Siegfried Valentiner. Die Grundlagen der Quantentheorie. 2nd enlarged ed. Braunschweig, 1919 (Sammlung Vieweg, issue 15).

Recently the question of the theory of quanta, or atoms of energy, which initially arose on the basis of the theory of radiation, has begun to encompass ever broader areas of physics, finding important applications in the theory of specific heat (Nernst), in the theory of the photoelectric effect (Einstein, Sommerfeld), and finally in the theory of the structure of the atom, where quantum theory has proved to be an indispensable component. Meanwhile, no handbook devoted to this branch of physics had existed until now, and Valentiner, by publishing a booklet of 92 pages that treats this question in an elementary way, has with great success filled a substantial gap in the literature.

The exposition of the theory begins with a systematic substantiation of the theory of radiation; then Planck’s law and its experimental verification, Einstein’s equation, generalizations of quantum theory, and, finally, its application to the theory of spectral lines (series) are examined in sequence.

This booklet may be recommended to anyone beginning to engage with the subject for their first steps in the field of the theory of quanta.

P. Lazarev.