ON HEAT AND LIGHT. | fj(J 



Having expofed this apparatus to the fun, I found, that the It was heated 



refervoir B, on which the dired rays fell, was heated fenfibly ™ ore T :ck } 7 

 • i , , r • * , • , r , , -. than the other 



quicker than the refervoir A, which was expoied to the action byafpeftrum of 



of the concentrated rays near the focus of the lens. 6 ,ines or onc * 



The temperature of the apparatus and of the atmofphere at diam. P 

 the beginning of the experiment being 53° F. = 9° \ R. the 

 refervoir A required twenty-three minutes thirty feconds to 

 raife it to the temperature of 80* F. = 21° f R; but the 

 refervoir B, which was expofed to the direct rays of the fun, 

 acquired the fame temperature in eighteen minutes thirty 

 feconds. 



To reach the temperature of 100° F. ~ 30° £ R. took the 

 refervoir A one hour and three minutes, but the refervoir B forty* 

 ("even minutes fifteen feconds only. 



The following table will fhow the progrefs of this experi- 

 ment from the beginning to the end. 



General reftilts. 



As a confiderable part of the light that fell on the lens before This difference 

 the refervoir A, was loft in palling through it, it is evident, fenced to lighc 



...,/- • iri i bei "g loft in 



that the quantity received by this reiervoir was lets than that pa fij ng through 



received by the refervoir B, which was expofed to the direct the lens, 

 rays of the fun ; and we have feen, that the latter was heated 

 more rapidly than the former. 



As we know not exactly how much light was loft in palling This experiment 

 through the lens, we cannot determine from the remits of this is not <ka/ive ; 

 experiment, whether convergent rays be more or lefs efficacious , 



in exciting heat than parallel rays; but the difference in the 



times 



