In determining relative motions, one usually uses general differential equations, which are obtained from the equations of absolute motion through a transformation of coordinates. For solving particular problems, such a method in most cases turns out to be insufficient, because integration of the equations of relative motion is rarely accessible. The complex form of these equations presents another inconvenience, that the meaning of the heterogeneous terms entering into them is not always sufficiently clear; and this circumstance can easily be the cause of inaccuracy or obscurity of exposition.

But the connection between absolute and relative coordinates, which is expressed by the transformation formulas and which serves to obtain differential equations, can obviously lead us directly to the integrals of relative motion, and precisely in those cases when the absolute motion is known.

Lacking the ability to integrate the general equations of hydrodynamics, we are forced to resort to an indirect method, the verification method, to solve problems about the motion of a fluid; we can, for example, make some assumption about the motion of the particles of the fluid, give the function p a certain form, and then, using the general equations, draw conclusions about the conditions under which the assumptions made take place. Obviously, for lack of anything better, this method can lead us to the solution of many problems of hydrodynamics; but even in this direction, little has been done; in the simplest case, when the movement of a homogeneous and completely free liquid mass is considered, only one question is developed about the uniform rotational movement of the liquid without changing the relative position of its particles and, consequently, without changing the appearance of the surface.

With his love for figurative geometric thinking, Zinger captivated young mechanics, directing their work along the path followed by the great geometers Newton, Poinsot, Poncelet, and Chasles.

The elegance of his presentation and the depth of his scientific ideas attracted many students to Zinger... One of the most significant features of Zinger's lectures was that in them he drew the attention of his listeners ... to the guiding ideas and forced them to clearly grasp the difference between the inner meaning of each question or method and those established ... techniques and transformations that constitute, as it were, the outer shell of pure speculation.

... special interest and deserves attention in many respects. Higher geometry, unfortunately still very little widespread, especially among us, is one of the sciences that has arisen and developed only in recent times: it is also called new geometry; and yet, both in content and in its fundamental principles, and especially in its method, it stands closer than all other sciences to the geometry of the ancients.

When I watched Kaufman collect and study plants, when I listened to his stories, my eyes were opened: the grass, the forest, and the soil appeared to me in a completely new light, full of the deepest interest.

There is no need to be a specialist to study our native flora successfully and profitably; what is needed is that love for the work and desire which transforms the considerable and not always easy work of collecting and identifying plants into a familiar favourite pastime and little by little turns a simple amateur into an experienced connoisseur. Unfortunately, our circumstances are such that of the many amateurs, very few manage to cope with the various difficulties that are inevitable for any beginner. In most cases, an amateur, interested and enthusiastic about the matter, from the very beginning gets lost in a heap of errors, contradictions, difficulties and cannot find not only advice or instructions from an experienced guide, but even a satisfactory book, so much as applicable to his needs. Involuntarily, despite his enthusiasm and desire, he has to abandon the matter and stop at the first step. On the other hand, there can be no good guides to local flora until the necessary factual material is collected with the help of the same amateur work. We believe that in the activities of our learned societies one of the most important duties and essential tasks should consist in encouraging and developing amateur work and in attracting to it the greatest possible number of people, because only with their assistance can we obtain from a multitude of unexplored places those factual data of which we are still so poor and which we have needed for so long.

His few articles devoted to philosophical issues are always distinguished by the clarity of the author's fundamental views and the unique depth of his conclusions. One may not agree with his views, but even the harshest critic must give credit to the serious thoughtfulness and independent firmness of his philosophical convictions.

The translation by V Ya Zinger of the work of Michel Chasles (1793-1880) devoted to the history of geometry was a landmark in the period of infancy of the Russian history of mathematics. ... Neither the translator's nor the editor's name was provided on the cover of the Russian publication. However, it is common knowledge that Vasily Yakovlevich Zinger was the translator and the editor of this publication. ... His student, Konstantin Alekseevich Andreev (1848-1921), stated that "as a young man Vasily Yakovlevich was very passionate about Chasles' works and closely scrutinised them. . . He translated one of Chasles' fundamental works ... into Russian in full, however, he did not do it diligently, he did not pursue editing details; instead, he did it as quickly as he was reading and speaking, because he always had a ready-to-use clear and precise phrase for each established or accepted idea." Thus, owing to the efforts of Moscow Society of Mathematics and V Ya Zinger, Russian historians of science were able to read the work of M Chasles, the acknowledged leader of French school of geometry of that time, in their native language.

Professor Zinger did not gain fame by the abundance of his scholarly works, but by the nature of these works. Everything he wrote, with its depth of content, was distinguished by clarity, completeness and concreteness of form. There are mathematical works which, once read, are remembered forever, just as a painting by a famous artist, briefly seen in an art gallery, is then clearly depicted in the imagination. The works of V Ya Zinger belong to this kind of works... His students, both mathematicians and mechanics, also tried to work in this direction... We honour the memory of a mathematician who can rightly be called the head of the Russian geometric school.