206 FRAGMENTS OF SCIENCE. 



and permitting the calorific rays beyond the red to pass 

 freely through it. This substance was then employed to 

 filter the beams of the electric light, and to form foci of . 

 invisible rays so intense as to produce almost all the effects 

 obtainable in an ordinary fire. Combustible bodies were 

 burnt and refractory ones were raised to a white heat by the 

 concentrated invisible rays. Thus, by exalting their rc- 

 frangibility, the invisible rays of the electric light were 

 rendered visible, and all the colors of the solar spectrum 

 were extracted from utter darkness. The extreme richness 

 of the electric light in invisible rays of low refrangibility 

 was demonstrated, one-ninth only of its radiation consisting 

 of luminous rays. The deadness of the optic nerve to those 

 invisible rays was proved, and experiments were then 

 added, to show that the bright and the dark rays of a 

 solid body raised gradually to intense incandescence, are 

 strengthened together ; intense dark heat being an inva 

 riable accompaniment 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 im 

 portance to us is due to the fact that their periods are 

 attuned to the special requirements of the eye. 



Among the vapors of volatile liquids vast differences 

 were also found to exist, as regards their powers of absorp 

 tion. 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 molecules equally asserted. 

 The position of a vapor as an absorber of radiant heat was 

 shown to be determined by that of the liquid from which it 

 is derived. Reversing our conceptions, and regarding the 

 molecules of gases and vapors 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 



