1875.] Aérial Locomotion. 245 
heaviest part is placed as low as possible beneath the point of suspension. 
The bird, as it descends with its wings outspread, will thus present its ventral 
region downwards, without its being necessary to make an effort to keep its 
equilibrium; 1t will take this position passively, like a parachute set free in 
space, or like the shuttlecock when it falls upon the battledore.”—(“ Animal 
Mechanism,” p. 216.) 
Dr. Pettigrew likens the wing of the bird to a boy’s kite 
(Proc. Roy. Inst. of Great Britain, March 22, 1867)— 
“‘ The wing of the bird acts after the manner of a boy’s kite, the only dif- 
ference being that the kite is pulled forwards upon the wind by the string and 
the hand, whereas in the bird the wing is pushed forwards on the wind by the 
weight of the body and the life residing in the pinion itself.” 
Similar in substance is the subjoined passage from Prof. 
Maney (p..220) :— 
‘*Tn the last two forms, the wing, directed more or less obliquely, derives 
its point of resistance from the air, like the child’s plaything called a kite, but 
with this difference—that the velocity is given to the kite by the tractile force 
exerted on the stving when the air is calm, while the bird when it hovers 
utilises the speed which it has already acquired either by its oblique fall or by 
the previous flapping of its wings.” 
Dr. Pettigrew attaches great importance to the activity of 
the wing and its small size. Thus he remarks (Trans. Roy. 
soc. Edin., vol. xxvi., p. 408)— 
“The surface exposed by a natural wing, when compared with the great 
weight it is capable of elevating, is remarkably small. This is accounted for 
by the length and great range of motion of natural wings, the latter enabling 
the wings to convert large traés of air into supporting areas. It is also ac- 
counted for by the multiplicity of the movements of natural wings, these 
enabling the pinions to create and rise upon currents of their own forming, 
and to seleé and utilise existing currents.” . . . ‘ The problem of flight would 
seem to resolve itself into one of weight, power, velocity, and small surfaces, as 
against comparative levity, debility, diminished speed, and extensive surfaces.” 
—(P. 386.) 
Analogous in many respects to the foregoing is the fol- 
lowing from Prof. Marey (p. 222) :— 
“The part played by the wing in flight is not merely passive, for a sail or a 
parachute ought always to have a surface in proportion to the weight which it 
has to support; but, on the contrary, when considered in its proper point of 
view, as an organ which strikes the air, the wing of the bird ought, as we 
shall see, to present a surface relatively less in birds of a large size and of 
great weight.” 
Again :— 
‘“‘ Animals of large size and great weight sustain themselves in the air with 
a much less proportionate surface of wing than those of smaller size.””—(P. 222.) 
Dr. Pettigrew dwells upon the relative speed attained by 
the different parts of the wing (Trans. Roy. Soc. Edin., vol. 
XXVi., pp. 399—442). He says the wing as a rule is long and 
narrow. 
“As a consequence a comparatively slow and very limited movement at the 
root confers great range and immense speed at the tip, the speed of each portion 
