Mabch 10, 1911] 



SCIENCE 



385 



Each atom or molecule may be regarded as 

 a center of activity due to its kinetic energy 

 of translation, with continual absorption and 

 restitution of the ether's energy, normally 

 equal in amount. The manner in which this 

 molecular activity maintains, in effect, the 

 supposed spherical shadow requires explana- 

 tion which I shall attempt in a future paper. 



Of the several components into which the 

 composite motion of each atom can be re- 

 solved, that one lying in the direction of an 

 attracting body will be the greatest, because 

 the waves from that direction, being partially 

 intercepted by the attracting body, are weak- 

 est; and the atom will be pushed in that direc- 

 tion by the superior waves behind it. If free 

 to fall, the atom will continually absorb more 

 energy from the stronger waves behind it than 

 it restores to the weaker waves in front, and 

 will thus acquire additional kinetic energy of 

 translation in the line of fall, measured di- 

 rectly by the number of waves involved, i. e., 

 by the distance moved. Conversely, if the 

 atom be forced away from the attracting body, 

 restitution of energy wiU exceed absorption, 

 and the energy expended in moving the atom 

 against attraction will be transferred to the 

 ether. 



It will be seen that gravitation is a push 

 toward the attracting body, and not a pull.. 

 It is clear, also, that the velocity which a fall- 

 ing body can acquire tends asymptotically to 

 a limit, which is the velocity of the ether 

 waves which push it- — the velocity of light, if 

 transverse waves are involved. 



I have already intimated that any kind of 

 ether waves capable of imparting motion (not 

 internal vibration) to the atoms of matter 

 will fulfil the requirements of my theory, but 

 have thus far discussed only transverse waves. 



Let us now consider longitudinal waves — 

 waves of compression and rarefaction, like 

 sound waves in air and in elastic liquids and 

 solids. The " spherical shadow " conception 

 which I have employed in connection with 

 transverse waves applies equally well here. 



So far as I am aware, longitudinal waves in 

 the ether are unknown; but that such waves 



have not been observed is not convincing 

 argument that they do not exist. 



Assuming then that some, or perhaps much, 

 of the intrinsic energy of the ether is em- 

 bodied in longitudinal waves, we have only to 

 find some motive action of such waves on 

 atoms of matter to account for gravitation. 

 Adequate motive connection may perhaps be 

 eifected by the locally alternating flow and 

 ebb — acceleration and retardation of the ether 

 in which the atoms are enmeshed, incident to 

 its wave motion. We have ample reason for 

 believing that the ether does obtain a grip of 

 some sort on the atoms of an accelerating 

 (falling) body, and a retarding (rising) body, 

 from which it follows that accelerating and re- 

 tarding ether, as in a wave of compression, 

 must grip a comparatively stationary atom. 



Certain facts of astronomy apparently re- 

 quire that gravitational attraction between 

 bodies, however distant from each other, must, 

 in effect, be instantaneous; that is to say, the 

 line of apparent attraction between them is a 

 straight line joining their centers. I believe 

 my theory meets this condition, but I shall 

 reserve discussion of the point for a future 

 paper. 



I feel much diffidence in presenting the fore- 

 going rough draft of a theory of gravitation; 

 but I can not avoid the belief that it contains 

 some germs of truth, perhaps the real key to 

 the great mystery, though, if this be true, I 

 have, no doubt, used the key clumsily and im- 

 perfectly. 



If the ether-wave theory of gravitation is, in 

 the main, the true one, it offers some hope of 

 experimental verification. Provided the waves 

 are of one principal frequency, or even of sev- 

 eral, we may find something, doubtless of 

 molecular magnitude only, which will oscillate 

 in unison with them so that resonance can oc- 

 casionally be established and a cumulative 

 effect obtained sufficient to manifest itself as 

 heat. 



In searching for some natural phenomenon 

 of this nature, I thought of the thermal con- 

 dition of the upper atmosphere as a possible 

 case. The mean molecular velocity of a gas at 

 some temperature, in connection with the 



