Experiments upon Heat. 6 g 
by 16 grains of raw silk ; and as the specific gravity of raw 
silk is to that of water as 1734 to 1000, the volume of this 
silk was equal to the volume of 9,4422 grains of water ; and as 
1 cubic inch of water weighs 253,185 grains, its volume was 
equal to °’°37 2 94 a cubic incl1 » and > as the s P ace 
it occupied amounted to 2,05755 cubic inches, it appears 
that the silk filled no more than about part of the space 
in which it was confined, the rest of that space being filled 
with air. 
In the experiment N° 1, when the space between the bulb 
of the thermometer and the glass globe, in the centre of which 
it was confined, was filled with nothing but air, the time 
taken up by the thermometer in cooling from 70° to io° was 
57 6 seconds; but in the experiment N° 4, when this same 
space was filled with 54 parts air, and 1 part raw silk, the 
time of cooling was 1284 seconds. 
Now, supposing that the silk had been totally incapable of 
conducting any heat at all, if we suppose, at the same time, 
that it had no power to prevent the air remaining in the globe 
fi m conducting it, in that case its presence in the globe could 
only have prolonged the time of cooling in proportion to the 
quantity of the air it had displaced to the quantity remaining, 
that is to say, as 1 is to 54, or a little more than 10 seconds. But 
the time of cooling was actually prolonged 708 seconds, (for in 
the experiment N° 1, it was 57 6 seconds, and in the experiment 
N° 4, it was 1284 seconds, as has just been observed) ; and this 
shows, that the silk not only did not conduct the heat itself, 
but that it prevented the air by which its interstices were filled 
from conducting it ; or, at least, it greatly weakened its power 
of conducting it. 
