CH. xix.] INSTABILITY OF ATOM 187 



and chemical properties of such substances, and the 

 deduction of a series or family likeness akin to 

 Mendelejeff's series on this hypothetical constitution, 

 is to be found worked out in a masterly manner 

 by Professor J. J. Thomson in the Philosophical 

 Magazine for March, 1904. 



If at the present time there were other confirmatory 

 evidence of this mode of regarding the atom if it 

 were possible to understand what is meant by positive 

 electricity existing as a permeable sphere with a large 

 number of electrons sown in it it would be proper to 

 give a further account of this remarkable and attractive 

 theory; but inasmuch as the light which has quite 

 recently fallen upon the whole subject is of a flicker- 

 ing and undecided nature, tending somewhat in the 

 direction of confusion and uncertainty rather than con- 

 firmation of this promising but still necessarily vague 

 hypothesis see Chaps. XV. and XVII. and Chap. 

 XX. I think it better to leave its further discussion 

 and development to a future time, and meanwhile 

 await further theoretical and experimental evidence. 

 For it is neither theory alone nor experiment alone 

 which can be of service in this matter : progress 

 must be achieved by a combination of the two, 

 welded together by genius ; and it is just this 

 combination of theory and experiment ingenious 

 experiment combined with advanced mathematical 

 theory to which of late years all the finest advances 

 in physical science have been due. 



