Prof. J. C. Maxwell on Molecules. 467 



distant worlds, tells us also that each of them is built up of mo- 

 lecules of the same kinds as those which we find on earth. A 

 molecule of hydrogen, for example, whether in Sirius or in Arc- 

 turus, executes its vibrations in presisely the same time. 



Each molecule, therefore, throughout the universe bears im- 

 pressed on it the stamp of a metric system as distinctly as does 

 the metre of the Archives at Paris or the double royal cubit of 

 the Temple of Karnac. 



No theory of evolution can be formed to account for the simi- 

 larity of molecules ; for evolution necessarily implies continuous 

 change, and the molecule is incapable of growth or decay, of 

 generation or destruction. 



None of the processes of nature, since the time when nature 

 began, have produced the slightest difference in the properties 

 of any molecule. We are therefore unable to ascribe either the 

 existence of the molecules or the identity of their properties to 

 the operation of any of the causes which we call natural. 



On the other hand, the exact equality of each molecule to all 

 others of the same kind gives it, as Sir John Herschel has well 

 said, the essential character of a manufactured article, and pre- 

 cludes the idea of its being eternal and self-existent. 



Thus we have been led, along a strictly scientific path, very 

 near to the point at which science must stop. Not that science 

 is debarred from studying the internal mechanism of a molecule 

 which she cannot take to pieces, any more than from investiga- 

 ting an organism which she cannot put together. But in tracing 

 back the history of matter, science is arrested when she assures 

 herself, on the one hand, that the molecule has been made, and 

 on the other, that it has not been made by any of the processes 

 we call natural. 



Science is incompetent to reason upon the creation of matter 

 itself out of nothing. We have reached the utmost limit of our 

 thinking faculties when we have admitted that because matter 

 cannot be eternal and self-existent it must have been created. 



It is only when we contemplate, not matter in itself, but the 

 form in which it actually exists, that our mind finds something 

 on which it can lay hold. 



That matter, as such, should have certain fundamental pro- 

 perties — that it should exist in space and be capable of motion, 

 that its motion should be persistent, and so on, are truths which 

 may, for any thing we know, be of the kind which metaphysi- 

 cians call necessary. We may use our knowledge of such truths 

 for purposes of deduction ; but we have no data for speculating 

 as to their origin. 



But that there should be exactly so much matter and no more 



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