ELISHA MITCHELL SCIENTIFIC SOCIETY. 73 



first imperfect list of these weights. These took two 

 directions. First the ratios to some common standard 

 or unit as hydrog-en, and secondly the relations between 

 the weights of elements of the same group or famil3\ 

 The first subject was looked into simultaneously in the 

 year 1815 by Prout in England and Meinecke in Ger- 

 man3\ The second was naturally taken up some years 

 later, the first to suggest numerical regularities being 

 Dobereiner in 1817 and he has been followed by a 

 number of others. 



Prout's hypothesis has always attracted the most 

 attention. It may well be divided into two parts: 

 first, an assumption that the atomic w^eights are all 

 whole multiples of hydrogen. This w^as afterwards 

 modified so as to read that they were all integral mul- 

 tiples of the half atom of hydrogen. This half atom, 

 or rather bod}^ having half the atomic weight, was 

 called pantog-en. The second was a deduction from 

 the first assumption. If they were multiples of 

 hydrogen, then they must be composed of hydrogen or 

 of pantogen. Why this should be the case or was at 

 all a necessar}' deduction no one seems to have attemp- 

 ted to show. 



The first assumption has been examined and worked 

 over bv many investigators with a view to proving its 

 truth or falsity. If proved true, it would be interest- 

 ing and useful, but it could never justl}^ be claimed 

 as showing that the elements were formed of hydro§*en 

 or the hypothetical pantogen. If we take the list of 

 atomic weights as calculated by Ostwald and select 

 those in regard to which we can feel sure that the 

 weight is approximately correct and if we disregard 

 variations of less than one tenth from the unit, then we 

 find that twentv-three out of thirtv-five are inteo-ral 



