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PROCEEDINGS

OF THE

AMERICAN ACADEMT

ARTS AND SCIENCES.

Vol. XLIII.

FROM MAY, 1907, TO MAY, 1908.

BOSTON:
PUBLISHED BY THE ACADEMY.

1908.

^.^^.'^

JSnibtrsitg ^rcss:
John Wilson and Son, Cambridge, U.S.A.

H-l I 0

CONTENTS.

Page

I. Studies on Fluorite : (IV.) The Kathodo-Luminescence of Fluorite.

By H. W. Morse 1

II. (I.) New Species of Senecio and Schoenocaulon from Mexico. By
J. M. Greenman. (II-) New or otherwise Noteivorthy Sper-
matophytes, chiefly from Mexico. By B. L. Robinson. (HI.)
New Plants from Guatemala and Mexico collected chiefly by
C. C. Deam. By B. L. Robinson and H. H. Bartlett.
(IV.) Diagnoses of Neio Spermatophytes from Mexico. By
M. L. Fernald 17

III. Maturation Stages in the Spermatogenesis of Vespa maculuta Linn.

By E. L. Mark and Manton Copeland 69

rV^. The Physiological Basis of Illumination. By Louis Bell . . 75

V. On the Determination of the Magnetic Behavior of the Finely Divided
Core of an Electromagnet lohile a Steady Current is being
Established in the Exciting Coil. By B. O. Peirce ... 97

VI. The Demagnetizing Factors for Cylindrical Iron Rods. By C. L. B.

Shuddemagen 183

VII. Outlines of a New System of Thermodynamic Chemistry. By

G. N. Lewis 257

VIII. The Quantitive Determination of Arsenic by the Gutzeit Method.

By C. R. Sanger and O. F. Black 295

IX. The Determination of Arsenic in Urine. By C. R. Sanger and

O. F. Black 325

IV CONTENTS.

Page

X. The Transition Temperature of ]\fanganous Chloride : A New

Fixed Point in Thermometry. By T. W. Richards and

F. Wrede 341

XL Difference in Wave-Lengths of Titanium XX 3900 and 3913 in

Arc and Spark. By N. A. Kent and A. H. Avery . . 351

XII. A Revision of the Atomic Weight of Lead. Preliminary Paper.

— The Analysis of Lead Chloride. By G. P. Baxter
AND J. H. Wilson 363

XIII. A Simple Method of Measuring the Intensity of Sourid. By

G. W. Pierce 375

XIV. Longitudinal Magnetic Field arid the Cathode Rays. By John

Trowbridge 397

XV. Note on Some Meteorological Uses of the Polariscope. By

LoDis Bell 405

XVI. The Sensory Reactions of Amphioxus. By G. H. Parker . . 413

XVII. On Delays before avayvwpitrfu in Greek Tragedy. By W. P.

Dickey 457

XVIII. A New Method for the Determination of the Specific Heats of

Liquids. By T. VV. Richards and A. W. Rowe . . . 473

XIX. Pisistratus and his Edition of Homer. By S. H. New-
hall 489

XX. Positive Rays. By John Trowbridge 511

XXI. Concerning the Use of Electrical Heating in Fractional Distilla-
tion. By T. W. Richards and J. H. Mathews . . . 519

XXII. Records of Meetings 527

Report of the Council 547

Biographical Notice

Samuel Cabot 547

CONTENTS. V

Pagk

Officers and Committees fok 1908-09 557

List of Fellows and Foreign Honorary Members .... 559

Statutes and Standing Votes 567

RuMFORD Premium 578

Index 579

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 1. — Juxe, 1907.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

STUDIES ON FLU QUITE.

lY.— THE KATHODO-LUMINESCENCE OF FLUORITE.

By Hakby W. Moksk.

With a Plate,

Investigations on Light and Heat made and published, wholly or in pabt, with Appropriation

from the rcmi-ord fund.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

STUDIES ON FLUORITE.

IV. THE KATHODO-LUMINESCENCE OF FLUORITE.
By Hakby W. Mokse.

Presented by John Trowbridge. Received March 20, 1907.

I, In previous papers which have been presented to the American
Academy by the author, data on the light emitted by crystals of fluor-
ite from various localities, excited by light ^ and by heat,^ have been
discussed. The present research contains data on the spectra of the
light emitted by various fluorites under excitation by kathode rays.

It was found in the first research that many fluorites, if not all, give
discontinuous spectra when excited by the light from certain sparks.
The metals which have strong ultra-violet lines in their spark spectra,
used as terminals for the passage of a strong spark, excite lines of
fluorescence in these fluorites ; and while these lines are in most cases
somewhat diff"use and broad in appearance, they are in other cases
apparently as sharp as the metallic lines which excite them.

In the later paper, data has been given on the light emitted, in two
typical cases, by fluorites under excitation by heat alone. Here again
the spectra are discontinuous, and contain, beside broad-banded por-
tions, lines which are quite sharp.

The spectroscopic side of the luminescence of fluorite is not ex-
hausted by a study of the fluorescence and thermo-luminescence
spectra. This mineral is most remarkable in the great variety of
ways by which its luminescence can be excited, and it is known to
emit light under the influence of kathode rays, X-rays, and radium
radiation, as well as by simply rubbing or breaking a crystal.

Parallel with the spectroscopic investigation of the light emitted by
the crystals under various excitations, a careful series of investigations

^ The Fluorescence Spectrum of Fluorite, Astrophysical Journal, 21, 83
(Mar. 1905) ; Studies on Fluorite, I. These Proceedings, 41, 587 (Mar. 1906).
2 Studies on Fluorite, II. These Proceedings, 41, 593 (Mar. 1906).

4 PROCEEDINGS OF THE AMERICAN ACADEMY.

has been made on the impurities which are present in the natural min-
eral. The first of these investigations ^ was made on the gases con-
tained in fluorite, and the results of this research are wholly negative
as far as the question of the source of luminescence is concerned.
Nothing other than the ordinary gases was found in any case, and no
relation between the occluded gases and the emission of light under
excitation was discovered.

At the present time, careful chemical analyses of a series of fluorites
from many parts of the world are being carried out, in the hope of find-
ing a clue to the source of the light-emission. The results of these
analyses, as far as they have gone, are most interesting. Many fluorites
are found to contain quite evident amounts of rare earths,* and from
one specimen, at least, enough neodymium and praseodymium have
been separated to give a quite measurable absorption spectrum. The
author intends to report the results of these investigations to the
American Academy as soon as possible.

II. The spectra of a large number of fluorites, excited by kathode
rays, have been examined and photographed. Of this large number,
seven will be described in this paper. The crystals examined were :

1. Fluorite from Amelia Court-House, Virginia. This region is a
famous one because of the occurrence of this fluorite, which has re-
markable properties, and also for many other minerals containing rare
earths. Very large microlite crystals were found near the fluorite de-
posits. The crystals of fluorite from this region are what are called
"chlorophanes," par excelleiice. They are very sensitive to heat, emit-
ting light strongly at the temperature of boiling water, and so strongly
at 300° as to be bright objects even in a well-lighted room. The fluor-
ites occur in colors varying from dark brown and dark purple to light
green. All show the same thermo-luminescence spectrum, and the
same kathodo-luminescence spectrum. The spectrum of thermo-lumi-
nescence of this variety has been given at length in a previous paper.^
The details of the kathodo-luminescence spectrum are given in Table I,
and the appearance of this spectrum is seen in Figure 1, Plate o.

2. Fluorite from Trumbull, Conn. This is also a brilliant "chloro-
phane," which shows the same thermo-luminescence spectrum as the
Virginia crystals, and a kathodo-luminescence spectrum which is very
closely related to that of the other mineral. Details of the latter
spectrum are given in Table II, and the appearance of the spectrum is
seen in Figure 2 of the plate.

3 Studies on Fluorite, III. These Proceerlings, 41, 001 (Mar. 1906).
* See also llumplircys, Astroi>hysieal Journal, 20, 260 (1004).
5 Studies on Fluorite, II. These Proceedings, 41, 593 (Mar. 1906).

MORSE. — THE KATIIODO-LUMINESCENCE OF FLUORITE. t»

3. Fluorite from Westmoreland, N. H. This is a clear, light-green
fluorite, which shows no very strong fluorescence, but which is most
brilliant in thermo-luminescence, giving out a purple light, the spec-
trum of which has been fully described in a previous paper.^ Its
kathodo-luminescence spectrum is in many respects very different from
all the others described. The details of this spectrum are given in
Table III, and a photograph of the spectrum is reproduced in Figure 3
of the plate.

4. Fluorite from Hardin County, Ohio. This is a clear pink variety
of no very strong fluorescence or thermo-luminescence, but which
shows a fairly strong kathodo-luminescence. Its spectrum is shown in
Figure 4, and the detail of the lines is given in Table IV.

5. Purple fluorite from Weardale, England. This locality has fur-
nished some of the most beautiful fluorspar crystals of the world, and
this particular crystal was cut from a large and perfect natural crystal.
It is the same crystal as No. 5 of the paper on the fluorescence of
fluorite,'^ and it is characterized by a fine series of layers of diff'erent
colors, in planes parallel to the natural faces of the crystal. (Table V
and Figure 5.)

6. Green Weardale crystal. A deep green variety from the same
locality, showing a kathodo-luminescence spectrum very much like that
of the purple variety, but diff'erent in some strong lines. Table VI, of
wave-lengths, and Figure 6 of the plate, show its characteristics.

7. Yellow Weardale crystal. From the same locality, but of deep
straw-yellow color. Not very strong in fluorescence or thermo-lumi-
nescence, but giving a fine purple kathodo-luminescence. Shown in
Figure 7 and described in Table VII.

III. After the preliminary study of the method, exposure, condi-
tions for brightest luminescence, etc., the crystals described were cut
from the natural crystals and their faces polished. This treatment
permits of excluding the lines of gases in the tube as completely as
possible, and gives a field of light which is regular and smooth. The
crystals were then mounted in the vacuum tube so that one of the
polished faces was exposed directly to the kathode bombardment,
the spectroscope being so placed that it would take in all the light
possible from the polished face of the crystal.

The form of tube shown in the figure (Figure ^) is convenient
for this special purpose. The crystal is mounted on the little table
which forms the end of the stop-cock, and so mounted it can be turned

6 Studies on Fluorite, II. These Proceedings, 41, 503 (Mar. 1906).
' The Fluorescence Spectrum of Fluorite, Astrophysical Journal, 21, 83
(Mar. 1905) ; Studies on Fluorite, I. These Proceedings, 41, 587 (Mar. 1906).

PROCEEDINGS OF THE AMERICAN ACADEMY.

to any desired position in front of the rays, or a new face can be ex-
posed when this is necessary, without loss of time. In the preliminary
examination, a number of small bits of lluorite were mounted on the
revolving table, near the edge, and these could then be brought one
after the other into the kathode rays, and their spectra studied with
a hand spectroscope. During the entire research the kathode stream
was controlled by means of a permanent magnet, and with it the
brightest luminescence could be brought out near the slit ; or, if the
crystal had been mounted a little too low or too high, the kathode
stream was brought into the most favorable position for bright lumi-
nescence by means of the magnet.

Figure A.

The large aperture spectroscope already described ^ was used for the
photography of the spectra, and Cramer Tri -chromatic plates were found
to give a fairly flat spectrum down as far as wave-length 6000.

It was found that the time of exposure could not be increased beyond
a certain point with any advantage. The well-known phenomenon
of discoloration of the crystal faces takes place, and before long the
layer of color becomes so dense that practically no more kathode excita-
tion gets through it, and the luminescence stops. About half an hour
is the limit of profitable exposure for a single crystal face under the
conditions of excitation used in this work, and if the intensity of the
kathode stream is greatly increased, this time is reduced to a few min-
utes. The time varies with different crystals, and some of them remain
unattacked for a much longer period than others. When a longer
exposure than half an hour was found necessary, the crystal was simply

8 The Fluorescence Spectrum of Fluorite, Astropliysical Journal, 21, 83
(Mar. 1905) ; Studies on Fluorite, I. Tliese Proceedings, 41, 587 (Mar. 1906).

MORSE. — THE KATHODO- LUMINESCENCE OF FLUORITE. 7

turned through 90° and a new face presented, so that the exposure
coukl be continued to about two hours with a single crystal. The
luminescence light passes almost undimmed through the thin layer of
color on the face of the crystal, so that a face which has been completely
protected from further excitation by the kathode beam is still quite
transparent to light, and may therefore be turned toward the slit, while
a new face is exposed to excitation.

The tube was kept connected with the pump during the entire series
of experiments, and the vacuum was brought back to the most favorable
point whenever necessary. For some crystals no pumping was required,
and the vacuum remained at the right point for many hours. In other
cases constant use of the pump was necessary. The Westmoreland
crystal (No. 3), although one of the clearest and least colored of the
series, gave off hydrogen in measurable quantities, and the spectrum
of the gases in the tube changed slowly after this crystal was introduced,
until finally the original nitrogen (air) spectrum had almost entirely dis-
appeared and only hydrogen was visible. This is evidently closely con-
nected with the fact that this same Westmoreland fluorite contains a
considerable percentage of hydrogen in the gases which it holds oc-
cluded. Analysis of the gases given off from this fluorite on heating
showed that while the amount of gas present was small compared with
some other fluorites, it contained about 52 per cent of hydrogen.^ The
evolution of hydrogen at room temperature, under the influence of
the kathode discharge, is an interesting qualitative confirmation of the
analyses.

IV. In the following tables the abbreviations

sh., sharp v. sh., very sharp

dif , diffuse v. dif , very diff"use

q. sh., quite sharp max., maximum

are used. Bands are indicated by brackets enclosing the numbers
representing their boundaries.

Intensities are given on a scale of 1 to 10, int;reasing.

In tables IX and X the strong' lines and those common to several
crystals have been collected. A few important relations may be men-
tioned.

The band from X 5570 to A 5610 is a universal constituent of all
these spectra.

The strong line at X 5667 is present in all but one. It is just as cer-

' See also Humphreys, Astrophysical Journal, 20, 2G6 (1904).

PROCEEDINGS OF THE AMERICAN ACADEMY.

tainly absent from the spectrum of the Ohio crystal, and it is replaced
by the line at X 5676.

Table X shows the most common lines and their occurrence in the
seven spectra under analysis. Comparison with the tables of wave-

TABLE I.

Amelia

Court House (Va.) Fluorite.

Wave-length.

Intensity.

Remarks. Wave-length.

Intensity.

Remarks.

4310

f5375

4332

i to

strong

band.

4350

q. sh.

15407

M360
- to
.4378

5455

dif.

rather weak band.

5535

dif.

5608

dif.

4415

dif.

'5665

r 4544

4663

5733

max.

strong band

4775

r4800
-' to
14832

^780

sharp edge.

rather weak band.

C5804

\ to

weak band

I 4857

q. sh.

U886

5295

dif.

5962

dif.

5332

dif.

6040

dif.

TABLE n.

Trumbull, Conn., Fluorite.

Wave-length.

Intensity.

Remarks. Wave-length.

Intensity.

Remarks.

4145

dif.

5666

8 rather dif.

4335

dif.

5693

4350

q. sh.

5710

dif.

(4365

5731

V. sh.

\ to

strong flat banc

5750

V. sh.

U380

5774

V. sh.

4417

dif.

r5795

4510

dif.

1 to

band.

5398

broad.

'5837

5433

[5860
^ to
15890

5487

band.

5506

5539

broad.

6055

dif.

[5555

\ to

rather weak band.

Ueio

sharp edge

MORSE.

THE KATHODO- LUMINESCENCE OF FLUORITE.

lengths of the spectra produced by fluorescence ^^ and by thermo-lum-
inescence ^^ shows immediately that while the spectra are similar in
general appearance, and while the strong lines in the kathodo-spectra are
in about the same part of the spectrum as those in the fluorescence-
spectra, there are no coincidences of importance. The three lumines-
cences are totally diff"erent as far as the wave-lengths of the principal
lines are concerned. And a moment's consideration of the facts about

TABLE III.

Westmoreland,

H., Fluorite

Wave-length.

Intensity.

Remarks.

Wave-length.

Intensity.

lemarks.

4722

V. dif.

(5573

4777

V. dif.

band.

4857

q. sh.

(5608

4892

dif.

5667

dif.

5142

dif.

5727

q. sh.

5187

dif.

i 5767

max

or sh. edge

5244

dif.

< to

band.

5332

(5822

5370

q. sh.

(5870
j to

5398

q. sli.

diffuse band.

5433

15912

5468

q. sh.

( 5980
] to

5513

dif.

weak band with 2

max.

' 6055

TABL

IV.

Fluorite from H

ARDIN Co.,

III.

Wave-length.

Intensity.

Remarks.

Wave-length.

Iuteu.sity. Remarks.

4898

dif.

5676

q. sh.

5192

dif.

5735

q. sh.

5262

dif.

'5767

5345

5375

q. sh.

- 5783

max.

band.

5400

q. sh.

5434

V5822

5468

q. sh.

( 5872
] to

5517

dif.

fairly strong

band.

5538

q. sh.

(5914

I 5572

(5978

j to

fairly

strong band.

] to

band.

'5619

(6053

max.

'■'* The Fluorescence Spectrum of Fluorite, Astrophysical Journal, 21,
(Mar. 1905) ; Studies on Fluorite, I. These Proceedings, 41, 587 (Mar. 190G).
11 Studies on Fluorite, II. These Proceedings, 41, 593 (Mar. 1906).

83,

PROCEEDINGS OF THE AMERICAN ACADEMY.

the fluorescence spectra makes this result necessary as far as that
method of excitation is concerned. The fluorescence spectrum of a crys-
tal of fluorite is a function of the exciting source, and changes completely
when the exciting wave-lengths are changed. It is therefore improbable
that any one of the fluorescence spectra should show more than approx-
imate or accidental coincidences with many lines excited by either heat
or kathode luminescence. There are lines which appear in the fluores-
cence spectra of a crystal under excitation by several different sources,

TABLE V.

Purple

Weardale

(Eng.) Fluorite.

Wave-length.

Intensity.

Remarks.

Wave-length.

Intensity.

Remarks.

4727

5669

rather dif.

4782

5754

max.

in band.

4796

5780

4 max. of band

4944

(5810 max.

5337

j to

band.

5374

(5857

5407

[5871

5467

] to

rather weak band

5509

(5908

5542

6045

(5571

6114

] to

band.

•

(5612

TABI

.E VI.

Green Weardale

(Eng.) Fluorite

Wave-length.

Intensity.

Remarks.

Wave-length.

Intensity.

Remarks.

4730

q. sh.

5517

dif.

4780

sh.

5537

q. sh.

• 4795

sh.

(5575

(4854

] to

rather weak band.

(5606

band.

(4867

5667

10 sh.

and strong

4890

dif.

5726

q. sh.

4915

broad.

5761

4947

dif.

5774

q. sh.

5333

broad.

5809

q. sh.

5370

q. sh.

5833

q. sli.

5396

q. sh.

( 5861
to

sharp edge here.

5408

q. sh.

strong

band.

5439

broad.

( 5893

5470

broad.

6040

q. sh.

5506

q. sh.

6110

q. sh.

MORSE. — THE KATHODO-LUMINESCENCE OF FLUORITE.

and these might be expected to be a property of the crystal, and to per-
sist under other forms of excitation. None of these lines appear in
either the thermo-luminescence or kathodo-luminescence of these crys-
tals. That the same substance can, however, give the same spectrum
under excitation by light and by heat has been shown by Becquere],^^
and Urbain ^^ has proven that the same spectrum, modified only slightly,
is shown by the same substance under excitation by kathode rays.
The necessary conclusion from the author's experiments is, however,
that this is by no means always the case. The purple Weardale fluorite
(No. 5) has been most carefully studied both in fluorescence and in
kathodo-luminescence, and there is no relation whatever between these
spectra as far as the wave-lengths of lines are concerned. The West-
moreland fluorite, and that from Amelia Court-House, have been inves-
tigated in both thermo-luminescence and kathodo-luminescence, and
no coincidences of importance are visible.

Plate 0 gives a very good idea of the relation between the kathodo-
luminescence spectra of the seven crystals examined. The two upper
spectra are very evidently similar. They are both "chlorophanes,"

TABLE VII.
Yellow Weardale (Eng.) Fluorite.

Wave-length.

4332

4350
( 4365

j to broad flat band.
(4382

4419

4512
(4542
] to
(4705

4736

4752

4767

4785

4796
i 4814
] to
(4833

4860

4917

Intensity.
2
8

8
2
4

8
2
1
5
5
2

4
4

Remarks.

sh.

dif.

dif.
q. sh.

sh.
sh.

band.

dif.
dif.

Wave-length. Intensity. Remarks.

max.

2
1

q. sh.
q. sh.
jand between

sh.

broad band.

sh.

2
3
2

1
3

q. sh.
q. sh.
q. sh.
q. sh.
dif.

^2 Journal de pliysique, 68, 444, and 69, 169.
" Comptes rendus, 143, 825 (1906).

PROCEEDINGS OF THE AMERICAN ACADEMY.

TABLE VIII.
SUMMARY.

Wave-length.

Am. C-H.

Trumb.

West.

Ohio.

p. Wr.

G. Wr.

Y. Wr.

4145

1 d.

4310

4333

3d.

4350

3s.

5 S.

8 s.

C4360

\ to

St.

U380

4416

2d.

5d.

8d.

4511

1 d.

4543

(4d.

4663

]bnd.

4705

(2d.

4722

2d.

4728

4 s.

4736

8 s.

4752

4767

4776

2d.

4781

3 s.

4785

5 s.

.4796

4 s.

5 s.

4800

(

4814

\ w. bnd.

1 bnd.

4832

(

4856

3 s.

4 s.

! bnd.

4860

4d.

4867

-■

(

4891

2d.

1 d.

4898

2d.

4917

3 b.

4d.

4946

1 d.

5142

1 d.

5190

2d.

5244

2d.

5262

1 d.

5295

5334

1 b.

5345

5373

j St.

5 s.

5s.

3 s.

5397

5 b.

5 3.

5 s.

1 s.

5408

1 bnd.

5 s.

MORSB. — THE KATHODO- LUMINESCENCE OF FLUORITE.

TABLE VIII. {Continued.)

Wave-length.

Am. C-H.

Trumb.

West.

Ohio.

P. Wr.

G. Wr.

Y. Wr.

5-435

2 b.

5455

2d.

5469

2s.

3s.

5 b.

3 s.

5487

5508

2 s.

5513

8d.

5517

2d.

1 d.

jbnd.

5538

2 dif.

4 b.

1 s.

3 s.

5550

(

5." 72

j w. bnd.

jst. bnd.

Ihnd.

(

5610

2d.

(

(3 bnd.

h bnd.

(bnd.

5666

[\Q

4d.

10 s.

5676

10 s.

5693

5710

2d.

5727

< bnd.

4 s.

3 s.

2 s.

5732

3 s.

5755

/•

d. m.

5772

8 s.

5 s.

3 s.

5782

. s.

4d.

5795

' bnd.

5804

5810

- bnd.

I'm.

5 s.

2 s.

5822

5833

- bnd.

5 s.

5837

1 s.

5860

- bnd.

5870

5885

\ bnd.

jbnd.

3d.

5892

" bnd.

■ bnd.

(

5910

5962

2d.

5980

bnd.

6040

3d.

^ bnd.

8 s.

6045

6054

2d.

^m.

1 s.

6112

1 s.

(In the above summary s., sharp; d., diffuse; m., ma.^amum in band;
w., weak; bnd., band; St., strong; are used. Bands are indicated by
brackets.)

PROCEEDINGS OF THE AMERICAN ACADEMY.

TABLE IX.
STRONG LINES.

And those Common to Several Crystals.

Wave-length.

Am. C-H.

Trumb.

West.

Ohio.

P. Wr.

G. Wr.

Y. Wr.

4350

3s.

5s.

8s.

4416

3d.

5d.

8d.

4730

4780

4785

4796

4856

3s.

4 s.

4d.

4917

5372

5398

5408

5470

5512

5538

I 5570

] to

bnd.

^nd.

bnd.

( 5610

5667

5676

5730

5775

5810

bnd.

5885

bnd.

6040

bnd.

(s., sharp; d., diffuse; m., maximum in band; bnd., band; intensities on
increasing scale of 1 to 10.)

TABLE X.

The Most Common Lines of the 7 Crystals.

5372

in 5

5810

in 7

5398

5885

5538

6050

5667

6 or 7

■ ( 5570

5730

I to

5775

(5610

MORSE. — THE KATHODO-LUMINESCENCE OF FLUORITE. 15

and the spectrum is therefore concealed in some degree beneath the
broad green band which is characteristic of both. The similarity in
many of the sharper lines is, however, perfectly apparent.

The spectra of Figures 3 and 4 are quite different from each other
and from the other spectra shown. The larger part of the luminescence
lines are in the same part of the spectrum as in the others, but the
lines are not the same. Figure 4 is more like the spectra 5, 6, and 7
than it is like the ones preceding it in the plate. The three lower
figures are all of fluorites from Weardale. They are very similar in
most of their lines, but show evident differences in the strength of
individual lines and groups of lines.

In none of these spectra are the lines quite as sharp as the lines of
fluorescence. They are all diffuse in comparison with sharp metallic
lines.

V. While work on this research was in progress, a paper by Urbain ^"^
appeared in which the cause of the luminescence of fluorite was definitely
connected with the presence of the rare earths terbium, samarium, and
dysprosium. The particular fluorite which was cited by Urbain was
one which had been examined several years before by Becquerel,^^ both
in the phosphoroscope and in thermo-luminescence. It is a " chloro-
phane " which gives a brilliant green luminescence under all of the va-
rious methods of excitation, and from the table of wave-lengths which
accompanies the paper it is quite evident that the spectrum of this
chlorophane in kathodo-luminescence is very similar in all important de-
tails to the spectra of the chlorophanes of the author's Tables I and II,
and of Figures 1 and 2. But the resemblance of this spectrum to the
kathodo-luminescence spectra of terbium, samarium, and dysprosium,
dissolved in various oxides and sulphates, is very slight indeed, and
Urbain's conclusions from this resemblance may possibly be unjustified.
He prepared from the fluorite in question substances which did give
spectra corresponding in every detail with the spectra of the rare earths,
and also synthesized a fluorite, which was like the original one, from
such preparations. The proof seems a very strong one, but it is one
which requires further test. The kathodo-luminescence spectra of the
rare earths, in spite of their perfectly definite appearance and their
evident persistence as a property of some definite substance or element,
have proven most elusive. Crookes ^^ spent some fifteen years in fol-

" Comptes rendus, 143, 825 (1906).

^5 Journal de physique, 68, 444, and 69, 169.

^^ A large number of papers by Crookes on this subject are to be found in the
Proceedings of the Royal Society, the Transactions, and in the Cliemical News,
from 1880 to 1890 especially.

16 PROCEEDINGS OF THE AMERICAN ACADEMY.

lowing certain definite bands in these spectra. Lecoq ^"^ about as long
Baur and his students thought that they had settled the matter finally. ^^
Urbain ^^ has done wonderful work in separating the elements of the
rare earths, and his opinion is undoubtedly of more importance than
that of any one else. An explanation along these lines must include
not only the case of a single chlorophane, but it must cover also the
cases where the fluorescence, thermo-luminescence, and kathodo-lumi-
nescence of the same crystal of fluorite are all difiierent, even in their
minute details.

While the author cannot expect to test the question by synthesis,
further study of the rare elements which are present in fluorites is
already under way, and examination of the light emitted by these same
fluorites under excitation by other means will also be taken up as soon
as possible.

The author's thanks are due to the American Academy for a gener-
ous appropriation from the Rumford Fund, which has been of the
utmost assistance in this work.

The Jefferson Physical Laboratory,

Harvard University. Marcli 20, 1907.

" Papers by Lecoq de Boisbaudran on this subject, to the number of tliirty or
more, are to be found in the Coniptes rendus, beginning with volume 100, and
continuing for many years.

" Ber. d. d. Chem. Ges., 33, 1748, and 34, 2460.

" A very complete bibliography of all tlie literature on the yttrium and cerium
earths is that of Meyer, Bibliographie der seltenen Erden. (Leopold Voss,
Leipzig, 1905.)

EXPLANATION OF PLATE.

The upper spectrum is that of the spark between cadmium terminals, and the
numbers indicate wave-lengths.

The seven numbered spectra are kathodo-luminescence spectra of tlie fol-
lowing :

1. Fluorite from Amelia Court-House, Virginia.

2. Fluorite from Trumbull, Conn.

3. Fluorite from Westmoreland, N. H.

4. Fluorite from Hardin Co., Ohio.

5. Purple fluorite from Weardale, England.

6. Green fluorite from Weardale, England.

7. Yellow fluorite from Weardale, England.

Morse — Studies on Fluorite. IV.

CD.

Proc. Amer. Acad. Arts and Sciences. Vol. XLI

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 2. — Juxe, 1907.

CONTRIBUTIONS FROM THE GRAY HERBARIUM OF
HARVARD UNIVERSITY.

New Series. — No. XXXIV.

I. New Species of Senecio and Sckoenocaulon from Mexico. By
J. M. Greenman.

II. New or otherwise Noteworthy Spermatoph3rtes, chiefly from
Mexico. By B. L. Robinson.

III. New Plants from Guatemala and Mexico collected chiefly by

C. C. Deam. By B. L. Robinson and H. H. Bartlett.

IV. Diagnoses of New Spermatophytes from Mexico. By M. L.

Fernald.

CONTRIBUTIONS FROM THE GRAY HERBARIUM OF HARVARD
UNIVERSITY. — NEW SERIES, NO. XXXIV.

Presented by B. L. Robinson, February 13, 1907. Received February 23, 1907.

I. NEW SPECIES OF SENECIO AND SCHOENOCAULON

FROM MEXICO.

By J. M. Gkeenman.

Schoenocaulon calcicola Greenman, n. sp., bulbis ovoideis 1.5-2
cm. diametro ; caudice erecto cylindrato 5-10 cm. longo a reliquis atro-
brunneis vel nigrescentibus fibrosis squamarum foliorumque exterio-
rum circumdato ; foliis lineari-attenuatis 3-10 dm. longis 2-5 mm.
latis 7-13-nerviis utrinque laevibus margins paulo hirtellis ; scapo
nudo 5.5-7.5 dm. alto aliquanto flexuoso subancipiti glabro basin
versus purpureo ; inflorescentia laxiflora 1-2 dm. longa 8-10 mm. an-
thesi diametro ; bracteis parvis late ovatis tenuibus brunnescentibus ;
floribus sessilibus vel breviter pedicellatis ; perianthio 6-partito, seg-
raentis linearibus 2.5-3 mm. longis acutiusculis saepissime basi
bidentatis ; staminibus perianthio longioribus ; capsulis maturis ob-
longo-lanceolatis ca. 1 cm. longis glabris reflexis. — Hillsides, Las
Sedas, Oaxaca, Mexico, alt. 1830 m., 1 August, 1894, C. G. Pringle,
no. 5754 (tjT^e, in hb. Gray) ; calcareous banks. Las Sedas, alt. 1830 m.,
19 July, 1897, C. G. Pringle, no. 6740 (hb. Gray, hb. Field Mus.).
The latter number was distributed as /S*. intermedium Baker, a species
from which S. calcicola is readily separated by its reflexed fruit.

Schoenocaulon caricifolium Greenman, n. comb. Veratrum cari-
cifoUum Schlecht. Ind. Sem. Hort. Hal. 8 (1838). Asagraea carici-
foVia Kunth, Enum. PI. iv. 666 (1843). Although this species has
been treated by several authors as conspecific with Schoenocaulon
officinale Gray, yet an examination of some of the original material,
collected by Ehrenberg, of which there is now a specimen in the Gray
Herbarium, shows very clearly that it can scarcely be regarded as iden-
tical with Dr. Gray's species. 8. caricifolium differs from 8. officinale
in having narrower leaves, shorter scapes and inflorescence, and rela-
tively shorter and distinctly inflated capsules. — Mexico, without defi-

20 PROCEEDINGS OF THE AMERICAN ACADEMY.

nite locality, Ehrenherg (hb. Gray). Specimens secured by C. Conzatti
and V. Gonzalez at Etla, Canada de San Gabriel, State of Oaxaca, alt.
3000 m., 8 August, 1897, no. 323 (hb. Gray), are apparently referable
to this species.

Schoenocaulon Ghiesbreghtii Greenman, n. sp., caudice erecto
10-12 cm. alto reliquis brunneis aut nigrescentibus fibrosis squamarum
et foliorum primorum obtecto ; foliis linearibus attenuatis 4-8 dm.
longis 2-6 mm. latis 7-13-nerviis utrinque glabris ; inflorescentia
1-1.2 dm. vel ultra longa 1.5-2 cm. diametro densiflora; bracteis late
ovatis 2.5 mm. longis obtusis 5-nerviis; floribus sessilibus vel breviter
pedicellatis ; perianthio profunde 6-partito, lobis anguste oblongis
4-4.5 mm. longis obtusis integris vel subintegris 3-5-nerviis; fila-
mentis perianthio duplo vel ultra longioribus uniforme recurvatis ;
fructu ignoto. — State of Chiapas, Mexico, without more precise lo-
cality, Dr. Ghieshreght, no. 672 (type, in hb. Gray) ; without definite
locality, alt. 2130 m., Berendt (hb. Gray). This species is rather strik-
ing on account of the recurved filaments. In this respect it resembles
>S'. tenuifoUum Robinson & Greenman, but in other and more essential
characters it is amply distinct.

Schoenocaulon jaliscense Greenman, n. sp., bulbis oblongo-
ovoideis 2.5-3.5 cm. diametro ; caudice erecto cylindrato 1-1.5 dm.
alto a reliquis atrobrunneis vel nigrescentibus fibrosis squamarum
foliorumque exteriorum obtecto ; foliis gramineis 6-10 dm. longis
2-7 mm. latis 9-13-nerviis utrinque glabris margine inconspicue hir-
tellis ; scapo erecto 8 dm. vel ultra alto nudo subancipiti aliquid
glauco ; inflorescentia elongata 1 usque ad fere 5 dm. longitudine
1-1.5 cm. diametro simplici vel raro ramum lateralem gerenti ; bracteis
parvis scariosis suberoso-marginatis ; floribus breviter pedicellatis ;
perianthio alte 6-partito, segmentis lineari-oblongis ca. 2.5 mm. longis
integris vel basi bidentatis apicem obtusum versus paulo ampliatis
incrassatisque ; staminibus perianthio longioribus ; filamentis persis-
tentibus ; capsulis immaturis nee non pedicellis et segmentis perianthii
plus minusve glaucis et purpurascentibus ; fructu erecto oblongo-ovato
quam 1 cm. breviore. — Cool grassy sides of canons, near Guadalajara,
Jalisco, Mexico, 11 November, 1889, C. G. Pringle, no. 2938 (type, in
hb. Gray) ; Rio Blanco, Guadalajara, 1903, C. G. Pringle, no. 11,853
(hb. Gray) ; Cerro de San Felipe, Oaxaca, Mexico, alt. 2000 m.-, 29
August, 1897, C. Conzatti & V. Gonzalez, no. 449 (hb. Gray).

Senecio (§ Eremophili) ctenophyllus Greenman, n. sp., herbaceus
annuus vel perennis basi saepe lignosus ; caulibus erectis 3-4 dm. altis
simplicibus vel ramosis arachnoideo-tomentosis ; foliis lanceolatis 2-9 cm.
longis 1-2.5 cm. latis plus minusve pectinato-divisis arachnoideo-

ROBIXSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 21

tomentulosis ; foliis inferioribus petiolatis, summis sessilibus ; inflores-
centiis terminalibus coryinboso-cymosis tomentosis ; capitulis uumerosis
8-9 mm. altis heterogamis calyculatis ; involucri campanulat'i squamis
ca. 13 lineari-lanceolatis 5 mm. longis acutis nigro-penicillatis ceterum
glabratis vel sparsissime tomentulosis ; floribus femineis liguliferis 5-8,
corollis glabris, ligulis flavis ; floribus disci ca. 25 ; achaeniis cano-
hirtellis. — Barranca below Sandia Station, Durango, Mexico, alt. 21,35
m., 15 October, 1905, C. G. Pringle, no. 10,105 (type, in hb. Gray).
This species has the general aspect of S. eremoph'dus Richards., H. chi-
huahuensis Wats, and S. MacDougalii Heller, but differs from all of
them in being tomentulose throughout and in having narrower leaves
with mostly simple slender and entire lateral teeth or divisions.

Senecio (§ Tomentosi) loratifolius Greenman, n. sp., herbaceus
perennis ; caulibus erectis 3 dm. altis lanato-tomentosis ; foliis alternis
elongato-lanceolatis vel subloratis 0.5-1.7 dm. longis 4-12 mm. latis
acutis vel obtusis integris membranaceis juventate supra arachnoideo-
tomentosis denique glabratis subtus persistenter albo-tomentosis ; foliis
inferioribus basi sensim angustatis et subpetiolatis, superioribus sessili-
bus et amplexicaulibus ; inflorescentiis cymosis terminalibus ; capitulis
paucis 8-9 mm. altis heterogamis calyculatis ; involucris campanulatis
tomentosis, squamis ca. 13 lineari-lanceolatis 6-7 mm. longis ; flori-
bus femineis ligulatis 8-12, corollis glabris flavis ; floribus disci ca.
35 quam squamis involucri vix longioribus ; achaeniis hispidulis. —
^lountains near Saltillo, Coahuila, Mexico, alt. 2133 m., 5 October,
1905, C. G. Pringle, no. 13,676 (type, in hb. Gray). This species is
related to *S'. umhracuUferus Watson, but differs amply in foliar char-
acters, especially in having thinner leaf-texture, glabrate upper leaf-
surface, and more distinctly amplexicaul upper leaves.

11. NEW OR OTHERWISE NOTEWORTHY SPERMATO-
PHYTES, CHIEFLY FROM MEXICO.
By B. L. Eobinson.

Tigridia morelosana Robinson, n. sp., bulbo ovoideo acurainato 4-
6 cm. longo 2-3.2 cm. diametro atrobrunneo, radicibus fibrosis; caule
gracillimo flexuoso 3 dm. alto saepissime 1-2-foliato glabro modice
compresso ; foliis basilaribus anguste lanceolato-linearibus attenuatis
plicato-nervosis ca. 3 dm. longis ca. 8 mm. latis utrinque viridibus
glabris laevibus ; foliis caulinis linearibus vel anguste spathiformibus ;

22 PROCEEDINGS OF THE AMERICAN ACADEMY.

spathis saepissime 2 longipedunculatis 3-6-floris, foliolis oblongo-lance-
olatis acutissimis 2-4 cm. longis margine tenuibus subscariosis ; pedi-
cellis gracillimis 2-3 cm. longis glabris ; sepalis purpureis 14 mm.
longis 6 mm. latis anguste obovatis obtusis basi angustatis in media
parte atromaculatis ; petalis ovatis 12 mm. longis acutiusculis cordatis
brevissime stipitatis supra mediam partem purpurascentibus tenuibus
infra mediam partem flavescentibus firmiusculis 6 mm. latis ; columna
4 mm. alta ; antheris oblongis apiculatis in summa columna sessilibus ;
ramis styli 6 filiformibus antberas subaequantibus. — Sierra de Te-
poxtlan, Morelos, Mexico, alt. 2350 m., 5 September, 1905, C. G.
Prbigle, no. 13,657 (type, in bb. Gray).

Amaranthus squamulatus Robinson, n. comb. Sderopus squam-
ulatus Anderss. Om Galapagos-oarnes Veg., Stockb. Akad. Handl.
1853, 162 (1854), & Om Galapagos-oarnes Veg. 60 (1859). Sderopus
squarriUosus Anderss. ex Gray, Proc. Am. Acad. v. 169 (1861), by cler-
ical error. Amhlogijne squarralosa Gray, 1. c (1861). AmaraiUhus
squarridosus Uline & Bray, Bot. Gaz. xix. 170 (1894) ; Rob. & Greenm,
Am. Jour. Sci. 1. 147 (1895); Rob. Proc. Am. Acad, xxxviii. 136
(1902).

Schoepfia Pringlei Robinson, n. sp., fruticosa vel arborescens 5 m.
alta ramosa ; ramis teretibus leviter flexuosis a cortice griseo rugoso
tectis ; ramulis plus minusve angulatis fuscescenti-puberulis ; foliis al-
ternis coriaceis ovato-lanceolatis obtusis vel acutiusculis vel etiam
falcato-acuminatis integerrimis opacis utrinque viridibus glaberrimis
subtus vix pallidioribus obscure pinnatinerviis 4-5.5 cm. longis 1.5-2.3
cm. latis ; basi cuneatis brevissime petiolatis ; pedunculis axillaribus 4
mm. longis puberulis cupulas 2-4 plus minusve racemosas gerentibus,
pedicellis vix ullis ; cupulis puberulis saepissime 2-partitis, lobo majore
obscure 2-3-dentato floram solitariam subtendente ; calyce carnoso
rugoso turbinato ; corolla extus glaberrima 6 mm. longa 5-6 mm. di-
ametro viridescenti-flava, tubo 4 mm. longo subgloboso, lobis 5 ovato-
deltoideis acutiusculis 3 mm. longis recurvis ; staminibus 5 ; filamentis
omnino corollae adnatis ; antberis breviter oblongis albidis ; eorum in-
sertionibus pubentibus ; ovario fere supero, parte libera ovoidea sub-
carnosa ruguloso-papillosa ; stylo 3.3 mm. longo ; stigmate disciformi
obscure 3-lobato; fructu ignoto. — Uruapan, Micboacan, Mexico, alt.
1525 m., 1 November, 1905, C. G. Prlngle, no. 10,123 (type, in bb. Gray).
Tbis species differs in its much larger corolla and more lanceolate leaves
from the plant of the West Indies and Florida, which has generally
passed as S. Schreherl Lam. or S. arborescens R. & S. From S. mexi-
cana DC. (known to the writer only from description) it appears to dif-
fer in its leaves, which are often fully twice as long as those described

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 23

by DeCandolle and in its decidedly urceolate almost globose rather
than cylindric corolla ; also in the fact that the corolla-lobes are more
than half as long as the tube. S. x'at'vifoUa Planch., to judge from
Nelson's n. 1836, so identified at the Royal Gardens at Kew, has a
much more slender corolla. S. angulata Planch, is described by Hems-
ley, Biol. Cent. -Am. Bot. i. 185, as having flowers only one and one-
half lines long and branches angled, while in the present species the
branches are terete and even the branchlets are scarcely angled, the
flowers being furthermore fully 3 lines long. The genus, however, is
much in need of a thorough revision.

Mimosa (§ Habbasia) buceragenia Robinson, n. sp., valde armata
3-5 m. alta ; ramulis viridibus albido-costatis puberulis in costis acu-
leatis ; aculeis sparsis recurvatis 4 mm. longis basi albidis compressis
4-5 mm. latis apice brunnescentibus induratis ; foliis 10-12 cm. longis
5-6 cm. latis ; petiolo et rhachibus et rhachillis breviter molliterque
pubescentibus ; petiolo 2 cm. longo supra cum gland ulo conspicuo ob-
longo sessili ca. 2 mm. longo instructo subtus cum aculeo saepius uno
armato ; rhachi aculeis 2-3 parvis instructa ; stipulis binis subulato-
filiformibus ca. 3 mm. longis erectis ; pinnis ca. 11-jugis; foliolis ca.
25-jugis linearibus utrinque viridibus glabris acutiusculis 4-5 mm.
longis ca. 0.8 mm. latis saepe leviter falcatis basi valde obliquis ;
floribus virescentibus spicatis ; spicis densis saepissime in axillis binis
pedunculatis ca. 4.5 cm. longis 8 mm. diametro ; calyce cupulato
brevissime 5-dentato ; petalis 5 anguste lanceolatis; staminibus 10;
ovario stipitato ; fructu ignoto. — Valley near Treinte Station, in the
vicinity of Cuernavaca, Morelos, Mexico, alt. 1220 m., 26 September,
1905, C. G. Pringle, no. 10,073. A species which, to judge from its in-
florescence, belongs in the series LeiJtostachyae, but well marked in this
series by its conspicuous petiolar glands.

Pedilanthus spectabilis Robinson, n. sp., caulibus teretibus eras-
sis foliosis griseis minute granuloso-pulveruHs vix 1 m. altitudine ;
foliis ovato-oblongis brevissime crassiusculeque petiolatis 8-9 cm.
longis 4-6 cm. latis integris supra glabriusculis subtus breviter molli-
terque pubescentibus apice rotundatis saepissime retusis distincte
mucronulatis basi breviter cordatis ; inflorescentia terminali dichotoma
bracteosissima densiuscula ca. 1.6 dm. lata; bracteis late ovatis cor-
datis sessilibus oppositis integris 4-5 cm. longis et latis internodia
valde superantibus acute acuminatis caudato-attenuatis utrinque puber-
ulis rubro-purpureis margine tomentellis ; pedicellis griseo-tomentosis ;
involucro albido 18 mm. longo basi leviter invaginato, labio superiore
profunde bipartite, lobis linearibus acutiusculis 6-7 mm. longis quam
labio inferiore multo brevioribus margine tomentellis ; stipite ovarii

24 PROCEEDINGS OF THE AMERICAN ACADEMY.

glabro nutanti ; filamentis glabris ; stylo 1 cm. longo ; capsula ca. 1 cm.
diametro obtuse 3-lobata subsphaerica ; seminibus viridescenti-griseis
angulatis 6 mm. longis. — Canon walls of limerock, Iguala Caiion,
near Iguala, Guerrero, Mexico, alt. 760 m., 28 December, 1906, C. G.
Pringle^ no. 13,914 (type, in hb. Gray). This noteworthy species is
probably the most showy of the genus. It differs from P. bracteatus
(Jacq.) Boiss. in having pubescent leaves, denser inflorescence, and
larger much more caudate-acuminate and strongly colored bracts.

Bonplandia linearis Robinson, n. sp., herbacea ramosa dense caes-
pitosa gracilis 4 dm. vel ultra alta ubique glanduloso-pubescens ; ramis
erectis vel ascendentibus ; foliis alternis anguste linearibus 3-4.5 cm.
longis vix 2 mm. latis sessilibus attenuatis cum lobis lateralibus 2 an-
gustis late patentibus instructis; racemis erectis laxifloris 1-1.5 dm.
longis ; floribus saepissime geminis in pedicellis erectis ca. 1 cm. longis
nutantibus ; calyce tubuloso 15-striato et venoso-reticulato anthesi 8
fructifero 11 mm. longo leviter curvato paulo nigrescenti, dentibus
lanceolato-deltoideis acutis ; corolla cyanea ca. 2 cm. longa ; tubo gra-
cili ad orem calycis leviter deflexis ; lobis anguste obovatis retusis late
patentibus ca. 12 mm. longis ; filamentis subaequalibus glabris longe
exsertis ; stylo filiformi glabro, ramis stigmatiferis 3 linearibus papil-
losis 1.2 mm. longis; ovario ovoideo glabro. — Lava fields, near Corn
Station, above Uruapan, Michoacan, Mexico, 26 January, 1907, C. G.
Pringle, no. 10,364 (t)q)e, in hb. Gray). This species obviously belongs
to the hitherto monotypic genus Bonplandia. It differs strikingly from
the common B. geminiflora Cav. in its narrowly linear leaves.

Brittonastrum Barberi Robinson, n. sp., herbaceum 4-6 dm. vel ul-
tra altum ; caulibus gracilibus suberectis simplicibus basi rubescentibus
alibi pallide viridibus ubique crispe griseo-puberulis ; foliis ovato-lance-
olatis crenatis obtusis vel superioribus acutis vel etiam subattenuatis
2-3.5 cm. longis 1-2 cm. latis subtus pallidioribus utrinque crispe griseo-
puberulis superioribus distantibus ; petiolis 2-5 mm. longis ; inflore-
scentia anguste paniculata 8-22 cm. longa 5 cm. diametro superne
densiuscula ; bracteis inferioribus lanceolatis subsessilibus 1-1.5 cm.
longis superioribus valde reductis ; inflorescentiis secundariis ascen-
dentibus multifloris griseo-puberulis vel -pulverulis inferioribus plus
minusve distantibus ; bracteolis subulatis minimis et pedicellis pur-
purascentibus ; calyce anguste tubulato anthesi deorsum attenuate
fructifero deinde turgido 10-12 mm. longo pulcberrime purpureo
griseo-puberulo et atomifero, dentibus lanceolatis parvis acutis erectis
1.5-2 mm. longis; corolla molliter puberula anguste tubulata' leviter
curvata 2.6 cm. longa, limbo valde ringenti, labio superiore erecto sub-
■cucullato inferiore deflexo ca. 2 mm. longo; staminibus juxta labium

KOBINSOX. — NEW SPERMATOPHYTES, CHIEFLY FROJI MEXICO. 25

superius exsertis. — Near Colonia Garcia in Sierra Madres, Chihuahua,
Mexico, alt. 221»0 m., 17 July, 1899, C. H. T. Toicnsend d'- C. M. Bar-
ber, no. 79 (type, in hb. Gray). Previously collected in imperfect speci-
mens at Los Pinitos, Sonora, Mexico, alt. 2000 m., 11 October, 1890,
C. V. Hartman, no. 122 (hb. Gray), and in southwestern Chihuahua,
August to November, 1885, Dr. E. Palmer, no. FF in part. This
species differs from the nearly relaited B. neo-mexlcanum Briq. in its
much longer corolla, more pedicellate flowers, shorter petioles, etc.,
from B. canum (Gray) Briq. in its shorter pedicels, longer less acutely
toothed calyx, etc., from B. paUidum (Lindl.) Briq. by its ovate-lance-
olate relatively narrower leaves, longer deep crimson calyx, and longer
corolla.

Brittonastrum ionocalyx Robinson, n. sp., herbaceum ; caulibus
quadrangularibus breviter molliterque canescenti-puberulis ; foliis del-
toideo-ovatis sinu patulo cordatis grosse crenatis obtusis 3-5.5 cm.
longis 2.5-4 cm. latis ubique molliter puberulis supra pallide viridibus
subtus vix pallidioribus albo-nervosis, petiolo 6-10 mm. longo ; inflo-
rescentia 11-17 cm. longa terminali 5-6 cm. diametro densiuscula;
bracteis infimis ovatis serrato-dentatis ca. 1 cm. longis, ceteris gradatim
minoribus ; cymis furcatis compositis minute granuliferis vel glanduloso-
puberulis ; floribus erectis vel paulo nutantibus ; calyce cylindrato pul-
cherrime purpureo griseo-puberulo et atomifero anthesi 1 cm. longo
fructifero vix accrescenti dentibus lanceolatis acutis 2 mm. longis erectis
nee patulis nee induratis ; corolla purpureo-coccinea 2.5 cm. longa
leviter curvata externe molliter puberula, faucibus vix dilatatis, limbo
ringenti, labio superiore erecto, inferiore pendulo ; staminibus sub labio
superiore modice exsertis. — Sandia Station, Durango, Mexico, alt.
2288 m., 15 October, 1905, C. G. Pringle, no. 10,146 (type, in hb.
Gray). This species differs from B. pallidum (Lindl.) Briq. in its deep
purple calyx and much more exserted corolla, as well as in its more
compound inflorescence ; from B. coccineum (Greene) Briq. in its much
shorter calyx-teeth ; from B. hetonicoides (Lindl.) Briq. in its much
shorter petioles ; and from the real B. mexicanum (HBK.) Briq. in its
very different foliage. To B. ionocalyx should be referred with scarcely
a doubt Wright's no. 1532 from mountains east of Santa Cruz, Sonora,
which appears to differ only in the fact that the leaves are a trifle less
cordate at base.

Brittonastrum Palmeri Bobinson, n. sp., herbaceum a basi hori-
zontali radicanti erectum 6-9 dm. altum ; caule unico simplici acute
quadrangulari saepius flexuoso vel torto ubique breviter crispeque
griseo-puberulo ; foliis deltoideo-ovatis grosse crenatis acutiusculis vel
subacuminatis utrinque griseo-tomentellis vel glabriusculis subtus paulo

26 PROCEEDINGS OF THE AMERICAN ACADEMY.

pallidioribus 3-6 cm. longis 2.4-3.6 cm. latis basi cordatis; petiolis
4-10 mm. longis ; iiiflorescentia terminal! ca. 1.5 dm. longa interrupte
spiciformi, verticellastris inferne subremotis superne approximatis densis
multifloris, cymulis brevibus densissimis, bracteis inferioribus foliaceis
ovatis vel ovato-lanceolatis 2-2.5 cm. longis petiolatis superioribus
lanceolatis vel linearibus ; pedicellis brevissimis purpureis griseo-
puberulis, calyce subcylindrato anthesi 1 cm. longo puberulo inferne
viridi superne laete purpureo vel violaceo, dentibus argutissimis
lineari-lanceolatis ca. 3 mm. longis maturitate subiuduratis saepe cur-
vatis plus minusve patentibus ; corolla purpurea gracili griseo-puberula
apicem versus deorsum curvata 2 cm. longa, labiis brevibus superiore
subgaleato ; staminibus breviter exsertis. — Alvarez, San Luis Potosi,
Mexico, 5-10 September, 1902, Dr. Edward Palmer, no. 53 (type, in
hb. Gray), distributed as Cedronella mexicana Benth. Previous col-
lections of what appears to be the same species have been made as
follows : Mexico, without precise locality, Sumichrast (hb. Gray), Coul-
ter, no. 1078 (hb. Gray) ; in mountains near Morales in valley of San
Luis Potosi, 1876, Schaffner, no. 682 (hb. Gray) ; region of San Luis
Potosi, 1878, Parry & Palmer, no. 762 (hb. Gray). This species
differs clearly from B. meximnum (HBK.) Briq. in its deltoid-ovate
leaves, shorter corolla, etc. It appears to differ in the same respects
from B. cocdneum (Greene) Briq., known to the writer from descrip-
tion, ■■ — a characterization which fails to convince the reader that
B. Goccineum is distinct from the real B. mexicanum. B. Palmeri
differs from B. betonicoides (Lindl.) Briq. in its much shorter petioles,
longer calyx-teeth, etc.

Brittonastrum Wrightii (Greenman) Robinson, n. comb. Cedro-
nella Wrkjht'd Greenman, Proc. Am. Acad. xli. 244 (1905). The sep-
aration of the American simple-leaved species of Cedronella as a new
genus Brittonastrum now generally accepted necessitates the transfer
of Dr. Greenman's excellent species C. Wrightii.

Russelia Pringlei Robinson, n. sp., caulibus subsimplicibus 1 m.
vel ultra longitudine teretibus ca. 8-costatis niveo-tomentosis ; inter-
nodiis 5-6 cm. longis ; ramis elongatis gracilibus 4-6-angulatis griseo-
tomentosis ; foliis oppositis vel ternis inaequalibus lanceolato-ovatis
1.5-2 cm. longis 6-10 mm. latis acutatis basi subcuneatis serrato-den-
tatis supra viridibus crispe puberulis et squamiferis rugosis subtus
pallidioribus densius squamiferis et praesertim in venis nervisque
griseo-tomentellis ; inflorescentia 3-4 dm. longa 3-4 cm. lata ; cymulis
oppositis vel ternis ; verticellis 3-5 cm. distantibus ; pedicellis fili-
formibus griseo-pubescentibus 3-4 mm. longis ; calycis 5 mm. longi
lobis ovato-lanceolatis caudato-acuminatis dorso squamiferis ; corolla

ROBINSON. — NEW SPERM ATOPHYTES, CHIEFLY FROM MEXICO. 27

coccinea tubiformi 16 mm. longa glaberrima, lobis rotundatis 1.5 mm.
longis ; capsula ovoidea acuminata 6 mm. longa glabra. — On vertical
walls of limerock, Iguala Canon, near Iguala, Guerrero, Mexico, 28
December, 1906, C. G. PrhujU, no. 10,367 (type, in hb. Gray). A
species peculiar in its terete canescent-tomentose stem.

Stemodia macrantha Robinson, n. sp., suffrutescens 1 m. vel ultra
alta ; caulibus decumbentibus gracilibus teretibus pubescentibus ; ramis
saepius simplicibus erectis vel ascendentibus viridibus patenter pilosis
3-6 dm. longis, internodiis 3-10 cm. longis ; foliis lanceolato-ovatis
utroque angustatis 5-6 cm. longis 2.5-3 cm. latis basi cuneata excepta
crenato-serratis supra atroviridibus adprease pilosis subtus paulo palli-
dioribus in costis et venis lateralibus pinnatis hirsutulis ; petiolis 1 cm.
longis hirsutulis superne alatis ; inflorescentia terminali 1-4 dm. longa
perlaxa folioso-bracteata, pedicellis filiformibus flexuosis glanduloso-
pubescentibus unifloris 2-4 cm. longis ascendentibus ex axillis brac-
tearum saepissime ternis vel quaternis orientibus ; calycis laciniis
glanduloso-pulverulis et hispidulis lanceolato-linearibus superioribus
anthesi usque ad 7 mm. longis infimis paulo brevioribus omnibus a
basi gradatim angustatis sed apice vero obtusiusculis ; corolla 1.8-2
cm. longis, tubo viridi-flavescenti cylindrato ca. 13 mm. longo 4 mm.
diametro purpureo-nervio intus externeque piloso ad fauces distincte
sursum curvato, limbo laete purpureo, lobis suborbicularibus subae-
qualibus apice saepissime retusis ; staminibus brevioribus mediae parti
tubi affixis 3 mm. longis longioribus paulo supra basin tubi affixis
8 mm. longis omnibus inclusis antheriferis glabris ; capsula ovoidea
5 mm. longa atrobrunnea a calyce persistenti circumdata. — Shaded
bluffs of the deep barranca, near the foot of the Falls of Tzararacua,
below Uruapan, Michoacan, Mexico, 28 January, 1907, C. G. Pringle,
no. 10,356 (type, in hb. Gray). This species is amply distinguished
from its Mexican congeners by its much larger flowers, which in fact
are decidedly showy for the genus.

Lobelia Nelsonii Fernald, var. fragilis Eobinson & Fernald, n. var.
a forma typica recedit foliis utrinque viridibus juventate sparse pilo-
sulis mox omnino glabratis lineari-lanceolatis multo brevioribus, maxi-
mis ca. 7 cm. longis 8-10 mm. tantum latis. — Mexico, C. G. Pringle,
no. 10,360 (type, in hb. Gray). This variety shares with the typical
form the soft woody stems and branches as well as- all the more impor-
tant characteristics of the inflorescence. The varietal name is suggested
by the extreme brittleness of the branches, at least when dried. The
variety, like the tyi)ical form, has numerous showy flowers with bright
scarlet corolla. Both plants seem worthy of cultivation.

Piqucria (Subg. Phalacraea) longipetiolata Robinson, n. sp.,

28 PROCEEDINGS OF THE AMERICAN ACADEMY.

repens subglabra ; caule tenui flexuoso prostrate nodis radicante, inter-
uodiis saej^ius perlongis (ad 1 dm.) glabris aiigulato-costatis ; foiiis
oppositis, limbo late ovato 1.8-3.5 cm. longo 1.2-2.7 cm. lato supra
basin integram crenato-dentato supra viridi sparse bispidulo subtus
paulo pallidiore glabro basi obtuso vel breviter acuminato apice obtuso,
petiolo obcompresso (dorsoventraliter) limbum longitudine aequante ;
capitulis parvis ca. 9-tloris cymosis, cymis ca. 7-13-capituliferis termi-
nalibus ; involucri campanulati squamis ca. 6 obovatis viridibus obtusis
ciliatis 3 mm. longis ; corollae tubo proprio brevi glanduloso-puberulo,
faucibus campanulatis quam tubo longioribus subglabris, limbi denti-
bus 5 late ovatis obtusis ; acbaeniis immaturis siirsum hispidulis basi
rectiusculis. — Colombia, near R. Flautas, R. Paez Valley, Tierra Aden-
tro, Central Cordillera, alt. 2900 m., 26 January, 1906, H. Pittier, no.
1208 (hb. U. S. Nat. Mus. ; fragment in hb. Gray). This species stands
nearest P. calUtricha Robinson, Proc. Am. Acad. xlii. 15 (1906), but
differs in having smaller more coarsely and simply toothed leaves with
much longer petioles. It is also a smoother plant and has fewer-
flowered heads.

Stevia alatipes Robinson, n. sp., herbacea perennis ca. 1 cm. alta
hirsuta ; radice fibrosa ; foiiis radicalibus ovatis vel obovatis crenato-
serratis ca. 8 cm. longis 4-5 cm. latis pinnatinerviis utrinque hirsutis
baud vel vix punctatis apice rotundatis basi angustatis in petiolum
alatum decurrentibus ; foiiis caulinis oppositis 2-4-jugis oblanceo-
latis vel fere spatulatis in petiolum alatum basi attenuatis ; intioresceutia
laxissime pauciramosa ; ramis nudiusculis, capitula pauca parva sacpo
aggregata ferentibus ; bracteis 7 mm. longis lanceolatis sessilibus her-
baceis ; pedicellis ad 1 cm. longis filiformibus glanduloso-puberulis ;
capitulis ca. 12 mm. longis 4-floris ; involucri squamis 5 viridibus lan-
ceolato-linearibus acutis inaequalibus ca. 7 mm. longis ; corollis 7 mm.
longis, tubo viridescenti puberulo, limbo albo ; acbaeniis nigrescentibus
3.2 mm. longis minute puberulis ; pappo e squamis 3 brevibus albis et
aristis 3 albidis 5-6 mm. longis barbellatis composito. — Pine forests,
Uruapan, Michoacan, Mexico, alt. 1680 m., 14 November, 1905, C. G.
Pringle, no. 10,124 (type, in hb. Gray). Near S. elatior HBK. but
readily separable by its much larger basal leaves with long-attenuate
base, its aggregated heads, etc.

Stevia Lozanoi Robinson, n. sp., caule tereti purpureo pilis crispis
griseis brevibus pubescenti supra laxe ramoso folioso ; ramis divergenti-
ascendentibus subsimplicibus gracilibus ca. 1 dm. longis foliosis in
corymbos subdensos capitiformis terminantibus ; foiiis inferioribus
ignotis, superioribus linearibus sessilibus alternis integris 4-5 cm. longis
3-7 mm. latis utrinque obscure viridibus punctatis 1-3-nerviis sparse

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 29

pubesceiitibus margine saepe purpurascenti-hispidulis apice obtusis basi
attenuatis ; corymbis 3-4 cm. diametro convexis 10-20-capitulatis ; ca-
pitulis 1.5 cm. lougis breviter pedicellatis vel etiam sessilibus, bracteis
linearibus 3-6 mm. longis herbaceis ; squamis involucri ca. 6 linearibus
acutis purpureis 7 mm. longis pilis crispis atomisque resinosis tectis ;
flosculis 5 ; corollis 8 mm. longis, tube purpureo pubescenti gradatim a
basi sursum leviter ampliato, limbo albo patenti 5-lobo, lobis oblongis
obtusiusculis ; achaeniis gracilibus 5 mm. longis sursum praesertim in
angulis hispidulis ; pappo e squamulis 5 albidis brevissimis et aristis 5
purpureis divergentibus scabratis composito. — Sandia Station in moun-
tains of northwest Durango, Mexico, alt. 2290 m., 12 October, 1905,
C G. Pringle, no. 10,092 (type, in hb. Gray). A species evidently re-
lated to S. laxijiora DC. and S. serrata DC, but readily distinguished
by its numerous separate dense corymbs and entire leaves. Named for
Sr. Filemon L. Lozano, faithful and efficient companion and assistant
of Mr. Pringle in his recent journeys to ^Mexico.

Stevia Plummerae Gray, var. durangensis Robinson, n. var., foliis
tenuibus lanceolato-oblongis 6-9 cm. longis 1.5-2 cm. latis supra mediam
partem serratis nee dentatis supra pilis brevissimis crispis griseo-puber-
ulis subtus molliter pubescentibus ; corollis albis. — Barranca below
Sandia Station, Durango, Mexico, alt. 2135 m., 13 October, 1905, C. G.
Pringle, no. 10,106 (type, in hb. Gray). Nearer var. alba Gray, Syn.
Fl. i. pt. 2, 92, than to the typical form, but differing in its thinner
larger less strongly reticulated and much more pubescent leaves.

Eupatorium acutidentatum Robinson, n. sp., herbaceum erectum
6 dm. altum ; caule gracili tereti striato viridi vel purpurascenti crispe
puberulo subsimplici vel modice oppositirameo ; foliis oppositis ovato-
lanceolatis tenuibus argute serrato-dentatis basi cuneata et apice at-
tenuato integris a basi 3-5-nerviis 3.6-5 cm. longis 1.8-2.2 cm. latis
supra laete viridibus scabriusculis subtus vix pallidioribus in nerviis
sparse pubescentibus, petiolo puberulo ca. 5 mm. longo ; capitulis ca.
12-floris 1 cm. longis numerosis graciliter pedicellatis in corymbos valde
convexos collectis, pedicellis 5-8 mm. longis griseo-puberulis ; invo-
lucri squamis anguste oblongis vel lanceolatis attenuatis herbaceis
griseo-puberulis inaequalibus laxe imbricatis interioribus quam flosculis
dimidio brevioribus ; corollis albis glabris, tubo proprio gracili quam
faucibus gradatim sed valde ampliatis distincte breviore ; achaeniis
nigrescentibus 3 mm. longis prismaticis deorsum paululo angustatis
sursum hispidulis ; pappi setis minute barbellatis corolla fere aequi-
longis basin versus roseis. — Barranca below Sandia Station, Durango,
Mexico, alt. 2135 m., 15 October, 1905, C. G. Pringle, no. 10,095 (tyi^e,
in hb. Gray). This species is obviously close to E. betulaefolium

30 PROCEEDINGS OF THE AMERICAN ACADEMY.

(Greene) Robinson, n. comb. {Kyrstenia hetulaefoUa Greene, Leafl. i.
10, 1903.) It differs, however, in having decidedly narrower leaves,
which are entire at the attenuate apex ; the bracts are also of different
form, being narrowly lanceolate, quite entire, and strongly attenuate ;
furthermore the involucral scales are of a more herbaceous texture.
Whether these distinctions will prove constant cannot be foretold ; but
on the whole they appear rather too significant to permit the placing
of the present plant under E. hetulaefoUam as a variety.

Eupatorium campechense Robinson, n. sp., subglabrum ; ramis
teretibus striatulis glaberrimis lignescentibus modice medullosis ; foliis
oppositis petiolatis lanceolatis attenuatis saepe falcatis 3-nerviis crassi-
usculis nitidulis 8-10 cm. longis 2.4-3 cm. latis glabris vel in nerviis
primariis obscure puberulis subremote serratis ; petiolo ca. 1 cm. longo
obcompresso supra canaliculato glabro vel papilloso ; inflorescentiis
amplis oppositirameis ; capitulis numerosis ca. 5-floris graciliter pedi-
cellatis subdense corymbosis ; ramulis paniculae et pedicellis gracil-
limis puberulis ; involucri squamis 5-stachyis imbricatis stramineis
glaberrimis obtusis, extimis brevissimis ovatis ca. 1 mm. longis inter-
mediis gradatim longioribus ovato-oblongis, intimis (numero ca. 5)
anguste oblongis 7 mm. longis ; corollis tubulosis sine faucibus dis-
tinctis 6 mm. longis, dentibus limbi ca. 1 mm. longis lanceolatis re-
curvatis ; achaeniis prismaticis 5-angulatis fuscis in faciebus et in
costis pubescentibus 3.3 mm. longis deorsum modice angustatis ; pappi
setis ca. 20 levibus albidis 4-5 mm. longis. — Apazoli near Yohaltun,
Campeche, Mexico, 30 December, 1900, E. A. Goldman, no. 504 (type,
in hb. U. S. Nat. Mus. ; fragments in hb. Gray). A species well marked
and apparently without close ally.

Eupatorium chrysostyloides Robinson, n. sp., herbaceum sub-
erectum 1.3-4 dm. altum pilis crispis griseis brevibus hinc inde glan-
duliferis puberulum ; caule solitario modice curvato vel flexuoso obtuse
angulato pallide viridi folioso, in parte inferiore subsimplici ; foliis
oppositis longe petiolatis concoloribus viridibus nee lucidis late del-
toideo-ovatis 3-6 cm. longis 2.4-5 cm. latis obtusis vel modice acutis
grosse crenato-dentatis basi subtruncatis 3-nerviis in petiolum breviter
decurrentibus ; petiolo 1-4.5 cm. longo ; corymbis rotundatis multi-
capitulatis densiusculis ramos terminantibus ; pedicellis filiformibus
griseo-pubescentibus ; capitulis ca. 20-floris ca. 1 cm. longis 6 mm.
diametro ; involucri turbinato-cylindrati squamis numerosis anguste
lanceolatis viridibus palhde nervatis hispidulis acutissimis valde inae-
qualibus multiseriatis ; corollis viridi-albidis angustissimis brevissime
5-dentatis, faucibus nullo modo ampliatis ; styli ramis longissimis aureis
valde exsertis ; achaeniis 5-angulatis prismaticis 2.5 mm. longis basi

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 31

angustatis albo-callosis sursum paulo hispidulis, pappi setis ca. 25
laete albis minute barbellatis. — On limerock, Sierra Madre, above
Monterey, Mexico, alt. 915 m., 27 April, 1906, C. G. Pringle, no. 10,231
(type, in hb. Gray). This species belongs to a small but increasing
group of very nearly related plants, including E. Parrjil Gray,
E. chrysostylum Robinson, and E. sphenopodum Robinson. From all
these species, the present one differs in its exceedingly short crisped
pubescence.

Eupatorium durangense Robinson, n. sp., herbaceum 6-9 dm.
alt am ; caule tereti oppositirameo folioso purpurascenti ubique minu-
teque crispo-puberulo ; foliis oppositis ovatis deflexis breviter petio-
latis firmiusculis obtusis vel vix acutis paulo supra basin 3-5-uerviis
supra viridibus pilosellis subtus vix pallidioribus leviter reticulato-
venosis in nervis venisque sparse pubescentibus serratis 2-3 cm. longis
1.3-2.2 cm. latis scabrido-ciliolatis, petiolo puberulo supra concavo
2-3 mm. longo ; capitulis ca. 12-floris numerosis in corymbis convexis
terminalibus collectis, pediceliis 5-12 mm. longis filiformibus griseo-
puberulis ; involucri squamis pallide viridibus griseo-puberulis oblongo-
linearibus acutis valde inaequalibus sed laxe imbricatis interioribus ca.
4-5 mm. longis ; coroUis albis 6-7 mm. longis, tubo proprio gracili
fauces gradatim sed distincte ampliatos subcylindratos subaequanti;
achaeniis nigris gracilibus 5-angulatis in angulis sursum hispidulis ;
pappi setis simplicibus corollam aequantibus superne laete albis basin
versus roseis. — Barranca below Sandia Station, Durango, Mexico, alt.
2135 m., 15 October, 1905, C. G. Pringle, no. 10,096 (type, in hb.
Gray).

Var. angustius Robinson, n. var., foliis angustioribus ovato-lance-
olatis attenuatis maximis 3.2 cm. longis 1.7 cm. latis supremis saepe
alternantibus. — Mesa de Sandia, northwestern Durango, Mexico, alt.
2745 m., 14 October, 1905, C. G. Pringle, no. 10,097 (type, in hb.
Gray). This variety has something the appearance of E. Eobinsoni-
anum Greene, but may be readily distinguished by its more herba-
ceous involucre, thickish more pubescent and regularly deflexed leaves,
shorter stouter petioles, etc.

Eupatorium erythrocomum Robinson, n. sp., sufFrutescens laxe
procumbens ; caulibus tenuibus teretibus arcuatis ramosis atropurpu-
reis striatulis plerumque ca. 2 mm. diametro cum pilis moniliformibus
adpresse villosulis ; foliis oppositis ovatis vel ovato-lanceolatis breviter
petiolatis, limbo 2-2.8 cm. longo 1-1.2 cm. lato supra basin subrotun-
datam integram argute serrato apice acuto 3-nervio supra viridi glabri-
usculo subtus saepissime purpurascenti praesertim in nervis venisque
adpresse pilosis, petiolo tereti purpureo ca. 2 mm., longo, venis supra

32 PROCEEDINGS OF THE AMERICAN ACADEMY.

impressis, dentibus limbi utroque ca. 5 ; capitulis ca. 30-floris paucis
4-11 in corymbo terminali, pedicellis ca. 1 cm. longis erectis vel ascen-
dentibus subfiliformibus atropurpureis adpresse villosulis, bracteis
linearibus ; involiicri campanulati squamis ca. 15 lanceolati-linearibus
subaequalibus vix imbricatis obtusis vel acutiusculis pilosis ca. 5 mm.
longis margine praesertim apicem versus pulcherrime ciliatis ; corollis
albis 4 mm. longis, tnbo proprio gracili fauces ampliatos subcylindratos
subaequanti, dentibus limbi 5 acutiusculis hispido-pilosis ; achaeniis
prismaticis praesertim in angulis breviter hispidulis ; pappi setis pul-
cherrime roseis. — Steep rocks, Ixtaccihuatl, Mexico, alt. 2440 m.,
January, 1906, C. A. Pur pus, no. 1578 (type, in hb. Gray). This
attractive species of Ewpator'mm was submitted to the writer by Mr.
T. S. Brandegee. It approaches E. pruneUifoUum HBK., but differs
in its slender flexuous procumbent stems, and more evenly and sharply
serrate leaves, which are essentially glabrous above. E. oligocephalum
DC, an imperfectly known species, may also be of this affinity ; but it
is described as having glabrous involucral scales.

Eupatorium hospitals Robinson, n. sp., arboreum ; ramis 6-angu-
latis striatis molliter lignosis medullosis glabris ; foliis oppositis lance-
olato-oblongis serratis vel subintegris petiolatis penninerviis utrinque
glabris crassis siccitate nigrescentibus pellucide punctatis liiieolatis-
que caudato-acuminatis basi attenuatis 16-18 cm. longis 5-6 cm. latis ;
panicula terminali pyramidata oppositiramea patenter ramosa obsolete
pilosiuscula vel glabra multicapitulata ; capitulis in summis partibus
ramulorum sessilibus parvis ca. 6-floris ; squamis involucri valde inae-
qualibus, interioribus oblongis obtusis 5 mm. longis paucis caducis-
simis, exterioribus multo brevioribus imbricatis dorso margineque
pilosiusculis apice rotundatis persistentibus aetate patentibus ; flos-
culis vero similiter albidis vel viridescentibus ; corollis 4 mm. longis,
tubo proprio gracili, faucibus cylindratis saepius vix ampliatis ; achae-
niis ca. 3 mm. longis brunneis acute 5-angulatis basi attenuatis in
faciebus concavis pilosis ad angulos etiam hispidulis ; pappi setis sor-
didis ca. 35 corollam subaequantibus. — E. vanillosmoides Hemsl., Biol.
Cent. -Am. Bot. ii. 102 (1881), not Sch. Bip. ex Bak. in Mart. Fl. Bras. vi.
pt. 2, p. 346 (1876). — Mirador, Vera Cruz, Mexico, Liehmann, no. 43
(type, in hb. Gray), Sartorius (hb. Gray) ; Orizaba, Mexico, October,
1855, Hchaffmr (hb. Gray), Botteri, no. 613 (hb. Gray). This well
marked species appears never to have been described. The plant in
question has been repeatedly distributed as Eupatorium vanillosmoides
Sch. Bip., but the species to which Schultz really gave this name was
a Brazilian plant of entirely different affinity, referred by Mr. Baker
(Fl. Bras. vi. pt. 2, p. 346) to the synonymy of E. pyrifoUum DC. It

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 33

is true Schultz well knew the Mexican plant, and ascribed to it the
same specific name {canillosmoides), but under another generic name.
In describing this hitherto ancharacterized Mexican plant it seems
unwise to take up the nomen nudum E. vanillosmoides Hemsl., a name
inadvertently ascribed by Mr. Hemsley to Schultz, although, as we
have seen, Schultz used this binominal combination for quite a differ-
ent plant of Brazil. To avoid probable confusion the Mexican plant is
herewith given a new and distinctive name. The designation chosen
is suggested by the fact that some of the internodes below the inflo-
rescence are often swollen, hollowed, and provided with a somewhat
regular rounded ingress for small insects, probably ants. These en-
largements are not always present, and are doubtless of the nature of
galls developing through insect irritation, and later serving as nesting
places for the insects.

Eupatorium hymenolepis Kobinson, n. sp., gracile patente ramo-
sum ; caule tereti nigrescenti obsolete strigilloso ; ramis gracillimis
fiexuosis ; foliis oppositis longe petiolatis ovatis vei rhomboideis basi
abrupte angustata acuta excepta grosse serratis apice caudato-attenuatis
6-7.5 cm. longis 2-3.5 cm. latis tenuibus utrinque viridibus in nervis
adpresse pilosiusculis subtus baud pallidioribus supra sparse strigillo-
sis ; cymis parvis 6-l()-capitulatis graciliter pedunculatis saepissime
nutantibus ; capitulis parvis 3.5 mm. longis ca. 18-floris ; involucri
companulati squamis valde inaequalibus albo-scareosis in media parte
tantum viridi-striatis, interioribus lineari-oblongis obtusissimis, exterior-
ibus brevioribus acutis vel acuminatis ; coroliis albis 2.5 mm. longis
glabris basin versus modice angustatis ; dentibus 5 ovato-deltoideis
brevibus patentibus ; styli ramis albis paulo clavellatis ; achaeniis ni-
gris 5-angulatis 1.3 mm. longis basi albo-callosis sursum minute his-
pidulis, costis albidis ; pappi setis gracillimis ca. 20 corolla distincte
brevioribus. — Falls of Tzararacua, near Uruapan, Mexico, 28 January,
1907, C. G. Pringle, no. 10,355 (type, in hb. Gray). This species
somewhat resembles E. hjmenoplujllum Klatt, but has slightly firmer
leaves 3-nerved from the very base instead of from a point somewhat
above the base ; it differs also in its involucre. From E. Gonzalezii
Robinson, to which it also bears some resemblance, it may be readily
distinguished by its more attenuate leaves and scarious involucral
scales.

Eupatorium isolepis Robinson, n. sp., suffruticosum ; caulibus te-
retibus fiexuosis oppositirameis brunneo-purpureis pubescentibus, pilis
moniliformibus transverse purpureo-striatis ; foliis oppositis graciliter
petiolatis ovatis acuminatis serratis tenuibus subpellucidis subconcol-
oribus supra glabris subtus in nervis sparse pilosis penninerviis basi

VOL. XLIII. 3

34 PROCEEDINGS OF THE AMERICAN ACADEMY.

rotundatis paululo in petiolum saepe subdecurrentibus 3-6.5 cm. longis
1.6-4 cm. latis; petiolo 1-4 cm. longo subtus convexo subglabro supra
canaliculato villoso ; capitulis 9 mm. longis 6 mm. diametro 20-floris
numerosis ad apices ramorum glomerato-aggregatis, corymbis rotun-
datis densiusculis ca. 4 cm. diametro ; pedicellis filiformibus puberulis
2-6 mm. longis ; involucri campanulati squamis ca. 10 elliptico- vel obo-
vato-oblongis aequilongis apice rotundatis saepius pulcherrime ciliatis
dorso pubescentibus 3.2 mm. longis 1.5 mm. latis pallide viridibus ;
corollis albis, tubo proprio gracili 2 mm. longo glabro, faucibus cam-
panulatis giabris, dentibus limbi 5 deltoideis pilosiusculis ; antheris
vix connatis apice longe appendiculatis ; achaeniis nigrescentibus 5-
angulatis 1.5 mm. longis sursum praesertim in angulis hispidulis apice
cupula albida coronatis ; pappi setis capillaribus vix barbellatis laete
albis vel saepissime pulcherrime roseis corollam fere aequantibus ca-
ducis. — Open moist places, rocks of barranca, Ixtaccihuatl, Mexico, alt.
2440 m., C. A. Parpus, no. 1496 (type, in hb. Gray) ; also in the Valley
of Mexico, Schaffner, no. 201 (hb. Gray). This species differs from E.
pazciiarense HBK. in its very obtuse involucral scales ; from E. photinum
Robinson, in its thin pubescent less attenuate leaves. It is perhaps
most nearly related to E. Schaffneri Gray, but it differs from that
species in its more attenuate-acuminate and more regularly serrate
leaves which are pinnately veined, while in E. Schaffneri they are
palmately nerved from the very base.

EuPATORiUM PHOENicoLEPis Robinson, var. guatemalensis Robinson,
n. var., foliis quameis formae typicae multomajoribus 12-14 cm. longis
9-10 cm. latis tenuioribus cordatis supra scabriusculis subtus in nervis
venisque laxiuscule pubescentibus nee tomentosis; involucri squamis
et floribus necnon achaeniis formae typicae simillimis. — Vol. Atitlan,
Department of Solala, Guatemala, alt. 2500-2700 m., 16 February,
1906, W. A. Kellerman, no. 5199 (type, in hb. Field Museum of Natural
History ; fragment in hb. Gray) ; between Patahil and San Lucas, De-
partment of Solala, Guatemala, 15 February, 1906, W. A. Kellerman,
no. 5194 (hb. Field Mus.).

Eupatorium saltillense Robinson, n. sp., fruticosum 9-15 dm.
altum oppositirameum ; rarais teretibus late patentibus arcua,to-ascen-
dentibus a cortice brunneo-griseo obtectis foliosis ; foliis ovatis tenuibus
translucentibus integris vel obsolete serratis vel plus minusve distincte
serrato-dentatis vix discoloribus supra sparse pilosulis obscurissime
punctatis vel omnino epunctatis subtus minute glanduloso-punctatis et
praesertim in nervis venisque puberulis apice obtusis vel obtusiusculis
numquam attenuatis basi angustatis in petiolo decurrentibus et margine
saepissime revolutis, limbo 4-5.8 cm. longis 2.3-3.3 cm. latis, nervis

ROBIXSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 35

subtus albidis prominulis, venis lateralibus utrinque ca. 5 inaequidis-
tantibus maximis supra basin orientibus ; petiolis 5-8 mm. longis levi-
ter marginatis basi linea transversa connexis ; inflorescentiis corymbosis
valde convexis oppositirameis multicapitulatis ; bracteis inferioribus
petiolatis ovatis foliis similibus sed multo minoribus superioribus
anguste linearibus sessilibus ; pedicellis rectis filiformibus patenti-
ascendentibus pilis crispis obtectis ; capitulis parvis numerosissimis
saepissime 5-floris S mm. longis ; squamis involucri ca. 8 linearibus
vix imbricatis sordide puberulis acuiiusculis interioribus 4-5 mm.
longis extimis 1-3 multo brevioribus ; coroUis glabriusculis 4.6 mm.
longis albidis vel roseis, tubo proprio gracili quam faucibus subcylindratis
breviore, dentibus limbi ovato-deltoideis ; achaeniis nigris prismaticis
griseo-puberulis 3 mm. longis ; pappi setis praesertim basi pulcberrime
roseis corollam vix aequantibus. — Mountains near Saltillo, Coabuila,
Mexico, alt. 2135 m., 5 October, 1905, C. G. Princjle, no. 10,080 (type,
in bb. Gray). Tbis species is obviously related to E. mkranthum Less.
It differs, however, in many small characters. The leaves are thin and
translucent while in E. micranthum they are thickish and quite opaque.
In E. salt'dlense they are also much broader relatively to their length
and not attenuate. The nervation is furthermore quite different, for
in E. micranthum the lateral veins leave the midnerve in a pretty reg-
ular pinnate fashion, while in E. saltUlense they are less numerous and
less regular and give the leaves somewhat the appearance of being 3-
nerved from a point above the base.

Eupatorium sexangulare (Klatt) Robinson, n. comb. Piptocaiyha
se.rangularis Klatt, Botanisches Beiblatt zur Leopoldina, 1895, p. 1.
Mr. H. A. Gleason, during a recent examination of the Yernonieae in
the Gray Herbarium, called my attention to the type of Dr. Klatt's
Piptocarpha sexangularis, which appeared wholly irreconcilable with
the genus in which it had been placed and indeed with any other genus
of the Vernonieae. Unfortunately the specimen, although showing well
the stem, leaves, inflorescence, involucral scales, etc., has but very few
flowers, and these have been so damaged by decay or insects that it is
impossible to state precisely the form of the anthers or style-tips ; nev-
ertheless there can be no doubt that the plant is a Eupatorium, and as
it appears to be unlike any species previously referred to that genus, it
may be simply transferred thither. In its sharply angled stem and
large thickish lanceolate leaves it bears considerable resemblance to the
plant here described as E. hospitale. It may be readily distinguished,
however, by the different venation of the leaves, entirely glabrous
achenes, etc.

Eupatorium sphenopodum Robinson, n. sp., herbaceum oppositi-

36 PROCEEDINGS OF THE AMERICAN ACADEMY.

rameum molliter hirsutum, pilis longis patentibus plus minusve monili-
formibus albis viseidulis inaequalibus ; foliis oppositis deltoideis vel
ovato-deltoideis longe petiolatis late cordatis grosse duplicateque cren-
ato-dentatis tenuibus utrinque praesertiin subtus in nervis pubescenti-
bus, limbo 11-12 cm. longo 8-10 cm. lato, petiolo sursum alato ca. 7 cm.
loiigo birsuto ; pauicula oppositiramea ; capitulis ca. 11-lioris 10-11 mm.
longis 4-5 mm. diametro ; pedicellis gracilibus rectis valde inaequalibus
2-12 mm. longis ; involucri squamis lanceolatis attenuatis peracutis
3-4-seriatis valde imbricatis viridibus albo-nerviis hispidulis adpressis ;
corollis angustissime tubulosis 3.5 mm. longis viridiscenti-albidis,
faucibus vix ullis; dentibus limbi brevissimis erectis ; styli ramis valde
exsertis aurantiacis vel maturitate brunnescentibus valde clavatis ;
achaeniis fuscis prismaticis 2.7 mm. longis deorsum modice angustatis
basi callosis plus minusve curvatis in faciebus et in costis sursum his-
pidulis ; pappi setis inaequalibus ca. 20 vix scabratis laete albis co-
rollam fere aequantibus. — On shaded cliffs of limerock, Sierra Madre,
above Monterey, Mexico, 1000 m. alt., 16 July, 1906, C. G. Pr ingle, no.
10,259 (type, in hb. Gray). This species is closely related on the one
hand to E. chrysostylimi Robinson and on the other to E. Parryi Gray.
From the former it differs in its more slender freely branched less pu-
bescent stems, large bluntly toothed leaves and much longer pedicels.
From E. Parryi it differs in having much larger leaves (of which
even the uppermost are opposite), winged petioles, and smaller fewer-
flowered heads.

Eupatorium thyrsiflorum (Greene) Robinson, n. comb. Kyrstenia
thyrsijiora Greene, Leatl. i. 9 (1903). The genus Kyrstenia Neck.
does not seem to the writer in any way satisfactorily separable from
Eupatorium. When all species are duly considered the two groups
appear to merge by imperceptible gradations. There seems, however,
to be little doubt that Professor Greene's K. thyrsijiora is specifically
distinct and may be appropriately transferred to the older genus.
From the more typical material of the species, with leaves in varying
degree toothed and somewhat narrowed at the base, the following plant
may be varietally separated.

Var. holoclerum Robinson, n. var., foliis ovatis integris vel obsolete
crenato-serratis basi fere rotundatis. — Near the city of Durango,
Mexico, April to November, 1896, Dr. E. Palmer, no. 755 (type, in hb.
Gray). Distributed as E. occidentale, var. arizonicum Gray.

Eupatorium triangulatum Alam. ex DC. Prod. v. 172 (1836). After
a careful examination of the types of this species in the DeCandoUean
herbarium at Geneva, and of E. ruhricaule HBK. at the Museum of
Natural History at Paris, the writer can find no differences of moment.

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 37

DeCanclolle does not appear to have seen the plant of Humboldt and
Bonpland, and the distinctions on which he attempted to separate
E. triangulatum were deduced from the description of Kunth, but on
comparison of the plants themselves these distinctions do not appear
to be definite or important. The species should certainly be united and
stand under the older name E. rubricaule HBK.

Brickellia betonicaefolia Gray, PI. Wright, ii. 72 (1853). In the
typical form of this rather variable species the leaves are ovate-oblong
and tlat, the larger 6 cm. long, 3 cm. wide ; petioles very short, scarcely
over 2 mm. long ; longer scales of the involucre rather attenuate.

Var. HUMiLis Gray, 1. c. Leaves ovate-oblong, flat, essentially sessile,
the largest 3.8 cm. long, 1.5 cm. wide; longer scales of the involucre
linear, attenuate. '^

Var. elliptica Robinson, n. var., foliis late ellipticis planis 3-4 cm.
longis 1.8-0 cm. latis subsessilibus ; squamis involucri atropurpureis
interioribus lanceolati-linearibus attenuatis. — Barranca below Sandia
Station, Durango, Mexico, alt. 2135 m., 13 October, 1905, C. G. Prlngle,
no. 10,102 (type, in hb. Gray).

Var. conduplicata Bobinson, n. var., caule 6-9 dm. alto ; foliis 2-3
cm. longis 1.4-1.8 cm. latis saepissime conduplicatis ; petiolo gracile
4-5 mm. longo ; squamis involucri interioribus oblongi-linearibus atro-
purpureis vix attenuatis. - — San Luis Potosi, Mexico, on rocky hills,
San Jos6 Pass, 16 August, 1890, C. G. Pringle, no. 3171 (distributed as
B. betonicaefolia Gray T). Mountains near General Cepeda, Coahuila,
Mexico, alt. 1920 m., 7 October, 1905, C. G. Pringle, no. 10,081 (type,
in hb. Gray).

Brickellia saltillensis Bobinson, n. sp., caulibus teretibus 9-12 dm.
altis gracilibus striatulis pallide viridibus vel leviter purpurascentibus
molliter breviterque pubescentibus foliosis ; foliis alternis petiolatis in
axillis proliferis, laminis late ovatis obtusis vel subacutis serratis tenui-
bus utrinque viridibus brevissime pubescentibus basi rotundatis 4-5.5
cm. longis 2-4 cm. latis a basi 3-nerviis laxe reticulato-venosis ; petiolo
1-1.4 cm. longo pilis crispis glanduloso-puberulo ; foliis parvis ellipticis
2-4 in axillis ; panicula angusta 7-30 cm. longa 4-7 cm. diametro fol-
ioso-bracteata ; cymulis saepissime 3-capitiilatis ; pedicellis gracillimis
filiformibus glanduloso-puberulis nutantibus ; capitulis ca. 14-floris 1.8
cm. longis ; involucri subturbinati squamis exterioribus viridibus striatis
lanceolatis attenuatis dorso puberulis, interioribus lanceolati-linearibus
attenuatis purpureo-tinctis 1-1.2 cm. longis ; corollis albidis angustis-
sime tubulosis 8-9 mm. longis glabris, faucibus nullis, limbi dentibus
brevissimis erectis ; styli ramis nigrescentibus vix clavatis longe ex-
sertis; achaeniis columnaribus 4.5 mm. longis adpresse pubescentibus

38 PEOCEEDINGS OF THE AMERICAN ACADEMY.

fuscis basi callosis, pappi setis ca. 22 aequalibus tenuibus laete albis 5
mm. longis vix scabratis. — On mountains, Saltillo, Mexico, alt. 2135
m., 5 October, 1905, C. G. Pringle, no. 10,082 (tjq^e, inhb. Gray).

Lagascea helianthifolia HBK., var. adenocaulis Robinson,
n. var., caule (3-4 m. alto) usque ad summam partem dense glandu-
loso-puberulo nee piloso ; foliis longiuscule oblanceolato-oblongis at-
tenuatis supra scabris subtus paulo pallidioribus molliter tomentellis. —
Hedgerows, Uruapan, Micboacan, Mexico, 24 January, 1907, C. G.
Pringle, no. 13,907 (type, in bb. Gray). A transition between this
variety and the typical spreading-pilose form is shown by L. C. Smith's
no. 964 from the mountains of San Juan del Estado, Oaxaca.

Lagascea helianthifolia HBK., var. levior Robinson, n. comb.
Noma helianthi folia Cass., var. levio7- Robinson, Proc. Am. Acad,
xxxvi. 468 (1901).

Lagascea helianthifolia HBK., var. suaveolens Robinson, n.
comb. L. suaveolens HBK. Nov. Gen. et Spec. iv. 25 (1820)' Nocca
helianthifolia Cass., var. suaxeolens Robinson, 1. c.

Lagascea Palmeri Robinson, n. comb. Nocca Palmeri Robinson,
1. c. 471 (1901).

Lagascea Pringlei Robinson, n. comb. Nocca Pringlei Robinson,
1. c. 469 (1901).

Guardiola Palmeri Robinson, n. sp., glaberrima atroviridis com-
pacte ramosa foliosa 3.5 dm. alta basi lignescens ; caulibus teretibus
striatulis gracilibus, ramis oppositis ascendentibus ; foliis oppositis
petiolatis ovatis vel subreniformibus integerrimis vel plus minusve
repandis nee angulatis nee dentatis 1.5-3 cm. longis 1.2-2.8 cm. latis
utrinque leviter reticulato-venosis subtus vix pallidioribus apice rotun-
datis basi late cordatis, petiolo 5-7 mm. longo ; inflorescentiis in api-
cibus ramorum folioso-bracteosis 1-3-capitulatis ; pedicelHs 3-7 mm.
longis ; capitulis 12-14 mm. longis 6-8 mm. diametro ; involucri sub-
cylindrati fusoo-viridis 1 cm. longi 4-5 mm. crassi squamis oblongis
obtusiusculis striatulis leviter convexis nullo modo carinatis ; radiis
ca. 3 ; corollae tubo gracili glaberrimo 5 mm. longo, ligula elliptica
4 mm. longa 2.2 mm. lata bidentata alba; achaeniis immaturis con-
cavo-convexis obovato-oblongis 4.6 mm. longis glabris ; floribus disci ca.
10 gracillimis, tubo corollae ca. 9 mm. longo, faucibus brevissimis
campanulatis, lobis limbi 5 lineari -oblongis obtusis recurvatis albis ;
filamentis albis tomentosis quam antherae virides multo brevioribus. —
Outer circle of mesas, Otinapa, Durango, Mexico, alt. about 2450 m.,
25 July-5 August, 1906, Dr. E. Palmer, no. 377 (type, in hb. Gray).
This species in its few scattered heads, broad clearly petiolate leaves,
and unkeeled involucral scales, closely approaches G. Rosei Robinson ;

KOBINSON. — NEW SPERMATOPIIYTES, CHIEFLY FROM MEXICO. 39

but it differs from that species in its decidedly smaller untoothed
leaves, which are rounded at the apex.

Zinnia tenella Robinson, n. sp., erecta gracilis annua tenuiter pilis
subappressis griseis in novellis copiose pubescens in parte inferiore
simplex supra saepissime 3-5-ramea 1.5-2.7 dm. alta; foliis tenuibus
lanceolatis integris utrinque viridibus appresso-puberulis et sparse
atomiferis obtusiusculis 3-nerviis patentibus vel deflexis basi cuneatis
brevissime petiolatis 1.5-3.5 cm. longis 4-10 mm. latis; capitulis sae-
pissime 1-5 terminalibus graciliter pedunculatis erectis ca. 7 mm. diam-
etro (ligulis exclusis) aequi-altis ; involucri campanulati squamis paucis
(ca. 8) late oblongis obtusissimis subaequalibus appressis tenuiter
appresso-puberulis ca. 5 mm. longis ; ligulis ca. 5 patentibus late ob-
longis aurantiacis extus prope apicem saepe viridi-striatulis vel reti-
culatis minutissime puberulis et granuliferis 7.5 mm. longis 5-6.5 mm.
latis ; achaeniis florum liguliferorum obovatis concavo-convexis margine
ciliatis in summa parte bidentatis 4 mm. longis (immaturis) ; corollis
florum (ca. 15) disci 3 mm. longis sursum leviter ampliatis infra lim-
bum brevissimum aurantiacum plus minusve purpureo-lineatis ; paleis
tenuibus ovato-oblongis acutis carinatis ciliolatis apice saepissime au-
rantiacis ; achaeniis obovatis. — Very common on grassy plains and
hills, Tejamen, Durango, Mexico, alt. about 2135 m., 21-27 August,
1906, Dr. E. Palmer, no. 500 (type, in hb. Gray). This species resem-
bles in many respects Z. linearis Benth. It differs, however, in having
broader leaves and a more slender erect and simple habit. It is espe-
cially to be distinguished from the related species by its fewer subequal
iuvolucral scales.

Cymophora Robinson, n. gen., Compositarum HeliantMearum.
Capitula homogama parva cymosa ; disco parvo leviter convexo ;
paleis lanceolato-oblongis acutis carinatis flosculos amplectentibus.
Involucrum anguste campanulatum, squamis paucis ovato-oblongis
obtusis saepe mucronulatis subherbaceis striatis subaequalibus. Co-
rollae tubulosae, tubo proprio brevissimo, faucibus cylindratis, limbo
vel aequaliter 5-dentato vel flosculorum exteriorum plus minusve
irregulari sed vix radiatiformi. Antherae connatae basi obtusae vel
obscure sagittato-auriculatae apice distincte appendiculatae. Styli
rami breves recurvato-patentes filiformes graciliter et distincte appeti-
diculati, appendicibus capillaribus rectis ca. 0.1 mm. longis. Achae-
nia anguste obconica pilis curvatis longiusculis albis villosa, pappo
nullo. — Herba annua pubescens et glandulifera ; foliis oppositis late
ovatis subintegris ; corollis albis ; antheris purpureis.

C Pringlei Robinson, n. sp., caulibus laxe oppositeque ramosis
patente pilosis 3-4 dm. altis ; ramis arcuato-curvatis vel flexuosis

40 PROCEEDINGS OF THE AMERICAN ACADEMY.

teretibus ; foliis tenuibus a basi 3-nerviis breviter petiolatis, limbo
late ovato integerrimo vel obsolete repandoobtusiusculo 2-6 cm. longo
1.6-4 cm. lato utrinque sparse adpresseque pilosis supra viridi subtus
pallidiore basi obtuso saepissime obliquo ; cymis compositis laxis glan-
duloso-pubescentibus ; capitulis ca. 10-floris 7 mm. longis 3.5 mm.
diametro ; pedicellis filiformibus rectis glanduloso-puberulis 6-10 mm.
longis ; involucri squamis ca. 6 subaequalibus (una vel duabus extimis
valde minoribus exceptis) pallide viridibus striatis convexis nee cari-
natis ; achaeniis nigrescentibus 2.2 mm. longis 0.6 mm. diametro
ubique villosis apice rotundatis plus minusve margine squamacea
cupulata coronatis. — Iguala Canon, Guerrero, Mexico, alt. 760 m.,
22 September, 1905, C. G. Pr ingle, no. 10,068 (type, in hb. Gray).

This plant appears to stand near Eleutheranthera, with which it
shares many characters. It differs, however, markedly in its anthers,
which are appendiculate and connate, in its non-accrescent involucre,
and densely puberulent achenes. Furthermore in Eleuthcranthera
the achenes have a nipple- shaped contracted summit which is here
lacking.

Perymenium globosum Robinson, n. sp., caule quadrangulato
griseo-brunneo angulis rotundatis faciebus sulcatis, internodiis 7-9 cm.
longis ; foliis oppositis petiolatis ovato-oblongis serratis rugosis acumi-
natis basi rotundatis vel abrupte breveque cuneatis supra scabris
strigillosis subtus vix pallidioribus scabriusculis in nervis venisque his-
pid ulo-pubescentibus 8-12 cm. longis 4-5 cm. latis, petiolo 1.8 cm.
longo flexuoso supra canaliculato ; capitulis corymbosis, corymbis com-
positis 8-18 cm. latis ; bracteis inferioribus foliaceis, bracteolis lineari-
subulatis 3-5 mm. longis, pedicellis filiformibus flexuosis 1-2 cm. longis
adpresse griseo-pubescentibus ; involucri squamis ovatis acutis viridi-
bus ca. 3 mm. longis ; disco valde convexo ; flosculis liguliferis ca. 7,
ligulis linearibus aureis patentibus 6-8 mm. longis; paleis oblongis
conduplicatis apice vix acutiusculis flavidis ; capitulis fructiferis de-
presso-globosis 8 mm. diametro ; achaeniis disci obovatis crassiusculis
atrobrunneis plus minusve bullatis 2 mm. longis 1 mm. latis glabris a
basi styli conica indurata coronatis ; pappi aristis ca. 15 flavidulis in-
aequalibus plerisque 1 mm. longis. — Uruapan, Michoacan, Mexico,
C. G. Prlngle, no. 10,354. This species is nearly related to P. cerbesi-
noides DC, but differs in having broader and less attenuate pales,
greener involucral scales, and leaves 3-nerved not from the base but
from a point nearly 1 cm. above the base.

Verbesina montanoifolia Rob. & Greenm., var. leptopoda Robin-
son, n. var., pedicellis subaequalibus quam eis formae typicae longioribus
(ca. 1 cm. longis) et gracilioribus ; capitulis paulo minoribus. — By

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 41

Streams, Tarascon, Mexico, 28 October, 1905, C. G. Pringle, no. 10,118
(type, in hb. Gray). According to note of Mr. Pringle this variety grows
to a height of 3-4.5 m.

Verbesina pedunculosa Robinson, n. comb. Actinomeris peduncu-
losa DC. Prod. v. 576 (1836). Verbesina Capitaneja Nees, Linnaea,
xix. 729 (1S47) ; Rob. & Greenm. Proc. Am. Acad, xxxiv. 540 (1899).

Verbesina pleistocephala Robinson, n. comb. Encelia pleistoce-
phala J. D. Smith, Bot. Gaz. xiii. 189 (1888), & Eniim. PI. Guat. i. 22
(1889). Verbesina Donnell-Smithii Coult. Bot. Gaz. xx. 50 (1895) ;
J. D. Smith, Enum. PL Guat. iv. 88 (1895); Rob. & Greenm. Proc.
Am. Acad, xxxiv. 556 (1899).

Coreopsis Pringlei Robinson, n. sp., fruticosa ramosa ; ramis tereti-
bus a cortice ochraceo-griseo obtectis ; ramulis striatis viridibus plus
minusve 6-angulatis foliosis ; foliis oppositis petiolatis bipinnatifidis
pallide viridibus glaberrimis vel vix pilosiusculis 2-4 cm. longis 1-3 cm.
latis, segmentis patentibus angustissime linearibus leviter acutatis in-
tegris vel cum lobis secundariis paucis similibus instructis 4-16 mm.
longis 0.6-0.8 mm. latis ; capitibus terminalibus solitariis vel ad 3-5
corymbosis pedunculatis erectis vel nutantibus 3 cm. latis (ligulis pa-
tentibus inclusis) ; pedunculis 1-4 cm. longis nudis vel in media parte
cum bractea unica lineari instructis ; involucri campanulati squamis
exterioribus ca. 8 herbaceis lineari-oblongis 3-5 mm. longis 1 mm.
latis apice rotundatis basi pilosiusculis, squamis interioribus ovato-
oblongis subscariosis acutatis ca. 6 mm. longis striatis flavido-brunneis ;
ligulis ca. 8 juventate supra aureis subtus flavidis maturitate laete
flavis oblongis ca. 1.2 cm. longis 4-6 mm. latis, nervis atrobrunneis ;
paleis linearibus pallidis brunneo-lineolatis apice obtusis eroso-ciliatis ;
achaeniis disci linearibus valde obcompressis in facie interiore et in
marginibus valde villosis in facie exteriore subglabris 5 mm. long's
(vix maturis) ; pappi aristis 2 pallidis villoso-plumosis attenuatis 3-4
mm. longis. — Dry ledges, San Juan del Rio, Queretaro, Mexico, alt.
1920 m., 8 September, 1905, C. G. Pringle, no. 10,050 (type, in hb.
Gray). This species is related to C. rhyacophila Greenman, but differs
in its linear-oblong round-tipped outer involucral scales and much
narrower leaf-segments, as well as in its shorter petioles and more
decidedly ligneous stem.

Tridax platyphylla Robinson, n. sp., herba perennis laxe ramosa
pubescens ; caulibus teretibus viridibus vel purpurascentibus striatulis
pubescentibus ; foliis membranaceis oppositis petiolatis supra basin 3-
nerviis, lamina late ovata 6.3-11.5 cm. longa 4.5-10 cm. lata dentata vel
leviter 3-lobata supra viridi sparse pubescenti cum pilis basi tuberculo-
incrassatis subtus vix pallidiore in nervis appresso-pubescenti apice

42 PROCEEDINGS OF THE AMERICAN ACADEMY.

acuta vel obtusiuscula vel brevissime acuminata basi cuneato-attenaata ;
capitibus laxe corymbosis longe pedicellatis radiatis, disco leviter con-
vexo ; involucri squamis paucis subaequalibus ovatis vel late oblongis
acutis herbaceis hirsutulis ca. 7 mm. longis ; flosculis disci numerosis,
corollis anguste tubulosis aurantiacis 7 mm. longis externe glabris,
tubo proprio brevi basi ampliato ; faucibus multo longioribus paulo et
gradatim amplioribus 5-nerviis, limbi dentibus 5 brevibus ovato-lanceo-
latis acutiusculis apice puberulis ; achaeniis turbinato-cylindricis 2.8
mm. longis sericeis, pappi setis plumosis numerosis attenuatis plus
minusve inaequalibus ca. 2.6 mm. longis ; flosculis radiatis 5, ligulis
albis late oblongis vel suborbicularibus patentibus apice 3-dentatis
6-10 mm. longis. — River ledges, Balsas Station, alt. 600 m., 27 Sep-
tember, 1905, Guerrero, Mexico, C. G. Pringle, no. 10,075 (type, in hb.
Gray). This species is habitally similar to T. tenuifoUa Rose, which,
however, has smaller leaves and pappus decidedly longer than the
achenes.

Galinsoga filiformis Hemsl., var. epapposa Robinson, n. var.,
habitu foliis inflorescentia, etc., formae typicae simillima ; achaeniis
omnino epapposis apice annulo albido inconspicuo coronatis ; foliis caul-
inis quam eis formae typicae paululo minoribus. — San Ram6n, Du-
rango, Mexico, 21 April- 18 May, 1906, Dr. E. Palmer, no. 127 (type,
in hb. Gray). This puzzling plant, which according to the notes of the
collector was found in numbers, much dried, on stony ridges among
trees and bushes, differs in its lack of pappus from any other Galinsoga.
Its otherwise close correspondence with G. filiformis, however, would
seem to show that it is merely a new instance of a calvous form of an
ordinarily pappus-bearing species. Similar cases are familiar in sev-
eral neighboring genera, e. g. Calea, Jaegeria, etc. The phenomenon
seems to present an ecological problem of interest, and it is to be hoped
that collectors who have an opportunity to study these plants in the
field may bear the matter in mind and endeavor to learn the conditions
which determine the presence and absence of pappus in these in other
respects essentially identical forms.

Flaveria bidentis Robinson, n. comb. Ethulia hidentis L. Mant. i.
110 (1767). Flaveria chilensis Gmel. Syst. 1269 (1796); Johnston,
Proc. Am. Acad, xxxix. 285 (1903). Milhria Contrayerba Cav. Ic. PI.
i. 2, t. 4 (1791). The author has examined the type of Ethulia bidentis
in the Linnaean Herbarium and finds that, as given in the Index Kew-
ensis, it is the plant which has long passed as Flaveria Contrayerba.
The Vienna rules of nomenclature require the restoration of the earlier
specific name.

Pericome macrocephala Robinson, n. sp., griseo-pulverula vel

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 43

puberula oppositiramea ; caulibus fragilibus subteretibus leviter
angulato-striatis glabriusculis brunneis paulo lignescentibus ; foliis
triangulari-hastatis 5-6 cm. longis 4-5 cm. latis caudato-attenuatis sub-
integris basi abrupte cuneatis, auriculis subacuminatis, petiolo gracili
2-2.7 cm. longo ; inflorescentiis corymbosis termiualibus 6-8 cm. latis
subplanis 9-15-capitulatis ; pedicellis gracilibus rectis vel leviter arcuatis
sursum modice incrassatis pubescentibus 1-2 cm. longis ; capitulis 1.7
cm. longis 1.2 cm. diametro homogamis multitlosculosis; involucri cupula
ovoideo-subcylindrata 1.2-1.4 cm. longa griseo-puberula multistriata
deutibus brevissimis caudiformibus plus minusve patentibus ; corollis
laete flavis 1 cm. longis, tubo proprio gracillimo 3 mm. longo glandu-
loso-puberulo, faucibus anguste tubulosis sursum paululum ampliatis,
dentibus limbi 4 brevibus ovato-oblongis obtusis ; achaeniis nigrescen-
tibus anguste oblongis valde compressis margine et apice fimbriato-
ciliatis. — A showy plant growing in large masses on talus in moun-
tains near San Ram6n, Durango, Mexico, 21 April-18 May, 1906, Dr.
E. Palmer, no. 69 (type, in hb. Gray). In habit and floral struc-
ture this species closely approaches P. caudata Gray, but differs from
it conspicuously in having heads nearly twice as large. The form of
the involucre also is different, being ovoid-subcylindric in the species
here described while it is considerably more campanulate in P.
caudata.

Loxothysanus Robinson, n. gen , Compositarum Helenkarum.
Capitula homogama. Involucrum campanulatum vel turbinatum,
squamis paucis uniseriatis aequalibus plerumque obovatis vel oblance-
olatis acutis vel saepissime obtusiusculis herbaceis puberulis. Recep-
taculum parvum planiusculum onustum. Flosculi modice numerosi
tubulosi hermaphroditi fertiles. Corollae albidae, tubo proprio gracili
puberulo vel glandulifero fauces campanulatas subaequante, limbo 5-
lobato. Styli rami breves recurvati filiformes vix infra apicem incras-
sati brevissime et obtusiuscule appendiculati. Antherae basi breviter
sagittato-auriculatae apice obtuse appendiculatae. Achaenia gracilia 5-
angulata sursum hispidula deorsum longiuscule angustata. Pappi
squamae 5-8 oblongae erosae eis in margine exteriore achaenii quam aliis
valde brevioribus. — Frutices humiles vel suffrutices ramosi erecti vel
procumbentes. Capitula pauca mediocra axillaria vel laxe corymbosa.
Flosculi vel omnes regulariter 5-dentati vel exteriores obscure subbila-
biati. Folia opposita petiolata, limbo ovato vel orbiculari paucilobato
vel vix crenato. (Nomen a Ao^o?, obliquus, et ^uo-avos, fimbriae, pap-
pum unilateraliter abbreviatum designat.)

L. sinuatus (Less.) Robinson, n. comb., foliis ovatis sinuatis pler-
umque 3-lobatis basi obtusis vel subtruncatis vel late cordatis ; capitulis

44 PROCEEDINGS OF THE AMERICAN ACADEMY.

corymbosis ; involucri squamis ca. 12 oblanceolatis acutis vel acutius-
culis. — Bahia sinuata Less. Linnaea, v. 160 (1830). B. nejjetaefoUa
Gray, Proc. Am. Acad. v. 184 (1861). — On rocky soil in Central and
Southern Mexico. The following specimens have been examined. On
cliffs near Hacienda de la Laguna, Schiede, no. 358 (hb. Berlin, frag-
ments in hb. Gray) ; between San Luis Potosi and Tampico, Palmer,
no. 1090 (hb. Gray) ; bare mountain ledges, Tamasopo Canon, San Luis
Potosi, Pringle, no. 3096 (hb. Gray) ; Wartenburg near Tantoyuca,
prov. Huasteca, Ervenberg, no. 65 (hb. Gray) ; steep banks of barrancas,
Zacuapan, Vera Cruz, Purjyus, no. 1862, in part (hb. Gray).

L. fllipes Robinson, n. sp., fruticulus gracillimus procumbens ra-
mosus ; ramis curvato-ascendentibus foliatis breviter pubescentibus ;
foliis graciliter petiolatis, limbo suborbiculari 1-1.8 cm. diametro cre-
nato supra viridi obscure tomentello subtus incano-tomentello ; petiolo
1-1.5 cm. longo filiformi flexuoso puberulo ; capituHs ca. 30-floris ax-
illaribus ; pedunculo 2-3.5 cm. longo filiformi; involucri subturbinato-
campanulati squamis ca. 7 obovatis obtusiusculis anthesi ca. 3 mm.
longis ; corollis 2.8 mm. longis, tubo proprio gracili glanduloso-puberulo
ca. 1 mm. longo, faucibus campanulatis limbum fere aequantibus ;
pappi squamis interioribus ca. 0.4 mm. longis exterioribus 0.2-0.3 mm.
longis ; achaeniis 2.8 mm. longis deorsum valde angustatis. — Steep
banks of barrancas, Zacuapan, Vera Cruz, Mexico, May, 1906, Pur pus,
no. 1862, in part (type, in hb. Gray).

This plant, which was sent to the writer by Mr. T. S. Brandegee,
proves to be a near relative and evident congener of the problematic
species originally decribed as Bahia sinuata by Lessing and later rede-
scribed by Dr. Gray as B. nepetaefolia. Both plants differ from the
more typical species of Bahia in general habit, in the broad leaf-blades,
which are very shallowly if at all cleft or lobed, in the absence of rays,
and in the strongly unsymmetrical pappus. To judge from Dr. Gray's
description and notes relating to his B. nepetaefolia, he was much in-
clined to regard the plant as belonging to a separate genus and only
referred it to Bahia from a reluctance to increase the number of mono-
typic genera. The discovery by Mr. Purpus of a second plant main-
taining perfectly the generic distinctions of the first seems now to
warrant fully the recognition of the two as an independent genus.

Tagetes stenophylla Robinson, n. sp., perennis erecta usque ad
1 m. altitudine ramosa glaberrima basi suffrutescens ; caule tereti cos-
tato folioso glaucescenti ; ramis ascendentibus gracilibus in pedunculos
longos nudos apicem versus purpurascentes et modice incrassatos ter-
minantibus ; foliis 2-4 cm. longis pinnatifidis, rhachi anguste lineari,
segmentis etiam linearibus angustissimis utrinque ca. 3 acutis vel setu-

ROBINSON. — NEW SPERxMATOPHYTES, CHIEFLY PROM MEXICO. 45

liferis simplicibus vel serael lobatis, lobis similibus angustis ; pedun-
culis 5-l() cm. longis apice saepe nutantibus ; involucri anguste ovoidei
l.f) cm. longi basi rotundati vel panic turbinati pallidi vel purpureo-
tincti squamis 5 alte connatis a lineis binis glandularum linearum no-
tatis apice aureis obtiisis tomentosis ; flosculis liguliferis 5 ; ligulis
aureis obovato-oblongis 10-12 mm. longis 6-8 mm. latis apice obcor-
datis saepe obliquis ; achaeniis disci compressis lineari-oblongis nigre-
scentibus 3 mm. longis sursum strigillosis ; pappi aristis 5 connatis
quarum 2 multo longioribus apice liberis attenuatis sursum barbellatis.
— Dry soil of fields near Uruapan, Michoacan, Mexico, 25 January,
1907, C. G. Pringle, no. 10,361 (type, in hb. Gray). Tbis species bas
mucb in common witb P. UnifoUa Seaton, but differs from it in baving
more deeply colored rays and obtusisb not at all caudate-acuminate
teetb of tbe involucral cup.

Cacalia Goldsmithii Robinson, n. sp., perennis herbacea erecta, cau-
dice parvo ovoideo sursum fulvo-lanato ; caule subrecto vel leviter flex-
uoso glabro simplici gracili 1-2-foliato 6-7 dm. alto ; foliis radicalibus
louge petiolatis ovatis repando-dentatis vix lobatis 1 dm. longis 6-9
cm. latis pinnatim nervatis firmiusculis utrinque glabris laxe reticulatis
apice rotundatis basi late cordatis, dentibus cuspidatis, nervis venisque
utrinque prominulis, petiolo gracili nudo 14-16 cm. longo basi vix
dilatato ; folio caulino inferiore radicalibus simili sed minore basi obtuso
nee cordato petiolo 12 cm. longo flexuoso nee appendiculato nee au-
riculato ; folio caulino superiore multo minore oblongo dentato, petiolo
2 cm. longo basin versus modice ampliato caulem amplectente ; corymbis
compositis planis ca. 50-capitulatis ; bracteis linearibus ; capitulis ca.
13-floris contiguis ; involucri simplicis baud calyculati campanulato-
subcylindrici squamis ca. 8 oblongis 7 mm. longis 2-3 mm. latis dorso
planiusculis apice obtusiusculis ciliatis ; corollis albido-ocbroleucis 8 mm.
longis fere ad mediam partem quinquifidis, lobis oblongis obtusis ; pappi
setis sordidis tubum proprium vix superantibus ; acbaeniis compressis
breviter oblongis glabris. — On level pastures. Hacienda San Marcos,
Jalisco, Mexico, alt. about 350 m., 12 July, 1905, Rev. P. Goldsmith,
no. 8 (type, in bb. Gray). This species is probably nearest C. Palmeri
Gray, but differs in its thinner smooth ovate rather than suborbicular
leaves as well a^ in its larger more numerously flowered heads.

Cacalia Hoi wayana Robinson, n. sp., herbacea erecta 1-2 m. alta;
caule tereti medulloso striato atropurpureo glanduloso-puberulo ; ra-
dicibus carnosis ; foliis longipetiolatis orbicularibus subcentrali-peltatis
9-13-sinuato-lobatis supra laete viridibus subtus vix pallidioribus
utrinque sparse pubescentibus laxe reticulato-venosis 1.5-2 dm. diame-
tro, lobis acutis 2-4 cm. longis 1.5-5 cm. latis oblongis sinuato-

46 PROCEEDINGS OF THE AMERICAN ACADEMY.

dentatis (nee lobatis) et cuspidato-denticulatis ; petiolo 1.5-2 dm. longo
atropurpureo griseo-piloso ; inflorescentia ampla pyramidata, bracteis
inferioribus saepe petiolatis foliis similibus sed multo minoribus, brac-
teis superioribus angustissime linearibus vel subfiliformibus atropurpu-
reis glanduloso-pilosis ; capitulis numerosis in summis ramis ramulisque
nutantibus ca. lO-floris 2 cm. longis ; involucri subcylindrici calyculo
bracteolarum subfiliformium suffulti squamis lineari-lanceolatis ca. 10
ca. 1.5 cm. longis in carina atropurpurea griseo-puberulis margine albido
subscarioso levibus ; corollis 13 mm. longis glabris, tubo proprio gracili
8 mm. longo, faucibus vix ullis, limbo in lobis linearibus profuude par-
tito ; achaeniis 5 mm. longis adpresse iomentulosis ; pappi setis tenui-
bus laete albis corollam aequantibus. — ■ Uruapan, Michoacan, Mexico,
11 October, 1899, E. W. D. Holway, no. 3617 (type, in hb. Gray); 12
November, 1905, C. G. Prlngle, no. 13,672 ; in granitic soil on the
Sierra Madre of Michoacan or Guerrero, alt. 1100 m., 6 September, 1898,
E. Langlasse, no. 576. This species is near C. peltata HBK., but is
readily distinguished by its leaves, which are less deeply lobed, the
lobes not again sinuately lobed, and by the smaller exceedingly narrow
bractlets, those of C. peltata being foliaceous.

Cacalia LAEVIGATA Sch. Bip. ex Klatt, Leopoldina, xxiv. 125 (1888).
Senecio heteroideus Klatt, 1. c. (1888). Cacalia long i pet iolata Robinson &
Greenman, Am. Jour. Sci. 1. 157 (1895). When in 1895 the authors
of C. longlpetiolata characterized that species they knew C laevigata
only from Klatt's description. A drawing and some fragments of the
type of C. laevigata, subsequently received at the Gray Herbarium by
the purchase of the Klatt Herbarium, prove beyond doubt the identity
of C. long ipet iolata with C. laevigata, a correspondence which could
scarcely have been inferred from the brief and in some respects mislead-
ing characterization of C. laevigata given by Klatt.

Cacalia michoacana Robinson, n. sp., herbacea perennis pilis crispis
griseis puberula ca. 9 dm. alta ; caule simplici leviter flexuoso striato
atropurpureo medio folioso basi et apice nudiusculo ; caudice crasso
lanato ; foliis ca. 10 suborbicularibus palmato-lobatis 3-6 cm. longis
5-8 cm. latis crassiusculis utrinque reticulato-venulosis et in venis pu-
berulis supra laete viridibus subtus pallidioribus basi subtruncatis vel
latissime cordatis, lobis 5-7 brevibus triangularibus margine cuspidato-
denticulatis ; capitulis ca. 6 ramos ascendentes inflorescentiae termi-
nantibus ca. 30-floris 1.5 cm. longis 2 cm. diametro longe pedicellatis ;
involucri atropurpurei campanulato-subcylindrici squamis principalibus
ca. 15 lineari-lanceolatis dorso atropurpureis carinatis margine albis
tenuibus subscariosis, involucro basi squamis minimis calyculato ; co-
rollis 1 cm. longis, tubo proprio viridescenti gracillimo 5 mm. longo,

ROBINSON. — NEW SPERMATOPHYTES, CHIEFLY FROM MEXICO. 47

faucibus cyliudricis et limbo 5-lobato flavescentibus, lobis linearibus
recurvatis ; pappi setis laete albis tenuibus aequalibus corollam fere
aequantibus. — On pine-covered crater cone, Uruapan, Michoacan,
Mexico, alt. 1680 m., 31 October, 1905, C. G. Pringle, no. 10,117
(type, in hb. Gray). Habitally near C. laevigata Sch. Bip., but differing
conspicuously in its considerably smaller heads, narrower carinate dark
purple involucral bracts, and less deeply lobed leaves.

Perezia arachnolepis Robinson, n. sp., herbacea erecta a basi plus
minusve decumbenti 1.5 m. alta; caule tereti striato purpureo glabro
usque ad inflorescentiam perlaxam simplici ; caudice fulvo-lanato ; radi-
cibus fibriformibus duris atrobrunneis ; foliis oblanceolato-oblongis vel
oblongo-linearibus sessilibus sagittato-amplexicaulibus usque ad 1.6
dm. longis 1.7-5.8 cm. latis firmis utrinque viridibus reticulatis supra
glabris subtus vix pallidioribus sparse puberulis vel glabris argute den-
ticulatis apice acutis vel breviter acuminatis ; inflorescentia perlaxa
8-16-capitata ; capitibus ramos elongatos sursum valde squamosos ter-
minantibus ca. 3 cm. diametro ; involucro valde turbinato, bracteis
pedunculi in squamas involucri gradatim transeuntibus anguste lanceo-
latis vel linearibus apice subulatis margine arachnoideo-lanatis ; co-
rollis purpureis 1.3 cm. longis glabris; antheris etiam purpureis ;
achaeniis atrobrunneis sursum hispidulis 3 mm. longis. — Cafions,
Chapala Mountains near Guadalajara, Jalisco, Mexico, 13 December,
1889, C. G. Pringle, no. 2935 (type, in hb. Gray), and in barranca of
Rio Blanco near Guadalajara, 29 November, 1905, C. G. Pringle, no.
13,668 (hb. Gray).

Perezia lepidopoda Robinson, n. sp., precedenti valde affinis her-
bacea erecta 7-8 dm. vel ultra alta glaberrima ; caule purpureo recto
tereti striato foliosissimo in parte superiore ramos simplices valde
patentes multi-bracteatos unicapitatos gerente ; foliis anguste oblongis
vel oblongo-linearibus attenuatis acutissimis saepissime recurvatis vel
reflexis conduplicatis subcartilagineis concoloribus sessilibus sagittato-
vel hastato-amplexicaulibus argute et dupliciter sinuato-dentatis 6-13
cm. longis 8-22 mm. latis utrinque glabris viridibus reticulato-venosis,
dentibus lanceolato-subulatis 2-4 mm. longis divaricatis acutissimis ;
ramis pedunculiformibus ca. 12 cm. longis a bracteis numerosissimis
fere a basi sed praesertim apicem versus tectis, bracteis inferioribus
1-2 cm. longis anguste lanceolatis sagittatis denticulatis, superioribus
anguste linearibus peracutis adpressis hinc inde contortis in squamas
involucri gradatim transeuntibus ; capitibus (omnibus valde immaturis)
usque ad 3 cm. diametro multifloris ; involucri turbinati squamis
lineari-lanceolatis acutissimis viridibus vel purpurascentibus striatulis
obsolete puberulis. — Valley near Cuernavaca, Morelos, Mexico, alt.

48 PROCEEDINGS OF THE AMERICAN ACADEMY.

1220 m., 17 October, 1900, C. G. Pringle, no. 9253 (type, in hb.
Gray). This species is clearly separated from the preceding by its
much narrower leaves and merely puberulent more subulate involucral
scales. It belongs to a group of several obviously diverse yet nearly
related plants which have been provisionally referred to the merely in-
ferential F. turhlnata La Llav. & Lex. The latter, however, described
as having ovate leaves and short-peduncled heads, must certainly have
been a plant quite different from either here characterized.

Ill NEW PLANTS FROM GUATEMALA AND MEXICO,
COLLECTED CHIEFLY BY C. C. DEAM.

By B. L. Robinson and H. H. Bartlett.

Polypodium { Goniophlebium ) hispidulum Bartlett, n. sp., rhi-
zomate crassitudine 3-5 mm. simplici vel furcato ad arborum truncos
repenti longitudine usque ad 12 cm., aetate aperto foveolato-rugoso
juventate paleis tecto, paleis deltoideo-linearibus secus lineam medi-
anam ferrugineis margine straminellis ; frondibus inter se propinquis
6-12 cm. longis 4-7.5 cm. latis ; stipitibus gracilibus 0.5-3.5 cm.
longis exigue pilosis supra canaliculatis subtus semiteretibus ; laminis
fere usque ad costam pinnatipartitis utrinque hispidulis atroviridibus
circumscriptione valde variabilibus ovatis semiovatis vel aequilater-
aliter triangulis prout segmenta duo inferiora reducta aut baud reducta
sunt; segmentis integerrimis approximatis lanceolatis 3-9-jugis basi
dilatatis contluentibus apice obtusis, maximis 6 mm. latis 3.5 cm. longis,
terminale 1.5-6 cm. longo maxime variabili ; nervo mediano flexuoso,
nervis lateralibus alternis utrinque 10-11 baud procul a basi furcatis,
ramis anticis liberis in segmentis superioribus soriferis, ramis posticis
arcuatis marginem nee attingentibus, aut simplicibus aut furcatis aut
anastomosantibus areolarum seriem unam formantibus ; soris rotundis
medio inter nervum medianum et marginem uniserialiter dispositis ca.
1 mm. diametro ; sporangiis glabris ca. 20. — Los Amates, Department
of Izabal, Guatemala, 11 February, 1905, C. C. Deam, no. 117 (type, in
hb. Gray). The same fern, collected by Tuerckheim at Cubilquitz,
Department of Alta Verapaz, December, 1900, was distributed as
Polypodium puhescens Hook, et Grev., in John Donnell Smith's " Plants
of Guatemala," no. 8053. P. jmbescens is, without doubt, the nearest
related species to P. hispidulum. It has, however, a much larger frond,
with irregularly laciniate segments, which at the base of the frond are

ROBINSON AND BAETLETT. — PLANTS FROM GUATEMALA AND MEXICO. 49

widely separated and not at all confluent. The segments are also
prevailingly opposite in F. puhescens, whereas in P. hispidulum they
are alternate.

Paspalum guatemalense Bartlett, n. sp., perenne 6 dm. altum
simplex vel ramosum ; internodiis glabris lateraliter compressis, acie
ad folii axillam versus canaliculatis ; foliorum vaginis equitativis pilo-
sis (praecipue juxta margines et ad ligulae basin) quam internodiis aut
brevioribus aut longioribus margine brunneo-scareosis ; ligula 2.5 mm.
longa textura marginibus vaginarum simili ; laminis lineari-lanceolatis
10-15 mm. latis 6-15 cm. longis apice acutis basi rotundatis vel sub-
cordatis utrinque dense pilosis ; spicis 1-3 sessilibus inter se 2.5-3.5
cm. distantibus 3-6 cm. longis ; rhachi angusta glabra vel scabriuscula ;
pedicellis minute hispidulis ; spiculis gemiuatis altera breviter altera
lougius pedicellata, geminis secus rhachin in seriebus duabus alternis ;
spiculis suborbicularibus 2.1 mm. longis 1.9 mm. latis glabris albican-
tius viridibus antice planis postice valde convexis ; gluma inferiore in
spiculis geminorum superioribus suborbiculari apice rotundata quam
spicula 6-plo breviore, in spiculis geminorum inferioribus longiore
eccentrica late ovata obtusa vel acutiuscula ; gluma secunda membra-
nacea quam spicula paulo breviore 5-nervata, nervis juxta marginem
anastomosantibus ad apicem in mucronem perbrevem terminantibus ;
gluma tertia membranacea quam secunda longiore 3 (-5)-nervata ;
gluma quarta paleaque cartilagineis obscure nervatis ; staminibus sty-
lisque ut in speciebus generis reliquis. — A swamp at Gualan, Depart-
ment of Zacapa, Guatemala, January 20, 1905, C. C. Deam, no. 427
(type, in hb. Gray). P. guatemalense is a member of Fournier's genus
Dimorphostachijs. Following his arrangement of the group, the affinity
of the new species is with Dimorphostac-hys ^chaffneri Fourn., D.
variabilis Fourn., and D. Ghiesbreghtii Fourn. Of these, only D.
Schajfneri is represented in the Gray Herbarium. It may be at once
distinguished from P. guatemalense by its glabrous foliage and larger
ovate spikelets, acute at the apex. D. variabilis and D. Ghiesbreghtii
both have pubescent spikelets, whereas those of P. guatemalense are
perfectly glabrous.

