1 '24 Transactions. — Miscellaneous. 



are in motion through the great ocean of aether, they carry along with them 

 the sether they contain, or whether the fether passes through the soHd as 

 the water of the sea passes through the meshes of a net when it is towed 

 along by a boat. 



" The experiment (to determine this question) was tried at different times 

 of the year, but only negative results were obtained. We cannot, however, 

 conclude absolutely from this experiment that the sether near the surface of 

 the earth is carried along with the earth in its orbit. If the gather is mo- 

 lecular, the grouping of the molecules must remain of the same type, the 

 configuration of the groups being only slightly altered during the motion."* 

 The density of the aether is extremely small compared with that of air, even 

 in the vacuum of a Sprengel air-pump. 



One who has made a special study of the subject of this paper in effect 

 remarks! : — The forces we have to deal with are vast, and, to om* ordi- 

 nary perceptions, occult. We need not, however, on this account doubt 

 their existence any more than we need doubt the existence of light in space 

 surrounding a luminous body, but which light we cannot see. Force is 

 meastu'ed by momentum. Wheti the mass is extremely small and the force great 

 the velocity must be proportionately great. In accounting for gravitation we 

 must look for an extreme velocity with extreme tenuity of matter. 



The pull exerted by the sun upon any of the planets is transmitted with 

 an " infinite velocity " — that is, the pull is made " instantaneously " both 

 at the sun and planet. If we try to gather in the logical meaning of this 

 we shall see that the force that causes the planet to gravitate to the sun 

 exists both at the sun and at the planet's place in space. If there is a 

 medium, then why should not the force be in the medium and not in the 

 sun ? That the force that causes gravitation should exist in space has been 

 the hope and the aim of perhaps most philosophers since the time of 

 Newton. This notion seems somewhat in conflict with what is strikingly 

 manifest — that all planetary bodies are held in their orbits by a central 

 body ; but, if we conceive the idea that the action of the central body is 

 directive and not productive, then the apparent antagonism is cleared away. 

 In this case the central body may so influence the aether of space as to cause 

 it to surround the body as the atmosphere surrounds the earth, the density, 

 say, and in any case the force, decreasing with the distance from the centre 

 of the body. 



If gravitation is owing to any action of the ffither, it would seem to be 

 most likely that of a current. If we hold a plank end-ways against a cur- 

 rent of water, the force necessary to hold it may not be much. If we hold 



* J. C. Maxwell's article, " Mthev." Encyc. Brit., 9th ed. 

 t S. Folver, Preston, July or October number, Journal of Science, 1878. 



