4 FKAGMENTS OF SCIENCE. 



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 terres- 

 trial and local one. From the phenomena of sound, 

 as displayed in the air, they ascended to the phenomena 

 of light, as displayed in the cether ; 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 aether 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 sether, but it is that 

 forced upon us by a more complete knowledge of its 

 phenomena. A body thus constituted may have its 

 boundaries ; but, although the sether may not be co- 

 extensive with space, it must at all events extend as far 

 as the most distant visible stars. In fact it is the 

 vehicle of their light, and without it they could not 

 be seen. This all-pervading substance takes up their 

 molecular tremors, and conveys 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 

 splendour of the firmament at night. 



If the sether have a boundary, masses of ponderable 

 matter might be conceived to exist beyond it, but they 

 could emit no light. Beyond the aether dark suns 

 might burn ; there, under proper conditions, combustion 

 might be carried on; fuel might consume unseen, and 

 metals be fused in invisible fires. A body, moreover, 



