4:2 HEAT OR CALORIC. 



(d.) Guiacum passed from yellow to green during the exposure at 

 the violet end, and returned to yellow at the red end : this is supposed 

 to be an anomaly, as Dr. Wollaston ascertained that the change to 

 green is connected with the absorption of oxygen, and this principle is 

 usually separated at the violet end. 



(e.) It is said that phosphorus, which kindles easily at the red ex- 

 tremity of the spectrum, is extinguished at the violet end. 



(/.) The combination of chlorine and hydrogen is effected rapidly 

 by the red rays, but without explosion ; but the aqueous solution of 

 chlorine becomes muriatic acid most rapidly in the violet rays : " the 

 violet rays produce upon moistened red oxide of mercury the same 

 effects as hydrogen gas." Davy. 



(g.) ''Persons who had persisted in a long course of pills, formed 

 by nitrate of silver (lunar caustic) and bread, acquired a blue tinge 

 in the skin, and in one case this was deepened by exposure to light.* 



CONCLUSIONS. 



11. THE SUNBEAMS CONTAIN THREE DIFFERENT KINDS OF 

 RADIANT MATTER. 



(a.) At least it is convenient, provisionally so to regard them, as 

 the effects are thus best understood. 



(6.) It is possible, however, that they may all be varieties of one 

 thing, and the apparent difference may be owing to unknown causes. 



(c.) The rays of the sun then appear to contain 



A. Rays that illuminate, but do not cause warmth or expansion; 

 they may be called colorific rays. 



B. Rays that cause warmth and expansion, but do not illuminate ; 

 they are opake, and may be called calorific rays. 



C. Rays that produce neither color, nor heat, nor expansion, but 

 that cause certain chemical effects; they also are opake and may be 

 called chemical rays : by some they have been called de-oxidizing or 

 hydrogenating rays. The first term is preferable, on account of 

 its brevity. 



12. These three kinds of rays all come from the sun in company; 

 hence the triple effect of the solar beam, in warming and causing 

 expansion, in illuminating or imparting color, and in producing cer- 

 tain chemical effects. 



13. In the moon's rays, there is chiefly light with little or no heat. 

 Mr. Brande has ascertained, that the lunar rays do not blacken 



muriate of silver. f 



Popular opinion ascribes to them the power of stimulating vegeta- 

 tion, and of causing putrefaction in fish and other animal bodies, upon 

 which they may chance to fall. 



14. Culinary fire, as all knoiv, emits both the luminous and the heat- 



* Cooper's Thomson, note, edit. 1818, Vol. I. p. 34. t lire's Diet. p. 567. 



