called the disgregation, and regarded as determined by the positions of the elementary parts of the body without reference to their velocities. In this respect it differed from the entropy. An immediate consequence of these relations is that for any reversible cyclic process
and therefore that the molecular vis viva of the body, must be a function of the temperature alone. This important result was expressed by Clausius in the following words: "Die Menge der in einem Körper wirklich vorhandenen Wärme ist nur von seiner Temperatur und nicht von der Anordnung seiner Bestandtheile abhängig."
To return to the equation
This expresses that heat tends to increase the disgregation, and that the intensity of this tendency is proportional to the absolute temperature. In the words of Clausius: "Die mechanische Arbeit, welche die Wärme bei irgend einer Anordnungsänderung eines Korpers thun kann, ist proportional der absoluten Temperatur, bei welcher die Aenderung geschieht."
Such in brief and in part were the views advanced by Clausius in 1862, in his memoir, "Ueber die Anwendung des Satzes von der Aequivalenz der Verwandlungen auf die innere Arbeit."[1] Although they were advanced rather as a hypothesis than as anything for which he could give a formal proof, he seems to have little doubt of their correctness, and his confidence seems to have increased with the course of time.
The substantial correctness of these views cannot now be called in question. The researches especially of Maxwell and Boltzmann have shown that the molecular vis viva is proportional to the absolute temperature, and Boltzmann has even been able to determine the precise nature of the functions which Clausius called entropy and disgregation.[2] But the anticipation, to a certain extent, at so early a period in the history of the subject, of the ultimate form which the theory was to take, shows a remarkable insight, which is by no means to be lightly esteemed on account of the acknowledged want of a rigorous demonstration. The propositions, indeed, as relating to quantities which escape direct measurement, belong to molecular science, and seem to require for their complete and satisfactory demonstration a considerable development of that science. This
