Ixii PROCEEDINGS. 



primordial matter was not hydrogen but something having half 

 that weight ; so that the hydrogen atom itself was composite. After- 

 wards, as methods of determining atomic weights became more 

 refined and the existence of various fractional values in atomic 

 weights could be maintained with certainty, this primordial matter 

 had to be still further subdivided, until its subdivisions became too 

 minute to" be capable of verification by chemical analysis. The 

 truth or falsity of the hypothesis could then no longer be tested 

 by experimental methods and the hypothesis itself retreated from 

 the territory of science into that of speculative philosophy. Mean- 

 time under the, stimulating influence of the atomic theory the 

 investigation of atomic weights and the properties of elements 

 contnued until,, a little more than fifty years after the publication of 

 Prout's hypothesis, these investigations blossomed into a general- 

 ization which recalled to chemists once more, this time with con- 

 vincing force, the conception that the atoms must after all be 

 composite substances. This was the Periodic Law of Mendeleeff and 

 Lothar Meyer. If we arrange the elements in a long line in the 

 order of their atomic weights and then observe successively their 

 properties, we find the same set of properties recurring again and 

 again at regular intervals. It is as if we were dealing with a 

 succession of generations, the individuals of each generation repro- 

 ducing more or less faithfully the characteristics of their respective 

 'ancestors. Now we are free to adopt either of two attitudes 

 towards this law. The facts are undeniable: and we may either 

 refuse to speculate about the cause, or we may allow ourselves to 

 indulge in that luxury. If we choose the latter course, it is diffi- 

 cult to avoid the conclusion that our elements are not the ulti- 

 mate forms of matter; and if we assume the atomic theory, it 

 follows that our atoms are composite. 



We now see that the idea of the composite character of atoms 

 is nearly as old as the atomic theory itself and in one form or other, 

 like the poor, has been with us always. But the validity of the 

 atomic theory has not thereby been undermined or in any way 

 affected. For the conception of an atom involved in it is not that 

 it is the smallest particle of matter capable of existence, but is 

 that minute mass of matter which maintains its individuality 



