concerning Heat. 163 



citing heat as convergent rays, I made the following 

 experiment. 



Experiment No. 3. Having removed the lens from 

 before the reservoir B, I suffered the direct rays of the 

 sun to fall on the blackened face of the reservoir, through 

 the circular hole, ^ inches in diameter, in the round 

 brass plate which had been constantly placed before that 

 lens in the preceding experiments. 



The reservoir A was placed behind its lens as in the 

 former experiments, and at the place where the solar 

 spectrum had 6 lines diameter. 



Having exposed this apparatus to the sun, I found 

 that the reservoir B, on which the direct rays fell, was 

 heated sensibly quicker than the reservoir A, which was 

 exposed to the action of the concentrated rays near the 

 focus of the lens. 



The temperature of the apparatus and of the atmos- 

 phere at the beginning of the experiment being 53 F., 

 = 9! R, the reservoir A required 23 minutes 30 

 seconds to raise it to the temperature of 80 F., = 2i| 

 R. ; but the reservoir B, which was exposed to the 

 direct rays of the sun, acquired the same temperature 

 in 1 8 minutes 30 seconds. 



To reach the temperature of 100 F., = 30! R., took 

 the reservoir A i hour and 3 minutes, but the reser- 

 voir B 47 minutes 15 seconds only. 



The following table will show the progress of this 

 experiment from the beginning to the end. 



