226 Mr. E. H. Cook on the Existence of 



given of this is that the different grouping of the molecules 

 along certain lines in the crystal determines a different ar- 

 rangement of the ether particles along these lines also. The 

 existence of this ether was, and is, considered of such impor- 

 tance by the supporters of the undulatory theory, that we find 

 attempts being made to determine experimentally some of its 

 properties. Thus Fizeau has arrived at the conclusion that 

 a moving body drags part of the ether along with it in its 

 motion. Stokes accounts for aberration by attributing to the 

 ether the properties of an elastic solid. In fact, all our phi- 

 losophers accept without reservation the material existence of 

 the luminiferous ether. It is impossible to fail to note the 

 analogy between some of the propositions of this theory and 

 those of the two-fluid theories of Magnetism and Electricity. 

 These fluids also are imponderable, invisible, yet all-pervading. 

 They interpose themselves between the molecules of bodies, 

 and are rendered evident to us only by the effects they pro- 

 duce when treated in certain ways. If we accept all these 

 theories, we must assume that between the molecules of every 

 unfortunate body we have five distinct fluids — two magnetic, 

 two electric, and the ether. Why do we not discard the four 

 and retain the ether ? and attribute to it some other proper- 

 ties which would enable it to perforin the functions of the 

 magnetic and electric fluids ? We should then only have to 

 imagine the existence of one hypothetical medium. But as 

 an effort of the imagination, the invention of five hypothetical 

 fluids is as easy as the invention of one. 



In order, then, to obtain for light the enormous velocity 

 which experiment has shown it to possess, the supporters of 

 the undulatory theory have boldly filled all space with a sub- 

 stance which, conforjning to the equation v — \ /-? , possesses 



very great elasticity and very little density. The velocity 

 with which light travels through air we may take to be 185,000 

 miles per second. Sound, let us suppose, travels at 1100 feet 

 per second. Light therefore travels 888,000 times as fast 

 through air as sound does. To find what proportion exists 

 between the density and elasticity of the air and ether, let us 

 suppose the velocity of sound through air to be equal to 1000 

 feet per second (in this calculation the correct velocity is, of 

 course, 916 feet per second). Then we have 



elast. of air : elast. of ether : : 1000 2 : (185,000 x 5280) 2 , 



assuming the density to remain constant. This gives us 

 954,138,240,000 as the number of times that the elasticity of 

 the ether is greater than that of the air ; assuming the density 



