204 



Historical Review of Experiments 



Having convinced myself by these experiments that 

 the fineness of the particles or fibres of the substance 

 used as a covering contributes very much to the warmth 

 of the same, I made the following experiments to 

 determine what effect the condensing of the covering 

 would have, the quantity of matter of which it was com- 

 posed remaining the same, but the thickness being 

 decreased. 



As I had already, by means of the foregoing experi- 

 ments, determined the warmth of coverings of raw 

 silk, wool, cotton, and linen when taking 16 grains 

 of each substance, and making thereof, about the bulb 

 of a thermometer, a globular covering half an inch 

 thick, I now took 16 grains of moderately coarse 

 threads of each of these four substances, and with them 

 I made four new experiments. 



Instead of filling with these threads the entire space 

 between the bulb of the thermometer and the inner 

 surface of the globe, in the middle of which was the 

 bulb, I wound it around the bulb of the thermom- 

 eter, so that the latter looked exactly like a little 

 ball. 



I now introduced, as before, the thermometer bulb 



