ON MATTER, FORCE, AND MOTION IN SPACE. 57 



there be any special material element producing the 

 phenomena of electricity and magnetism, that element 

 will be found in the ether of which we now speak 

 occupying not solely the regions of space around us, 

 but permeating the grosser forms of matter, and in 

 their conjunction undergoing changes of which electri- 

 city may be one manifestation. All this is pure hypo- 

 thesis at present, and insusceptible of proof ; but that a 

 closer approximation exists among those forces than 

 has been yet discovered, is one of those presumptions 

 well warranted by the whole course of modern en- 

 quiry. 1 



In any case, however, if gravitation and magnetism 

 be transmitted forces, we cannot well look elsewhere 

 than to ether, provisionally so called, as the mode of 

 transmission. A necessary existence to the explanation 

 of other phenomena, we cannot bring into conjunction 

 with it another occupant of interplanetary space, the 

 properties of which as a medium could be even more 

 inconceivable, thus blended, than those we assign to 

 ether alone. As regards gravitation, indeed, we have 

 one difficulty to surmount, which if accepting the pre- 

 mises, may well be deemed insuperable. Laplace has 

 concluded from certain considerations that this attractive 

 force must have velocity of transmission some million 

 times that of light an expression which plunges us at 

 once in the gulf of the Infinite, forcing us to regard 

 this wonderful power, acting unceasingly in the uni- 



1 In the 6th and 7th Definitions of the 'Principia,' Newton especially 

 uses the magnet to illustrate some of the fundamental laws of gravita- 

 tion. 



