40 



THE RADIATIONS OF IGNITED BODIES. [MEMOIR 1. 



platinum ; then taking an Argand lamp, surrounded by 

 a cylindrical metal shade, through an aperture in which 

 the light passed, and the flame of which I had found by 

 previous trial would continue for an hour of almost the 

 same intensity, I approached it to the paper sheet, until 

 the shadow cast by the copper disappeared. The dis- 

 tance at which this took place was then measured, and 

 the temperature of the platinum determined. 



The temperature of the platinum was now raised, the 

 shadow became more intense, and it was necessary to 

 bring the Argand lamp nearer before it was effaced. 

 When this took place, the distance of the lamp was 

 again measured, and the temperature of the platinum 

 again determined. 



In Fig. 5, a b is the strip of ignited platinum. It casts 

 a shadow, h, of the metal rod e on the white screen fg; 

 c is a metallic cylinder containing an Argand lamp, the 

 light of which issues through an aperture, d, and extin- 

 guishes the shadow on the screen. 



Fig. 5. 



In this manner I obtained several series of results, one 

 of which is given in the following table. They exhib- 

 ited a more perfect accordance among each other than I 

 had anticipated. 



The intensity of the light of the platinum is of course 

 inversely proportional to the square of the distance of 