Streptochaeta Sodiroana Hack. Noteworthy among the plants
collected by Mr. C. C. Deam in Guatemala is a specimen of the anom-
alous South American genus Streptochaeta. The genus consists of two
species, and in its spirally arranged (not distichous) flower-scales forms
a unique exception among the genera of grasses. When the generic
affinity of Mr. Deam's plant was discovered, it became evident that the
species might be identical with the Ecuadorian S. Sodiroana Hack. A
portion of the specimen was sent to Professor Hackel, who has kindly

VOL. XLIII. — 4

50 PROCEEDINGS OF THE AMERICAN ACADEMY.

confirmed the apparent identity. This is by no means an isolated case
of the occurrence of identical species in Ecuador and Guatemala, but
it has peculiar interest from the marked character and rarity of the
plant concerned. Mr. Beam's specimens were collected at Los Amates,
Guatemala, 10 February, 1905, and distributed as no. 97 of his set.
He writes that only a few plants were found, and that these were growing
in rather wet situations deep in the virgin forest. An interesting
morphological as well as systematic account of the species is given
in Professor Hackel's original characterization, Oest. Bot. Zeitschr. xl,
111 (1890).

Fuirena zacapana Bartlett, n. sp., rhizomate perpendiculari elon-
gato modice incrassato ; culmis 9 dm. longis gracilibus ascendentibus
hispidis vel ad basin glabriusculis ca. 8-foliis ; foliorum vaginis 1.5-3
cm. longis dense hispidis ; foliis linearibus utrinque hispidis usque ad
5 mm. latis, in partibus culmi inferioribus 1 cm. longis superne 9 cm.
longis ; capitulis 3-4, infimo solitario in axilla folii supremi peduncu-
iato, reliquis plus minusve approximatis ; spiculis in capitulo quoque
3-6 ovatis 4 mm. latis 8 mm. longis ; squamis brunneis pubescentibus
in spiculae basi suborbiculatis in apice ovatis trinerviis, in dorso recti-
aristatis ; sepalis 3 brunneis glabris duriusculis ovatis basi subcordatis
longe unguiculatis apice rotundatis infra apicem in dorso breviaristatis,
aristis retrorsum scabris ; setulis 3 cum sepalis alternantibus superne
retrorsum scabris quam achaenio multo brevioribus ; achaenio longe
stipitato mucronato sepala paene aequante. — In swamps, Gualan,
Department of Zacapa, Guatemala, 13 January, 1905, C. C. Deam,
no. 423 (type, in hb. Gray). This very distinct species is nearest to
F. simplea' Vahl, from which it differs in its lax habit, in the extreme
development of pubescence on the leaf-sheaths, in its short perianth-
bristles, and long-stiped achene.

Myriocarpa malacophyila Robinson & Bartlett, n. sp., arborea
4 m. altitudine ; ramis curvatis crassiusculis molliter lignosis siccitate
corrugato-rugulosis pallide griseis juventate tomentosis aetate glabra-
tis, lenticellis paucis sparsis ; foliis membranaceis late ovatis cordatis
breviter caudato-acuminatis serratis 17 cm. longis 11 cm. latis supra
more generis sparse pilosis et cystolithis radiantibus instructis subtus
molliter tomentosis griseis, apice caudiformi ca. 1 cm. longo, nervis
lateralibus utrinque 4-5; petiolo 1.7-2 cm. vel ultra longo tomentoso;
inflorescentiis omnino sessilibus ca. 1 cm. supra basin furcatis ; ramis
1-2 dm. longis griseo-tomentosis unilateraliter floriferis ; floribus 9
arete sessilibus ; calyculo 2-phyllo brevissimo villoso ; ovario lenticu-
lari-ovoideo 0.7-0.9 mm. longo villoso-hispidulo ; floribus <? etiam
sessilibus, sepalis 4 ovatis obtusis villosis, staminibus 4. ^ Gualan,

fc>

ROBINSON AND BARTLETT. — PLANTS FROM GUATEMALA AND MEXICO. 51

Department of Zacapa, Guatemala, 12 January, 1905, C. C. Deam,
no. 361 (type, in hb. Gray) ; Maria Madre Island, Tres Marias Islands,
May, 181)7, E. W. Nelson, no. 4275 (hb. Gray). This species appears
to be either monoecious, as in Mr. Beam's specimen, which has stami-
nate flowers at the base of some of the pistillate inflorescences, or it
may be dioecious, as in Mr. Nelson's specimen, in which all the flowers
are staminate. The species appears to stand nearest M. cordifoUa
Liebm., but differs in its ovate rather than suborbicular less rugose
leaves and wholly sessile inflorescences.

Polygonum longiocreatum Bartlett, n. sp., caule simplici ca. 7
dm. alto, ad nodos inferiores radicanti ; internodiis 1.5-2 cm. longis
glabris ; ocreis cylindricis eciliatis 1.5-1.7 cm. longis, in parte inferiore
caulis quam internodiis brevioribus, plus minusve inflatis, in parte
superiore imbricatis ; foliis lanceolatis 1.5-3 cm. latis 9-13 cm. longis
perbreviter petiolatis, apice basique acutis, utrinque glabris pellucido-
punctatis, margine nervisque subtus scabris ; spicis ca. 9, paniculatis
erectis 4-5 cm. longis ; pedunculis pedicellisque glabris ; ocreolis rubris
2 mm. longis tri-vel quadrifloris ; calyce rubro 5-partito ; staminibus 7
styloque (solum in extreme bifido) inclusis ; achenio lenticulari 2 mm.
longo nigro, ad basin rotundato, ad apicem abrupte acuto, faciebus
convexis. — In a swamp at Gualan, Department of Zacapa, Guatemala,
January 14, 1905, C. C. Deam, no. 374 (type, in hb. Gray). The ob-
vious affinity of P. longiocreatum is with Polygonum spectahile Mart.,
from which it differs in not having glandulose-scabrous peduncles. In
his treatment of P. spectahile in De Candolle's Prodromus, Meisner
cites two earlier-published species of Weddell as possible synonyms.
Dr. Small accepts, in his " Monograph of the N. A. Species of Poly-
gonum," one of Weddell's names, Polygonum ferrugineum, as an avail-
able name for P. spectahile Mart. Whether he applies the name
correctly or not, P. longiocreatum may be distinguished from the
P. ferrugineum of Small's monograph by the style, which in the former
is bifid only at the end, and by the long pedicellate flowers, small
achenes, and short-petioled leaves.

Ruprechtia Deamii Robinson, n. sp., frutico.sa (? solum visa);
ramis flexuosis glabris in specimine exsiccato sulcato-rugosis brunneis,
internodiis 7-30 mm. longis, ocreis membranaceis griseo-castaneis vix
0.6 mm. longis ; foliis magnis oblongis coriaceis penninerviis 10-18 cm.
longis 5.5-8 cm. latis integerrimis concoloribus utrinque prominulenter
reticulato-venulosis subtus in nervis patenter fulvo-pubescentibus et in
venulis puberulis, basi rotundatis vel modice angustatis, apice obtusis
vel rotundatis, petiolo brevissimo crassiusculo supra leviter canaliculato
ca. 3 mm. longo ; racemis numerosis fructiferis 2-6 cm. longis solitariis

52 PROCEEDINGS OF THE AMERICAN ACADEMY.

vel usque ad 3 fasciculatim aggregatis patentibus vel deflexis sub-
densifloris, tomentosis ; bracteis ovatis subacuminatis brunneis adpresse
villosis ; pedicello fructifero filiformi 2-3 mm. longo tomentoso ; calyce
fructifero ca. 3.5 cm. longo, tubo angaste ovoideo molliter subadpresse
tomentoso ca. 6-7 mm. longo ca. 4 mm. diametro, alls 2.5 cm. longis 5
mm. latis spatulato-oblougis glabriusculis 3-nerviis reticulato-venosis
apice rotundatis pallide viridibus subdiaphanis ; sepalis interioribus
subulatis glabris, parte libera ca. 4 mm. parte adnata ca. 1.5 mm. longa ;
achaenio attenuato-ovoideo obtusissime trigono, angulis tumidis leviter
sulcatis in parte superiore sulci pubescentibus ; stylis liberis, stigma-
tibus linearibus recurvatis. — -Gualan, Department of Zacapa, Guate-
mala, alt. 128 m., January 11, 1905, C. C. Beam, no. 231 (type, in hb.
Gray). This species belongs to the § Hexasepalae of Meisner, and
§ Pseudorivprechtia of Bentham and Hooker, these authors dividing
the genus on different characters. It is nearly related to li. Cmningti
Meisn., known to the author only from Meisner 's description (DC. Prod,
xiv, 179). If the characters there given are correct, the plant here
characterized is certainly distinct, as is shown by its larger leaves,
longer calyx, the presence of pubescence on the lower surface of the
leaves, decidedly rugose branches, spreading or deflexed racemes, etc.

Aeschynomene Deamii Robinson & Bartlett, n. sp., fruticosa
2 m. alta laxe ramosa aspectu glabra ; caulibus teretibus lignescenti-
bus striatulis fusco-brunneis glabris ; foliis petiolatis oblongis 5-7 ^m.
longis; foliolis ca. 18-jugis lineari-oblongis glabris utrinque viridibus
supra minutissime nigro-punctatis subtus pinnatim venosis basi obliquis
apice rotundatis mucronatis 9-10 mm. longis 2 mm. latis ; rhachi supra
sparse puberula subtus glabra ; petiolo 1 cni. longo ; stipulis 1.5 mm.
longis subulatis brunneis acutissimis ; racemis axillaribus 2-7-floris ;
pedunculis 10-17 mm. longis filiformibus glabris ; bracteis ovatis her-
baceis margine scariosis apice acutis supra basin afifixis basi rotundatis
liberis ; pedicellis anthesi ca. 4 mm. longis fructiferis ca. G mm. longis ;
calyce glabro 2-partito, labio dorsali ovato ca. 7 mm. longo ca. 5.5 mm.
lato obtusiusculo, labio ventrali angustiore ca. 9 mm. longo acuto ; vex-
illo obovato 12 mm. longo 10 mm. lato apice rotundato basi modice
angustato ; alis semiobovatis basi a latere superiore obtuse auriculatis ;
carinae petalis ca. 11 mm. longis; staminibus quinis connatis ; legu-
mine ca. 13-seminato ca. 1 dm. longo 6.5 mm. lato fragili utrinque
undulato, segmentis subquadratis margine crassiusculo faciebus glaber-
rimis levibus modice nervosis nee rugosis ; seminibus atrobrunneis
lunatis levissimis subnitidis 5 mm. longis 3 mm. latis. — San Felipe,
Department of Izabal, Guatemala, 15 February, 1905, C. C. Beam, no.
26 (type, in hb. Gray). In its numerous leaflets of oblong-linear shape

ROBINSON AND BARTLETT. — PLANTS FROM GUATEMALA AND MEXICO. 53

this species somewhat resembles A. americcma L., A. hispida Willd.,
and ^-1. sensitiva Sw. It has, however, flowers which are much larger
than those of ^-1. sensitiva, and somewhat larger than those of the other
species mentioned. It differs furthermore from A. hispida in its entire
not dentate bracts, and from both A. americana and ^1. hispida in its
essentially glabrous foliage and fruit.

Cassia emarginata L., var. subunijuga Robinson & Bartlett,
n. var., foliolis saepissime 2 late oblongo-ellipticis 6- 7 cm. longis 4-5
cm. latis supra molliter pubescentibus subtus flavido-tomentosis. —
Gualan, Department of Zacapa, Guatemala, 15 January, 1905, C. C.
Deam, no. 220 (type, in hb. Gray). This variety appears to agree in
flowers and fruit with the typical form, but it is noteworthy in habit
by reason of the striking reduction in the number of leaflets to two.
Occasionally, however, leaves with four leaflets occur on individuals on
which most of the leaves have but two leaflets ; so there is reason to
suppose that the plant is merely a varietal development from a form
with more numerous leaflets, rather than a separate species.

Mimosa (Habbasia) gualanensis Robinson & Bartlett, n. sp.,
ser. Lepitostachyarum, caulibus gracilibus lignosis 4 m. longis aculeatis
tomentellis, aculeis sparsis parvis valde recurvatis compressis inaequal-
ibus maximis vix 2 mm. longis brunneis ; foliis majusculis 27 cm. latis ;
pinnis 3-jugis 9-14 cm. longis; foliolis obovato-oblongis 2-4-jugis 4-5
cm. longis 2.4-3 cm. latis firmiusculis supra reticulatis utrinque glabris,
petiolo 7 cm. vel ultra longo rhachique valde armatis aculeis sparsis
numerosis recurvatis 0.7-2 mm. longis; rhacheolis etiam basin versus
aculeolatis ; spicis gracilibus 5 cm. longis densifloris breviter peduncu-
latis, pedunculis tomentellis; floribus 2 mm. longis; calyce 1.2 mm.
longo campanulato brevissime 5-dentato extus tomentello ; petalis 5
calyce subduplo longioribus oblanceolato-oblongis ; staminibus 10 ma-
turitate modice exsertis ; legumine immaturo 10 cm. longo 1.3 cm.
'lato 15-seminato piano tenui glabriusculo leviter arcuato, stipite cras-
siusculo tomentello tereti 5-6 mm. longo. — Gualan, Department of
Zacapa, Guatemala, 19 January, 1905, G. C. Deam, no. 224 (type, in
hb. Gray). This species, although clearly of the Leptostachyae, does
not appear to be very closely related to any other. It should probably
be placed near M. guatemalensis Benth., and M. spirocarpa Rose.

Tetrapteris emarginata Bartlett, n. sp., fruticosa procumbens
3-5 m. longa ; ramis oppositis glabris griseo-brunneis ; ramulis viridi-
bus nigro-punctatis ; foliis oppositis, aetate utrinque glabris, juventate
albo-sericeis pilis mox deciduis, forma valde variabilibus, in ramulo
florifero sessilibus vel perbreviter petiolatis suborbiculatis 1-1.5 cm.
diametro cordatis emarginatis saepe mucronulatis, in ramulo foliifero

54 PROCEEDINGS OF THE AMERICAN ACADEMY.

breviter petiolatis ovatis 4 cm. longis basi obtusis apice acutis ; ramulis
fioriferis in quasi-umbellas quadrifloras terminantibus ; pedunculis 7-8
mm. longis cum pedicellis aequilongis articulatis ; bracteis pedunculo-
rum bracteolisque pedicellorum lanceolatis minutis ; sepalis 5 albi-
cantius viridibus 2 mm. longis, 4 basi biglandulosis glandulis magnis ;
staminibus glabris calycem valde superantibus, omnibus basi coalitis ;
ovariis in unum pyramidatum faciebus concavis coalitis ; fructu albo-
lanuginoso dorso medio cristato crista integra glabra ; fructus alis
glabris viridibus rubro-tinctis anguste oblongis, duobus exterioribus
ca. 13 mm. longis, duobus interioribus ca. 9 mm. longis. Petala non
visa. — Gualan, Department of Zacapa, Guatemala, January 19, 1905,
C. C. Deam, no. 150 (type, in hb. Gray). T etrapteris emarginata
belongs among the glabrous-leaved species of Jussieu's § Tetrapteris
* Anisopterae. It may be easily distinguished from any of the Mexican
species by the leaves of the flowering branches.

Euphorbia ephedromorpha Bartlett, n. sp., basi lignescenti ; ra-
mis prostratis modice crassis longitudine usque ad 10 dm. saepe sim-
plicibus viridibus flexuosis aphyllis juventate valde compressis, aciebus
ambabus bialatis ; internodiis 2-4 cm. longis minute granulatis gla-
bratis vel perexigue pilosis, in marginibus alarum minutissime scabratis ;
nodis baud incrassatis corpore papillato (nonne cum folio aequivalenti X)
praeditis ; stipula una glanduliformi crateriformi pilosa recte super
papillam (de qua vide supra) et quam eandem parviore ; cymis axil-
laribus et terminalibus dichotomis 2-r2-cyathiis valde glanduloso-pilosis
bracteatis ; bracteis ad dichotomias oppositis 1.8 mm. longis linearispa-
tulatis dense glanduloso-pilosis ; cyathiis anguste conicis 3 mm. longis
glanduloso-pilosis ; pedicellis gracilibus cyathiis aequilongis ; involucri
segmentis propriis perbrevibus flabelliformibus ad mediam digitatim
7-8-laciniatis ; glandulis 5 planis transverse ovatis marginatis appen-
diculatis ; appendicibus rectis quam glandulo 8-plo quam involucri seg-
mentis triple longioribus anguste spatulatis glabris ; stylo brevi usque
ad basin bifido ; ovario 2 mm. longo glabriusculo stipitato, stipite
cyathio paulo longiore ; seminibus lilacinis ovoideis foveolatis. — Gua-
lan, Department of Zacapa, Guatemala, 11 January, 1905, C. C. Deam,
no. 232 (type, in hb. Gray). In regard to this species ]\Ir. Deam
"writes: " I recall the place where it grew very vividly. There is a road
leading from Gualan to the Motagua River, and as is the case with all
travelled ways in Guatemala, it is washed into deep gullies. This plant
(no. 232) was found in the nude, rocky, dry soil at the side of the road,
on an angle of about 75°. It grew prostrate in patches extending over
an area perhaps six feet square. The soil was of a red type, similar to
that around Chattanooga and Atlanta. I did not see it in any other

ROBINSON AND BARTLETT. — PLANTS FROM GUATEMALA AND MEXICO. 55

place." Eiiphorhia ephedromorpha, a unique plant in both habital and
technical characters, belongs to the § Alectoroctonum. The only Eu-
phorhia of the same affinity which has been seen is in the Gray Her-
barium from Cerro Quiengola, (Jaxaca, Mexico, Caec et Ed. Seler, no.
1611. It represents a clearly distinct new species of very similar habit,
but it cannot be described on account of the scantiness of the material.

Acalypha euphrasiostachys Bartlett, n. sp., fruticosa ramosa
1 m. altitudine ; ramulis junioribus molliter pubescentibus ochraceis
aetate glabriusculis rubentibus ; foliorum limbis ovatis 3-8 cm. longis
2-4. .5 cm. latis dentatis utrin(|ue molliter pubescentibus vel supra
solum secus nervos pilosis, apice acutis vel caudato-acutis, basi max-
ime variabilibus acutis rotundatis vel subcordatis ; petiolis limbo ca.
quintuple brevioribus ; spicis masculis axillaribus sessilibus ca. 1 cm.
longis nun(|uam ad basin bracteis femineis praeditis ; spicis femineis
axillaribus 2.5-7 cm. longis 4-7-bracteatis, dispositione formaque brac-
tearum speciebus alpinis generis Eupkrasiae persimilibus ; bracteis
femineis 8 mm. longis 10 mm. latis unifloris 13-dentatis, dentibus
modice longis alternis brevioribus ; calycis masculi segmentis 4 ovatis
0.5 mm. longis, feminei segmentis 3 ovatis ca. 1 mm. longis ; ovario
dense piloso; stylis viridibus bracteo exsertis 7 mm. longis multila-
cinuligeris. — Zacapa, Department of Zacapa, Guatemala, 24 January,
1905, C. C. Deam, no. 190 (type, in hb. Gray). A species near Watson's
Acahjpha multispicata, which has very similar fertile spikes.

Clusia quadrangula Bartlett, n. sp., arborea 5-6 m. alta ubique
glabra ; ramis modice crassis subteretibus ; foliis coriaceis ovatis 3-4
cm. latis 7-11 cm. longis, apice basique acutis, petiolo quam limbo
quintuple brevioribus ; nervis lateralibus numerosis parallelis utrinque
prominulis inter se 1-2 mm. distantibus angulo ca. 45° a costa abeunti-
bus; inflorescentia termiuali quam foliis superis duplo breviore ramosa,
ramulis angulosis plerumque in florem unum brevipedicellatum termi-
nantibus ; bracteolis infimis semi-ovatis basi connatis, sequentibus (a
sepalis non different) sepalisque 14-16 per paria decussatis coriaceis
semi-ovatis cordatis dorso carinatis, collective obpyramidatis quadrau-
gulis (ex quo nomen specificum) ; petalis 4 coriaceis late ovatis quam
sepalis duplo longioribus ; staminibus pernumerosis in receptaculo
elevato valde concavo pentagono dense aggregatis liberis, omnibus an-
theriferis, filamentis perbrevibus paene nullis, antheris rimula longitu-
dinal! dehiscentibus, connectivis baud productis. Flores feminei ignoti.
— Li\4ngston, Department of Izabal, Guatemala, February 17, 1905, C,
C. Deam, no. 56 (type, in hb. Gray). This Clusia has no obvious relation-
ship with any heretofore described species. Until pistillate flowers are
discovered it seems unwise to characterize a new section for its reception.

56 PROCEEDINGS OF THE AMERICAN ACADEMY.

Following Engler's treatment of Clusia in Flora Brasiliensis, it is ex-
cluded from all the sections of the genus except § Eudusia by the
character of the receptacle. From subsections Oxystemon and Chlamy-
doclusia of § Eudusia it is excluded by the muticous connective, and
from Cochlanthera, the sole remaining subsection, by the four petals
and very numerous stamens.

Rinorea deflexiflora Bartlett, n. sp., fruticosa 2.5 m. alta dichotome
ramosa glabra novellis inflorescentiisque puberulis exceptis ; ramis gra-
cilibus juventate brunneolis aetate albobrunneolis glabris; lenticellis
numerosis albis ; internodiis superioribus ca. 11 cm. longis ; nodis
modice incrassatis in gemmam floriferem terminantibas; foliis oppositis
cuneato-ovatis 4-12 cm. latis 8-24 cm. longis remote serratis caudato-
acuminatis basi angustatis subcordatis supra atroviridibus subtus palli-
dioribus ; petiolis 2-4 mm. longis ; stipulis subulato-lanceolatis 7 mm.
longis ; inflorescentiis ubique puberulis inter ramos dichotomiarum
terminalibus simplicibus 6 cm. longis; floribus ca. 15 longipedicellatis
nutantibus bracteatis ; pedicellis gracilibus 6 mm. longis dellexis ;
bracteis 3, una pedicellum subtendente, duabus infra pedicelli mediam
suboppositis ; sepalis 5 aequalibus acutis extus puberulis margine cili-
atis 2 mm. longis ; petalis 5 aequalibus oblongis 5 mm. longis baud
unguiculatis apice valde revolutis; staminibus 5 glabris 3.5 mm. longis
basi baud connatis; filamentis 1.3 mm. longis, anticis ad basin in dorso
glandulae oblongae 0.8 mm. longae adnatis ; connectivis in squamam
ovatam lacero-ciliatam antherae loculis dimidio longiorem productis ;
stylo glabro stamina superante ; ovario dense piloso. — Livingston, De-
partment of Izabal, Guatemala, February 18, 1905, C C. Deam, no.
61 (type, in hb. Gray). Four species of Rinorea or Alsodeia are now
definitely known from north of Panama. One of them, the Mexican
plant described by Watson as Alsodeia parvifolia, is of very doubtful
generic affinity. The other old species are Pcinorea silcatlca (Seem.)
0. K. and Rinorea guateraalensis (Wats.) Bartlett, n. comb. {Alsodeia
guatemalensis Wats., Proc Am. Acad. xxi. 458). Points which distin-
guish R. deflexiflora from the former are that in R. silvatica the
spikes are nodding, the flowers are nearly sessile, and the sepals are
almost as long as the petals. In R. guatemalensis the leaves are
broadest at the middle and are acute at the base, as contrasted with
the more cuneate, subcordate leaves of R. deflexiflora.

Hybanthus cymosus Bartlett, n. sp., fruticosus 3 m. altus ; ramis
gracilibus alato-angulatis glabratis supra straminellis subtus viridibus ;
internodiis foliis brevioribus ; foliis alternis ovatis 2-4 cm. latis 4.5-8
cm. longis serrato-crenatis glabratis basi acutis subsessilibus, apice
rotundato-obtusis ; stipulis liueari-subulatis usque ad 2 mm. longis \

ROBINSON AND BARTLETT. — PLANTS FROM GUATEMALA AND MEXICO. 67

floribus in cymas racemosas 15-30-floras axillares terminalesve_ aggre-
gatis ; cymarum bracteis perparvis ovato-deltoideis albidis ; pedunculis
3-8 mm. longis ; pedicellis 5 mm. loiigis breviter supra basin articu-
latis ; sepalis ca. 1.6 mm. longis puberulis subaequalibus ; petalis
glabris in fructu persistentibus, duobus posticis ovatis apice truncatis
2.4 mm. longis, duobus intermediis aequilongis subquadratis breviter
apiculatis ad basin antrorsum brevi-auriculatis, antico 1.9 mm. longo
trinervio inter mediam apicemque constricto, parte inferiore (ungue)
ampulliformi, parte superiore (limbo) multo parviore suborbiculari
apice bilobata ; staminibus 2 mm. longis inter antheras connatis tubum
formantibus, tribus posticis triangulo-appendiculatis, filamentis per-
brevibus liberis, duobus anticis appendicibus connatis, filamentis extus
ad basin glandulae late scutiformi adnatis, glandula gibbositati petali
antici conformali, loculis duobus contiguis antberarum anticarum
abortivis ; stylo corolla paululo longiore ; capsula glabra viridi 6 mm.
diametro 9 mm. longa. — Gualan, Department of Zacapa, Guatemala,
19 January, 1905, C. C Deam, no. 385 (type, in hb. Gray). A species
well marked by the combination of alternate leaves, numerous cymose
axillary inflorescences, and short lower petal. In general structure it
is most closely allied to such South American species as lonidium
atropurpureum St. Hil. and /. Sprucei Eichl.

Ipomoea anisomeres Robinson & Bartlett, n. sp., volubilis ; caule
gracili lignescenti glabro subtereti 3-6 m. longitudine a cortice brun-
nescenti-griseo obtecto aetate papilloso-scabrato ; foliis ovatis integris
profunde sinu patenti cordatis acutiusculis vel subattenuatis et in
apice emarginato cum nervo excurrenti apiculatis penninerviis 6-11
cm. longis 4-7 cm. latis utrinque glabris subtus pallidioribus ; petiolo
gracili glabro 3-5 cm. longo ; pedunculis axillaribus solitariis 3.5-6 cm.
longis in summa parte composite cymoso-ramosis ; pedicellis 1.5-2 cm.
longis modicegracilibus sursum plus minusve incrassatis glabris ; sepali .
glabris margine albis 2 exterioribus 1-3 mm. longis suborbicularibus
obtusisvix herbaceis 3 interioribus 1 cm. longis ellipticis apice rotundatis ;
corolla late infundibuliformi alba vel praesertim in faucibus purpuras-
centi 6.5-7 cm. longa, limbo 4-5 cm. lato subintegro, faucibus 1 cm.
diametro 3.5 cm. longis cylindratis deorsum in tubum brevem (ca. 1
cm. longum) proprium angustatis ; capsula ovoidea acuta 10-12 mm.
longa glabra biloculari ; seminibus 4 griseo-fuscis breviter pubescenti-
bus. — Gualan, Department of Zacapa, Guatemala, 12-14 January, 1905,
C. C. Beam, nos. 318 and 319 (types, in hb. Gray). This species appears
to fall into § Inaequlsepalae, as defined by Peter in Engl. & Prantl, Nat.
Pflanzenf. iv. Ab. 3, 29. The specific name alludes to the strikingly
unequal sepals.

58 PROCEEDINGS OF THE AMERICAN ACADEMY.

Ccrdia truncatif olia Bartlett, n. sp., arborea 5-7 m. altitudine ;
ramulis 2-3 mm. crassis liexuosis juventate griseo-ferrugineis pubes-
centibus aetate griseis glabris ad nodes incrassatis ; folionim cica-
tricibus reniformibus vel in ramulis vetustioribus lunatis, interdum
gemma accessoria inter cornua infra gemmam normalem praeditis ;
foliis late ovatis maximis infra mediam 5 cm. latis 7.5 cm. longis inte-
gerrimis vel apicem versus crenato-dentatis basi obtusis truncatis apice
plerumque abrupte acutis supra scabris atroviridibus subtus velutino-
pubescentibus griseo-viridibus, petiolis quam 8 mm. brevioribus ;
cyma dichotoma pauciflora foliis breviore omnino ferrugineo-pubes-
centi ; pedicellis gracilibus 2-7 mm. longis ; calyce campanulato ca. 1
cm. longo juventate 5 mm. diametro ad fructus maturitatem plus
minusve inllato 5-nervato 5-laciniato, laciniis irregulariter angusto-
deltoideis ; corolla alba (1) infundibuliformi 15 mm. longa extus intus-
que puberula usque ad mediam 5-lobata, tubo brevi, lobis rotundis 7
mm. latis ; staminibus 5 baseis loborum vix attingentibus, filamentis
5 mm. longis ; stylo stamina aequante apice bis bifido ; drupa (imma-
tura) ovoidea minute puberula mucronata calyce inclusa. — Zacapa,
Department of Zacapa, Guatemala, January 23, 1905, C. C. Deam,
no. 160 (type, in hb. Gray). In no. 160", collected at the same local-
ity, the flowers and foliage are greatly reduced in size, a variation no
doubt purely ecological. The shape of the leaves, which are remarkably
like those of Polygonum cuspidatum Sieb. et Zucc, sufhces to distin-
guish Cordia trimcatifolia from all other species of Sehestenoides.

Russelia rugosa Eobinson, n. sp., fruticosa; ramis ramulisque
6-angularibus tomentello-puberulis pallide griseis ; internodiis 5-8
cm. longis ; foliis oppositis vel ternis late ovatis obtusiusculis grosse
crenato-serratis basi integerrimis cuneatis supra scabris valde rugosis
atroviridibus subtus vix pallidioribus laxe reticulato-venosis breviter
pubescentibus 5.5-8 cm. longis 2.6-4.8 cm. latis, petiolo crassiusculo
5 mm. longo supra canaliculato pubescenti ; cymulis subsessilibus
axillaribus verticellastros parvifloros formantibus ; calycis lobis lanceo-
lato-line9.ribus angustissimis caudato-attenuatis sordide pubescentibus
nigrescentibus 5-6 mm. longis ; corolla tubiformi verisimiliter coccinea
11-12 mm. longa pubescenti ; capsula ovoidea nigrescenti levi nitida
4 mm. longa. — Gualan, Department of Zacapa, Guatemala, alt. 128 m.,
18 January, 1905, C. C. Dmm, no. 183 (type, in hh. Gray). A species
pretty well marked in the genus by its large and very rugose leaves.

Tetramerium gualan ense Robinson & Bartlett, n. sp., suffruti-
cosum 1 m. altum ramosum, novellis viscoso-pub^scentibus ; caulibus
subquadrangularibus lilacino-griseis minute albido-maculatis maturitate
subglabratis ; foliis oppositis petiolatis membranaceis subconcoloribus

KOBINSON AND BARTLETT. — PLANTS FROM GUATEMALA AND MEXICO. 59

scabriusculis ovatis acute subcaudateque acumiuatis integerrimis,
limbo 6-8 cm. longo 3.5-6 cm. lato piuuatim nervatis basi acutis in
nervis sparse puberulis aetate glabratis cystolithis conspicuis iustructis,
petiolo 1.5-2.5 cm. longo gracili supra canaliculato puberulo subtus
rotundato glabro ; spicis subdensis 2.5-4.5 cm. longis 1.3 cm. crassis
ramulos opj^ositos terminautibus ; bracteis obovatis cuneatis integer-
rimis acutis 5-nerviis utrinque glanduloso-pubescentibus 1 cm. longis
5 mm. latis, basi attenuatis ; bracteolis binis oblanceolatis acutis cym-
biformibus 9-10 mm. longis basi attenuatis in latere altero usque ad
mediam in altero vix supra basin connatis ; calyce 5-partito, lobis
anguste lanceolatis acutissimis apice hispidulis ; corolla subaequaliter
4-partita alba 1.5 cm. longa glabra, lobis anguste oblongis obtusis ca.
9 mm. longis ; staminibus 2 lobos corollae subaequantibus in summo
tubo insertis ; antherarum loculis 2 summo subaequi-altis basi loculo
uno plus minusve calcarato ; stylo clavato ; stigmate bifido ; capsuj.a
obovata acuminata glabra valde compressa ca. 2 mm. longa ca. 2 mm.
lata, stipite obcompresso 2 mm. longo ; seminibus 2 lenticularibus
fulvis 2.6 mm. longis in latere interiore glabriusculis in latere exteriore
crispo-pubescentibus. — Gualan, Department of Zacapa, Guatemala, 18
January, 1905, C. C. Beam, no. 397 (type, in hb. Gray). In the form
of its inflorescence and bracts this species approaches the members of
the genus which have sometimes been separated as He?i?-i/a.

Isertia Deamii Bartlett, n. sp., arbor parva 5 m. alta ; ramis ram-
ulisque crassis inferne subteretibus superne obtuse quadrangulis sor-
dide tomentosis ; internodiis 4-5 cm. longis ; foliis 20-30 cm. longis
8-11 cm. latis utrinque acutis supra glabris subtus griseo-tomentosis,
petiolo limbis 10-plo breviore ; stipulis 6-9 mm. longis triangulis per-
sistentibus ; inflorescentia foliis multo breviore paniculata ca. 10 cm.
longa, ramulis tomentosis ascendentibus 7-20 nnn. longis, pedicellis
2-5 mm. longis, bracteis bracteolisque triangulis parvis ; cal3^ce fuscato
hemi-ellipsoidali truncato nee distincte dentato ; corolla ca. 30 mm.
longa coccinea extus, lobis limbi exceptis, tomentosa, lobis 7 mm.
longis obtusatis extus glabris intus lanugine flavo tectis ; staminibus 6
inclusis tubo adnatis, antheris circum stigmata connatis ; stylo apice in
ramulos sex ca. 6 mm. longos terminanti ; bacca calyce coronata 6-
pyrena. — Puerto Barrios, Department of Izabal, Guatemala, 24
February, 1905, C. C. Beam, no. 48 {ty^Q, in hb. Gray). Isertia
Deamii, the third Middle- American species of the genus, is not similar
enough to either of the old species to be confused with them.

Liabura caducifolium Robinson & Bartlett, n. sp., fruticosum ;
caulibus teretibus striatulis griseo-fuscis glabris delapsu foliorum nu-
dis, internodiis 6-8 cm. longis ; inflorescentiis laxe corymboso-pan-

60 PROCEEDINGS OF THE AMERICAN ACADEMY.

iculatis, ratnis oppositis nudis patentibus vel arcuato-ascendentibus
multicapitulatis, bracteis lanceolatis utrinque acutis integerrimis gra-
ciliter petiolatis supra glabris subtus aracbuoideo-tomentosis, petiolo
planiusculo glanduloso-bispidulo ; pedicellis filiformibus 1-5 mm.
longis ; capitulis discoideis 6-floris ; involucri squamis 13 acutis cili-
olatis exterioribus ovato-lanceolatis 1 mm. longis interioribus gradatim
longioribus angustioribusque intimis linearibus vel liueari-lanceolatis
5 mm. longis ; flosculorum omnium corollis 6.5 mm. longis gracilibus
sursum gradatim ampliatis sine faucibus distinctis, dentibus limbi line-
aribus ad apicem obtusiusculum attenuatis ; pappi setis biseriatis
exterioribus brevibus paucis planiusculis interioribus ca. 40 capillari-
bus fulvescentibus sursum scabriusculis. Achaenia immatura. — Near
Acapulco, Guerrero, Mexico, between October, 1894, and March, 1895,
Dr. E. Palmer, no. 245 (type, in hb. Gray). Tbis species belongs to
§ Andromachia, and is closely related to L. glabrum Hemsl., but it
differs in its much looser corymbose-paniculate inflorescence, its shorter
involucre, and much more attenuate involucral scales.

Liabum Deamii Robinson & Bartlett, n. sp., scandens 3-5 m.
longum ; caulibus anthesi delapsu foliorum ignotorum nudis subtereti-
bus lanulosis albidis, internodiis 2-4 cm. longis, nodis crassiusculis ;
inflorescentiis ovoideis thyrsoideis multicapitulatis albido-lanuginosis
,1-1.5 dm. longis 5-8 cm. diametro; bracteis petiolatis ovatis integris
discoloribus supra leviter griseo-pubescentibus subtus albo-lanatis ;
ramulis 3-5-capituliferis ; capitulis discoideis 6-floris subsessilibus
vel brevissime pedicellatis ; involucri squamis ca. 13 obtusis exterio-
ribus ovatis ca. 2 mm. longis externe pubescentibus interioribus
gradatim majoribus 3-4 mm. longis ovato-oblongis apicem versus
pubescentibus ; flosculis 9 involucro longe exsertis, corollis glabris
verisimiliter flavidulis 7 mm. longis, faucibus cylindratis tubum pro-
prium graciliorem subaequantibus, dentibus limbi patentibus anguste
lanceolatis acutissimis; achaeniis 2.5 mm. longis deorsum angustatis
griseo-olivaceis modice compressis striatulis breviter pubescentibus ;
pappi setis 2-seriatis exterioribus paucis subpaleaceis 1-2 mm. longis
interioribus ca. 50 capillaribus sursum minute scabratis ca. 6 mm.
longis albidis. — ■ Gualan, Department of Zacapa, Guatemala, C. C.
Beam, no. 194 (type, in hb. Gray). This species clearly belongs to the
§ Andromachia, and appears to be nearest L. glabrum Hemsl., from
which it may be distinguished, however, by its pubescence and much
shorter involucre, the latter scarcely exceeding the acheues.

FERNALD. — NEW SPERMATOPHYTES FROM MEXICO. 61

IV. DIAGNOSES OF NEW SPERMATOPHYTES FROM

MEXICO.

By M. L. Fernald.

Carex ciliaris Fernald, n. sp., laxe caespitosa, caudice duro ; cul-
mis duriusculis 4-5 dm. altis acute triquetris superne ciliatis; foliis
quam culmo brevioribus lineari-attenuatis 2.5-3.5 mm. latis, nervis
marginibusque ciliatis raarginibus revolutis ; spicis 3-5, terminali cia-
vellata subsessili 1-1.5 cm. longa vel omnino mascula vel apice foeminea;
squamis masculis lanceolato-attenuatis pallide brunneis ; spicis foemi-
niis breviter oblongis 0.6-2 cm. longis 0.5 cm. crassis, superioribus
approximatis, inferioribus remotis et a bractea inflorescentiam aequanti
vel superanti subtentis ; squamis foemineis anguste ovatis acuminatis
media parte viridibus 3-costatis levibus marginibus pallidis ; perigy-
niis viridescentibus squamas aequantibus vel superantibus 4 mm. longis
ellipsoideo-triquetris, faciebus planis 3-5-nerviis, rostro breviter conico-
subulato byalino bidentato. — Oak woods, Lena Station, Hidalgo, Mex-
ico, alt. 2530 m., 26 August, 1905, C. G. Pringle, no. 10,039 (type, in
hb. Gray). Nearest related, apparently, to C. anistostachys Liebm.,
which, according to the description, has scabrous culms, the staminate
scales red-punctate, and the pistillate scales ciliolate.

Carex perlonga Fernald, n. sp., culmis 6 dm. altis laevissimis basi
a vaginis ferrugineis tectis ; foliis quam culmo plerumque brevioribus
4-5 mm. latis valde 1-3-nerviis serrulatis basi ferrugineis ; bracteis in-
ferioribus elongatis quam culmo longioribus, superioribus abbreviatis
setaceis ; spicis 7 solitariis inferioribus remotis superioribus approxi-
matis laxe ascendentibus vel pendulis lineari-cylindricis 5-10 cm. longis
3-4 mm. latis apice masculis ; squama mascula oblonga subacuminata
fulva medio viridi, foeminea oblongo-lanceolata acuminata albo-fulva
medio viridi ; perigynio viridi trigono-fusiformi striato 4 mm. longo,
ore obliquo subintegro. — Barranca below Trinidad Iron Works, Hi-
dalgo, Mexico, alt. 1585 m., 2 June, 1904, C. G. Pringle, no. 8863
(type, in hb. Gray). A species of the Polystachyae, unique in its soli-
tary not clustered spikes, thus closely approaching the Debiles.

Alnus firmifolia Fernald, n sp., arborea vel fruticosa 6-12 m.
alta ; ramis ramulisque atrobrunneis glabris cum lenticellis numerosis
munitis ; foliis elliptico-oblongis obtuse acuminatis vel apice rotundatis
basi angustatis 5-17 cm. longis 2-5.5 cm. latis firmis duriusculisque
supra glabris sublucidis subtus pallidis piloso-hispidis in nerviis promi-
nentibus ; petiolo crassiusculo glabro 0.7-1.2 cm. longo; inflorescentiis

62 PROCEEDINGS OF THE AMERICAN ACADEMY.

fertilibus 6-9 cm. longis, amentis maturis 3-5 oblongo-cylindricis atro-
brunneis pedunculatis 7-14 mm. longis 5-7 mm. diametro ; nuculis
cuneato-obovatis vel suborbicularibus rufobrunneis lucidis 1.5-2 mm.
longis. — Mountains about Cima Station, Mexico, alt. about 3000 m.,
30 August, 1905, C. G. Pr Ingle, no. 10,040 (type, in hb. Gray). Re-
sembling large-leaved A. jorullensts HBK., but quite lacking the close
covering of waxy or granular atoms which characterizes the lower leaf-
surface of that species.

Alnus Pringlei Fernald, n. sp., arbor parva ; ramis ramulisque
angulatis, juventissimis cinereo-puberulis mox glabratis ; foliis late
elliptico-ovatis 4.5-9 cm. longis 3-7 cm. latis apice breviter acuminatis
basi rotundatis, marginibus regularibus vel paulo sinuatis crebre serru-
latis, venis subtus prominentibus rufescentibus pilosis; petiolis 0.5-1
cm. longis piloso-ciliatis ; ramis floriferis elongatis ; amentis ^ 4-7
terminalibus anthesi 5-6 cm. longis ; pedunculis fructiferis 2 valde di-
vergentibus crassis ; amentis $ 3-4 sessilibus maturitate cylindricis
2.2-2.7 cm. longis 0.9-1.1 cm. diametro atrobrunneis ; nuculis crassis
late cuneatis et angulatis 2.5-3 mm. longis obscuris pallide brunneis. —
By streams, near Uruapan, Michoacan, Mexico, alt. about 1525 m., 13
November, 1905, C. G. Pringle, no. 10,125 (type, in hb. Gray). Most
nearly related to A. acuminata HBK., which has larger oblong-ovoid
ashy-brown strobiles 1.5 cm. thick, and larger thick-winged lustrous
nutlets.

Euphorbia ariensis HBK., var. villicaulis Fernald, n. var. Eume-
canthus Benthamianus Kl. & Garcke, in Kl. Tricocc. 42 (1860), not
Euphorbia Benthami Hiern, Cat. Welw. Afr. PI. i. 943 (1900). Eu-
phorhia ariensis Benth., PI. Hartw. 51, no. 387 (1840), not HBK.
Nov. Gen. et Sp. ii. 57 (1817). Caulibus in parte inferiore valde vil-
losis ; foliis quam eis formae typicae aliquid latioribus ; inflorescentia
laxiore. — In pine forests at Corn Station, Michoacan, Mexico, alt.
1970 m., 29 October, 1905, C. G. Pringle, no. 10,116 (type, in hb.
Gray). This locality is only about 48 km. to the west of Patzcuaro,
which was Hartweg's original station.

Heliotropium calcicola Fernald, n. sp., frutex gracilis 6-15 dm.
altus ; cortice brunneo exfolianti ; ramulis albido-strigoso-puberulis ;
foliis lanceolatis utroque atten uatis breviter petiolatis apice mucronatis
cum pilis minntis et lucidis utrinque obtectis 2-4.5 cm. longis
3-10 mm. latis margine revolutis ; spicis terminalibus et lateralibus
geminis 0.5, maturitate usque ad 2, cm. longis; pedunculis gracilibus
1.3-2 .cm. longis canescentibus ; calyce 1.5-2.5 cm. longo cum pilis
minutis adpressis canescenti, lobis lanceolatis ; corolla anguste urceo-
lata 3 mm. longa adpresse setulosa, lobis ovatis acuminatis ; stylo nullo ;

FERNALD. — NEW SPERMATOPHYTES FROM MEXICO. 63

nnculis subglobosis 1.3 mm. altis albidis adpresse setulosis. — Lime-
stone cliffs, Iguala Canon, Guerrero, Mexico, alt. 760 m., 28 September,
1905, G. G. Fringle, no. 10,062 (type, in hb. Gray). Not closely re-
lated to other Mexican species, perhaps nearest //. coriaceum Lehm.,
which is much coarser, densely villous, with broader rugose villous
leaves and larger Howers and fruits.

Salvia hispanica L., var. chiono calyx Fernald, n. var., foliis brac-
teisque supra viridibus et minute pubescentibus subtus paulo pallidi-
oribus et praesertim in nerviis breviter pilosis ; spicis pertenuibus 5-
10 cm. longis 1-1.5 cm. crassis ; floribus adpresse ascendentibus ;
calycibus conspicue denseque albo-pubescentibus. — Fields, Uruapan,
]\Iichoacan, Mexico, 16 October, 1904, C. G. Pringle, no. 8837^ (type,
in hb. Gray). A striking extreme of >S^. hisjxinica, the typical form of
which differs in its ordinarily thicker spikes of less appressed cinereous
calyces.

Salvia hispanica L., var. intonsa Fernald, n. var., foliis et parti-
bus superioribus caulis tomentosis : spicis brevibus cras.sis 1.5-5.5 cm.
longis 1.5-2 cm. crassis ; calycibus tomentosis patentibus. — Buena
Vista, Department of Santa Rosa, Guatemala, alt. 1680 m., December,
1892, Heyde & Lux, no. 4401, in exsicc J. D. Smith. Differing from
aS'. hispanica in the dense tomentum of its leaves, stems, and calyces.

Salvia (Vulgares) mucidiflora Fernald, n. sp., herbacea (?) aita ;
caule cinereo-pulverulento obtuse angulato faciebus profunde sulcato;
foliis rhomboideo-ovatis 3.5-10 cm. longis crenato-serratis subtus albidis
et tomento brevi densoque obtectis supra griseo-viridibus cum pilis brevi-
bus albis, basi cuneato integro in petiolum puberulum gradatira angus-
tato ; ramis brevibus patentibus ; racemis laxis 3.5-10 cm. longis ; rhachi
et pedicellis et etiam calyce dense albovillosis paene lanatis ; verticellis
o-6-floris subdistantibus ; bracteis late ovatis mucronatis 4-7 mm.
longis subpersistentibus laxe albo-villosis ; pedicellis 1-3 mm. longis ;
calyce anguste campanulato anthesi 7 mm. fructifero 8-9 mm. longo,
labio superiore acuminato ascendenti, inferiore rectiusculo cum lobis 2
deltoideis aristatis ; corolla azurea et alba 13-14 mm. longa, labio su-
periore villoso oblongo 6 mm. longo, inferiore violaceo patenti paulo
longiore ; stylo villoso. — San Ilam6n, Durango, Mexico, 21 April-18
i\Iay, 1906, Edw. Palmer, no- 18V (type, in hb. Gray). Nearest related
to 8. hnglspicata Mart. & Gal. but differing in its crenate- serrate
leaves and the long pubescence of the inflorescence.

Salvia (Vulgares) arthrocoma Fernald, n. sp., caulibus superne
pilosis, pilis pallidis nodulosis ; foliis rhomboideo-ovatis 4-8 cm. longis
supra basin cuneatam crenato-serratis apice acuminatis supra pilis
compressis adpresse setulosis et in venis pilis gracilibus nodulosis mu-

64 PROCEEDINGS OF THE AMERICAN ACADEMY.

nitis subtus in venis venulisque pilis gracilibus nodulosis pubescentibus ;
petiolis gracilibus 1.5-4 cm. longis ; raceme brevi, rbacbi a pilis nodu-
losis peculiaribus tecta ; verticellis 3-6-floris demum 1-1.5 cm. dis-
tantibus ; bracteis late ovatis longe acuminatis et calycibus in nervis
marginibusque pilis gracilibus nodulosis munitis ; pedicellis 3 vel usqiie
ad 5 mm. longis; calyce campanulato antbesi 5 fructifero 8 mm. longo
tubo valde costato, labiis deltoideo-acuminatis valde patentibus superi-
ore ascendenti 2-3 mm. longo quam lobo recto inferioris breviore ;
corolla 1 cm. longa, tubo faucibusque albidis, labiis obtusis ringentibus
apicem versus purpureo-tinctis, galea pilosa 4 mm. longa labium infe-
rius latius paulo superante. — Barranca below Trinidad Iron Works,
Hidalgo, Mexico, alt. 1620 m., 16 July, 1904, C G. Prhigle, no. 8940
(type, in hb. Gray). Somewbat suggesting S- fluciatiUs Fernald, but
clearly characterized by its slender jointed -hairs.

Salvia ( Vulgares) Lozani Fernald, n. sp., caulibus herbaceis gracil-
ibus decumbentibus basi saepissime radicantibus aliquid ascendenti-
bus demum 5-6 cm. longis minute glanduloso-setulosis, pilis patentibus ;
foliis regulariter remotis, jugis 4-6 cm. distantibus, foliis infimis sub-
orbicularibus 1.2-1.6 cm. longis superioribus ovatis vel oblongis 1.5-
2.5 cm. longis integris margine paulo revolutis basi rotundatis vel
subcordatis apice rotundatis supra viridibus glabris pallide nervatis
subtus pallidioribus et glandulis atrorubris punctatis; pedunculo 4.5-7
cm. longo ; verticellis 3 remotis 2-floris ; bracteis ovatis obtuse acu-
minatis glanduloso-setulosis 2-3 mm. longis ; pedicellis 1-2 mm.
longis ; calyce antbesi campanulato glanduloso-setuloso rubropunctato
4-5 mm. longo, labio superiore obtuso 2-dentato nigrescenti 2 mm.
longo, inferi ore pallidiore lato brevissimo ; corolla 17-18 mm. longa,
tubo infundibuliforme leviter ventricosa 8 mm. vel ultra longo, galea
breviter pubescenti 3-4 mm. longa, labio inferiore cyaneo albo-maculato
1 cm. longo, lobo medio 12 mm. lato. — Wet grassy places in pine for-
ests near Trinidad Iron Works, Hidalgo, Mexico, alt. 1770 ra., July-
August, 1904, C. G. Pringle, no. 8928 (type, in bb. Gray). Named for
Filemon L. Lozano, for several seasons Mr. Pringle's able field com-
panion. A unique species, nearest related perhaps to S. v'dlosa
Fernald. ,

Salvia (Candicantes) cliionophylla Fernald, n. sp., fruticosa de-
pressa ; ramis laxis gracilibus prostratis 3-6 dm. longis ; cortice pallide
brunneo pilis brevissimis crebris stellatis canescenti ; foliis elliptico-
ovatis vel breviter oblongis integris vel obscure crenatis utroque angus-
tatis 0.5-1.5 cm. longis cinereis dense stellato-puberulis juventate
canescentibus ; petiolis gracilibus 2-4 mm. longis ; racemis 0.5-1 dm.
longis; verticellis 3-6-floris demum 2-2.5 cm. distantibus; pedicellis

FERNALD. — NEW SPERMATOPHYTES FROM MEXICO. 65

2-4 mm. lougis ; calyce tubuloso-campanulato anthesi 6-7 fructifero 8-
9 mm. longo valde costato, tube lobis latis obtusis breviter acuminatis
duplo lougiore; corolla 1.5 cm. longa, tubo paulo exserto ; galea azurea
et alba pilosa 6 mm. louga a labio inferiore cyaneo superata. — On shelv-
ing rocks and gravelly slopes of the canon- wall, Chojo Grande, Coa-
huila, Mexico, 29 August, 1904, Ediv. Palmer, no 368 (type, in hb.
Gray). Nearest related to the upright narrow-leaved S. thymoides
Benth., which has a glandular calyx. »

Salvia (Scorodoniae) chalarothyrsa Fernald, n. sp., ramis gra-
cilibus retrorse molliterque pilosis ; foliis cordato-ovatis acuminatis
dentatis superioribus 2.5-4.5 cm. longis 2-3.5 cm. latis vix rugosis
utrinque adpresse pubescentibus, pilis planis ; petiolis 0.5-1.5 cm. longis
dense pilosis ; inflorescentia cylindrica laxe thjTsoidea 1.5-6 dm. longa ;
rhachi necuon pedunculis pedicellisque cum pilis mollibus patentibus
glanduloso-capitulatis tectis ; cymis 3-10-floris ua(_[ue ad 3-4 cm. dis-
tantibus, pedunculis 0.5-2 cm. longis ; bracteis lanceolatis vel lineari-
bus tarde deciduis ; calyce pedicellos aequante anguste campanulato
anthesi 4 fructifero 5-6 mm. longo glanduloso-hirsuto, lobis alte del-
toideis subaequalibus apice subulatis; corolla cyanea 12-13 mm. longa,
tubo pallido glanduloso-punctato panlo exserto, galea brevissima bre-
viter pilosa, labio inferiore multo longiore, lobo intermedio magno
emarginato 7-9 mm. lato. — Hills about Tuxpan, Jalisco, Mexico, alt.
1220 m., 27 October, 1904, C. G. Pr'mgle, no. 8856 (type, in hb. Gray).
A remarkable species in its thyrsiform inflorescence, related only to
8. thyrsijiora Benth., a species also from the Jalisco mountains, from
Tepic to western Michoacan.

Salvia (Inflatae) muralis Fernald, n. sp., fruticosa 1-2 m. alta;
ramis gracilibus firmis subteretibus cinereo-puberulis ; foliis anguste
ovatis 6-9.5 cm. longis 2-4.7 cm. latis remote crenato-dentatis obtuse
acuminatis basi subcuneatis vel rotundatis supra pallide viridibus ad-
presse setulosis subtus pallidioribus et glanduloso-punctatis dense
albo-pilosis in costa media et in nervis principalibus ; petiolo gracili
cinereo-puberulo 2-3 cm. longo ; ramis floriferis gracilibus brevibus ex
axillis superioribus inferne foliatis ; floribus saepissime geminis ; pedi-
cellis gracilibus 3-5 cm. longis ; calyce anthesi curvato tubiformi 1.5-2
cm. longo inferne constricto viridique superne patente expanso et
rubro-tincto sparse piloso, lobis deltoideis 5 mm. longis ; corolla cinna-
barina 4.5-6 cm. longa valde exserta pilosa tubulari-infimdibuliformi,
faucibus paulo gibbosis, galea pilosa 1.5-1.7 cm. longa labium inferius
subaequante ; staminibus styloque exsertis illo piloso. — Hanging
from fissures in limestone-cliffs, Iguala Canon, Guerrero, Mexico, alt.
762 m., 28 September, 1905, C. G. Pringh, no. 10,072 (type, in hb.

XLIII. — 5

66 PROCEEDINGS OF THE AMERICAN ACADEMY.

Gray). Nearly related to S. pubescens Benth., which has a shorter,
broader, and more colored calyx, shorter corolla, and nearly or quite
glabrous style.

Salvia (Cyaneae) atrocaulis Fernald, n. sp., caulibus nigrescen-
tibus vel purpurascentibus 1.8-2.4 m. altis basi 2-3 cm. crassis in par-
tibus inferioribus glabris inflorescentiam versus puberulis ; foliis late
cordato-ovatis utrinque viridibus supra sparse adpresso-setulosis et in
nerviis puberulis subtus glabris sed glanduloso-punctatis regulariter
dentato-serratis, limbo 7.5-15 cm. longo 5-12 cm. lato apice caudato-
acuminato ; petiole 4-14 cm. longo ; inflorescentia racemosa 1.5-3 cm.
vel ultra longa, rhachi puberula, verticellis 5-12-floris inter se denique
2-2.5 cm. disjunctis ; pedicellis puberulis anthesi 7 mm. fructiferis
12 mm. longis ; calyce anthesi 14 mm. fructifero 22 mm. longo glan-
duloso-punctato, in nervis cum pilis cadacis moniliformibus pubescenti,
lobis subulato-mucronatis deltoideis tubo anguste campanulato triple
brevioribus ; corolla 5 cm. longa violacea fere vel ornnino glabra, tubo
aliquid ventricoso labiis paulo longiore ; stylo barbato. — - Wet banks,
barranca below Trinidad Iron Works, Hidalgo, Mexico, alt. 1650 m.,
22 August, 1904, G. G. Prhigle, no. 8887 (type, in hb. Gray). Near-
est related to S. recuroa Benth., but differing in its dark stems, broader
firmer leaves, less pubescent calyx, and essentially glabrous corolla.

Salvia (Cyaneae) flaccidifolia Fernald, n. sp., verisimiliter fruti-
cosa \ ramis gracilibus superne decussatim bifariam pilosis ; foliis
graciliter petiolatis ; petiolis supra pilosis inferioribus limbum super-
antibus ; laminis ovatis cordatis caudato-attenuatis tenuissimis 3.5-9
cm. longis crenato-serratis supra atroviridibus adpresse setulosis subtus
pallide viridibus fere glabris in venis adpresse setulosis ; racemis 6-8
cm. longis, verticellis 6-8 remotis 3-6-floris ; bracteis ovatis aristatis
caducis ; pedicellis 2-5 mm. longis puberulis ; calyce anthesi 5-6 mm.
longis, labio superiore ovato aristato inferiore bilobo biaristato ; corolla
2-2.3 cm. longa cyaneo-purpurea, tubo valde ventricoso, labio superiore
recto 1 cm. longo, inferiore longiore pendulo valde dilatato. — Barranca
below Trinidad Iron Works, Hidalgo, Mexico, 1906, G. G.. Prhigle,
no. 10,298 (type, in hb. Gray). Nearly related to S. rectirva Benth.,
which it resembles in its very thin long-petioled leaves, but with much
smaller calyx and corolla.

Salvia (Tubiflorae) simulans Fernald, n. sp., caulibus glabris;
ramis erectis brevibus ; foliis ovatis abrupte acuminatis basi rotundatis
vel rotundato-cuneatis regulariter dentato-serratis 0.5-1 dm. longis
3.2-6.5 cm. latis supra adpresse setulosis et resinoso-punctatis subtus
glabris ; petiolis paulo pilosis 4-8 cm. longis gracilibus ; racemo prin-
cipali 1.5 dm. longo ; rhachi glanduloso-pulverula ; verticellis 5-15-floris

FERNALD. — NEW SPERMATOPHYTES FROM MEXICO. 67

demum 2 cm. distantibus ; pedicellis gracilibus glanduloso-pruinosis
1.5 usque ad 7 mm. longis ; calyce purpureo-tincto tubiformi anthesi
7-8 mm. fructifero 1 cm. lougo, tubo basi valde costato pruinoso, fau-
cibus paulo dilatatis levius costatis glabratis, labiis aristato-acumiiiatis
3-4 mm. longis inferiore bifido recto superiore sursum curvato ; corolla
rubro-purpurea 2.2-2.6 cm. longa, tubo et faucibus anguste cylindricis
sursum curvatis 1.5-1.7 cm. longis 2-3 mm. diametro, labiis approxi-
matis, galea dense pilosa labium inferius aequanti ; stylo barbato. —
Wet barranca below Trinidad Iron Works, Hidalgo, Mexico, alt.
1680 m., 22 August, 1904, G. G. Fringle, no. 8927 (type, in bb. Gray).
Strongly suggesting S. Martendi Gal., which, however, has the ventri-
cose corolla-tube of the Cyaneae. From that species, S. simulans,
which has the cylindric corolla-tube of the Tiibijlorae, is further dis-
tinguished by its rounded-cuneate leaf-bases, and especially by the
elongate galea.

Castilleja Conzattii Fernald, n. sp., suffruticosa; caulibus sim-
plicibus erectis glanduloso-puberulis ; foliis linearibus vel lineari-lance-
olatis 3-5-nerviis 2-7 cm. longis dense puberulis, inferioribus integris,
superioribus pectinatis, laciniis linearibus patentibus ; bracteis oblongis
1.5-2.5 cm. longis, summis coccineis trifidis, lobis lateralibus linearibus
vel spatulatis, intermedio majore anguste obovato integro vel obsolete
trilobo ; pedicellis 1 mm. longis ; calyce mediam tantum corollam pau-
lulo superante 1.5-1.8 cm. longo viridi et albo, antice et postice aequa-
liter fisso, lobis oblongis subtruncatis 6-6 mm. longis ; corolla viridi
et rubella 2.2-2.5 cm. longa, tubo 1.2-1.3 cm. longo, galea elongata,
labii lobis obtusis 1 mm. longis. — ■ Sta. Ines del Monte, Zimatlan,
Oaxaca, Mexico, alt. 820 m., 8-9 December, 1905, C. Conzafti, no. 1360
(type, in hb. Gray). Nearest related, apparently, to the variable C. an-
gustifoUa (Nutt.) Don, of the northwestern United States, from which
it differs chiefly in the broad middle lobe of the bracts.

Ruellia (Ophthalmacanthus) Pringlei Fernald, n. sp., fruticosa ;
ramis gracilibus flexuosis subteretibus glanduloso-villosis cinereis ;
foliis ovatis 3-10 cm. longis 1.5-4.3 cm. latis tenuibus utrinque mol-
liter pubescentibus basi cuneatis apice longe attenuatis ; petiolis gra-
cilibus sublanatis 1.5-3.5 cm. longis; pedunculis 1.5-3 cm. longis
cinereo-pubescentibus uniiloris ; bracteis lineari-spatulatis acutis 2.5-5
cm. longis ; calyce 3-4 cm. longo, laciniis lineari-lanceolatis 2.3-3 cm.
longis ciliatis ; corolla alba 7-8 cm. longa anguste infundibuliformi
valde exserta, limbi 5-6 cm. lati lobis breviter oblongis vel siiborbicu-
laribus retusis ; capsula immatura angusta 2.5-3 cm. longa 7 mm.
crassa glabra. — Hillsides, Balsas Station, Guerrero, Mexico, alt. 610 m.,
27 September, 1905, C. G. Prtat/le, no. 10,07 1 (type, in hb. Gray).

68 PROCEEDINGS OF THE AMERICAN ACADEMY,

Apparently nearest R. rosea (Nees) Hemsl., which is said, however, to
have the obtuse leaves short-petioled, the stem angled, and the rose-
colored corolla 2 inches long.

BiDENS ROSEA Sch. Bip., var. aequisquama Fernald, n. var., invo-
lucri squamis subaequalibus, eis seriei exterioris elongatis 5-8 mm.
longis. — Thickets near Uruapan, Michoacan, Mexico, alt. 1525 m.,
1 November, 1905, C. G. Pringle, no. 10,109 (type, in hb. Gray).
Differing from B. rosea in the very elongate segments of the outer in-
volucre, which in the original description of the species is said to be
shorter than the inner, and which in herbarium specimens measures
2-4 mm. long.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 3. — Juxe, 1907.

CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE
MUSEUM OF COMPARATIVE Z(JOLOGY AT HARVARD COLLEGE,
E. L. MARK, DIRECTOR.— No. 190.

MATURATION STAGES IN THE SPERMATOGENESIS
OF VESFA MACULATA Linn.

By E. L. Mark and Manton Copeland.

CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE
MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE,
E. L. MARK, DIRECTOR. — No. 190.

MATURATION STAGES IN THE SPERMATOGENESIS OF
VESPA MACULA TA Linn.

By E. L. Mabk and Manton Copeland.

Received May 27, 1907.

In a brief account of spermatogenesis in the honey bee, published
four years ago, Meves (: 03) showed that, contrary to the condition thus
far observed in the animal kingdom generally, the maturation divisions
of the primary spermatocjrtes resulted in the production of two "Rich-
tungskorper " and a single functional cell, instead of four functional
spermatozoa. The first of these two bodies was composed exclusively
of cytoplasm ; the second, however, was nucleated. Our observations
on the germinal cells of the honey bee published last year (Mark and
Copeland, = 06) confirmed in a general way those of Meves, differing
from his, however, in numerous details.

Meves states in a very few words in the paper cited that in the
spermatogenesis of Vespa germanica the first maturation division re-
sults, as in the honey bee, in the formation of a non-nucleated bud
of cytoplasm, but that the second gives rise to two cells of equal size,
both of which are metamorphosed into spermatozoa.

Having been able to collect, prepare, and examine the male germinal
cells of Vespa maculata Linn., we will set forth briefly in this paper
some of our observations.

At the end of the growth period following the last spermatogonial
division, the cells (compare Figure 1) closely resemble those of the
honey bee. The nucleus is relatively large, and the chromatin is for
the most part aggregated into a single, somewhat irregularly shaped
body. Lying against the cell membrane are the remnants of the inter-
zonal filaments of the preceding cell division, which have become
metamorphosed into a rather homogeneous mass, to which we have
given the name interzonal body (Figure 1, ^')-

PROCEEDINGS OF THE AMERICAN ACADEMY.

As the spermatocyte enters the prophase of the first maturation
division the centrosome, lying in contact with the cell membrane,
divides, and the two daughter centrosomes move apart (Figure 1)

until they arrive at opposite
poles of the cell (Figure 2).
Although the centrosomes dur-
ing their migration seem to
influence to some degree the
form of the cell, this modifica-
tion in outline is not so promi-
nent as in the honey bee. The
nucleus continues to lie close
to that one of the centro-
somes which in the cells ot
the honey bee we have desig-
nated as the dista,! centrosome
(Figure 2, dst.).

The stages immediately fol-
lowing this correspond strik-
ingly to those of the honey bee.
The chromatin, after passing
through a spireme condition,
gives rise to chromosomes
which lie scattered irregularly
through the nucleus (Figure
2). We have not as yet suc-
ceeded in determining the
exact number of the chromo-
somes, but believe that it is
not less than sixteen. The
nucleus now elongates, finally
becoming more or less spindle
shaped, but apparently fails
to reach the proximal pole of
the cell. Intranuclear spindle
fibres staining in iron haema-
toxylin have meanwhile made their appearance, extending from the
chromosomes first to the distal centrosome, and later in the opposite
direction, to a region near the proximal end of the nucleus, it being
now difficult to determine the exact extent of the nuclear membrane.
Thus the proximal ends of the spindle fibres often appear to converge to
a point at some distance from the corresponding centrosome (Figure

Figures 1-4. Primary spermatocytes. X
2800.

Figure 1. The two centrosomes moving
apart ; x, interzonal l)oi\y.

Figure 2. Centrosomes at opposite poles
of cell ; nucleus showing chromosomes ; prx.,
proximal centrosome; (ht., distal centrosome.

Figure 3. First spindle figure with intra-
nuclear spindle fibres.

Figure 4. Interzonal body at proximal
pole, immediately before its abstriction ;
spindle figure disappearing, and extranuclear
fibres j^rominent.

MARK AND COPELAND.

SPERMATOGENESIS OF VESPA MACULATA.

3) ; unlike the corresponding stage in the honey bee, there seems to be
no evidence that these fibres connect with the proximal centrosome ;
however, numerous extranuclear fibres extend from the distal centro-
some in the direction of the proximal
one.

At this stage the interzonal body
already lies near the proximal cen-
trosome.

The proximal end of the cell now
elongates (Figure 4), and there is
formed a small bud of cytoplasm
containing the interzonal body and
the proximal centrosome. This bud
remains for a time connected with the
cell by a neck-like process of cyto-
plasm, through which may be traced
extranuclear fibres. This connecting
process of cytoplasm becomes more
and more attenuated until a complete
detachment of the protoplasmic glob-
ule is effected.

This " Richtungskorper " consists
chiefly of the interzonal body, but in
most cases the interzonal body is
surrounded by more of the unmodi-
fied cell protoplasm than exists in
the corresponding globule of the honey
bee. Like the latter, it contains no
chromatin.

We have good evidence to show
that the proximal centrosome divides,
and that the two daughter centro-
somes, in some cases, at least, move
apart around the periphery of the
globule. This migration may begin
before the protoplasmic bud has be-
come completely separated from the
parent cell.

During the period of the abstriction of the interzonal body and
accompanying cytoplasm, which closely resembles that of the honey
bee, the development of the spindle figure is arrested, as in the bee,
not being carried- beyond the beginning of the metaphase. It is difii-

Fi CURES 5-8. Spermatocytes af-
ter the abstriction of tlie interzonal
body (i.e. .secondary spermatocytes)
X 2800.

FiGURK 5. Spindle figure of sec-
ond maturation division in tiic
beginning of the metaphase.

FiGDRE 6. Anaphase of second
maturation division.

Figure 7. Early telophase.

Figure 8. Late telophase. Sper-
matocyte nearly divided into two
spermatids.

74 PROCEEDINGS OF THE AMERICAN ACADEMY.

cult to determine the fate of the chromosomes and spindle fibres at
this time. The former appear to be aggregated to a greater or less
extent, and their individuality seems thereby to be obscured.

After the formation of the non-nucleated " Kichtungskorper " the
chromatin is found to occupy the equator of the spindle, where it has
regained the appearance of more or less distinct chromosomes. Thus
is formed a fairly characteristic spindle figure in the metaphase
(Figure 5). Division of the chromosomes now takes place, and the
daughter chromosomes migrate toward the poles of the spindle, leav-
ing stretched between them interzonal filaments (Figure 6). As the
cell enters on the telophase it elongates, and a constriction is then
formed at the equator (Figure 7). The constricting process is con-
tinued until the daughter cells remain connected to each other by only
an attenuated neck of cytoplasm, through which can be traced the
interzonal filaments. There result two spermatids, both apparently
destined to become functional spermatozoa, for these cells, unlike the
corresponding cells of the honey bee, are equal in size ; they are imme-
diately metamorphosed into spermatozoa.

Bibliography

Mark, E. L., and Copeland, M.

: 06. Some Stages in the Spermatogenesis of the honey bee. Proc. Amer.
Acad. Arts and Sci., Vol. 42, No. 5, pp. 103-111," 1 pi.

Meves, F.

: 03. Ueber " Richtungskbrperbildung " im Iloden von Ilyraenopteren.
Anat. Anz., Bd. 24, pp. 20-32, 8 Fig.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. Xo. 4. — September, 190".

THE PHYSIOLOGICAL BASIS OF ILLUMIXATION.

By Lolhs Bell.

Investigations os Light and Heat made or prBLisHED, wholly or di part, with AppEOPELiTioss

FROM THE ROJIFORD FOvD.

THE PHYSIOLOGICAL BASIS OF ILLUMINATION.

By Louis Bell.

Presented AprU 10, 1907. Received May 28, 1907.

The purpose of this paper is to point out that Avith the existing
knowledge of physiological optics artificial illumination can be removed
from the domain of empiricism and can be made to rest upon constants
which have a definite physiological basis and which can be and have
been predetermined with reasonable precision. For obvious reasons
data which relate to the sensation of sight cannot rank with exact
physical measurements, but they can nevertheless be evaluated closely
enough to give a reliable basis of judgment in planning illumination
to meet any given requirements.

Except for the aid received from accommodation and in binocular
vision from convergence, we see things in virtue of their dift'erences of
color and of luminosity. Of these two the latter is by far the more
important, particularly in distant vision. Objects of similar luminosity
but differing considerably in color blend into the general view in a most
astonishing fashion when at any considerable distance. Objects of sim-
ilar color but of different luminosity also fuse into the general field, and
if color and luminosity are both similar, things disappear in a way that
is positively amazing. Small colored areas of moderate luminosity blend
even at relatively short range, — a fact which the impressionists have
turned to extremely good use, albeit they often transfer to canvas the
color vagaries of the tired eye and the effects of simultaneous contrast
rather than the fleeting impressions which they hold so precious. One
of Monet's landscapes, however, is wonderfully interesting from the
standpoint of physiological optics, and especially in the existence of a
critical distance, within which the picture loses its magic.

Practically, therefore, vision depends very largely upon the power of
distinguishing differences of luminosity. And since objects in general
are luminous only in virtue of light reflected from them, their visibility
depends in turn upon their coefficients of reflection. So far at least as
problems of artificial illumination are concerned, objects seen do not

78 PROCEEDINGS OF THE AMERICAN ACADEMY.

range over a long scale of values of luminosity. Whatever the absolute
values of the light reflected, the relative values expressed by the coeffi-
cients of reflection range from about 0.80 to about .01, very few sub-
stances returning more than the former or less than the latter percentage
of the incident light.

The fundamental fact at the basis of vision is that the eye can per-
ceive, -^vithin a very wide range of absolute intensity, a substantially
constant fractional difference of luminosity. This is the purport of
Fechner's law, and the fractional diff"erence mentioned is well known
as Fechner's fraction. Its numerical value for normal eyes and ordinary
intensities of illumination is from .02 to .0055. The importance of this
law in practical seeing is enormous, for in a room well lighted by diffuse
daylight the illumination may vary from 100 meter-candles down to 10
or 20 in different parts of the room or at different times; and if power
of discriminating difference of luminosity changed much with the illu-
mination, one would be purblind most of the time. In some abnormal
eyes Fechner's fraction, with vision otherwise nprmal, is considerably
increased, with serious results. A case is cited by Krenchel in which
a patient was unable to get about in full daylight without stumbling
over things. His condition was most puzzling until a test showed
Fechner's fraction at a value of 0.1. At this value one could not dis-
tinguish between dark and light shades of brown and gray, having
coefficients of diffuse reflection of say .15 and .25 respectively, and
ordinary shadows on neutral surfaces would therefore disappear en-
tirely. With Fechner's fraction at 0.5 no contrast less than that be-
tween white and very dark pigments would be easily distinguished.

Now while Fechner's fi-action is fairly constant over a wide range of
intensities, one easily realizes that as twilight deepens his power of dis-
criminating shades is seriously impaired. It is this variation of Fech-
ner's fraction with the illumination which determines the minimum
amount of artificial (or natural) light which is effective in enabling one
to see things en masse in their natural relations. For general vision
any illumination above that required to bring Fechner's fraction for
the normal eye up to its steady value is needless, and, as we shall pres-
ently see, may be injurious.

Human vision, however, is frequently concerned with the observation
of fine details both far and near, and the power of seeing these is within
wide limits independent of the capacitj^ of the eye for distinguishing
small differences of luminosity. In the case mentioned by Krenchel
this visual acidty was normal in spite of the extraordinary lack of sen-
sitiveness to variations of light and shade. Acuity seems to depend on
the structure of the retina and the quality of the eye as an optical in-

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION. 79

strument rather than on the direct or secondary sensitiveness of the
nerve endings to stimulation by light. Great acuity is possibly com-
moner among savage peoples than in civilized races. Konig ^ has noted
it among the Zulus, whose color vision, by the way, was normal ; it has
been found in unusual degree among the Kalmucks, and Johnson ^ noted
it in the Congo peoples, in every case associated with slight hj^perme-
tropia. Some observations of Johnson (loc. cit.) would suggest that the
extremely dark hue of the fundus oculi and consequent diminution of
choroidal reflection found among the dark-skinned races may improve
the definition, although perhaps at the expense of sensitiveness. It is
of course well known that in the last resort the ability to separate
objects like neighboring points and lines depends on the minute struc-
ture of the retina, and is greatest in the fovea centralis, where the cones
are most closely packed. The fovea too is well known to be somewhat
less light sensitive than the retina in general. Using a wedge photom-
eter, I find for my own eye that there is a difference somewhat exceed-
ing one stellar magnitude between the foveal visibility and that outside.

Following out this line of investigation, it is not difficult to project
the fovea as a dull spot in the field of view. Using a wedge photometer
and fixing the eye at any point on a large sheet of white paper, one
finds, on rather quickly cutting down the light by sliding the wedge, a
roundish dark spot exactly in the axis and corresponding in diameter
with the projection of the fovea. It is not easy to hold vision of this
phenomenon since the axis of the eye inevitably tends to wander.

By drawing five rather faint crosses at the centre and corners of a
square, say a decimeter on a side, one can, by careful manipulation of
the wedge, make the central cross disappear in the foveal blind spot
while the corner crosses remain visible. The facts regarding the
independence of acuity and sensitiveness lend weight to the theory of
our confrere Professor Lowell regarding the bearing of this matter on
astronomical observations. Extreme acuity and extreme sensitiveness
being both rather rare, any considerable degree of independence must
render the coexistence of both in the same individual unusual in a very
much higher degree.

The failure of acuity in a dim light is familiar, and its variation with
intensity affords an independent criterion of the necessary requirements
in artificial illumination. Enough light must be provided to bring the
eye to its normal acuity as well as to its normal value of Fechner's
fraction. Fortunately the researches of Dr. Uhthoff^ and of Drs.

1 Nature, 31, 476. 2 Phil. Trans., 194, B. 61.

3 Graefe's Arch., 32, 171 ; 36, 33.

PROCEEDINGS OF THE AMERICAN ACADEMY.

Konig and Brodhun* on acuity and Fechner's fraction respectively
give us safe ground on which to travel in these respects.

In Figure 1 are shown the acuity curves and the shade-perception
curves of the normal eye for intensities up to 100 meter-candles.
Curves a and b give the values of Fechner's fraction for white light and
deep crimson light (X = 670 /^/a) respectively, while c and d give the acu-
ity curves for light orange (A=605 fx^) and yellowish green (A=575/x/>i)

respectively. The ordinates in the first case are -y, and in the latter

case are in arbitrary units. The most important feature of these curves
for the purpose in hand is that they are already becoming asymptotic
at low values of the illumination, and except for strong colors at about

.70
.60
.50

< 1A

.30

.20
irv-

.10

( ^

1 1 . ' 1 ; ,

10 20 30 40 50 60

Meter-candles

Figure 1.

100

the same point. At about 10 meter-candles they have turned well
toward the axis, and beyond 20 meter-candles the gain in shade-percep-
tion and acuity is very slow with further increase. Hence, when the
light reaching the eye has risen to 10 to 20 meter-candles, further in-
crease does very little in the way of assisting practical vision.

Artificial illumination can be safely based on this amount as a work-
ing intensity. Visual acuity is the controlling factor in most indoor
lighting. It varies noticeably with color, but for practical reasons,
which will appear later, the actual visibility of colored objects depends
not on the differences here shown so much as upon their general light-
reflecting power, which for dark hues is always low.

At great intensities both shade-perception and visual acuity consider-
ably decrease, the former at roughly 25,000 to 50,000 meter-candles, the
latter at much lower intensity. Neither function is likely to fail at any

* Sitz. Akad., Berlin, 1888.

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION. 81

intensity reached in the ordinary course of artificial lighting, though
acuity may be seriously interfered with by dazzling and consequent
rapid retinal exhaustion at intensities of a few hundred meter-candles,
and the same secondary cause also impairs shade-perception long before
its final decline.

It must be clearly understood that in specifying 10 or 20 meter-
candles as the intensity physiologically necessary to bring the eye into
its normal working condition, these intensities are those which become
visible to the eye, and not merely those that reach the objects under
observation.

The light reflected from any object is Ih where / is the incident
illumination and k the coefficient of reflection. Then, if a is the
normal illumination just indicated, the required incident illumina-
tion is

Taking, for example, a = 15 meter-candles, and assuming that one is
observing white or very light colored backgrounds for which k would
have a mean value in the vicinity of 0.6, the value of / should be about
25 meter-candles. If the background is dark fabric for which k would
not exceed 0.2, /would rise to 75 meter-candles, and for black fabrics
one could hardly get too much light. A typical application of the
principle may be taken in a draughting room where tracing has to be
done, and the drawing must be well seen through the tracing cloth, k
for tracing cloth is about .35, and the illumination which makes the
drawing visible is reflected from the drawing paper behind and passed
back through the tracing cloth. The drawing paper probably reflects,
if slightly off" white, as is common, about 60 per cent of the incident
light, and the final coefficient of the combination falls to about 0.25.
Taking the same value of a as before, /= 60 meter-candles. Ordinary
draughting rooms are found to be well lighted at this intensity. It
should be noted that draughtsmen generally use hard pencils, which
make marks contrasting rather weakly with the paper, so that strong
illumination is needed at all times.

In illumination out of doors, as upon the street, where no weak con-
trasts or fine details need to be made out, a may be taken very much
lower, but k is also low, and the minimum of about .25 or .30 meter-
candle often allowed between lamps is, as the curves show, consider-
ably too small for good seeing.

E^iect of Puinllary Aperture. The iris serves as an automatic stop
behind the cornea, adjusting itself so as to protect the retina from
too violent changes of brilliancy. It may vary in diameter of aperture

VOL. XLIII. — 4

PEOCEEDINGS OF THE AMERICAN ACADEMY.

from less than 1 mm. up to the full diameter of the visible iris, which
in the darkness may retreat even within the rim of the cornea, as
Du Bois-Reymond 5 has shown> The eye therefore works over' an
aperture range varying from /20 or more down to /2.5 or/2. Inci-
dentally the iris, acting as a stop behind the strongly refracting cornea,
produces a certain amount of typical "pincushion distortion " which is
evident in some optical illusions.

60
50
40

6-30
20
10

' — '

20 30

Meter-candles

Figure 2.

Data on the actual relation between intensity of incident light and
pupillary aperture are scarce and imperfect. So much depends on the
state of adaptation of the eye, individual sensitiveness, and probably
also upon the intrinsic brightness of the source, that reliable values of
the relation are difficult to obtain. From a reduction of Lambert's
data, however, I have plotted the curve of Figure 2, giving as abscissae
the illumination in meter-candles and as ordinates the area of the
pupil in square millimeters. The striking fact is at once in evidence
that this curve, like those of Figure 1, is rapidly becoming asymptotic in
the neighborhood of 10 meter-candles. In other words, the contraction
and expansion of the iris is less to protect the eye at high intensities

8 Centralbl. f. prakt. Augenheilkunde, 1888.

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION. 83

than to strengthen the retinal image at low intensities, even at the
expense of considerably impaired definition. The human eye seems,
however, to have become specialized for considerable acuity in a mod-
erate light rather than for such extreme sensitiveness as is found in
many nocturnal animals whose pupillary apertures vary over a much
wider range than in man.

The curves of Figure 1 show simple retinal sensitiveness, and in
reckoning from them one must at low illuminations take account of
the gain from increased aperture. At ordinary working values of the
illumination the gain is small, but at 1 or 2 meter-candles it is very
material and plays a most important part in practical vision. For
example, by curve a, Figure 1, an illumination of 0.5 meter-candle would
imply a value of Fechner's fi-action of about 0.2, which would in turn
imply very much impaired shade-perception. In point of fact, one
can see quite tolerably by a candle at the equivalent distance of 1.4
meters.

For if the pupil has adjusted itself to this situation the virtual
illumination is that corresponding to about 2 meter-candles, the equiv-
alent area of the pupil having increased to at least four times its ordi-
nary value, which is that to which the curves of Figure 1 pertain.
The result is a value of 0.1 or less for Fechner's fraction, which is
quite another matter.

Were it not for this assistance, it would be quite impossible to get
accurate photometric readings at the low intensities common upon the
photometer screen. Similarly it would be exceeding difficult to get
about at night, even by moonlight. In this latitude moonlight near
full moon may fall to about 0.2 meter-candle, which would give Fech-
ner's fraction at nearly .5, barring aid from the iris. With this aid
increasing the aperture perhaps 6 times, one can see to get about very
easily and can even read very large print. The same conditions have
an important bearing on vision in presence of a strong radiant. For
example, suppose that in a general illumination of 1 meter-candle one can

make out objects having a contrast -j = -15. Then let a light giving

20 meter-candles come fairly into the field of vision without materially
illuminating these objects. The pupil will close to about one third its
former area, giving a virtual illumination of about 0.3 meter-candles
and a shade-perception of about .30, in which, of course, the objects
disappear. Hence one cannot see well across a bright light, and even
objects illuminated by it lose in visibility unless the change in illumi-
nation from them is greater than the concomitant change in aperture
ratio.

84 PROCEEDINGS OF THE AMERICAN ACADEMY.

The loss ill visibility by the presence of a brilliant radiant in the
field of view is increased by the change in adaptation of the eye. It
is also probable that the intrinsic brilliancy of the radiant, as well as
the light received from it, has a bearing on the pupillary aperture.
Certainly at equal illuminations a well-shaded lamp gives higher visi-
bility than a bare one, both being assumed to be in the field of view.
There is therefore every reason for keeping such things as bare gas
lights and electric lamps entirely out of the visual field, only admitting
them thereto when they are so shaded as to keep the intrinsic brilliancy
to low limits.

The eye has been evolved under conditions that imply rather
moderate intrinsic brilliancy, admitting the general desire to keep the
direct rays of the sun out of one's eyes. Sky light, of course, varies
very widely in apparent intensity, being most intense in the presence
of white cloud of moderate density. An average all the year round
mean for the northern part of the United States, giving the intrinsic
brilliancy of an aperture fully exposed to the upper sky, would be from
measurements by Dr. Basquin,^ in the neighborhood of 0.4 candle power
per square centimeter. This is lower than the intrinsic brilliancy of any
flame, and approximates that of a bright lamp behind a thin opal shade.
The ordinary window, which is in a wall rather than the roof, and gets
its light largely from low altitudes and somewhat reduced by trees or
buildings, is much less brilliant.

For instance, a window 1 m. wide and 2 m. high would be unusually
effective if it gave 50 meter-candles at a point 5 m. within the room.
This illumination would imply a virtual intensity of about 1250 candles
at the window or an intrinsic brilliancy over the window area of 0.0625
candle power per square centimeter. Natural intrinsic brilliancies are
decidedly low, and the chief difference between natural and artificial
illumination, from the standpoint of wear and tear upon the visual
organs, is the high intrinsic brilliancy of artificial light. If radiants are
to be within the field of vision, they should be screened by diffusing
globes or shades down to a maximum intrinsic brilliancy of preferably
not above 0.1 or 0.2 candle power per square centimeter, certainly
not above double these figures. As I have pointed out in a former
paper,7 if one plots the pupillary apertures as ordinates and the

function —= as abscissae, the result is nearly a straight line, so
that if one measures the visual usefulness u of a certain illumination

8 The Illuminating Engineer, Jan., 1907.
' Trans. 111. Eng. Soc., July, 1906.

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION. 85

/ in terms of what one may call the admittance of the pupil, then
approximately

= cWl,

assuming that / is within ordinary ranges of intensity ; that is, the eye
works most efficiently at moderate illumination. The adverse factors in
lowering the illumination are the optical errors introduced by increase
of pupillary aperture and the general failure of shade-perception and
acuity as the illumination falls below about 10 meter-candles. Spheri-
cal aberration and astigmatism increase rapidly at large apertures, so
that definition of objects is much impaired. This doubtless plays its
part in the failure of acuity in very poor light, although a more promi-
nent fact is the increase of acuity as the eye is stopped down at illu-
minations considerably above the critical value at which the eye comes
into normal working condition.

This critical value to which shade-perception, acuity, and pupillary
reaction all point relates, it must be remembered, to the illumination
received from the objects viewed considered as secondary light-sources.
In too strong light thus received the eye is as seriously dazzled as if
the source were a primary one, and the usual effects of after images
and other evidences of retinal exhaustion and irritation at once appear.
In very insufficient illumination there is failure to see contrast and
detail, and there is an instinctive effort to push the eye near to the
object at the risk of straining the mechanism of accommodation se-
riously. The familiar success of this expedient opens up some of the
most curious questions of physiological optics.

Suppose, for instance, that one is viewing white letters on a dark
ground. Evidently the letter acts as a secondary source of illumina-
tion, which proceeds fi-om it, following the law of inverse squares. Now
by halving the distance to the eye the intensity at the pupil is quad-
rupled, and at first thought one would infer that inspection of the
shade-perception and acuity curves would give ample reason for the
gain in visibility. But at half the distance the object subtends double
the visual angle, and the retinal image is therefore quadrupled in area,
leaving the luminous energy per unit of area the same as before ; why,
therefore, any gain in visibility 1 A similar question in a more aggra-
vated form arises in accounting for improved vision through night
glasses.

The key to the situation is found in the fact, put on a sound experi-
mental basis by Dr. Charpentier,^ that for the visible brightness of

8 " La Lumiere et les couleurs," p. 138 et seq.

86 PKOCEEDINGS OF THE AMERICAN ACADEMY.

objects giving images less than about 0.15 mm. in diameter the simple
la^w of inverse squares holds. In other words, for weak stimuli at least,
the visibility of small objects is determined by the total light emitted
and by the distance and not by the surface brilliancy. It is as if
a retinal area of about 0.15 mm. diameter acted as a visual unit, all
stimuli acting upon this as a whole. As Charpentier (loc. cit.) puts
the case with reference to distance, " In a word, the apparent brightness
of a luminous object varies, other things being equal and within the
limits indicated, in inverse ratio with the square of its distance from
the eye."

As the eye then approaches a luminous object its apparent brightness
increases, and it is distinguished more plainly so long as its image di-
mension is anywhere within the limit mentioned. As this corresponds
to an object 2 mm. long at a distance of about 20 cm., the rule holds
for reading type and the observation of small objects generally. The
cause of this phenomenon is somewhat obscure. The natural suppo-
sition that it migiit well be due to spherical aberration and faulty
accommodation in an eye with its pupil expanded, fails, as Charpentier
(loc. cit.) shows, in two ways. First, the circle of diffusion in the eye
due to spherical aberration is much smaller than the critical diameter
in this case, and second, the phenomenon occurs when the eye is stopped
by a diaphragm. I have tried it with a wedge photometer provided
with a pair of 2 mm. apertures in line and separated by 6 mm., so
that the ray pencil was of very narrow aperture, and find it still very
conspicuous and apparently unchanged.

Charpentier and others are disposed to think its origin purely retinal,
resulting from the spreading of the stimulus over retinal elements ad-
jacent to those immediately concerned, and closely allied to the phe-
nomenon of irradiation.

This latter phenomenon, however, is charged by Helmholtz largely to
aberrations and dioptric faults generally. One of the best sources for
studying irradiation is an incandescent lamp filament. At a distance
of say 2 meters the apparent diameter of the filament at full incandes-
cence is 4 or 5 mm. Using the wedge photometer upon it, the diminu-
tion of apparent diameter is at first rapid, until it falls to about 0.5
mm., at which it remains nearly constant until it completely vanishes.
Stopping down the pencil of rays to 1 mm. or so cuts oif most of the
irradiation, but this seems to act in the main merely as a reduction of
intensity, since the same effect is produced by a similar reduction in
intensity by the wedge retaining the full aperture of about 5 mm. At
a few hundredths of a meter-candle most of the irradiation has disap-
peared. The apparent breadth of the filament decreases without any

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION. 87

marked shading off at the edges, something as if a slit were being
closed. The appearances indicate that beside the undoubted aberra-
tions which come into play, there is considerable spreading of light in
the retina at high intensities, reinforced very likely by reflection from
the choroid, producing an effect quite analogous to the halation observed
in a photographic plate.

The dimensions of the irradiation effect thus observed are inferior to
the dimensions required by Charpentier, but it is quite probable that
with a dark-adapted eye and feeble illumination, lessened contrast with
the chief image would render the outlying portions more conspicuous.

The increased visibility of rather large areas is a still more puzzling
matter, for which no satisfactory explanation has been produced. Inas-
much as all dealings like these with threshold sensibility have by this
condition eliminated the cones of the retina from action, and depend
upon rod vision entirely, it may be, since the rods are relatively more
numerous away from the fovea, that mere size of image insures its
falling on retinal areas relatively rich in active visual elements.

Aside from questions of intensity in artificial illumination is the
matter of steadiness. It is of course well known that violent transi-
tions of light and darkness, whether by moving the person or the eye,
or by changing the intensity of the light itself, are distressing and
injurious. The retina has a certain amount of visual inertia, which
furnishes protection against very rapid changes, else one could not use
Hghts successfully with alternating current. Flicker, from a practical
standpoint, is troublesome about in direct proportion to its magnitude
and in inverse proportion to its frequency. A change of intensity, how-
ever, covering some seconds, giving the iris plenty of time for readjust-
ment, is hardly noticeable, while one of the same numerical magnitude,
say 20 per cent each side of the mean, occurring once or a few times
per second, is most painful. Ordinary incandescent lamps run on alter-
nating current vary from 5 to 15 per cent on each side of the mean,
according to the thermal inertia of the filament, and the frequency.
With lamps of ordinary voltage and candle power the flickering is per-
ceptible at between 20 and 30 cycles per second, the new high-efiiciency
lamps being worse than the older ones. Practically all lighting is
done at above 30 '^, and troublesome flickering comes only from the
irregular fluctuations of bad service. It must not be forgotten that one
can impress serious fluctuations of light on the retina by compelling the
eye to confront great variations of illumination when it moves. No
artificial light should be arranged so that it forces the eye to make
sudden transitions from blackness to brilliancy. Figure 3 is given here .
as a horrible example of what should never be permitted. I am sorry

88 PROCEEDINGS OF THE AMERICAN ACADEMY.

to say that it is from the catalogue of a maker of reflectors who should
have known better. Note the blackness of the interior and the exces-
sive brilliancy of the light on the work.

In this connection should be mentioned the trouble that may come
from the glare of light reflected from white paper, a risk to which book-
keepers are especially subject. I have been in counting rooms where
I found every clerk with signs of bad eyes.

Much paper is too highly calendered, and from this cause gives a
combination of regular and difi"use reflection. Obviously a mirror
placed on one's desk would give at certain angles an image of the lamp

Figure 3.

of distressing brilliancy, and as the head might move this image would
dodge into and out of the field of vision, giving an added cause of
trouble. Glossy paper does somewhat the same thing. Figure 4 shows
from Trotter's data^ the relative reflection at various angles of inci-
dence from ordinary Bristol board (a) and from the nearly pure matte
surface of freshly set plaster of Paris (b). The sharp peak corresponding
to the angle of regular reflection is very striking. Light on a desk
should therefore come from the side or rear rather than from the front,
especially if the source is of high intrinsic brilliancy. For a similar
reason the direction of illumination should be such as to free the eye
from the effect of wavering shadows of the hand or head. The avoid-
ance of shadow from the hand is the rationale of the sound old rule

9 The Illuminating Engineer, 1, 488.

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION.

that the light should come from the left (left-handed people were
forgotten). Shadows from the head and shoulders are much more
troublesome, as they may exist to an annoying degree in rooms other-

■t 10

h- —

30 40 50 60

Angles of Incidence

Figure 4.

wise well lighted, and they are in fact difficult to avoid in the general
lighting of counting rooms and similar places.

Finally, one is nowadays often confronted by questions of color.
Until electric lighting in its more recent forms appeared there was a
sufficient similarity in the colors of artificial illuminants to place them
substantially on a parity. At present, strong colors are common, and

90 PROCEEDINGS OF THE AMERICAN ACADEMY.

are likely to be increasingly so, since, as I have noted in a previous
paper (loc. cit.), selective radiation is necessary to high luminous effi-
ciency. One has to deal with the yellow of the flaming arc, the yel-
lowish green of the Welsbach, the blue green of the mercury tube, and
the violet of the enclosed arc, all of which may have to be compared
with the deep orange of the Hefner lamp.

Practically the question of suitable color resolves itself into two parts,
— first, the effect of color on the proper functioning of the visual appa-
ratus, and second, its relation to our observation of colored objects. I
shall not take up here the theories of color vision, save to note that
many of their difficulties may now be charged to the existence of at least
two kinds of independent visual elements, the rods and cones, differently
distributed in the retina, and possessing two radically different types of
visual sensitiveness. That the cones are highly evolved rods has been
shown beyond much doubt by Cajal, and is in evidence in the simple rod
structure found in the parietal eyes of some fishes and lizards and in
lower organisms generally. Whether, as Mrs. Franklin ^° surmised, there
are definite intermediate phases of sensitiveness between the achromatic
vision of the rods and the full chromatic vision of the cones is an
important topic for research.

May I venture to suggest that there are some reasons for thinking
that there may even be a difference in kind between a simple photo-
chemical rod stimulation and the strongly selective stimulation of the
highly specialized cones 1 Selective activity does not necessarily con-
note chemical instability. They may coexist, as in some organic dye-
stuffs, or may be entirely independent, as in the fluorescence of heavy
paraffin oils. The presence of strong pigmentation at the rods and its
absence at the cones, coupled with the absence of visual purple in some
nocturnal creatures whose eyes are presumably specialized for very weak
light, suggests that the evolution of the retinal elements may have pro-
ceeded along more than one line. In fact, the Young-Helmholtz and
Hering doctrines may find in a heterogeneous retina a certain amount
of common ground. Be this as it may, mankind certainly has super-
imposed a very sensitive but achromatic rod vision, and a much less
sensitive but chromatic cone vision, the latter being mainly central
and the former mainly peripheral. The passage from predominant rod
vision to predominant cone' vision is shown in the sharp flexure of
the curves in Figure 1. The exact point at which the color sensitive
cones begin to get into action undoubtedly varies greatly in different
eyes, and in the same eye in different conditions of adaptation. As the

" Mind, N. S., 2, 473 et seq.

BELL. — THE PHYSIOLOGICAL BASIS OF XLLUMESTATION.

illumination is progressively diminished, color vision gets more and more
imperfect and uncertain, especially toward the red end of the spectrum.
The effect is shown very clearly in the variation of Fechner's fraction

with color as the intensity changes. Figure 5 shows the change in -y

with X for intensities of 15 meter-candles (a) and 0.75 meter-candles
{b) respectively from the data obtained by Konig and Brodhun (loc.

.^0

,60

.-50

.40

.30

.10

—

___

. — a

700 fi./j.. ■

600

Figure 5

500

400

cit.). Looking at the latter, it is evident that for the orange and red,
vision must be very poor indeed, and in no part of the spectrum really
good. In curve a color vision is pretty well established, although there
are still traces of the point of inflection, which, as we shall presently see,
falls near the point of maximum sensitiveness in very weak light, as if
the superimposed rod vision were still helping out at this moderate
intensity.

The Purkinje phenomenon, now well known to depend on the pro-
gressive failure of cone vision, also gives valuable evidence along the
same line. It was noticed more than twenty years ago by Professor

92 PROCEEDINGS OF THE AMERICAN ACADEMY.

Stokes ^^ that the phenomenon varied with the areas involved, and
recently Dow ^^ has found that for small areas (i. e., nearly central and
hence mainly pure cone vision) Purkinje's phenomenon appears only
below about 0.2 meter-candle. This figure would quite certainly have
been somewhat higher had he used instead of red and signal-green
glass the primary red and green, but it is clear from his results that
the superposition of rod vision has a very considerable efiiect at moder-
ate illuminations.

Finally, one must consider the luminosity curves at various intensities.
Figure 6 gives in curve a the relative luminosities of the spectrum
colors at fairly high intensity. The maximum is in the yellow, and the
falling off", especially on the red side, is very rapid. This seems to be
about the normal curve when the eye is fully in action. Curve b gives
the luminosity curve for an intensity of about 0.0007 meter-candle.
At this point color sensation is practically extinguished, and the maxi-
mum luminosity is perceptible, in what would seem the pure green were
the light brighter, very near the E line and at a point corresponding
to the inflection in the curves of Figure 5. This is practically the con-
dition of pure rod vision. Curve c. Figure 6, lends confirmatory evidence.
It is the luminosity curve obtained by Abney ^^ from a patient with pure
monochromatic vision. He had apparently an absolute central scotoma
(cones atrophied rather than replaced by rods 1 ), visual acuity greatly
subnormal (central vision absent), and nyctalopia. This is a typical
condition, nyctalopia being generally associated with central color sco-
toma, leaving peripheral vision but shghtly affected (Fick). The patient
apparently had no color perception, and his luminosity curve was prac-
tically identical with b, the normal curve for very weak light.

It would be most interesting to get proper tests for luminosity in one
of the rare cases of congenital hemeralopia which would present the
reverse condition of rods inactive and cones nearly normal. A com-
parison of such a case with luminosity in the hemeralopia associated
with retinitis pigmentosa, in which peripheral vision is progressively
contracted, might give valuable evidence as to the existence of retinal
elements intermediate in function between rods and cones.

To sum up this phase of the matter, rod vision seems to be predomi-
nant from the very threshold illumination up to several tenths of a
meter-candle, and to continue in force to all ordinary intensities, although
rather easily exhausted. It gives low visual acuity and shade-percep-
tion perhaps of the order of a tenth normal, but, such as it is, it is our

" Nature, 32, 537. " Phil. Mag., Aug., 1906.

13 Proc. Roy. Soc, 66, 179.

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION.

main nocturnal reliance. Cone vision begins to come perceptibly into
play at a few thousandths of a meter-candle, and at a few tenths is

1 ,

J<^

**=^

--'^''^

^-^

x^.

^»

■-^

o
o

8 a s

pretty well established, but does not become normal over the visual area
below five or ten meter-candles, and gains materially even beyond that,
especially in acuity, which is weak at the lower intensities.

94 PROCEEDINGS OF THE AMERICAN ACADEMY.

Acuity in practical degree is chiefly an attribute of cone vision. The
general theory of optical resolution requires acuity inversely as the
wave-length of the light concerned. In practice this difference is in
great measure masked by other and larger causes of variation. Chief
among these is the very low luminosity of the shorter wave-lengths on
the one hand and of the very long ones on the other. For example, in
comparing acuity at A. = 500 /ifx and A = 650 /u/* there is a proportional
difference really due to color, but a ratio of 2.5 : 1 in luminosity in fur-
ther favor of the green. Violet light favors acuity, if one can get
enough of it, but a luminosity of .02 of the maximum in the yellow
stands in the way.

Certain strongly colored lights, like the flaming calcium fluoride arc
and the mercury arc, give apparently extremely sharp definition in black
and white objects. In general this is not due to any advantage in color
as such, but to improvement in the conditions of chromatic aberration
in the eye. At rest for distant vision, the normal eye is in focus for the
rays of maximum luminosity, and the focus for blue lies perhaps 0.4 mm.
in front of the retina. That is, the eye is short-sighted for short rays.
In near vision the rear conjugate focus moves backwards and the eye
finds focus on the blue with less accommodation than usual. Thus
Dow ^* finds that, while the mercury arc gives easy and sharp definition
for near vision, at a distance of twenty feet or even less it becomes
difficult to get focus. Lord Rayleigh ^^ noticed some years ago that in
very weak light he became myopic and required a glass of— 1 diopter to
restore normal vision. This effect is of the order of magnitude required
by the shift of maximum luminosity into the green at very low intensi-
ties. Another phase of chromatic aberration is even more important.
Were it not for the existence of a very high maximum in the luminosity
curve, distinct vision would be impossible, since the difference of focus
between the red and violet in the eye is something like 0.6 mm. ; and
were these extreme colors highly luminous, there would be no focal sur-
face to which the eye could adjust itself Only the great predominance
of the central colors in luminosity gives the chance for a fairly sharp
image.

It is easy to show the difficulties into which equal luminosity
throughout the spectrum would plunge us. If one forms a grid of cer-
tain purples by cutting strips of tissue paper of the required color per-
haps 5 mm. wide and 100 mm. long and pasting them upon a dark
neutral background spaced about their width apart, one readily finds

" The Illuminating Engineer, 2, 26 et seq.
" Nature, 31, 340.

BELL. — THE PHYSIOLOGICAL BASIS OF ILLUMINATION. 95

the practical effect of chromatic aberration. From a distance of a
couple of meters sharp definition of the grid is quite impossible. The
purple chosen should give considerable absorption of the green, yellow,
and orange, leaving strong red and blue evenly balanced in luminosity,
and the background should be of not greatly different luminosity, so
that the eye must rely mainly upon color effects. The rays from the
grid are then of two widely different colors, for which the focal length of
the eye differs. There are therefore two image surfaces of about equal
intensity perhaps half a millimeter apart, and the effect is a curious
blur, the eye hunting in vain for something definite upon which to focus.

Interposing now a deep red screen (concentrated saffronine is good),
or a suitable blue screen, the image of the grid becomes nearly mono-
chromatic and appears sharply defined. This is an extreme case, but
any monochromatic light has an advantage in definition if other con-
ditions are at all favorable. It seems highly probable that the well-
known trouble found at twilight in trjdng to work by a mixture of
natural and artificial light is due to a similar cause. The predominant
hue of diffused sky light is strongly blue, while that of gas flames, incan-
descent lamps, and like sources, is strongly yellowish. At a certain
point in the fading of daylight the luminosities of these widely different
colors should balance closely enough to produce something of the effect
just described, although the usual difference of direction in the two su-
perimposed illuminations may play a part in the general unpleasant
effect.

There is, however, an inherent danger in using monochromatic or
strongly colored light for general purposes. Whatever may be the
nature of color vision, a strongly colored light utilizes only a part
of the visual apparatus. If of high intensity to make up for inherently
low luminosity, it rapidly exhausts that part, and produces, as is well
known, a temporary color blindness. There is at least a serious chance
that long continued use of colored light would produce persistent and
perhaps permanent damage to color perception. A light nearly white,
with its maximum luminosity near the normal wave-length, runs the
least chance of imposing abnormal strains on the visual apparatus.

In color discrimination the same rule holds good, for any considerable
departure irom white leads to entirely false color- values. In closing I
may mention an interesting question which arises with reference to
obtaining a light of high efficiency by building it up irom the mono-
chromatic primary components. Would the eye see clearly by such a
light, and could it discriminate colors properly 1 The answer is prob-
ably yes. The equation for white is roughly

W=.20B + .30G + .50B.

96 PROCEEDENQS OF THE AMERICAN ACADEMY.

These are quantities as determined by slit width in the spectrum or
a like process. There is sufficient predominance of luminosity in the
green to avoid trouble f^om chromatic aberration, and the actual work-
ing of the combination in giving photographs in natural colors is such
as to indicate proper color vision. As yet, however, no means are avail-
able for producing all three primary colors efficiently, and for white arti-
ficial light we are compelled to rely on what is in effect building up a
nearly continuous spectrum from heterogeneous components, unless as
usual we employ the continuous spectrum of an incandescent solid.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 5. —September, 1907.

CONTKIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

ON THE DETERMINATION OF THE MAGNETIC BE-
HAVIOR OF THE FINELY DIVIDED CORE OF AN
ELECTROMAGNET WHILE A STEADY CURRENT
IS BEING ESTABLISHED IN THE EXCITING COIL.

By B. Osgood Peiece.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

ON THE DETERMINATION OF THE MAGNETIC BEHAVIOR
OF THE FINELY DIVIDED CORE OF AN ELECTRO-
MAGNET WHILE A STEADY CURRENT IS BEING
ESTABLISHED IN THE EXCITING COIL.

By B. Osgood Peikce.

Presented December 12, 1906. Received June 22, 1907.

More than fifty years ago Helmholtz established, on theoretical
grounds, the now familiar equations for the manner of growth of a
current in a circuit of constant inductance under a given electromotive
force, and proved by a brilliant series of experiments ^ that the
predictions of this theory were fulfilled in practice. It appeared,
in particular, that if a circuit of resistance r containing a constant
electromotive force, E, were closed at the origin of time, the current,
/, would be given by the expression

E '■'

. 7 (1 - ^~^> (1)

if L were the "potential of the circuit upon itself," that is, the self-
inductance. The " induced current " (/) would satisfy the equation

. L rll E -rl

i — ---j- = — .eL, (2)

r at r

If, therefore, / were plotted against the time, the resulting curve
{OGQKC, Figure 1) would have as asymptote the straight line {ZCf)
parallel to the t axis at a distance E/i^ above it; the current in
the circuit at any time {OP) would be given by the corresponding

1 F. E. Neumann, Abh. d. Berl. Akad. 1845 and 1847; Helmholtz, Die Erhalt-
iing der Ivraft, 1847 ; Pogg. Ann., 83, 1851 ; 91, 1854; Phil. Mag., 42, 1871.

100 PROCEEDINGS OF THE AMERICAN ACADEMY.

ordinate {PQ) of the curve and the instantaneous value of the induced

current by the distance {NQ) at that time, of the curve from the

asymptote. The whole "amount" of the induced current up to

the given time would be represented by the shaded area {A) shut

in by the curve, the asymptote, and the ordinates, ^ = 0, t = OP. If

the electromotive force were suddenly shunted out of the circuit

after the current had reached its final value, the "extra current"

would have the value

E '■*

-..-Z. (8)

Helmholtz also studied the " forms " of the currents induced in the
secondary circuit of a small induction coil at the making and breaking
of the primary circuit, and, by using in the apparatus iron cores, some of
which were solid and some finely divided, he showed that the effect
of eddy currents in the iron upon the apparent duration of the induced
currents might be very appreciable. The results of Helmholtz's
experiments were confirmed with the aid of other apparatus, during
the next thirty years,^ by a number of physicists.

The mathematical treatment of the subject begun by Neumann and
Helmholtz was in 1854 pushed somewhat farther by Koosen, and in
1862 E. du Bois-E,eymond "^ published an elaborate discussion of the
equations laid down by Helmholtz for the determination of the cur-
rents in two neighboring circuits of constant self-inductances {Li, L^
and constant mutual inductance {M), and gave the solutions of the
simultaneous equations *

(4)

^■li + ^'-m + '■''■■" '^''

corresponding to a number of different sets of physical conditions,
in nearly the forms in which they now appear in textbooks. Du

2 Felici, Ann. de Chimie, 34, 1852; N. Cimento, 3, 1856; 9, 1859; 12, 1874;
13, 1875. Cazin, Compt. Rend., 60, 1865 ; Ann. de Chimie, 17, 1869. Guillemin,
Compt. Rend., 50, 1800. Berlin, Mem. de la Soc. des Sc. Nat. Strasbourg, 6,
1865. Bazzi and Corbianchi, N. Cimento, 4, 1878. Bartolli, Mem. d. Ace. d.
Lincei, 6, 1882. Bazzi, Att. d. Ace. d. Lincei, 6, 1882. Lemstrom, Pogg. Ann.,
147, 1872. V. Ettingshausen, Pogg. Ann., 159, 1876.

3 Koosen, Pogg. Ann., 91, 1854. E. du Bois-Reymond, Monatsberichte d. Berl.
Akad., 1861, 1862. Brillouin, These, 1880; Jour, de Phys., 10, 1881; Compt-
Rend., 1882.

PEIRCE. — BEHAVIOR OF THE CORE OP AN ELECTROMAGNET. 101

Bois-Reymond showed that if the secondary circuit contained no
battery, and if, after the primary current had been fully established,
its circuit were suddenly broken, the current induced in the secondary
circuit would have a form like that of the dotted curve (P) in Fig-
ure 2 ; if after a few seconds the primary circuit were again closed,
the secondary current when plotted against the time would yield
a curve either hke Q, or like Si in the same diagram. The lines in
this familiar figure have been drawn to scale for a certain pair of
circuits the self-inductances of which are equal, fixed quantities
and the resistances also fixed. Q, J?, 8 correspond to three different
values of the mutual inductance {M\ which are respectively half
as great, nine tenths as great, and equal to the self-inductance (Z)

TIME

FiGUKE 1.

If the current is expressed in absolute units (absamperes) and the time in
seconds, the shaded area represents the change in the total flux of magnetic
induction through the circuit, during the time OP.

of either circuit. These curves show the currents induced in the
secondary circuit when the primary is made ; the crest of any such
curve comes earlier the larger the value of M. The curve P, which
represents a current induced in the secondary circuit when the
primary circuit is broken, is drawn for the case M = hL, and there-
fore corresponds to the curve Q ; K dn Bois-Re}Tnond called atten-
tion to the fact that in such problems as this the areas V and W
must be equal. The curves like F corresponding to E and S could
be found merely by exaggerating all the ordinates of P in the ratio
9/5 or the ratio 2.

From the early days of induction coils, iron cores had been used
to increase the mutual inductance of the circuits, and, soon after
Helmholtz had given the equations for the currents in neighboring

102

PROCEEDINGS OF THE AMERICAN ACADEMY

circuits of constant inductances, coils containing iron were studied
from the point of view of the principles which he had laid down.
Helmholtz's own experiments and those of others soon showed,
however, that the introduction of masses of magnetic metal into the
space within the coils complicated very much their action. It ap-

FlGURE 2. -

The curves Q, R, S represent for different relative values of the mutual in-
ductance the current induced in thp secondary circuit of a certain induction
coil without iron, when the primary circuit is suddenly closed.

peared that the existence of eddy currents in the iron, if the coil were
solid, and the fact that the counter electromotive force in a circuit —
as measured by the time rate of change of the flux of magnetic induc-
tion through it — is by no means proportional to the rate of change
of the intensity of the current if a circuit "contains iron," made the
simple theory of Helmholtz inapplicable, as he himself had foreseen

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 103

that it would be. The subject interested many investigators,^ who
found it easy to exhibit the disturbing effects of eddy currents in
hindering rapid magnetic changes in solid masses of iron and in
thus modifying the characters of the induced currents ; but it was not
until much work had been done by many persons on the phenomena
attending magnetic induction in iron that the theory of the alternate
current transformer which had meanwhile come to be of much
practical importance was very well understood. With the general
introduction of dynamo-electric machinery the magnetic behavior of
the different kinds of iron used in its manufacture became of practical
interest, and several different magnetometric and ballistic methods of
studying permeability were invented and employed in making the
necessary measurements upon relatively small pieces of the metal.

Soon after the first hysteresis diagrams had been obtained as a
result of experiments either on comparatively thin iron or steel rings,
or on long, fine wires, it was found by engineers that, on account
of the considerable time required to establish a steady current in
the coil of a large electromagnet to which a given electromotive force
had been applied, the " reversed current," and even the " step-
by-step " ballistic methods which had proved effective in the cases
of slender toroids, were, in their old forms at least, not well fitted
for studying the magnetic properties of such massive closed iron
circuits as frequently occurred in practice. When there was a
gap in such a circuit, the problem, of course, offered no difiiculty,

« Faraday, Researches, 1831, 1832, 1846. Lenz, Fogg. Ann., 31, 1834. Henry,
American Journal of Science, 1832; Phil. Mag., 16, 1840. Dove, Fogg. Ann., 43,
1838 ; 54, 1841 ; 56, 1842. Beetz, Fogg. Ann., 102, 1857 ; 105, 1858. Fliicker,
Fogg. Ann., 87, 52; 94, 1855. Rayleigh, Phil. Mag., 38, 1869; 39, 1870; 23,
1887; 22, 1886. Bichat, Ann. de I'ficole Norm., 10, 1873. Sinsteden, Fogg.
Ann., 92, 1854. Magnus, Fogg. Ann., 38, 1836 ; 48, 1839. Schneebeli, Bull, de
la Soc. des Sc. Nat. de Neufchatel, 11, 1877. Blaserna, Giornn. di So. Nat., 6,
1870. Maxwell, Electricity and Magnetism, 2, iv. Donati and Foloni, N. Cimento,
13, 1875. Stoletow, Phil. Mag., 45, 1873. Auerbach, Wied. Ann., 5, 1878. Row-
land, Phil. Mag., 46, 1873 ; 48, 1874. Thomson, Phil. Trans., 165, 1875. J.
Hopkinson, Phif. Trans., 176, 1885. Von Waltenhofen, Fogg. Ann., 120, 1863.
Warburg, Wied. Ann., 13, 1881. Wiedemann, Lehre von der Elektricitat. Ewing,
Phil. Trans., 176, 1885; Froc. Roy. Soc, 1882, Magnetic Induction in Iron and
other Metals. Du Bois, The Magnetic Circuit. Fleming, The Alternate Current
Transformer. Ewing and Low, Froc. Royal Soc. 42, 1887 ; Phil. Trans., 180,
1889. Du Bois, Phil. Mag., 1890. Oberbeck, Wied. Ann., 22, 1884. J. and E.
Hopkinson, Phil. Trans., 177, 1886. Jouaust, Compt. Rend., 139, 1904. E. Hop-
kinson, Brit. Assoc Report, 1887. Tanakadate, Phil. Mag., 1889. Wilson, Froc.
Royal Soc, 62, 1898. Baily, Phil. Trans., 187, 1896. Many other references
may be found in these sources.

104 PROCEEDINGS OF THE AMERICAN ACADEMY.

but when large iron frames were completely closed, it became the
custom, in satisfying commercial contracts, to attempt to get informa-
tion about the permeability of the metal as a whole from tests, under
given conditions, upon small, thin specimen pieces made as nearly as
possible of the same material as the original, or else cut from it. It
was usually impossible, however, to be sure that the temper of the
small piece was sufficiently like that of the mass to make it a fair
representative of the whole, and the preparation of the specimens was
often troublesome, so that some more practical method of procedure
was seen to be desirable,^ and it seems to have occurred to a number
of different persons independently that a good deal might be learned
about the magnetic properties of the core of an electromagnet if
one determined the manner of growth of a current in an exciting
coil of a given number of turns wound closely about the core, when,
under given initial conditions, a constant, known, electromotive force
■was applied to the coil circuit.

The Determination of some of the Magnetic Properties op
THE Core of an Electromagnet from the March of a
Current in the Exciting Coil.

If, at any instant, the total flux of magnetic induction through the
n turns of the exciting coil of an electromagnet is N (maxwells), if r
is the resistance of the coil circuit (in ohms), i the current in it (in
amperes), and E the applied electromotive force (in volts), then

or — - = 10* • 7

■(?--> (6)

and if the final value {E/r) of the current be denoted by ^^ and the
change in N during the time interval ti to t^ by iVi.2,

N^,, = r■W■ fll^-i)dt. (7)

If, now, i be plotted against the time in a curve s (Figure 3) in
which / centimeters parallel to the axis of abscissas represent one
second, and an ordinate m centimeters long one ampere, the curve

6 Drysdale, Jour. Inst. Elec. Engineers, 31, 1901.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 105

■will have au asymptote, CY, parallel to the axis of abscissas, at a dis-
tance, KC, from it corresponding to E/r amperes, and, if OK represents
the time ti, and OL the time t^, the area FGDC, or Ai^, expressed
in square centimeters, is equal to

(L - 0 (it, (8)

so that ivi2 = J = — -J -. — -. (9)

In practice N usually differs from n 4>, where <^ is the induction flux
through the iron core of the electromagnet alone, by only a small fi-ac-
tion of itself, and, if a is the area of the cross section of the core at
any point, a certain average value of B, the induction, can be obtained
from the expression Njna, though in such cores as are used in large
transformers, H, and therefore B, would probably have very different
values at different points of the section. Really N is greater than n ^
by the amount of the magnetic flux, in the air about the core, through
the turns of the exciting coil, caused by the current in the coil itself
or by neighboring currents, if there are such.

Using this theory, a good many persons have studied at various times
the magnetic properties of different large masses of iron, and in 1893
Professor Thomas Gray of Terre Haute published in the Philosophical
Transactions of the Royal Society a long series of very beautiful
current curves,^ obtained, with simple apparatus handled with great
skill, from a 40 K. W. transformer belonging to the Rose Polytechnic
Institute. A number of diagrams '^ showing the manner of growth of
currents in the exciting coils of large electromagnets with solid cores
have been printed within the last dozen years ; of these the curves
^iven by Dr. W. M. Thornton are especially interesting.

If to the coil of an electromagnet, in series with a rheostat of
resistance r, a given electromotive force be applied, and if r be then
reduced by steps, at intervals so long that one is sure that the final
current belonging to each stage has been practically attained, the
curve which has elapsed times for abscissas and the corresponding

6 T. Gray, Phil. Trans., 184, 1898.

' Hopkinson and Wilson, Journal of the Institute of Electrical Engineers, 24,
1895. Thornton, Electrical Engineer, 29, 1902 ; Phil. Mag., 8, 1904 ; Electrician,
1903 Peirce, These Proceedings, 41, 1906. Several figures from this last paper
are here reproduced.

106

PROCEEDINGS OF THE AMERICAN ACADEMY.

values of the strength of the current for ordinates, will have the
general form of the line U in Figure 4, though, if the core be so large
that the building up time at each stage is long, the diagram will be
much drawn out horizontally. The curve which shows the march of
the current when the electromotive force is applied directly to the coil
without the intervention of the rheostat will resemble line V in the
same figure. The exact forms of these curves depend, of course, upon

SECONDS.

PlGUliE 3.

If / centimeters parallel to the horizontal axis represent one second, and an
ordinate m centimeters long one ampere, A • 10* • r/hn (where A is the area,
in square centimeters, of CDGF) represents the change in the magnetic flux
through the circuit during the interval KL.

the magnetic state of the core at the outset, and will be very different
if the iron has been thoroughly demagnetized before the observation
is made, or if it be strongly magnetized. Figure 5, which illustrates
this fact for some V curves, records some measurements made upon a
15 K.W. transformer {R) belonging to the Lawrence Scientific School.
In the case represented by each line the core was previously magne-
tized in one direction with the full strength of the current, and the
circuit was then broken and left open for a few seconds. With thft

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 107

electromotive force in it unchanged in intensity, but in some instances
changed in direction, the circuit was then closed again and a current
curve obtained. If the electromotive force has its old direction, such a
curve is said to be " direct " ; if the new direction is the opposite of the
old, the curve is called "reverse." In one case the magnetic journey
of the core during the rise of the current is represented approximately
by the portion Pi^J/of the corresponding hysteresis diagram (Figure 6) ;
in the other case the journey follows the arc QUZM. Lines 1, 2,
and 4 in Figure 5 are reverse lines, while 3 and 5 are direct.

In Figure 4 the line (9 1" corresponds to the final value (/^) of the
current, and if its length in centimeters is in i^ and if A is the area in
square centimeters shut in by 0 Y, YJl, and V, it is evident that in the

TIME.

p5=

ps=-

SECONDS.

Figure 4.

Curves which represent the growth of the current in the exciting coil of an
electromagnet when {V), the circuit which has the resistance r, is closed and
left to itself; and when (U), the circuit, is closed when it has a comparatively-
large resistance, which is then reduced to r by steps.

case represented by T" the whole change in induction flux through the
turns of the coil due to the current is

10' -E- A
lOY '

In the case represented by the line U, (10^ B/l) times the sum of the
terms formed by dividing each of the small shaded areas by the ordi-
nate, expressed in centimeters, of its upper straight boundary, gives
the change in the induction flux through the turns of the coil due to
the current when it grows in the manner indicated. Of course if the

108

PROCEEDINGS OF THE AMERICAN ACADEMY.

current is not allowed time to attain its final value at each stage, a
serious error may be introduced.

t
i

(n\

. \

-^V >

co\

- \

s ^

H 5

Tfi

-^J

■'n

■*^

-a

■*^

-4-^

■«->

'i*

"5 O

— '

« •z:

Ci^

FiGUR

es for

'T>

4-*

;-i

-t^

•ii

tt>

<*H

•^

1-.

-M

<4-l

e*-!

«
O

f— 1

c»

•S3a3dWV

The amount of flux which, in a given large mass of iron, in a given
magnetic condition at the outset, corresponds to a current of given final

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 109

strength in the exciting coil, usually depends in some slight degree upon
the manner of growth of the current. If after a large core has been
magnetized in one direction by the steady application of a given elec-
tromotive force until the current has reached its full value, the excit-
ing circuit be broken, and, after the direction of the electromotive force
has been reversed, closed again,
it sometimes happens that the
magnetic flux after the new cur-
rent has attained its maximum
value is slightly less when the
current follows the course of
the curve V than when it grows
by short stages in the manner
indicated by the curve U. If,
however, there are but two or
three steps, the difference is, as
a rule, of no practical impor-
tance, and if one has a suitable
oscillograph or other recording
instrument, it is possible to get
a set of current curves for any
given maximum value of the
current from which an extremely
good statical hysteresis diagram
may be obtained for the core.

If while a steady current from
a constant storage battery of
voltage E is passing through
the coil of an electromagnet, the
resistance of the coil circuit be
suddenly increased to a new
value 7\, so that the current (i)
will ultimately fall to a lower
value represented by ON in

Figure 7, the current curve, which has been a horizontal line, sinks in
such a manner as to become asymptotic to the horizontal line JYB. At
any instant after the change,

Figure

When a direct current curve is taken,
tlie core of the electromagnet makes a
magnetic journey represented approxi-
mately by the arc PFM ; in the case of a
reverse curve the core follows the line
QUZM.

= m,

(10)

in absolute units, so that in volts, ohms, amperes, and maxwells,

PROCEEDINGS OF THE AMERICAN ACADEMY.

dt.

(11)

If an abscissa I centimeters long corresponds to one second, and an
ordinate m centimeters represents one ampere, and if Ao,i stands for
the area in square centimeters bounded by the current curve, the
asymptote, and ordinates corresponding to the times to, ti, the change
in the flux of magnetic induction through the circuit during this time-
interval is (in maxwells)

(12)

If, after a current has been built up by stages in the coil of an
•electromagnet, in the manner indicated by curve U of Figure 4, the

SECONDS.

The shaded area represents on a certain scale the change in the flux of mag-
netic induction tlirough a circuit when the resistance of the circuit is suddenly
increased and then kept constant.

process be reversed, and the resistance of the circuit be increased by
steps, the current curve wiU look very much as the curve U would if
looked at from the wrong side of the paper when upside down.

As has already been stated, it is possible to get slightly different
hysteresis diagrams for a massive core originally demagnetized, when
the current is made to change from a given positive limit to the
negative limit in different ways ; and it is important, in predicting the
behavior of a magnet which is to be used for a given purpose, to
employ in computation the hysteresis diagram which corresponds to
the particular magnetic journey which the core will take in practice.
A single carefully made curve of the U tj^e with a dozen steps will,
however, give a result good enough for any commercial purpose, though

PEIKCE. — BEHAVIOE OF THE CORE OF AN ELECTROMAGNET. Ill

my own experience shows that it is not always easy to measure all the
small areas, especially the lower ones, with the desirable accuracy,
when the width (OF) of the whole diagram is only 12 or 14
centimeters.

If in the U diagram there is only one intermediate stage, and if the
core is in a given magnetic condition at the outset, the change in the
magnetic flux, due to a current of given final value, ought not to differ
by more than perhaps a fraction of one per cent from the correspond-
ing change when there is no intermediate step and the case is rep-
resented by V. Sometimes a series of U diagrams, each with but one

L ^

1-
z

tr
— )

p^iStW*

^^^^^

TIME.

Figure 8.

The areas between the asymptote and the curves Z and P are proportional to
the changes of magnetic flux through the circuit caused by direct and reverse
currents of the same final strength.

intermediate step, at a place determined by a proper choice of r, may
be made to yield very accurate information about the permeability of
the large mass of metal which will suit some special use of the magnet.
Figure 8, which resembles in general design some diagrams given by
Dr. Thornton, shows a " direct curve" (Z) and a "reverse curve " (P)
for a certain magnet. The area OZXY represents the change of
magnetic induction when the core covers the arc PFM (Figure 6) on
the hysteresis diagram belonging to the journey ; the area OPQXY
represents the change of magnetic flux when the core takes the
journey corresponding to the arc QUZM on the hysteresis diagram.
The doubly shaded area represents the flux change corresponding to
iheYmQ qUZMKP.

112 pkoceedings of the american academy.

The Uses of Exploring Coils wound upon the Core of an

Electromagnet.

If an electromagnet, in addition to its exciting coil, has another
wound about its core, and if the observer has means of obtaining the
intensity (/') of the current induced in this secondary coil, for given
current changes in the exciting coil, as a function of the time, it is
easy to study the magnetic properties of the core under the circum-
stances of the experiment. Let there be n' turns in the secondary coil,
let the resistance of its circuit be r' ohms, and let N' be the total in-
duction flux, in maxwells, through the turns of the coil at the time t,
then if I' is measured in amperes

dN'

^ = -10.././'. (13)

If ^' be plotted against the time in a curve in which V centimeters
parallel to the axis of abscissas represent one second and an ordinate
m' centimeters long one ampere, and if A' 1^2 represents the area
between the curve, the axis of abscissas and the ordinates correspond-
ing to the time ti, and t^, we have in absolute value,

iV/ - N^ = 10« • r' fr ■ dt = ^^^'''j'/f'^' = c/ ■ A\„ (14)

where q' is a known constant.

