AND ITS SELF-COtfSERVATIOH. 73 



matter the earth. On the other hand, it would seem 

 that imponderable matter is in this sense just that phase 

 of matter in which repulsion is so highly developed that 

 within a given volume (of any finite extent), the tendency 

 toward separation is vastly greater than the tendency 

 toward concentration, and that therefore in such volume 

 even gravity is masked, while weight would have no 

 existence at all. 



Thus, as all matter consists primarily of the interaction 

 of attraction and repulsion, and as there is no absolute 

 limit to the degree in which this interaction may vary 

 locally, so there is no absolute limit to the possible diffuse- 

 ness of matter in any given portion of space. 



It would seem, then, that throughout the spaces far 

 removed from large, dense masses of matter, there is dif- 

 fused what may properly be called imponderable matter. 

 And there seems no good reason why we should not adopt 

 for this imponderable matter the name, ether. It is the 

 " unseen universe "; nay, in some sense the unseeable uni- 

 verse, since it is that part of physical reality which, as 

 such, must forever elude all efforts to bring it to the test 

 of the chemist's balance. It seems in some sense to 

 especially court inquiries of the metaphysical kind, and 

 more or less to refuse answer to questions put in any 

 other form. 



Doubtless the reader has already observed that the 

 proof of the possibility of any change whatever in matter, 

 considered as constituted of absolutely balanced modes of 

 force, is not as yet by any means forthcoming in the 

 present essay. It is well, at least, to have this explicitly 

 called to mind, in order that the demand for such proof 

 may not be forgotten or in any degree slurred over. Nor 



