FACULTIES OF THE MIND. 253 
habit. The standard of temperature may be altered a few 
degrees, provided the change be slowly brought about. 
If it is attempted rapidly, a diseased state of the system, in 
general, is the consequence. In some cases, the sensibility 
of the nerves is, to a certain extent, destroyed by the 
change, so that the exposed parts cease to experience those 
painful impressions which, under other circumstances, 
would have been produced. . 
Man is the only being on this globe who, in the gratifi- 
cation of this desire, kindles a fire wherewith to warm 
himself. He makes use of friction or percussion to ex- 
cite the heat, in the first instance, and employs vegetables, 
or bitummous minerals, to increase and continue it. It 
is possible to ascertain, whether this was originally the 
diseovery of an individual, and subsequently communicated. 
by example or tradition, or whether it be really a cha- 
racter of this active power as it exists in man. It is at 
least certain, that the use of artificial heat is coeval and co- 
existent with our race. ‘The monkey may approach the 
fire which the savages have left, and warm himself at its 
glowing embers, but he is never prompted to secure a con- 
tinuance of the comfort, by the addition of fresh fuel, or 
by setting fire to combustible matter in another situation. 
2. Clothing—Many animals are produced at their 
birth, in such circumstances, that they stand im no need of 
any other clothing than the skin, and its natural appen- 
dices, and continue through life independent of the protec- 
tion of foreign bodies. Such animals are, of course, un- 
provided with this instinctive principle. But there are 
other animals which, during a part or the whole of life, 
stand in need of an artificial covering for their protection. 
Of those which cover themselves only during a certain 
part of life, there are some which derive the materials of 
their habitation from their own body, as the silk-worm, 
