me of the tropical animals like
the elephant and rhinoceros, or in man, who has learned to protect
himself in cold regions by making clothing for himself, this hair is
very short, and except where serving for ornament is quite scanty, no
longer being of use as a protection. But the great majority of all
mammals are well covered with a dense coat of hair. In many of those
living in the colder regions there is in reality a double coat. The
fur seal of the Alaskan Islands is so provided. A set of long hairs
deeply fastened in the skin forms a covering, which shows on looking
at the seal. Underneath this layer, and set but lightly into the skin,
is a short coat of very much finer hair known as the underpelt. When
the skin is taken from the seal it is split by machinery into a lower
and an upper layer. When so split the deep-seated pits of the long
hairs are cut, and these hairs come out. The fine underpelt thus laid
bare is what is commonly known as sealskin. Fashion has decreed that
this must be dyed a rich brown, although when taken from the animal it
is nearly mouse gray.

The birds have need for better clothing. To begin with, their blood is
much warmer, and hence needs better protection from outside cold. In
addition such of them as fly high must be prepared to stand great
variations in temperature. For these purposes birds need a covering of
the finest type. This clothing, in addition, must be extremely light
because the creature must carry it into the air in flight. All of the
requisite conditions are thoroughly met by the feather, which is the
lightest and warmest clothing known to man. If at night we wish,
regardless of expense, to keep ourselves warm with the lightest and
warmest of covering, we send to the Arctic Sea, and from the breast of
the eider duck we pluck the down which lies between the warm blood of
the duck with its temperature of one hundred and seven degrees and the
water in which the iceberg floats.

Young mammals and birds, before their clothing has well formed, are
naturally susceptible to cold; this leads to the first genuine
approach to a home among animals lower than man. Birds lay their eggs
long before the creatures inside of them are ready to emerge.
Accordingly they have learned to build nests in which to place these
eggs, and to protect them from the outside air; meanwhile the bird
keeps the eggs warm by close contact with its own body. The lowest of
the birds may lay their eggs simply o