When the primary current (/) in the exciting coil is growing, the
current in the secondary coil has a direction opposite to that of /, and
it is often desirable to emphasize this fact in a diagram by drawing
the i, t and /', t curves on opposite sides of the axis of abscissas ; but if
the relative values of i and /' are alone to be considered, it is some-
times more convenient to disregard their relative directions. If in any
case the current in the exciting coil of an electromagnet be made to
grow in the manner indicated by curve U in Figure 4, the i', t diagram
will consist (Figure 9) of a set of detached areas on the t axis. The
sum of any number of these areas when multiplied by 10^ r'/l' m' 71'
gives approximately the whole change in the induction flux through
the core up to the corresponding time, from the outset. In the "step-
by-step " ballistic method of determining the permeability of a closed
ring of rather small cross section the areas represented by the shaded
portions of Figure 9 are determined by discharging the induced
current through a calibrated ballistic galvanometer of long period, and
assuming that the first elongations of the suspended system measure

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 113

these areas directly. As will appear in the sequel, it is possible,
though not very easy, to get good results in this way, even if the
cross-section of the laminated core is as great as, say, 800 square
centimeters ; for this, however, a properly constructed galvanometer is
required.

The "time constant" of a circuit in which a current of given final
intensity is to be established is shorter the higher the electromotive
force used to generate the current ; it is desirable, therefore, to employ
a battery of rather high voltage and to reduce the current by non-
inductively wound resistance in series with the exciting coil of the
electromagnet. If a moving coil galvanometer is used, it is often neces-
sary to correct for the effect of the counter electromotive force induced
in the coil as it swings in the field of its own permanent magnet, and

TIME

Figure 9.

A portion of the record of an oscillograph in the circuit of a secondary coil
wound on the core of an electromagnet when the current in the exciting coil is
made to change by sudden steps in the determination of a hysteresis cycle.

it is always necessary to use steps so short and to make the period of
the galvanometer so long (perhaps 300 or 500 seconds) that the practical
duration of the induced current may be small in comparison. It is usual
to send the current to the exciting coil by means of a commutator and
a long series of manganine resistance coils capable of carrying the de-
sired currents ; these coils are often mounted in a frame furnished
with some device by which any or all of them can be shunted out of the
circuit at pleasure. Two rheostats, made for this purpose some years
ago by the Simplex Electric Company, have been found by the staff of
the Jefferson Physical Laboratory very satisfactory in practice. By
means of such a set of coils as those just described, one may easily get
either a progressive, step-by-step increase or decrease in the current,
or a reiteration of any particular step. One convenient way of arrang-
ing the apparatus for the repetition at pleasure of any desired step
has been recently described by A. H. Taylor.^ The method of rever-

8 A. Hoyt Taylor, Phys. Rev., 23, 1906. Mordey and Hansard, Elect. En-
gineer, 34, 1904. Searle and Bedford, Phil. Trans., 198, 1902. Drysdale, Jour.

Inst. Elect. Engineers, 31, 1901.

VOL. XLIII. — 8

Lamb and Walker, Electrical Eeview, 48, 1901.

114 PROCEEDINGS OF THE AMERICAN ACADEMY.

sals is usually unsatisfactory with large cores. A set of adjustable
electrolytic resistances fitted for carrying heavy currents is often
useful.

In the case of a very large closed electromagnet, even if the core be
laminated, it is extremely difficult to get very useful results by aid of
a ballistic galvanometer of short period, but if one has a suitable oscil-
lograph or other recording instrument at hand, it is easy to obtain a
diagram something like that shown in part in Figure 9, though it is
necessary to make sure that the intervals between the steps, unlike
those in this figure, are long enough to record the whole of each in-
duced current.

If the primary current (/, t) curves are to be used in studying the •
magnetic changes in the core of an electromagnet, the sensitiveness of
the oscillograph must be so adjusted that the deflection due to the
largest value of the current {U, Figure 4) will make a record on the
paper ; if the (/', t) curves are to be used, the steps may be as numer-
ous as one likes, and the sensitiveness of the recording instrument may
be so great that, starting from the base line, the record of the highest
induced current shall just fall on the drum. In this latter case the
areas to be measured may be made so large that any uncertainty as to
the exact time when any induced current may be considered to end is
unimportant. When many records are taken on the same paper, the
drum has an opportunity to revolve a good many times during the
operation, and it is not always easy to decipher the complicated maze
of curves. Of course the fact that an electromagnet has a closed secon-
dary circuit modifies somewhat the form of the building-up curve in the
primary, but, theoretically at least, this should not affect the value of
the magnetic flux due to the primary current if its final intensity is
given, and the difference is inappreciable if there are only a few turns
in the secondary coil.

Instead of changing the resistance in the primary circuit suddenly,
at each step. Dr. Thornton, in dealing with the frames of some very
large dynamos, made each step gradually, by moving an electrode
slowly in a trough of acidulated water from one stopping place to
another. Figure 10 is a close copy of one of his records published in
the " Philosophical Magazine " for 1904.

FlUXMETERS AND QUANTOMETERS.

Given an amperemeter of the ordinary d'Arsonval type, in which an
open-frame, low resistance, unshunted coil swings in the strong mag-
netic field between an interior soft iron core and the hollowed-out jaws
of a powerful magnet, it is often possible to make the controlling

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 115

springs so weak that if the coil circuit be suddenly closed on itself
while the coil is in motion, the damping effects of the induced currents
will bring the coil almost instantly to rest wherever it may happen to
be, and, until the circuit is broken, the coil will keep its position fairly
well. Several years ago Dr. R. Beattie ^ showed that if the ends of a
low resistance exploring coil (A) be electrically connected with an in-
strument of this kind, and if the flux of magnetic induction through A
be changed during the time interval T by an amount N, the coil will
move from its initial position to a new position through an angle pro-
portional to JV and, apart from pivot friction, practically independent,
within wide limits, of T.

/Hi

"jTfk—

y/n

— 0'

/////

yll

/////\

Time,

r^////////^

Figure 10.
Typical record for half a hysteresis loop, given by Dr. Thornton.

The " quantometer " first made by Dr. Beattie had a coil of twenty-
four and a half turns wound on a metal frame and suspended on a single
needle point between the poles of an electromagnet ; the ends of the coil
dipped into mercury cups fixed to the case of the instrument. In the
kind of fluxmeter now common, the coil is hung by a silk fibre (or a
quartz thread) from a spring, so as to avoid pivot friction ; a permanent
magnet is used, and the current is led into and out of the coil through
helices of very fine silver or copper gimp ; the resistance of this gimp
is sometimes much greater than that of the coil itself, and for laboratory
use it is often well to employ mercury cups, as Dr. Beattie did, so ar-
ranged as to minimize the disturbing effects of capillarity. The original
quantometer had a resistance of only one ohm.

Many persons who have attempted to use very strong electromagnetic
fields in d'Arsonval galvanometers have found that it is very difficult

9 R. Beattie, Electrician, Dec, 1902.

116 PROCEEDINGS OF THE AMERICAN ACADEMY.

to procure insulated copper or silver wire for the suspended coil so free
from paramagnetic properties that the coil shall not have a permanent
" set " in the field, too strong to be conveniently controlled by the tor-
sion of the gimp through which the current enters the coil. In the
case of a quantometer where there is practically no controlling moment
from the suspending fibre, the paramagnetic properties of the coil may
be very troublesome ; and in some of the most recent instruments the
angular movements of the coils, due to given changes of induction
through the turns of the exploring coils, are somewhat different ac-
cording as the movement is towards the left or towards the right. If
a telescope and scale be set up in such a position that the behavior of
the coil can be watched after it has moved through a considerable angle,
urged by a sudden, definite change of flux in the exploring coil, it will
often be found that the coil does not remain even approximately at
rest, but moves steadily and so rapidly that a considerable error is
introduced if the given change of flux through the exploring coil is
made slowly. It is desirable, therefore, to test an instrument of this
kind carefully before using it.

If great accuracy is not required, a good fluxmeter, of some standard
make, and of sensitiveness suited to the work to be done, is, in experi-
enced hands, a most useful instrument ; the time needed to establish a,
current of given strength in the coil of a large electromagnet with a
solid core may be several minutes, but a very good fluxmeter will,
nevertheless, show directly, with an error of not more than 2 per
cent, the change of magnetic flux through the core.

If the fluxmeter coil is not wound on a closed metal frame, the
mutual damping effect of currents in the coil and in the core which
it surrounds are not always effective unless the resistance of the ex-
ternal circuit, made up of the exploring coil and its leads, is fairly small
compared with the resistance of the suspended coil itself An instru-
ment, therefore, which works very well with an exploring coil of a small
number of turns often becomes quite useless when, in order to get the
required sensitiveness, the observer tries to employ an exploring coil
made of many turns of fine wire. On the other hand, if a fluxmeter of
this kind is too sensitive for a given piece of work, it is not always easy
to reduce the sensitiveness quickly.

If the flux changes to be measured are large, it is often convenient
to have a fluxmeter the coil of which consists of a few turns either
wound on a copper frame or else accompanied by several turns of stout
wire closed on themselves. It is possible to use such an instrument
with many different exploring coils and to change its sensitiveness
within wide limits by varying the resistance of the external circuit.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET, 117

In doing a small part of the work described below, I was able to use
either a Grassot Portable Fluxmeter, or a certain fixed laboratory
fluxmeter {F) furnished with a tall chimney to hold the 140 centi-
meter long fibre by which the coil was suspended. The cast-iron
magnet of this last mentioned instru-
ment had, when finished, the form
shown in plan in Figure 11 and was
45 mms. thick. The casting was
made with a web connecting the
poles, and this was removed after the
hole for the coil had been cut out
and finally reamed to a diameter of
exactly 5 cms. on a Browne and
Sharpe milling machine. The mag-
net was hardened and treated by Mr.
G. W. Thompson, the mechanician of
the Jefferson Physical Laboratory,
who has had much experience in
this kind of work. During the proc-
ess the poles were held in position
by an iron yoke. The core (shaded
in the diagram) within the coil is
41.3 mms. in outer diameter, and is
about 7 mms. thick. The instru-
ment was constructed and set up
by Mr. John Coulson, who has
helped me in countless ways during
the progress of the work. It was

comparatively easy to substitute one of the set of coils belonging to
this fluxmeter for another. For certain purposes it was convenient to
have a coil of 200 turns of stout insulated wire which was wound about
the magnet, though the latter had a large permanent moment.

Figure 11.

Plan of one of the permanent
magnets of the fluxmeter F; the
shaded area represents the cross-sec-
tion of the soft iron core.

The Coefficients of Self-Induction of a Circuit which

HAS AN Iron Core.

When many years ago it was found that the induction ^ at a given
point in a piece of iron exposed to a given magnetic field H is not only
not in general proportional to the intensity of the exciting force, but is
not even determined when H is given, it became evident that no such
constant can exist in the case of an inductive circuit which "contains"
a magnetic metal as was assumed in the conception of Neumann's

118 PROCEEDINGS OF THE AMERICAN ACADEMY.

"Electrodynamisches Potential/'^Oand that the different common defi-
nitions of self-induction, when applied to an electromagnet of the
usual form, really describe physical quantities which are widely
different from one another. The ambiguity in the use of the term
" self-induction " still exists, and it will be convenient in this paper to
adopt the notation used by Sumpner ^^ in his article on " The Varia-
tions of the Coefficients of Induction." If, in absolute value, / is the
strength of a current growing in the coil of an electromagnet with
laminated core, if iV is the total flux of magnetic induction through
the turns of the coil, and e the counter electromotive force of induc-
tion, we may call the ratio of e to the time rate of change of the
current, Zi, the ratio of N to the current, L^, and the ratio, to P, of
twice the contribution (7") made by the current to the energy when
there are no other currents in the neighborhood, Lz, so that

T (fl 1,T T T T dN

(15)

If then for a particular magnetic journey, taken at a given speed, N is
given as a function of /in the form of a curve like OPQ, in Figure 12,
the value, at any point P on the curve, of Lx is the slope of the
curve or the tangent of the angle XKP ; the value of X2 at P is the
slope of the line OP or the tangent of the angle XOP; the value of Z3 is
the ratio of twice the curvilinear area OPD to the area of the square
erected on OJ. Similar definitions are sometimes given for such a
magnetic journey as is represented by the line MGPQ of Figure 13.

In the paper just cited Sumpner gives a very interesting graphical
method of constructing a curve which shall show the manner of growth
of the current in the coil of the electromagnet when the curve which
connects N and / is given.

The Electromagnets used in doing the Work
described below.

A number of electromagnets were used in carrying on the experi-
mental work described in this paper.

Though the investigation had to do primarily with magnets the
cores of which were laminated or otherwise finely divided so as to get

" Neumann, Abh. d. Berl. Akad., 1845.
11 Sumpner, Phil. Mag., 25, 1888.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 119

rid in great measure of the disturbing effects of eddy currents, one or
two large magnets with massive cores were useful for purposes of com-
parison. One of these (P), which weighs about 1500 kilograms, has
the general shape shown in Figure 14. The outside dimensions of the
frame proper are about 101 cms. X 80 cms. X 40 cms. The base is
of cast iron and of rectangular cross-section (20 cms. X 40 cms.), the
cylindrical arms are of soft steel 25 cms. in diameter, the rectangular
pole pieces are 4.5 cms. thick, and the area of each of the opposed

FlGDEE 12.

This illustrates different meanings
of the word inductance.

Figure 13.

faces is about 580 square centimeters. The four coils have together
2823 turns, and a resistance at 20° C. of about 12.4 ohms.

Figure 15 shows in outline the electromagnet Q, which weighs about
300 kilograms : the core has a square cross- section of about 156 square
centimeters area, and is built up, cobhouse-fashion, of soft iron plates
about one third of a millimeter thick, each of which was immersed in
thin shellac and then thoroughly baked in an electric oven before it
was used. Each of the spools, which are practically alike, weighs about
30 kilograms and has four coils, an inner one forming a single layer,
the next forming three layers, and the two outer ones wound together
side by side from two supply spools, and each equivalent to five layers ;
in all, both spools together have 3883 turns. The whole core frame is
about 74 cms. long and 62 cms. broad. One stratum 2.5 cms. high

120

PEOCEEDINGS OF THE AMERICAN ACADEMY.

and reaching across the middle of the core (Figure 16 a) within one of
the spools, is made up of five portions insulated from one another, and
each of these is surrounded by an exploring coil of insulated wire.

Figure 16^ shows the form of the cross-section of the rectangular
core frame of a 15 kilowatt transformer (i?) constructed for experi-
mental purposes and belonging to the Lawrence Scientific School.
Besides a low-resistance primary coil, this transformer has 19 similar
coils each of about 85 turns, any number of which may be connected
to form a secondary circuit. The outside dimensions of the core frame
are about 78 cms. and 34 cms. ; the area of the cross-section of the
finely divided core is about 108 square centimeters.

Figure 14.

The electromagnet P. This magnet has a solid core which weighs about 1500
kilograms.

Magnet S has a core consisting of two round solid pieces 76 cms.
long and 7.4 cms. in diameter with axes 24 cms. apart, connected
together at the ends (so as to form a rectangular frame) by two massive
iron blocks. This magnet has two spools, each of which has two coils
formed by winding two strands side by side; the whole number of
turns is 1724.

The core of magnet T forms a square 58 cms, long on the outside
and 53.5 cms. wide. Its cross-section is a rectangle 7.5 cms. by 6.7
cms. The core is built up of sheet metal 0.38 of a millimeter thick.

Through the kindness of Dr. George Ashley Campbell I have been
aJlowed to use also seven toroidal coils (of inductances between 0.3 and
13 henries) wound on cores made of very fine (No. 38 B. & S.) iron wire.
Such cores are, of course, extremely expensive, but the disturbing

PEIRCE. — BEHAVIOR OP THE CORE OF AN ELECTROMAGNET. 121

effects of eddy currents in them are practically negligible for the
purposes of this paper.

The Demagnetizing of the Core of -a Large Electromagnet.

In order to be able to study satisfactorily the magnetic properties of
a given piece of iron or steel, it is usually necessary that one should
know with some accuracy the magnetic state of the specimen at the
outset, and, especially when the metal has the form of a closed ring or
frame, the previous history of which is unknown, the only safe pro-

FlGUKE 15.

The electromagnet Q, which has a laminated core made of sheet iron one
third of a millimeter thick and weighs about 300 kilograms.

cedure is to demagnetize the iron as completely as possible before one
makes any experiments upon it. If the metal has the form of a long
rod in a solenoid, or of a slender ring wound about uniformly with
insulated wire and magnetized in the direction of its circumference, it
is easy to send through the coil which surrrounds the iron a long
series of currents alternately in opposite directions, which, starting with
a value that shall subject the core to a magnetic field at least as
strong as any to which it has been previously exposed, gradually de-

122

PROCEEDINGS OF THE AMERICAN ACADEMY.

crease in intensity to zero. One common way of doing this is to
attach the coil to the secondary of a sufficiently powerful alternate
current transformer so arranged that the primary coil may be slowly
withdrawn to a long distance from the secondary. In the case of the
soft iron wire the demagnetization is sometimes accomplished by
heating the wire red hot.

It is often a matter of considerable difficulty to remove entirely the
effects of previous magnetization from the completely closed massive
core of a large transformer : even if the source of a current in the
exciting coil has a high voltage, several seconds may be required to
established the current, and the use of an alternating demagnetizing
current in the coil, with any commercial frequency, is barred out. If
a powerful storage battery be connected to the exciting coil through a
commutator and a suitable "liquid rheostat," one may begin with a
sufficiently strong current (Iq) and, after reversing this several times

Figure 16.

Forms of ,the cross-sections of the laminated cores of tlie electromagnets
Q and R.

by hand, increase a little the rheostat resistance so as to decrease the
current slightly, then reverse this weaker current a number of times,
and thus proceed until the current is reduced to a very small value ;
but if the core is very large, the operation may take a couple of hours
even if the number of steps is not excessive, and after all, it is not
easy to teU whether the work has been successful. If the initial
current was strong enough, if the stages were sufficiently numerous
and properly spaced, and if the number of reversals at each step was
great, one may, of course, expect to find the core pretty thoroughly
demagnetized, but to test the matter it is usually necessary to undo
what has been accomplished by determining the amount of magnetic
flux sent through the core when a current of given intensity (7) is sent
through the exciting coil. This amount ought to be the same whether
this testing current has the same direction as that of the last applica-
tion of the large current (I^) or the opposite direction, and unless one

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 123

has a hysteresis diagram for the core obtained by using currents which
range exactly between +/(, and — /„ the whole work must be done twice.
The determination of the flux changes may be made very conveniently
with the help of a fluxmeter, but if the highest accuracy is required,
it is better to take an oscillogram of the building-up curves of the
current when the core starts from its state of supposed neutrality.

If the core of a large electromagnet is not quite closed, it is compara-
tively easy to demagnetize the iron almost completely and to prove
that this has been done ; indeed, if the gap has the proper width, the

Figure 17.

iron practically demagnetizes itself in a wonderful manner. An in-
stance of this was given by Professor Thomas Gray in the case of a
40 K. W. transformer, and I found that the hysteresis diagram for a
certain electromagnet which has a solid core the area of which in its
slenderest part is more than 450 square centimeters, consists prac-
tically of a single straight line when the air gap has a width of 35
millimeters. With this magnet, using an excitation of either 7800
ampere-turns or 15,800 ampere-turns, I obtained current-time curves
which were wholly indistinguishable even when much enlarged and

124

PROCEEDINGS OF THE AMERICAN ACADEMY.

superposed on a screen, whether the current had the same direction as
its predecessor or the opposite direction.

If the core of an electromagnet happens to be a straight bar, or ac
straight bundle of wire, it may be demagnetized by a long series of
currents which have alternately one direction and the other, and which
slowly decrease in intensity from an initial value which may be con-
siderably smaller than the current which magnetized the iron. Figure
17 shows the results of experiments upon a rod of soft steel 80 diame-
ters long in a long solenoid. The arrangement of the apparatus is
shown in Figure 18. The extreme value of the magnetizing field was
27 gausses, and the average moment per cubic centimeter which the

Figure 18.

field caused was 246. At the outset the core was thoroughly demag-
netized, then a series of steady currents, each a little stronger than the
last, was sent through the coil, and the moment of the rod was deter-
mined for each direction of the current. This gave the curve WXOQ V.
Then the hysteresis diagram VGKWMZVv^Si^ obtained, and after the
core had returned to the condition indicated by the point V, the
current was somewhat decreased until the core " reached " the point B,
and then this current was reversed in direction one hundred times,
after which (when the current had the positive direction) the iron had
exactly arrived at the point on the curve OIQ V beneath B. The core
was then brought to V again, the current was decreased, — this time
until the core reached the point P, — this current was reversed one
hundred times, and it was then found that when it ran in positive

PEIRCE, — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 125

direction the core had arrived at the point Q. This process, repeated
for many points on the line GPV, yielded the curve VQACG. If
after being at V the core was brought to a point between P and iV,
and if after it had been many times reversed the current was decreased
by short steps with many reversals at each stage, the core traversed
the curve U, whereas if the first drop carried the core no farther than
P, the procedure led the core to the origin along the curve /. The
lowest point of the curve VQA G lies, of course, nearly over the point
Z. The shaded diagram in the upper part of the figure shows a
similar curve obtained at another time and drawn strictly to scale.
If after many reversals of a comparatively small current the core which
started at L reached the point F, and if the current was then slowly
increased, the core made the journey indicated by the line FL. The
shaded diagram in the lower part of the figure is a reduction of a curve
obtained with a large induction coil the core of which is a compact
round bundle of fine wire 7.5 cms. in diameter and about 85 cms. long.
The curves oec, cak, cek, in this diagram correspond to OIQ V, VPG,
VQAG in the larger figure. The retentiveness of a core of these
dimensions is, of course, very small.

Even if much time has been spent in demagnetizing a large closed
core by sending through the exciting coil currents alternately in one
direction and in the other, of intensities gradually decreasing to a very
small final value, it frequently happens that after a much larger
current has been put for, say, twenty times through the coil alternately
in one direction and the other, the hysteresis cycle does not "close,"
for the change of flux caused by applying the given current in one
direction is not equal to the flux change caused by applying the same
current in the other. This fact often makes the accurate determina-
tion of a hysteresis diagram for such a core a long and trying piece of
work. Some toroidal cores I have never succeeded in demagnetizing
completely. The demagnetizing apparatus which I have usually
employed in the course of the work here described consists first of a
storage battery of forty large cells, a set of rheostats made up of
metallic and liquid resistances intended for heavy currents, and a
commutator run from the main shaft of the laboratory machine shop,
and so arranged as to reverse the direction of the current from the cells
every ten seconds. Starting with no resistance in the rheostats,
resistance was gradually introduced into the circuit until the current
had become very small. After this procedure, the secondary circuit
of a specially constructed transformer was attached to the exciting coil
of the magnet, and from an initial voltage of about 660, at 60 cycles
per second, the electromotive force was gradually decreased until the

126

PROCEEDINGS OF THE AMERICAN ACADEMY.

current became too small to measure. In some cases it seemed better
to omit the second part of the process.

The Establishment of a Steady Current in the Coil of an

Electromagnet.

If the circuit of the exciting coil of an electromagnet contains a
battery of storage cells of constant voltage E, and if this circuit be
suddenly closed, the strength of the current will rise more or less
gradually from its initial zero value to E/7- amperes, where r is the
whole resistance of the circuit in ohms. In the case of a given magnet,
with a given electromotive force in the coil circuit, the manner of
growth of the current depends very largely, as we have seen, upon the

SECONDS.

Figure 19.

Currents from a battery of 20 storage cells in the circuit of a coil of 2788
turns belonging to the magnet Q. Before the middle curve was taken, the core
was carefully demagnetized. The upper and lower curves represent direct and
reverse currents, respectively. The areas Fand IF are equal.

magnetic state of the core when the circuit was closed. The three
curves of Figure 19, which are carefully made reproductions of the
photographed records of an oscillograph, show the march of the current
from a battery of 20 storage cells in the circuit of a coil of 2788 turns
belonging* to the magnet Q under three different sets of conditions. If
after the core had been demagnetized as thoroughly as possible, by the
method already described, the circuit was suddenly closed, the current
followed the middle curve of the three. If the current was allowed
practically to attain its maximum value, and if then a commutator in
the circuit was reversed and, at intervals of a few seconds, reversed
again and again, and if finally the circuit was broken, it was possible
by closing the commutator again in the proper direction, to make the
new current follow either the upper or the lower curve of the diagram.
If this current coincided in direction with the last current through the

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGMET. 127

coil, the current was " direct," and its rise was represented by the upper
curve. If the new current had a direction opposite to that of the last
current through the coil, the current was "reverse," and followed the
lower curve. The areas V and W are practically equal.

It is evident that, other things being equal, the rapidity of rise of
the current in a circuit which contains a coil wound around the core of
an electromagnet will depend very much upon the number of turns in
the coil. Figure 20 shows reverse curves from the magnet B. The
actual strengths of the currents were 6, 3, and 1.5 amperes respectively,
and the numbers of turns in the exciting coils were 85, 170, and 340.

}^i3M^^^^j^m

z
llJ

TIME.

Figure 20.

Curves showing the growth of currents in coils of 340 turns, 170 turns, and 85
turns belonging to the magnet R. The same electromotive force was used for
all the cases, and the final values of the currents were 6 amperes, 3 amperes, and
1.5 amperes.

The electromotive force was the same in all three cases. The horizon-
tal units are tenths of seconds.

Although the typical current curve for the coil of an electromagnet
wound in many turns about the core has two points of inflexion if the
core is laminated, both of these disappear if the change of the magnetic
flux through the circuit due to the current is small enough, and
occasionally one finds an oscillogram which seems to have only one
point of inflexion. Some of the direct curves shown in Figures 5, 23,
and 28 are ever}^here convex upward. Among the nearly three
thousand photographed oscillograph records taken for use in this paper
no one is concave upward at the very start, but a curve of this kind, with
one point of inflexion, has been shown by Dr. Thornton, and I have

128

PROCEEDINGS OF THE AMERICAN ACADEMY.

many curves which become concave upward very near the origin. In
current curves belonging to the coil of an electromagnet which has a large
closed, solid core, there are often two points of inflexion, but many of
even the reverse curves are everywhere convex upward. Figure 21
shows curves taken for the coil of the large magnet P in the circuit of
which was a storage battery of voltage 84. When each current started,
the core was nearly neutral.

^^____

--^

r ^__^

yj '

.CONDS.

Figure 21.

Curves showing the manner of growth of currents of various final strengths
in the coil of 282.3 turns belonging to the magnet P. The gap was closed and
the core was nearly neutral at the beginning of each current. The applied vol-
tage was the same (84) for all the curves.

When the coil of a transformer, the core of which is built up of such
thin plates of soft iron as are used in the best practice, is subjected to
an alternating electromotive force of extremely high frequency, the
disturbing effect of eddy currents in the iron are, of course, very ap-
parent, but the manner of growth of a current under a constant electro-
motive force is usually not very greatly affected by such currents.

The fact that the susceptibility of the iron is by no means constant,
materially alters the shape of a current curve when iron is introduced
into a circuit ; nevertheless, it is instructive to compare the manner of

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 129

growth of a current in the coil of an electromagnet which has such a
core, with that of a current in a circuit of fixed inductance, without
attempting at the outset to account mathematically for the differences,
though it will be easy to do so later on.

In the case of a simple circuit, without iron, of resistance r ohms
and constant inductance, L henries, which contains a constant electro-
motive force of E volts, the rise of the current / when the circuit is
suddenly closed follows the law

/=^(l-e-X),

(16)

and attains the fractional part k of its final value {E/r) in the time

t = loge (1 — Jc),

(17)

which is independent of the ultimate current strength and involves
only the time constant (X/r) of the circuit. If the circuit is made

1-
z

/^ ^

a/ 1

f b/

^^.^

SECO

NDS.

FiGUKE 22.

Curves which show the manner of growth of currents in a coil of 1394 turns
belonging to the magnet Q, to a given final value, when the applied voltages
were 82, 41, and 20.5, nearly. In each case the core was neutral at the outset.

up partly of non-inductively wound resistance wire, and partly of
helices, r may be kept constant, while L is changed, by changing the
relative proportions of the two parts ; or r may be altered while L is
constant, by increasing or decreasing the non-inductive portion of the
circuit.

rOL. XLIII. — 9

130

PROCEEDINGS OF THE AMERICAN ACADEMY.

If Ejr and L are given, different values of E may be used by giving
properly corresponding values to the non-inductive resistance, and if
the " building-up time " of the current under given initial conditions
in the core be defined as the number of seconds required for the current
to attain any arbitrarily chosen fractional part of its final value, this
time will be inversely proportional to E. In the case of a circuit
which has one or more iron cores the phenomenon is much less simple,
and if the cores be of solid metal, the effects of eddy currents may
complicate the problem seriously; but although under these circum-
stances the law of proportionality no longer holds, it is almost univer-
sally true that the establishment of a current of given final intensity

z
u

fr^

■^^"^

Qf /

^ ^

z 1

SECONDS.

Figure 23.

Direct and reverse current curves for the maj^net Q with a given final excita-
tion of 2650 ampere turns, under applied voltages of 82, 41, and 20.5, nearly.

in the coil of a given electromagnet can be accelerated by increasing
very much the applied electromotive force and then introducing a
sufficient amount of non-inductive resistance to make Ejr the same as
before.

Figure 22 shows current curves for the magnet Q under a fixed final
excitation of 2650 ampere-turns. In curves A, B, C, the currents
were caused by 40 cells, 20 cells, and 10 cells, respectively, and these
currents were made equal by adding to the circuit in each case a
suitable non-inductive resistance. Before each of these curves was
taken, the core of the magnet was carefully demagnetized by the
elaborate process described above. After the magnet Q had been put
a good many times through a cycle with a given maximum excitation

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 131

of 2650 ampere turns, under one of the voltages just named, direct and
reverse curves were taken with the help of the oscillograph. Careful
reproductions of these curves are given in Figure 23 : to avoid con-
fusion the reverse curves are drawn from a separate time origin.

If in a circuit which contains no iron, E and r be kept constant,
while L is changed, the building-up time as defined by equation (17)
will be proportional to L. Of course no such simple relation holds
when the circuit includes the magnet Q; Figure 24 shows current
curves for the same final value of 2.60 amperes, under an applied elec-

FlGUEE 24.

The manner of establishment of a current of final strength 2.60 amperes, in the
coil circuit of the magnet Q, under a voltage of 82, when the number of active
turns was 407, 823, 1394, or 2788.

tromotive force of about 82 volts, for exciting coils of 407 turns, 823
turns, 1394 turns, and 2788 turns. For convenience, the curves are
drawn from different time origins. The dotted line which crosses curve
Q calls attention to the fact that if curves P and Q were drawn from
the same origin, the former would cross the latter.

If in a circuit without iron E and L were kept constant while r was
varied, the building-up time {LIr) would be inversely proportional to
the resistance of the circuit, or, since the electromotive force is fixed,
directly proportional to the current strength. There is no approxima-
tion to this in a circuit which contains iron. The current curves
shown in Figure 25 were obtained from the electromagnet Q when

132

PR0CEEDINGS OF THE AMERICAN ACADEMY.

2788 turns were used in the exciting coil and a battery of 40 storage
cells with a voltage of about 82 furnished the electromotive force.
Curve C evidently corresponds to a case where the total resistance
in the circuit is about twice as great as in the case represented by A,
but for every value of k the building-up time is greater for C than
for A, though the difference becomes very small at the end. A com-
parison between A and D shows the same fact. Before each of the
curves A, B, C, D, was taken the core of the magnet was carefully de-
magnetized. Figure 26 exhibits current curves taken for different
values of r with the same coil of the magnet Q and with the same elec-
tromotive force as the curves just mentioned. In each of the cases

Figure 26.

Currents in the coil of the electromagnet Q for four different values of r when
E and the number of magnetizing turns were fixed. At the starting of each
current the core was magnetically neutral.

shown in Figure 26 the core was put several times through a cycle
before the direct and reverse oscillograms were taken. The records are
reproduced as accurately as possible ; B, C, and D run together in a
complicated manner, and the same tendency is shown in the reverse
curves G, H, I, but in general the longer building-up times belong to
the lower currents.

If in an inductive circuit without iron r and L are fixed, the build-
ing-up time will be independent of the value of E, but this is not the
fact if the circuit contains an electromagnet. Figures 27 and 28 show
current curves obtained from the coil of 2788 turns belonging to the
magnet Q. In all the curves of each diagram the value of r was the
same, but the voltage of the battery in the coil circuit had three differ-

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 133

Direct and reverse current curves in tlie coil of the electromagnet Q for five
different values of r when E and the number of active turns were kept fixed.

1-
z

a.
a.

D
O

-^^

' —

SECONDS.

Figure 27.

Currents in the coil of 2788 turns belonging to the magnet Q for three differ-
ent values of the applied voltage with the same value of r. At the starting of
each current the core was magnetically neutral.

134

PROCEEDINGS OF THE AMERICAN ACADEMY.

ent values the largest of which (belonging to the curves C, M, N) was
about 82 : in this case the current was almost exactly 2.50 amperes.
Before each of the curves A, B, C was taken the core was thoroughly

SECONDS

Figure 28.

Direct and reverse currents in a coil of 2788 turns belonging to the magnet
Q for three different values of the applied voltage, but the same value of r.

demagnetized : R, P, M are direct curves, but 8, Q, N are reverse
curves. It is evident that the building-up times are not even approxi-
mately independent of E.

Figure 29 shows the records of an oscillograph in a secondary circuit
in which were a few turns of wire wound around the core of the magnet
Q. The primary circuit contained, besides the storage battery, a rheo-
stat and an exciting coil of 1394 turns.

When the primary circuit

TIME.

Figure 29.

was suddenly closed with such a resistance in the rheostat that the final
strength of the current was 1.1 amperes, the induced current had the
value indicated by the curve Q; when the rheostat resistance was
suddenly removed so as to bring the final strength of the current up to

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 135

CURRE^4T.

2.3 amperes, the induced current curve was B. The sum of the areas
under the curves Q and R was 74.3 square centimeters. The curve P
shows the current record in the secondary-
circuit when the primary circuit was sud-
denly closed with no resistance in the rheo-
stat : the area under this oscillogram was
74.6 square centimeters. All the currents
were reverse currents. Most of the area
determinations of this paper were made
with a Coradi " Grand pianim^tre roulant
et h. sphere."

Figure 30 shows a careful reproduction
of the record of an oscillograph in the
primary circuit of the arrangement just
described. These curves- were taken on
the same day as those of the last figure.
In this case the flux change due to the
current which gave the curve T was
to the sum of the flux changes caused
by the partial currents as 1130 to 1126.
These numbers do not show any real dif-
ference between the corresponding physi-
cal quantities, but point to difficulties of
measurement.

The Effect of the Magnetic Charac-
teristics OF the Core upon the Man-
ner OF Growth of a Current in the
Coil of a Large Electromagnet.

If under the application of a constant
electromotive force to the coil circuit of
an electromagnet a current grows grad-
ually in the coil to its full value, the
magnetic flux in the core at any moment
depends, as we have seen, not only upon S
the instantaneous strength of the current,
but also upon the magnetic state of the ^ ■
core at the beginning. Moreover, if the Figure 30.

core is solid, it is clear that the magne-
tizing field to which the interior of the iron mass is exposed may be
quite different at any instant from what it would be if eddy currents
were nonexistent. If, however, the core is built up of such thin sheets.

136

PEOCEEDINGS OF THE AMERICAN ACADEMY.

of iron as are used in good transformers, a fair approximation to the
form which the current curve will have under any given circumstances
can be made if one has an accurate statical hysteresis diagram of the
core for the range required, and if the core is made of very fine var-
nished wire, as in the case of loading coils for long telephone circuits,
a' hysteresis diagram obtained either from a long " step-by-step series "
of measurements or from one or more oscillograms, enables one to pre-
dict with accuracy what the form of a current curve will be for any
practical case. These last statements are based on experiments such
as those recorded below.

As a result of a long series of measurements, it appears that when
the core of the magnet Q has been well demagnetized and a series of
steady currents each a little stronger than the preceding one are estab-
lished in the exciting coil, the magnetic flux through the core in
thousands of maxwells follows fairly accurately the course indicated
in the following table :

TABLE I.

Ampere Turns.

Magnetic Flux.

Ampere Turns.

Magnetic Flux.

100

1100

1208

200

146

1200

1238

300

386

1300

1262

400

622

1400

1285

500

787

1500

1309

600

929

1600

1331

700

1013

1700

1352

800

1086

1800

1369

900

1137

1900

1390

1000

1176

2000

1409

Figure 31 reproduces the table graphically in the full curve : the
vertical unit is a thousand maxwells, and the horizontal unit is 139.4
ampere-turns, to suit the case when the particular exciting coil used
has 1394 turns. The ordinates of the dotted curve represent twice the
corresponding values of the slope (X) of the other. A template of the
curve B was made as accurately as possible from a large piece of sheet

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET.

137

zinc ; this was fastened down on a table over a number of sheets of co-
ordinate paper, and the value of A was determined by measuring on the
paper the position of a straight edge which touched the template at
any desired point.

TABLE II.

Current in
Amperes.

Log [(13.94)A].

Current in
Amperes.

Log [(13.94)A].

0.00

0.445

0.55

1.135

0.05

0.860

0.60

1.025

0.10

1.248

0.65

0.943

0.15

1.602

0.70

0.860

0.20

1.715

0.75

0.797

0.25

1.672

0.80

0.746

0.30

1.594

0.90

0.700

0.35

1.496

1.00

0.635

0.40

1.399

1.10

0.621

0.45

1.312

1.25

0.606

0.50

1.209

1.30

0.591

If after the core of Q had been demagnetized, a steady electromotive
force of E volts were applied to the exciting circuit of resistance
?• ohms, containing the coil of 1394 turns, and if eddy currents were
nonexistent so that the core followed the statical magnetizing curve,
the march of the current (in amperes) would be given by the equation

E -ri= 13.94.x-

di
dt'

(18)

whence

r 13.94 A ,.
Jr. E — ri

(19)

If from an actual current curve obtained from Q for a given journey
of the core we were to determine the corresponding magnetizing curve
for the metal (flux versus coil current), we should find that the values
of the flux, for small values of the current, at least, would fall short of
the flux values which the same currents would cause if they were to act

PROCEEDINGS OF THE AMERICAN ACADEMY.

for some time because the magnetizing field is less than that due to
the coil current by that due to the eddy currents. If, therefore, from
the numbers of Tables I and II we were to determine the form of a
current curve for Q, corresponding to any journey of the core, this
would fall somewhat below the actual curve at the beginning. The
core of Q has, however, a typical magnetizing diagram, and the theo-
retical curves are instructive as showing what the actual curves would
be if the same core were more finely divided. The effect of eddy cur-
rents can be seen in the curves for this magnet given above.

CURRENT.

-SLOPES

Figure 31.

Magnetization curve for the core of the magnet Q which at the outset is in a
neutral state. The ordinates of tlie clotted curve represent twice the slopes of
the other curve.

The boundary of the shaded area in Figure 32 shows twice the value

of the integrand

13.94\

w =

E — ri

(20)

for the case E = 26, r = 20 : the horizontal unit is one tenth of an
ampere. The vertical line corresponding to / = 1.3 is evidently an
asymptote. The area under the curve from the beginning to the ordi-

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 139

nate representing any given value of the current shows, in twentieths of
a second, the time required, under the given conditions, after the cir-
cuit is closed for the current to attain this value. It is easy to deter-
mine a series of such areas with the help of a good planimeter, and the
full curve of Figure 32 actually represents the growth of the current in
the case mentioned according to my measurements of the large dia-
gram of which Fig. 32 is a very much reduced copy : for this curve the
horizontal unit is one tenth of a second and the vertical unit is one
fifth of an ampere. This curve has the general form of most of the

riGORE 32.

The ordinates of the boundary of the shaded area represent 2 (dt/di) for
E = 2%, r — 20. P shows the tlieoretical form of the corresponding current
curve.

current curves which one obtains with a transformer the core of which
is at the outset neutral, but it is evident that in any case where the
final value of the current is small enough the asymptote will be moved
so far to the left that the integrand curve will rise continually from
the beginning, without the maximum and minimum values, and the
current curve will have the everywhere convex shape that we find in
practice when we cause the current to grow by short steps in the man-
ner indicated by the curve U in Figure 4.

Figure 33 shows building-up current curves (^4, b, c) for E= 26,
and r = 20, 40, and 60, respectively. The dotted curves B and C are
copies of b and c with ordinates so magnified that the curves have the

140

PROCEEDINGS OF THE AMERICAN ACADEMY.

same asymptote as A. According to this diagram the current attains
75 per cent of its own final value more quickly when r is 40 than when
r is 20, but B crosses A at the point .v and the current seems to reach
practically its full strength sooner in the latter case. The curve C first
crosses the curve A and then B. It would be easy to show from a
series of oscillograph records for similar cases that the characteristics
of the theoretical curves correspond in general to fact.

TENTHS OF SECONDS.

Figure 33.

Forms of current curves for Q deduced from theoretical considerations. The
coil has 1394 turns and contains a storage battery of voltage 26. C is everywhere
convex upward : A and B have two points of inflexion.

If with the core of the magnet Q initially neutral a steady current
of given strength be established in the coil of 1394 turns, by use of a
storage battery of voltage E, the integrand will be for every value of
the current inversely proportional to E (since B/r is given), and the
building-up time will be inversely proportional to the applied electro-
motive force, as it would be if the inductance were fixed. For a given
exciting coil, the general shape of the curve for a given current is
independent of the applied voltage. Curves A, C, and I) of Figure 34
are the current curves computed for E = 26, 52, 104, and r = 20, 40, and
80 : the maximum value of the current is the same in every case. G
and E are the current curves computed for E = 26, r — 80, and for
E= 104, r = 320.

As has been explained already, it is difficult to obtain an accurate
hysteresis diagram for a very large core by the ordinary ballistic
methods with such galvanometers as are usually to be found in the

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 141

testing room, but it is fairly easy to attach extra weights to the
suspended system (Figure 35) of a good d'Arsonval or Thomson Mirror
galvanometer which shall so increase the moment of inertia that the
time of swing shall be lengthened to five or ten or twenty minutes.
With an instrument thus modified it is usually possible, by changing
the intensity of the current in the exciting coil by small steps, to deal
satisfactorily with very large masses of iron. It is of course desirable
to use a rather high electromotive force in the exciting coil in order

TABLE III.

Ampere Turns.

Flux in Thousands
of Maxwells.

Ampere Turns.

Flux in Thousands
of Maxwells.

1812

1371

-131

772

1394

1351

-148

734

1255

1340

-181

552

1031

1316

-234

332

809

1285

-294

474

1211

-392

-465

392

1186

-474

-661

294

1148

-809

-1010

234

1121

-1031

-1128

181

1099

-1255

-1214

148

1070

-1.394

-1265

131

1060

-1812

-1371

000

953

to make the building-up time short, and to reduce the current to the
desired strength by introducing extra non-inductively wound resistance
into the external circuit. In order to test this matter thoroughly, I
measured with great care, by aid of a modified Rubens-du Bois
"Panzer Galvanometer," the flux changes in the core of the magnet Q
(the area of the cross-section of which is more than 150 square centi-
meters), corresponding to a hysteresis cycle for an excitation of 1812
ampere turns. I then determined the same total flux change by
means of planimeter measurements of the areas under a long series of

142

PROCEEDINGS OF THE AMERICAN ACADEMY.

oscillograph records; all the testing instruments were different in the
two cases, and no comparison was possible until the final results were

TENTHS OF SECONDS.

Figure 34.

Theoretical forms of current curves in a coil of 1394 turns belonging to the
magnet Q. In practice these would be somewhat modified by eddy currents.

obtained and were found to differ
from each other by onl}^ one part
in about fourteen hundred. The
labor of reducing the oscillograms
I was very great, and this extremely
close agreement must be consid-
ered accidental, since it is not
easy to make a large mass of iron
go over exactly the same magnetic
journey twice.

Hysteresis diagrams for the

magnet Q and corresponding to

maximum excitations of 1812,

5370, and 10,880 ampere turns

are given in Figure 36. Some

results of measurements of the

Tlie horizontal rod AB is threaded ^^^ changes in the core for the

and the brass masses C,X> can be screwed ,. . c ,-, ■,

on the rod as far as is necessary. The ^^'^t of these cycles are given m

system must be accurately b.alanced. I able 111

Figure 35.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 143

tO.OOO AMPERE TURN
PiGDRE 36.

Hysteresis diagrams for the core of the magnet Q.

JURE

37.

TENTH

SOFAI

VIPERG

144

PROCEEDINGS OF THE AMERICAN ACADEMY.

After a curve had been drawn on a very large scale to represent the
numbers of Table III, a zinc template was made from it, by aid of
which and a long "straight-edge" the slopes of the curve could be
determined with some accuracy. The next diagram (Figure 37) shows
the slope as a function of the strength of the current.

When the slope for any point of the curve is multiplied by
(13.94) / {E — ri), where E and r are given, the result is the value of
dt/di for the reverse current curve when the applied voltage is E
and the resistance ?•, for the given value of i. Figure 38 exhibits
dt/di for ^=19.5, and r = 15.

The actual curve was drawn on a large scale, and the area X from
^ = 0 to ^ = e, for a number of different values of i were measured by a
planimeter in terms of the unit square of the figure ; this area ex-
pressed in tenths of seconds the time required for the reverse current
to attain the strength i. A few values of X are shown in the next
table.

TABLE IV.

A'/IO.

X/IO.

0.05

0057

0.50

1.750

0.10

0.155

0.60

1.875

0.15

0.494

0.70

1.985

0.20

0.878

0.80

2.088

0.25

1.141

0.90

2.188

0.30

1.325

1.00

2.294

0.35

1.471

1.10

2.412

0.40

1.579

1.20

2.632

Every form of current curve which I have met in practice can be
closely imitated by a theoretical curve ; but all these curves have at
the outset a direction differing widely from the horizontal. Dr.
Thornton, however, shows a beautiful curve which at the beginning is
convex downward and has at the start a direction not very different
from that of the axis of abscissas.

Before one uses an oscillograph for purposes of accurate measure-
ment, one must make sure that the instrument has been properly set
up. When the drum which carries the sensitive film or paper is at

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 145

TENTHS OF AMPERES.

Figure 38.

The value of dt/di for a reverse current in a coil of the magnet Q when
E = 19.5 and r = 15.

Figure 39.

The full curve shows the rate of increase of the flux of magnetic induction
through the core of the magnet Q while a reverse current of 1.3 amperes is being
establislied in the exciting coil of 1394 turns. The current curve is shown on an
arbitrary scale bj^ the dotted line.

VOL. XLIII. — 10

146

PROCEEDINGS OF THE AMERICAIT ACADEMY.

rest, a current sent through the conductor should give a perfectly
straight record accurately perpendicular to the base line, and the
length of this record should be proportional to the strength of the
current. It sometimes happens that an oscillograph which records
accurately the march of a moderate current lags in its indications a
very little behind the strength of a comparatively feeble current owing
to the viscosity of the oil used for damping, which only then becomes
troublesome. I have myself had sad experience in drawing from the
records of an instrument of this sort, which I thought I had carefully
calibrated, elaborate inferences which were contrary to fact. If, however,

•

1.0

•

0.5

•

SECONDS

Figure 40.

Theoretical forms of direct and reverse current curves for a coil of 1394
turns belonging to the magnet Q when the resistance of the circuit is 8 ohms
and the applied voltage is 10.4.

one has at hand, first, a well-constructed and mounted ballistic gal-
vanometer with a period of from eight to ten minutes, and means of
damping the swings of the suspended system (electromagnetically or
otherwise) without touching it, and secondly, some kind of chrono-
graph designed to close and after a given interval to open again any
circuit to which it may be attached, it is easy to test almost any
supposed fact about the growth of the flux through the core of an
electromagnet.

The toroids I used had cores made of extremely fine, varnished iron
wire, costing about four dollars per kilogram. For some of these I deter-
mined by ballistic methods, as carefully as I well could, the hysteresis
diagrams for several excitations, and then compared with these other
diagrams obtained from the oscillograph records of current curves for

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 147

the same magnetic journeys of the cores, but I could not detect any
differences which did not lie far within the small uncertainty which
the viscosity of the oil in the oscillograph may be supposed to cause.
It does not seem worth while to print a long series of numbers to
illustrate this kind of comparison though the labor was great.

If, then, the core of an electromagnet is made of iron wire not more
than one tenth of a millimeter in diameter and carefully varnished, it
seems to be true within the limits of accuracy of my measurements
and for the comparatively moderate excitations used, that if the core

lU
D.

- —

■•

^_^

—

>S.

FlGDKE 41.

Theoretical forms of direct and reverse current curves for a coil of 1394 turns
belonging to the magnet Q, when the resistance of the circuit is 15 ohms and the
applied voltage is 19.5.

is in a given magnetic state at the start, the change of the flux of
magnetic induction caused by a current which grows from zero with-
out decreasing to a given final intensity, is quite independent of the
manner of growth of this current. It may grow continuously or by
steps, and if eddy currents are not appreciable, the condition of the
core at the end is the same. According to this, one would get exactly
the same hysteresis diagram from an accurately drawn current curve
of the form V (Figure 4) corresponding to any change of current in the
exciting coil as from the corresponding U diagram or from any slow
step-by-step ballistic method. Nothing of the nature of time lag, if it
exists at all, affects the growth of the induction in the iron appreci-
ably. Even in the case of an ordinary transformer, where the effects

148

PROCEEDINGS OF THE AMERICAN ACADEMY.

of eddy currents are very noticeable at the early portions of most cur-
rent curves, the whole change of flux due to a given current in the coil is
the same apparently whether the current grows steadily or by steps ; in
this case an accurate diagram of the U form and a step-by-step ballis-
tic method with a proper galvanometer may be expected to yield

I-*

2
UI

1.0

0.5

(

0.1 0.2 0.3

Figure 42.

SECONDS

Theoretical form of reverse current curve for a coil of 1394 turns belonging
to the magnet Q, under an electromotive force of 208 volts. The resistance of
the circuit is 160 ohms.

identical results within the limits of the measurements. This state-
ment seems to be justified by such comparisons of the two as that
recorded on page 142, which required many days in the making. From
a current curve we may expect to get a hysteresis diagram good enough
for any commercial purpose, but differing slightly at the beginning
from the statical diagram found ballistically. Of course, it would
not be easy to get any very accurate information, as some of the curves

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 149

given in this paper show clearly, from a current curve taken in the
exciting coil of a magnet which has a large solid core.

It will be evident from what precedes that it is possible to predict
accurately the building-up curve of a current in the coil of an electro-
magnet with fine wire core, from
a corresponding hysteresis dia-
gram obtained by aid of a ballis-
tic galvanometer of long period,
and one of the old methods of
procedure.

Figure 43 shows two reverse
current curves for a toroidal
magnet of about one third of a
henry inductance belonging to
the American Telephone and
Telegraph Company. The final
strength of the current was the

same (1.42 amperes) in both cases, but the applied electromotive
force was 10.9 for the left-hand curve and 21.5 for the other. The
disturbing effects of eddy currents were here (as will be shown in the
sequel) wholly inappreciable. We should be justified in expecting
that each of these current curves would yield by aid of a good plani-
meter a hysteresis diagram substantially the same as any ballistic
step-by-step method would furnish for the same magnetic journey of
the core.

Figure 43.

SECOND&

The Influence of Eddy Currents upon the Apparent Magnetic
Behavior of the Core of a Large Electromagnet in the
Coil of which a Current is growing.

If after the solid core of a large electromagnet had been demagnetized
we were to establish a steady current in the exciting coil by applying
to its circuit a constant electromotive force, eddy currents would, of
course, be set up in the core, and at any instant during the growth of
the current in the coil the iron at the centre of the core would be sub-
jected to a magnetic field weaker than the field belonging to a steady
current of intensity equal to the instantaneous strength of the coil
current. If, therefore, we were to attempt to determine the magnetic
properties of the core from the record of an oscillograph in the coil cir-
cuit, we should find that the induction through the core corresponding
to a given instantaneous current intensity in the coil was less than
the flux belonging to a steady current of the same intensity as deter-

150 PROCEEDINGS OF THE AMERICAN ACADEMY.

mined from a statical hysteresis diagram. The same phenomenon
appears when an electromagnet with finely laminated core has a sec-
ondary coil. The closing on itself of a secondary coil wound on the core
of an electromagnet when a current is being established in the primary
will, therefore, expedite at first the rise of this current, but the area over
the current curves ought to be the same in the two cases, and we must
expect, therefore, the building-up time to be somewhat longer when the
secondary coil is closed than when its circuit is broken.

It is to be expected, of course, that the curves which show the march
of the current in the primary circuit will be noticeably different in form
when the secondary circuit is closed and when it is open ; for this is
often the fact in the case of two neighboring circuits which have fixed
self and mutual inductances {L^, L^, 31) if one of them containing an
electromotive force E be suddenly closed at the time ^ == 0, while the
other, which contains no electromotive force, is closed. Here

(21)

where ?\, ro are the resistances of the circuits and I^, I^ the currents in
them.

If . A = ^^, and f. = ^^,

where S=ULo-M\ Q = r.- L^ + r^- U, B-=Q--A7\-n- 8;
Ii^-7r^[B-^e^'{r,-L,-n-L, + E) +ie>''(r,-L,-rvL,-B)l (22)

I, = ^^[e'" - e^'l (23)

flU = -^, a.d /(^-/,).. = ^. (2,)

Figure 44 illustrates a typical case where ^S* is positive : the heavy
line shows the current in the primary circuit when n == 3 ohms, r^, =
2 ohms, L^ = 3 henries, L2 = 2 henries, 31 = ^/6/S henries, jE\ = 12
volts, when the secondary is closed ; the lighter curve shows the rise of
the current in the same circuit when the secondary circuit is open.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 151

au(

/i = 4(l-ie ^ -ie~'0,
ii = 4 (1 - e-^).

(25)
(26)

The slope of the first curve is at the outset somewhat greater than
that of the secondary curve, but eventually becomes less, the curves
intersecting at a point Y. The area between the curve and the asymp-
tote drawn parallel to the axis of abscissas is the same for both cases.

If the circuits just described had in common a large closed iron core,
the current curves for open and closed secondary circuit would be

2
LJ

cc
o

—

TIME.

Figure 44.

Currents in the primary circuit of an induction coil with air core, when the
secondary circuit is closed (full curve) and when the secondary is open.

much less like each other than the curves of Figure 44 are, even if the
core were not solid. We may illustrate this fact by some oscillograms
from a transformer which has a laminated core.

Figure 45 shows two typical reverse current curves for the exciting
coil of the magnet Q which has 2788 turns, when the circuit of a
secondary coil of 1095 turns is (i>) open and iC) closed. Both curves
rise very rapidly at the start, and then bend suddenly, so as to become
almost horizontal for a time, but in the first fifth of a second the curve
taken when the secondary is closed attains 40 per cent of its final
value, and the other curve only 18 per cent ; yet the second curve
reaches half its height about two fifths of a second sooner than the
first does ; and when the secondary is open the current in the primary

152

PKOCEEDINGS OF THE AMERICAN ACADEMY.

circuit reaches 98 per cent of its maximum strength in about |ths of
a second less time than when the secondary is closed. In this case the
final current was 2.80 amperes. Of course the degree of divergence of
the current curve for the primary circuit when the secondary is closed,
from the corresponding curve when the secondary is open, depends
very much upon the number of turns of the secondary and upon its
resistance.

SECONDS.

FlGUKE 45.

Reverse current curves for the coil of 2788 turns belonging to the magnet Q,
when the circuit of a secondary coil of 1095 turns was closed (C) and open {D).
The resistance of the primary circuit, which contained a battery of 40 storage
cells, was 30 ohms.

Figure 46 shows both reverse and direct curves for the magnet Q
when the primary and secondary coils were geometrically alike and
each had 1394 turns. The resistance of the primary circuit was about
16.7 ohms.

The curves of Figure 47 belong to a primary coil of 82.3 turns of the
magnet Q. The lines which have 0 as origin represent currents of
about 2.05 amperes due to a storage battery of 10 cells ; the lines which
start at A' were caused by currents of 7.55 amperes from a battery of
40 cells. •

Figure 48 shows direct and reverse curves for a current of 3.30 am-
peres (due to a storage battery of 40 cells) in a coil of 1394 turns

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROJL\GNET. 153

belonging to Q. The curves M, iV were taken with a secondary coil
of 16 turns and comparatively high resistance closed ; the boundaries

SECONDS.

Figure 46.

Direct and reverse current curves for a coil of 1394 turns belonging to the
magnet Q when a secondary circuit of 1394 turns was closed and open.

of the shaded areas m, n show the forms of the currents induced in
this secondary as obtained from an oscillograph in the circuit. Since

SECONDS.

Figure 47.

Direct and reverse curves representing currents in a primary coil of 823 turns
belonging to the magnet Q, for open and closed secondary circuit. The second-
ary coil had 2788 turns. For the curves which start at 0 the voltage was about
20.6 ; for the curves which begin at X the voltage was about 82 and the maximum
current 7.55 amperes.

154

PROCEEDINGS OF THE AMERICAN ACADEMY.

the number of turns in this secondary was so small and the resistance
large, the forms of the curves M, N are not very different from what
they would have been if the secondary circuit had been open. The
curves F, W were taken with another secondary circuit of 1095 turns
closed on itself : the boundary of the area v shows on an arbitrary
scale the form of the induced current in this last mentioned secondary
circuit.

It is not to be expected, of course, that a current curve for the ex-
citing coil of an electromagnet which has a large solid core will be so
much altered in general appearance by the closing of a secondary coil

ElGOKE 48.

as it would be if the core were divided so as to prevent in large measure
the effects of powerful eddy currents which are present when the iron is
in one piece.

Even in the case of an electromagnet the core of which is built up of
broad varnished pieces of sheet iron, eddy currents in this iron may
radically change the form of a current curve unless the sheets are very
thin. Figure 49 illustrates this fact by an actual example drawn to
scale.

Figure 50 shows curves belonging to a certain transformer. M is a
piece of a statical hysteresis curve ; N is a similar curve obtained from
a reverse current oscillogram. Although the core of this magnet is
made up of varnished pieces of sheet iron, the effects of eddy currents,
as will be shown more clearly in the sequel, are here very noticeable.

Some instances of the phenomenon just mentioned suggest a possible

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 155

pure time-lag 12 of magnetization, like that observed by Ewing and Lord
Rayleigh, large enough in the case of a very large core to affect some-
what the forms of the current curves ; in fact, I have spent a very long
time and have made many measurements upon a great number of oscil-
lograph records in order to see whether any such lag could be shown ;
but after all allowances have been made for the effects of eddy currents,
nothing tangible, if anything at all, remains, for such moderate excita-
tions as I have used with closed, finely divided cores.

—

..y.

^AREA

S.__

— - *

— -

—^

C,'

,.■'

/
/

^IK

■^

0.5

_^i—

^-^

—

^_ —

.— -

— "

„

SECONDS.

Figure 49.

The full line represents the actual form of a reverse current curve in the coil
of a certain transformer the core of which is laminated ; the curve sketched out
bv dashes represents the theoretical form as obtained from the statical hysteresis
diagram. The dotted curve represents on an arbitrary scale the areas between
the real curve and the asymptote ; the flux change being nearly proportional to
the time.

If to a circuit — without iron and unaffected by any neighboring
currents — which has a fixed inductance L, and resistance r, be applied
a fixed electromotive force, E, the current-time curve will follow the
equation

and the current will attain the intensity Io = E/(r + h) at the time ^o
such that

" G. "Wiedemann, Galvanismus, 3, 738. Ewing, Magnetic Induction, § 84.
Gumlich und Schmidt, Electrotechnische Zeitschrift, 21, 1900. Riicker, In-
augural Dissertation, Halle-Wittenberg, 1905.

156

PROCEEDINGS OF THE AMERICAN ACADEMY.

rt„

e L -

r ^-h

If, however, the resistance of the circuit at the outset had been
(r + h) and if after the final value of the current /o for this resistance

had been estabHshed, the
extra resistance had been
suddenly removed from the
circuit, the current curve
from that instant on would
have followed the equation

rtf ]^ _rt/_

or, smce

rtn

^0 = 7(1-^ "^)'

It is clear, therefore, that
in the case of a circuit of
this kind the last (upper)
portion of a step curve of
the form U (Figure 4) will
have exactly the same shape
as the corresponding part of
the V curve, although the
lower portions may be very
different.

If in the case also of a
circuit which has one or
more finely divided iron
cores the flux of induction
through the circuit can be
considered as a single val-
ued (given) function of the
current strength when the
magnetic state of the iron at the outset is given, the upper portion of a
curve of the f^type (Figure 4) belonging to the circuit will be identical
with the corresponding i^art of a curve of the V type. We need con-
sider only a U curve with one intermediate step. If the induction {N)

AMPERES.

Fig ORE

J/ is a portion of a statical hysteresis dia-
gram for a certain transformer under an excita-
tion of 1812 ampere turns. Nis, a similar curve
obtained from a reverse current oscillogram.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 15T

through the circuit corresponding to a current of intensity lis 4> (/),
and if the resistance of the circuit is H, the differential equation which
determines the growth of the current is

E-RI

= dt.

Since ^ is known, the coefficient of dl is known after values have been
assigned to the constants E and R. If with a given E, R has the
value r, the curve obtained by plotting the coefficient of dl against /
'will have a shape something like that of the line KG DP of Figure 51,
which has the line / = E/r for an asymptote. If with the same value
of the electromotive force R has the value (r + h), the curve will have a
shape something like that of the line KB DA, which has the vertical
asymptote I=E/{r-\-h)
which passes through Q. If
with the core in the state for
which the diagram is drawn,
the circuit be closed at the
time ^ = 0, and if the resis-
tance be (r -f- h), the time
required for the current to
attain any value 1' less than
E/{r -\- h) is proportional to
the shaded area under the
curve KB DA from the ordi-
nate axis up to the vertical
line X =■ I'. If, however, the
resistance of the circuit had been r, the time required for the current
to grow to the intensity /' would be represented on the same scale by
the area under the curve KCDP from cc = 0, to x= I' . If the circuit
were closed when its resistance was (r -j- li), and if the current were
allowed practically to reach its final value for this resistance, as repre-
sented by the line OE, and if then the resistance h were suddenly
shunted out, the current would grow to its new final value at a rate
determined by the fact that the time required to reach the current OB
must be equal, on the scale of the diagram, to the area EFPH. If the
circuit had been closed first when its resistance was r, the time required
for the current to grow from the intensity OE to the intensity OH
would still be equal, on the scale used, to the area EFPH, and the
shape of the current curve, from E/{r -\- k) on, would be the same as
before. Of course the iV" of this theory need not be the same as the
N of the statical hysteresis diagram for the given magnet ; it might

CURRENT.

FlGUKE 51.

158

PROCEEDINGS OF THE AMERICAN ACADEMY.

have for any value of / a value which in the case of the statical curve
belonged to a current weaker by any given constant or otherwise deter-
mined amount. The curve FP must, however, have the same form
for a continuously growing current and for one which suddenly begins
to increase from the value OE.

As a matter of fact, experiment seems to show that if the core of an
electromagnet is made of varnished wire so fine that eddy currents are
practically shut out, the upper portion of a f/" curve with a single inter-
mediate step is exactly like the corresponding portion of the V curve.
Figure 52 represents a set of current curves obtained from a number

SECONDS.

Figure 52.

Current curves for a coil with fine wire core. The second part of a two-stage
current is exactly the same as if the current were allowed to grow at once to its
final value.

of toroidal coils (with very fine wire cores) connected up in series ; the
current came from a storage battery of ten cells. When the circuit had
its normal resistance, the final value of the current was represented by
OA ; it was possible, however, to close the circuit with such an extra
amount of resistance that the final value of the current should be repre-
seutable on the same scale as before, by the line OK. The extra resist-
ance could then be suddenly shunted out of the circuit by closing a
switch at any time after the lower current had practically attained its
maximum strength. When the core had been previously demagnetized,
a diagram of this kind had the form OHDXU ; but if the circuit had
from first to last its normal resistance, the current curve had a shape
accurately represented — when the starting point was shifted to the proper

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 159

point (P) on the time axis — by PDXU. The upper part of the curve
was in no way distinguishable from the corresponding portion of the U
diagram. Mr. John Coulson and I have taken many records of this
kind and have not been able to detect any difference between the
upper parts of the different kinds of curves. The second part of the
U diagram starts off at exactly the same angle with the horizontal that
the other curve has when the line KG is crossed. The area OKDHO
when divided by the length 0^ should be the same as the area PSTDP
divided by the length OA.

If eddy currents are present, the upper portions of a Z7 diagram and
of a V diagram do not entirely agree. Figure 53 represents diagrams

FlGTJKE 53.

Growth from an originally neutral core of a current in a transformer with
a laminated core. The effects of eddy currents are here noticeablte.

for the magnet Q which has a laminated core, although eddy currents
are not entirely shut out. If the upper part of the 6^ diagram {GDQ)
be shifted to the left, it will be found to agree with the curve PCO from
P to C, but beyond C the two are quite different, as the dotted line
indicates. When the V current, the growth of which is represented
by the line OCP, has reached the strength OA, the induction flux
through the core is only a small fraction of the flux when a steady
current of final strength OA is established in the coil in the manner
represented by OKG. The existence of eddy currents is indicated
clearly by the fact that the first portion of the curve GDQ is nearly
vertical. These diagrams were obtained when the core had been well
demagnetized. Figure 54 shows similar diagrams for direct curves
(dotted) and for reverse curves (full).

160

PROCEEDINGS OF THE AMERICAN ACADEMY.

The Growth of the Induction Flux in the Core of an Elec-
tromagnet WHILE THE Exciting Current is Temporarily
Constant.

It sometimes happens that if a number of secondary coils of low
resistance, wound upon the core of an electromagnet, are closed on
themselves, the building-up curve of a current in the exciting coil is
for a comparatively long time almost exactly parallel to the time axis.
During this time it is difficult to detect any change in the intensity
of the current, and yet the flux of magnetic induction through the
core is increasing at a very nearly constant rate. This fact, which
has a certain pedagogic interest, is easily illustrated. The curve

SECONDS.

Figure 54.

Direct and reverse current curves for a transformer with a laminated core.
The existence of eddy currents is clearly shown.

OPQU (Figure 55) shows a nearly t)^ical case, and the line OKLG
represents on a different scale the induced current in one of the second-
ary circuits. To a person watching an amperemeter in the primary
circuit, the current seems to have attained its final value in less than
a second, and if he leaves the instrument at the end of, say, five sec-
onds, he feels sure that the current has become steady. Meanwhile the
induction flux, as measured on the scale of the diagram by the area
between the curve and the line YU (or, on a different scale, by the
area under the curve OKLG), is constantly growing. Of course if the
core is very large, the whole building-up time may be a minute or
more, and the phenomenon may then become very striking.

The magnet T has three coils. The first {A) has 750 turns, the

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 161

second {B) 250 turns, and the third {€), which is made of wire of very
large cross-section, has a small unknown number. Figure 56 reproduces
accurately the records of two oscillographs, one in the coil A, the other
in B, when C was closed. OMQL is a part of the building-up curve
for the main circuit {A), and Ochk is a corresponding portion of the
record of the induced current in B. In the case represented by the
full line OMQTVW, the coil C was suddenly opened at about 1.05
seconds after the start : Ocbznda shows the record of the induced
current in B under these circumstances. The scales of the two oscillo-
graphs were, of course, not the same. The sudden jumps in the
oscillograms might have been predicted, in amount as well as in direc-
tion, by the principle of the " Conservation of Electromagnetic ]\Io-
. Y

03
LJ
DC

UJ
Q.

SECONDS.

Figure 55.

menta." We shall return to the subject of the sudden changes brought
about in the currents in inductively connected circuits when the
inductances of the system are impulsively changed.

The Effectrtiness of Fine Subdivision in the Core of an Electro-
magnet FOR the Prevention of Electromagnetic Disturbances
due to Eddy Currents, when a Steady Electromotive Force is
applied to the Circuit of the Exciting Coil.

In order to determine approximately the magnitude of the effect of
eddy currents upon the growth of a current ^^ in the coil of an electro-
magnet the core of which is made of fine iron wire, we may consider
the case of a very long solenoid consisting of N turns of wire per cen-
timeter of its length, wound closely about a long prism of square cross-

" The influence of eddy currents in the formation of a regularly fluctuating
current in the exciting coil of a transformer under a given, alternating electro-
motive force has been studied by J. J. Thomson for cores of square cross-suc-
tion built up of iron sheets, and by Heaviside for round cylindrical cores cut
radially. See the Electrician for April, 1892, and Heaviside's Electrical Papers,
1, xxviii.

VOL. XLIII. — 11

162 PEOCEEDINGS OF THE AMERICAN ACADEMY.

section (2aX2a) built up uniformly (Figures 59 and 60) of a large
number of varnished filaments of square cross-section (c X c), or else
consisting of a bundle of infinitely long straight wires. The axis of
the prism shall be the z axis, and the .r and ^ axes shall be parallel
to faces of the prism. The electric resistance of the solenoid per centi-
meter of its length shall be w, the constant applied electromotive force
per centimeter of the length of the prism shall be £J, and the intensity
of the current in the coil shall be C Within the core, the magnetic
field (ff) will have the direction of the ;:; axis, and if q is the current

flux at any place

4:Trq = Cm\H, (27)

or 4 -n-q^ = -g— , 4 TT^y = — — , 4 Trq^ = 0.

Within any filament of iron in the core, H satisfies the equation

dH p fc-H c

dt 4:TTjJi

m-w)'

where p is the specific resistance of the iron and fi is its permeability,
which for the present purpose shall be regarded as having a fixed
value.

When there are no Foucault currents in the core, the intensity (H) of
the magnetic field within has at every point the boundary value Hs
or 4 TT JVC, but if positively directed eddy currents exist, H may be
greater at inside points than at the surface. We need not distinguish
between the flux p through the turns of the coil per centimeter of its

length, and N times the induction flux Mil Hdxdy through the
core, so that we may write

or by virtue of (28),

E =

4:7rN

-mm-W)'-^- <-)

where the integration extends over a cross-section of the core.

The vector H is always perpendicular to its curl, and the intensity
of the component of the current at any point in the iron, in any direc-

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 163

tion, 5, parallel to the xy plane at any instant, is equal to 1/4 tt times
the value at that point, at that instant, of the derivative oi H m &
direction parallel to the xy plane, and 90° in counter clockwise rota-
tion ahead of ^\

Along any curve in the iron parallel to the xy plane, H must be
constant if there is no flow of electricity across the curve. At every
instant, therefore, the value of H at the boundary common to any two
filaments must be everywhere equal to Hs- If the coil circuit is
broken, H must be constantly zero at the surface of every filament.

Two or three general theorems concerning solutions of differential
equations of the form

'\dx-^ dy-J ~ dz'

will be helpful to us.

If V and ir represent any analytic functions of x, y, z, and if L (zr),
M{v) represent the adjoint differential expressions

the corresponding form of the generalized Green's Theorem may be ex-
pressed by the equation,

fffl' ■ ^ 0-'') - "' ■ ^^^(^')] • dx dy dz =

9 I 1 [ i' ■ a~ ~ ^'' ■ a~ ) ■ ^0^ (^' n) -dS — I I IV V ■ cos (z, n) • dS ; (33)
and it is easy to prove that
j j I '■ L(w) dxdydz = g I J r f ^ • cos (x, n) -{- ^- cos (y, n) \dS

164 PROCEEDINGS OF THE AMERICAN ACADEMY.

If IV and V are identically equal, the last equation becomes

///"■ • ^ ^'"^ ■ ^"'^^^^ = ^11" (S

cos (x, w) + -o- • COS (jj,n) \dS

(I) If >So is a closed cylindrical surface the generating lines of which
are parallel to the z axis, and if 12, rJ' — two functions which within
So satisfy the equations L (n) = 0, L (fi') = 0 — (1) vanish at all points

TIME.

FiGDKE 66.

of So and at all points within S^ for which z is positively infinite, and
(2) have the given constant value Qo at all points in the .ri/ plane
within >So ; then if we apply (35) to the difference between O and O',
using as a field of volume integration the space inside S^on the positive
side of the xi/ plane (Figure 57), we shall learn that in this space fi and O'
must be identically equal. The value of fi within So is in no way
affected by conditions which a physical extension of the function
might be required to satisfy outside >So.

(11) If So is a closed cylindrical surface, the generating lines of
which are parallel to the z axis, if W is a function which within So
satisfies the equation L ( W) = 0, and if

(1) ^Fand dW/dz vanish at all points within and on So for which
z is positively infinite,

(2) W has a given constant value (Wo) at all points on the ,ri/
plane within So-

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 165

(3) IF on Sf^ is a function ( IT^) of z only, such that if n indicates
the direction of the external normal to >.%

»''»+^/C^')*=»'

(36)

where k is a given positive constant, and the line integral is to be
taken around the perimeter of a right section of Sq made by the plane
z — z; and, hence, if

(4) / / ( -o~ ) '-^"^i taken over so much of the xi/ plane as lies within

So, is given, then TF is uniquely determined.

If we assume that two different functions ( W, W) may satisfy all
these conditions, and denote their difference by it,

L (u) = 0, within >So,

u and dti/dz vanish at all points
within Sq, for which z is positively

infinite,

u vanishes at all points on the .ri/
plane within aS'„,

ii on >So satisfies the equation

Us + ^

/G~)---

(37)

Figure 57.

If we use the space bounded by ^S'^, the x>/ plane, and the plane
2; = GO , as a field of volume integration, and denote the whole bound-
ary by S; then, since cos (z, a) vanishes on So, and u, cos {x, »),
cos (3/, ?i), vanish on the portions of the planes z = 0, z= ^ used as
boundaries, (35) yields the equation

Now ti has the same value at all points on the perimeter (s) of any
right section of Sq, so that

166

PROCEEDINGS OF THE AMERICAN ACADEMY.

and (38) becomes

where /• is intrinsically positive ; but each of these last integrals has
an integrand that must be either zero or positive at every point in its
domain, so that ii must be independent of ,r and y, and must vanish
on *S^o at every point. It follows that u is everywhere zero and that

Tr= w.

It is evident that the condition (3) might have been stated in the
form of the equation

where the integration is to be extended over so much of the i>lane
c = c as lies within /S'q.

If the space within Sq were cut up into portions (filaments) by the
cylindrical surfaces Si, S^, S3, ■ ■ ■ , the generating lines of which were
parallel to the ;:; axis, and if within each filament
L (TI'} vanished, while, in addition to the other
requirements enumerated above, W were constrained
to have at every point of the surface of every filament
the value (^Vg), which points with the same z co-
C) n 0> ordinate on the surface >% had, — though the normal

1 derivative of W at the common surface of two fila-

FiGURE 58. ments were not expected to be continuous, — we

might assume as before that two different functions

could satisfy all these conditions and denote their difference by ti.

We could then apply (35) to every filament separately (Figures 57

and 58) and obtain from each an equation of the form

(42)

where B denotes a cross-section of the filament. If, then, all these
equations were added together, the resulting equation would be

/--xf(S4)--ixr[G"y

^.y

which is (35). In this case also, therefore, W is determined.

'hdA =0,
(43)

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 167

(III) If *So is a closed cylindrical surface the generating lines of
which are parallel to the z axis, if F is a function which within Sq
satisfies the equation Z ( F) = 0, and if

(1) Fand dV/dz vanish at all points within and on /S'^ for which z
is positively infinite,

(2) V has a given constant value ( V^) at all points on the .ry plane
within *Sq,

(3) V on So is a function ( Vg) of z only, such that, if n indicates
the direction of the external normal to *So

Vs+l-^ + ^-JJ (^+ ^>-%=0, • (44)

where I and k are given positive constants, the line integral is to be
taken around the perimeter (s) of a right section of So made by the
plane z — z, and the double integral over the section ; then V is
uniquely determined.

(IV) Let *So be a closed cylindrical surface which completely surrounds
(Figure 58) several other mutually exclusive, closed cylindrical surfaces
(Si, So, Ss, • • • ) the generating lines of which are parallel to those of >So
and to the z axis ; and let the intersections of these surfaces with the
plane c = c be denoted by ■% Si, S2, S3, ■ ■ • . Let the portions of the
plane z = z within Si, S^, S3, • • • , be denoted hy Ai, A^, A3, ■ ■ • , and
the portion within S^ but outside Si, S-., S3, • • • , be denoted by A^.
Let Tg, Ti, To, T3, • • • , represent the volumes of the prisms (bounded
by the planes z — 0, z = co) of which the cross-sections made by the
planes c = c are A^, A-^, A^, A3, • • • .

In the regions T^J, tj, to, rg, • • •, let the scalar function U satisfy
the equations

dU (c'U dH^\ ....

dU_ (c-U d-U\

168 PROCEEDINGS OF THE AMERICAN ACADEMY.

where ^,„ gi, g^, g% are given positive constants, and let the value ( U^
of U on the cylindrical surfaces be a function of z only (the same for
all the surfaces), such that

Z7^ +

where l\, h, h, h are given positive constants. Then if U has the
constant value ^o at all points in so much of the xi/ plane as lies
within Sq and the value zero at all points on and within /S', for which z
is positively infinite, IT is determined in the positive space within Sq.
For if we assume that there could be two such functions and apply
(35) to their difference («) in each of the regions r,,, ti, tj, Tg, • • • ,
multiply the resultant equations by k^^, ki, k-i, h, ■ ■ ■ , and add them
together, it will be easy — to show in the way indicated under (II)
— that u is zero everywhere inside S^y on the positive side of the
.0:1/ plane.

It is to be remembered that

??+?? (47)

is an invariant of a transformation of orthogonal Cartesian co-ordinates
in the xy plane.

(V) In an important special case similar to that stated in (IV),
^'i, ^'2, ^3, • ■ • , are all equal, ^1, g-^, g^, ■ • ■ , are all equal, and all the
w^ areas ^4i, A^, Az, ■ ■ ■, are alike in form, however they may be
oriented. In the region t^, U is everywhere equal to Cs, which is, as
before, a function of z only, and the surface condition becomes

^H-..f^..|X/-(|f.f)u. («)

where / and k are given positive constants.

If in this case we find for every one (t,„) of the regions ti, t^, T3, • • • ,
the function (Wm), which within (r,„) satisfies the equation

dir,„ fd'w„, 8hv,n\ .,,,.

dz ^' V 3.r ' dr

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNOT. 169

and at the boundary the surface condition

Ws + I-

' s

"='//(^ + |f)"-«. CO)

and which has the given constant value U^^ on so much of the xy plane
as lies within >% and the value zero when z is infinite, and if we assign
to the function without 8,^ where it is not defined, the value zero, then,
apart ft'om differences of orientation, all these functions will be alike.
If after this we define a function within >Sy by assigning to it within
every one of the regions ti, r^, T3, • • • , the same value as the w func-
tion belonging to this region, and give to it in Tq the common value w's.
the function thus determined will be the unique function U described
above.

If after a steady current of intensity Ejw has been running for some
time in the coil of the solenoid under consideration, so that the mag-
netic field within the core (which in this case
shall be built up, in the manner shown in
Figure 59, of filaments of square cross-
sections) has everywhere the given constant
value i/ii, the coil circuit be very suddenly
broken, the value of H falls instantly, not
only at the outer surface of the prism, but
also at the surface of every filament, to zero.
Inside every filament

(51)

FlGURK 59.

When ^ = 0, H = Hf^ everywhere within the iron, and when t is in-
finite, the field intensity is everywhere zero. According to (I), there-
fore, we may consider ever}^ filament by itself.

If we seek a solution of the equation (51) which shall be of the form
JT- YT, where X involves x alone, F involves y alone, and T' is a
function of t alone, we shall obtain the expressions

X=^i-coscur-l-^2-sina^, V = Bi • cos (3y + B^ ■ sin (3y, T = e~''''^,

(52)
where

X^ = '-^^p^ ■ (53)

4 ^(U

170 PROCEEDINGS OF THE AMERICAN ACADEMY.

If we use as normal function the product

Amn ■ e-^^' ■ sin — ^ • sin — -, (54)

c c

where A^ = Trp(m^ + ??^) (4 f^c') and m and n are positive integers,
and write

W!=oon:=oo

H = > ^Amn e ^ ' • sm — ^ ■ sm — -, (55)

mrrl n^l

this expression will satisfy all conditions if A^n he so taken that when
t = 0, the second number of the equation shall be equal to Hq for all
values of x and i/ within the filament. We have, therefore, the
equation i*

A^n = i^ Cdx fsin^.sin^-^^ (56)

c^ ,

c/o ■•

■Jo C

and

'Amn

16^0

when

m and

n are

both odd

)

when either m or m is even, so that

^' = rT5[(2 i- + 1)-^ + (-V + I)']- (58)

From (58) it appears that the whole flux of magnetic induction
through the core at the time t is

i=l A-=l

or, if g = 7rp/4 /^c^

^* Byerly, Treatise on Fourier's Series, etc., § 71. Kiemann-Weber, Die par-
tiellen Differential-gleichungen der mathematischen Physik, Bd. II, § 99.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 171

Ufi-Ho- c''^^e-<^^y+^y-' ^'^ e-^'i'^+m

2^(-2j+ir 2^'(2 k + If

j—l k—l

(60)

In these equations absolute electromagnetic units are to be used, and
for good soft iron we may assume that 7rp/4 is very approximately equal
to 8000. It is evident that for different values of c when fi. is given,
e~^'^ will have the same numerical value for values of t proportional to
c"; for instance, if c = 20, ^ = 10, e"^'' will have the same value as it
would if c were 1 and t, 1/40. If c is fixed, e"^'' will have the same
value for values of t proportional to /x.

It is possible to show that if c = 1 and fx = 200, — to take a special
case, — the series

«=Xw^^' («i)

k=0

'k+ ly

has at different times the approximate values given in the following
table :

TABLE Y.

1.2337

0.01000

0.6734

0.00025

1.1450

0.02000

0.4494

0.00050

1.1084

0.02500

0.3679

0.00100

1.0565

0.05000

0.1353

0.00200

0.9830

0.07500

0.04979

0.00250

0.9534

0.10000

0.01832

0.00500

0.8374

0.20000

0.00034

From the numbers in this table it is easy to compute, for cores of
square cross-section, the fractional part of the original induction flux
through the core which remains after the circuit of the exciting coil has
been broken for a given time. For a solid core, the area of the square
section of which is 100 square centimeters, the results are given in the
next table, when fi is 200.

If the core were built up compactly of varnished square rods of one
square centimeter in cross-section, the times in the table should be

172

PROCEEDINGS OF THE AMERICAN ACADEMY.

divided by 100, and if the core were made up of 10,000 slender fila-
ments, the flux would sensibly disappear during the first thousandth of
a second. It is easy to get similar results for any other value of /u.

TABLE VI.

Time in Seconds

after the Breaking

of the Circuit.

Fractional Part
of Original Flux
still remaining.

Time in Seconds

after the Breaking

of the Circuit.

Fractional Part
of Original Flux
still remaining.

0.000

1.000

0.298

0.025

0.861

2.000

0.133

0.050

0.807

2.500

0.089

0.100

0.733

5.000

0.012

0.200

0.635

7.500

0.0010

0.250

0.597

10.000

0.0002

0.500

0.461

If the cross-section of the core were a circle of radius a, and if, after
a uniform magnetic field of strength Ho had been established in the
core the exciting circuit were suddenly broken, the intensity of the
field at any time, at any point distant r centimeters from the axis
would be given by the expression ^^

2H,
a

(62)

where /8^ = p«'-^/4 tt/a and the whole flux through the core would be

Hrdr or 4 ^M^o^. ^ ' (63)

In these equations Hija is the /th root in order of magnitude of the
Bessel's Equation

J,(?Ki) = 0. (64)

^5 Heaviside, Electrical Papers, 1, xxviii. Peirce, These Proceedings, 41, 1906.
Byerly, Treatise on Fourier's Series, etc., p. 229.

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 173

The first ten roots are as follows :

TABLE VII.

111!.

n<!.

2.404826

18.071064

5.520078

21.211637

8.653728

24.352472

11.791534

27.493479

14.930918

30.634006

From these numbers the /3's can be found, and then from (G3) the flux
in the core after any interval. When the time is short, the series con-
verges very slowly, and the computation is long and troublesome, but
for relatively large values of t the work is not difficult.

The next table shows the fractional part (Q) of the original flux re-
maining in a core, the cross-section of which is a circle of 20 centi-
meters diameter, and in which /j. is 200 ; 1 second, 4 seconds, and 8
seconds after the breaking of the exciting circuit : the corresponding
fraction for a core of square cross-section (20 cms. X 20 cms.) is given
for comparison. The actual value of the original flux is of course a
little larger in the second case because the area of the cross-section is

greater.

TABLE VIIL

n for the
Round Core.

n for the
Square Core.

0,588
0.270
0.106

0.597
0.298
0.133

After 16 seconds n for the round core would be 0.016. In the case
of a round core of exactly the same cross-section area as the square
solid core, and the same original flux, the fractional part remaining
after one second would be 0.630.

If the square core of the solenoid — the area of the cross-section of
which is A square centimeters — be made of a bundle of infinitely long,

174

PROCEEDINGS OF THE AMERICAN ACADEMY.

straight iron wires, placed close together (Figure 60), and if, after a

steady current of intensity Elw has been running for some time through

the solenoid, so that there is a magnetic field of

r^^rW^ uniform intensity ^o = 4 ttNE/w in the core, the

^r)rY~)(p applied electromotive force be suddenly shunted

OOCXD ^^^ ^^ ^^® solenoid circuit, the current (C) in the

OOOOO coil will gradually die out. At any instant the

BOOOQO field, in so much of the space A as is occupied by
OOQQQ air, is 4 ttNC, for eddy currents in the wires act
TiGURE 60. like solenoid sheets and do not affect the field

without the wires. Within each wire there are
eddy currents, of course, and at every point in the wire, at every
instant, the field intensity, H, must satisfy the equation

(65)

The induction flux through the turns of the solenoid per centimeter
of its length shall be j), so that

E — J- = wC, or, in this case, ■— = — wC.
at at

If there are n^ wires in the core and the area of the cross-section of
each of them is B,

p = A 7rN^C{A - n^B) + ixN ffH-dx dy

(66)

where the double integral is to be extended over the cross-sections of all
the wires ; hence

"""IS

dt '

dccdy = 0; (67)

and if the wires fill the square space as full as possible,

A—n'B = 0.2146 A, nearly.

If Hs represents the strength of the magnetic field in the air space
within the solenoid,

H^+il^i^A-n'B/J^ + '"-''

'If

dt '

dxdy = 0. (68)

- PEIECE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 175

The function H thus defined falls under theorem (V) above, and it is
evident that we ought to seek, for a single wire, a function ts which
within the wire shall satisfy (65), at the surface shall fulfil the
condition ^

and which when # = 0 shall have the value H^ and when t is infinite,
the value zero. When we have to deal with a single wire of radius
b (= a/n) alone, it is obviously -"convenient to use polar co-ordinates
with origin at the point where the axis of the wire cuts the xy plane,
and if we do this (65) and (67) take the forms

, 4 7rA^2

or cr

p C V dm~\ , ^

where I, k, n, and b are given, positive constants.

If we attempt to find a solution of (70) in the form of the product
of a function of t, and a function of r, we arrive, of course, at the nor-
mal form

e-^'' [L ■ J,{mr) + M-K, (mr)], (73)

but Bessel's Functions of the second kind will not be needed here,
and we may write, 31 = 0,

S7 = 2 I^,n ■ e-^" ■ Jo (mr), (74)

where either m or (3 may be assumed at pleasure and the other com-
puted from the equation

m^p = 4 irix(S\ (75)

If for 7)1 in the equation (74) we use the successive roots of the trans-
cendental equation

M^f>)=^^-M^f>) (76)

176 PROCEEDINGS OF THE AMERICAN ACADEMY.

the series will satisfy (70) and (72), and if the coefficients can be so
chosen as to make

^L,„-J,{mr)=H, (77)

equation (74) will give the function sought.

Although the development (77) is not one of those for which the
coefficients can be found by the usual devices, it is easy to solve the
problem, for such cases as are of practical interest, to any desirable
approximation.

We shall find it instructive, however, to inquire first what the solu-
tion would be if the second term of (72) were lacking, for, in view of the
fact that the permeability of the iron is relatively large compared with
that of the air, it seems likely that in some instances, where the series
is very convergent, this modified problem and the real one will have
nearly equal numerical answers.

We have, then, so to choose Z,„, ^S, and m, subject to (75) that the
value of the series (77) shall be Hq when ^ = 0, for all values of r up
to h ; and that at every instant

o -\-r^

2 77?? W

^'(l),. = «- (-)

It is necessary, therefore, that m shall be a root of the transcenden-
tal equation

J^ (mb) = ^ — - -mb- Ji {mb), (79)

which may be written in other forms by virtue of the relations

= -Jiix), I a- ■ Ja (x) d,r = a- • Ji(.v). (80)

It will be convenient to illustrate the effect of making b small (and
therefore n large) while a is kept constant, by a numerical example.
Let us assume that the cross-section of the solenoid is a square of 10
centimeters side-length, so that a = 5 ; let the solenoid have 10 turns
of insulated wire per centimeter of its length, and let the resistance of
these 10 turns be t^j-th of an ohm, so that in absolute units iv = 1(>V16.
If, then, we take the specific resistance of the core to be (10V327r)

PEIRCE. — BEHAVIOR OF THE CORE OF AX ELECTROMAGNET. 177

absohms at the room temperature (Fleming and Dewar), 2ttN^p/iv
will be equal to yV, and the equation for m takes the form

But 16 1 = K ^ ^ • -^n (^^0

-4' (A^ + ,,^^6^) To (;«/.)' ^^-^

and hence nr = 2 AZTo V-^^^^^^A(^ (gg)

The whole flux of magnetic induction through the iron of the core is
then jxn^ times the integral of zs taken over the circle of radius b in
which 57 is defined ; that is

^ = i.^XHyiS~f^^4f}^„ (84)

Since A = 10/w^, the coefficient of the series may be written 400 TrfxH^/n-,
and we may assume that jx = 100.

The time rate of change of the total induction flux through the turns
of the solenoid, per centimeter of its length, is

9950 • 10^ -^^-^^ e-^'' , ,
1 Z^vis •"2- (86)

If the square core is built up of 100 circular rods, each 1 centi-
meter in diameter, »^ = 100, A = 1/10, and the ms are defined by the
equation

J^ {mb) = 10 mb • Ji (mb) (87)

in which b = 1/2.

It is not difficult to show by trial and error from Meissel's tables ^^
that the first five roots of this equation have values approximately
equal to those given in the following table :

16 Byerly, Treatise on Fourier's Series, etc., p. 229.

" Meissel, Tafel der Bessels'schen Functionen, Berliner Abhandlungen, 1888 ;
Gray and Mathews, Treatise on Bessel's Functions, pp. 247-266 ; Peirce and
Willson, Bulletin of the American Mathematical Society, 1897.

VOL. XLIII. — 12

178

PROCEEDINGS OF THE AMERICAN ACADEMY.

TABLE IX.

»ii6= 0.44168

log /8i2 = 0.79077

mj2 = 0.78032

m^b = 3.858

log ;3./ = 2,6733

TTia^ = 59.527

^36= 7.030

log ;83-2 = 3.1946

7773-^ = 197.672

77146 = 10.183

log ^342 = 3.5164

77742 = 414.798

77)56 = 13.331

log 35^ = 3.7504

7775-2 = 710.884

A mere inspection of these values shows that the value of ^ can be
computed with an accuracy much more than sufficient for any practical
purpose from the first two terms of the series (85), if t is as great as
xioth of a second, and from the first term alone if t is as great as 3^0 th
of a second. Let ^0 represent the first term of (85), then

<^o =

but

400 ttZTq e-G-i768i
(0.78032)(0.20508)'

400

= 2499.55,

(0.78U32)(0.20508)
which differs from 2500 by about ^V^h of one per cent only.

(88)

If there were no eddy currents in the iron, the total induction flux
through the rods which make up the core would be

^' = TTfia-H'

(89)

and if O were the strength of the current in the exciting coil at the
time ty we should have

^/,aW- "^ = -tvC' = ~l';S'' (90)

and

where
and

dt 4 ttN

h = w/4 7rWV/x = 6.332573 +

(91)

(92)

In the case under consideration we should have very nearly

0' = 2500 ttHo e-«-33^573< (93)

4 ^NC = H', = H, e-e-3325T3/. (94)

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 179

When there are eddy currents the vahie of Hs is given with suffi-
cient accuracy by the first term of (83) very soon after the electromo-
tive force has been shunted out of the circuit, that is by the equation,

and the ratio of ^ to irb'^trixHs is practically equal to the constant
2051/2000, for it is easy to find a very convergent geometrical series
every term of which is greater than the corresponding term of the
series which begins with the second term of (85), and the sum of this
geometrical series is extremely small except for very small values of t.

According to this analysis, the current in the solenoid will ha%'e
fallen in the first second to the fraction 0.002025 or to the fraction
0.001777 of its original value according as there are or are not eddy
currents in the iron.

If the ten centimeter square iron core of the solenoid were built up of
straight rods only one millimeter in diameter, we should have b = 1/20,
n = 100, and A. = 1/1000 ; the m's would need to be roots of the
equation

J^ (mh) = 1000 mb ■ Ji {mb). (96)

By using differences of the third order it is possible to show from
Meissel's table that the first root is approximately equal to 0.044715 +
and the second to 3.83. For the first, then. A- + m^b^ = 0.002000,
and /S^ = 6.33077. For the second root, /3^ = 46500, and the second
terms of the series (83) and (85) become negligible almost immedi-
ately after the electromotive force has been removed from the circuit.

In this case

<f>, = 2500 ttHo- e-6-3307'' (97)

very nearly ; and

-^, = Hs = H,- e-6-33077^ , (98)

^ttJS

so that the disturbing effects of the eddy currents are comparatively
slight. At the end of one second, the current will have fallen to the
fraction 0.001777 of its original value or to the fraction 0.001781,
according as eddy currents were absent or existent. These differ by
only about one two hundred and fifty thousandth part of the original
current strength. We may note in passing that a very approximate
value (correct to four significant figures) of the first root of the equa-
tion might be found by equating to unity the coefficient of the first
term of the series (83).

180 PROCEEDINGS OF THE AMERICAN ACADEMY.

If the core of the solenoid were made of wire one tenth of a milli-
meter in diameter, such as is now in common use in coils intended for
loading long telephone circuits, we should have b = 1/200, 7i = 1000,
A = 1/lOOUOO, and m would need to satisfy the equation

J^ (mb) = 100000 mb ■ Jx (mb). (99)

It is easy to see that the first root of this has a value very nearly
equal to 0.0044721, and that the effects of eddy currents would be
quite inappreciable.

Having considered somewhat at length — on the supposition that
the induction flux in the air spaces of the core might be neglected —
the manner in which a current in the solenoid would decay if the
electromotive force were suddenly removed from the circuit without
changing the resistance, we may now return to the more general case
to which the equations (74) and (76) belong, and remark that in the
ideal case where eddy currents are supposed to be absent (68) takes
the form

whence H's = Ho ■ e-^-^^^^'K (101)

It is clear at the outset that the larger roots, at least, of the two
equations (76) and (79) will be very different, since the second mem-
ber of (76) soon has a negative coefficient. If then the coefficients of
the series (77) could be found, the series (74) and (83) would not re-
semble each other in appearance for large values of b and small values
of the time. If, however, b is fairly small, as it usually is in practice,
we may dismiss all thought of the infinite series, since it is easy to
choose the coefficients of two or three terms of the form (73) so that
the initial condition shall be satisfied very approximately. In many
cases one term suffices.

Let us consider first the case — already treated in another way — of
a square core of 100 square centimeters cross-section, built up of long
straight wires 1 millimeter in diameter; so that b = 1/20, n = 100,
1/3' = 1.36620 m'b'^, hr = 1000, and the equation for 7)ib has the form

J. , , 1000.r ^ , , ^ ^ ,

•^^")=l-1.3662U.r-^'^'')- ('«->

PEIRCE. — BEHAVIOR OF THE CORE OF AN ELECTROMAGNET. 181

It is possible to show by a rather long application of the method of
trial and error, using third differences in Meissel's table, that the value
of the first root is 0.044654+ and this corresponds to m = 0.89308,
/3- = 6.31351, Jo(mb) = 0.9994891+.

If, then, we consider the single term

Q = ff, e-«-3i35« . To (0.89308 r), (103)

Q will satisfy (70) and will vanish when t is infinite. "When t is zero,
Q will be equal to Hq for r = 0, and wiU differ from Hq by about one
twentieth of one per cent when r = b. The second root of (102) is
roughly equal to 3.8 and the corresponding value of /3^ is about 45,000,
so that the exponential factor would soon be very small. An inspection
of the graph of ./(, {x) shows that if we were to use several terms of the
form L • e~^'' ■ Jo (^'^^)) "^6 could easily form a function which should
differ very little from H^ for any value of r up to b, when t was zero ;
but it is clear that after the lapse of about l/5000th of a second, all
the terms beyond the first would be negligible, and there is no practi-
cal advantage in using more than one term.

We may assume then that the value of H in any one of the iron rods
is given fairly accurately, except at the very beginning, by (103). Since
AttNC = JIs the current in the solenoid falls in the first second to
0.001808 of its original value, or to 0.001812 times that value accord-
ing as eddy currents are absent or present. These fractions differ
from each other by about one two hundred and fifty thousandth part of
the original current strength. Another close approximation to the
value of H may be made by dividing (103) by J^ (mb) and another by
multiplying the second member of (103) by

l + J^, (104)

These changes would not affect the relative rate of decay of the
current.

The nearness of the approximation to the value of the field attain-
able by a single term is evidently much increased as the diameter of
the iron wire of which the core is built up is decreased. If as before
(1 = 5, but \ib = 1/200, n = 1000, the value of the first root of the
equation for mb will be 0.00446616, nearly, and the value of Joimr)
will not change by so much as 1/I0(i000th part of itself as r changes
from 0 to b. A single term, therefore, will represent H with great
accuracy. In this case the effect of eddy currents is wholly inappre-

182 PROCEEDINGS OF THE AMERICAN ACADEMY.

ciable. Of course this statement does not apply to the case of an
alternate current of very great frequency.

In the problem just considered the electromotive force was suddenly
shunted out of the solenoid circuit after a steady current had been
established in it, and, on the assumption that the permeability of the
iron was fixed, the value of the magnetic field within the core was
determined as a function [H^JXt, 7-)] of the time and the space co-
ordinates. The function / satisfies (65) and (68), vanishes when t
is infinite, and is initially equal to unity. If the solenoid circuit
containing an applied electromotive force E be suddenly closed at the
time ^ = 0, and if the ultimate value (iTrNJE/w) of the magnetic field
in the core be denoted by H^ , the value of the field at any time will
be given by the equation

H=H^[l-f(t,r)]. (105)

The function defined by this equation vanishes, when ^ = 0, for all
values of r, and when t is infinite is equal to 11^ . It satisfies at all
times the equation (65) and the surface equation

and such a function is evidently unique.

Although in practice the permeability is not fixed, the analysis of
this section enables us to shut in between narrow limits the effects of
eddy currents in many cases, and to assert, when this is the truth, that
in a given instance the effects of such currents will be negligible, if the
pieces of which the core is built are properly varnished.

It is sometimes possible to get interesting information about the
magnetic properties of the core of a transformer which has several coils,
and about the excellence of the insulation of the sheets of which it is
made, by observing the sudden changes in the currents in the coils when
the inductances of the system are impulsively changed, or by studying
the rate of propagation of the induction flux into the core, but these
subjects must be left for the next instalment of this paper.

The Jefferson Physical Laboratory,
Harvard University,

Cambridge, Mass.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 6. — September, 1907.

CONTEIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

THE DEMAGNETIZING FACTORS FOR
CYLINDRICAL IRON RODS.

By C. L. B. Shuddemagen.

THE DEMAGNETIZING FACTORS FOR CYLINDRICAL

IRON RODS.

By C. L. B. Shuddemagen.

Presented by B. O. Peirce, AprU 10, 1907. Received June 25, 1907.

Outline of the Subject,

It has long been known that when an unmagnetized iron bar is
placed in a fixed magnetic field H' and thereby becomes magnetized,
the actual force H within the iron is not so great as the original per-
manent magnetic force at the same point before the iron was introduced.
The vector difference Hi, between the original force and the actual
force resulting after the iron is brought in, is called the " demagnetizing
force" due to the magnetism which has been induced in the iron. An
original uniform field does not in general induce a uniform demagneti-
zing field within a piece of iron ; in fact, it is commonly accepted that
there is only one practical exceptional case : an iron ellipsoid placed
so that a given one of its axes is parallel to the direction of the original
uniform field. In this case the demagnetizing force for a given ellipsoid
with a given axis parallel to the field is simply proportional to the
resulting uniform intensity of magnetization /; and the proportionality-
factor N is found by theory to depend only on the dimensions of the
ellipsoid, that is on the semi-axes a, b, and c. Moreover, when the
ellipsoid is a body of revolution, so that b = c, then we have a simple
formula expressing N as depending solely on the value of the ratio a/b.
This AT" is commonly called the "demagnetizing factor" for the
ellipsoid.

Lord Rayleigh ^ first pointed out how from a knowledge of N a
hysteresis curve obtained for an iron ellipsoid of revolution and plotted
on the B vs. H' plane, could be " sheared back " into the limiting hys-
teresis curve for an ellipsoid of the same cross-section, which would be
approached as the length of the axis which lies parallel to the field
grows longer and longer. The same process is evidently applicable to
a simple magnetization curve obtained by letting the applied field U'

1 Phil. Mag., 22, 175-183 (1886).

186 PROCEEDINGS OF THE AMERICAN ACADEMY.

range from 0 to its maximum value, increasing continuously, and the
iron being initially unmagnetized. The curve obtained by back-
shearing is called the " normal " curve of magnetization for the kind
of iron used. As the applied field H' is now the same as the resulting
field H, the demagnetizing field having disappeared, this normal curve
gives us the true permeability /x and susceptibility k for every H, and
is therefore the characteristic curve of the iron which we must use
in order to get correct values for the physical quantities mentioned.
Ewing and other investigators have made much use of this back-
shearing process in working out hysteresis curves obtained for long
iron wires, it being assumed, while experimental determinations were
still lacking, that cylindrical iron wires could be regarded as behaving
magnetically like ellipsoids of the same length and cross-section, pro-
vided the ratio of length to diameter was not too small.

The first attempt to find numerical values for the demagnetizing
eftect in cylindrical iron rods was made in 1894 by Du Bois^ in dis-
cussing the only magnetization curves with varying length of rods
which had up to that time been published: six by Ewing, obtained
ballistically,^ and a few by Tanakadatd, taken by a magnetometric
method.* From these results Du Bois constructed a table of values
for N for values of ill ranging from 10 to 1000, where in = ratio oi
length L to the diameter D, of the rod. He evidently considered that
N remains practically constant for the whole range of magnetic in-
tensity. Du Bois's values of N for cylinders are from 10 per cent to
20 per cent smaller than for the corresponding ellipsoids, that is ellip-
soids having the same ratio of length to maximum cross-section.

In 1895 C. B. Mann published^ an extended series of results,
obtained magnetometrically, for the demagnetizing factors of iron
cylinders. The leading points brought out by this investigator, for
the rods experimented on, most of which were of small diameter, are:
(1) The .^'s for cylinders are very nearly constant for all intensities
of magnetization below /= 800 ; after this point they increase rapidly
as / increases. (2) For the range in which the iV's are practically
constant, they vary but a very few per cent from the values of the N's,
for the corresponding elHpsoids. Mann does not believe that ballistic
and magnetometric determinations of N will give comparable results.

The most recent work on the demagnetizing factor which I have
seen, is embodied in a short but extremely suggestive paper published

2 Magnetische Kreise, Berlin, 1894, pp. 36-45; Wied. Ann., 46, 485-499 (1892).

3 Phil. Trans., 176, II, 535 (1885). ''^

4 Phil. Mag., 26, 450(1888).

5 Dissert., Berlin, 1895; Phys. Rev., 3, .359-369 (1896).

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 187

in 1901 by Carl Benedicks.^ This investigator, while working on the
subject of pole-distances in cylindrical rods, interested himself in a
few careful experiments on the demagnetizing factors. He gets for a
hard steel rod of diameter 0.8 cm. and a length equal to 25 diameters,
hysteresis curves by means of both the magnetometric and the ballistic
methods. Then by turning it down on the lathe, he transforms the
same specimen of iron into an ellipsoid of revolution of length equal to
30 diameters, and gets a hysteresis curve magnetometrically. This
last curve is, by means of the known ellipsoid iV for m = 30, back-
sheared into the "normal" curve, which, according to Benedicks, can
then be used to determine the N for any point on either the ballistic
or the magnetometric curve for the cylinder. The result is that the
magnetometric N behaves qualitatively exactly like that of Mann, but
the ballistic iV^, after likewise remaining practically constant up to
/ = 800, decreases rapidly as / is further increased.

The present paper is an attempt to contribute to the subject a
discussion of the demagnetizing factor for cylinders as determined
ballistically. It will appear later that the curve on the B vs. ff' plane
(or the /vs. H' plane) which determines the back-shearing from a
magnetization curve of a finite cylinder to the limiting normal curve,
is quite different from the straight line which obtains in the case of
the ellipsoid of revolution. It has, in fact, two opposite curvatures :
one near the origin, and the other soon after the maximum value of
the susceptibility has been passed. The first curvature is not very
marked, and it turns out, as has been found before for the magneto-
metric N, that up to values oi B = 10,000 (or /= 800) the ballistic N
is not far from constant. The upper part of the curve, however, has a
violent turn toward the ^-axis (or /-axis) just as has been observed
by Benedicks for his short steel cylinder. Theoretical reasons can be
given to account in a general qualitative way for these experimental
results.

Hitherto it has been the common custom, for lack of experimental
evidence on the subject, to regard the N for iron cylinders, leaving
out of consideration the variation of this coefficient with the /, as de-
pending only on the ratio m = L/D, and not on the absolute dimen-
sions of the rod. As practically all the previous results have been
obtained from experiments on iron cylinders having a diameter of less
than 1 mm., that is, mere iron wires, the question has naturally not
received any attention. In the present work the writer had at his

6 Bih. Svenska Vet.-Akad. Handlingar, 27, (1), No. 4, 14 pp. (1902) ; Wied. Ann.,
6, 726-761 (1901).

188 PROCEEDINGS OF THE AMERICAN ACADEMY.

disposal two magnetizing solenoids very much longer than any which
have ever been used before, as far as he knows. Thus it was made
possible to obtain complete series of magnetization curves, yielding
tables of values for N, for a large number of iron rods, ranging in
diameter from 0.23$ 1 cm. to 1.905 cms. The results disclose quite a
marked dependence of N on the D, the L/D and / being considered
constant. In fact the general rule may be stated that the value of N
decreases as the diameter of the iron rod increases.

In the work both the "reversal" and the "step-by-step" methods
have been used, and the results obtained may be interesting to some
who have had occasion to observe the peculiar disagreements in the
results given by these two methods. As a rule the iV's calculated
from reversal curves will be smaller than those obtained from the
"step-by-step" method under the same conditions.

Introduction.

When a piece of homogeneous isotropic soft iron of any shape is
placed in a magnetic field, it will always become magnetized, and the
induced magnetism will in general show its existence by changing the
original field outside the iron. The only exceptional cases are those
in which the iron is "endless," that is, it is in the form of an anchor
ring or a rod of infinite length, with the magnetizing solenoid wound
directly over the iron. Whenever an apparent magnetic distribution
of superficial charge o- and volume charge p is induced by polarization
on or in any body of iron, the magnetic field H^ due to it combines
with the magnetizing field H' to give a resultant field H, so that the
actual field which determines the intensity of magnetization / is given
at every point by the vector equation

H=H' + Hr,

and / ■= kH, where k = susceptibility of the iron. Outside the iron

H will usually be less than H' in some portions of space, and in others

it will be greater than ff'. But inside the iron H will in general,

perhaps always, be less than JI'. Thus in the case of a sphere of soft

iron placed in a uniform field ff', we shall have, from the theory given

in most of the text-books on electricity and magnetism,*^ a uniform field

4-
of intensity H=H' — — / ^vithin the sphere at any point A, while the

■f Maxwell, II, §§ 437-438; Webster's Electricity and Magnetism, p. 371;
Peirce's Newtonian Potential Function, p. 205.

SHUDDE.MAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 189

intensity is H' — 3"-^+ ^T^/at the point 5 just outside the sphere on

that line of H' which passes through the centre of the sphere, while at
all points C just outside the sphere and lying in a plane passing through
the centre of the sphere and perpendicular to the //'-line mentioned,

the intensity will be H' — —I. Figure 1, reproduced from Figure

76 on page 373 of Webster's " Theory of Electricity and Magnetism,"
shows the resultant lines of force in this case. For a ring or an
infinite rod of constant cross-section with the magnetizing solenoids
properly arranged, we should get H, = 0, and H = H'.

Figure 1.
A sphere of permeability 3 in a uniform magnetic field.

At any point in an iron body subjected to a magnetizing field H',
the strength of the field Hi can be regarded as a function of /. If in
particular we write the scalar equation

Hi = NI

and remember that in practical cases the Hi is a field opposed to H',
or tending to demagnetize the iron, then we may speak of the factor
xVas the "demagnetizing factor" of the particular body of iron at the
point considered, with reference to the permanent magnetizing field
used, which in all practical cases will be a uniform one. Since Hi is
in general an unknown function of /, therefore N is also some function
of /. As the Hi in the cases to be considered will be directed exactly
oppositely to H' in that part of the iron which we shall be interested

190 PROCEEDINGS OF THE AMERICAN ACADEMY.

in, we shall hereafter use the scalar values for H', Hi, and /, so that
our first equation will become

H = H' -Hi = H' - NI.

The only case of a magnetized body not endless, in which we can
always calculate what the Hi will be,' is where an iron ellipsoid is
placed with one of its axes parallel to a uniform magnetizing field H.
If the equation of the ellipsoid is

1- — -^ — =1

a^ b- c^

then it is shown in text-books on the mathematical theory of electric-
ity and magnetism,^ that if there exists on the ellipsoid a surface dis-
tribution of magnetic matter everywhere equal to

o- = /• cos {x, n)

where / is a constant, and (x, n) is the angle between the positive
direction of the .^--axis and the exterior normal to the ellipsoid, the
volume density p being zero throughout the ellipsoid, then the mag-
netic field due to this distribution is constant at every point within
the ellipsoid and equal to

where Kq = I

^ 0

Hi = 2TrabcIKQ,
ds

(s + a)\s + b)^(s + c)^

This field Hi is directed parallel to the negative direction of the ^--axis,
and tends to demagnetize the iron ; we see furthermore that it is di-
rectly proportional to /. The constant / is simply the intensity of
magnetization, uniform within the ellipsoid. To keep this magnetic dis-
tribution in equilibrium it is sufficient if we apply a uniform magnetic
field parallel to the positive .r-axis, of such a strength H', that when
diminished by the demagnetizing field Hi, there will remain in the
ellipsoid the uniform resultant field H=I/k, where k is the suscepti-
bility corresponding to the magnetization /, for the kind of iron under
consideration. Of course if the o- has initially been chosen greater
than the maximum value of magnetic intensity attainable, it will be

8 Max\Yell, II, §§ 437 and 438 ; Webster, Elec. and Mag., §§ 192, 196 ; Peirce,
Newtonian Potential Function, § 69.

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 191

impossible to realize such a distribution. If we have a possible case,
then

Now the factor 2-!rahc • K^ is constant for a given ellipsoid, and is called
its " demagnetizing factor " N. When the iron is an ellipsoid of revo-
lution {b = c), we can integrate ^o ^^^^ g^t a simple formula for K as
a function of a/b, the ratio of the length of the ellipsoid to its greatest
diameter.^ It is, when written in terms of in,

N= ^^^log(2mVm^^^+ 2ra^ - 1) - ^'^

(m^ — 1)^ \\f — 1

"When 1 is negligible in comparison with m^ the formula assumes the
simple form

-•-I- 47r ,,

K= ^(log2m- 1).

This N does not depend, therefore, on the softness of the iron nor on
the magnetizing field, provided the iron ellipsoid was initially demag-
netized and our magnetizing field has been continuously increased from
zero to its final value.

If the iron is perfectly "soft," or incapable of retaining magnetism
when the magnetizing force H' is withdrawn, then any field H' will
produce a unique magnetization. The uniform H' along the major
axis of the ellipsoid of revolution will therefore produce such a magnet-
ization as we found would be kept in equilibrium by the same H'.
As the iron we deal with in practice is not " soft," but shows hyster-
esis, we find it necessary to define susceptibility as the ratio of I/H
when the iron is slmrly carried from zero magnetization to the value /,
the magnetizing field to increase slowly and continuously up to the
proper value H'. Under these conditions it is reasonable to suppose
that any magnetizing field will give a unique magnetic distribution,
and our results hold true.

Suppose we desire to measure the susceptibility of a specimen of
iron in accordance with our ideal definition, so that it may be free
from ambiguity ; let us consider the suitability for this purpose of the
various experimental methods now in use. The fluxmeter is an instru-
ment recently invented, which attempts to give permanent deflections
which are proportional to the changes of magnetic induction through
a secondary circuit, and these deflections are independent of the time-

9 Maxwell, II, §§ 437-438.

192 PEOCEEDINGS OF THE AMERICAN ACADEMY.

intervals in which these changes complete themselves. The perform-
ance of this instrument is as yet far from satisfactory. If it could be
made perfect, we should have an ideal method for permeability deter-
minations, for we could then increase the magnetizing field as slowly
as we please, reading off the corresponding magnetic inductions for
any desired values of the field. It is probable that the oscillograph
methods are at present much more to be preferred, as they can be
made to record accurately the slow and long-continued changes of
magnetic induction through large masses of iron.

A very good method to use is the " step-by-step " magnetization,
where ballistic throws are produced in a Thomson galvanometer, or in
a D'Arsonval galvanometer when we use proper precautions to secure
the proportionality of throws to the flux changes. These changes in
magnetic induction through a secondary coil wound around the iron
specimen to be tested are most conveniently obtained by sudden de-
creases (or increases) in the resistance of the primary circuit, consisting
usually of a storage battery and the magnetizing solenoid. By this
arrangement it is not difficult to obtain cyclic hysteresis curves. It
has been shown ^^ that the maximal induction B (ox I) which is
reached varies with the number of steps taken, the difference being
most marked in the region of greatest permeability. As the num-
ber of steps is increased continually in different experiments, the B
vs. H curves move nearer the ^'-axis, but soon approach the limiting
curve for a slow continuous change of H', which, as we saw before,
is the one curve that, after the proper back-shearing, will give values
for the permeability (and susceptibility) conformable to the ideal
definition. Lastly in order of accordance with the ideal definition of
susceptibility comes the " reversal " method of measuring ballistic in-
duction throws, which is entirely contrary to a slow magnetization,
but which is often the most convenient of all the methods to use, and
which gives the most self-consistent determinations ; that is, repeated
magnetizations will give almost identical results. Both the " step-by-
step " and the " reversal " methods of measuring magnetic induction
may give results depending on the particular experimental conditions
employed, unless one takes proper precautions. Thus the time-constant
L/R of the primary circuit should be only one or two per cent of the
time it takes the galvanometer-needle to reach its greatest deflection,
which time will be the quarter-period of the needle suspension system.
It should be noted that when there is a great bulk of iron in the mag-

10 F. Rucker, Diss. Halle, 1905, 106 pp. 20 plates ; Elektr. ZS. 26, 904-905, 979
(1905).

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 193

netizing solenoid, the L may be enormously large. There are two ways
of realizing the condition of the smallness of the time-constant as com-
pared with the quarter-period: (1) We may use a storage battery of
high E.M.F. in the primary circuit, which will necessitate large /I's in
the circuit in order to give magnetizing fields of the desired intensity ;
(2) It is quite possible to increase the moment of inertia of the needle-
suspension so as to give a complete period of several minutes. Several
of the experimental series obtained in this investigation by means of
the reversal and step methods illustrate very forcibly how these two
different methods may lead to various determinations of the suscepti-
bility. Finally, the magnetometric methods are often very useful,
especially in accurate determinations of magnetic moment of short iron
magnets. With none of these magnetometric methods can we measure
the / at any particular part of the iron bar, but get instead a mean
value of /(moment/volume of bar) for the whole rod. Plotting /vs.
H' curves for various lengths of soft iron cylinders, we can find mean
demagnetizing factors N, by means of which a "normal " curve can be
constructed. But it will be seen, after a little reflection, that the curve
Mean / vs. Mean H which we get here is not necessarily the same, or
even approximately the same, as the " normal " curve of / vs. H, which
gives corresponding values of / and H in the middle of the bar imme-
diately surrounded by the secondary coil, and which may be regarded
as an extremely close approximation to the / and i/ at a single point
in the iron. It is this fact which accounts for the wide difference which
has been found between the lA^as determined ballistically and the A" as
determined magnetometrically. It is hardly likely that the process of
back-shearing a magnetometric magnetization curve will yield a curve
from which anything like the true susceptibilty can be found.

Returning now to our iron ellipsoids of revolution, we see that if we
know the ratio of the length to the diameter of one of them, we can
calculate exactly what the demagnetizing factor N will be. Ewing and
Du Bois, in their texts on magnetism, give tables of values of N (see
page 204) for various ratios a/b. It foUows from a paper by Lord
Rayleigh,!^ that if we magnetize any iron ellipsoid of revolution
having a known ratio a/h, from zero magnetism to full saturation,
measuring the / ballistically by means of a small secondary coil around
the middle part of the rod, and plot out the curve / vs. H', we can
" back-shear " this curve parallel to the i/'-axis by the amount
Hi = ^H — NI, and thus construct the "normal magnetization"
curve, for which H = H', and from which alone the true susceptibility
can be found for every /.

11 Phil. Mag., 22, 175-183 (1886).

VOL. XLIII. — 13

194 PROCEEDINGS OF THE AMERICAN ACADEMY.

Suppose now that we have any elongated piece of iron with a secon-
dary coil wound around it near the middle and connecting with the
terminals of a ballistic galvanometer. Suppose also that the normal
magnetization curve for the kind of iron used were known, say, by
taking measurements ballistically on an anchor-ring made of the same
material. (As a matter of fact this method does not apply, for by
welding the ends of a rod together to form a ring, we change the mag-
netic behavior of the iron unavoidably, to say nothing of diiferences
which exist in two dift'erent specimens of iron made from the same
kind of iron.) If we now find experimentally the actual magnetization
curve, and plot it together with the normal curve on the /vs. H' plane,
and plot on a similar plane, which we shall call the /vs. (H'—H) or the
/ vs. Hi plane, the differences of the abscissae (which are A/T— Hi = Nl)
of the two curves for each /, against this same /, we shall call this last
curve the " iV-curve " for the particular piece of iron and the particular
position of the secondary coil, it being understood that we have placed
the iron in a definite position in a given magnetic field, or distribution
of lines. The / of the actual magnetization curve is the average / ex-
isting in the volume of iron immediately surrounded by the windings of
the coil. In general we do not know what the form of the iV^-curve may
turn out to be, until we obtain it experimentally ; in the ellipsoid of
revolution placed with its major axis parallel to the uniform field, this
i\"-curve will, according to theory, obviously be a straight line through
the origin and making with the /-axis the angle whose tangent is equal
to iV^' (ratio oi H scale unit to /scale unit).

Now since ellipsoids of revolution are not very easily constructed,
the case most important for magnetic measurements in laboratory
practice is that of the cylindrical iron rod with ends squared off, and
the secondary coil wound around just in the middle part of the rod, a
uniform magnetizing field, such as can be secured inside a long solenoid,
being used to produce the H'. Here we do not obtain a uniform /by
placing the rod in a uniform field, and although the problem is de-
terminate nathematically, no one has as yet succeeded in obtaining
the solution. The great difficulty lies in the fact that the susceptibiHty
is not constant throughout the rod for any given H. The lines of
magnetization run parallel only through the middle cross-section of
the rod, where the secondary coil is wound. If, then, we wish to know
the iV-curves for some kind of iron in the form of cylindrical rods, our
only resource is to find experimentally a series of / vs. H' curves for
greater and greater values of in = L/D, where / = length, and D =
diameter of the rod. Then we must find, by some extrapolation
method, or otherwise, the limiting curve as m becomes larger and

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 195

larger. We may then plot out the abscissa-differences between this
normal curve and all the others, and thus actually construct the N-
curves.

The only experimental magnetization curves for a number of varying
m's which had been published before 1895 are those obtained by

15000

•

—

' — '

,/<

r«

4°

lOf

il:

f—

500

0 /

i —

LO
IGC

R£

]

Ewing's magnetization curves for a soft iron wire of diameter 0.158 cm.

Ewnng 12 for m =: 50, 75, 100, 150, 200, and 300 (see Figure 2), and
some by Tanakadat^ for rather small values of m, his highest being
about m = 39. Ewing's iron cylinder was a wire of diameter = 0.158
cm. and original length = 47.5 cms., the other m's being obtained by
cutting off pieces from each end. The maximum permeability for this
iron was found to be /x = 3500. Tanakadate's iron wires were of

12 Phil. Trans., 176, II, 535 (1885).

196 PROCEEDINGS OF THE AMERICAN ACADEMY.

diameter = 0.153 cm., the length varying from 2 to 6 cms., also of
diameter == 0.115 cm. and a length originally 33.4 cms. For the shorter
specimens he used Gauss's A position, that is, the rod is placed east
and west and the magnetometer is placed in the prolongation of the
rod's axis; for the longer wires Ewing's method was used, in which
the solenoid and wire are placed vertically, with an extra solenoid to
compensate for the earth's field, and the magnetometer being placed east
or west of one end of the wire.

Du Bois subjected these data to a very extensive discussion. He
developed the proposition that, provided the length of the rod is
sufficiently great compared with its diameter, then i\^m^ = constant.
This constant he finds fi:om Ewing's curves to be equal to 45, provided
m k 100. The reason why this formula cannot possibly hold for
short rods is that the theory of Du Bois assumes that the average
magnetization intensity / in the whole rod differs but very little from
the / within the secondary coil in the middle of the rod ; in other
words, that the magnetization is practically uniform. Of course this
is never realized for finite rods and ordinary fields ff', but it seems at
first sight as if the magnetization in a rod of large m should be fairly
uniform. If we follow Du Bois's method, which gave him the necessary
data to construct his table of values for N in case of cyHnders, we may
measure abscissa-differences, which are proportional to N, for the
curves for rods of large in's, and form three or four simultaneous
equations, each of which Hnearly contains cc, the abscissa-difference of
the normal curve and the / vs. H' curve for the largest m used in the
equations. Any two of these equations give x, and we can thus con-
struct the normal curve, which gives us immediately all the A"-curves
by plotting abscissa-differences as before. Du Bois, from the meagre
data at his command, found values for AT for various m's and has col-
lected the results in tabular form (see table, page 204) in his book " Die
Magnetischen Kreise in Theorie und Praxis " ("The Magnetic Circuit
in Theory and Practice," translated by Atkinson). He apparently con-
siders the A^-curves to straight lines, as far as practical purposes are
concerned, that is A^ is not a function of H (or i) ; at any rate he
does not mention giny such variation of A"^. And as to the question
whether or not the A^ for a given m and 1 varies with the diameter
of the rod, no data were at hand.

Now there is no reason to believe the AT-curves for cylindrical rods
of the same diameter to be straight lines ; and since we know that the
building up of magnetization, and perhaps even the final result, is very
decidedly modified by the bulk of iron magnetized, it is quite likely
that thick massive rods of iron really give different values for AT from

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 197

those calculated by Du Bois for the " iron wires " used by Ewing and
Tanakadatd. And, lastly, it is quite possible that the N may vary with
the degree of softness and other physical characteristics of the iron
magnetized. The present investigation was therefore undertaken to
test as accurately as possible the true nature of the iV-curves, whether
they are really straight lines or not, and their possible variation with
the diameter of the rod. Moreover, a table of values of N determined
carefully by the ballistic method for thicker rods than has been done
so far, would be quite useful in the practice of electrical engineering
as, for instance, in the designing of dynamo machinery.

Before discussing the experimental results let us consider theoreti-
cally the iV-curves for a given kind of iron and a given diameter, the
length alone being varied. We shall attempt to show that this back-
shearing curve has two opposite curvatures. Let us suppose that we
know the normal magnetization curve of our iron. We want to learn
something about the nature of the iV'-curve for a cylindrical rod of
homogeneous isotropic iron whose length is finite but otherwise arbi-
trary. All the facts which we need are these : (1) The / has a maxi-
mum value I^, which is reached asymptotically by increasing the
magnetizing force H^ indefinitely. (2) In any finite cylindrical iron
rod, no matter how short, the lines of magnetization can apparently be
made straight, or / made uniform, by applying an infinite H\ And
whenever I/H, the susceptibility, has rather small values, then the con-
dition of uniform / is with some approximation realized. (3) Although
the normal curve and all other Ivs.H' curves for rods of finite length
do not run into the origin tangential to the ZT'-axis, they do make a
very small angle with it. In other words, the susceptibility approaches
a small value k = 15, or thereabouts, as the H' decreases indefinitely. ^^
(4) The normal curve has one, and only one, point of inflection.

With regard to the second part of (2) it might be noted that the non-
uniformity of / in an iron cylinder placed parallel to the lines in a uni-
form magnetic field is measured in a rough way by the largeness of
the ratio Hi/H, the demagnetizing force divided by the resulting force,
at the point considered. Now Hi = NI — NkH, so that this ratio is
merely Nk. Therefore, if we suppose for the moment that N for a
given finite rod is nearly constant for a considerable range of /, it follows
■:hat the magnetization will be the nearer to uniformity the smaller
the susceptibility is.

Let us then consider the iV-curve for a rod for which m = nii, say.

" C. Baur, Wied. Aun., 11, 399 (1880). Lord Rayleigh, Phil. Mag., (5), 23,
225-245 (1857).

198

PROCEEDINGS OF THE AMERICAN ACADEMY.

In Figure 3 let P and Q be two points on the / vs. H' curve for ttti,
where Q, has the ordinate of the point of inflection Qq, and P is any-
other point of the magnetization curve. Now suppose the rod were
magnetized by an infinite H' to the maximum I^, so that all the
Tra^/oo li^ss ^^6 straight and enter and leave the rod at the squared-ofi"
ends {a being the radius of the rod). In this case the distribution of
magnetism which we may consider the cause of the demagnetizing force
Hi, or AZT, is wholly superficial, and as far away from the secondary
coil, where / is measured, as possible, and it has a perfectly definite
value AZToo , say, which we lay off on the / vs. {H'—H) plane, getting
the point K, and we draw the line OK. We see now that if, as we in-

FlGURE 3.

Diagram illustrating magnetization and back-shearing curves.

crease / from zero to I^ by continually increasing H', the lines of mag-
netization were always straight, then the demagnetizing force would
always be proportional to /, no matter what the susceptibility might be,
and the i\r-curve would be the straight line OK. Another case where
the iV-curve would be a straight line OKx would be realized if the sus-
ceptibility were a constant for all values of / from 0 to I^. In this
case no volume density would appear by magnetization, and any two
fields Hi and H^, giving separately the surface densities of magnetism
o-i and 0-2, could be superposed, so that a magnetizing field Hi + H^'
would give the superficial distribution o-i + o-j. This last supposition
would result in there being no limit to the intensity of magnetization.
As a matter of fact the / is uniform only for an infinite H'. At the
point P, HP is not the origin, more or less lines of induction will leave

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 199

the iron rod along the curved surface, as is well known. Now from the
mathematical theory we know that in the case of " soft " iron B, or ^x.H,
is a solenoidal vector, continuous throughout all space, whether iron
or air, not containing any fixed magnetic charges. Wherever lines of
induction leave the surface of the iron we must therefore have positive o- ;
for the vectors H and /, although not solenoidal in the iron, have always
the same distribution as the vector B, I is zero outside the iron, and
(T ^= I- COS (ji, I). This means that a part of the surface distribution
o- of the magnetism is closer to the middle of the rod than it would be
if / were uniform. There is also some magnetic matter in the form of
volume distribution p. This, however, does not materially influence the
argument, although it complicates matters somewhat. We shall come
back to the volume charge later. Therefore, as far as the surface mag-
netism is concerned, the demagnetizing force ^Hp is for every point P
actually greater than it would be if / were uniform. We thus reach
the result that the iV-curve has the end-points 0 and K, but lies every-
where else to the right of the straight line OK. Indeed for the most
part the iNT-curve will be very decidedly to the right, for a very large
number of the lines of induction will leave the iron rod before reaching
the ends of the rod. The demagnetizing factor N^ is the minimum
value of N, although ^H^ is by no means vanishingly small. Near the
origin the ratio of H to I is comparatively large, although of course
still a fraction, so that according to (2) the / is more nearly uniform
than for higher points on the curve, so long as we do not pass the
point of maximum susceptibility, which is the point of tangency of a
line drawn from the origin to the normal magnetization curve ; therefore
the xY-curve is more nearly tangent to the line OK&t the origin than for
points a little more removed. As we increase H^ from 0 to some point
Q whose /is of the order of /at Qq, the lines of magnetization increase
continually, but a larger and larger fraction of lines leave the rod be-
fore reaching the ends, and JV increases continually. Again, as we
follow the magnetization curve from any very large but finite value of
H' down toward Q, the /-lines spread out in greater and greater pro-
portion, and the AT increases for quite a long interval. This shows
that the curvature of the A''-curve changes sign at some point Q^, which
is a point of inflection for the A'-curve, and probably the only one-
We should expect, therefore, that the curve drawn in the second part of
Figure 3 on the / vs. NI plane represents roughly the qualitative be-
havior of an A"-curve for a finite rod.

