Mlscellanks, 189 



le strongest by the black surfaces. Now, since the effect was the 

 line, whatever the chemical composition of the coloring matter, it is 

 proper to infer that it is wholly independent of the coloring matter, 

 and that is derived simply from the action of the color. 



But are these two circumstances of color and surface, the only ones 

 which communicate to bodies the faculty of absorbing calorific rays ? 

 In order to ascertain this point, .it was necessary in the first place 

 to proceed independently of the said circumstances of surface and 

 color. For this purpose, we took white fabrics of silk, of cotton, of 

 wool, of hemp and of flax ; all exactly equal in the size of the thread, 

 in the tissue and in the shade. The five tissues were applied with 

 gum to the disks, exposed to the sun, and presented to the instrument. 

 We obtained the following order for the absorbing power : silk, wool, 

 cotton, jiax and hemp. This is just the inverse order of their con- 

 ductibilities. 



There are no very great differences in the tone or the tints which 

 the common metals present; and if we except lead and tin, we can 

 communicate to them all nearly the same degree of polish. We cov- 

 ered, therefore, several disks with equal sized metallic layers, and in 

 submitting them to the instrument, we obtained the same result. 

 The scale of the conductibility of the metals is, as is known, copper, 

 silver, gold, steel- iron, tin and lead. Our experiments upon the ab- 

 sorbing f^wers of different substances show, therefore, that it Is pre- 

 cisely the reverse of their powers of conduction. 



Many mineral substances are found which affect the yellowish col- 

 or of wood : we selected therefore, plates of wood and of stone, 

 equd'as nearly as possible as to the state and color of their surfaces ; 

 and we repeated upon them the same experiments as upon the met- 

 als and the tissues. The woods, which were worse conductors than 

 the minerals, were nevertheless, those which showed the greatest ab- 

 sorbing power. Finally, we compared lead with a stone of similar 

 color. The substance possessed of least conductibility, proved the 

 most absorbant; that is to say, the stone gave an absorbing force su- 

 perior to that of the lead. 



At first, we were tempted to believe that this inverse relation be- 

 tween the absofbing and conducting powers, exists only in appear- 

 ance ; and is derived from the resistance, more or less considerable, 

 which the motion of the caloric experiences from the action of the 

 bodies : so that the caloric, not being able to pass freely through the 

 internal strata of the non-conducting substances, accumulates at Its 



