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Important Scientific Books

The Grand Strategy of Evolution

By WILLIAM PATTEN
PROFESSOR OF BIOLOGY, DARTMOUTH COLLEGE

66

One of the most significant and original contributions to general theoretical biology that has appeared in years.”—Raymond Pearl, Professor of Biometry, Johns Hopkins University.

“ A book which it is an inspiration to read and a duty to recommend. It is the sort of book which carries mot the burr or the shell or the boxes or burlaps in which nature or man has packed the makings of knowledge and wisdom; but really in shape to be converted into immediate understanding. It is the kind of book which is a liberal education in itself.

No book in the entire post-Darwinian literature equals this volume as a guide to the congruity between the constructive processes of nature and the moral economics of 'the psychic factors.' It would be difficult to overstate the service which Professor Patten has performed in teaching the lesson that the problem of life, personal and public, is not to be solved by 'fighting the cosmic process,' but by 'accepting nature's constructive rightness as the ethical standard, and by adopting her constructive methods as the moral code.'”—Albion W. Small, Professor of Sociology, University of Chicago, in “ The American Journal of Sociology."

LARGE 8VO CLOTH, $5.00 NET

SANITARY ENTOMOLOGY

Illus. $10.00 net Edited by W. Dwight Pierce, M.D., Con

sulting Entomologist, Formerly of U. S. Bureau

of Entomology. A volume by ten expert entomologists on how insects cause or carry disease, how these insects live, and how to prevent disease by controlling the insects. THE UNITY OF THE ORGANISM

Illus. 2 vols. $5.00 net By William E. Ritter, Ph.D., Director of the

Scripps Institute for Biological Research, Uni

versity of California. The author reviews the history and doctrine of "elementalism," and opposes to it his doctrine of the unity of the living being BIOLOGY IN AMERICA Illus. $10.00 net By R. T. Young

A comprehensive consideration of the progress of biology in this country.

LIFE AND DEATH, HEREDITY AND

EVOLUTION IN UNICELLULAR OR-
GANISMS

Illus. $2.50 net
By H. S. Jennings, Professor of Zoology in the

Johns Hopkins University. One-celled organisms presented as an opportunity for solving some of the deeper problems of life. CHEMISTRY AND CIVILIZATION

Illus, $2.50 net By Allerton S. Cushman, A.M., Ph.D., Di

rector, Institute of Industrial Research, Wash

ington, D. C. A general view of all that chemistry has done, is doing, and hopes to accomplish for mankind in the future. MARS

Illus. $2.50 net By William H. Pickering, Harvard College Ob

servatory, Jamaica. The results of a lifelong study of the planet Mars—its snows,

its

seas, its marshes, and its canals.

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Repeated object lessons have demonstrated that nearly all progress in science has resulted in important advances in industry

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G-E Research Laboratory

Schenectady, N. Y.

Among the many products developed by the General
Electric Company's research laboratories the following
are of special interest to manufacturers:

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For further information address Supply Department, Schenectady Office,

General Electric

Company

General Office
Schenectady, N.Y.

Sales Offices in all large cities

35B-48

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Argon.

Interference Refractometer, Rayleigh-Hilger for Gases. This instrument is designed for work on the refractometry of gases, of which the refractive indices differ so little from unity that a very high degree of sensitivity is required in any refractometer to be used with them. Some idea will be obtained as to the sensitivity of the instrument when it is stated that it is possible by means of it to detect the presence of .01% of hydrogen in air, a quantity which causes a change of refractive index of only .000,000,015. The principle underlying the design of the instrument is that of the interference bands formed by two adjacent slits in collimated light, and observed by means of a telescope. The arrangement is, in fact, a diffraction grating with only two openings. The means whereby the system of bands thus obtained is made to indicate the refractive index of a substance is provided by the sideway shift of the whole band system when any change is made in the optical path of one of the interfering beams; part of the optical path being, of course, the substance under examination.

Quantities of Gases in Air Detectable by Rayleigh Interference Refractometer
Minimum observable shift assumed to be 1/40 band.
Hydrogen.

.01%
Helium.
.006% Chlorine..

.003% Nitrogen.

Sulphur Dioxide
.034% Carbon Monoxide

.03% Nitric Oxide. .0065% Water..

.04% Carbon Dioxide.

.0095% .15% Hydrogen Sulphide. .0045% Ammonia.

.017% Bibliography of Rayleigh Interference Refractometer, Original Arrangement and Laboratory Type Lord Rayleigh.

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Proc. Roy. Soc. (A) vol. 59, p. 201 (1896).
Proc. Roy. Soc. (A) vol. 64, p. 97 (1898).

Proc. Roy. Soc. (A) vol. 62, p. 225 (1897). Ramsay & Travers ..

Proc. Roy. Soc. (A) vol. 64, p. 190 (1899).

Proc. Roy. Soc. (A) col. 67, p. 331 (1900). Travers...

Study of Gases," Macmillan, 1901. s

Technologic Papers of the Bureau of Standards. J. D. Edwards.

No. 113

Jour. Amer. Chem. Soc. 39, p. 2382, 1917. Adams.

Jour. Amer. Chem. Soc. 39, p. 1181, 1916. 45940. Refractometer, Interference, Rayleigh-Hilger, for gases, with double gas tube 100 cm. long, but without illuminating lamp.

..654.75 NOTE-By the substitution of a Liquid Cell in place of the Gas Tube, the Rayleigh Interference Refractometer can be converted into an instrument for the investigation of liquids, or can be furnished for this purpose without the Gas Tube. Prices on application.

Prices subject to change without notice

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ARTHUR H. THOMAS COMPANY

WHOLESALE, RETAIL AND EXPORT MERCHANTS LABORATORY APPARATUS AND REAGENTS WEST WASHINGTON SQUARE

PHILADELPHIA, U. S. A.

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THE ELECTRON THEORY OF

MAGNETISM1 EVER since the time of Faraday it has been known that all varieties of matter can be grouped in three classes on the basis of magnetic behavior, ferromagnetic, paramagnetic and diamagnetic.

It would be far too much to claim that the electron theory has as yet given anything like a complete account of the phenomena witnessed in connection with these three types of magnetism; but it is the only theory proposed which has been in any way satisfactory and which appears to hold out any hope for the future.

In accordance with the plans of this symposium I shall restrict myself to a consideration of the more general aspects of the theory and its simplest applications. For the sake of logical completeness I shall have to refer to many matters well known. The extension of the theory and its application to more special and complex cases, in so far as they can be handled on this occasion, will be treated by my colleagues.

The first electrical theory of ferromagnetism was proposed by Ampère just about one hundred years ago. On the basis of his own experiments on the behavior of electric circuits and magnets, and on the assumption, already justified, that magnetism is a molecular and not a molar phenomenon, he concluded that the molecule of iron is the seat of a permanent electrical whirl and thus essentially a permanent magnet with its axis perpendicular to the whirl. When the iron is fully magnetized, all the whirls are oriented alike, and

1 A paper read as a part of the symposium on recent progress in magnetism held at the joint meeting of the American Association for the Advancement of Science, Section B, and the American Physical Society, December, 1920. Revised, January,

1921.

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