Introduction.

§ 1. Mechanical analogy for the behavior of gases.

Even Clausius made a strict distinction between the general mechanical theory of heat—which is essentially based on the two theorems designated as the "main laws of thermodynamics" The First and Second Laws of Thermodynamics following his precedent—and the special theory of heat. The latter, firstly, makes the specific assumption that heat is a molecular motion, and secondly, seeks to form a more precise mental image of the nature of this motion.

The general theory of heat also requires certain hypotheses that go beyond the bare facts of nature. Nevertheless, it is clearly much more independent of arbitrary assumptions than the special theory. It would be a useless repetition of the well-known principles—which Clausius already clearly explained and upon which he based the division of his book into two parts—to explain once again how desirable and necessary it is to separate its theorems from those of the special theory of heat, and to demonstrate the independence of the former from the subjective assumptions of the latter.

In recent times, the mutual relationship between these two branches of the theory of heat has undergone a shift in certain respects. Through the pursuit of the extremely interesting analogies and differences shown by the behavior of energy in various fields of physics, the so-called "Energetics" A 19th-century school of thought that sought to explain all physical phenomena through energy transformations without relying on atomic or molecular models was created. This movement is averse to the idea that heat is a molecular—