68 Inquiry concerning the Natzire of Heat, 



bodies, or their power of affecting the temperatures of 

 other warmer bodies, at equal intervals of temperature^ is, 

 or is not, equal to .the intensity of the action of the 

 calorific rays which proceed from hot bodies. To as- 

 certain this point, I made the following very simple 

 and decisive experiment. 



Experiment No. 23. Having placed the thermoscope 

 on a table, in the middle of a large quiet room, at the 

 temperature of 72 F., I presented to one of its balls, at 

 the distance of 3 inches, the flat circular end of one of 

 the horizontal cylindrical vessels (A) above described, 

 with an oblique cylindrical neck, this vessel being filled 

 with pounded ice and water ; and, at the same moment, 

 an assistant presented to the opposite side of the same 

 ball of the thermoscope, at the same distance (3 inches), 

 the flat end of the other similar and equal cylindrical 

 vessel (B), filled with warm water at the temperature 

 of 112 F., the opposite ball of the thermoscope being 

 hid and defended, by means of screens, from the actions 

 of the bodies presented to the other ball, as also from 

 the calorific rays which proceeded from the bodies of 

 the persons present. 



From this description it appears, that while one of 

 the balls of the thermoscope was so defended by screens 

 that it could not be sensibly affected by the radiations 

 of the neighbouring bodies, the other ball was exposed 

 to the simultaneous action of two equal bodies, at equal 

 distances (two vertical metallic disks, 3 inches in di- 

 ameter, placed on opposite sides of the ball, at the 

 distance of 3 inches) ; one of these bodies being at the 

 temperature of 32 F., or 40 degrees below that of the 

 ball, while the other was at 112 F., or 40 degrees 

 above the temperature of the ball. 



