462 Molecules, Ultimates, Atoms, and Waves. [October, 



wave to the departure of the individual particles from their 

 points of rest would attain the enormous proportion of 

 between 102 and 103 billions to 1. On the supposition that 

 the departure exceeds the radius of the particle, the diameter 

 of an ethereal particle would be to the length of this 

 shortest wave, while passing through quartz, in the ratio of 

 1 to upwards of 50 billions. To such an extreme degree do 

 these estimates render it probable, that the divisibility of 

 matter is actually carried in the case of the individual particles 

 of the luminiferous ether — a circumstance rendering it less 

 improbable that even the ultimate of hydrogen, the lightest 

 with which we are acquainted, ma}' consist of a considerable 

 number of more minute atoms. 



There is another circumstance tending to support this 

 supposition, namely, the peculiar action which certain bodies 

 exert on the ether irrespective of their specific gravity — an 

 action in which hydrogen is pre-eminent over all other sub- 

 stances. To illustrate this point, take the following six 

 media, the refractive indices, and specific gravities of which 

 are as under — that of hydrogen being adopted as the 

 standard of unity. 



Refractive Index. Sp. gr. 



Hydrogen . . . . . . 1*000138 1*000 



Oxygen 1*000272 16*000 



Atmospheric air . . . . 1*000294 14*500 



Tabasheer 1*111450 28,449 



Water 1*336000 n>798 



Chromate of lead . . . 2*974000 70,829 



Since light travels about 11,721 inches in the millionth of 

 a second in the free ether, and as its speed is retarded by 

 each medium in proportion to its refractive index, the 

 spaces through which light would pass in the millionth of a 

 second while traversing the above six media would be as 

 under: — 



Inches. Inches. 



Hydrogen . . 11,719*38 Tabasheer . . . 10,545*68 

 Oxygen . . . 11,717*81 Water .... 8,773*20 

 Atmospheric air 11,717*55 Chromate of lead 3,941*16 



Hence, to traverse a given space, say a million of inches, 

 light would require, for the several media, the following 

 periods expressed in millionths of a second : — 



The free ether . . 85*3170 Tabasheer . . . 94*8255 



Hydrogen . . . 85*3287 Water 113*9873 



Oxygen .... 85*3402 Chromate of lead . 253*7326 



Atmospheric air . 85*3420 



