74 
Sir Benjamin Thompson's 
in any considerable degree, the air from conducting, or giving 
a passage to the heat, had it been capable of passing through 
it, yet they might very much impede it in the operation of 
transporting it. 
But there is another circumstance which it is necessary to 
take into the account, and that is the attraction which subsists 
between air and the bodies above mentioned, and other like 
substances, constituting natural and artificial clothing. For, 
though the incapacity of air to give a passage to heat in the 
manner solid bodies and non-elastic fluids permit it to pass 
through them, may enable us to account for its warmth under 
certain circumstances, yet the bare admission of this principle 
does not seem to be sufficient to account for the very extraordi- 
nary degrees of warmth which we find in furs and in feathers, 
and in various other kinds of natural and artificial clothing ; nor 
even that which we find in snow ; for if we suppose the par- 
ticles of air to be at liberty to carry off the heat which these 
bodies are meant to confine, without any other obstruction or 
hinderance than that arising from their vis inertia , or the force 
necessary to put them in motion, it seems probable that the suc- 
cession of fresh particles of cold air, and the consequent loss of 
heat, would be much more rapid than we find it to be in fact. 
That an attraction, and a very strong one, actually subsists 
between the particles of air, and the fine hair or furs of beasts, 
the feathers of birds, wool, &c. appears by the obstinacy with 
which these substances retain the air which adheres to them, 
even when immersed in water, and put under the receiver of 
an air-pump ; and that this attraction is essential to the 
warmth of these bodies, I think is very easy to be demon- 
strated . 
