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wings.

A few modern birds still do this. It is
possible that the Archacopteryx could not rise in
flight from the earth escept against strong
winds, to go with the wind possibly they had
to flutter backward just as many insects
do yet.

Their long tail was very helpful in preserivng
the birds balance while in air, but later it was
shorter to allow birds the more easily to turn quickly
and fly faster.

Why than did birds put on feathers?
Live in the air requires the expenditure of
much more energy than lift on land or in the
water. In the air medium a vast ammount
of fuel must be consumed, so much that the
normal temperature of a bird varies with the
species from 102° to 110°. The normal temperature
of man is 98 1/2. Excepting some of the rapid flying
insects no animal works at such a high
temperature as the birds; [a dragon fly can out-
strip a swallow]; it can do more than any bird-
it can fly foreward, backward, and sidewise, to
right or left and change its course instantly
without turning]; no other vertebrate expends
so much energy per hour for so long a period.

To retain the heat in this bird furnace