It remains to be shown that the volume distribution does not invali-
date the argument just given. From the theory of magnetism we know
that this can be expressed in the form

200 PEOCEEDINGS OF THE AMERICAN ACADEMY.

hjl y ■ COS {JIkJi r)
P = .

where ^ = the permeability, k,c and hy the gradients of the suscepti-
bility and resultant magnetic potential function, respectively, and
{Hk, hy) is the angle made by the directions in which k and F increase
most rapidly. For we have by Poisson's Equation,

V-r=-47rp,
and from the fundamental equation of magnetic polarization,

p = _ Divergence / = - [|; (x-V) + |^ (<< F) + ^ (kZ)~^ •

VdK_ dV dK dV 8k ar"|

I dx dx dy dy dz dz J

K'VW + ^.

Eliminating the v^P^'we get the equation above. Now A^, hy, and jx
are all intrinsically positive. The Jik becomes zero under special con-
ditions, and is vanishingly small when the iron becomes fully satur-
ated. Therefore the sine of o- is governed by the cos (/?«, h^ alone.
Considering only the half of the iron cylinder on which the positive o-
appears, we see that V always increases from the end of the rod
toward the centre, while p does so as long as the magnetization at the
centre of the rod has not been pushed beyond the maximum suscepti-
bility point. Under these conditions (/?«, hy) is an acute angle, and
therefore p is positive. Therefore the argument regarding the curva-
ture of the iV-curve in the neighborhood of the origin is even strength-
ened all the more on account of the positive p intensifying the
demagnetizing force. Thus the lower curvature is proved (although
not quite rigorously, mathematically speaking), and since the i\-curve
must end in the point K, there must be a curvature in the upper part
of the ^-curve directed oppositely to the first one.

An interesting fact perhaps worth noticing in regard to the volume
distribution p of the magnetism is that as soon as the point of maxi-
mum susceptibility has been passed over, which will first occur at the
centre of the rod, there will appear some negative p near the centre of
the rod in that half of the rod which always carries the positive sur-

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 201

face distribution. This is due to the fact that Qik, Ar) now has become
an angle of 180° at points in the axis of the rod and near the centre
of the rod, while further away from the centre but still along the axis,
where the k has not yet reached its maximum, the angle (/?«, h^ is still
zero. Somewhere between the two regions will be a curved surface
for all points, of which k has its maximum susceptibility, and Ju is
zero, and the angle (/?«, h^ is discontinuous by tt, so that p is every-
where zero on the curved surface, which separates the regions of posi-
tive and negative p. As the iron is subjected to higher and higher
fields H', this curved surface moves further and further away from the
centre, until finally there is only negative p left in that half of the iron
rod which has the positive surface magnetism. This occurs j ust as soon
as every point in the iron has been magnetized past the point of maxi-
mum K. The presence of this negative p may perhaps account very
largely for the fact that N is not far from constant for quite a long
range of /. When saturation of the iron ^vith magnetism is approached
more and more, the k becomes nearly constant throughout the rod and
continuously approaches zero, so that /^k, and therefore the negative p,
are both becoming vanishingly small. C. G. Lamb i* gives a set of
curves, reproduced in Figure 4, showing the variation of ^ along an
iron rod from centre to end for various applied fields, which illus-
trate the matter with perfect clearness. Of course the ^, when found,
as Lamb did, by ballistic methods, with a search coil placed at varying
distances from the centre, is the mean value of ^ for the iron sur-
rounded by the search coil, but it shows the variations along the rod
very well indeed.

All the A"-curves found in the experimental series of the present
paper do not deviate to a very great extent from straight lines for
values of B less than 10,000 or thereabouts. They show quite defin-
itely the two curvatures which we were led to expect by theoretical
considerations. Above this point, however, the iV-curves have an
ever-increasing tendency to turn to the left, and at last actually do
move from right to left, so that finally we have not only the i/^/I (= iY)
merely decreasing, but even the Hi decreasing. At first this was very
puzzling, for it would seem natural to suppose that, although K must
really decrease when the iron bar shows saturation, just as we were
expecting from the theory, as long as more and more lines of magnetic
induction are thrown into the rod when as yet unsaturated with mag-
netism, there is more and more magnetism induced, which ought to
increase the demagnetizing field //,■ continuously.

" Phil. Mag., (5), 48, 262-271 (1899).

202

PROCEEDINGS OF THE AMERICAN ACADEMY.

This, however, is not at all the case, and the actual facts emphasize
the fallacy of considering the magnetization in long iron rods, when
not completely saturated, as even approximately uniform. As will ap-
pear from the results obtained in this investigation, the values of N
are not far from being constant below B = 10,000, and they are of the
order of magnitude as those found by Du Bois from Ewing's curves,
although always somewhat smaller. But let us now find what these
iV^-values would be if our various rods were really uniformly magne-
tized. In other words, let us find the position of K of the straight line

3000

2000

1500 vn

»^ 1000

500 £
IK

Centre 22 20 18 16 U 12 10 8 6 4

Figure 4.

Lamb's curves showing the change in permeability along an iron rod. The
distances along bar are given in inches.

OK in Figure 3. Our rod has the length L and diameter D, so that
uniform magnetization would mean tt {Bl'ifl units of free positive
magnetism on one end of the rod and the same number of negative
units on the other end. If L is large compared to Z>, we may regard
the demagnetizing field-intensity Hi (or NP) at the centre of the rod

as caused by a single point-pole of strength 27rf — j/ata distance
of X/2 units of length from it. Then

SHUDDEMAGEN. — DEMAGNETIZING FACTOES FOE lEON EODS. 203

Ul^

Therefore, for uniform magnetization,

Nm" := 2 TT = 6 • 28+ .

This value for iVm^ it will be noticed, is considerably less than the
constant 45 as found by Du Bois from experimental data, and which
constant led him to construct a table of values for N which, as we
shall see later, is probably quite accurate for the iron wires of small
diameter used by Ewing and Tanakadatd. Yet the conditions which
Du Bois assumed in order that his theory might be applicable are pre-
cisely those which we have here assumed. For the shorter rods Km^
would be smaller yet, for the two reasons that the magnetism o- (or 2)
on the squared-ofF ends of the cylinder must now be considered further
off than the distance Z/2, and much of it acts at a small angle ; of
course the resultant Hi, which is now really given by a double integral,
is directed along the axis of the rod. It is now clear that Figure 3
does not begin to show the tremendous sweep to the left, of the upper
portion of the iV-curve, which has been found by Benedicks ^^ for
his rod of steel where m was 25, and which really occurs in every one
of the xV-curves obtained ballistically.

Let us now compare the values of lY for various ellipsoids of revolu-
tion, and those obtained by Du Bois for cylindrical rods, with the
limiting values of N for uniform magnetization. The values for the
shorter rods are calculated from the same formula as the longer ones.

The explanation of the great difference between the actual demagne-
tizing force under non-saturating fields and the demagnetizing force in
case of uniform / is of course found in the fact that in the former case
quite a large part of the lines of force leave the curved surface of the
iron rod very near the middle of the rod, so that the contributions
A-3//r" to the demagnetizing force count up very heavily in com-
parison with the magnetism nearer the end of the rod. An ideal
uniformly magnetized rod of the same diameter, and having the same
number of lines through its middle section as one which is actually
magnetized in practice to less than saturation, must be only about
VWiS, or 0.374 times as long, if it is to produce as much demagne-

15 Bih. Svenska Vet.-Akad. Handlingar., 27, 1, No. 4, 14 pp. (1902); Wied.
Ann., 6, 726-751 (1901).

204

PEOCEEDINGS OF THE AMERICAN ACADEMY.

TABLE I.

Demagxetizixg Factors. (X.)

m = l:d

or ajb.

Ellipsoid.

Cylindrical Rods.

Du Bois.

Uniform I.

0.2549

0.2160

0.063

0.1350

0.1206

0.028

0.0848

0.0775

0.016

0.0579

0.0533

0.010

0.0432

0.0393

0.0070

0.0266

0.0238

0.0039

0.0181

0.0162

0.0025

0.0132

0.0118

0.0018

0.0101

0.0089

0.0013

0.0080

0.0069

0.00098

0.0065

0.0055

0.00078

100

0.0054

0.0045

0.00063

150

0.0026

0.0020

0.00028

200

0.0016

0.0011

0.000157

300

0.00075

0.00050

0.000070

400

0.00045

0.00028

0.C00039

tizing force at the middle point of the rod as the other suffers. This
induced magnetism (both o- and p) near the centre of a rod of iron
magnetized to a value of B somewhat below 10,000, can be readily
recognized by its effect on a small compass needle, which will be de-
flected the moment it is moved a few centimeters from the middle
part of the rod toward either end.

It might be of interest to note that the highest possible demagne-
tizing force would be obtained by placing a very large slab of iron, with
plane parallel faces, perpendicular to the lines of an infinite magnetizing
field H' ; the value of Hi would be 4kTrI^ , when the slab is infinite in
extent, but has any finite thickness. This Hi would, moreover, have

SHUDDEMAGEN. — DEMAGNETIZING FACTOKS FOR IRON RODS. 205

the same value at any point whatever in the iron slab. The value of
X, the demagnetizing factor, is 47r throughout the slab. As in soft
iron a negative force of H' less than 10 c.g.s. units of field intensity is
sufficient to demagnetize the remanent magnetization which exists in
the iron after the original magnetizing field is withdrawn, and the
value of 4-/^ is about 200,000 of c.g.s. units, it is easily seen that on
removing the infinite field the demagnetizing field ZT, would instantly
demagnetize the slab completely.

A diagram of the apparatus and its arrangement, as used prac-
tically throughout the present investigation, is shown in Figure 5.

Figure 5.

Diagram of apparatus used in the Jefferson Physical Laboratory in obtaining
magnetization curves for the present investigation.

Experimental Methods and Apparatus.

(t is a Thomson four-coil ballistic galvanometer with astaticised mag-
netic suspension, controlled by a permanent magnet S-N, and not
shielded at all magnetically, for it was found that when shielded with
three large cylindrical iron shells and heavy iron plate tops and
bottom, certain unknown magnetic disturbances were caused in these
shields, and effectually prevented the needle, which was then non-
astatic, from coming to rest. E is the storage battery of from 5 to 20
cells, giving about 2 volts each, for furnishing the current in the
primary coil. S is a large solenoid of the following dimensions:

206 PROCEEDINGS OF THE AMERICAN ACADEMY.

Length = 207.7 cms.
Outside diameter = 5.97 cms.
Inside diameter = 3.63 cms.

This solenoid was wound on a tube of pasteboard with two wire coils
of 3386 turns each, — of No. 18 wire, in six layers, — which were used
in parallel, so that

H' = A-)iC/10 = 20.5 • (No. of amperes used).

Later on in the work a still longer solenoid was built, in order to ex-
periment on very thick iron rods. A is a " P-3 " amperemeter, that
is, one of the type so successfully used in the laboratory of the course
Physics 3 in Harvard University ; it reads with great accuracy up to
1.5 amperes. K is a double reversing knife switch, connected to the
solenoid S, and also tO a demagnetizing solenoid D, with an iron core
in the small coil, which could be connected to the light circuit L. R
is a rheostat in series with a system of variable resistance coils, to
regulate the current. P is a reversing key to change direction of
ballistic throw in the galvanometer, 7^ is a tapping key arrangement
with small ^battery, for bringing the galvanometer magnet needle to
rest. Its circuit contains a very high resistance W. Z is the galva-
nometer scale with telescope, at 116 cms. distance from magnet
system. II' is a resistance box in the secondary circuit ; by varying
this resistance the throws were kept under control, so as to give good
accuracy in the readings.

The " P-3 " galvanometer was frequently compared with a Weston
milliamperemeter with shunt, and the sensitiveness of the galvano-
meter was often determined during the course of the work by charging
a condenser of one microfarad capacity from a battery of four Samson
(wet) cells whose voltage was read off on a voltmeter. The sensitive-
ness, given in centimeter divisions of throw per coulomb, ranged from
1.24 to 1.60. In the latter part of the work the condenser was
charged by connecting across a standard resistance of 10 ohms, say,
through which about 1 ampere was flowing, thus getting about 10
volts.

In the earlier half of the experiments the "reversal" method was
used with great convenience and accuracy in the readings. The
magnet suspension does not hold. its zero very closely, but is slowly
tossed about by magnetic disturbances over a range of 1 mm. scale
reading, and sometimes more. ]\Ioreover, the zero position, which is
quite definite at any one time, often changes slowly during the course

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 207

of the day. With the reversal method no attempt to read the zero
was made, but instead a number of throws were taken alternately in
the plus and minus directions, and then averaged. These throws often
agreed regularly to about 1 part in 1000, when taken with a little
care. The reversal method, however, has a possible error due to the
time-constant of the primary circuit being comparatively large when
there is much iron in the solenoid S, and also to the slow establish-
ment of the magnetism in a thick iron rod. This was counterbalanced
by making the complete period of the astatic system about 25 seconds,
and finally 31 seconds.

The step-by-step method was used only in one series of experiments
with the first solenoid >S'. This method is much harder to carry
through successfully, especially since the battery £J must maintain its
voltage without appreciable drop while furnishing an increasing cur-
rent for about half an hour, and the zero reading must be taken care-
fully every little while. Usually several curves were obtained for each
length of the iron rod used, so that a good average curve could be
constructed. As is well known, the two methods do not give the same
magnetization curve, the one by the step method usually, but not
always, lying below the reversal method curve.

The iron rods tested in the first solenoid were all of soft Bessemer
steel, six feet long and of diameters ranging from 0.2381 cm. (= ^^
inch) to 1.270 cms. (= ^ inch). The secondary coils consisted of
from 30 to 400 turns of fine insulated wire wound directly over the
middle of the rod. It was found necessary to reverse the magnetism
about six times before reading the actual throws, otherwise the read-
ings come out too low. After sufficient data had been collected to
construct a curve, equal lengths of the rod were cut off from each end,
so as to reduce nt from one value to the next. The ends of the rod
were then filed smooth and plane. Then a curve was obtained for the
shortened length of the rod.

After proper reduction of the observations, the magnetization curves
B vs. H' were carefully constructed for all the m's used, on a large
sheet of millimeter paper of the dimensions 43 X 53 cms.

The next problem was to devise some means of getting at the normal
curve (m = cc ). In the earlier part of the investigation frequent use
was made of the principle which leads to Du Bois's experimental formula
iVm^ = 45^ when m ^ 100. It was found that so long as B did
not exceed the value 8000, the formula was fairly well satisfied for
m ^ 150, provided only one system of simultaneous equations was
used. That is, supposing we had plotted out the actual magnetization
curves for m = 300, 250, 200, and 150. If we take all these into

208

PROCEEDINGS OF THE AMERICAN ACADEMY.

account, reckoning therefore the distance in any units of length, say
millimeters, from the normal curve to the one for m = 300 as our un-
known X, we shall find the whole set of equations giving a good average
value for x, and thus we may construct what might be called " the
normal curve based on in = 300." Now if we use only the curves for
250 to 150, so that our next x is the unknown distance from normal

160

■ — p

^
^

/»

IOC

/ *■

;

/
/

*?'

o /

500

. I

/•

'//

^^^

—

, — ■

0 6 10 15 80

Figure 6. [Table II.]

Reversal magnetization curves for a Bessemer soft steel rod of diameter
0.6350 cm.

curve to the curve of 250, we shall again find values for x which satisfy
all the equations moderately well. But the normal curve thus deter-
mined, which is the normal curve based on ui = 250, will lie slightly
to the right of the first one constructed, — at least every case tried gave
this result. Similarly, the normal curve based on ill = 200 will lie to
the right of the one based on in = 250, and so for the one based on
175. For higher values of B than 8000 the formula fails to hold at

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 209

all. It should be noticed that as the iron rods become nearly saturated
with magnetism, the magnetization curves bend around and become
more and more parallel to the i/'-axis, so that a very slight displace-
ment of the curves up or down may result in proportionately large
errors in the construction of the ^-curves. The only thing to do is

10 i&

Figure 7. [Table III.]

Reversal magnetization curves for a Bessemer soft steel rod of diameter
1.270 cms.

to construct by " trial and error " methods a normal curve which will
give the best possible results for the whole body of iN'^-curves.

To be absolutely consistent the ^V-curves should be constructed from
magnetization curves on the / vs. H' plane, for N is defined by
H = H'— NI. Substituting in this the value for / from the funda-
mental equation B = H -\- 47r/, we get

VOL. XLIII.

•14

210

PROCEEDINGS OF THE AMERICAN ACADEMY.

But as even for the high value ff = 30, B is somewhere near 15,000,
we see that the error introduced by neglecting the H in the brackets is
but 1 part in 500, which is much less than the experimental errors.
Therefore, since the ballistic throw is proportional to B, it is very

O 0 10 16

Figure 8. [Table IV.]

Reversal magnetization curvfes for a Bessemer soft steel rod of diameter
b.4763 cm.

much more convenient to construct the iNT-curves from the formula

H=H'-KB/i7r.

Experimental Results for Demagnetizing Factors.

Let us now tabulate the actual values obtained for the end correc-
tions, or demagnetizing factbrs iV, of a number of rods of Bessemer
steel (copper coated), which is a very homogeneous soft iron. Later on
we shall see just how these values were determined, and give the

shuddemage:^. — dexMagnetizing factors for iron rods. 211

necessary data from which the most important table was constructed.
It might be noted here that the results for the extremes of magnetiza-
tion B = 1000, and B— 12,000 are somewhat less reliable, for reasons
which will appear. The numbers 10 to 150 are the values of m used,

TABLE II. [Figure 6.]

October 2, 1906.

Diam. — 0.63-50 cm. = 1/4 in.

Reversals.

Values of ^V X 10*.

111 = 10

100

125

150

1000

1990

1010

D 311

199

132

, .

. .

, .

, ,

2000

1028

4 328

199

137

104

. •

• .

3000

3 329

204

137

101

4000

333

205

138

101

5000

333

206

140

102

6000

332

206

139

101

7000

330

205

139

101

8000

205

139

101

9000

204

139

100

10000

202

137

11000

134

12000

132

13000

14000

15000

•

■ •

• ■

• •

■n 1

1 1

(•

\-^ -. , 1

i. T-j.-

• _ J

Below each value of in is given the series of values of N ■ 10* obtained,
one for each interval of 1000 c. g. s. units of B, or gausses. Of course
in all these experiments the column under the highest number m gives
values for the first curve obtained, for in is always decreased by each
sawing off of the ends of the iron rod.

See Figure 6 for the magnetization curves of October 2, 1906.

212

PROCEEDINGS OF THE AMERICAN ACADEMY.

The normal curve as determined is indicated in all these figures by
the dots spaced every 1000 units of B.

Figure 7 exhibits the curves taken on October 4, 1906, and shown
in Table III. It will be seen that these curves are very much flatter
than those of the \ in. rod and the tV ii^- I'od which follows this one.

100

400

Figure 9. [Table IV.]

Curves showing variation of magnetic induction with different lengths of a
Bessemer soft steel rod of diameter 0.4763 cm. The numbers affixed to the
curves give the constant currents in amperes through the solenoid.

Figure 8 shows the original curves of October 9, 1906, and presented
in Table IV.

From the data of these curves Figure 9 was also drawn. This shows
the curves of constant cun-ent as the rod is increased in length. The
numbers afhxed to the curves give the current in amperes, so that the

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 213

applied field H' in the solenoid can be found by multiplying by
the factor 20.5. It is seen that at first the induction increases very
rapidly and nearly linearly. Then after a sharp bend the curve ap-
proaches a maximum induction asymptotically. It is interesting to
see how for higher currents this maximum is reached very much sooner

TABLE III. [Figure 7.]

October 4, 1906.

Diam. = 1.270 cms. = 1/2 in.

Reversals.

lues of

X >: 10*.

m =10

100

120

144

1000

1820

590

300

190

126

. .

2000

614

317

198

135

3000

635

325

203

137

4000

331

204

139

100

5000

331

204

139

100

6000

331

204

139

100

7000

205

139

100

8000

205

139

100

9000

203

139

100

10000

137

11000

132

12000

123

13000

• .

• •

14000

• •

15000

• ■

• •

than for lower currents. As regards curvatures, the sharp bend, and
approach to a maximum value, these curves bear a close resemblance
to the magnetization curves, when plotted on the / vs. H' plane.

See Figure 10 for the magnetization curves accompanying Table V,
October 20, 1906. These are also quite steep.

214

PROCEEDINGS OF THE AMERICAN ACADEMY.

No figure is given for the results obtained on Novendber 6, 1906, and
collected in Table VI. The curves are very steep.

See Figure 11 for the magnetization curves corresponding to Tables
VII and VIII, of November 16, 1906. The curves passing through the
crosses are the ones obtained by using the method of steps, while the

TABLE IV. [Figure 8.]

October 9, 1906.

Diam. = 0.4763 cm, = 3/16 in.

Reversals.

Values of iV X 10*.

m = 10

100

125

150

175

200

1000

2001

1023

638

434

319

196

133

2000

1049

659

449

329

199

132

• .

. .

3000

665

458

331

205

185

101

4000

461

336

209

140

104

5000

461

335

206

140

104

6000

336

205

140

103

7000

204

139

103

8000

204

138

102

9000

204

137

100

10000

201

135

11000

1.32

12000

130

13000

• •

122

14000

. .

15000

• •

• ■

• •

ones through the dots were found by means of the reversal method.
The vertical arrow-points indicate the probable position of the normal
curve by steps, and the oblique arrows give the reversal one. Several
series of step curves were taken for each ni so that a good average
curve could be constructed. It will be noticed that the step curves
all lie below the others, except the one for in = 400.

SHUDDEMAGEX. — DEMAGNETIZING FACTORS FOR IRON RODS. 215

No figure was made for the curves, which are exhibited statistically
in Table IX, of December 1, 190G.

The work up to this point indicates that the thicker rods have
smaller demagnetizing factors than the thin rods. To test this matter

TABLE V. [Figure 10.]
October 20, 1906.
Diam. = 0.3969 cm. = 5/32 in.
Reversals.

Values of ^V x

101.

= 30 40

70
74

80
59

100

125
23

150

200
16

250

300

1000

27 199

133

. .

2000

45 211

141

103

3000

53 216

145

107

4000

.54 216

148

107

5000

57 217

147

107

6000

o
O

55 216

146

107

7000

217

147

108

8000

217

145

107

9000

215

146

107

10000

214

145

106

11000

214

144

107

12000

214

143

104

13000

. .

141

102

• •

14000

. .

130

• •

15000

• •

more carefully, a very long solenoid was built, probably the only one
of its size ever constructed. The wire was wound in a double coil
over a thick brass tube, making in all eight layers. The wire used
was the Annunciator No. 18, of diameter = 1 mm., with red insulation.
The dimensions of the solenoid are:

216

PKOCEEDINGS OF THE AMERICAN ACADEMY.

Length of windings = 485.3 cms. = 15 ft. 11 t^^ in.

Outside diameter = 5.96 cms.

Inside diameter =2.86 cms.

Number of turns = 10452 for each of the two coils.

TABLE VI. [No Figure.]

November 6, 1906.

Diani. = 0.2381 cm. = 3/32 in.

Eeveesals.

Values of N X 10'.

m = 50

100

150

•200

300

1000

(180)

102

(54)

. .

2000

(165)

110

(6)

3000

160

110

(9)

4000

160

118

(5)

5000

159

113

GOOO

159

114

7000

158

113

8000

158

113

7 '

9000

157

112

10000

159

112

11000

158

112

(3)

12000

153

108

(3)

13000

150

104

• •

14000

143

. .

15000

• •

The two coils were used in parallel, so that the magnetizing field is
H' = 27.064 c.g.s. units for each ampere.

The first rod tried in this solenoid was one of 0.9525 cm. diameter
(= I inch), and was a complete failure, although it gave some very
interesting results. No two consecutive step method magnetization
curves would agree. The rod was 15 feet long, so that m = 480.

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 217

The rod was carefully demagnetized and magnetized, apparently under
similar conditions each time. Parts of eight different magnetization
curves are shown in Figure 12 and illustrate the wide divergence at
the higher inductions. The reason for this peculiar behavior of the
fron was made clear when the rod was demagnetized and taken out of

15000

^_=.

<r'i

^
/

IOC

/■

\'/

/ ,

'¥

'//

-"v

5000

■^

}

Figure 10. [Table V.]

Reversal magnetization curves for a Bessemer soft steel rod of diameter
0.3969 cm.

the solenoid, and then tested with a small pocket compass for con-
sequent poles. It was found that the rod was quite strongly magne-
tized, and had polarity in the order i\"-*S-X-AS', the two middle poles
being both near the middle of the rod. Evidently this rod had once
been lifted around a warehouse by means of an electric crane with an
electromagnet lifting device, so that it had been subjected to quite

218

PROCEEDINGS OF THE AMERICAN ACADEMY.

a high magnetizing field. Besides, it is probable that the iron of this
particular rod, which was not of the usual Bessemer steel, is not very
homogeneous. In such cases it has been the experience of men who
have had much to do with magnetization of iron in a practical way —
as, for instance, Mr. Thompson, the mechanic of the Jefferson Physical

10 15 20

Figure 11. [Tables VII and VIIL]

Step and reversal magnetization curves for a Bessemer soft steel rod of diam-
eter 0.3175 cm.

Laboratory — that heating the iron specimen white hot and then
allowing it to cool slowly will not get rid of the consequent poles.
Nor will subjecting the iron to higher magnetizing fields, and then
decreasing the field while reversing constantly, so as to demagnetize,
help the matter, for the poles come back straightway in their old
positions.

After this the iron rods used in the long solenoid were carefully tested

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 219

for consequent poles before they were bought for the work. Even then
some peculiarities were noted in the results, which are due to some
irregularity in the polarity which was not apparent in the test with a
small compass needle. It should be noticed that such irregularities as

TABLE VII. [Figure 11.]

November 16, 1906.

Diam. = 0.3175 cm. = 1/8 in.

Step Method.

Values of 3

' X 10*.

m = 30

100

150

200

400

1000

376

227

142

. .

2000

382

280

145

. •

.3000

381

232

148

• •

4000

382

230

140

5000

386

2.32

148

6000

388

232

149

7000

389

2.34

150

8000

234

150

9000

237

150

•^2

10000

237

149

11000

237

147

12000

146

13000

• •

142

14000

■ •

• ■

• •

15000

■ •

• *

shown in Figure 12 are very mach more pronounced when the step
method is used. In fact, with the reversals it would probably turn out
that a very smooth curve would be obtained, but which would lead to
erroneous results in the demagnetizing factor.

No figure is given for the series whose results are tabulated in
Table X, of January 16, 1907. This table should be compared with

220

PROCEEDINGS OF THE AJIERICAN ACADEMY.

that for the rod of same diameter worked out beginning on October 9.
It will be noticed that these values for iV are considerably larger than
those of the earlier series. This again shows very clearly the difference
between the reversal and the step method.

TABLE VIII. [Figure 11.]

November 16, 1906.

Diam. = 0.3175 cm. = 1/8 in.

Reversals.

Values oi N X 10«.

m = 30

100

150

200

400

1000

365

224

1.36

2000

372

227

142

. .

3000

371

227

143

. .

4000

372

228

145

5000

372

228

142

6000

872

227

144

7000

372

228

144

8000

368

228

143

9000

228

142

10000

226

140

11000

222

134

12000

• ■

131

1.3000

• •

125

. .

14000

. .

■ •

(22)

. .

1.5000

• •

• ■

• •

Figure 13 gives the experimental curves corresponding to Table XI,
January 18, 1907. They were taken by the step method, and each
curve was based on three or four separate magnetizations from zero to the
highest value of H', so that good average results might be obtained.
It will be noticed that the curve for m — 200 passes very nearly
through two sets of observations, but that on either side of it lie

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 221

observation-points at quite a distance off. Most of the other curves
are in much better agreement with their points. There were also
taken a number of magnetization curves for the initial length of the
rod, 15 feet, which made m = 329 ; these curves resembled the ones

TABLE IX. [No Figure.]

December 1, 1906.

Diam. = 0.6350 cm. = 1/4 in.

Reversals.

Values of y x 10*.

m = 50.

100

1000

. .

2000

137

107

3000

144

105

4000

143

105

5000

145

105

6000

145

105

7000

144

103

8000

141

102

9000

141

101

10000

141

11000

142

12000

140

13000

136

14000

15000

• •

• ■

for the rod with pronounced consequent poles. It thus appears that
there must have been some irregularity in the demagnetized rod near
one or perhaps both ends of the rod. As the rod was cut down from
m = 329 to m = 200, most of these irregularities were cut off. Then at
the next shortening practically all the rest was eliminated. For m = 30
a reversal curve, represented in the figure by crosses, was also taken.

222

PROCEEDi:NrGS OF THE AMEEICAN ACADEMY.

See Figure 14 for the original curves, from iii = 15 to m = 240, from
which Table XII, of January 22, 1907, was constructed. It will be seen
that on the figure there appear a number of crosses. These represent
magnetization curves, not actually drawn, which were taken with the

TABLE X. [No Figure.]

January 15, 1907.
Diam. = 0.4763 cm. = 3/16 in.
Step Method. Long Coil.

Values of N X

10^.

m =80

100

150

200

300

1000

. .

2000

3000

4000

5000

6000

4.5

7000

4.5

8000

10.5

9000

10.5

10000

10.5

11000

10.5

12000

13000

14000

15000

■ •

• •

reversal method. This brings out a most interesting point. The thick
brass tube opposes a sudden change in the magnetizing field, by virtue
of eddy currents, and thus the establishment of the field is somewhat
delayed and the magnetization of the iron takes place more slowly.
The step method magnetization also is slower than the step method
when used in a plain solenoid wound on a tube of pasteboard, as is the

SHUDDEMAGEX. — DEMAGNETIZING FACTORS FOR IRON RODS. 223

first solenoid. But as the reversal method has now almost overtaken
the step method, we may conclude that both are very nearly at their
limiting positions, reached for very slow establishment of the magnet-
izing field, which are probably very nearly the same.

TABLE XI. [Figure 13.]

January 18, 1907.
Diam. = 1.111 cms. = 7/16 in.
Step Method. Long Coil.

Values of N X 10^.

m = 30

100

150

200

1000

341

20:i

141

. .

. •

2000

347

208

144

103

3000

348

208

145

105

4000

348

207

146

106

5000

348

210

144

106

6000

351

211

145

106

7000

351

213

145

107

8000

351

214

145

107

9000

351

213

145

106

10000

210

144

104

11000

211

142

103

12000

. .

140

100

13000

. .

140

14000

. .

15000

• •

Figure 15 gives the original curves of Table XIII, taken on February
21, 1907, and following. As it was found that in the long solenoid
the reversal method gives us practically the same results as the steps
method, it was now used throughout because of its convenience and
accuracy. Compared with the results of the rod of " cold rolled shaft-
ing " these values are somewhat smaller, but not more perhaps than is

224

PROCEEDINGS OF THE AMERICAN ACADEMY.

due to the slight difference between the step and reversal methods which
still remains. It is thus probable that the material of these two rods is
not of very great importance. The curve for m = 240 was also taken,
but was very nearly coincident with that for m = 200.

When this rod, which we will call Rod No. I, was tested for conse-
quent poles, there was also selected another one of the same diameter

160

=*=*

=====

?=-'

5^-^

7 ,

.■f

-'6

--'

"1^

:^-

10000

///

'^'a

y//.

'//

'/A

'III

50(

1
I

■'

Figure 12.

Effect of consequent poles in an iron rod. The magnetization curves shown
were taken under apparently the same conditions.

from the same lot of iron. Both were 20 feet long, and pieces of 1
foot and 4 feet were cut off from the ends. Rod No. II was magnetized
at m = 240, and gave the higher curve marked by the crosses. The
pieces of 4 feet length had been mixed up so that it was impossible to
say which belonged to Rod No. I and which to the other one. Test
pieces of m = 60 were now prepared from both of these pieces, all of
these rods of diameter 1.905 cms. being wound with 50 secondary turns

SHUDDEMAGEN. — DEMAGXETIZIXG FACTORS FOR IRON RODS. 225

in the centre. The short rods now gave the magnetization curves which
are merely indicated by crosses near the curves for m = 80 and ut = 60
of Rod No. 1. It is now evident which rod each of the small pieces came
from. Of course the magnetic induction was now measured at a distance

TABLE XII. [Figure 14.]

January 22, 1907.
1.905 cms. = 3/4 in. Cold Rolled Shafting.

Diam.

Step Method. Long Coil.

Values of X X

10*.

m = lo

80
61

100

150

200

240

1000

1960

1067

661

338

195

140

. .

2000

1064

663

333

198

147

100

. •

• •

3000

1075

673

342

203

150

107

(6)

■ .

4000

•

671

344

207

150

107

5000

669

344

208

148

106

6000

341

210

148

103

7000

342

210

146

102

8000

338

208

144

100

9000

341

207

141

10000

204

137

11000

200

134

12000

129

13000

124

• •

14000

• •

15000

• •

of about 9.5 feet in the original 20 feet rods, but still the normal curves
would probably not differ much. On the other hand, the normal curve
for Rod No. I is quite different from that for Rod No. 11.

With the help of the tracing cloth scale to be described below, Figure
16 was constructed, it being assumed that the maximum / is practi-

VOL. XLIII. — 15

226

PROCEEDINGS OF THE AMERICAN ACADEMY.

cally reached when B= 17,000. This body of iV-curves shows the
curvatures which we were led to expect, and also the tremendous turn to
the left as the curves get near the point of complete saturation. This
curve might be said to embody the most important results obtained
about the xV-curves. The one corresponding to m = 20, after going

15<

DOO

:=3

:r::

/■

'""'^

/■

IOC

pp/

}

r'-^

>•'

50 C

•iC

'/.

iT*'

10 15

Figure 13. [Taisle XL]

Step magnetization curves in long coil for a Bessemer soft steel rod of diam-
eter 1.111 cms.

out nearly straight far beyond the limits of the figure, sweeps back to
the left and just shows in the upper left-hand corner. It will be noticed
that the points of observation for all the curves become uncertain after
B = 12,000; this is to be expected because the magnetization curves
there become almost horizontal and run into one another, and the find-
ing of the abscissa-differences is a very difficult matter.

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 227

Method of Eeducing Observations.

As a typical illustration of the whole work, let us consider the reduc-
tion of the observations taken on the largest iron rod used in the long

TABLE XIII. [FiGi-RE 15.]
Februari/ 21, 1907.

Diam. = 1.905 cms. = 3/4 in. Bessemer Steel.
Reversals in Long Coil.

Values of .V X 10^. '

m = 15

100

150

200

1000

1009

658

332

201

139

2000

1019

663

331

211

141

102

3000

1032

668

336

209

140

102

4000

1032

665

339

212

144

102

5000

1042

657

340

213

, 142

103

6000

1045

659

335

207

140

103

7000

1040

662

335

207

141

102

8000

662

335

204

1.38

9000

661

332

200

136

10000

662

327

197

1.31

11000

324

194

128

12000

320

188

123

13000

• •

315

185

117

14000

303

171

104

15000

158

-n 1

AT T

1_ _

-y ^

■. Ti

solenoid. This is the series on Rod No. I, begun on February 21. It
usually takes about two days to take a series of observations, and the
reductions and plotting of curves take about two or three days
more.

When using the reversal method, the observations were taken under

228

PEOCEEDINGS OF THE AMERICAN ACADEMY.

1 1

\ \

\ '

. ^

V ^

S\\

io\

Iv\

v\\

\ '

\w^

v\ N

f>\

s,^

VS.

\,'

\ \

•«^

s^X

:^-

\\i

\\1

\\\

o
o

9-<

u
o

the headings : current in solenoid, resistance in the box B ', and bal-
listic throws observed. In the case of the step-by-step method the
zero reading of the galvanometer was also necessary.

We start from the fundamental equation of a current through whose
circuit the magnetic flux varies :

—

„

'il

' 1

. \

. o

! !"^

—

\\\

— '

u \

r\"

a:
c

, \

\ '

i \

\ ^

\\\

\V\

V-

. \

— .

\,'

L ..-

V
■*■-

. ^

\,^

"^^

-V

§^

\\-

!?^

^m-

'W[

o
o

t-t

K a

-a
o

>->

o
o

f*4 3

<u
t-
u

a
o

+-•
c4
tsj

230

PROCEEDINGS OF THE AMERICAN ACADEMY.

where E — electromotive force in the circuit, not due to changes in
flux,

—

1600

•

)

o o
o o

o
o

3
3

lOQO

;

5000

\ 1

y^'

ill

}

i^--

—

j//^

.^-

1
1

{

Figure 16. [Table XIII.]
Back-shearing curves for Bessemer soft steel rod of diameter 1.905 cms.

N = total magnetic flux of induction through the circuit in the
direction of the magnetic lines due to the current C, times the number
of turns of wire in the circuit,

t = time variable,

C = actual current at time t flowing in the direction in which E
acts,

SHUDDEMAGEX. — DEMAGNETIZING FACTORS FOR IRON RODS. 231

R = total resistance of the circuit.

If we apply this equation to our secondary coil circuit, which includes
the ballistic galvanometer, we have, since E=0,

or Q = \X/R,

where Q = total charge through galvanometer,

^JSf = number of flux-turns of change in the magnetic induction
through the circuit.

This equation is expressed in c.g.s. units. If we use as our units
the ampere, ohm, microcoulomb, and gauss, as we have done, then we
must use the equation,

Q = Ai\7(100i?).

We have also Q = T/S,

where T = actual throw in centimeters of scale reading produced by
the discharge of Q microcoulombs through the galvanometer, and *S' =
sensitiveness of galvanometer, expressed in centimeters of deflection
obtained by discharging 1 microcoulomb through the galvanometer.
Now in the reversal method as used in these experiments,

Ai\" = 2 BA}i = 2 B7r(D/2)\

wiiere B = the magnetic induction in gausses, or number of lines of
induction per square centimeter passing through the middle of the iron
rod,

A = cross-section of rod in square centimeters,

n = number of turns of secondary coil ^ound around the middle of
the rod,

D = diameter of the rod, as before.

This gives us

2 Biv{D/'2)-n _ T

100 • R ~ S '
5 100-^

T 2 STT{D/2f ■ n

This formula is the most convenient for our purposes. As in our series
we had the data

232 PROCEEDINGS OF THE AMERICAN ACADEMY.

S = 1.489
I) = 1.905 cms.
n = 50 turns

B 100 • R

we get ^ - 2(1.489) tt (0.9525)- • 50 '

The right-hand member is a constant for any given R In the work on
the series of curves the R had values ranging from 117 to 7117 ohms ;
the galvanometer and secondary coil circuit having itself 117 ohms, of
which the galvanometer had about 99 ohms, and the coil 18 ohms,
the other resistance being added, when convenient, from the resistance
box E '. The constants for these various ^'s were found and written
down. Then all we have to do to find the B for any observation is to
multiply the observed throw in centimeters by the proper constant.
This was done either by means of logarithms or a very good slide rule.
If we use the step-by-step method, the formula simply drops the
factor 2 and becomes,

A5 100 R

T S7r(D/'2yn
For the long solenoid we have simply

H' = — V (No. of amperes used)
= 27.064 (No. of amperes).

Having found the values of B and H', they were multiplied by 3
and 2 respectively, in order to facilitate the plotting of the points of
observation. Then the magnetization curves were drawn by free-hand
so as to fit the points as closely as possible.

This gives us the curves from m= 15 to 200 in Figure 15. To find
the corresponding normal curve (m = cc) a graphical device was found
to be of the very greatest utility. Not only was an enormous amount
of time saved, which otherwise it would have been necessary to spend
in almost endless computations, but the device was a positive aid in
determining the position of the normal curve. On a large sheet of
tracing cloth were drawn about seventeen horizontal lines, so that when
properly placed over the sheet of millimeter paper on which the mag-
netization curves had been drawn, they coincided with the lines B = 0,
1000, 2000, etc., up to 16,000. By means of lines radiating out from
a point on the lowest of theee horizontal lines, each one of the lines

SHUDDEMAGEX. — DE.MAGXETIZING FACTORS FOR IRON RODS. 233

above was divided into a large number of equal intercepts, each of
which represented exactly 0.0010 of jV, the demagnetizing factor, for
the particular B corresponding to the line. The larger of these inter-
cepts were further subdivided into tenths by means of short dashes, and
each horizontal line was numbered for every 0.0010, beginning from
zero on the left. Thus the tracing cloth was simply a large transparent
scale through which the X corresponding to every ff. could be imme-
diately read off. The error in the inaccurate spacing of the divisions
of the scale was about 1 part in 200.

Now suppose we arbitrarily say for the moment that the i\" for the
curve m = 200, all along the curve, shall be 0.0016, or the value of N
for the corresponding ellipsoid of revolution. By placing the tracing
cloth so that any desired line coincides with its corresponding B below,
and the magnetization curve for in = 200 crosses at K = 16 units, we
can read off the number of units for each of the other curves. After
doing this for all of the horizontal lines of our scale, we have a table of
values similar to that given for the rod of February 21, only the column
for m = 200 will consist wholly of numbers 16.

This table is thus our first approximation. We may now put away
our magnetization curve sheet with the scale, and proceed to get a
better approximation by merely studying the table. It will be noticed
that all the other columns will have values less than for the corres-
ponding ellipsoids. The only logical thing to do is to decrease the 16's
somewhat, at the same time decreasing every other number in the same
row by the same amount, so as to give a table consistent as a whole
when compared with the table for ellipsoids ; and this gives us something
similar to the table given. At the best approximation, the values for
ni = 200 will still be a unit or two in doubt, but this will make but a
small eiTor in the rods 30 to 50 diameters long. Of course individual
values of N in the table are subject to errors in the drawing of the
curve as well as observational errors, but when all the values of N
for a certain length of rod are considered, a smooth curve could easily
be drawn throughout the range of B in the experiment. We have,
however, preferred to leave the tables as given directly fi-om the last
approximation.

Should any one not be quite satisfied with the values as tabulated
for any one series of experiments, he may easily change the whole table
to suit himself, but he must do this subject to the condition of adding
or subtracting the same number for any one row as it is given here.

234

PROCEEDINGS OF THE AMERICAN ACADEMY.

TABLE XIV.

Observer.

Method.

Length

Sol-
enoid.

H'.

Range in
111 used.

Remarks.

Ewing, 1885

Ball.

Steps

0.158

47.5 to
7.9

0-35

300-50

Tanaka-
date, 1888

Magn.

(.100

j-153
.115

2-6
33.4

9.25

11.9

38.4

• •

90
13.1-39.2

Made in Japan.
Made in England.

Gauss A
Ewing's

C.R.Mann,

1895

Magn.

2.370
-.237

11.850

9.620

25.08
-4.18

30
30
38.5

20-1300

22-660

2-300

5-50

300-50

L constant, D
turned down.

D constant, L
cut down.

Gauss A
«

1.924
-.1924

0.0836

Benedicks,
1902

Magn. .

0.8
0.8

20
20

• •

23-206
23-206

25
25

All observations
made on hj'ste-
resis cycles.
Normal curve
obtained by el-
lipsoid results.

Ball.
Steps

Jefferson

Physical

Laboratory,

1907

Ball.
Rev.'s

0.2381

182.8
-11.91

207.7

a
li

((

485.3

1-26.3
1-30

1-29

3.4

-22.3

768-50
576-30

461-30

384-10

288-10

100-50

144-10

384-80

329.5
-30

397 sec. turns.
230 "

ii {( it

180 "
130 "
100 "

30 "

60 "
195 "

50 " "

50 "

Steps
Rev.'s

0.3175

0.3969

182 8
-9..53

182.8
-11.91

tt
i(
It

Steps

Stepsand
Rev.'s

0.4763
0.6350

1270

0.4763

1.111

1.905

182.8
-4.76

182.8
-6.35

3.7
-22

63.5
-31.75

4.7

-30.8

182.8
-12.70

3.4
-20.3

182.8
-38.10

1.8-
26

366.4
-33.33

1-34
2.4-33.7
1.8-44

457.2
-19.05

240-10
240-15

Rev.'s

457.2
-28.58

shuddemagen. — demagnetizing factors for iron rods. 235

Discussion of Investigations on the Demagnetizing Factors.

It was considered worth while to collate briefly the leading experi-
mental conditions which have been used in the determinations of N for
iron cylinders. Table XIV on the preceding page has therefore been
constructed from available data.

It will be noticed that Mann used some very thick iron bars in the
first two of his experimental series. However, a given diameter re-
mained constant only throughout a single magnetization curve, say for
in = 5 ; after this the bar was turned do^vn to a smaller diameter on
the lathe, so that in was thereby increased. If now the ballistically

1000

1400

rsiaoo -.

z
o

P
111

100

auo

soo

iioo

400 500 600 700

MAGNETIZING FORCE 3C

Figure 17.

Mann's magnetization curves obtained magnetometrically. The bars vary in
diameter from 2.370 cms. to 0.237 cm., while the length remains constant.

obtained results of the present paper can be at all related to magneto-
metric experiments on similar iron rods, they would lead us to expect
that had Mann cut down his longest rod of 25.08 cms. from m = 50 to
111 = 5, the values of X thereby obtained would not have agreed with
those which he did get by turning down the bar from m = 5 to m =
50. In fact the two sets of values for X, belonging to the two methods
"sawing off" and "turning down" respectively, would probably have
diverged more and more as m was decreased, the " turning down "
values for i\" being always less because the diameters of the bars of
this method are the greater, as carried out.

As noted in the outline at the head of this paper, Mann found that

236

PROCEEDINGS OF THE AMERICAN ACADEMY.

the values of N as determined magnetometrically are nearly constant
up to / = 800, but after this they increase enormously. This behavior

1
1

— t

* \

';\

' — cr

\ «

— 3-

\
\

^-^

■-,^

^^,

•4

•O

^^ —

;;v^

_ __

'»

■

*t;;

:3—

■a

'~'

'-...

(

'""^ "

-i^_

■flw_.

a
o

>
u

-«^
_N

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 237

of the i\-curves is undoubtedly closely related to the change in the
pole-distance ratio //Z, which probably approaches the value unity for
complete saturation. The magnetization curves taken magnetometric-
ally tend to diverge, or spread apart, for high magnetizations, whereas
those taken ballistically all converge rapidly to the maximum ordinate
/^o- Figure 17 is reproduced from Mann's paper,^^ and shows the curves
from in = 5 to m = 50 obtained from his first cylinder. The method
by which Mann gets at the position of the " normal " magnetization
curve for an infinite rod is to assume that the magnetometric iV for a
cylindrical rod of in = 300 is the same as for an ellipsoid of the same
length and central cross-section, namely iV = 0.00075.

In his investigation Benedicks obtained the value of JSf for only one
rod of hard steel (m = 25), but did this very thoroughly, using both
the ballistic step and magnetometric methods. His normal curve is
determined by transforming the steel cylinder into an ellipsoid of
in = 30, obtaining magnetometrically the magnetization curve for thi's
ellipsoid, and back-shearing this curve into the normal curve by means
of the known demagnetizing factor for this ellipsoid, which is
JSl = 0.0432. Theoretically the method is perfect, but we rather doubt
whether it can be depended upon to give uniformly agreeing results in
practice. The magnetization curves obtained by Benedicks are shown
in Figure 18, which has been reproduced from his article ^'^. The figure
shows the two types of iA"-curves, — the magnetometric and the balhs-
tic, — and their opposite behavior for high magnetizations. Benedicks
also publishes the A^-curves as he derives them from Ewing's original
six curves, all showing a behavior similar to that of his own curve
Xfiai- These iV^-curves are practically identical with those shown in
Figure 19 of this paper ; these were determined by our methods
directly from Ewing's curves shown in Figure 2, which were recon-
structed from the original figure ^^ in order to have both figures on
exactly the same scale as our own curves, for purposes of comparison.
See Figure 16, which shows the i\^-curves for our Bessemer steel rod of
diameter 1.905 cms.

We might note that Benedicks gets no curvature in the iNT-curve
near the origin, because he takes his observations from hysteresis
cycles of magnetization, the maximum applied field being about
H' = 206 units.

Benedicks criticizes Mann's assumption that N = 0.00075 for an

" Phys. Rev., 3, 359-369 (1896).

" Bihang Svenska, Vet.-Akad. Handlingar, 27 (1), Xo. 4, 14 pages (1902).

18 Phil. Trans., 176 (1885), Plate 57, Figure 3.

238

PROCEEDINGS OF THE AMERICAN ACADEMY.

iron cylinder of m = 300, as being unwarranted. He determines K by
botb the ballistic and magnetometric methods for a rod of m = 300
by back-shearing the ballistic curve into the normal curve, using
N'^^i = 0.0005, according to Du Bois, thus finding the N to be 0.0028
for the magnetometric method. He would, therefore, correct Mann's

ifiooo -^

■^

- ■ \

)

IQDOO —

"1-

^000-

r—

■ 1

Figure 19.

Back-shearing curves for Ewing's soft iron wire of diameter 0.158 cm.
mined from results found in the present paper.

Deter-

values of N by adding 0.0020 to each N throughout. Now it seems
to us quite clear, as remarked somewhere in the earlier part of this
paper, that we have no right to assume that the normal / vs. H curve,
as obtained ballistically, should be even approximately the same as the
Mean / vs. Mean H curve of the magnetometric method. This as-
sumption is rendered particularly doubtful when we see the very wide

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 239

difference ■ between the magnetization curves for m = 300 by the
ballistic and magnetometric methods as observed by Benedicks and
published in the " Bihang," and when we consider at the same time
that both these curves cannot possibly be very far away from their

TABLE XV.

Values of N.

Ellifsoio.

ClXINOEB.

B.'vllistic.

Magnetometric.

Du Bois.

Benedicks.

Jeff. Phys. Lab.

Mann.

Benedicks.

0.7015

■ . .

. . .

0.68000

. . .

0.2549

0.2160

. . .

0.1820-0.2001

0.25500

. . .

0.1350

0.1206

. . .

0.1000-0.1075

0.14000

. . .

0.0848

0.0775

. . .

0.0635-0.0671

0.08975

• • •

0.0579

0.0533

0.0444

0.0445-0.0465

0.06278

0.0658

0.0432

0.0393

. . .

0.0331-0.0388

0.04604

. . .

0.0266

0.0238

0.0204-00234

0.02744

0.0181

0.0162

. . .

0.0139-0 0160

0.01825

0.0132

0.0118

. . .

0.0100-0.0116

0.01311

0.0101

0.0089

. . .

0.0076-0.0088

0.00988

0.0080

0.0069

0.0060-0.00G9

0.00776

•

0.0065

0.0055

. . .

0.0050-0.0056

0.00628

•

100

0.0054

0.0045

. . .

0.0041-0.0046

0.00518

125

0.0036

. . .

0.0028-0.0032

150

0.0026

0.0020

. . .

0.0019-0.0023

0.00251

•

200

0.0016

0.0011

. . .

0 0011-0.00125

0.00152

300

0.00075

0.0005

0.0004-0.0007

0.00075

•

limiting positions for the infinite rod. On the other hand it is quite
reasonable to suppose that the N for any iron ellipsoid is always
greater than the .A^ for the corresponding cylinder, obtained by either
of the two methods ; because by adding the extra mass of iron to an

240

PROCEEDINGS OF THE AMERICAN ACADEMY.

TABLE XVI.
The Demagnetizing Factors in the Range of Practical Constancy.

Reversals in Short Coil :

in.

D = 0.2381.

0.3175.

0.39G9.

0.4763.

0.6350.

1.270.

2001

1990

1820

. . •

> . .

1049

1028

( 1000)

• . .

. > .

665

653

635

. . .

461

(458)

(445)

372

355

336

332

331

228

216

206

205

204

159

(155)

147

140

139

113

(113)

107

103

101

100

(81)

(54)

(50)

100

125

• < •

. . •

(28)

150

19+

200

11+

300

. . .

• • •

TABLE XVII.

Principle of Step Method .

Dn Bois.
D = 0.158.

D = 0.3175.

0.4763.

1.111.

1.905.

1.905
(Rev. '8
in Long

Coil).

Percentage

Difference

between 0.3175

and 1.905.

2160

1960

1206

. . .

1075

1045

775

• • .

. . .

* • •

671

662

25
30

533
393

388'

• ■ •

350'

(465)
343

(455)
336

15 5'

238

234

212

209

162

(160)

■

145

149

142

118

(116)

• •

106

103

89
69

(88)
69

66"

'66*

" 63

' 62

16'

(

90
100

55
45

(56)
46

"43 '

'41'

" 41

' 41

12.2

(

125

• • ■

> •

• ■

. .

150

200

12.5

12-

800

• • •

. . .

• • •

• •

The figures in parentheses are interpolated ; all others have been obtained ex-
perimentally. For purposes of comparison, the values of Du Bois are given in
Table XVII. The numbers given in these tables represent N ■ lO'*, as in the ear-
lier tables.

SHUDDEMAGEN. — DEMAGNETIZING FACTORS TOR IRON RODS. 241

ellipsoid in order to form the corresponding cylinder, the surface mag-
netism o- is shifted nearer to the ends of the rod and should exert less
demagnetizing force. To be sure, we now have some volume magne-
tism, p = — Divergence /, in the cylinder, which does not exist in the
ellipsoid, but the effect of this
is probably always extremely
small. On the whole we feel •^^^[
certain that oMann's value is jj
quite near the truth, and is
probably even a trifle too ^^
large.

Table XV, on page 239,
gives briefly all the results .030
obtained on demagnetizing
factors for the region in which
they are practically constant, Q25
that is, for the iron cylin-
ders up to about / = 800, or
B = 10,000.

The values of iV as obtained ^^^
for the various diameters of
rods in the present investi-
gation are given in Tables .015
XVI and XVII on the pre-
ceding page. They were ta-
ken from the tables given for
each separate rod, and are
fairly constant over the range
from B = 3000 to ^ = 9000.

.010

.005

100

150

.5 JIO

Figure 20.

The values of N of these
tables have been plotted in
Figure 20 against the corre-
sponding diameters of the
rods. The points connected
by straight lines are the re-
versal method values, while
those left unconnected are
the ones taken by the prin-
ciple of steps. It seems to be shown that the values of N experience
a rapid drop from D = 0.238 to about D = 0.50, and then remain
nearly constant as the diameter is further increased.

For practical use in finding permeabilities Table XVIII has been

VOL. XLIII. 16

Curves showing the variation in A' for
different diameters of iron rods. The num-
bers near curves give the corresponding
values of m.

242

PROCEEDINGS OF THE AMERICAN ACADEMY.

constructed. The induction is assumed to be observed experimentally
by the step method, and the K of the table is used in the equation

H=H' -KB.

TABLE XVIII.

Values op K.

D = 0.3175

D = 1.1 to 2.0 cms.

. . . -

0.00852

....

0.00533

....

0.00366

0.00309

0.00273

0.00186

0.00166

0.00127

0.00116

0.000925

0.000845

0.00055

0.000505

100

0.000366

0.000326

150

0.000183

0.000167

Problem.

Suppose the magnetic susceptibility in a soft iron rod similar to
Bessemer steel is to be tested ballistically. Suppose the rod is neither
very thick nor long, and the ballistic galvanometer (Thomson) is not very
sensitive. In order to get the greatest possible throw we may wind a
large number of turns of wire of secondary coil around the middle of
the rod, being careful not to exceed the point of maximum sensitive-
ness. This is reached when an additional turn of wire adds propor-
tionately more resistance to that already in the galvanometer circuit
than it adds turns to the total number of turns. Of course as long as
the secondary coil is wound on in a single layer, and the resistance of
the galvanometer is not negligible, this condition can never be reached ;
but where the coil is built up in several layers the resistance finally
predominates. Suppose we have :

Galvanometer resistance = 12 ohms.

Sensitiveness = 0.0695 mm. throw per microcoulomb.

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 243

Dimensions of Iron Rod: Diameter = 5 mms. Length = 20 cms., so
that 111 = 40.

Secondary Coil: 480 turns of fine wire. Length = 3 cms. Resist-
ance = 19.42 ohms.

We therefore neglect the leakage of induction through the secondary
coil. If we have no extra resistance in the galvanometer circuit the
formula gives for the method of reversals :

100 -i?

42-31

= 2400.

T /S'-2 7r(0.25)-480 0.00695 TT- 0.60

This shows that we need no extra resistance for the secondary circuit.
Suppose we magnetize in a solenoid 31 cms. long and wound with
5 layers of wire, 113 turns in each layer. Then we have

W = ■ (No. of amperes) = 22.9 (amperes).

10-31

We get the following observations:

Current in Solenoid.

BalUstic Throw.

0.-198 ampere

1.82 centimeters.

0.664 "

2.59

0.837 "

3.36

0.975 "

3.97

1.120 "

4.55

1.257 "

5.02

giving the calculated results :

H'.

11.4

4370

15.2

6210

19.15

8070

22.3

9530

25.66

10900

28.80

12040

244 PROCEEDINGS OF THE AMERICAN ACADEMY.

Now taking ]Sf= 0.0217 for m — 40, we have

H=H' - NI=ff' - KB

and K = N/A tt, since we may neglect II in comparison with B. We
get, therefore,

^=0.00173,

and may now calculate /f and the other quantities from the B of the

above table. This gives us

£.

AH = KB.

M-

4370

7.55

3.85

1185

348

6210

10.73

4.47

1390

493

110

. 8070

13.94

5.21

1548

641

123

9530

16.47

5.83

1634

758

130

10900

18.85

6.81

1600

865

127

12040

20.82

7.97

1520

960

120

We chose the value of N as would correspond to the ballistic step
method. Had we, however, used the method of reversals with a
solenoid wound on a pasteboard tube, or a split brass tube, then the
ballistic throws observed would have been a little more than twice as
great as those we found. If we take them as exactly twice as great,
and if we assume that the time-constant of the solenoid is the same as
fop the short solenoid used in the earlier half of this work, then we
should have

N = 0.0206

A" =0.00164

and the calculated values of the demagnetizing fields, the resultant
fields, and the permeabilities would be :

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 245

iJ-

lAl

4.23

1030

10.20

5.00

1240

13.22

5.93

1360

15.60

6.70

1420

17.90

7.76

1410

19.70

9.10

1320

This shows again how greatly different results obtained by step and
reversal methods can be, if the observations are not properly corrected
by using the appropriate N.

Distribution of Magnetic Induction.

In our theoretical discussion of the shape of the iY-curves we found,
page 197, that we might expect that the magnetization is much nearer
uniformity when the applied field H' is quite small, than it is in the
region of large susceptibility. Now several articles have been published
on the distribution of magnetic induction in iron rods,^^ but the mag-
netizing fields which these writers used were of much greater strength
than are necessary in order to investigate this particular question.
However, Benedicks ^^ found a very neat inverse relation between the
susceptibility k and the pole-distance» in a short bar magnet. This is
very clearly shown by Figure 21, which has been reproduced from his
article. The curve called "Distance des Poles " has the ordinates l/L,
where L = actual length of the bar magnet, and / = distance between
poles, the method of determining / being based on the formula

t* -*mean

/n,

19 Phil. Mat;., (5), 46, 478-494 (1898), " On the Distribution of Magnetic Induc-
tion in Straight Iron Kods," J. W. L. Gill; Phil. xMag., (5), 48, 262-271 (1889),
" On the Distribution of Magnetic Induction in a Long Iron Bar," C. G. Lamb.

20 Journ. de Physique, (4), 1, .302-307 (1902), "Etudes sur la Distance des
Poles des Aimants " ; Bihang Svenska Vet.-Akad. Handlingar, 27, (1) No. 5,
23 pp. (1902), " Untersuchungen iiber den Polabstand Magnetischer Zylinder."

246

PROCEEDINGS OF THE AMERICAN ACADEMY.

in which the /mean is the magnetization as determined magnetometri-
cally, and the /max. is found from the B as determined ballistically
at the centre of the rod in the usual way. For this rod m = 300.
The abscissae represent H', the magnetic field applied from without.
Similar curves had also been previously published by Dr. L. Holborn,^!
only the susceptibilities were taken directly from the unsheared mag-
netization curve of a short cylinder.

Although these experiments of Holborn and Benedicks practically
prove the increased uniformity of magnetization for low fields, it is
perhaps a better plan to settle this point by a more direct method. It
was therefore thought that it might be of interest to compare the

1 '

94
92
90

T^fn

— «-

160
140
120
100
80
60
40
20
0

Yisti

nee

des

PoU

-f

%
1
t

, /

84
82
80
78

>*-

Svsc

-phi

ilite

Vw.

-»-

}U\i

._.

— .

...

-X

10 20 30 40 50 60 70 60 90 iOO 110 120 130 140 150 160 170 1S0 130 200

Figure 21.

Benedicks's curves, showing variation of the pole-distance ratio and the suscep-
tibility in an iron rod. The abscissae give the field H' in c. g. s. units.

actual magnetic induction which passes through various cross-sections
of some of our iron rods, for practically the whole range of magnetiza-
tion from zero to saturation. To do this one might use a secondary
search-coil, fitting loosely around the iron rod, which can be suddenly
displaced along the rod by any desired distance. This would require
two observers ; but it could not be used conveniently in this work
since the rods in which the magnetic induction was tested were 1.905
cms. in diameter, and the inner diameter of the brass tube around
which the solenoid coils were wound was not much larger. Another
method would be to wind coils around different parts of the rod and
get the actual induction passing through each coil. This would do

21 Sitzber. Akad. d. Wiss., Berlin, 1, 159-162 (1808).

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 247

well enough for the lower intensities of H' but would be an exceedingly
insensitive method to use when the field //' is very high, since then
the induction is nearly constant along the bar except at the very ends,
so that the experimental error might easily be even greater than the
actual difference in the magnetic induction between the central part
of the rod and any other part. The best method seems to be to read
the reversal method ballistic throw from a coil wound directly over the
middle of the rod, and then, connecting any other coil, wound around
the rod nearer the end, in series with the central coil but in opposition
to it, observe the ballistic throw due to the difference in the flux

r —

SOcu. _-

- — 50

i*--

-»--T

No. 11.

-f- TJ ~ -1

'■

No. A.

CD MN

(4 —

— ..<«

No.B.

(No.l)

* * i a

No.B.

t^^

— V* 14 *T« 14 -n^ 14 *\

Fig ORE 22.

Diagram showing arrangement of secondary coil and switch-board used in the
work on the distribution of magnetic induction along an iron rod.

through the two coils. This was the idea adopted. Figure 22 shows
diagrammatically the arrangement of the coils in one of the four different
cases which were tried ; the others were similarly arranged. The po-
sitions of all the secondary coils are shown in the diagrams drawn to
scale and marked with the distances between the centres of the coils.

All the ends of the coils were led into small mercury cups in a small
switchboard. The extremities Bi, C«, D^, Ei, and one terminal of the
ballistic galvanometer were all dipped into cup F. If now the copper
connector is placed in the position J. (7 as shown, then the ballistic
throw observed on reversing the current in the primary solenoid is that

248

PROCEEDINGS OP THE AMERICAN ACADEMY.

due to those lines of magnetic induction which thread through the
centrally placed coil A^Az and do not also pass through the coil C1C2,
provided we neglect the lengths A1A2 and C'l C^ of the secondary coils
in comparison with the distance AiCi between the two coils. In
other words, the ballistic throw measures the magnetic leakage be-
tween the coils which are connected in opposition. When the con-
nector is placed across from A to F, then we get simply the throw

100

__J— ^

y^/

^_^

85
80

•

10(

)00

20000

Figure 23.

Curves showing variations in the distribution of magnetic induction in rod
No. II. D = 1.905 cms. and m = 240. The ordinate-axis represents percentage
of magnetic induction.

due to the whole magnetic flux of induction through the central coil
A-^Ai'va. precisely the manner which was used in all of the preceding
work on magnetization curves for different in'.s\

In this work on the distribution of the magnetic induction the extra
resistance which had to be thrown into the galvanometer circuit by
means of the resistance box R' in order to regulate the throw, varied
greatly. For a connection like that shown in the figure usually no
extra resistance was needed ; in fact for low as well as for high magne-
tizing fields the magnetic induction approaches uniformity, so that in
either case the ballistic throw is very low. Thus while in a certain

SHUDDEMAGEX. — DEMAGNETIZING FACTORS FOR IRON RODS. 249

case in = 25, and B = 21120, the extra resistance i?' had to be made
as high as 10,000 ohms in order to keep the throw for the central coil
alone from exceeding the length of the scale, yet when the coil nearest
to the central one was connected in opposition to it, only a weak de-
flection was obtained with no extra resistance in the galvanometer
circuit.

The curves which are shown represent four different rods, all having
the largest diameter used, 1.905 cms., but two of these had the same
length, the lu being = 60, so that for these rods the results are com-

bined in one figure.

The data for these four rods are as follows:

TABLE XIX.

Bessemer

Rod
D = 1.905.

Turns
per
Coil.

Length

of each

Coil.

Range of JFT'.

Range of B.

Maximum
Battery
Voltage.

No. II.
No. B.
No. A.

(No. I)

240

60
60
2-5

110

3.7 cms.
23 "
3.6 "
1.3 "

0.77-63.0
0.50- 66.8
0.25- 67.7
3.7 -440 0

1620-16800

84-16980

25-16800

650-21120

20
20
20
40

Bessemer Rod.

Length of Solenoid.

No. of
Coils.

Distances between Coils in Cms.

No. II.
No. B.

No. A.

(No. I)

485.3 cms.

€i it

107.2 "

5
5
3
4

50, 50, 50, 50 ; 29 to end.
14, 14, 14, 14 ; 1.1 to end.
2-5, 25; 7.1 to end.
7.5, 7.4, 8.0 ; 0.4 to end.

The coils are designated as follows, beginning with the central one :

No. II. 5-6-7-8-9.
No. A. CD-MN-XY.

No. B. A-B-C-D-E.
(No. I) 1-2-3-4.

The results are given graphically by Figures 2,3, 24, and 25 in this
way: The induction B in the middle part of the rod, as found from
reversing the current in the solenoid while only the central coil is in-
cluded in the galvanometer circuit, is plotted horizontally ; while the
ordinates give the ratio of the corresponding inductions in the parts of

250

PROCEEDINGS OF THE AMERICAN ACADEMY.

the rod surrounded by the other coils, to the induction at the centre.
Thus, suppose for a given constant H' we had obtained throws corre-
sponding to the central coil alone, and also for this coil when connected
in opposition to every one of the other coils in turn. In an actual case
we had for Rod B: H' =■ 59.5, the induction for the central coil was
B — 16,560, leakage between CD and MN was 630, and between
CD and X Y 7910, lines of induction per unit cross-section. From
these results we get for the actual magnetic induction through MN

100

10000

Figure 24.

Curves showing variations in the distribution of magnetic induction in rods
No. A and No. B. D = 1.905 cms. and m = 60.

15,920 lines, and through X Y 8650 lines. Now, denoting the B
through the central coil at any time by 100 per cent, we shall have
96.3 per cent of this induction passing also through the coil M N,
and 52.3 per cent through X Y. These two numbers are therefore
plotted against B = 16,560. Figures 23, 24, and 25 exhibit all the
observations taken. The slight zigzag arrangement of the points is
due to the fact that the current did not stay quite constant during the
time of observing the throws from all the coils on a rod. All the rods
have been referred to previously by the same designations, except
(No. I), which is merely one of the enql-pieces cut from the long rod

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 251

No. I mentioned before. The crossing of the curves for coils MN
and C at a high induction is merely another instance of the great
difl'erence in magnetic quality of Rods A and B (or Rods I and II)
which was already noticed in the magnetization curves of Figure 15.

From the curves in Figures 24 and 25 we see that for low fields
there is quite an increase in the induction for coils not at the middle
of the rod as compared with the induction through the central coil.
This means that for these low fields the magnetization is more nearly

100

k.-.

100

20C

)00

Figure 25.

Curves showing variations in the distribution of magnetic induction in rod
(No. I). D = 1.905 cms. and m = 25.

uniform. The range in H' for which the sharp upward bend of these
curves occurs is precisely the same range for which the susceptibility
changes most rapidly and is from H' = 0 to about H' = 5. After this
we have quite a long interval for which the susceptibility is high, and
the magnetization furthest removed from uniformity ; here the curves
showing percentage of induction as compared to that through the
middle coils have their minimum and run along very nearly parallel to
the i?-axis. However, as the induction through the middle of the rod
increases past B = 10,000, all the curves begin to rise, slowly at first,
then more rapidly. This indicates that the susceptibility is again

252

PROCEEDINGS OF THE AMERICAN ACADEMY.

decreasing, and that the magnetization is becoming gradually more
and more uniform. At about 5 = 17,000 the curves rise the fastest,
showing that the middle portions of the rod are very nearly saturated
and take up more magnetization only very slowly, while for the coils
nearer the end the magnetization is still rapidly increasing. Figure
25, for the short rod (in = 25), shows that after B is about 20,000
under the middle coil, the curves all have points of inflection and now
approach the ordinate 100 per cent asymptotically. If we now con-
sider Figure 23, for the very long rod (in = 240), we see that here we
have a case of the magnetization being always very much nearer uni-
formity, so that the curves for coils 6, 7, and 8 are already in the
asymptotic stage for B = 15,000 under the coil 5, and the points of
inflection are near B = 10,000. When B = 15,000, the curve for the
coil 9, nearest the end of the rod, shows a tremendous upward shoot
from a long horizontal course near the ordinate 50 per cent. Since the
figure only gives the observations in the range of percentages from 80
to 100, it might be well to give the missing values here :

B in Coil 5.

Percentage : -~.

B in Coil 5.

Percentage : -=7.
-05

2720

50.3

11730

65.30

3420

52.5

12030

65.67

4720

51.1

12330

67.00

6420

51.2

12680

68.70

7800

54.5

133.30

71.90

9000

56.5

14130

76.66

10470

60.8

. . .

-• • •

In the case of the long rod the lowest fields used were still too high to
show a rise in the curves, corresponding to increased uniformity of
magnetization, as is seen in the other two figures.

The results show that near the middle of a rod the induction is
practically the same for quite a little range, especially if the rod is fairly
long. Thus the curve 6 in Figure 23 shows that in the rod of length
about 458 cms. and m — 240, the induction for a distance 50 cms.
from the middle of the rod is always within about 2 per cent of the
induction at the middle portion. And curve B in Figure 24 proves
the induction at 14 cms. from the middle of the rod of length about

SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 253

114 cms. and m = 60 to be always within about 4 per cent of the
central induction. These facts justify the use of a secondary coil
several cms. in length, provided the in of the rod is not too small.

The conclusion to be reached from the work on the induction dis-
tribution is that for low field-intensities, as well as for high ones, the
magnetization of the iron rod is much more nearly uniform than it is
in a long interval corresponding to rather high susceptibilities.

Discussion of Results obtained.

When we look over the tables we readily see a number of interest-
ing things. It is apparent that in general different methods or even
different experimental conditions will give different normal curves,
and hence different susceptibility curves. A striking result, and one
which was obtained entirely unexpectedly, is that in the long solenoid,
which was wound on a thick brass tube, the method of reversals agrees
very closely indeed with the step-by-step method. This may in fact
turn out to be quite a useful observation, for it points to the proba-
bility of getting values for the susceptibility of some kind of iron in
the form of a short rod, which conform very closely to the ideal defini-
tion of susceptibility, which requires slow, continuous increase of the
magnetizing field. Thus by winding our solenoid on very thick brass
tubes, a large E. M. F. from a storage battery may be suddenly turned
on, without giving almost instantaneously the full value of the magne-
tizing field within, on account of the eddy currents in the brass tube
acting as a sort of " brake."

The most important results described in this paper about the de-
magnetizing factor N for cylindrical iron rods are the following:

(1) The demagnetizing factor is not a constant, but shows two
opposite curvatures, when plotted as abscissa-differences (ff, = NI) on
the / vs. Hi plane ; while for the highest values of / it falls to about
I or ^ of its value for unsaturated / 's.

(2) For values of i? less than 10,000 the A^ is practically constant.

(3) Using a solenoid made of wire wound on a non- metallic tube, or
a split brass tube, the reversal method gives values for iV considerably
lower than the step-by-step method.

(4) If the magnetizing solenoid is wound on a thick brass tube, the
reversal and step methods practically agree, and values of K derived
fi-om curves taken in this way are regarded as the most desirable for
scientific purposes, as they will give most accurate values for the
susceptibility or the permeability of the iron.

(5) The demagnetizing factors are largest for thin rods. The differ-

254 PROCEEDINGS OF THE AMERICAN ACADEMY.

ences between the corresponding N's for a rod of 0.3175 cm. diameter
and one of 1.905 cms. diameter range from 10 to 16 per cent, both sets
of vahies being taken to conform to the conditions stated in (4).

(6) Most of the rods used in this work have their iV^'s in the range
of practical constancy considerably smaller than the values given by
Du Bois, but as the diameters of the rods decrease, a very close
approach to Du Bois's values is obtained.

(7) The magnetization is furthest away from uniformity in the
region of highest susceptibilities, and becomes more uniform for very
low as well as for very high applied fields.

In conclusion it is my pleasant duty and privilege to thank Professor
B. 0. Peirce for suggesting this research and for his constant interest
in the work throughout the year. I also desire to state that the
astaticised galvanometer system is due to the skill of Mr. John Coulson,
Professor Peirce's assistant; and that the construction of the magnetiz-
ing solenoid was most successfully carried out by Mr. Thompson, the
mechanic of the Jefferson Physical Laboratory.

Literature on the Demagnetizing Factor.

J. A. Ewing: "Experimental Researches in ^Magnetism," Phil.
Trans., 176, 523-640 (1885). (Plate 57, Fig. 3.)

A. Tanakadatd : " Mean Intensity of Magnetization of Soft Iron
Bars of Various Lengths in a Uniform Magnetic Field," Phil. Mag.,
(5), 26, 450-456 (1888).

H. E. J. G. Du Bois : " Zur mathematischen Theorie des Ferromag-
netismus," Wied. Ann., 46, 485-499 (1892) (also in "Magnetische
Kreise in Theorie und Praxis," Berlin, 1894, p. 37).

C. R. Mann : " Ueber Entmagnetisirungsfaktoren kreiscylindrischer
Stabe," Dissertation Berlin, 1895 ; " Demagnetization Factors for
Cylindrical Rods," Phys. Rev., 3, 359-369 (1896).

Ascoli e Lori : " Sopra il fattore smagnetizzante nei cilindri di ferro,"
Rendic. R. Acad. d. Lincei, 3:2, 190 (1894); Ascoli: "Sul fattore
smagnetizzante nei fasci e nei cilindri di ferro," Rendic. R. Acad. d.
Lincei, 6 : 2, 129 (1897).

Carl Benedicks : " Ueber die Entmagnetisirungsfaktoren kreiscylin-
drischer StJibe," Wied. Ann., 6, 726-761 (1901) ; "Sur les facteurs
d^magnetisants des cylindres," Bihang Svenska Vet.-Akad. Handlingar,
27, (1), No. 4, 14 pp. (1902).

H. E. J. G. Du Bois : " Entmagnetisirungsfaktoren kreiscylindrischer
Stabe," Wied. Ann., (4), ?, 942-943 (1902).

shuddemagen. — demagnetizing factors for iron rods. 255

Literature on Related Subjects.

Eduard Riecke : " Zur Lehre vou den Polen eines Stabmagnetes,"
Wied. Ann., 8, 299-325 (1879).

C. Baur : " Neue Untersuchungen iiber den Magnetismus," Wied.
Ann., 11, 394-413 (1880).

F. Kohlrausch : " Ueber den Polabstand, den Inductions- und
Temperatur-coefficient eines Magnetes und liber die Bestimmung von
Tragheitsmomenten durch Bifilarsuspension," Wied. Ann., 22, 411-424
(1884).

Lord Rayleigh : "I. On the Energy of Magnetized Iron," Phil. Mag.,
(5), 22, 175-183 (1886) ; "Notes on Electricity and Magnetism. — III.
On the Behavior of Iron and Steel under the Operation of Feeble
Magnetic Forces," Phil. Mag., (5), 23, 225-245 (1887).

H. E. J. G. Du Bois : " On Magnetization in Strong Fields at
Ditferent Temperatures," Phil. Mag., (5), 29, 293-306 (1890).

0. Grotrian : " Der Magnetismus eiserner Hohl- und Voll-cylinder,"
Wied. Ann., 50, 705-741 (1893); "Zur Magnetisirung von eisernen
Cylindern," Wied. Ann., 52, 735-748 (1894) ; also, 54, 452-475 (1894).

Gustav Rossler : " Untersuchungen iiber die Magnetisirung des
Eisens durch sehr kleine und durch sehr grosse Kriifte," Elekt. ZS, 14,
97-99, 114-116, 133-134, 149-151, 161-163 (1893).

H. E. J. G. Du Bois : Note on Rossler's article, Elekt. ZS, 14, 208
(1893).

P. Culmann : Note on Rossler's work, Elekt. ZS., 14, 345 (1893) ;
" Ueber die Giiltigkeit eines von Kirchhoff in der Theorie des Electro-
magnetismus aufgestellten Satzes," Wied. Ann., 48, 380-383 (1893).

J. L. W. Gill : " On the Distribution of Magnetic Induction in
Straight Iron Rods," Phil. Mag., (5), 46, 478-494 (1898).

Dr. L. Holborn : " Ueber die Vertheilung des inducirten Magnetis-
mus in Cylindern," Sitzungsberichte d. Akad. d. Wiss. zu Berlin, l,
159-168 (1898).

F. Kirstaedter : " Zur Magnetisirung eiserner Hohl- und Voll-
ringe," Wied. Ann., 65, 72-85 (1898).

C. G. Lamb : " On the Distribution of Magnetic Induction in a
Long Iron Bar," Phil Mag., (5), 48, 262-271 (1899).

Carl Benedicks : " LTntersuchungen iiber den Polabstand magrie-
tischer Zylinder," Bihang Svenska Vet.-x\kad. Handlingar, 27, (1),
No. 5, 23 pp. (1902) ; " Etudes sur la distance des poles des aimants."
.Journ. de Phys., (4) 1, 302-307 (1902).

G. T. C. Searle and T. G. Bedford : "The Measurement of Magnetic
Hysteresis," Phil. Trans., A 198, 33-104 (1902) ; Abstract of this paper
in Proc. Roy. Soc, 68, 348-352 (1901).

256 PBOCEEDINGS OF THE AMERICAN ACADEMY.

H. Meldau : " Magnetisirung eiserner Z.ylinder," Phys. ZS. 4, 479-
480 (1903).

Raymond Jouaust : " Les phenomfenes de viscosity magn^tique dans
les aciers doux industriels et leur influence sur les methodes de
mesure," Comp. Rend., 139, 272-274 (1904).

Franz Riicker : " Beitrage zur Kenntnis der stufenweisen und ste-
tigen Magnetisirung," Dissertation, Halle, 1905, 106 pp., 20 plates ;
Elekt. ZS., 26, 904-905, 979 (1905).

Jefferson Physical Laboratory,
Harvard University.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 7. — Octobeb, 1907.

CONTRIBUTIONS FROM THE RESEARCH LABORATORY OF PHYS-
ICAL CHEJVIISTRY OF THE MASSACHUSETTS INSTITUTE OF
TECHNOLOGY. — No. 17.

OUTLIXES OF A NEW
SYSTEM OF THERMODYNAMIC CHEMISTRY

By Gilbeet Newtox Lewis.

CONTRIBUTIONS FROM THE RESEARCH LABORATORY OF PHYS-
ICAL CHEMISTRY OF THE MASSACHUSETTS INSTITUTE OF
TECHNOLOGY. — NO. 17.

OUTLINES OF A NEW SYSTEM OF THERMODYNAMIC

CHEMISTRY.

By Gilbert Newton Lewis.

Received July 10, 1907.

In the rapid development of theoretical chemistry, in which the
two laws of energy have played so important a role, two thermody-
namic methods have been widely used. The first, employed by Gibbs,
Duhem, Planck, and others, is based on the fundamental equations of
entropy and the thermodynamic potential. The second, employed
by such men as van't Hoff, Ostwald, Nernst, and Arrhenius, consists
in the direct application to special problems of the so-called cyclic
process.

The first method is general and exact, and has been a favorite with
mathematicians and physicists, those who were already familiar with
the use of the potential theory in mechanics. But unfortunately, ex-
cept in name there is little analogy between physico-chemical equi-
librium and the equilibrium in a mechanical system, and it is perhaps
for this reason that the method has failed to commend itself to the
majority of chemists. It must be admitted that it is the second
method to which we owe nearly all of the advances that have been
made during the last thirty years through the application of thermody-
namics to chemical problems, and which is now chiefly used by inves-
tigators and in the text-books of physical chemistry.

Yet the application of this method has been unsystematic and often
inexact, and has produced a large number of disconnected equations,
largely of an approximate character. An inspection of any treatise on
physical chemistry shows that the majority of the laws and equations
obtained by the application of thermodynamics, are qualified by the
assumption that some vapor behaves like a perfect gas, or some solu-

260 PROCEEDINGS OF THE AMERICAN ACADEMY.

tion like a perfect solution.^ As examples may be cited the mass
law, the law of change of solubility with the temperature, the law of
the lowering of vapor pressure by a solute, the law of Nernst for the
electromotive force of a concentration cell, and many other equally im-
portant generalizations.

It is probable that no one of these laws is ever strictly true. As
approximations to the truth they have been of the greatest service.
But now that their utility has been demonstrated, the attention of a
progressive science cannot rest upon their acknowledged triumphs,
but must turn to the investigation of their inaccuracies and their limi-
tations. From the study of the deviations from the simple gas laws
has grown one of the most interesting chapters of chemistry. So from
a study of the deviations from such a law as the mass law we may ex-
pect results of the highest value.

In such more exact investigations the old approximate equations of
thermodynamic chemistry will no longer suffice. We must either turn
to the precise, but rather abstruse, equations of entropy and the ther-
modynamic potential, or modify the methods which are in more com-
mon use, in such a way as to render them exact.

The latter plan is the one followed in the present paper, the aim of
which is to develop by familiar methods a systematic set of thermody-
namic equations entirely similar in form to those which are now in
use, but rigorously exact.

The following development is necessarily brief and concise, but I
have hoped, nevertheless, to make it intelligible to any chemist who is
familiar with the simpler theorems of elementary calculus.

The Escaping Tendency.

The meaning of the term "escaping tendency" maybe illustrated by
an analogy taken from another branch of applied thermodynamics, —
the theory of heat.

The conception of temperature owes its utility to the existence of
two fundamental laws of heat exchange. When two bodies are brought
together and there is no transfer of heat from one to the other, they
are said to be at the same temperature ; but if such a transfer takes
place, the body which loses heat is said to be at a higher temperature
than the other. Now the two laws of temperature are the following :
(1) Two bodies which have the same temperature as a third, have the

^ We may speak of a perfect solution as we speak of a perfect gas, that is, one
whicli obeys the laws of an infinitely dilute solution.

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 261

same temperature as each other. (2) If a body A has a higher tem-
perature than the body B, it has a higher temperature than any other
body of the same temperature as B.

These are not self-evident truths, but empirical laws. If they did
not exist, the idea of temperature would lose all value. Temperature
determines the distribution of energy in a system, and we may regard
the temperature of a body as a measure of the tendency of its internal
heat to escape into other bodies.

There are in chemistry two laws which are in every way analogous
to the laws of thermal exchange. If a system is composed of several
parts. A, B, C, D, containing a given molecular species, X, the two fun-
damental laws concerning the distribution of X throughout the system
are the following: (1) If when the phases A and B are brought to-
gether there is no transfer of X from one to the other, and if the same
is true of A and C, then when B and C are brought together there will .
likewise be no transfer of X. (2) If X passes from the phase D to the
phase A when they are brought together, then it will also pass from D
to B, or to C, or to any phase which is in equilibrium with A as regards
the distribution of X. It is obvious that these two laws follow directly
from the fundamental laws of thermodj-namics, for if they were not
true a system could be constructed capable of perpetual motion.

The escaping tendency of a given molecular species in a given state
is therefore analogous to temperature, and the two laws of escaping tend-
ency are as follows: If the escaping tendency of a given molecular
species, X, is the same in two phases, then X will not of itself pass from
one phase to the other. If the escaping tendency of X is greater in
one phase, it will pass from this phase into the other, when the two are
brought together.

Let us illustrate the meaning of the escaping tendency by an exam-
ple. When in a pure liquid a small quantity of some other substance
is dissolved, the vapor pressure of the liquid is diminished, its freezing
point is lowered, its boiling point is raised, its solubility in another sol-
vent is diminished.^ All these laws are comprised in the simple state-
ment, that the escaping tendency of the solvent is diminished by the
addition of the solute.

The idea of temperature was understood long beiore any suitable
measure of temperature was found. Then the mercury thermometer
was invented, later the gas thermometer, and finally in the absolute

2 So also the tendency of the liquid to take part in any chemical reaction is
diminished, hut until a later section of tliis paper our discussion willhe limited
to processes in which a given molecular species passes from one phase to another
without any otlier change.

262 PROCEEDIiSrGS OF THE AMERICAN ACADEMY.

thermodynamic scale we possess the ideal measure of temperature.
So indeed the idea of escaping tendency, although not distinctly formu-
lated, has been tacitly recognized and used, and as a measure of the
escaping tendency the vapor pressure has been employed. Now if all
vapors obeyed the laws of a perfect gas, probably no better measure
could be found. But this is never strictly the case, and the more the
vapor departs from the ideal condition the more unsatisfactory is the
vapor pressure as a measure of escaping tendency. By introducing a
more satisfactory measure of escaping tendency we may gain advan-
tages similar to those which resulted from the substitution of the
absolute scale of temperature for the mercury scale.

Such a measure of the escaping tendency I have described and used
in a previous paper.^ It was called the fugacity, and so defined that
the fugacity of a perfect gas is equal to its pressure. The fugacity of
an imperfect gas differs, however, from the gas pressure by an amount
which is greater, the more the gas deviates from the gas law.

The idea of fugacity is thus evolved from the use of vapor pressure
as a measure of escaping tendency. When a substance is in equilib-
rium with its vapor, the fugacity, in order to fulfil the laws of escap-
ing tendency, must be the same iii both. The fugacity of a substance
is therefore equal to its vapor pressure if the vapor behaves like a per-
fect gas. Speaking in terms not very precise, we may say that the
fugacity of a substance is equal to the vapor pressure that the substance
would have if its vapor were a perfect gas. It has been shown in the
preceding paper that for a given substance in a given state the fugacity
is a definite property of which the numerical value can in most cases
be readily determined, and which is well suited to serve as an exact
measure of the escaping tendency.

In many thermodynamic equations it is convenient to use concentra-
tions instead of pressures. Likewise we shall find it desirable to intro-
duce besides the fugacity, which has the dimensions of pressure, another
quantity which has the dimensions of concentration. This quantity
we will call the activity, and denote by the symbol ^. The activity will
be defined in terms of the fugacity, i/', by the following equation,

where R is the gas constant and T is the absolute temperature. Since
the fugacity of a perfect gas is equal to its pressure, it is obvious that

3 The Law of Pliysico-Chemical Change. Zeit. phys. Chem., 38, 205 (1901);
These Proceedings, 37, 49 (1901).

LEWIS. — A NEW SYSTEM OF' THERMODYNAMIC CHEMISTRY. 203

the activity of a perfect gas is equal to its concentration. If R has its
ordinary value, ^ will be given in mols per liter.

Both the fugacity and the activity are well adapted to serve as
measures of the escaping tendency. Indeed, for isothermal changes
the equations in which the two quantities enter are as a rule identical.
However, since the equations for the change of fugacity with the tem-
perature are a little less simple than those of the activity, we shall
choose the latter quantity for our present purpose. We shall start
with a simple definition of the activity, and proceed to show that the
change of the activity with the variables which determine the state of
the system may be expressed by a series of exact equations which are
of the same form as many of the familiar approximate equations for
vapor pressure, solubility, etc.

On account of the large scope of this undertaking our consideration
will be limited to those systems which are completely determined by
the temperature, the pressure, and the composition of the various
phases. How the work may be extended to include other variables,
such as surface tension, has been indicated in the preceding paper.

Fundamental Laws and Assumptions.

The following work will be based on the two laws of thermodynamics
and upon the law that every gas and every solution as the concentra-
tion diminishes approaches as a limit the perfect gas and the per-
fect solution. Besides these we shall use the following definitions of
the activity.

When the activity of a substance is the same in two phases, that
substance will not of itself pass from one phase to the other.

When the activity of a substance is greater in one phase than in
another, the substance will pass from the one phase to the other, when
they are brought together.

The activity of a perfect gas is equal to its concentration.

The activity of the solute in a perfect solution, at constant tempera-
ture and pressure, is proportional to its concentration.

We shall see that these statements suffice to define the activity of
a substance in any state, and except in unusual cases enable us to
calculate its numerical value.

No further assumptions are necessary, but since our aim tvill be to
lay stress rather on the exactness of the results obtained than upon the
mathematical rigor of the method by ivhich they are demonstrated, we
shall adopt as working aids the following assumptions :

(1) For every molecular species we will assume that an ideal solvent

264 PROCEEDINGS OF THE AMERICAN ACADEMY.

may be found (or imagined) in which that species dissolves to form a
perfect solution, at all concentrations up to that of the saturated
solution.

(2) We may further assume that the ideal solvent chosen is one
which suffers neither increase nor decrease of volume when the sub-
stance in question is dissolved at constant temperature and pressure.
In other words, the volume of the ideal solution is the same as that of
the ideal solvent it contains.*

(3) In dealing with mixtures, use will be made of any kind of
semipermeable membrane, real or imaginable, that may prove serviceable.

Probably in no case can the ideal solvent or the perfect semiperme-
able membrane be actually found. They will be employed as conven-
ient fictions for the purpose of obtaining results which could be obtained
without their aid, but by less simple methods.

Equations of a Solution in the Ideal Solvent.

Let us consider the vapor of a substance X, together with a solution
of X in an ideal solvent. From the laws stated in the preceding sec-
tion it may readily be shown that as the quantity of X is diminished,
and the solution and the vapor become less concentrated, the ratio
between the concentrations of X in the two phases approaches a con-
stant value.^ In other words, if c represents the concentration of X in
the solution, c' in the vapor, then at infinite dilution,

c' = pc,

where p is a constant, when the temperature and pressure are constant,
and may be called the distribution coefiicient between solution and
vapor at infinite dilution. This equation is merely the exact statement
of Henry's law.

Since the two phases are kept in equilibrium, the activity of X must
always be the same in one phase as in the other, that is,

i = i'.

* This assumption is of minor consequence, and is introduced merely to sim-
plify some of the mathematical work. It can be omitted without materially
changing tlie following work.

" Since our purpose is to develop a set of exact equations, but not to place too
much emphasis upon the formal rigor with which those equations are obtained,
it will not be necessary to repeat the proof of propositions which have already
been proved elsewhere and which can obviously be obtained by familiar methods.

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 265

At infinite dilution the vapor of X becomes a perfect gas, and by defi-
nition

^' = c'.
Hence at infinite dilution

I = c' = pG.

i is the activity of X in the ideal solvent, and c is its concentration,
and by definition $ is proportional to c for all concentrations which we
shall consider. Hence, not merely at infinite dilution but in general
one of the fundamental equations of the ideal solution is,

$ = pc. H*6

From this another useful equation may be obtained. In the case of
the ideal solution we have for the osmotic pressure, IT, the equation,

n = cRT.

Hence ^^m^' ^^^*

The quantity p varies with the temperature. In order to find the
law of this variation we may once more consider the equilibrium at
infinite dilution between the vapor of X and the solution of X in the
ideal solvent.

Since we are dealing here with the ideal solution and with a perfect
gas, the following special form of the equation of van't Hofif can be
proved by familiar methods to be entirely exact.

(IV)

where In signifies natural logarithm, and U(iy^ is the increase of
internal energy when one mol of X passes from the ideal solvent into
the infinitely attenuated vapor.

With the aid of these equations we are now prepared to undertake
a systematic study of the laws of physico-chemical change. It is to be
noted that /row each one of the following exact equations two important
approximate equations may be obtained directly, — one for solubility,

6 Numbered equations, sucli as those of the ideal solution, which are only true
under special conditions, will be marked with the asterisk.

' Since it will be necessary to use the symbol U for various kinds of internal
energy change, a particular value of U will be designated by the number of the
equation in which it first appears.

266 PKOCEEDINGS OF THE AMERICAN ACADEMY.

by substituting for tbe activity tbe concentration of a saturated solu-
tion, and one for vapor pressure, by substituting for the activity the
concentration of the saturated vapor.

The Influence of Pressure and Temperature upon the Activity

OF A Simple Substance.

Let us consider a pure substance in any state, — solid, liquid, or
gaseous, — and find the effect upon its activity : first, of a change of
pressure at constant temperature, and second, of a change of temperature
at constant pressure. Since the equations we are about to obtain are
special cases of equations IX and XII, of which a complete proof is
given in a later section, a less thorough derivation will here suffice.

In the preceding paper a formula was obtained (equation 14) for
the influence of pressure on the fugacity of a pure substance, namely,

ainf

dF T RT

where i/' is the fugacity and v the molecular volume. Combining this
equation with equation I of the present paper, we find, since BT i^

constant,

'2 In A V

RT'

/a In A

This is a perfectly general equation for the influence of pressure upon
the activity of a pure substance. Since the second member of this
equation is always a positive quantity, it is obvious that an increase of
pressure always causes an increase in the activity.

In order to determine the influence of temperature, let us consider
a substance X, in contact with its saturated solution in an ideal solvent.
The solubility as measured by the osmotic pressure, 11, varies with the
temperature according to the well-known equation

/ainn\

<3 _ VI*

which, since we are dealing with the ideal solution, can be shown to be
entirely exact. Q is the total heat absorbed when one mol of X dis-
solves reversibly in the ideal solvent. It is obviously the sum of three
terms, — the increase in internal energy, the osmotic work done, and
the work done against the external pressure, F. (According to one of
our fundamental assumptions the volume of the ideal solvent does not

LE^VIS. — A NEW SYSTEM OF THERMODYNAMIC CHEmSTRY. 267

change when X dissolves.) The first of these terms we will call ZTivn) ;
the second, according to the principle of van't Hoff, is equal to ET ; and
the third is equal to —Pi\ where v is the molecular volume of pure X.
We may write equation VI, therefore, in the form

/ainnX _ U^,.,,,+ RT-Pv ,

\ dT Jp . RT'

Now the activity, ^, of X in the pure state is always equal to that in
the saturated solution. The latter is related to IT, according to equation
III, by the formula,

Substituting this value of n in equation VII gives,

(m-(

d\np\ 1 _ L\vn) + RT-Pv
dT jp^ T~ RT'

Substituting for the second term the value given by equation IV, and
simplifying, we have,

a In A _ ?7,v„) + ^iv, - Pv
dT Jp RT^

ZTJvn) is the increase in internal energy when a mol of X dissolves in
the ideal solvent and U'^lv^ is the increase when it passes from that
solution into the state of infinitely attenuated vapor. The sum of
these two is the increase in internal energy when a mol of X is evapo-
rated and the vapor expanded indefinitely, or in other words it is the
increase in internal energy when a mol of X evaporates into a vacuum.
This important quantity, which we may call for the sake of brevity the
ideal heat of evaporation, will be designated by the symbol Y. Sub-
stituting it in the last equation gives,

VIII

This is the general equation for the effect of temperature on the
activity of any pure solid, liquid, or gas. Except in very rare cases
the second member is positive and ^ increases with T.

268 proceedings of the american academy.

Applications of the Preceding Equations.

A few examples will serve to illustrate the raode of application of
equations V and VIII.

Two phases of the same substance, ice and water, for example, are in
equilibrium at a given temperature and pressure. If the pressure on
either phase alone is increased, the activity in that phase is increased,
and the phase must disappear. If the pressure upon both phases is
increased by the same amount, the activity is increased more in the
phase of largest molecular volume, namely the ice, and it will disappear.
By increasing the pressure on the ice by the amount dP, and that on
the water by a greater amount, dP', it is possible to maintain equilib-
rium. Let us see what relation these two increments of pressure
must bear to each other. Let $, P, v, and $', P', v', represent the
activity, pressure, and molecular volume of the ice and the water, re-
spectively. From equation V,

c? In f = -jT77,dP, and d In ^' = -^4P'.
lb 1 li, 1

In order to maintain equilibrium we must always keep I equal to ^'.
Hence,

d^ = di', or d\a^ = d In i'.

Therefore the condition of continued equilibrium is,

^dP — -jyyj^dP' and

MT RT dP' V

In order to maintain equilibrium the increments of pressure on the
two phases must be inversely proportional to the molecular volumes.^

As a second illustration let us consider the same system of ice and
water subject to a simultaneous change of pressure and temperature.
The effect of increasing the pressure equally on both phases is to in-
crease the activity of the ice more than that of the water. An increase
of temperature has the same effect. By increasing the pressure and at
the same time lowering the temperature, equilibrium may be maintained.
The condition of equilibrium, as in the preceding case, is,

dhi^ = d\n^>,

but in this case the change in t and in i' is due in part to change in
temperature, in part to change in pressure, that is,

8 For a proof of this equation by otlier metho'ds, see Lewis, Z. physik. Chem.,
35, 343 (1900) ; These Proceedings, 36, 115 (1900).

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 269

dlni =

m/'<^)/''

Equating the second members of these equations and substituting for
the partial differential coefficient their values from equations V and
VIII,

Y — Pr V Y' — Pi' r<

Y-Pv-Y' + Pi' v'-v .J.
RT^ ^^=-EF'^^-

The numerator of the first fraction is obviously equal to the heat of
fusion of one mol of ice. Calling this Q, we have

dT _ {v' - V) T
dp- H '

which is the familiar equation of Thomson for the change of freezing
point with the pressure.

As a third illustration of the application of these equations we will
consider a general method for determining the numerical A^alue of the
activity of a substance. Let us first consider a gas which is at such
a pressure as no longer to obey the gas law. According to equation V
we may wTite, for the influence of pressure on the activity, at constant
temperature,

v •

d\\\.i = syhdP.
Ill

From this equation we may find the activity at one pressure when it is
known at any other, if we know the molecular volume, r, as a function
of the pressure, P. For this purpose we may use any empirical
equation, such as that of van der Waals, namely.

P = 1I- «

v-b

Differentiating this equation, substituting the value of dP in the pre-
ceding equation, and integrating between v and -y', we obtain the
equation,

270

PROCEEDINGS OF THE AMERICAN ACADEJUY.

ln[^(v-b)]-ln[^'{v>-h)] =

+ -F

v-b v'-b BTv BTv'

From this equation, assuming that the van der Waals formula is true
and that the constants a and b are known for a given substance, the
activity of that substance can be found at the volume v when it is
known at any other volume, v'. At infinite volume the activity of the
gas, by definition, is equal to its concentration, which is the reciprocal
of its molecular volume. It is evident, therefore, that if in the above

equation v' approaches infinity, ^' approaches — , or -; r, and the sec-

v' v' — b

ond, fourth, and sixth terms in the equation approach zero. Omitting

these terms, therefore, and rearranging slightly, we have,

ln^ =

v-b BTv

-\u{v- b).

From this equation $ can be found for any gas at any volume, v, pro-
vided the formula of van der Waals holds, and the values of a and b
are known. Similarly any other empirical equation of condition may
be used.

According to Amagat's experiments upon carbon dioxide at 60° the
molecular volumes of this gas at 50, 100, 200, and 300 atmospheres, are,
respectively, 0.439, 0.147, 0.0605, and 0.0527 liters. From these data
I have calculated the values of a and b at this temperature and found,

a = 3.1; b = O.OU

(pressure being expressed in atmospheres, volume in liters, and R con-
sequently having the value 0.0820).

Substituting these values in the above equations, we obtain the
values for the activity of carbon dioxide at 60° given in the following
table :

|,c.

2.3

1.6

0.70

100

6.8

2.6

0.38

200

16.5

3.2

0.19

300

10.0

4.2

0 22

LEYTIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 271

The first column gives the pressure, the second gives the concentration

in mols per liter [ - ), the third gives the activity, also in mols per

liter, and the fourth gives the ratio of activity to concentration, which
for a perfect gas is always unity. The increase in this quotient between
200 and 300 atmospheres is interesting, and the whole table shows how
little either the pressure or the concentration of a compressed gas
is suited to act as a measure of the escaping tendency.

If instead of determining the activity of gaseous carbon dioxide we
desired to determine that of CO2 in some other phase, for example in
a solution of sodium bicarbonate in water at a given temperature and
concentration, it would be only necessary to know the pressure or the
concentration of carbon dioxide gas in equilibrium with that phase.
For the activity there would be the same as in the gas, and the latter
could be determined by the above method.

This, therefore, is a perfectly general method for determining the
numerical value of the activity. However, it is to be emphasized that
in most cases ivliere the conception of activity is useful, it is not necessary
to know the numericnl value, hut only the ratio of the activities in two
given states. This will be illustrated in another section.

Influence of Pressure, Temperature, and Concentration upon
THE Activity of the Constituents of a Binary Mixture.

The equations in this section will apply not only to a homogeneous
liquid mixture, but also to a gaseous mixture, or solid solution, in fact
to any homogeneous phase
whatever which is composed
of the two molecular species,
Xi and X2. The composition
of a binary mixture we shall
express, following Ostwald,
by the molecular fractions
(Molenbruche), Ni and No,
so defined that Ni + N2 = 1-
By one mol of the mixture
we shall mean that amount
which contains Ni mols of

Xi and N2 of X2 . Later, in dealing with mixtures of more than two
constituents, the fractions Ni , N2, N3, etc., will be similarly defined,
so that Ni + N2 + N3 + . . . = 1.

The influence of pressure upon the activity of either constituent of

flGLKE 1.

272 PROCEEDINGS OF THE AMERICAN ACADEMY.

a binary mixture may be found by means of the apparatus shown in
Figure 1. A contains the mixture of Xi and Xj. D is a piston
which determines the pressure on A. E is a membrane permeable only
to Xi . B contains a solution of Xi in its ideal solvent. F is a piston
permeable only to the latter. Above F is the pure solvent.

The pressure on the piston F is the osmotic pressure, IT, of the ideal
solution in B. In general if the pressure, P, on D is changed, the
equilibrium will be disturbed and the substance Xi will pass through
E, unless at the same' time the pressure on F is changed by a suitable
amount. Let us find the mathematical expression for the change in 11,
which just compensates a given change in P.

Starting with the piston F at E and with a large {better, an infinite)
amount of the mixture in A, occupying the volume V, let us perform
isothermally the following cycle of reversible operations.

(1) Keeping the pressure F constant on the piston D, and keeping
the pressure on F also constant and equal to the corresponding osmotic
pressure, n, raise F until one mol of Xi passes into B, where it occu-
pies the volume v' . The diminution in the volume of A we will denote
by the symbol v. The work done by the system by means of the pistons
F and D is, therefore,

A^ = Uv' - Pv. .

(2) Now increase the pressure on the piston J) to P + dP, and at
the same time increase the pressure on F to IT + dU, dll being the in-
crement in n which is necessary to prevent Xi from passing in either
direction through E. The volume of A will change from V~v to
(V — dV) — (v — dr), and the volume of the solution will change
fromw' to v' — dv'. The work done by the system by means of the
pistons F and D is,

A. = -Udv' -P(dV-dv).

(3) Keeping the pressures on the two pistons constant and equal to
U + dn and F -f dP respectively, lower F to E, forcing the mol of Xj
back into A. The work done by the two pistons is

^3 = - (n -f dn)(:v' - dv') + (F + dP)(v - d7^).

(4) Change the pressure in A back to P. The piston F is station-
ary, and the work done by the piston D is,

A, = FdV.

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 273

The surface C does not change its position during these operations
(according to the definition of the ideal solvent). The total work
done by the system is therefore equal to the sum of ^i, A^, A3, and
Ai, and since the cycle is isothermal and reversible this sum is equal
to zero, by the second law of thermodynamics. Equating the terms to
zero and simplifying gives,

i-dP - v'dn = 0.

v' , the molecular volume in the ideal solution, is equal to -pj- . Sub-
stituting this value in the last equation gives,

The activity of Xi , $, is the same in the mixture A and the solution B
and its value in terms of 11 is given by equation III. Substituting for
n and expressing in the equation the constancy of temperature and com-
position,^ we have,

9 In A v

dP )t,n RT (IX)

This is the general equation for the influence of pressure upon the
activity of one constituent of a binary mixture. The quantity v is of
very great importance in the thermodynamics of mixtures. It is the
increase in volume of an infinite quantity of a mixture when one mol
of the constituent in question is added to it. We will call v the ^wr-
tial molecular volume of that constituent.

Similarly we may define the partial molecular energy, entropy, etc.,
and these quantities play the same r6le~ in the thermodynamics of
mixtures that the molecular volume, energy, entropy, etc., do in the
treatment of pure substances.

An important difference between the partial molecular volume in a
mixture and the molecular volume of a pure substance is that while
the latter is always positive the former need not be. Therefore the
activity of one of the constituents of a mixture may either be increased
or diminished by increase of pressure on the mixture.

9 We will use the subscript N with tlie p.artial diiierential coefficient to denote
constancy of composition in the mixture.

VOL. XLIII. — 18

274 PROCEEDINGS OF THE AMERICAN ACADEMY.

If a mixture contains Xj and X2 in the proportion of N't, mols of the
former to ^^2 of the latter, the relation of the partial molecular volumes,
V 1 and -v 2 is readily seen. If we add to an infinite quantity of the
mixture iVj mols of Xj, the mixture will increase in volume by NiVi.
Then adding N^ mols of X2 the volume increases by AVv Altogether
we have done nothing more than add one mol more of the original mix-
ture. The total change of volume must therefore equal v, the volume
of one mol of the mixture. Hence,

A'lFi + ^^2^2 = v. X

From equation IX we have the following two equations for the two
constituents :

BT'

\ dP )t,n~
\ dF )t,n~

Adding these two, we obtain the important equation,
'A^iain^i + N.d\xiL\ v 10

(:■

dP )t,n RT

The influence of temperature upon the activity of one of the con-
stituents of a mixture may also be determined with the aid of the
apparatus of Figure 1. Starting with the piston F at E, we may per-
form the following cycle of reversible operations, keeping the pressure
constant upon both D and C.

(1) At the temperature 7" raise the piston F until 1 mol of Xi passes
into B, where it occupies the volume v'. The pressure on F is kept at
such a pressure, 11, that the activity of Xi is always the same in B as
in A.

(2) Lower the temperature to 7" — dT, moving the piston F so that
none of Xi passes through K The volume of B is changed to v' — dc?
and the osmotic pressure to IT — d^.

^° The equation is written in this form rather than in the more conventional
form,

-.(^i..--=(m,=^.'

in order to emphasize the peculiar significance of the term N-^d In |i + N«d In lo-
in general we shall see that the equations of a mixture may be obtained from
tliose of a pure substance by substituting tliis series of terms in place of (?ln|.

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 275

(3) Lower F once more to E, under the constant pressure n — dn.

(4) Kaise the temperature to T.

The total work done by the pistons D and C is zero, since they are
under constant pressure and finally return to their original positions.
The whole work done by the system is, therefore, the work done by the
piston F, This is obviously the sum of the following four terms :

Ar = Uv',
A2 = - Udv',

A, = - (n- dn)(v' - do'),

The sum of these terms, neglecting the differential of the second order,
is v'dU.. This is the total work done by the system during the cycle,
and therefore from the second law of thermodynamics,

v'dii = ^dT,

where Q is the heat absorbed in process (1). Q is the sum of three
terms. The first is the increase in internal energy when one mol of Xi
passes from A to B, which we may call L\xu)- The second is the
osmotic work, IIi'', which is equal to jRT. The third is the work done
by the pressure P acting on piston J), which is equal to — Fv where v
is the partial molecular volume of X^ as before.
Hence,

, ^n _ g/jxii) + FT-Pv
^ dT~ T

AT I ^^

J\ ow -y' = — ij- ,

and theretore — ^™- = ^^^^

Combining this equation with equations III and IV, as we did in
deriving equation VIII, we have

/gin A ^ r;

V ST )p,N

+ lTax^ - Pv

(Xii) -r c'(iv)

HT^

The sum of l\xn) and L\iv) is the increase in internal energy when
one mol of Xi passes from an infinite quantity of the mixture into a

276 PEOCEEDINGS OF THE AMERICAN ACADEMY.

state of infinitely attenuated vapor. We will denote this quantity by
Y. It bears the same relation to the value Y of a pure substance as
the quantity v does to v. We may call it the partial " ideal heat of
evaporation. "

The above equation then becomes,

/a In A
\dT J

Y — Pv

— YTT

which is a general equation for the influence of temperature upon the
activity of one of the constituents of a mixture when the pressure and
the composition are constant. ^^

Just as equation X was proved we may show that for one mol of the
mixture,

Y = N^, + K,%. XIII

Hence we obtain an equation analogous to equation XI, namely

' Nid In ^1 + N,d In L\ Y -Pv

(■

— XIV

dT )p,N BT^

Here as before v is the volume occupied by one mol of the mixture
and Y the increase in internal energy when one mol of the mixture is
converted into infinitely attenuated vapor, or in other words when it
evaporates in a vacuum. ^^

^^ The approximate equation for the vapor pressure of oue constituent of a
binary mixture obtained from equation XII is,

'd In /)

\ dT )p,N~ RT^'

where Q is the partial heat of vaporization (including tlie external work). This
is in a simpler form than tlie equation obtained by Kirchhoff,

(^^\ (f)

\ dT Jp,x RT^

(see Nernst, Theoretische Chemie, 4 Edit., p. 118).

^2 Equation XII bears tlie same relation to XIV that the equation of Kirchhoff
does to one obtained by Nernst, namely,

p p_ _ _ Q{^

(IT ~ RT^

(Nernst Theor. Chem., 4 Edit , p. 117).

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY,

277

Finally we must determine bow the activities of the components of a
mixture vary when the composition is changed at constant temperature
and pressure. In order to solve this problem we may employ the ap-
paratus shown in Figure 2. A contains a mixture of Xi and X2. Ei is
a membrane permeable only to Xi, E2 one permeable only to X2. In Bi
and B2 are" ideal solutions of Xi and X2. The two pure ideal solvents
lie above the pistons, Fi and F2, which are permeable only to these
solvents. D is a piston which exerts a constant pressure on A. The
pressure at Ci and C2 Avill also be held constant. We may perform the
following isothermal cycle of reversible operations, starting with ATj
mols of Xi and A^2 niols of X, in A, and none of these substances in Bi
and B2, the pistons Fi and F2 being at Ei and E2.

(1) Keeping the pressures on Fi and Fo constant and at such values,
ITj and n,, as to maintain equilibrium with the mixture in A, raise
these two pistons at such

rates that as Xi and Xj
pass into Bi and B2 the
remaining mixture in A
still keeps its original com-
position. Finally, when all
the mixture has disap-
peared from A there will
be A"i mols of Xi in Bi
where it exerts the os-
motic pressure Hi, and oc-
cupies a volume which we
will call Vi, and there will
be i\'"2 mols of Xo in Bo,
volume ^^2-

(2) By simultaneous movements of the pistons Fi and F2 change the
volumes in Bi and Bo to ]\ — d Vi and V^ — d T,. The osmotic pres-
sures will change to Di -1- dn^ and Ha -f dlls- T!ie solutions in Bi and
Bo are now able to exist in equilibrium, not with the original mixture,
but with a mixture containing Xi and Xg in another proportion, say A"i
mols to ]S\ — (^-^"2 mols.

(3) Form a mixture of this composition in A by lowering the pistons
Fi and Fo. This operation will be just the reverse of (1), except that
Xi and X2 enter the mixture in the constant proportion, not of jS\ to
i\"o but of Ki to X2 — dX^ At the end of this process all of Xi and
all but dNi of Xo will have passed into A.

(4) Finally force into A the remaining dN2 mols of Xo, whereby the
whole system returns to its original condition.

FlGUKE 2.

the osmotic pressure being ITo, and the

278 PROCEEDINGS OF THE AMERICAN ACADEMY,

The work done during this cycle at D, Ci, and C2, is zero, since in
each case the final position is the same as the initial, and the pressure
is constant throughout the cycle. Therefore the total work done by
the system during the cycle is that done by the pistons Fi and F2,
which is as follows :

In operation (1),

^i = niFi + n2F2.

In operation (2),

In operations (3) and (4), except for a differential of the second
order,

As + A, = -(n,+ cUhXV, - dW) - (Ho + dn.^(V, - dV,).

By the second law of thermodynamics the sum of these terms, the total
work of a reversible isothermal process, r ust be zero. Hence,
neglecting differentials of the second order,

VidUi + Vodlh = 0.
Since we are dealing with ideal solutions,

^. N,BT , .. N,RT

hence N^d In Hi + N.d In Ho = 0.

Now the activity ^1 of Xi in A is always the same as in Bi, and fa in A
is the same as in B2 ; hence, applying equation III (p and T being
constants) we have,

N^d In ^1 + Nd In ^^ = 0, XV

which may also be written

(

dNi ) p,T

OjSz JP,T

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 279

It is not possible from thermodynamics alone to predict how the
activity of each of the constituents of a binary mixture will change with
a change in composition. But if the change in one of the activities is
known, the change in the other may be found from the above simple
relation. ^"^

Mixtures of More than Two Components.

In the derivation of equations IX and XII no use was made of the
provision that the mixture contained but two constituents, and these
equations therefore show the effect of pressure and of temperature upon
the activity of one of the constituents of a mixture of any number of
constituents. In the same way that equations XI, XIV, and XV were
found we may obtain the following equations :

/ Nid In ^1 + N^d In $, + A^3 gin 4 +

V S-t" JT,N

(

iSlnft

K^oh

le^2+iV^Gaini3

+ • • •

i8 In c^i

.Y^a In c^2 + i\"35 In ^3

+ ■ • ■

P,N

XVI

Y-Pv

XVII

XVIII

Dilute Solutions.

Equations XV and XVIII assume a very simple form when one of
the constituents of a mixture is present in such small amount as to
constitute a perfect solution. If a mixture consist of a very small
amount of a substance Xi and a large amount of a substance Xg, we may
call the latter the solvent and the former the solute. If the solute is
extremely dilute, then, according to equation II, its activity ^i is pro-
portional to its concentration and therefore to J\\. Hence,

c^lnc^i = d\nNi,
and equation XV becomes,

N^d\ni^ = -dA\ XIX*

or d\n$, = -^' XIX* A

13 An approximate equation which is a special form of equation XV is
Duhem's equation for the vapor pressures of a binary mixture, namely,
Nid In pi + Nod In p2 ^ 0. This equation is true only when the vapors obey
the gas law. See Lewis, Journ. Amer. Chem. Soc, 28, 509 (1906).

280 PROCEEDINGS OF THE AMERICAN ACADEMY.

This equation states that the relative lowering of the activity of a
solvent by the addition of a small quantity of a solute is equal to the
number of mols of solute divided by the number of mols of solvent.

This statement comprises in itself practically all the laws of dilute
solutions. Raoult's law is a special but only approximate form of
equation XIX, for equation XIX is true of every solution when infi-
nitely dilute, but Raoult's law is not true even at infinite dilution,
except when the vapor of the solvent is a perfect gas.

If the solute, Xi, is dissolved, not in a pure solvent, but in a mixture
of X2, X3, etc., then for the perfect dilute solution we find in place of
equation XIX,

N2d\n $, + Nsdlni3+ ■ • ■ =- d]S\. XX*

Some Applications of the Preceding Equations.

Equations I-XX can be combined in a very great variety of ways'
to give important results. A few examples, however, will suffice to
show the manner in which these equations may be employed.

First, as a simple example, we may derive the formula for the lower-
ing of the freezing point of a perfect solution. According to equation
XIX, the activity of a pure liquid is always lowered by the addition of
a solute. If therefore a liquid and solid are together at the freezing
point and a solute is added to the liquid, the activity of the latter will
become lower than that of the solid, and the solid will melt. On the
other hand, if we start again with liquid and solid at the freezing point
and lower the temperature, we see from equation VIII that the activity
of the solid will decrease faster than that of the liquid and the liquid
will disappear. It is obvious, therefore, that by adding a solute to a
freezing mixture and at the same time lowering the temperature by a
suitable amount, the equilibrium between solid and liquid can be main-
tained. The necessary condition for the maintenance of equilibrium
is that the activity 1^2 of the solvent X2 in the liquid state remain equal
to the activity ^'2 of X2 in the solid state. Hence,

d\ni'., = d\n.^2'

Now, assuming that the solid does not dissolve any of the solute, the
change in activity of the solid Xo is due merely to change of tempera-
ture, and thus from equation VIII,

din ^'2 = .jrp.2 ^ dT.

LE\nS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY'. 281

But the activity of the solvent in the liiiuid phase is changed both by
the change in temperature and by the presence of dj\\ mols of solute.
That is,

dT J 'V ^-^^1 J
Whence by means of equations XII and XIX

Equating the second members of this equation and the one above,
Y'2 - Pv', ^^ ^ %- Pi, _jj,_ dJS\

HI" pr iVo'

or — iVs

dT RT''

2 7 AT

dN^ Y'2 - Pi)', - Y2 -1- Pc.2

But it is obvious on inspection that the denominator of the second
member is merely the heat of fusion of one mol of solid, which we may
call Q. If the solution is very dilute we may also simplify by writing
N2 = 1. Hence,

dT _ RT'

d^\~ Q

This is the familiar equation of van't Hoflf for the lowering of the
fi'eezing point by a dissolved substance.

As a second example we may study the following system, A mix-
ture of X2 and X3 in the molecular proportion of 1V2 to JVs are in equi-
librium with a second phase consisting of pure X,. Let us determine
the change in activity of X3 when a small quantity d]S\ of a substance
Xi is dissolved in the mixture. At constant temperature and pressure
the activity ^''2 of the pure phase of X, is a constant, and therefore
the activity, $2, of Xj in the mixture is also constant. Equation XX
therefore becomes,

iWlnc^3 = -^^i. XXI

This interesting equation has, I believe, not hitherto been obtained,
even in an approximate form. Its meaning may be illustrated by the
following example : If a saturated solution of salt in 1000 grams of
water is in contact with solid salt, and 1 gram of sugar is added, then

282 PROCEEDINGS OF THE AMERICAN ACADEMY.

the activity of the water is lowered by the same per cent as when
1 gram of sugar is added to 1000 grams of pure water.

An interesting system is one composed of two phases, both of which
are mixtures of the same composition. An important example of such
a system is a constant boiling mixture and its saturated vapor. Here
A^2, ^"^^3) etc., which are the molecular fractions in the one phase, are
equal respectively to N'^, N's, etc., in the other phase. If the condi-
tions are changed by changing the temperature or pressure or by adding
a third substance Xi to one or both of the phases, then equilibrium can
only be maintained by keeping the activity of each component the same
in both phases ; thus we may write as usual,

d\ni2 = <^ln ^'2, «^ In ^3 = d\n i's ,

etc. ; but since N2 = N'^, etc., we may write

iVs^lncfs + A^s^lnfs + • • • = N'.dhxt'^. + A^'s^^ln^^'s +• • •

Now the first member of this equation represents a change which may
be the resultant of the changes produced by change of temperature,
change of pressure, and the addition of dNi mols of the solute Xi.
Each of these changes is represented alone by equations XVI, XVII, or
XX. Therefore,

(

P.N ^^J^

(

A^2ainf2 + A^^ainc^s

+ • • •

A^2Sln^2+ N^dlnS^

+ ■ • •

\ dP J T,N ^^^

liT

dNi = - dNr.

dNx jT.P

We may therefore write the sum of these as follows :

N^d\xxL^N^d\slk^^ • ■ ' ^^-^^^dT+^dP-dN^.
Likewise we find

iV'2^1n^'2 + iV's^lnfs + • • • = ^' ~^f dT + -^dP - dN'„

where dN'i is the number of mols of the solute in one mol of the second
phase. Equating the second members of these two equations we have,

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 283

The numerator of the first term, which we may call Q, is obviously the
heat absorbed when a mol of the mixture passes from the first phase to
the second, and (y — v') is the decrease in volume accompanying the
same change. Thus,

% dT + ^^ dP - dA\ + dN', = 0. XXIP

This extremely general equation shows how the variations in temper-
ature, pressure, and quantity of solute must be regulated in order to
maintain equilibrium in such a system. Several special cases are
worthy of notice. If pressure and temperature are the only variables,
in other words if dNi and dN'i are zero, then the equation becomes,

dP Q

dT {v'-v)T

This equation is identical with the familiar Clapeyron-Clausius equa-
tion. It shows, for example, that the vapor pressure from a constant .
boiling mixture varies with the temperature in the same way that the
vapor pressure of a pure substance does.

If in equation XXII, dP and dN'i are zero, there remains an equation
for the change in temperature which compensates for the addition of a
solute soluble in one phase only, namely,

dT=^dX,.

Thus, for example, the boiling point of a constant boiling mixture is
changed by the addition of a non-volatile solute according to the same
law as that which applies in the case of a simple solvent. ^^ Q is of
course the heat of vaporization of one mol of the mixture.

In the same way, by making c?!" equal to zero in equation XXII, a
formula may be derived for the lowering of the vapor pressure of a con-
stant boiling mixture when a solute is added at constant temperature.

1* Tliis equation I have already proved in a less rigorous way (.Journ. Amer.
Chem. Soc, 28, 7G6, 1906). It has considerable practical importance, as it in-
creases the number of solvents iu which molecular weights may be determined
by the boiling point method.

284 PROCEEDINGS OF THE AMERICAN ACADEMY.

If instead of the system considered above we study a system of the
type represented by a mixture at its eutectic point, we may derive
a set of equations, entirely similar to the above, which show the change
of the eutectic temperature with the pressure, and the change of the
eutectic temperature at constant pressure, or of the eutectic pressure at
constant temperature, when a solute is added to the mixture.

These examples will suffice to show the way in which equations
I-XX may be applied to the derivation of other thermodynamic
equations.

The Laws of Chemical Equilibrium.

Hitherto we have considered only those processes in which each
molecular species persists without any change except that of passing
from one phase to another. We will now consider those processes in
which the molecular species react with each other to form new species,
and it will be shown that the activity of a given species is not only a
measure of the tendency of that species to escape into some other phase,
but is also a perfect measure of the tendency of the species to take
part in any chemical reaction. In other words, the activity is an exact
measure of that which has been rather vaguely called the "active
mass " of a substance.

Let us consider the reaction represented by the following equation,

aA ■\-hB+ ■ ■ ■'^oO+ 2^P + • ■ ',

where a mols of the substance A, h mols of B, etc., combine to form o
mols of 0, p mols of P, etc. The several substances may exist in the
pure state, or in mixtures ; may be in one phase or in different phases,
and there may be other substances present which take no part in the
reaction. In other words, we are considering any system whatever in
which a given chemical reaction occurs. Let us find the conditions for
equilibrium in this reaction.

We may choose a liquid which is an ideal solvent for each of the
substances taking part in the reaction. If this ideal solvent is brought
in contact with the system through a membrane permeable only to the
substances which take part in the reaction, these substances will enter
the solvent, and when the system comes to a final condition there will
be equilibrium in the chemical reaction, both in the original system
and in the ideal solution. Moreover, the activity of each of the mole-
cular species must be the same throughout the original mixture and in
the ideal solution.

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 285

Now ill the ideal solution it is easy to show rigorously, as van't Hoff
has done, that the couditioii of equilibrium at a given temperature is,

-7~ni7. ^ constant.

where (7.,, etc., represent the concentrations. But in this solution the
concentrations are proportional to the activities, and therefore,

'-^ = K. XXIII

where K is another constant. Since the activities ^^, etc., are not only
the activities in the ideal solution, but also in the original system, it
is obvious that equation XXIII expresses a law of extraordinary gen-
erality.

The above quotient, which we have called K, has a value which, for
a given reaction at a given temperature, does not depend upon the
medium iu which the reaction occurs, nor upon the concentrations, nor
upon the pressure, nor upon the nature or number of the phases which
are concerned in the reaction. In other words K depends only upon
the temperature and the specific nature of the reaction. It is there-
fore a better measure of the true " affinity " of a chemical reaction
than any quantity that has hitherto been used for this purpose.

The equilibrium ratio, A", changes with the temperature according
to a simple law. We may imagine the substances taking part in a
given reaction all vaporized in a space so large that each vapor be-
haves like a perfect gas. If the reaction reaches equilibrium under
these conditions, it is easy to show that the following equation of van't
Hoff is entirely exact, namely,

fopp . . .

0'[Ci- ■ ■ n

? l^i '

ciT iir-

where C^, C^, etc., represented the concentrations, and U is the increase
in internal energy when the reaction occurs in this extremely attenu-
ated gaseous phase.

Since we are dealing with infinitely attenuated vapors, C^, etc., may
be replaced by |^, etc., whence

clT ~ UT^

286 PROCEEDINGS OF THE AMERICAN ACADEMY.

Since at constant temperature K is independent of the conditions
under which a reaction occurs, it is obvious that the change with the
temperature of the equilibrium ratio of the reaction in any system
whatever is given in equation XXIV. The important quantity U, the
heat of reaction in the dilute gaseous phase, is equal to the heat of re-
action in any other condition less the algebraic sum, for all the sub-
stances taking part in the reaction, of the quantities which we have
denoted by the symbol Y.

The importance of this quantity U has been recognized by Berthelot,
who wrote in 1875,^^ " J'ai dt^fini sp^cialement la chaleur de comblnai-
son atomique, laquelle exprime le travail rdel des forces chimique, et
doit etre rapportde k la reaction des gaz parjaits, operee a volume
constant."

The following interesting example will serve to illustrate the simul-
taneous application of equation XXIII or XXIV with the preceding equa-
tions. Let us prove the theorem first demonstrated by Stortenbeker,^^
namely, that the freezing point of a substance like CaCl2 • 6H2O which
partly dissociates in the liquid phase, is not changed by the ad-
dition to the liquid of a small quantity of either of the products of
dissociation (CaCL or H2O). When the solid, CaCU-GHaO, melts,
there are in the liquid Nx mols of CaC]2 • 6H2O, to N^ mols of CaCls
and N^ mols of H2O, where N^ = 6i\^2- Let us find the effect produced
by adding dN^ mols of H2O at constant temperature and pressure.
According to equation XVIII,

(N,d In ^1 + Nod In h + N^d In ^A

\ SN3 Jp,T~

From this equation, since iVg = 6 N^, it is obvious that,

i\"if/ln ii + N. (din .^o -f 6 c?ln $^) = 0.

Now since the CaCl2 • 6H0O, CaCL, and HoO are in equilibrium,
equation XXIII states that,

Taking the logarithm of both members and differentiating we have,

c? In ^2 + Qdln^s = dhi^i.

" Ann. Chim. Phys., 4, 1 (1875).
" Zeit. phys. Chem., 10, 183 (1802).

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY'. 287

Combining this equation with the above gives,

Nid In ^1 + N^d In ii = 0, or d hi ^i = 0.

That is, the activity of the CaCL • 6 HgO in the liquid phase is not
changed by the addition of a small quantity of water, and it will there-
fore remain in equilibrium with the solid CaCl2 • 6 H2O without change
in the fi-eezing point.

This example illustrates the general manner of treatment of systems
in which molecular species may change through dissociation, association,
or through the mutual reaction of two or more species.

A little consideration of the simultaneous use of equations XXIII and
XXIV with the preceding equations shows why it is that such equations
as V and VIII hold for the activity of a molecular species such as
H2O, in a given pure phase, regardless of whether this phase is really
composed entirely of the species H2O or in part also of others such as
(H20)2, (H20)3, (H"^ + 0H~), etc., provided always that these other
species can be formed from, and are in equilibrium with, the molecular
species HgO.

It may seem, at first sight, that equations XXIII and XXIV, as well
as the preceding equations, while entirely exact and general in their
scope, may not be readily applied to certain concrete problems where
the value of the activity cannot be obtained from existing data. As a
matter of fact, however, it is seldom important to know the numerical
value of the activity in any one state, but rather the ratio between the
activity of a substance in one state and that in another, and this ratio
may be obtained in a variety of ways.

In fact one of the most important problems to which the equations
derived in this paper may be applied, concerns the dissociation of salts
in aqueous solutions into their ions, although from the nature of the
ions we are never able to determine the numerical values of their
activities. Let us consider the dissociation of such a substance as
hydrochloric acid in aqueous solution, according to the reaction,

HCl - H+ + Cl-

According to the ordinary mass law,

ChCci

= K.

HCl

Now this equation has been shown to be false, if we calculate the
concentration of the ions from conductivity data. In all probability

288 PROCEEDINGS OF THE AMEEICAN ACADEMY.

this calculation is correct for solutions more dilute than tenth normal,^^
at least we may say that the conductivity data furnish the only means
ive have at iwesent for calculating the ion concentrations. Every other
method ivhich has been employed measures not the concentrations, but the
activities of the ions.

