446 



Of the Propagation of Heat 



with in its passage through the substances, or solid •parts ^ 

 of which they are composed, — in that case, the warmth 

 of covering would be always, ceteris -paribus^ as the 

 quantity of materials of which it is composed ; but that 

 this is not the case, the following, as well as the fore- 

 going, experiments clearly evince. 



Having, in the experiment No. 4, ascertained the 

 warmth of 16 grains of raw silk, I now repeated the ex- 

 periment with the same quantity, or weight, of the ravel- 

 ings of white taffety, and afterwards with a like quantity 

 of common sewing-silk, cut into lengths of about two 

 inches. 



The following table shows the results of these three 

 experiments : — 



Here, notwithstanding that the quantities of the silk 

 were the same in the three experiments, and though in 

 each of them it was made to occupy the same space, yet 

 the warmth of the coverings which were formed were 

 very different, owing to the different disposition of the 

 material. 



