G. A. KRAMERS and H. HOLST. The Structure of the Atom and Bohr’s Theory. Series: “Nature and Culture,” book 20, translated from the English, edited by S. I. Vavilov. Gosizdat, 1926. Pp. VIII + 156. Price 1 ruble 50 kopecks.

This small book, written with the participation of Kramers—Bohr’s closest collaborator—represents the best popular exposition of the modern theory of the atom. The first four chapters, probably belonging to Holst, provide a certain introduction, reproducing the basic data on atoms, ions, and electrons, as well as information from the fields of spectral analysis and radioactivity. In them, the average student of a physics-and-mathematics faculty will probably find nothing new, but this summary will in any case be very useful to most readers. The last three chapters (Bohr’s theory of the hydrogen spectrum. Various applications of Bohr’s theory. The structure of the atom and the chemical properties of the elements) constitute the central part of the book. Here, in a very readable form, an exposition is given of the physical foundations of Bohr’s theory, with many important experimental data reported along the way. The exposition is conducted in the spirit of Bohr’s later works, where the correspondence principle is brought to the fore. Unlike most popular booklets, the authors do not try to depict only the triumphs of the theory, but very insistently emphasize its imperfections and unresolved difficulties. This “objectivism,” also so characteristic of Bohr, favorably distinguishes the little book.

The translation has been done carefully. Only on p. 151 is silver called “bivalent” instead of “monovalent.” There are almost no misprints, unless one counts the accidentally preserved English name “sodium,” instead of “natrium,” in the diagram table; this, of course, is purely a technical misprint, all the more so since “natrium” appears everywhere in the text. The rendering of foreign names suffers from the same shortcomings as in Russian translations generally. In particular, on p. 113 Kramers’s name is supplied with erroneous initials (N. A. Kramers), as though deliberately so that readers should not identify him with the author of the book, who is called G. A. Kramers. In reality this is one and the same person. The book is neatly and well produced; the only very annoying thing is that it is printed on excessively thin paper.

G. Landsberg.