According to equation XXIII the activities of the undissociated acid
and the ions are connected by the equation,

Cuci

If therefore the mass law is false, it must be because the activity is not
simply proportional to the concentration for one or more of these three
substances. The problem, therefore, is to determine how the activity of
the undissociated substance and the activity of the ions vary with the
concentrations of both. It seems that all the facts which are at present
known concerning electrolytic dissociation can be explained by the
assumption that the ions are normal in their behavior ; in other words,
that the activity of each ion is simply proportional to its concentration,
but that the undissociated portion of a strong electrolyte is abnormal in
its behavior, the activity being proportional to the concentration of the
nndissociated substance multiplied by a quantity which depends solely
on the total ion concentration, and increases with the latter. ^^

This simple statement suffices to explain qualitatively all the known
anomalies of strong electrolytes. The exact quantitative formulation
of this principle can hardly be made until still more experimental
work has been done.

However, these considerations illustrate the method of treating
chemical equilibrium when the ordinary mass law fails ; in other words,
when for one or more of the reacting substances the activity is not
proportional to its concentration. For 'a complete analysis of such a
case it is necessary to know how the activity of each of the reacting
substances changes with its concentration and with the concentration
of the other substances present.

" The data upon wliicli this paragraph is based are chiefly those contained
in tlie very complete and instructive summary by A. A. Noyes, entitled, " The
Physical Properties of Aqueous Salt Solutions in Relation to the Ionic Theory."
(Technology Quarterly, 17, 293, 1004).

^8 Probably, strictly speaking, the activity of the ions is likewise a function
of the concentration of the undissociated substance, decreasing as the latter in-
creases ; but since the concentration of the undissociated substance always is very
small in dilute solutions of strong electrolytes, its influence on the activity of the
ions is therefore of minor importance.

lewis. — a new system of thermodynamic chemistry. 289

The Relation of Activity to Free Energy and Thermodynamic

Potential.

It is interesting to see what relation the activity bears to certain
other quar^tities which have been previously used for a similar purpose,
especially the fi'ee energy of Helmholtz, which is itself intimately
related to the various thermodynamic potentials.

The diminution in free energy which accompanies a given isothermal
process, that is, the maximum work which the process may accomplish,
is not a definite quantity until we define not only the process but also
the system which is to be considered. To illustrate, we may consider
a cylinder containing liquid and vapor, and a piston operated on by
a spring which exerts a force exactly balancing the vapor pressure.
When the piston moves out an infinitesimal distance, the decrease in
fi'ee energy of the water and vapor is equal to pdV, but on the other
hand the free energy of the spring increases by^x/F, so that the free
energy of the system comprising water, vapor, and spring does not
change. In general we shall depart from the most common usage and
consider the larger system, and we may therefore define the diminution
in free energy of a given isothermal process as the maximum work
which the process is able to accomplish, exclusive of the work done
against the external pressure or pressures. The negative of this quan-
tity, the increase in free energ}', we shall denote by A^'.-"-^ In a system
whose properties are determined when the temperature, the pressure,
and the compositions of the various phases are fixed, the general
condition of equilibrium is that,

8(^ = 0.

Let us now consider the change in free energy when one mol of a
given molecular species passes from one state where its activity is t", to
another state where its activity is ^'. This change may be effected as
follows : (1) Pass one mol reversibly from the first state into an ideal
solvent. The solution will have the osmotic pressure n and the vol-
ume V. (2) Change the concentration reversibly until the volume
becomes v' and the osmotic pressure reaches such a value, n', that the

" The completely general definition of free energy is given by the equation,

- A5 = Tr„„, + PJ\ + P\V\ H- . . . - Pj:, - P'„V\^ - • • .

TFmax is the total work obtainable in the process in which system I, comprising
one portion of volume V, at pressure P^, another of volum.e Fo, at pressure Po-
etc., passes over into system II, comprising one portion of volume Vn, at pressure
P2, another of volume Po, at pressure P'o, etc. The free energy as thus defined
is identical with the thermodynamic potential, C, of Gibbs.

VOL. XLIII. — 19

290 PEOCEEDINGS OF THE AMERICAN ACADEMY.

solution is now in equilibrium with the substance in the second state.
(3) Let the substance pass reversibly out of the ideal solution into
the second state. In the first step A^^- = — Uv. In the second,

A2(^ = BT In —. In the third, Aog = n'y'. Since by equation III

the activities are proportional to the osmotic pressures in the ideal
solution, and since ILv = IL'v', the total increase in free energy is,

A5 = i?rin|- XXV

This is a general equation for the change in free energy in the passage
of one mol of a given species from one state to another when the species
itself does not change.^*^ When we are dealing with the most general
case of chemical reaction, when a mols of A, b mols of B, etc., combine
to form 0 mols of 0, p mols of P, etc., the total change in free energy
will obviously be equal to that which accompanies the transfer of the
factors of the reaction from the original system to another system
where there is equilibrium, and the transfer of the products from this
equilibrium system to the original system. By a combination, there-
fore, of equations XXIII and XXV, we find,

AS: = ET\n ;°:f' - ET\n K XXVI

Here A^^ is the increase in free energy in any reaction when i^, ^s,
etc., are the activities of the factors, ^o. ^p, etc., those of the products,
and K is the equilibrium ratio.

Electromotive Force Equations.

The change of free energy of a reversible galvanic cell is a direct
measure of the electrical work of the cell. If E is the electromotive
force of the cell, and F is the Faraday equivalent, then,

A^- = - mFE,

where m is the number of Faraday equivalents which pass through the
cell during the reaction in question, and in the direction in which the
electromotive force E tends to send the current.

20 It would have been possible at the beginning to define the activity by means
of tliis equation, and tliis would liave led to a development of our set of equations,
wliicli fi-om a mathematical standpoint would have been simpler than the one
here adopted.

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 291

This value of Ajv may now be substituted in equations XXV and
XXVI. The former gives a formula for the electromotive force when
only one substance takes part in the electrolytic process, as in certain
concentration cells. The latter gives a general equation for any
reversible cell whatever. These are,

mF k

E= ^>/r- ^>^- XXVIII

mF mF t^^'e

In XXVII, m is the number of Faraday equivalents accompanying the
passage of one mol ; in XXVIII, it is the number accompanying the
disappearance of a mols of A, h mols of B, etc.

One application of equation XXVII is of special interest. We may
take it for granted that whenever two phases are in contact and a given
molecular species is present in one of them, it will be present to some
extent in the other. For example, if a rod of metallic silver dips into
a solution of silver nitrate, we may suppose that silver ions are present
not only in the solution, but also in the metal. The process which
takes place at this electrode during the passage of a current may
therefore be regarded as consisting in the passage of silver ions out of
the electrode into the solution, or vice versa. Equation XXVII gives
us, therefore, an expression for the single potential difference between an
electrode and an electrolyte. If the ion in question is an elementary
one (and monatomic) m is equal to v, the valence of the ion, and we
may write equation XXVII in the following form,

E = %\Jf XXIX

vF $s

where E is the single potential difference, iji is the activity of the ion
in question in the electrode, and ^5 is the activity of the same ion in
the electrolyte. It is obvious that the quantity $^ is very similar
to the electrolytic solution pressure of Nernst, but while the latter
depends at a given temperature, not only upon the character of the
electrode but also upon the nature of the medium in which the elec-
trol5i;e is dissolved, f j/ depends solely upon the character of the elec-
trode. Moreover, while equation XXIX is universally true, the
equation of Nernst is obviously only true when the activity of the ion
in the electrolyte is proportional to its concentration. We have in
the application of equations XXIX (or XXVII) to the electromotive

292 PEOCEEDINGS OF THE AMERICAN ACADEMY.

force of concentration cells a remarkably useful means of determining,
in the case of imperfect solutions, how the activity of a given molecular
species varies with the concentration.

Summary.

It has been shown that a quantity named the activity, and closely
related to the fugacity of the preceding paper, may be so defined that
it serves as an ideal measure of the tendency of a given molecular
species to escape from the condition in which it is. With the aid of
this quantity a series of equations has been obtained, which have the
same form as the approximate equations now in common use, but
which are perfectly exact and general. The utility of these equations
has been illustrated by their application to a number of special prob-
lems. From each equation two approximate equations can be immedi-
ately obtained, one for the vapor pressure of a substance, the other for
its solubility. From equations XXIII, and following, important approxi-
mate equations are obtained by substituting concentrations for activi-
ties. The most general of the equations are collected for reference in
the following list :

For a pure substance,

/gin A _j;

V dF Jt~ It'

mnt\ _Y-Pv

For one constituent of a mixture,

/a]nj\ _ J^

V dP Jt^n" Rf ^^

a In A _Y- Pv
dT )p,N~ RT' '

XII

For all the constituents of a mixture,

fX,d\n^,+K,d In c<, + • • • \ _ V

\ dP Jr^y-Rf' ^^^

Xl\nl,+N,d\nt^+ . . .\ _Y - Pv ^_,^

^^ JP,N RJ-

LEWIS. — A NEW SYSTEM OF THERMODYNAMIC CHEMISTRY. 293

(

N^ In $1 + ^\^ In ^2 + •
For a perfect dilute solution,

= 0.

XVIII

F,T

dKi

XX*

P, T

For the most general case of chemical equilibrium at a given
temperature,

= A" (a constant).

XXIII

For the change in the equilibrium ratio of any reaction with the
temperature,

dlnK U

dT in

,'i-2

XXIV

For the increase in free energy when one mol of a given substance
passes from one state to another,

A5 = i?rin^- XXV

For the increase in free energy in any chemical reaction,

Ar^ = IlT\n^^,

-BTlnK.

XXVI

A'=B'

For the electromotive force of any reversible cell,

mF niF flt^- • •

For the single potential at any electrode,

XXVIII

XXIX

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. S. — October, 1907.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY
OF HARVARD COLLEGE.

THE QUANTITATIVE DETERMINATION OF ARSENIC
BY THE GUTZEIT METHOD.

By Chaeles Eobekt Sangee and Otis Fishee Black.

With Tvto Plates.

THE QUANTITATIVE DETERMINATION OF ARSENIC
BY THE GUTZEIT METHOD.

By Charles Robeet Sanger and Otis Fxshek Black.

Several attempts have been made to apply the so-called Gutzeit
reactions to the quantitative determination of arsenic, especially in
England since the epidemic in 1900 of arsenical poisoning from beer.

Kelj-nack and Kirkby^ suggested that an approximate valuation
of the amount of arsenic in a sample of beer may be made by compar-
ing the stain produced on mercuric chloride paper by the arsenical
hydrogen from a given portion of the sample with that produced by a
definite quantity of a standard solution of arsenic.

Bird 2 made a careful study of the conditions under which the arseni-
cal stain on mercuric chloride paper may be best obtained and identi-
fied, -vsith especial reference to the interference of the hydrides of
sulphur, phosphorus, and antimony. Although his work is extremely
suggestive of a quantitative application, he himself considers that the
test is only approximately quantitative, in that the stain obtained from
a given amount of substance, say beer, may be shown to be greater or
less than the stain representing a fixed limit of arsenic for that amount.
He also regards it as a true negative test.

Treadwell and Comment ^ compared the stain obtained from the
action of arsine on argentic nitrate paper with a series of stains fi'om
definite quantities of a standard solution of arsenic. The method,
applied by these authors to the detection of arsenic in mineral waters,
is said to have given good results.

Dowzard, * after describing a modification of the Gutzeit test which
allows the detection of minute traces of arsenic in a small volume of
solution, suggested the preparation of a standard set of stains, which
should be kept in a tightly stoppered bottle in a dark place.

^ Arsenical Poisoning in Beer Drinkers, p. 88. London, Balliere, Tindall, and
Cox, 1901.

2 Analyst, 26, 181 (1901).

3 'Treadwell, Kiirzes Lehrbuch der Analytischen Chemie, 2, s. 138 (1902).
* Chem. News, 86, 3 (1902).

298 PEOCEEDINGS OF THE AMEKICAN ACADEMY.

Thomson^ attempted to make the reaction quantitative by passing
the arsenical hydrogen through a tube in which was hung a cotton
thread or a paper, saturated with mercuric chloride solution, which,
from the intensity of the stain produced upon it, should show the
amount of arsenic present. Thomson states, however, that his results
were untrustworthy.

Goode and Perkin ^ made a series of experiments to ascertain if the
Gutzeit test could be made quantitative, and if a set of standards could
be prepared which should be at least as permanent as the standard
mirrors of the Berzelius-Marsh process. Stains were made as usual
on paper treated with mercuric chloride, but the impossibility of mak-
ing them permanent led to their abandonment for quantitative pur-
poses, except that a given stain might be matched with freshly
prepared standards.

Langmuir,7 in order to detect the presence of undecomposed arsine
in the Marsh test, placed in the end of the exit tube a slip of paper
moistened with a saturated solution of mercuric chloride. It appar-
ently did not occur to him that this might also be used quantitatively,
but he seems to have employed the ordinary color stains successfully
in the approximate analysis of glycerine for arsenic.

Aside from the above-quoted authors, there are doubtless many who
have been able to use the Gutzeit reactions as a means of approximate
analysis, but we have not met with a careful study of the conditions
under which the reactions maybe employed quantitatively with any
degree of accuracy.

The chief difficulty in differentiating between stains caused by vari-
ous amounts of arsine on either argentic nitrate or mercuric chloride
paper lies in the fact that the action is partly over the surface and
partly within the fibre of the paper. Further, a single layer of paper
is not always sufficient to retain all the arsenic evolved, and stains
from equal amounts of arsine may not always be of the same density.
These difficulties disappear almost entirely if one allows the arsenical
hydrogen to act not against, but along a surface. The principle, there-
fore, of the modification we suggest in order to make the Gutzeit re-
actions more accurately quantitative, is to allow the arsine to pass
over a strip of paper impregnated with mercuric chloride and to com-
pare the band of color thus obtained with a series of bands prepared
from known amounts of a standard solution of arsenic. We think that

" Royal Commission on Arsenical Poisoning, Final Report, 2, 58. London,
Eyre and Spottiswoode, 190.3.
'fi Jour. Soc. Chem. Ind., 25, 507 (1006).
T Jour. Amer. Chem. Soc, 21, 133 (1899).

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 299

the failure of Thomson to get good results was merely due to unsuit-
able conditions.

Our experience has not only confirmed the conclusion which has been
reached by most of those who have investigated the Gutzeit reactions,
that the use of mercuric chloride is preferable to that of argentic
nitrate from a qualitative standpoint, but it has also shown that the
former reagent is the one better suited to the quantitative analysis.

A careful study of the conditions of the reaction, following the prin-
ciple stated above and made for the most part without knowledge of
the work of the above-quoted authors, has shown that the reaction
can be made the basis of a simple and fairly accurate quantitative
method with no more than ordinary analytical precautions.

The Method.

Sensitized Mercuric Chloride Paper. For this purpose we used
at first a smooth filter paper of close texture, but we have recently em-
ployed to greater advantage a cold pressed drawing paper made by
Whatman. The latter not only gives better color results, but also, on
account of its greater strength, withstands better any subsequent treat-
ment for development or identification of the color. A square meter
of this paper weighs about 160 grams (4 1-4 ounces per square yard).
It is cut into strips having a uniform width of 4 mm., and we use for
this purpose a carefully made brass rule of exactly this width. The
cutting may be done with a sharp knife, but more accurately and in
large quantity by the machine which should be accessible at any print-
ing office.

The strips, which must be clean and free from dust, are sensitized
by drawing them repeatedly through a five per cent solution of recrys-
tallized mercuric chloride until they are thoroughly soaked. They are
then placed to dry on a horizontal rack of glass rods or tubing, and,
when dry, are at once cut into short lengths of 7 cm., discarding the
ends by which the strips were held during the immersion. A bundle
of these strips is placed in a stoppered tube or bottle containing calcic
chloride covered by cotton wool, and is kept in the dark until needed.

The Reduction Apparatus. (See Figure A.) This consists of a
glass bottle of 30 c.c. capacity, closed by a pure rubber stopper with
two holes. Through one of these holes passes a small thistle tube,
about 15 cm. long, reaching to the bottom of the bottle and constricted
at its lower end to an opening of about 1 mm. The other hole carries
an exit tube bent first at a right angle, then back again in the same

300

PROCEEDINGS OF THE AMERICAN ACADEMY.

plane in the form of a cz. To this is fastened by means of a rubber
stopper a short bulb tube about 12 mm. in diameter, terminating in a
longer tube which has a bore of slightly over 4 mm. The bulb of this
tube (deposition tube) is loosely filled with clean absorbent cotton
which has been kept over sulphuric acid to insure uniform dryness.
Instead of the bulb tube, the rubber stopper of the exit tube may
carry a short piece of glass tubing of about 12 mm. diameter, in which
is placed the absorbent cotton, and to which, by means of another
rubber stopper, is attached the deposition tube.

Figure A.

The simplicity and compactness of this apparatus allow a number of
determinations to be carried on at the same time by the use of several
pieces. It is important, however, that the bottles be of the same size,
and it is also advisable to have the rest of the apparatus of as nearly
definite size as possible.

Beagenfs. "We have used zinc and hydrochloric acid in preference
to zinc and sulphuric acid, as the action goes on more regularly and
without the addition of a sensitizer. The chance for the formation of
hydrogen sulphide is also less. The zinc, known as Bertha spelter, is
from the New Jersey Zinc Company of New York, and has been proved
by exhaustive tests to be free from arsenic. It contains not over 0.019

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 301

per cent of lead and not more than 0.013 per cent of iron. The hydro-
chloric acid is obtained of the Baker and Adamson Company of Easton,
Pennsylvania, and has been shown by careful analysis to contain not
over 0.02 milligram of arsenious oxide per liter. The dilution em-
ployed, one part of acid to six of water, is equivalent to a normality of
about 1.5. The quantity of diluted acid used in the analysis would
not contain over 0.00004 mg. of arsenious oxide, an amount beyond
the practical limit of the delicacy of the method.^ No evidence of
sulphur, phosphorus, antimony, or arsenic has been obtained from these
reagents when used in long continued blank tests.

Procedure. Three grams of carefully and uniformly granulated zinc
are placed in the bottle, and a strip of sensitized paper is slipped into
the deposition tube to a definite distance, the paper being wholly within
the tube. Fifteen cubic centimeters of diluted acid are then added
through the thistle tube, and the evolution of hydrogen is allowed to
continue for at least ten minutes. At the end of this time the rate of
flow of the gas has become as regular as possible, and the atmosphere
in the deposition tube has a nearly definite degree of saturation with
aqueous vapor. On these two conditions depends chiefly the uni-
formity of color bands from equal amounts of arsenic. In this time,
also, the absence of arsenic in reagents and apparatus is assured, in the
great majority of cases, by the non-appearance of color on the sensitized
paper, but the blank test may be as long continued as circumstances
demand.

The solution to be tested is then introduced, either wholly or in
aliquot part, which may be determined by weighing or measuring. In
the former case we use a side-neck test tube of about 30 c.c. capacity,
and weigh to the second decimal place. Unless the amount of arsenic
be exceedingly small, it is not necessary to add the whole of the solu-
tion, but in that case the volume must be obviously not over 15 c.c,
on account of the capacit)^ of the bottle.

After introduction of the solution the color appears upon the paper
in a few minutes and the deposit reaches its maximum within thirty
minutes. The band of color thus obtained is then compared with a set
of standard bands. From the amount of arsenic as estimated from the
comparison, and the amount of solution from which the band was
obtained, the calculation of the arsenic in the entire solution is
simple.

8 We are also indebted to the Baker and Adamson Company for a preparation
of hydrochloric acid containing a still smaller quantity of arsenic, tlie use of
which will be later explained in the discussion of the absolute delicacy of the
method.

302 PROCEEDINGS OF THE AMERICAN ACADEMY.

Standard Color Bands. A standard solution is made by dissolving
one gram of re-sublimed arsenious oxide in a small quantity of sodic
hydroxide free from arsenic, acidifying with sulphuric acid and making
up to one liter with recently boiled water. Of this solution (I) 10 c.c.
are diluted to a liter with freshly boiled water, giving a solution (II)
which contains 0.01 mg. or 10 micromilligrams (mmg.) of arsenious
oxide per cubic centimeter. In testing the delicacy of the method we
have also prepared solutions containing 1 mmg. (Ill) and 0.1 mmg.
(IV) per cubic centimeter.

From definite portions of solution II, measured from a burette, a
series of color bands is made by the above procedure, using a fresh
charge of zinc and acid for each portion. Figure 1 (Plate 1) shows in
colors the actual size of the set of bands made by us, corresponding to
the following amounts of arsenious oxide in micromilligrams: 2, 5,
10, 15, 20, 25, 30, 35, 40, 50, 60, 70. The color in the lowest values
is a lemon yellow, shading from this to an orange yellow and through
orange yellow to reddish brown in the higher values.

Preservation and Development of the Color Bands. The rapid fading
of the stains has been a serious obstacle to the use of the Gutzeit re-
action for a quantitative method, and it became very soon evident to
us that some means of preserving the color bands must be found before
the method could be considered an entirely practical one. It was
clear that the chief factors in the change of color were light and mois-
ture, the latter being by far the more important. Concerning the
mechanism of the reactions, either for the formation of the color or for
its decomposition with water, the work of those who have investigated
the reactions was not sufficient to guide us.

The early work of Rose ^ on the action of arsine on excess of mer-
curic chloride in solution showed that a yellowish brown precipitate
was formed having the empirical formula AsHgsCls. This was con-
sidered by Rose to be made up of mercurous chloride and a compound
of mercury and arsenic, to which the formula As2Hg3 might be given.

Mayen^on and Bergeret ^° consider the compound to be a ijiixture
of arsenic and mercurous chloride.

Franceschi,^! apparently without knowledge of Rose's work, passed
arsine through an aqueous solution of mercuric chloride. The liquid
became at first a light yellow, then red, and there was precipitated a
substance at first yellow, but with excess of gas a dark red, "of the

9 Pogg. Annal., 51, 423 (1840).
" Comptes Rendues, 79, 118 (1874).
" L'Orosi, 13, 289 (1890).

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 303

color of Spanish tobacco." For this compound Franceschi assumes
from the analysis and properties the formula AsHHg2Cl2, which he

writes:

-H
As - HgCl
-HgCl

Lohmann,^^ who does not mention the results of Franceschi, finds
the reaction to run in a similar manner. But the red product decom-
posed with water, becoming black, and with such rapidity that an
analysis was impossible except through the decomposition products.
From this the formula AsHgsCla was assigned. Lohmann considers
that the reaction is always

3 HgCIo + A3H3 = AsHg3Cl3 + 3 HCI,

whether the precipitation is complete or not, and that the decomposi-
tion of the product depends (a) on the presence of mercuric chloride,
in which case arsenic and mercurous chloride are the products, or (b)
on absence of mercuric chloride, in which case mercury, arsenious acid,
and hydrochloric acid are the products.

Partheil and Amort ^^ note the formula given by Franceschi,
AsHHg2Cl2, but evidently assume that it was for the yellow body (if
such indeed exists) and not for the red, which was clearly indicated
from Franceschi's paper. On this assumption and from Lohmann's
work, they consider that the following is the reaction for the formation
of the yellow body:

2 HgClo -f AsHa = AsHHg2Cl2 -f 2 HCI

and for the red:

3 HgCl2 + AsHs = AsHgsCla + 3 HCI

These reactions were given by Franceschi and by Lohmann respec-
tively, but both of these authors were dealing with the red body.
Partheil and Amort further consider these bodies to have the following
structure, respectively:

-H

-HgCl

As - HgCl

and

As - HgCl

-HgCl

- HgCl

12 Pharm. Zeitutig, 36, 748 and 756 (1801).

IS Ber. d. deutsch. Chem. Gesell.,31, 594 (1898).

304 PROCEEDINGS OF THE AMERICAN ACADEMY.

Passing excess of arsine through the solution in which the red body
is suspended, Partheil and Amort obtain a black precipitate to which
they give the formula AsoHga, and this derives support from the re-
actions with alkyl iodides described by these authors in a succeeding
paper. ^* The investigation is given somewhat more fully in a later
paper by Partheil. ^^ On partial precipitation of a mercuric chloride
solution by arsine, a yellow body was obtained, to which, from a single
analysis of an evidently impure substance, the formula AsHeHgCl was
assigned. From this experiment and from the results of Franceschi
and of Lohmann, Partheil considers that there should be added to the
two substances given above a third, with the structure

-H
As-H
- HgCl

"While the evidence appears to show that the hydrogen of arsine is
replaced by the mercurous chloride group to a greater or less extent,
the formula for the red substance does not seem to us to have been
conclusively proved, and the reactions of decomposition are decidedly
in doubt. Nothing has been brought forward to show definitely the
relation of the yellow compound or compounds, if such exist, to the red.
Lack of time prevents us at present from studying the reaction quanti-
tatively, but it is hoped that the investigation may be taken up later by
one of us. Nevertheless the following qualitative reactions have made
it possible to treat the bands of color so that they may be kept for a
considerable time, either in their original form or by means of a quasi
development and fixation.

The removal of the relatively large excess of mercuric chloride from
the paper by treatment with absolute ether or alcohol did not offer a
solution of the difficulty, as the colors faded rapidly even when kept in
the dark and over sulphuric acid. The color is quickly bleached by
boiling with water, as is well known. Cold water acts more slowly, the
color not being completely changed until after a day or two, and then
not bleached, but converted to a dull gray. Bird,^^ and also Goode
and Perkin,^7 have observed the action of hydrochloric acid upon the
original color, which is thereby considerably changed. Goode and
Perkin also note the action of ammonia upon the original color, but do
not find the action of service in preparing standards.

From the evident effect of even a slight amount of moisture we were

" Ibid., 31, 596 (1898). " Archiv. d. Pharm., 237, 121 (1899).

1* Loc. cit. " Loc. cit.

SANGER AND BLACK. — QUANTITATIVE DETERmNATION OF ARSENIC. 305

led to adopt the suggestion of Panzer, ^^ as applied to the standard
Marsh mirrors, for the preservation of our standards. A clean, dry,
glass tube, about 5 ram. in diameter, is sealed at one end, at which is
placed a small quantity of phosphorus pentoxide covered by a bit of
dry cotton wool. The strip is then inserted, colored end down, fastened
by a drop of Canada balsam, and the tube is sealed. The set of stand-
ards prepared in this way can be used for several months, although the
brilliancy of the color is lost after a few weeks.

The color band may be developed by treatment with rather concen-
trated hydrochloric acid, of a normality of about 6 (one part acid to
one of water). This is done in a small test tube, at a temperature not
exceeding 60° and for not over two minutes, else, with this concentration
of acid, the paper is likely to become disintegrated. The strip is then
thoroughly washed with running water and dried. The color on the
wet strip is a brilliant dark red in the higher values, while the smaller
amounts show a deeper yellow than in the initial set. The length of
the bands is considerably greater than that of the original. On drying,
the color becomes duller. These bands must also be sealed as above
with phosphorus pentoxide, and are somewhat more permanent than
the initial set. Figure 2 (Plate 1) represents the set obtained by
development of the initial set with hydrochloric acid.

If the original color band is treated for a few minutes with normal
ammonic hydroxide, a dense coal black color is produced, of slightly
gi'eater length than the original. This color is far more permanent
than the others, but it is nevertheless necessary to seal the dry strips
in glass, using fresh, powdered quicldime instead of phosphorus pent-
oxide. Figure 3 (Plate 2) shows the set obtained by development of
the initial set with ammonia.

General Precautions.

As far as concerns the reduction of the arsenic, no other precautions
are necessary than those which must be observed in the proper conduct
of the Berzelius-Marsh method when applied to small amounts. The
solution to be reduced should contain no interfering organic matter,
nor any metals which prevent or retard the formation of arsine. Sul-
phur in any form reducible to hydrogen sulphide should be absent. It
is well known that small amounts of hydrogen sulphide interfere with
the Gutzeit reactions, and it is the custom of most analysts to pass the
arsenical hydrogen over paper or cotton wool containing plumbous
acetate, or even through a lead solution, before it reaches the mercuric

18 Zentralbl., 74 (1), 821 (1UC3).

VOL. XLIII. — 20

306 PROCEEDINGS OF THE AMERICAN ACADEMY.

cliloride. As we have been careful to eliminate the sulphur before
testing, we have not found this necessary, except in certain cases, when,
with a sufficiently long deposition tube, it is very simple to insert a
strip of paper saturated with normal plumbous acetate and dried.
Phosphites and hypophosphites will also have been oxidized before
introduction of the solution, and there is little danger in ordinary work
from small amounts of phosphine which might result from the acci-
dental presence of reducible compounds of phosphorus. Antimony
should of course be absent, but very small amounts of stibine do not
interfere with the recognition, though they may prevent the estimation
of arsenic. Free nitric acid must be avoided. Arseniates require
especial treatment, as will be discussed below.

Special Precautions.

In order to be certain of uniformity in length and color of the bands
from the same amount of solution, the following points must be
observed:

1. The reduction bottles must be of equal capacity and the deposi-
tion tubes of equal bore.

2. The amount of zinc must be the same always, and the granulation
must be uniform.

3. The volume and concentration of the acid must be definite.

4. The absorbent cotton must be perfectly clean and reasonably dry,
and is therefore best stored in a desiccator before use. The amount
used should be approximately the same in all cases, packed in the bulb
tube to about the same density.

5. The sensitized paper must be acted upon by a gas in which the
moisture is as nearly constant as possible. For this reason the paper
cannot be allowed to become moist, nor can the gas be dried. In the
first case the band is short and imperfectly shaded ; in the second, it is
scattered along the whole length of the strip, or eyen partially escapes
the paper. This we have shown by attaching a hard glass tube with
capillary, in which, on heating, a mirror of arsenic was obtained. Con-
versely, under carefully regulated conditions, no evidence of escaping
arsenic was found, either by the use of a hot tube or by the iutroduc"^
tion of a second strip of sensitized paper,

6. After ten or twelve runs with the same bottle, the atmosphere of
the deposition tube becomes too moist, and the bands are consequently
too short. ^ It is then necessary to replace the cotton. In order to
get a sufficient degree of saturation in the next run, the evolution of
hydrogen must go on for a longer time than usual before adding the

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 307

test solution, say for an hour. This preliminary saturation may be
also conveniently secured by leaving zinc and acid in the apparatus
over night.

By observation of the above precautions we have obtained fairly
regular and uniform bands of color from equal amounts of arsenic, —

TABLE I.

No. of
Analysis.

A?,©.,
taken.

Total
Weight
Diluted
Solution.

Weight
Diluted
Solution
taken for
Analysis.

Reading of
Baud.

As,03
found.

A.=„03
found,
Mean.

Per cent

AfoOj
found.

mg.

grm.

grin.

mg.

0.05

21.21

5 75

0.009

00.33

6.05

0.012

0.043

0.038

0.10

24.13

5.74

0 024

0.100

7.10

0.027

0.091

0.096

96.

0.25

24.95

3.5

0.037

0.26

2.7

0 025

0.23

0.25

100

0.50

20.11

1.0

0.018

0 47

1.3

0.025

0.50

0.49

1.00

25.02

0.39

0.014

0 90

0.76

0.028

0.92

0.91

1.00

23.76

0.35

0.013

0.88

0.48

0.022

1.09

0.99

1.50

23.88

0.47

0 027

1.37

•

0.47

0.027

1.37

2.00

25.51

o.r.G

0.055

2.15

0.51

0.035

1.75

1.95

2.50

27.04

0.19

0.015

2.13

0.34

0.028

2.24

2.19

\.verage pci

'centascG .

. 93

using apparatus of definite size, reagents of definite concentration, care-
fully sensitized paper, and by passing the arsenical gas over the paper
in a condition of moisture which is as carefully regulated as possible.
Without these precautions, which involve no great care, the method
will not give satisfactory quantitative results.

308 pkoceedings of the american academy".

Analytical Data.

The method, as far as it concerns the determination of arsenic in a
solution properly prepared for reduction, was tested by the analyses
of solutions containing varying amounts of arsenic, which, with the ex-
ception of Nos. 5, 8, 7, and 9, were unknown to the analyst (see Table I).
In analysis No. 9 the arsenic was present as arsenic acid. In Nos. 5, 8,
7, and 9, the comparison was made with standards which had been kept
over three months, and the reading of the bands was confirmed by the
standards obtained by development of the initial bands with ammonia.

We do not claim for the method, under ordinary circumstances, a
greater accuracy than from five to ten per cent.

Analytical Notes.

Sensitized Paper. We have found that the prepared paper, if kept
dry and away from the light, does not lose its sensitiveness to a great
extent after several months. On long keeping there is apparently a
very slight reduction to mercurous chloride, since an old paper after
treatment with hydrochloric acid and washing gives a slight darkening
with ammonia or auric chloride (for this test, see below). Although
this change does not greatly influence the result, it is better not to use
paper which has been kept too long.

Contrary to Goode and Perkin,^^ we have found no advantage in
using mercuric bromide instead of the chloride. Neither the aqueous
solution of the former, which is, in addition, too dilute, nor the alco-
holic solution, gives a paper of greater sensitiveness than that prepared
from the chloride. The alcoholic solution of the chloride, since it
evaporates more rapidly, leaves a less even surface of the salt upon
the paper than is obtained by the slower evaporation of the aqueous
solution.

Apparatus. In case it is necessary to examine larger quantities of
solution for arsenic, a larger reduction bottle will naturally suggest
itself in this case, slight variations from the procedure may be found
necessary, and the absolute delicacy of the method may be some-
what less.

We have found no sign of arsenical contamination from the rubber
stoppers used in the apparatus, and we have therefore not lessened the
simplicity of the apparatus by making it entirely of glass. The stop-
pers are boiled with dilute alkali and washed before use.

" Loc. cit.

SA:!fGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 309

Although we have not tried it for ourselves, it would seem obvious
that the electrolytic reduction of the solution could be employed if
desired.

Reagents. From the delicacy of the method, as discussed below, the
zinc used by us is evidently highly sensitive. Indeed, the amount of
iron present, to which metal, from the work of Chapman and Law,20
Parsons and Stewart, ^i and others, may be attributed the insensitive-
ness of most samples of zinc, is about one-seventh of the amount in a
zinc which Chapman and Law show to be sufficiently sensitive in the
Marsh process.

We have also in this connection studied the effect of the presence
of other metals on the sensitiveness of the zinc. The retention of
arsenic by the addition of platinic chloride or cupric sulphate, con-
firmed by one of us ^^ (S) several years ago, is well known. With a
bright platinum foil in contact with our zinc and using either sulphuric
or hydrochloric acid, we have never noticed any loss of arsenic in the
Marsh procedure. Similarly, there is no diminution in the delicacy of
our method when platinum foil is used. The use of zinc carefully
covered with copper after the procedure of Lockemann ^3 makes no
difference whatever in the results, nor does the addition of tin or lead
salts to the solution during the reduction.

The zinc is granulated by pouring the metal, melted in a porcelain
casserole, from a height of six feet through a hot porcelain sieve into
two feet of cold water.

The estimation of the arsenic in the hydrochloric acid was made on
samples of 100 c.c. in two ways. The acid was distilled to half its
volume, a treatment which we have shown in the following paper ^4 to be
sufficient to expel all the arsenic. The distillate was collected in
35 c.c. nitric acid and evaporated with a small amount of sulphuric
acid. Again, the acid was allowed to drop slowly into hot nitric acid
and the mixture was then evaporated. Several residues obtained by
both of these procedures from lots of 100 c.c. gave closely agreeing re-
sults, both from the reading of the Marsh mirrors and the Gutzeit
color bands. The mean of all determinations was 0.002 mg. for 100
c.c, or 0.02 mg. per liter.

20 Analyst, 31, 3 (19(X)).

21 Jour.'Amer. Chem. Soc, 24, 1005 (1902).

22 These Proceedings, 26, 21 (1891) ; Amer. Chem. Jour., 13, 431 (1891).

23 Zeitschr. f. ansjew. Chem., 18, 41G (1905).

24 These Proceedings, 43, 327 (1907) ; Jour. Soc. Chem. Ind., Vol. 26 (1907);
Zeitschr. f. anorg. Chem., Vol. 56 (1907).

310 PROCEEDINGS OF THE AMERICAN ACADEMY.

This acid was shipped in carhoy, and we have not observed any in-
crease of arsenic in the acid on standing, such as might result from
the action upon the glass if the latter contained arsenic. It is better,
however, that such acid should be shipped, or at least stored, whether
concentrated or dilute, in ceresine bottles.

We have noticed that the nitric acid from the carboy, which gave no
test for arsenic, took up traces from the storage bottle on long stand-
ing. We have therefore stored the nitric acid in cei'esine. A slight
but unimportant amount of paraffine is taken up. 50 c.c. lots of this
acid, evaporated with a small quantity of sulphuric acid, gave residues
which showed no traces of arsenic. It must be borne in mind that a
nitric acid residue contains the arsenic as arsenic acid and that the
procedure must accordingly be modified as explained below.

The second sample of hydrochloric acid, referred to in the footnote
above, was shipped in ceresine, and the diluted acid is also kept in
ceresine. Two 100 c.c. lots of this acid were dropped into nitric acid
and evaporated with sulphuric acid. The residues were reduced with
sulphurous acid free from arsenic and gave color bands equal to 0.3
and 0.5 mmg. arsenious oxide respectively. This is equivalent to 0.004
mg. of arsenious oxide per liter.

P^'ocedure. At the end of a run, a slight annular sublimate is often
observed on the inside of the deposition tube where the color band is
in contact with the glass. With very small amounts of arsenic this
sublimate is white, but is ordinarily slightly colored. It is probably
due to transference of mercuric chloride, either through volatilization
or capillary action, and a slight color "reaction may take place on the
deposit. The amount is without influence on the result, but the tube
should be cleaned with a bit of dry cotton before being used again.

The temperature during reduction should not be allowed to rise
very much, as the moisture equilibrium in the deposition tube is
disturbed from the excess of moisture carried over. For this reason
the procedure of Bird,^^ which consists in heating the liquid under
redaction to the boiling point, is not adapted to this method.

We have found no advantage in using very large amounts of zinc,
as recommended by many, especially in the Marsh process, nor do we
think it necessary that the zinc should be entirely dissolved.

Standard Bands. We have long noticed that solutions of the dilu-
tion of 0.01 mg. per cubic centimeter undergo a change on standing,

25 Loc. cit.

SANGER ANK BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 311

with the result that a given volume "will not yield the same depth of
band as when first prepared, or, in the Marsh process, the same inten-
sity of mirror. In more dilute solutions the change is very rapid, and
solution IV, containing 0.1 mmg. per cubic centimeter, is of no value as
a standard in a day or two. The use of boiled water for dilation
greatly retards the change, which would lead to the conjecture that
the I'eaction might be one of oxidation, with formation of arsenic acid,
which, as shown below, does not give the same depth of color in a given
time as its eiiuivalent of arsenious acid. Yet the treatment of an old
solution with sulphurous acid does not increase the amount of arsenic
from a given portion of it, as far as we have been able to determine.
Solution IV (0.1 mmg.) should be freshly prepared before use; solu-
tion II (10 mmg.) will hold its strength for a few weeks, and solution I
(1 mg.) should not be used if it has stood for a very long time.

The deposit of color is of course on both sides of the paper. If the
strip exactly bisects the tube and the flow of hydrogen is the same in
both segments, the intensity of color should be the same on each side
of the strip. It often happens that there is a slight difference, and in-
consequence the band may appear on one side greater than the stand-
ard, on the other less. The set of standards is also a series of mean,
though not greatly varying color densities, and when viewed from one
side or the other may not seem regularly graded. The set should be
mounted in such a way that both sides of the strip can be examined,
and the mean density of the test band should be compared with the
mean density of the standard. The judgment is greatly assisted by
treating the band or its duplicate with hydrochloric acid or ammonic
hydroxide (particularly the latter), and comparing the result with the
corresponding standards.

Treatment of the Bands. Whatever may be the formula of the red
compound, it is probable that the reaction is only complete in the
presence of an excess of hydrochloric acid. As previously mentioned,
the color fades completely on treatment with hot water. Cold water
brings about a gradual fading, but this is succeeded by a secondary
reaction by which a gray substance is formed. This action of water
was further studied by treatment with sodic acetate. A set of stand-
ard bands was immersed in half-normal sodic acetate for two hours in
the cold. The red color gave place to a uniformly graded light yellow
with a tinge of orange. The set, after pressing between filter paper,
was then sealed while still moist. In twenty-four hours the yellow
had changed to a dull white, with no color except in the higher values.

312 PROCEEDINGS OF THE AMERICAN ACADEMY.

On the next day there was a change to a faint gray, becoming darker
on further standing.

The black color with amnionic hydroxide suggests the presence of
mercurous chloride, but it is not clear whether a decomposition into
mercurous chloride takes place before the black color is formed. If
the red band is treated with hydrochloric acid, washed, and then
placed in ammonic hydroxide, the color is not an intense black, but
rather grayish in tone.

Another reaction of interest is that with auric chloride. If the
band, after treatment with hydrochloric acid, is placed in a small test
tube with a few drops of hundredth normal auric chloride and allowed
to stand for five or ten minutes, a beautiful purple color results. The
reaction is characteristic for larger amounts of arsenic.

The reaction of the formation, development, and decomposition of
the color bands are susceptible of various interpretations, but, as we
have said before, a quantitative study is necessary before expressing
an opinion, not only as to the formula of the red body and the mech-
anism of its formation and decomposition, but also on the existence
of intermediate yellow compounds or their formulae.

Bird 26 tas applied Bettendorff's reaction to the stains, substantially
as follows : The disk of paper containing the color is extracted with
one or two cubic centimeters of warm, concentrated hydrochloric acid.
The extract is oxidized by a few drops of bromine in hydrochloric acid
and treated in a small test tube with an equal volume of 30 per cent
stannous chloride. On warming, the pinkish brown color appears.

Interference of the Hydrides of Sulphur, Phosphorus,

AND Antimony.

There is considerable confusion in the statements of various authors
as to the color stains from these gases on mercuric chloride paper, and
even Bird's more careful study is open to the common criticism that
the descriptions are not given with reference to known amounts of the
hydrides. In determining to what extent these substances interfere
in our method, we have at first ascertained by trial how much of the
particular hydride will give a comparable band on the mercuric chlo-
ride paper under the same conditions, — particularly in the same time.
We then studied the effect of a given treatment upon each color band,
and afterward compared the effect of each reagent upon the four ap-
proximately equivalent bands.

25 Loc. cit.

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 313

Hxjdrogen Sulphide. In a freshly prepared solution of sulphurous
acid, which gave no test for arsenic, the amount of sulphur was deter-
mined by titration with iodine. A solution was made containing
1 mg. of sulphur per cubic centimeter, and from this, in turn, a second
containing 0.01 mg. Of this solution amounts corresponding to 10,
30, 50, and 70 mmg. sulphur were added to separate reduction bottles
and the action continued for thirty minutes. Bands of a pale yellow
were obtained, slightly darker in shade than those from phosphine.
The respective lengths corresponded to those from 2, 25, 30, and
40 mmg. arsenious oxide. Fresh strips of paper were now substituted
and each experiment was continued for thirty minutes longer. No
additional band was obtained from the first ; from the others the
values were approximately 1, 5, and 10 mmg. This shows that under
the same conditions and in equal time the band from 50 mmg. sulphur
will be of about the same length as that from 30 mmg. of arsenious
oxide, and further, that the reduction of the sulphurous acid is not com-
pleted in thirty minutes, like the arsenic, but requires a longer time.

The color of the sulphur band is somewhat brightened by hydro-
chloric acid (6 N) but not essentially changed, nor was the length
increased. Auric chloride produced a dirty light brown. Ammonia
on the originq,l band gave also a light brown color.

Phosphine. A sample of sodic hypophosphite, containing no arsenic
on testing, was shown by analysis to contain 28.94 per cent of oxidiz-
able phosphorus (theory, 29.23). Of this a solution was made contain-
ing 1 mg. of phosphorus per cubic centimeter, from which two others
were prepared having 0.1 and 0.01 mg. to the cubic centimeter. Of
the last solution, 10, 30, 50, and 70 mmg. were reduced for thirty min-
utes in separate bottles. From 10 mmg. no color was obtained, from
30 mmg. a very faint indication, and from 50 and 70 mmg. bands cor-
responding in length to only about 2 and 10 mmg. of arsenious oxide
respectively. After continuing the action for thirty minutes longer,
with fresh strips, there was again no color on the first, a faint indication
on the second, and about 1 and 10 mmg. on the third and fourth. It
was evident that the reduction was very slow. Next were taken 100,
300, and 500 mmg. After thirty minutes the length of the first band
corresponded to about 2 mmg. of arsenious oxide, the second 30, and
the third 50, showing that not over one tenth of the phosphorus had
been reduced in the given time. On opening the bottles the odor of
phosphine was strong.

To obtain a band from the hypophosphite equal to that from
30 mmg. arsenious oxide in the standard time, an amount equivalent

314 PROCEEDINGS OF THE AMERICAN ACADEMY.

to 200 or 300 mmg. phosphorus is necessary. The color of the bands
was a bright yellow, somewhat resembling that from hydrogen sul-
phide. Hydrochloric acid makes the band a bright lemon yellow, but
without increasing its length. The yellow turns slowly brown when
exposed to light. Auric chloride acts very slowly, giving at first a
characteristic brownish red, which changes to purple. Ammonia acts
more slowly than on the arsenic band, giving a less intense black.

Stihine. The solutions used were made from a sample of pure tar-
tar emetic, which had been shown to be free from arsenic. They con-
tained respectively 1.0, 0.1, and 0.01 mg. of antimonious oxide per
cubic centimeter. Volumes corresponding to 10, 30, 50, and 70 mmg.
of the oxide were added to separate bottles and the reduction carried
on for thirty minutes. No color was obtained in any case. Hydrochlo-
ric acid did not develope. Auric chloride brought out slowly a purple
color, duller finally than that of a similarly treated arsenic band. Am-
monia turned the band quite quickly black, and a comparison with the
arsenic ammonia standards showed amounts equal to about 20 to 40
per cent of the arsenic values. On further reduction for thirty minutes,
with fi-esh strips, there was no additional deposit on the paper which
could be developed by ammonia. Continuing the experiments, it was
found necessary to add 100 mmg. of antimonious oxide before any vis-
ible band was obtained, and 200 mmg. before the band appeared to be
of the same length as that from 30 mmg. of arsenious oxide. The color
was a faint gray when first visible ; darker with increasing amounts.
The development with hydrochloric acid and auric chloride or with
ammonia showed of course that the paper had been originally affected
over a much gi-eater length than was then visible.

These results agree with those obtained by Franceschi,27 who
found by the action of stibine on mercuric chloride a white body to
which he gave the formula SbHHgsClo, analogous to the formula as-
signed by him to the red arsenic compound. Dowzard,^^ also, was
unable to obtain a stain on mercuric chloride paper from 0.01 to
0.1 mg. of tartar emetic, v;hile irom 0.2 mg. he got a faint black-
ish brown color, a result which is essentially confirmed by our
experiments.

Comparative Effect of Reagents. From the necessary amounts of
each substance, as shown by the above trials, approximately equal
color bands were prepared from arsine, stibine, phosphine, and hydro-
s' L'Orosi, 13, 397 (1890). 28 jour. Chem. Soc, 79, 715 (1901).

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OP ARSENIC. 315

gen sulphide, with a reduction of thirty minutes' duration. Each set of
four was then treated with various reagents and the effects compared.

Initial Baud. The arsenic band appears in a few minutes and is
nearly complete before the others begin to form. The deposit is char-
acteristic and unmistakable. The phosphorus and sulphur bands are
a uniform pale yellow, rather difficult to distinguish from each other.
The antimony band is a faint gray.

Exposure to Air. On standing over night in rather moist, warm
air, the arsenic baud was slightly bleached, the others unchanged. On
longer exposure the phosphorus band was turned slightly brown on
the upper side, and the sulphur band became slightly dark on the
upper edge. Heating to 105° had no additional effect on any of the
bands.

Cold Water. The initial set was placed in cold water. After fifteen
minutes the antimony band was bleached completely, the phosphorus
became paler, while the arsenic and sulphur were unchanged. After
fourteen hours the arsenic was considerably bleached, but was still orange
red, while the phosphorus had become a very faint yellow and the sul-
phur was unchanged.

Hot Water. The set was boiled with water for one minute. The
arsenic and antimony bands were changed to a grayish white, the
phosphorus was bleached to a faint yellow, while the sulphur was
unchanged. On standing, the sulphur band became light brown.

Hydrochloric Acid. The set was warmed to 60° with hydrochloric
acid (G N) for one minute and thoroughly washed. The arsenic band
was lengthened and became the usual brilliant red. The antimony
was turned slightly gray. The phosphorus became a brilliant lemon
yellow, and the sulphur was also brightened, but not so strikingly.
On drying, the colors became duller, and on the upper end of the
sulphur band was a fringe of dark gray.

Auric Chloride. The dried set from the last treatment was im-
mersed in auric chloride (n/100) for five minutes. The arsenic band
became at once a brilliant purple ; the antimony changed more slowly.
The phosphorus slowly turned a characteristic red brown, then to pur-
ple, and the final colors of these three bands differed chiefly in inten-
sity. The sulphur band had only a slight brownish tinge.

AmuTouia. The set was placed in normal ammonic hydroxide for
five minutes. The arsenic band became at once a brilliant black ; the
antimony also quickly, but the band was longer and duller in shade.
The phosphorus turned slowly black and was not equal finally to the
other two in intensity. The sulphur band was not blackened, but
changed slightly to a pale brown, somewhat darker on dryinf

ig-

316 PROCEEDINGS OF THE AMERICAN ACADEMY.

From these results it will be seen that if we have a color hand from
pure material, within or above the range of the 4 mm. arsenic stand-
ards, the differentiation of arsenic from antimony, phosphorus, and
sulphur is perfectly simple. With smaller amounts, or especially with
mere traces, there can be no confusion with antimony, since stibine
gives no yellow color on the paper. With sulphur, while the small
initial band might be mistaken for arsenic, the treatment with hot
water, ammonia, and auric chloride will easily identify it. But with
phosphorus there is likely to be a doubt if the 2 mm. band ^9 is very
small, since the amount and length of the color do not permit the
same comparison as in the larger bands. As we have shown, however,
that even as much as 0.1 mg. of phosphorus gives very little color in
thirty minutes of reduction, and as this is a quantity which can be easily
oxidized in the preparation of the solution for analysis, we should have
little to fear from smaller amounts than 0.1 mg. Such amounts might
be considered quite accidental.

Effect of Hydrogen Sulphide, Phosphi7ie, or Stibine on the Arsenic
Band. Very ditt'erent is it, however, when the arsenic solution also
gives by reduction as much of any one of these gases as would alone
yield a band equal to the arsenic band in length. This is shown by the
following experiments.

Hydrogen Sulphide. Amounts of the respective solutions, equal to
30 mmg. of arsenious oxide and 50 mmg. of sulphur, were added to-
gether to a bottle and reduced for thirty minutes. Instead of the short,
well-defined band of the arsenic, a band nearly three quarters of the
length of the strip was formed, of a reddish yellow color. Hydrochlo-
ric acid turned it slightly redder, but the appearance was not definitely
characteristic of arsenic. On another similar band ammonia brought
out splotches of black on a red ground. The arsenic had evidently
acted as an accelerator in the reduction of the sulphurous acid, and the
resulting band was due to a mixture of the arsenic and sulphur com-
pounds, spread over a greater surface.

Phosphine. Solutions containing 30 mmg. arsenious oxide and
200 mmg. phosphorus were added to a bottle and reduced for thirty
minutes. The band was longer than the corresponding band of ar-
senic, but with the characteristic appearance of the latter, — well
shaded, except that it was somewhat lighter at the top. Hydrochloric
acid converted the color to the well-marked red of arsenic and the
length agreed with the hydrochloric acid standard for 30 mmg. Auric

29 For the use of tlie 2 mm. band, see below.

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 317

chloride acted more slowly than with arsenic alone, giving a slight
brownish red at first and finally a somewhat lighter purple than the
pure arsenic color. There was apparently little increase in evolution
of phosphine in the presence of the arsenic, and the arsenic compound
in the mixed band was not appreciably obscured.

Stibine. Solutions containing 30 mmg. arsenious oxide and 70 mmg.
antimonious oxide were reduced together for thirty minutes. The re-
sulting band was pale red in color and over twice as long as the band
from 30 mmg. of arsenious oxide. Hydrochloric acid gave a color not
essentially different, which faded on drying to a rather dirty brownish
red. The evolution of the two hydrides was apparently more rapid
than either alone, and the mixed baud was longer than from either
amount.

It is evident from the above results that if we have with the arsenic
an amount of hydrogen sulphide even below that required to give a
band of the same length as the arsenic, the latter will be so altered as
to make its quantitative estimation impossible and its detection doubt-
ful. But, as unavoidable amounts of hydrogen sulphide would be held
back completely b)^ lead acetate paper, we should have no difficulty in
estimating the arsenic if the solution had not been properly oxidized
before testing. Even if the solution contains considerable reducible
sulphur, the lead acetate paper will protect the mercuric chloride
strip.

We have also little to fear from phosphine, since we should not put
a solution into the reduction bottle until the phosphorus had been
oxidized as completely as possible. Accidental amounts of phosphine
would not affect the quantitative estimation of the arsenic. We have
not thought it necessary, for this reason, to verify the statement of
Dowzard ^'^ that phosphine is held back by cuprous chloride in hydro-
chloric acid solution, nor have we sought any other reagent which
could be adapted to this purpose under the conditions of our method.

In the presence of stibine arsenic may be qualitatively recognized,
but not quantitatively determined, when the amount of antimony is
enough to give, if alone, an ammonia band equal to that of the arsenic.
But we should not test a solution without getting rid of any antimony
it might contain, and the methods for that purpose are satisfactory.
Slight traces of antimony would not affect the determination.

If the arsenic is accompanied by any two or all three of the sub-
stances in question, cases which we think would seldom arise, their in-

3* Loc. cit.

318

PROCEEDINGS OF THE AMERICAN ACADEMY.

fluence on the determination of the arsenic could be predicated from
the foregoing investigation.

To sum up, then, yre think that small amounts of arsenic can be
determined by our method without danger of interference from sul-
phur, phosphorus, and antimony, provided the solution to be tested is
freed as carefully as possible from these substances and the additional
precaution is taken to place a strip of lead acetate paper in front of
the test paper.

From the comparative rarity of the hydrides of selenium and tellu-
rium and the unlikelihood of their occurrence in ordinary practice, we
have made no study of their action on mercuric chloride paper. One
would suppose from analogy, also, that the reactions in small amount
would be similar to that of hydrogen sulphide. We note in this con-
nection that Rosenheim -^^ states that hydrogen selenide has no influ-
ence on the Gutzeit test, unless in large quantity, if lead acetate paper
is used.

The results of the above experiments are tabulated for comparison
as follows :

TABLE II.

Eeactions of Color Bands within the Range of the Arsenic Standards

FROM ApPROXIxMATELY EQUIVALENT AMOUNTS OF ArSINE, StIBINE, PhOSPHINE,

AND Hydrogen Sulphide.

Element.

Amounts
taken for
Reduction.

30 mmg.
(AS2O3).

200 mmg.

(SboOg).

200 mmg.
(P)-

Initial
Band.

Orange

yellow
to red

Faint
gray

Pale
yellow

50 mmg. Dull
(S). yellow

Action of
Air.

Slightly
faded

Un-
changed

Pale

brown
where
exposed
to light

Un-
changed

Cold
Water.

Consid-
erably
bleached

Bleached

Consid-
erably
bleached

Un-
changed

Hot
Water.

Grayish

white

Grayish
white

Faint
yellow.

Un-
changed.
Onstiind-
ing, light
brown.

Hydro-
chloric
Acid.

Dark

red

Grayish

Bright
lemon
yellow

Brighter
yellow

Auric
Chloride.

Bright
purple

Dull
purple

Red
brown
to
purple

Slightly
brown

Ammonia.

Dense
black

Dull
black

Gray
black

Pale
brown.

31 Chem. News, 83, 277 (1901).

sanger and black. — quantitative determination of arsenic. 319

The Procedure in Presence of Arseniates.

It is well known that the reduction of an arseuiate solution to arsine
goes on more slowly than that of an arsenite. This is provided for in
the Marsh procedure by continuing the reduction for a longer time when
arsenic acid is present ; fully an hour, or, if small amounts are present,
still longer. The deposition of the mirror being in a comparatively
small compass, its size and appearonce are not appreciably changed,
within the range of the standards, by the slower accumulation of the
arsenic particles. In the Gutzeit procedure the case is different for
two reasons. The formation of the color bands is over a greater sur-
face and the standard set is based on the deposition of the color in a
short time, which, in turn, depends upon a comparatively quick reduc-
tion of the arsenious acid. Not only will some arsenic escape reduction
during this time, if arsenic acid is present, but the slower congregation
of the particles will result in a shorter band. Hence, from a given
amount of arsenic as arseniate, the reading of the color after thirty min-
utes is invariably low. The subsequent reduction may be studied frac-
tionally for sixty to ninety minutes, with successive strips, although the
colors from the last fractions may only be shown by the 2 mm. strips (see
below). The proportion of color within thirty minutes has been shown
by us from repeated trials to be reasonably definite. It is rarely over
50 per cent of the standards, rarely under 40 per cent, and the bands
formed are somewhat denser in appearance. This implies that the band
from an arseniate, though shorter, contains more arsenical substance
than a band of the same length from an equivalent amount of arsenite,
and this is borne out by the fact that the subsequent color estimations
from the continued reduction do not apparently carry the total per-
centage of arsenic to more than 80.

There ave two ways of approximately estimating the value of the
color bands derived from arseniates. We may either make a series of
standards from known amounts of arsenic as arsenic acid, with which
the test band from an arseniate may be compared, or we may multiply
the reading of the ordinary standards by 2 or 2.5. Either of these
alternatives will answer, more simply the latter, — though both are
obviously inexact, — if one's object is only to get a rough idea of the
amount of arsenic present. The estimation can be made, however,
within the ordinary limits of the method, if the arseniate is converted
to arsenite before reduction to arsine.

Before arriving at the procedure finally adopted, we studied the
effect on the reduction of an increase of temperature and also that of
various catalyzers. A solution containing 10 mmg. of arsenious oxide

320 PROCEEDINGS OF THE AMERICAN ACADEMY.

as arsenic acid was prepared by evaporating 10 c.c. of solution I repeat-
edly with nitric acid and making up to one liter. The bottles were
heated during the reduction in an air bath in such a way that all above
the necks protruded. At 60° the bands obtained from 3 c.c. of the
arseniate solution after thirty minutes of reduction were only about 43
per cent of the standard for 30 mmg. of arsenious oxide. Parallel trials
with 3 c.c. of the arsenite solution gave bands of the standard length.
Another experiment at 90° gave no better results. The bands from
the arseniate solution were not over 50 per cent of the standard, while
the parallel arsenite reductions gave shorter bands than at ordinary
temperature, owing to the larger amount of moisture carried over.
That a reduction at the boiling point would cause a practically com-
plete conversion to arsine, as claimed by Bird, seems improbable, while
the moisture equilibrium would be so disturbed as to invalidate the
procedure.

Returning to the reduction at ordinary temperature, it was found
that no increased effect was produced Avithin the standard time by the
addition of stannous chloride or potassic iodide. Platinum in contact
with the zinc, even when the acid was more concentrated, was of no
service, and the use of copper-covered zinc did not help. An appre-
ciable increase but not a complete reduction was effected by sesquisul-
phate of titanium. It was evident that the use of a catalytic agent did
not solve the problem with such small amounts of arsenic, and we
were therefore forced to a reduction of the arseniate to arsenite before
testing. For this purpose we found sulphurous acid the simplest
substance, since comparatively little is needed, no excess of reagent
need be left in solution, and it can easily be prepared free from
arsenic.

The sulphurous acid solution was made from pure copper and pure
sulphuric acid, and was saturated at 0°. The solution gave no test for
arsenic when tested in quantities larger than would be used in an
analysis. The tests were made after boiling' out the sulphur dioxide
from the samples.

"We tested the efficacy of the sulphurous acid as follows : Four por-
tions of the arsenic acid solution, corresponding to 10, 20, 30, and 40
mmg. of arsenious oxide, were evaporated in small glass dishes with
6 c.c. of the sulphurous acid until the excess of sulphur dioxide was
apparently expelled. On adding the residues to the reduction bottles,
the color bands came up quiclcly as in the case of arsenites, and in thirty
minutes all the bands were equal to the corresponding standards in
length and intensity of color. Subsequent trials conducted similarly
confirmed these results. The precaution was taken to use the lead

SANGER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 321

acetate paper, on which in some eases there was a slight deposit of the
sulphide. ^^

In practice, when the solution contains an arseniate, or when the
substance has been oxidized, say by nitric acid, one may add a suffi-
cient quantity of sulphurous acid to the entire solution or to the ali-
quot portion taken for reduction. In analysis No. 9, Table I, we
followed the latter plan, adding 10 c.c. of sulphurous acid in two parts,
the second after partial evaporation. The excess of sulphur dioxide
is then expelled, but the evaporation must not be carried too far, as
chlorides, if present, would cause a loss of arsenic. In testing the
residues the lead acetate paper should be used.

The Absolute Delicacy of the jMethod.

For most practical purposes the set of standards from 2 to 70 mmg.
is sufficient. Amounts of arsenic between 2.0 and 0.5 mmg. can be ap-
proximated by the 4 mm. strip, but in studying the limit of delicacy
we have allowed the action to take place within a smaller compass.
The ordinary strip is cut in two, and these pieces are again divided
lengthwise, giving a piece 2 mm. wide and 35 mm. long. This is in-
serted in a tube of slightly more than 2 mm. in diameter, which is
fitted into the usual deposition tube by a washer of rubber tubing.
With these small strips a series of standards may be made from
10 mmg. down. "The yellow color appears definitely, though of course
slightly, from 0.5 mmg. Treated with hydrochloric acid, ammonia, or
hydrochloric acid and auric chloride, the indication is much sharper,
and from this amount up to 10 mmg. the gradation of the 2 mm. stan-
dards is well marked. From 0.3 mmg. the yellow color is exceedingly
faint, but development with the reagents brings it out. At 0.2 mmg.
the formation of yellow is no longer seen, but treatment with hydro-
chloric acid gives a faint but definite color, which under the glass is
seen to be greater than the effect produced by 0. 1 mmg. Development
with ammonia or auric chloride is also definite. From 0.08 mmg. a
faint fringe of color is visible under the glass after treatment with
hydrochloric acid, and the indication is even sharper with ammonia
or auric chloride. From 0.05 mmg. no results were obtained. These
tests were made on two solutions, prepared at different times.

Between 0.05 and 0.08 mmg. is clearly the limit at which we have
been able to detect any arsenic by the mercuric chloride paper under
the conditions of our method. It is safe to set this limit at 0.08 mmg.

32 We have found tliat tlie lead acetate paper is more sensitive to liydrogen
sulphide than the mercuric chloride.

VOL. XLIII. — 21

322 PROCEEDINGS OF THE AMERICAN ACADEMY.

(0.00008 mg.) of arsenions oxide, "which is equivalent to 0.00006 mg.
of metallic arsenic or one seventeen-thousandth of a milligram.

In the above tests, on quantities under 10 mmg., the hydrochloric
acid containing 0.004 mg. arsenious oxide per liter was used. This, in
15 c.c. of the diluted acid, assured a quantity of arsenic far below the
above limit, while blank tests of over an hour's duration gave negative
results. The deposits from these small amounts were formed within
thirty minutes, and each reduction was continued thirty minutes
longer.

Although the method is a very delicate one, as shown by the above
tests, we are far from claiming that 0.08 mmg. of arsenious oxide can
be recognized by it with certainty under the varying conditions of
analytical practice. We are not so much concerned with the absolute
delicac}', however, as with the amount which may be considered a
practical limit, the recognition of which is definite under all conditions,
and which, when obtained from an aliquot portion of a solution, may
safely be used as a factor in the quantitative determination of the
arsenic. In this particular we agree fully with Chapman and Law,'^^
who have expressed the opinion that in the Marsh method 5 mmg.
should be taken as a practical limit, and that one's efforts should be
directed tov/ard recognizing this amount with certainty. We consider,
therefore, that 1 mmg. (0.001 mg.) of arsenious oxide may be set as
the practical limit of our method, although less than one tenth of this
amount may be recognized under favorable conditions. The color
produced on the large or small strip by 1 mmg. need not be confused
with that from hydrogen sulphide, stibine, or phosphine, if these are
unavoidably present, while the more minute traces of color, though
not easily confounded with those from the first two, are similar in
appearance to that from the last. We have found by trial that 0.1
mmg. of arsenious oxide, if present as arseniate, can be recognized after
reduction with sulphurous acid.

Previous estimates of the delicacy of the Gutzeit test have not been
under 0.1 mmg., so far as we know, with the exception of that made
by Dowzard,^* who states that one fifteen-thousandth to one twenty-
thousandth of a milligram can be recognized by the modification
described by him. This figure is practically the same as ours.

The Use of the Method.

The method naturally suggests comparison with the Marsh in the
present accepted form of the latter. In the modification described by

33 Zeits. f. angew. Chem., 20, 67 (1907). 34 Lqc. prim. cit.

SAKuER AND BLACK. — QUANTITATIVE DETERMINATION OF ARSENIC. 323

one of us (S.) in 1891,"^^ in which a standard set of mirrors was em-
ployed for the first time, the absolute limit of delicacy was placed at
1 mmg. of arsenious oxide. The most important improvement in pro-
cedure which has been made of late years is the cooling of the capil-
lary tube, described by Gautier,-^^ Thomson, "^7 Lockemann,*^^ and
others. By this means the scattering of the deposit of arsenic is pre-
vented and the mirror takes a more compact and hence more easily
identifiable form. In spite of this advantage, we have not been able,
as yet, to reach the absolute limit of delicacy in the Marsh process
which is set by Thomson at 0.4 mmg. of arsenious oxide, by Locke-
mann and others at 0.1 mmg. arsenic. We cannot think that this
failure is due to insensitiveness of the zinc, but to other reasons not
yet discovered. Sanger and Gibson ^^ have shown, for example, that
the nature of the antimony mirror depends upon the kind of glass
tubing used, and they suggest that a gTeater or less oxidation of the
stibine may take place in the accidental presence of air, if the glass
contains a catalyzing agent. If this were true, it is easy to imagine a
slight retention of the arsenic from the same cause, since the oxide
formed would be fixed by the base of the glass. This point will be
soon investigated in this laboratory.

Not only, as far as our experience goes, has the Gutzeit method
proved to be more sensitive than the Marsh, but we think it will be
found so by others. In certain lines of work, in which the sample
may be tested directly or quickly freed from interfering substances,
the Gutzeit in the form proposed by us may be preferable to the
Marsh, particularly when the routine analysis of a large number of
samples is concerned. In toxicological or legal work it will serve as a
valuable adjunct to the ]\Iarsh method, since the exhibits from both
methods can be presented and will corroborate each other, qualita-
tively or quantitatively. Though not convertible, like the Marsh
mirror, to a definite and obvious compound of arsenic, yet the color
band can be easily differentiated from the effect produced by other
substances on mercuric chloride.

We have not studied the application of the method to the analysis
of many products, though we have used it successfully for the deter-
mination of arsenic in wall paper, in the urine, and in certain salts.

^' Loc. cit.

36 Bull. Soc. Cliim., 27, 1030 (1902).

3T Chem. News, 88, 228 (190:3) ; also, 94, 156 and 166 (1906).

38 Loc. cit.

39 These Proceedings, 42, 719 (1907) ; Jour. Soc. Chem. Ind., 26, 585 (1907J ;
Zeits. f. anorg. Chem., 55, 205 (1907).

324 PROCEEDINGS OF THE AMERICAN ACADEMY.

Its usefulness will depend upon its adaptability to the needs of the
analj'-st, and it may be modified to meet his conditions. For instance,
in the examination of beer, if the analyst must add the sample to the
reduction bottle without previous treatment, there should be adequate
provision for* the retention of hydrogen sulphide, the prevention of
frothing, etc. We are not at all sanguine of the success of the method,
however, unless the test solution has had adequate treatment before
reduction.

During the study of the interference of sulphur, phosphorus, and
antimony, as given above, the possibility of quantitatively determin-
ing small amounts of these substances by this method, particularly of
antimony, suggested itself. We desire to note also that the principle
of allowing the gas to be tested to act along the surface of the react-
ing substance has a useful application in other cases, notably in the
determination of fluorine, and we are at present engaged in developing
a method for the estimation of small amounts of that substance
according to this principle.

In conclusion, it gives us pleasure to acknowledge our indebtedness
to the C. M. Warren Fund of Harvard University for material assist-
ance in the preparation of the colored plates used in this article.

Harvard University, Cambridge, Mass., U. S. A.,
August, 1907.

Sanger and Black. -Arsenic by Gutzeit Method.

PLAt 1.

ii^

5 10 15 20

25 30 35 40 50 60 70

Fig. 1.

Standard Arsenic Bands in Micromilligrams of AS2O3

Initial.

5 10 15 20

25 30

Fig. 2.

Standard Arsenic Bands in Micromilligrams of As^Og
Hydrochloric Acid Development.

35 40 50 60 70

pROc Amer. Acad. Arts and Sciences. Vol. XLIII.

Sanger and Black.— Arsenic by Gutzeit Method.

Plate 2.

ill

2 5 10 15 20 25 30 35 40 50 60 70

Fig.

Standard Arsenic Bands in Micromilligrams of As^Oa
Ammon:a Development.

Proc. Amer. Acad. Arts and Sciences. Vol. XLIII.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 9. — October, 1907.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF
HARVARD COLLEGE.

THE DETERMINATION OF ARSENIC IN URINE.

By Chaeles Robert Sa^'GEB a>'D Otis Fishee Black.

THE DETERMINATION OF ARSENIC IN URINE.
By Charles Robeet Sanger and Otis Fisher Black.

Presented January 9, 1907. Received August 20, 1907.

Some years ago one of us (S.) had occasion to make a number of
analyses of urine in cases of suspected chronic arsenical poisoning.^ In
looking up the literature of the subject at that time, it was found that
the analysis of the urine in case of chronic arsenical poisoning had
been comparatively rare. In the twenty-three cases cited by Sanger
in which the urine had been examined and the methods of analysis de-
scribed, the latter were generally open to adverse criticism. They were
usually tedious and often involved the use of many reagents, thereby
adding to the possibility of introduction of arsenic. The amounts of
arsenic found, in the absence at that time of any method for the deter-
mination of small quantities, could only be judged from the descrip-
tions of the mirrors, but probably did not exceed 1 mg. of arsenious
oxide per liter, and in many cases must have been less than 0.1 mg.
In the only analysis found in which quantitative results were given,
the amount was stated to have been 16.8 mg. in 1700 c.c, but the
method of analysis was not given, hence this case was not included in
the twenty-three above mentioned.

The method used by Sanger for the treatment of the urine was based
on that proposed by Gautier ^ for the general treatment of animal
tissue. To a measured volume of urine was added about one tenth the
volume of concentrated nitric acid, and the whole was evaporated over
a free flame. As the mass neared drjmiess the flame was lowered, and
more acid was added, if necessary, in order to avoid carbonization at
the end. Deflagration often ensued, but it was thought that loss of
arsenic should not be feared in presence of excess of nitric acid. To
destroy the organic matter completely, the residue fi'om evaporation
was transferred to a smaller dish, treated with sulphuric acid, and
heated for some time, with addition of nitric acid, until a clear, white,
partly melted mass was obtained. The residue, free from nitric acid,

1 These Proceedings, 29, 148 (1894).

2 Ann. d.-Chim. et d. Phvs , [5] 8,384 (1876); Bull. Soc. Chim., [2] 24, 250
(1875).

328 PROCEEMNGS OF THE AMERICAN ACADEMY.

was diluted with water and introduced into the Marsh flask. The
amount of arsenic was determined by Sanger's ^ modification of the
Berzelius-Marsh method.

In the twenty cases of suspected arsenical poisoning referred to in
the above paper, thirty-one samples of urine were examined by this
method, and in no instance was the amount of arsenic (as arsenious
oxide) greater than 0.07 mg. per liter. The analytical precautions
were such as to preclude the introduction of arsenic from any outside
source. Prior to these analyses but one instance had been found in
which a method for the quantitative estimation of arsenic in urine had
been described. Hubbard,^ in studying the elimination of arsenic by
the kidneys, added the urine directly to the Marsh flask and deter-
mined the weight of the mirror according to the gravimetric Berzelius-
Marsh method, first applied by Gautier,^ and afterwards elaborated by
Chittenden and Donaldson ^ and others. While the amounts of
arsenic found by Hubbard (varying from 0.35 to 1.12 mg. per liter)
were undoubtedly a close approximation, the method cannot be applied
to minimal amounts with certainty on account of the impossibility of
accurately weighing small mirrors and the effect of the presence of
organic matter on their deposition.

The treatment described above has been used by several analysts 7
in the determination of arsenic in urine. Unfortunately it was not
accurately tested by the analysis of urines containing known amounts
of arsenic, partly on account of lack of time, partly through acceptance
of the Gautier method. The assumption that all of the arsenic pres-
ent was accounted for was probably incorrect, as our present work
will show.

The method is a troublesome one, requiring much time for evapora-
tion and the destruction of the organic matter, as care must be taken
to have the latter entirely eliminated, since the accurate determination
of the arsenic is impossible in its presence. The use of large quanti-
ties of nitric acid is unpleasant and may introduce error. These con-
siderations, together with the much more important one of possible loss
of arsenic, have led us to substitute for the destruction of the organic
matter with nitric acid a distillation of the arsenic from the evaporated
urine by means of hydrochloric acid.

3 These Proceedings, 26, 24 (1891) ; Amer. Chem. Jour., 13, 4:31 (1891).
* rhysiciau and Surgeon, Ann Arbor, Mich., 4, 348 (1882) ; Contr. Chem. Lab.
Univ. Mich., 1, Part I (1882). b Loc. cit.

6 Amer. Chem. Jour., 2, 235 (1881).

7 Putnam-Worcester, Bost. Med. Surg. Jour., 124, G23 (1891); Wood, Ibid.,
128,414 (1893); and others.

SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 329

The distillation of arsenic from organic matter by hydrochloric acid,
first used successfully by Schneider ^ and Fyffe,^ is a common proced-
ure and needs no explanation. We have not been able, however, to
find any instance of its application to the analysis of urine. The only
serious objection is the difficulty of obtaining hydrochloric acid with a
negligible amount of arsenic. Fortunately such an acid is obtainable
at low cost in this country, ^^ and one does not have to resort to the
troublesome methods of purification, which to some are prohibitive of
the use of hydrochloric acid in arsenic work.

Not only is the distillation method more accurate, but it will also
be shown that, in point of time for the entire operation, the advantage
is greatly in its favor, particularly, as we have said before, if the careful
elimination of the organic matter is made a prerequisite to the intro-
duction of the solution into the Marsh flask.

The Method.

Apjjarafus. For distillation, a 300 c. c. round-bottom flask is used,
with a neck about 20 cm. long. The side tube, which is about half-
way up the neck, is 20 cm. in length, and is bent downward in the
middle at an obtuse angle, so that it passes into an upright condenser
parallel to the neck of the boiling flask, which is closed by a short glass
tube sealed off at each end, over which is slipped a short piece of rub-
ber tubing. A glass-stoppered boiling flask could advantageously be
used. The cooling tube is 50 cm. long, with a jacket of 35 cm. The
side tube of the flask passes through a rubber stopper in the neck of
the condenser and as far into the cooling tube as possible. The con-
densing tube passes at the bottom through a rubber stopper, over which
is slipped a wide tube 15 cm. long, similar to a chloride of calcium
tube, having a bulb of about 25 c.c. capacity near the lower end, which
terminates in a tube of ordinary bore. To this end is fused a tube of
equal diameter about 15 cm. long. The arrangement is practically a
pipette-shaped adapter, similar to that used in ammonia distillation,
and is intended to prevent the rise of distillate into the condenser in
case of back pressure. The distilling apparatus is conveniently set up
in duplicate, mounted on two stands (see Figure A), and is placed in
the hood under a strong draught.

Distillation. 200 c.c. of urine are evaporated in a porcelain dish
over a low flame or on the steam bath to about 35 c.c, cooled, and in-

8 Pogg. Ann., 85, 483 (1851).

9 Jour. f. prakt. Chem., 55, 10-3 (18-52).

1" Baker and Adamson Chemical Company, Easton, Pa.

330

PROCEEDINGS OF THE AMERICAN ACADEMY.

troduced into the flask, which is then connected with the condenser.
Under the adapter is placed a small flask containing 25 c.c. concen-
trated nitric acid, which should just cover the end of the adapter.
There are then added, through a long funnel tube, 100 c.c cool, con-

PlGURE A.

centrated hydrochloric acid, in which the amount of arsenic is as small
as possible and accurately determined. The stopper of the flask is at
once inserted.

Distillation is begun with a low flame and is continued at such a
rate that the volume of the liquid in the flask is reduced to about half
in the course of thirty to forty minutes. Repeated trials have shown
that all the arsenic, in the quantities for which this method is intended,
goes over by this operation, whether the arsenic is present as arsenious
or arsenic acid. As by far the greater part of the arsenic goes over

SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 331

with the gaseous hydrochloric acid and meets the concentrated nitric
acid, no loss is to be feared from the dilution of the nitric acid by the
acid distillate. Comparatively little organic matter is distilled, and
this is entirely destroyed by the subsequent procedure.

Treatment of the Distillate. To the distillate are added 25 c.c. con-
centrated nitric acid, in order to decompose completely during evapora-
tion any excess of hydrochloric acid and thus guard against loss of
arsenic. The mixture is then evaporated to a small bulk, three to
five cubic centimeters of concentrated sulphuric acid added, and the
evaporation continued until the nitric acid is expelled. To destroy the
slight amount of organic matter which usually remains, a few drops of
nitric acid are added, and the heating is continued until only the small
residue of sulphuric acid is left, which must be colorless. The residue
is then diluted with water to a measured volume of about 25 c.c, or,
if preferred, to a quantity which is weighed in a side-neck test tube to
the second decimal place.

Determination of the Arsenic. The subsequent procedure, as in the
paper above referred to, follows closely the method of Sanger ^^ for
determining small amounts of arsenic, except that the capillary tube
should be cooled at the deposition point of the mirror, as advised by
Gautier,^^ Thomson,^"^ Lockemann,^* and others. An aliquot portion
of the ultimate solution, accurately measured or weighed, is introduced
into the Marsh flask, the entire apparatus having been in action for a
sufficient time to show absence of arsenic. This time varies according
to the importance of the test in hand, but should not be less than twenty
minutes. If, after the addition of the solution, a mirror does not make
its appearance in the capillary tube within ten minutes, a larger portion
or the whole of the solution is added. After the appearance of the
mirror the heating of the tube is continued for a sufficient time to
insure the complete deposition of the arsenic, which usually occurs
within an hour. During this time the flow of hydrogen is regulated
by the constant generator, so that the height of the flame at the end
of the heated tube is about one millimeter, the regular deposition of
the mirror being dependent on this condition. The mirror obtained
is compared with a set of standards, which is prepared as explained in
the paper referred to. From the amount of solution used and the

" Loc. cit.

" Bull. Soc. Chim., [2] 27, 1030 (1902.)

" Chem. News, 88, 228 (1003).

" Zeitschr. f. angew. Chem., 18, 416 (1905).

332 PROCEEDINGS OF THE AMERICAN ACADEMY.

volume of urine taken, the quantity of arsenic per liter is calculated.
Should the mirror exceed in size the standard of 0.06 mg., it may be
necessary to obtain another mirror from a smaller portion of the solution
or from a smaller volume of urine, since the reading of mirrors above
0.06 mg. is not accurate.

The determination of the amount of arsenic in the solution may also
be made by the modification of the Gutzeit method described by us in
the preceding paper. ^^ In this case, owing to the size of reduction flask
used, the volume of the solution should not exceed 20 c.c, of which an
aliquot part or all may be taken. This method consists briefly in
allowing the arsenical hydrogen to pass through a tube containing a
strip of paper saturated with a five per cent solution of mercuric
chloride and dried. The resulting band of color is compared with
a set of standard bands.

Reagents. The zinc used, known as Bertha spelter, irom the New
Jersey Zinc Company of New York, has been used in this laboratory
for many years, and has been exhaustively tested for arsenic with nega-
tive results. It contains not over 0.013 per cent of iron and not more
than 0.019 per cent of lead. The amount taken is from five to ten
grams. We have used it in a rather finely granulated form in the
reduction bottle, reserving the larger pieces for the constant generator.
As the metal is too pure to generate hydrogen with sufiicient rapidity
from sulphuric acid, we place in the reduction bottle a thin disk of
platinum foil nearly as large as the bottom of the bottle. With this
the evolution of the hydrogen is most regular. That the platinum
does not cause arsenic to be held back, we have assured ourselves by
obtaining mirrors of equal size and same appearance as those formed
without the disk. The deposition of platinum on the zinc by use of
platinic chloride is, however, not allowable, as one of us has shown, ^^
and cupric sulphate is equally inadmissible. The formation of a coat-
ing of copper on our zinc, after the procedure of Lockemann,!^ does
not add to its sensitiveness, nor does the addition of tin or lead salts
to the solution during reduction. In the constant generator, the zinc
is sensitized, according to the suggestion of Gooch,!^ by treatment
with a solution of cupric sulphate, but we take the precaution to pass
the hydrogen from the generator through a ten per cent solution of

" These Proceedings, 43, 297 (1907) ; Jour. Soc. Chem. Ind., Vol. 26 (1907) ;
Zeitschr. f. anorg. Chem., Vol. 56 (1907).
" Loc. cit., p. 39.
" Loc. cit.
18 Amer. Jour. Science, [3] 48, 292 (1894).

SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 833

cupric sulphate in order to retain any hydrogen sulphide which may
be formed.

The sulphuric acid is from the Baker and Adamson Chemical Com-
pany, and has never shown a trace of arsenic when tested in greater
quantity and for a longer time than in a single determination. In the
constant generator it is used at a dilution of 1 to 8 ; in the reduction
bottle somewhat more dilute (1.5 normal).

The hydrochloric acid is also obtained of the Baker and Adamson
Company. Two grades ^^ have been used : the ordinary chemically
pure acid (A), which was found by repeated trials to contain 0.4 mg.
arsenious oxide per liter ; and a second (B), in which we have determined
by careful analysis an amount equal to 0.02 mg. per liter.

The nitric acid is an ordinary, chemically pure acid, tested in large
quantity after evaporation with sulphuric acid and found to be entirely
free from arsenic, both by the Marsh and Gutzeit tests.

Utensils. All glass and porcelain vessels were new, and, after freedom
from arsenic was assured by blank tests, were reserved for this purpose
alone.

Analytical Results.

BlanJc Tests. 1. 100 c.c. hydrochloric acid (A) were diluted with
35 c.c. water and distilled into 25 c.c. nitric acid. From the evaporated
distillate a mirror was obtained equal to 0.04 mg. arsenic. ^o Amount
per liter, 0.4 mg.

2. 100 c.c. acid (A) were added, drop by drop, to 50 c.c. hot nitric
acid in a porcelain dish. The mixture evaporated with sulphuric acid
gave a mirror equal to 0.04 mg. arsenic. Amount per liter, 0.4 mg.

3. 100 c.c. hydrochloric acid (B) were diluted with 35 c.c. water and
distilled into 25 c.c. nitric acid. The evaporated distillate gave a
mirror which was judged to be about 0.003 mg. arsenic.

4. 200 c.c. acid (B) were added, drop by drop, to 100 c.c. hot nitric
acid and the resulting mixture evaporated with sulphuric acid until
the nitric acid was expelled. From this was obtained a mirror which
was read as 0.002 mg. arsenic.

From analyses 3 and 4 it was evident that there was a trace of

" A third grade (C) has been obtained from the same source since the comple-
tion of the analytical work on this paper. In this acid, which is of exceptional
purity, the amount of arsenic is not over 0.004 mg. per liter.

2*5 In these analyses "arsenic," unless otherwise specified, means arsenious
oxide.

334 PROCEEDINGS OF THE AMERICAN ACADEMY.

arsenic in the acid (B), probably about 0.002 mg. in 100 c.c. or
0.02 mg. per liter.

5. 300 c.c. urine were evaporated to 30 c.c. and distilled with 100 c.c.
hydrochloric acid (A) into 25 c.c. nitric acid. One half of the solu-
tion from the evaporated distillate gave a mirror equal to 0.02 mg.
arsenic ; the other half, a color band (Gutzeit) equal to 0.02 mg. The
amount of arsenic per liter is therefore 0.4 mg., which confirms the
results of analyses 1 and 2, and the test shows the urine to be free
from arsenic.

6. 200 c.c. urine were evaporated to 30 c.c, and distilled with 100 c.c.
acid (B) into 25 c.c. nitric acid. The distillate, evaporated with a
little more nitric acid, gave a mirror which, as nearly as could be
judged, was equal to 0.002 mg. This confirms, within the limits of
reading, the results of analyses 3 and 4, and enables us to fix the cor-
rection for 100 c.c. of this acid at 0.002 mg. This has been since
confirmed by the analysis of the acid by the Gutzeit method. The
correction is only appreciable, as will be seen from Series B, below, when
the entire solution gives a very low mirror, and entirely disappears
when the miiTor, even if a low one, is obtained from a small part of the
solution (see Series C).

The third grade of hydrochloric acid (C), which will hereafter be
used in all urine work in this laboratory, was tested as in analyses 2
and 4. After reduction of the residues from two lots of 100 c.c. with sul-
phurous acid, color bands were obtained equal to 0.3 and 0.5 micro-milli-
grams (0.001 milligram) of arsenic. This is equivalent to 0.004 mg.
arsenic per liter. The correction for 100 c.c. of this acid, 0.0004 mg.,
would be practically inappreciable under ordinary conditions of the
Marsh procedure, even if the mirror was obtained from the entire solution.

Analyses. For use in the subsequent analytical work, a solution of
arsenious acid was made as follows : One gram of pure arsenious oxide,
twice resublimed, was dissolved in a small amount of sodic hydroxide
free from arsenic. After acidification with sulphuric acid, this solu-
tion was made up to a liter. Of this, 10 c.c. were diluted to a liter,
giving a solution containing 0.01 mg. arsenious oxide to the cubic
centimeter.

7. 150 c.c. urine, to which had been added 0.025 mg. arsenic, were
evaporated to 25 c.c and distilled with 100 c.c. hydrochloric acid con-
taining 0.035 mg. arsenic. The total amount was 0.06 mg. 25 c c.
of distillate were collected in 25 c.c. nitric acid, and from this was ob-
tained a mirror equal to 0.06 mg. 50 c.c. more of the distillate were
collected in 15 c.c. nitric acid, and from this no mirror was found.

SAJTGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 335

8. By the same procedure as in analysis 7, and also with 150 c.c.
. urine, 25 c.c. distillate gave 0.06 mg. arsenic, equal to the amount

taken. 50 c.c. additional distillate gave no mirror.

9. With 200 c.c. urine and the same amount of arsenic, the same
procedure gave 25 c.c. distillate containing 0.06 mg. arsenic, and
50 c.c. additional distillate yielded no further mirror.

The results of analyses 7, 8, and 9 show that by distilling one half
the contents of the flask, according to the method above described, all
the arsenic passes over.

The following series shows that by the former method of destrojdng
the organic matter by evaporation with nitric acid a very large error
is made :

SERIES A.

Nitric Acid Method.

No of Analj'sis.

Volume of Urine
taken.

AsoOj added.

AsoOs recovered.

Per cent
recovered.

10
11
12
13

c.c.
500

500

800

100

mg.
250

2.5

0.3

mg.
6.0

0.44

0.00
0.00

In analyses 10 and 11, actual deflagration took place; in Nos. 12
and 13 the residues were blackened.

The next series, B, p. 336, gives the results of a preliminary trial of
the distillation treatment, and shows that by the distillation method
very small amounts of arsenic can be recovered with practical com-
pleteness. As a more severe test of the method, 0.01 mg. arsenic
was added to a liter of urine and the analysis carried out as usual,
using acid B (Analysis 39). A mirror was obtained fully equal to the
standard for 0.01 mg.

Even with the correction for this acid, we thus recover from 80 to
100 per cent of the amount of arsenic taken, which shows that, con-
sidering the amount of organic matter involved and the hydrochloric
acid used, the method is a delicate one. By the use of an acid of such
purity as that of grade C, it will be possible to eliminate entirely the
correction for arsenic in the acid, even if the amount of arsenic in the

336

PKOCEEDINGS OF THE AMERICAN ACADEMY.

SERIES B.
Distillation Method.

No. of Anal-
ysis.

Volume
Urine taken.

AS2O3 added.

As^Oa in 100
c.c. HCl.

Total
AF2O3 taken.

A.2O3
recovered.

Per cent
recovered.

c.c.

mg.

200

0.10

0.04

0.14

100

0.15

0.19

0.16

0.05

0.09

100

0.15

0.19

0.10

0.20

0.24

100

Average per cent recovered, Nos. 16 to 2

0 . . . .

....

. 92

0.07

0.002

0.072

0.077

107

0.06

0.002

0.06

0.04

0.042

0.04

0.03

0.032

0.03

0.02

0.022

0.02

0.01

0.012

0.01

AverJiP'f T^pr r'pnf rppovprpfl. N^ns /ift tn P

3 . . . .

. 95

— o- i-^- -^•■

entire test solution is as low as 0.01 mg., since the correction is only
four per cent of this quantity, which is well within the limit of accu-
racy of the method itself "With larger amounts than 0.01 mg. the cor-
rection for this acid is of course of even less account.

Presence of Arseniates in the Urine. The compound in which arsenic
occurs in the urine has never to our knowledge been thoroughly inves-
tigated. To determine accurately the condition of such small amounts
as would ordinarily occur would be a matter of considerable difficulty-
Schmidt and Bredtschneider 21 claim to have found arsenic acid and

Moleschott's Untersuchungen, 6, 146 (1859).

SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 337

no arsenious when arsenic was ingested as the trioxide. Selmi ^^ states
that he found in the urine of a dog poisoned by arsenic a volatile com-
pound of the element. The reference gives no analytical details and
the original is not accessible to us. It is not improbable, however,
from the analogy to phosphorus, that arsenic finds its way into the
urine as an arseniate. If this be the case, the question will perhaps
be asked if small amounts of arseniate, when distilled with hydrochlo-
ric acid, would be recovered in the distillate or would require a pre-
liminary reduction before distillation.

Mayerhofer ^3 has shown that if arsenic acid is distilled with a suf-
ficiently large quantity of hydrochloric acid, it is converted to arsenic
trichloride, chlorine being given off, since the pentachloride does not
exist under ordinary conditions. In our method the concentration of
the hydrochloric acid in 100 cc. of its solution would be so great
compared with that of the arseniate that a complete conversion to tri-
chloride might be predicted. That this is the case is shown by the
following analyses, in which the arsenic acid used was prepared by
evaporating a measured quantity of arsenious acid solution to dryness
with nitric acid before adding to the urine.

SERIES C.

Distillation Method in Presence of Aeseniates.

No. of
Analysis.

Volume
Urine
taken.

AB0O3

added, as
HjAsOi.

AsoOj in
100 c.c. HCl.

Total AS2O3
taken.

AfoOa
recovered.

Per cent
recovered.

40
41

c.c.

200

mg.
0.25

0.50

mg.
0.002

mg.
0.252

0.502

mg.
0.25

0.50

99.2
99.6

Analyses of Urine. The method was finally tested by the analysis
of six samples of urine to which varying amounts of arsenic had been
added by one of us, the amounts not being known to the analyst.

22 Mem. d. Accad. d. Scienze, Bologna, [4] 1, 299 (1882) ; ref., Gazz. Chim. Ital.,
12,558(1882).

23 Ann. Chera. u. Pharm., 158, 326 (1871).

VOL. XLIII. — 22

338

PROCEEDINGS OF THE AMERICAN ACADEMY.

SERIES D.
Distillation Method.

No. of
Anal-
ysis.

As,03

per

Liter.

Volume
Urine
taken.

pres'ent

in
Volume
taken.

Total

Af203

iu
Volume
taken.

AF2O3

found

in
Volume
taken.

Corrected
(Cor-
rection,
0.04 mg. )

AS2O3

found

per

Liter.

Per

cent

found.

mg.
0.5

c.c.
200

mg.
0.10

mg.
0.14

mg.
0.15

0.11

mg.
0.55

110

2.0

0.40

0.44

0.38

0.34

1.70

1.0

0.20

0.24

0.23

0.19

0.95

1.5

0.30

0.34

0.33

0.29

1.45

0.8

0.16

0.20

0.17

0.13

0.65

1.2

0.24

0.28

0.24

1.20

100

Average

per cent

found .

. 95

To show the calculation of the analysis, one example will suffice :

No. of
Analysis.

Volume Urine
taken.

Volume of
Solution used.

Volume of
Solution taken.

Reading of
Mirror.

Reading of
Mirror, Average.

c.c.

200

c.c.
50

c.c.

mg.

a) 0.025

b) 0.030

mg.
0.028

Amount in solution
Less correction for

taken, 10 X 0.028 . . ,
nci

. = 0.28 mg.
0.24 "
= 1.2 "

Amount ner litpr nr

ine, 5 X 0.24

Comparison of Methods. In order to compare more fairly the distil-
lation method with the method of evaporation, the latter was slightly
modified to secure the most favorable conditions for the recovery of
the arsenic. 200 c.c. urine were evaporated to about 50 c.c, and then
treated with 25 c.c. conceiitrated nitric acid and 5 c.c. sulphuric acid.
Evaporation was continued until the fumes of sulphuric acid appeared,
which left a dark residue containing a large amount of organic matter.
By successive addition of small amounts of nitric acid and heating,

SANGER AND BLACK. — DETERMINATION OF ARSENIC IN URINE. 339

this residue was oxidized after a very long time, so that it appeared
nearly colorless. The diluted residue was then added to the reduction
bottle. A series of analyses was made by this method in which the
amounts of arsenic were not known to the analyst.

SERIES E.
Nitric Acid Method, Modified.

No. of
Analysis.

AsoOj per
Liter.

Volume
Urine taken.

AsjO, present

in Volume

taken.

As.,03 found
in Volume

taken.
(Corrected.)

As,03

foimd per

Liter.

Per cent
found.

mg.

c.c.

mg.

0.8

200

0.16

0.13

0.65

1.0

0.20

0.08

0.40

0.5

0.10

0.50

100

2.0

0.40

0.24

1.20

1.2

0.24

0.12

0 60

1.5

0.30

0.18

0.90

'erage per c

ent found .

. 65

From comparison of Series D and E, it will be seen that the distilla-
tion method is more accurate than the evaporation method, even if
the latter is carefully conducted so that the loss from carbonization is
avoided as far as possible. But the time needed for a proper treatment
with nitric acid by the latter method is very great, and the manipula-
tion uncleanly. The entire preparation of the solution for testing, in
the distillation method, does not consume more than three fifths of the
time required in the other, and the procedure is much cleaner.

Use of the Method.

We have not studied the question of how small an amount of
arsenic can be recovered from the urine by this method, but have been
content to show that very small amounts, even as little as 0.01 mg.
per liter, can be detected and estimated with reasonable accuracy.
(Series A and Analysis No. 39.) For the examination of abnormal
urine, — in studying the elimination of arsenic through the kidneys,
for instance, — it would be seldom necessary to consider a quantity

340 PKOCEEDINGS OF THE AMERICAN ACADEMY.

smaller than 0.01 mg., although the delicacy of the Marsh and Gutzeit
methods permits a fairly exact estimation of much smaller amounts.
If the question of the occurrence of arsenic in normal urine is to
be investigated, — and we hope that opportunity for such an important
study may be found at some future time in this laboratory, — the deli-
cacy of the methods is secondary in importance to that of the source
and manner of collection of the urine. The absolute delicacy of the
Marsh method is claimed by Thomson 2* to be 0.0004 mg. of arsenious
oxide, by Lockemann^s and others, 0.0001 mg. arsenic, and we have
been able to recognize by our modification of the Gutzeit method as
little as 0.00008 mg. of arsenious oxide. But until it is shown that a
urine has had absolutely no arsenical contamination, such extreme
delicacy is apt to be misleading.

The use of the method in the analysis of other liquids containing
organic matter suggests itself, for example in the more exact determin-
ation of arsenic in beer. Although the distillation of small quantities
of arsenic from animal tissue with hydrochloric acid has been rejected
by Lockemann ^5 and others, either on account of the amount of arsenic
in commercial, pure acid, or the difficulty of purifying the acid, yet
we believe that the distillation of organic matter with acid of only
0.004 mg. arsenic to the liter would not introduce a serious error into
an investigation of the normal occurrence of arsenic in the organs
of man.

Hakvard Univeksity, Cambridge, Mass., U. S. A.,
August, 1907.

2* Loc. cit. 25 Loc. cit.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 10. — November, 1907.

CONTRIBUTIONS FROM THE FIRST CHEMICAL INSTITUTE OF
THE ROYAL FRIEDRICH-WILHELM UNIVERSITY OF BERLIN.

THE TRANSITION TEMPERATURE OF MANGAN0U8

CHLORIDE: A NEW FIXED POINT

IN THERMOMETRY.

By Theodore W. Richards and Franz Wrede.

Investigations on Lioht and Heat made and fcblished, ■wholly or m pakt, with Appropriation

PROM the Rumpord Fund.

CONTRIBUTIONS FROM THE FIRST CHEMICAL INSTITUTE OF THE
ROYAL FRIEDKICH-WILHELM UNIVERSITY OF BERLIN,

THE TRANSITION TEMPERATURE OF MANGANOUS

CHLORIDE: A NEW FIXED POINT

IN THERMOMETRY.

By Theodoke W. Richards and Franz Wrede.

Presented by T. W. Richards. Received October 7, 1907.

In several previous articles one of us ^ has set forth in detail the
advantages of the transition temperatures of crystallized salts as fixed
points for thermometry. A number of suitable salts have been sug-
gested, and in particular the sulphate and bromide of sodium have
been carefully investigated. For these salts the transition tempera-
tures, referred to the international hydrogen scale, have been found to
be, respectively, 32.383° C. and 50.674°C. ; and both of these salts have
been shown to give points constant and definite enough for convenient
use for the above-mentioned purpose.

Among the salts studied by Richards and Churchill in an approxi-
mate fashion was manganous chloride (MnCl2 • 4H2O). This salt has
also been investigated roughly by Kuznetzoff, and by Dawson and
Williams.2 AU of these investigations were merely approximate ; no
attempt was made to correct the thermometer for the errors of ordinary
thermometry. Therefore they were none of them suitable for defining
the point with sufficient exactness for the present purpose. On the
other hand all of the investigators agreed in maintaining that the point
was constant and definite. Therefore it promises well ; and the pres-

1 T. W. Richards, Am. J. Sci. [4], 6, 201 (1898) ; Richards and Churchill, These
Proceedings, 34, 10 (1899) ; Richards and Wells, These Proceedings, 38, 431 (1902),
41, 435 (1906). These four papers are all to be found in full in tlie Zeitschr.
fur phys. Chem., the references being respectively 26, 690 (1898) ; 28,313 (1899) ;
43, 465 (1903) ; 56, 348 (1906). The present paper also will appear in German in
that periodical.

2 Kuznetzoff, Chem. Centralblatt, 1899, I, 24fl ; Dawson and Williams, Zeit.
fiir phys. Chem., 31, 59, 1899.

344 PROCEEDINGS OF THE AMERICAN ACADEMY.

ent paper recites briefly a series of experiments giving much greater
definiteness to the point in question and making it available for the
verification of thermometers.

Preparation op the Manganous Chloride.

As material for preparation the purest manganous chloride and
nitrate of commerce were used. Several preparations made in different
ways assured certainty in the product.

The manganous chloride was purified in the first place by crystalliza-
tion and centrifugal treatment. Through these processes it was passed
four times, after solution in ordinary distilled water, and twice after
solution in the purest water. Porcelain and platinum dishes were
used. This preparation was called la. Two more crystallizations gave
16, which was found to have essentially the same transition point.
Sample Ic was made from the two last mother liquors by further re-
crystallization. This also gave the same point. During these crystal-
lizations traces of iron were found to exist in the otherwise very pure
initial salt ; these traces disappeared in the very early stages of the
crystallization. This was proved by qualitative tests, which were care-
fully verified by suitable blank determinations.

The purity of the salt, as indicated by the transition temperature, is
shown by the following table. Obviously the transition temperature
may be used as a guide concerning the freedom of the salt from every-
thing except isomorphous substances, especially for the present purpose.
The crude original substance had a transition temperature of 57.91°:
the first fraction, 58.03° : the second, 58.05° ; the fourth, 58.072° ;
the sixth, 58.089° ; the eighth, 58.090° ; and the ninth, 58.089°.

For the preparation of the chloride from the nitrate of manganese,
this nitrate was recrystallized until wholly free from iron. It was
precipitated as carbonate by means of redistilled ammonium carbonate.
This substance was prepared by distillation with water in a platinum
condenser and collected in a platinum dish in which the manganous
carbonate was precipitated. The precipitate was boiled with many
portions of pure water until no more trace of nitric acid was found in
the wash water. It was then dissolved in concentrated pure hydro-
chloric acid and the chloride was three times recrystallized to eliminate
the traces of chlorine due to the excess of nitric acid, and also the
traces of hydrochloric acid. The salt gave the same transition tem-
perature as the previous sample, although it had been passed through
such different treatment. Therefore it seems reasonable to infer that
both samples were pure.

EICHARDS AND WREDE. — TEMPERATURE OF MANGANOUS CHLORIDE. 345

It is perhaps worthy of note that manganous chloride has been found
by Kahlenberg, Davis, and Fowler ^ to be only very slightly hydrolyzed
at 56°, a temperature very near the transition temperature, 58°. The
hydrolysis at this temperature is not enough to cause, during the time
of the transition experiment, any considerable chance for the forma-
tion of the higher oxides of manganese by action of the air on the
slightly hydrolyzed solution. This is of course particularly true of the
highly concentrated saturated solution at 58°.

Determinatign of Transition Temperature.

Great care was taken in this work. Besides common thermometers
for the determination of the temperature of the thermostat, etc., three
instruments of great precision were used.

These were as follows :

1. Normal thermometer (of Jena glass, 5S"^ about 48 cm. long.
The scale of this thermometer extended from 0° to 100" with bulbs
between 5° and 18°, and between 65° and 95°. This instrument was
made by Richter of Berlin especially for this determination, and was
used in the preliminary experiments which were made to show the
constancy point of the purest salt. The results are given in the sixth
column of Table I. An accident to the thermometer prevented its
exact calibration, but its results are exact relatively to one another,
and in this respect are just as good as if this calibration had been
carried out.

2. A Beckmann thermometer, No. 30, Richter (Jena glass, No. 59™).
This thermometer was somewhat larger than usual and made with
great care. Its column showed an unusually slight tendency to ad-
here to the glass, and gave, as will be seen, extraordinarily constant
readings. The scale was divided into one-hundredths. All deter-
minations made with the other thermometers were also made with this
instrument, which thus served as a means of comparing and controlling
them. The results are given in the Tables. The particular point in
question, 0.508° on this scale, was standardized with great care by the
Physikalisch-Technischen Reichsanstalt and found to correspond to the
temperature 58.090° on the international standard. After it had been
standardized, the same thermometer was used again for determining
the transition temperature, and gave the same results, thus showing
that the mercury in the bulb had remained constant in amount under
the very careful treatment which it had received.

On account of the breaking of thermometer 1, we desired to confirm

' Kahlenberg, Davis, and Fowler, J. Am. Chera. Soc, 21, 1, 1899.

346 PROCEEDINGS OF THE AMERICAN ACADEMY.

the results of the Beckmann instrument with another carefully standard-
ized normal thermometer which had been directly compared with the
standard of the Reichsanstalt. Accordingly another one was procured.

3. Normal thermometer No. 512, Richter (Jena glass, 59"^). This
thermometer was 65.5 cm. long ; the whole scale between 0° and 100°
was divided into one-tenth degrees. The scale itself had a length of
57 cm. This instrument was tested with the greatest care in the
Reichsanstalt, not only as regards its calibration and behavior under
pressure, but also as regards the exact position of particular points,
especially the point 59.090°. This was found to read upon this
thermometer 58.330°, referred to the hydrogen standard, after cor-
rection for the ice point and for external pressure; the error here
being -1-0.240°.

The observed values for the transition point in question, determined
with the third thermometer, and also the correction for the tempera-
ture of the thread, external pressure, and position of the ice point, are
to be found in Table II. Further, in that table are given the exact
temperature computed in terms of the hydrogen scale, and also the
control determinations made simultaneously with the Beckmann ther-
mometer. The errors of the small extra thermometers for the thermo-
stat, etc., were also carefully determined at this point in their scales.

In order to carry out the determination of the transition temperature
with a mercury thermometer, it is necessary to have the stem of the
thermometer at the same temperature as the bulb. With high tem-
perature the error, due to neglect of this precaution, may be very great.
In determining a transition temperature, it is impracticable to immerse
the whole thermometer in the melting mixture ; therefore some other
device is necessary in order to maintain the thread of the thermometer
at the right temperature. In the past we have used two devices for
this purpose. In one case the thermometer was surrounded by a glass
tube, through which circulated water of the right temperature. This
device works very well, except that it is difficult to prevent cooling of
the water. The other device consisted in a deep thermostat, above
which the thermometer just projected. In the present series of deter-
minations we have altered this latter arrangement by making the
thermostat of glass, using a very tall glass beaker 52 centimeters in
height and 14 centimeters in diameter, surrounded at the sides with
asbestos paper and with long narrow windows in front and behind for
observation. A sketch of this apparatus is given in the accompanying
diagram. Into the water was immersed, quite to its top, a strong, very
large tube (A) closed below, of about 5 centimeters diameter. In this
there was contained, isolated by pieces of cork, the slightly smaller

RICHARDS AND WREDE. — TEMPERATURE OF MANGANOUS CHLORIDE. 347

tube (B) designed to contain the substance. This tube, and also the
stirrer, were made out of good insoluble glass. Because the mercury-
thread, which we needed to consider, was 2 centimeters shorter than

the second tube, it was contained entirely within it when the ther-
mometer was raised about a centimeter above the bottom of the tube.
This inner tube was closed by a cork cover (C), which was bound by
means of two small glass tubes (t and p) to the cork stopper (K) of
the outer tube. The two little tubes binding these two pieces of cork

348 PROCEEDINGS OF THE AMERICAN ACADEMY.

served to admit the thermometer (®) and the stirrer. The tempera-
ture in the outer very large tube fluctuated but very slightly, and that
in the inner tube containing the substance was almost exactly con-
stant. There was no difficulty in regulating the heat of the water in
the thermostat to within less than one tenth of a degree by an ordinary
gas regulator. For reading the thermometer (0), a telescope with a
very exact micrometer was used, by means of which the smallest scale
divisions could easily be divided into hundredths. The danger of irreg-
ular readings of the thermometer through the various media, which
might cause errors due to parallax, was wholly overcome, in that on the
one hand all the glass walls were arranged as vertically as possible,
and the telescope was made exactly horizontal, and on the other hand
every reading of the thermometer was made both from before and from
behind. Obviously, the mean of these two readings must represent the
true value, even if a slight displacement due to refraction had been
present. The thermometer was so arranged that it could easily be
turned on a vertical axis, so that there was no difficulty in making
these readings. As a matter of fact, the readings before and behind
never differed more than four thousandths of a degree, and usually
differed much less than that. The true value was always taken as the
mean of these readings. In the case of the Beckmann thermometer,
the telescope was so placed that the scale division lines appeared
perfectly straight through the tube, without a trace of bending.

The concordance of the results furnishes yet another proof that these
methods of reading were entirely satisfactory and thoroughly trust-
worthy. The great advantage of this apparatus is that the tempera-
ture of the scale can be kept indefinitely at a temperature as nearly as
possible to the true value, and this is no small advantage, because with
such a length of thread a single tenth of a degree difference of tempera-
ture causes a thread -correction of tuo o°- We conclusively proved that
it was not possible to attain the necessary constancy if even a milli-
meter of the mercury thread projected beyond the thermostat into the
temperature of the room.

As has been said, in Table I the accurate results with the first ther-
mometer and the Beckmann are given, and also the corrections, in so far
as these could be determined. The final determinations with the large
new thermometer are given in Table II. On the basis of these results,
we think it is safe to say that the transition temperature of manganous
chloride for the transition from the crystal form with 4 molecules of
water into that with 2 of water, has a value 58.089° (±0.005) referred
to the international hydrogen scale.

In conclusion, it is a great pleasure to express our thanks to the

RICHARDS AND WREDE. — TEMPERATURE OF MANGANOUS CHLORIDE. 349

TABLE I.

Thermometer I.

Prepa-
ration
No.

Reading of
Beckmann
Thermom-
eter.

Cor-
rected
Press.

Result cor-
rected to H2
Standard
(Reichs-
anstalt).

Observed
Reading.

Correction (xn'inj'^)-

Result not
corrected
to H, Stan-
dard.

Thread.

Ice.

Press.

58.087

-2

-1

58.084

0.5078

-I

58.089°

58.081

-2

-1

58.081

58.077

-2

-1

58.079

58.077

-2

-1

58.081

58.084

-1

-2

58.081

0.5079

-2

58.088

58.084

-1

-2

58.081

58.085

-2

58 084

58.082

58 077

-2

58.078

0.5081

-I

58 089

58 081

-1

-2

58.082

0.5082

-1

58.089

58.083

-1

-2

58.083

58.081

58.089

-5

-2

58.085

0.5075

-1

58.089

-4

-2

58.086

TAB

LE II.

Ib+Ic

New Thermometer.

58.3.34

-2

58.332

+ 11

58.330
58.334

-0
-6

58.329

58.330

-2

0.5072°

-I

58.088

58.331

= 58.091°

cor.

68.324

-0

-1

58 330

= 58.090°
cor.

0.5076°

-1

58.089

Total . .

. . . 68.(

)89o

350 PROCEEDINGS OF THE AMERICAN ACADEMY.

Director of the laboratory, Professor Emil Fischer, and to the President
of the Physikalisch-Technischen Reichsanstalt, Professor Warburg, for
their interest in and support of this investigation, and to Dr. Griitz-
macher of the Reichsanstalt for his prompt and thorough testing of
our thermometer.

Summary.

1. For the transition temperature of manganous chloride from the
tetrahydrate to the dihydrate the point 58.089° upon the international
hydrogen scale has been found. This point is probably not more than
0.005 degree in error.

2. This transition temperature of manganous chloride was found to
be suitable for serving as a fixed point in thermometry, on account of
the ease of preparation of the salt and the satisfactory definiteness
of the transition.

3. In this paper is described a tall transparent thermostat which
makes it possible to determine exactly the temperature of the whole
length of the thermometer.

First CnEMiCAL Institute of the
University of Berlin,
August 1, 1907.

Proceedings of the American Academy of Arts and Sciences
Vol. XLIII. No. 11. — November, 1907.

DIFFERENCE IN WA VE-LENGTHS OF TITANIUM
XK 3900 AND 3913 IN ARC AND SPARK.

Bt Norton A. Kext and Alfred H. Avfry.

INTESTIOATIOSS on LISHT AND HbaX made and published, WHOIXT OB IN FAJBT, WITH ArFKOF&lAHON

VBOM THB KuUi'OBO FUNS.

DIFFERENCE IN WAVE-LENGTHS OF TITANIUM
AA 3900 AND 3913 IN ARC AND SPARK.

By Nobton a. Kent and Alfred H. Avery.

Presented by J. Trowbridge October 9, 1907. Received October 9, 1907.

In June, 1905, one of the writers of the present paper published the
results of a careful series of experiments dealing with the variation
in the wave-length of certain lines of the spark spectra of titanium,
iron, and zinc with the electrical conditions of the discharge. ■•■ Sub-
sequently Keller, working under Kayser, published a paper ^ in which
the suggestion was made that the apparent non-coincidences of the
spark and the comparison arc lines were due to the fact that the slit
was not accurately adjusted to parallelism with the grating ruling;
and the statement was made that the plumb-line method of adjustment
employed by the writer was of less delicacy than the spectroscopic.

The substance of Keller's explanation of the manner in which shifts
could be introduced by orientation of the spectrometer slit is as
follows: Given a perpendicular grating ruling, an astigmatic instru-
ment such as the concave grating will give a perpendicular line image
for every point of the line source as object. If, then, the line source
or slit be at an angle (say clockwise as one faces it) with the grating
ruling, each spectral line will be a composite of lines arranged as in
Figure 1.

The result will be an image which is apparently rotated in the direc-
tion of the slit. If, then, on one photographic plate two exposures be
made, one each of arc and spark, and the position of the adjacent tips
of the images of any spectral line be measured by a comparator, any
displacement desired may be introduced by a rotation of the slit.

But Keller's explanation does not apply to the method of exposure
employed by the writer of the former paper — a method of triple
exposure, two of the arc (the first and the third) superimposed hori-
zontally but not wholly vertically and spanned by the spark exposure,
as in Figure 2.

* These Proceedings, 41, No. 10, July, 1905.

' Ueber die angebliche Verschiebung der Funkenlinien. Inaugural-Disser-
tation Christian Keller. 1906.

VOL. XLIII. — 23

354

PROCEEDINGS OF THE AMERICAN ACADEMY.

It is difficult to see how non-parallelism of slit and ruling could in
this case introduce a shift. Keller seems to have overlooked the fact

Figure 1.

AA', direction of grating rul-
ing; EE', direction of slit; LL',
direction of resultant line.

Figure 2.

AA', two exposures of an arc line
superimposed horizontally, but not
vertically ; FF', spark line.

that this triple method was employed, for no mention is made of it in
his paper. However, despite the fact that it was not apparent how

KENT AND AVERY. — WAVE-LENGTHS OF TITANIUM. 355

the above mentioned criticism could apply, it seemed advisable to
test the matter, and the following experiments were undertaken to
decide the two following questions:

(1) Is the plumb-line method of adjustment of slit and grating rul-
ing to parallelism more or less accurate than the spectroscopic 1

(2) Will an orientation of the slit introduce a shift if the triple
method of exposure be used 1

Conditions of Experiment.

The conditions under which the present work was carried on were,
as far as possible, those of the previous series of experiments. By the
courtesy of Professor Trowbridge and Professor Sabine every facility
of the Jefferson Physical Laboratory was placed at our disposal. The
grating — a 6" Rowland concave, of 20,000 lines to the inch and 21 -foot
radius of curvature, an excellent instrument — was kindly loaned by
Professor Trowbridge, and the mount was that belonging to the labora-
tory and located on the third story of the building. The beams were
heavy timbers supported wholly from the walls of the building. The
slit, grating holder, camera-box, rheostat, transformer, and condenser
were those used in the former work. The usual precautions relative
to temperature changes were taken, the whole "mount being wrapped
in several layers of newspaper. The vibrations of the building due to
wind and heavy machinery necessitated working at times when these
disturbing influences were absent. All plates not showing horizontal
coincidence of the arc exposures were rejected. The current used for
both arc and spark was the 110 volt, 66 cycle alternating current of
the Cambridge Electric Light Company. The frequency of the current
used in the previous work was 133, but as the transformer was built
for 66 cycles no difficulty was experienced in this regard. The volt-
meter, ammeter, and wattmeter were of Thompson form, and of ranges
0 — 65 volts ; 0 — 60 amperes ; and 0 — 45 hecto- watts, respectively.
Thus the conditions were the same as those formerly employed in all
respects but location, frequency of current, and grating.

Results obtained.

(1) Relative merits of plumb-line and spectroscopic methods of adjust-
ment. The grating holder was fitted with two opposing screws moving
in a horizontal direction and controlling the orientation of the grating.
It was found by trial that by the unaided eye the parallelism of either
end of the ruled space of the grating with the silk thread of a plumb-
line suspended from the grating holder could be adjusted so that the

356

PROCEEDINGS OF THE AMERICAN ACADEMY.

TABLE I.

Shift of spark lines \\ 3900 and 3913 to red from position of arc lines.

Metal used- Titanium Carbide, 85 per cent Ti, 15 per cent C.

Arc vertical: length 3mm. Spark horizontal: length 9 mm.

End of spark image always used.

Capacity of condenser : 0.0226 microfarads.

Times of exposures : arc 5 + 5 seconds, spark 75 seconds.

Shift in

Constants of
Primary Circuit.

A 3900.68

Orientation of Slit.

Date.

Clockwise
360°.

Clockwise
180°.

Parallel, or 0°.

Counter clock-
wise 180^.

Kent.

Avery.

Kent.

Avery.

Kent.

Avery.

Kent.

*Avery.

Mar. 9

0.035

0.041

, ,

. .

, ,

0.021

0.081

. .

, ,

. .

, ,

• .

. .

, ,

^ ,

. .

• .

Mar. 16

40.8

15.5

, ,

. •

. ,

42.0

15.5

. .

. ,

, ,

• .

38.5

19.0

0.019

0.023

, ,

40.0

16.6

0.020

0.027

, ,

, a

40.0

16.5

0.012

0.022

, ,

a »

39.0

21.0

0.027

0.028

, ,

40.5

17.0

0.007

0.013

, ,

Mar. 23

39.8

19.0

0.029

0.030

, ,

40.0

19.0

0.025

0.021

, .

37.5

21.5

0.018

, ,

40.0

18.0

0.015

o.b'io

, ,

, .

39.3

18.0

, ,

0.014

0.013

, ,

. ,

•

39.0

19.0

0.032

0.042

^ ,

• «

40.0

18.8

0.016

0.023

, ,

. .

40.0

19.3

. .

, ,

Apr. 12

41.0

500

16.0

. .

, ,

0.014

0.018

" 13

39.0

500

19.0

. .

, ,

0.008

0.010

40.0

490

17.5

0.023

39.5

450

17.5

0.039

0.029

40.0

500

22.0

. .

0.025

0.019

40.0

450

19.0

0.016

0.010

40.0

450

19.0

0.032

0.042

40.0

500

19.0

. ,

, ,

41.0

450

15.0

. .

0.025

0.026

40.5

490

17.0

. .

o.b'io

0 018

, ,

41.0

460

16.6

0.020

0.021

, ,

41.0

450

16.0

0.025

0.021

• •

, ,

40.5

450

16.0

0.018

0.026

. .

, ,

101

Apr. 27

40.0

450

17.0

^ ,

, ,

. ,

0.008

0.012

102

89.0

450

19.0

, ,

. ,

, .

0.011

0.009

110

41.0

450

19.0

. .

, ,

112

42.6

450

15.0

, J

, ,

. ,

, ,

114

41.0

450

15.5

, ,

. ,

, .

116

41.0

550

19.0

. .

^ ,

0.014

0.019

117

41.8

550

18.5

0.018

0.016

119

41.5

520

19.6

0.015

0.018

. .

, ,

120

42.0

480

17.5

0.013

0.022

•

122

41.3

500

19.0

0.014

. .

123

41.3

500

17.0

0.013

0.012

. .

, ,

124

41.5

500

17.0

0.011

0.010

• •

•

Mean

0.0 il

0.024

0.016

0.0-20

0.021

0.019 0019

Means of means at all orientations A 3900.68

A 3913.58

Kent 0 018

0017

Avery 0.020

0 019

KENT AND AVERY. — WAVE-LENGTHS OF TITANIUM.

TABLE I -continued.

Plates : Seed " Gilt Edge," No. 27.

Developer : Metol, adurol, liydroeLinon.

Second order spectrum.

Width of slit: 0 025 to 0.050 mm. ; length : 5 mm.

Length of grating lines : 14 mm.

357

Tenth-Metres. 1

A 3913.58.

Orientation of Blit.

Counter clock-

Clockwise

Parallel, or 0^.

Counterclock-

Counter clock-

wise 360^.

3C0°.

180 .

wise 180°.

wise 360°.

Kent.

Avery.

Ken

t.
0

Avery.

Kent.

Avery.

Kent.

Avery.

Kent.

Avery.

Kent.

Avery.

0.03

0.035

0.018

0.028

. .

0.012

. .

, ,

0.014

0013

0.029

0.034

. .

0.027

0.040

0010

0.023

. .

, ,

0.011

0.013

0.006

0.020

• •

•

0.015

0.017

• •

0.008

0016

0.026

0.022

^ ,

, ,

0.010

0.019

. .

, ,

• •

0.023
0.004

0.024
0.012

• •

• ■

0.018
0.015

0.017
0.015

0 029
0.021
0.014

0 033
0.029
0.017

• •

;;

• •

0.031

0.026

, .

^ ,

0.016

0.020

. .

, ,

^ ,

, ,

0.012

0.016

• •

0.016
0 005
0.023
0.042

o.bi7

0.005
0.025
0.034

0.015

. .

0.024

0 029

0.016

0.008

, ,

0.032

0.027

, .

0.028

0.023

0.018
0.021

0.012
0.023

o.bio

0.016

0.024
0.020

• •

0.020

0006
0.014

0.0 i 8

0.019
0.014

0.024

0.022

0 012

0.007

. .

, ^

. .

0 012

0 009

0.015

0009

. .

0.014

0 012

0.014

0.011

• •

0 016

0.025

• •

0.013
0.015

o.bio

0010

0.013

0014

0.013

0 018

0.012

0012

. ,

J ,

0.012

0016

, ^

, ,

, ^

^ ,

•

0.007

0 014

• •

•

• •

0.015

0 017

0.018

0.021

0.017

0.020

0 019

0021

0.018

0.017

0.015

0.017

Weighted means of all measurements

0.019

0.018

Weighted means at parallelism

0.021

0.020

Means as given by previous investigation under similar conditions

0.019

0.018

358 PROCEEDINGS OF THE AMERICAN ACADEMY.

separate settings made by each of us agreed to within 45° on the head
of one of the screws. This means that the grating can be set by
plumb-line to within 3.3 minutes of arc.

Opening the slit and hanging the bob so that the thread could be
seen through it, the various settings made by each of us agreed to 10°
on a divided head fitted to the tangent screw. This means by calcu-
lation 1.7 minutes of arc of rotation of the slit.

On the other hand, using full length of slit, as in the previous case,
and appropriate width, about 1/1000 inch, various exposures of the arc
were taken on the same plate in the manner customary in making
focus plates, except that the camera box was left clamped and the slit
was oriented. Plates so taken showed no difference in the spectra
when the scale on the divided head of the tangent screw was rotated
90° clockwise or counter clockwise from the position of parallelism as
determined by plumb-line, making a change of 15.3 minutes in the
orientation of the slit — a change nine times as great as that in the
case of the plumb-line. However, the relative merits of the two
methods must not be taken as nine to one, but merely as about four to
one, for the plumb-line adjustment for the grating is only about one
half as accurate as that for the slit.

The above facts make it extremely probable that the adjustment of
the slit in the previous investigation was good. And, further, if with
full length of slit no change in definition could be detected for a rota-
tion of 90°, it is all the more probable that with a slit of 5 mm. length,
as used in making regular exposures, the definition was the best
obtainable.

(2) Further, as to shift as a function of the orientation of the slit,
series of plates were taken with the slit oriented approximately 1° and
0.5° of arc clockwise and counter clockwise, including a series at
parallelism ; or 360° and 180° counter clockwise, 0°, 180°, and 360°
clockwise on the divided head. If orientation introduce shift, the
shift-orientation curve should either show a point of inflection at zero
orientation or cross the displacement axis at that point. Table I, on
pages 356 and 357, is self-explanatory. The data given in the table
and the curves of Figure III show that for the two lines studied the
shift is not influenced by the orientation of the slit.

The values of the shift obtained are, within the limits of error of
experiment, the same as those obtained in the previous investigation.

The average deviation from the mean of two measurements (of the
shift of a line) on any one plate is 0.003 (Kent) and 0.004 (Avery)
t. m. for A 3900.68 ; and 0.002 (Kent) and 0.003 (Avery) t. m. for
X 3913.58. It will be noticed that the value of the shift given on the

KENT AND AVERY. — WAVE-LENGTHS OF TITANIUM.

359

SHIET-ORIENTATION CURVE FOR Ti. \\ 3900 AND 3913.

3900 <»-

3913
3900

180
Counter clockwise

180
Clockwise

Figure 3.
Abscissas, Orientation in degrees. Ordinates, Shift in t. m. X 10^.

3900
3913

^^^3900
3913

TABLE II.

Arc and Arc.

Plate
No.

Date.

K 3900.68.

A 3913.58.

Orientation of Slit.

Parallel, or 0°.

Counter clock-
wise SGC^.

Parallel, or 0^.

Counter clock-
\vise 360^.

Kent.

Avery.

Kent.

Avery.

Kent.

Avery.

Kent.

Avery.

106
107
109

April 27

-0.001
0.001

0.003
0.002

0.002

0.005

-0.002
0.004

0.002
0.003

0.003

0.002

360

PROCEEDINGS OF THE AMERICAN ACADEMY.

different plates varies considerably. This is probably due to the fact
that it was difficult to set the very end of the spark image accurately
upon the slit. As shown in the previous paper, the part of the image
employed influences the character of the line and the value of the

shift.

During the progress of the work it was suggested to us that the use
of the tip of the spark line as that part of the line upon which to set
the thread of the microscope in measuring was perhaps objectionable
owing to the fact that there might be a shift due to diffraction result-
ing from reducing the virtual aperture of the grating by strips of
black paper set only roughly perpendicular to the ruling, the measure-
ment being made by a mm. scale. Three exposures on one plate were
therefore made, — all of the arc, and the first and third superimposed
as usual. No shift was shown when the slit was either parallel or
oriented, as indicated in the table on page 359.

At the end of the series of experiments the water rheostat was cut
out of the transformer circuit, and in its place was inserted a choke
coil of closed magnetic circuit of U form with adjustable armature.
When adjusted roughly to show maximum power as measured by the
wattmeter, with a spark-length as indicated in Table III, the shift was
increased to 0.032 t. m. in the mean for X 3900.68 and 0.033 t. m. for
\ 3913.58.

TABLE III.

Conditions same as in Table I, except spark -length - 9 mm. in plate 125 and 15 mm.
in plates 126 to 128. Time of exposures for spark = 60 seconds.

Plate
No.

Date.

A3900.G8.

A 3913.58.

Circuit.

Orientation of Slit : Parallel, or 0°.

Amperes.

Watts.

Volts.

Kent.

Avery.

Kent.

Avery.

125
126
127

128

April 27

ii
it

50
49
50
50

1000
950
800
800

28
27
24
26

0.040
0.033

o.o;jo

0.026

0.038
0.033
0.030
0.029

0.031
0.030
0.032
0.022

0.040
0.049
0.029
0.031

Means

0.032

0.029

0.037

KENT AND AVERY. — WAVE-LENGTHS OF TITANIUM. 361

It is the purpose of the author of the former paper to study with an
echelon the position of the narrow and less diffuse lines of the titanium
spectrum.

In conclusion we wish to acknowledge the kindness shown us by
Professor Trowbridge and those associated with him in so generously
putting at our disposal all the facilities of the Jefferson Physical Labo-
ratory ; and our thanks are due also to the Rumford Committee for
the grant made in aid of this research.

Department of Physics, Boston University.
June, 1907.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 12. — December, 1907.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF
HARVARD COLLEGE.

A REVISION OF THE ATOMIC WEIGHT OF LEAD.

PRELIMINARY PAPER. — THE ANALYSIS OF LEAD CHLORIDE.

By Gkegoky Paul Baxtee and John Hunt Wilson.

CONTRIBUTIONS FKOM THE CHEMICAL LABORATORY OF

HARVARD COLLEGE.

A REVISION OF THE ATOMIC WEIGHT OF LEAD.

PRELIMINARY PAPER. — THE ANALYSIS OF LEAD CHLORIDE.
By Gregory Paul Baxter and John Hunt Wilson.

Presented November 13, 1907. Received October 18, 1907.

Although lead is one of the most common elements, its atomic
weight has received comparatively Httle attention, the value at present
accepted being based almost wholly upon the work of Stas.^ Of the
earlier determinations of this constant those of Dobereiner ^ and Long-
champs ^ can hardly be considered as possessing other than historic
interest. The first results which can lay claim to accuracy are those
of Berzelius,* who obtained values ranging from 206.7 to 207.3 by re-
duction of litharge in a current of hydrogen. Berzelius also synthe-
sized the sulphate from metalHc lead with the result 207.0.^ Shortly
after. Turner ^ criticized the first method employed by Berzelius and
attributed the irregularity of his results to the action of lead oxide on
the silicious matter of the tube at the temperature employed in the
reduction. By the conversion of both the metal and the oxide into
sulphate Turner in a painstaking research deduced the values 207.0

^ Earlier work on the atomic weight of lead has been carefully summarized
by Clarke. Smithsonian Miscellaneous Collections, Constants of Nature, "A
Recalculation of the Atomic Weights," 1897.

