44 Larmor, Physical Aspect of the Atomic Theory. 



Daltonian principle of identity of all atoms of the same 

 substance, — they are the same to the remotest limits 

 of our universe, as Huggins demonstrated — may well 

 arise from these atoms being the limited number of 

 definite intimate types of structure into which more 

 ultimate atoms can arrange themselves. These ultimate 

 atoms would be limited as regards their relations at 

 a distance, for they would in this respect involve only 

 the few fundamental types of strain-centres which are 

 capable of subsisting in the simple aether. The keystone 

 of such a physical scheme is the aether : and the only 

 ground for postulating the presence of this medium is the 

 extreme simplicity and uniformity of the constitution 

 which suffices for its functions. Needless to say, there 

 remain many unresolved features, some still obscure, but 

 hardly contradictory. But should it ever prove to be 

 necessary to assign to the aether as complex a structure 

 as matter is known to possess, then it might as well be 

 abolished from our scheme of thought altogether. We 

 would then fall back on simple phenomenalism ; proximate 

 relations would be traced, but we need not any longer 

 oppress our thought by any regard to a common setting 

 for them ; the various branches of physical science would 

 cultivate with empirical success independent modes of 

 explanation of their own, checked only by the mutual 

 conservation of the available energy, while the springs of 

 their orderly connexion would be out of reach. That 

 time, however, is not yet. 



