TEE PERIODIC LA\Y. i55 



in 1815, with no author's signature, in Thomson's 'Annals of Philoso- 

 phy.' Prout had noticed that the 'atomic weights of many of the 

 lighter elements seemed to be exact multiples of that of hydrogen; 

 hence he made the suggestion that all the different atoms may be 

 merely aggregations of the simple hydrogen atom, and that this hydro- 

 gen atom is really the primitive element from which all other sub- 

 stances are made. 



This was the first attempt to determine a relation between the 

 apparently different kinds of matter, and it was more than eighty 

 years before the advocates of the theory were finally forced to abandon 

 it. There have been few laws in chemistry, and certainly no false 

 hypotheses, which have given rise to so much investigation as that 

 which has been occasioned by Prout's hypothesis. That it could have 

 60 long retained adherents among chemists, many of them men of 

 great prominence, is due to the fact that it seems on its face to be true. 

 When it was first published, a very considerable number of the atomic 

 weights were approximately multiples of the weight of the hydrogen 

 atom, far more than could be accounted for by chance. It seemed rea- 

 sonable to believe that, with the meager facilities for accurate work at 

 that day, the atoms of the few other elements would prove, when they 

 should be accurately determined, to be also exact multiples of the 

 hydrogen atom. This view Avas held by many chemists until a Belgian 

 chemist, Jean Servais Stas, undertook to determine the atomic weight 

 of a few of the elements with an accuracy far greater than had been 

 known up to that time. Prout's hypothesis had been sustained by 

 rounding off the decimals to whole numbers; Stas, before he began this 

 work an earnest believer in the hypothesis, endeavored to determine 

 at least one place of decimals so accurately that it could not hereafter 

 be neglected, and his work is one of the classics of chemistry. He 

 proved clearly that the atoms of several elements, at least, could not 

 be multiples of that of hydrogen. Some of the supporters of the 

 hypothesis then assumed that it was not the hydrogen atom, but a half 

 of it, or some other fraction, which is the original matter, from which 

 all other atoms are derived. The hypothesis may be said to have finally 

 ended its long career when Professor Morley, of Adelbert College, 

 showed that there is no simple ratio between the atomic weights of 

 oxygen and hydrogen; that, instead of being 16:1, it is 15.879:1. For 

 accuracy Professor Morley's work may be justly compared with that of 

 Stas, but in conception of experiment and in difficulty of execution it 

 far surpasses that of the Belgian chemist. 



But while it may be considered as absolutely proved that a large 

 share of the atoms have weights which are not exact multiples of that 

 of hydrogen, yet it remains true that many of those which have been 

 determined with the greatest degree of certainty do approach with 



