Experiments upon Heat. 
57 
The bulb of the thermometer being 
surrounded by Eider down. 
Heat lost. 
16 grains. 
32 grains. 
64 grains. 
(Exp. No. 11.) (Exp. No. 12.) 
(Exp. No. 13.) 
70 ° 
— 
— 
— 
6 o° 
97 " 
111" 
112" 
5 o° 
117 
128 
130 
4 °° 
H 5 
i 57 
165 
3 °° 
192 
207 
224 
20° 
267 
3°4 
326 
10° 
486 
5^5 
658 
Total times 
1304 
1472 
1613 
Without stopping at present to draw any particular conclu- 
sions from the results of these experiments, I shall proceed to 
give an account of some others, which will afford us a little 
further insight into the nature of some of the circumstances 
upon which the warmth of covering depends. 
Finding, by the last experiments, that the density of the 
covering added so considerably to the warmth of it, its thick- 
ness remaining the same, I was now desirous of discovering how 
far the internal structure of it contributed to render it more or 
less pervious to heat, its thickness and quantity of matter re- 
maining the same. By internal structure, I mean the dispo- 
sition of the parts of the substance which forms the covering ; 
thus they may be extremely divided, or very fine, as raw silk as 
spun by the worms, and they may be equally distributed 
through the whole space they occupy ; or they may be coarser, 
MDCCXCII. I 
