on the Subject of Heat. 



227 



The accompanying figure represents the vertical sec- 

 tion of one of these boxes in a horizontal position. 

 The stopper is also shown by diagonal lines, and a part 

 of the thermometer in its proper place. 





In order to diminish the loss of heat which might 

 take place through the bottom and the sides of the box, 

 each one was covered inside and outside with well-sized 

 paper, then coated three times with copal varnish, and, 

 in addition to this, they were covered during the experi- 

 ment with an envelope of fur. 



When one of the boxes was placed for a certain 

 length of time in the sun, so that its rays fell vertically 

 upon the metallic disk, there was a certain amount of 

 heat excited in the same ; and, as this heat was evenly 

 distributed within the box by means of the metallic 

 threads, it was possible to observe very exactly the vari- 

 ous degrees of heat by means of the thermometer ; if 

 all three boxes were placed at the same time in the sun, 

 it was possible to determine with certainty the relative 

 amounts of heat excited at the surface of the three differ- 

 ent metals used in the experiment. 



