G. Olson. Dynamic Analogies. Translated by B. L. Korobochkin, edited by M. A. Aizerman. IL, Moscow, 1947.

Olson’s booklet (more correctly, “Olson”) considers analogies between mechanical, electrical, and other linear systems with a finite number of degrees of freedom. The exposition is conducted from the standpoint of network theory, which constructs such systems: various analogous systems are considered, and formulas are given that determine their behavior, as well as formulas for passing from one system to another analogous to it. A chapter of considerable size contains a description of methods for correcting circuits. With the exception of one chapter (Chapter 10), all the chapters have a sharply expressed reference character.

Undoubtedly, as a reference book in the practical work of an engineer, the booklet will be very useful. However, its shortcoming is the absence of a generalizing

presentation of the basic questions of analogizing. The book is marked by an American practicality—almost businesslike efficiency. In this respect it will in many ways not satisfy the Soviet research engineer and will not at all appeal to the Soviet physicist. Naturally, one would have wished the editor to introduce into the book additions from Soviet literature, in which questions of analogies are considered from a considerably deeper point of view. Such a general treatment of the Russian literature is given in A. V. Kharkevich’s book; this should have been stated in the editor’s preface. The Russian literature cited by the editor ought to have been incorporated into Olson’s book.

Now a few particular remarks.

Already from the example of a double pendulum one can see that the choice of generalized coordinates substantially changes the character of the dynamical connection; the question of the choice of coordinates is needlessly passed over by the author.

It is nowhere stated that many of the practical systems considered by the author are nonlinear and that in them phenomena unexpected from the point of view of linearity may be observed. For the practical engineer, for whom, apparently, the book is intended, it is necessary to know this and to be able, from this point of view, to estimate the limits of applicability of analogies.

Dampers, as an acoustic system, are treated too primitively.

The set of definitions at the end of the book makes a somewhat strange impression: it is not compiled according to the usual principles accepted in terminology, but rather follows the formulas needed by the author. For example: “Mass is defined as the number which, when multiplied by \(2\pi\) and by the frequency, is equal to the positive term of the coefficient of the imaginary part of the mechanical translational impedance.”

In the list of Russian literature, the Journal of Technical Physics is called Technical Physics. Why allow such inaccuracies?

N. N. Andreev