372 THE EOYAL INSTITUTION. [CHAP. VI. 



ing power is three times as strong in an exhausted 

 receiver as in the open air,' and, ' fully proves that 

 radiation is not caused by undulations in the atmo- 

 sphere. It is strongest when no atmosphere is present.' 

 He ends his account of the effects of radiant heat thus : 

 6 Were it not for this terrestrial radiation of earthly 

 bodies, the heat would accumulate from the rays of the 

 sun until at last the whole world would be unin- 

 habitable. 



6 But, besides the effects produced by the two species 

 of radiant matter radiant light and radiant heat there 

 are other effects chemical effects that take place 

 caused by the action of some radiant matter that 

 comes to us from the sun, perhaps a single substance 

 that, independent of light and heat, causes effects by 

 its own power.' And then he showed an experiment of 

 chlorine and hydrogen exposed to light. 



He says, 'There is a very singular analogy that 

 exists between the rays at the violet end of the spectrum, 

 hydrogen gas, and the negative pole of the voltaic 

 battery ; and opposed to it stands the analogy of the 

 rays at the red end of the spectrum to positive electri- 

 city ; they produce opposite effects to the first-mentioned 

 arrangement, but act similar to each other. 



6 If that sublime idea of the ancients that there is 

 only one species of matter in the universe, and that its 

 different properties depend on the difference of size, 

 shape and other qualities should be confirmed, it 

 would simplify the science in a most eminent degree, 

 and at the same time it would raise it to the acme of 

 perfection.' 



