68 
Sir Benjamin Thompson's 
All the different substances which I had yet made use of in 
these experiments for surrounding or covering the bulb of the 
thermometer, fluids excepted, had, in a greater, or in a less de- 
gree, confined the heat, or prevented its passing into or out of 
the thermometer so rapidly as it would have done, had there 
been nothing but air in the glass globe, in the centre of which 
the bulb of the thermometer was suspended. But the great 
question is, how, or in what manner, they produced this effect ? 
And first, it was not in consequence of their own non-con- 
ducting powers, simply considered ; for, if instead of being only 
bad conductors of heat, we suppose them to have been totally 
impervious to heat, their volumes or solid contents were so ex- 
ceedingly small in proportion to the capacity of the globe in 
which they were placed, that, had they had no effect whatever 
upon the air filling their interstices, that air would have been 
sufficient to have conducted all the heat communicated, in less 
time than was actually taken up in the experiment. 
The diameter of the globe being 1 ,6 inches, its contents 
amounted to 2,14466 cubic inches; and the contents of the 
bulb of the thermometer being only 0,08711 of a cubic inch, 
(its diameter being 0,55 of an inch) the space between the 
bulb of the thermometer and the internal surface of the globe 
amounted to 2,1446— 60,0871 1 = 2,05755 cubic inches; the 
whole of which space was occupied by the substances by which 
the bulb of the thermometer was surrounded in the experi- 
ments in question. 
But though these substances occupied this space, they were 
far from filling it ; by much the greater part of it being filled 
by the air which occupied the interstices of the substances in 
question. In the experiment N° 4, this space was occupied 
