrains of Omar," collected and translated, and in his "Fitz-
Gerald's Omar," with a Persian text and close prose translation.

2 Burrage, in "Twenty Years," page 101.

RECORDS OF MEETINGS. 469

Sessions of Friday, October 7, 1921.

The meeting was called to order at ten o'clock.

Dr. Nies, President of the American Oriental Society, gave an
account of the Society's plans for the establishment of a School of
Living Oriental Languages, and of its recent steps for enlarging
its resources with a view to more extensive publication of works
upon the Orient.

Professor Pelliot spoke upon Native and Foreign Scholarship
in the field of Sinology, with an account of his explorations in
Chinese Turkestan from 1906 to 1909, and in particular of the
Grottoes of Touen-houang, and of the vast importance of their
contents for the future investigation of the history of China.

]\Ir. Shuttleworth described a hill-festival in the Western Him-
alayas, and illustrated his description with pictures from his col-
lections.

At the close of the formal Sessions, the afternoon hours were left
unassigned, in order that the guests might use them for further
study of the Egyptian and Japanese Galleries of the Museum, and
for other similar visits.

A farewell gathering was held in the evening, in the iEsculapian
Room of the Harvard Club. Here dinner was served, Mr. Lan-
man presiding. Brief addresses were made by President Lowell
of Harvard, by Dr. Cowley of Oxford, by Professor Pelliot of Paris,
by JNIr. Burrage of Boston, and by Professor George Foot Moore
of Harvard. The dominant note of these utterances was that of
satisfaction over the opportunity which such meetings offer for
personal acquaintance among the workers in these fields, and for
mutual sympathy and encouragement.

BIOGRAPHICAL NOTICES.

JOHN WALLACE BAIRD

ARLO BATES

CHARLES PICKERING BOWDITCH

SETH CARLO CHANDLER

ELIOT CHANNING CLARKE

WILLIAM GILSON FARLOW

JULIUS VON HANN

HENRY LEE HIGGINSON

FRANKLIN PAINE MALL

SIR WILLIAM OSLER

WILHELM PFEFFER

EDWARD CHARLES PICKERING

JOHN ELLIOTT PILLSBURY

ARTHUR SEARLE

WILLIAM THOMPSON SEDGWICK

ELMER ERNEST SOUTHARD

BARRETT WENDELL

ANDREW DICKSON WHITE

Page

R. M. Yerkes 471

Edward Robinson 473

A. M. TozzER 476

E. S. King 478

G. F. Swain 482

C. L. Jackson 481

R. DeC. Ward 489

M. A. DeW. Howe 493

W. T. Councilman 495

H, A. Christian 496

D. H. Campbell 499

J. H. Metcalf 502

W. H. Dall 506

E. S. King 508

Edmund B. Wilson 512

C. M. Campbell 516

Robert Grant 518

W. D. Bancroft 520

JOHN WALLACE BAIRD. 471

JOHN WALLACE BAIRD (1869-1919).

Fellow in Class II. Section 3, 1916.

In the untimely death of John Wallace Baird American science and
particularly his science, psychology, have suffered a grievous loss.
Born at Motherwell, Ontario, May 21, 1869, of Scottish parents,
Baird early learned the virtues and rewards of self-reliance, devotion
to duty, cooperation and loyalty.

He was one of twelve children, all of whom lived to celebrate the
fiftieth anniversary of the marriage of their father and mother.
Charles Baird, the father, was an industrious and successful Canadian
farmer of sterling worth in home, church and state. The mother,
Agnes Browning, possessed exceptional patience and wisdom and rare
skill as singer of old ballads and narrator of family and neighborhood
traditions.

Undoubtedly our colleague's essential education was gained at home.
His formal education began in the " little red school house" and ended
in the university. His undergraduate work in the University of
Toronto was interrupted by years of school teaching, which enabled
him to pay his own way. After graduating from the university in
1897, he devoted himself almost uninterruptedly to the study of
psychology, first in his own university and subsequently in Leipzig.
For two ^ears he was a fellow in psychology at the University of
Wisconsin and for one year at Cornell, where in 1902 he was granted
the degree of doctor of philosophy. Thereupon he was appointed
assistant in psychology at Cornell. After one year, this appointment
was followed by that of research assistant in psychology, Carnegie
Institution of Washington. At the end of his year's work as Carnegie
research assistant, Baird accepted his first major academic appoint-
ment, that of instructor in psychology, Johns Hopkins University.
This was followed after two years' service by appointment to an as-
sistant professorship in psychology in the University of Illinois. In
1910, at the end of his fourth year in Illinois, he accepted an assistant
professorship in psychology at Clark University, where, in 1913, he
was given the status of professor of psychology.

Ever a serious minded and diligent student, Baird, at first alter-

472 PKOCEEDINGS OF THE AMERICAN ACADEMY.

nately and later simultaneously, studied and taught until he had
mastered his chosen profession of teacher and investigator in psychol-
ogy and had achieved academic position of eminence, influence and
rare opportunity for service. His appointment as Carnegie research
assistant in psychology gave him an excellent chance to demonstrate
his originality, resourcefulness and enthusiasm for research. The
result of the year's work was a report on " The color sensitivity of the
peripheral retina," which stands as his most important publication,
for subsequently he gave himself increasingly to his advanced students
and his research was conducted largely by and through them.

During nine years of fruitful service to Clark University, John
Wallace Baird achieved immortality by training many able students
for ps^x'hological research. With a genius for friendship he pursued
his path of duty and opportunity single mindedly, whole heartedly
and with entire forgetfulness of self. Honors he never sought; praise
he shrank from. His students learned to respect, admire and love
him because of his devotion to their interests and the obvious sincerity
of his belief in constructive work in teaching and research.

In April, 1917, despite physical unfitness for the strain of work in
Washington, Baird undertook to assist in directing the work of the
committee for psychology of the National Research Council. In
December he was compelled to go to the Johns Hopkins Hospital for
treatment of a recurring malady and there, on February 2, 1919, in his
fiftieth year, his life ended.

The career of our lamented colleague is a consistent lesson in un-
selfish and loyal devotion to family, friends, country and human wel-
fare. His life clearly was sacrificed to duty, for his fatal illness with
its frequent and long continued periods of acute pain resulted from a
terrible ordeal of strength in which he saved others from a watery
grave. The sort of sacrifice which he willingly made at a time of
exceptional anxiety and risk, he continued to make throughout his
life, defying bodily suffering and manfully doing his full duty until the
end.

John Wallace Baird's life of generous service has received fitting
tribute of respect and affection in a memorial volume bearing his name
published by Clark University.

Robert M. Yerkes.

ARLO BATES. 473

ARLO BATES (1850-1918).

Fellow in Class III, Section 4, 1900.

Arlo Bates was born in East JVIachias, Maine, December 16, 1850,
the son of Dr. Niran, and Susan (Thaxter) Bates. The strange name
that was given to him was due to a family idiosyncrasy which origi-
nated with his grandfather, who had a theory that every man should
have " a name that is all his own and nobody else's." So he called his
son Niran; Niran upon the same principle begat Arlo, and Arlo in his
turn begat Oric. You will search the dictionaries of biography and
mythology in vain for any of these names, they are merely combina-
tions of letters with no significance, but unique and calculated to
impress the bearer from birth with the sense of individuality which
was a family characteristic, not least strongly marked in the subject
of this memoir.

He was educated at Bowdoin College, where he received the degree
of S.B. in 1876, A.M. in 1879, and Litt.D. in 1894. Already while an
undergraduate his strong instinct for literature as a profession began
to manifest itself, he became the editor-in-chief of the college paper
called The Bowdoin Orient, and thus started on his chosen career.
Shortly after his graduation he resolved to try his fortune in Boston,
and moved to the city in the same year, to remain a resident of it until
his death on August 26, 1918.

His first venture in Boston was a paper which he named The Broad-
side. This led an unprosperous existence during the years 1878-79
and was then abandoned. In the following year he was made editor
of the Sunday Courier, a journal which had once been highly esteemed,
when it numbered among its contributors many of those whose names
were associated with the North American Review, but had sadly de-
generated when he took hold of it, and was living then chiefly on its
name and advertisements. Its proprietor gave him a free hand in the
conduct of his own columns, with tiie result that during the thirteen
years that he remained its editor he was able to restore it to something
of its old prestige. It became again one of the accepted Sunday pap-
ers, and was extensively read for its editorials, literary reviews and
notes on current topics, for all of which he was responsible and most
of which he wrote himself.

474 PROCEEDINGS OF THE AMERICAN ACADEMY.

The period of his connection with the Courier was, in one respect at
least, the happiest and also the most unhappy in his career, both the
result of his marriage. In 1882 he was married to Miss Harriet L.
Vose, of Brunswick, Maine, who under the name of Eleanor Putnam
was a well-known magazine writer, and the author of a book on Old
Salem. Their union was a singularly ideal and sympathetic one,
sharing as they did to the full their intellectual tastes as well as their
devotion to each other, but after only four years of this companionship
she died, and to the end of his life he never ceased to mourn her. She
left him one child, Oric, to whom his affection was transferred and
centered more and more as the boy grew up.

His literar}^ career began soon after his arrival in Boston. His first
attempts were not successful in finding a publisher, but not discour-
aged by this experience he persevered, and in 1881 published his first
novel, "Patty's Perversities." For the next twenty-seven years he
continued a fairly regular output of novels, poems and essays, in spite
of his arduous professional labors. "Who's Who in America" for
1916-17, the last volume issued before his death, gives a list of twenty-
three titles with their dates, ending with "The Intoxicated Ghost" in
1908. While these books won and held for him the respect of his
literary associates they did not achieve the wide popularity for which
he had hoped, and it was doubtless the disappointment at this result
which led him to abandon writing during the last ten years of his life.
He was slow to recognize that his real strength lay not in fiction or
poetry but in essays. Of these he published only three volumes, the
two series of "Talks on Writing English" and the "Talks on the Study
of Literature," all of which are of permanent value, and delightful
reading because of his critical ability, his high standard of purity in
the use of our language, and his exhilarating freedom of thought and
expression.

In 1893 he resigned his position on the Sunday Courier to accept the
professorship of English literature in the Massachusetts Institute of
Technology. There he entered enthusiastically upon the most diffi-
cult task of his life and the one in which he achieved his greatest suc-
cess. To imbue a lot of young students who went to the Tech to fit
themselves for the most practical professions, with little or no time, as
they thought, for "ornamental" studies, to imbue them with the sense
that ability to express themselves in clear sound English should be an

ARLO BATES.

475

essential element of their training, and that the basis of this should be
a knowledge and appreciation of the masters of their language, was no
easy matter in that atmosphere of practical work, but he did it. The
testimony of many students who sat under him, as well as the com-
mendation of his associates on the faculty, leave no doubt of that, and
it is still further shown by the fact that many who were not regularly
connected with the Institute enrolled themselves as special students in
order to have the advantage of his teaching. During the twenty-
three years that he occupied his position he maintained it on a level
with the best teaching in any of our universities, and he had the satis-
faction of knowing that the seed he had planted was bearing good fruit.
But there was another and a darker side to the picture. The period of
his service in the Tech was the most turbulent in its history. Con-
troversies arose, spread and would not down. Questions of policy,
administration, the possible union with Harvard, every kind of prob-
lem that can disrupt a governing board, were discussed, not always
with academic calm. Divisions of opinion were sharp and sometimes
bitter. Into these he threw himself whole-heartedly, strong as always
in his convictions, and vehement in his expression of them. Even
before the clouds rolled away he found himself in a minority, out of
sympathy with the new spirit that was growing in the institution in
spite of his efforts, distrustful of its changes, and unwilling as always
to compromise. Disheartened at the outcome ias well as by the slight
prospect of continued usefulness under the conditions that had thus
been brought about, he retired in 1915, shortly before the Tech moved
from Boston to Cambridge, and three years before his death.

Thus another disappointment was added to his life, and if I seem to
dwell unduly upon these it is because they are essential to a knowledge
of his character and its development. Highly sensitive as he was, and
of a temperament that was naturally prone to melancholy, he was
less fitted than a more robust personality would have been to with-
stand these slings and arrows, for as such he regarded them.

No account of Arlo Bates would be complete without at least a
reference to his association with the Tavern Club, where for twenty
years it is hardly too much to say that he was the life and soul of the
club, contributing to an extent equalled by few others towards the
distinctive character which gave it its reputation. Always ready to
prepare a skit, a burlesque, a miracle play, or any kind of original

476 PROCEEDINGS OF THE AMERICAN ACADEMY.

entertainment, and equally ready to take part in any or all of them,
the "moroseness" which many who did not know him well regarded
as characteristic was there shown to be merely skin deep and easily
punctured. Some of his wittiest and most brilliant work was done in
the plays which he wrote for the club, and it is a pity that there was so
small a public to enjoy them. But those who had the privilege will
never forget it nor the affection in which they held him.

He was elected a Fellow of this Academy March 14, 1900, and a
Member of the National Institute of Arts and Letters in 1904. An
account of his life and work, with tributes from various sources, was
published in the Technology Review for November, 1918, Vol. XX,
pp. 615 ff.

Edward Robinson.

CHARLES PICKERING BOWDITCH (1842-1921).

Fellow in Class III, Section 2, 1892.

Charles Pickering Bowditch was born in Boston on September 30,
1842, and died in Jamaica Plain on June 1, 1921. He was the son of
Jonathan Ingersoll Bowditch and Lucy 0. (Nichols) Bowditch. He
entered Harvard College in 1859 and was graduated in the Class of
1863 after having been suspended for his participation in some college
pranks. He received the Master's Degree in 1866.

As a member of the Presidential party he witnessed Lincoln's First
Inauguration on March 4, 1861. He served in the Civil War as 2d
Lieutenant, 1st Lieutenant, and Captain in the 55th Massachusetts
Volunteer Infantry and later he was Captain in the 5th Massachusetts
Volunteer Cavalry of which his brother, Henry, was a Major.

He spent the year 1865 in the oil regions of Pennsylvania and from
1865 to 1872 he was in charge of the Estate of William W. Wadsworth
at Geneseo, New York, and from 1866 to 1872 he was Trustee of the
Estate of Allen Ayrault at the same place. He returned to Boston in
1872 and, except for periods of travel in Europe, the Orient, Mexico,
Central America, and California, he resided in Boston until his death.

Mr. Bowditch's grandfather, Nathaniel Bowditch, was the Fifth
President of the American Academy, serving from 1829 to 1838 and
succeeding John Quincy Adams as President. His father, J. Inger-

CHARLES PICKERING BOWDITCH. 477

soil Bowditch, was Treasurer of the Academy from 1842 to 1852. Mr.
Charles P. Bowditch was elected a member of the Academy in 1892
and was its Treasurer from 1905 to 1915 and President from 1917 to
1919.

He was also a member of the following societies : Boston Society of
Natural History, serving as Vice President from 1895 to 1907, the
American Geographical Society, the American Antiquarian Society,
and numerous American and European Anthropological organizations.
His historical-genealogical interests are shown in his membership in
the ]\Iassachusetts Historical Society, the Bostonian Society, the
Colonial Society of Massachusetts, and the New England Historical-
Genealogical Society. Each of these institutions is indebted to him
for generous support. His varied interests are shown by this list of
organizations of which he was a member. As a man of affairs he was
an officer in many corporations and numerous benevolent enterprises
and a Trustee of many estates.

After a pleasure trip to Mexico and Yucatan in 1888 his main avoca-
tion was the iuAestigation of Central American antiquities and, more
especially, the Maya system of hieroglyphic writing. In this study he
was Lne most outstanding figure in America. His book, " The Numer-
ation, Calendar Systems, and Astronomical Knowledge of the Mayas"
(1910), was the most important book published up to that time on the
Central American hieroglyphic writing. He added much to the
knowledge of this subject and blazed a trail which will always remain
open to future students of this subject. This book, together with
numerous pamphlets, show the results of an acute mathematical mind
and most painstaking study. He was a worthy foe to speculative
theories and his deductions are based on mathematical calculations
and sound common sense.

Mr. Bowditch's connection with the Peabody Museum of Harvard
University was a long and a close one. From 1888 to the time of his
death he was its greatest benefactor. In 1894 he became a Trustee
of the Museum and always took the greatest personal interest in the
welfare of the institution and its varied activities. His patronage of
the Central American work of the Museum covered many sides. He
financed and planned annual expeditions to the Maya field, beginning
in 1891 and continuing in an almost unbroken series down to the
present time. The scientific results of these expeditions were pub-

478 PROCEEDINGS OF THE AMERICAN ACADEMY.

lished, for the most part at Mr. Bowditch's expense, in six folio vol-
umes of Memoirs and several volumes of Papers. The collections
acquired by these expeditions now fill the greater part of two large
halls in the Museum. He brought together a large library of the
books and manuscripts relating to Mexico and Central America which
he gave to the Museum in addition to over fifty thousand pages of
photographic reproductions of early manuscripts and rare books on
the history and languages of these countries. He established Fellow-
ships in Maya research in the Archaeological Institute of America and
in the Peabody Museum. He was in great part responsible for the
establishment of the teaching of Anthropology in Harvard University.

Mr. Bowditch's patronage of the study of Central American antiqui-
ties was a patronage based on personal investigations, study, and an
intimate knowledge of this field. American Antliropology has perhaps
no other case where an effort in one field of interest has been so long
continued, so intense, and so productive of results.

A list of the published and unpublished articles written by him
together with a list of his editorial work is printed in the American
Anthropologist (N.S.) v. 23, 1921.

Alfred M. Tozzer.

SETH CARLO CHANDLER (1846-1913).

Fellow in Class I, Section 1, 1883.

Seth Carlo Chandler was born in Boston, Mass., on September
16, 1846, the son of Seth Carlo and Mary (Cheever) Chandler. He
died on December 31, 1913, after a career of remarkable achievement.

As a boy he developed early, showing a fine combination of mental
and practical capability. AYhile still attending the English High
School of Boston, he was chosen to perform some computations for
Professor Benjamin Pierce of Harvard University. This circumstance
seems to have developed Chandler's mathematical bent and led him,
after graduation in 1861, to become the assistant to the distinguished
astronomer. Dr. B. A. Gould. ^Yhile the other lads of sixteen vears
may have pursued collegiate courses, Chandler found in Gould his
university. Here was the beginning of a life-long friendship. Under
Gould he worked with the title of Aid in the U. S. Coast Survey from

SETH CARLO CHANDLER.

479

1864 to 1870. On October 20, 1870, he married Caroline Margaret
Herman of Boston, who with several daughters survives him. Dr.
Gould was now in the Argentine Republic, founding the national ob-
servatory at Cordoba. Chandler had declined Gould's invitation to
go with him, possibly having in view his impending marriage. Feeling
now the need of more lucrative employment than afforded by science,
he became life insurance actuary from 1870 to 1885. Here his mathe-
matical ability discovered various interesting laws. For example, he
derived an accurate formula showing the distribution by age of appli-
cants for life insurance.

In 1881 he moved to Cambridge and took part in the work of the
Harvard Observatory. In 1886 he became a private investigator, or
as he called it an "amateur" astronomer. In 1904 he removed to
Wellesley Hills, Mass., where he lived until his death. To give any
adequate account of his scientific work is impossible in this sketch.
It is to be found in more than 200 papers published chiefly in the
Astronomische Nachrichten, the Astronomical Journal, and the
Annals of the Harvard College Observatory.

His Aloaacantar, an equal-altitude instrument floating in mercury,
gave results of greatest precision, and furnished him with the first
intimations of changes in latitude. To the series of masterly papers
by Chandler on the variation of latitude, appearing in 1891-1894,
Professor H. H. Turner has rendered a magnificent tribute in his book
"Astronomical Discovery." No better bird's-eye view can be found
of this great discovery, so contrary to the accepted opinions of the
astronomical world at that time. Chandler's courage and sound
practicality are shown in these words, written in 1893. " It should be
said, first, that in beginning these investigations last year, I deliber-
ately put aside all teachings of theory, because it seemed to me high
time that the facts should be examined by a purely inductive process;
* * * and that the entangled condition of the whole subject required
that it should be examined afresh by processes unfettered by any pre-
conceived notions whatever. * * * I am not much dismayed by the
argument of conflict with dynamic laws, since all that such a phrase
means, must refer merely to the existent state of the theory at any
given time."

Facts won against theory. With great industry he skillfully coordi-
nated thousands of observations and proved conclusively that the

480 PROCEEDINGS OF THE AMERICAN ACADEMY.

changes in latitude occurred according to two superposed oscillations,
one of fourteen months, the other of a year. With this key he un-
locked many mysteries of the past. His work harmonized the Wash-
ington observations for latitude. He "added a hundred feet to
Bradley's monument," and showed that Pond's apparent errors at-
tested the excellent quality of his observations. Variation of latitude
explained also the difficulties experienced by Airy with his Reflex
Zenith Tube.

For these researches he received in 1895 the Watson Gold Medal of
the National Academy of Sciences, and in 1896 the Gold Medal of the
Royal Astronomical Society. The latter was given also in considera-
tion of Chandler's work on variable stars. These objects were a
favorite study of his. Three successive catalogues of variables, pre-
pared by him, may be mentioned.

He was editor of the Astronomical Journal from 1896 until, on
account of ill-health, he resigned and became associate editor in 1909.
Among his numerous activities. Chandler was interested in the trans-
mission of astronomical intelligence by telegraph. He devised the
" Chronodeik " for determining the time. He studied cometary orbits,
and made computations which led to the discovery, in cooperation
with the Harvard Observatory, of the position of the small planet Eros
on photographs made at the observatory four years before the planet
was known to exist.

Chandler was elected a Fellow of this Academy in 1883. For his
Almacantar he was awarded in 1884 the medal of the Massachusetts
Charitable Mechanics Association. He received in 1891 from De
Pauw University, Indiana, the honorary degree of LL.D. He was a
member of the National Academy of Sciences, and a Foreign Associate
of the Royal Astronomical Society. He was a member of various
other scientific associations. For many years he served efficiently on
the Gould Fund Committee of our Academy; also on the Bache Fund
Committee of the National Academy.

Dr. Chandler possessed what may seem unusual in a scientific mind,
keen business judgment. He was able to gauge the underlying
financial conditions accurately, so much so that his advice in such
matters carried weight with friends engaged directly in the business
world. This was of great service to him in his affairs relating to
trusteeship, the duties of which he faithfully and efficiently discharged.

SETH CARLO CHANDLER.

