concern physics. In 224 pages Planck sets forth the mechanics of the point and of systems, dwelling in considerable detail on Lagrange’s equations and Hamilton’s principle, which have acquired such great significance in modern theoretical physics.

With the brevity of the textbook and the clarity of the exposition of the subject, Planck’s book can conveniently serve as an aid both for university lectures and for independent study of the subject.

P. Lazarev.

K. Fajans. Radioactivität und die neueste Entwickelung der Lehre von den chemischen Elementen (Sammlung Vieweg, Heft 45). Braunschweig—1919.

Fajans’s booklet is of enormous interest for physicists and chemists, as well as for biologists and physicians, giving a clear and precise conception of the complex field of radioactive transformations. Particularly interestingly presented are those chapters of the doctrine of radioactivity in which the connection of radioactive transformations with the periodic system is treated, and where we find all the most recent investigations in this field brought together.

If we add to this that, in an appendix, the author gives a description of Rutherford’s remarkable experiments on the disintegration of nitrogen, then we must acknowledge that Fajans’s book gives a very modern picture of the structure of matter in connection with radioactivity, and this book may be confidently recommended to anyone wishing to become seriously acquainted with these branches of science. Fajans’s book has been translated into Russian and will be published by the publishing department of the People’s Commissariat of Health.

P. Lazarev.

Proceedings of the Institute of Physico-Chemical Analysis, edited by N. S. Kurnakov and B. N. Menshutkin. Volume I, issue 1, Petrograd, 1919.

The extensive first issue (300 pp.) of the Proceedings contains an article by N. S. Kurnakov explaining the tasks of the Institute of Physico-Chemical Analysis. Further, this issue contains a number of original works carried out at the Institute; the issue concludes with Le Chatelier’s article on solutions.

There is no need for us to expatiate on the significance of the Institute and its works for the development of questions of physico-chemical analysis, and we can only welcome an institution which, amid a number of difficulties, succeeds in conducting intensive and purposeful scientific investigation.

P. Lazarev.