llinaceous tribe, including pheasants,
this area is somewhat exceeded, but they are known to be very poor
fliers. Residing as they do chiefly on the ground, their wings are
only required for short distances, or for raising them or easing their
descent from their roosting-places in forest trees, the shortness
of their wings preventing them from taking extended flights. The
wing-surface of the common swallow is rather more than in the ratio of
two square feet per pound, but having also great length of pinion, it is
both swift and enduring in its flight. When on a rapid course this bird
is in the habit of furling its wings into a narrow compass. The greater
extent of surface is probably needful for the continual variations of
speed and instant stoppages for obtaining its insect food.

'On the other hand, there are some birds, particularly of the duck
tribe, whose wing-surface but little exceeds half a square foot,
or seventy-two inches per pound, yet they may be classed among the
strongest and swiftest of fliers. A weight of one pound, suspended
from an area of this extent, would acquire a velocity due to a fall of
sixteen feet--a height sufficient for the destruction or injury of most
animals. But when the plane is urged forward horizontally, in a manner
analogous to the wings of a bird during flight, the sustaining power is
greatly influenced by the form and arrangement of the surface.

'In the case of perpendicular descent, as a parachute, the sustaining
effect will be much the same, whatever the figure of the outline of the
superficies may be, and a circle perhaps affords the best resistance of
any. Take, for example, a circle of twenty square feet (as possessed
by the pelican) loaded with as many pounds. This, as just stated, will
limit the rate of perpendicular descent to 1,320 feet per minute. But
instead of a circle sixty-one inches in diameter, if the area is bounded
by a parallelogram ten feet long by two feet broad, and whilst at
perfect freedom to descend perpendicularly, let a force be applied
exactly in a horizontal direction, so as to carry it edgeways, with the
long side foremost, at a forward speed of thirty miles per hour--just
double that of its passive descent: the rate of fall under these
conditions will be decreased most remarkably, probably to less than
one-fifteenth part, or eighty-eight feet per minute, or one mile per
hour.'

And again: 'It has before been shown how utterly inadequate the mere