8 FRAGMENTS OF SCIENCE 



spaces are occupied by matter, it is able to offer proofs 

 almost as cogent as those which can be adduced of the 

 existence of an atmosphere round the earth. Men's minds, 

 indeed, rose to a conception of the celestial and universal 

 atmosphere through the study of the terrestrial and local 

 one. From the phenomena of sound, as displayed in the 

 air, they ascended to the phenomena of light, as displayed 

 in the ether ; which is the name given to the interstellar 

 medium. 



The notion of this medium must not be considered as 

 a vague or fanciful conception on the part of scientific 

 men. Of its reality most of them are as convinced as 

 they are of the existence of the sun and moon. The 

 luminiferous ether has definite mechanical properties. It 

 is almost infinitely more attenuated than any known gas, 

 but its properties are those of a solid rather than of a 

 gas. It resembles jelly rather than air. This was not 

 the first conception of the ether, but it is that forced 

 upon us by a more complete knowledge of its phenom- 

 ena. A body thus constituted may have its boundaries; 

 but, although the ether may not be co- extensive with 

 space, it must at all events extend as far as the most dis- 

 tant visible stars. In fact it is the vehicle of their light, 

 and without it they could not be seen. This all-pervad- 

 ing substance takes up their molecular tremors, and con- 

 veys them with inconceivable rapidity to our organs of 

 vision. It is the transported shiver of bodies countless 

 millions of miles distant, which translates itself in human 

 consciousness into the splendor of the firmament at night. 



If the ether have a boundary, masses of ponderable 

 matter might be conceived to exist beyond it, but they 

 could emit no light. Beyond the ether dark suns might 