481

He was very fond of good music of the old school, Beethoven,
Gounod, and Verdi being among his favorites. He did not care for the
modern composers, and never listened to their work if he could avoid
it. A forced hearing of Debussy or Brahms, it is said, was sure to
bring forth some humorous but scathing criticism at the finish. His
contention was that music was for the pleasure of the senses only, and
attempts to make it appeal to the intellect were disastrous. He read
almost everything except the modern novel. This he was apt to class
as " cheap stuff." Relaxing from his scientific work, he would become
absorbed in some other subject, for instance the American Civil War,
and read volume after volume about it. In French, Dumas was a
favorite author. In such periods of reading Kenan's Life of Christ,
Saint Paul, and the Bible would come in close succession. Tales of
adventure, detective stories, history, and biography as related to
history appealed to him.

Dr. Chandler was devoted to his family and their interests. Al-
though the family dinner table was a large one and he might be much
preoccupied, having been called several times before responding, it is
said that he never failed to notice instantly the absence of any mem-
ber of the family group. He found much satisfaction in restoring his
grandfather's homestead at Strafford, Vermont, where he enjoyed the
long summer vacations with his family. The writer, who spent a
summer some years ago at Strafl'ord, remembers the delightful way
Dr. Chandler entered into the community life. His daughters with
others had become interested in dramatics, and he took great pleasure
in conveying the "band of strolling players" as he called them, over
to neighboring villages to give performances.

He was fond of driving, preferring horses to an automol)ile. " Not
to own a machine" he said, " from l)eing a proof of aristocracy had now
become a mark of respectability." He enjoyed books on magic and
gave sleight of hand exhibitions at Strafford. The " Old City Wizard"
was a title bestowed upon him in those days. It was a pastime of his
at Strafford to design, make, and sail beautiful little yachts, two or
three feet in length. He used to say that he was sailing the exact
model of one of the "Cup Defenders" years before she was launched.
To a clever local mechanic who assisted him in some parts of the
construction, it was a wonder that the models should have the exact
displacement predicted by their designer. Such was his life at Straf-

482 PROCEEDINGS OF THE AMERICAN ACADEMY.

ford. To live out of doors in the country with his family was an ideal
vacation for him.

Dr. Chandler was an entertaining conversationalist, and a delightful
companion, an English astronomer remarking that it was worth cross-
ing the Atlantic to visit him. He was cordial and constant in friend-
ship, so unpretentious that many who met him only in later life were
unaware that he had any claim to distinction. To those who know his
work, " he has left the remembrance not so much of mere talent as of
positive genius." The creative power of his intellect combined with
courageous and unflagging industry produced a record of notable
achievements, linking his name inseparably with the history of
astronomy of his time.

Edward S. King.

ELIOT CHANNING CLARKE (1845-1921).

Fellow in Class I, Section 4, 1887.

Mr. Clarke was born in Boston on May 6, 1845, and was the son of
the Rev. James Freeman Clarke and Anna H. Clarke. His father
was one of the most distinguished Unitarian clergymen of his day, a
leader in thought, and the author, among other things, of a book
entitled "Ten Great Religions," which occupies a high place in theo-
logical literature.

The first ten years of Mr. Clarke's life were passed in Boston and in
Meadville, Pa., the home of his mother's family. In 1855 his parents
settled at Jamaica Plain. He was educated in the public schools,
preparing for college at the Eliot High School, and was graduated
from Harvard College in 1867. He was Chief Marshal of his class.
He took some special studies at the Massachusetts Institute of Tech-
nology in 1867-68, and in February, 1868, he began his career as a
civil engineer on the bridge then building over the Mississippi River
at Quincy, Illinois. His uncle, Thomas Curtis Clarke, was a noted
civil engineer, a member of the firm of Clarke, Reeves & Co., Bridge
Builders, of Phoenix, Pa., and in 1896 President of the American
Society of Civil Engineers. Mr. Clarke's firm was building the bridge
over the Mississippi River and the work offered a good opportunity
for the nephew to begin his engineering experience. Later, he was

ELIOT CHANNING CLARKE. 483

engaged upon other engineering works, viz., the bridge over the
Mississippi River at Hannibal, Mo., and other structures built by the
Phoenix Co., the Chicago Water Works Tunnel, and the Chicago
Sewerage System.

In the dull times which followed the Panic of 1873, Mr. Clarke re-
turned to Boston to take further special studies at the Institute of
Technology in 1875-76. In July of the latter year he was appointed
Engineer in charge of a survey for a main drainage system for Boston.
The project was adopted and construction was begun in 1877. It was
carried through to completion in 1884 under the supervision of INIr.
Clarke, who published a description of the work in 1885. At this
time he was recognized as one of the leading sanitary engineers of the
United States. In 1885 he received the Norman Medal of the Ameri-
can Society of Civil Engineers for his paper entitled "A Record of
Tests on Cement Made for the Boston Main Drainage Works." In
the work which this paper describes a great deal of cement had been
used and Mr. Clarke had made some novel and valuable experiments.
Among other things, he was one of the first to prove and to advocate
the importance of fine grinding of cement, showing that the coarse
grains had very little cementing quality. In 1884 he became Chief
Engineer of the Massachusetts Drainage Commission, which was
appointed to design methods of preventing pollution of the waters of
the Charles, Mystic and Blackstone River basins.

Shortly after this time he gave up his strictly engineering work to
become the Manager of mill properties at Lowell, to which his atten-
tion was devoted for a number of years. His retirement from engi-
neering was a distinct loss to the profession.

Mr. Clarke was a man of wide interests. He was a Fellow of the
American Academy of Arts and Sciences, and its Treasurer for eleven
years. He was a member of the Massachusetts Natural History
Society, the Massachusetts Horticultural Society, the Colonial So-
ciety, and the Corporation of the Massachusetts Institute of Tech-
nology. He served also as a trustee of the Massachusetts Scliool for
the Feeble Minded, as trustee and vice-president of the Provident
Institution for Savings, as director of the State Street Trust Co. and
of other companies. He was interested in astronomy and prepared a
work on that subject.

Mr. Clarke was married in 1878 to Alice V. Sohier, by whom he had

484 PROCEEDINGS OF THE AMERICAN ACADEMY.

five children, three of whom survive him. He is also survived by one
sister, Miss Lillian Freeman Clarke.

Mr. Clarke was a man of great engineering ability, a clear thinker,
an efficient organizer, a good administrator and a most lovable man.
Before leaving his chosen profession for business, he had reached a
position of preeminence in it, and in his business career he showed the
same rare qualities. A host of friends mourned his passing.

George F. Swain.

WILLIAM GILSON FARLOW (1844-1919).

Fellow in Class II, Section 2, 1874.

It is ccrtninly presumptuous for one not a botanist to write about Dr. Farlow,
but an intimate friendship of over 50 years makes it possible for me to speak of
him as a man, and 1 hope I have succeeded in presentin;^ an adequate picture
of his botanical achievements by constructing u mosaic from the facts and
opinions of the four experts, who have written about him already.

By the death of William Gilson Farlow the Academy' has lost one
of its most distinguished fellows, since it was his rare good fortune to
begin his scientific work, when a great body of material had been col-
lected by such pioneers as Curtis in fungi, Harvey in algae, Tuckerman
in lichens, Sullivant in mosses and many others, and the science in
this country had reached the point where it needed some man with
breadth and grasp enough to draw all these scattered parts into a
connected whole. In Farlow it found the genius, enthusiasm and
character needed for this great work and the training, which developed
and supplemented these natural gifts. He occupies, therefore, the
same conunanding position in cryptogamic botany that Asa Gray
holds in the development of our knowledge of flowering plants.

He was born in Boston December 17, 1844, the son of John Smith
Farlow, a prosperous public-spirited citizen and Nancy Wight (Blanch-
ard) Farlow, both of Massachusetts parentage. From his father he
inherited strong tastes for botany and music. In fact, John K. Paine,
then recently established in Cambridge, urged him to become a pro-
fessional musician, but the call of botany was too strong and music
sank into a delightful recreation after his exacting scientific work.

He was educated at the Quincy Grammar School and English High
School in Boston, followed by a year at the Boston Latin School, which

WILLIAM GILSON FARLOW, 485

with his training in Harvard College made him a sound classical
scholar. In after years he was fully alive to the greater breadth of
view and roundness of intellect given him l)y this training in the
humanities, as well as to the value of his Latin and Greek in giving
him a mastery of the force of scientific terms and names.

It is said that his attention was first drawn to l)otany when a boy by
finding hepaticas in the woods near his father's place in Newton.
However this may be, he made such rapid progress in the science that
by his senior year we lower classmen spoke of him with bated breath
as a prodigy of botanical learning.

This progress was largely due to the fact that in college he encount-
tered the first of his two great teachers — Asa Gray, who gave him a
solid foundation for his later professional studies; but instead of
embarking on these at once after his graduation in 1866, following the
advice of Asa Gray, he took up the study of medicine, and after
studying anatomy for a year under Jefl^ries Wyman — a man whose
casual talk was a liberal education, he entered the Harvard Medical
School in November, 1867, and graduated from it in 1870, securing
before his graduation the coveted appointment of surgical interne at
the Massachusetts General Hospital under that great surgeon, Henry
J. Bigelow; so that he took up his higher botanical studies with a much
more roundefl general education than falls to the lot of most scientific
men, the effect of which could be traced throughout his life in his un-
usual sanity and Ijreadth of view.

In 1870 he began his special botanical education by serving for two
years as assistant to Asa Gray, whose inspiring teaching gave him a
comprehensive knowledge of flowering plants and made him thoroughly
familiar with the systematic outlook on the science, while his example
helped to make him a botanist in the broadest sense of the word,
instead of a mere specialist on the cryptogamic side.

Even at this early day he had selected his line of work — the crypto-
gams — and began to study the algae in the herbarium at Cambridge
and also in the field at Woods Hole, where in 1871 he joined a scientific
party under S. F. Baird, publishing in this year his first paper " Cuban
Seaweeds."

At that time there were no facilities in America for studying crypto-
gams, so again following the advice of Asa Gray, he decided in 1872
to go to Europe, where he spent the better part of two years in study

486 PROCEEDINGS OF THE AMERICAN ACADEMY.

at Strassburg under Anton De Bary, then the first authority on fungi
in the world. He was very fortunate in working under two such men
as De Bary and Asa Gray, each a master in his own field, and these
lay so far apart, not only in matter, but in methods of treatment,
that he gained from them a remarkably broad and comprehensive
grasp of the science.

It was indeed a new botanical atmosphere into which he was plunged
at Strassburg. Systematic botanists were spoken of scornfully as
"hay collectors," and with the zeal of new converts most German
botanists prided themselves on their ignorance of flowering plants.
De Bary himself was not free from this sort of narrowness, but Asa
Gray had impressed the importance of systematic work and flowering
plants so thoroughly on Farlow, that he did not allow himself to be
swept off his feet even by the flood of new ideas with which he was
continually deluged by De Bary and the eminent students he had
drawn about him, such as Graf Solms and Rostafinsky.

When I heard Farlow talk with De Bary in the Strassburg labora-
tory I heard two naturalists discussing the question on equal terms,
except for the greater knowledge and experience of the older man — a
very striking contrast to the state of almost abject pupilage, in which
we chemical students were kept by our German professors. The
difference lay, of course, in the students, not in the professors.

During his stay with De Bary he grew familiar with the whole field
of work in the morphology and development of fungi and in plant
anatomy, and toward the end of the time published a paper on " An
Asexual Growth from the Prothallus of Pteris cretica," which was
attacked so heartily that he returned to America with his reputation
made.

Although the larger part of his time in Europe was spent with De
Bary, he gave shorter periods of study to lichens under J. Mueller at
Geneva, and to algae with Bornet and Thuret at Antibes, and travelled
extensively, visiting most of the celebrated botanists and herbaria.

These years of study in Europe brought his education to an end and
made him, so far as is known, the only American cryptogamic botanist
capable at that time of doing original work himself and of teaching it
to advanced students. More than this, they put the finishing touch
to the cultivation of the qualities that made him great — his strong
and piercing intelligence, his phenomenal memory, the discriminating

WILLIAM GILSON FARLOW. 487

judgment and devotion to truth that made him refuse to accept con-
clusions, until they were absolutely established, and the unusual
breadth of view so often mentioned already. To these must be added
an insatiable love of work, as well as great and constantly increasing
stores of learning.

As soon as he reached America his appointment as Assistant Pro-
fessor of Botany in Harvard University put him in a position to make
the most of these treasures and to raise cryptogamic botany in the
United States from a mere sketchy appendix in a general course of
botany to the rank of an independent study.

For five years he was stationed at the Bussey Institution of Harvard
University, although his teaching was in the college, and then in 1879
he was transferred to Cambridge as Professor of Cryptogamic Botany.

These five years at the Bussey Institution, however, had an im-
portant influence on his life as well as on the botanical development
of the country, since they called his attention to the fungous diseases
of plants, and he threw himself into work in this virgin field with such
energy that he is acknowledged as one of the founders of phytopathol-
ogy in the United States — a study which has since reached such
proportions that we lead the world in it at present.

His papers in this field are numerous and important. Among them
may be mentioned studies of potato rot, grape mildew, black knot,
onion smut, gymnosporangia, fungous diseases of hollyhocks, roses,
and even of salted codfish.

After he was settled in Cambridge, his plans included the establish-
ment of a herbarium and a library of cryptogamic botany, in addition
to the teaching and research properly belonging to his professorship.

The first step towards his herbarium had been taken even before his
return from Strassburg, as then Asa Gray bought for him the famous
collection of fungi made by the Rev. M. A. Curtis. To this nucleus
were added later many other famous collections, which had been
either bequeathed to the University, or purchased by him. Con-
spicuous among them were Tuckerman's lichens, Sullivant's, James's,
and Kennedy's mosses and hepatics, Faxon's sphagna, and, quite as
important as these, his own rich collections of fungi and algae. His
father's wealth enabled him also to make his library — like his her-
barium — the fullest and best in the country and both were always
open to botanists qualified to use them.

488 PROCEEDINGS OF THE AMERICAN ACADEMY.

As a lecturer he was peculiarly happy, for to the authority of a
master he added a clear style, the faculty of bringing essential points
into strong relief, and a humorous quality, which riveted the attention
of his hearers; but even more important than his lectures was his
work with students in research. Here his inspiring personal teaching
— for he never left them to an assistant — developed many distin-
guished students, among them such masters as Roland Thaxter,
William Trelease, W. A. Setchell, Ivingo Miyabe, and Herbert M.
Richards.

His scientific papers average three a year for the whole forty-five
years of his active work, if the papers of his students are included, as
they should be. They have been characterized as " clear, concise and
accurate," the well-considered careful utterances of a master, who
never yielded to the temptation of rushing into print, and also was
char}^ of establishing new species out of the great wealth of material
at his disposal, since he had a profound contempt for bad species, as
shown by his caustic remark about the manufacturers of them.

"If a difference can be imagined, it is a new species; if it can be
seen, it is a new genus."

Nearly two-thirds of his papers have to do with fungi, including the
studies of plant diseases already mentioned ; while somewhat less than
one-third deal with algae, many of these with the contamination of
water supplies by them. One published in 1S79 was reprinted 38
years later by Professor Whipple as "one of the classics of state
sanitation." It is written in a popular style, as are several of his
papers on fimgi.

Other useful papers consist of reports on the cryptogams collected
by various exploring expeditions and of lists of cryptogams found in
special localities. For example, a list of the seaweeds of the New
England coast, (published in 1881) "included keys, descriptions,
critical notes and plates," and according to Professor Riddle "still
remains our only scientific manual of the seaweeds of this region."

Quite as important as this was the " Provisional Host Index of the
Fungi of the United States" published in 18SS and 1890 with ^Mr. A.
B. Seymour, which has proved of the greatest use to working botanists.

Of his bibliographical papers the most important was a "Biblio-
graphic Index to North America Fungi," of which the Introduction
and the first 312 pages, prepared in collaboration with JNIr. A. B.

WILLIAM GILSON FARLOW. ' 489

.Seymour, were published by the Carnegie Institution in 1905 and
although the publication has not been continued, the collection of data
went on until his death. This was perhaps his greatest work, and
some idea of its magnitude can be obtained from the facts that at the
time of his death the Index included about 350,000 references, and the
312 pages published in 1905 brought the alphabetical list of that day
only through Badhamia. As the work is essentially finished, it is
hoped that it may soon be published since it will be of untold value to
specialists.

Another great work left unfinished at his death is an account of
selected species of American fleshy fungi, which was to be illustrated
with over 100 colored plates. These have been executed under his
direction with the utmost care, but although the plates were finished,
the pressure of his other botanical undertakings prevented him from
even beginning the descriptions of the species. It would be well, if
these descriptions could be supplied by another hand, so that what
promises to be a classical work may see the light.

In discussions of nomenclature he threw his powerful influence in
favor of sane and stable methods for naming fungi, thus helping to
check the extreme radicalism of many American botanists, and pre-
serving relations with the better men abroad.

But his papers alone — important as they are — did not make him
"the creator of cryptogamic botany in the United States." It was
the man himself — his personality, his breadth, his wise conservative
judgment, his learning, his helpfulness, and his devotion to truth.

American botanists were brought in contact with this commanding
influence by means of his papers and his students and even more
effectively by his direct personal intercourse with them, for he was
always ready to give them generous help, and they were more than
ready to make use of it, submitting their puzzles to his excellent judg-
ment, reinforced as it was by a reading that covered the whole litera-
ture of the cryptogams, not in abstracts, but in the original sources;
borrowing specimens from his herbarium for comparison ; asking him
to look up references in journals hard to find outside his library; or
even sending him specimens to determine. Some idea of the volume
of this work is given by the fact that a single correspondent confesses
to 100 letters in his own handwriting.

His achievements earned wide recognition. Two genera were

490 PROCEEDINGS OF THE AMERICAN ACADEMY.

named after him, Farlowia among the algae, and Farlowiella among
the fungi, beside a great number of species. Harvard, Wisconsin and
Glasgow conferred the degree of LL.D. upon him, and Upsala on the
two hundredth anniversary of the birth of Linnaeus, at which he
represented our Academy, crowned him with laurel as one of its
Doctors of Philosophy.

He was elected a fellow of our Academy' in 1874, and was also a
member of the National Academy of Sciences, the Philosophical
Society, the Linnaean Society and the French x'Vcademy of Sciences.
He served as president of the New England Botanical Club, of which
he was one of the founders, of the American Association for the Ad-
vancement of Science; of the x\merican Society of Naturalists, and
of the Botanical Society of America.

There is little more to be said about his life, which was passed in
Cambridge during term time, with the exception of a few journeys to
Europe and botanical excursions on this continent, the most im-
portant being one to Mexico and California with Asa Gray in 1885.
Most of his work in the field, however, was done in the White Moun-
tains, where his vacations were usually passed. A walk in the woods
with him introduced one to a new world largely microscopic, but full
of interest and even beauty.

In 1900 his marriage to Miss Lilian Horsford made his life one of
complete happiness until his death on June 3, 1919.

Farlow's most striking characteristic — • apart from those I have
already pictured in connection with his scientific work — was the
humor which permeated and irradiated all he said, making even his
common talk amusing and delightful, but this humor is so elusive that
it evaporates between the pen and paper, so that I can refer to no
example of it. On the other hand, his wit often flashes out in all but
his most serious papers.

His hatred of affectation, sham and superficiality was intense, and
his outspoken denunciation of them, driven home by his incisive
humor, made so deep an impression that many, who knew him mostly
by hearsay, thought him a sarcastic pessimist, but his friends saw that
his attacks were directed only against those who deserved them, and
knew that the real nature of the man was affectionate and kindly,
making him the most staunch and faithful of friends, and the sym-
pathetic helper even of those who had no claim on him whatever.

JULIUS VON HANN. 491

It is pleasant to think of his declining years when full of well-
earned honor, happy in his troops of friends, happier in his family
with his mind undimmed by any weakening of his faculties, he was
able to continue in active work until the brief sickness, which brought
the end.

Chakles Loring Jackson.

JULIUS VON HANN (1839-1921).

Foreign Honorary Member, Class II, Section 1, 1902.

Nearly half a century ago Julius von Hann began to take his place
as the universally acknowledged leader of meteorological science, and
for many years previous to his death he stood out head and shoulders
above his fellow-workers. He grew up with and himself was, as it
were, a large part of the rapid modern development of meteorological
science. He was able, through his intense application and industry,
and because of his great intellectual powers, not only himself to con-
tribute largely to the advance of his science but also to keep closely
in touch with all the work which was being done by investigators and
writers everywhere. For years his many contributions to the Metcor-
ologische Zeitschrift, often modestly signed J. H., were never-failing
evidence of his truly extraordinary grasp of his subject and of the
universal range of his reading. He was, as fully as any one human
being can be, a living encyclopedia of his chosen science. And this is
in no sense to be taken as suggesting that his mind was merely a store-
house of dry, hard facts. He was very human . He saw the many and
varied relations of meteorology and climatology to human life and
activities, and he was always on the lookout for opportunity to em-
phasize these relations. His writings were always clear, vivid, and
interesting. His "Handbuch der Klimatologie," for example, which
inevitably has to deal largely with "dry" statistical details, is en-
livened throughout by carefully selected, vivid, first-hand descriptions
of weather types and of human or botanical responses to the climatic
environment.

His fellow-workers who remain are dynamic or physical meteorolo-
gists, or climatologists, or are specializing in this or that subdivision of
their science. This is a natural and inevitable situation at the present

492 PROCEEDINGS OF THE AMERICAN ACADEMY.

stage of our knowledge of the atmosphere. It cannot well be other-
wise. But it leaves a great gap which no one man can ever fill, because
meteorology has now grown to such an extent that specialization is the
rule, and no single mind will ever again master all of its details.
Hann's "Lehrbuch der Meterologie " is the one absolutely indis-
pensable textbook in that science. Upon his " Handbuch der Klima-
tologie" all studies of climatology must, for years to come, be based.
This extraordinary grasp of the whole wide range of his science he
maintained practically till the day of his death.

