26 Presidential Address 



whole or fractional numbers; and the 

 atomic theory of matter sprang into sub- 

 stantial though at first infantile existence. 



The hypothesis of Prout, which in some 

 modified form seems likely to be sub- 

 stantiated, is that all atomic weights are 

 commensurable numbers; in which case 

 there must be a natural fundamental 

 unit underlying, and in definite groups 

 composing, the atoms of every form of 

 matter. 



The small number of degrees of freedom 

 of a molecule, and the subdivision of its 

 total energy into equal parts correspond- 

 ing thereto, is a theme not indeed without 

 difficulty but full of importance. It is 

 responsible for the suggestion that energy 

 too may be atomic! 



Mendelejeff's series again, or the detec- 

 tion of a natural grouping of atomic 

 weights in families of seven, is another 

 example of the significance of number. 



Electricity was found by Faraday to be 

 numerically connected with quantity of 

 matter ; and the atom of electricity began 

 its hesitating but now brilliant career. 



