Mabch 10, 1911] 



SCIENCE 



383 



Let us assume, then, that the ether is en- 

 dowed with very great kinetic energy nor- 

 mally uniform in distribution. 



Kinetic energy implies motion of something 

 possessed of inertia. Now, inertia is a funda- 

 mental attribute of the ether. Sir J. J. 

 Thomson holds that all inertia is inertia of 

 the ether. The ether is highly elastic also, 

 which, with its inertia, enables it to possess 

 kinetic energy in wave form, as exemplified 

 in radiation. By the term wave, I mean 

 progressive motion locally periodic; doubtless 

 the ether as a whole is stationary. Hence we 

 may consider the kinetic energy of the ether 

 as consisting in ether waves of some kind. 



These waves, vast in aggregate energy, 

 eternal in persistence, without finite source or 

 destination, are imagined as being propagated 

 in straight lines in every conceivable direc- 

 tion. This isotropic distribution of kinetic 

 energy, essential to my theory of gravitation, 

 was, for me, a difficult conception until I 

 reflected that isotropic radiant energy is ap- 

 proximately realized in the interior of any 

 furnace with uniformly heated walls. 



Any kind of waves capable of exerting mo- 

 tive action on the atoms or molecules of mat- 

 ter will fulfil the requirements; but I shall 

 first consider the transverse, electromagnetic 

 waves of radiation because these are the kind 

 of ether waves we are familiar with. 



Of course intrinsic ether waves, if of the 

 radiation kind, can not be of any frequency at 

 present known to us as radiation, because 

 then all bodies would become heated. But we 

 can easily imagine them of such extremely 

 low frequency that the molecules or atoms of 

 matter can not respond to them — can not 

 vibrate in unison with them — molecular reso- 

 nance can not be established; hence no con- 

 version of the ether energy directly into heat 

 in the ordinary way can take place. 



We are familiar with the dissipation or de- 

 generation of the higher forms of energy into 

 heat, and the continual degradation of heat to 

 lower degree; that is to say, less violent 

 molecular vibration and more general distri- 

 bution. As is well knovsm, it is only through 



this degradation or running down of natural 

 energy that we are enabled to utilize some of 

 it. Lord Kelvin called this function of en- 

 ergy " motivity " (we now call it entropy), 

 and said the motivity of the universe tends to 

 zero. 



We know that ordinary radiation waves in 

 the ether persist indefinitely and without 

 change of frequency or direction until they 

 encounter matter, when they are absorbed and 

 converted into heat, only to be radiated again, 

 usually in longer waves, to some colder body. 

 This degradation of wave frequency continues 

 until we can no longer follow it. I beg to 

 suggest that the ultimate destination of this 

 wave energy is that vast reservoir of kinetic 

 energy intrinsic to the ether. We may liken 

 the waves of radiant energy, which we appre- 

 hend as light and heat, to wind ripples on the 

 surface of water, which continually degenerate 

 in wave frequency until they are absorbed 

 into and become a part of the mighty swell of 

 the ocean. 



Thus we may, perhaps, regard the ether's 

 intrinsic energy as energy in its lowest form 

 — Kelvin's zero of " motivity." But fortu- 

 nately we may and do get some of this energy 

 back in available form in several ways, as, for 

 instance, when a falling body is arrested and 

 develops heat; some of our wind ripples are 

 then returned to us. 



When two gigantic astronomical bodies col- 

 lide under the influence of gravitation, as 

 sometimes happens, we witness in far distant 

 space the birth of a nebula. The incon- 

 ceivably vast amount of heat developed by the 

 collision converts both bodies into luminous 

 vapor which expands with incredible rapidity 

 into the nebulous cloud. This heat energy 

 must in course of time degenerate back into 

 the ether whence it came, though billions of 

 years may be required; and during all this 

 time the energy has " motivity." We may 

 picture the stupendous result of the collision 

 as only a local splash in the ether's mighty 

 ocean of energy. 



Having postulated that the ether is endowed 

 with very great intrinsic kinetic energy in 

 wave form of some kind; that the waves are 