Somehow, when a man like this passes away, a bare statement of the
essential facts of his life and a list of his contributions to science seems
unnecessary and futile. Yet there is something singularly significant
in the fact that this man, living a very simple life, with very few
changes of residence, extended his interests and his reading to all parts
of the world. He knew the geographical and climatological conditions
of almost every corner of the globe as intimately as if he had himself
lived there. Hann — for thus, and not as von Hann, he will oftenest
be recalled — was born March 23, 1839, near Liuz, in Austria. He
began his professional life as a school-teacher. At the age of twenty-
nine he entered the Central-Anstalt fiir IVIeteorologie in Vienna.
From 1874 to 1897 he was its Director, an office from which he retired
at the age of fifty-eight. For many years he was a professor at the
University of Vienna, first of Physical Geography and later of Physics.
His work for meteorology did not cease when he ceased to be Director.
He went to Graz as Professor at the University, and there, in the
Physical Institute, he UTote liis "Lehrbuch der Meteorologie," whose
three editions bear the dates 1901, 1906, 1915. A fourth edition,
supervised by Siiring, is now in course of preparation. In 1900, Hann
returned to Vienna as Professor of Cosmical Physics, a position which
he held until his retirement in 1910. The " Handbuch der Klimatolo-
gie" he wrote while in Vienna. The three editions of this book bear
the dates 1883, 1897, 1908-1911. These two books are Hann's
monumental publications. It is almost literally true that no student
of meteorological science can do a day's work without referring to
them. Throughout his long editorship and joint editorship of the
Meteor ologische Zeitschrift (1866-1920) he steadily contributed to the
pages of that journal a series of articles and notes which are invaluable,
for in these he revised, summarized, commented upon, and put into

HENRY LEE HIGGINSON.

493

permanent form a vast body of meteorological and climatological
material. In 1906, in commemoration of forty years of his editorship,
a special Harm Band of the Zeitschrift was issued. Two other major
publications are the Atlas der Meteorologie, forming Part III of the
Berghaus Physikalischer Atlas (1887) which was for years the standard
meteorological atlas of the world, and Die Erdc als Gauzes; ihre
Atmosphdre und Hydrosphdrc (1st edition, 1872; 3d edition 1880;
5th edition 1896).

Hann was the recipient of many honors, and was made a member of
many learned societies, both in Europe and abroad. He was the first
foreigner to receive the Symon's Gold IVIedal of the Royal Meteoro-
logical Society (1904).

Hann died in Vienna, October 1, 1921, in his eighty-third year. No
more fitting tribute could possibly be written of him than that con-
tained in the notice of his death sent out by his former colleagues in
Vienna. "Ein Leben ununterbrochener Geistesarbeit und reinster
Forschung im Dienste der Wissenschaft ist abgeschlossen. Aber
ungeziihlte Fader fiihren von Hann's Werken in alle Lander der Erde
und wirken in seinem Sinne fort."

R. DeC. Ward.

HENRY LEE HIGGINSON (1834-1919).

Fellow in Class III, Section 4. 1912.

The "Life and Letters of Henry Lee Higginson," by Professor Bliss
Perry, published in the autumn of 1921, affords so full and accessible
a record of the career and character of this Fellow of the Academy
that anything beyond a brief summary would be superfluous for the
present purpose.

Two conspicuous anomalies in the life of so eminent a citizen of
Boston and son of Harvard were that he was born in New York
(November 18, 1834) and that he was a mem.ber of Harvard College
for only a few months in the freshman year of his class of 1855. He
was, however, of pure New England descent, and when he was in his
fourth year his family left New York and provided him with that
Boston background which he was to adorn for more than eighty years.
The brevity of his connection with Harvard, for which he was prepared

494 PROCEEDINGS OF THE AMERICAN ACADEMY.

at the Boston Latin School, was due to a weakness of his eyes. Of the
ten 3'ears between his leaving college and the outbreak of the Civil
War, more than five were spent in two visits to Europe, and a year and
a half, in the interval between them, as a clerk in the counting house
of S. & E. Austin, Boston merchants. The second of his European
visits, from 1856 to 1860, was devoted largely to the study of music,
pursued to the extent of physical injury, and also to the end of reach-
ing the reluctant decision that his talents would not justify his becom-
ing a professional musician. It was then, however, that he deter-
mined, if he could ever compass it, to enrich the lives of his countrymen
with music as his own life had been enriched by the music of Vienna
and other European cities.

The disappointed student returned to iVmerica only a few months
before the outbreak of the War of Secession. His immediate future
could not long remain uncertain. As an officer, first of the Second
Massachusetts Infantry and then of the First Massachusetts Cavalry,
he proved himself an admirable soldier. Serious wounds received in
June, 1863, incapacitated him for much of the second half of the war.
In December, 1863, he married Ida Agassiz, daughter of Louis Agassiz.
In the years immediately following the war he sought his fortune,
in company with his young wife, through oil in Ohio and cotton in
Georgia, but without success. In 1868 he joined the Boston banking
and brokerage firm of Lee, Higginson & Co., with which he was con-
spicuously identified for the remaining fifty-one years of life.

By 1881 his labors and good fortune enabled him to realize the
dream of his young manhood through establishing the Boston Sym-
phony Orchestra. This he maintained, at a very large personal cost,
for thirty-seven years. The fortune which he spent upon it was the
measure of his devotion to his city, his country, and his kind. But it
was not expressed through this interest only, for his gifts to Harvard
College, through a long period of years, gifts devoted primarily to the
happiness and health of the student body, placed him among the great
benefactors of that institution. To friends and others in need he was
constantly holding out a helping hand. Though his name is most
associated with the art of music and with education, he gladly furthered
many another good cause, local and national. He was withal a
strongly individual figure, outspoken in praise and blame, much
swayed by his affections, endowed with many of the most lovable

FRANKLIN PAINE MALL. 495

human qualities. By his death on November 14, 1919, in Boston,
his comminiity lost its foremost figure, and his country a pattern of
the highest patriotism.

M. A. DeWolfe Howe.

FRANKLIN PAINE MALL (1862-1917).

Fellow in Class II, Section 3, 1901.

Franklin Paine Mall, 1862-1917, was born in Iowa of German
extraction, his father being one of the 1848 immigrants. Nothing is
known of his boyhood education, which was mainly in a boarding
school near his home. He studied medicine in the University of
Michigan, and received the ]\I.D. degree in 1883, before attaining his
majority. He then went to Germany and spent several A^ears in study
at Heidelberg and Leipzig, at the latter place in the laboratories of
Ludwig and His, these being men of the highest rank in science and
who exerted a great influence on his life. From 1886 to 1889 he was
Fellow and Instructor in Pathology at the Johns Hopkins LTniversity
under Professor Wm. H. Welch, from 1889 to 1892 Adjunct Professor
of Vertebrate Anatomy at Clark LTniversity, and from 1892 to 1893
Professor of Anatomy at the University of Chicago. He returned to
Baltimore in 1893 as Professor of Anatomy in the newly formed Johns
Hopkins Medical School, which position he held to his death, being
also the Director of the Carnegie Institute of Embryology which was
established at the Johns Hopkins Medical School in 1912.

Such are the brief facts concerning the official career of the man who,
in the great renaissance of medicine during the last fifty years probably
did more in America than any other man to make possible this rebirth
and growth. He was a great teacher, as such bringing to medical
teaching the ideal that knowledge is to be sought not in lectures or
books but by the study of nature, the student acquiring primary
knowledge by independent work which might be extended by reading
and at the same time receiving training in scientific methods which
would increase individual power. This method at the time of its in-
duction was novel, was resisted by both students and faculty, but was
steadily carried out in his laboratory, and has become the accepted
method of the best teachers.

496 PROCEEDINGS OF THE AMERICAN ACADEMY.

He was a great scientific investigator. As such his work was
thorough, he touched no subject on which his investigations did not
throw light and in most cases he left the subject standing clearly, the
obscurities gone. He was a leader, not a follower, his researches were
carefully planned, he used all methods of approach, and was fertile in
devising new methods of work. His individual contributions, of which
there are more than a hundred, and the five hundred contributions
from his laboratory, rank with highest contributions to the science of
anatomy.

He was active in the promotion of opportunities for the advance of
medical science in all places, his advice was always sought and valued,
and his influence has been very great in the advance of medical teach-
ing in this country and elsewhere. He led a simple and quiet life, was
a good citizen, a good friend.

For account of his life and work see Johns Hopkins Hospital Bulle-
tin, Memorial Service held May, 1918; Anatomical Record, January,
1918.

\V. T. Councilman.

SIR WILLIAM OSLER (1849-1919).

Fellow in Class II, Section 4, 1897.

In 1849 William Osier was born in Tecumseh, Ontario, Canada, the
son of Reverend F. L. Osier. Beginning his medical training at the
University of Toronto, he continued it at McGill whence he received
his M.D. degree in 1872. Two years were spent in study abroad at
London, Berlin and Vienna. Returning to Montreal in 1874 he was
made Lecturer on the Institutes of Medicine at McGill, and shortly
afterwards was given the Professorship. This began what continued
to be, for him, the chief interest of his life, for Osier, more than anything
else, was a teacher, first at McGill, later at the University of Pennsyl-
vania, then at Johns Hopkins, where he exerted his greatest influence
as an inspiring leader of an increasingly large group of students, and
finally at Oxford, where, as Regius Professor of Medicine, he held a
unique position of influence on both American and British medicine.

In the early days of his medical career Osier was a diligent student of
pathology and contributed important studies in this field, notably on

SIR WILLIAM OSLER. 497

blood platelets. Chiefly, however, in this period he was laying a
foundation for his future clinical work in a thorough and extensive
knowledge of pathological anatomy gained from making post mortem
dissections with the enthusiasm of a keen minded, enthusiastic, in-
defatigable worker. This interest in pathological anatomy he never
lost and his knowledge of it proved an ever ready help in his subsequent
career as a clinician, teaching the principles of the practice of medicine
in the wards of the various hospitals where he served.

At the Johns Hopkins Hospital he inaugurated what was to prove,
perhaps, the most important contribution to methods of teaching
medicine of the half century in the latter days of which we now live,
namely, the learning of medicine by laboratory practice rather than
by lecture and recitation, for he made of the hospital wards the labora-
tory of clinical medicine in which the same observational methods
were pursued as in the laboratories of natural science and the facts of
pathological anatomy and physiology were correlated with the pheno-
mena of disease as seen in the individual patients. Into this laboratory
method he brought the humanizing and inspiring influence of a per-
sonality keenly interested in helping and stimulating his fellows and
one by nature endowed with a winsomeness, charitableness and humor
that made of him for students and patients a lifelong friend. Though
a laboratory, yet the wards were always clearly recognized as the place
in which each individual patient must receive the best possible pro-
fessional care and the kindly considerative aid that is due to a fellow-
man in distress. Though laboratory director. Osier in his wards was
ever the true physician.

In all of his very numerous contributions to medical science and
practice as well as in his textbook of medicine, Osier shows a A'cry dis-
tincti^'e and delightful literary style. He is direct, simple and logical.
Examples that illustrate and clarify are chosen with great discretion.
In his addresses quotations evince both his knowledge of the best in
literature and his ability to emphasize or impress his point by apt
quotation. Always greatly interested in the historical background of
medicine, he makes much use of historical reference in his writings.
There is ever the quaint turn of his humor or some epigrammatic line
to enliven the description or discussion. His words are chosen with
great charm of diction and still it is rare that his meaning is at all
ambiguous. In almost all of his writing there is a personal element

498 PROCEEDINGS OF THE AMERICAN ACADEMY.

that, for those who knew him, recalls vividly to memory the picture
of the man and his personality. His publications were numerous and
varied, for the most part dealing with clinical medicine. A bil)liog-
raphy published in 1919 shows 730 titles. His practice of medicine
has remained, since the first edition in 1892, the most popular textbook
for English speaking students as well as having been translated into
French, Spanish and Chinese. A new edition has been issued at three
year intervals and through this book Osier exerted a tremendous in-
fluence on the practice of medicine for in it Osier's personality domi-
nates in a truly remarkable way when one considers the difficulty of
introducing any personal note inherent in a textbook necessarily con-
densed when covering such a voluminous topic as the practice of
medicine.

Through all the years of his activities as investigator, teacher,
medical writer and hospital chief, Osier remained an active consultant,
aiding fellow physicians in the solution of difficult problems in diagno-
sis. His own optimism radiated courage to the patients and his
delightful personality and charm endeared him to innumerable physi-
cians who brought him patients. He was most intolerant of unkind
criticism of others and would never allow patients or physicians to
bring to his ears unsavory gossip of fellow practitioners. He believed
in and practiced direct honesty in dealing with patients and physi-
cians, but a different opinion or advice from him never carried with it
the sting of a rebuke nor the implication than an unjustifiable error
had been made by another.

Osier was distinctly more a scholar than almost any of his medical
contemporaries. He had a deep interest in the classics. That he, a
physician, should be president of the British Classical Association, as
he was in 1919, was a recognition by scholars of his classical learning.
His interest in medical history has already been referred to. In this
connection he was, all of his life, an ardent bibliophile and his library
of early editions of medical classics and allied topics was a veritable
treasure house. To many his name recalls the picture of a delightful
eagerness and radiant charm of manner as, standing in his library
either earlier in Baltimore or later in Oxford, with one of his choice
volumes in hand, he turns the pages and talks of the author or his
writings. This is the mental picture rather than that of physician,
for, however much his life's work was that of inspiring medical men, he

WILHELM PFEFFER. 499

seemed peculiarly in his proper setting by his beloved books. He
took a great interest in both the Bodleian Library at Oxford and in the
Oxford Press, and to both he gave much thought and time, serving
each in official capacity.

When Osier left Baltimore for Oxford he was almost universally
conceded to be the leading man in American medicine. At Oxford he
merely widened his sphere so as to become the leader for British as
well as American medicine. He died Dec. 29, 1919 of complications
following pneumonia. The death of his only son in the World's War
and the strain incident to his own activities in connection with the
problems of the sick and wounded were important contributing
factors. In his lifetime he moulded in many very important ways
medical thought and medical teaching. He was greatly beloved by
students, fellow practitioners and patients by reason of his human
friendliness and his kindliness. To his students and medical col-
leagues he was ever an inspiring leader stimulating to diligence in
medical work and exemplifying in himself what the ideal physician
and medical teacher and writer should be.

Henry A. Christian.

WILHELM PFEFFER (1845-1920).

Foreign Honorary Member in Class II, Section 2, 1897.

The death of Professor Wilhelm Pfeffer, on the 30th of January,
1920, removed one of the outstanding figures of the scientific world.
With the exception of Strasburger, he probably influenced the work
of the last generation of American botanists more deeply than any
other man.

The last two decades of the nineteenth century was a period of re-
markable development of botany in America. A number of factors
contributed to this, but undoubtedly the most important was the in-
fluence of the work of the great German botanists of the previous
twenty years. Through the translation of Sachs's famous text-book
and several other important German works American botanists were
introduced to the results of the investigations of the morphologists and
physiologists, who made Germany at that period the leader in botani-
cal science. Up to this time, one may almost say that physiology and
comparative anatomy in botan}-, did not exist in America. As a

500 PROCEEDINGS OF THE AMERICAN ACADEMY.

result of this newly aroused interest, many of the younger botanists
looked forward to studying in Germany.

It is true that a small number had found their way abroad in the
seventies, but it was not until a decade later that the real exodus to the
German laboratories began. For ten years or more there were always
to be found American students in the principal botanical laboratories
of Germany, especially in Strasburger's laboratory in Bonn and in
Pfeffer's at Leipzig. These young Americans applied themselves to
the acquirement of the latest methods of research, particularly in the
field of histology and cytology with Strasburger, and physiology under
Pfeffer's direction. It is hardly necessary to point out the results of
this training on the subsequent development of botanical teaching and
research in America.

Pfeffer was almost the last of that remarkable band of distinguished
investigators who for nearly half a century made Germany the center
of botanical progress in Europe.

The writer spent the summer semester of 1887 in Pfeffer's laboratory
in Tubingen, just before he removed to Leipzig where the rest of his
life was spent.

The old Suabian towTi of Tubingen is most picturesquely placed in
the beautiful Neckar Valley, south of Stuttgart, and near the northern
border of the Black Forest. This region is one of the most attractive
in Germany, and the quaint old town, and the amiable South German
people, who still clung to their picturesque customs and peasant
costumes, made it a most satisfactory abiding place — aside from the
scientific advantages of the University.

The laboratory was at this time one of the best equipped in Ger-
many. It boasted a line of distinguished botanists as directors, two
of whom, Yon Mohl and Hofmeister, were worthy predecessors of
Pfeffer. LTnder Pfeffer's able direction the facilities for work in
physiology were probably at that time unequalled.

Sachs, at this period had practically ceased active work and Pfeffer
was generally recognized as his legitimate successor.

Pfeffer was an indefatigable worker but found time to supervise
carefully the work of his students and to give them the benefit of his
valuable criticism and assistance. At this time he was but forty-two
years old but looked older, his tall, thin and somewhat bent figure and
strongly marked features making him seem older than his years.

WILHELM PFEFFER. 501

Pfeffer was born, the son of an apothecary, in the village of Greben-
stein near Cassel, March 9, 1845. He stiuhed at Gottingen where he
took his doctorate in 1865, in Marburg, where he afterward taught as
docent, in Berlin and Wiirzburg, in the latter University working
under Sachs.

In 1873 he was appointed professor extraordinarius in Bonn, and
four years later went as full professor to Basel, where he remained only
a year, after which he went to Tubingen. He held the position in
Tubingen until his final removal in 1887 to Leipzig where he remained
until his death in 1920.

In Leipzig he developed the great laboratory which for more than
thirty years was the Mecca for students of plant physiology from all
parts of the world. Throughout his long career in Leipzig he was
generally recognized as the first physiologist of his generation.

^Yhile Pfeffer 's name is primarily associated with strictly physiologi-
cal problems, as a young man he published several morphological
papers of considerable importance. Especially valuable was a paper
on the development of the gametophyte and embryo of Selaginella, a
paper that for a long time was the most important contribution to the
subject.

It is, however, upon the very numerous and important contributions
to plant physiology that his fame rests. These cover an extensive
range of subjects, some of fundamental importance, not only biologi-
cally, but to physics and chemistry as well. His remarkable investi-
gations in osmotic pressure have strongly influenced the work of
subsequent workers in pure physics and chemistry, and their great im-
portance has been fully recognized by these investigators. Pfeffer's
extensive studies on plasma membranes and the phenomena of irrita-
bility include many papers of the first importance. During his stay in
Tubingen he inaugurated a series of publications " Untersuchungen
aus dem botanischen Institut zu Tubingen" modelled on the similar
publication issued from the botanical Institute in Wiirzburg under the
direction of Sachs. This publication ceased on Pfeffer's departure
from Tubingen.

Pfeffer's best known work is his great text-book, Handbuch der
Pflanzenphysiologie. This was translated into English and was for
many years the standard work on the subject.

Pfeffer's name is also associated with the well-known periodical.

502 PROCEEDINGS OF THE AMERICAN ACADEMY.

Pringsheims Jahrbiicher fiir wissenschaftlicher Botanik. After the
death of Pringsheim, this was issued for several years under the joint
editorship of Pfeffer and his distinguished colleague, Strasburger.

Shortly before the outbreak of the war Pfeffer's old students were
invited to contribute to a "Festschrift" to celebrate the fiftieth
anniversary of his doctorate and his seventieth birthday. The volume
appeared in 1915, but the circumstances of the war resulted in the
absence of many names which under normal conditions would cer-
tainly have appeared in it.

Pfeffer survived the horrors of the Great War, in which he lost his
only son, and saw the collapse of the great German empire, in whose
upbuilding he and his scientific colleagues played such an important
role. He had the satisfaction, however, of knowing that their work
would survive the downfall of the imperial government and that his
name will always rank high in the annals of science.

Douglas Houghton Campbell.
EDWARD CHARLES PICKERING (1846-1919).

Fellow in Class I, Section 1, 1867.

In the death of Edward Charles Pickering after a servdce of forty-
two years as Director of the Harvard College Observatory, the Ameri-
can Academy loses an interested and important Fellow and the Science
of Astronomy one who was at his death the dean of astronomical
research in America.

He was born in Boston, Massachusetts, July 19, 1846, of a distin-
guished and highly cultivated New England family. In 1865, he
graduated from the Lawrence Scientific School with the degree of S.B.
He was immediately thereupon appointed instructor in mathematics
in that institution, but the following year he became assistant in-
structor in Phxsics in the Massachusetts Institute of Technology, and
two years after was made Thayer Professor of Ph^^sics.

From the very outset of his teaching his peculiar bent of mind was
revealed and the work of research and organization which constituted
his great contribution to modern science was begun.

He planned and put into practical shape for use in systematic class
instruction the experimental laboratory method in the teaching of

EDWARD CHARLES PICKERING. 503

Physics which did much to make the Institute of Technology famous
and has since been accepted and adopted universally as an indis-
pensable method of instruction in that subject. To the laboratory
which he had organized and built up the Corporation of the Institute
in 1872 at his suggestion gave the name Rogers Laboratory of Physics
and the additional title of Director of the Laboratory was conferred
upon him.

In the autumn of 1876 he Avas called to become the Director of the
Harvard College Observatory, and accepting this invitation he entered
upon the duties of the position in February, 1877. His selection by
President Eliot seemed at the time a radical innovation for Professor
Pickering was a physicist rather than an astronomer of the old school.
However, the appointment was justified for it presaged the trend of
the New Astronomy along the lines of Physics, a development in which
Professor Pickering has borne a most honorable part.

As Director of the Observatory he showed great administrative
abilit}^ and secured a large financial support for his projects, the en-
dowment growing from a few hundred thousand to a million dollars.

Instead of venturing into the realm of speculative and picturesque
astronomy, he was content to be what he called himself " a collector of
astronomical facts," the interpretation of which he was perfectly
willing to leave to the future. The posthumous value of the work of
such men as Herschel and Argelander appealed especially to him and
shaped the large investigations that he undertook, whose importance
could not be completelj' revealed perhaps for centuries.

Immediately upon his appointment to his new position. Professor
Pickering chose as his particular field of labor the photometry of the
stars. Soon after the introduction of the dry plate, in general photo-
graphy, he was led to investigate its applicability to the study of the
stars and their spectra in which work he was a pioneer. He also
realized the great value of the objective prism in stellar spectroscopy
and made constant use of it in his studies of stellar spectra.

The Observatory under Professor Pickering has made its largest
eontril)ution to astronomy in four fields.

(1) Photometry. With the aid of the meridian photometer in-
vented by him, he de\ised a scale of photometric magnitudes, deter-
mining these for eighty thousand stars upon a basis of more than two
million observations.

504 PROCEEDINGS OF THE AMERICAN ACADEMY.

(2) A scale of photographic magnitudes. It was shown later that
these are convertible into visual magnitudes through reference to the
spectral types of the stars.

