USEFUL PROJECTS. 
all, as has been abundantly shown 
by the foregoing experiments. 
Hence it appears why those furs 
which are the finest, longest, and 
thickest, are likewise the warmest ; 
and how the furs of the beaver, of 
the otter, and of other like quadru- 
peds which live much in water, and 
the feathers of water-fowls, are able 
to confine the heat of those animals 
in winter, notwithstanding the ex- 
treme coldness and great conduct- 
ing power of the water in which 
they swim. The attraction between 
these substances and the air which 
occupies their interstices, is so 
great, that this air is not dislodged 
even by the contact of water, but, 
remaining in its place, it defends 
the body of the animal at the same 
time from being wet, and from be- 
ing robbed of its heat by the sur- 
rounding cold fluid ; and it is possi-. 
ble that the pressure of this fluid 
upon the covering of air confined 
in the interstices of the fur, or fea- 
thers, may at the same time increase 
its warmth, or non-conducting pow- 
er, in sucha manner that the animal 
may not, in fact, lose more heat 
when in water than when in air: 
for we have seen by the foregoing 
experiments, that, under certain 
circumstances, the warmth of a co- 
vering is increased, by bringing its 
component parts nearer together, 
or by increasing its density even at 
the expence of its thickness, But 
this point will be further investi- 
gated hereafier. 
Bears, wolves, foxes, hares, and 
other like quadrupeds, inhabitants 
of cold countries, which do not of- 
ten take the water, bave their fur 
much thicker upon their backs than 
upon their bellies. The heated air 
Occupying the interstices of the 
hairs of the animal tending natural- 
A13 
ly to rise upwards, in consequence 
of its increased elasticity, would 
escape with much greater ease from 
the backs of quadrupeds than from 
their bellies, had not Providence 
wisely guarded against this evil by 
increasing the obstructions in those 
parts, which entangle it and confine 
it to the body of the animal. And 
this, I think, amounts almost to 2 
proof of the principles assumed re- 
lative to the manner in which heat 
is carried off by air, and the causes 
of the non-conducting power of 
air, or its apparent warmth, when, 
being combined with other bodies, 
it acts as a covering for confining 
heat. 
The snows which cover the sur- 
face of the earth in winter, in high 
latitudes, are doubtless designed by 
an all-provident Creator, as a gar- 
ment to defend it against the pierc- 
ing winds from the polar regions, 
which prevail during the cold sea- 
son. 
These winds, notwithstanding the 
vast tracks of continent over which 
they blow, retain their sharpness as 
long as the ground they pass over is 
covered with snow; and it is not 
till, meeting with the ocean, :hey 
acquire from a contact with its 
waters, the heat which the snows 
prevent their acquiring from the 
earth, that the edge of their cold- 
ness is taken off, and they gradually 
die and are lost. 
The winds are always found to 
be much colder when the ground 
is covered with snow than when it 
is bare; and this extraordinary cold- 
ness is vulgarly supposed to be com- 
municated to the air by the snow ; 
but this is an erroneous opinion ; 
for these winds are in general much 
colder thaa the snow itself. 
They retain their coldness, be- 
cause 
