298 Dr. Herschel's Experiments on the Solar > and 



covered the mirror, but left all the rest of the apparatus un- 

 touched. 





No. 2. 



No. 3. 





In the Focui. 



Standard. 



0' 



57* 



54 



1 



55\ 



54 



H 



55 



54 



6 



54 



54 



Here, in six minutes, the thermometer lost the 3^ degrees of 

 heat again, which it had gained before. I uncovered the mirror 

 once more. 



o' 54 54 



ti 56 54 



3i 57 54 



5 57i 54 



And, in five minutes, the 3^ degrees of heat were regained. 

 In consequence of which, we are assured that certain rays came 

 from the candle, subject to the laws of reflection, which, though 

 they might not be the rays of light, for that our experiment does 

 not determine, were evidently invested with a power of heating 

 the thermometer placed in the focus of the mirror. 



3d Experiment. Reflection of the Heat that accompanies the Solar 



prismatic Colours. 



In the spectrum of the sun, given by a prism, I placed my 

 small steel mirror, with a thermometer in its focus.* It was 

 covered by a piece of pasteboard, which, through a proper 

 opening, admitted all the visible colours to fall on its polished 

 surface, but excluded every other ray of heat that might be, 

 either on the violet or on the red side, beyond the spectrum. 



* See Plate XII. Fig. 2. 