(3) A system of classification of variable stars. Light curves have
been determined for a large number of these and many thousand
measures of their brightness have been made on a uniform scale for
all of the sky.

(4) A system of classification of stellar spectra which has been
universally adopted. The new Henry Draper Catalogue contains
estimates based on this system of all stars to approximately the ninth
magnitude, about 200,000 in number.

Through the establishment of an observatory at Arequipa in 1891
after two years of preliminary study it became possible to include
measurements made on the stars throughout the southern heavens
within the scope of the work of the Harvard College Observatory.

At a later date, 1911, an observing station was established at Mande-
ville, Jamaica, which has been devoted particularly to the study of the
moon and the planets.

In this short article it is not possible to go into detail or even to
mention the great variety of investigations carried on to a successful
completion. The volumes of the Harvard Annals, more than eighty
of which were published during Professor Pickering's directorship, can
alone give any idea of this.

A word, however, should be said of the "photographic library"
which now contains over a quarter of a million photographic plates
that together weigh one hundred and twenty tons. Through the vise
of short focus lenses and automatic following apparatus there has
been kept a "sky patrol" the results of which furnish the history of
all the stars down to the tenth magnitude and measuring back for
many years. By its use whenever any noteworthy stellar change is
discovered the plates will reveal its past history- and character, while
otherwise one might have to wait years to understand the nature of
the phenomena.

Through the use of this library, it is possible to find the history of
the stars, as one turns back the pages of a book already printed.
What may still be hoped for from this crystallized past of the heavens
is shown by what it has already done in recording the extraordinarily
favorable position for observation of the minor planet Eros at its

EDWARD CHARLES PICKERING. 505

opposition in 1893, though it was not actually known even to exist
until several years later in 1898.

Professor Pickering strongly believed in associative work. To him
is due the organization of the American Astronomical Society in 1898
(originally called the Astronomical and Astrophysical Society) which
now has a membership of over three hundred from all parts of the
country, and has been of great service in stinmlating research and
promoting acciuaintance among astronomers. The American Asso-
ciation of Variable Star Observers, a body composed chiefly of amateur
observers of these objects, also originated with him.

Professor Pickering was elected a Fellow of the Academy in 1867 at
the age of twenty-one years and is said to have been the youngest
member ever chosen. He was averse to holding office, probably be-
cause during many years regularity of attendance at the meetings of
the Academy would have interfered with his professional duties. He
was a member of the Council from 1878 to 1884 and a member of the
Committee on the Library from 1877 to 1883. He rendered great
service to the Academy and to scientific research through his unpre-
cedentedly long and devoted work as a Member of the Rumford
Committee. This began in 1869 and continued up to the time of his
death with a break, however, from 1890 to 1892, during which interval
he was awarded the Rumford Premium "for his work on the photo-
metry of the stars and upon stellar spectra." He contributed to the
Proceedings twenty-six papers, three of them in collaboration with
others. There will shortly be published by the Academy a memoir
containing the results of researches upon the photometry of faint stars,
carried on at various observatories with the use of a form of photo-
meter devised by him for this especial service.

In 1874, Professor Pickering married Miss Lizzie Wadswortli Sparks,
a daughter of the Reverend Jared Sparks, the historian, and a former
President of Harvard University. Mrs. Pickering died in 1906.

To those who had the privilege of a personal acquaintance with
Professor Pickering his great mind will always seem secondary to his
greater heart, his generous friendship and his social charms.

He was never a narrow specialist interested only in his own branch
of science. All astronomy-, indeed all science, received his interest
and encouragement. His broad sympathy included such dissimilar
interests as mountain-climbing and music. He was the founder of

506 PROCEEDINGS OF THE AMERICAN ACADEMY.

the Appalachian Mountain Club and its first President. Music was
an inspiration to him in his work, not as a relaxation alone, but as a
stimulant which helped him to solve mathematical and physical
problems.

He had the cooperative mind and the highest unselfishness actuated
all his relations with his fellow astronomers. He subordinated his
own individuality in his work and even the interests of his observatory
to the good of astronomical science. All the honors of the astronomical
world were showered upon him and upon the institution which under
his direction had led the c[ueen of sciences into new triumphs in un-
trodden fields.

As it was said of Sir Christopher Wren that his monument was Saint
Paul's Cathedral, so the monument of Professor Pickering is found in
the ninety volumes of the Annals of Harvard College Observatory, a
monument which as long as man looks up at the heavens and wonders
and interprets, should be an honorable and enduring one.

Joel H. Metcalf.
JOHN ELLIOTT PILLSBURY (1846-1919).

Fellow in Class II, Section 1, 1893.

This distinguished naAal officer and oceanographer was born at
Lowell, Massachusetts, December 15, 1846, the son of John Oilman
and Elizabeth Wimble (Smith) Pillsbury. His early education was
received in the public schools, and at the age of fourteen he was ap-
pointed a page in the House of Representatives.

In 1862 he received from President Lincoln a nomination to the
U. S. Naval Academy, from which he graduated in 1867, being com-
missioned ensign in 1868 and lieutenant in 1872.

He married Florence Greenwood Aitchison of Portland, Maine, "
August 26, 1873. Elsie Greenwood, later wife of Edward B. Richard-
son of Brookline, Mass., was the only issue of this marriage.

In 1875 he was ordered to the Hydrographic Ofiice of the Navy
Department and the following year detailed to the JJ. S. Coast Survey,
where he gave ten years of service and placed his name permanently
on the roll of those who have materially added to our knowledge of the
secrets of the Ocean.

JOHN ELLIOTT PILLSBURY. 507

The investigation of the Gulf Stream was undertaken by the Survey
on account of its importance to navigation as well as its scientific
interest, and work was begun in 1883 with the schooner Drift, which,
as her name implies, proved inadequate for the purpose and was re-
placed by the Coast Survey Steamer Blake.

New methods of current measurement and improved instruments
for recording observations were devised by Pillsbury, and by the aid
of the recently introduced steel cable anchorage was had, sometimes
at a depth of over two miles. Observations extended from Tobago
on the southeast to Hatteras on the north, and the movements and
temperatures of this important current were definitely fixed over a
great part of its course. Among the interesting new results of the
work were the determination of daily fluctuations in the rate of flow
more or less coincident with the tidal action, and the contribution of
wave effect, driven b\- the trade winds, in increasing the movement of
the stream.

During the Spanish War he commanded the dynamite cruiser
Vesuvius and participated in the attack on San Juan, Porto Rico.
He was later promoted to Commander and through the various grades
to Rear Admiral and Chief of the Bureau of Navigation in 1908. He
received all the medals for service and efficiency in the line of duty
which under the law are granted by the Navy Department.

In 1909 he became a member of the Board of Managers of the
National Geographic Society, Vice-president in 1915, and President
of the Society in April, 1919; dying on December 30th of the same
year.

A summary of his lifework is given in the Bulletin of the National
Geographic Society of October 16, 1919. An account of the Gulf
Stream work and results was given by ^Admiral Pillsbury in the
National Geographic jVIagazine of August, 1912, and in Hydrographic
Office publication No. 110, in 1894. A memoir on Charts and Chart-
making was published in Proceedings of the U. S. Naval Institute
No. 29, in February, 1894. An excellent portrait of the Admiral ap-
peared in the National Geographic Magazine, volume 37, p. 341, in
April, 1920.

The Admiral was elected a member of this Academy, April 12, 1893.

WlLLL\M HeALEY DaLL.

508 PROCEEDINGS OF THE AMERICAN ACADEMY.

ARTHUR SEARLE (1837-1920).

Fellow in Class 1, Section 1, 1877.

Arthur Searle, who died October 23, 1920, was born in London on
October 21, 1837. His father, Thomas Searle, was an American pitizen
and a descendant of Governor Thomas Dudley of Massachusetts.
His mother, Anne Noble, came from Derby, England, being English
by birth as well as by ancestry. Thomas Searle seems to have been
naturally fitted for the life of a scholar and a man of letters, but the
restricted means of the family deprived him of a college education, and
forced him into mercantile business at an early age. At the time of
his marriage in 1834 he was a partner in a firm of London bankers.
It was during this sojourn in England that his son Arthur was born in
1837, and two years later his other son George. As a consequence of a
commercial panic Thomas returned in 1840 to America with his family
to look after business interests. His wife soon died, and two years
after in 1843 he himself passed away, leaving the care of the two boys
to his elder brother and a sister in Brookline, Mass.

Both boys were sent early to private schools in Brookline and Rox-
bury, partly for the reason as Searle afterward suspected, to make life
easier for their elders, not accustomed to such lively youngsters. The
last school days were passed at the Brookline High School. Entering
Harvard College at the age of fourteen years, he was graduated in
1856, as the second scholar of his class. In 1859 he received his Master's
degree. Ai-thur, though only six years old at the time of his father's
death, had found in him a companion and an instructor. Under such
influence, the scholarly aspirations of the father seemed to have been
as seed to find fruition in the son's life. The boy had an alert mind.
At the age of seven he began his habit of psychological introspection
by the discovery, while meditating on some subject, that it was he
himself who was thinking. Thus, he became aware of the personal
identity that was Arthur Searle. Before this time he had made his
first experiment in physics, namely, as to the effect of centrifugal force
acting on a bit of wood placed inside the whirling rim of his aunt
Becky's spinning wheel. At eleven years he was interested in the
revolution in France, and began to have political opinions, which were
always conservative. But anything of a scientific nature fascinated

ARTHUR SEARLE. 509

him. The electric telegraph, anaesthetic surgery, the discovery of
the planet Neptune in 1846, all appealed to his mind. Nor was he less
gifted in other respects. His avidity for knowledge gave him even
then the reputation of being a " walking dictionary." As a schoolboy,
mathematics could be easily acquired while feeding his rabbits, and at
college he found that he had already performed the chemical experi-
ments which were being taught from a text-book without any provision
for laboratory practice by the students. All branches of knowledge
inside or outside the college curriculum interested him intensely, and
he studied them all eagerly and thoughtfully. His first article was
published in the Harvard Magazine, while he was still a student. It
was on the plurality of worlds, and seemed prophetic of his future
career, as he had no thought at the time of making astronomy a pro-
fession.

It was twelve years after graduation that Searle found his calling.
The intervening time was a course in the university of life. Ill health
led him to engage in farming for a time. Teaching, statistical work,
and experience in a broker's office, all were tried. He also joined in a
project to raise sheep in California, but the scheme after a brief trial
was abandoned. Before returning home from California, he filled
temporarily the place of an absent professor at Santa Clara.

In 1868, his brother George, who had been employed at the HarAurd
Observatory, resigned to study for the Catholic priesthood, and Arthur
was asked to take his place. This he did, little thinking that at last
he had found a permanent place with congenial occupation. Tlie
following year he was appointed Assistant, to be promoted to Assistant
Professor in 1883, and Phillips Professor of Astronomy in 1887. In
1912 he became Phillips Professor Emeritus. Besides his Obser\atory
work he also conducted astronomical courses at Radcliffe College from
1891 to 1912. He was married in 1873 to Emma Wesselhoeft, daugh-
ter of Dr. Robert Wesselhoeft of Boston. Mrs. Searle died in 1914.
Two daughters survive their parents.

His earliest work at the Harvard Observatory was as a computer
and observer. In the latter capacity he made observations of stars,
double stars, nebulae, satellites of the planets, asteroids, and comets.
These observations are contained in the Annals of Harvard College
Observatory, Volumes 11, 13, 14, and 33; also in the Proceedings of
this Academy, Volume 16. In 1889 he published in the .\nnals of

5U) PROCEEDINGS OF THE AMERICAN ACADEMY.

Harvard College Observatory, Volume 19, Part 1, the results, which he
had gathered, of the early meteorological observations made at the
Observatory from 1840 to ISSS. Among these were included various
miscellaneous observations relating to the aurora, lightning, meteors,
earthquakes, and to some extent to the zodiacal light.

The zodiacal light was the subject of his first independent investiga-
tion. Beginning in 1874 he continued his observations of the zodiacal
light and the Gegenschein until 1895, when the increasing use of
electricity for street illumination made such work impossible in Cam-
bridge. The residts of these observations are contained in the
Astronomische Nachrichten, Volumes 99, 102, 109, IIG, 124, and 126,
Proceedings, Volume 19, Memoirs, Volume 11; and the Annals of the
HarA ard College ObserA'atory, Volumes 19, Part 2, and 33, Nos. 1, 2,
and 3. Summaries of information written by him on the subject
appear in the ^Monthly AVeather Review and elsewhere.

The several lines of his inquiry dealt with the permanence, position,
and magnitude of the ordinary western zodiacal light; the normal
distribution of light in the zodiac and vicinity; and the position,
parallax, and brigiitness of the Gegenschein. His studies led him to
faAor the hypothesis ascribing the phenomenon to light reflected from
small meteoric bodies. He published a statement on the "Meteoric
Theory of the Gegenschein" also in the English periodical, Observatory,
August, 1899. Although he considered the meteoric hypothesis as the
most probable explanation, he felt that his series of obser\'ations
should be extended to reach a definite conclusion. The research
shouUl include the orbital movements and the light of asteroids and
periodic comets. He expressed the hope that younger observers more
favorably located might carry out his plan.

In the Observatory he was frequently engaged in the business
management, particularly during the interim between Director Win-
lock's death and Professor Pickering's appointment. It was at this
time that he publishetl Volume 8 of the Harvard Annals, containing
his account of the history of the Observatory from 1835 to 187{), with a
description of the buildings, instruments and of work done. The
volume included also a series of illustrations of Sun, planets, and other
celestial objects, which had been drawn mostly by Trouvelot during
Winlock's directorship.

Professor Searle spent ten years — from 1S8S to 1898 — in making

ARTHUR SEARLE. 511

the meridian circle observations for the Zone Catalogue of 8337 Stars
between 9° 50' and 14° 10' of South Declination in 1855 for the Epoch
1900.0. The results fill Volumes G2, 65, 66, 67, and 70 of the Harvard
Annals. The Catalogue itself, contained in Volume 67, was published
in cooperation with the Astronomische Gesellschaft. The reduction
and publication of these observations with the superintendence of
other computers consumed most of his time and energy until he retired
in 1912. With his customary modesty, he regarded this not as a
personal undertaking but as a large piece of routine work. Neverthe-
less, the various investigations related to meridian circle observations,
which lie undertook in the course of the work, show his skill and in-
genuity in meeting such problems. They are indicated in the Intro-
duction to the Catalogue just mentioned. Reference may be made
here to "Results of Accessory Series of Observations made with the
Meridian Circle," and "Comparison of Results obtained with differ-
ent Forms of Apparatus in Meridian Observations," in the Annals of
Harvard College Observatory, Volumes, 33, No. 11, and 41, No. 7.
In 1908 he published in the Harvard Annals, Volume 60, No. 1,
"Geometrical Methods in the Theory of Combining Observations."
In the Annals, Volume 29, No. 6 are his observations of /3 Persei, and
surrounding comparison stars.

Besides various articles in periodicals, he published "Outlines of
Astronomy" in 1874, followed by a second edition in 1875. In 1910
his "Essays I-XXX" appeared, which, among other topics, discussed
"Space and Time," interesting in the light of the theory of relativity.

Professor Searle became a Fellow of the Academy in 1877, at the
same time with Professor Charles R. Cross, who recently died. His
scientific papers presented to the Academy, and not already mentioned
are in the Proceedings, Volumes 19, 24, and 55. The last paper " Orbits
Resulting from Assumed Laws of Motion" was a result of an extensive
investigation begun in 1882, forming an important part of a treatise
which he had practically completed at the time of his death. Reading
this paper on the balanced effect of "inward" and "outward" forces
on a moving body, one is carried back to the initial physical experi-
ment, which he performed in his childhood with the help of his aunt's
spinning wheel.

He was very much of a mathematician, and when any question of
the sort arose he was consulted. The results will be found in various

512 PROCEEDINGS OF THE AMERICAN ACADEMY.

places. For example, in the paper on "Stellar Photometry" pub-
lished in the Proceedings, Volume 11, the discussion of the path de-
scribed by stars at various declinations in the field of a telescope when
the axis is not properly adjusted, was prepared by him. Not only a
mathematician, he was proficient in many languages. "A Note on
the Battle of Pharsalus" was the result of re-reading Caesar's "De
Bello Civili," which he did for recreation. He amused himself in
writing verse both in Latin and in English. One of these poems
written at the time of his wife's death has been published since his own
death; the Latin version in the Harvard Graduates' Magazine, the
English version in Popular Astronomy.

Professor Searle was the most modest of men. His extremely
retiring disposition probably accounts for his not accepting Dr.
Gould's invitation in 1869 to go as his assistant to Cordoba. Later,
he might have been appointed director of another observatory, if he
had been willing. His life flowed in a quiet stream. It was as he
would have it. The turmoil of strenuous life did not attract him.
From youth he was not keen for even the ordinary pleasures of society,
and yet he had many warm friends, and a host of acquaintances. All
who knew him well, were delighted with his conversational powers.
His sense of humor and the merry twinlde in his eye as he recounted
some episode were passports to friendliness. His philosophical studies
made his thinking clear. When he spoke, it was as one having the
authority of careful thought. In discussing any subject he had a
succinctness of expression which swept away all intricacies and left the
matter in outlines readily understood. He was of a type, not so com-
mon at the present day, of a scholarly gentleman, versed in many
branches of learning, and keenly susceptible to the delights of music,
of art, and the manifestations of nature.

Edward S. King.

WILLIAM THOMPSON SEDGWICK (1855-1921).

Fellow in Class II, Section 3, 1886.

William T. Sedgwick, a Fellow of the American Academy of Arts
and Sciences since 1886, died suddenly in Boston, January 25, 1921,
at the age of 66 years, while still in the full tide of his activities as a

WILLIAM THOMPSON SEDGWICK. 51

Q

teacher, investigator and public servant. The son of William and
Anne Thompson Sedgwick, and a descendant of Robert Sedgwick,
who settled in Boston in 1636, he was born in West Hartford, Connecti-
cut, December 29, 1855, and throughout his life cherished the tradi-
tions of his New England origin and training. He graduated with
high rank from the Sheffield Scientific School of Yale University in
1877, and taught physiological chemistry in Chittenden's laboratory
in 1878-1879. In 1879 he became Fellow and subsequently Assistant
in Biology at Johns Hopkins University, where he took the degree of
Ph.D. in 1881, and in the same year married Mary Catherine Rice of
New Haven. He received the honorary degrees of Sc.D. (Yale, 1909)
and LL.D. (University of Cincinnati, 1920) and was a member of
many learned societies, serving as president of the American Society of
Naturalists, of the American Public Health Association, and of the
Societ}' of American Bacteriologists, of which he was one of the
founders and the first president. He was a member of the Interna-
tional Health Board of the Rockefeller Foundation, of the Advisory
Board of the United States Hygienic Laboratory, of the Public Health
Council of Massachusetts, of the Royal Sanitary Institute of Great
Britain, and of other important organizations. He served as president
of the Boston Civil Service Reform Association in 1900 and of the
State Association in 1901; and from 1897 down to the time of his
death was curator of the Lowell Institute of Boston.

In 1883 he became Professor of Biology in the Department of
Biology, later known as the Department of Biology and Public Health,
at the Massachusetts Institute of Technology, then under the presi-
dency of Francis Walker. As head of that department he began a
service in the teaching of general Ijiology and in the public health
movement in America that continued for nearly forty years and
brought distinction alike to himself and to his institution, rendering
his laboratory one of the important centers of biological work in
America. The culmination of the honors that he received came in the
last year of his life when he served as exchange professor to the uni-
versities of Cambridge and of Leeds, and also as a representative of
the Intitute of Technology, Harvard University, the American Public
Health ^Association and the U. S. Public Health Service at the Inter-
national Health Conference at Brussels. In both capacities, as
foreign observers have testified, his lectures and addresses made a

514 PROCEEDINGS OF THE AMERICAN ACADEMY.

deep impression, carrying a message from America to the older world
that went far beyond the merely technical aspects of his subject.

He was the author of important technical papers and general
addresses, too numerous to be listed here, and also of several larger
works. Among these may be mentioned the "General Biologv," a
text-book published jointly with E. B. Wilson (1886), "The Human
Mechanism," published with Theodore Hough (1906), "A Short
History of Science," with H. W. Tyler (1917), and above all the
"Principles of Sanitary Science" (1902) which at once took its place
as the standard work on the subject and assured Sedgwick's position
as one of the foremost leaders in this field.

Sedgwick's life was the uneventful one of a teacher and investigator,
happy in his work, in his friends and in a home life singularly con-
genial and rich; but even its bare outline impresses us with his versa-
tility and the wide range of his interests. He was a born teacher, one
who loved his work and kept always in view a higher ideal than merely
to impart information. He knew how to inspire his students and
followers with his own buoyant eagerness, thoroughness and tenacity
of purpose. He taught them to think straight, aim high and work
hard. A sane and good humored optimism was inseparable from his
personality; and not less characteristic were the sturdy common sense
and shrewd sense of humor with which he was wont to illuminate the
dry technicalities of his subject, driving home the underlying principles
by the use of homely and telling illustrations that made them living
realities never to be forgotten. In these respects Sedgwick was indeed
a teacher unrivalled, as many generations of "Tech" students can
bear witness. He made comrades of his students, and they gave to
him affectionate and enduring friendship. Alike by precept and by
the example of his own life he taught them that man does not live by
bread alone; that the student of science fails to attain his largest
measure of success if his mind be not kept open to the larger world of
literature, art and human fellowship. His students felt towards him
an almost filial regard and learned to look to him in their later lives
for wise and helpful counsel. In this respect he has with good reason
been compared to Dr. Ai-nold, but as one of his former students has
finely said: " The master of Rugby was far off on the snowy heights.
Sedgwick was in the midst of the rush of life and he held us by the
hand."

WILLIAM THOMPSON SEDGWICK. 515

Though Sedgwick's early inclination was towards the study of
physiology and medicine he later gravitated irresistibly into sanitary
science and conservation of the public health; and in this fiehl he was
one of the earliest and most prominent pioneers. He and his many
pupils contributed more than any other to the emancipation of these
subjects from medicine in the narrower sense, and their recognition as
important independent branches of applied biology which offer the
widest opportunities for public service outside the practise of medicine.
To this end he contributed by important studies on epidemics, largely
in connection with the work of the State Board of Health of Massa-
chusetts and the Lawrence Experimental Station, by the work of
numerous students trained in his laboratory, and especially by the
publication in 1902 of his authoritative work on Sanitary Science and
the Public Health, referred to above, which has recently been charac-
terized by competent authority as still the best existing epitome of
the subject.