In recalculating the data of earlier determinations the following atomic
weights have been used in this paper :

0=16.000; Ag= 107.88; CI = 35.46; N= 14.01; S = 32.07
Richards and Wells, Pub. Car. Inst., No. 28 (1905) ; Richards and Forbes, Ibid.,
No. 69, p. 47 (1907) ; Richards and Jones, Ibid., No. 69, p. 69; Report of Inter-
national Committee on Atomic Weights, Jour. Amer. Chem. Soc, 29, 110
(1907).

2 Schweig. Jour., 17, 241 (1816).

3 Ann. Chim. Phys., 34, 105 (1827).
* Pogg. Ann.. 19, 314 (1830).

5 Lehrbuch, 5th ed., 3. 1187 (1845).

6 Phil. Trans., 527 (1833).

366 PROCEEDINGS OF THE AMERICAN ACADEMY.

and 207.6 respectively, and by converting the nitrate into sulphate,
204.2. Marignac "^ converted metallic lead into the chloride by heat-
ing in a stream of chlorine and obtained the result 207.42. Both
Marignac ^ and Dumas ^ analyzed lead chloride. Marignac, who dried
the salt at 200°, by titration against silver found the atomic weight of
lead to be 206.81, and from the ratio of lead chloride to silver chlo-
ride, 206.85. Dumas subsequently showed that lead chloride, even
when dried at 250°, retains moisture and is somewhat basic, and in
one analysis in which corrections are applied for these errors, found a
somewhat higher value, 207.07, as was to be expected. Chloride
analyses by early investigators are, however, to be universally dis-
trusted, owing to neglect of the very considerable solubility of silver
chloride, thus producing too low results.

Stas's work upon the syntheses of lead nitrate and sulphate from the
metal is undoubtedly the most accurate contribution upon the subject,
although a careful consideration of his work discloses minor defects,
many of which he recognized himself. The metallic lead used in the
syntheses was finally fused under potassium cyanide. Whether or not
this treatment introduced impurities into the metal is uncertain.
Stas himself suspected the presence of alkalies in the metal. Since
the nitrate could not be dried above 150° without decomposition, it un-
doubtedly contained moisture, and Stas calls attention to this point.
The sulphate was made by treatment of lead nitrate, resulting from
the nitrate syntheses, with sulphuric acid. The sulphate was dried
finally at dull redness, and was probably free, or nearly free, from mois-
ture, although it may have contained traces of lead oxide resulting from
occluded nitrate, as well as sulphuric acid. Most of these probable errors
tend to lower the observed atomic weight, so that Stas's value from the
series of nitrate syntheses, 206.81, and that from the sulphate series,
206.92, are to be regarded as minimum values. The reader of Stas's
own account of his work upon lead cannot fail to be impressed with
the fact that he was somewhat dissatisfied with the outcome of his
research. Mention should also be made of the work of Anderson
and Svanberg ^^ on the conversion of lead nitrate into oxide, although
the method was primarily employed in an endeavor to fix the atomic
weight of nitrogen. Their results yield the value 207.37.

The discrepancies between the. results of these various experiments

' Lieb. Ann., 59, 289 (1846).

8 Jour. Prakt. Chem., 74, 218 (1858).

9 Lieb. Ann., 113, 35 (IBGO).
" CEuvres Completes, 1, 383.

" Ann. Chim. Phys. (3), 9, 254 (1543).

BAXTER AND WILSON. — THE ATOMIC WEIGHT OF LEAD. 367

only serve to emphasize the need of a redetermination of the value in
question, and it was with this object in view that the work embodied
in this paper was undertaken.

The search for a suitable method for determining the atomic weight
of lead failed to reveal any more promising line of attack than those al-
ready employed for the purpose. With an element of so high an atomic
weight as lead, in any method involving the change of one of its
compounds into another, errors which may be insignificant with
elements of small atomic weight are magnified in the calculations to
undesirable proportions. Furthermore, during the following investi-
gation, reduction of the chloride and oxide in hydrogen was investi-
gated far enough to show that complete reduction of either compound
was extremely difficult, if not impossible, without loss of material from
the containing vessel by sublimation, aside from the fact that all
available material for containing vessels is acted upon by either the
fused salt or the reduced metal. The elimination of moisture from
lead nitrate or lead sulphate without decomposition of the salts
seemed likely to prove a stumbling block in the use of these substances.
Finally, in spite of the slight solubility of lead chloride, the determin-
ation of the chlorine in this salt by precipitation with silver nitrate
was chosen as presenting fewest difficulties. In the first place, the
determination of a halogen can be effected with great accuracy. In the
second place, the elimination of moisture irom lead chloride is an easy
matter, since the salt may be fused in a platinum vessel in a current
of hydrochloric acid gas without attacking the platinum in the least
and without the production of basic salts. In the third place, silver
chloride, which has been precipitated from a dilute solution of lead
chloride by means of silver nitrate, does not contain an amount of
occluded lead salt large enough to be detected.

Purification of Materials.

Water. — All of the water used in either the purification or the
analyses was distilled twice, once from an alkaline permanganate solu-
tion and once from very dilute sulphuric acid. Block tin condens-
ers were used in both distillations, and rubber and cork connections
were avoided. Generally receivers of Jena glass were employed, but
in certain cases the water was collected in platinum or quartz vessels.

Hydrochloric acid. — Commercial C. P. hydrochloric acid was diluted
with an equal volume of water and distilled with a quartz condenser,
only the middle fraction being collected.

Nitric acid. — Nitric acid was distilled with a platinum condenser,

368 PROCEEDINGS OF THE AMERICAN ACADEMY.

until free from chlorine. Two distillations were invariably sufficient
to accomplish this end, if the first third of each distillate was rejected.

Silver. — Pure silver was obtained by methods already many times
employed in this laboratory. Silver nitrate was dissolved in a large
volume of water and the silver was precipitated as chloride with an
excess of hydrochloric acid. The precipitate was thoroughly washed
and reduced with alkaline invert sugar. The reduced silver, after
being washed, was dried and fused on charcoal in the flame of a clean
blast lamp. After the buttons had been cleaned by scrubbing with sand
and etching with nitric acid, they were dissolved in pure dilute nitric
acid and the silver was precipitated as metal with ammonium for-
mate.^^ This silver was washed and fused in the flame of a blast lamp
on a crucible of the purest lime. The buttons were cleaned as before,
and then electrolyzed.^^ Finally the electrolytic crystals were fused
in a boat of the purest lime in a porcelain tube in a current of pure
electrolytic hydrogen, i* The bars of silver were cut in pieces with a
fine steel saw, etched with dilute nitric acid until fr'ee from iron, washed,
dried, and heated in a vacuum to 400°C. The silver was kept in a
desiccator containing solid potassium hydroxide.

Lead chloride. — Three samples of lead chloride from two entirely
different sources were employed. Sample A was prepared from me-
tallic lead. Commercial lead was dissolved in dilute nitric acid, and
the solution, after filtration, was precipitated with a slight excess of
sulphuric acid. The lead sulphate was thoroughly washed, suspended
in water, and hydrogen sulphide was passed in until the sulphate was
almost completely converted into sulphide. Next the sulphide was
washed with water, dissolved in hot dilute nitric acid, and the solution
was freed from sulphur and unchanged sulphate by filtration. The
lead nitrate thus obtained was crystallized twice, dissolved in water,
and precipitated in glass vessels with a slight excess of hydrochloric
acid. The chloride was washed several times with cold water and then
crystallized from hot water eight times, the last five crystallizations
being carried out wholly in platinum, with centrifugal drainage after
each crystallization. In crystallizing the lead chloride the whole sam-
ple was not dissolved at one time, but the same mother liquor was used
for dissolving several portions of the original salt. Needless to say,
the chloride was not exposed to contact with the products of combus-
tion of illuminating gas, lest lead sulphate be formed.

Sample B was prepared from commercial lead nitrate. This salt was

12 Richards and Wells, Pub. Car. Inst., No. 28, 19 (1905).
W Abraliall, Jour. Chem. Soc. Proc, 1892, p. CGO.
" Baxter, These Proceedings, 39, 249 (1903).

BAXTER AND WILSON, — THE ATOMIC WEIGHT OP LEAD. 369

dissolved and crystallized from dilute nitric acid once in glass and six
times in platinum vessels, with centrifugal drainage. Hydrochloric
acid was then distilled into a large quartz dish, and the solution of
the nitrate was slowly added with constant stirring with a quartz rod.
The chloride was freed from aqua regia as far as possible by washing
with cold water, and was once crystallized fi'om aqueous solution in
quartz dishes to remove last traces of aqua regia. Finally the salt
was crystallized three times in platinum.

It could reasonably be expected that both of these samples were of a
high degree of purity ; nevertheless, upon heating the salt in an atmos-
phere of hydrochloric acid, the salt itself turned somewhat dark, and
upon solution of the fused salt in water a slight dark residue remained.
Although in a few preliminary experiments attempts were made to
determine this residue by filtration and ignition, it was subsequently
found that even a small filter paper adsorbs appreciable amounts of
lead compounds from a solution of the chloride, which cannot be re-
moved by washing with water. From three to thirteen hundredths of
a milligram of residue were obtained in several blank experiments, by
ignition of filters through which half per cent solutions of lead chloride
had been passed, with subsequent very thorough washing. In order to
avoid the uncertainty of this correction, further attempts were made
to obtain a sample of the salt which would give a perfectly clear solu-
tion in water after fusion, and thus render filtration unnecessary. With
this end in view a considerable quantity of Sample A was fused in a
large platinum boat in a current of hydrochloric acid. The fused salt
was powdered in an agate mortar, dissolved in water in a platinum
vessel, and the solution was freed from the residue by filtration through
a tiny filter in a platinum funnel into a platinum dish, where it was
allowed to crystallize. This sample was then twice recrystallized with
centrifugal drainage. Notwithstanding the drastic treatment to which
it had been subjected, when a portion of this material was fused in hy-
drochloric acid, the same darkening as before was observed, and the
same residue was obtained. The suspicion that the difiiculty was due
to dissolving of the filter paper by the solution of the salt ^^ led to
a second more successful attempt by crystallization from hydrochloric
acid solution in platinum vessels. In this way it was found possible
to prepare salt which showed no tendency to darken upon heating, and
which, after fusion, left absolutely no residue upon solution in water.
Portions of Samples A and B were thus recrystallized three times
more. Since these two specimens of material gave identical results,

" Mr. P. B. Goode in this laboratory has recently found a similar ditficultj
with the chlorides of the alkaline earths.
VOL. XLIII — 24

870 PROCEEDINGS OF THE AMERICAN ACADEMY.

for two final experiments, portions from each of these samples were
mixed and then subjected to three additional crystallizations. This
last sample was designated Sample C.

Method of Analysis.

The lead chloride contained in a weighed platinum boat was first
fused in a current of pure dry hydrochloric acid gas. This gas was
generated by dropping concentrated sulphuric acid into concentrated
hydrochloric acid, and after being washed with a saturated solution of
hydrochloric acid, was passed through five towers filled with beads
moistened with fireshly boiled concentrated sulphuric acid, to dry the
gas. It has already been shown that phosphorus pentoxide may not
be used for this purpose.^^ After the salt had cooled, the hydro-
chloric acid was displaced by dry nitrogen, and this in turn by dry air.
Nitrogen was prepared by passing air charged with ammonia over red-
hot rolls of copper gauze, the excess of ammonia being removed by means
of dilute sulphuric acid. The gas was passed over beads moistened
with a dilute silver nitrate solution and over solid caustic potash to
remove sulphur compounds and carbon dioxide respectively, and was
finally dried by concentrated sulphuric acid and phosphorus pentoxide.
The air was purified and dried in a similar fashion. The apparatus
for generating the hydrochloric acid and for purifying the hydrochloric
acid and nitrogen was constructed wholly of glass with ground-glass
joints. The platinum boat containing the fused chloride was next
transferred to a weighing bottle without exposure to moist air, by
means of the bottling apparatus, which has frequently served for a
similar purpose in many atomic weight investigations in this labora-
tory. 17 After standing some time in a desiccator in the balance room,
the weighing bottle was weighed. In most of the analyses the lead
chloride was dissolved from the boat by prolonged contact with boil-
ing water in a Jena glass flask. In the last two analyses, in order
to show that no error was introduced through solubility of the glass,
the solution was prepared in a large platinum retort, and was not
transferreil to the precipitating flask until cold.

Very nearly the necessary amount of pure silver was then weighed
out and dissolved in redistilled nitric acid diluted with an equal
volume of water in a flask provided with a column of bulbs to pre-
vent loss by spattering. After the silver was all dissolved, an equal
volume of water was added, and the nitrous fumes were expelled

" Baxter and Hincs, Jour. Amer. Chem. Soc, 28, 779 (1906).
" Richards and Parker, These Proceedings, 32, 59 (1896).

BAXTER AND WILSON. — THE ATOMIC WEIGHT OF LEAD. 371

by gentle heating. The solution was then further diluted until
not stronger than one per cent, and added slowly, with constant
agitation, to the solution of lead chloride contained in the precipi-
tating flask. The precipitation and handling of the silver chloride
were conducted in a room lighted with ruby light. The flask was
shaken for some time and allowed to stand for a few days, with
occasional agitation, until the supernatant liquid had become clear.
Thirty cubic centimeter portions of the solution were then removed
and tested with hundredth normal silver nitrate and sodium chloride,
in a nephelometer,^^ for excess of either chloride or silver, and, if
necessary, standard silver nitrate or sodium chloride was added, and
the process of shaking and testing repeated until the amounts of silver
and chloride were equivalent. The test solutions were always returned
to the flask, since they contained appreciable amounts of silver chlo-
ride, and the weight of silver chloride subsequently obtained was cor-
rected for the quantity thus introduced. Furthermore, if an excess of
silver was found, a negative correction of an equivalent quantity of
silver chloride was necessary.

After the exact end point had been obtained, about two tenths of a
gram of silver nitrate in excess was added in order to precipitate the
dissolved silver chloride, and the flask was thoroughly shaken, and
allowed to stand again until the solution was perfectly clear. The
silver chloride was washed, first several times with a very dilute silver
nitrate solution containing four hundredths of a gram per litre, and
then eight times with pure water. It was next transferred to a Gooch
crucible and dried for several hours in an electric oven, the tempera-
ture being gradually raised to 180°, and was cooled in a desiccator and
weighed. In every case the moisture retained by the precipitate was
determined by fusion in a small porcelain crucible. The silver chlo-
ride, dissolved in the filtrate and washing, was determined by comparison
with standard solutions in the nephelometer in the usual manner.
Care was taken to treat both tubes in exactly the same manner, and
final readings were taken only when the ratio had become constant.
Before proceeding to the nephelometer tests, however, the filtrate and
washings were passed through a very small filter in order to collect a
small quantity of asbestos shreds mechanically detached from the Gooch
crucible. The filter was ignited and weighed, the ash being treated
with a drop of nitric and hydrochloric acid in order to convert any
reduced silver into chloride. In order to find out whether lead or
silver nitrates were appreciably adsorbed by the filter paper, a solution

" Richards and Wells, Am. Ch. J., 31, 235 (1904) ; 35, 510 (1906).

372

PKOCEEDINGS OF THE AMERICAN ACADEMY.

THE ATOMIC WEIGHT OF LEAD.

Series I. PbClj : 2 Ag.

Ag = 107.930 CI = 35.473

Number

of
Analysis.

Sample

of
PbClj.

Weight of

PbCU
in Vacuum.

Weight of

Agin
Vacuum.

Weight of
Ag added or
subtracted.

Corrected
Weight
of Ag.

Atomic

Weight of

Pb.

grams

gram

grams

4.67691

3.630G1

-0.00074

3.62987

207.179

3.67705

2.85376

0.00000

2.85375

207.189

4.14110

3.21388

+0.00020

3.21408

207.173

4.56988

3.54672

0.00000

3.54672

207.185

•5.12287

3.97596

-0.00028

3.97568

207.201

3.85844

2.99456

0.00000

2.99456

207.186

4.67244

3.62628

0.00000

3.62628

207.189

3.10317

2.40837

0.00000

2.40837

207.188

4.29613

3.33427

-0.00020

3.33407

207.202

Averag(

. 207.188

Series II. PbCl.

, : 2 AgCl

•

Number

of
Analysis.

Sample

of
PbCl^.

Weight of
PbCU in
Vacuum.

Weight of
AgCl in
Vacuum.

Loss

Fusion.

Weight

Asbestos.

wt. AgCl
from
Wash

Waters.

Corrected
Weight
of AgCI.

Atomic
Weight
of Pb.

gi-ams

grams

gram

grams

4.07691

4.82148

0.00100

0.00021

0.00204

4.82273

207.188

414110

4 20848

0.00020

0.00008

0.00180

4.27016

207.192

5.12287

5.28116

0.00054

0.00013

0.00197

5.28272

207.181

3.85844

3.97759

0.00035

0.00033

0.00192

3.97949

207.136

3.10317

3.19751

0.00045

0 00014

0.00189

3.19909

207.261

4.29G13

4.42730

0.00020

0.00004

0.00268

4.42982

207.204

Averag
A vera g

207 193

^e, rejec

ting the least satisfactory analyses, 13 and 14 . . .

207.191

Averag

■■e of Ser

ies I and II

207.190

BAXTER AND WILSON. — THE ATOMIC WEIGHT OF LEAD. 373

containing lead nitrate, silver nitrate, and nitric acid of the concentra-
tion of these filtrates, was passed through several small filter papers,
which were then very carefully washed. In four cases, after incinera-
tion of the papers, there was found, —0.00001, +0.00002, -f 0.00003,
+0.00001 gram of residue, exclusive of ash. This correction is so small
that it is neglected in the calculations. In all the analyses the plati-
num boat behaved admirably, the loss in weight never amounting to
more than a few hundredths of a milligram.

The balance used was a short arm Troemner, easily sensitive to a
fiftieth of a milligram. The gold-plated brass weights were carefully
standardized to hundredths of a milligram. All the weighings were
made by substitution with tare vessels as nearly like those to be
weighed as possible.

Vacuum corrections : The values of the density of lead chloride as
given by various observers range from 5.78 to 5.805,^^ the mean of
the more accurate determinations being 5.80. This gives rise to
a vacuum correction of +0.000062 for each apparent gram of lead
chloride, the density of the weights being assumed to be 8.3. The
other vacuum corrections applied were silver chloride, +0.000071, and
silver, —0. 000031.

All analyses which were carried to a successful completion are
recorded in the preceding tables.

The close agreement of the averages of the two series is strong
evidence that no constant error, such as occlusion, affects the results.
Furthermore, in all, 19.55663 grams of silver produced 25.98401 grams
of silver chloride, whence the ratio of silver to silver chloride is 132.865,
a value in close agreement with the result 132.867 obtained by Richards
and Wells.20 Furthermore, the different samples, A, B, and C, all
give essentially identical results.

It appears, then, that if the atomic weight of silver is taken as 107.93
(0 = 16.000), the atomic weight of lead is 207.19, nearly three tenths
of a unit higher than the value now in use. If the atomic weight of
silver is 107.88, a value probably nearer the truth than 107.93, lead
becomes 207.09, a number still much higher than that depending upon
Stas's syntheses, as is to be expected.

"VVe are greatly indebted to the Carnegie Institution of "Washington
for assistance in pursuing this investigation, also to Dr. Wolcott Gibbs
and to the Cyrus M. Warren Fund for Research in Harvard University
for many indispensable platinum vessels.

Cambkidge, Mass., October 18, 1907.

^9 Landolt-Bornstein-Meyerlioffer, Tabellen. 20 Lqc_ (.jt

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 13. — February, 1908.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

A SIMPLE METHOD OF MEASURING THE INTENSITY «

OF SOUND.

By George W. Pierce.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

A SIMPLE METHOD OF MEASURING THE INTENSITY

OF SOUND.

By George W. Pierce.

Presented January 8, 1908. Received January 4, 1908.

I. Introduction.

In the course of a series of experiments on Detectors for Electro-
magnetic waves the writer has found a number of solid substances
which, when supplied with contact electrodes and put into electric
circuits, serve as rectifiers for small electric oscillations. Some of
these substances used in connection with a galvanometer prove to be
extremely sensitive and constant in their action and permit the meas-
urement of the currents generated by the vibration of the diaphragm
of a magneto-telephone under the action of sound waves even when
the telephone is at a considerable distance from the source of sound.

With the use of this device the relative intensity of sound at differ-
ent positions in a room may be measured, and many interesting results
as to the acoustic properties of an auditorium may be obtained.

The study of the rectifiers themselves is the subject of a series of
papers by the writer, on " Crystal Rectifiers for Electric Currents and
Electric Oscillations." Part I of this series of papers appeared in the
Physical Review for July, 1907, Vol. XXV, pp. 31-60. The rectifier
there investigated is Carborundum. Several other crystal bodies,
some of which are in their action much more sensitive than car-
borundum, possess similar properties and are being experimentally
studied in detail with reference to their electrical characteristics and
with reference to their use in electric-wave telegraphy.

The results of this study will constitute the subject matter of
succeeding parts of the Physical Review article.

II. Molybdenite as a Rectifier for . Electric Oscillations.

One of the most sensitive of the rectifiers thus far investigated is
Molybdenite. The present paper deals with the use of the molyb-
denite rectifier in the measurement of sound.

378

PROCEEDINGS OF THE AMERICAN ACADEMY.

Molybdenite is also an extremely sensitive detector for electric
waves in wireless telegraphy, and may also be employed in experi-
ments on telephony and in many other experiments where it is required
to measure small electric oscillations.

The manner of mounting and employing the substance is substan-
tially the same in these several applications, and is capable of several
variations, only one of which will be given here. Molybdenite, M0S2,
is a mineral occurring in nature in the form of hexagonal prisms with
eminent cleavage parallel to the base, and may be scaled off in thin
sheets, a few sq. cm. in area, resembling bits of tin-foil. In the present
experiments a thin sheet so obtained was mounted in the manner
shown in the sectional drawing of Figure 1.

Figure 1. — Rectifier.

A thin, circular piece of molybdenite ^ (M, Figure 1), about 1 sq. cm.
in area, is clamped tightly between a piece of mica N and the hollow
brass post A, by means of a brass cap C screwed down on the post A.
The molybdenite is thus held in electrical connection with the annular
surface of the end of the hollow brass post A, which is in turn metal-
lically connected with the binding post G. Separated from A by an
air space, a small pointed brass rod B is screwed up through a metallic
strip H attached to a second binding post F. The binding posts and
the holder for the molybdenite are rigidly supported by a porcelain
base PP. The seat of the action of the molybdenite as a rectifier is
at the small region of contact between the molybdenite and the pointed
rod. In the construction of the rectifier this contact is adjusted by
screwing the rod up through H until a galvanometer in series with
the device and a soui'ce of alternating voltage (of about .05 volt) gives

^ Molybdenite free from iron should be used.

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 379

a maximum deflection. The adjustment of the contact is made once
for all, and subsequent accidental changes of the apparatus is prevented
by filling the cavity about H with melted wax or plaster of Paris.

When made in this manner the rectifier will stand considerable
abuse in the way of jar and overload. It is, however, subject to
changes due to the expansion and contraction of the mounting, and
due also possibly to a temperature coefficient of the molybdenite itself.
Eft'ort to get a mounting without such changes with temperature and
a study of the temperature coefficient of the substance itself are now
in progress. Up to the present it is found advisable to use the rectifier
in a thermostat at constant temperature, when accurate quantitative
agreement between observations extending over a considerable period
of time is required.

Whether or not the direct current obtained from the molybdenite
in contact with two unequal electrodes is a thermo-electric action due
to the unequal heating of the electrodes by the oscillating current is
at present not known. It will be seen that the conditions are favor-
able for such thermo-electric action. In order not to commit one's
self to any particular theory as to the nature of the action, the device
is here referred to as a "rectifier," in that the current in one direction
due to an impressed voltage is very different from the current in the
opposite direction under the same voltage.

III. Electric Circuits Employed with the Molybdenite
Rectifier in Experiments on Sound.

In the measurement of sound, the rectifier was at first placed
directly in series with a sensitive galvanometer and a Bell magneto-
telephone receiver. With this arrangement, when sound was made in the
neighborhood of the receiver, the vibration of the telephone diaphragm
generated electric oscillations in the circuit. These oscillations passed
through the rectifier more strongly in one direction than in the oppo-
site direction, and caused a deflection of the galvanometer.

However, on account of the high resistance of the rectifier, and in
order to take advantage of electrical resonance in the circuits, it was
found better to employ an arrangement of circuits containing a
step- up transformer, as is shown in Figure 2.

In Figure 2 PS is a transformer, the primary P of which is con-
nected in series with the telephone T and an adjustable condenser C.
The secondary S of the transformer is connected in series with the
rectifier R, the galvanometer G, and a calibrating device at W. By
adjusting the condenser C, the electric circuit TCP was brought to

380

PROCEEDINGS OF THE AMERICAN ACADEMY.

resonance with the alternating voltage impressed on the system by the
periodic impact of the sound waves. This adjustment was easily made
experimentally.

The proper choice of the transformer PS and the telephone T was a
more difficult problem. A theoretical solution of this problem was not
at hand, on account of lack of knowledge of the characteristics of the
telephone when used as a generator of oscillatory currents and on ac-
count of the fact that the current through the crystal in the secondary
is not a simple function of the voltage in this circuit (see Figure 6).
Some aid in the choice was had in the following considerations, which
served to point vaguely the direction in which experiment was to be
made :

1. Since the primary circuit was to be brought to resonance with the
oscillations, the inductance of the primary circuit is negligible, if we

(DM

Figure 2. — Electric circuit.

may neglect the reaction of the secondary circuit on the primary. With
this approximation it follows from elementary considerations that the
resistance of the primary coil should be eciual to the resistance of the
telephone. Experiment soon showed that the reaction of the secondary
circuit was not negligible, and since the effect of the reaction of the
secondary is to increase the apparent resistance of the primary, it fol-
lows that the resistance of the primary coil should be somewhat less
than that of the telephone.

2. The iron core of the transformer should be such as to be properly
magnetizable by the current generated by the telephone, which in fre-
quency and intensity approaches to the current used in telephony.
Whence it seemed probable that the small terminal transformers used
in telephony would have about the proper amount of iron for use in
the present experiments.

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 381

3. The resistance of the secondary of the transformer and that of the
galvanometer should be high because the resistance of the crystal for a
small current is several thousand ohms.

Guided by these considerations, and by the results of preliminary
experiments with several small induction coils, two transformers were
wound, of which the one that proved the more satisfactory had the
following dimensions :

Length of iron core, 9.5 cm.
Diameter of iron core, 1 cm.
Depth of channel, 1.5 cm.
In this channel were three coils of which either pair could be used as
primary and secondary. These three coils had respectively 16, 280,
and 7 "20 ohms resistance.

With this transformer experiments were made with three different
telephones, of which a Siemens and Halske " Lautsprecher," rewound to
466 ohms, and provided with a small conical sound collector 10 cm. in
diameter, proved the most sensitive. This telephone was ordinarily
used with the 280 ohm primary and the 720 ohm secondary. The
other two telephones used had resistances of 53.8 and 99.8 ohms re-
spectively, and were used with the 16 ohm primary and the 720 ohm
secondary.

Exjyerirnent I. Adjustment of the Receiving Telephone Circuit to
Resonance with the Sound. — After having made a preliminary selec-
tion of the pitch to be employed in a particular experiment, it becomes
important to adjust the electrical circuit to resonance with this pitch.
The following data is given to show the manner in which this adjust-
ment is made, and to show the effect of such a resonant adjustment in
increasing the sensitiveness of the apparatus.

An organ-pipe Ftfi giving 705 complete vibrations per second, sup-
plied by air from bellows operated by an electric blower and set up in
the Constant Temperature Room ^ of the Jefferson Physical Laboratory,
served as source of the sound.

The telephone receiver, having a resistance of 53.8 ohms, and pro-

' This room is described in Professor Sabine's paper on " Architectural Acous-
tics, Part I, Reverberation," published in the American Architect, Vol. XLVIII,
April-June, 1900, and in Contributions from the Jefferson Physical Laboratory,
Vol. IV, 1900. This room was used in some of the present experiments because the
apparatus for producing the sound happened to be in place there. The appara-
tus was in use by Professor Sabine, and together with other parts of the appa-
ratus, including two of the receiving telephones, was kindly placed by him at my
disposal.

382

PROCEEDINGS OF THE AMERICAN ACADEMY.

vided with a conical sound-collector 29 cm. in diameter, was placed at
a distance of about 1.5 meters from the organ-pipe. The 16 ohm prim-
ary and the 720 ohm secondary of the transformer, Figure 2, were em-
ployed. The galvanometer G was a d' Arson val type and had a resistance
of 538 ohms, and gave a throw of one scale division (A inch) for a
current of 1.53 X 10"^ amperes.

The condenser C, Figure 2, having a total capacity of 1 microfarad,
and adjustable by steps of .05 microfarads, was given various values,
and the corresponding throws of the galvanometer when the pipe
was sounded were taken. In taking these readings the pipe was left
sounding until the coil of the galvanometer had completed its swing.

The results are recorded in Table I.

TABLE I.

Adjustment of Electric Circcit to Resonance with
Sound Frequency.

Capacity of C
in Microfarads.

Current through Galva-
nometer in Microamperes.

.00

.000

.20

.064

.30

.308

.45

.477

.50

.470

.60

.320

.80

.206

1.00

.157

C short-circuited

.061

The curve of Figure 3 is plotted from the data of Table I. The hori-
zontal dotted line through the figure is the current with the condenser
short-circuited. This curve gives an idea of the advantage obtained
by the use of the proper capacity in the primary circuit of Figure 2.
The maximum of the curve shows a value of the current that is
nearly eight times the current obtained when the condenser was
short-circuited.

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 383

4 f T

.ii±ii:=i:

3 j ^^.;—

I /

IV. Stationary Sound Waves. Distribution of Intensity.

In taking the data of Experiment I, the position of the telephone re-
ceiver and that of the organ-pipe were left constant. When the tele-
phone was removed to different parts of the room, very striking evidence
of a stationary-wave system
was obtained. This station-
ary system was, however, ex-
tremely complicated. In
some positions, for example,
a very slight change of the
inclination of the sound-col-
lecting cone, without any
motion of the receiver as a
whole toward or away from
the source of sound, would
cause several hundred per
cent change of the reading of
the galvanometer. Professor
Sabine has already called at-
tention to the existence in
this room of a striking inter-
ference system. The follow-
ing paragraph descriptive of
the phenomenon is quoted from his writings on the subject :

" This room is here described at length because it will be frequently
referred to, particularly in this matter of interference of sound. While
working in this room with a treble c gemshorn organ-pipe blown by a
steady wind pressure, it was observed that the pitch of the pipe appar-
ently changed an octave when the observer straightened up in his chair
from a position in which he was leaning forward. The explanation is
this : The organ-pipe did not give a single pure note, but gave a funda-
mental treble c accompanied by several overtones, of which the strong-
est was in this case the octave above. Each note in the whole complex
sound had its own interference system, which, as long as the sound re-
mained constant, remained fixed in position. It so happened that at
these two points the region of silence for one note coincided with the
region of reinforcement for the other, and ^nce veisa. Thus the ob-
server in one position heard the fundamental note, and in the other,
the first overtone. The change was exceedingly striking, and as the
note remained constant, the experiment could be tried again and
again. With a little search it was possible to find other points in the

.3 .4

CAPACITY.

MICROFARAD.

Figure 3. — Resonance curve.

384

PROCEEDINGS OF THE AMERICAN ACADEMY.

room at which the same phenomenon appeared, but generally in less
perfection."*^

Before undertaking the study of the complicated distribution of
sound intensity in a room with highly reflective walls, it was decided
to become better acquainted with the present experimental method by
an examination of a much simpler interference system ; namely, that
produced as nearly as may be by a single reflecting surface. This is
done in Experiment II following. Afterward, in Experiment III, it is
shown to be practicable to extend the investigation to a quantitative
determination of the distribution in a large auditorium.

Experiment II. Stationary Wave Produced hy a Single Reflecting
Surface. — The arrangement of apparatus is shown in Figure 4. In
order to reduce the effects of reflection from the walls of the room,

1 0

l{T|l|l|||l|l|>|l{l|l|l|>|>|l{l|l|l|l|l|l|0

S ' P
W

6.10 M

Figure 4. — Position of apparatus in constant temperature room.

they were curtained off with felt, F, 1.1 cm. thick, hung at a distance
of about 50 cm. from the walls. Felt of the same thickness was also
placed overhead, separated from the ceiling by about 50 cm.

The organ-pipe, FJf 4, 705, serving as a source of sound, was placed
at P, near the center of the room. The telephone receiver, used in
Experiment I, was placed at T, about 70 cm. from the pipe. Leads
ran from the telephone to the condenser and transformer, which
together with the observer and galvanometer were in a distant
room.

A reflecting surface of wood, 73 cm. wide hy 122 cm. high, was placed
vertically at W, and was mounted on a track so as to be capable of dis-

3 Sabine, loc. cit. p. 8.

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 385

placement along the scale S. The open end of the pipe was placed at a
height of 61 cm., and was therefore on a level with the middle of the
reflector.

to .8

<^ a

<t
O
q:
O .4

■-/

/-■

■\j

A ^-

10 20 30 40 60 60 70 80 90 100 UO 120 130

DISTANCE FROM WALL TO PIPE —CM.

■*^,

.04

10 20 30 40 50 60 70 80 90 100 UO 120 130

DISTANCE FROM WALL TO PIPE — CM.

10 20 30 40 50 80 70 80 90

DISTANCE FROM WALL TO PIPE — CM.

Figure 5. — Curve 1, stationary wave in terms of current in secondary.
Curves 2 and 3, stationary waves in terms of voltage in secondary.

The distance from the reflector W to the pipe P could be varied and
was read off on the scale S. Readings of the galvanometer were taken
with the reflector at various stages, 5 cm. apart, along the scale. The
values of the current in the galvanometer circuit are plotted against

VOL.

xLiii. — 25

386 PROCEEDINGS OF THE AMERICAN ACADEMY.

the distance of the reflector from the pipe, in Curve 1 of Figure 5.
This curve shows the stationary wave system set up hy the interfer-
ence of the direct and the reflected waves. The distances between al-
ternate nodes and alternate loops of the curve give the following values
of the wave-length :

49.7, 49., 45.8, 51, 46.5 ; Average, 48.4.

The velocity of sound at the temperature of the room, 18°, was 34200
cm. per second, whence the period

34200 ^^^^

^ = l8T-=''^^'

while the actual value of the pitch of the pipe FJ 4 is 705 vibrations
per second. This agreement is evidently better than is to be expected
from the method, on account of the uncertainty of locating the nodes
and loops of the curve.

It is seen, however, that the points of the stationary wave lie well on
the curve. A repetition of the observation on a succeeding day gave
substantial agreement with Curve 1. It is to be observed that the
first maximum, with the reflector in the neighborhood of 23.5 cm. from
the pipe, is weaker than the second and third maxima. This is prob-
ably caused by the fact that the wind-chest on which the pipe was
mounted intercepted the reflected wave more strongly when the re-
flector was close up than when it was more distant from the pipe.

The horizontal dotted line through the curve at 3.30 gives the mag-
nitude of the current when the reflector was removed. It is seen that
the peaks of the curve above the line of no reflector are much greater
than the neighboring depressions of the curve below the line. This
distortion was found to be chiefly due to the current-voltage character-
istic of the rectifier, and is eliminated by the calibration of the recti-
fier with an alternating voltage, and by plotting the stationary wave
in terms of alternating voltage instead of galvanometer current.

In making the substitution of voltage for current it would be in-
structive to impress the known alternating voltage on the primary of
Figure 2, and take the corresponding throws of the galvanometer in
the secondary. We should then be able to know the voltage generated
by the telephone when we know the galvanometer current. However,
on account of the influence of the transformer, this could be properly
done only with an alternating voltage of the same frequency as the
sound, in this case 705 cycles. A generator for this frequency was not

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 387

at the writer's disposal, so it was decided to calibrate the secondary
circuit instead of the primary. For this, a 60 cycle alternating voltage
could be employed without much error ; for a preliminary experiment
had shown that the impedance of the secondary of the transformer was
practically negligible in comparison with the resistance of the rectifier,
and that the current-voltage characteristic of the rectifier, as far as
tests could be made with means at hand, was independent of the
frequency.

The calibration of the secondary circuit was made as follows : The
slide wire of a potentiometer was inserted at W in Figure 2, and a source
of alternating voltage was applied at AV. The drop of potential in W

1.8
L4

O -8

o
5 .

FiGI

.0
JRE

6. -

■Cui

8
VOL

reni

.TS AL

-vol

tern;
taare

^TING

cha

ract

srist

ic ol

rec

tifie

was known from the resistance of W and the readings of an alternat-
ing current ammeter at I. The alternating voltage in W was varied
by varying the resistance of W, and the corresponding direct current
in the galvanometer was read. These values are plotted in Figure 6.

If now we replace the current values in Figure 5 by the correspond-
ing voltage values in the secondary of the transformer we obtain Cui've
2 of Figure 5. This curve is independent of the rectifier, and shows
the number of alternating volts at the terminals of the secondary of the
transformer of Figure 2 for various positions of the reflecting wall in
Figure 4. Except for distortion of the wave when the reflector was
too close to the pipe this curve is nearly symmetrical about the line
of no reflector.

388 PROCEEDINGS OF THE AMERICAN ACADEMY.

Curve 3 of Figure 5 is another curve obtained in the same way with
a slate reflector at W and a pipe of slightly higher pitch, and with the
Siemens and Halske telephone, which had a much smaller sound col-
lecting cone, 10 cm. in diameter. This curve is somewhat more nearly
symmetrical in character.

It should be noted in respect to these curves that there was still con-
siderable reflection from the room, in spite of the felt curtains, and
that these reflected waves act in a manner to distort the stationary
system.

The curves of Figure 5, although taken under somewhat artificial
conditions are in themselves instructive, in showing the marked effect
of a reflecting wall on the loudness and quality of sounds. When a
speaker or an orchestra is at any given distance in fi'ont of a reflecting
wall certain tones will be greatly reduced in intensity while tones of a
different pitch will be gi-eatly intensified, thus it may be changing
completely the emphasis and quality of the composition. When there
is only a single strongly reflecting wall (the other walls being strongly
absorbtive) this distortion occurs over practically the whole room, al-
though, of course, at different points in the room different notes will be
suppressed or emphasized depending on the phase difference between
the direct and reflected waves to the auditor.

Experiment III. Interference of Hound Waves in a Large Lecture
Boom. — In order to extend the investigation to the study of the dis-
tribution of sound intensity in a room of considerable proportions, an
organ-pipe and the telephone receiver were set up in the large lecture
room of the Jefferson Physical Laboratory. This room, of which a
diagram is shown in Figure 7, is IH.G meters long, 12.7 meters wide,
and 7.7 meters high at one end. It contains seats for about 300 stu-
dents. These seats are progressively raised toward the back of the
room so that the height of the ceiling above the seats in the rear is
about 4 meters. The walls of the room are of brick.

The organ-pipe used as a source of sound, G^. 76S, was placed at the
position P in the diagram, and was supplied with wind at a constant
pressure from a reservoir, from which the air supply to the pipe was
turned on and off by an electro-pneumatic valve operated by a battery
and clock work.

The Siemens and Halske telephone receiver, 466 ohms, with the
sound-collecting cone 10 cm. in diameter, was used as a receiver for
the sound and was provided with a long double lead so that it could
be placed anywhere in the room.

The first position chosen for the receiver was at the extreme rear of

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 389

the room (1, Figure 7), where a small track 10 cm. wide and 2 meters
long was run out perpendicularly from the wall. The telephone was
placed on this track with the opening of the sound collector toward the
wall, and readings of the galvanometer were taken with the telephone
at various distances from the wall. The results obtained are plotted in
Curve 4 of Figure 8. The abscissae of this curve are the distances in
centimeters from the wall measured to the opening of the sound col-

iji

_ uUUUlJUU

"finnnnnn

_ - - ■■ ^i^_

Figure 7. — Diagram of large lecture room. P is the position of the source
of sound ; 1, 2, and 3, positions of the receiver.

lector ; the ordinates are the corresponding values of the current ob-
tained in the galvanometer when the organ-pipe was sounded. The
first reading, .73 X 10"'' amperes, was obtained with the opening of the
sound collector of the telephone jammed tight against the brick wall.
On withdrawing the receiver from the wall by stages of 5 cm., while
keeping the opening of the sound collector always toward the wall, the
succeeding values of the curve were obtained, showing the occurrence
in this part of the room of very decided maxima and minima of

390 PROCEEDINGS OF THE AMERICAN ACADEMY.

sound intensity. The irregularities of the curve were actually exist-
ent in the interference system and were verified by a repetition of the
experiment.

In the above curve the current obtained at the best of the maxima
was 3.30 X Kr'' ampere. When it is noted that this was at a distance
of 15 meters from the source of sound, it will be seen that the receiving
apparatus possesses quite remarkable sensitiveness. Of course, too
much importance must not be given to the distance from the source
as a determining factor of the intensity, for, as will soon appear, this
particular position, accidentally chosen, in the rear of the room was
a position in which the sound was more intense than at many places
much nearer to the source. However, even with a galvanometer of
only moderate sensitiveness it was possible to extend the investigation
satisfactorily to any part of the room. Curves of results at two other
positions in the room are discussed below.

The question arises, how may we determine the exact region of
space to which the indications belong'? In Curve 1 of Figure 8 a
maximum was found when the opening of the receiver was 5 cm. from
the wall. Is the maximum of sound vibration at the opening of the
cone, and, therefore, 5 cm. from the wall or is it inside the cone or
outside the cone ? Can we locate its exact position 1 In attempting to
answer these questions it was decided to try the effect of reversing the
telephone so that the opening pointed away from the wail. With the
telephone thus reversed Curve 5 of Figure 8 was obtained. Unfortu-
nately, on account of the size of the telephone and cone, it was not
possible to extend the observations to points nearer the wall than
40 cm. The distance measurements for this curve were also made
from the wall to the opening of the cone. By a comparison of this
curve with Curve 4 we may get some evidence of the location in space
of the sound vibration.

The two maxima of Curve 5 probably correspond respectively to the
two right hand maxima of Curve 4, as is evidenced by their distance
apart, and their relative amplitudes, and by the distance apart of the
minima of Curve 5 as compared with the minima at 75 and 108 of
Curve 4. Now it is seen by inspection that these two curves would be
brought into coincidence as to location of maxima and minima, if,
instead of having measured from the wall to the opening of the cone
of the telephone, we had measured to a point 5.7 cm. outside of the
cone ; that is to say, the indications of the galvanometer are indica-
tions as to the relative amplitude of the sound vibration at a point b.l cm.
outside of the opening of the sound-collecting cone.

While this reasoning is not entirely conclusive without further

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 391

evidence, because of the possible actual disturbance of the stationary
system by the reversal of the telephone, yet the result seems highly
probable on account of its agreement with the familiar fact that the
maximum of motion of the air column of a tubular resonator is outside
the end of the resonator. The sound-collecting cone of the present
apparatus is a resonator for the pitch employed — in fact, the particu-
lar pitch was selected by a preliminary experiment which showed that
the air column of this cone was in resonance with the pitch — and this
resonant air column, according to deductions from the above experi-
ment, is thrown into most active vibration when a region just outside
(5.7 cm.) the opening of the cone is coincident with a region of large
displacement.

This result enables us to locate the actual position of the nodes and
loops of Curve 4, Figure 8. Each point of the carve belongs to a
region of space 5.7 cm. nearer to the wall than the corresponding
abscissa ; therefore, the first maximum of motion, which was obtained
with the opening of the cone 5 cm. from the wall, is really .7 cm.
behind the wall, — that is to say, practically coincident with the wall.

In order to examine the distribution of sound intensity in the
neighborhood of another portion of the wall of the room, the telephone
receiver and its track were placed at 2 in Figure 7, and the galvan-
ometer readings were taken with the opening of the cone turned
toward the wall and placed at various distances from the wall. Curve
6 of Figure S was obtained as representative of the distribution at this
position. Here again the corrected position of the first maximum is
practically coincident with the wall. The interference system in this
locality is much more irregular than in position 1, and the maxima
with the exception of the maximum at 90 cm. are less intense than
those at position 1. This is interesting when we note the fact that
the distance of the position 2 from the source of sound is only one
half as great as the distance of position 1. For hearing this particu-
lar note the position at the back of the room is more favorable than
the much nearer position at the side of the room, notwithstanding the
fact that the side position was directly in firont of the lip of the pipe
and was unobscured by intervening objects, while a line running irom
the source of sound to the position in the rear of the room passed
immediately over the backs of numerous benches with which the room
was furnished.

At a third position in the room, position 3, Figure 7, an interval
of 100 cm. was investigated. The results obtained are shown in
Curve 7, Figure 8. These distances (abscissae) are measured fi-om
an arbitrary origin. The opening of the cone of the telephone was

392

PROCEEDINGS OF THE AMERICAN ACADEMY.

turned toward the spot marked " 8 " in the elevation drawing of
Figure 7. Here again a fairly definite stationary system was found.
This position is also less favorable for hearing this particular tone
than the position 1 in the rear of the room.

30 40 60 60 70 80

DISTANCE FROM WALL — CM

UJ
Q. J2

/ '

^ \

30 40 50 60 70 80

DISTANCE FROM WftLL — CM

Figure 8. — Stationary waves in large lecture room.

These experiments were made in the large lecture room which is
immediately over the machine shop of the laboratory, and were
apparently not in any way affected by the very considerable vibration
and noise of several motors and lathes in almost continual operation.
The rectifier is, however, extremely sensitive to electric waves ; and
electric disturbances, when they happen to be in syntony with the
rectifier circuit may prove troublesome. In the course of the present

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 393

experiments the breaking of a chronograph circuit by an electric clock
in a distant room gave noticeable deflections. Most of these electric
disturbances may be easily tuned out by a change of the inductance
or capacity either in the disturbing circuit or in the rectifier circuit.
By wearing a head telephone connected in series with the galvan-
ometer during the observations, the observer may easily recognize any
foreign disturbances by their characteristic tones in the telephone.

It was not the purpose of the present note to multiply observations
on the acoustic properties of a particular room. However, apart from
the interest attaching to the method of the experiment, the result that
for a sustained tone, even in a large room, there are practically all
over the room definite positions of sharp maxima and minima of
intensity is rather a striking fact when brought out objectively. The
results show that an auditor may sometimes greatly improve his
hearing of a discourse or a musical rendition by a slight motion of
his head so as to bring his ear into a position of maximum intensity.
Perhaps he already unconsciously does this, which may account for
the fixed attitude of an audience in close attention.

The occurrence of these definite maxima and minima of intensity
of sound, due to reflection from the walls, should be borne in mind
when one attempts to interpret any experiment on sound performed
in a closed room. As Professor Sabine has repeatedly emphasized, the
mere fact that the walls are distant from the source of sound, while
the observer, or sound-receiving apparatus, is near to the source, is
not sufficient precaution against the influence of reflection, because
the reflecting surfaces are on all sides and act many times, and may
combine in their action in such a manner as to be a very considerable
factor in the resulting intensity.

The curves of Figure 8 are plotted in terms of current in the
galvanometer. It was shown above, in Experiment II, how the indi-
cations of the galvanometer may be made independent of the rec-
tifier by substituting voltage from the curve of Figure 6 for the
corresponding current values. When this substitution is made, the
proportional differences between the maxima and minima, expressed in
voltage values, become somewhat smaller than these differences ex-
pressed in current values. However, on account of the intermedia-
tion of the telephone receiver between the sound vibrations and the
electrical indications, it is still not possible, without further calibration
of the apparatus, to obtain absolute or even relative values of the
sound intensity. Several methods of obtaining this calibration in
terms of sound intensity suggest themselves. One method is to
employ the distance law in connection with experiments performed

394 PROCEEDINGS OF THE AMERICAN ACADEMY.

in the open. Another method, which is perhaps more interesting,
would be to study directly the characteristics of the magneto-telephone
when used as a generator, by measuring directly the amplitude of
vibration of the telephone diaphragm and then measure with the rec-
tifier the resulting alternating voltage.

V. Sensitiveness of the Method.

The galvanometer employed in the above experiments was not
particularly sensitive. Its resistance was decidedly too low and
entirely inappreciable in comparison with the resistance of the rec-
tifier. A galvanometer of the highest attainable resistance would
hardly be appreciable in resistance in comparison with the resistance
of the rectifier. Also the transformer employed between the telephone
circuit and the rectifier circuit did not have high enough resistance in
its secondary. With evident improvements in these respects the sensi-
tiveness of the apparatus could be greatly increased, in case one should
desire to measure extremely feeble sounds. However, without such
improvements the sensitiveness of the apparatus seems to greatly
exceed that of any of the physical methods heretofore employed for
the measurement of sound.

For a deflection of .2 millimeters on the galvanometer scale, the
power in the galvanometer circuit, calculated from the current-voltage
curve of Figure 6, amounted to 1.53 X 10"^ ergs per second, while
Lord Rayleigh '^ finds the minimum energy that will affect the human
ear to be 1.11 X 10"^ ergs per second, for a pitch of 2730 vibrations
per second. That is to say, with the apparatus of the present experi-
ments, in order to get .2 mm. deflection it is necessary to develop
energy in the galvanometer circuit at about the rate at which energy
is received by the human ear at minimum audible intensity. On
account of the inefficiency of the magneto-telephone receiver when
used as a phono-electric generator, energy at a rate much greater than
this is required by the magneto -telephone receiver in order that this
amount of power may get into the electric circuits.

The use of a carbon transmitter in place of the magneto-telephone
receiver for the sound receptor, while not so constant as the magneto-
telephone, is of course enormously more sensitive. With this arrange-
ment the condenser C of Figure 2 was replaced by a battery of four
storage cells, and a transformer of lower resistance primary was em-
ployed. Preliminary tests showed that the galvanometer would then

* Lord Rayleigh, Proceedings of the Royal Society, 1877, Vol. 26, p. 248.

PIERCE. — A METHOD OF MEASURING THE INTENSITY OF SOUND. 395

be thrown off the scale when a small organ-pipe was sounded almost
anywhere on the same floor of the building, even when the passage of
the sound from the pipe to the transmitter was through long corridors
and several partly closed doors. "With the pipe at P and the trans-
mitter, without sound-collector, placed at 3 in the room shown in
Figure 7, a delicate Weston ammeter gave a whole scale deflection,
which corresponded to a current of 392 microamperes. With the use of
this ammeter instead of the galvanometer readings could be taken with
great rapidity and may be easily made self-recording.

To test further the sensitiveness of the apparatus with the carbon
transmitter substituted for the magneto-telephone receiver, this trans-
mitter was supplied with long leads and placed outside the building.
An assistant was sent off across an open field. When the assistant
blew a small organ-pipe, C 5, 1024, at a distance of 100 meters away, a
deflection of 5 mm. corresponding to a current of 3.06 X ,l(r^ amperes
was obtained. A locomotive whistle at a distance of perhaps a mile
gave 75 millimeters deflection.

Jefferson Physical Laboratory,

Harvard University, Cambridge, Mass.
December 27, 1907.

Proceeding's of the American Academy of Arts and Sciences.
Vol. XLIII. No. 14. — February, 1908.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

LONGITUDINAL MAGNETIC FIELD AND THE

CATHODE HAYS.

By John Trowbridge.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

LONGITUDINAL MAGNETIC FIELD AND THE
CATHODE RAYS.

By John Trowbridge.

Presented December 11, 1907. Received January 6, 1908.

In a previous article on the Magnetic Field and Electric Discharges ^
I described various phenomena which occur under the effect of a lon-
gitudinal field, both at the auode and the cathode. The present
article deals with the effects of the field on the cathode rays after they
have passed into the region beyond the anode. The form of tube which
contained the rarefied gas was similiar to that generally employed to
study the canal rays : a cylindrical tube with a concave aluminium cath-
ode, an iron anode with an orifice at its centre, and a prolongation of
the cylindrical tube behind the anode. Two exactly similiar tubes of
this form, equal in size, were connected by the same adjunct to the
exhausting pump, and were, therefore, under the same pressure.

In one of these tubes (Figure 1) the back of the anode, or iron termi-
nal, was completely shielded from the prolongation of the tube in which
canal rays are usually studied. A glass tube passed through the orifice
in the iron terminal and was welded to the walls of the prolonged larger
tube. No rays could enter the canal ray region except through the
orifice in the iron terminal. In the companion tube the back of the ter-
minal was not protected, and rays could pass over the periphery of the
iron terminal and also through the orifice at the centre of the terminal.

It was found that the tube (Figure 1) apparently reached a much
higher state of exhaustion than the companion tube, which I shall call
B, although they were connected by the same large adjunct to the
pump and, therefore, there could be no question of slow transpiration.
One tube, A, was close to the X-ray stage, while B was hardly beyond
the stratification stage.

I replaced these tubes by two spherical bulbs (Figure 2) similiar to
those commonly employed as X-ray tubes ; these tubes also had pro-
longations, or canal regions, similiar to those of the previously mentioned

, ^ These Proceedings, 28.

400

PROCEEDINGS OF THE AMERICAN ACADEMY.

cylindrical tubes. In one, A, the back of the terminal was protected as
in Figure 1 ; in the other, B, the back was not protected. The same
phenomenon was observed. Tube A came up nearly to the X-ray
stage, while the other was apparently far below this stage.

Figure 2 is a photograph of the state of the two tubes. It is evi-
dent that the mere appearance of the discharge between the terminals
is no criterion of the state of exhaustion unless one carefully considers

the forms of the tubes and the extent of
wall surface submitted to the bombardment
of the cathode rays. The difference which
I describe is probably due to the walls of
the prolongation of the vacuum tubes, A
being more protected from this bombard-
ment than those of tubes B.

The forms A apparently showed the canal
rays as perfectly as the forms B, when the
iron terminal was made the cathode ; and
these rays did not seem to be modified by
the protection of the edges of the orifice in
the iron tube by the glass tube. The canal
rays, therefore, come entirely from the space
between the anode and the cathode.

A solenoid (S, Figure 1) was next slipped
over the prolongation of the tubes. This
prolongation, therefore, formed the core of
the solenoid, and the rays passing through
the orifice in the terminal could be sub-
mitted to a longitudinal magnetic field.
By a proper adjustment of the position
of the solenoid the cathode beam passing
through the orifice in the iron terminal or
the anode could be brought to a sharp
focus on the end of the prolongation tube.
This was also the case in tube B ; but in
the latter there was also a phosphores-
cent ring surrounding the focus of the central beam which was due
to bringing to a focus the rays which passed over the periphery of the
circular iron anode. The phenomenon of focussing or convergence
of the rays is due to these rays seeking the weakest part of the
magnetic field. The field formed by the iron disc terminal outside
the solenoid, together with that of the short solenoid, had two
channels in which the field was weakest : one through the orifice at

oo o o

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OCXS) o

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Figure 1.

TROWBRIDGE. — MAGNETIC FIELD AND THE CATHODE RAYS. 401

the centre of the iron terminal, the other around the periphery of this
terminal.

It was to be expected that the Canalstrahlen could not be brought
to convergence by this application of a longitudinal magnetic field.
The phosphorescence of these rays remained unaffected.

Phosphorescence of the Canal Rays.

In most cases the phosphorescence caused by the Canalstrahlen is
similiar in color to that produced by the cathode rays. When, how-

FlGlRE 2.

ever, the Canalstrahlen fall upon lithium chloride, there seems to be a
marked difference. Professor J. J. Thomson in his treatise on Con-
duction of Electricity through Gases ^ describes a form of tube in which
a layer of lithium chloride can be bombarded alternately by both kinds
of rays, and says that when the layer is struck by the Canalstrahlen it
shines with a bright red light ; the lines of the lithium spectrum are
very bright, and when the direction of the discharge is reversed, so that
the layer is struck by the cathode rays, its color changes from bright red
to steely blue, giving only a faint continuous spectrum but not the
lithium lines. The layer speedily becomes black in hydrogen.

2 University Press, Cambridge, 1906, p. 042.

VOL. XLIII. — 26

402 PROCEEDINGS OF THE AMERICAN ACADEMY.

I have succeeded in producing the red phosphorescence by the cath-
ode rays, thus annihilating the distinction, in this case, between the
two kinds of rays. The method adopted seems to have a general
application in the study of phosphorescence and is as follows :

The vacuum tube was of cylindrical form. Figure 1 shows the arrange-
ment. A represents the circular iron terminal with its central orifice
perforated by a glass tube ; S, the solenoid ; L, the ground-glass stopper
with the layer of lithium chloride at its end.

When the solenoid is excited, the cathode rays can be brought to a
sharp focus on the layer at L, and the apparatus can be called in pop-
ular language a magnetic lens. A very intense cathode beam can be
made to converge at L by suitably adjusting the solenoid. The rays seek
the weakest part of the magnetic field. Immediately on striking the
layer of lithium chloride the red phosphorescence appears at the centre
of the focus, and is surrounded by the blue phosphorescence ; either the
red or the blue can be produced at pleasure.

It seems, therefore, that if w is the number of cathode particles, m their
mass, V their velocity, and ;/ the number of positive particles, m^ their
mass, i'' their velocity, that the equation

holds on the unit of area, and that the distinction, in this case between
the color produced by the cathode rays and the Canalstrahlen disap-
pears. The production of the two colors is a question of energy on the
unit of area.

I have examined the phosphorescence of the other metals of the same
groUp as lithium chloride. Caesium chloride gives a very bright blue
color for both the cathode and the canal rays, and the blue lines of the
spectrum appear with the application of the cathode beam. Rubidium
gives both a red and a blue color ; the red, however, is much less bright
than in the case of lithium chloride. All of these salts are quickly de-
composed. Calcium tungstate recovers from fatigue very quickly, and
is not decomposed appreciably, even after long exposures. Its use for
X-ray screens is therefore substantiated by these experiments.

Application of a Longitudinal Magnetic Field to X-ray Tubes.

In the article on the Magnetic Field and Electric Discharges,^ I
stated that the application of a longitudinal field at the anode might
form a useful method of concentrating the cathode rays. Since this

' These Proceedings, 28.

TROWBRIDGE.

MAGNETIC FIELD AND THE CATHODE RAYS.

403

article was written I have studied the subject more carefully, and have
devised a safe and practical method, which is analogous to that I have
used in the study of the phosphorescence of the Canals trahlen.

The form of tube is shown in Figure 1. A is an iron disc ^node
(Figure 3) with a perforation at its middle. S is a solenoid which can
be adjusted along an appendix to the X-ray bulb. F is the usual focal
plane of polished platinum. Opposite this focal plane the glass is
blown thin to permit the egress of the X-rays. The cathode beam is
brought to a focus at F by adjustment of
the longitudinal field of the solenoid. f^

The dimensions of the apparatus are as
follows :

Diameter of the spherical bulb, 10 cm.
Distance between the concave aluminium ca-
thode and the iron disc anode, 6 cm. Length
of the cylindrical appendix containing the
focal plane, 10 cm. Internal diameter of the
cylindrical appendix, approximately 3 cm.
The outer diameter of the solenoid was 10
cm., the internal diameter 6 cm. Length,
4 cm. There were 10 layers of no. 18 wire,
Brown and Sharpe gauge. The solenoid
was excited by two or five storage cells. A
narrower appendix and a smaller bulb oppo-
site the focal plane would give a stronger
field with less current.

When the cathode stream is made to con-
verge by the solenoid on the focal plane F,
the intensity of the X-rays is increased in
a marked manner. Judging the intensity
by the distance at which equal intensity is Figure 3.

obtained with and without the magnetic

field, I have more than doubled the intensity of the X-rays by the
application of the field. The method has the advantage of producing
the X-rays from a sharp focus and should, therefore, give better
definition.

It may be urged that the amount of energy employed in exciting the
magnetic field could, with equal advantage, be added to that which ex-
cites the tube ; but this would result in possible strain or danger to
the tube and would not result in bringing the stream to a sharp focus.
The large bulb need not be blown thin, and therefore the danger of per-
foration can be greatly lessened ; moreover, the application of the mag-

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404 PROCEEDINGS OF THE AMERICAN ACADEMY.

netic field serves as a rectifier, and when a Leyden jar is used it allows
only the oscillation from the cathode to reach the focal plane.

The canal rays appear to fatigue certain substances, — for instance,
lithium chloride and rubidium chloride, — and after the application of
these rays the blue phosphorescence of the cathode rays is diminished.
It can, however, be restored by increasing the strength of the cathode
beam. This can be accomplished by the following arrangement. A
storage battery was connected to the exhausted tube through a large
running water resistance, and a spark gap was inserted in the circuit.
The coatings of a small Leyden jar were connected to the spark gap ;
the spark seemed continuous to the eye. Under the effect of the
longitudinal magnetic field a very brilliant phosphorescence could be
produced even after extreme fatigue of the group lithium, caesium, and
rubidium chlorides. It is therefore probable that the cathode phos-
phorescence can be restored by stronger and stronger cathode rays
condensed in the manner I have described.

Jefferson Physical Laboi;atory,
Harvard University.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 15. — March, 1908.

NOTE ON SOME METEOROLOGICAL USES OF THE

POLABISCOPE.

By Louis Bell.

Ikvestioations on Lioax and Heat made and pcblished, wholly or in part, with Appropriation

FROM THE RUUFORD FUND.

NOTE ON SOME METEOROLOGICAL USES OF THE

POLARISCOPE.

By Louis Bell.

Presented January 8, 1908. Received January 27, 1908.

This is merely a preliminary notice of certain facts regarding atmos-
pheric polarization which may prove to have some prognostic value.
They were incidental to a proposed study of the character of autumnal
haze which the writer undertook last year at Mount Moosilauke, N. H.
This peak, 4811 feet high, has an almost uninterrupted sweep of horizon
over a radius of one hundred miles or so and offers an excellent chance
for investigating the distribution and nature of the haze that veils the
landscape in early autumn. For instruments I took along a Savart
polariscope, merely a Savart plate with a bit of tourmaline as analyzer,
an extemporized double-image polarimeter of the type outlined in the
early and valuable paper of Professor E. C. Pickering,^ a couple of
carefully calibrated photographic wedges for determining opacities,
and a direct vision spectroscope.

A prolonged easterly storm, about the only thing which could have
defeated the program, cut short observations upon the summit, but a
week of preliminary observations at Breezy Point (elevation 1650 feet)
at the base of the mountain yielded results which seem to be of suffi-
cient interest to put upon record.

These were made mostly with the Savart polariscope, an instrument
which, from its very wide field of view and great sensitiveness, showing
even one or two per cent of polarization, enables sky conditions to be
very readily investigated. The character of the sky polarization, with
its general symmetry and maximum in a plane at 90° solar distance, is
well known, but the nature and causes of its casual variations have not,
perhaps, received the attention that is their due. Nearly everything in
the landscape polarizes by reflection to a greater or less extent, the
more as the specular component of reflection is the greater. For
example, the glossy upper surface of a maple leaf polarizes strongly at
fairly large angles of incidence, while the mat lower surface has only

* These Proceedings, 9, 1 et seq.

408 PROCEEDINGS OF THE AMERICAN ACADEMY.

a trifling effect — which facts explain the old observation of Spottis-
woode that ivy leaves polarize particularly well. Grass, trees, stones,
especially if wetted, all produce their effect, which, when sky polariza-
tion is cut off by white cloud, is generally a maximum in the vertical
plane.

I have several times observed this terrestrial polarization carried up
by reflection into low-lying cloud as noted by Pickering (loc. cit.), or
even into near-by dense fog otherwise entirely neutral. A completely
cloudy sky is otherwise practically free of polarization, but in a partially
clear sky white cumuli commonly show some effects with the Savart
plate, and light cirri often give bands almost as strongly as the clear
sky. This may be due to the usually considerable height of cirri,
— quite enough to allow noticeable polarization to have origin below
them, — or to their letting through considerable polarized sky light
from above, — a phenomenon which I observed from the summit
station in the case of rather thin layers of cloud in which it was
immersed.

One of the most striking features of the sky polarization observed
from Breezy Point was the extent to wb.'ch it appeared while originating
over short stretches of air. Mounts Kineo and Cushman, about three
miles distant and dark with a heavy growth of conifers, repeatedly
showed strong polarization effects from intervening haze, and at times
slopes within a mile brought out the bands, although less conspicuously.
On several occasions the polarization on Kineo and Cushman was sen-
sibly as considerable as on peaks at ten or fifteen miles distance.
Similarly, in the brief observations on the summit, the Green Mountains
and the almost effaced Adirondacks showed little if any more polari-
zation than the peaks in the same direction in the middle distance,
although the former were eighty to one hundred miles away and the
latter only twenty to forty miles. These results follow from the ex-
ponential relation between distance and apparent absorption, but show
clearly the magnitude of the effects due to comparatively short reaches
of air.

At no time was I able to repeat the results obtained by Tyndall in
the apparent clearing up of the haze by observation through a crossed
Nicol. In this case the mountains remained dim, Nicol or no Nicol,
showing that the typical autumnal haze, often whitish blue near the
horizon, acts mainly by general obstruction and diffusely reflecting
a good deal of light, the polarized component being usually only
moderately strong.

Haze in general is well known to be due simply to suspended par-
ticles of one sort or another, and haze which produces polarization, as

BELL. — SOME METEOROLOGICAL USES OF THE POLARISCOPE. 409

well as the ordinary sky polarization, is well known to be due to par-
ticles, whether of dust or water, or of other nature, small compared with
the wave-length of light. Lord Rayleigh ^ has given the theory of this
action in considerable detail.

The polariscope integrates the effect of such particles along the line
of sight, and this information may have considerable meteorological sig-
nificance. The light- scattering particles which produce sky polariza-
tion are much finer than those which produce coronae and similar
phenomena, with the beginnings of ordinary reflection. In artificial
fogs the nuclei gradually grow from the polarizing dimensions to those
which scatter white light and become visible. It is not easy to assign
exact dimensions to the finer particles. They are quite certainly much
less than a quarter wave-length in diameter, that is, say 100 ^^.|x, and
probably run very much smaller. From the very exhaustive work of
Barus ^ it appears that the diameter of the particles to which visible
fog and coronae in a fog chamber of laboratory dimensions are due
range from .0005 /i. upwards, those near this limit showing as fog, while
the coronae began to form as the diameters reached 10 /a and above.
The fog particles to which lunar coronae are due often rise to greater
dimensions, 20 or 30 yu..

Now such fog particles are the preliminary to rain, which forms by
the accretion of these particles to a size that readily falls ; and it is
well known that water vapor, even when saturated as shown by the
psychrometer, will not begin to condense to visible fog unless in the
presence of nuclei about which aggregation takes place. These may
be of very fine dust , or even of water particles electrically charged to
an extent that resists the surface tension that would otherwise promote
evaporation. Such charged aqueous nuclei may exist in unsaturated
air at very small diameters, down to 1 or 2 /t^, as has been shown by
J. J. Thomson,* by Wilson,^ and by others. Between these almost mo-
lecular dimensions and those indicated by coronae are the light scat-
tering particles active in sky polarization. Their effect, that is, the
amount of light scatiered, varies, as Rayleigh ^ has shown, as the inverse
fourth power of the wave-length of the light affected and directly as
their volume, assumed to be small compared with a wave-length. Now

plotting the resulting equation, /= -V, one obtains a group of curves
shown in Figure 1 which discloses the cause of the familiar intense blue

2 Phil. MasT., 1871, p. 107 et seq. ' Smithsonian Cont., No. 1373.

* The Disci large of Electricity through Gases.

5 Phil. Trans., 1897. « Rayleigh, loc. cit.

410

PROCEEDINGS OF THE AMERICAN ACADEMY.

of the scattered light. As larger particles grow during the process of
nucleation or are present as dust, the blue gets weak and whitish
from the scattering of white light. Near the horizon, where the light

1— 1
II
<

i-t

1 — "^ "

"-;

•^

5 1

X in ft /A X 10°

FlGURE 1.

traverses a long reach of atmosphere and coarser dust is common, one
gets the familiar weakening of the sky blue.

The process of increasing nucleation, which results in cloud formation
and frequently in subsequent rain, can be followed very closely by the
polariscope. A fall in polarization, particularly when the spectroscope

BELL. — SOME METEOROLOGICAL USES OF THE POLARISCOPE. 411

shows the presence of much aqueous vapor, indicates the progress of
nucleation.

On several occasions I noted this phenomenon in the Breezy Point
observations. Starting with strong polarization on the distant hills to
the southward and a strong rain band visible in the spectroscope, the
next few hours showed a conspicuous weakening of the polarization,
followed presently by the formation of visible clouds, and in at least
two cases by precipitation. In short, if from change of temperature or
other cause cloud is due to form in any particular direction, the nuclea-
tion which precedes visible fog formation is bound, other things being
equal, to cut down the polarization. The prognostic value of this pro-
cess depends largely upon the rate at which it progresses. In two
instances which I noted, the decrease toward the south occupied most
of an afternoon. Of course a drifting in of coarser dust particles would
produce weakening of polarization, but the concurrence of weaken-
ing with a heavy rain band intimates very strongly that nucleation is
progressing.

A detailed study of the changes would require the use of a sensitive
polarimeter, by which variations from the theoretical polarization could
be accurately measured. Observations of this kind, made where there
is a wide sweep of horizon, should frequently disclose incipient cloud
formation and the causes which produce it. The use of a spectro-
polarimeter would be very desirable, as showing by the change in the
quality of the scattered light the progress of events. The nature of
the minute nuclei, whether dust or water particles, is not definitely
known. After a heavy rain storm the lower strata seemed to have
been cleared pretty effectively of polarizing nuclei, while the upper sky
remained much as before. On one occasion, more than twenty years
ago, I was taking rain band observations on Moosilauke and was favored
with a day in which the distant peaks, even up to one hundred miles,
stood out almost as black as silhouettes, while the sky took on a deep
hue almost startling in its unfamiliarity. A polarimeter would cer-
tainly have given extremely interesting results had it been at hand.
It seems quite possible that one might get a fairly clear idea of the
relative number and distribution of nuclei in the upper air by such
means.

It would certainly be interesting also to find out whether the appar-
ently very strong absorption of ultra-violet rays by the atmosphere is
due to any genuine absorption or merely to a serious loss of light by
lateral scattering, which Rayleigh has shown may perhaps be due to
the air molecules themselves. In the lower strata my observations
pointed rather to dust than to minute water nuclei, since a whitish

412 PROCEEDINGS OF THE AMERICAN ACADEMY.

haze showed powerful polarization on near-by peaks, making it clear
that the haze was extremely heterogeneous. The conditions which
would produce stable water nuclei of strongly polarizing size on a clear
day would tend to reduce larger droplets to the similar order of mag-
nitude instead of leaving them to superimpose specular reflection.

I am not disposed to suggest that in the polariscope we have a
meteorological tool of vast importance, but my preliminary observations
certainly show that it gives a most instructive view of the very early
stages of atmospheric nucleation, and especially if combined with rain-
band observations it should have material prognostic value as regards
comparatively local conditions. There is also a chance for forming a
clearer idea of the conditions of nucleation in the upper air, including
the very high altitudes, since polarization is manifest after the sun is
so far below the horizon as to illumine only the upper strata. I bring
the preliminary facts to notice here in the hope that some one with a
suitable location and opportunity for systematic observation may find
them useful as a guide to further work along this line.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 16. — April, 1908.

CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE
MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE.
E. L. MARK, DIRECTOR.— No. 195.

THE SENSORY REACTIONS OF AMFHIOXUS

By G. n. Tarkek.

CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE
MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE.
E. L. MARK, DIRECTOR. — No. 195.

THE SENSORY REACTIONS OF AMPHIOXUS.i

By G. H. Paekeb.

Presented March 11, 1908. Received March 5, 1908.

Table of Contents.

Introduction 415

Li^ht 416

Heat 428

Mechanical stimulation .... 431

Chemical stimulation 436

luterrehition of sensory meciian-

isms in ampliioxus 439

Central nervous system and sen-
sory mechanisms in ampliioxus 441

Sensory meclianisms in amphioxus
and their relations to vertebrate
sense organs 443

Summary 449

Bibliography 450

1. Introduction.

Whatever position may be assigned to amphioxus in the classifi-
cation of the chordates, it is now generally admitted that this animal
retains many of the more primitive features of the ancestors of the
vertebrates. Such features not only occur in its anatomy and em-
bryology, but are to be expected in its activities. As the structure
of amphioxus throws light on the complex organization of the verte-
brates, so its activities, may give some indication of the way in which
the more complex functions of these animals have come into being.
It is from this standpoint that I have undertaken the study of the
sensory reactions of amphioxus.

The material upon which this work was based is the so-called West
Indian amphioxus or lancelet, Branchiostoma caribbaeum Sundevall, a
close relative of the common European form, B. lanceolatum (Pallas).
This material was collected and studied during the summer of 1905
while I was at the laboratory of the Bermuda Biological Station
located at Hotel Frascati, Flatts Village, Bermuda. The living

^ Contributions from the Bermuda Biological Station for Research, No. 12.

416 PROCEEDINGS OF THE AMERICAN ACADEMY.

lancelets were obtained from the Flatts Inlet, which leads from the
outer waters to Harrington Sound. This inlet, through which a
strong tidal current is almost always running in one direction or the
other, contains long stretches of coarse coral and shell sand, and it
was in these sandy stretches, especially near the open mouth of the
inlet, that the lancelets were found in abundance. They likewise
occurred, as recorded by Barbour (;05, p. 110), in the sandspit near
the inner end of the inlet opposite Hotel Frascati, but they were by no
means so abundant there as in the coarse shelly stretches which were
near the outer mouth of the inlet and at low tide were still covered
by several feet of water. From this source, with the assistance of
some of the negro boys from the neighborhood, a daily supply of large,
vigorous lancelets was obtained, and, as the animals were available in
the laboratory almost immediately after they were caught, the con-
ditions were unusually favorable for a study of their sensory reactions.
For experimental purposes these lancelets proved to be very satis-
factory. They could be kept for a number of days in a vigorous
condition in large glass jars containing sea water and some coral sand,
provided that from time to time the sea water was renewed, and their
resistance to the adverse conditions of operative experiments was as
great as that of B. lanceolatum (Haeckel, '80, p. 141).

In the shoal water of Harrington Sound northwest of Trunk Island
the expeditions from the laboratory on several occasions dredged
Andrew's lancelet, Asymmetron lucayanum Andrews, but this species
was not sufficiently accessible nor abundant to make it a satisfactory
form for experimentation. In testing the sensory reactions of the
lancelets I therefore limited my work to the more common species,
Branchiostoma caribbaeum, and attempted to determine the re-
actions of this species to light, to heat, and to mechanical and chemical
stimuli.

2. Light.

Although the sensitiveness of amphioxus to light was known to
Costa ('39, p. 4) 2 and many other earlier investigators, and has since
been generally admitted, much difference of opinion has been expressed
as to the degree of this sensitiveness. Willey ('94, p. 10) declares that
" if a lighted candle is carried into a dark room in which amphioxus
are being kept in glass jars, the excitement produced among the small

2 The statements concerning the reactions of amphioxus to lisht given by
Costa do not occur in his first account of this animal (Costa, '34, p. 49) as
cited by Krause ('97, p. 513), but in his later and more lengthy description
(Costa. '39, p. 4).

PARKER, — THE SENSORY REACTIONS OF AMPHIOXUS. 417

fish is indescribable," and Nagel ('9P, p. 79) states that "plotzliche
Belichtung liisst dann die samtlichen Exemplare wild durchs Wasser
jagen." Hesse ('98i\ p. 461) confirms these observations and records
that light calls forth vigorous swimming. On the other hand, Niisslin
('77, p. 23), who also tried sudden illumination, affirms that amphioxus
is only very slightly sensitive to light, and Rohon ('82, p. 38) ex-
presses the belief based on experimental evidence that the so-called
light reactions of this animal are really reactions to heat, and that it
is not sensitive to light at all, or at most only to a very slight degree,
— an opinion concurred in by Kohl ('90, p. 185).

In consequence of this difference of opinion the first question to be
settled was, whether amphioxus was or was not sensitive to light. I
therefore repeated the experiments made by Willey, Nagel, and Hesse,
and with confirmatory results. When sunlight, daylight, lamplight,
or even candle-light was allowed to fall into a previously darkened
glass dish containing a dozen or more amphioxus, the whole company
swam about for a minute or so in wild confusion and then dropped as
though exhausted to the bottom. At first sight this seemed to be
conclusive evidence of the great sensitiveness of amphioxus to light,
but a more careful scrutiny of the steps in the experiment showed that
this was not necessarily so. When light first fell upon the dish, all
the lancelets did not begin at once to swim about excitedly. What
usually happened was that a few moved slightly, and in doing so they
touched others ; these then sprang suddenly into active locomotion,
and in an instant the whole assembly was swimming in wild confusion.
Thus it would seem that, while light was the initial stimulus for a
few individuals, the wild and excited swimming which gave the im-
pression of great sensitiveness to light was not due directly to this
factor, but to mechanical stimulation caused by mutual contact.

To test this h}^othesis I placed a shallow dish of sea water con-
taining twenty live amphioxus in a dark room and, after about an
hour, I threw upon it the light of a strong lamp ; in a few seconds all
the animals were swimming as though in the utmost excitement. I
then let them rest in the dark for a full hour, whereupon, without
illuminating the dish, I felt for one with a glass rod, and, having
touched it, I soon heard an agitated movement in the dish such as
had followed the previous sudden illumination. Upon turning on
the light the animals were found to be in as much commotion as at
the trial in which light had been the initial stimulus. I then took the
twenty animals that had been used in these two experiments and put
each one in a separate dish of sea water and placed each dish in an
approximately light-proof compartment by itself After an hour I

VOL. XLIII. — 27

418 PROCEEDINGS OF THE AMERICAN ACADEMY.

illuminated dish by dish in turn with the sauie lamp that had caused
the whole assembly of lancelets to swim wildly about when together,
and noted the individual reactions. Of the twenty animals tested,
twelve reacted, some more, some less, but none vigorously ; eight ab-
solutely failed to give any response whatsoever, even after continued
illumination. The twenty animals were then placed together in a
single glass dish, and, after about an hour, they were suddenly sub-
jected to bright illumination, with the result that they exhibited the
same commotion as was seen in the first of these experiments. I
therefore conclude that the wild swimming recorded by Willey, Nagel,
and Hesse is not, as they believed, evidence of great sensitiveness to
light, but is the result of the mechanical stimulation of one amphioxus
touching another, and that amphioxus, as stated by Niisslin, is really
only very slightly sensitive to light.

Rohon's belief that the so-called light reactions of amphioxus are
really reactions to radiant heat is not supported by my observations.
Contrary to the statements of Rohon, amphioxus is responsive to
light that has passed through a heat screen ; nor does Rohon seem
to have been aware of the fact, pointed out later by Krause ('97,
p. 514), that a few centimeters of sea water is as effective a heat screen
as the alum solution that he used, and that consequently in all his
experiments that were carried on with some depth of sea water, the
animals that were supposed to be subjected to radiant heat were as
a matter of fact as completely shielded from it as though they were
behind an alum screen. Kohl's concurrence in Rohon's opinion does
not seem to be founded on any observations of his own, for he ('90,
p. 182) states that he had no opportunity to work with living material.
I therefore believe that the slight initial locomotor response that am-
phioxus usually makes when a beam of light is suddenly thrown on
it is dependent upon the light waves themselves and not upon radiant
heat.

Although amphioxus is assuredly not so sensitive to light as many
investigators have supposed it to be, it does show a capacity to
respond to a considerable range of this form of stimulus. Nagel
('96, p. 80) stated that its characteristic reactions could often be
called forth by a relatively weak stimulus, such as the diffuse light of
a cloudy day. In my own experience animals that have been kept in
the dark for some time will usually react to light of not more than a
few candle-meters intensity, but the same individuals after lengthy
exposure to ordinary daylight will often fail to respond to a beam of
strong sunlight. Obviously the capacity of the animal to respond to
light is more or less determined by its previous condition, its sensi-

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 419

tiveness diminishing with continual exposure to light and increasing
when the light is excluded from it. But even under the most favor-
able circumstances the reactions to light as compared with those to
other kinds of stimuli are relatively slight in amphioxus.

Although amphioxus shows much diversity as to the intensity of
light to which it will react, in another respect its responses to this
form of stimulus are very uniform. In all the tests I carried out, I
never observed a reaction to a rapid diminution of light, and the
reactions to light that did occur were always the result of a rapid
increase of intensity. When an animal was resting quietly on its side
in a shaded aquarium and a beam of sunlight was suddenly thrown
upon it, it would usually respond by one or two vigorous locomotor
leaps, after which it might come to rest even in the sunlight. If now
the sunlight was suddenly cut off, no response followed. That this
failure to respond was not due to exhaustion from over-exposure to
light was easily shown by quickly throwing on the sunlight a second
time, whereupon a reaction much like the first one usually followed
immediately. In fact, a moderately rapid alternation of full light and
shadow was generally followed for a number of times by reactions to
the light and no reactions to the shadow till, after numerous trials, the
animal ceased to respond at all. Amphioxus is therefore stimulated
only by such rapid changes of light intensity as involve an increase in
the illumination. This agrees fairly well with Nagel's statement
('94, p. 811 ; '96, p. 80) that sudden shadow calls forth from amphi-
oxus either faint responses or none at all. In my experience the latter
part of this statement is correct.

Having ascertained that amphioxus is sensitive to light, the next
question that naturally arises is what portion of its body serves as the
receptive organ for this stimulus. Numerous answers have already
been given to this question. The conspicuous pigment spot at the
anterior end of the nerve-tube discovered, according to J. Miiller ('39,
p. 198), by Retzius, was held by the former ('44, p. 95) and many other
investigators to be a primitive eye. Hasse ('76, p. 287) believed that
the light receptors were two lateral patches of integumentary cells,
one on each side of the flattened anterior end of the animal. Niisslin
("77, p. 25) was of opinion that the extreme anterior portion of the
dorsal fin was the part sensitive to light. Krause ('88, p. 136), who
discovered in the substance of the nerve-tube a pigment that he believed
resembled visual purple, was thereby led to assume that this tube was
the receptive organ for light. Nagel ('94% p. 811) claimed that the
whole outer skin was receptive to light. Hesse ('98', '98'^) maintained
that the numerous small pigment spots of the nerve-tube were each a

420 PROCEEDINGS OF THE AMERICAN ACADEMY.

single eye comparable to the eye of a planarian ; and to these Joseph
(: 04) added certain large cells in the anterior part of the tube which,
from their structure, he believed also to be light-receptors.

To ascertain what part of the body of amphioxus is sensitive to light,
I had planned to use local stimulation, and with this in view I arranged
an acetylin light with a condensing lens and a pinhole diaphragm, so
that I could have at command a small beam of strong light with which
to test locally the various parts of the animal's body. Unfortunately
the strongest artificial light that I could get was insufficient to call
forth an invariable reaction, and I was at last driven to use con-
centrated sunlight for this purpose. This was obtained by mounting
a mirror in an open space adjacent to the laboratory, and so directing
it that a horizontal beam of sunlight was thrown through a window
into the laboratory. This beam of light was screened of its heat by
being made to pass through seven centimeters of water contained in a
glass vessel with flat sides, and it was concentrated by a large lens
whose principal focus was about twenty-five centimeters. A few centi-
meters nearer the lens than its principal focus and in the cone of con-
centrating light, an iron diaphragm with a pinhole was placed that
intercepted all the light except that which passed through the pin-
hole. In this way a well-circumscribed minute beam of intense light
was obtained, and by means of this beam the body of the amphioxus
was explored while it rested in a glass dish of sea water with flat sides.
It was found by experiment that the dish containing the amphioxus
could be moved about with considerable freedom without disturbing
the animal. In this way the beam of light was brought to bear on any
desired part of the animal's body.

My first experiments were directed toward ascertaining the value of
the so-called eye-spot at the anterior end of the nerve-tube as a recep-
tive organ for light. Experiments had already been made on this
organ by Nagel ('94^, p. 811 ; '96, pp. 40, 80), who recorded that after
the animal's anterior end, including the eye-spot, had been cut off,
the lancelet was found to be as sensitive to light as ever, a condition
confirmed by Hesse ('98i\ p. 461). I repeated this experiment on
six lancelets. All were first tested with light and found to respond
when suddenly illuminated. The anterior tip of the body with the eye-
spot was then cut off, and after an hour all were tested again. I was
unable to distinguish in this second test that the lancelets were any
less sensitive to light than before the removal of the eye-spot, and my
results thus confirm those of Nagel and Hesse.

Although these results demonstrate conclusively that the so-called
eye-spot is not essential to the light reactions of amphioxus, they do

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 421

not show that this spot may not be a Hght-receptive organ. To test
this possibility I attempted by means of the minute beam of light
already described to illuminate the spot exclusively, and to see if a
reaction resulted. This was by no means easily done, for the spot is
so small that its position in the living animal cannot well be observed
directly, but must be surmised. Furthermore, when the light enters
the substance of the animal, it becomes much scattered, and hence
may reach other parts than those it is intended to illuminate. Never-
theless, it was possible on a number of animals to throw intense light
on the eye-spot without getting a response, though, when the light was
moved to a position somewhat posterior to the spot in question, a
vigorous response followed. I therefore conclude that not only is the
so-called eye-spot of amphioxus unessential to its light reactions, but
that this organ is in no sense a light-receptor. These physiological
results, then, support the view long ago advanced by Stieda('73, p. 51)
on the basis of anatomical evidence, that this spot is not a visual organ.
For this reason I shall in future call it simply the anterior pigment
spot, though its nervous nature seems well established by the recent
work of Edinger (:06). In a similar way I tried to get reactions from
lancelets by directing the beam of light on the flattened sides of their
anterior ends, where, according to Hasse ('76), light-receptive organs
were supposed to be located. In no instance did I get a reaction, and
I therefore agree with Niisslin ('77, p. 12) and with Kohl ('90, p. 183)
in denying the existence of light-receiving organs in this region.

Lancelets from which the anterior end of the dorsal fin had been
removed were as sensitive to light as before the removal, nor did
normal lancelets react to the small beam of light when it was thrown
on this part of the fin. I therefore believe that Niisslin ('77, p. 25)
was in error when he declared that the anterior end of the dorsal fin
was the portion of the animal that was sensitive to light.

The part of the body of amphioxus that can be stimulated by light
extends from a point a little behind the anterior end posteriorly to
the tip of the tail. A beam of concentrated sunlight thrown across
the body in any region between these two points always elicits some
response. Krause ('97, p. 514) states that the anterior end somewhat
distal ^ to the anterior pigment spot is most sensitive to light, and
that the tail end is not sensitive at all. My results, as already stated,
are almost precisely the reverse of these. I have found the anterior
end, both in front of the anterior pigment spot and at least immediately
posterior to it, insensitive to light, and the tail end extremely sensi-

* By distal Krause means, judging from the context, posterior.

422 PROCEEDINGS OF THE AMERICAN ACADEMY.

tive. As Krause in his first description of the animal ('88, pp. 132
135) stated that it rests with its tail out of the sand, and in his
later account ('97, p. 513) that the head usually projects, a fact well
established since the time of J. Milller ('41, p. 399), is it not possible
that in his study of the light reactions of this somewhat ambiguous
form Krause has fallen into the not unnatural error of confusing
the ends ?

The extent of the region that is sensitive to light in amphioxus very
nearly coincides with that of the nerve tube, and evidence obtained by
local stimulation points to this structure as the part of the animal
stimulated by light. Krause ('88, p. 132; '97, p. 513) has advanced
the opinion that the bluish coloring matter that appears in the walls
of the tube when this structure is treated with alkali is similar to the
visual purple of the retina, and is in this way connected with the light
receptive function of the tube. On treatment with alkali this coloring
matter, according to Krause, becomes visible around the pigment spots
in the tube, and among these are included the anterior pigment spot as
well as the series of smaller spots that extend through almost the whole
length of the tube ; but it has just been stated that by local stimula-
tion the anterior pigment spot can be shown to be insensitive to light,
and since this coloring matter is as characteristic of that spot as of the
other spots in the tube, I do not believe that the blue substance de-
scribed by Krause has any essential connection with the light-receptive
apparatus. As Hesse ('98% p. 556) has pointed out, Krause's belief
that the blue is analogous to visual purple is unsupported by any good
evidence, for this material shows no such relation to light as is charac-
teristic of visual purple. It therefore seems to me that Krause's view
is untenable.

Since amphioxus shows no response when strong light is thrown on
the anterior end of its nerve-tube in front of the third or fourth seg-
ment, a region in which occur certain large cells supposed by Joseph
(: 04, p. 21) to be sensitive to light, I conclude that these cells are not
open to that kind of stimulation and that the light-receptive organs
must lie posterior to this region.

Although it is impossible, for reasons already given, to illuminate
amphioxus locally with great precision, the exact portion of the animal
that is stimulated by light can be determined with fair accuracy.
This portion corresponds to the region in which the nerve-tube contains
the small eye-cups described by Hesse. This correspondence is so pre-
cise that it seems very probable that these organs are the true photo-
receptors. It must not be forgotten, however, that, in all regions where
light has proved stimulating, this agent in its passage into the more or

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 423

less transparent animal first penetrates the skin, and it is not impossi-
ble that the receptive organs for light really lie in this layer, as main-
tained by Nagel ('94^ p. 811) and Jelgersma (:06, p. 390). This
opinion is strengthened by what has recently been made out concern-
ing the sensitiveness to light of the skin of certain reptiles, amphibians,
and fishes, particularly ammocoetes (Parker, : 03*^, : 05'').

Since I was unable to devise an experiment whereby the nerve-tube
in amphioxus could be illuminated without having the light pass through
the skin, I cannot be absolutely sure where the light-receiving organs
lie, but there is a certain amount of indirect evidence on this question,
all of which points in one direction. As has already been shown, the
skin on the anterior end of the animal is not sensitive to light, this
form of sensitiveness beginning posteriorly at no special region so far as
the skin is concerned, but exactly where the eye-cups first occur in the
nerve-tube. This evidence, so far as it goes, favors Hesse's view that
these eye-cups are the true light-receptive organs. Another piece of
evidence has to do with the exact distribution of the animal's photo-
receptiveness and that of the eye-cups. If different regions on the
length of a lancelet are tested for their sensitiveness to light, they will
be found to vary considerably. The most sensitive region is that
which extends from a point several segments behind the anterior tip of
the nerve- tube posteriorly over about one quarter of the length of the
animal ; the region next in sensitiveness is the most posterior quarter
of the animal ; and the least sensitive part of the whole region which
is at all sensitive is approximately the middle half. In a series of
trials in which was determined the relative intensity of the minimum
amount of light necessary to stimulate in these three regions, it ap-
peared that, if the minimum intensity for the anterior portion, the
most sensitive part, is called 1, that for the posterior part was 1.5, and
for the middle part 25.0, while an intensity of 0.5 was not stimulating
to any part of the animal. If, now, the distribution of the eye-cups
described by Hesse be taken into account, a striking correspondence to
the sensitiveness to light will be found. In Branchiostoma caribbaeum
the most anterior eye-cups occur in the third segment, and the remain-
ing cups form a more or less segmentally arranged series reaching to
the last segment of the body, which is practically the tip of the tail.
In this series, so far as numbers are concerned, three general regions
can be distinguished. The first region, the one in which the cups are
most numerous, extends from about the fourth segment to about the
twentieth ; the region second in abundance covers about the last twelve
segments of the body ; and the third region, or the one in which they
are fewest, is the middle portion of the body between the two regions

424 PROCEEDINGS OF THE AMERICAN ACADEMY.

just defined. Hesse ('98^, p. 457) states that in Branchiostoma lan-
ceolatum the eye-cups are most abundant anteriorly and diminish
in numbers posteriorly, till in the tail there may be not more than
one cup to a segment. But this description, as Boeke ( : 02, p. 352)
and Joseph (:04, p. 18) have noted, is somewhat defective. In five
specimens of B. lanceolatum from Naples that I have examined, the
distribution was essentially like that in B. caribbaeum, in that, in ad-
dition to the considerably increased number of cups anteriorly, there
was also an increase in the number in the tail region. This confirms
Joseph's statement (:04, p. 18) for this species and agrees with the
discovery of Boeke (:02, p. 352), that in young pelagic individuals of
B. lanceolatum there are to be seen two groups of eye-cups, one anterior
and the other posterior, corresponding to the two concentrations men-
tioned. These two groups presumably unite later to form one series.
The general plans of distribution of the cups in the two species, then,
undoubtedly agree, and, since these plans of distribution correspond
to the different degrees of sensitiveness to light for the different parts
of the body in B. caribbaeum, I believe that the eye-cups described by
Hesse, and not the skin, are the light-receptive organs.

In Branchiostoma caribbaeum, as in B. lanceolatum according to
Hesse ("98'', p. 458) and Boeke (:02, p. 351), the ventral eye-cups, as
well as those of the right side, point in the main ventrally, while those
of the left side point mostly dorsally. Hesse states further that in
B. lanceolatum the cups of the two sides tend toward the right, and he
suspected that this might be correlated with a possible habit of resting
on a particular side. But in testing this hypothesis Hesse ('98'',
p. 459) found that the animals rested about as frequently on one side as
on the other, and he therefore abandoned it. In B. caribbaeum I could
not see that the cups were directed more toward the right than toward
the left, but it was apparent that the majority pointed ventrally. This
position seemed to me entirely consistent with the habits of this species,
for it naturally lies in the sand with the ventral side obliquely xqiper-
most, the majority of eyes being thus directed toward the most prob-
able source for light. However, individuals that were in a glass dish
without sand were, so far as I could see, equally sensitive to light fall-
ing on them in any direction.

If the Hght-receptive organs in amphioxus are the eye-cups of the
nerve-tube, any part of the animal containing these organs might be
expected to retain its sensitiveness to light. Nagel (94"^, p. 811 ; '96,
p. 79), after cutting these animals in two transversely, found that both
halves still reacted promptly to light, but less energetically than the
whole animal did. Krause ('97, p. 514) declared that after halving

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 425

amphioxus the posterior part is much less reactive to light than the
anterior, and Hesse ("98'', p. 462), who repeated these experiments,
could get only a trembling response to light from the anterior half and
no response at all from the posterior one. My own results agree ex-
actly with those of Hesse. I tested six fresh animals with strong sun-
light, and, having found them sensitive to it, I cut each one transversely
in two. After an hour, and again after two hours, I tested them with
strong sunlight : the anterier halves always trembled markedly, but I
could perceive no reaction at all to light from the posterior halves.
When, however, I touched the posterior halves with very dilute nitric
acid in sea water, they sprang and wriggled forward through the water
most energetically, showing that they were still capable of active re-
sponse. I am therefore convinced that cutting the animal in two has
a profound effect upon its powers of reaction to light, greatly dimin-
ishing this capacity in the anterior half and practically nullifying it in
the posterior half

Although amphioxus reacts to light thrown upon almost any part
of its body except the anterior end, its reactions are characteristically
different in accordance with the region stimulated. When light is ap-
plied to the sensitive anterior fourth of the body, amphioxus almost
invariably gives a vigorous backward spring, often accompanied with
backward swimming. If light is applied to the less sensitive middle
portion of the body, there is usually a slight backward spring, but
sometimes the animal simply curls the body slightly. If the light is
applied to the most posterior fourth, the animal almost invariably
springs forward. In extreme cases, at least, the resulting movement is
the most effective one for removing the animal from the source of
stimulation. This is still more clearly seen when a beam of strong
light parallel with the longitudinal axis of the amphioxus is directed
against its anterior or its posterior end. In the former case the animal
darts backward, and in the latter forward ; in each instance it moves
away from the source of light. For animals generally backward swim-
ming is unusual, since the majority of negatively phototropic animals
when illuminated from in front first orient by turning the anterior ^nd
away from the light before they begin active locomotion, whereas in
amphioxus the locomotion is executed without the initial step of ori-
entation. The case is parallel to that of a positively phototropic
pycnogonid described by Cole (:01, p. 201) ; this animal moves toward
the source of light either with the anterior or the posterior end first.
In the pycnogonid, however, the two kinds of movement are associated
with somewhat different types of locomotion, for the animal s/.ri7ns
backward toward the light or creeps forward toward it, whereas in
amphioxus the reaction in both cases is simply swimming.

426 PROCEEDINGS OF THE AMERICAN ACADEMY.

As a result of such a system of reactions, Branchiostoma caribbaeum
falls under the bead of negatively phototropic animals, and this is also
the case with B. lanceolatum, which, according to W. MiiUer ('74, p. 7)
and others, avoids light as far as possible when in captivity, and with
Asymmetron lucayanum, whose habit, according to Andrews ('93,
p. 214), is to collect on the side of the dish away from the light. Evi-
dence of the same kind is also at hand for B. caribbaeum. If, into the
middle of a large square glass vessel so placed that the sunlight falls
obliquely into it through one side, living lancelets are dropped one by
one, they fall to the bottom as a rule without response, whereupon
they often begin swimming, and in practically every trial come to rest
near the side of the glass away from the sun.

If a large glass aquarium is arranged so that one side and the halves
of the two ends adjacent to it, as well as the corresponding portion of
the top, are covered with light-proof paper and a number of amphioxus
are allowed to swim freely about in it, they will be found during the
day resting almost exclusively on the bottom of the darkened part,
whereas during the night they will be found about equally distributed
over the bottom.

Since amphioxus swims away from a source of light, it is negatively
phototropic (Parker, :06, p. 61), and, since it is active in the light and
comes to rest in darkened situations, it is photokinetic (photodynamic).

Light acts on amphioxus in a distinctly local way, and not as it
does on animals, like most vertebrates, which possess eyes capable of
forming images. This power enables a vertebrate to discriminate at a
distance areas of light from areas of shade in a general field. If an
amphioxus lying quietly in deep shade is stimulated to locomotion by a
minute beam of strong light, it will dart off in almost any direction
irrespective of the shadows and lights about it. Should it by accident
come into the sunlight, it usually continues to swim ; should it come
into shade, it usually comes to rest. The light about amphioxus has
little or no influence on the animal except when it falls with full
intensity on the animal's body. This is dependent upon the fact that
amphioxus is not very sensitive to light, and therefore reflected light
of low intensity does not stimulate it, and, further, that the light-
receptive organs of the animal have no adequate means for the forma-
tion of images.

Under ordinary conditions amphioxus is buried in the sand, except-
ing for one end. Which end this is has been a matter of some dispute.
Yarrell ('36, p. 468) stated that the specimen from which he took his
description was found by Mr. Cough with its tail sticking out from
under a stone ; and Steiner ('86, p. 497) declared that the animal

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 427

usually rests with its tail out of the sand, a statement repeated by
Krause ("83, pp. 132, 135). Subsequently and without explanation
both Steiner ('88, p. 41) and Krause ('97, p. 513) abandoned this
opinion for the opposite one. That the animals ordinarily rest with
the anterior end out of the sand was the opinion of J. Miiller ('41,
p. 399 ; '44, p. 84), Nlisslin ('77, p. 18), Rohon ('82, p. 37), Willey
('94, p. 9), Nagel ('96, p, 79), and others, and any one who carefully
inspects a number of lancelets at rest will soon be convinced that this
is the normal position. Although the extruded anterior end is the
portion of the animal least sensitive to light, lancelets in their resting
positions in ordinary sand will respond quickly enough to this stimulus.
Thus in a large dish of coral sand, over which there were a few inches
of sea water, the anterior ends of twenty-three lancelets were counted
in dim light. As a result of throwing on a beam of very strong light,
most of the heads were quickly withdrawn under the sand, only two
remaining visible. This reaction is doubtless dependent on the stimu-
lation of the most anterior eye-cups, and as a rule the resting position
of the animal is such that this naturally occurs.

The negative phototropism of amphioxus has led to the belief that
during the day it remains buried in the sand, except perhaps for its
anterior end, but that during the night it leaves the sand and leads
a more active existence. W. Miiller ('74, p. 7) states that Branchi-
ostoma lanceolatum is nocturnal, and at twilight comes to the surface
of the sandbank in which during the day it is buried. Rice ('SO, p. 9)
mentions that individuals of this species which were seen swimming
at night in the Naples Aquarium were quiescent in the daytime, and
Rohon ('82, p. 36) and Krause ('97, p. 513) also speak of this species
as having nocturnal habits. B. caribbaeum showed no evidence of
such habits. All inspections of the aquaria that I made after night-
fall, and with caution as far as light was concerned, demonstrated that
the lancelets remained in the same position in the dark as in the light.
Further, several glass vessels containing coral sand and known numbers
of lancelets that were sunk over night to the natural level of the sand
in the bed of the inlet, contained, when taken up the next day, the
same numbers of animals, thus indicating that the lancelets had re-
mained buried and had not come out on the surface of the sand, where
the current would surely have swept them away, even supposing that
they had not started swimming. Although this experiment was tried
only a few times, the results always led to the same conclusion, and it
therefore seems probable that at least B. caribbaeum is essentially a
burrowing animal, and that it leaves its native sand only when forced
to by the accidental action of currents, etc.

428 PROCEEDINGS OF THE AMERICAN ACADEMY.

3. Heat.

The reactions of ampliioxus to heat have been scarcely more than
touched upon by the numerous investigators who have studied the re-
actions and habits of this animal. As has already been pointed out, the
opinion of Rohon ('82, p. 38) and of Kohl ('90, p. 185), that the light
reactions of amphioxus are really reactions to radiant heat, is erroneous ;
moreover it is not to be expected that animals like amphioxus, which
live always under some depth of water, would have any special organs
for the reception of radiant heat, since such heat penetrates water only
a centimeter or two and hence would almost never reach these forms.
The kind of heat that is a factor in the environment of amphioxus is
the molecular vibration such as we recognize in the temperature of
water, and this certainly has a distinctly circumscribing influence on
the lancelets.

In testing the effect of heat on amphioxus, the temperature of the
water in which they were living in the Flatts Inlet, 31° C. (July, 1905),
was taken as the normal, and two series of experiments were conducted,
one at temperatures above this and another at temperatures below it.

When lancelets were transferred from sea water at 31° C to sea water
at 35° C, they responded by darting about several times and then sink-
ing quietly in the characteristic way to the bottom of the dish. Their
subsequent reactions were essentially normal.

When transferred to sea water at 37° C, they made several quick
darts, and finally fell quietly to the bottom, where they rested. When
under these circumstances dilute acid was applied to them, they were
found still to be actively responsive.

When transferred to water at 40° C, they made one or two sudden
plunges, after which they dropped to the bottom, while their semi-
transparent substance gradually whitened. When touched with dilute
acid, the animals quivered slightly, but did not react otherwise. In a
short time they were dead.

At 42° C. the animals darted once or twice, whitened quickly, and
dropped to the bottom dead. Bert ('69, p. 21) states that water at
41° C. kills amphioxus in two minutes.

At 45° C. no locomotor response at all was given, and the animals
began to whiten at once ; they were apparently dead before they
reached the bottom of the dish.

It is plain from these records that heat has at least two influences
on amphioxus. It stimulates them to momentarily vigorous locomo-
tion, and it also brings about death by the coagulation (whitening) of
certain materials in their living substance. The coagulation begins

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 429

apparently at about 40° C, and may be so rapid at 45° C. as to
prevent the characteristic locomotor reaction which occurs at lower
temperatures.

Having ascertained something of the general effect of heat on amphi-
oxus, I next endeavored to determine what parts of its body were
sensitive to this stimulus. To this end I used a temperature 39° C,
a little lower than that which caused coagulation. I attempted to
apply this temperature locally by touching the animal in the region
to be tested with a sharply bent glass tube kept at the required
temperature by a rapid flow of hot water through it. The bent tube
thus heated was applied successively, but at considerable intervals, to
the anterior end, middle, and tail of several animals, and their reactions
recorded. As a check on this method the bent tube filled with water
at 31° C. was also applied to the animals, with the outcome that the
mechanical stimulation was found to be so considerable that the results
dependent upon temperature could not be rightly judged, and the
method was therefore necessarily abandoned.

I next tried running a gentle stream of warm sea water on different
parts of the lancelet's body while it was resting in a dish of sea water
at 31° C, and I checked this method by using the same strength of
stream, but at the normal temperature. This procedure proved much
more satisfactory than the use of the bent tube, for the current of
water at the normal temperature seldom, if ever, gave rise to a re-
sponse, while that at 39° C. very generally did.

"When the heated current was applied to the anterior end of a lance-
let, the animal very usually swam immediately backward a short dis-
tance. When it was applied to the tail, the animal often moved
forward. When it was applied to the middle of the body, the reaction
never was locomotor, but only a slight bending or jerking of the body,
and even this was apparent in only about one out of every ten trials.

The reactions of amphioxus on being immersed in warm water or
touched by a current of warm water follow so quickly on the appli-
cation of the stimulus that I am convinced that stimulation takes
place on the surface of the animal, for there was scarcely time for the
heat to reach by conduction any relatively deep-lying part. I there-
fore conclude that heat is a sensory stimulus for amphioxus, and that
it is very probably effective for the whole outer surface of the animal,
the head being most sensitive to it, the tail less, and the middle
portion of the body least.

In a second series of tests, water cooler than 31° C was used
with which to stimulate the amphioxus. When animals were trans-
ferred from water at 31° C. to water at 25° C, they swam about with

430 PROCEEDINGS OF THE AMERICAN ACADEMY.

more energy than at the normal temperature. Finally they dropped
quietly to the bottom.

At 20° C. they swam very energetically and near the top of the
water, but finally dropped to the bottom ; subsequently, on being
touched with a rod, they swam, but not so energetically as at the
normal temperature.

At 15° C. they swam vigorously, but soon dropped to the bottom.

At 10° C. they passed into the water without swimming, dropped to
the bottom, and remained quietly there.

At 5° C. they behaved as at 10° C. After remaining on the bottom
at 5° C. for five minutes, they were removed to water of ordinary tem-
perature, where their reactions seemed to be entirely normal.

Five active amphioxus were then dropped into water at 4° C, and
after half an hour they were tested and all found to be dead. The
temperature of the water at the end of half an hour had fallen to
2.5° C. This experiment was several times repeated, and always with
the result that death followed exposure to extreme cold for half an
hour or so.

Cold water from 25° C. to 15° C is certainly stimulating to amphi-
oxus. At 10° C. and lower no response is given, but death may
intervene, particularly at lower temperatures, from unknown causes.

All attempts at local stimulation with cold water were entirely
unsuccessful. Water at 15° C, when applied as a current to the
anterior end, tail, or trunk, was without effect, though, as already
mentioned, immersion in water at this temperature called forth vigor-
ous swimming. A current of water at 2° C, when applied locally to
the anterior end, tail, or trunk, gave rise, as might have been
expected, to no reaction.

The reactions to cold water, when they occurred, were quite as quick
as those to warm water, and must therefore have been the result of
a very superficial stimulation ; but whether this was a stimulation of
the whole outer surface, or of a special part of it, or of some special
region hke the entrance to the mouth, I am unable to say.

The fact that amphioxus swims away from any source of considerable
heat places it among negatively thermotropic animals. That it can
be stimulated to active, non- directive swimming by both heat and
cold shows it to be thermokinetic. That it should be stimulated by
cold, but not influenced in a directive way by this stimulus as it is
by heat, favors the view that it possesses, like some higher vertebrates,
separate receptors for heat and for cold.

pakker. — the sensory reactions of amphioxus. 431

4. Mechanical Stimulation.

As has been pointed out already, the apparently great sensitiveness
of amphioxus to light is really sensitiveness to mechanical stimulation,
a form of sensitiveness long ago remarked by Merkel ('80, p. 7), who
observed that a vigorous amphioxus would respond by very active
locomotion to the lightest touch of the forceps.

To test the reactions of amphioxus to mechanical stimulation I
first used a course pig-bristle mounted so that the rounded end could
be brought into contact with any part of the animal's exterior. When
the anterior end of an amphioxus resting in a shallow dish of sea water
was touched even lightly with the bristle, the animal usually sprang
backward, though occasionally forward. The backward spring was
often accompanied by a somersault-like movement, whereby the animal
became turned end for end. When the stimulus was applied to the
posterior part of the body, the result was almost invariably a forward
leap. This portion of the body, though sensitive, was not so much so
as the anterior end. The middle of the body was much less sensitive
than either of the ends, and when the tip of the bristle was applied to
it, there was often no reaction. When, however, a reaction did occur,
it was almost always a backward leap.

In general the reactions of amphioxus to mechanical stimulation
resemble in essential respects their reactions to light, showing that
the anterior end of the animal is most sensitive to such stimuli, the
posterior end less so, and the middle of the body least, and that back-
ward locomotion usually results from stimuli applied at the anterior
end or the middle, and forward locomotion from stimuli at the
posterior end.

By means of local stimulation the sensitiveness of different portions
of the body could be roughly determined. At the anterior end, though
the rostrum can be stimulated, the most sensitive parts are the oral
hood and the buccal cirri. When any of these parts is touched, back-
ward locomotion almost invariably follows. If the hood, but especially
the cirri, are touched only very lightly, they close and open with a
sudden movement not unlike winking. In resting animals this is
often carried out in what seems to be a spontaneous manner, but
close inspection shows that it is dependent upon the accumulation
on the cirri of debris from the current of water usually passing in at
the anterior end. When the cirri become fairly covered with minute
particles of coral sand, etc., this winking movement loosens these
particles, and at the same time vigorously expels the water from just
within the anterior opening of the animal, and thus removes the ac-

432 PROCEEDINGS OF THE AMERICAN ACADEMY.

cumulated debris. This reaction is doubtless dependent upon the
mechanical stimulation caused by the particles of sand, etc., on the
cirri, for, as already stated, the momentary contact of the end of
the bristle with the cirri will call it forth.

The great sensitiveness of the anterior end of amphioxus, which has
already been noticed by Krause ('88, p. 146), is resident chiefly in the
outer surface of the oral hood. This part of the animal is easily stimu-
lated by contact with any moving body and is the region especially
concerned with the reception of stimuli when, through the movements
of a few individuals, a whole assembly is set in violent commotion.
It is also probable that this part is especially stimulated when an
amphioxus, almost buried in sand, is made to draw back under the
sand by directing a fine stream of water on the exposed anterior end.

In the middle-trunk region the firm dorsal and lateral walls, and
even the delicate ventral one, are relatively insensitive to mechanical
stimulation.

The whole of the caudal region is more sensitive to mechanical
stimuli than the trunk region, but less so than the anterior end.
The surface about the atrial pore is especially sensitive to touch, and
a stimulation of this region not only results often in forward loco-
motion, but also in a wave of contraction that passes anteriorly from
the atrial opening over perhaps half the length of the thin ventral
atrial wall.

As amphioxus is so easily stimulated by gross mechanical disturb-
ances, it is not surprising to find that it will respond to such delicate
mechanical stimuli as sound waves. If a glass vessel that contains
resting amphioxus partly buried in the sand is gently tapped on the
side, the animals, as Rice ('80, p. 8) long ago observed, usually with-
draw temporarily below the sand, or at least move their cirri in a way
that resembles winking. That this is not due to the vibration of par-
ticles of sand against their bodies is seen from the fact that at least
the reaction of the cirri can be called forth from animals that are rest-
ing on a bed of cotton wool in a glass vessel of sea water when the
walls of the vessel are tapped. Another common form of response to
sound vibrations, often seen under the conditions just mentioned, is a
wave-like contraction of the atrial membrane. This membrane in fact
is so placed that it may be especially open to stimulation by sound
waves, for it is suspended between the atrial cavity and the outer space,
both of which are filled with sea water.

It is very probable that all these reactions to sound depend upon the
stimulation of some part of the tactile mechanism, for in the first place
amphioxus has no special organ that can serve it as an ear (Stieda,

PARKER. — THE SENSORY REACTIONS OF AlVIPHIOXUS. 433

'73, p. 52), and secondly, many sound vibrations can be sensed through
our tactile organs as well as our ears.

That mechanical stimulation serves as a basis for thigmotropic, geo-
tropic, and even rheotropic reactions cannot be doubted, though Lyon
(:05) has shown that rheotropism in certain fishes depends more upon
sight than upon touch. All three kinds of reactions are shown by
amphioxus.

The thigmotropism of amphioxus is evident from the following ex-
periments. Ten amphioxus were liberated in a flat-bottomed glass
aquarium containing a depth of 10 centimeters of sea water and five
centimeters of coral sand. After half an hour all the animals had
buried themselves in the sand, and after an hour and a half seven of
them had come to rest with their anterior ends a little above the level
of the sand, their usual position (p. 426). That these reactions were
not the result of the light that fell into the dish from above is seen
from the fact that similar reactions were obtained from animals that
were liberated in a covered glass dish of sea water containing a layer of
sand between one and two centimeters thick and illuminated by a mir-
ror from below only. Under these circumstances the amphioxus came
to rest in the sand, but in such positions that in many cases their bodies
were exposed to light through the glass bottom of the dish, though their
anterior ends projected into the darkness above the sand. Thus it is
evident that they did not enter the sand to escape the light. Moreover,
amphioxus will rest quietly, much as when it is in sand, provided all
but its anterior end is covered with small fragments of glass. Through
this covering the light may pass to the animal, and apparently this does
not disturb it, for its quiescence seems to depend merely upon the
contact of its body with the particles of glass. I therefore believe that
amphioxus is thigmotropic.

The movements by which amphioxus buries itself are not without
interest. As a rule the animal dropped passively through the sea
water to the sand below. When it came in contact with the sand, it
sometimes gave a sudden spring and disappeared below the surface.
More frequently, however, it straightened out upon the sand, as noted
by Miiller ('44, p. 84) and by Willey ('94, p. 10), and later, particularly
if it was moved by a current, it would arch and disappear below the
surface, as described by Rice ("80, p. 8). Its disappearance into the
sand was so quickly accomplished that it was impossible for me to as-
certain by direct observation whether the animal entered the sand with
the anterior end first or the tail first. Steiner ('86, p. 497) maintains
that the anterior end of the animal enters the sand first, and that it
may continue to burrow through the sand till this end emerges. He

VOL. XLIII. 28

434 PROCEEDINGS OF THE AMERICAN ACADEMY.

further asserts that the animals are incapable of burrowing with the
tail first. Miiller ('41, p. 399), however, in his description of the ani-
mal's habits implies that it enters the sand tail first, and often burrows
only far enough to cover the main portion of the trunk, leaving the
anterior end exposed. I attempted to ascertain the truth of the matter
by carefully uncovering animals that had buried themselves, thus
determining by direct inspection which end had probably entered
the sand first. I also noted in instances where the animal had failed
to cover itself completely which end was left exposed. These instances
were more conclusive than those of completely covered animals, for in
these cases there was no chance for an unobserved reversal of ends as
might occur where the animals were for a short time out of sight. In
the great majority of these cases the animals had evidently entered the
sand tail first, though there were some instances, especially among the
imperfectly covered ones, in which it was clear that they had entered
with the anterior end first. Other evidence on this question was de-
rived from animals on which a slight operation had been performed.
Amphioxus from which a part of the tail had been removed entered
the sand only after many trials, whereas others whose rostrum had
been cut off but whose tail was intact seemed to have no difficulty in
making their way into the sand. These observations are in agreement
with what was noticed in animals that had partly or completely buried
themselves, and I am therefore convinced, notwithstanding Steiner's
statement to the contrary, that amphioxus usually enters the sand tail
foremost.

In one respect the amphioxus buried in the sand were very different
from those lying freely on the surface. The free individuals were
usually very straight, as though held in form by the stiffness of the not-
ochord. The buried individuals, on the other hand, had when in the
sand a very tortuous outline, as though they had crowded their way in
between the coarse pieces of shell and coral. Such individuals imme-
diately became straight on being released from the sand.

Rheotropism, though present, is not a prominent feature in the re-
actions of amphioxus. In the inlet at the small landing pier in front of
Hotel Frascati large schools of small fish could be seen definitely ori-
ented in reference to the swift current. These schools maintained a
more or less constant position by swimming against the current about
as rapidly as the current would have carried them in the opposite
direction. When living amphioxus were dropped into these schools,
they drifted among the small fish on the way to the bottom without as
a rule the least locomotor movement, and, when they did move, they
never showed any tendency to orient to the current. Moreover, when

PARKER. — THE SENSORY REACTIONS OF AMPIIIOXUS. 435

they were placed in a floating aquarium the sides of which were of
netting so as to permit a strong current of sea water to pass through it,
they either drifted to the far end of the aquarium or swam irregularly
about and without reference to the current, though a few small fish
that were caught and put into the aquarium swam against the current
with precision.

These observations are in agreement with what Lyon (:05) found as
to the rheotropism of certain fishes, namely, that in large general cur-
rents their orientation is dependent not upon the direct stimulus of
the current, but upon the possession of a visual organ capable of form-
ing an image whereby they could fix their position in reference to mo-
tionless objects on the banks and in the bed of the stream. Since
amphioxus does not possess visual organs of such a character, orienta-
tion under these circumstances is not to be expected.

If, however, an amphioxus is put into a large cylindrical vessel filled
with sea water and the water is made to whirl in it, the animal is quickly
stimulated to swimming and swims vigorously against the current.
After a short period of active swimming, in which the animal will often
progress more rapidly than the current moves in the opposite direction,
it will drop to the bottom as though exhausted and be carried round
and round by the water. It was evident from the movements of the
animal that the stimuli to its locomotion were the momentary contacts
with the inner sides of the vessel next which it was often swept and in
all probability the varying rates of those parts of the current that
touched the sides of the animal. To such an irregular current amphi-
oxus undoubtedly reacts, /. e., under these circumstances it is rheotropic.

Amphioxus can also be shown to be slightly geotropic. This fea-
ture does not appear in its swimming, for though Steiner ('86, p. 498 ;
'88, p. 43) afiirms that the whole animal, or even a quarter of it, will
swim with full equilibrium, and is so quoted by Ayers ('92, p. 318)
and by Sherrington ('99, p. 1276), my own observations agree with
the statements of Rice ('80, p. 8) and of Willey ('94, p. 10), that in
swimming amphioxus may move with any side uppermost and may
continually change that sida This change of attitude during loco-
motion was so constant a phenomenon among the many amphioxus
that I watched that there is not the least question in my mind that
this animal during locomotion assumes no uniform position in reference
to gravity.

In its resting state, however, amphioxus shows some slight response
to gravity. As it lies on the sand it may rest for considerable periods
of time with any side uppermost, but after it has burrowed and come
to rest near the surface of the sand, it usually lies, as Rice ('80, p. 8)

436 PROCEEDINGS OF THE AMERICAN ACADEMY.

and Hesse ('98^". p. 459) have noted, with the ventral side uppermost
and always with the anterior end higher than the posterior. This
relation of the two ends might be supposed to be due to the need of
having the anterior end in clear water, and therefore to be a reaction
to the water and sand in the surroundings and not directly to gravity,
but that this assumption is false is seen from the following experi-
ments. If several amphioxus are placed in a closed box made of
coarse wire gauze and filled with sand and the whole immersed in
sea water, in a few hours they will be found at the top of the sand with
their anterior ends projecting into the sea water. If now the box is
cautiously inverted, some of the animals will keep their original
positions, and thus their anterior ends will project from the under side
of the box into the adjacent sea water ; but they will remain here only
a short time, for sooner or later they wiU make their way upward
through the sand to the top. In a similar way if, after they have
come to rest at the top, the box is rotated through a quadrant so that
their anterior ends project sidewise into the sea water, they will again
desert this position and move to the top. Further, if in a funnel
whose stem has been broken off short an amphioxus is buried in sand
in such a way that its anterior end projects downward out of the small
end of the funnel into the sea water, it will leave this lower end and
make its way upward through the sand to the top, even if, in doing
so, it emerges on sand above the level of the water. It is therefore
evident that amphioxus will come to rest in the sand only when its
anterior end is above its posterior one, and, from the conditions under
which this occurs, such responses seem to be strictly geotropic.

5. Chemical Stimulation.

The chemical sense of amphioxus, as remarked by Nagel ('94^ p. 192),
is not unlike that of a worm in that its seat is the whole outer surface
of the animal and not simply the region around the mouth. This
sense is doubtless serviceable chiefly as a means toward escape from
unfavorable chemical surroundings and probably has little or nothing
to do with the direct feeding habits of the animal. As is well known,
amphioxus does not seek its food, but takes what is brought to it in
water currents, selecting from this supply only in the crudest fashion,
if in fact it can be said to select at all. Nagel ('94b, p. 58) has shown
that the outer surface of amphioxus is sensitive to chloroform, etc.,
and declares that, notwithstanding the presence of the so-called
olfactory pit near the anterior end, one part of the animal's body is
about as sensitive to chemical stimulation as another, though the tail
may possibly be more sensitive than any other portion.

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 437

In testing amphioxus for chemical responses I used solutions of
sour, sweet, bitter, and alkaline substances, as well as solutions of
certain oils and other materials. All these solutions were made up
in sea water, and, where the strength is expressed as parts of a molec-
ular solution, sea water was used as a basis for this mixture instead
of distilled water.

For a sour substance I used nitric acid. If a pipette full of sea water
is discharged gently on the side of a resting amphioxus, there is usually
no reaction. On animals thus previously tested a few drops of a
^ solution of nitric acid were discharged successively on the an-
terior end, on the middle, and on the posterior end. In all these trials
vigorous locomotion was induced ; backward when the region of appli-
cation was the anterior end or the middle, and forward when it was
the posterior end. When a ^^f^^ solution was applied to the anterior
end or to the tail, the characteristic reactions were obtained, but there
was usually no reaction when this solution was applied to the middle
of the animal. A -^ solution called forth no reaction when applied
to the middle or the tail, but only when applied to the anterior end.
A ifyg- solution called forth no reactions at all. Hence to solutions
of nitric acid the anterior end is most sensitive, the tail next, and the
middle least.

A more detailed study of the anterior end showed the following
conditions. In an animal that in its normal state responded when
this end was stimulated by a -^'^^ solution of nitric acid, the re-
moval of the rostrum and the olfactory pit made no observable differ-
ence in its responses, thus confirming Nagel's statement ('94^, p. 192)
that the olfactory pit is not essential to the special chemical sensi-
tiveness of the anterior end. This pit, which was first described by
KoUiker ('43) and was believed by him to be olfactory in function,
was found in living animals to be lined with ciliated epithelium, by
the movement of which particles of carmine were carried into it firom
its poste?-ior edge and discharged from it nnteriorlij. Cutting off also
the buccal cirri left the animal still receptive to a ff^ solution.
When, however, enough of the anterior end was removed to take away
the velar tentacles, what remained could be stimulated only by a
^!^^ or a stronger solution of nitric acid. The high degree of sen-
sitiveness of the anterior end is therefore dependent upon parts not
farther posterior than the velar tentacles. Since these tentacles and
the buccal cirri are abundantly supplied with groups of sense cells
(Willey, '94, p. 20), it is not impossible that the great sensitiveness
of the anterior end is due to these groups of cells ; but to this question
I can give no conclusive answer.

438 PROCEEDINGS OF THE AMERICAN ACADEMY.

To make an alkaline solution, one per cent of potassic hydrate was
added to sea water, with the result that a somewhat milky precipitate
was formed. The filtrate from this mixture had a strongly alkaline
taste, but it did not call forth any response when it was applied either
to the tail or to the middle of amphioxus. At the anterior end it
caused the animal to dart backward vigorously.

For a bitter material picric acid was used. About a "^ solution
is very near saturation in sea water. To this solution, when applied
to the tail, middle, and anterior end, amphioxus reacted with charac-
teristic locomotion. All three regions were also stimulated by a ^3^
solution, but locomotion usually did not result. At yffg occasional
slight reactions were obtained, but only when the solution was applied
to the anterior end, the tail and middle being apparently insensitive
to this strength.

When a ten per cent solution of cane sugar in sea water was dis-
charged freely over the anterior end, the middle, or the tail of
amphioxus, no reaction of any kind was given.

No reactions were observed when the surface of the animal was
bathed with sea water containing the following substances in solution :
ether, chloroform, turpentine, oil of bei'gamot, and oil of rosemary.
However, when any of these materials in a pure state was applied
directly to the skin of amphioxus, a vigorous locomotor response was
elicited, as Nagel ('94'', p. 58) had previously found for chloroform and
oil of rosemary.

A one per cent solution of alcohol in sea water called forth no
response when applied to the anterior end, the middle, or the tail of
amphioxus. A five per cent solution stimulated the anterior end and
tail but not the middle, and a ten per cent solution stimulated all
three parts.

Not only are many chemical solutions stimulating to amphioxus,
but fresh water is likewise. When animals were dropped into sea
water to which had been added one- fourth fresh water, the animals
were observed to swim for a time more vigorously than in pure sea
water. When the sea water was diluted by an equal volume or more
of fresh water, the amphioxus swam most vigorously, and in very
dilute sea water or in fresh water they quickly died, as already ob-
served by Bert ('69, p. 21) and by Johnston (:05, p. 115). These
various mixtures were also locally stimulating. The mixture of one-
fourth fresh water and three-fourths sea water induced a slight back-
ward movement when applied to the anterior end, but apparently
stimulated no other part of the body. All mixtures containing more
than one-fourth fresh water stimulated both the anterior end and the

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 439

tail, but not even pure fresh water stimulated the middle of the animal.
When any of these stimulating mixtures were applied to the head,
the animal swam backward ; when they were applied to the tail, the
locomotion was forward.

These experiments show that the surface of amphioxus is stimu-
lated by solutions of nitric acid (sour), potassic hydrate (alkaline),
picric acid (bitter), and alcohol, and by strong ether, chloroform,
turpentine, etc. It is also stimulated by sea water diluted with fresh
water, a mixture of which may prove fatal. Such stimuli were most
effective at the anterior end of the animal, less so at the tail, and
least of all at the middle, and the reactions were always such as to
enable the animal to avoid the stimulus. So far as these tests go,
amphioxus may be said to be uniformly negatively chemotropic.

6. Interrelation of Sensory Mechanisms in Amphioxus.

The distribution of sensitiveness of amphioxus to the stimuli dis-
cussed in the preceding sections follows a very simple plan. To light,
heat, mechanical and chemical stimuli, the anterior portion of amphi-
oxus is more sensitive than the tail, and the tail is more sensitive than
the middle region of the trunk. A more accurate comparison of the
distribution of sensitiveness has shown that a response to light cannot
be elicited when the most anterior part of the body is illuminated,
though this region is very easily stimulated by either heat, mechanical
or chemical means. This fact and the agreement of the degrees of sen-
sitiveness to light with the numbers of eye-cups in different parts of
the nerve-tube have been given a reason for the conclusion that the
light receptors in amphioxus are the eye-cups themselves and not the
nerve terminals in the skin. Since the receptors for heat, mechanical
and chemical stimuli, lie in the skin, they must be distinct from the
photoreceptors. Further evidence of this separateness is, however,
seen in results obtained by exhaustion. If the tail of an amphioxus is
stimulated by concentrated sunlight ten or twelve times, the animal
will reach a state in which it no' longer responds to the illumination.
Wbile in this state it will react, however, with great certainty when its
tail is stimulated by water as 37° C, by contact with a camel's-hair
brush, or by a f^ solution of nitric acid. Thus from the standpoint
of exhaustion the receptors for light can be shown to be physiologic-
ally distinct from those for the other stimuli.

The extent to which separate receptors in the skin might be distin-
guished for the several effective stimuli cannot be judged by the distri-
bution of sensitiveness for these stimuli, because, so far as I could make

440 PROCEEDINGS OP THE AMERICAN ACADEMY.

out, this distribution was the same for all such stimuli. Evidence on
this point was to be had, however, from the following experiments on
exhaustion. After about twenty applications of a ff solution of
nitric acid to the tail of an amphioxus, the animal usually ceased to
respond to this stimulus. But on testing the same part of its body
with water at 37° C. or with contact from a camel's-hair brush, it was
found to be immediately responsive. In a similar way about thirty
vigorous strokes of a camel's-hair brush were needed on the tail of an
amphioxus before it ceased to react to this form of stimulation, where-
upon it was found still to be sensitive to water at 37° C. and to a solu-
tion of nitric acid. Finally after an animal had ceased to react to
water at 37 C. it was still sensitive to contact with the brush and to
acid. Thus, notwithstanding the fact that the distribution of sensitive-
ness for these several stimuli is such as to leave the question as to sep-
arate receptors unsettled, exhaustion shows very conclusively that their
operations are physiologically distinct (Parker, :07, p. 724),and as there
is no evidence that they may not be represented by separate terminal
organs in the skin, I believe that such organs are probably present.
To what extent a further discrimination might be possible, as, for in-
stance, the separation of terminal organs for cold and for heat, or for
the different kinds of chemical stimuli, cannot be stated, for no experi-
ments in this direction were undertaken.

