ELECTRONIC THEORY OF MATTER 289 



negative electricity and nothing else. All its newly-dis- 

 covered, as well as all its long-known, properties can thus 

 be explained even the long-standing puzzle of "cohesion" 

 shows signs of giving way. The only outstanding still in- 

 tractable physical property is "gravitation," and no satis- 

 factory theory of the nature of gravitation has been so far 

 forthcoming. I doubt, however, if it is far away. It 

 would seem to be a slight but quite uniform secondary or 

 residual effect due to the immersion of a negative electron 

 in a positive atmosphere. It is a mutual force between one 

 atomic system and another, which is proportional to the 

 number of electrons in each. It is quite doubtful whether 

 it is displayed by an isolated, or disembodied electron, but 

 the act of immersing an electron in its attracting atmos- 

 phere may develop it. We know too little about electricity, 

 especially about positive electricity, to be able to justify or 

 expand such a guess ; but, as a guess and no more, I venture 

 to throw it out ; believing it to be a static residual strain 

 effect, inherent in the constitution of each atom. 



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