The interest in public welfare displayed in these various activities,
was but one side of a larger interest in educational and civic problems
that drew him into many other forms of public service. He was a
valued member or trustee of many public institutions, in and outside
of Boston. He played a prominent part in the struggle for civil
service reform in Massachusetts in 1900-1901, and then and later
delivered many public addresses on subjects connected with the general
welfare. During his long service as curator of the Lowell Institute he
became widely known to the citizens of Boston, winning general
esteem by the breadth of view and enlightened regard for the pul)lic
interest with which for so many years he administered his important
trust.

, As one who had the privilege of intimate friendship with him for
more than forty years, the writer may be permitted finally to empha-
size Sedgwick's high minded and noble character. He was a man of
vision, of lofty ideals, of faith in the eternal fitness of things. No
man was less self-seeking or more appreciative of others. He was
kindly, generous and human, with a gift for friendship that made him
the center of an always enlarging circle of friends and enriched his life
with widely varied human interests. To those friends he gave a
loyalty and ever ready helpfulness that knew no change with the
passing years. He exemplified the best traditions of his profession as

516 PROCEEDINGS OF THE AMERICAN ACADEMY.

an inspiring teacher and a leader of research in his chosen field. His
friends and colleagues rejoiced in his achievements as if they had
belonged in part to them; and they will cherish the memory of his
happy and useful life.^

Edmund B. Wilson.

ELMER ERNEST SOUTHARD (1876-1920).

Fellow in Class II, Section 4, 1911.

Dr. Elmer Ernest Southard died in New York City on February 8,
1920 after a very brief illness at the age of forty-three.

When stricken down by the fatal infection he was busily engaged
in making a series of communications dealing with his special field of
work. He was at the height of his power, and his accompHshments
might well be considered an earnest of still richer productivity in
the years to come. A man of incessant industry, with a keen and alert
intellect, restlessly searching after the solution of age-long problems,
he had a personality which won him many warm friendships, and a
talent for inspiring his associates and pupils.

After an education in the public schools of Boston, and at Harvard
College, he graduated from the Medical School in 1901. Immediately
after graduation he began to occupy himself with that sphere of in-
vestigation with which he later continued to identify himself so closely.
He became early associated with the pathological work of the Massa-
chusetts State Hospitals for the Insane. In 1909 he became Bullard
Professor of Neuropathology. In 1912 he was appointed Director of
the newly established Boston Psychopathic Hospital (at that time
called the Psychopathic Department of the Boston State Hospital).

The value of a scientific worker is only in part to be estimated by
the published results of his personal investigations. Equally im-
portant may be the influence of the worker on associates and pupils,
on the community where he lives, on the whole body of professional
workers who are working in the same field as himself. The influence

1 The writer desires to acknowledge his indebtedness to appreciative reviews
of Professor Sedgwick's life and work by two of his former pupils, Samuel C.
Prescott {Technology Review for April, 1921) and C. E. A. Winslow {Journal oj
Bacteriology, May, 1921).

ELMER ERNEST SOUTHARD. 517

of Dr. Southard radiated widely throughout the country,, and there
are many serious workers in widely scattered centers who owe their
inspiration to him. His publications witness to the great industry of
the man. They cover a wide field; they furnish an important body
of material which has been incorporated in the general body of knowl-
edge which pertains to the disciplines of neuropathology and of
psychiatry.

In the Southard Memorial Number of the Bulletin of the Massa-
chusetts Department of Mental Diseases a complete bibliography of
his works is published, with brief comments and abstracts (pp. 30-199).
The earlier communications deal with the more technical aspects of
morbid processes, involving the central nervous system. They are
detailed studies of tissue reactions which do not involve the cate-
gories of the personality. In later communications the reactions of
the individual began to play a prominent role, and the question of the
correlation of structural damage with functional inefficiency became a
central problem. One of the fundamental problems of psychiatry,
namely, the basal conditions underlying mental deterioration, or, to
put it in another way, the etiology of so-called "dementia prae-
cox," was a subject of much careful investigation on his part. These
are problems of very complex nature, and in the formulation of his
views Dr. Southard not only brought together much interesting
material, but showed a lightness of touch and ingenuity of expression
which charmed those who read his papers.

The position of Director of the Psychopathic Hospital brought with
it new responsibilities and interests which reflected themselves in his
investigations. He had passed from the investigation of mere tissue
to the study of the morbid activity of the individual, and now he was
brought to deal with the problems of mental health in relation to
community life. Work of this type necessarily brings a great variety
of problems, and in regard to them Dr. Southard showed his usual keen
insight and fertility of resources. He contributed papers on the
treatment of special types of disease, on hospital organization, on the
training of special types of workers, on the relationship of the hospital
to the community, on the possibility of making available to industrial
organizations the principles which had been worked out in the limited
sphere of the hospital.

The war brought its special problems in his field, and he contributed

518 PROCEEDINGS OF THE AMERICAN ACADEMY.

a book on "Shell-shock and Other Neuropsychiatric Problems pre-
sented in 589 Case Histories from the War Literature, 1914-1918."

Throughout all these various interests the fundamental fascination
of the problem of the relation of structure to function continued, and
in a boldly outlined program for research into the basis of feeble-
mindedness he sought to determine the "minimum brain machinery
with which speech and thought processes get performefl." Two Re-
search Series have already been published — the Waverley Researches
in the Pathology of the Feeble-Minded (Memoirs of the American
Academy of Arts and Sciences, Vol. XIV, No. II. May, 1918; Vol.
XIV, No. III. December, 1921). In these researches Dr. Southard
and his associates have furnished a standard for scientific work in this
field.

A general survey of the work done by Dr. Southard shows a growing
breadth of vision and steadily maturing genius, and those working in
this special field of medicine realize what a tragedy it was when it
was suddenly deprived of one of its most brilliant workers.

C. M. Campbell.

BARRETT WENDELL (1855-1921).

Fellow in Class III, Section 4, 1889.

Barrett Wendell, a member of this Academv since 1889 was born in
Boston on October 23, 1855, and died on February 9, 1921. He was
the son of Jacob and Mary Bartoldi (Barrett) Wendell. His first
American ancestor on the paternal side was Evart Jansen Wendell,
who came from Emden in East Friesland to New York about 1640
when some twenty-five years old.

Entering Harvard with the Class of 1876, he was compelled by ill
health to leave college for a year; consequently he took his A.B.
degree with the Class of '77. During 1877-8 he attended the Harvard
Law School and later was a student in offices both in New York
and Boston, but his early intention to follow the law was abandoned
for the work of teaching and writing English following his appointment
in 1880 as an instructor at Harvard. He served the college in this
capacity until 1888 when he was made an Assistant Professor. Ten

BARRETT WENDELL. 519

years later he became a full Professor of English, holding that office
until 1917, when he resigned and was chosen Professor Emeritus.

During the thirty-seven years of his incumbency at Harvard
Wendell was a positive constructive force in the fields of English
composition and of comparative literature. He substituted for more
formal methofls a frank incisiveness of speech and an independence of
outlook that challengefl the interest and won the affection of nearly
three generations of students. The class room audiences who found
his controversial attitude engaging never failed to perceive the wisdom,
genial humor and passionate sympathy with what is best in literature
that underlay his marked and sometimes whimsical peculiarities. To
the individual seeking aid he gave of himself in generous measure
never to be forgotten b^^ the recipient.

From the outset of his career as a teacher of English Wendell was
also an industrious writer. Before the appearance in 1891 of his
"English Composition," a text book widely adopted, he had pub-
lished two novels, "The Duchess Emilia" in 1885 and "Rankell's
Remains" in 1887. In the following order appeared " Cotton ^Mather,"
1891; "Stelligeri and Other Essays Concerning America," 1893;
"William Shakespeare, a Study in Elizabethan Literature," 1894;
"A Literary History of America," 1900; "Raleigh in Guiana,"
"Rosamond" and " A Christmas IVIasque," 1902; "The Temper of the
Seventeenth Century in English Literature" (his lectures at Trinity
College, Cambridge, England, in 1902-1903-1904), 1904; "History
of Literature in America" (written in collaboration with Chester N.
Greenough), 1904; "Liberty, L'nion and Democracy — the National
Ideals of America," 1906; "The France of Today," 1907; "The
Privileged Clas.ses," 1908; "The Mystery of Education," 1909; and
finally, in 1920, "The Traditions of European Literature," the second
and concluding volume of which was interupted by his final illness.

Of these writings it may be said that his "Cotton Mather" and his
"English Composition" stand out in the product of his early period;
his "A Literary History of America," which contradicted the judg-
ments of the sages and aspersed some idols, has become with time a
standard treatise; his "The France of Today" (delivered originally
as Lowell lectures) opened the eyes of Americans to their ignorance of
French racial characteristics. The sympathetic insight displayed in
this book was so deeply appreciated by the French people that since

520 PROCEEDINGS OF THE AMERICAN ACADEMY.

his death one of the lecture halls of the Sorbonne has been renamed
after him "Hall Barrett Wendell." "The Traditions of European
Literature," only one volume of which he completed, was a labor of
love, the fruition of years of discerning scholarship. The period from
Homer to Dante was covered by the first volume and the second would
have brought the survey down to modern times.

During his sabbatical vacations Wendell visited Europe at various
times. In 1902-3 he represented Harvard University at the 300th
anniversary of the Bodleian Librar}^ at Oxford, and was Clark lecturer
at Trinity College, Cambridge, England. In 1904-5 he was the first
of the annual lecturers on the Hyde foundation at the Sorbonne and
other French uniA-ersities. In 1911 he went around the world, travel-
ing in India, China and Japan.

Wendell was a member of the American Academy of Arts and
Letters, of the Massachusetts Historical Society, and a Fellow of the
American Academy of Arts and Sciences. He received from Columbia
University in 1913 the honorary degree of Doctor of Letters (Litt. D.) ;
Harvard University conferred upon him the same degree in 1918, and
Strassburg University, France, that of Doctor of Laws (LL.D.) in
1920.

Wendell was a man of pronounced individuality, warm in his
sympathies, singularly loyal in his attachments, and free from little-
ness. He never concealed his convictions, which were often critical
of modern tendencies and points of view. If he seemed to champion
the past at the expense of the present, it was because of his insistence
on standards and his veneration for the summits not the table lands
of tradition. His conversation had the charm of freedom from the
commonplace.

Wendell was married on June 1, 1880, to Edith Greenough of
Quincj, who, with two sons and two daughters, survive him.

Robert Grant.
ANDREW DICKSON WHITE (1832-1918).

Fellow in Class III, Section 2, 1868.

' Andrew Dickson White was born in Homer, November 7, 1832, and
died in Ithaca, only twenty-five miles from his birth-place, on Novem-
ber 4, 1918. As a student at Hobart College and later at Yale, he

ANDREW DICKSON WHITE. 521

was impressed with the inadequacy and narrowness of the college
training of those days. This feeHng increased as he grew older and
when Ezra Cornell consulted him as to the best employment of some of
his wealth for the public benefit, Mr. White soon succeeded in inspiring
him with the vision which became embodied in Cornell University.
Mr. White became of course the president of the new university and
it is to him that we owe the placing of scientific and technical courses
on a level with the humanities. The development of Cornell has been
a striking illustration both of the power of the ideal and of Mr. White's
wisdom. It is scarcely an exaggeration to say that Cornell has been
successful in so far as it has followed the ideals of its first president.
The principles that he laid down over fifty years ago are likely to guide
the course of the University for years to come.

People wondered in the early days why a man like Goldwin Smith
should leave Oxford and come to Cornell; but it was the spirit of
protest in him that made him love Cornell to the end of his life. At
Cornell they were trying to do something new and worth while. It
was the spirit of Andrew D. W'hite that appealed to Goldwin Smith.

Though Mr. White's real reputation will rest on the work that he
did in starting Cornell University as the embodiment of an ideal, this
was by no means the whole of his work. His " History of the Warfare
of Science with Theology in Christendom" and his Autobiography are
the two works which the general public knows, and it is sometimes
forgotten that he was one of the founders of the American Historical
Association and its first president. W'hile president of Cornell Uni-
versity he was also professor of Modern European history. In 1887
he presented to Cornell his historical library and it was only fitting
that the combined departments of history and political science should
be known officially as "The President White School of History and
Political Science."

Mr. White's diplomatic career was varied and honorable. He was
minister plenipotentiary to Germany from 1879 to 1881 and to Russia
from 1892 to 1894 and later ambassador to Germany from 1897 to
1902.

A man of means and a wonderful host, he kept open house in Ithaca.
Distinguished visitors to this country always visited Mr. ^^ liite and
no one who lived in Ithaca during the last years of Mr. White's life can
fail to realize what he meant to the social life of the faculty. The

522 PROCEEDINGS OF THE AMERICAN ACADEMY.

University very properly bears the name of its founder, Ezra Cornell;
but no one will question that it was Andrew D. ^^hite who put the
breath of life into the young institution.

Honors of course came to Mr. White in profusion. He enjoyed
them keenly but they did not change him. A list of these, with other
information, may be found in an obituary notice published in the
Memoirs of the New England Historic Genealogical Society, Vol. 73,
p. LX (1919).

Wilder D. Bancroft.

i

Class I.
Elihd Thomson,

Clasi III.

Arthur P. Ruoo.

American Academy of Arts and Sciences

OFFICERS AND COMMITTEES FOR 1922-23

PRESIDENT.

Gkoucio I'\ Moore.

VICE-PRESIDENTS.

Class II.
Haiivey Cushi.vg,
CORRESPONDING SECRETARY.
Harry \V. Tyler.
RECORDING SECRETARY.

Charles B. Gulick.

TREASURER.

Harold Murdock.i

LIBRARIAN.

Arthur G. ^^'EBSTER.

COUNCILLORS.

Class II.

Edward M. East,

Terms expire 1923.

Reid Hunt,

Terms expire 192-1.

Walter B. Cannon,

Terms expire 1925.

Charles Palache,

Terms expire 191^6.
COMMITTEE OF FINANCE.
John Trowbridge,
RUMFORD COMMITTEE.

Theodore Ly'man, Chairman,

Class I.
Desmond FitzGer.\ld,

FoRRis J. Moore,

William S. Franklin,

Edward V. Huntington,

Henry P. Walcott,

Class III.

KiRsopp Lake ,

Ephraim E.merton.

Albert Matthews.

William C. Wait.

Harold Murdoch.

Arthur G. Webster,
Elihu Thomson,

Harry M. Goodwin.
Charles L. Norton.

Louis Beli

Percy W. Bridgman,

C. M. WARREN COMMITTEE.

James F. Norris, Chdirmnn,
Henry P. Talbot, Walter L. Jennings, Lawrence J. Henderson,
Gregory Pv Baxter, Arthur D. Little, Frederick G. Keyes.

COMMITTEE OF PUBLICATION.

Louis Derr, of Class 1, Chairnmn,
Herbert V. Neal, of Class II, Alrert A. Howard, of Class III.

COMMITTEE ON THE LIBRARY.

Arthur G. Webster, Chairman,
Harry M. Goodwin, of Class I, Thomas Barbour, of Class II,

William C. Lane, of Class III.

auditing committee.

George R. Agassiz, John E. Thayer.

house committee.
John O. Sumner, Chairman, Wm. Sturgis Bigelow, Robert P. Bigelow.

COMMITTEE ON MEETINGS.

The I'uEsiDK.NT,

The Recording Secretary,

George H. Parker, Edwin B. Wilson, Edward K. Rand.

1 Appointed Nov. 8, 1922, to fill the term of H. H. Edes, deceased.

LIST

OP THE

FELLOWS AND FOREIGN HONORARY MEMBERS.

(Corrected to October 20, 1922.)

FELLOWS.— 579.

(Number limited to six hundred.)

Class I. — Mathematical and Physical Sciences. — 195.
Section I. — Mathematics and Astronomy. — 46,

Charles Greeley Abbot Washington, D. C.

Walter Sydney Adams Pasadena, Cal.

George Russell Agassiz Boston

Raymond Clare Archibald Providence, R. I.

Solon Irving Bailey Cambridge

Edward Emerson Barnard Williams Bay, Wis.

George David Birkhoff Cambridge

Ernest William Brown New Haven, Conn.

William Elwood Byerly Cambridge

Florian Cajori Berkeley, Cal.

William Wallace Campbell Mt. Hamilton, Cal.

Julian Lowell Coolidge Cambridge

George Cary Comstock . . Madison, Wis.

Leonard Eugene Dickson Chicago, 111.

Philip Fox Evanston, 111.

Fabian Franklin New York, N. Y.

Edwin Brant Frost . . Williams Bay, Wis.

Frank Lauren Hitchcock Belmont

Edward Vermilye Huntington Cambridge

Dunham Jackson Miimeapolis, Minn.

526 FELLOWS.

Oliver Dimon Kellogg Cambridge

Edward Skinner King . Cambridge

Carl Otto Lampland Flagstaff, Ariz.

Joseph Lipka Cambridge

Joel Hastings Metcalf Portland, ]\Ie.

George Abram Miller Urbana, 111.

Clarence Lemuel Elisha Moore Watertown

Eliakim Hastings Moore Chicago, lU.

Frank Morley Baltimore, Md.

Forest Ray Moulton Chicago, 111.

Henry Bayard Phillips Boston

William Henry Pickering Cambridge

Charles Lane Poor \ • • • N^^^' York, N. Y.

Roland George Dwight Richardson .... MiddletowTi, Conn.

Henry Norris Russell Princeton, N. J.

Frank Schlesinger New Haven, Conn.

Harlow Shapley . Cambridge

Vesto Melvin Slipher Flagstaff, Ariz.

Frederick Slocum Middletown, Conn.

Virgil Snyder Ithaca, N. Y.

Joel Stebbins Madison, Wis.

William Edward Story Worcester

Henry Taber Worcester

Harry Walter Tyler Newton

Robert Wheeler Willson Cambridge

Frederick Shenstone Woods Newton

Class I., Section II. — Physics. — 56.

Joseph Sweetman Ames Baltimore, Md.

Samuel Jackson Barnett Washington, D. C.

Carl Barus Providence, R. I.

Louis Agricola Bauer Washington, D. C.

Louis Bell Newton

Percy Williams Bridgman Cambridge

George Ashley Campbell New York, N. Y.

Leslie Lyle Campbell Boston

Emory Leon ChaflFee Belmont

FELLOWS.

527

Daniel Frost Comstock Cambridge

William David Coolidge Schenectady, N. Y.

Henry Crew Evanston, 111.

Harvey Nathaniel Davis Cambridge

Arthur Louis Day Corning, N. Y.

Louis Derr ; . . Brookline

William Johnson Drisko ^^'inchester

William Duane Boston

Alexander Wilmer Duff Worcester

Arthur Woolsey Ewell Worcester

William Suddards Franklin Cambridge

Harry Manley Goodwin Brookline

George EUery Hale Pasadena, Cal.

Edwin Herbert Hall Cambridge

Hammond Vinton Hayes Boston

John Charles Hubbard New York, N.Y.

Gordon Ferric Hull Hanover, N. H.

Charles Clifford Hutchins ....... Brunswick, Me.

Frederic Eugene Ives Philadelphia, Pa.

James Edmund Ives W'ashington, D. C.

William White Jacques Boston

Edwin Crawford Kemble Cambridge

Norton Adams Kent Cambridge

Frank Arthur Laws Boston

Henry Lefavour Boston

Theodore Lyman Brookline

Thomas Corwin Mendenhall Ravenna, O.

Ernest George Merritt Ithaca, N. Y.

Albert Abraham Michelson Chicago, 111.

Dayton Clarence Miller Cleveland, O.

Robert Andrews IMillikan Chicago, 111.

Harry Wheeler INIorse Los Angeles, Cal.

Edward Leamington Nichols Ithaca, N. Y.

Ernest Fox Nichols New Haven, Conn.

Charles Ladd Norton Boston

George Washington Pierce Cambridge

IMichael Idvorsky Pupin New York, N. Y.

Frederick Albert Saunders Cambridge

528 FELLOWS.

John Stone Stone New York, N. Y.

Maurice deKay Thompson BrookHne

Ehhu Thomson Swampscott

John Trowbridge Cambridge

Arthur Gordon Webster Worcester

David Locke Webster Palo Alto, Cal.

Edwin Bidwell Wilson Brookline

Robert Williams Wood Baltimore, Md.

John Zeleny New Haven, Conn.

Class I., Section III. — Chemistry. — 51.

Wilder Dwight Bancroft Ithaca, N. Y.

Gregory Paul Baxter Cambridge

Arthur Alphonzo Blanchard Cambridge

Marston Taylor Bogert New York, N. Y.

Bertram Borden Boltwood New Haven, Conn.

William Crowell Bray Berkeley, Cal.

Russell Henry Chittenden New Haven, Conn.

Arthur Messinger Comey Cambridge

Charles William Eliot Cambridge

Henry Fay Boston

George Shannon Forbes Cambridge

Edward Curtis Frankhn Palo Alto, Cal.

Frank Austin Gooch New Haven, Conn.

LawTcnce Joseph Henderson Cambridge

Charles Loring Jackson Boston

Walter Louis Jennings Worcester

Grinnell Jones Cambridge

Frederick George Keyes Cambridge

Elmer Peter Kohler Cambridge

Charles August Kraus Worcester

Arthur Becket Lamb Cambridge

Irving Langmuir Schenectady, N. Y.

Gilbert Newton Lewis Berkeley, Cal.

Warren Kendall Lewis Boston

Arthur Dehon Little Brookline

Charles Frederic Mabery Cleveland, O.

FELLOWS. 529

Forris Jewett Moore Boston

George Dunning ]\Ioore Worcester

Edward Williams Morley West Hartford, Conn.

Edward INIueller Cambridge

Samuel Parsons MuUiken Boston

Charles Edward Munroe Forest Glen, ]\Id.

James Flack Norris Boston

Arthur Amos Noyes Pasadena, Cal.

William Albert Noyes Urbana, III.

Thomas Burr Osborne New Haven, Conn.

Samuel Cate Prescott Brookline

Ira Remsen Baltimore, Md.

Robert Hallowell Richards Jamaica Plain

Theodore William Richards Cambridge

Martin Andre Rosanoff Pittsburgh, Pa.

Stephen Paschall Sharpies Cambridge

Miles Standish Sherrill Brookline

Harry Monmouth Smith Brookline

Julius Oscar Stieglitz Chicago, 111.

