Rudolf Clausius

"There is no doubt that Clausius with this paper created classical thermodynamics. Compared with his work here, all preceding except Carnot's is of small moment. Clausius exhibits here the quality of a great discoverer: to retain from his predecessors major and minor—in this case, from LaPlace, Poisson, Carnot, Mayer, Holtzmann, Helmholtz, and Kelvin—what is sound while frankly discarding the rest, to unite previously disparate theories, and by one simple if drastic change to construct a complete theory that is new yet firmly based upon previous partial success. ...By no means disregarding the results of experiment, Clausius was the first theorist of thermodynamics who was not enslaved to them... those which to him seemed dubious were to be rejected... Clausius had another handle... his kinetic theory of gases... Both Rankine's model and Clausius' model... led to a theory... "dynamical"... [F]aith... gave... Rankine and Clausius... confidence... while Kelvin, not yet an atomist, wavered. ...[I]n the molecular theory Clausius was not only the wiser man but also the better physicist."

"The name and fame of Professor Clausius stand as high in this country as in his own. ...his writings ...fell into my hands at a time when I knew but little of the Mechanical Theory of Heat. In those days their author was my teacher; and in many respects I am proud to acknowledge him as my teacher still."