158 DISCOURSE ON THE STUDY 



phenomena of light and the resistance of comets 

 give us reason to believe fills all space, and which, 

 in analogy to all the elastic media known, may be 

 supposed to possess a temperature and a specific 

 heat of its own, which it is capable of communi- 

 cating to bodies surrounded by it. Now, if we 

 consider that the heat radiated by the sun follows 

 the same proportion as its light, and regard it as 

 reasonable to admit with respect to stellar heat 

 what holds good of solar ; the effect of stellar radia- 

 tion in maintaining a temperature in space should 

 be as much inferior to that of the radiation of the 

 sun as the light of a moonless midnight is to that 

 of an equatorial noon ; that is to say, almost incon- 

 ceivably smaller. Allowing, then, the full effect 

 for this cause, there would still remain a great 

 residuum due to the presence of the ether. 



(161.) Many of the new elements of chemistry 

 have been detected in the investigation of residual 

 p/ienomena. Thus, Arfwedson discovered lithia by 

 perceiving an excess of weight in the sulphate pro- 

 duced from a small portion of what he considered as 

 magnesia present in a mineral he had analysed. It 

 is on this principle, too, that the small concentrated 

 residues of great operations in the arts are almost sure 

 to be the lurking places of new chemical ingredients : 

 witness iodine, brome, selenium, and the new metals 

 accompanying platina in the experiments of Wol- 

 laston and Tennant. It was a happy thought of 

 Glauber to examine what every body else threw 

 away. 



(162.) Finally, we have to observe, that the de- 

 tection of a possible cause, by the comparison 01 



