278 KINETIC THEORIES OF GRAVITATION. 



the momeutuin of vibration is transferred to the elastic air. And these 

 two qualities of the vibrating bell — cohesion and elasticity — as Sir 

 John Herschel has well remarked, " we have no means of analyzing 

 further, and must therefore regard them, till we see reasons to the con- 

 trary, as ultimate phenomena, and referable to the direct action of an 

 attractive and a repulsive/orce."* But in a kinetic system there is no 

 room for such abstractions. How then are they to be displaced and su- 

 perseded % We wait in vain for an intelligent or an intelligible answer. 



But after this long list of difficulties, supposing the vibrating parti- 

 cles set in motion, still by the Demiurgus, with his right and left pro- 

 pulsions, by what power (short of his incessant repercussion) is the 

 vibrating particle enabled to transmit without decline or iuterruptioUy 

 these setherial waves of gravitation — let us say for a single year, we 

 might as well have said for a single minute ? Here again we listen 

 vainly for an answer ! 



And thus, step by step, have we been led to the culminating vice of 

 &very kinetic sytem ; its utterly reckless violation of any rational concep- 

 tion of the conservation of energy. And yet remarkably enough, the 

 ostensible impulse and occasion of such creeds have usually been a 

 strong veneration for this much-abused principle, and the consciousness 

 of a special mission to restore and to vindicate its neglected authority ! 

 Not unfrequently the vibrations communicated to the telegraphic aether 

 by a trembling atom have been supposed to be transmitted unimpaired 

 to that or to other atoms, and back again, in endless and magnificent 

 cycles of "perpetual motion." And as "there is no limit to the vis viva 

 ■which such a medium may conserve" within its boundless bosom, such 

 projectors have the Bank of the Infinite on which to draw in every 

 dynamic emergency, without the fear of a depleted treasury, and with- 

 out any necessity being felt for inquiring too nicely into the balance of 

 the depositor's account. And thus, as Leray has intimated, suns and 

 stars are maintained for ever blazing on a borrowed capital of motion. 



In opposition to all this ideal programme of an illimitable ocean of 

 dynamic, with its treasures lying loose in space, to be absorbed by every 

 projected ball or stone, it may be simply declared that from ohservation 

 we have no reason whatever to believe the aether to be in any case a 

 source of energy. We have absolutely no experience of any undulations 

 originating in its broad expanse. It is never self-luminous; and even 

 in the case of electricity there is always required the disturbance cf a 

 material element. Nor is there any ascertained fact to warrant the sup- 

 position that the aether is a reservoir of force, — in any other sense than 

 that without the possession of intrinsic tension it would be incapable of 

 transmitting energy. So far therefore as sober experience is accepted 

 as our guide, we only know that a mechanical impulse of suitable char- 

 acter being committed to the aether, it is a faithful vehicle of energy, 

 never adding to, and never abstracting from its charge. 



* Prelim. Discourse ou the Study of Natural Philosophy, part ii, chap, ii, sec. 80. 



