would be. [6]

Having considered the purity of the air, let us next take a view of
the changes in temperature which it undergoes, and the effects which
these have upon the constitution.

We find the air sometimes considerably below the freezing point;
nay, even so much as 20 or 30 degrees; it is then intensely cold;
and on the other hand, the thermometer sometimes indicates a great
degree of heat. We then find ourselves much relaxed, and our
constitutions exhausted.

To understand how this happens, let us consider for a moment the
nature of heat, and cold.--Heat is one of those stimuli which act
upon the excitability, and support life: for if it was totally
withdrawn, we should not be able to exist even a few minutes; and
cold is only a diminution of heat. When heat is present, in a proper
degree, or the atmosphere is about that degree of heat which we call
temperate, it just gives such a stimulus, and keeps the excitability
exhausted to such a degree, as to preserve the body in health; but
if it continue for a considerable time to be much warmer than this
temperature, the consequence must be, from the laws already laid
down, an exhaustion of the excitability, and a consequent relaxation
and debility; for, when the excitability has been exhausted by the
violent application of heat, long continued, the common stimulant
powers which support life, cannot produce a sufficient effect upon
it, to give to the body that tone which is compatible with health.
On the contrary, when the heat of the air falls below what we call
temperate, or when cold is applied to the body, from the accustomed
stimulus of heat being diminished, the excitability must accumulate,
or become more liable to be affected by the action of the external
powers.

This, however, very seldom produces bad effects, unless the exciting
powers be improperly or quickly applied; for we can bear a
considerable diminution of heat without any bad consequences; and in
all cases I hope I shall be able to make it appear, that much more
mischief arises from the too great action of heat, than from the
diminution of it. Nature never made any country too cold for its
inhabitants. In cold climates, she has made exercise, and even
fatigue habitual to them, not only from the necessity of their
situation, but from choice; their natural diversions being all of
the athletic or violent kind. But the softness and effeminacy of
modern manners, has both deprived us of our natural