A substance should also be chosen which is known to be a poor conductor
of heat. That generated by the system will thus be retained where it is
needed, instead of being dispersed into the atmosphere.

We might add that the better the material for accomplishing these
purposes, the less will be needed to be worn; for we do not wish to wear
or carry about with us any more material than is necessary. It so
happens that all of these qualities are found combined in _flannel_. The
value of this article worn next to the skin cannot be over-rated, for
while it affords protection from cold during the winter months, it is
equally beneficial during the heat of summer, because it imbibes the
perspiration, and being very porous, allows it to escape. The skin
always feels soft, smooth, and pliable, when it is worn; but, when
cotton takes its place, it soon becomes dry and harsh. Its natural
adaptability to these purposes, shows that it is equally a comfort and a
source of health. Where the skin is very delicate, flannel sometimes
causes irritation. In such cases a thin fabric of linen, cotton, or
silk, should be worn next the skin, with flannel immediately over it.
Where there is a uniform and extreme degree of heat, cotton and linen
are very conducive to comfort. But they are unsuitable in a climate or
season liable to sudden fluctuations in temperature.

The value of furs, where people are exposed to extreme cold, cannot be
overestimated. They are much warmer than wool, and are chiefly used as
wraps on going outdoors. They are too cumbrous and expensive for
ordinary wear in this latitude, but in places near the poles they
constitute the chief clothing of the inhabitants.

The quantity of clothing worn is another important item. The least that
is necessary to keep the body well protected and evenly tempered when