...of electricity. However, these tasks have already been placed on the agenda by the commission for the study of the Kursk magnetic anomaly, and one may think that the observations will yield interesting material and illuminate the question from a new point of view.

V. Priklonsky.

V. Trofimov. — The Application of Aerology to Ballistics. (Publication of the Commission for Special Artillery Experiments.) Petrograd. 1920. (“Artillery Journal,” 1920, Nos. 3–4).

The study of the high layers of the atmosphere, besides its general interest, is of enormous importance for a number of special questions. The World War and the successes of artillery, especially long-range artillery, set new tasks before aerology, and the work of the military engineer-technologist V. M. Trofimov is undoubtedly of importance, especially now, when we have so few manuals on aerology.

In a short article (37 pp.) the author gives the basic concepts concerning the atmosphere, its structure and composition, and thermodynamic processes, proceeding from the polytropic change of state, and he dwells in particular detail on the statics of the atmosphere.

Applying the hypothesis of the constancy of the temperature gradient (for the troposphere) or of the constancy of temperature (for the stratosphere), the author derives the dependence between pressure, temperature, density, and height in the form of six equations, which include two parameters: \(Z\)—the height of a homogeneous atmosphere—and \(Kg\)—a quantity connected with the exponent of the polytrope. Of especially great interest is the solution of the problem for the mean annual state of the atmosphere and the approximate application of the general expressions in determining pressure and density for altitudes of 10 kilometers and above 10 kilometers. The last pages contain tables of meteorological elements based on the results of ascents by balloons and kites and, what is especially important, schemes for calculating the necessary quantities. In compiling the article, the latest achievements of science were taken into account, including the works of Bjerknes.

Despite the abundance of mathematical material, the article is read easily and with great interest. Some difficulty is presented by the notations for determining the elements of humidity, taken from the technology of gases; quite unexpectedly, in the middle of the article, the notation for density is changed.

V. Priklonsky.

A. Einstein. Ether and the Principle of Relativity. Translated from the German by A. P. Afanas'eva. Petrograd, 1921. Scientific Publishing House.

The brochure is a translation of Einstein’s remarkable address, delivered at a ceremonial meeting of Leiden University on May 5, 1920. Having set forth the physical facts that made the hypothesis of ether inevitable, Einstein, in a few words, outlines that inescapable...