44 BRUSH— KINETIC THEORY OF GRAVITATION. 



constituent parts. The energy shadows of two gravitating bodies 

 interblend, so that the energy density between them is less than else- 

 where, and they are pushed toward each other by the superior energy 

 density, or wave pressure, on the sides turned away from each other. 



At the April meeting of the American Philosophical Society in 

 19142 I presented a discussion of above theory which I commend to 

 the attention of those interested in the general subject of gravita- 

 tion — the greatest of all outstanding physical problems. 



While it is easy to picture the formation of the initial energy 

 shadow of a single body of matter, I have always found it difficult to 

 account for the maintenance of such a shadow. But when we con- 

 sider two or more bodies (and there can be no manifestation of 

 gravitation without involving two or more bodies), there is no 

 trouble in picturing the interblending energy shadows between them, 

 and this is the essence of the theory under discussion. 



That the ether really is endowed with vast intrinsic energy in 

 some form or forms is the belief of many eminent physicists, and 

 it seems to me highly probable that all energy has its source and 

 destination in the ether ; that is to say, that energy in all the various 

 forms in which we observe it comes in some way from the ether 

 and is energy of the ether. 



In this connection I beg to propose the hypothesis that the ether 

 is abstract energy — energy pure and simple, quite apart from any- 

 thing else. If the quantum theory of energy is tenable, then we 

 may perhaps regard the ether as a vast atmosphere of energy quanta 

 in violent agitation possibly somewhat like the molecules of a hot 

 gas, though almost infinitely finer grained. 



In support of my contention that ethereal energy is the cause 

 and essence of gravitation, I wish to emphasize particularly, what 

 seems to me an obvious fact, that the energy acquired by a falling 

 body comes from the ether, and is restored to the ether when the 

 body undergoes negative gravitational acceleration. (See Discus- 

 sion above referred to.) 



For many years I have sought for some experimental method of 

 attacking the gravitation problem, but without success until a few 



2 Proc. Amer. Phil. Soc, Vol. LIIL, No. 213, Jan.-May, 1914. 



