The Decline of Mechanism in Modern Physics by A. D'AbroReview by: I Bernard CohenIsis, Vol. 32, No. 2 (1940), pp. 380-382Published by: The University of Chicago Press on behalf of The History of Science SocietyStable URL: http://www.jstor.org/stable/226270 .

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380 ISIS, XXXII, 2

Like all the other natural sciences, Physics advances by two distinct roads. On the one hand it operates empirically, and thus is enabled to discover and analyse a growing number of phenomena-in this instance, of physical facts; on the other hand it also operates by theory, which allows it to collect and assemble the known facts in one consistent system, and to predict new ones for the guidance of experimental research. In this way the joint efforts of experiment and theory, at any given time, provide the body of knowledge which is the sum total of the Physics of the day.

After reading the book, one is struck forcibly by two things. One, that contemporary physics is by no means simple, that one of the jobs tor each physicist is to order the subject in so far as he is able, at least for himself. For it is only by resolving some of the apparent contra- dictions that seem to have arisen in the last generation, that he is able to see that his science represents progress in its development rather than chaos. Two, that DE BROGLIE, like most scientists of the first rank, has a deep feeling for the human side of science. This is made clearest in the last part of the book, in an address to the students of the Lvcee Pasteur, with which we end this review. Although written for youth, the message contains much of value for the world at large in these perilous times. It ends with the statement :

Let me conclude by hoping that you will preserve throughout your life, as a precious fruit of your work here, the zeal to pursue all that is loftiest in the intellectual, the esthetic or the moral sphere. For without such zeal a civilization, however great the perfection of its material aspects, would soon be no better than a complicated form of barbarism.

Cambridge, MUass. I BERNARD COHEN.

A. D'Abro.-The decline of mechanism in modern physics. x+982 p. New York, Van Nostrand, 1939. ($IO.OO).

Starting from the thesis that the quantum theory, like the theorv of relativity, is a mere refinement of classical theories, so that an under- standing of it requires an historical background, this book presents a semi-popular exposition of the growth of the new ideas in physics. One of the virtues of this presentation is the introduction of the mathematical development, without which the new theories could never have been constructed. Thus the author introduces chapters on such subjects as HAMILTON'S equations and the problem of three bodies, the theory of functions and groups, the theorv of matrices, etc. Due to this triple combination-the historical, the philosophical, and the mathematical- plus the large amount of experimental data and information, the book becomes in many ways an ideal one from which to learn about modem physics.

By mechanistic theories the author means those in which are considered

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REVIEWS 38I

only physical magnitudes which are characteristic of classical mechanics; e.g. force, momentum, mass, strains, etc. All other theories are con- sidered to be non-mechanistic. Mechanistic theories may be exemplified by atomistic theories like the kinetic theory of gases (dealing with discrete media) or the theory of elasticity (dealing with continuous media). Non- mechanistic theories comprise field theories and " phenomenological " theories such as thermodvnamics. From this point of view, the trend of modem physics is decidedly away from mechanism; in fact, Mr.D'ABRo shows that such theories as relativity, the BoHR theory of the atom, and even the classical theory of electricity and magnetism, may be con- sidered non-mechanistic.

The book is divided into three parts. Part I (I I6 p.) treats of the historical origins of physics; the differences between mechanistic, field, and phenomenological, theories; and such general problems as causality, the assumptions in science, and the conceptual changes in physical theories. Part II (323 p.) contains expository chapters on the mathematics needed for physical theory, and an extremely able summary of the physical theories of the classical period. Part III (533 p.) deals with contemporary physics, presenting the various theories from relativity and PLANCK'S original quantum theory to the work of such physicists as BOHR, DE BROGLIE, HEISENBERG, SCHR6DINGER, BomR, and DIRAC. This part of the book, larger than the first two parts together, ends with a discussion of the controversies on quantum mechanics and of the status of causality in the quantum theory.

This book has occasional faults. Mr D'ABRo apparently has a great dislike for philosophers as a class, and so occasionally makes very unreliable statements about philosophical problems and about the work of the Greek scientists or DESCARTES, to mention but two examples, whom he would simply dismiss as philosophers. Then too, much of the early historical material is inaccurate. Like many writers in our time, Mr. D'ABRO is very careful of his historical data when they refer to the last seventy-five years or so, but for anvthing earlier than that period he does not seem to care too much for reliability. This unreliability takes two distinct forms. One of these is the simple error of fact such as (p. 276)-" ... the phenomenon of double refraction, discovered by HUYGENS..." The phenomenon was discovered, or at least described for the first time, by ERASMUS BARTHOLIN; and HUYGENS in his Traiti de la lumiere says so. Of course, it matters little for quantum mechanics whether the phenomenon of double refraction was discovered by HUYGENS or by x or Y or z.

Of a more serious nature, perhaps, are the many loose or general statements which tend to be very misleading, such as (p. I3)-" The

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382 ISIS, XXXII, 2

eighteenth century... did not contribute any physical facts of importance." Think of electricity, aberrations or photometry ! Other statements of this kind would attribute to NEWrON the position of being the first to "discover and apply " the methods of theoretical physics.

Yet, despite such faults, this book is a valuable one-indispensable to anyone interested in the philosophy of physics or in the development of contemporary physics. If it taught nothing else than the simple lesson that we can no longer think of physics in terms of the old familiar models -a great temptation, since the language of much of classical physics and quantum physics is the same Mr. D'ABRO's book would represent a significant contribution indeed.

Cambridge, Mass. I BERNARD COHEN.

Dayton C. Miller.-Sparks, lightning, cosmic rays. An anecdotal history of electricity. XVII+192 p. New York, The Macmillan Co., 1939.

($2.50). This book originated in the dedicatory meetings held by the Franklin

Institute in 1938 in honor of BENJAMIN FRANKLIN. Actually, these are the Christmas Week Lectures for Young People of December, 1937. The main concern is, therefore, with the scientific investigations of FRANKLIN, which are largely related to the nature of electricity. Although the book is called an " anecdotal " history, it is not a collection of anecdotes in the sense of, say, MORITZ'S Memorabilia mathematica, but rather a genuine history of electrical experiment and discovery with notices of the scientists who in each case were responsible.

The first chapter-Sparks-sets forth the history of electricity " from its first recognition by the Greek philosophers to the middle of the eighteenth century." Although this chapter contains 53 pages, not so much as a single whole page is devoted to the subject before the time of GILBERT! For the rest, the chapter is extremely good. There are many illustrations of early electrostatic machines-and also modern ones for the purposes of explication and comparison. It seems particularly useful, too, that when Prof. MILLER comes, in turn, to each subject, he introduces not only the pre-FRANKLIN materials, but continues the idea further so that there is established a close continuity in the reader's mind between the earliest and most modern aspects of the subject. Thus, the section on the Leyden jar begins with VON KLEIST and vAN MUSSCHEN-

BROEK but develops the idea of " capacity " through CAVENDISH and FARADAY.

The second chapter-Lightning-describes the experiments of FRANK-

LIN, culminating in the famous kite experiment. In this section, Prof. MILLER strays somewhat from his main subject of electricity, and

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