To all the forms of effective stimuli that I employed, amphioxus
responded in but one way, namely, with such movements as would
remove it as directly as possible from the presence of the stimulus.
When the stimulus was applied to the anterior end or to the middle
trunk region, the animal moved backward, and when the application
was to the tail, it moved forward. In not a single kind of stimulus did
the animal move regularly toward the stimulus. This negative re-
sponse, which seems to pervade the whole sensory activity of amphioxus,
is the basis of its habit of retreat and characterizes much of what it
does. Even feeding, which is so usually a positive operation with
animals, is in amphioxus a relatively passive affair and unconnected
with any seeking reactions. It therefore seems that the whole sensory
system of amphioxus is employed as the initial mechanism in removing
the animal from possible danger rather than as an apparatus for leading
it successfully into new territory. This feature, as Steiner ('88, p. 42)
has already remarked, is perhaps the most striking peculiarity of the
sensory reactions of amphioxus.

The negative response of amphioxus to stimulation is of importance
in considering the question of the direction in which it swims. Rice
('80, p. 8) declares that amphioxus always swims with its anterior end

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 441

foremost and that he never saw it move with its tail in advance.
Steiner ('86, p. 497 ; '88, p. 41) also asserts that the animal moves with
the anterior end foremost. The locomotion of amphioxus is a rapid,
curiously, irregular wriggle, often accompanied with somersault-like
movements which make it impossible to be sure at any moment
whether the animal is swimming backward or forward. The results of
momentary stimulation, however, show very conclusively that amphi-
oxus can swim both backward and forward, and that the direction of
swimming at the beginning of any course is dependent upon the part of
the animal's body that was stimulated. But how long amphioxus
keeps to one form of movement I was unable to discover. The fact
that it usually buries itself in the sand tail first (p. 433) leads me to
believe that, though it can swim forward, as maintained by Rice and by
Steiner, it usually swims backward.

Another feature of the reactions of amphioxus is their great energy,
which is quickly followed by what seems to be complete collapse. For
a few moments the animal swims with the utmost vigor, and then drops
down quite motionless, as though it had become entirely exhausted
(Rice, '80, p. 9). That this is not exhaustion is seen from the fact that
a slight stimulus will usually cause a second round of activity ; but
after a few such efforts, the animal becomes unresponsive to further
stimulation and is doubtless temporarily exhausted.

7. Central Nervous System and Sensory Mechanisms

IN Amphioxus.

To what extent the uninjured central nervous system of amphioxus
is essential to its sensory reactions has already been briefly alluded to
in the account of this animal's reactions to light (p. 424), but now that
the other classes of stimuli have been described a more extended dis-
cussion of this subject may be undertaken. Steiner ('86, p. 498 ; '88,
p. 43), who was apparently the first to investigate the functions of the
central nervous system in amphioxus, states that after an animal had
been cut into two, three, or even four parts, all the parts reacted to
mechanical stimulation by swimming forward, and from these observa-
tions he concluded that the central nervous system of amphioxus is a
metameric structure without sufficient differentiation to allow one to
divide it into brain and spinal cord. Although his description of the
reactions of the pieces of amphioxus might lead one to infer that these
fragments reacted exactly as the whole animal did, it is plain from his
further account that such fragments were less sensitive than when they
made a part of the whole animal ; for he goes on to remark that, when

44:2 PROCEEDINGS OF THE AMERICAN ACADEMY.

the sensitiveness of the fragment becomes much lowered, it is only
necessary to put the piece in very dilute picric acid to call forth the
characteristic locomotion again. Johnston (:05, p. 124), however, states
that even a small piece of the tail of amphioxus can swim well and be-
haves much as the whole animal does. Nagel ('94^, p. 811 ; '96, p. 79)
declares that both halves of an amphioxus react promptly to light, but
less energetically than the whole animal does. But Danilewsky ('92)
maintains that the halves react, at least to mechanical stimuli, very
differently ; the anterior half is quite sensitive to this form of stimulus,
but the posterior half can be brought to react only with difficulty.
Krause ('97, p. 514) declares that the anterior half reacts vigorously
to light and the posterior half only slightly. Hesse ('98^, p. 462),
however, states that after division the anterior part only trembles on
being illuminated and the posterior part gives no reaction whatever.

My own observations on B. caribbaeum lead me to believe that
whether reactions will be given by both halves of this amphioxus or
not depends quite as much upon the nature of the stimulus as upon
any other factor. To light, as already stated, I have never been able
to get any response from the posterior half, though the anterior half
regularly trembled whenever strong light was thrown upon it. In
these respects my results agree exactly with those of Hesse, and they
were, moreover, so uniform and regular that I am led to suspect the
accuracy of Kra use's and of Nagel 's statements, at least so far as
they apply to the posterior half of amphioxus. After the nerve-tube
is cut, this part seems no longer able to respond to light. That this
is due to the small number of eye-cups in this region, as Hesse be-
lieved, is not true, for, as a matter of fact, these cups are almost as
numerous in the tail region as in any other part of the animal. In
my opinion the failure of the posterior half of amphioxus to react to
light is not due to the lack of sensitiveness, but to the interruption
of some centrally situated, reflex path. In the posterior half, appar-
ently, the sensory neurones that are stimulated by light cannot trans-
fer their impulses directly to the motor neurones of the same region,
but only indirectly through the anterior part of the nerve-tube ; hence
when this is removed the reflex ceases. It is in this way, rather than
through altered sensibility, that an explanation of this phenomenon
will, I believe, be found.

To mechanical, and especially to chemical, stimuli I found both
halves of amphioxus to be responsive, not, however, as Steiner de-
scribes, but rather as stated by Danilewsky, in that the anterior part
was found to be quite sensitive and the posterior part slightly so.
These observations suggest that the central tracts over which photic

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 443

impulses pass are separate from those which transmit sensory impulses
from the integumentary terminals. Since they show, further, that the
anterior half of the nerve-tube is different in function from the pos-
terior half, they are opposed to Steiner's view of a metameric nervous
system with equivalent segments, and favor the opinion advanced by
Ayers ('90^, p. 223) and supported hy Danilewsky ('92), that the
anterior end of the nerve-tube of amphioxus is already a primitive
brain and the posterior portion a spinal cord.

8. Sensory Mechanisms in Amphioxus and their Relations
TO Vertebrate Sense Organs.

The conditions presented by the sensory mechanisms in amphioxus
give some clue to what was probably a step in the differentiation of the
sense organs in primitive vertebrates. In these forms tactile organs
doubtless covered the whole exterior, as they now do the body of amphi-
oxus and that of the higher vertebrates, but these primitive ancestors,
like amphioxus, probably possessed nothing by way of differentiations
of these organs. Such differentiations are represented by the lateral-
line organs and the ears, both of which occur in the cyclostomes and the
higher vetebrates, but are wholly unrepresented in amphioxus, for the
ear supposed by Peters ('77, p. 854) to have been seen in this animal is
well known not to occur there. From the embryology of these organs it
seems probable, as Ayers ('92) has pointed out, that specialized tactile
organs gave rise to lateral-line organs, and that from certain of these
lateral-line organs the ear was differentiated. This history, based upon
morphological considerations, is parallel to what is known of the physi-
ology of these parts, for the lateral-line organs are stimulated by
material vibrations of low rate (Parker, :05'; lOS"; :03t'), possibly also
effective as tactile stimuli, and the ear is stimulated by material vibra-
tions of a higher rate, such as we recognize as sound. In my opinion the
stimuli for these three sets of sense organs may often overlap and the
three sets of organs constitute a genetic series, in which the tactile organs
are the oldest members and the ear the newest. Although the primitive
functions of these parts were doubtless (1) touch, (2) reception of slow
vibrations, and (3) hearing, all these parts, but especially the ear,
became involved more or less in the reflexes of equilibrium. This
relation, however, I believe to have been entirely a secondary one, and
not in any way to represent the original function of these organs as
intimated by Lee ('98) ; hence I have avoided any such expression as
equilibration sense. Amphioxus thus represents an ancestral verte-
brate with tactile organs, but without lateral-line organs or ears, and

4-44: PEOCEEDINGS OF THE AMERICAN ACADEMY,

in it the equilibration reflex can be said scarcely to have developed as
yet. In this respect it is like a young lobster before the statocyst has
been formed (Prentiss, : 01), and its powers of orientation to gravity,
revealed in only a slight geotropism when at rest, are correspondingly
small.

As the receptive organs for mechanical stimuli probably represent a
primitive stage from which the lateral-line organs and the ears of the
higher forms have developed, so the receptors for light doubtless give
some idea of what served as a source for the lateral eyes of vertebrates.
It has already been pointed out that the only organs that are known
to be light receptors in amphioxus are the eye-cups. Hesse ('98b,
p. 462), however, who was most instrumental in establishing this fact,
does not regard these organs as in any way the homologues of the
vertebrate eye, and in this opinion he is followed by Joseph (:04, p. 25),
But I must confess that to me the evidence seems to point very defi-
nitely to the conclusion already drawn by Boveri (:04, p. 411) that the
sensory cell of each eye-cup is homologous to a rod- or a cone-cell. In
my opinion the eye-cups of amphioxus represent a diffuse sensory
material from which an eye, like the lateral eye of the vertebrate, or
even a series of eyes, as suggested by Locy ('97), could have developed,
much as the ears of these animals have been differentiated from their
lateral-line organs. The objection to this view raised by Joseph (:04,
p. 24) that the photo-receptors of amphioxus do not occur in the exact
region from which the lateral eyes may have arisen does not appear to
me to be really serious.

The steps whereby the lateral eyes have come into existence are by
no means easily retraced, and it is for this very reason that any indi-
cation such as that afforded by amphioxus is of the utmost importance.
Whatever has been the exact course followed by the eye in its differ-
entiation, two remarkable but well-recognized features have resulted ;
first, the retinal elements of the lateral eyes are inverted in relation to
the stimulus as compared with the great majority of sense organs, and,
secondly, the retina in vertebrates develops not directly from the
external ectoderm, but as an outgrowth frohi the brain. It is rather
striking that two investigators have published, apparently quite inde-
pendently, essentially the same explanation of these facts. Balfour
('85, p, 508) long ago pointed out that, if we imagine that the retinal
part of the lateral eye was involved in the infolding that gave rise to
the central nervous organs, then the final positions of the rods and
cones at the surface of the retina away fi'om the light would be satis-
factorily explained, for this surface is the morphologically external
surface of the ectoderm. This explanation assumes that the eye was

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 445

functional on the exterior of the vertebrate ancestor before this animal
had an infolded central nervous system, and that in the course of its
differentiation it had passed as a functional eye into the deeper parts
of the head and out to the surface again, a process not so difficult to
understand when it is kept in mind that the bodies of many tunicates
and of amphioxus are relatively transparent. Essentially the same
explanation has been brought forward recently by Jelgersma 0 06), who
believes that the eye in its transition between its supposed place of
origin in the skin and its final position in the vertebrate head is well
represented by the eye of the larval tunicates. Boveri (: 04) has called
attention to the strong probability that the lateral eye has been derived
from photoreceptors in the central nervous system, and has pointed out
that the eye-cups of amphioxus are the probable source. He has not,
however, attempted to trace these eye-cups back, as Jelgersma (:06,
p. 393) has done, to a possible origin in the skin, but implies that they
may have arisen in place.

Although I believe that the explanation first advanced by Balfour as
to the origin of the lateral eyes of vertebrates has some truth in it,
there are certain aspects of it which in view of the present investiga-
tions need further consideration. Its first assumption is that the skin
of the ancestral vertebrate contained photoreceptors. The fact already
mentioned, that the skin of some amphibians and fishes, particularly
ammocoetes (Parker, :03s :05b), {g gQ supplied, would lead to the ex-
pectation that the skin of amphioxus would also contain such organs.
My own studies have given no grounds for this belief, and, though I
have not been able conclusively to prove the contrary, the evidence
seems to favor the idea that the skin of amphioxus is not sensitive to
light. As nothing is known, so far as I am aware, of the condition of
the skin in this respect in tunicates, adult or young, the belief that the
skin of the ancestral vertebrate contained photoreceptors must remain
a pure hypothesis, and it is conceivable that the photoreceptors of the
vertebrate eye may have arisen, not in the skin before the central
nervous system was differentiated, as suggested by Balfour and by
Jelgersma, but, as intimated by Boveri, fi-om the cells of the central
nervous system itself, in positions much as we find them now in
amphioxus.

The assumption of an external origin for the vertebrate photo-
receptors is helpful only in that it appears to offer an explanation of
the inverted positions of the rods and cones in the vertebrate retina.
But this explanation requires that from the time the photoreceptors
were formed in the skin till they made a part of an organized retina,
they should occupy the morphologically outermost portion of the cellular

446 PROCEEDINGS OF THE AMERICAN ACADEMY.

layer in which they were imbedded and that the individual photo-
receptors should be so oriented that their sensory ends would be toward
the morphologically outer surface of this layer and their nervous ends
away from it. In amphioxus it is true that the photoreceptors lie near
the morphologically outer surface (the surface of the central canal),
but their orientation is by no means constant in relation to this surface.
In some the sensory ends point toward this surface, but in most such
is not the case, and in a few they may even point away from this sur-
face. It therefore seems to me obviously impossible to explain the
orientation of the retinal rods and cones as transferred from the skin
to the retina through a series of stages in one of which as much free-
dom of position is shown as among the photoreceptors of amphioxus.
Nor, as Metcalf (:06, p. 528) has pointed out, is the condition more
favorable in the larvae of the tunicates, for here the photoreceptor
cluster in the brain is so large compared with the thickness of the
cellular wall in which it is imbedded (Froriep, : 06, p. 145) that its
orientation is no more related to the morphologically outer surface of
the wall than that of the eye-cups of amphioxus is. For these reasons
I believe that the inversion of the vertebrate rods and cones in relation
to the light is not due to their origin from definitely oriented external
photoreceptors, and since there is no positive evidence of the existence
of these receptors in the skins of animals that may fairly represent an-
cestors of the vertebrates, it seems to me that we are not warranted in
assuming their presence at all. I therefore agree with Boveri in
believing that the photoreceptors of vertebrates have arisen in the
central nervous system and not in the skin, as assumed by Balfour and
by Jelgersma.

If the unusual position and orientation of the rods and cones in
the vertebrate retina are not due to the origin of these bodies from ex-
ternal photoreceptors, how then are these peculiarities to be accounted
for? The position of the photoreceptor near the central canal is due
in my opinion to the method of growth of the nerve-tube, for the epi-
thelium surrounding the central canal is the source of the various cells
in the wall of the tube. When, therefore, a new type of cell, like the
photoreceptor, appears, it would be natural to expect it to arise from
this undifferentiated material, and, in my opinion, the photoreceptors
of amphioxus and of the tunicate larvae are in their position of origin.
This position is retained by their derivatives the rod- and cone-cells.

The very exact orientation of the rods and cones involves factors
quite different from those that govern their general position. The
eye-cups of amphioxus show only a very slight degree of orientation,
but so far as this goes, it is correlated with habit, in that the majority

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 447

of the eye-cups are directed ventrally and the animal usually rests in
the sand obli(|uely with the ventral side uppermost. Thus the ma-
jority of the eye-cups are in a position to receive effective stimulation.
If we imagine the body of amphioxus to be increased in muscular
strength, etc., whereby it would approach more nearly the condition in
the fishes and would consequently add much to its thickness, it follows
that the posterior portion would become less transparent and the pho-
toreceptors of the anterior end would be the only ones left in position
for effective stimulation. With the development of the mouth cavity,
the gills, etc., the source of light for the anterior photoreceptors would
become chiefly lateral and dorsal, and their orientation would doubtless
conform to this plan of illumination. If in accordance with this scheme
each eye-cup assumed the best possible orientation, it would lie with
its open end directed laterally and perhaps somewhat dorsally, i. e., the
contained sense cell would be oriented with its sensory end away from
the light and its nervous end towards this stimulus. With the dis-
appearance of the surrounding pigment cells as the cluster of photo-
receptors became a single retina, these elements would be oriented as
the rods and cones are. It is in this way, I believe, that the rods and
cones of the vertebrate eye have become inverted, rather than that the
inversion is inherited from a condition on the external surface of the
body.

Not only may the rod- and cone-cells be thus oriented at the begin-
ning, but it seems to me that their subsequent relations to the surround-
ing parts tend to keep them so. The chief factor in this respect is the
supply of materials necessary for their activity. Directed as they are
away from the central dioptric part of the eye, their sensory ends,
which are the parts most quickly exhausted by activity, are turned
toward the chief blood-supply, the choroid layer of the eye, and are,
therefore, in a most advantageous position to receive new materials for
metabolism. That important substances reach them from this side is
seen in the fact, well attested by experiment, that if the retinal pigment
layer is removed from a live retina, the regeneration of the visual pur-
ple in the rods is much retarded, if not completely stopped, though
simply placing the layer back again upon the retina will cause this
process to be resumed. Thus the inverted position of the rod- and
cone-cells is the one best adapted to keep their most easily exhausted
parts nearest the supply of materials necessary for their activities and
still hold them open to access to light. This factor is doubtless one
that has tended to retain the rod- and cone-cells in their inverted
positions.

The condition of light receptors in amphioxus lends no support to

448 PROCEEDINGS OF THE AMERICAN ACADEMY.

such views of the origin of the lateral eyes of vertebrates as have been
advanced by Sharp ('85), Burckhardt (:02), and others, according to
which the lens is regarded as having been derived from the primitive
retina, now replaced by a photoreceptive differentiation of a deeper
ganglionic part. I agree with Boveri in looking upon the eye-cups
of amphioxus and, I may also add, the corresponding elements of the
tunicate eye as the forerunners of the vertebrate retina, and, though
I was at first inclined to ascribe to these a direct origin from the
external skin, I now believe that we at least have no good reason for
this assumption.

The chemical sense is the only one in amphioxus that seems to
possess a well-marked special organ, the so-called olfactory pit, and
yet for this organ both Nagel's experiments and mine gave no signs
of sensitiveness other than that which characterizes the skin of the
anterior end. Notwithstanding this negative evidence, the morpho-
logical relations of this pit are such that I believe it is very probably
the homologue of the olfactory organ of the higher vertebrates. That
a special function has not been discovered for the olfactory pit in
amphioxus is perhaps not surprising when it is remembered that no
direct physiological evidence whatsoever is at hand bearing on the
function of the olfactory organs of fishes. That these organs are un-
doubtedly of great significance in the life of a fish is attested by the
extent of their surfaces and by the size of the connected parts of
the brain, and yet, so far as the habits of fishes are concerned, we
have no conclusive evidence as to their real uses.

The outer surface of amphioxus is sensitive to a variety of sub-
stances, such as nitric acid, picric acid, alcohol, etc., and to all these
substances the animal responds by withdrawing. Nothing could be
discovered about its reactions that could lead to the belief that the
chemical sense was connected with feeding. This sensitiveness was
found in amphioxus to be dependent, not upon nerves from the region
of the mouth that had invaded the outer skin, as Herrick (:03) has
shown for many fishes, but upon the segmental nerves of the region
stimulated, for the posterior third of an amphioxus will react, like the
whole animal, to effective chemical stimuli. The chemical sense of
amphioxus is, then, not especially associated with its mouth or its
feeding habits, but is a general integumentary sense, the function of
which seems to be to help the animal to escape an unfavorable chemical
environment. Apparently this is the primitive function of the chem-
ical sense as it is met with in the skins of many animals, and this
unspecialized sense has afforded a basis from which in the region of
the mouth the specialized senses of smell and taste (both of which are

PARKER. — THE SENSORY REACTIONS OF AMPHIOXUS. 449

chiefly concerned with food discrimination) have been differentiated.
This unspecialized chemical sense has been retained in the skin of the
frog and other amphibians and in the irritable mucous surfaces of the
higher vertebrates, but its chief representatives in the higher forms are
its derivatives, the senses of taste and of smell. Of these, amphioxus
possibly possesses the sense of smell.

Amphioxus may, therefore, be said to be an animal that possesses
in potentia at least the sense organs of the vertebrates. Its outer
surface is provided with tactile organs, but it does not possess the
derivatives of these, the lateral-line organs and the ear. Its outer
surface also contains undifferentiated chemical sense organs, but it
cannot be said to have a sense of taste, and the only evidence of a
sense of smell is morphological. Its outer surface, like that of the
higher vertebrates, contains temperature organs. Amphioxus also has
in the walls of its nerve-tube photoreceptors, which may well be the
forerunners of the rod- and cone-cells of the vertebrate retina. It is
thus an animal of fundamental importance for the understanding of
the vertebrate sense organs.

'■&'•

9. Summary.

1. Amphioxus is only very slightly sensitive to light.

2. It responds to a rapid increase of light, but not to a rapid
decrease.

3. The only known photoreceptors in amphioxus are the eye-cups
in the wall of the nerve-tube.

4. Amphioxus is photokinetic and negatively phototropic.

5. Amphioxus is stimulated by water warmer than that in which it
lives (31° C.) and is killed in water at 40° C. or higher.

6. It is also stimulated by water colder than 31° C. and is killed by
lengthy exposure to water of 4° C. or lower.

7. It is thermokinetic and negatively thermotropic.

8. The outer surface of amphioxus, especially the oral hood and the
tentacular cirri, is sensitive to mechanical stimuli.

9. Amphioxus is also sensitive to sound vibrations.

10. It is thigmotropic, and slightly rheotropic and geotropic.

11. The outer surface of amphioxus is sensitive to solutions of
nitric acid, potassic hydrate, picric acid, alcohol, and to strong ether,
chloroform, turpentine, oil of bergamot, and oil of rosemary, but not
to solutions of sugar. It is also stimulated by diluted sea water and
by fresh water.

12. Amphioxus is negatively chemotropic.

VOL. XLIII. — 29

450 PROCEEDINGS OF THE AMERICAN ACADEMY.

13. The photoreceptors in amphioxus are anatomically distinct from
the receptors for thermal, mechanical, and chemical stimuli, and these
three are at least physiologically distinct one from another.

14. To all stimuli that induce locomotion amphioxus responds by
forward movements when the stimuli are applied to the tail, and by
backward movements when they are applied to the middle or to the

'anterior end.

15. Amphioxus generally buries itself tail first, and in all probability
usually swims tail first, though it may reverse both processes.

16. When amphioxus is cut in two, both halves lose much in sensi-
tiveness, the posterior proportionally much more than the anterior.
The anterior part of the nerve-tube is brain-like, the posterior part
cord-like.

17. The skin of amphioxus contains tactile organs, but amphioxus
possesses no derived organs such as lateral-line organs and ears.

18. The photoreceptors of amphioxus are the eye-cups of the nerve-
tube, and these probably represent the elements from which the rod-
and cone-cells of the lateral eyes of vertebrates have been derived.

19. The rod- and cone-cells of the vertebrate retina are inverted,
not because they have retained a morphological position dependent
upon an external origin, but because of their orientation acquired as
effective eye-cups in the nerve-tube of a primitive vertebrate.

20. The chemical sense organs of amphioxus are located in the
skin and are chiefly important as organs for testing the character of
the chemical environment rather than for the selection of food. From
these undifferentiated chemical sense organs have probably been de-
rived the organs of taste and smell, of which the former are appar-
rently not present in amphioxus and the latter may be represented by
the so-called olfactory pit.

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Proceedings of the American Academy of Arts and Sciences.

Vol. XLIII. No. 17. — May, 1908.

ON DELAYS BEFORE avayv(oplaei<i IN GREEK

TRAGEDY.

By William P. Dickey.

460 PROCEEDINGS OF THE AMERICAN ACADEMY.

chapter xvi. Such portions of this chapter as serve my purpose will
be mentioned later.

My study of the above-mentioned passages of Aristotle has natur-
a,lly referred me to recognition scenes in the Odyssey, from which
it appears that such scenes are as old as Greek literature. It is in-
teresting to note that the Homeric recognition scenes are compara-
tively simple,* but none the less effective and in keeping with the
general character of the epic. A brief examination of these scenes
follows. At the beginning of the fourteenth book of the Odyssey
Odysseus returns to Ithaca, and, in the guise of a beggar, presents
himself at the hut of Eumaeus, the swineherd, where he receives a
warm reception. One might expect that Odysseus, overjoyed by his
safe return, would disclose his identity at once, but not so ; even an
epic poet could show ingenuity in delaying recognition scenes so as
to make them occur where they suited his purpose best. In this par-
ticular case it was necessary to interpose a delay until Telemachus
could return from Sparta, and incidentally the poet had an opportunity
to pit Eumaeus and Odysseus against each other as story-tellers,
whereby the latter became acquainted with the general situation of his
household affairs. Finally Telemachus appears at the hut of Eu-
maeus at the beginning of Book XVI, yet there is no spontaneous
recognition between father and son ; but after Eumaeus has gone to
the palace to inform Penelope of the arrival of Telemachus, Athena
(172^) transforms Odysseus, the beggar, into Odysseus, the prince,
who (188) declares to his startled son dAXa Trarrjp reds ct/xi. In spite
of this divine manifestation, Telemachus doubts, and delays his final
acquiescence until 214,^ after Odysseus has explained the transforma-
tion. Therefore, since we cannot regard this recognition as complete
until 214, and inasmuch as the evidence is all in at 188, and what
follows to 213 is a mere explanation, or resumi^, of the real evidence,
I must consider the intervening verses a conscious delay which I shall
designate as secondari/, as distinguished from that more general and
longer delay (in this case from the beginning of Book XVI to verse
172), which may properly be called ■primary. Let us take another
case and see if we can detect a similar delay.

* I am inclined to believe, however, that the recognition scenes show some
development, though it is not my purpose now to discuss the relative chronology
of books of the Odyssey on the basis of recognition scenes. Throughout this
paper my references to ' Homer ' are in the generic sense.

6 ^, Kol xpuo"*'!? H^^V iTrefJ-acrcrar 'Aerjvr]. (I quote Cauer's text of the Odyssey.)

* Od. XVI, 213-214: TTjXe'juaxos 5e' | dfxcptxvOfU irartp' ia0\hy oSvptTO SaKpva

DICKEY. — ON DELAYS BEFORE RECOGNITIONS. 461

In Book XIX, SSff.*^ we find Odysseus, in response to her request,
before Penelope ready for the interview in which he hears her story
of her trials with the suitors, and in which he, upon request, discloses
his fictitious lineage, adding a charming account of himself as host
of Odysseus in Crete, and closing with the utterance of his belief that
Odysseus will return. However much Odysseus might naturally have
desired a recognition at this point, the poet would not allow it. The
' primary' delay in this case was to continue to Book XXIII, about which
I shall have something to say later. To continue with Book XIX, we
see that Odysseus so endeared himself to Penelope by his specious
stories that she gave an order that he be well entertained. Then fol-
lows the bath scene and the recognition of Odysseus by his old nurse,
Eurycleia. It will be observed that this recognition is preceded by
a ' primary ' delay, and so managed that the scar on the foot of
Odysseus is to be recognized by Eurycleia only, who is made to keep
the secret and become an aid to her master in executing his plans.
The general order of Penelope to her maids to wash the feet of Odys-
seus and prepare his bed is met by his objection and his suggestion
that some aged,^ sober-minded woman, who had borne as many sor-
rows as himself, might touch his feet, etc. The ' primary ' delay in this
case extends from 317 (where Penelope says to her maids, a\Xd /jllv,
dfjicjiLTroXoL, diroviij/aTe, kixtO^tc S' tvvrjv) to 376, where Euryclcia, after a
touching reminiscence of her master, says : tw o-e TroSa? vti/'w, a/xa t'

avTr]<i U.-qveXoTreLT]'; | Koi cridev etve/c', Itru fxoL opuyperaL evSoOl ^d/xos j ki^Sco-iv,
aXX' aye vvv ^vvUl CTros, ottl k€v etTro) * | ttoXKoX hrj ^elvoi TaXaireLpiOL ivOdB'
iKovTo, I dAA' ov TTw Tiva (jirj/xt ioLKora oioe ISecrdai, \ <x><i crv hifxas
<f>u)V7jv re TToha^ t' 'OSucr^i eot/cas^ — almost a case of recognition

€K ayXXoyicrfiov — to which OdySSCUS replies, w yprjv, ovtw <^ao-iv oaoL
lSov 6(fi6aX/j.ota-LV | T//>ieas dfi(j>OTipov?, fxdXa eiKeXo) aXXrjXoui' | ififxevan^ w?
(TV irep avT-q i'n-Lcfipoveovcr' dyopeveiS'^^ Following close upon this in-
tuition of Eurycleia occurs the statement in 392-393, avrtVa 8' cyvw ]
ouA-T^v, ktX. To be sure, the old nurse recognized the scar and im-
mediately gave utterance to fj /xaA' '08va-(rev<; ia-a-t, (fiiXov Te/cos,ll ktX.,
but, in effect, the poet's zeal for accounting for the scar really delays
for the reader the completion of the recognition until 474 — a rather
remarkable continuation of the ' secondary ' delay, which was possible
for the epic, but impossible, I take it, in a similar case, for tragedy.
A third case of recognition in the Odyssey that deserves notice is

' 0(1. XIX, 53 : ?/ 5' Uv iK 6a\diJ.oio inp'Kppwv IlTji'eA.iJireio kt\.
8 Vid. XIX, 346-348. » Od. XIX, 376-381.

10 Ibid. XIX, 383-385. " Ibid. XIX, 474.

462 PEOCEEDINGS OF THE AMERICAN ACADEMY.

found in Book XXI, 193 ff.^^ where Odysseus reveals himself to Phi-
loetius, the neatherd, and Eumaeus, the swineherd. In this case the
' primary ' delay is obvious ; the poet purposely delayed this scene
until it suited his purpose best, which was to prove the loyalty of these
servants and to secure their services for the work in hand against the
suitors. Here also a ' secondary ' delay occurs, though it is short ^^
and pointed. Odysseus makes sure of their loyalty, declares himself,
and produces the scar as evidence.

Again, in Book XXII, 35,1'* Odysseus reveals himself to the suitors, a
recognition long delayed by the poet. This recognition is momentarily
expected from the time that Odysseus strung the mighty bow (XXI,
409, •'•^ and in 412, jxviqcmqpcnv 8' ap a-^0% yiuero fieya), but the poet in-
terposes a slight delay until Odysseus has slain Antinous. Then he
declares himself to the suitors and predicts their destruction. ^^

Finally, we have to consider the recognition scene between Odysseus
and Penelope, which is consummated in Book XXIII. How skilfully
did the poet pass by many opportunities and delay this scene until the
serious business of housecleaning had been finished ! ^^ In the begin-
ning of Book XXIII Eurycleia, under orders from Odysseus, goes to
awake ^^ Penelope and to announce that her husband is present. Here
begins the ' secondary ' delay, which is rather longer than in the cases
noted above, the conclusive evidence beginning at 183 w ywai, ktX., and
concluding at 204^^ — an account of Odysseus' massive bed in his
chamber fashioned about an olive shrub. It will be observed that the
poet has made more of this recognition scene than any of the others.
Penelope is rather obstinate and hard to convince ; she will not accept
the statements of the old nurse, even when she hears of the scar, — an
evidence of the poet's good taste, — but must test him according to
signs 20 hidden from the rest. Thereupon Odysseus convinces her by
his story of the bed mentioned above. In this case it appears that
Penelope reasoned thus : only Odysseus could have such knowledge

^^ j3oii(co'\e Kal <tv, av(pop&4, tiros ti ne fivOriarat/jLyjv kt\.

13 193-206.

1* S> Kvves, ov fx' (T^ ((pdaKed' vTrorpoirov oiKaS' 'iKiffQai ktK.

15 XXI, 409 : . . . rdwa-ev ixiya t61ov 'OSutrcreiys.

18 Od. XXII, 41 : vvv v/uv Kol TTaffiv oKldpov Treipar' ecprfirrai.

" I maintain that our poet in thus delaying this recognition scene displays no
little knowledge of human nature.

1* XXIIT, 5 ff. : eypeo, H-qveKoirtia, (pi\ov reKOi, 6(f)pa i5i]ai, ktX.

1^ 203-204 : . . . Af'xos, t)/ tis ^Stj | avSpHv aWoae 6fJKf, ra/xiiv vno TrvOfxtv
e'Aaiijs.

2" Od. XXIII, 109-110 : ecrri yap i^ixlv \ ff7)fj.ad' & 5?; Kal vuii KfKpvfifi^va tSfifP
cltt' ^Wo;;'.

DICKEY. — ON DELAYS BEFORE RECOGNITIONS. 463

about the bed, etc. ; this man has the knowledge, therefore he is Odys-
seus — a clear case of dvayvoipto-ts ck avXXoytcrixov, which Aristotle ^^
recognizes as second best.

Thus stand the Homeric recognition scenes that have come to my
knowledge 22 — scenes comparatively simple, and yet such, I think, as
show some development from the simple to the complex. In view of
the foregoing study I conclude that the poet had full control over his
recognitions, and did not insert them in a haphazard way, but with due
regard for the purpose for which they were intended, in consequence of
which his skill and ingenuity in the matter of ' primary ' delays had
free play ; and that there is just reason for postulating 'secondary'
(or shall I say prefatory f) delays which in the case of the epic are, in
effect, announcements to the reader or hearer that recognitions are
about to take place. Now, that ' primary ' delays before recognitions
in Greek tragedy are evident is likely to be conceded by all. The im-
portance of recognition scenes in Greek tragedy must be obvious to
every student of Greek literature, regardless of his knowledge of Aris-
totle's Poetics. That the Greek tragic poets show much variety and
skill in handling such scenes, particularly in the matter of delaying
them to the point where they considered them most effective in their
particular plots, must be patent to any one who has read the plays in
which recognition scenes occur. Therefore, in the following study of
recognition scenes in Greek tragedy, what I have chosen to call ' pri-
mary ' delays I shall consider only incidentally, and shall give most of
my attention to the special delays which I assume usually appear be-
fore the final act of recognition, and which, for the want of a better
name, I have denominated ' secondary.'

With deep regret that I am unable to determine the nature of the
many recognition scenes, which we know existed in intervening litera-
ture,23 I must take a long step from the Odyssey to the Choephori of
Aeschylus ; and, having passed from epic to tragic poetry, I am sorely
disappointed in finding extant so few of the many tragedies ^4= that
had recognition scenes — Aeschylus furnishes us a single recognition
scene ; Sophocles, two ; Euripides, five, if w-e count two for the Iphigenia
in Tauris.

21 Poetics, XVI, 12.

22 It does not seem worth while to record ray private consideration of that
excellent recognition scene (XVII, 292 ff.) in which "Apyos was ■n-pcvTayoovia-Tris.

2' The No'tTToi of the Trojan Cycle, the source of the Choephori, the Electras,
Helen ; the Oj5jirt{5««a of the Theban Cycle ; the 'Op^areta of Stesichorus, etc.

2* Our knowledge of lost tragedies in which recognitions existed is too meagre
to be of any value for this report.

464 PROCEEDINGS OF THE AMERICAN ACADEMY.

The Choephori of Aeschylus.

In considering the recognition scene of the Choephori I shall try to
avoid any generalizations on Aeschylus's mode of dealing with recogni-
tion scenes, except to state that it seems likely that the real father
of Greek tragedy probably adhered more closely to the models of
his predecessors, and that his recognition scenes were simpler than
those of his successors. What then is the nature of the recognition
scene in the Choephori ? I consider it somewhat as follows. Knowing
that every form of the legend upon which this drama is built requires
an di/ayvwptcrt5, the audience ^^ at the very outset has a preposses-
sion that there is to be a recognition scene, and it seems safe to assume
that to this the nimble-witted Greeks look forward, eager and curious
to see how Aeschylus is going to handle the scene. This preposses-
sion of the audience is reinforced by the action of Orestes in 6-7.^^

-rrXoKa/JLOv 'Ivo-X!^ Opeirri^pLov, \ tov SeuVfpov 8e rovSe TrevdrjTrjpLov. After
this it is only a question of delay, and, in this case, the ' primary '
delay continues to 165 where Electra says, viov SkfxvOov rovSe Kotvutvricrarc,
and 167, 6pw To/xaiov rovSe fSocTTpvxov, the beginning of the ' secondary '
delay. These words of Electra mean to the audience that the recogni-
tion is about to take place, and I venture to say that every Greek in
the audience ' sits up and takes notice ' accordingly. This ' second-
ary ' delay continues through 211, where Electra says, TrdpeaTL 8' (iSis
Koi (f>pevwv KaTa(f>Oopd. By the locks of hair and the footprints Electra
is almost convinced, and yet in doubt. For the resolution of this
doubt Orestes appears at the psychological moment and the final act
of recognition takes place, not only through Orestes' reiteration of the
evidence already adduced, but by producing a piece of weaving (tSoC 8'
v<^aa-p.a tovto, 231), adding thereto all the expression of which a good
actor 27 is capable. Thus ends the recognition, which occurs rather
early in this play as compared with recognitions in Sophocles and Eurip-
ides. It suited Aeschylus' dramatic economy to make it thus. Surely
there is no evidence that it fell flat. The reason for its early occur-
rence does not here concern me ; and as it stands it supports my theory
of a ' secondary ' delay.

25 Throughout this inquiry I try to consider the matter from the point of view
of the audience.

26 I quote the Oxford text, edited by A. Sidgwick.

" I am inclined to believe that modern critics too often underestimate histri-
onic ability and effectiveness, which must have meant much to the Greeks.

dickey. — on delays before recognitions. 465

Sophocles.

Electra.

The recognition scene in the Electra of Sophocles presents some
striking differences as compared with that of the Choephori ; first in
the length of the ' primary ' delay and in the skilful management of
the ' secondary ' delay made possible by the introduction of the urn
filled with the supposed ashes of Orestes. The recognition is expected
from the beginning. The audience knows that Orestes is present, and
he heightens the interest by saying in 80, ^8 Sip'ia-Tlv rj Swtt^vos 'UXeKrpa,
upon hearing her Iw yu.ot/Aot in 77, likewise by depositing locks of hair
at his father's tomb (/capaToyaot? ;^At8ars, 52), which is particularly rein-
forced by the announcement of Chrysothemis in 900-901, co-xaxTys 8' opaj
I TTvpas vnoprj fioa-Tpvxov TeTjx-Qfxevov, although developments have been
such that Electra cannot on such evidence share the belief of her sister
that Orestes has recently visited the tomb. Finally, the appearance of
Orestes and Pylades (1098), face to face with Electra, must signify to
the audience that the long delayed recognition is about to take place.
At this point begins the ' secondary ' delay, which is skilfully drawn
out until Orestes is made to end it in 1221-1223, rrjvSe irpoo-fSXeij/acrd
fJLOv \ a"0payt8a Trarpos (.KfiaO' el (Ta(f)TJ Aeyw.

Oedipus Tyrannus.

In this drama, which appears to have the most complicated plot of
any extant Greek tragedy, one should expect to find a most highly de-
veloped recognition scene ; such is the case. From the announcement
of the oracle (106-107 ^9) to wreak vengeance on the murderers of Laius,
the audience must look forward to the recognition, knowing that the
self-discovery of Oedipus means his ruin. The plot is complicated, and
an opportunity for delay is given by the introduction of the Corinthian
element. The final act of recognition depends on the convergence of
the evidence of the Theban and Corinthian herdsmen, the former pos-
sessing the key to the situation. This the audience understands, and
therefore must take special interest in Oedipus' decision (859-860,

dXX' o/xoj; Tov aypoT-qv \ 7re/ii/^ov Ttva a-reXovvTa ixrjSk tovt dc^Tjs) tO SUmmon

the peasant who was present at the murder of Laius. But the 'pri-
mary ' delay is extended by the introduction of the Corinthian herds-
man, who shows that Oedipus is not the son of Polybus and Merope,

28 I quote the text of Dindorf.

29 TovTov Qav6vTos vvv iTrL(TTi\\€i (ia<pu)s I TOWS ahroevras X*'pi rift,upe7v riva.

VOL. XLIII. — 30

466 PROCEEDINGS OF THE AMERICAN ACADEMY.

and we are brought to the ' secondary ' delay at 1117 (eyvoiKa ydp, a-a<^'

icr^i Adiov yap ^v | eiTrep ti? aXXos ttio-tos ws yofxev<; avrjp^ where the

Theban herdsman is brought in and identified by the chorus. Then
follows the triangular colloquy between the Corinthian, Oedipus, and
the reluctant Theban herdsman, that brings us to the recognition (and

TrcptTTcreia) in 1182 (lou tov * to, ttuvt' av i$rJKoi (Ta(f)rj, kt\.), where OedipuS

is finally convinced. Here again we find a well-defined case of a
' secondary ' delay.

Euripides.

Ion.

In this drama Euripides has tried his hand at complicating the plot,
but has cheated the imagination of the audience by disclosing every-
thing in the prologue. The ' primary ' delay is purposely made long
and handled with some skill, but I have no doubt that the audience
marked the beginning of the ' secondary ' delay, which really begins at
1261 ^^ ( (L Tavp6ixop(f>ov 6/jifxa Kyjcfjicrov Trarpos, ktA.), where lon, after the
frustration and discovery of Creusa's plot to kill him, discovers her at
the altar and prepares to kill her. This delay is further prolonged
and accentuated by the necessity for the appearance of the Pythian
priestess (1320, cTrio-xfs, w rrai ktX.), whom the poet, in dire straits, has
to call upon to produce the evidence ^^ whereby the recognition may
be effected at 1437, a> cfttXTdrr) fioi fi^rep, ktX., and 1439, w tIkvov, ktX.
Here we find another case of ' secondary ' delay, and that rather long.

Iphigenia in Tauris.

Likewise in this play Euripides, by his rather long prologue, ac-
quaints the audience with the general situation. Immediately follow-
ing Iphigenia's misinterpretation of her dream, whereby she concludes
that her brother is dead, Orestes appears at 67 (opa, (fivkaaa-e fjirj rts iv
o-TtySo) ISpoTwv, words addressed to Pylades), and, in fact, is an-
nounced to the audience by Pylades in 71, ifioiy', 'OpeVra. Here be-
gins the real ' primary ' delay, which is well managed in view of the fact
that Iphigenia and Orestes think each other dead. It is worthy of note
in this connection to observe the epic flavor that Euripides gave the

3° I quote the text of Nauck, 3d ed.

31 A recognition is effected in the Rudens of Plautus (1154 ff.) in a similar
manner, apparently a direct imitation of the scene in the Ion ; Creusa establishes
her identity by describing, previous to seeing, the ' swaddling clothes ' of her son ;
similarly. Palaestra describes certain crepundia in order to prove that she is the
daughter of Daemones.

DICKEY. — ON DELAYS BEFORE RECOGNITIONS. 467

drama by giving the herdsman, who acts in the capacity of a herald,
such a long speech (260-339) in which to report the capture of Orestes
and Pylades ; and thereby he adds to the delay before the recognition.
No doubt the audience begins to suspect that the recognition is going
to happen pretty soon after the herald's report of their capture ; and
certainly the searching questions, begun by Iphigenia at 472, n? apa fJLrjrrjp
7} T€Kovar' v/j.a.'i Trore | Trarr/p t' ; a8eX<f)y ^^ t, ktX., and Continued at some
length, reinforced by her decision (reached by her examination of the
captives), to send a letter by one of the captives to her friends at Argos,
etc., signify to the audience that the recognition scene is on. I should say,
therefore, that the 'secondary' delay begins at 472, and that the recog-
nition is really complete at 773, when Iphigenia says to Orestes, ^S' ^v
opas a-v ; but he is not allowed to declare himself until 795 (w cfuXTaTt]
fjLOL o-v'yyov', ktX.), when Iphigenia has finished reading the letter. Mark-
ing the real completion of the recognition at 773, we have before us a
' secondary ' delay of three hundred verses in which the poet shows ex-
traordinary skill in handling a delicate situation in a manner quite as
satisfactory to the audience, I imagine, as to Aristotle, ^-^ who puts his
stamp of approval upon this recognition scene. On this splendid scene,
whereby Orestes recognized his sister, Euripides spent his force and had
to resort to inferior means to make Orestes known to Iphigenia. From
the very nature of the case (for the second recognition is but a neces-
sary sequel to the first), there is no ' primary ' delay to the second rec-
ognition, and therefore the short delay that does occur before the
recognition, — a delay made necessary by the necessity of manufactur-
ing convincing evidence, — must be called ' prefatory ' rather than
'secondary.'

Helen.

The prologue to this play explains practically everything except the
whereabouts of Menelaus. Perhaps the audience had a presentiment
from the beginning that Menelaus would appear at the proper time,
and that there would be a recognition. This latter is practically cer-
tain when Menelaus appears on the scene at 386, and particularly
when he hears in 470 ('EXeVr; kut oIkov; iarl, ktX.) that Helen is in the
house. At 528 Helen appears again, having learned from Theonoe
that her husband is still alive, and everything is ready for the recogni-
tion. The 'secondary ' delay begins at 541 (ea n? ovtos;), when Helen
sights Menelaus, and leads up to the recognition that is completed at

32 Does not Euripides 'give the situation away' by not calling for an

33 Poetics, XVI, 11.

468 PROCEEDINGS OF THE AMERICAN ACADEMY.

622-623, where Menelaus says, toOt' ea-r^ eKeivo ■ ^vix^efSaaLV ol Xoyoi I
01 TrjaS' aXrjOeiS, ktX.

Electra.

I have purposely reserved for the last the consideration of the recog- *
nition scene of Euripides's Electra, which contains the disputed passage
mentioned at the beginning of this paper. My consideration of this
scene shows nothing very different from what has been noted in the
other Euripidean recognition scenes. As usual, Euripides states his
case in the prologue, and straightway brings on Orestes '^'*, who has
paid a visit to his father's tomb during the night and made offerings
of his hair, with the accompanying rites. The appearance of Orestes
assures a recognition, and with the audience there is only the question
of how Euripides will bring it about. They wondered, no doubt, how
his treatment would differ from those of Aeschylus and Sophocles.
Orestes meets Electra (220, /teV, w rakaiva, ktA.) and assures her that
her brother is alive but in exile (236), learns the status of the family
affairs, assures himself of her willingness to assist in slaying the mur-
derers of their father, learns that there is only one who would be able
to identify him (287, Trarpds -ye TraiSaywyos a.p-^alo<; yepwv), after which
he is about at a loss for words, when the peasant, the nominal husband
of Electra, appears just in time to relieve the situation. After receiving
an explanation about the presence of the strangers, he extends to them
the hospitality of his home, for which he is censured by Electra, and
despatched forthwith to the aged guardian ^5 of Agamemnon to re-
quest that he lend material aid in providing a banquet for the stran-
gers. The peasant goes out at 430, and is not allowed to return.
During the supposed meantime, which is a pretty short time, the
chorus is called upon to entertain the audience until the old man
(Trpecr/Sus) can arrive with a young offspring of his flock ^^, some
fresh cheese and old wine. It happens, however, that the old gentle-
man has stopped by the tomb of Agamemnon, whereon he discovered

the shorn locks of hair (515, $av6rj'? re xat'i"'?? l3o(TTpvxov<; KeKapfxlvovs)

which, he ventures to assert to Electra, may have been offered by
Orestes, and thereby provokes a discussion with Electra that has given
certain latter-day scholars considerable trouble.

With the situation thus before us, let us see about the ' secondary '
delay before the recognition. As stated above, the audience is assured
of a recognition by the presence of Orestes. It may be thought that

34 82 ff.

3^ 409 : f A.0' ojy iraXaihv Tpo(phy tfiov (pi\ov TrarpSs.

36 494 ff.

DICKEY. — ON DELAYS BEFORE RECOGNITIONS. 469

the 'secondary ' delay begins at 220, with the meeting of Orestes and
Electra, but I am convinced that this whole scene between them, and
even up to the arrival of the old man (487), is a part of the ' primary '
delay. I think the mention of the old man in the prologue is signifi-
cant to the audience : that is, he is to play an important part in the
drama, perhaps in the recognition scene ; and this belief of mine is
strengthened by the statement of Electra (285) that only one of her
friends (the -n-atSaywyos) would know Orestes — and, finally, the old
man is to appear ostensibly for another purpose, but in reality to effect
the recognition for which the parties concerned (Orestes and Electra)
are present and ready when he arrives at 487 and inquires for Electra,
I assume, therefore, that the eagerly awaited arrival of the old man is
a signal, so to speak, to the audience that the recognition is about to
be effected. Hence the 'secondary' delay begins at 487, and the
recognition is actually completed in 577-578, when Electra says,
o-v/x/JoAotori yap | rot? crots 7re7ret(r/xat Ovfxov. It is not my purpose to
discuss the disputed passage at length from an artistic point of view
in order to combat the view of Mau, whom Mr. Tucker ^"^ follows ;
but I wish to call special attention to the fact that, even counting the
disputed passage, the ' secondary ' delay before the recognition is only 90
verses in length (from 487 to 577) — and even this can reasonably be
shortened if we eliminate the introductory remarks of the old man
about his provisions, etc., and make the weeping of the old man

(501—502, cyw Sf Tpv)^ei TwS' i/xCjv iri-rrXow K6pa<; | SaKpvoLCTi re'y^a? i^o/xofj-

$aa-6at. deXco) the real signal for the beginning of the recognition scene,
thus making the ' secondary ' delay before the recognition 76 verses in
length. In the first event we find a ' secondary ' delay (i. e., from the
time that the signal appears to be given to the audience that the recog-
nition is about to take place until it is actually effected) of 90 verses ;
in the second event, a delay of 76 verses. By eliminating 518-544,
the interpolated passage, according to Mau, my figures for the delay
would become 63 and 49 respectively. Let us see how these figures
compare with those given for ' secondary ' delays found in other trage-
dies, especially those of Euripides.

' Secondary ' delays before recognitions :
Aeschylus — Choephori : 235-1 65 = 70

Sophocles — Electra : 1221-1098 = 123

Oedipus Tyrannus : 1182-1117 = 65

3' The Choephori of Aeschylus, Introd. p. Ixxi ff.

470 PROCEEDINGS OF THE AMERICAN ACADEMY.

Euripides — Ion : 1437-1261 = 176

Iphigenia in Tauris : 773-472 = 301

Helen : 622-541 = 81

Electra : 577-487 = 90, or 577-501 = 76

By eliminating 518-544 : 63 49

From these statistics I am not disposed to draw any dogmatic con-
clusions. To my mind they only show in a general way (a) a tendency
toward a lengthening of the ' secondary ' delay (and, even this state-
ment must be taken with some reservation, for I find it impossible, in
view of the uncertain date of some of the plays, to reduce this matter
to a chronological basis), particularly on the part of Euripides ; ^^
(b) ' secondary ' delays of about equal length (accepting the full text
of the Electra) in the Helen and the Electra, which appear to be plays
of about the same date ; (c) a ' secondary ' delay in the Electra (reject-
ing the disputed passage) shorter than appears in any extant tragedy,
and it seems to me unlikely that this should be the case. It appears
that the very nature of the case is such in this ' secondary ' delay of the
Electra as to warrant the assumption that the audience would expect
the loquacious old man to give a pretty full report ^^ of his side trip to
the tomb of Agamemnon, in spite of the fact t^at the poet apparently
made use of it to criticise one of his predecessors.*^

38 This is especially true in the case of his better tragedies, to which distinc-
tion the Helen and the Electra can lay no claim.

39 Otherwise I fail to see any motive for mentioning his visit to the tomb.

*" In addition to the foregoing consideration of the bearing of delays before
recognitions on our passage, I wish to add gratuitously at this point some observa-
tions made while pursuing my investigation, which may lend further weight to
my final conclusion. In the first place, I believe that the locks of hair deposited
on the tomb of Agamemnon, though primarily deposited as a religious act of
filial duty, had become fixed in the Orestean legend as one of the recognized
means of bringing about the recognition. Aeschylus skilfully followed the
legend ; Sophocles delicately acknowledged the legend with negative results in
the case of Chrysotherais ; Euripides acknowledged and expressed his disapproval
of the legend. This assumption, if justified, makes it necessary to retain the
disputed passage.

In the second place, why does Euripides use arvfxfioXoKxi (577) instead of (rv/x-
P6\cfi 1 May it not be that Electra, perhaps unconsciously, includes the proofs or
tokens in tlie disputed passage with the scar in 57-3 1 In other cases (cf . Or. 1 130 ;
Ion 1386) wlien Euripides uses (tv/x^oXop, the singular and plural seem to be
properly differentiated.

Finally, in FA. 568, after the irpta^vs has said to her in the preceding verse,
$\f}pov vvv els t6vS\ Si t^kvov, rhv (pi\raTov, Electra says iraA.oi SeSoiKa /xij av y'
ovKfr' e6 (ppovfis. Now, what is the force of iraAat here (cf. its use in El. 357,
where tlie reference is certain), and, in fact, the justification of the statement, if

DICKEY. — ON DELAYS BEFORE RECOGNITIONS. 471

In summarizing the results of my investigation it appears (1) that
there is sufficient evidence, in both epic and tragic poetry, for ' primary '
and ' secondary ' delays before dvayi'wpto-ei? ; (2) tendency to lengthen
the 'secondary' delay, presumably for dramatic effect — a tendency
that is strikingly illustrated by Euripides in contrast with Aeschylus
and Sophocles ; (3) there is no reason to expect an abnormally short
' secondary ' delay in the Electra of Euripides, but rather the contrary,
in order to give the old man an opportunity to satisfy the uatural
curiosity of Electra and the audience by giving them a detailed
account of his startling discoveries at the tomb of Agamemnon —
an opportunity that is met, in part, by the passage in question. In
conclusion, therefore, I have no hesitancy in accepting the disputed
passage (El. 518-5-44), considering it so much bombast (to delay the
recognition), wrongly employed by an indiscreet poet for critical pur-
poses — a passage that 'smacks ' *^ not ' of the age of Zoilus,' but of
the age and flavor of Socrates and Aristophanes, the latter of whom
might well have preferred charges against Euripides for encroaching
on his literary province.

there is not a reference to the old man's statements in the disputed passage ? It
appears to me that the whole verse is a kind of reiteration and echo of Electra 's
reproacli in 524, ovk &^t avSpSs, Si y^pov ao(pov \eyeis.
^ Tucker's Choephori, p. Ixxii.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 18. — June, 1908.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF
HARVARD COLLEGE.

A NEW METHOD FOR THE DETERMINATION OF
THE SPECIFIC HEATS OF LIQUIDS.

By Theodore William Richards and Allan Winter Rowe.

Invbstioations on Light and Hbat made and pcblished, wholly ok in part, with Appeopbiation

raOM THE RUKLFOBD FUNO.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY
OF HARVARD COLLEGE.

A NEW METHOD FOR THE DETERMINATION OF THE
SPECIFIC HEATS OF LIQUIDS.

By T. W. Richards and A. W. Rowe.

Presented May 13, 1908. Received April 29, 1908.

During the course of an extended research upon heats of neutral-
ization now in progress, it became necessary to devise some method for
the accurate determination of the specific heats of the reacting solu-
tions. Obviously an accurate value for any thermochemical measure-
ment can only be obtained when the factors involved in the calculation
are accurately ascertained ; and it is well known that the existing data
on this subject are by no means satisfactory. The recognized sources
of error of the majority of the earlier methods and the discrepancies
observed in the values obtained by the different experimenters using
them ^ limit any dependence which can be placed in the constants
thus obtained. Further, the truth of the assumptions upon which
the corrections for their errors are based is by no means adequately
proved. To obviate the necessity of these corrections, and thus elim-
inate the uncertainty attending their use, a new method has been
devised. A brief discussion of the earlier forms of apparatus may
assist in a better understanding of the difficulties encountered in devis-
ing this method and the means by which they were surmounted.

Of the various methods recorded, that of Andrews ^ has been, perhaps,
the most frequently used. This depended upon the transference of a
heated object or " calorifer " from a source of heat to the calorimeter,
\Vhich contained either water or the liquid to be studied. A compar-

^ The following is a typical example :

Specific Heat of NaOH
'fg Sp. Ht. Observer.

49.5 0.816 Hammerl.

25.6 0 869 Hammerl.
229 0.847 Thomsen.

2 Pogg. Ann., 75, 335 (1848).

476 PROCEEDINGS OF THE AMERICAN ACADEMY,

ison of the observed rise with water and with the liquid under investi-
gation gave a simple means of determining the relative heat capacities.
A variant of this method consisted in using either water or the studied
liquid in the calorifer, the calorimeter always being filled with the
former. This method, with various independent modifications, was
used by Schuller,^ Person,* Pfaundler,^ Marignac,^ Hammerl,^ and a
number of other investigators. The simplicity of this procedure, and
the elimination of many doubtful factors by using comparative results,
are strong arguments for its use ; but the interchange of heat by radi-
ation between both the calorifer and the calorimeter and their envi-
ronments, coupled with the unavoidable lag of the thermometer,
introduces elements of uncertainty fatal to the highest accuracy.

The ingenious device of Thomsen,^ whereby measured amounts of
hydrogen are burned, under constant pressure, inside the calorimetric
system, gave concordant results ; but the values obtained are subject
to some of the same corrections as those demanded by the Andrews
method. Pfaundler,^ using electrical energy as his source of heat,
attempted automatically to eliminate the radiation -correction by heat-
ing simultaneously two calorimeters, one containing water, the other
the liquid under investigation. If the rise of temperature were the
same, the loss by radiation would cancel. But as varying heat capac-
ities involve varying amounts of electrical energy to secure this result,
the electrical heat unit enters the computation, and by its uncertainty
detracts irom the absolute accuracy of the determination. This device
has been recently applied in a modified form by Magie ^^ with consid-
erable success ; but it is by no means easy to find a heat-producing
electrical resistance suitable for immersion in electrolytes.

Several other different methods have been suggested by others,
but these also are not wholly free from defect. In one, the radiation
method of Dulong and Petit,^^ the hot object was enclosed in an evac-
uated and blackened chamber, losing its heat by radiation. The
chamber was placed either in an ice bath or in a water bath of suffi-
cient size to be unaffected by the heat given up by the cooling object.
The relative temperatures of the hot object and its environment, and

3 Ann. de Chim. et Ph., 3, 33, 487.

* Fogg. Ann., 136, 70, 235 (1869).

0 Wien. Ber., 62, (2), 379 (1870).

6 Arch. Gen., 2, 39, 217 (1870) ; 2, 55, 113 (1876).

' C. R., 90, 694 (1880).

8 Thermochem. Untersuch., 1, 24 et seq. (1882) ; Pogg. Ann., 142, 337 (1871).

9 Wien. Ber., 59, (2), 145 (1869) ; 100, (2a), .352 (1891).

10 Phys. Rev., 9, 05 (1899) ; 13, 01 (I'-'Ol) ; 14, 193 (1902) ; 17, 105 (1903).
" Ann. de Chim. et Ph., 2, 10, 395 (1819).

RICHARDS AND ROWE. — THE SPECIFIC HEATS OF LIQUIDS. 477

the time required to secure thermal equilibrium, gave the necessary
data. The uncertainty of the true law ot cooling is enough to seri-
ously impair the accuracy of any results thus obtained, however.

Quite a diiferent procedure was adopted by Hesehus,^^ ^Jjq balanced
the heating effect of the calorifer in a calorimeter at room temperature
by the additions of successive portions of cold water. In this way
he eliminated any cooling of the calorimeter. Waterman ^^ improved
this method, and made a series of apparently excellent determinations
of the specific heats of metals. Using a Pfaundler resistance coil as a
source of heat, Litch ^* has studied in this way the specific heat of
water. Satisfactory as these methods may appear upon first sight to
be, however, the unavoidable warming of the cold water during its
transference to the warm calorimeter introduces an element of uncer-
tainty just as great as the uncertainty in the ordinary cooling cor-
rection ; hence no real gain was made. The method is not really
adiabatic.

In 1905 a new method was described by Richards and Lamb,^^
eliminating most of the earlier sources of error while maintaining aU
the advantages of the older procedure except simplicity. Two por-
tions of liquid — one hot, the other cold — were rapidly discharged
from their respective containers and mixed in a calorimeter, the tem-
perature of the mixture being that of the environment. Obviously,
the cooling experienced by the warm liquid during transference is bal-
anced by the warming of the cold liquid. The method involves a
somewhat high degree of mechanical complexity, and is further com-
plicated by the necessity of making supplementary determinations of
the heats of solution or dilution where the two liquids possess any
degree of mutual solubility.

More recently a new method of calorimetry, by a strictly adiabatic
procedure, has been described by Richards, ^^ and its applicability has
been experimentally proved by the same investigator with the assist-
ance of Forbes,^'^ Henderson,^^ and Frevert.^^ Here the environ-
ment of the calorimeter is caused to increase in temperature as the
calorimeter itself becomes warmer. The studied transformation in the
calorimeter thus takes place without interchange of heat with the sur-
roundings. Further, since both the initial and the final temperatures
are stationary, the error due to the lag of the thermometer disappears.

" Jour. Soc. Ph. Chim. Russ., Nov., 1887; Jour, de Phys , 7, 489 (1888).

" Phvs. Rev., 4, 161 (1896). " Ibid., 41, 10 (1905).

" Ibid., 5, 182 (1897). " Ibid., 41, 10 (1905) ; 42, 573 (1907).

" These Proceedings, 40, 659 (1906). " Ibid., 42, 673 (1907).

« Ibid., 41, 8 (1905).

478 PROCEEDINGS OF THE AMERICAN ACADEMY.

The use of this method obviates at once the greatest source of error
in calorimetric work of all kinds, namely, the correction for cooling.
As the method may be employed in any kind of calorimetric work,
there seemed to be no reason why it should not be applicable to work
on specific heats ; and the present paper will show that it is indeed
of great service there. The application is extremely simple : the
substance to be studied should obviously be placed in a calorimeter
surrounded on all sides by a jacket, the temperature of which can be
changed to correspond exactly with the warming of the substance by
some known source of heat.

It was first necessary to decide upon the exactly quantitative source
of energy to be used for heating the substance within the calorimeter.
Some experimenters have used merely the heat of a warmer body ;
others have used electrical heat ; and Thomsen availed himself of the
heat of combustion of hydrogen. Of course many other chemical
reactions might be employed for this purpose, as Ostwald and Luther
have pointed out ^o ; and after much consideration there was selected
for this present work the heat of neutralization of pure sulphuric acid
and sodic hydroxide as the most convenient, especially because it is
not very changeable with the temperature.

Definite amounts of acid and alkali were allowed to react in a
platinum flask surrounded by the liquid in the calorimeter, and the
rise of temperature in the whole system was carefully noted. By
comparing the rise of temperature under these conditions with the
rise shown when pure water is in the calorimeter, a comparative
measurement of the heat capacity of the liquid is made. A few words
will suffice to explain the disposition of the apparatus and the method
of its use.

Apparatus.

A diagrammatic sketch of the apparatus in vortical section is seen in
Figure 1. First, the environment of the calorimeter will be described.
The jacket (A) was made of heavy sheet copper and was provided with
an outflow cock ( 10 for convenience in emptying. The soldered joints
were heavily coated with shellac to prevent corrosion by the alkaline
solution with which it was filled. The capacity was 17.5 liters. A
rotary, vaned stirrer (E), with a speed of 145 turns per minute, insured
thermal homogeneity in the contents of the jacket. To raise the
temperature, crude sulphuric acid was run into the jacket through
the funnel (F), into the alkali contained in the jacket, and the heat
of neutralization thus liberated was rapidly disseminated throughout

20 Ostwald-Luther, Phys. chem. Messungen (1902), p. 204.

FlOUKE 1.

480 PROCEEDINGS OF THE AMERICAN ACADEMY.

the entire mass of liquid. The acid was contained in the burette (B)
empirically graduated to give a rise of 0.1° for each scale division.
The Beckmann thermometer (T), graduated in twentieths of a degree,
indicated the temperature. The cover (C) was similarly constructed,
the capacity being 6 liters. It was furnished with an oscillating
stirrer (S) with a speed of 45 strokes per minute, and the Beckmann
thermometer (Q) similar to that in the jacket. In the same way acid
was admitted from the burette (D), suitably graduated. Copper tubes,
permitting the passage of those portions of the apparatus which pro-
jected below the cover, were soldered to the bottom, and the joints
were protected by a coating of shellac. The cover must fit tightly,
otherwise evaporation will cause a slight cooling effect. The vessel
was thoroughly cleaned at the end of each day's work. The inner
cylinder (E) used to hold the calorimeter proper, was of sheet copper,
nickel plated, and burnished on the inner surface. It was mounted on
three legs, fitting into holders soldered to the bottom of the jacket,
and was provided with the ring or apron (G), which prevented any
portion of the liquid in the jacket from being thrown by the rapid
stirring into its interior space.

Inside this inner cylinder and separated from it by points of dry
cork was the calorimeter proper ( W). This was a platinum can of
0.7 liter capacity, weighing 107 grams. During an experiment this
was filled with water, or with the liquid the specific heat of which was
to be measured. Thermal homogeneity of the calorimeter contents
was secured by the two-stage perforated platinum stirrer (/) driven
at a speed of 45 oscillations per minute. The temperature was accu-
rately indicated by a large-bulbed, Beckmann thermometer (M), which
was graduated in hundredths of a degree and capable of being read
within titVtt- ^ small auxilliary thermometer (L) gave the tempera-
ture of the exposed stem. Thus far the apparatus is essentially simi-
lar to that used by Richards, Henderson, and Frevert.

The heat-producing system presents the chief novelty. It was made
up of two parts, a bottle (JT) and a burette (Z). The former was
made of platinum, with a capacity of 0.17 liter and weighing 52.64*
grams. In this was placed a definite weight of a somewhat dilute,
exactly known solution of sulphuric acid. The liquid was agitated
by the platinum stirrer (J), alternating 145 times per minute. The
bottle rested upon the glass triangle (N), thus permitting a free circu-
lation of the calorimeter liquid around the entire surface. Tightly
fastened into the neck by a small rubber stopper was the tip of the
burette (Z), which contained a concentrated solution of soda. The dis-
charge of this solution into the acid, and the consequent heat evolved

RICHARDS AND ROWE. — THE SPECIFIC HEATS OF LIQUIDS.

481

by the reaction, formed the heat-producing action upon which the
method is based. Since the alkali was the only part of the reacting
system which, from its position, might, at the beginning of an experi-
ment, have a different temperature than that of the remainder of the
system, one neeSed to measure its temperature accurately. To this
end the thermometer {K) ^i was immersed in the liquid, in which
the stirrer {0) oscillated 145 times per minute. Concentric layers of
heavy white silk aided in protecting the liquid mass from outside
fluctuations of temperature. The drainings which collected in the
lower end of the delivery tube after the admission of the soda to the
bottle were expelled by blowing with a rubber bulb through the side
tube (i^).

It is of the utmost importance that the stirring should be efficient.
The entire system of stirrers was driven by a small electric motor, a
system of wooden pulleys giving the
required reductions in speed. The
stirrers of the bottle, jacket, and burette
formed one system, and those of the
calorimeter and cover, a second. It was
found advantageous to attach th« vari-
ous oscillating stirrers to metal rods
working in sleeves and actuated by
cords fastened eccentrically to the
proper pulleys. In this way uniformity
of travel and stroke were secured, the
friction of the rods in the sleeves being
reduced by good lubrication to a negli-
gible quantity.

As uniformity of composition in the
acid used in the bottle within the
inner vessel of the calorimeter is a
fnndamental condition for the accuracy
of the process, the familiar device
shown diagrammatically in Figure 2
was used for delivering it. The acid
was stored in the 2-litre Jena flask {A)
closed with a perforated rubber stopper.
Through the siphon {S) the acid could
be drawn into the burette {B). The
auxiliary tube {T) equalized the pressure in the two containers. After

21 The thermometer was a very accurate one, made especially for this purpose-
It has a range of but 8 degrees, graduated in tenths.
VOL. XLIII. — 31

FlOUKE 2.

482 PROCEEDINGS OF THE AMERICAN ACADEMY.

filling the burette, the inflow cock (O) was closed. When the acid was
to be drawn from the burette, the cock (E) connecting with the outside
air through the wash bottle (D) was opened and the pressure thus
equalized. As the wash bottle was filled with acid of the same con-
centration as that in the reservoir, the tension of aqueous vapor of the
air introduced was the same as that obtaining in the system. The
flask was always shaken before anything was drawn from it. By this
means an acid was secured of unvarying composition, as shown by
numerous experiments. In a similar way, with the addition of a soda-
lime tower for the removal of carbon dioxide, the alkaline solution was
maintained at constant strength.

It is needless to say that the thennometers were compared with
Sevres standards with the greatest care, especially that designated
31. Successive standardizations at different times were gratifyingly
concordant.

Conduct of an Experiment*

The calorimeter proper ( W, Figure 1) was partly filled with about 0.47
litre of the desired liquid, ^ either pure water to serve as a standard,
or a solution to be studied. It was then brought to the temperature
selected for the experiment, accurately weighed, and placed inside the
jacket (E, Figure 1). This latter contained its charge of dilute crude
alkaline solution, and was also near the selected initial temperature.
About 0.1 litre of pure acid (1.34 normal) was then run into the plati-
num bottle (X, Figure 1), weighed carefully, and placed in a thermostat
to bring it to the desired temperature. The innermost short burette
(Z) was filled to the mark with about 0.02 litre of pure alkaline solu-
tion and brought near the reciuired temperature. The whole apparatus
was then rapidly assembled in the form already described. A few
minutes after the stirrers were put in operation, the whole system was
in thermal equilibrium, as was shown by the constant readings of the
various thermometers. The temperatures of the calorimeter and the
pure alkaline solution, indicated by the thermometers 31 and K re-
spectively, were then carefully recorded, the stirrer in the bottle was
disconnected, and the pure alkali discharged into the bottle as rapidly
as possible. The immediate temperature rise, as the heavy alkali sank
through the acid, was paralleled outside by running acid into jacket
and cover. The bottle-stirrer (J) was then agitated by hand, this
permitting excellent control of the mixing of pure acid and alkali and
the resulting rise in temperature. When the mixing was almost com-
plete, as shown by the rise of the thermometer 31, the stirrer was
reconnected with the motor and the final mixing done mechanically.
The changes in the calorimeter throughout the experiment were care-

RICHARDS AND ROWE. — THE SPECIFIC HEATS OF LIQUIDS. 483

fully duplicated in the jacket and cover. At the end of some nine
minutes the final equilibrium was attained, the thermometer readings
becoming constant, at a temperature about four degrees above the
initial temperature.

The calculation was exceedingly simple except for two features, each
of which concerned the sodic hydroxide. The first of these was a
correction needed because the alkaline solution had not exactly the
temperature of the calorimeter at the moment of delivery. If warmer,
the alkali brought with it a slight excess of heat ; if cooler, it caused
a slight deficiency. This correction was easily calculated by multiply-
ing the water equivalent of the alkaline solution by the difference of
temperature. When the alkali was too warm, this small product was
subtracted from the total ; when too cold, added. The other unusual
feature involved not the total amount of alkali, but only the excess of
this solution over and above the constant amount (19.30 grams) needed
to neutralize the acid. It was intended that the alkaline solution
should be of such concentration as to evolve enough heat on dilution
to raise itself through the range of temperature of the experiment. If
this were the case, it would not be necessary to know very exactly the
amount of the alkali ; any excess would not aifect the final temper-
ature. The alkali was made up as nearly as was possible on the basis
of the previously known data to accomplish this result, and was nearly
enough so for the present purpose. Its concentration was 8.97 normal.

The data and calculation of a specimen experiment may now be
given without further preamble.

Specimen Experiment with Water in Calorimeter.

No. 4, February 27, 1908.

Data concerning temperature :

Initial temperature of calorimeter 16.489°

Final temperature of calorimeter 20.237°

Rise of temperature during experiment . . . 3.748°

Temperature of sodic hydroxide 16.44°

Ditference between this and initial temperature 0.05°

Data concerning heat capacity, exjyressed^ in terms of the water-equivalent:

Water in calorimeter 474.97 grm.

Calorimeter and fittings, equivalent to . 11.35 "
103.71 grm. of dilute acid (sp. ht. = 0.94) . 97.49 "
19.3 grm. alkaline solution needed to neu-
tralize acid (sp. ht. = 0.84) 16.21 "

Total heat capacity 600.02 grm.

484

PROCEEDINGS OF THE AMERICAN ACADEMY.

Total heat observed =^ &00m X Z.li8° .... 2248.87 cal. (18°)
Correction for heat needed to warm 20.9

grm. alkaline solution through 0.05° . . +0.88 "
Total heat, corrected, from neutralization of 103.71

grams acid 2249.75 cal.

2249.75
Heat evolved from 100 grm. dilute acid ^ " '' — 2169.3 cal.

This process was repeated until there seemed to be no doubt as to
the exact amount of heat evolved by the heat of neutralization of
exactly 100 grams of this particular dilute acid by a slight excess of this
particular alkaline solution under these perfectly definite conditions.
The data and results of a series follow.

In the following table, Ti is the initial temperature of the system
and T^ — Ti is the observed rise. The other values are self-explanatory.

Results with Water.

No.

HoSOi

Total Water
Value.

NaOH
Correction.

T,.

To - Ti.

Corrected
Heat.

Heat per
100 grams.

grams.
103.74

grams.
597.19

calories.
-4.74

Centigrade.
16.030

Centigrade.
3.776°

calories (18°)-
2250.3

calories (18°)
2169.1

103.74

597.19

-3.51

16.37°

3.774°

2250.3

2169.1

103.69

600.02

+7.02

16,--'6°

3.736°

2248.7

2168.7

103.68

599.98

+6.44

16.37°

3 740°

2249.4

2169.5

103.71

600.02

+0.88

16.49°

3.748°

2249.8

2169.3

an . . .

. . .

. . . .

2169.14

The maximum variation from the mean here is only 8 parts in 22,000,
or about 0.02 per cent. As will be seen upon inspection, the correction
for the difference in temperature of the alkali is sometimes additive
and sometimes subtractive in the different experiments, hence the con-
cordance of the observed results in connection with these values is
excellent testimony as to the accuracy of the correction.

The amount of heat evolved by the neutralization of 100 grams of
sulphuric acid under these conditions was now used as the standard
in warming various definite solutions through about the same range
of temperature. In order to accomplish this purpose, the solutions

RICHARDS AND ROVTE. — THE SPECIFIC HEATS OF LIQUIDS. 485

were successively placed in the calorimeter, and the flask for conduct-
ing the heat-producing neutralization was immersed in each just as it
had previously been immersed in the pure water.

As an example, a series of results with a special solution of hydro-
chloric acid may be given. This acid was chosen for determination
because, being involved in another research, its specific heat was" a
matter of immediate interest.

Below are given the data and method of calculating a single experi-
ment, as well as the data of a series.

Specimen Experiment with a Solution.

No. 3, May, 1908.

Weight of dilute sulphuric acid in platinum bottle . 103.72 grm.

Data concerning temperature :

Initial temperature 16.23G°

Final temperature 19.960°

Temperature rise 3.724°

Temperature of alkali 16.13°

Excess over initial temperature —0.11°

Heat, producing this effect :

Calculated heat evolved by reaction =

103.72X2169.14 2249.83 cal. (18°)

Heat taken by alkali = 20.9 X 0.S4 X 0.11 —1.93 "
Total heat actually available in process . . 2247.90 cal.

Data concerning heat capacity, in terms of water equivalent : ^^

Water value of calorimeter 10.87 grm.

Water value of acid 97.50 "

Water value of alkali 16.21 "

Total 124.58 grm.

Heat used by system exclusive of solution = 124.58 X

3.724° =463.94 cal. (18°)

Heat needed to raise 488.35 grams of hydrochloric
acid contained in calorimeter

= 2247.90-463.94 = 1783.96 (18°)

22 As these amounts are constant in all the determinations, slight constant
errors in them would have only a vanishingly small pernicious effect upon the
final results. The method is a comparatn-e one, and small errors of this kind
cancel out.

486

PROCEEDINGS OF THE AMERICAN ACADEMY.

Hence, specific heat of hydrochloric acid of concen-

1784.0

iration HCl 200.0 HoO

488.35 X 3.724

= 0.9809

The experimental data for this series are found in the accompanying
table. Several experiments where the manipulation was faulty were
rejected, but if they had been included the average would have re-
mained essentially unchanged.

The Specific Heat of HCl 200 HoO.

No.

HCl.

HjSOi.

"^NiOH-

Ti-

T^-T,.

Correction
NaOH.

Specific
Heat.

grams.

488.31

grams.
103.71

16.38°

16.39°

3.727°

calories.

0.00

0.9810

488.25

103.68

16.14

15.99

3.732

+2.63

0.9806

488.35

103.72

16.18

16.24

3.724

-1.93

0.9809

488.34

103.70

10.30

16.40

3.723

-1.76

0.9812

ean . .

....

. . . .

. 0.9809 23

As will be seen, the maximum variation from the mean is 0.03
per cent. This experimental error is as low as could possibly be
expected.

Heat of Dilution.

It is obvious that this apparatus can be applied to the accurate de-
termination of the heat of dilution of any solution put into the burette
(>^, if water instead of sulphuric acid is placed in the platinum flask
(A'). The liquid to be diluted is run into the bottle as before, and there
mixes with a weighed amount of pure water. A series of three experi-
ments on the dilution of a concentrated solution of sodic hydroxide is
given below. The results are calculated in kilojoules, as the best
standard for permanent record ; in the experiments previously recorded
this was unnecessary because the method was a comparative one and
the dimension of heat energy was eliminated in the result. 0.100 litre
of pure water was contained in the platinum bottle.

22 The corresponding values obtained from the results of Thomsen (loc. cit.)
and Marignac (loc. cit.) are respectively 0.979 and 0.983.

RICHARDS AND ROWE. — THE SPECIFIC HEATS OF LIQUIDS. 487

The Heat of Dilution of Sodic Hydroxide NaOH • 5.85 HoO.

No.

Water Value.

NaOH.

T, — Tj.

Corr. (NaOH).

Heat evolved by

Pilutiou to
NaOH -43.5 HjO.

1
2

grams.
601.79

601.80

602.01

grams.
21.39

21.43
21.59

0.132
0.129
0.155

calories.

- 4.5

- 3.2

-18.5

kilojoules.
3.82

3.78

3.77

Mean . . , .

. . 3.79

The variation from the mean falls within the probable experimental
error (0.001°).

Obviously any thermochemical effect produced by the mixing of two
liquids could be measured in the same way. It is to be noted that
the method has a great advantage over other methods in that great
speed in the execution of the experiment is not at all necessary. By
the old methods, speed was essential because of the correction for
cooling ; but here there is no correction for cooling because the per-
formance is strictly adiabatic. The reaction may extend over hours,
if necessary.

It should be noted that the correction concerning the sodic hy-
droxide could be wholly avoided if the pure alkaline liquid were con-
tained in a receptacle within the calorimeter, instead of being held in
a burette above it. Such a receptacle has been used successfully by
Richards and Henderson ^^ and was not introduced in these prelimi-
nary experiments on account of its slightly greater complexity. In
the future it will be adopted, and with it we hope to secure yet more
accurate results.

Experiments are now under way for the determination of the specific
heats and heats of dilution of various solutions at different concentra-
tions and at different temperatures, by the methods just described.

It is a pleasure to acknowledge the generous aid of the Carnegie
Institution of Washington, without which we should have been greatly
hampered in this work. The present and future results of this investi-
gation will be published in greater detail by that Institution, in one of
its shortly forthcoming regular publications.

2* These Proceedings 41, 11 (1905) ; Zeit. phys. Chem., 52, 551 (1<J05).

488 PKOCEEDINGS OF THE AMERICAN ACADEMY.

Summary.

The results of this paper may be briefly summarized as follows :

1. A new method for the accurate determination of the specific heats
of liquids has been described, using the adiabatic calorimeter and a
chemical source of heat.

2. The heat capacity of a solution of hydrochloric acid of molal
concentration HCl + 200 H2O has been measured.

3. The method has been applied to the accurate determination of
heats of dilution.

4. A solution of alkali was used whose heat of dilution automat-
ically compensates for any excess which might have been added.

Chemical Laboratorv of Harvard
College, April 27, 1908.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 19. — June, 1908.

PISISTRATUS AND HIS EDITION OF HOMER.

By Samuel Habt Newhall.

PISISTRATUS AND HIS EDITION OF HOMER.
By Samuel Hart Newhall.

Presented by M. H. Morgan. Received May 13, 1908.

In dealing with the life and works of any great character in history,
especially a man whose figure in the world has conceivably been mag-
nified through the mists of distant time, it is essential carefully to
discriminate between fact and fable, between a clear statement, how-
ever incidental, found in any reliable writer, whether he makes the
assertion on his own authority or on that of some author known to
us, and a mere tradition to which the writer refers without stating his
authority, however prevalent the story may have been in his own life-
time, and even for many years previous. For it is possible, though
not perhaps probable, that a tradition could be very old and very wide-
spread without having the slightest foundation on fact. In dealing,
then, with the literary work of Pisistratus, a prominent and influential
person in the early days of Hellas, it is especially necessary to distin-
guish between uncompromising statements made by authorities con-
cerning his work, and mere references to a commonly accepted tradition
introduced by such listless preludes as ol iraKaiol (paa-iv and similar ex-
pressions. In this article I shall try to make a satisfactory answer to
two questions : first, did Pisistratus really do any literary work in
connection with the Homeric poems ? and, secondly, how thorough and,
so to speak, professional were his services ? that is, did he produce a
text edition of the Iliad and the Odyssey 1 These questions are by
no means new, but it is time that they were once more considered
together, and perhaps something new may be brought forward in
answering them.

First, I desire to present a few passages from the ancient authors
which point to a certain amount of literary activity on the part of
Pisistratus in connection with the Homeric poems, though they could
not be considered indicative of anything so thorough and systematic
as a regular edition. Strabo, the geographer, who manifests a wide
interest in literature, briefly tells the following story (IX, 394, 10) :

Kai (j)acnv oi jxev YleKTicrTpaTov, ol 8e 'SoXwva trapeyypa-^avTa iv rai vemv Kara-
Xoyat fiera to enos tovto, Atas 8' (k 'EuXcifuvos ayei' 8voKai8(Ka vfjas, e^ijf tovto,

492 PROCEEDINGS OF THE AMERICAN ACADEMY.

arrjae S' liyoiv, If ^ h.6rjva'iaiv laravTO (fiaXayyes, fiaprvpi )(pr]craadai ra TroirjTri rov

TTjv prjcrov e$ apx^i 'Adrjvaicov Inap^ai. This bit of evidence, if true, though
we must bear ru mind that it is based on tradition, and that, too, tra-
dition which ascribes an act to either one of two men, points to an
insertion which might more properly be called malicious than literary.
This inserted line, popularly said to have been an interpolation, is
verse 558 of the Iliad B, and stands in all known manuscripts, with
the exception of seventeen. ^ But in the best manuscript it is lacking,
as La Roche points out in his edition of the Iliad.^ By " the best
manuscript " I understand him to mean the Venetus A. Accordingly,
in his text, he encloses this line in brackets. Aristotle also, in his
Rhetoric,"^ makes Homer, as a writer of historical accuracy, the final
court of appeal for the Athenians in their contest for the possession
of the much-disputed Salamis, though unfortunately he does not men-
tion the name of PisistratuS : nepX 5e paprvpaiv, p,apTvpes elcTi SiTTOi, ot pev
TroKaiol, ot 5e T7p6cr(f)aTOi, koI tovtcov ot pev pere^ovTe? rov Kivdvvov, ol 8 €kt6s.
Xeyo) 8e TToKaiovs pev rovs re tvoitjtcis Kal ocrcov aXXcov yvcopipai' eiai Kpiafis
(jiavepai, oiov 'Adrjvaloi 'OprjpM paprvpi ixpr]aavTO nepl ^aXaplvos- 1 hlS re-
mark of Aristotle's, of course, has no direct connection with Pisistratus.
I quote it here merely to show that at least Strabo's story of the use
of Homer as a witness in the dispute about Salamis is true on the
authority of Aristotle. In Quintilian (V, 11, 40) we have a slightly
more pertinent reference to the same circumstance. His words are
these : neque est ignobile exemplum (i. e. of auctoritas) Megarios ab
Atheniensibus, cum de Salamine contenderent, victos esse Homeri
versu, qui tamen ipse non in omni editione reperitur, significans
Aiacem naves suas Atheniensibus iunxisse. Here we see the verse in
question is quoted in a translation with the added suggestion that per-
haps it is not genuine from the fact that it is not contained in all the
manuscripts. This statement, however, about the use of Homer as
historical testimony may very well have been made by Quintilian on
the authority of Strabo, his predecessor, Quintilian's own more inti-
mate and critical literary knowledge prompting him to note the omis-
sions in certain manuscripts, with which Strabo, very naturally, was
unfamiliar.

On the authority of Hereas, a Megarian writer of uncertain date, we
are informed by Plutarch (Theseus, XX) that Pisistratus inserted verse
630 of the eleventh book of the Odyssey : Aeivos yap piv erfipev i'pcos Uavo-

TTT/iSor A'iyXrjs. Toiiro yap to eVos e/c rcoi' 'HctloSov Tleia-ia-TpaTov i^eXelv (prjaiu

1 Cf. T. W. Allen in Class Rev., XV, p. 8 (1901).

2 Footnote to II., II, 558.

3 1, p. 1375, 26.

NEWIIALL. — PISISTRATUS AND HOMER. 493

Hpeas 6 Mfyapevs, wairep av ttoKiu efx^aXfiv eis t^v 'OnTjpov vfKviav to, Qrjcrfa
U^ipidoov re dfcov d/jtSeifcera reKva, )^api^6p.fvov ^ AOrjvnioii. The manUSCnptS,

according to La Roche,* read in this place, ipiKvdea for dpiSflKera, which
change he himself adopts in his edition, explaining the variation by
the well warranted supposition that either Hereas or Plutarch, in ac-
cordance with the prevailing custom of the ancients, was quoting from
memory. This passage shows that even before the time of Plutarch it
was believed by one writer at least that Pisistratus inserted this verse
in the Odyssey. Diintzer,^ then, has some warrant for his supposition
that in the time of Hereas credence was given to the story of the
Pisistratean edition of the Homeric poems, provided we take it for
granted that the poems did not exist in writing before the time of
Pisistratus, — a point on which authorities differ. If they had previ-
ously been reduced to manuscript form, then the insertion of a line by
a ruler, merely to tickle the vanity of his subjects, can hardly be con-
sidered indicative of an entire recension of the poems.

Ascribed to Dieuchidas, the Megarian historian, we find a statement
which, though vague, has reference, nevertheless, to an activity of some
sort on the part of Pisistratus in connection with the Homeric poems.
The exact date of Dieuchidas himself is a matter of some uncertainty,
though he is confidently placed by Wilamowitz ^ in the fourth century
B. c, and by W. Christ, who refers to Wilamowitz, among the earlier
Atticists, which would make his sphere of activity fall in the first part
of the third century b. c. The statement is contained in Diogenes

LaertiuS (1, 57), and reads as follows : rd re 'Onrjpov e'l vtto^oX^s y/ypat^e
(i. e. SoXui'), payj/aSelcrdaL, oiov ottov 6 TvpwTOi eXrj^ev, iKfldev ap)(fcrdai rov
i)(6p.evov. p.a\Xov ovv "ZoXoav" Op.ripov ecjiaiTKrev ^ UeirriaTpuTos, Sis <pT]cn At,ev)(i-

8as iv Tre/iTTTo) MiyupiKav. It is obviously impossible to determine the
exact nature of the services of Pisistratus to Homer as indicated by
the word " ecptaTia-ev." Even the very reading of the text itself after
the word " neto-iarparo? " has been questioned by scholars, not, however,
because the manuscript is corrupt, but merely because the sequence of
the next sentence is deemed too abrupt. Ditntzer (ibid., p. 8), ^ith
Ritschl and Lehrs, finds himself compelled to indicate a lacuna after
that word. Two insertions into the text have accordingly been pro-
posed, one by Diintzer himself and the other by Ritschl, both being
relative clauses descriptive of the literary activity of Pisistratus.
That the reputed collection of poems by Pisistratus can find no sup-
port in this reference to Dieuchidas has already been pointed out by

4 Horn. Textkritik, p. 13.
^ Horn. Abliandlungen, p. 5.
8 Horn. Untersuchungen, p. 241.

494 PROCEEDINGS OF THE AMERICAN ACADEMY.

Lang7 It does show, however, that Diogenes Laertius found a state-
ment in Dieuchidas expressive of his belief in some service performed
by Pisistratus for Homer.

So far, the cited passages which attest a mere literary dabbling on
the part of Pisistratus have been rather unsatisfactory ; they are,
briefly, a reference by Strabo to a mere tradition which ascribed the
insertion of a line either to Solon or Pisistratus ; second, the insertion
by Pisistratus of another line in another place according to Plutarch,
who is quoting from a writer about whose date we know only this,
that, appearing in Plutarch, he must have written earlier than the
year 80 a. d., which approximately marks the date of Plutarch's ac-
tivity ; third and last, the statement of Dieuchidas, as quoted by
Diogenes Laertius, saying that Solon did more to elucidate Homer
(if that is the best way to translate e<pa)Tiafv) than did Pisistratus.

Next, let us consider a few passages in authorities of the time of
Cicero and later, who make definite statements about what might with
fairness be called a Pisistratean edition of Homer. The earliest refer-
ence of this sort in any Latin author occurs in, the De Oratore HI,
137, where Cicero says with reference to Pisistratus : qui primus
Homeri libros, confusos antea, sic disposuisse dicitur ut nunc habemus.
The use of the word " dicitur " in this place is significant, showing, as
it does, that Cicero is careful not to make the statement on his own
authority, but introduces the story as one commonly believed in his
own day or as transmitted by previous writers. It is reasonable to
suppose that Cicero is indebted for his information on this point either
to the Alexandrian scholars, or to some of the philosophers of Greece,
or to the rhetoricians of the school of Pergamos, though such a state-
ment is of course merely conjectural.

More definite information about the edition of Pisistratus is pre-
served to us in the scholia ^ of the Townley manuscript at the beginning
of Book K of the Iliad. It runs thus : <^ao-i ttjv pa'^cpBiav Icj)" 'o^rjpov

Ihiq TfTd)(6ai Koi fifj eivai fiepos t^s 'iXtaSoj, vtto Se UeiaiaTpaTov reraxdai els

Tijv iToiT)(Tiv. This scholion is one of our most important bits of evidence
and must be carefully considered. First we must note that no literary
forgery on the part of Pisistratus is implied, but merely the assigning
of a place in the Iliad to a poem which had been separately composed
by Homer. Since the insertion of an entire book is a fundamental
change to make in any piece of literary work, I think I am justified in
considering this passage as pointing in the direction of an entire re-
cension of Homer by Pisistratus. The use of the word " ^acrt " in this

' Homer and his Ape, London, 190G, p. 46.
8 Ed. Maass, Ox. 1887, p. 341.

NEWIIALL. — PISISTRATUS AND HOMER. 495

passage does not bring to the "source hunter" the despair which is usu-
ally attendant on such expressions, because, in this case, it is possible
with some degree of accuracy to determine the sources of the Townley
scholia. Let us briefly consider this point. The codex Venetus A
of the Iliad has the following subscription : TrapuKeirat ra 'Apta-ToviKov

OTifiela Koi TO Ai8vp,ov Trepi r^? Api(rTap)(eLOV diopdacrecos, riva 8e koi Ik. ttjs
'iXiaK^y 7r/Jocra)8t'as 'HpaiStavoi) (cat e'/c twv fiiKavopos nepi (TTiyfiijs. "he dates

of these four men are as follows : Aristonicus, 66 b. C.-19 a. d., Didy-
mus in the time of Augustus, Herodian under Marcus Aurelius, and
Nicanor probably under Hadrian. Of their connection with the Town-
ley scholia W. Christ^ says that to "extracts from the works of these
men the scholia of our manuscripts go back. Such are best preserved
to us in Venetus, 454 (A) ; next in worth stand the Townley scholia.
... To the works of these men there were added in later times also
scholia from other grammarians, and especially from the z^nj/xara of
Porphyrins." Without doubt, therefore, our Townley scholia rest on
really ancient authorities and have the same source as the scholia of
Venetus A. Jebb ^^ also agrees with Christ in deeming Aristonicus,
Didymus, Herodian, and Nicanor, together with Porphyrins, the sources
of our scholia. ^^

A clear and valuable reference to the collection of the Homeric
poems by Pisistratus or his associates is to be found in Pausanias
(VH, 26, 6). When speaking of a certain city in Greece named

Aovovaira, he makes the remark : p.vrjp.ov€V{iv 8e koi "O/xTjpov eV KaraKoyco
tS)u (tvu 'Ayapffivovi (f>aaiv avTrj: TTOi-qcravTa enos,

Ol 9' 'Tireprjairjy re Kal alireiv^v AovSeffirav,

TletcritTTpaTov Se, r^vina '4nrj to. 'Ofirjpov StfcrTrncr/xei/a re Koi oKKa aWa-xpv fxvq-
fiovevopeua rjdpo'i^ero, tj aiiTov YlficrlcrTpnTOV, fj t6)V riva eTaipcoif p-eraiToiricraL to

ovofia vTTo dyvoias. The word '^ r]6poi(eTo" in this passage must clearly
refer to a writing down of the poems or to the collection of such por-
tions as may have existed in writing before the time of Pisistratus. It
is furthermore interesting to note that Pausanias is the earliest extant
writer to mention anything like a school of revisors and collectors as-
sociated with Pisistratus. Later we shall have other and more detailed
references to such a body of coworkers.

9 Griesch. Lit. Gesch., ed. iv, Munich, 1905, p. 71.

" Homer, Glasgow, 1887, p. 100.

" It is obviously dangerous as well as unnecessary for our present purposes
to make any one -of these four or five authorities the ultimate source of this
scholion. That is a point which cannot be definitely settled. Sufficient it is if
I have merely hinted at the real antiquity and trustworthiness of our Townley
scholia.

496 PROCEEDINGS OF THE AMERICAN ACADEMY.

As alone and unassisted in a similar literary undertaking, Pisistra-
tus is' described by Aelian (XIII, 14): varepov Se (i. e., after Lycurgus,

who had just been mentioned) neio-to-Tparoy a-wayaycbv dn6(pr)Vf TTjv 'iXtdSa

Koi 'ohvaaeiav. The word " dTr((f>r]v( " without a context might be of doubt-
ful significance, but when, as here, it is combined with " awayayav,"
a word which can refer to nothing but a written collection, there can
be little doubt that it means "publish " in the modern sense of the
word. It should be noted, however, that nothing of the nature of a
critical edition is here implied, merely a published collection.

In a seventh ^^ century scholion ^^ to the Tpafi^iaTiKr) of Dionysius
Thrax we have the following account of a Pisistratean school, which
though interesting is not without obvious historical inaccuracies. It

runs thus : eKfjpv^ev iv ndar] rfi 'EXXaSi tov €)(ovTa 'OfiTjpiKoiis (ttixovs dyayflv
npos avTov . . . Kai fiera to iravras a-vvayayelv, TraptKaXeaev f^8opr]KOVTa 8vo
ypapfxaTiKovs avvBelvai, to. tov 'O/iijpou (kuo-top kut I8iav, cttcos av ho^j] tm (tvvti-
BivTL KaXa>s e^eti' . . . koi p.fTa to €Ka(TT0v crvvdf'ivia kuto ttjv eavTov yvwfirjv,
els iv (Tvvrjyaye TrdvTOi tovs TTpo\e)(6evTas ypap,naTiKovs. . . . ovtoi ovv uKpoacra-
fievoi ov rrpos e'piv, dWd npos to dXrjdes Kai irdv to tji Tex^rj dpixo^ov, eKpivav
TrdvTfs Koivfj KQi 6po<pcovcx}S, KpaTTJcrai Tr/U (TVv6ecTiv Te Ka\ 8i.6pd(oa-iv K^KTTapxov
Koi ZrjvoSoTov. Ka\ nd\iv (Kpivaif Tav 8vo (TVv6i<Tf(ov Te koi diopdaaecov ^eKTiova

TTjv 'ApidTdpxov. We shall later consider the glaring falsity of this last
statement about Aristarchus and Zenodotus when we find a similar
statement ridiculed by Tzetzes of the twelfth century. The same
scholia likewise contain an epigram on Pisistratus, which, as its date
has never been determined, loses much of its importance for our pres-
ent investigation. The following is an extract:

rhv fxiyav ev ^ov\fi Ufiff^ffTparov, ts Thv''OfjLT]pov
^dpoicra cnTopd57]y rh irplv dei56fj.(voi'.

Suidas^* also, the lexicographer, under the word ""Oprjpos," relates
the story of the collection of poems made by Pisistratus. His words

are these: va-rtpov Se a-wfTtSr] koI avveTaxdr] inro ttoXXcov, koI paXiaTa vno

TietatcTTpaTov, tov twv ^Adr)vaiuiv rvpdvvov. For this statement Suidas may
very well have had Pausanias as his authority. This is not unlikely,
inasmuch as the two accounts are substantially similar, that is, in both
Pisistratus was only one of several who collected the Iliad and Odyssey.

" The principal commentators on Dionysius Tlirax wrote in the sixth and
seventh centuries. We probably have here a note by Heliodorus, who wrote in
the seventh century, though we cannot determine with certainty the author of
this scholion.

13 In Bekker's Anccdota, p. 7G7 ff.

14 Ed. Bernhardy, Halle, 1853, 2, 1096.

NEWIIALL. — PISISTRATUS AND HOMER. 497

By the use of the expression Ino noWav Suidas rather implies different
collections separated by considerable lapses of time, so that it seems to
me very possible that, as Lachmann ^^ suggests, he may have misin-
terpreted his sources, misunderstanding a reference to the different
collectors of the Pisistratean school as an allusion to compilers among
the predecessors of Pisistratus.

Coming now to Tzetzes, a commentator of the twelfth century, we
find that at one time in his life he believed in a collection of Homer
by a Pisistratean school of seventy-two, though, as will appear later,
he subsequently rejected this theory, expressing the greatest disgust
with Heliodorus,^^ whom he had used as his authority. His first
belief he expresses in the following words : ^'^ Ufia-laTpaTos 8e 6 (piXoXoya-

TOTOs, iv )(p6vois Tov 'S.oXdiuos rvpavvTjcras if Toii Adfjvaiv, KTjpvyfj.a f^fKTjpv^e rov
fXOvra eTTT] 'OpTjpov., dnonopi^ecv avTa npos avTov, Koi eKaarov enovs ;(puo-oCi'
dvTicpopTL^eadai. vopicrpa. ovtco Se avvayeipas avrd, e^8opr]KOVTa kol 8vo ypappa-
TiKo'is fvl (KacTTO} eVeScoKe /car Idiav TedecopiKevai Koi uvvdeivaL avrd ' cKelvos 8e
TT]V ivos €<daTov avTojv avvOecnv aTTfypa(f)fTO. vcrrepov oe opov Trdiras avpuyayav
irapaKKrjcrecn, peydXais re Scopeais eKeivovs de^ioiadpevos, vnedfi^t rfju diroypacpT^v
TTis ej/6s iKauTov crvvdfiKrjs, koi ij^icocrev avTovs (fitXaXrjBaii koi dcpiXe^dpcos dne'iv,
oTov apa elr] KpeiTTcov fj (Tvudecrii ' Koi Travres ttjv Apiardp^ov Kcil Ztjvod .tov vnep-
f^€KpLvav. fK dveiv 8e TrdXn/, ttjv 'Apia-Tdp^ftov, Ka6 r]v vvv to Traphv tov 'Oprjpov

^ijiXtov (TvvTideiTai. Evidently, at some later time, Tzetzes got new light
on this subject, and realizing the absurdity of making the Alexandrian
Aristarchus and Zenodotus the contemporaries of Pisistratus, and boil-
ing with indignation when he reflected how he had been taken in, thus
expressed his new belief, prefacing it with a brief note in which he
makes poor Heliodorus the scapegoat of his disgust by the amusing
epithet of opprobrium Tw /3S6Xvp(a. The passage runs thus: Ueiadfls^^

'HXtoScopo) TO) j38eXvpa) einov crvvQelvai tov Oprjpop €n\ IletcrtoTparou e^doprjKovTa
bvo crocpoiis, u>v e^8oprjK0VTa 8vo dvai Ka\ tov Zr]v68oTov koi tov 'Apta-Tap^ov.
KaiToi T f aa d pcov dvdpav «Vt UeicncrTpdTov avvQiVTOiV tov "Oprjpov. oiTives
flcTLV ovToi ' imKoyKvXos. OvopdKpiTos AOrjvdlos, Zainvpos MpaKXed^TTjs Koi

'Opcfxiis KpoTavidTTjs. This last statement I have found in no author
before Tzetzes, so that I am at a loss to know his authority. In this
passage the expression enl Ueta-iaTpdTov could be interpreted as meaning

18 Betrachtung ii. Homers Ilias, Berlin, 18-17, p. 32.

IS This fact serves to strengthen my belief that Heliodorus was the composer
of the cited scholion to Dionysius Thrax, since there he expounds at length the
story of the school of seventy-two.

" Exegesis to Iliad, ed. G. Hermann. Leip., 1812, p. 45, 1. 27.

" See Ritschl's Opuscula, I, 205, which contain Tzetzes' Prolegomena to the
scholia of Aristophanes. The word printed as iniKSyKvXos has been variously
emended, but the MSS. are hopelessly defective at this point.

VOL. XLIII. — 32

498 PROCEEDINGS OF THE AMERICAN ACADEMY,

merely that " in the time of Pisistratus " this collection of Homer took
place, did not Tzetzes elsewhere give us a more definite statement of
his opinion. On page 207 of his prolegomena to the scholia of Aris-
tophanes we find these words : ra? 'OnrjpeLOVi 8e KaTe^alperov npo 8iaKoaio)P
Koi Trkeioviou eviavrav TiToXefiaiov rod '^iXa8e\(f)ov Koi rrji Biopdcoaecoi Ztjvoootov
avvTiOeiKev (TiTovdiJ IleicricrTpaTOi napa tu>v Tecrcrdpcov tovtcov aocficov ' inl Koy/cu-
"Kov, ^OvofiaKpiTov re 'Adrjvaiov, Zcorrvpov re 'HpoKXearov koi KpoToovLUTOv 'Op(f)eu>s,
OvTco p.€v (V )(p6voLi rov YlfiaLCTTpdrov rolv Teacrapcn tovtoh ao(pols at Ofj,r]piKa.\
(Tvyypa(pai T€p,a)(^!.ois Trfpi(pep6p.fvai a-vufridrjcTav /cat j3i'/iAot eyivovro. Meuce

we see .that Tzetzes regarded Pisistratas as an active participant in
the work of collection, though he was assisted by these four men.

There can be little doubt, I think, that for these prolegomena he was
drawing on the ancient scholia. John Williams White,^^ in speaking
of Tzetzes' interlinear notes to the Aves in codex Urbinas, says : "He
was writing a brief commentary on the Aves based on the old scholia
with additions 'by the editor.' " By some scholars, however, Tzetzes
is held in very low esteem as an authority. For example, Sandys ^o
says of him: "His inordinate self-esteem is only exceeded by his ex-
traordinary carelessness. He calls Simonides of Amorgus the son of
Amorgus, makes Naxos a town in Euboea, describes Ssrvius Tullius as
' consul ' and ' emperor ' of Rome, and confounds the Euphrates with
the Nile. He is proud of his rapid pen and remarkable memory ; but
his memory often plays him false, and he is for the most part dull as a
writer and untrustworthy as an authority." With regard to the pass-
age already quoted from Tzetzes, Monro ^i writes: " Everything points
to the conclusion that the story is a mere fabrication. He does not
give his authority, and it can scarcely be imagined that he had access
to sources unknown to the generality of Byzantine scholars." But is
not this unjustly making light of the character of Tzetzes 1 The worst
that Sandys cares to say about him is that he was careless ; but is it
carelessness that gives birth to such a circumstantial statement as this ?
I cannot see how such a detailed story could have come full-grown like
Minerva from the head of any writer unless his fault had been some-
thing much more serious than carelessness ; but this no one would say
of Tzetzes. I prefer then to follow Mr. White in believing Tzetzes to
have based his prolegomena on the old scholia with some additions,
and accordingly I think it most probable that for this statement he
must have found some authority in the scholia.

" Harvard Studies, XII, 104.

20 Hist, of Class. Scholarship, ed. ii, 419.

21 Od.. XIII-XXIV, ed. i, Ox., 1901, p. 406.

NEWIIALL. — PISISTRATUS AND HOMER. 499

Let US now briefly consider references to any of these four associates
of Pisistratus in literature earlier than the time of Tzetzes. In Herod-
otus (VII, 6) these words are applied to Onomacritus : au8pa 'Adrjvalov

Xpr](Tp.oK6yov re Kal Siaderrjv xp-qa-p-av ratv Movaaiov . . . i^rjKddr] yap vtto

'in7Tdp)(ov Toil iieto-toT-paroii 6 'Ovop.aKpiTos i$ 'Adrjvtav. As a Contemporary
of Hipparchus, so, without doubt, he was also a contemporary of Pi-
sistratus. Thus Herodotus vouches for the chronology of Tzetzes so
far as Onomacritus is concerned. But we must admit that in all
probability the connection of Onomacritus with Pisistratus in the
Homeric collection was unknown to Herodotus ; hence his silence in
this place. The only other of these four men to whom I have been
able to find a reference in an ancient author is Orpheus, — not the great
Orpheus, but one of Croton, who is referred to by Suidas (p. 1176),
under the words 'Op(Pfvs Kporcoviarris in the following manner : eVoTroto?,

Of TlficriaTpaTa) crvvelvai rai rvpawco Aa-KK-qTndbrjs (prjalv kv rw eKTco /St/SXiw tcov

TpappariKoiv. This writer Asclepiades was, according to Sandys (p. 160),
a native of Myrleia in Bithynia, and was born at some period between
130 and 180 b. c. As Orpheus was an epic poet and associated with
the tyrant Pisistratus, according to Asclepiades, I think we are justi-
fied in inferring that the connection was doubtless of a literary nature.
This fact, of course, is not enough to vindicate the whole story of
Tzetzes, but it shows that in the case of at least one of these four men,
his connection with Pisistratus was known even before the beginning
of our era, and that in this one regard the so-called fabrication of
Tzetzes shows a remarkable coincidence with the truth.

In the commentary of Eustathius on the Iliad and Odyssey, written
about the year 1175 of our era, and shortly after the time of Tzetzes,
are found two different accounts of the Pisistratean collection, obviously
drawn from different sources. In the first, we are surprised to find
him giving credence to the story we have met before of the Pisistratean
school dominated by Aristarchus and Zenodotus. In the second, Pi-
sistratus himself is mentioned as sole author of a probable recension.
The passages are as follows, first from his commentary to the first book

of the Iliad (p. 5, 1. 28) : ol he a-wdipevoi ravTTjv (l. C- 'iXtaSa), kot tmTayfjp,
S)S (pacri, TlficriaTpaTov tov tS)v Adrjvaiav Tvpavvov, ypapfiariKol Ka\ diopdaxrdpfvoi
Kara to eKeivois dpecKov, ajw Kopv(paLOi Api(rTap)(os Ka\ fieT eKiivov Zr]v68oTos 8ia
TO fTTipTjKes Kal dvfTf^LTrjTov Kal SiaTovTO TTpocTKopes KUTiTepov avTo els noWd.

This undoubtedly refers to a Pisistratean collection, but not one in
which Pisistratus took a personal part. The second of these passages
(Vol. II, p. 309, 1. 17) is identical in meaning with the Townley scho-
lion already quoted, and almost identical in form. The source of both

is doubtless the same : (\>a(Tl be ol naXaiol Tr]v pa-^ablav Tavrrjv v(^ 'Opf]pov

500 PROCEEDINGS OF THE AMERICAN ACADEMY.

ISla TfTCLxdni Kai firj iyKaToKeyrivai, rots fifpeai r^? 'iXiaSos, vno Se Jlftcricrrparoi;
TfTax^dai els ttjv TToirjaiv.

It is necessary, I think, at this point to consider briefly from what
authorities Eustathius drew his information. Diintzer^a seems ag-
nostic on this point, though confident in the real antiquity of such
sources. "It is difficult," he writes, "to see whom Eustathius means
by ot naXaioi in his note on the beginning of Iliad K. We cannot say
that he means any particular scholar of the Alexandrian school. On
the other hand, much less can we say that the supposition of the
insertion of a book by Pisistratus was wholly unknown to the Alexan-
drians. So the supposition of Lehrs, that the old Alexandrines had no
knowledge of the especial critical significance of the arrangement of
the Homeric poems by Pisistratus, is unfounded." Eustathius, as we
know,23 further used as sources an epitome made from the commen-
taries of the four men whom I have previously mentioned as probable
sources of our Townley scholia, viz., Aristonicus, Didymus, Herodian,
and Nicanor. Likewise the A«^«s- of Aristophanes, the rhetorical dic-
tionary of Dionysius, the encyclopaedic lexicon of Apion, and Herod-
orus and the Paralipomena of Porphyrins. Furthermore, I have noted
at least one place in Eustathius (Vol. I, p. 230, 1. 46) where he quotes
directly from Strabo (IX, 394, 10) in very nearly his exact words,

2o\o)v 5e ^ neia-ia-TpaTos irapeveypayj/fv evravBa ptra tov 'Oprjpov arixov to,

(TTria-e S' &yaji/, V 'Mrjvalwv 'IffravTo (pdXayya
Koi oZtcd paprvpi rw iroir)Tr\ ('xplja-aTo rod rijv vTjorov i^ dpx^is 'A0r)va[av V7r6p$ai,

i)s 6 ytwypacpos laropfl. And finally Sengebusch,^* who refers in turn
to the opinion of Lehrs, holds exactly the same view as Christ. Im-
portant therefore are the statements of Eustathius, inasmuch as he
himself, though a comparatively late writer, drew his information, so
far as we can ascertain, from writers even as early as the Alexandrian
school.

In a document three centuries later than Eustathius, that is, in a fif-
teenth century manuscript in the library of the Collegio Romano, con-
taining fifteen plays of Plautus, is preserved a version of the Pisistratean
story identical with the account of Tzetzes. Ritschl conjectures that
these scholia are drawn from Tzetzes, as they are, without a doubt. The
similarity is conclusive. Towards the end of the Poenulus they run

22 Horn. Abhandlungen, Leip., 1872, p. 4.

" See Christ, Griesch. lit. Gesch., oil. iv, p. 72.

2* Ilomerica Dissertatio, I, Leip., 1870, p. 40.

NEWIIALL. — PISISTRATUS AND HOMER. 501

thus -.25 Ceterum Pisistratus sparsam prius Homeri poesim ante Ptol-
emaeum Philadelphum annis ducentis et eo etiam amplius sollerti cnra
in ea quae nunc extant redegit volumina, usus ad hoc opus divinum
industria quattuor celeberrimorum et eruditissimorum hominum, vide-
licet, Concyli, Onomacriti Athenien. Zopyri Heracleotae et Orphei
Crotoniatae. Nam carptim prius Homerus et non nisi difficillime
legebatur. This of course is a quotation from the passage of Tzetzes
written after he had revolted from Heliodorus and his behef in the
school of seventy-two grammarians. These scholia also contain a few
sentences adapted from the Prolegomena of Tzetzes in the place where
he applies to Heliodorus the epithet of tw ^^eXvpa. They read as fol-
lows : Quum etiam post Pisistrati curam et Ptolemaei diligentiam Ari-
starchus adhuc exactius in Homeri elimandum collectionem vigilavit.
Heliodorus multa aliter nugatur quae longo convitio Cecius repre-
hendit. Nam ol' LXXII duobus doctis viris a Pisistrato huic negotio
praepositis dicit Homerum ita fuisse compositum. Qui quidem Zenodoti
et Aristarchi industria omi'ibus praelatam comprobarint, quod constat
fuisse falsissimum. Quippe cum inter Pisistratum et Zenodotum fue-
rint anni supra ducentos. Aristarchus autem quattuor annis minor
fuerit ipso et Zenodoto atque Ptolemaeo. This shows better than any-
thing else the utter falsity of the account given in Bekker's Anecdota
(p. 767 ff.). By the clause " Quum etiam post Pisistrati, etc." the text
recension of Zenodotus and Aristarchus is unquestionably meant. But
these are not quoted as the words of Tzetzes ^6 but of Heliodorus, as
the "multa aliter" clearly indicates. Without doubt, "Nam ol' LXXII,
etc.," down to "comprobarint" comes from Heliodorus, and "quod
constat " to the end from Tzetzes. But these late scholia add no new
testimony to that already given by Tzetzes himself.

Our last and probably latest reference to the collection of Homeric
poems by Pisistratus is found in two lives ^'^ of Homer which were
made from the collation of facts preserved in fourteenth and fifteenth
century manuscripts. A passage from one of them reads : nepuau 8e

Tas noXets f}8e ["O/irjpo?] ra iroirjfjiaTa, vaTepov 8e UeiaiarpaTOS avra crvvrjyayfVi
&)s TO eTriypapp.a tovtov St^XoI

rhf fxiyav iv $ov\ais Xlnffiffrparov, os Tbv''Ofj.r)pov
i^6pot(Ta ciropaSrif rh irpXv aeiSo/xefoy,

25 These scholia were first published by F. W. Ritschl, and can be found in
Vol. I of his Opuscula, p. 6, or in his Alexandrinisclie Bibliotheken, Breslau,
1838, p. 4.

26 See Ritschl, Op., I, 33.

2' See Jahn's Neue Jahrb. fiir Philologie u. Paedagogik, 9es Suppbd., p. 508.

502 PROCEEDINGS OF THE AMERICAN ACADEMY.

The second life draws its facts from practically the same manuscripts
as the preceding, and in the following portion is very similar to it :

TO. 8e TTOiTifiara avTov to, dXrjd^ (TTTopdhrjv nporepov d86iifva Xleta/o-rparos ^Adrjvalos
(TVveTa^ev, ojs hrfkoi to cpepo/jLCvov eniypappa 'Adrjurjatv eniyfypappevov iv et/cdi/t

aiiToii Tov neto-to-r/jciTou. e'xfi 8e o)8e . . . and then follows the same epigram.
Briefly summing up the testimony of such accounts as we may con-
sider reliable for an Homeric edition by Pisistratus or Pisistratus and
his associates, the result is as follows. The accounts in Cicero, the
Townley scholia, Aelian, Suidas, and Eustathius all point to a collec-
tion of the poems by Pisistratus alone and unassisted. The accounts
in Pausanias, Tzetzes, and, of course, the scholia to Plautus, are the
only ones which indicate any kind of a Pisistratean school. I do not
think, however, that we ought to consider this as strong evidence that
Pisistratus was not assisted by a board of associates in his work of
collecting. Naturally if he, a ruler in absolute authority and eager
for fame in letters, chose to be the proud supervisor of such a literary
undertaking, even though his co-workers were ever so numerous, the
edition which was produced would be called by subsequent writers
" Pisistratus's Edition " and the " Collection which Pisistratus made,"
while his helpers would be gradually disregarded, just as we, for in-
stance, refer to our Bible as "King James's Version."

The fact that the story of a collection of Homeric poems by Pisis-
tratus, or Pisistratus and certain associates, was known by Cicero and
several reputable writers after him is very significant. No one would
presume to say that, as in the case of Tzetzes, so also in the case of
Cicero, this story is a fabrication. In fact, he himself uses the word
"dicitur," which we may translate "we are told." What, then, was
his authority and the authority of these subsequent writers 1 It seems
at least probable that the Alexandrian School, for instance, must have
played a part in handing down the tradition. The most that can be
said against this is that neither Aristarchus nor any of his successors
in any of their writings which are extant in whole or in part mention
the connection of Pisistratus with Homer as a collector or reviser ; but
this is obviously an unfair objection because, without doubt, only small
portions of all their writings have come down to us. And yet Flach 28
derives especial satisfaction from the contemplation of such facts as,
for instance, that Aristarchus never so much as implies that the inser-
tions into the text of Homer especially compHmentary to the Athenians
were found only in the manuscripts that came from Athens, although,
if this were the state of things, we should expect him to mention it.

28 Peisistratus u. seine Lit. Tatigkeit, Tiibingen, 1885, p. 39.

NEWIIALL. — PISISTRATUS AND HOMER. 503

As to whether Homer had existed in writing before the time of
Pisistratus or not, that is not so important a question, and with regard
to it only general inferences can be drawn from the statements of the
ancients themselves. The testimony of Pausanias^Q and the first ^o
and second 31 lives of Homer tend to show that until the time of
Pisistratus, at least, oral tradition was the medium of transmission.
Cicero, "^2 however, the Townley scholia, -^"^ and Suidas ^^ give evidence
which is more definite and points directly to a written tradition. The
evidence then is quite fairly divided ; but bn the whole I feel safer in
favoring a written Iliad and Odyssey before the days of Pisistratus,
since the tradition recorded by Cicero is likely to have been older and
more reliable than the one mentioned by Pausanias, and especially be-
cause the Townley scholia ought to outweigh any evidence contained
in the lines of Homer based merely on manuscripts which are them-
selves inferior to the Townley. Furthermore, in addition to Suidas,
there are several other authors whose testimony in favor of a written
Homer before Pisistratus is sure. Plutarch says in his life of Lycur-
gus,"^^ when referring to the state of the Homeric poems in Greece in
the time of the great lawgiver [ol "EXXrjvfs] iKiKT-qvTo 8e ov noXkol nfprj nvd
[tov 'OfiT]pov], where it seems that a word like eKtKrrjVTo must refer to a
tangible written copy. Aelian also (XIII, 14) in speaking of Lycurgus

writes : nparos e's ttjv 'EXXaSa eKOfxicre ttjv 'OjjLTjpov nolrjcnu. Here again the

supposition of a manuscript seems imperative. Plutarch likewise,
in his life of Solon (X, 1), referring to his insertion of a verse, says:

ifi^aXovra yap avrov inos els V€a>v Karakoyov enl Trjs 8lkt]s duayvaivai, where thlS

last word cannot leave us in a moment's doubt. Here SUrjs refers to
the trial in which the Lacedaemonians were made arbiters between the
Athenians and Megarians. Diogenes Laertius (1, 2, 48), with reference
to this same performance of Solon's, uses the word fyypd\l/ai, prefacing
it however by eviot. 8e (paa-iv. I therefore cannot agree with these words
of Bonitz,*^^ " that this was the first time that the whole of the poems
was written down may be clearly inferred from the form and character
of the numerous statements in regard to it." Christ and Jebb, both on
grounds other than I have taken, favor the theory of a written trans-

29 Poems said to have been p.vr}[jLoviv6ixiva.

2" ["0/U7jpor] ifSe to votijiLiaTa.

2^ Poems said to have been irpoT^pov d56fj.fva.

32 " Libros " of Homer referred to.

33 71. K said to have been TeroxSai v(p' 'Onrjpov.
3* fypa<pi''Ofxripos.

36 Plutarcli I, p. 82, 1. 9, ed. Sintenis, Leip., 1884.
36 Origin of Homeric Poems, N. Y., 1880, p. 27.

504 PROCEEDINGS OF THE AMERICAN ACADEMY.

mission. Jebb ^7 is of the opinion that " it cannot be proved that the
Homeric poems were not committed to writing either when originally
composed or soon afterwards. For centuries they were known to the
Greek world at large chiefly through the mouth of rhapsodes. But that
fact is not inconsistent with the fact that the rhapsodes possessed writ-
ten copies. On the other hand, a purely oral transmission is hardly
conceivable." The judgment of Christ (p. 65) is thus expressed:
"Fully one hundred years before the Athenian Tyrants, the Ionic
books were reduced to writing, and it would truly be strange if the
honor of a written copy should have fallen to the lot of an iambic or
elegiac poet sooner than to the great national poet. Also the testi-
mony shows that Pisistratus made nothing more than a complete Iliad
and Odyssey. Probably before that time certain parts had been re-
duced to writing to aid the memory, as, for example, the Catalogue of
Ships."

Perhaps at this point it would not be out of place to make a brief
excursus on stories which, for the most part, without mentioning the
name of Pisistratus, tell us of other men who are reported to have done
work of some kind in connection with the Homeric poems. Since in
making this excursus a chronological arrangement of evidence by
authors (the system I have adopted up to this point) does not seem
necessary or even advisable inasmuch as it would cause confusion
through the separation of all passages by different authors, though
referring to the same historical personage, I have thought it best to
arrange the following passages in the chronological order of the differ-
ent persons whose activity is described therein. In La Ptoche's Homer-
ische Textlcritik im Altertum (p. 7) there is published an interesting
fragment of HeracHdes who lived at about the middle of the second

century B. C. AuKoCpyos iv Sd^w erfXevTrjae ' Ka\ rrjv 'Oyirjpov ttoitjctiv napa
Tcov dTToyovcov Kp(a)(f)vXov Xa^av npcoTos difKop-icrev els 'n.eXoTT6vvr](rov. Tllis, of

course, is another story entirely, and, even if true, is nothing to influ-
ence our belief in the nature of the services that Pisistratus may have
performed for Homer at a much later date.*^^ Similar also is a state-
ment made about Lycurgus by a much later writer in the second half
of the first century a. d. Plutarch (Vol. I, p. 82, 1. 2) tells how
Lycurgus, when he was in Asia, realizing that the Homeric poems con-
tained educational elements as well as political qualities, determined
to bring them |to Athens. Then comes the significant part : ^v yap

Tis 7S7 86^a T03V inav ap,avpa napa toIs KXXrjcriv, fKeKTr]VTO 8e ov ttoXXoI p-fprj

3T Homer, Boston, 1887, p. 114.

38 This fragment is additional evidence for a written Homer before the days
of Pisistratus.

NEWIIALL. — PISISTRATUS AND HOMER. 505

Ttvd, (TTTopd^riv Trjs Troir^crfoiy, wf eTv\f, 8ia(f)fpOfievi]s- yvuipiprju be avrrju Kal

fiaXicrTa Trpcoros cnoirjaf AvKovpyos. This again is interesting as throwing
light on the life of Lycurgus and the early history of the Homeric
poems, though it is not of a nature to influence our judgment as to
the truth or falsity of the Pisistratean story. And lastly Aelian (XIII,
14) makes substantially the same statement about Lycurgus when he

writes : o\//€ fie AvKovpyos 6 AaKe8aip,6vios ddpoau Trptoros es ttjv 'E\Xd8a enopiae

TTju 'OpTjpov TToiTjaiu. So mucli for Lycurgus.

We have already seen that the insertion of verse 558 of Iliad B was
said by Strabo to have been ascribed by one tradition to Pisistratus
and by another to Solon. To this I can add two accounts by some-
what later writers who, from hearsay or report, make Solon the author
of the same interpolation without any mention of Pisistratus. The
first of these is from Plutarch's life of Solon (X, 1) : ov prjv dXXd rav

Meyapecjv enipevovToiv TroWa KaKa /cat hpatvTes iv toj ivokep.a kol Trdaxovres inoir)-
aauTO AaK(8aipoviovs diaWaKTas Koi StKocrTos. Ot pev oiiv ttoWol t<o 'SoXavt
avvayavicracrdai Xeyovai ttjv 'Opfjpov 86^ai> ' (p^aXovra yap avTou enos els vecav

KardXoyov eni t^? Sikj/s dvayvavai, — then follow verses 557 and 558 of
Iliad B. Diogenes Laertius (1, 2, 48) also writes with regard to Solon :

e'fioi 8e (f>a(Ti Kal eyypd^^rai avrov els tov KardXoyov tox) 'Oprjpov perd tov (v. 557,

V. 558). And, to end the discussion of Solon, we have in Diogenes
Laertius still another passage already quoted (1, 57) which bears
testimony merely to a certain literary activity in connection with
Homer on the part of Solon, earlier of course than the time of Pi-
sistratus. In a certain respect, expressed by ecftiina-ev, according to
Dieuchidas the Megarian, Solon is said to have surpassed Pisistratus :

Tu re 'Opfjpov e^ inro^oXrjs yeypa(pe pa'yf/cpdeladai, oiov ottov 6 npcoros eXrj^ev,
eKeideu apj^eadai tov e)(6pevov. pdXXov ovv '^okuiv Oprjpov e(pa>Ticrev rj Ilejcri-
(TTpaTos, S)s (prjai Aiev)(i8as ev irepnTtp MeyaptKcjv.

Hipparchus, the elder of the sons of Pisistratus, is the only other
man to whom I have found activity in connection with the Homeric
poems ascribed. In one account he is said to have brought them to
Greece, in the other, to Athens, and in both to have ordered the rhap-
sodes to sing them at the Panathenaic festival. The first account,
contained in the pseudo-Platonic dialogue Hipparchus (228 B) runs

as follows : 'l7r7rap;^<jp, bs tuiv UeicricrTpdTov TraiScov ^v Tvpea^vraros Ka\ aocfxi)-
Taros, OS aXXa re TroAXa Ka\ KnKci epya (TO(f)ias direSei^aTO, Kal rd 'Oprjpov enrj
irpcoTos eKopiaev eis rrjv yjjv ravTrjvi, kcu rjvdyKarre tovs pay^o)8ovs Uavadrjvaiois
(^ I'TToXijx^ews ((pe^rjs avTu 8uevai, acrnep vvv en ot8e noiovo'iv. NoW the

question whether Plato or somebody else wrote the dialogue which
contains this information is not essential to this investigation. But it
is necessary for us to ascertain as nearly as may be when it was writ-

506 PROCEEDINGS OF THE AMERICAN ACADEMY,

ten, and something, if possible, about the writer. Accordingly a slight
digression on its authenticity will not be out of place.

That the genuineness of this dialogue was doubted, even in antiquity,
has been maintained by some, notably Wolf, on the authority of the
following passage in Aelian (VIII, 2) : ovk coero yap 8el.v ov8evi (pdovdv

a-o(pias, are av KaXos Kai dyados. Xe'-yei Se IlXdrwi^ raiiTa, ei 8f] 6 "liVTTapxos IlXd-

T(ov6s €<TTi Tto ovTL. But thls coutaius, at the very end, as Grote ^^ points
out, a conjectural emendation. Hercher in his edition ascribes the
reading 6Wt with no following word to the emendation of Perizonius,
doubtless in his edition of 1701.*^ But the manuscripts read rw ovn
na6r]Tf]i. Grote's contention is that " if you construe the passage as it
stands without such conjectural alteration, it does not justify Wolfs
inference ' that the genuineness oi" the Hipparchus was doubted in
antiquity.' " But if we do not emend with Perizonius we have an his-
torical error, the suggestion that Hipparchus might have been the
pupil of Plato, a mistake which Mr. Grote probably with perfect justice
considers " nowise impossible in the case of Aelian." But if we do not
emend, I fail to see the connection of the statement " if Hipparchus is
really a pupil of Plato " with the preceding. It is entirely lacking in
logical sequence.

There is also another argument, which, so far as I can discover, has
not been adduced by any one as yet, but which to me is conclusive in
favor of adopting the emendation of Perizonius. Aelian, in the same
book, and only a few lines before the disputed passage, has these words

(VlII, 2) : "inrrapxas 6 TleiaicTTpaTov naii ti pecrl3vTaTus mu tcov JJficncrTpdTov
KOI (TocfxaraTos fjv Adrjuaiciiv. ovtos koL to Op,r]pov eVjy TrpooTos iKopucrev is rds
'Adrjvas, KoX r]vdyKa(rf tovs payj/aBovs rois IIava6r]vaiois avrd adeiv. Now, after

a comparison of this with the passage from the Hipparchus (228 B) which
I have just quoted, I do not think that there can be any doubt that
Aelian was quoting outright from pseudo-Plato. What could be more
natural then that a few lines later he should make a reference to the
book Hipparchus from which he had just quoted and which was still
running in his mind, and probably to our very passage containing the

words, OS aXAa rt ttoXXu koI KaXd epya <ro(j)Las dirfSd^aro, which WOuld make

a very tolerable precedent for Aelian's, — ovk aero ydp Bdv ov8evi (pdove'iv
a-o(f)ias, are (bv koXos koX dyados. It therefore sccms to me by all means
preferable and even necessary to adopt the emendation of Perizonius
and to agree with Wolf that the authenticity of the Hipparchus was
doubted even as early as Aelian (fl. 180).

