BIBLIOGRAPHY*

R. A. MILLIKAN — Electrons (+ and −) protons, photons, neutrons and cosmic rays, L. Cambr. Univ. P. 1933, X, 492 p. 98 Fig. Sh. 15.

R. A. MILLIKAN — Electrons (+ and −), protons, photons, neutrons and cosmic rays.

The book under review is the third, revised edition of the author’s well-known book The Electron. Since the first two editions appeared in 1917 and 1924, i.e. before the decisive turning point in modern physics, the new edition required the addition of new sections occupying half the space in the book.

To a considerable extent the content of the first eleven chapters, devoted to experimental work—chiefly Millikan’s own—on the determination of the elementary charge corresponds to the old material. These works are widely known and have already become classics. Nevertheless, it will be of great benefit even to a specialist to review once again the experimental material and theoretical justification relating to one of the central problems of physics—the question of the nature of the electron.

Of much greater interest is the second part of the book, devoted to questions that have become current during the last decade. The second part begins with an exposition of the basic ideas and propositions of the wave theory of matter. Here one immediately senses that Millikan is not a theorist but an experimenter. Having said a few words about de Broglie’s ideas, the author, without wasting time, turns to a demonstration of experiments with the diffraction of an electron beam and to a comparison of these experiments with the diffraction of X-rays. The photographs presented speak more to the experimenter’s heart than the heap of mathematical formulae with which the pages of books on the wave theory of matter are nowadays strewn.

The next chapter is devoted to electron spin. In this chapter too Millikan the experimenter remains true to himself. We would look in vain for any mention of Dirac’s name and his works, which completely solved the problem of the spin of the electron. Instead of an exposition of the theory, Millikan gives a broad picture of the state of spectroscopy at the time when it became clear that it was impossible to explain spectra while remaining at the standpoint of the point electron. In our time even educated young physicists already have a poor idea of how the deciphering of spectra proceeded step by step, and for this reason Millikan’s account is extremely valuable.

The subsequent chapters set forth experiments that led to the discovery of cosmic rays, positrons, and neutrons. As is known, the existence of the positron had been predicted by Dirac’s theory long before its discovery. But this circumstance is of little interest to Millikan, and he does not mention it. What is essential for him are the photographs in the Wilson chamber on which the traces of positrons are visible. The book presents all the interesting photographs of the Wilson chamber, and the reader becomes accustomed to the new particles, whose existence was until quite recently considered impossible.

The penultimate chapter is devoted to the neutron, the splitting of the atomic nucleus, and artificial radioactivity. It contains a vast body of experimental material that introduces the reader to the most current problems of modern physics. It is characteristic that throughout the book there are almost no mathematical formulae. It is known that modern physicists often abuse the mathematical apparatus necessary for research, but not always appropriate in exposition.

The book under review gives a vivid example of how, while remaining at an absolutely scientific level, it is possible to present the results of the newest investigations in physics in the style of Faraday’s classical researches.

And Millikan’s book will be of great benefit to many contemporary physicists who have lost this skill.

Yu. B. Rumer

* Based on materials of the Critical-Bibliographical Institute.