Book Reviews

H. Witte, Raum und Zeit im Lichte der neueren Physik (Sammlung Vieweg Tagesfragen aus den Gebieten der Naturwissenschaften u. d. Technik), third edition, 1920, p. 88.

The small book by H. Witte is written for a very broad circle of readers. Its content is an exposition of the “special” principle of rela-

…of A. Einstein’s relativity. The author makes absolutely no use of mathematical symbolism, resorting at the most difficult points, following Cohn’s example, to a model he has constructed of a system at rest and in motion. One cannot fail to note that such a mode of exposition is extremely cumbersome; let us point out, for example, that to describe the scheme of Michelson’s experiment (and a very approximate one at that) the author requires more than 10 pages. In general, the absence of a mathematical formulation of Einstein’s principle deprives the exposition of obligatory force. If, in many monographs on the same question, the physical forest is very often not visible for the mathematical trees, then in Witte’s booklet, to be sure, the trees are not visible, but the outlines of the forest are also sufficiently vague and, in our opinion, will be quite distinct only to a reader already acquainted with the mathematical form of the principle.

The first part of the book is very interesting; there the author, known for his profound critical analysis of the concept of ether, examines the principal features of the scientific concept of space and time, grouping them into two groups:

I {
  a) Arbitrary, but once and for all definite, choice of origin and coordinate axes.
  b) ” ” ” spatial scale.
II {
  a) ” ” ” zero point of time.
  b) ” ” ” unit for measuring time.
}

The very choice of a coordinate system is limited by its fulfillability in it of the laws of nature. According to Witte, the development and generalization of the principle of relativity amounts to the successive elimination of all the indicated features of time and space.

Unfortunately, the outlines of the “remainder,” i.e. of the contemporary conception of time and space left after the removal of the basic features, are by no means clear in Witte’s exposition.

The book under review does not touch upon Einstein’s new works, which have completed the theory of relativity and given it a dizzying generality. Therefore the appearance of a new edition of the book in 1920 without any additions seems somewhat strange.

S. Vavilov.

P. P. Lazarev. Foundations of the Theory of the Chemical Action of Light. Part One. General Photochemistry. Petrograd. 1919. Pp. 60 + IV. Part Two. Special Photochemistry. Petrograd. 1920. Pp. 70 + II. Part Three. Applications of Photochemistry. Petrograd. 1920. Pp. 64.

The first beginnings of photochemical investigations go back to the 18th century; however, despite the full importance of certain old works on photochemistry (for example, the classic investigations of Bunsen and Roscoe), these works represent only a fortunate, promising…