BIBLIOGRAPHY.

E. GRIMSEHL. Course of Physics, for students, teachers, and for self-education;

Part I. Physical measurements, mechanics, physics of molecular forces, pp. 448; State Publishing House, Moscow–Leningrad, 1924. Price 5 rubles.
Part II. Theory of heat; theory of weather. Pp. 276, State Publishing House, 1925. Price 3 rubles 50 kopecks.
Part III. Theory of waves; acoustics; optics, pp. 523, State Publishing House, 1926. Price 6 rubles.

There is no doubt that in physics it is more difficult than in any other science to establish a division into strictly separate departments, since all the tendencies of modern progress lead precisely toward the erasing of boundaries between departments. It is therefore natural to wish, as a basic guide for students, for a complete course written by one person or at least according to a single plan. Separate monographs, or even textbooks, covering one or another field of physics, must inevitably presuppose that a number of matters have been set forth in other books; but neither the plan nor the manner of exposition of those books is known to the author. Therefore the student often finds himself in a difficult position: the conclusion to which the book he is reading refers is known to him, at times, in so different a form that he does not always succeed in understanding the arguments being presented. Of course, a certain amount of independent work on a book is useful and necessary, but nevertheless, for an initial acquaintance, as a basic guide, a unified course is desirable, one embracing all of physics in the scope of higher educational institutions.

In the Russian language there has until now been no such satisfactory course. The attempt by the State Publishing House to fill this gap by issuing Grimsehl’s course is highly timely. Three parts of the textbook have already appeared, and the remaining two, covering the doctrine of electricity, are being prepared for publication. When the edition is completed, we shall have a book capable of serving the physics-and-mathematics faculties and the physics-and-technical divisions of pedagogical faculties. Yet even with the appearance of this generally good course, one cannot consider that the need for a modern physics textbook has been fully satisfied. By a modern textbook I understand not so much a book that has not omitted an exposition of the very latest scientific achievements, as a course wholly permeated with the spirit of modern conceptions: the doctrine of molecules and electrons, establishing an inner connection between the separate chapters. Grimsehl’s book is not distinguished by such a character. The very arrangement of the material, by virtue of which electricity is assigned the final volume, already serves as an expression of a somewhat outmoded tradition. In general, a large part of the course presents a formal description of phenomena; where the essence of the conceptions is discussed, they turn out to be included in the exposition somewhat mechanically, not always merging with it organically. Such a character of exposition may be carried out quite consci-

...apparently dictated by the desire to separate the description of strictly established facts from more or less hypothetical notions. It seems to me, however, that, given the considerable perfection of modern hypotheses, such rigorism—especially in a textbook—is more harmful than useful. All the more so because it has also affected the distribution of the material and the proportions of the parts. Thus, in the first part, formal mechanics of a rigid and gaseous body is expounded to a high degree of detail, with a selection of excellent illustrations and experiments, while the chapter entitled “molecular physics” is allotted only thirty pages. In the second part, the last forty pages are devoted to the kinetic theory of heat, while two hundred and eighty are occupied by the exposition of the formal doctrine of heat and the principles of thermodynamics. In the third part, the general theory of waves is set forth excellently. Acoustics unfortunately does not touch upon questions of technical acoustics, although in other parts of the course the author readily speaks of the technical applications of physics. The greater part of optics is occupied by geometrical optics; physical optics recedes, to a certain extent, into the background. Geometrical optics is presented very thoroughly and vividly and contains far more extensive information than is usually practiced in university courses, though it does not go into excessive detail. It must be acknowledged as very successful that in many cases the path of rays is illustrated not by drawings, but by photographs of rays in dusty air. Even if in some cases such photographs are less clear than drawings (where necessary, drawings are also included), they bring the reader closer to the real picture and do not inspire in him exaggerated ideas about the excessive precision of the geometrical constructions of optics.

Conversely, physical optics must be recognized as insufficiently complete. There was no place for the concept of spectral regularities, not to mention the modern theory of spectra. Very little space is devoted to questions of the transformation of radiant energy, and nothing is said about electro-optical phenomena. Although the doctrine of electricity is reserved for the next volume of the textbook, nevertheless it can hardly be considered desirable that, after reading the volume devoted to optics, the reader should not receive even a hint of the electromagnetic nature of light. In the chapter on interference, the concept of coherence is explained quite inadequately. The five lines devoted to it, of course, do not achieve results. This is all the more annoying because, in the general theory of waves, a number of excellent experiments are described and many photographs are given of waves on the surface of a liquid. On the basis of these experiments one could have explained both the concept of coherence and its significance for interference. In the chapter on the polarization of light there is no indication that polarized light, falling on a glass plate even at the angle of total polarization, is not reflected completely. Owing to this, the theory of the Nörrenberg apparatus and the action of a pile of plates remain unclear; moreover, even the pile itself is not described. Other sections, on the other hand, are written with due completeness. In particular, sufficient space is devoted to the important question of the distribution of energy in the spectrum and to the laws of black-body radiation. An account is given of the quantum theory of radiation, properly connected with the concept of the distribution of energy among degrees of freedom, and the criticism of the law of equipartition is already encountered in the 2nd part (the doctrine of heat capacity). Thus, alongside certain shortcomings of exposition, one can and should emphasize its outstanding merits. One may say that everything that is expounded in detail is expounded excellently.

Among the special features of the exposition must be included the extremely detailed description of experiments, often with such details (down to specifying the dimensions of the apparatus) that the book can serve as a guide for setting up demonstrations or carrying out a laboratory experiment. This makes it especially useful for the teacher. But for the student, too, these details can hardly be considered superfluous. An excessively schematic description of experiments, often encountered in textbooks, does not create the necessary concrete picture. On the contrary, indicating the dimensions of the apparatus will often help reproduce the phenomenon, even if at the time it was not observed in a lecture.

The Russian translation is entirely satisfactory. At times, to be sure, there occur passages that are not altogether comprehensible (for example, Part III, p. 28, on group velocity), as well as certain roughnesses of style, unavoidable in collective work.

On the whole, with the appearance of this book we have obtained a sufficiently complete manual for universities. It is, admittedly, somewhat extensive and, above all, extremely expensive (the whole course will comprise more than 2,000 pages and cost over 20 rubles). But one should not close one’s eyes to the fact that, for the time being, this is the only—though still imperfect—university-level textbook. For technical schools it is of little use, owing to its breadth. One can only wish that the State Publishing House will find it possible not to stop with the publication of this textbook, but will continue to enrich the Russian market with good textbooks.

Gr. Landsberg.