70 FEAGMENTS OF SCIENCE. 



raised gradually to incandescence, are strengthened to- 

 gether; intense dark heat being an invariable accom- 

 paniment of intense white heat. A sun could not be 

 formed, or a meteorite rendered luminous, on any other 

 condition. The light-giving rays constituting only a 

 small fraction of the total radiation, their unspeakable 

 importance to us is due to the fact, that their periods 

 are attuned to the special requirements of the eye. 



Among the vapours of volatile liquids vast differ- 

 ences were also found to exist, as regards their powers 

 of absorption. We followed various molecules from a 

 state of liquid to a state of gas, and found, in both 

 states of aggregation, the power of the individual mole- 

 cules equally asserted. The position of a vapour as an 

 absorber of radiant heat was shown to be determined 

 by that of the liquid from which it is derived. Re- 

 versing our conceptions, and regarding the molecules 

 of gases and vapours not as the recipients but as the 

 originators of wave-motion; not as absorbers but as 

 radiators; it was proved that the powers of absorption 

 and radiation went hand in hand, the self-same chemical 

 act which rendered a body competent to intercept the 

 waves of ether, rendering it competent, in the same 

 degree, to generate them. Perfumes were next sub- 

 jected to examination, and, notwithstanding their ex- 

 traordinary tenuity, they were found vastly superior, 

 in point of absorptive power, to the body of the air in 

 which they were diffused. We were led thus slowly up 

 to the examination of the most widely diffused and 

 most important of all vapours the aqueous vapour of 

 our atmosphere, and we found in it a potent absorber 

 of the purely calorific rays. The power of this sub- 

 stance to influence climate, and its general influence 

 on the temperature of the earth, were then briefly 

 dwelt upon. A cobweb spread above a blossom is 



