The italics in this passage, as well as in all past and future quotations, are mine.
In justice to Professor Newcomb, however, we must look at his entire sentence, which is this: "No elasticity is assigned to the molecules in the kinetic theory, but only an insuperable, repulsive force, which causes the molecules to repel each other when they are brought sufficiently near together." This information, Professor Newcomb hopes, will "relieve me." I am indeed relieved! What the learned Professor tells me in the last part of his sentence certainly simplifies matters to the last degree. All that needs be assigned to the molecules is an "insuperable repulsive force." Such a force is the greatest convenience for the physicist that can possibly be devised; it not only effects a simple and satisfactory solution of the difficulties set forth in my fourth and eighth chapters, but it enables us at once to get over every other difficulty that may be suggested. It is singular that Sir Isaac Newton did not understand this when he was distressed about the mechanism of gravitation; for, obviously, all that is required to explain it is to assign to the molecules an attractive force. Sir Isaac's ignorance is all the more remarkable because, coming to think of it, I now recollect that the philosophy of which Professor Newcomb is the able exponent was very clearly set forth, just fourteen years before the appearance of Newton's "Principia," in a profound metaphysical treatise published by one Jean-Baptiste Poquelin (otherwise called Molière) under the somewhat whimsical title "Le Malade Imaginaire." Toward the close of that great work (which is in the form of dialogues), one of the interlocutors, Bachelierus, philosophizes as follows:
Domandatur causam et rationem quare
Opium facit dormire.
A quoi respondeo
Quia est in eo
Cujus est natura
Of course, we are not to be embarrassed by anything John Bernoulli has written about "insuperable forces" as mathematical or physical, functions; nor is it worth while to be disturbed by considerations respecting the effect of their assumption upon the doctrine of the conservation of energy.
Professor Newcomb's indignation at my treatment of the kinetic theory of gases is very great indeed. "There is no theory of modern physics," he says, "the processes supposed by which are invisible to