Diogenes Laertius, who flourished at some time near the beginning

39 Plato, London, 1888, II, 85. " See Christ, p. 762.

NEWIIALL. — PISISTRATUS AND HOMER. 507

of the third century, contains the following very possible reference to
the dialogue under consideration and to the man whom he supposed

to be the author (2, 122): St'/xcof ^Adrjvalos, a-KVTOTo^oi' ovTos (pxofjievov
ScoKparous eTrt to epyacrTrjpLOV Koi duiXeyoixevov Tivd, iov ifivTjjj.ovevei' vTroarjixeiayaeis
eVoietTO " odfv (tkvtikovs avrov tovs 8ia\6yovs icaXova-iv. elcri 8e rpe'is icai rpid-

KovTa iv eVi (pepofiefoi ^i^Xico, — then follows a list of thirty-one titles,
among which is the title Trepl cfuXoKfpdovs, which is the subject under dis-
cussion in the pseudo-Platonic Hipparchus. In order to fix the date
of this Simon I must quote another passage from Diogenes Laertius'
life of Simon (2, 123), which reads as follows: ovtos, (paai, nparoi SieXf'xdr}

TOVS \6yovs TOVS 'SoxpaTiKovs, enayyeiXafxevov Se IleptKXeovs 6pe\lreiv avTov kcu
KfXfvovTos aTnivai Tfpos aiiTov, ovk af {(prj ttju TTapprjo'iav anoboa-Qai. This

then places his sphere of activity in the age of Pericles, making him a
little older than Plato hiijiself Accordingly Boeckh, connecting the
Hipparchus and the Minos, as works by the same author (basing his
decision on evidences of style, apart from the statement of Diogenes to
the same effect), published at Heidelberg in 1810 these two dialogues
and two others in a separate edition which he called " Simonis Socra-
tici, ut videtur, dialogi quattuor." Grote, as I have already implied
from my previous quotation of his opinion, considers the Hipparchus
one of the inferior works of Plato. Steinhart as quoted by Fritzsche *^
dates the composition of the Hipparchus in the Macedonian Age (say
from 350-320 B. c.) deducing his opinion from internal evidence.
First, Hipparchus is lauded, whereas the murderers fail in the common
meed of praise, two things which would be more in accord with the
spirit of the Macedonian Age than that of the Periclean, for instance ;
and secondly, the ratio of gold to silver is mentioned as twelve to one
(231 D), facts which he considers significant enough to warrant his
conclusion. This, of course, if true, would place its composition slightly
after the death of Plato. All testimony, therefore, which can be ad-
duced tends to show that if not by Plato himself it was composed by
some author almost contemporaneous with him.

I might mention here again, for the sake of completeness, the refer-
ence in Aelian to the literary importation by Hipparchus, but as Aeli-
an's sole authority for this story is doubtless the pseudo-Plato, it really
has no important evidence to add.

To summarize, then, briefly, this little excursus, the accounts of
Lycurgus given by Heraclides, Plutarch, and Aelian contain abso-
lutely nothing to influence our belief as to the activity of Pisistratus.
The only story about Solon which seems to concern Pisistratus at all

" Stallbaum, Plato, ed. ii, Leip., 1885, b. II, 304.

508 PROCEEDINGS OF THE AMERICAN ACADEMY.

is the account of Dieuchidas which, we must remember, is quoted at
second hand, and contains those words, juaXAoi/ e'^wno-ei' ktX, which seem
too vague and doubtful in their significance to be given very much
weight. The only account, therefore, which conflicts with the suppo-
sition of a Pisistratean edition is contained in the pseudo-Plato. This
story I hesitate to reject hastily because of its antiquity. But yet
there are several facts in connection with it which we must face:
first, the author is doubtful, practically unknown ; second, the story
is found nowhere else except in Aelian, so far as I can discover ; third,
it is practically contradictory to the statements I have quoted about
Lycurgus, to say nothing of the accounts of Pisistratus,*^ which are
based on good authority. How such a plausible story, if true, could
have been so nearly forgotten, or how so disregarded by subsequent
writers, had the pseudo-Plato possessed a good reputation for histor-
ical accuracy, is past understanding. Very plausible is the supposition
that it may have been a confusion of two or more stories. This opin-
ion is favored by Flach when he writes (p. 21) : " The author of pseudo-
Plato was not reliable in comparison with Dieuchidas,"*^ he makes
noticeable historical blunders, and was probably lightly recording some
local tradition. This tradition arose from an analogy with Solon and
from the fact that Hipparchus was a patron of literature, as shown by
his calling over Anacreon from Samos in 522 b c, after the death of
Polycrates." On the whole I am forced to admit this rather plausible
explanation of the practically unique account in the pseudo-Plato.

Finally, then, what inference are we justified in deducing with
regard to the literary activity of Pisistratus in connection with the
Homeric poems 1 We must endeavor to avoid any conclusions which,
however plausible, are not fully justified by our evidence. For ex-
ample, Monro says (p. 406) : " The Pisistratean edition is excluded by
the account adopted in the pseudo-Platonic Hipparchus, which leaves
no room for a collection of Homeric verses." But it is not just that
the authority of this one anonymous writing should outweigh all other
passages which testify to a collection of Homeric poems by Pisistratus,
and are drawn from such reliable sources as Cicero, Aelian, Pausanias,
and the scholia of our second best manuscript. Neither can I agree

*2 The only way in which I can reconcile this with the accounts about Pisis-
tratus is by supposing that Hipparchus introduced the Homeric poems into Greece
a good many years prior to the death of Pisistratus his father. But this suppo-
sition seems rather improbable.

*3 Flach gives no credence to the stories about Pisistratus, but believes in the
greater Homeric activity of Solon. Hence the mention of Dieuchidas, who says
'ZoKwv fxaWov f<paiTL(Tev kt\.

NEWIIALL. — PISISTRATUS AND HOMER. 509

with Monro in any such statement as that such a collection " may be
shown to be unknown to the Alexandrian grammarians," for their
works are preserved to us in such an incomplete state that it is abso-
lutely impossible to say exactly what they did mention and what not.
T. W. Allen, in the Classical Review,'** assuming the reality of this
silence, has an explanation which is possible. He writes : "If Pisis-
tratus were the reputed father of the koi.vti, it is natural that we find
no mention of him in the scholia. The grammarians ignore the koivt)
because it was in every one's hands, and because it had suffered by
transmission. The same account explains the absence of reference to
the Athenian edition."

The explanation of the sources of the so-called Pisistratean legend
by those who disbelieve in it has aff"orded critics the exercise of much
originality and ingenuity, but it is based for the most part on merest
conjecture. Flach (p. 41) is of the opinion that the story of Pisistra-
tus's edition came from Megarian historians of little scientific impor-
tance, and was "boomed" by the scholars of the Pergamean school
that they might find a great literary man to belittle the Homeric
scholars of their rival school, the Alexandrian. Likewise Nutzhorn,*^
who disbelieves in the Pisistratean recension, makes light of the testi-
mony of Cicero, saying that Cicero drags in Pisistratus here merely as
an added example of the point he is trying to establish, — how neces-
sary it is for the great statesman to be a learned man as well. How-
ever that may be, unless Nutzhorn is willing to admit that Cicero in
this place is deliberately falsifying evidence (i. e., the tradition which
he cites), I fail to see that his remark has any point. Desire on the
part of Cicero to illustrate a principle aptly cannot be said to imply
the use of fictitious examples. Interesting also, and more probable,
is the conjecture of Dilntzer (p. 17), who makes Dicaearchus in his
Bios 'EXXaSo? the authority for the statement of Cicero. This opinion
is based on the fact that Dicaearchus was an author of general popu-
larity with Cicero, as shown by his references to him on several occa-
sions, his work being of great importance in the literary history of
Greece.

After such a discussion of conjectures we are reminded of the words
of Wolf:'*^ "Nunc vero nihil opus est coniecturas capere. Historia
loquitur. Nam vox totius antiquitatis et, si summam spectes, consen-
tiens fama testatur Pisistratum carmina Homeri primum consignavisse
litteris, et in eum ordinem redegisse quo nunc leguntur. Hoc pos-

^ XV, p. 8 (1901).

*5 Die Entstehungsweise tier Ilom. Gedichte, Leip., 1869, p. 48.

*® Prolegomena ad Homerum, ed. ii (posthumous), Berlin, 187G, c. xxxiii.

510 PROCEEDINGS OF THE AMERICAN ACADEMY.

terius Cicero, Pausanias et reliqui omnes qui mentionem rei faciunt,
iisdem prope verbis et ut viilgo notissimum perhibent." At first
thought this statement seems too sweeping to be literally true, but
when one bears in mind that the only statement by an ancient au-
thority really contradictory to the idea of a Pisistratean edition of
Homer is contained in the pseudo-Plato of doubtful authority, and
when one remembers that the accounts, even as old as Cicero, were, as
is most probable, drawn from much older authorities which are now
lost, then one can see that this statement, though framed in bold lan-
guage, was not made without due deliberation. The statement, " pri-
mum consignavisse litteris," however, does not seem to have equal
justification. On the contrary, available evidence seems to indicate
that even before the time of Pisistratus the Homeric poems, at least
large portions of them, already existed in writing.

All our testimony clearly shows, I think, that Pisistratus, who was
a Tvpavvos interested in literature, with the help, as is most likely, of
several poets or literary men of his court, was the first to make a
careful collection or edition (though in no sense of the word a critical
edition) of the Iliad and Odyssey, on the basis of what scattered writ-
ten copies were available, filling in the gaps (if there were any) in the
written Homer from the mouths of the rhapsodes. That this collec-
tion was more or less for private use and convenience it is reasonable to
suppose, and that it showed no accuracy of critical discrimination is a
necessary supposition in consideration of its early date.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 20. — June, 1908.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

POSITIVE BAYS.

By Johx Tkowbridge.

CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY,

HARVARD UNIVERSITY.

POSITIVE RAY'S.

By John Trowbridge.

Presented May 13, 1908. Received May 18, 1908.

My intention in undertaking thi.s investigation was to endeavor to
measure the group velocity of the positive rays by producing a stand-
ing wave, or a stratum of maximum collisions in an exhausted tube in
the space between the anode and the cathode. In the case of an oscil-
lating circuit, if we call X the wave length, v the velocity of light, t the
time of a half oscillation, s the distance between the anode and the
cathode, v' the velocity of the positive rays, we have

Eq. 1,

X = vt

Eq. 2,

s = v't

, vs
''= X

If, by tuning a circuit containing a condenser, self-induction, and
the exhausted tube, the strata of maximum collisions could be formed
at the orifice in the cathode, it was thought that none of the positive
rays would enter the canal region ; if, on the other hand, the positive
rays swung, so to speak, with the oscillations of the circuit, a maxi-
mum fluorescence could be obtained on a suitably placed willemite
screen.

The circuit was arranged as follows : A Leyden jar, L, Figure 1, was
charged by a storage battery of ten thousand cells, through a large
resistance of running water, B. The discharging circuit included an
adjustable self-induction, I, a tube filled with rarefied hydrogen, T,
and a spark, S. K was an iron electrode, with an orifice two milli-
meters in diameter at its centre. A glass tube welded to the sides of
the tube C entered this orifice. The end of the tube C was coated
with willemite.

VOL. XLIII. — 33

614

PROCEEDINGS OF THE AMERICAN ACADEMY.

At first I studied the effect of increasing the self-induction on the
admittance of the mixture of anode and cathode rays to the region C.

Figure 1.

The phosphorescence on the screen at the end of the tube was ob-
served with a spectrophotometer, and also with a photometer consisting
of crossed nichol prisms.

In Figure 2 the intensity of light is plotted along the axis of Y,
and the wave lengths of the circuit along X. The phosphorescence

appeared suddenly at wave length 380 meters, and increased to a
maximum at wave length 620. The curve then continued parallel to
the axis of X. In determining the wave lengths I employed the ad-

TROWBRIDGE. — POSITIVE RAYS.

515

FiGDKE 3.

mirable wave metre of Professor G. W. Pierce.^ This instrument ena-
bled me to make measurements in a few moments which otherwise would
have required days of labor.

On placing the tube C between
the poles of an electromagnet,
which produced a field just suf-
ficient to divert the cathode rays
from the screen, I found that the
changes in the phosphorescence
represented in Figure 2 were
produced by the cathode rays, for
the phosphorescence due to the
positive rays remained constant
through the range measured. The
positive rays were defiected in
the direction opposite to that in

which the cathode rays were thrown, by a field of 530 lines to the
centimeter, and produced a narrow band on the willemite screen,
which showed a slight discontinuity (Figure 3), although the pressure
did not exceed ^^ ^^^' I was surprised to find that
the group of positive rays was so readily deflected by
a comparatively weak magnetic field. The length of
the band of phosphorescence was 1.5 cm. It is to be
noted that the band occurred only on one side of the
middle point of the phosphorescent screen.

On discovering that changes in self-induction had
no effect upon the intensity of the phosphorescence
produced by this group of positive rays, I resolved
to damp out all oscillations by introducing a large
water resistance in the oscillating circuit. While the
dimensions of the discharge tube between the anode
and the cathode remained the same as in the experi-
ments described above, the canal region was changed
from a circular tube of 3 cm. diameter to the form
shown in Figure 4 in plan P and end section E. The
width of the cross-section was 3.5 cm. It will be
noticed that it had a flattened egg-shaped section, to
enable me to place it between the poles of an elec-
tromagnet. When all oscillations were damped, and a magnetic field
of 500 lines to the centimeter was excited, the positive rays produced

Figure 4.

^ Contributions from the Jefferson Pliysical Laboratory, 4 (1907).

616

PROCEEDINGS OF THE AMEEICAN ACADEMY.

a narrow, sharply defined band of fluorescence, which is represented in
the photograph. Figure 5. The middle of the end of the tube is indi-
cated by the sharp pointers on the photograph, and it will be seen that
the phosphorescent band extends to approximately equal distances on
both sides of the middle of the screen. At first I thought that I was
dealing with a mixture of positive and negative rays, and various the-
ories of molecular attraction occurred to me ; but experiment showed
that all negative rays had been driven out of the field. Moreover, by
producing a difference of electrostatic potential, the entire phospho-
rescent band, or magnetic spectrum, moved in the direction the positive

FiGUKE 5.

rays should move. In Figure 5 it will be noticed that the band moved
to the smaller pointer ; whereas, if the portion of the band to the right
of the pointers was made up of negative rays, and that to the left of
positive rays, the band would not have moved parallel to its original
position.

In order to ascertain why the band spread to the right and left of
the middle of the screen I introduced a septum of glass in the middle
of the tube constituting the canal region (Figure 6). This septum was
welded to the end of the tube and was coated on both sides with
willemite. The band of phosphorescence now appeared mainly on one
side of the partition. By greatly weakening the magnetic field the
negative rays were brought upon the screen to the left of the partition,
while the positive rays appeared on the right of this partition, thus

TROWBRIDGE.

POSITIVE RAYS.

517

ilGURE 6.

proving again that the band (Figure 5) was made up of positive
rays. A large storage battery proved the best means of studying
the positive band, for the phenomenon was
not confused by the make and break of
mechanical or electrolytic interrupters. It
was soon discovered that a narrow phospho-
rescent band was formed on the side of the
septum which shielded the end of the tube.
The explanation of the band in the tube
without the septum was evidently this : the
pilot spark produces a number of positive
rays of different velocities which spread out
in the form of a cone, of which the apex is
the narrow orifice in the cathode terminal.
Under the influence of the magnetic field
these rays whirl around in the field somewhat
in the manner indicated by the dotted lines (Figure 6).

In the expression o = — rr-- — • P can have many values, depending

mil sm I

upon the values of v'. The narrowness of the band results from the
electrodynamic attraction of the whirls in a manner similar to the at-
traction of electrical currents all moving in the same direction. The
band may be called a magnetic spectrum, since it is produced by many
rays of diffel-ent velocities.

W. Wien ^ has shown that positive rays emanate from the anode, and
that these rays can be diverted by an ordinary horseshoe magnet.
The rays which I have investigated are undoubtedly of the same na-
ture as those studied by Wien. Their connection, however, with the
pilot discharge from a condenser is an added point of interest.

Jefferson Physical Laboratory,
Harvard University.

2 Wien, Ann., 65, 449-450 (1898).

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. iS^o. 21. — June, 1908.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF
HARVARD COLLEGE.

CONCERNING THE USE OF ELECTRICAL HEATING
IN FRACTIONAL DISTILLATION.

By Theodore W. Richards and J. Howard Mathews.

Invbstiqations on Lioht and Heat made and published, wholly or in paet, with Appkopblation

feou the rumfokd fcnd.

CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF

HARVARD COLLEGE.

CONCERNING THE USE OF ELECTRICAL HEATING IN
FRACTIONAL DISTILLATION.

By Theodore William Richards and Joseph Howard Mathews.

Received May IS, 1908.

In the course of a research ^ now in progress in this laboratory it
became necessary to fractionate a number of organic liquids in order
to prepare them in a state sufficiently pure for investigation. The
process of distillation was at first carried out in the usual manner, but
some of the substances required very many successive systematic dis-
tillations in order to furnish enough material boiling within a reason-
able limit of temperature, and, indeed, in more than one case the task
seemed hopeless.

A part of the research in question involved the determination of the
latent heat of vaporization of the various substances by means of a
modification of Kahlenberg's method, ^ to be described later. In the
course of these experiments it was noticed that each organic liquid
boiled at a much more constant temperature when heated electrically
by the platinum coil of this apparatus than it had during its previous
fractional distillations in an ordinary boiling flask This led to the
use of the hot platinum coil instead of the gas burner as a source of
heat in the preliminary fractional distillation, with a very great gain
in the efficiency of this process.

Probably the reason for this difference in efficiency between the two
methods lies in the difference in the extent of superheating. The suc-
cess of fractional distillation might be supposed to be impaired when
superheating occurs, for in this case the higher boiling fractions would
naturally have more tendency to come over with those of lower boiling
point. In order that the most effective separation may be made, the

1 J. Am. Chem. Soc, 30, 8 (1908) ; also Z. phys. Chem,, 61, 449 (1908).

2 Kahlenberg, Journ. Phys. Chem., 5, 215 (1895).

522 PROCEEDINGS OF THE AMERICAN ACADEMY,

temperature of the liquid should never exceed the true boiling point of
the mixture.

Very considerable superheating occurs when a liquid is boiled in
a glass flask by the application of heat from outside. On the other
hand, we found that very little superheating of a liquid occurs when
the liquid is heated by means of an electric current passing through a
suitable resistance wholly immersed in the liquid. S. Lawrence Bige-
low has suggested this methqd of heating in the determination of the
molecular weights of a substance in solution by measuring the eleva-
tion in boiling points ; its satisfactory application to this problem is
an indication of its efficiency in obviating superheating. It is clear,
therefore, that the electrical method of heating might be expected to
give more complete separation during the process of practical distilla-
tion than the ordinary method.

The matter is so obvious that probably others have thought of this
before ; but because we have never seen the method in use, nor have
been able to find a reference to it in chemical literature, we venture to
call attention to it in this brief paper.

The extent of the increased efficiency is best indicated by two par-
allel experiments, alike in every essential respect except the difference
in the source of heat, and the fact that into the ordinary boiling flask
Markovnikov capillary tubes were placed to relieve the superheating
to some extent. Even with this precaution added to the old way, the
diff'erence in result was very marked, as the following figures show.

0.1 liter of a specimen of normal butyl alcohol, dried with anhydrous
copper sulphate, needed sir distillations in order to secure 75 milli-
liters of liquid boiling within the limits of 1 degree (117.0°-118.0° at
759 mm.), using the ordinary method of outside heating by a gas
flame.

The same volume of the original liquid by only two fractional distil-
lations with electrical heat yielded the same volume of distillate of a
much higher grade of purity, having boiling-point limits only 0.6 apart
(117.3°-117.9°).

Similarly, 120 milliliters of ortho cresol which in one distillation
gave 100 milliliters within 0.8° (190.0°-190.8° at 765,0 mm.) gave an
equal amount boiling within 0.3° (189.9°-190.2° at 758.5 mm.) by the
new method. Numerous other examples might be cited, but these
are sufficient to show the great advantage to be derived from electrical
heating.

A word concerning an advantageous form of apparatus is not out of
place, although a heating resistance-coil may be immersed under the
liquid in any ordinary distilling apparatus. In order to economize

RICHARDS AND MATHEWS.

ELECTRICAL HEATING.

523

material, a narrow cistern was blown into the bottom of a common
stout distilling flask. Into this depression the heating coil was placed.
The coil consisted of about 40 centimeters of platinum wire having a
resistance of about 0.7 ohms. A
current of from ten to fifteen am-
peres was led to the resistance wire
from above by heavy copper wires
encased in glass tubes, into the ends
of which the ends of the platinum
wire were sealed, contact being made
by a drop of mercury. It is necessary
that these copper wires be heavy
(about 2.5-3.0 mm. in diameter), so
that they may not become heated
by the current and thus superheat
the vapor coming into contact with
the glass tubes encasing them. For
this reason it might be well to intro-
duce the electrical connection from
below, through the glass walls of the
cistern ; but obviously the present
arrangement can be most easily
made. It is necessary that the coil
and mercury contacts be entirely
covered by the liquid at all times.
The diagram illustrates the arrange-
ment. The coil was more compact
than that represented in the figure,
so that it was possible to distil all
but four or five milliliters without
uncovering the resistance.

It is almost needless to call attention to the fact that short-circuit-
ing through the liquid may cause slight decomposition when electro-
lytes are thus heated ; hence the method is not well applicable to
liquids of this class.

Because the bubbles of vapor arise only from the small area of the
hot resistance wire, ebullition proceeds quietly, and there is never any
tendency to "bump." This method of heating is therefore especially
applicable to fractional distillations under reduced pressure, where so
much trouble is usually experienced from the explosive formation of
vapor. Concentrated sulphuric acid, for example, boils as quietly
under greatly reduced pressure when so heated as does water or

524 PROCEEDINGS OF THE AMERICAN ACADEMY.

alcohol under ordinary pressures. The method of heating dispenses
entirely with the necessity of passing air through the liquid in vacuum
distillations, and heavy viscous liquids may be advantageously dis-
tilled in this way. By combining this method of heating with the
Hempel, Wurtz, Linnemann, or other fractionating towers, great effi-
ciency may be expected. However, where the amount of material is
small, the towers cannot be advantageously used, because of the loss
of material required to wet the considerable area of their condensing
surfaces ; and it is very convenient to have at hand an economical
method fully as efficient as the ordinary method where the tower is
used.

The method may also find successful application in the distillation
of inflammable liquids, and may therefore be of some industrial impor-
tance where power may be obtained cheaply. Moreover, low boiling
liquids, ordinarily requiring special precautions, can be distilled as
expeditiously as those of high boiling point, since superheating is
impossible.

In brief, this article describes experiments showing the great gain
in the efficiency of separation obtainable by the use of electricity as a
source of heat in fractional distillation. An advantageous form of
apparatus for this purpose is described.

The Chemical Labokatort of Habvakd College.

Proceedings of the American Academy of Arts and Sciences.
Vol. XLIII. No. 22. — Jclt, lOOS.

RECORDS OF MEETINGS, 1907-1908.

REPORT OF THE COUNCIL: BIOGRAPHICAL NOTICE.

Samuel Cabot. By Charles Lokixg Jackson.

OFFICERS AND COMMITTEES FOR 1908-1909.

LIST OF THE FELLOWS AND FOREIGN HONORARY
MEMBERS.

STATUTES AND STANDING VOTES.

RUMFORD PREMIUM.

INDEX.

(Title Page and Table of Contents).

RECORDS OF MEETINGS.

Nine hundred seventj-flfth Meeting^.

October 9, 1907. — Stated jMeeting.

The President in the chair.

There were present twenty-four Fellows.

The Corresponding Secretary, pro tempore, read letters from
G. W. Pierce, accepting Fellowship ; from the California Acad-
emy of Sciences, thanking the Academy for the contribution of
its publications ; from Arthur McDonald, asking the Academy
to form resolutions regarding the establishment of laboratories
for the study of the criminal, pauper, and defective classes, and
transmitting a pamphlet on the subject; from C. van Over-
bergh, Directeur general de TAdministration de TEnsignment
Superieur des Sciences et des Lettres, enclosing a copy of the
report of the International Congress for the Study of the Polar
Regions, and requesting the publications of the Academy; from
St. C. Hepites and I. St. Murat, notifying the Academy of their
appointment as Directors of the Roumanian Meteorological In-
stitute and Service Central des Poids et Mesures ; from Vilh.
Thomsen, President of the International Congress of Orien-
talists, inviting the Academy to send delegates to the Fifteenth
Congress, in August, 1908; from President Capellini, two com-
munications relative to the celel)ration of the anniversary of the
death of Aldrovandi ; from the Societd G^ologique de Belgique,
notifying the Academy of the death of its Secretary, Henri-
Joseph Fourir; from the Astrophysical Observatory, Potsdam,
notifying the Academy of the death of H. C. Vogel ; from the
Kon. bohmische Gesellschaft der Wissenschaften, notifying the
Academy of the death of Johann Gebauer, and also of the death
of J. Bohuslav, Freih. v. Rieger.

528 PROCEEDINGS OF THE AMERICAN ACADEMY.

The Chair announced the following deaths : —

Charles F. Folsom, Resident Fellow, of Class II, Section 4 ;
H. C. Vogel, Foreign Honorary Member of Class I, Section 1 ;
and of Henry G. Denny, a former Resident Fellow.

On the recommendation of Professor Webster, it was

Voted, That an unexpended balance of $93.46 from the in-
come of the Rumford Fund, returned by Professor Edwin H.
Hall, be reappropriated to the use of the Rumford Committee.

The following gentlemen were elected Resident Fellows of
the x\cademy : —

James Flack Norris, of Boston, in Class I, Section 3 (Chem-
istry).

William Hultz Walker, of Newton, in Class I, Section 3
(Chemistry).

Mr. A. T. Thompson showed the use of his reflectoscope in
projecting photographs and opaque objects upon the screen.

On motion of tlie Recording Secretary, it was

Voted, That the thanks of the Academy be tendered to ^Nlr.
Thompson for his interesting exhibition of the I'eflectoscope.

Dr. Theodore Lyman gave a paper entitled " The Absorp-
tion of the Air for Light of very Short Wave Lengths."

The following paper was presented by title : —

"Difference in Wave Lengths of Titanium XX 3900 and 3913
in Arc and Spaik," By Norton A. Kent and Alfred H. Avery.
Presented by John Trowbridge.

Nine hundred seventy-sixth Meeting.

November 13, 1907.

Vice-President Walcott in the chair.

There were present twenty-seven Fellows.

The following letters were read : —

From Wm. H. Walker, accepting Fellowship ; from Dr. G.
Hellman, aimouncing his appointment as Director of the Kun.
Preuss. Meteorologisches Institute of Berlin ; from the Verein
fiir Naturwissenschaft in Bi'aunschweig, announcing the death
of Professor Dr. Rudolf Blasius.

The Chair announced the following deaths: —

Edward G. Gardiner, Resident Fellow in Class II, Section 8.

RECORDS OF MEETINGS. 529

Sir Benjamin Baker, Foreign Honorary Member in Class I,
Section 4.

The following communications were given : —

" The Volcanoes of the Azores." By Professor W, H.
Pickering.

"The Linnaean Celebration at Upsala, Sweden." By Pro-
fessor W. G. Farlow.

The following paper was read by title: —

"A Revision of the Atomic Weight of Lead. Preliminary
Paper: The Analysis of Lead Chloride." By Gregory Paul
Baxter and John Hunt Wilson.

Nine hundred seventy-seventh Meeting.

December 11, 1907.

The President in the Chair.

There were present seventeen Fellows.

Letters were read from Arthur L Davenport, announcing the
death of his father, George E. Davenport ; from the Sixteenth
Liternational Congress of Americanists, inviting the Academy
to send delegates.

The Chair announced the death of George E. Davenport,
Resident Fellow in Class II, Section 2, and also of Professor
Minton Warren, whose nomination had been read to the Acad-
emy at its last meeting.

On motion of Professor Davis, it was

Voted, That in reference to the death of Professor Warren
the President be authorized to take such action as he thinks
proper.

On motion of Professor Davis, it was

Voted, That the House Committee be authorized to provide
a simple collation for the Members at the meetings of the
Academy.

The followinsf communications were given: —

'• The Most Recent Exploration in Palestine." By Professor
D. G. Lvon.

"The Centenary Celebration of the Geological Society of
London." By Professor W. 'Si. Davis.

The following papers were presented by title : —

VOL. XLIII — o4

530 PROCEEDINGS OF THE AMERICAN ACADEMY.

"The Influence of Hysteresis upon the Manner of Establisli-
ment of a Steady Current in the Primary Circuit of an Induc-
tion Coil." By B. O. Peirce.

" Some Effects of Heavy Pressure on Arc Spectra." By W.
J. Humphreys. Presented by C. R. Cross.

" The Effect of a Magnetic Field on the Cathode Rays." By
John Trowbridge.

Nine hundred seventy-eighth Meeting.

January 8, 1908. — Stated Meeting.

The President in the chair.

There were present twent}- Fellows.

Letters were read from the Secretaries of the Third Inter-
national Congress for the History of Religions, enclosing the
first announcement of the Meeting to take place at Oxford in
September, 1908, and inviting the Academy to send a Repre-
sentative; from the Physikalische Verein of Frankfort, inform-
ing the Academy of the opening of the new Institute Building,
and inviting the Academy to send Delegates ; from the Com-
mittee of Organization, informiuQ- the Academv of the First
Congress of Chemistry and Physics to be held at St. Petersburg
in January, in memory of D. I. Mendeleeff.

The following deaths were announced bv the Chair : —

Lord Kelvin, Foreign Honorarv Member in Class I, Sec-
tion 4 ; Charles A. Young, Associate Fellow in Class I, Sec-
tion 1 ; Thomas D. Seymour, Associate Fellow in Class III,
Section 2.

The following Delegates were appointed to represent the
Academy at the Fifteenth International Congress of Oriental-
ists, to be held at Copenhagen in August, 1908 : —

Charles R. Lanman, George F. Moore.

In answer to an inquiry by Professor Webster, on motion of
Colonel Livermore, it was

Voted, That the Corresponding Secretary be requested to
ascertain and report to the Academy on the measures to be
taken in reference to the Nobel Prizes.

Le Baron Russell Briggs was elected a Resident Fellow in
Class III, Section 4 (Literature and tlie Fine Arts).

RECORDS OF MEETINGS. 531

The following communications were presented: —
"Cretan Chronology." By President VV. W. Goodwin.
" The Polariscope and the Weather." By Dr. Louis Bell.
The following paper was read by title: —
" A Simple Method of Measuring the Intensity of Sound."
By George VV. Pierce.

Nine hundred seventy-ninth Meeting.

February 12, 1908.

The Corresponding Secretary ^:>rfl tempore in the chair.

There were present twenty-four Fellows.

Letters were read from the Sub-director of the Museo Nacio-
nal, ^lexico, felicitating the Academy on the New Year; from
the Committee of the Fourth International Conorress of Mathe-
maticians to be held at Rome, April 6-11, 1908.

The death of Edward H. Strobel, Resident Fellow in Class III,
Section 1, was announced.

The following report of the House Committee was read and
accepted : —

" At the meeting of the Academy held on the elevemth of Decem-
ber, the House Committee were instructed to consider and report
whether it would be advisable for the Academy to provide a light re-
past, consisting of crackers, ale, and cheese, at the conclusion of the
meetings.

" We find that the expense involved would be about twenty-five
dollars for tables and dishes, and an annual outlay of about twenty-
five dollars. After consulting the Treasurer, we recommend that these
sums be expended, the initial outlay being paid by the appropriation
for House expenses, and the current expense charged to the appropria-
tion for the expense of meetings.

" The Committee have, as has been announced, provided a ventilator
in the meeting-room, with an air-shaft reaching above the roof, which
it is hoped will prove effective. If not, it can be made more so by
putting an electric fan into the air-shaft,

"Meanwhile it has been urged upon them that the present meeting-
room shall be given up, and a larger and pleasanter one be constructed
in the front of the house in the third story. A room could be made
covering about six hundred and fifteen square feet, about a third more

532 PROCEEDINGS OF THE AMERICAN ACADEMY.

than the area of the present room, which covers four hundred and
sixty-five square feet. The cost would be about thirteen hundred
dollars (§1300), a larger sum, considerably, than the means at the
Treasurer's command can supply. But if the ventilation now pro-
posed proves on trial unsatisfactory, and it is found that the cost of
these changes can be raised, as has been suggested, by subscription,
and, at the close of the season, the Academy so vote, the alteration can
be made in the course of the summer."

On motion of Professor Webster, and seconded by Professor
Kiniiicutt, it was

Voted, That the House Committee be requested to consider
the question of raising funds for the carrying out of the plans
for a meeting-room on the third floor.

Professor George F. Moore was apjiointed a Delegate to the
Third International Congress for the History of Religions, to be
held at Oxford in September, 1908.

Piofessor Jaggar informed the Academy that tliere was a bill
pending in the Legislature for a new topographical survey of
the State.

Professor T. A. Jaggar gave the following communication: —

"Volcanoes of the Aleutian Islands."

The following papers were read by title: —

" Measuiements of the Internal Temperature Gradient in
Common Materials." By Charles B. Thwing. Presented by
C. R. Cross.

"The Variation of the Thermomagnetic Effect in Soft Iron
with Strength of the Magnetic Field and Temperature Gra-
dient." By L. L. Campbell. Presented by John Trowbridge.

Nine hundred eightietli Meeting.

March 11, 1908. — Stated Meeting.

Vice-President Trowbridge in the chair.

There were present twelve Fellows.

Letters were read from L. B. R. Briggs, accepting Fellow-
ship; from William W. Goodwin, declining re-election as Presi-
dent of the Academy ; from the Geological Society of London,
thanking the Academy for delegating Professor W. M. Davis

RECORDS OF MEETINGS. 533

to attend its centenary, and presenting to the Academy the
volume, "The History of the Geological Society of London";
from the Acaddmie des Sciences, Agriculture, Arts et Belles-
Lettres, of Aix, requesting delegates from the Academy to
attend the celebration of the centenary of its Reconstitution ;
from the Gesellschaft von Freunden der Naturwissenschaften,
notifying the Academy of its fiftieth anniversary.

The Chair announced the following deaths : —

Asaph Hall, Class I, Section 1 ; Israel C. Russell, Class H,
Section 1; Augustus St. Gaudens, Class HI, Section 4; E. C.
Stedman, Class HI, Section 4, Associate Fellows.

Tlie Chair appointed for Nominating Committee : —

Charles R. Cross, of Class I.

Charles S. Minot, of Class II.

Morris H. Morgan, of Class HI.

It was

Voted, To meet on adjournment on the second Wednesday in
April.

Dr. G. H. Parker presented the communication: —

" The Influence of Light on the Daily Activities of Animals."

The following papers were read by title : —

"The Damping of the Quick Oscillations of a Twisted Fibre
by the Resistance of the Air and by the Torsional Forces." By
B. O. Peirce.

" Notes on Superheated Steam : I, Its Specific Heat ; II, Its
Total Heat ; III, Its Joule-Thomson Effect." By Harvey N.
Davis. Presented by W. C. Sabine.

" The Sensory Reactions of Amphioxus." By G. H. Parker.

" On Delays before apayvcoplaea in Greek Tragedy." By
W. P. Dickey. Presented by M. H. Morgan.

Nine hundred eighty-first Meeting.

April 8, 1908. — Adjourned Stated Meeting.

The Academy met by invitation of Professor Elihu Thomson
at the Algonquin Club, 217 Commonwealth Avenue.
Vice-President Trowbridge in the chair.
There were present forty-nine Fellows and four guests.

534 PROCEEDINGS OF THE AMERICAN ACADEMY.

The following gentlemen were elected members of the
Academy : —

Louis Derr, of Brookline, as Resident Fellow in Class I, Sec-
tion 2 (Physics).

John Uliic Nef, of Chicago, as Associate Fellow in Class I,
Section 3 (Chemistry).

On the recommendations of the Recording Secretary, the
Chairman of the Rumford Committee, and the Chairman of the
Publishing Committee, it was

Voted. To make the following appropriations : From the in-
come of the General Fund, for House expenses, i$425 ; for
Books and binding, $340 ; for Meeting expenses, 135 ; from the
income of the Rumford Fund, for the furtherance of research,
1141.90 (the unexpended balance of a previous grant) ; from the
income of the Publication Fund for publication, -$800.

Vice-President Trowbridge announced that the Rumford
Premium had been awarded to Mr. Edward Goodrich Acheson
for the application of heat in the electric furnace to the indus-
trial production of carl)orundum, graphite, and other new and
useful substances. He then called upon the chaiiman of the
Rumford Committee, Professor Charles R. Cross, who gave a
short account of the previous awards of the Rumford Medal,
followed by a brief analysis of Mr. Acheson's work and the
circumstances which influenced the Committee to recommend
the award to him.

Vice-President Trowbridge then presented the medal in the
name of the Academy to Mr. Acheson, who expressed his ap-
preciation of the honor conferred upon him, saying : " The
medal has been a great incentive to me from lioyhood, and I
had hoped sometime to attain it. To-night my dream has come
true."

On the invitation of the Chair he then gave an account in
detail of his discoveries, illustrated by a number of interesting
demonstrations.

The following papers were presented by title : —

"The Invariants of Linear Differential Expressions." By
Frank Lwin. Presented by Maxime Bocher.

"Contributions toward a Monograph of the Laboulbeniaceae.
Part IL" By Roland Thaxter.

RECORDS OF MEETINGS. 535

Nine hundred eighty-second Meeting.

May 13, 1908. — Annual Meeting.

Vice-Peesident Walcott in the chair.

There were present twenty-eight Fellows.

Letters were read from Thomas Dwight, Theodore Hough,
and Arthur Michael, resigning Fellowship; from Louis Derr,
accepting Fellowship ; from the Third International Congress
of Botany, two circulars referring to the Congress.

The death of Gustavus Hay, Resident Fellow in Class I,
Section 1, was announced by the Chair.

The annual report of the Council was read.^

The annual report of the Treasurer was read, of which the
following is an abstract: —

General Fund.

Receipts.

Investments $2,833.37

Assessments 1,830.00

Admission fees 70.00

Rent of offices 1,204.00 $5,933.41

Expenditures.

General expenses $3,034.25

Library 1,759.67

Income transferred to principal 758.49 $5,552.41

Balance, April 30, 1908 ^ \ T 381.00

$5,933.41

KuMFORD Fund.

Receipts.

Balance, April 30, 1907 $ 186.86

Investments 3,027.90 $3,214.76

^ See p. 547.

536 PROCEEDINGS OP THE AMERICAN ACADEMY.

Expenditures.

Research $1,200.00

Publication 571.99

Library 222.74

Medal . . ' 341.50

Income transferred to principal 127.35 $2,463.58

Balance, April 30, 1908 \ \ T 751.18

$3,214.76

C. M. Warren Fund.

Receipts.

Balance, April 30, 1907 $ 762.97

Investments 700.33 $1,463.30

Expenditures.

Research $ 150.00

Vault rent 4.00

Premium on bonds charged off 90.00

Income transferred to principal 241.37 $ 485.37

Balance, April 30, 1908 ~7 . ~. 977.93

$1,463.30

Publication Fund.

Beceipts.

Balance, April 30, 1907 $ 212.84

Investments 3,179.02

Sale of publications 148.20 $3,540.06

Expenditures.

Publication $3,046.55

Vault rent 12.50

Income transferred to principal 136.71 $3,195.76

Balance, April 30, 1908 344.30

$3,540.06

KECORDS OF MEETINGS. 537

The following reports were also presented : —

Report of the Librarian.

Of the library catalogue there remains to be done the serial publi-
cations on general science, comprising the two lower floors of the stack
building, and the few books on literature, the fine arts, and religion.
The Academy is fortunate in having this work done by so accomplished
a cataloguer as Miss Wyman, and at such a moderate cost, the last
advantage resulting from the fact that Miss Wyman gives only a por-
tion of her time to the Academy.

The Assistant Librarian is endeavoring to complete the sets of Soci-
ety publications now in the library by sending to the various societies a
request for each missing number, and offering in return to complete their
sets of the Academy's publications. In a great many cases the request
is complied with, in others the numbers requested are scarce or out of
print. These could perhaps be purchased of second-hand booksellers
were money available for the purpose. This lack of money is much to
be regretted, as in time it will be practically impossible to purchase
them.

The accessions during the year have been as follows : —

By gift and exchange . . .
By purchase — General Fund
By purchase — llumford Fund

Total 251 2941 76

The bound volumes in the library have been counted since the last
report, and there are now 29,089 volumes. Hereafter in this report
the accessions will be given in volumes, and not by parts, as heretofore,
and will represent the volumes placed on the shelves during the pre-
ceding year.

80 books have been borrowed from the library by 24 persons, includ-
ing 13 Fellows, and two libraries (Clark University and the University
of Cincinnati).

All books borrowed during the year have been returned for the
annual examination. Of the books reported as still out a year ago,
all have been returned.

The expenses charged to the library are as follows : Miscellaneous,
.S519.67 (which includes S175.93 for cataloguing); Binding, .S;585.55
General, and .S5G.35 llumford. Funds ; Subscriptions, .S654.45 General,
and .SI42.75 Rumford, Funds; making a total of §1240.00 for the

Vols.

Parts of Vols.

Pams.

Maps.

Total.

234

2076

2391

538

550

327

332

538 PEOCEEDINGS OF THE AMERICAN ACADEMY.

General, and $199.10 for the Rumford, Funds, as the cost of subscrip-
tions and binding. Of the appropriation of S50.00 from the Rumford
Fund for books, five have been purchased at a cost of $23. 64.

Although $585.55 from the income of the General Fund was spent
for binding, there are still 400 volumes waiting to be bound. There
has never been an adequate amount appropriated for binding, and we
are now exchanging with more societies and universities than ever
before. Societies are now publishing more volumes, and these contain
more plates than formerly, which makes the binding more expensive.

A. Laavrence Rotch, Librarian.
May 13, 1908.

Report of the Rumford Committee.

From the amount available for the purpose, the Committee during
the year 1907-08 has made grants as follows, for the furtherance of
researches in light and heat : —

June 12, 1907. P. W. Bridgman, of the Jefferson Physical
Laboratory, for the continuation of his work on the optical and
"thermal properties of bodies under extreme pressure .... $400

Oct. 9, 1907. p. W. Bridgman, in addition to the above ap-
propriation, for the same purpose 400

Jan. 8, 1908. Dr. L. J. Henderson, of the Harvard Medical
School, in aid of his research on a new method for the direct
determination of physiological heats of reaction ...... 200

Feb. 12, 1908. Professor Joel Stebbins, of the University of
Illinois, for his research on the use of selenium in photometry . 100

Feb. 12, 1908. Mr. Willard J. Fisher, of Cornell University,
for his research on the viscosity of gases 100

Reports stating the progress of their respective investigations have
been received from Messrs. P. W. Bridgman, A. L. Clark, E. B. Frost,
L. J. Plenderson, L. R. Ingersoll, N. A. Kent, F. E. Kester, H. W.
Morse, E. F. Nichols, A. A. Noyes, J. A. Parkhurst, T. W. Richards,
R. W. Wood.

Since the last annual meeting the following papers have been pub-
lished at the expense of the Rumford Fund, the first-mentioned in the
Memoirs, the others in the Proceedings : —

"High Electromotive Force." John Trowbridge, May, 1907.

"Studies on Fluorite : IV, The Kathodo-Luminescence of Fluorite."
H. W. Morse. June, 1907.

"The Physiological Basis of Illumination." L. Bell. September,
1907.

RECORDS OF MEETINGS. 539

" The Transition Temperature of Manganous Chloride : A New
Fixed Point in Thermometry." T. W. Richards and F. Wrede. No-
vember, 1907.

"Difference in "Wave-Lengths of Titanium AX .3900 and 3913 in
Arc and Spark." N. A. Kent and A. H. Aver}-. November, 1907.

"Note on Some Meteorological Uses of the Polariscope." L. Bell.
March, 1908.

At its meeting of Jan. 8, 1908, the Committee, at the request of the
Librarian, voted an appropriation of $50 for the binding of books and
periodicals relating to light and heat.

The Committee is endeavoring to make a complete list of all appa-
ratus purchased in past years through appropriations from the Rum-
ford Fund, and hence at present the property of the Academy, to the
end that such apparatus, if suitable, may be available for purposes of
research in the future.

Charles R. Cross, Chairman.

May 13, 1908.

Report of the C. M. "Warren Committee.

The C. M. Warren Committee beg leave to report that grants have
been made during the past year to the following persons, in aid of the
researches specified : —

Dr. Frederic Bonnet, Jr., "Worcester Polytechnic Institute . $150

"The Effect of Lanthanum, Cerium, and Neodymium Oxides
upon Porcelain Glazes, especially as regards their Electrical
Conductivity."

Professor James F. Norris, Simmons College 250

"A Study of the Structure of Triphenyl Methyl."

The work of Professor J. Bishop Tingle on the "Study of the Action
of Certain Secondary Amines on Camphoroxalic Acid," to aid which
research a grant of §50 was made by the Warren Committee in 1907,
has been published in the American Chemical Journal, and acknowl-
edgment made in the paper for the grant received from the Warren
Committee.

A report of the progress made has also been received from Dr. Fred-
eric Bonnet, Jr., and the result of his investigations will, it is hoped,
be published the coming year.

Leonard P. Kinnicutt, Chairman.
May 13, 1908.

640 proceedings of the american academy,

Report of the Publication Committee.

Between May 1, 1907, and May 1, 1908, there were published of the
Proceedings, three numbers of Volume XLII (Nos. 27-29), and six-
teen numbers of Volume XLIII ; also one biographical notice, — in all
567 + V pages and four plates. Five numbers of Volume XLIII
(Nos. 1, 4, 10, 11, and 15) were paid for from the income of the Rum-
ford Fund.

There has also been published, at the expense of the Rumford Fund,
one Memoir (Volume XIII, No. 5, pp. 188-215, plates xxv-xxvii).

There are in press two numbers of the Proceedings ; and an exten-
sive Memoir of some three hundred pages, illustrated with forty-four
plates, is in type. This will complete Volume XIII of the Memoirs.

The Academy placed at the disposal of the Publication Committee,
from the income of the Publication Fund, $3200. Of this amount,
$3046.55 have been paid by the Treasurer on bills approved by the
chairman of the Committee, leaving a balance of .$153.45.

Bills aggregating $473.51 incurred in publishing Rumford papers
have been forwarded to the chairman of the Rumford Committee for
approval.

Report of House Committee.

During the last year the lower story of the Academy's House has
been occupied by the three physicians to whom it has been leased ;
the second story by the Academy itself, the Meeting Room being in
the rear, and the Reception Room and the Librarian's Office being
in the front ; the third story by the dwelling rooms of the Assistant
Librarian, and the fourth story by storerooms and workroom, and a
bedroom for the Janitor. Under this arrangement the building has
been almost constantly occupied in one part or another, and its con-
tents have been properly guarded.

The bills approved by the Secretary of the Academy and the Chair-
man of this Committee, and paid by the Treasurer, have amounted to
$1624.62, of which $1200 was e.specially appropriated at the begin-
ning of the year, and the balance, amounting to $414.62, was made up
from unappropriated funds in the hands of the Treasurer by a subse-
quent vote of the Academy. These amounts include $11.50 spent for
the tables and dishes used for the slight repasts which have been fur-
nished to the members at the close of the meetings. The sum of $1 6.02,
which has been the total cost of five such entertainments, coming to
about $3.30 apiece, has been charged to the expense of the meetings.

RECORDS OF MEETINGS. 541

The Committee have spent S1G3.77 in improving the ventilation of
the Meeting Room, an amount induded in the previous statement.

The ventilation will probably be still further improved by the change
recently made in the seating, which will enable the southern windows
to be opened. This will, we expect, make the ventilation entirely
satisfactory.

But some objection has also been made to the general aspects of the
Meeting Room and its somewhat contracted appearance. The Acad-
emy accordingly at the February meeting directed this Committee to
consider and report upon the practicability of building a somewhat
larger jNIeeting Room in the front of the third story, over the present
Reception Room. We find that this could be done at a cost of between
81200 and 81500, the new room promising to be about one-third
larger than the present one.

But as the Academy has not this amount of money in hand, and, as

the leases of the first floor will expire within a reasonable time, we

think that it would be better for the Academy to try meanwhile to

raise money enough to enable it to dispense with the leasing of the

first floor and to fit up a commodious meeting room there, and we

recommend that steps be taken towards this end.

William R. Ware, Chairman.
May 13, 1908.

Financial Report of the Council.

The income for the year 1908-09, as estimated by the Treasurer, is

as follows : —

(■Investments $1786.97

General Fund J Assessments 1800.00

[Rent of offices 900.00 $4486.97

PUBLICmON FuND^^PP^®^°''^"''^"''^®'*°^^''*^ ^ ^^^'^^

ICentennial Fund investments 2236.75 82796.27

RuMFORD Fund Investments 82698.04

Warren Fund Investments $ 632.83

The above estimates, less 5 per cent to be added to the capital,
leaves an income available for appropriation as follows : —

General Fund $4262.62

Publication Fund 2656.46

Rumford Fund 2563.14

Warren Fund 601.19

.>i_ IE '.^zi:: - r rnz axz3l;:3:s acadeht.

•jzyrj^^l rTXJX

900
250
15«^ S41I10

Pr3i: 7 :>- Frsix

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Rrxjz^ r-ii»-

SIOJO

150

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. •

700

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82563

C M. Wiz.szy ?

iS 5*30

rtr*i'ri. ii

wae

r '

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r : : '

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la- ~:

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wing

_- : :.-T r - "-id . . i4vO

: iie.:f-^R_^ } i5o3

- e of the C. M. Warren F:i::d . 500

r vear '.-= ten dol-

♦-i-^CcXr

EuiB L" THOi&jv. Jl-'i-Pre^id-ynt for Clam I,
Hz>-BT P. WAJLCirr. r:s^-Fr^^id<ntfor Cla*i IL
JoKv C. Gray. Vi<tf-Prejddent for Cl>m TTT.
Y^viTzs H. Haix- Corre^T '' 5

BBOOBIi^ OF ITRFICTGS. 513

William Watson, Ref-orimg Secretary.
Chaelil? p. BowtjItch. Triaxurtr.
A. Laweevce Rotch. Lihriruin.

Cov : ; r* /or TtireJ: Tean.

Wn.T.T.AM L. HOOPEE. of Clas5 I.
Haeold C. Eenst, of Class II.
Flzl^eeic J. Stimson- of Class IIL

Finance ComrfdtUe.

JoH>f Teovtbeidge,
EuoT C. Claeke,
Feaxcis Baetlett.

Ruwford C: ' :e.

Chaeles R. Ceoss. AErax^ G. Webstze.

El>WAED C. PlCKEEESG. ElIZT THOMSON.

EEA53IU5 D. Leavitt. Tse-ji^oee W, Richabds,

Louis Bell.

C. M. Warren C: "e.

LECtXAED P. KcTsicm. Chaeles R. Sanger.
robeet h. richaeds. asthte a. xotes-
Henbt p. Talbot. The<ji>oee W. Richazis,

Geoege D. Mcwjee.

The followiiig standing committees were chosen : —

PubU<^ati

Wallace C. Sabine, of Class I. Eovr^sZ' L. AIaek. of Class II.
Ceaweord H. Tor. of Class HI.

Library Commiftte.

Haeby M. G'XC'vriN.oi Class I. Samuel Hensha^. c; Cli^s II.
HzNEY W. Haynes. of Class 111.

-!:■ j^i:u>^ Cr ■'"■;:.

A. LAvrr.zNcz Lowell. Ii^ujehic J. Stlmsos.

Houie Cor

William R. Waee. A. L absence Rorrz.

MOESIS H. MOEGAN.

544 PROCEEDINGS OF THE AMERICAN ACADEMY.

On motion of the Recording Secretary, the following Resolu-
tion was unanimously adopted : —

Resolved, That the Fellows of the American Academy desire
to place upon record their grateful appi'eciation of the services
of tlieir retiring President, William W. Goodwin, during the
five years in which he has presided over their deliberations.

The following gentlemen were elected members of the
Academy :

Douoflas Wilson Johnson, of Cambridge, as Resident Fellow
in Class II., Section 1 (Mathematics and Astronomy).

Charles Hyde Warren, of Auburndale, as Resident Fellow in
Class II., Section 1.

Emil Fischer, of Berlin, as Foreign Honorary Member in
Class I., Section 3 (Chemistry), in place of the late D.
Mendeleeff.

Professor A. G. Webster gave a communication entitled :
" Absolute Measurements of Sound.''

The following papers were presented by title : —

" A new Method of Determining the Specific Heats of Solu-
tions. By T. W. Richards and A. W. Rowe.

" Positive Rays." By John Trowbridge.

" Variation of the Thermomagnetic Effect in Soft Iron."
By L. L. Campbell. Presented by John Trowbridge.

"The Latent Heat of Fusion and the Specific Heat in the
Solid and Liquid State of Salts Melting below 600° C." By
H. M. Goodwin and H. T. Kalmus.

" Pisistratus and his Edition of Homer." By Samuel Hart
Newhall. Presented by M. H. Morgan.

AMERICAN ACADEMY OF ARTS AND SCIENCES.

Report of the Council. — Presented May 13, 1908.

BIOGRAPHICAL NOTICE.
Samuel Cabot By Charles Loring Jackson.

REPORT OF THE COUNCIL.

The Academy has lost fourteen members by death since the
last report of the Council, — five Resident Fellows, Charles F.
Folsom, Edward G. Gardiner, George E. Davenport, Edward
H. Strobel, Gustavus Hay ; six Associate Fellows, T. D. Sey-
mour, C. A. Young, Asaph Hall, I. C. Russell, A. St. Gaudens,
E. C. Stedman ; three Foreign Honorary Members, H. C. Vogel,
Sir Benjamin Baker, Lord Kelvin.

Three Resident Fellows have resigned.

Seven Resident Fellows have been elected.

One Resident Fellow has been elected to Associate Fellow-
ship.

The roll of the Academy now includes 187 Resident Fellows,
92 Associate Fellows, and 65 Foreign Honorary Members.

SAMUEL CABOT.

Samuel Cabot, the fourth of the name, was born February 18,
1850, in Boston, where his father was an eminent surgeon. His grand-
father, a successful East India merchant in the days before commercial
supremacy had left New England, married Elizabeth Perkins, the daugh-
ter of Thomas Handasyd Perkins, founder of the Perkins Institution
for the Blind. His mother, Hannah Lowell Cabot, was the daughter
of Patrick Tracy Jackson, of Boston, celebrated for the introduction
of the manufacture of cotton goods into America at Waltham and
Lowell, and of Lydia Cabot, of Beverly. He was therefore descended
on each side from a family noted for rugged independence, sturdy hon-
esty, and devotion to high ideals.

He was the oldest son but second child in a numerous family domi-
nated by the high ideals of which I have j ust spoken, as his father was
one of the most vigorous supporters of the antislavery cause when
this could not be done without sacrifice, and in this and all other mat-
ters the pursuit of the highest at any cost was impressed on the chil-
dren by the precept and example of both parents. The life in his
earlier days in Boston, and in the summer at Canton, was of necessity
simple ; those were the days of small fees, when a surgeon, even of his
father's eminence, gained an income barely sufficient for the support of

548 SAMUEL CABOT.

a large family. In fact, it was characteristic of Dr. Cabot that even to
the day of his death he remained an uncompromising opponent to the
high charges for surgical work which had already appeared. But if
the life was simple, it was very full and happy ; the family circle was
bound together by a warm, almost passionate affection, and was sur-
rounded by troops of friends both in Boston and in the country. All
the burning questions of the day were discussed continually with great
energy by the brothers and sisters, each one of whom was thoroughly
convinced of the truth of his or her opinion and never backward in
proclaiming it. The home atmosphere was therefore stimulating, both
morally and mentally.

He was educated in the public schools, finally at the Boston Latin
School, from which he graduated in 1866. Here he proved himself a
painstaking but not brilliant scholar, as, like so many healthy boys,
his interests were in athletic sports, especially baseball and football,
rather than in his books.

On leaving the Latin School he was naturally attracted by the Mas-
sachusetts Institute of Technology, then in its infancy, since he in-
herited strong scientific tastes from his father, who was an excellent
ornithologist and in his younger days had made scientific journeys.
It is probable, however, that the impulse to chemistry came from the
Jacksons, as his contemporaries in this family included nine profes-
sional chemists divided among three branches of the family, which had
separated in the seventeenth century. If this does not indicate a
strong family taste for chemistry, but is a mere coincidence, it is cer-
tainly a strange one, as chemistry is distinctly an unusual profession.
Accordingly he entered the Institute in the third class received by it,
and devoted his attention to chemistry principally under the direction
of Professor F. H. Storer.

In 1870 he became chemist of the Merrimack Print Works at Lowell,
and, while holding this position, introduced successfully a process for
recovering alizarine from the spent residues of the madder root by the
use of sulphuric acid, which was new to this country, — a remarkable
achievement for a young man of twenty-two. It is striking to note
that even as a beginner he was not content with the mere routine work
of his position, but entered at once the field in which he was destined
to reap such abundant harvests, for his principal merit lies in making
effective, on a commercial scale, new processes, whether of his own in-
vention or foreign ones as yet unknown in America. This adaptation
of foreign processes is not by any means the simple matter which it
might appear at first sight; great judgment is necessary in selecting
the one best fitted to the needs of this country, and, after this is done.

SAMUEL CABOT. 549

the details must in many cases be reinvented, or, when not carefully
guarded secrets, they usually need extensive modifications to fit them
to American conditions, which differ in many and unexpected ways
from those abroad. It would be a mistake, however, to suppose from
this early success that he was a precocious genius, who leaped to results
by some intuitive process ; on the contrary, his mind moved rather
slowly, and his early successes were obtained by patient, well-directed,
persistent labor.

In 1.S73 he went to Europe to complete his chemical education, and
studied for the first half year with Emil Kopp, in the Zurich Polytech-
nicum, where he gave part of his time to the analysis of aniline black,
a dyestuff then recently introduced. The second half of the year was
devoted to travel, and especially to visits to laboratories and chemical
works. At this time he was only twenty-four years old, but it was
striking to see the most eminent chemists receiving him as a fellow-
chemist, and discussing scientific matters with him as with a contem-
porary. The acquaintanceships made at this time, and the practical
knowledge acquired, were of life-long value to him.

In 1874, after his return to America with greater attainments and
enlarged horizons, he attempted to establish at the Lowell Bleachery
the Solvay process for making sodic carbonate, then only eleven years
old, but without success. This is an excellent example of the difficul-
ties in introducing foreign manufacturing processes. There was no
lack of judgment in the selection of the process, as is shown by the
enormous development of it at Syracuse, where it was started under
the auspices of the mother company in Belgium ten years later ; the
details also seemed to be sufficiently well known, but the working out
of these details so as to secure success needed not only the highest
ability of the technical chemist, but also mechanical engineering of a
most difficult and unusual sort, which at that time was beyond him.
His failure, therefore, was not surprising or mortifying, and he had the
happy faculty of learning from his failures, and, like Peter the Great,
making them the school for later victories. After this he spent a
short time in the office of his uncle, Henry Lee, learning business
methods.

His only chemical papers date from this period, 1872-1877. They
are seven in number and of good quality for a beginner, but he evi-
dently soon realized that the publication of original researches was not
his line of work, since he could be employed much more usefully for
the community and himself in perfecting chemical manufactures. With
this end in view he became the most expert consulting chemist for in-
dustrial work in this part of the country, and continued to give advice

550 SAMUEL CABOT.

of this sort, as he could find time, until his own manufactures absorbed
his whole attention.

It was in 1877 that he began business on his own account in part-
nership with Frederick Nourse. They established a coal-tar distillery
at Chelsea, from which he hoped to develop an industry in fine organic
chemicals similar to that which was then showing such wonderful
growth in Germany, but the time was not ripe for such a growth in
America ; in fact, even now, thirty years afterward, this industry has
not yet emerged from its infancy. Accordingly he turned his attention
to the less varied list of products for which he found a demand.
Among these, lampblack was the most important, and he at once im-
proved the apparatus for its manufacture in his usual thorough, pains-
taking way. Mr. Nourse retired from the partnership in the autumn
of 1878, and after this he had sole charge of the business, keeping
himself a firm grasp on all departments of it, with the assistance of a
series of able managers, — his brother-in-law, Mr. C P. Nichols,
Mr. Edward Cunningham, Mr. W. R. Cabot, and Mr. M. G. Bennett.

Always on the lookout for new fields of work, his attention was
called at an early day to the gas region of Pennsylvania, in which he
hoped to find mineral wealth similar to that of the Midland region of
England. Although these hopes were not fulfilled, the investigation
led him to the establishment in 1882-1883 of a plant at Worthington,
Pennsylvania, for making carbon black by burning natural gas against
a cast-iron plate beneath which the burner and black-box revolved.
This method, which was in part, perhaps wholly, original with him, is
still in use in the largest factory for this product. After a few years,
however (in 1888), his brother, Godfrey L. Cabot, who had worked
with him for a short time, took this business off his hands, and has car-
ried it on successfully ever since.

At about the same time he began the manufacture of sulpho-naphthol
— one of the most excellent disinfectants known ; and another profit-
able new industry, rendered effective by him somewhat later, was the
preparation of creosote shingle stains. Many attempts had been
made in foreign countries to use creosote as a basis for paint, but none
of these had been crowned with success. He, however, had the pene-
tration to see that such a paint or stain would be specially adapted for
use with shingles, which were essentially unknown abroad, and after
this a painstaking study of the details and great care and thorough-
ness in the manufacture led to a complete victory over the difficulties,
which had proved too much for his predecessors. His insulating felt
for deadening sound, keeping out cold, and fireproofing, was an en-
tirely original idea. It consisted of eel-grass quilted between two

SAMUEL CABOT. 551

layers of asbestos or feltiug, and proved especially well adapted for
these purposes, thus furnishing a use for a very cheap and hitherto
worthless material.

Not every experiment was a success, however ; as with all inventors,
his path was strewn with failures, for it was not enough to make a
process work, but it must also pay. Thus, for instance, he invented a
set of stains on a creosote basis for interior use in houses, but, although
admirable from the technical and artistic standpoints, the demand for
them was so small that it was not worth while to manufacture them.

At the time of his death his principal products were shingle-stains,
lampblack, deadening-felt, sulpho-naphthol, benzol, naphtha, brick pre-
servative, sheep dip, mortar colors, black varnish, and coal-tar pitch. I
give this list to show how far he had departed from his original plan of
establishing a varied manufacture of fine chemicals, as it seems to me
a remarkable proof of his sagacity that he was able to select products
for which there was a demand, instead of wasting his energies on lines
of work for which the country was not prepared.

One of his most interesting achievements was the successful estab-
lishment of a system of profit-sharing with the operatives of his fac-
tory. I am fortunately able to give an account of it in his own words,
taken from an address on the subject delivered a few years ago before
the American Social Science Association.

"At a very early period in my business experience it appeared to
me that the rewards ordinarily offered to the wage- earner were not
such as to stimulate him to the best exertion nor foster in him the best
and kindest feelings toward his employer.

"Even to-day is it not true that in the great majority of cases the
wage-earner's only stimulus is the desire to hold his job 1 In fact, is
not the fear of discharge the only incentive to exertion in a large ma-
jority of cases ?

" Feeling as I did, and still do, that men can always be led more
successfully than they can be driven, that Hope as leader and captain
can accomplish more than Fear as tjTant and slave-driver, I set myself
— ignorantly and crudely to be sure, but earnestly — to try to do bet-
ter things. My method has grown to be essentially as follows :

" Every man who enters my employ is given the current rate of
wages for similar work. If he desires also to participate in the profit-
sharing, he is required to sign a paper in which he promises to do his
work as quickly and carefully as possible, remembering that the greater
the jdeld the larger the profits, and to give me sixty days' notice before
leaving me.

" On my part, I promise to divide, at the expiration of each six

552 SAMUEL CABOT.

months, a certain fraction of the profits among the participants, strictly
in proportion to the wages of each during that period. This sum in
each case is divided into two equal parts, one of which is given in cash
to the employee and the other is deposited in a savings-bank by me as
his trustee.

" This fund in the bank is in the nature of an insurance upon the
life of the employee, and is given over with interest to his executors,
if he dies. It, however, does not come back into my hands. If he
should, for instance, refuse to give me sixty days' notice on leaving
me, although he had already received an equal amount in cash upon
the promise to give me such notice, the money would not come back
to me, but would simply be distributed among the other participants
at the next division.

" The same is true in case of his discharge for cause.

" In case of sickness I am empowered at my discretion to draw upon
his fund, though in temporary cases I always put sick men on half-
pay for a considerable time without recourse to their fund. I also
have the right to lend him money upon it to build a house. And now
let me give you a few figures.

" The system was begun a little over seventeen years ago, and has
gone on uninterrupted up to the present time. The profit-sharers at
the outset numbered 21, and to-day number 42. The total amount paid
out by me has been $40,464 during that period. Now the natural
question which you all will ask, I think, is. Has this been a good bar-
gain ? I thnik you will all agree that in the ultimate analysis no bar-
gain is a good bargain that is not profitable to both sides. Well, there
will, I think, be no dispute that from the workman's point of view the
bargain has been a good one, as he has a very considerable addition to
his wages, which were as high as other labor of the same kind ; and I
may say that the average wages have steadily advanced as the effi-
ciency and skill increased.

" But now comes the question of my own investment : "What
means have I of knowing that the efficiency of the workmen has been
increased to an amount equivalent to the $40,464 which I have
exjiended 1

" I will now give you a few more statistics which bear upon this
question. Let me remind you that the same proportion of the profit
was paid to the 21 men who first entered the agreement that is now
paid to the 42 men who compose the present corps. But now note this
very significant fact. While the first payments averaged about 10 per
cent upon the wages of each man, the last payment — which was larger
than usual, to be sure — was exactly 21-i% per cent of their wages.

SAMUEL CABOT. 553

" It seems to me obvions that, if we can draw any inference from
these facts, it is that, inasmuch as my profit compared to the wages
paid has increased, the efiiciency of my workmen has improved.

" But, above all, my own observation has convinced me that the
morale of my employees is much superior to the average, and that they
are more contented and willing by far than is usual in similar establish-
ments. In fact, I am satisfied that this bargain has been a good bar-
gain, a good one for both parties to it, and that the extra money I have
laid out has been well and profitably invested.

" I have, for obvious reasons, not laid any emphasis upon the philan-
thropic side of this enterprise, especially as I am sure it can be recom-
mended to many, if not to most, manufacturers, and to their employees,
purely upon its utilitarian advantages ; but it is obvious that it stimu-
lates both sobriety and thrift in workmen, and that it can be made to
assist men of family to build homes for themselves, thus surrounding
the factory with the homesteads of men who are interested in its
success and that of the neighborhood.

" From my seventeen years' experience, therefore, gentlemen, I can
cordially recommend profit-sharing on this or a similar plan as of
marked advantage to both employer and employed."

I have quoted this paper almost entire, because it seems to me to
show the man — his desire for the good of others, joined to sound busi-
ness common sense, and the practical wisdom needed to make the
scheme eff'ective. That it was effective is shown by the fact that,
when a new hand was inclined to be indolent, the other workmen
insisted on vigorous work from him if he was to stay in the factory,
for, said they, " We will not have our profits cut down by the lazy or
inefficient." It will be observed that the success of this system de-
pended on an absolute trust on the part of the men in the upright- *
ness of their employer. The slightest suspicion that it would not be
carried out equitably, or that in some underhand way it would redound
to the profit of the chief, would have ^vTecked it at once. And here
the comparatively small number of men was a potent factor, as they
were all able to know Mr. Cabot personally, and to realize his absolute
honesty and fairness. That they also learned to love him appeared
from the impressive sorrow with which they attended his funeral.

This absolute honesty and fairness was also conspicuous in his busi-
^ness relations. He would often make concessions beyond what could
be justly demanded, if he thought the claim was made in good faith,
while, on the other hand, he would not yield an inch when this was
not the case, but proved a dangerous and pertinacious adversary. In
one case at a very early stage in his career a man who had circulated

554 SAMUEL CABOT.

malicious stories about his goods was forced to sign a written retrac-
tion couched in the most abject terms.

His business activities would have been enough to exhaust the
energy of most men, but he found time and strength for the enthu-
siastic pursuit of many other interests. He was a most devoted son
of the Institute of Technology, always ready with advice or more
material help. In 1889 he was elected to the Corporation intrusted
with its government, and in spite of his strong opinions and fighting
blood won and kept the respect and affection of all his fellow-members.
He was a member of the executive committee for many years, and very
active on committees in charge of special departments, serving at various
times on those on chemistry, chemical engineering, physics, botany,
biology, modern languages, and English. His principal interest was
naturally in the Chemical Department, which he watched over with
unceasing care. He even induced Professor Lunge to come to Boston
from Zurich to examine it, and make suggestions in regard to the best
methods for teaching industrial chemistry.

Nor did he confine his attention to the Institute of Technology, as
for many years he was a member of the " Committee to visit the
Chemical Laboratory " of Harvard University, and in this capacity
gave much useful advice about the organization of the course in indus-
trial chemistry, in which he advocated the teaching of broad general
principles rather than instruction in details, showing in this way a
power of rising above the narrowing tendency of the highly specialized
work by which alone a chemical manufacturer attains success.

He was devoted to athletics throughout his life, telling with gusto
in one of his last years how he had beaten a much younger man at
tennis, and about the same time causing the publication of a delight-
*ful volume of reminiscences by the idol of his boyhood, Lovett, the
pitcher of the Lowells. This interest influenced his relations with the
Institute of Technology, as he was a member of the Advisory Council
on Athletics, and gave a tract of land in Brookline for a playground.
He also established an annual prize for the greatest improvement in
athletics, and gave a silver cup, on which the names of the victors
were inscribed each year. It is almost needless to add that his influ-
ence was always used in maintaining the highest ideal of sportsmanship.
In addition to these gifts for athletics he gave his house in Brookline
for a dormitory, and was always ready to answer any pressing need.

He threw himself with the same enthusiasm into other recreations. '
Thus he made a careful study of the theory and construction of aero-
planes, for many years carrying on experiments in the summer on kites,
studying especially the resistance of the air to various forms, and the

SAMUEL CABOT. 555

effect of atmospheric currents. While in Europe in 1896 he saw
Maxim and Lilienthal, and provided the latter with money to carry on
his work ; and in this country he stood ready to help the Wright
brothers, when the time should come to make their experiments
public.

Another engrossing pursuit was the study of the authorship of the
plays of Shakespeare. He espoused the Baconian theory with great
vigor, and defended his position by elaborate and costly investigations.
His fine taste for art made him an authority on this subject also, and
proved of great use to him in some of the branches of his business.

He was elected a fellow of our Academy in 1893, and served on the
C. M. Warren Committee from its establishment in the same year until
his death. That he held no other ofiice was from his own choice, since
he was at one time elected treasurer of the Academy, but declined to
serve. He was also a member of the Society for Chemical Industry.

In 1878 he married Helen Augusta Nichols, of Lowell, and they had
two children, a daughter and a son. In his family and society his
genial, affectionate nature won all hearts. It made one happier for the
whole day simply to exchange a few words with him in the street.

This life, so full of various beneficent activities, was brought to an
end by a sudden attack of pneumonia, November 26, 1906.

In looking back at his life the most striking characteristic was, I
think, his very high standards. It was not enough that he should be
successful from a worldly point of view, but in all his undertakings
the good of the country was a prime consideration ; the introduction
of new and useful processes, the utilization of waste materials, were his
objects quite as much as his own personal advantage. Further, all his
products must be of the highest quality, all his processes brought to
the highest perfection. His probity was without a flaw, and anything
mean or underhanded aroused in him a scorching, disdainful wrath, — for
he was always a fighter, never afraid of an outspoken expression of his
opinion ; yet even in his more vehement controversies his antagonists
could never lose sight of his sincerity of purpose and his large, warm
heart. With all his vehemence of opinion his character was a singu-
larly gentle and affectionate one, so that his genial nature won the love
of all who knew him well. His thoroughness in all his pursuits, and
the good judgement with which he selected or abandoned his manu-
facturing experiments, have been dwelt on sufiiciently in the narrative
of his life ; but not enough has been said there of his generosity — always
on the watch to help the deserving, yet concealed so carefully that in
one case at least even the person benefited did not know from whom
the help had come. To these he added a modesty and humility which

556 SAMUEL CABOT.

led him always to undervalue his ability and attainments, a purity so
feminine that it was respected even by the wilder men whom he
chanced to encounter in his youth, and a strong and vivid imagination
both in his experiments and recreations.

His ruddy face under a mass of curly hair always beamed with a
genial light ; and he seemed to glow with exuberant life and enthu-
siasm while he discussed some important subject in a slow rather
hesitating manner, as if his abundant ideas found difficulty in gaining
utterance. It seems impossible to believe that this overflowing vitality
is no longer with us.

Charles Loring Jackson.

Class I.

Elihu Thomson,

American Academy of Arts and Sciences

OFFICERS AND COMMITTEES FOR 1908-09.

president.
John Trowbridge,
vice-president.

Class II.

Henry P. Walcott,

CORRESPONDING SECRETARY.

Edwin H. Hall.

recording secretary.
William Watson.

treasurer.

Charles P. Bowditch.

LIBRARIAN.

A. Lawrence Rotch.

COUNCILLORS.
Class II.

James C. White,
Tertns expire- 1909.
John E. Wolff,
Terms ex fire 1 910.

H.AROLD C. Ernst,
Terms expire 1911.

COMMITTEE OF FINANCE.

Eliot C. Clarke,

rumford committee.
Charles K. Cross, C/iairmun,
Edward C. Pickering,
Theodore W. Richards,

Class III.

John C. Gray.

Class I.
Ira N. Hollis,

Henry P. Talkot,

William L. Hooper,

John Trowbridge,

Erasmus D. Leavitt,
Arthur G. Webster,

Class III.
William R. Ware.

George L. Kittredge.

Frederic J. Stimson.

Francis Bartlett.

Elihu Thomson.
Louis Bell.

C. M. WARREN COMMITTEE.
Leonard P. Kinnicutt, Chairman,
Robert H. Richards, Charles R. Sanger,

Arthur A. Noyes.

Henry P. Talbot,

Theodore W. Richards, George D. Moole.

COMMITTEE OF PUBLICATION.

Edward L. Mark, of Class II, Ckainnan,
Wall.ace C. Sabine, of Class I, Crawford H. Toy, of Class III.

COMMITTEE ON THE LIBRARY.

A. Lawrence Rotch, Chain/ian,

Harry M. Goodwin, of Class I, Samuel Henshaw, of Class II,

Henry W. Hayxes, of Class III.

AUDITING COMMITTEE.

A. Lawrence Lowell,

Frederick J. Stimson.

HOUSE COMMITTEE.

William R. Wake, Chairman.

A. Lawrence Rotch,

Morris H. Morgan-

LIST

OF THE

FELLOWS AND FOREIGN HONORAEY MEMBERS.

(Corrected to June 1, 1908.)

RESIDENT FELLOWS. — 189.

(Number limited to two liundred.)

Class I. — Mathematical
Section I. — 14.

Mathematics and Astronomy.

Cambridge.
Cambridge.
Cambridge.
Wellesley Hills.
Boston.

Solon I. Bailey,
Maxime Bocher,
William E. Byerly,
Seth C. Chandler,
Percival Lowell,
Edward C. Pickering,
William H. Pickering,
John Ritchie, Jr.,
Arthur Searle,
William E. Story,
Henry Taber,
Harry W. Tyler,
O. C. Wendell,
P. S. Yendell,

Cambridge.

Dorchester.

Cambridge.

Worcester.

Boston.

Cambridge.

Dorchester.

Section H. — 27.

Physics.

A. Graham Bell, Washington, D.C.

Louis Bell, Boston.

Clarence J. Blake, Boston.

Francis Blake, Weston.

George A. Campbell, New York.

Harry E. Clifford, Xewton.

Charles R. Cross, Brookline.

Louis Derr, Brookline.

and Physical Sciences,

A. W. Duff,
H. M. Goodwin,
Edwin H. Hall,
Hammond V. Hayes,
William L. Hooper,
William W. Jacques,
Frank A. Laws,
Henry Lefavour,
Theodore Lyman,
Charles L. Norton,
Benjamin O. Peirce,
George W. Pierce,
A. Lawrence Rotch,
Wallace C. Sabine,
John S. Stone,
Elihu Thomson,
John Trowbridge,
A. G. Webster,
Robert AV. Willson,

, — 78.

Worcester.

Roxbury.

Cambridge.

Somerville.

Newton.

Boston.

Brookline.

Boston .

Cambridge.

Boston.

Swampscott.

Cambridge.

Worcester.

Cambridge.

Section HL -
Chemistry.

19.

Gregory Paul Baxter, Cambridge.

Arthur M. Comeyi Cambridge.

James M. Crafts, Boston.

Charles W. Eliot, Cambridge.

Charles L. Jackson, Cambridge.

Walter L. Jennings, Worcester.

500

EESIDENT FELLOWS.

Leonard P. Kinnicutt,
Charles F. Mabery,
George D. Moore,
.lames F. Norris,
Arthur A. Noyes,
Robert 11. Richards,
Tlieodore W. Richards,
Charles R. Sanger,
Stephen P. Sharpies,
Francis H. Storer,
] lenry P. Talbot,
William II. Walker,
Charles II. Wing,

Worcester.

Cleveland, O.

AVorcester.

Boston.

Jamaica Plain.

Cambridge.

Boston.

Newton.

Boston.

Section IV. — 18.

Technolofjy and Engineering.
Comfort A. Adams,

Cambridge.

Alfred E. Burton,
Eliot C. Clarke, •
Heinrich O. Hofman,
Ira N. liollis,
L. J. Johnson,
Arthur E. Kennelly,
Gaetano Lanza,
E. D. Leavitt,
William R. Livermore,
Hiram F. Mills,
Cecil H. Peabody,
Andrew H. Russell,
All)ert Sauveur,
Peter Schwamb,
11. L. Smyth,
George F. Swain,
William Watson,

Boston.

Jamaica Plain.

Cambridge.

Boston.

Cambridge.

New York.

Lowell.

Brookline.

Paris.

Cambridge.

Arlington.

Cambridge.

Boston.

Class II. — Natural and Physiological Sciences. — 59.

Sfxtion I. — 16.

Geology^ Mineralogy^ and Physics of
the Globe.

II. H. Clayton,
Algernon Coolidge,
William O. Crosby,
William M. Davis,
Benj. K. Emerson,
O. W. Huntington,
Robert T. Jackson,
T. A. Jaggar, Jr.,
Douglas W. Johnson,
William H. Niles, ■
Chirles Palache,
John E. Pillsbury,
Rol)ert DeC. Ward,
Charles II Warren,
John E. Wolff.
J. B. Woodworth,

Milton.

Boston.

Jamaica Plain.

Cambridge.

Amherst.

Newport, R. I.

Cambridge.

Camliridge.

Cambridge.

Washington.

Cambridge.

Auburndale.

Cambridge.

Section II. — 11.

Botany.

F. S. Collins,
WiUiam G. Farlow,
Charles E. Faxon,
Merritt L. Fernald,
George L. Goodale,
John G. Jack,
Edward C. Jeffrey,
B. L. Robinson,
Charles S. Sargent,
Arthur B. Seymour,
Roland Thaxter,

Maiden.

Cambridge.

Jamaica Plain.

Cambridge.

Jamaica Plain.

Cambridge.

Brookline.

Cambridge.

— 21.

Section III.
Zoology and Physiology.
.Alexander Agassiz, Cambridge.
Robert Amory, Boston.

RESIDENT FELLOWS.

5G1

Henry P. Bowditch,
William Brewster,
Louis Cabot,
Walter B. Cannon,
William E. Castle,
Sanmel F. Clarke,
\V. T. Councilman,
Harold C. Ernst,
Samuel Ilenshaw,
Edward L. Mark,
Chai'les S. Minot,
Edward S. Morse,
George H. Parker,
William T. Porter,
James J. Putnam,
Samuel H. Scudder,
William T. Sedgwick,

Jamaica Plain.

Cambridge.

Brookline.

Cambridge.

Williamstown.

Boston.

Jamaica Plain.

Cambridge.

]\Iilton.

Salem.

Cambridge.

Boston.

Cambridge.

Boston.

James C. White, Boston.

William M. Woodworth, Cambridge.

Section IV. — 11.

Medicine ami

Edward H. Bradford,
Arthur T. Cabot,
Reginald H. Fitz,
Frederick I. Knight,
Samuel J. Mixter,
W. L. Richardson,
Theobald Smith,
O. F. Wadsworth,
Henry P. Walcott,
John C. Warren,
Francis H. Williams,

Surgenj.

Boston.

Jamaica Plain.

Boston.

Cambridge.

Boston.

Class III. — Moral and Political Sciences. — 52.

Section I. — 8.
Philosophy and Jurisprudence.

Cambridge.
Cambridge.

James B. Ames,
Joseph H. Beale, Jr.,
John C. Gray,
Francis C. Lowell,
Hugo Miinsterberg,
.Josiah Royce,
Frederic J. Stimson,
Samuel Williston,

Boston.

Cambridge.

Dedham.

Belmont.

Section II. — 19.
Philology and Archceology.

Charles P. Bowditch, Jamaica Plain.
Lucien Carr, Cambridge.

VOL. XLIH. — 36

Franklin Carter,
J. W. Fewkes,
William W. Goodwin,
Henry W. Haynes,
Albert A. Howard,
Charles R. Lanman,
David G. Lyon,
George F. Moore,
Morris H. ^Morgan,
Frederick W. Putnam,
Edward Robinson,
Edward S. Sheldon,
Herbert Weir Smyth,
F. B. Stephenson,
Crawford H. Toy,
John W. White,
John H. Wright,

Williamstown.

Washington.

Cambridge.

Boston.

Cambridge.

New York.

Cambridge.

Boston.

Cambridge.

562

RESIDENT FELLOWS.

Section III. — 12.

Political Economy and History.

Charles F. Adams,
Thomas N. Carver,
Andrew McF. Davis,
Ephraim Emerton,
A. C. Goodell,
Charles Gross,
Henry C. Lodge,
A. Lawrence Lowell,
James F. Rhodes.
William Z. Ripley,
Charles C. Smith,
F. W. Taussig,

Lincoln.

Cambridge.

Salem.

Cambridge.

Nahant.

Boston.

Newton.

Boston.

Cambridge.

Section IV. — 13.
Literature and the Fine Arts.

Francis Bartlett,
Arlo Bates,
L. B. R. Briggs,
Kuno Francke,
Edward H. Hall,
T. W. Higginson,
George L. Kittredge,
William C. Lane,
Charles Eliot Norton,
Denman W. Ross,
William R. Ware,
Herbert L. Warren,
Barrett Wendell,

Boston.

Cambridge.

Cambridge,

Cambridge.

Milton.

Cambridge.

Boston.

ASSOCIATE FELLOWS.

563

ASSOCIATE FELLOWS.

92.

(Number limited to one hundred. Elected as vacancies occur.)

Class L — Mathematical

Section I. — 12.

Mathematics and Astronomy.

Edward E. Barnard, "Williams Bay,

Wis.
S. W. Burnham, AV.illiams Bay, Wis.
George Davidson, San Francisco.
Fabian Franklin,
George W. Hill,
E. S. Holden,
Emory McClintock,
E. H. Moore,

Simon Newcomb,
Charles L. Poor,
George M. Searle,
J. 2s. Stockwell,

Baltimore.

W. Nyack, N.Y.

New York.

Morristown,N.J.

Chicago.

Washington.

New York.

Washington.

Cleveland, O.

and Physical Sciences. — 36.
Section III. — 10.

Chemistry.

Wolcott Gibbs, Newport, R.L
Frank A. Gooch, New Haven.
Eugene W. Hilgard, Berkeley, Cal.
S. W. Johnson, New Haven.
J. W. Mallet, Charlottesville,Ya.

E. W. ]\Iorley, W. Hartford, Conn.
Charles E. Munroe, Washington.
John U. Nef, Chicago, 111.

J. M. Ordway, New Orleans.

Ira Remsen, Baltimore.

Section IV. — 8.

Section II. — 6.

Physics.

Carl Barus, Providence, R.I.

G. E. Hale, Williams Bay, Wis.

T. C. Mendenhall, Worcester.
A. A. Michelson, Chicago.
E. L. Nichols, Ithaca, N. Y.

M. I. Pupin, New York.

Technology and
Henry L. Abbot,
Cyrus B. Comstock,
W. P. Craighill,
John Fritz,
James D. Hague,
F. R. Hutton,
William Sellers,
Robt. S. Woodward,

Engineering.

Cambridge.
New York. [Va.
Charlestown, ^V'.
Bethlehem, Pa.
New York.
New York.
Edge Moor, Del.
Washington.

Class II. — Natural and Physiological Sciences. — 32.

Section I. — 9.

Geology^ Mineralogy, and Physics of
the Globe.

Cleveland Abbe,
George J. Brush,

Washington.
New Haven.

T. C. Chamberlin,
Edward S. Dana,
Walter G. Davis,

Chicago.
New Haven.
Cordova, Arg.

Samuel F. Emmons, Washington.

G. K. Gilbert,
R. Pumpelly,
Charles D. Walcott.

Washington.
Newport, R.I.
Washington.

564

ASSOCIATE FELLOWS.

Section II. — (
Botany.

L. H. Bailey,
D. H. Campbell,
J. M. Coulter,
C. G. Piingle,
John D. Smith,
W. Trelease,

Ithaca, N. Y.
Palo Alto, Cal.
Chicago.
Charlotte, Vt.
Baltimore.
St. Louis.

Section III. — 9.

Zoology and Physiology.

Joel A. Allen, Xew York.

AV. K. Brooks, Lake Roland, Md.

C. B. Davenport,

Cold Spring Harbor, N. Y.

F. P. Mall.

Baltimore.

S. Weir Mitchell,
H. F. Osborn,
A. E. Verrill,
C. O. Whitman,
E. B. Wilson,

Philadelphia.
Xew York.
New Haven.
Chicago.
New York,

Section IV. — 8.

Medicine and Surgery.

John S. Billings, New York.

W. S. Halsted, Baltimore.

Abraham Jacobi, New York.

W. W. Keen, Philadelphia.

William Osier, Baltimore.
T. Mitchell Prudden, New York.

Wm. H. Welch, Baltimore.

11. C. Wood, Philadelphia.

Class III. — iMoral and Political Sciences. — 24.

Section I. — 6.

Philosophy and

Joseph H. Choate,
]\Ielville AV. Fuller,
AA'illiam W. Howe,
Charles S. Peirce,
G. W. Pepper,
T. R. Pynchon,

Jurisprudence.

New York.
Washington.
New Oileans.
Milford, Pa.
Philadelphia.
Hartford, Conn.

Section II. — 6.

Philology and Archteology.
Timothy Dwight, New Haven.
B. L. Gildersleeve, Baltimore.
D. C. Gilmau, Baltimore.

T. R. Lounsbury, New Haven.
Rufiis B. Richai-dson, New York.
A. D. White, • Ithaca, N.Y.

Section HI. — 7.

Political Economy and History.

Henry Adams, Washington.

G. P. Fisher, New Haven.

Arthur T. Hadley, New Haven.

Henry C. Lea, Philadelphia.

Alfred T. Mahan, New York.

H. J\Iorse Stephens, Ithaca.

W. G. Sumner, New Haven.

Section IV. — 5.

Literature and the Fine Arts.

James B. Angell,
H. H. Furness,
R. S. Greenough,
Herbert Putnam,
John S. Sargent,

Ann Arbor, Mich.
Wallingford, Pa.
Florence.
Washington.
London.

FOREIGN HONORARY MEMBERS.

565

FOREIGN HONORARY MEMB E RS. — 65.

(Number limited to seventy-five. Elected as vacancies occur.)

Class I. — Mathematical and Physical Sciences. — 20.

Skction I. — 6.
Mathematics and Astronomy.
Arthur Auwers, Berlin.

George H. Darwin, Cambridge.
Sir William Huggins, London.
Felix Klein, Gottingen.

Emile Picard, Paris.

II. Poincare, Paris.

Section II. — 5.

Pliy><ics.
Oliver Heaviside, Newton Abbot.

Marburg.
Cambridge.
Witham.
Joseph J. Thomson, Cambridge.

F. Kohlrausch,
Joseph Larmor,
Lord Rayleigh,

Section III. — 6.
Chemistry.
Adolf Flitter von Baeyer, Munich.

Emil Fischer,
J. II. van't Hoff,
Wilhelm Ostwald,
Sir H. E. Roscoe,
Juhus Thomseu,

Berlin.

Leipsic.

Loudon.

Copenhagen.

Section IV. — 3.

Technology and Engineering.

]\Iaurice Levy, Paris.

H. Muller-Breslau, Berlin.
W. Cawthorne Unwin, London.

Class II. — Natural and Physiological Sciences. — 22.
Section I. — 4.

Geology, Mineralogy, and Physics of
the Globe.

Sir Archibald Geikie, London.

Julius Hann, Vienna.

Albert Heim, Zurich.

Sir John Murray, Edinburgh.

Section II. — 6.
Botany.
E. Bornet, Paris.

A. Engler,

Berlin.

Sir Joseph D. Hooker, Sunuingdale.

W. PfefEer, Leipsic.
H. Graf zu Solms-

Laubach, Strassburg.

Eduard Strasburger, Bonn.

566

FOKEIGN HONORARY MEMBERS.

Section III. — 5.

Zoology and Physiology.

Ludimar Hermann,
H. Kronecker,
E. Ray Lankester,
Elias Metschnikoff,
jNI. Gustav Retzius,

Kbnigsberg.

Bern.

London.

Paris.

Stockholm.

Section IV. — 7.

Medicine and Surgery.

Emil von Behring, Marburg.

Sir T. L. Brunton, London.

A. Celli, Rome.

Sir V. A. H. Horsley, Loudon.

R. Koch, Berlin.

Lord Lister, London.

F. V. Recklinghausen, Strassburg.

Class III. — Moral and Political Sciences. — 23.

Section I. — .5.
Philosophy and Jurisprudence.

A. J. Balfour,

Prestonkirk.

James Bryce,

London.

Ileiurich Brunner,

Berlin.

Adolf Harnack,

Berlin.

A. V. Dicey,

Oxford.

Sir G. 0. Trevelyan,

F. W. Maitlaud,

Cambridge.

Bart.,

London.

Sir Frederick Pollock,

John ]\Iorley,

London.

Bart.,

London.

Pasquale Villari,

Florence.

Section

II.

— 7.

Philology and Archceology.
Ingram Bywater, Oxford.

F. Delitzsch,
Hermann Diels,
W. Dorp f eld,
Sir John Evans,
H. Jackson,

Berlin.
Berlin.
Athens.
Berkhampsted.
Cambrids:e.

G. C. C. Maspero, Paris.

Section III. — 5.
Political Economy and History.

Section IV. — 6.

Literature and the Fine Arts.

E. de Amicis,
Gaston Boissier,
Georg Brandes,
S. H. Butcher,
Jean Leon Gerome,
Rudyard Kipling,

Turin.

Paris.

Copenhagen.

London.

Paris.

Burwash.

STATUTES AND STANDING TOTES.

STATUTES.

Adopted May 30, 1854 : amended September 8, 1857, November 12, 1862,
May 24, 1864, November 9, 1870, 31ay 27, 1873, January 26, 1876,
June 16, 1886, October 8, 1890, January 11, one? J% 10, 1893, May
9, a«rf Ocifo^er 10, 1894, March 13, JjunV 10, and May 8, 1895, May
8, 1901, January 8, 1902, J/a^ 10, 1905, February 14 a«c? J/arcA 14,
1906.

CHAPTER I.
Of Fellows and Foreign Honorary Members,

1. The Academy consists of Resident Fellows, Associate Fellows, and
Foreign Honorary Members. They are arranged in three Classes, ac-
cording to the Arts and Sciences in which they are severally proficient,
viz. : Class I. The Mathematical and Physical Sciences ; — Class II.
The Natural and Physiological Sciences; — Class III. The Moral and
Political Sciences. Each Class is divided into four Sections, viz. :
Class I., Section 1. Mathematics and Astronomy; — Section 2. Physics;
— Section 3. Chemistry ; — Section 4. Technology and Engineering.
Class II., Section 1. Geology, Mineralogy, and Physics of the Globe; —
Section 2. Botany; Section 3. Zoology and Physiology; — Section 4.
Medicine and Surgery. Class III., Section 1. Theology, Philosophy,
and Jurisprudence; — Section 2. Philology and Archaeology; — Sec-
tion 3. Political Economy and History; — Section 4. Literature and

the Fine Arts.

2. The number of Resident Fellows residing in the Commonwealth
of Massachusetts shall not exceed two hundred, of whom there shall not
be more than eighty in any one of the three classes. Only residents in
the Commonwealth of Massachusetts shall be eligible to election as Resi-
dent Fellows, but resident fellowship may be retained after removal from

568 STATUTES OP THE AMERICAN ACADEMY

the Commonwealth. Each Resident Fellow shall pay an admission fee
of ten dollars and such annual assessment, not exceeding ten dollars,
as shall be voted by the Academy at each annual meeting. Resident
Fellows only may vote at the meetings of the Academy.

3. The number of Associate Fellows shall not exceed one hundred,
of whom there shall not be more than forty in either of the three classes
of the Academy, Associate Fellows shall be chosen from persons resid-
ing outside of the Commonwealth of Massachusetts. They shall not be
liable to the payment of any fees or annual dues, but on removing within
the Commonwealth they may be transferred by the Council to resident
fellowship as vacancies there occur.

4. The number of Foreign Honorary Members shall not exceed
seventy-five; and they shall be chosen from among persons most eminent
in foreiOT countries for their discoveries and attainments in either of the
three departments of knowledge above enumerated. There shall not be
more than thirty Foreign Members in either of these departments.

CHAPTER II.

Of Officers.

1. There shall be a- President, three Vice-Presidents, one for each
Class, a Corresponding Secretary, a Recording Secretary, a Treasurer,
and a Librarian, which officers shall be annually elected, by ballot, at
the annual meeting, on the second Wednesday in May.

2. There shall be nine Councillors, chosen from the Resident Fellows.
At each annual meeting, three Councillors shall be chosen, by .ballot,
one from each Class, to serve for three years ; but the same Fellow shall
not be eligible for two successive terms. The nine Councillors, with the
President, the three Vice-Presidents, the two Secretaries, the Treasurer,
and the Librarian, shall constitute the Council. Five members shall
constitute a quorum. It shall be the duty of this Council to exercise a
discreet supervision over all nominations and elections. With the con-
sent of the Fellow interested, they shall have power to make transfers
between the several sections of the same Class, reporting their action to
the Academy.

3. The Council shall at its March Meeting receive reports from the
Rumford Committee, the C. M. Warren Committee, the Committee on
Publication, the Committee on the Library, the President and Record-

OF ARTS AND SCIENCES. 569

ing Secretary, and tlie Treasurer, proposing the appropriations for their
work during the vear befjinnini; the following May. The Treasurer at
the same meeting shall report on the income which will probably be
received on account of the various Funds during the same year.

At the Annual Meeting, the Council shall submit to the Academy,
for its action, a report recommending the appropriations which in the
opinion of the Council should be made for the various purposes of the
Academy.

i. If any office shall become vacant during the year, the vacancy shall
be filled by a new election, at the next stated meeting, or at a meeting
called for this purpose.

CHAPTER III.

Of Nominations of Officers,

1. At the stated meeting in March, the President shall appoint a
Nominating Committee of three Resident Fellows, one for each Class.

2. It shall be the duty of this Nominating Committee to prepare a list
of candidates for the offices of President, Vice-Presidents, Corresponding
Secretary, Recording Secretary, Treasurer, Librarian, Councillors, and
the Standing Committees which are chosen by ballot; and to cause this
list to be sent by mail to all the Resident Fellows of the Academy not
later than four weeks before the Annual Meeting.

3. Independent nominations for any office, signed by at least five
Resident Fellows, and received by the Recording Secretary not less than
ten days before the Annual Meeting, shall be inserted in the call for the
Annual Meeting, which shall then be issued not later than one week
before that meetincj.

4. The Recording Secretary shall prepare for use, in voting at the
Annual Meeting, a ballot containing the names of all persons nominated
fur office under the conditions given above.

5. When an office is to be filled at any other time than at the Annual
Meeting, the President shall appoint a Nominating Committee in accord-
ance with the provisions of Section 1, which shall announce its nomina-
tion in the manner prescribed in Section 2 at least two weeks before
the time of election. Independent nominations, signed by at least five
Resident Fellows and received by the Recording Secretary not later
than one week before the meeting for election, shall be inserted in the
call for that meeting.

570 STATUTES OF THE AMERICAX ACADEMY

CHAPTER IV.

Of the President.

1. It shall be the duty of the President, and, in his absence, of the
senior Vice-President present, or next officer in order as above enumer-
ated, to preside at the meetings of the Academy; to direct the Recording
Secretary to call special meetings ; and to execute or to see to the execu-
tion of the Statutes of the Academy. Length of continuous membership
in the Academy shall determine the seniority of the Vice-Presidents.

2. The President, or, in his absence, the next officer as above enumer-
ated, shall nominate members to serve on the different committees of the
Academy which are not chosen by ballot.

3. Any deed or writing to which the common seal is to be affixed
shall be signed and sealed by the President, when thereto authorized
by the Academy.

CHAPTER V.

Of Standing Committees.

1. At the Annual Meeting there shall be chosen the followinsf Stand-
ing Coramitlees, to serve for the year ensuing, viz. : —

2. The Committee on Finance to consist of three Fellows to be
chosen by ballot, who shall have, through the Treasurer, full control and
management of the funds and trusts of the Academy, with the power of
investing and of changing the investment of the same at their discretion.

3. The Rumford Committee, to consist of seven Fellows to be chosen
by ballot, who shall consider and report to the Academy on all applica-
tions and claims for the Rumford premium. They shall also report to
the Council in March of each year on all appropriations of the income of
the Rumford Fund needed for the coming year, and shall generally see
to the due and proper execution of the trust. All bills incurred on ac-
count of the Rumford Fund, within the limits of the appropriation made
by the Academy, shall be approved by the Chairman of the Rumford
Committee.

4. The C. M. Warren Committee, to consist of seven Fellows to be
chosen by ballot, who shall consider and report to the Council in March
of each year on all applications for appropriations from the income of the
C. M. Warreu Fund for the coming year, and shall generally see to the due

OF ARTS AND SCIENCES. 571

and proper execution of the trust. AH bills incurred on account of the
C. M. Warren Fund, within the limits of the appropriations made hy the
Academy, shall be approved by the Chairman of the C. M. Warren
Committee.

5. The Committee on Publication, to consist of three Fellows, one
from each class, to whom all communications submitted to the Acad-
emy for publication shall be referred, and to whom the printing of the
Proceedings and Memoirs shall be entrusted. This Committee shall re-
port to the Council in March of each year on the appropriations needed
for the coming year. All bills incurred on account of publications, within
the limits of the appropriations made by the Academy, shall be approved
by the Chairman of the Committee on Publication.

6. The Committee on the Library, to consist of the Librarian ex
officio, and three other Fellows, one from each class, who shall examine
the Library and make an annual report on its condition and management.
This Committee, through the Librarian, shall report to the Council in
March of each year, on the appropriations needed for the Library for the
coming year. All bills incurred on account of the Library, within the
limits of the appropriations made by the Academy, shall be approved by
the Librarian.

7. The President and Recording Secretary shall be a Committee on
the general expenditures of the Academy. This Committee shall report
to the Council in March of each year on the appropriations needed for
the general expenditures for the coming year, and either member of the
Committee may approve bills incurred on this account within the limits
of the appropriations made by the Academy.

8. An auditing Committee, to consist of two Fellows, for auditing the
accounts of the Treasurer, with power to employ an expert and to ap-
prove his bill.

9. In the absence of the Chairman of any Committee, bills may be
approved by a member of the Committee designated by the Chairman
for the purpose.

CHAPTER VI.

Of the Secretaries.

1. The Corresponding Secretary shall conduct the correspondence of
the Academy, recording or making an entry of all letters written in its
name, and preserving on file all letters which are received ; and at each

572 STATUTES OP THE AMERICAN ACADEMY

meetiug he shall present the letters which have been addressed to the
Academy since the last meeting. Under the direction of the Council,
he shall keep a list of the Resident Fellows, Associate Fellows, and
Foreign Honorary Members, arranged in their Classes and in Sections
in respect to the special sciences in which they are severally proficient;
and he shall act as secretary to the Council.

2. The Recording Secretary shall have charge of the Charter and
Statute-book, journals, and all literary papers belonging to the Academy.
He shall record the proceedings of the Academy at its meetings; and
after each meeting is duly opened, he shall read the record of the pre-
ceding meeting. He shall notify the meetings of the Academy, apprise
officers and committees of their election or appointment, and inform the
Treasurer of appropriations of money voted by the Academy. He shall
post up in the Hall a list of the persons nominated for election into the
Academy ; and when any individual is chosen, he shall insert in the
record the names of the Fellows by whom he was nominated.

3. The two Secretaries, with the Chairman of the Committee of
Publication, shall have autherity to publish such of the records of the
meetings of the Academy as may seem to them calculated to promote
its interests.

4. Every person taking any books, papers, or documents belonging to
the Academy and in the custody of the Recording Secretary, shall give a
receipt for the same to the Recording Secretary.

CHAPTER TIL

Op the Treasurer.

1. The Treasurer shall give such security for the trust reposed in
him as the Academy shall require.

2. He shall receive all moneys due or payable to the Academy and
all bequests and donations made to the Academy. 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 approval).
He shall sign all leases of real estate in the name of the Academy. All
transfers of stocks, bonds, and other securities belonging to the Academy
shall be made by the Treasurer with the written consent of one member
of the Committee of Finance. He shall keep an account of all receipts
and expenditures, shall submit his accounts annually to the Auditing

OP ARTS AND SCIENCES. 573

Committee, and shall report the same at the expiration of his term of
office or whenever called on so to do by the Academy or Council,

3. The Treasurer shall keep separate accounts of the income and
appropriation of the Rumford F'uud and of other special funds, and
report the same annually.

4. The Treasurer may appoint an Assistant Treasurer to perform his
duties, for whose acts, as such assistant, the Treasurer shall be responsi-
ble ; or the Treasurer may employ any Trust Company, doing business
iu Boston, as agent to perform his duties, the compensation of such As-
sistant Treasurer or agent to be paid from the funds of the Academy.

CHAPTER YIIL
Of the Librarian and Library.

1. It shall be the duty of the Librarian to take charge of the books,
to keep a correct catalogue of them, to provide for the delivery of books
from the Library, and to appoint such agents for these purposes as he
may think necessary. He shall make an annual report ou the condition
of the Library.

2. The Librarian, in conjunction with the Committee on the Library,
shall have authority to expend such sums as may be appropriated, either
from the General, Rumford, or other special Funds of the Academy, for
the purchase of books, periodicals, etc., and for defraying other necessary
expenses connected with the Library.

3. To all books in the Library procured from the income of the
Rumford Fund, or other special funds, the Librarian shall cause a stamp
or label to be affixed, expressing the fact that they were so procured.

4. Every person who takes a book from the Library shall give a
receipt for the same to the Librarian or his assistant.

.5. Every book shall be returned in good order, regard being had to
the necessary wear of the book with good usage. If any book shall
be lost or injured, the person to whom it stands charged shall replace
it by a new volume or set, if it belongs to a set, or pay the current
price of the volume or set to the Librarian ; and thereupon the remain-
der of the set, if the volume belonged to a set, shall be delivered to the
person so paying for the same.

6. All books shall be returned to the Library for examination at
least one week before the Annual Meeting.

574 STATUTES OF THE AMERICAN ACADEMY

7. The Librarian shall have custody of the Publications of the
Academy. With the advice and consent of the President, he may effect
exchanges with other associations.

CHAPTER IX.

Of jMeetings.

1. There shall be annually four stated meetings of the Academy;
namely, on tlie second Wednesday in May (the Annual Meeting), on
the second Wednesday in October, on the second Wednesday in January,
and on the second Wednesday in March. At these meetings, only, or at
meetings adjourned from these and regularly notified, or at special meet-
ings called for the purpose, shall appropriations of money be made, or al-
terations of the statutes or standing votes of the Academy be effected.

Special meetings shall be called by the Recording Secretary at the re-
quest of the President or of a Vice-President or of five Fellows. Notifi-
cations of the special meetings shall contain a statement of the purpose
for which the meeting is called.

2. Fifteen Resident Fellows shall constitute a quorum for the trans-
action of business at a stated or special meeting. Seven Fellows shall
be sufficient to constitute a meeting for scientific communications and
discussions.

3. The Recording Secretary shall notify the meetings of the Academy
to each Resident Fellow ; and he may cause the meetings to be adver-
tised, whenever he deems such further notice to be needful.

CHAPTER X.

Op the Election op Fellows and Honorary Members.

1. Elections shall be made by ballot, and only at stated meetings.

2. Candidates for election as Resident Fellows must be proposed by
two Resident Fellows of the section to which the proposal is made, in
a recommendation signed by them ; and this recommendation shall be
transmitted to the Corresponding Secretary, and by him referred to the
Council. No person recommended shall be reported by the Council as a

OF ARTS AND SCIENCES. 575

candidate for election, unless he shall have received the approval of at
least five members of the Council present at a meeting. All nominations
thus approved shall be read to the Academy at any meeting, and shall
then stand on the nomination list until the next stated meeting, and until
the balloting. No person shall be elected a Resident Fellow, unless he
shall have been resident in this Commonwealth one year next preceding
his election. If any person elected a Resident Fellow shall neglect for
one year to pay his admission fee, his election shall be void; and if any
Resident Fellow shall neglect to pay his annual assessments for two
years, provided that his attention shall have been called to this article,
he shall be deemed to have abandoned his Fellowship ; but it shall be in
the power of the Treasurer, with the consent of the Council, to dispense
(siib silentio) with the payment both of the admission fee and of the
assessments, whenever in any special instance he shall think it advisable
so to do.

3. The nomination and election of Associate Fellows shall take place
in the manner prescribed in reference to Resident Fellows.

4. The nomination and election of Foreign Honorary Members shall
take place in the manner prescribed for Resident Fellows, except that
the nomination papers shall be signed by at least seven members of the
Council before being presented to the Academy.

5. Three-fourths of the ballots cast must be affirmative, and the
number of affirmative ballots must amount to eleven to effect an elec-
tion of Fellows or Foreign Honorary Members.

6. If, in the opinion of a majority of the entire Council, any Fellow —
Resident or Associate — shall have rendered himself unworthy of a
place in the Academy, the Council shall recommend to the Academy
the termination of his Fellowship; and provided that a majority of two-
thirds of the Fellows at a stated meeting, consisting of not less than
fifty Fellows, shall adopt this recommendation, his name shall be stricken
off the roll of Fellows.

CHAPTER XL

Op Amendments of the Statutes.

1. All proposed alterations of the Statutes, or additions to them, shall
be referred to a committee, and, on their report at a subsequent stated
meeting or a special meeting called for the purpose, shall require for

576 STATUTES OF THE AMERICAN ACADEMY

enactment a majority of two-thirds of the members present, and at least
eighteen affirmative votes.

2. Standing votes may be passed, amended, or rescinded at a stated
meeting, or a special meeting called for the purpose by a majority of two-
thirds of the members present. They may be suspended by a unanimous
vote.

CHAPTER XIT.

Of Literary Performances.

1. The Academy will not express its judgment on literary or
scientific memoirs or performances submitted to it, or included in its
publications.

OF ARTS AND SCIENCES. 577

STANDING VOTES.

1. Communications of which notice has been given to the Secretary-
shall take precedence of those not so notified.

2. Associate Fellows, Foreign Honorary Members, and Resident
Fellows, who have paid all fees and dues chargeable to them, are en-
titled to receive one copy of each volume or article printed by the
Academy on application to the Librarian personally or by written order
within two years of the date of publication. Exceptions to this rule
may be made in special cases by vote of the Academy.

3. The Committee of Publication shall fix from time to time the price
at which the publications of the Academy may be sold. But members
may be supplied at half this price with volumes which they are not
entitled to receive free, and which are needed to complete their sets.

4. Two hundred extra copies of each paper accepted for publication
in the Memoirs or Proceedings of the Academy shall be placed at the
disposal of the author, free of charge.

5. Resident Fellows may borrow and have out from the Library six
volumes at any one time, and may retain the same for three months, and
no longer.

6. 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.

7. Works published in numbers, when unbound, shall not be
taken from the Hall of the Academy, except by special leave of the
Librarian.

8. Books, publications, or apparatus shall be procured from the
income of the Rumford Fund only on the certificate of the Rumford
Committee that they, in their opinion, will best facilitate and encourage
the making of discoveries and improvements which may mei'it the Rum-
ford Premium ; and the approval of a bill incurred for such purposes
by the Chairman shall be accepted by the Treasurer as proof that such
certificate has been given.

9. A meeting for receivinsr and discussing scientific communications
may be held on the second Wednesday of each mouth not appointed for
stated meetings, excepting July, August, and September.

VOL. XLIII. — 37

578 STATUTES OF THE AMERICAN ACADEMY.

RUMFORD PREMIUM.

In conformity with the terms of the gift of Benjamin, Count Rumford,
granting a certain fund to the American Academy of Arts and Sciences,
and with a decree of the Supreme Judicial Court for carrying into effect
tl)e general charitable intent and purpose of Count Rumford, as ex-
pressed in his letter of gift, the Academy is empowered to make from
the income of said 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 in heat, which shall have
been made and published 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 being always given to such discoveries
as shall, in the opinion of the Academy, tend most to promote the good
of mankind ; and to add to such medals, as a further premium for such
discovery and improvement, if the Academy see fit so to do, a sum of
money not exceeding three hundred dollars.

INDEX.

Academie des Sciences, Agriculture,
Arts et Belles-Lettres, of Aix,
Letter from, 533.

Acheson, E. G., receives Rumford
Medal, 534.

Activities of Animals, The Influence
of Light on the Daily, 533.

Air, The Absorption of the, for Light
of very Short Wave-Lengths, 528.

Air, Damping of the Quick Oscilla-
tions of a Twisted Fibre by the
Resistance of the, and by the
Torsional Forces, 533.

Aldrovandi, Anniversary of Death
of, 527.

Aleutian Islands, Volcanoes of, 532.

Amphioxus, The Sensory Reactions
of, 413, 533.

Animals, The Influence of Light on
the Daily Activities of, 533.

Arc and Spark, Difference in Wave-
Lengths of Titanium \X 3900 and
3913 in, 351, 528.

Arc Spectra, Some Effects of Heavy
Pressure on, 530.

Arsenic in Urine, The Determina-
tion of, 325.

Arsenic, The Quantitative Determina-
tion of, by the Gutzeit Method,
295.

Assessment, Annual, Amount of, 542.

Atomic Weight of Lead, A Revision
of, 363, 529.

Avery, A. H. See Kent, N. A., and
Avery, A. H.

Azores, Volcanoes of the, 529.

Baker, Sir Benjamin, Death of, 529.
Bartlett, H. H. See Robinson, B. L.,
and Bartlett, H. H.

Baxter, G. P., and Wilson, J. H., A
Revision of the Atomic Weight
of Lead. Preliminary Paper. —
The Analysis of Lead Chloride,
363-373, 529.

Bell, Louis, Note on Some Meteoro-
logical LTses of the Polariscope,
405-412, 531; The Physiological
Basis of Illumination, 75-96.

Black, O. F. See Sanger, C. R., and
Black, O. F.

Blasius, R., Death of, 528.

Bohuslav, J., Death of, 527.

Bowditch, C. P., Report of Treasurer,
535.

Briggs, L. B. R., elected Resident
Fellow, 530; accepts Fellowsliip,
532.

Cabot, Samuel, Biographical Notice
of, 547.

California Academy of Sciences,
Letter from, 527.

Campbell, L. L., The Variation of
the Thermomagnetic Effect in
Soft Iron with Strength of the
Magnetic Field and Temperature
Gradient, 532, 544.

Cathode Rays, Longitudinal Magnetic
Field and the, 397, 530.

Chemical Laboratory of Harvard
College, Contributions from, 295,
395, 363, 473, 519.

Chemistry, Thermodynamic, Outlines
of a New System of, 257.

Chloride, Manganous, Transition Tem-
perature of, 341.

Coil, An Induction, The Influence of
Hysteresis upon the Manner of
Establishment of a Steady Cur-

580

INDEX.

rent in the Primary Circuit of,
530.

Committees, Standing, appointed,
543; List of, 557.

Congress of Chemistry and Pliysics,
Letter from, 530.

Copeland, Manton. See Mark, E. L.,
and Copeland, Manton.

Council, Report of, 547; Financial
Report of, 541.

Cretan Chronology, 53 L

Cross, C. R., Report of the Rumford
Committee, 538.

Current, Steady, The Influence of
Hysteresis upon the Manner of
Estabhshment of a, in the Pri-
mary Circuit of an Induction
Coil, 530.

Damping of the Quick Oscillations of
a Twisted Fibre by the Resistance
of the Air and by the Torsional
Forces, 533.

Davenport, A. I., Letter from, 529.

Davenport, G. E., Death of, 529.

Davis, H. N., Notes on Superheated
Steam: I. Its Specific Heat; II.
Its Total Heat; III. Its Joule-
Thomson Effect, 533.

Da\'is, W. M., The Centenary Cele-
bration of the Geological Society
of London, 529.

Deam, C. C, New Plants from Gaute-
mala and Mexico, collected by,
48.

Demagnetizing Factors for Cylindri-
cal Iron Rods, 183.

Denny, Henry G., Death of, 528.

Derr, Louis, elected Resident Fellow,
534; accepts Fellowship, 535.

Dickey, W. P., On Delays before
avayvapia-fis in Greek Tragedy,
457-471, 533.

Differential Expressions, Invariants
of Linear, 534.

Distillation, Fractional, Concerning
the Use of Electrical Heating in,
519.

Dwight, Thomas, resigns Fellowship,
535.

Electrical Heating, concerning the
Use of, in Fractional Distilla-
tion, 519.

Electromagnet, Magnetic Behavior
of the Finely Divided Core of an,
while a Steady Current is being
established in the Exciting Coil,
97.

Farlow, W. G., The Linnaean Celebra-
tion at Upsala, Sweden, 529.
Fellows, Associate, deceased, —

Hall, Asaph, 533.

Russell, I. C, 533.

St. Gaudens, A., 533.

Seymour, T. D., 530.

Stedman, E. C, 533.

Young, C. A., 530.
Fellows, Associate, elected, —

Nef, J. U., 534.
Fellows, Associate, List of, 563.
Fellows, Resident, deceased, —

Davenport, G. E., 529.

Folsom, C. F., 528.

Gardiner, E. G., 528.

Hay, G., 535.

Strobel. E. H., 531.
Fellows, Resident, elected, —

Briggs, L. B. R., 530.

Derr, Louis, 534.

Johnson, D. W., 544.

Norris, J. F., 528.

Walker, W. H., 528.

Warren. C. H., 544.
Fellows, Resident, List of, 559.
Fernald, M. L., Diagnoses of New

Spermatophytes from Mexico,

61-68.
First Chemical Institute of the Royal

Friedrich-Wilhelm University of

Berlin, Contributions from, 341.
Fischer, Emil, elected Foreign Hon-
orary Members, 544.
Fluorite, Studies on, 1 ; The Kathodo-

Luminescence of, 1.
Folsom, C. F., Death of, 528.
Foreign Honorary Members, de-
ceased, —

Baker, Sir Benjamin, 529.

Kelvin, Lord, 530.

Vogel, H. C, 528.

INDEX.

581

Foreign Honorary Members, elected, —

Fischer, Emil, 544.
Foreign Honorary Members, List of,

565.
Fourir, Joseph, Death of, 527.
Fractional Distillation, Concerning the

Use of Electrical Heating in, 519.

Gardiner, E. G., Death of, 528.

Gebauer, Johann, Death of, 527.

General Fund, 535, 541; Appropria-
tions from the Income of, 534,
542.

Geological Society of London, Cen-
tenary Celebration of the, 529;
Letter from, 532.

Gesellschaft von Freunden der Natur-
wissenschaften, Anniversary of,
533.

Goodwin, H. M., and Kalmus, H. T.,
The Latent Heat of Fusion and
the Specific Heat in the Solid
and Liquid State of Salts melt-
ing Below 600° C, 544.

Goodwin, W. W., Cretan Chronology,
531; Letter from, 532.

Gray Herbarium of Harvard Uni-
versity, Contributions from, 17.

Greek Tragedy, On Delays before
dvayvapiaeis (Recognitions) in,
457, 533.

Greenman, J. M., New species of
Senecio and Schoenocaulon from
Me.xico, 17-21.

Guatemala, New Plants from, 48.

Gutzeit Method, The Quantitative
Determination of Arsenic by the,
295.

Hall, Asaph, Death of, 533.

Harvard College. See Harvard Uni-
versity.

Harvard University. See Chemical
Laboratory, Gray Herbarium,
Jefferson Physical Laboratory,
and Zoological Laboratory.

Hay, G., Death of, 535.

Heat, Latent, of Fusion, and the
Specific Heat in the Solid and
Liquid State of Salts melting
Below 600° C, 544.

Heat, Specific, in the Solid and Liquid

State of Salts melting Below

600° C, 544.
Heating, Electrical, Concerning the

Use of, in Fractional Distilla-
tion, 519.
Heats of Liquids, Specific, A New

Method for the Determination

of the, 473, 544.
Hellman, G., Announcement from,

528.
Hepites, St. C, Letter from, 527.
Homer, Pisistratus and Ids Edition

of, 489, 544.
Hough, Theodore, resigns Fellow-

sliip, 535.
House Committee, Report of, 531,

540.
Humphreys, W. J., Some Effects of

Heavy Pressure on Arc Spectra,

530.
Hysteresis, The Influence of, upon

the Manner of Establishment of

a Steady Current in the Primary

Circuit of an Induction Coil,

530.

Illumination, The Physiological Basis
of, 75.

Intensity of Sound, A Simple Method
of Measuring the, 375, 531.

International Congress for the History
of Religions, Letter from, 530.

International Congress for the Study
of the Polar Regions, Report of,
527.

International Congress of American-
ists, Letter from, 529.

International Congress of Botany,
Circulars from, 535.

International Congress of Mathe-
maticians, Letter from, 531.

International Congress of Orientalists,
Invitation from, 527.

Invariants of Linear Differential Ex-
pressions, 534.

Iron Rods, Cylindrical, Demagnetiz-
ing Factors for, 183.

Iron, Soft, The Variation of the Ther-
momagnetic Effect in, with
Strength of the Magnetic Field

582

INDEX.

and Temperature Gradient, 532,
544.
Irwin, Frank, The Invariants of Linear
Differential Expressions, 534.

Jackson, Charles Loring, Biographical
Notice of Samuel Cabot, 547.

Jagger, T. A., Volcanoes of the Aleu-
tian Islands, 532.

Jefferson Physical Laboratory, Con-
tributions from, 1, 97, 183, 375,
397, 5n.

Johnson, D. W., elected Resident
Fellow, 544.

Kalmus, H. T. See Goodwin, H. M.,
and Kalmus, H. T.

Kathodo-Luminescence of Flourite, 1.

Kelvin, Lord, Death of, 530.

Kent, N. A., and Avery, A. H., Differ-
ence in Wave-Lengths of Tita-
nium XX 3900 and 3913 in Arc
and Spark, 351-361, 528.

Ivinnicutt, L. P., Report of C. M.
Warren Committee, 539.

Laboulbeniaceae, Contributions
toward a Monograph of, 534.

Lanman, C. R., appointed Dele-
gate, 530.

Lead, A Revision of the Atomic
Weight of, 363, 529.

Lead Chloride, The Analysis of, 363,
529.

Lewis, G. N., Outlines of a New Sys-
tem of Thermodynamic Chemis-
try, 257-293.

Librarian, Report of, 537.

Library, Appropriations for, 542.

Light, The Influence of, on the Daily
Activities of Animals, 533.

Light of very Short Wave-Lengths,
The Absorption of the Air for,
528.

Linear Differential Expressions, In-
variants of, 534.

Linnaean Celebration at L^psala,
Sweden, 529.

Liquids, A New Method for the De-
termination of the Specific Heats
of, 473, 544.

Luminescence, Kathode-, of Fluorite,
1.

Lyman, Theodore, The Absorption
of the Air for Light of very Short
Wave-Lengths, 528.

Lyon, D. G., The Most Recent Ex-
ploration in Palestine, 529.

Magnetic Behavior of the Finely Di-
vided Core of an Electromagnet
while a Steady Current is being
established in the Exciting Coil,
97.

Magnetic Field and Temperature
Gradient, The Variation of the
Thermomagnetic Effect in Soft
Iron with Strength of the, 532,
544.

Magnetic Field, Longitudinal, and the
Cathode Rays, 397, 530.

Manganous Chloride, Transition Tem-
perature of, 341.

Mark, E. L., Report of the Council,
547; Report of the Publication
Committee. See Zoological Lab-
oratory of the Museum of Com-
parative Zoology at Harvard
College, Contributions from.

Mark, E. L., and Copeland, Manton,
Maturation Stages in the Sper-
matogenesis of Vespa maculata
Linn., 69-74.

Massachusetts Institute of Tech-
nology. See Research Laboratory
of Physical Chemistry.

Mathews, J. H. See Richards, T. W.,
and Mathews, J. H.

Maturation Stages in the Spermato-
genesis of Vespa maculata Linn.,
69.

McDonald, Arthur, Letter from, 527.

Measurements, Absolute, of Sound,
544.

Measurements of the Internal Tem-
perature Gradient in Common
Materials, 532.

Meteorological Uses of the Polari-
scope, Note on Some, 405, 531.

Mexico, Diagnoses of New Sper-
matophytes from, 61.

Mexico, New and Otherwise Note-

INDEX.

583

worthy Spermatophj'tes, Chiefly

from, 21.
Mexico, New Plants from, 48.
Mexico, New species of Senecio and

Schoenocaulon from, 17.
Michael, Artliur, resigns Fellowsliip,

535.
Moore, G. F., appointed Delegate,

530. 532.
Morse H. W., Studies on Fluorite:

(i /.) The Kathodo-Lumines-

cence of Fluorite, 1-16.
Museo Nacional, Mexico, Letter from,

531.
Museum of Comparative Zoology at

Harvard College. See Zoological

Laboratory.

Nef, J. U., elected Associate Fellow,

534.
Newhall, S. H., Pisistratus and his

Edition of Homer, 489-510, 544.
Norris, J. F., elected Resident Fellow,

528.

Officers, elected, 542; List of, 557.

Oscillations, The Quick, of a Twisted
Fibre, Damping of, by the Re-
sistance of the Air and by the
Torsional Forces, 533.

Overbergh, C. van, Letter from, 527.

Palestine, The Most Recent Explora-
tion in, 529.

Parker, G. H., The Influence of Light
on the Daily Activities of Ani-
mals, 533; The Sensory Reac-
tions of Amphioxus, 413—455,
533.

Peirce, B. O., The Damping of the
Quick Oscillations of a Twisted
Fibre by the Resistance of the Air
and by the Torsional Forces, 533 ;
The Influence of Hysteresis upon
the Manner of Establishment of
a Steady Current in the Primary
Circuit of an Induction Coil, 530;
On the Determination of the
Magnetic Behavior of the Finely
Divided Core of an Electromagnet

while a Steady Current is being
established in the Exciting Coil,
97-182.

PhysikaHsche Verein, Frankfort, Let-
ter from, 530.

Physiological Basis of Illumination,
The, 75.

Pickering, W. H., The Volcanoes of
the Azores, 529.

Pierce, G. W., accepts Fellowship,
527; A Simple Method of
Measuring the Intensity of Sound,
375-395, 531.

Pisistratus and liis Edition of Homer,
489, 544.

Plants, New, from Guatemala and
Mexico, 48.

Polariscope, Note on Some Meteoro-
logical L^ses of the, 405, 531.

Positive Rays, 511, 544.

Pressure, Hea\^, Some Effects of,
on Arc Spectra, 530.

Publication, Appropriation for, 534,
542.

Publication Committee, 543; Report
of, 540.

Pubhcation Fund, 536.

Rays, Positive, 511, 544.

Reactions, The Sensorj', of Amphi-
oxus, 413, 533.

Recognitions, On Delaj's before, in
Greek Tragedy, 457, 533.

Records of Meetings, 527.

Research Laboratory of Physical
Chemistry of the Massachusetts
Institute of Technology, Con-
tributions from, 257.

Richards, T. W., and Mathews, J. H.,
Concerning the Use of Electrical
Heating in Fractional Distilla-
tion, 519-524.

Richards, T. W., and Rowe. A. W.,
A New Method for the Determi-
nation of the Specific Heats of
Liquids, 47.3-488. 544.

Richards, T. W., and Wrede, Franz,
The Transition Temperature of
Manganous Chloride : A New
Fixed Point in Tiiermometry,
341-350.

584

INDEX.

Robinson, B. L., New or Otherwise
Noteworthy Spermatopliytes,
Chiefly from Mexico, 21-48.

Robinson, B. L., and Bartlett, H. H.,
New Plants from Guatemala and
Mexico collected Chiefly by C. C.
Deam, 48-60.

Rods, Cylindrical Iron, Demagnetiz-
ing Factors for, 183.

Rotch, A. L., Report of Librarian,
537.

Rowe, A. W. See Richards, T. W.,
and Rowe, A. W.

Royal Friedrich-Wilhelm University
of Berlin. See First Chemical
Institute of the Royal Friedrich-
Wilhelm University of Berlin.

Rumford Committee, Report of, 538;
Reports of Progress to, 538.

Rumford Fund, 535; Appropriations
from the Income of, 534, 542;
Papers published by Aid of, 1, 75,
341, .351, 405, 473, 511.

Rumford Premium, 578; Presenta-
tion of. 534.

Russell, I. C, Death of, 533.

St. Gaudens, A.. Death of, 533.

St. Murat, I., Letter from, 527.

Salts Melting below 600° C, The
Latent Heat of Fusion and the
Specific Heat in the Solid and
Liquid State of, 544.

Sanger, C. R., and Black, O. F., The
Quantitative Determination of
Arsenic by the Gutzeit Method,
295-324; The Determination of
Arsenic in Urine, 325-340.

Schoenocaulon from Mexico, New-
Species of, 17.

Senecio and Schoenocaulon from
Mexico, New Species of, 17.

Sensory Reactions of Amphioxus,
The, 413, 533.

Seymour, T. D., Death of, 530.

Shuddemagen, C. L. B., The Demag-
netizing Factors for Cylindrical
Iron Rods, 183-256.

Solutions, A New Method of Deter-
mining the Specific Heats of,
473, 544.

Sound, Absolute Measurements of,
544.

Sound, A Simple Method of Measur-
ing the Intensity of, 375, 531.

Specific Heats of Solutions, A New
Method of Determining the, 473,
544.

Spectra, Arc, Some Effects of Heavy
Pressure on, 530.

Spermatogenesis of Vespa maculata
Linn., Maturation Stages in the,
69.

Spermatopliytes, Chiefly from Mexico,
New and Otherwise Noteworthy,
21.

Spermatopliytes from Mexico, Diag-
noses of New, 61.

Standing Committees, appointed, 543;
List of, 557.

Standing Votes, 567.

Statutes, 567.

Steam, Notes on Superheated, 533.

Stedman, E. C, Death of, 533.

Temperature, Transition, of Manga-
nous Chloride, 341.

Temperature Gradient, The Internal,
in Common Materials, Measure-
ments of, 532.

Temperature Gradient, The Variation
of the Thermomagnetic Effect
in Soft Iron with Strength of the
Magnetic Field and, 532, 544.

Thaxter, Roland, Contributions
toward a Monograph of the La-
boulbeniaceae. Part II., 534.

Thermodynamic Chemistry, Outlines
of a New System of, 257.

Thermomagnetic Effect in Soft Iron,
The Variation of the, with
Strength of the Magnetic Field
and Temperature Gradient, 532,
544.

Thermometry, A New Fixed Point
in, 341.

Thwing, C. B., Measurements of the
Internal Temperature Gradient
in Common Materials, 532.

Titanium XX 3900 and 3913 in Arc
and Spark, Difference in Wave-
Lengths of, 351, 528.

INDEX.

585

Torsional Forces, The Damping of the
Quick Oscillations of a Twisted
Fibre by the Resistance of the
Air and by the, 533.

Transition Temperature of Manga-
nous Chloride; A New Fixed
Point in Thermometry, 341.

Treasurer, Report of, 535.

Trowbridge, John, Longitudinal Mag-
netic Field and the Cathode Rays,
397-404, 530 ; Positive Rays,
511-517, 544.

Urine, The Determination of Arsenic
in, 325.

Upsala, Sweden, The Linnaean Cele-
bration at, 529.

Vespa maculata Linn., Maturation
Stages in the Spermatogenesis
of. 69.

Vogel, H. C, Death of. 528.

Volcanoes of the Aleutian Islands,
532.

Volcanoes of the Azores, 529.

Walker, W. H., elected Resident
Fellow, 528; accepts Fellow-
ship, 528.

Warren, C. H., elected Resident
Fellow, 544.

Warren (C. M.) Committee, Report
of, 539.

Warren (C. M.) Fund, 536; Appro-
priation from the Income of,
542.

Warren, Minton, Death of, 529.

Wave-Lengths, Diiference in, of
Titanium X\ 3900 and 3913 in
Arc and Spark, 351, 528.

Wave-Lengths, very Short, The Ab-
sorption of the Air for Light of,
528.

Webster, A. G., Absolute Measure-
ments of Sound, 544.

Wilson, J. H. See Baxter, G. P., and
Wilson, J. H.

Wrede, Franz. See Richards, T. W.,
and Wrede, Franz.

Young, C. A., Death of, 530.

Zoological Laboratory of the Museum
of Comparative Zoology at Har-
vard College, E. L. Mark,
Director, Contributions from, 69,
413.

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