﻿Principles of Molecular Physics. 1 83 



not rest upon sufficient proof, and contained a good deal of 

 arbitrary assumption. Professor Norton, of course, is not of 

 my opinion, and argues that my objections "are destitute of 

 any real force. " This was his undoubted right ; and, had he 

 confined himself to the defensive, I should have deemed a reply 

 unnecessary; but, as he goes on to attack my own theory with 

 arguments which have a plausible appearance, I think it worth 

 while submitting his article to examination. 



The contents of his ably written paper may be summarized, 

 as it appears to me, in the three following propositions : — 



1st. That in molecular science all our general principles are 

 but probable hypotheses. 



2nd. That his own principles are not arbitrary assumptions. 

 3rd. That I in my ' Elements of Molecular Mechanics y assume 

 principles destitute of sufficient proof. 



To these three propositions I beg ieave to offer a short reply, 

 which, I hope, will be of interest to all who are engaged, either 

 directly or indirectly, in promoting molecular science. 



I. 



And to begin with the first proposition, Professor Norton 

 says : 



" No theory of molecular physics can, in the nature of things, 

 have any other foundation than general principles to be regarded as 

 hypotheses that have been rendered more or less probable, either by 

 induction from observation, or by a priori reasonings. Molecular 

 physics cannot be erected, like mathematics, upon a foundation 

 known to be eternally sure, that of self-evident truth." 



These words express an opinion, which is by no means un- 

 common among physicists, for the obvious reason that they 

 cannot, by the help of physics alone, undertake to establish 

 fundamental principles ; a work, which requires a higher know- 

 ledge of speculative science, than it is the fashion for them to 

 acquire. Hence I do not wonder that mere physicists, even 

 with their hands full of good scientific materials, can build only 

 hypothetical theories. The cement, which alone can keep 

 together the stones of a scientific building, is an article which 

 cannot be prepared by the skill of the chemist, but only 

 by the application of general philosophy to experimental truth; 

 and only in proportion as physicists are conversant with general 

 philosophy can they hope to build theories of a character truly 

 scientific, viz. independent of hypotheses ; for hypothesis begins 

 there only, where real science ends. I do not wish to develope 

 this point at greater length. I am satisfied that this mere hint 

 will suffice for those whose judgment is of any weight in matters 

 of this sort. They will see at once that I had good reasons for 