Henry Paul Talbot Newton

Richard Chase Tolman Washington, D. C.

William Hultz Walker Boston

Willis Rodney Whitney Schenectady, N. Y.

Robert Seaton Williams Cambridge

Alpheus Grant Woodman Watertown

Class I., Section IV. — Technology and Engineering. — 42.

Henry Larcom Abbot Cambridge

Comfort Avery Adams Cambridge

Bernard Arthur Behrend Boston

William Herbert Bixby Chicago, 111.

Francis Tiffany Bowles Boston

Charles Francis Brush Cleveland, O.

William Hubert Burr New Canaan, Conn.

John Joseph Carty New York, N.Y.

Harry Ellsworth Clifford Newton

Arthur Powell Davis Washington, D. C.

530 FELLOWS.

Theodore Harwood Dillon '..... Cambridge

Gano Dunn New York, N. Y.

William Frederick Durand Palo Alto, Cal.

Frederic Harold Fay Boston

Desmond FitzGerald Brookline

John Ripley Freeman Providence, R. I.

George Washington Goethals New York, N. Y.

John Haj's Hammond New York, N. Y.

Rudolph Hering Montclair, N. J.

Ira Nelson HoUis Worcester

Hector James Hughes Cambridge

Alexander Crombie Humphreys New York, N. Y.

Dugald Caleb Jackson Cambridge

Lewis Jerome Johnson Cambridge

Arthur Edwin Kennelly Cambridge

Gaetano Lanza Philadelphia, Pa,

Charles Thomas Main W' inches ter

Lionel Simeon Marks Cambridge

Edward Furber Miller Newton

Frederick Law Olmsted Brookline

Charles Francis Park Boston

William Barclay Parsons New York, N.Y.

Harold Pender . Philadelphia, Pa.

Albert Sauveur Cambridge

Peter Schwamb Arlington

Henry Lloyd Smyth Cambridge

Charles Milton SpofFord Brookline

Charles Proteus Steinmetz Schenectady, N. Y.

George Fillmore Swain Cambridge

George Chandler Whipple Cambridge

Robert Simpson Woodward Washington, D. C.

Joseph Ruggles Worcester Boston

FELLOWS.

531

Class II. — Natural and Physiological Sciences. — 185.
Section I. — Geology, Mineralogy, and Physics of the Globe. — 55.

Wallace Walter Atwood Worcester

George Hunt Barton Cambridge

Norman Levi Bowen Washington, D. C.

Isaiah Bowman Washington, D. C.

John Casper Branner Palo Alto, Cal.

Thomas Chrowder Chamberlin Chicago, 111.

John Mason Clarke Albany, N. Y.

Henry Helm Clayton Canton

Herdman Fitzgerald Cleland Williamstown

William Otis Crosby Jamaica Plain

Reginald Aldworth Daly Cambridge

Edward Salisbury Dana New Haven, Conn.

William Morris Davis Cambridge

Benjamin Kendall Emerson Amherst

William Ebenezer Ford New Haven, Conn.

James Walter Goldthwait Hanover, N. H.

Louis Caryl Graton Cambridge

Herbert Ernest Gregory New Haven, Conn.

William Jackson Humphreys t Washington, D. C.

Ellsworth Huntington jNlilton

Oliver Whipple Huntington Newport, R. I.

Robert Tracy Jackson Peterborough, N. H.

Thomas Augustus Jaggar Honolulu, H. I.

Douglas Wilson Johnson New York, N. Y.

Arthur Keith Washington, D. C.

James Furman Kemp New York, N. Y.

Alfred Church Lane Cambridge

Andrew Cowper Lawson Berkeley, Cal.

Charles Kenneth Leith Madison, Wis.

Waldemar Lindgren Brookline

Frederic Brewster Loomis Amherst

Alexander George McAdie Readville

John Campbell Merriam Washington, D. C.

William John Miller Northampton

532 FELLOWS.

Charles Palache Cambridge

Raphael Pumpelly Newport, R. I.

Percy Edward Raymond Cambridge

William North Rice Middletown, Comi.

Austin Flint Rogers Palo Alto, Cal.

Robert Wilcox Sayles Cambridge

Waldemar Theodore Schaller Washington, D. C.

Charles Schuchert New Haven, Conn.

William Berryman Scott Princeton, N. J.

Hervey Woodburn Shimer Watertown

Thomas Wayland Vaughan Washington, D. C.

Charles Doolittle Walcott Washington, D. C.

Robert DeCourcy Ward Cambridge

Charles Hyde Warren New Haven, Conn.

Da\id White Washington, D. C.

Herbert Percy Whitlock New York, N. Y.

Bailey Willis Palo Alto, Cal.

Arthur Winslow Boston

John Eliot Wolff Cambridge

Jay Backus Woodworth Cambridge

Frederick Eugene Wright Washington, D. C.

Class II., Section II. — Botany. — 34.

Oakes Ames North Easton

Irving Widmer Bailey Cambridge

Liberty Hyde Bailey Ithaca, N. Y,

Edward Wilber Berry Baltimore, Md.

Douglas Houghton Campbell Palo Alto, Cal.

George Perkins Clinton New Haven, Conn.

John Merle Coulter Chicago, 111.

Bradley Moore Davis Ann Arbor, Mich.

Edward Murray East Jamaica Plain

Rollins Adams Emerson Ithaca, N. Y.

Alexander William Evans New Haven, Conn.

Merritt Lyndon Fernald Cambridge

George Lincoln Goodale Cambridge

Robert Aimer Harper New York, N. Y.

FELLOWS. 533

John George Jack East Walpole

Edward Charles Jeffrey Cambridge

Fred Da\'ton Lambert Tufts College

Jacob Goodale Lipman New Bruaswick, N. J.

Burton Edward Livingston Baltimore, Md.

George Richard Lyman Washington, D. C.

Elmer Lr.w Merr;il Manila, P. L

\Yinthrop John Vanleuven Osterhout Cambridge

Charles Vancouver Piper Washington, D. C.

Alfred Rehder Jamaica Plain

Benjamin Lincoln Robinson Cambridge

Charles Sprague Sargent Brookline

William Albert Setchell Berkel( y, Cal.

Arthur Bliss Seymour Cambridge

Erwin Frink Smith Washington, D. C.

John Donnell Smith Baltimore, Md.

William Codman Sturgis New York, N. Y.

Roland Thaxter Cambridge

William Trelease Urbana, 111.

William Henry Weston, Jr Cambridge

Class II., Section III. — Zoology and Physiology. — 57.

Nathan Banks Cambridge

Thomas Barbour Cambridge

Francis Gano Benedict Boston

Henry Brj'ant Bigelow Concord

Robert Payne Bigelow Brookline

William T. Bovie Milton

Jolm Lewis Bremer Boston

Charles Thomas Brues Boston

Hermon Carey Bum pus Providence, R. L

W^alter Bradford Cannon Cambridge

Thorne IVIartin Carpenter ■ Boston

William Ernest Castle Belmont

Charles Value Chapin Providence, R. I.

Benjamin Preston Clark Boston

Samuel Fessenden Clarke Williamstown

534 FELLOWS.

Edwin Grant Conklin Princeton, N. J.

Joseph Augustine Cushman Sharon

William Healey Dall Washington, D. C.

Charles Benedict Davenport .... Cold Spring Harbor, N. Y.

Oilman Arthur Drew Woods Hole

Cecil Kent Drinker Boston

Alexander Forbes Milton

Samuel Henshaw Cambridge

Leland Ossian Howard Washington, D. C.

Herbert Spencer Jennings Baltimore, Md.

Charles Willison Johnson Brookline

Charles Atwood Kofoid Berkeley, Cal.

Frederic Thomas Lewis Waban

Ralph Sta^^ner Lillie Worcester

Jacques Loeb New York, N. Y.

Richard Swann Lull New Haven, Conn.

Edward Laurens Mark Cambridge

Ernest Gale Martin Palo Alto, Cal.

Albert Davis Mead Providence, R. L

Gerrit Smith Miller Washington, D. C.

Edward Sylvester Morse Salem

Herbert Vincent Neal Tufts College

Henry Fairfield Osborn New York, N. Y.

George Howard Parker Cambridge

William Patten Hanover, N. H.

Raymond Pearl Baltimore, Md.

John Charles Phillips Wenham

Henry Augustus Pilsbry Philadelphia, Pa.

Herbert Wilbur Rand Cambridge

Arthur Clarence Redfield Boston

William Emerson Ritter La Jolla, Cal.

Percy Goldthwait Stiles Newtonville

John Eliot Thayer Lancaster

William Lyman Underwood Btlmont

Addison Emory Verrill W hitneyville, Conn.

John Broadus Watson Washington, D. C.

Arthur Wisswald Weysse Bi ston

William Morton Wheeler Boston

FELLOWS. 535

Harris Hawthorne Wilder Northampton

Edmund Beecher Wilson New York, N. Y.

Frederick Adams Woods BrookUne

Robert Mearns Yerkes Washington, D. C.

Class II., Section IV. — Medicine and Surgery. — 39.

Edward Hickling Bradford Boston

Charles Macfie Campbell Cambridge

Alexis Carrel New York, N. Y.

Henry Asbury Christian Boston

Stanley Cobb Ponkapoag

RufusCole NewYork,N.Y.

Harvey Cushing Boston

David Linn Edsall Cambridge

Simon Flexner New York, N.Y.

Joseph Lincoln Goodale Boston

Robert Battey Greenough Boston

Ross Granville Harrison New Haven, Conn.

William Henry Howell .... Baltimore, Md.

Reid Hunt Brookline

Henry Jackson Boston

Elliott Proctor Joslin Boston

William Williams Keen Philadelphia, Pa.

Robert Williamson Lovett Boston

Frank Burr Mallory Brookline

William Jam -s Mayo Rochester, Mmn.

Samuel Jason Mixter Boston

Francis Weld Peabody Brookline

Theophil Mitchell Prudden New York. N. Y.

William Lambert Richardson Boston

Milton Joseph Rosenau Boston

Frederick Cheever Shattuck Boston

Theobald Smith Princeton, N. J.

Charles Wardell Stiles Washington, D. C.

Richard Pearson Strong Boston

William Sydney Thayer Baltimore, Md.

Ernest Edward Tyzzer Wakefield

536 FELLOWS.

Frederick Herman VerhoeflF . Boston

Henry Pickering Walcott . . Cambridge

John Warren Boston

John Colhns Warren Boston

WilHam Henry Welch . . . Baltimore, Md.

Francis Henry Williams Boston

Simeon Burt W'olbach Boston

Horatio Curtis Wood Philadelphia, Pa.

Class HI. — Moral and Political Sciences. — 199.

Section I. — Theology, Philosophy and Jurisprudence. — 52.

Thomas Willing Balch Philadelphia, Pa.

Simeon Eben Baldwin New Haven, Conn.

Willard Bartlett Brooklyn, N. Y.

Joseph Henry Beale Cambridge

Charles Henry Brent Buffalo, N. Y.

Howard Nicholson Brown Boston

Charles W' arren Clifford New Bedford

Edmund Burke Delabarre Providence, R. I.

James De Normandie Roxbury

Frederic Dodge Belmont

Edward Staples Drown Cambridge

William Harrison Dunbar Cambridge

William Herbert Perry Faunce Providence, R. I.

William W'allace Fenn Cambridge

Frederick Perry Fish Brookline

Paul Revere Frothingham Boston

George Angier Gordon Boston

Alfred Hemenway Boston

William Ernest Hocking Cambridge

Charles Evans Hughes Washington, D. C.

Frederick Jolm Foakes Jackson New York, N. Y.

Charles P^rancis Jennej^ Boston

William Lawrence Boston

Frederick Lawton Boston

Arthur Lord Plymouth

FELLOWS. 537

William Caleb Loring Boston

Nathan Matthews Boston

William JMcDoiigall Cambridge

Samuel Walker McCall Winchester

Edward Caldwell Moore Cambridge

John Bassett Moore New York, N. Y.

James Madison ISIorton Fall River

George Herbert Palmer Cambridge

Charles Edwards Park Boston

Leighton Parks New York, N. Y.

Francis Greenwood Peabody Cambridge

George Wharton Pepper Philadelphia, Pa.

Roscoe Pound Belmont

Elihu Root New York, N. Y.

James Hardy Ropes Cambridge

Arthur Prentice Rugg W'orcester

Austin Wakeman Scott Cambridge

Henry Newton Sheldon Boston

Moorfield Storey Boston

William Howard Taft New Haven, Conn.

William Jewett Tucker Hanover, N. H.

William Gushing Wait Medford

Eugene Wambaugh . Cambridge

Edward Henry Warren Brookline

Winslow Warren Dedham

Samuel Williston Belmont

Woodrow Wilson Washington, D. C

Class III., Section II. — Philology and Archceologi/ . — 56.

Francis Greenleaf Allinson Providence, R. I.

William Rosenzweig Arnold Cambridge

Maurice Bloomfield Baltimore, Md.

Franz Boas New York, N. Y.

Carl Darling Buck Chicago, 111.

Eugene Watson Burlingame Albany, N. Y.

Edward Capps Princeton, N. J.

George Henry Chase Cambridge

538 FELLOWS.

Walter Eugene Clark Chicago, 111.

Roland Burrage Dixon Cambridge

Franklin Edgerton Philadelphia, Pa.

William Curtis Farabee Philadelphia, Pa.

Jesse Walter Fewkes Washington, D. C.

Jeremiah Denis Mathias Ford Cambridge

Basil Lanneau Gildersleeve Baltimore, Md.

Pliny Earle Goddard New York, N. Y.

Charles Hall Grandgent Cambridge

Louis Herbert Gray New York, N. Y.

Charles Burton Gulick Cambridge

Roy Kenneth Hack Cambridge

William Arthur Heidel Middletown, Conn.

George Lincoln Hendrickson New Haven, Conn.

Bert Hodge Hill Athens, Greece

Elijah Clarence Hills Bloomington, Ind.

William Henry Holmes Washington, D. C.

Edward Washburn Hopkins New Haven^ Conn.

Joseph Clark Hoppin Pomfret, Conn.

Albert Andrew Howard Cambridge

William Guild Howard Cambridge

Ales Hrdlicka Washington, D. C.

Eugene Xavier Louis Henry Hyvernat .... Washington, D. C.

Carl Newell Jackson Cambridge

Hans Carl Gunther von Jagemann Cambridge

James Richard Jewett Cambridge

Alfred Louis Kroeber Berkeley, Cal.

Kirsopp Lake Cambridge

Henry Roseman Lang New Haven, Conn.

Charles Rockwell Lanman Cambridge

John Livingston Lowes Cambridge

David Gordon Lyon Cambridge

Clifford Herschel Moore Cambridge

George Foot Moore Cambridge

Hanns Oertel New Haven, Conn.

Chandler Rathfon Post Cambridge

Edward Kennard Rand Cambridge

George Andrew Reisner Cambridge

FELLOWS. 539

Edward Robinson New York, N. Y.

Fred Norris Robinson Cambridge

Rudolph Schevill Berkeley, Cal.

Edward Stevens Sheldon Cambridge

Herbert Weir Smyth Cambridge

Franklin Bache Stephenson Washington, I). C.

Charles Cutler Torrey New Haven, Conn.

Alfred Marston Tozzer Cambridge

Clark \Yissler New York, N. Y.

James Haughton Woods Cambridge

Class III., Section III. — Political Economy and Hislorij. — 45.

Wilbur Cortez Abbott Cambridge

Brooks Adams Quincy

George Burton Adams New Haven, Conn.

Charles INIcLean Andrews New Haven, Conn.

John Spencer Bassett Northampton

Charles Jesse Bullock Cambridge

Thomas Nixon Carver Cambridge

Edward Channing Cambridge

Jolin Bates Clark New York, N. Y.

Archibald Cary Coolidge Boston

Richard Henry Dana Cambridge

Clive Day New Haven, Conn.

Davis Rich Dewey Cambridge

Ephraim Emerton Cambridge

Henry Walcott Farnam New Haven, Conn.

Max Farrand New Haven, Conn.

William Sott Ferguson Cambridge

Irving Fisher New Haven, Conn.

Worthington Chauncey Ford Cambridge

Edwin Francis Gay New York, N. Y.

Frank Jolinson Goodnow Baltimore, Md.

Evarts Boutell Greene Champaign, 111.

Arthur Twining Hadley New Haven, Conn.

Albert Bushnell Hart Cambridge

Charles Homer Haskins Cambridge

540 FELLOWS.

Isaac ISIinis Hays Philadelphia, Pa.

Charles DoAMier Hazen New York, N. Y.

George La Piana Cambridge

Henry Cabot Lodge Nahant

Abbott Lawrence Lowell Cambridge

William IVLacDonald New York, N. Y.

Charles Howard Mcllwain . Cambridge

Roger Bigelow ]\Ierriman Cambridge

Samuel Eliot INIorison Boston

William Bennett INIunro Cambridge

Charles Lemuel Nichols Worcester

James Ford Rhodes Boston

William INIilligan Sloane New York, N. Y.

John Osborne Sumner Boston

Frank William Taussig Cambridge

William Roscoe Thayer Cambridge

Frederick Jackson Turner Cambridge

George Grafton Wilson Cambridge

George Parker Winship Cambridge

Allyn Abbott Young . . Cambridge

Class III., Section IV. — Literature and the Fine Arts. — 46.

Irving Babbitt Cambridge

George Pierce Baker Cambridge

William Sturgis Bigelow Boston

Le Baron Russell Briggs Cambridge

Charles Allerton Coolidge Boston

Frederick Shepherd Converse Boston

Samuel McChord Crothers Cambridge

Wilberforce Fames New York, N. Y.

Edward Waldo Emerson Concord

William Emerson Cambridge

Arthur Fairbanks Cambridge

Frank Edgar Farley Middleton, Conn.

Arthur Foote Brookline

Edward Waldo Forbes Cambridge

Kuno Francke Gilbertsville, N. Y.

FELLOWS. 541

Daniel Chester French New York, X. Y.

Horace Howard Furness Philadelphia, Pa.

Robert Grant Boston

Morris Gray Boston

Chester Xoyes Greenough Cambridge

James Kendall Hosmer Minneapolis, Minn.

Mark Antony DeWolfe Howe Boston

Archer Milton Huntington New York, N. Y.

George Lyman Kittredge Cambridge

William Coolidge Lane Cambridge

John EUerton Lodge Boston

Charles ^Martin Tornov Loeffler Medfield

Charles Donagh Maginnis Brookline

Allan Marquand Princeton, N. J.

Albert Matthews Boston

Harold Murdock Brookline

William Mian Neilson Northampton

Thomas Nelson Page Washington, D. C.

William Lyon Phelps New Haven, Conn.

Arthur Kin^slev Porter Cambridge

'o

Herbert Putnam Washington, D. C.

Denman Waldo Ross Cambridge

Paul Joseph Sachs Cambridge

John Singer Sargent London, Eng.

Ellery Sedg\^-ick Boston

Henry Dwight Sedg^^'ick Cambridge

Richard Clipston Sturgis Boston

Charles Howard Walker Boston

Owen Wister Philadelphia, Pa.

George Edward Woodberry Beverly

Charles Henrv Conrad Wright Cambridge

542 FOREIGN HONORARY MEMBERS.

FOREIGN HONORARY MEMBERS.— 71.

(Number limited to seventy-five.)

Class I. — Mathematical and Physical Sciences. — 24.
Section I. — Mathematics and Astronomy. — 8.

Johann Oskar Backlund Petrograd

Arthur Stanley Eddington Cambridge

Godfrey Harold Hardy Oxford

Jacques Salomon Hadamard Paris

Felix Klein Gottingen

Tullio Levi-Civita Rome

Charles Emile Pieard Paris

Charles Jean de la Vallec Poussin Louvain

Class I., Section II. — Physics. — 7.

Svante August Arrhenius Stockholm

Oliver Heaviside Torquay

Sir Joseph Larmor Cambridge

Hendrik Antoon Lorentz Leyden

Max Planck Berlin

Sir Ernest Rutherford Manchester

Sir Joseph Jolin Thomson Cambridge

Class I., Section III. — Chemistry. — 4.

Fritz Haber Berlin

Henri Louis Le Chatelier Paris

Wilhelm Ostwald Leipsic

William Henry Perkin Oxford

Class I. — Section IV. — Technology and Engineering. — - 5.

Heinrich Miiller Breslau Berlin

Ferdinand Foch Paris

Joseph Jacques Cesaire Joffre Paris

Vsevolod Jevgenjevic Timonoff Petrograd

William Cawthorne Unwin London

FOREIGN HONORARY MEMBERS. 543

Class II. — Natural and Physiological Sciences. — 22.
Section I. — Geologxj, Mineralogy, and Physics of the Globe. — 10.

Frank Dawson Adams Montreal

Charles Barrois Lille

Waldemar Christofer Brogger Christiania

Sir Archibald Geikie Haslemere, Surrey

Viktor Goldschmidt Heidelberg

Albert Heim ■ Zurich

Emanuel tie jNIargerie Paris

Gustaf Adolf Frederik MolengraaflF Delft

Sir William Napier Shaw London

Johan Herman Lie Vogt Trondhjem

Class II, Section II. — Botany. — 5.

John Briquet Geneva

Hugo de Vries Lunteren

Adolf Engler Berlin

Ignatz Urban Berlin

Eugene Warming Copenhagen

Class II. — Section III. — Zoology and Physiology. — 3.

Maurice Caullery Paris

Sir Edwin Ray Lankester London

George Henry Falkiner Nuttall Cambridge

Class II., Section IV. — Medicine and Surgery. — 4.

Rt. Hon. Sir Thomas Clifford Allbutt Cambridge

Sir Thomas Barlow, Bart London

Francis John Shepherd Montreal

Charles Scott Sherrington Oxford

Class HI. — Moral and Political Sciences. — 25.
Section I. — Theology, Philosophy and Jurisprudence. — 5.

Rt. Hon Arthur James Balfour Prestonkirk

Heinrich Brunner Berlin

544 FOREIGN HONORARY MEMBERS.

Albert Venn Dicey Oxford

Raymond Poineare Paris

Rt. Hon. Sir Frederick Pollock, Bart London

Section II. — Philology and Archceology. — 9.

Friedrich Delitzsch Berlin

Hermann Diels Berlin

Wilhelm Dorpfeld Athens

Henry Jackson Cambridge

Hermann Georg Jacobi Bonn

Arthur Anthony Macdonell Oxford

Alfred Percival Maudslay Hereford

Ramon Menendez Pidal Madrid

Eduard Seler Berlin

Section III. — Political Economy and History. — 6.

