A. A. Friedmann. An Essay on the Hydromechanics of a Compressible Fluid.
266 pp. in 4°. Petrogosizdat (lithogr.).

The work of A. A. Friedmann is the first attempt in Russia to continue and develop the hydrodynamic ideas of the elder and younger Bjerknes. As is known, meteorology is now undergoing a crisis of growth and, from an accumulation of observations and of means derived from observations, is turning into a physico-mechanical science constructed on the basis of mathematical analysis. For this transformation, however, the existing mathematical apparatus is far from sufficient: one has to investigate a vortical medium, taking into account its non-uniformity, compressibility, and temperature, whereas the theory of vortices has been built precisely on the ignoring of one or another of these factors. The extremely complex form of the equations linking together the various phenomena occurring in space requires the use of vector analysis. All these circumstances compel one to regard with special interest the work of A. A. Friedmann, in which both the works of Bjerknes and the author’s own results are set forth. A. A. Friedmann, being a pupil of Bjerknes and of Academician B. B. Golitsyn, is well acquainted with both the theory and the practice of meteorology; at the same time he has a full command of mathematical analysis. Therefore he has succeeded in giving a good exposition of the foundations of the method and in examining a number of practically important special cases. Work in this direction is all the more interesting since the possibility is not excluded of applying it to the most urgent problems of physics—to the question of the essence of matter and of the origin of gravitation, electricity, and magnetism. As is known, the elder Bjerknes and Lord Kelvin gave hydrodynamic models of the atom, and pos—

a return to hydrodynamical models may be possible when relativism exhausts itself and runs into contradictions.

A. A. Friedmann’s book, unfortunately, has been published by lithographic means and in a very small number of copies, so that it will probably soon become a bibliographical rarity.

V. A. Kostitsyn.