Physical significance of entropy or of the second law

J. F. KLEIN
Professor of Mechanical Engineering, Lehigh University
NEW YORK
D. VAN NOSTRAND COMPANY 23 MURRAY AND 27 WARREN STREETS 1910
COPYRIGHT, 1910, BY JOSEPH FREDERICK KLEIN
THE SCIENTIFIC PRESS ROBERT DRUMMOND AND COMPANY BROOKLYN, N. Y.
In this little book the author has in the main sought to present the interpretation reached by BOLTZMANN and by PLANCK. The writer has drawn most heavily upon PLANCK, for he is at once the clearest expositor of BOLTZMANN and an original and important contributor. Now these two investigators reach the result that entropy of any physical state is the logarithm of the probability of the state, and this probability is identical with the number of complexions of the state. This number is the measure of the permutability of certain elements of the state and in this sense entropy is the measure of the disorder of the motions of a system of mass points. To realize more fully the ultimate nature of entropy, the writer has, in the light of these definitions, interpreted some well-known and much-discussed thermodynamic occurrences and statements. A brief outline of the general procedure followed will be found on p. 3, while a fuller synopsis is of course given in the accompanying table of contents.
J. F. Klein.
Lehigh University, October, 1910.
Now this instinct of the true engineer to understand things down to the bottom is worthy of all encouragement and respect. For this reason and because the matter is of prime importance to the technical world, the final meaning of entropy (i.e., of the Second Law) must be clarified and realized. Indeed, we may well go beyond this somewhat narrow view and say that this is well worth doing because change of entropy constitutes the driving motive in all natural events ; it has therefore a reach and a universality which even transcends that of the First Law, or Principle of the Conservation of Energy.
The second mode will furnish checks and confirmations of the results developed by the first, or we may say that the combination of the two modes will give the well-established characteristic equations and relations of bodies and their physical elements.