Adolf Harnack Berlin

Alfred Marshall Cambridge

Rt. Hon. John Morley, Viscount Morley of Blackburn . . . London

Henri Pirenne Ghent

George Walter Prothero London

Rt. Hon. Sir George Otto Trevelyan, Bart London

Section IV. — Literature and the Fine Arts. — 5.

Georg Brandes Copenhagen

Thomas Hardy Dorchester

Jean Adrien Antoine Jules Jusserand Paris

Rudyard Kipling Burv\'ash

Sir Sidney Lee London

STATUTES AND STANDING VOTES

STATUTES

Adopted November 8, 1911: amended May 8, 1912, January 8, and
May 14, 1913, April 14, 1915, April 12, 1916, April 10, 1918, May 14, 1919,
February 8, and April 12, 1922.

CHAPTER I

The Corporate Seal

Article 1. The Corporate Seal of the Academy shall be as here
depicted:

Article 2. The Recording Secretary shall have the custody of the
Corporate Seal.

See Chap. v. art. 3; chap. vi. art. 2.

546 STATUTES OF THE AMERICAN' ACADEMY

CHATTER II

Fellows and Foreign Honorary Members and Dues

Article 1. The Academy consists of Fellows, who are either
citizens or residents of the United States of America, and Foreign
Honorary Members. They are arranged in three Classes, according to
the Arts and Sciences in which they are severally proficient, and each
Class is divided into four Sections, namely:

Class I. The Mathematical and Physical Sciences
Section 1. Mathematics and Astronomy
Section 2. Physics
Section 3. Chemistry
Section 4. Technology and Engineering

Class II. The Natural and Physiological Sciences

Section 1. Geology, Mineralogy, and Physics of the Globe

Section 2. Botany

Section 3. Zoology and Physiology

Section 4. Medicine and Surgery

Class III. The Moral and Political Sciences

Section 1. Theology, Philosophy, and Jurisprudence
Section 2. Philology and Archaeology
Section 3. Political Economy and History
Section 4. Literature and the Fine Arts

Article 2. The number of Fellows shall not exceed Six hundred,
of whom not more than Four hundred shall be residents of Massachu-
setts, nor shall there be more that Two hundred and ten in any one
Class.

Article 3. The number of Foreign Honorary Members shall not
exceed Seventy-five. They shall be chosen from among citizens of
foreign countries most eminent for their discoveries and attainments
in any of the Classes above enumerated. There shall not be more
than Twenty-five in any one Class.

Article 4. If any person, after being notified of his election as
Fellow or Resident Associate, shall neglect for six months to accept

OF ARTS AND SCIENCES. 547

in writing, or, if a Fellow resident within fifty miles of Boston shall
neglect to pay his Admission Fee, his election shall be void; and if
any Fellow resident within fifty miles of Boston or any Resident
Associate shall neglect to pay his Annual Dues for six months after
they are due, provided his attention shall have been called to this
Article of the Statutes in the meantime, he shall cease to be a Fellow
or Resident Associate respectively; but the Council may suspend the
provisions of this Article for a reasonable time.

With the previous consent of the Council, the Treasurer may dis-
pense {sub silentio) with the payment of the Admission Fee or of the
Annual Dues or both whenever he shall deem it advisable. In the case
of officers of the Army or Navy who are out of the Commonwealth on
duty, payment of the Annual Dues may be waived during such absence
if continued during the whole financial year and if notification of such
expected absence be sent to the Treasurer. Upon similar notification
to the Treasurer, similar exemption may be accorded to Fellows or
Resident Associates subject to Annual Dues, who may temporarily
remove their residence for at least two years to a place more than fifty
miles from Boston.

If any person elected a Foreign Honorary Member shall neglect for
six months after being notified of his election to accept in MTiting,
his election shall be void.

See Chap. vii. art. 2.

Article 5. Every Fellow resident within fifty miles of Boston
hereafter elected shall pay an Admission Fee of Ten dollars.

Every Fellow resident within fifty miles of Boston shall, and others
may, pay such Annual Dues, not exceeding Fifteen dollars, as shall
be voted by the Academy at each Annual Meeting, when they shall
become due; but any Fellow or Resident Associate shall be exempt
from the annual payment if, at any time after his admission, he shall
pay into the treasury Two hundred dollars in addition to his previous
paj^ments.

All Commutations of the Annual Dues shall be and remain perma-
nently funded, the interest only to be used for current expenses.

Any Fellow not previously subject to Annual Dues who takes up his
residence within fifty miles of Boston, shall pay to the Treasurer within
three months thereafter Annual Dues for the current year, failing wliich

548 STATUTES OF THE AMERICAN ACADEMY

his Fellowship shall cease; but the Council may suspend the provi-
sions of this Article for a reasonable time.

Only Fellows who pay Annual Dues or have commuted them may
hold office in the Academy or serve on the Standing Committees or
vote at meetings.

Article 6. Fellows who pay or have commuted the Annual Dues
and Foreign Honorary Members shall be entitled to receive gratis one
copy of all Publications of the Academy issued after their election.

See Chap, x, art. 2.

Article 7. Diplomas signed by the President and the Vice-
President of the Class to which the member belongs, and countersigned
by the Secretaries, shall be given to Foreign Honorary Members and
to Fellows on request.

Article 8. If, in the opinion of a majority of the entire Council,
any Fellow or Foreign Honorary Member or Eesident Associate shall
have rendered himself unworthy of a place in the Academy, the
Council shall recommend to the Academy the termination of his
membership; and if three fourths of the Fellows present, out of a
total attendance of not less than fifty at a Stated Meeting, or at a
Special INIeeting called for the purpose, shall adopt this recommenda-
tion, his name shall be stricken from the Roll.

See Chap, iii.; chap. vi. art. 1; chap, ix, art. 1, 7; chap. x. art. 2.

CHAPTER III

Election of Fellows and Foreign Honorary Members

Article 1. Elections of Fellows and Foreign Honorary Members
shall be made by the Council in April of each year, and announced
at the Annual Meeting in May.

Article 2. Nominations to Fellowship or Foreign Honorary
Membership in any Section must be signed by two Fellows of that
Section or by three voting Fellows of any Sections; but in any one
year no Fellow may nominate more than four persons. These nomi-
nations, with statements of qualifications and brief biographical data,
shall be sent to the Corresponding Secretary.

OF ARTS AND SCIENCES. 549

All nominations thus received prior to February 15 shall be forth-
with sent in printed form to every Fellow, with the names of the pro-
posers in each case and a brief account of each nominee, and with
the request that the list be returned before March 15, marked to
indicate preferences of the voter in such manner as the Council may
direct.

All the nominations, with any comments thereon and with the
results of the preferential indications of the Fellows, received by
March 15, shall be referred at once to the appropriate Class Commit-
tees, which shall report their decisions to the Council, which shall
thereupon have power to elect.

Persons nominated in any year, but not elected, may be placed on
the preferential ballot of the next year at the discretion of the Council,
but shall not further be continued on the list of nominees unless
renominated.

Notice shall be sent to every Fellow not later than the fifteenth of
January, of each year, calling attention to the fact that the limit, of
time for sending nominations to the Corresponding Secretary will
expire on the fifteenth of February.

See Chap, ii.; chap. vi. art. 1; chap. ix. art. 1.

CHAPTER IV
Officers

Article 1. The Officers of the Academy shall be a President (who
shall be Chairman of the Council), three Vice-Presidents (one from
each Class), a Corresponding Secretary (who shall be Secretary of the
Council), a Recording Secretary, a Treasurer, and a Librarian, all of
whom shall be elected by ballot at the Annual Meeting, and shall hold
their respective offices for one year, and until others are duly chosen
and installed.

There shall be also twelve Councillors, one from each Section of each
Class. At each Annual Meeting three Councillors, one from each
Class, shall be elected by ballot to serve for the full term of four
years and until others are duly chosen and installed. The same Fellow
shall not be eligible for two successive terms.

550 STATUTES OF THE AMERICAN ACADEMY.

. The Councillors, with the other officers previously named, and the
Chairman of the House Committee, ex officio, shall constitute the
Council.

See Chap, x, art. 1.

Article 2. If any officer be unable, through death, absence, or
disability, to fulfil the duties of his office, or if he shall resign, his place
may be filled by the Council in its discretion for any part or the whole
of the unexpired term.

Article 3. At the Stated Meeting in March, the President shall
appoint a Nominating Committee of three Fellows having the right
to vote, one from each Class. This Committee shall prepare a list of
nominees for the several offices to be filled, and for the Standing Com-
mittees, and file it with the Recording Secretary not later than four
weeks before the Annual Meeting.

See Chap. vi. art. 2.

Article 4. Independent nominations for any office, if signed by
at least twenty Fellows having the right to vote, and received by the
Recording Secretary not less than ten days before the Annual Meet-
ing, shall be inserted in the call therefor, and shall be mailed to all
the Fellows having the right to vote.

See Chap. vi. art. 2.

Article 5. The Recording Secretary shall prepare for use in
voting at the Annual Meeting a ballot containing the names of all
persons duly nominated for office.

CHAPTER V
The President

Article 1. The President, or in his absence the senior Vice-Presi-
dent present (seniority to be determined by length of continuous
fellowship in the Academy), shall preside at all meetings of the Acad-
emy. In the absence of all these officers, a Chairman of the meeting
shall be chosen by ballot.

OF ARTS AND SCIENCES. 551

Article 2. Unless otherw^ise ordered, all Committees which are
not elected by ballot shall be appointed by the presiding officer.

Akticle 3. Any deed or writing to which the Corporate Seal is to
be affixed, except leases of real estate, shall be executed in the name of
the Academy by the President or, in the event of his death, absence, or
inability, by one of the Vice-Presidents, when thereto duly authorized.

See Chap. ii. art. 7; chap. iv. art. 1, 3; chap. vi. art. 2; chap. vii.
art. 1; chap. ix. art. 6; chap. x. art. 1, 2; chap. xi. art. 1.

CHAPTER VI

The Secretaries

Article 1. The Corresponding Secretary shall conduct the corre-
spondence of the Academy and of the Council, recording or making an
entry of all letters written in its name, and preserving for the files all
official papers which may be received. At each meeting of the Council
he shall present the communications addressed to the Academy which
have been received since the previous meeting, and at the next meeting
of the Academy he shall present such as the Council may determine.

He shall notify all persons who may be elected Fellows or Foreign
Honorary Members, or Resident Associates, send to each a copy of the
Statutes, and on their acceptance issue the proper Diploma. He shall
also notify all meetings of the Council; and in case of the death,
absence, or inabiHty of the Recording Secretary he shall notify all
meetings of the Academy.

Under the direction of the Council, he shall keep a List of the
Fellows, Foreign Honorary Members, and Resident Associates, ar-
ranged in their several Classes and Sections. It shall be printed
annually and issued as of the first day of July.

See Chap. ii. art. 7; chap. iii. art. 2, 3; chap. iv. art. 1; chap. ix. art. 6;
chap. x. art. 1; chap. xi. art. 1.

Article 2. The Recording Secretary shall have the custody of the
Charter, Corporate Seal, Archives, Statute-Book, Journals, and all
literary papers belonging to the Academy.

Fellows or Resident Associates borrowing such papers or documents
shall receipt for them to their custodian.

552 STATUTES OF THE AMERICAN ACADEMY

The Recording Secretary shall attend the meetings of the Academy
and keep a faithful record of the proceedings with the names of the
Fellows and Resident Associates present; and after each meeting is
duly opened, he shall read the record of the preceding meeting.

He shall notify the meetings of the Academy to each Fellow and
Resident Associate by mail at least seven days beforehand, and in his
discretion may also cause the meetings to be advertised; he shall
apprise Officers and Committees of their election or appointment,
and inform the Treasurer of appropriations of money voted by the
Academy.

After all elections, he shall insert in the Records the names of the
Fellows by whom the successful nominees were proposed.

He shall send the Report of the Nominating Committee in print
to every Fellow having the right to vote at least three weeks before the
Annual Meeting.

See Chap. iv. art. 3.

In the absence of the President and of the Vice-Presidents he shall,
if present, call the meeting to order, and preside until a Chairman is
chosen.

See Chap, i.; chap. ii. art. 7; chap. iv. art. 3, 4, 5; chap. ix. art. 6;
chap. X. art. 1, 2; chap. xi. art. 1, 3.

Article 3. The Secretaries, with the Chairman of the Committee
of Publication, shall have authority to publish such of the records of
the meetings of the Academy as may seem to them likely to promote
its interests.

CHAPTER VII
The Treasurer and the Treasury

Article 1. The Treasurer shall collect all money due or payable to
the Academy, and all gifts and bequests made to it. He shall pay all
bills due by the Academy, when approved by the proper officers, except
those of the Treasurer's office, which may be paid without such ap-
proval; in the name of the Academy he shall sign all leases of real
estate; and, with the written consent of a member of the Committee
on Finance, he shall make all transfers of stocks, bonds, and other

OF ARTS AND SCIENCES. 553

securities belonging to the Academy, all of which shall be in his official
custody.

He shall keep a faithful account of all receipts and expenditures,
submit his accounts annually to the Auditing Committee, and render
them at the expiration of his term of office, or whenever required to
do so by the Academy or the Council.

He shall keep separate accounts of the income of the Rumford Fund,
and of all other special Funds, and of the appropriation thereof, and
render them annually.

His accounts shall always be open to the inspection of the Council.

Article 2. He shall report annually to the Council at its INIarch
meeting on the expected income of the various Funds and from all
other sources during the ensuing financial year. He shall also report
the names of all Fellows and Resident Associates who may be then
delinquent in the payment of their Annual Dues.

Article 3. He shall give such security for the trust reposed in liim
as the Academy may require.

Article 4. ^Yith the approval of a majority of the Committee on
Finance, he may appoint an Assistant Treasurer to perform liis du-
ties, for whose acts, as such assistant, he shall be responsible ; or, with
like approval and responsibility, he may employ any Trust Company
doing business in Boston as his agent for the same purpose, the com-
pensation of such Assistant Treasurer or agent to be fixed by the
Committee on Finance and paid from the funds of the Academy.

Article 5. At the Annual Meeting he shall report in print all his
official doings for the preceding year, stating the amount and condition
of all the property of the Academy entrusted to him, and the character
of the investments.

Article 6. The Financial Year of the Academy shall begin with
the first day of April.

Article 7. No person or committee shall incur any debt or
liability in the name of the Academy, unless in accordance with a
previous vote and appropriation therefor by the Academy or the
Council, or sell or otherwise dispose of any property of the Academy,

554 STATUTES OF THE AMERICAN ACADEMY

except cash or invested funds, without the previous consent and ap-
proval of the Council.

See Chap. ii. art. 4, 5; chap. vi. art. 2; chap. ix. art. 6; chap. x. art.
1, 2, 3; chap. xi. art. 1.

CHAPTER VIII

The Librarian and the Library.

Article 1. The Librarian shall have charge of the printed books,
keep a correct catalogue thereof, and provide for their delivery from
the Librar3^

At the Annual Meeting, as Chairman of the Committee on the Li-
brary, he shall make a Report on its condition.

Article 2. In conjunction with the Committee on the Library he
shall have authority to expend such sums as may be appropriated by
the Academy for the purchase of books, periodicals, etc., and for de-
fraying other necessary expenses connected with the Library.

Article 3. All books procured from the income of the Rumford
Fund or of other special Funds shall contain a book-plate expressing
the fact.

Article 4. Books taken from the Library shall be receipted for to
the Librarian or his assistant.

Article 5. Books shall be returned in good order, regard being had
to necessary wear with good usage. If any book shall be lost or
injured, the Fellow or Resident Associate to whom it stands charged
shall replace it by a new volume or by a new set, if it belongs to a set,
or pay the current price thereof to the Librarian, whereupon the
remainder of the set, if any, shall be delivered to the Fellow or Resi-
dent Associate so paying, unless such remainder be valuable by reason
of association.

Article 6. All books shall be returned to the Library for examina-
tion at least one week before the Annual Meeting.

Article 7. The Librarian shall have the custody of the Publica-
tions of the Academy. With the advice and consent of the President,
he may effect exchanges with other associations.
See Chap. ii. art. 6: chap. x. art. 1, 2.

OF ARTS AND SCIENCES 555

CHAPTER IX
The Council

Article 1. The Council shall exercise a discreet supervision over
all nominations and elections to membership, and in general supervise
all the affairs of the Academy not explicitly reserved to the Academy
as a whole or entrusted by it or by the Statutes to standing or special
committees.

It shall consider all nominations duly sent to it by any Class Com-
mittee, and act upon them in accordance with the provisions of
Chapter III.

With the consent of the Fellow interested, it shall have power to
make transfers between the several Sections, reporting its action to
the Academy.

See Chap. iii. art. 2, 3; chap. x. art. 1.

Article 2. Seven members shall constitute a quorum.

Article 3. It shall establish rules and regulations for the transac-
tion of its business, and provide all printed and engraved blanks and
books of record.

Article 4. It shall act upon all resignations of officers, and all
resignations and forfeitures of Fellowship or Resident Associateship;
and cause the Statutes to be faithfully executed.

It shall appoint all agents and subordinates not otherwise provided
for by the Statutes, prescribe their duties, and fix their compensation.
They shall hold their respective positions during the pleasure of the
Council.

Article 5. It may appoint, for terms not exceeding one year, and
prescribe the functions of, such committees of its number, or of the
Fellows of the Academy, as it may deem expedient, to facilitate the
administration of the affairs of the Academy or to promote its interests.

Article 6. At its March meeting it shall receive reports from the
President, the Secretaries, the Treasurer, and the Standing Commit-
tees, on the appropriations severally needed for the ensuing financial
year. At the same meeting the Treasurer shall report on the expected
income of the various Funds and from all other sources during the
same year.

55G STATUTES OF THE AMERICAN ACADEMY

A report from the Council shall be submitted to the Academy, for
action, at the March meeting, recommending the appropriation which
in the opinion of the Council should be made.

On the recommendation of the Council, special appropriations may
be made at any Stated Meeting of the Academy, or at a Special Meet-
ing called for the purpose.
See Chap. x. art. 3.

Article 7. After the death of a Fellow or Foreign Honorary
Member, it shall appoint a member of the Academy to prepare a bio-
graphical notice for publication in the Proceedings.

Article 8. It shall report at every meeting of the Academy such
business as it may deem advisable to present.

See Chap. ii. art. 4, 5, 8; chap. iv. art. 1, 2; chap. vi. art. 1; chap. vii.
art. 1; chap. xi. art. 1, 4.

CHAPTER X

Standing Committees

Article 1. The Class Committee of each Class shall consist of the
Vice-President, who shall be chairman, and the four Councillors of the
Class, together with such other officer or officers annually elected as
may belong to the Class. It shall consider nominations to Fellowship
in its own Class, and report in writing to the Council such as may
receive at a Class Committee Meeting a majority of the votes cast,
provided at least three shall have been in the affirmative.
See Chap. iii. art. 2. ,

Article 2. At the Annual Meeting the following Standing Com-
mittees shall be elected by ballot to serve for the ensuing year:

(i) The Committee on Finance, to consist of three Fellows, who,
through the Treasurer, shall have full control and management of the
funds and trusts of the Academy, with the power of investing the funds
and of changing the investments thereof in their discretion.

See Chap. iv. art. 3; chap. vii. art. 1, 4; chap. ix. art. 6.

(ii) The Rumford Committee, to consist of seven Fellows, who shall
report to the Academy on all applications and claims for the

OF ARTS AND SCIENCES. 557

Rumford Premium. It alone shall authorize the purchase of books,
publications and apparatus at the charge of the income from the
Rumford Fund, and generally shall see to the proper execution of the
trust.

See Chap. iv. art. 3; chap, ix. art. 6.

(iii) The Cijnis Moors Warren Committee, to consist of seven Fel-
lows, who shall consider all applications for appropriations from the
income of the Cyrus Moors "Warren Fund, and generally shall see to
the proper execution of the trust.
See Chap. iv. art. 3; chap. ix. art. 6.

(iv) The Committee of Puhlication, to consist of three Fellows, one
from each Class, to whom all communications submitted to the
Academy for publication shall be referred, and to whom the printing
of the Proceedings and the Memoirs shall be entrusted.

It shall fix the price at which the Publications shall be sold; but
Fellows may be supplied at half price with volumes which may be
needed to complete their sets, but which they are not entitled to
receive gratis.

Two hundred extra copies of each paper accepted for publication in
the Proceedings or the Memoirs shall be placed at the disposal of the
author without charge.

See Chap. iv. art. 3; chap. vi. art. 1, 3; chap. ix. art. 6.

(v) The Committee on the Library, to consist of the Librarian, ex
officio, as Chairman, and three other Fellows, one from each Class,
who shall examine the Library and make an annual report on its
condition and management.

See Chap. iv. art. 3; chap. viii. art. 1, 2; chap. ix. art. 6.

(vi) The House Committee, to consist of three Fellows, who shall
have charge of all expenses connected with the House, including the
general expenses of the Academy not specifically assigned to the care
of other Committees or Officers.

See Chap. iv. art. 1, 3; chap. ix. art. 6.
(vii) The Comviittee on Meetings, to consist of the President, the
Recording Secretary, and three other Fellows, who shall have
charge of plans for meetings of the Academy.
See Chap. iv. art. 3; chap. ix. art. 6.

558 STATUTES OF THE AMERICAN ACADEMY

(viii) The Auditing Committee, to consist of two Fellows, who shall
audit the accounts of the Treasurer, with power to employ an
expert and to approve his bill.

See Chap. iv. art. 3; chap. vii. art. 1; chap. ix. art. 6.

Article 3. The Standing Committees shall report annually to the
Council in March on the appropriations severally needed for the ensu-
ing financial year; and all bills incurred on account of these Commit-
tees, within the limits of the several appropriations made by the
Academy, shall be approved by their respective Chairmen.

In the absence of the Chairman of any Committee, bills may be
approved by any member of the Committee whom he shall designate
for the purpose.

See Chap. vii. art. 1, 7; chap. ix. art. 6.

CHAPTER XI

Meetings, Communications, and Amendments

Article 1. There shall be annually eight Stated Meetings of the
Academy, namely, on the second Wednesday of October, November,
December, January, February, March, April and May. Only at
these meetings, or at adjournments thereof regularly notified, or at
Special Meetings called for the purpose, shall appropriations of money
be made or amendments of the Statutes or Standing Votes be effected.

