310 On the Velocity of the calorific Rays 



The numerous and important experiments of that excel- 

 lent and most indefatigable philosopher Dr. Herschel, mani- 

 festly show, that rays of a nature different from light, on 

 which depends the vivifying heat of the sun, are also 

 emitted by him, and are subject to similar laws of reflection 

 and refraction. By the experiments also of the admirable 

 Scheele and Senebier, as further cultivated by Messrs. Rit- 

 ter and Bockman in Germany, and by Dr. Wollaston in 

 England, we have still more recently detected a third sort 

 of rays, fairly separable by the prism from those of light 

 and caloric, and which, beyond the visible boundary of the 

 violet colour, are found to produce very peculiar effects, 

 heretofore falsely imputed to the sun's light. 



These two discoveries will probably be thought important 

 by the philosophical chemist. At any rate, they will de- 

 mand of him to review and new model certain received 

 opinions, and may ultimately lead to no small improvement 

 of his science, by discarding from it several imaginary ef- 

 fects of light, and tracing the same to their real sources by 

 a more enlarged experience. 



Ever since considering the sun's emanations as so com- 

 pounded, and as consisting at least of three different prin- 

 ciples, namely, light, caloric, and rays also of what has 

 been called the deoxidizing principle, — it has appeared a cu- 

 rious question, how far these radiations may differ in re- 

 spect to the velocity with which they are emitted or sent 

 forth by the sun. This inquiry seems not only interesting 

 on its own account, but because, were their velocities found 

 unequal to any considerable degree, we should have an ad- 

 ditional argument of much force in favour of such rays 

 being of a nature entirely different. 



In a valuable philosophical work lately published by a 

 very respectable author, there is an observation relating to 

 this subject expressed in the. following terms : u That as 

 the ravs of light and of caloric, emitted by the sun, accom- 

 pany each other, it cannot be doubted that they move with 

 the same velocity*." But as to this, so far as the meaning 

 is understood, there seems to be some mistake or oversight. 

 If by the rays so accompanying one another be meant that 

 all the constituent particles of each of the two kinds, at the 

 same instant emitted, still keep contiguous, each to each, 

 in their progress forward from the sun, then surely they 

 must move with the same common velocity. This, how* 



* Sec Mr. Thomson's System of Chemistry, 2d edit. Edinburgh, 1804, 

 vol. 1. page 306. 



ever,- 



