1872.] Natural and Artificial Flight. 201 
flapping its wings. Once launched into space, its motion- 
less outspread pinions, which act as true kites, cause it even 
in a calm to descend not vertically, but in a downward and 
forward curve; and if a breeze be blowing, the air plays on 
the under surface of the wings in such a manner as enables 
it to pursue a horizontal course, or to ascend, descend, 
or wheel in any direction whatever. Weight is therefore a 
principal factor in flight. By its aid a flying animal is 
actually enabled to rest on the wing. But for this arrange- 
ment, the protracted migratory journeys of birds would be 
impossible.” 
“The Wing at all times thoroughly under control.—The 
advantage which the wing derives from being movable in 
all its parts consists in this, that it can be intelligently 
wielded even to its extremity. This enables the insect, bat, 
and bird, to tread and rise upon the air as a master—to sub- 
jugate it in fact. The wing, no doubt, abstracts an upward 
and onward recoil from the air, but in doing this it exercises 
a selective and controlling power: it seizes one current, 
evades another, and creates a third; it feels and paws the 
air as a quadruped would feel and paw a treacherous 
yielding surface. It is not difficult to comprehend why this 
should be so. If the flying creature is living, endowed 
with volition, and capable of directing its own course, it is 
surely more reasonable to suppose that it transmits to 
its travelling surfaces the peculiar movements necessary to 
progression, than that those movements should be the 
result of impact from fortuitous currents which it has no 
means of regulating. ‘That the bird requires to control the 
wing, and that the wing requires to be in a condition to 
obey the behests of the will of the bird, is pretty evident 
from the faét that most of our domestic fowls can fly 
for considerable distances when they are young and when 
their wings are flexible; whereas when they are old and the 
wings stiff, they either do not fly at all or only for short dis- 
tances, and with great difficulty. This is particularly the 
case with tame swans. This remark also holds true of the 
steamer or race-horse duck (Anas brachyptera), the younger 
specimens of which only are volant. In the older birds the 
wings become too rigid and the bodies too heavy for flight. 
Who that has watched a sea-mew struggling bravely with 
the storm, could doubt for a moment that the wings 
and every individual feather of the wings are perfectly 
under control ? The whole bird is an embodiment of anima- 
tion and power. The intelligent active eye, the easy grace- 
ful oscillation of the head and neck, the folding or partial 
VOL.) 11. (N.S.) 2.0 