The Stated Meeting in May shall be the Annual Meeting of the
Corporation.

Special Meetings shall be called by either of the Secretaries at the
request of the President, of a Vice-President, of the Council, or of ten
Fellows having the right to vote; and notifications thereof shall state
the purpose for which the meeting is called.

A meeting for receiving and discussing literary or scientific com-
munications may be held on the fourth Wednesday of each month,
excepting July, August, and September; but no business shall be
transacted at said meetings.

Article 2. Twenty Fellows having the right to vote shall consti-
tute a quorum for the transaction of business at Stated or Special

OF ARTS AND SCIENCES. 559

Meetings. Fifteen Fellows shall be sufficient to constitute a meeting
for literary or scientific communications and discussions.

Article 3. Upon the request of the presiding officer or the Record-
ing Secretary, any motion or resolution offered at any meeting shall
be submitted in writing.

Article 4. No report of any paper presented at a meeting of the
Academy shall be published by any Fellow or Resident Associate
without the consent of the author; and no report shall in any case be
published by any Fellow or Resident Associate in a newspaper as an
account of the proceedings of the Academy without the previous
consent and approval of the Council. The Council, in its discretion,
by a duly recorded vote, may delegate its authority in this regard to
one or more of its members.

Article 5. No Fellow or Resident Associate shall introduce a
guest at any meeting of the Academy until after the business has been
transacted, and especially until after the result of the balloting upon
nominations has been declared.

Article 6. The Academy shall not express its judgment on
literary or scientific memoirs or performances submitted to it, or
included in its Publications.

Article 7. All proposed Amendments of the Statutes shall be re-
ferred to a committee, and on its report, at a subsequent Stated Meet-
ing or at a Special IVIeeting called for the purpose, two thirds of the
ballot cast, and not less than twenty, must be affirmative to effect
enactment.

Article 8. Standing Votes may be passed, amended, or rescinded
at a Stated Meeting, or at a Special Meeting called for the purpose,
by a vote of two thirds of the members present. They may be
suspended by a unanimous vote.

See Chap. ii. art. 5, 8; chap. iii. chap. iv. art. 3, 4, 5; chap. v. art. 1;
chap. vi. art. 1, 2; chap. ix. art. 8.

560 STATUTES OF THE AMERICAN ACADEMY

STANDING VOTES

1. Communications of which notice has been given to either of the
Secretaries shall take precedence of those not so notified.

2. Fellows or Resident Associates may take from the Library six
volumes at any one time, and may retain them for three months, and
no longer. Upon special application, and for adequate reasons
assigned, the Librarian may permit a larger number of volumes, not
exceeding twelve, to be drawn from the Library for a limited period.

3. Works published in numbers, when unbound, shall not be taken
from the Hall of the Academy without the leave of the Librarian.

4. There ma}^ be chosen by the Academy, under such rules as the
Council may determine, one hundred Resident Associates. Not
more than forty Resident Associates shall be chosen in any one Class.

Resident Associates shall be entitled to the same privileges as Fel-
lows, in the use of the Academy building, may attend meetings and
present papers, but they shall not have the right to vote. They shall
pay no Admission Fee, and their Annual Dues shall be the same as
those of Fellows residing within fifty miles of Boston.

The Council and Committees of the Academy may ask one or more
Resident Associates to act with them in an advisory or assistant ca-
pacity.

5. Communications offered for publication in the Proceedings or
Memoirs of the Academy shall not be accepted for publication before
the author shall have informed the Committee on Meetings of his
readiness, either himself or through some agent, to use such time as the
Committee may assign him at such meeting as may be convenient both
to him and to the Committee, for the purpose of p esentinu' to the
Academy a general statement of the nature and significance of the
results contained in his communication.

OF ARTS AND SCIENCES. 561

RUMFORD PREMIUM

In conformity with the terms of the gift of Sir Benjamin Thompson,
Count Rumford, of a certain Fund to the American Academy of Arts
and Sciences, and with a decree of the Supreme Judicial Court of
Massachusetts for carrying into effect the general charitable intent and
purpose of Count Rumford, as expressed in his letter of gift, the Acad-
emy is empowered to make from the income of the Rumford Fund, as
it now exists, at any Annual Meeting, an award of a gold and a silver
medal, being together of the intrinsic value of three hundred dollars,
as a Premium to the author of any important discovery or useful
improvement in light or heat, which shall have been made and pub-
ished by printing, or in any way made known to the public, in any
part of the continent of America, or any of the American Islands;
preference always being given to such discoveries as, in the opinion of
the Academy, shall tend most to promote the good of mankind ; and,
if the Academy sees fit, to add to such medals, as a further Premium
for such discovery and improvement, a sum of money not exceeding
three hundred dollars.

i

INDEX.

Abbot, C. G., accepts Fellowship,
439. ^

Abbott, W. C, accepts Fellowship,
439.

Acadcmie Royale de Belgique, 150th
anniversary of, 444, 447.

Adams, W. S., elected Fellow, 458.

Acrography, 442.

Aeronautical Science, Recent Devel-
opments in, 442.

Air, The Joule-Thomson Effect in,
448.

Allbutt, Sir T. C, elected Foreign
Honorary Member, 459.

Allen, J. H., death of, 440.

Ames, A. Jr., The Dioptrics of the
Eye as Related to Pictorial Art,
443; The Phj^siology of Vision
and the Technique of Art, 446.

Amory (Francis) Fund, 451.

Animals from Prehistoric Times, Col-
lection of Skeletons of, 441.

Archaeological Methods used by the
Harvard-Boston Expedition, 443.

Armaments, The Recent Conference
on the Reduction of, 446.

Art, the Physiology of Vision and the
Technique of, 446.

Ascomvcetes, Note on Two Remark-
able, 423.

Assessments, Annual, 456.

Babbitt, I., accepts Fellowship, 439.
Banks, Nathan, elected Fellow, 459.
Barker, F. D., The Parasitic Worms

of the Animals of Bermuda. I.

Trematodes, 213, 446.
Barnett, S. J., accepts Fellowship,

439.
Bassett, J. S., accepts Fellowship,

439.
Bell, Louis, Notes on the Earlv Evo-
lution of the Reflector, 67, 440,

441.
Bennitt, Rudolf, Additions to the

Hvdroid Fauna of the Bermudas,

239, 446.
Bermuda, The Echinoderms of the

Challenger Bank, 351, 448.

Bermuda, The Parasitic Worms of the
Animals of, I. Trematodes, 213,
446.

Bermuda Biological Station for Re-
search, Contributions from, 213,
239, 351.

Bermudas, Additions to the Hydroid
Fauna of the, 239, 446.

Berry, E. W., accepts Fellowship, 439.

Biographical Notices, 470; Commit-
tee on, 444.

Bouton, C. L., death of, 445.

Bowditch, C. P., death of, 440.

Bowen, N. L., accepts Fellowship,
439.

Bowen, R. H., The Phenomenon of
Polymegaly in the Sperm-Cells
of the Family Pentatomidae,
388 459

Bowles, F. T., gift from, 442.

Branner, J. C, accepts Fellowship,
439.

Bridgman, P. W., The Effect of Pres-
sure on the Thermal Conductiv-
ity of Metals, 75, 440; The
Effect of Tension on the Electri-
cal Resistance of Certain Ab-
normal Metals, 39, 440; The
Failure of Ohm's Law in Gold
and Silver at High Current Den-
sities, 129, 440.

Brues, C. T., Some Hymenopterous
Parasites of Lignicolous Itoni-
dida?, 261, 443.

Bryce, Viscount James, death of, 444.

Buck, C. D., accepts Fellowship, 439.

Cajori, F., accepts Fellowship, 439.

Calorie, The Ratio of the, at 73° to
that at 20°, 375, 448.

Campbell, C. M., accepts Fellow-
ship, 439.

Campbell, L. L., accepts Fellowship,
439.

Canavan, M. M. See Fernald, W. E.,
and others.

Cannon, W. B., New Evidence for
Nervous Control of Some In-
ternal Secretions, 444.

564

INDEX.

Carpenter, T. M., elected Fellow,
459.

Cavalier, J., addressed the Academy,
459.

Challenger Bank, Bermuda, The
Echinoderms of the, 351, 448.

Channing, Edward, elected Fellow,
459.

Clark, H. L., The Echinoderms of the
Challenger Bank, Bermuda, 351,
448.

Clarke, E. C, death of, 440.

Cobb, Stanley, elected Fellow, 459.

Cole, R., accepts Fellowship, 439.

Coleridge, A Neglected Note Book of,
447.

Conductivity of Metals, The Effect of
Pressure on the Thermal, 75, 440.

Converse, F. S., accepts Fellowship,
441.

Council, Report of, 448.

Councilman, W. T., resigns Fellow-
ship, 443.

Cram, R. A., resigns Fellowship, 441.

Cross, C. R., death of, 441.

Cryptogamie Laboratories of Har-
vard University, Contribution
from, 289.

Davis, A. P., accepts Fellowship, 441.

Day, C, accepts Fellowship, 439.

Derr, Louis, Report of the Publica-
tion Committee, 454.

Dunn, Gano, elected Fellow^, 459.

Durand, W. F., accepts Fellowship,
439.

Echelon Spectrum Lines, Grid Struc-
ture in, 1, 440.

Echinoderms, The, of the Challenger
Bank, Bermuda, 351, 448.

Eddington, A. S., elected Foreign
Honorary Member, 458.

Edes, H. H., Report of the Treasurer,
449.

Edison, T. A., elected Fellow, 459.

Emerson, R. A., accepts Fellowship,
439.

Emerson, W., accepts Fellowship,
441; transferred from Class I.,
Sect. 4 to Class III., Sect. 4, 448.

Endogoneae, A Revision of the, 289,
448.

Eye, The Dioptrics of the, as Related
to Pictorial Art, 443.

Farley, F. E., accepts Fellowship, 439.
Farrand, M., accepts Fellowship, 439.

Fauna, Hydroid, of the Bermudas,

Additions to the, 239, 446.
Feeble Minded, Waverley Researches

in the Pathology of the, 440.
Fellows deceased (7) —
J. A. Allen, 440.
C. L. Bouton, 445.
C. P. Bowditch, 440.
E. C. Clarke, 440.
C. R. Cross, 441.
J. W. Hammond, 447.
H. F. Mills, 440.
Fellows elected (19) —
W. S. Adams, 458.
Nathan Banks, 459.
T. M. Carpenter, 459.
Edward Channing, 459.
Stanley Cobb, 459.
Gano Dunn, 459.
T. A. Edison, 459.
J. L. Goodale, 459.
E. C. Kemble, 458.
George La Plana, 459.
R. W. Lovett, 459.
William McDougall, 459.
A. K. Porter, 459.
A. C. Redfield, 459.
A. F. Rogers, 459.
P. J. Sachs, 459.
R. C. Tolman, 458.
W. H. Weston, Jr., 459.
C. H. C. Wright, 459.
Fellows, List of, 525.
Fellows resigning Fellowship (2)
W. T. Councilman, 443.
R. A. Cram, 441.
Ferguson, W. S., accepts Fellowship,

439.
Fernald, W. E., Southard, E. C,
Canavan, M. M., Raeder, O. J.,
and Taft, A. E., Waverley Re-
searches in the Pathology of the
Feeble Minded, 440.
FitzGerald, D., On a great Collection
of Skeletons of Animals from
Prehistoric Times at the Rancho
la Brea, near Los Angeles, Cal.,
441.
Flight, Meteorological Phenomena in

Relation to, 442.
Foreign Honorary Members deceased

(2)
Viscount Bryce, 444.
Julius von Hann, 440.
Foreign Honorary Members elected

(3)
Sir T. C. Allbutt, 459.

i

1

i

4

INDEX.

565

A. S. Eddington, 458.
E. de Margerie, 459.
Foreign Honorary Members, List of,

542.
Franklin, E. C, accepts Fellowship,

439.
Frothingham, P. R., accepts Fellow-
ship, 439.

Galaxy, The, Its Content and Di-
mensions, 442.
General Fund, 449; Appropriations

from the Income of, 443, 444,

445.
Gibbs, J. W., Some Features in the

work of, 447.
Gold and Silver at High Current

Densities, The Failure of Ohm's

Law in, 129, 440.
Goodale, J. L., elected Fellow, 459.
Greek Novel, The, 440.
Grid Structure in Echelon Spectrum

Lines, 1, 440.
Gulick, C. B., The Greek Novel, 440.

Hall, E. H., member of Committee on
Biographical Notices, 444.

Hammond, J. W., death of, 447.

Hann, Julius von, death of, 440.

Hardy, G. H., accepts Foreign Hono-
rary Membership, 439.

Harrison, R. G., accepts Fellowship,
439.

Harvard University. See Crypto-
gamic Laboratories of Harvard
University.

Harvard-Boston Expedition, Archae-
ological Methods used by the,
443.

HeLmholtz, H. von and his Signifi-
cance for a Century of Science,
44L

Hocking, W. E., accepts Fellowship,
439.

Hou.se Committee, Report of, 455.

House Expenses, Appropriation for,
445.

Howell, W. H., accepts Fellowship,
439.

Humphreys, W. J., accepts Fellow-
ship, 439.

Hyvernat, E. X. L. H., accepts Fel-
lowship, 439.

Insect Spermatogenesis, Studies on,
IV. The Phenomenon of Poly-
megaly in the Sperm-Cells, 388,
459.

Internal Secretions, New Evidence
for Nervous Control of Some,
444.

Inverse Hyperbolic Functions of a
Comiilex Variable, A Table and
Method of Computation of Elec-
tric Wave Propagation, Trans-
mission Line I'nenomena, Op-
tical Refraction, and, 173, 443.

Ives, F. E., accepts Fellowship, 439.

Jenney, C. F., accepts Fellowship,

439.
Joule-Thomson Effect in Air, The,

448.

Keith, A., accepts Fellowship, 439.

Kellogg, O. D., accepts Fellowship,
439.

Kemble, E. C, elected Fellow, 458.

Kemp, J. F., accepts Fellowship, 439.

Kent, N. A., and Taylor, L. B., The
Grid Structure in Echelon Spec-
trum Lines, 1, 440.

Laboratory Products, 447.

La Plana, George, elected Fellow, 459.

Lawton, F., accepts Fellowship, 439.

Le Chatelier, The General Conditions
of Validity of the Principle of,
19, 440.

Library, appropriation for, 445.

Library Committee, Report of, 451.

Light, Ultra-Violet, Atmospheric At-
tenuation of, 363, 444.

Lipman, J. G., accepts Fellowship,
439.

Loeffler, C. M. T., accepts Fellow-
ship, 441.

Loomis, F. W., The Heat of Vapori-
zation of Mercury, 448.

Lorentz, H. A., Reception to, 446;
Some Features in the Work of
the late J. W. Gibbs, 447.

Lotka, A. J., The General Conditions
of Validity of the Principle of Le
Chatelier, 19, 440.

Lovett, R. W., elected Fellow, 459.

Lowes, J. L., accepts Fellowship, 439;
A Neglected Note Book of Cole-
ridge, 447.

Lyman, Theodore, Report of the
Rumford Committee, 452.

Maginnis, C. D., accepts Fellowship,

439.
Main, C. T., accepts Fellowship, 439.

566

INDEX.

Margerie, E. de, elected Foreign Hon-
orary Member, 459.

Maj^o, W. J., accepts Fellowship, 439.

McAdie, A., Aerography, 442.

McDougall, William, elected Fellow,
459: _ _ •

Mercurj^, The Heat of Vaporization
of, 448.

Merriam, J. C, accepts Fellowship,
439.

Merrill, E. D., accepts Fellowship,
439.

Metals, The Effect of Pressure on the
Thermal Conductivity of, 75,
440.

Metals, The Effect of Tension on the
Electrical Eesistance of Certain
Abnormal, 39, 440.

Meteorological Phenomena in Rela-
tion to Flight, 442.

Miller, G. S., accepts Fellowship, 439.

Mills, H. F., death of, 440.

Molengraaff, G. A. F., accepts For-
eign Honorary Membership, 439.

Nominating Committee, 446.
Norris, J. F., Report of the C. M.
Warren Committee, 453.

Officers elected, 457; List of, 523.

Ohm's Law, The Failure of, in Gold
and Silver at High Current Den-
sities, 129, 440.

Orientalists, Special Meeting of, 460.

Parasites, Some Hymenopterous, of
Lignicolous Itonididce, 261, 443.

Patten, W., accepts Fellowship, 439.

Peabody, F. W., accepts Fellowship,
439.

Pentatomidae, The Phenomenon of
Polymegalj^ in the Sperm-Cells
of the Family, 388, 459.

Phelps, W. L., accepts Fellowship,
439.

Pierce, G. W., Artificial Electric Lines
with Mutual Inductance be-
tween Adjacent Series Elements,
193, 443; A Table and Method
of Computation of Electric Wave
Propagation, Transmission Line
Phenomena, Optical Refraction,
and Inverse Hj'perbolic Func-
tions of a Complex Variable,
173, 443.

Pilsbry, H. A., accepts Fellowship,
441.

Piper, C. v., accepts Fellowship, 439.

Pirenne, Henri, elected Foreign Hon-
orary Member, 459.

Polymegaly, The Phenomenon of, in
the Sperm-Cells of the Family
Pentatomidae, 388, 459.

Porter, A. K., elected Fellow, 459.

Post, C. R., accepts Fellowship, 439.

Publication Committee, Report of,
454.

Publication Fund, 450; Appropria-
tion from the Income of, 445.

Raeder, O. J. See Fernald, W. E.,
and others.

Reale Universita di Padova, 700th
anniversary, 440, 445, 447.

Records of Meetings, 439

Redfield, A. C, elected Fellow, 459.

Reflector, Notes on the Early Evolu-
tion of the, 67, 440, 441.

Refraction, Optical, and Inverse Hy-
perbolic Functions of a Complex
Variable, A Table and Method of
Computation of Electric Wave
Propagation, Transmission Line
Phenomena, 173, 443.

Reisner, G. A., Archaeological Meth-
ods used by the Harvard-Boston
Expedition, 443.

Resistance, Electrical, of Certain Ab-
normal Metals, The Effect of
Tension on the, 39, 440.

Rogers, A. F., elected Fellow, 459.

Romberg, Arnold, The Ratio of the
Calorie at 73° to that at 20°, 375,
448.

Royster, P. H., The Joule-Thomson
Effect in Air, 448.

Rumford, Count, photograph of
Gainsborough's portrait of, 439.

Rumford Committee, Report of, 452.

Rumford Fund, 449; Appropriations
from the Income of, 445; papers
published by aid of, 1, 75, 363,
375.

Rumford Premium, 561.

Rumford Historical Association, ac-
cepts replica of Rumford Medal,
439.

Russell, H. N., accepts Fellowship,
439.

Sachs, P. J., elected Fellow, 459.

Schaeffer, E. R., Atmospheric At-
tenuation of Ultra- Violet Light,
363, 444.

INDEX.

567

Schlesinger, F., accepts Fellowship,

439.
Scott, A. W., accepts Fellowship, 439.
Shaple}', Harlow, The Galaxy: Its

Content and Dimensions, 442.
Societe Asiatique de Paris, 100th

anniversary of, 445, 448.
Southard, E. E. See Fernald, W. E.,

and others.
Spectrum Lines, Grid Structure in

Echelon, 1, 440.
Standing Committees elected, 457;

List of, 523.
Standing Votes, 560.
Statutes, 545; amendment to, 443,

444, 445, 447.
Stebbins, J., accepts Fellowship, 439.
Stiles, C. W., accepts Fellowship,

439.
Sumner, J. O., Report of the House

Committee, 455.

Taft, A. E. See Fernald, W. E.,
and others.

Taylor, L. B. See Kent, N. A., and
Taylor, L. B.

Thaxter, Roland, Note on Two Re-
markable Ascomycetes, 423; A
Revision of the Endogonea,', 289,
448.

Thayer, W. S., accepts Fellowship,
439.

Thompson, Sir Benj., Count Rum-
ford, photograph of Gainsbor-
ough's portrait of, 439.

Thomson, Ehhu, Laboratory Prod-
ucts, 447.

Tolman, R. C, elected Fellow, 458.

Treasurer, Report of, 449.

Transmission Line Phenomena, Op-
tical Refraction, and Inverse
Hyperbolic Functions of a Com-
plex Variable, A Table and
Method of Computation of Elec-
tric Wave Propagation, 173, 443.

Trematodes, The Parasitic Worms of
the Animals of Bermuda, 213,
446.

Ultra-Violet Light, Atmospheric At-
tenuation of, 363, 444.

University of Virginia, medal of
100th armiversary, 439.

Variable, Complex, A Table and
Method of Computation of Elec-

tric Wave Propagation, Trans-
mission Line Phenomena, Opti-
cal Refraction, and Inverse Hy-
perbohc Functions of a, 173, 443.

Vision, The Physiology of, and the
Technique of Art, 446.

de Vries, H., accepts Foreign Hono-
rary Membership, 439.

Walker, C. H., accepts Fellowship,
439.

Ward, R. DeC, Some Meteorological
Phenomena in Relation to Flight,
442.

Warner, E. P., Recent Developments
in Aeronautical Science, 442.

Warren (C. M.) Committee, Report
of, 453.

Warren (C. M.) Fund, 450; Appro-
priation from the Income of, 445.

Warren, John, accepts Fellowship,
439.

Wave Propagation, Electric, Trans-
mission Line Phenomena, Opti-
cal Refraction, and Inverse Hy-
perbolic Functions of a Complex
Variable, A Table and Method
of Computation of, 173, 443.

Waverley Researches in the Pathol-
ogy of the Feeble Minded, 440.

Webster, A. G., Hermann von Helm-
holtz and his Significance for a
Centur}^ of Science, 441; Report
of Library, 451.

Weston, W. H. Jr., elected Fellow,
459.

Whitcher, A. W., photograph of
Gainsborough's portrait of Benj.
Thompson, 439.

White, D., accepts, Fellow.ship, 439.

Willard, Rev. Joseph, silhouette of,
439.

Wilson, G. G., The Recent Confer-
ence on the Reduction of Arma-
ments, 446.

Winslow, A., accepts Fellowship, 439.

Wisconsin Academy of Sciences,
medal of 50th anniversary, 439.

Woodward, R. S., account of cen-
tennial of Univ. of Virginia, 440.

Worms, The Parasitic, of the Animals
of Bermuda. I. Trematodes,
213, 446.

Wright, C. H. C, elected Fellow, 459.

Young, A. A., accepts Fellowship, 441.

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