250 Acrial Locomotion. [April, 
inclines considerably, both downwards and backwards ; while near its extremity 
it is horizontal and somewhat slighty turned up.” .... We admit that the 
wing revolves on an axis.” .... “It was necessary therefore, for the lever, 
while fixed to the feathers of the bird, to glide freely on the rod in the direction 
of its length; and yet that it should cause it to receive, under the form of 
torsion, all the changes of inclination that are transmitted to it by the wings 
of the bird.” .... ‘For this purpose we must return to the dotted figure 8, 
which is the impression of the torsions of the wing of the different instants.” 
Dr. Pettigrew points out that the wing acts as a true 
kite, both during the down and up strokes. He remarks— 
(Trans. Roy. Soc. Edin., vol. xxvi., p. 343) :— 
‘“‘If, as I have endeavoured to explain, the wing, even when elevated and 
depressed in astri€tly vertical direction, inevitably and invariably darts for- 
ward, it follows, as a consequence, that the wing flies forwards as a true kite, 
both during the down and up strokes, and that its under concave, or biting 
surface, in virtue of the forward travel communicated to it by the body in 
motion, is closely applied to the air, both during its ascent and descent ; a fac 
hitherto overlooked, but one of considerable importance, as showing how the 
wing furnishes a persistent buoyancy alike when it rises and falls. The angle 
made by the wing of the bat and bird with the horizon is constantly varying, 
as in the insect wing.” 
Professor Marey, in his earlier writings (‘‘ Revue des 
Cours Scientifiques de la France et de l’Etranger,” Mars, 
1869) describes the wing as making a backward angle of 
45 with the horizon during its descent, and a forward angle 
of 45 during tts ascent. 
This view was shown by Dr. Pettigrew to be untenable, 
and we find it greatly modified in Professor Marey’s later work. 
Thus, at fig. 111, p. 263, where the angles of inclination 
made by the wing during its rise and fall are given, the 
under surface of the wing is represented as forming a kite, 
during quite three-fourths of one entire revolution of the 
wing. 
At no point is the wing represented as making, during its 
descent, a backward angle of 45°. Nor is this all. At p. 274, 
Professor Marey states that— 
“In free flight the axis of the bird is horizontal, or rather turned somewhat 
upward. Restored to this proper position, a fresh direction would be given to 
each of the positions of the wing. Then, probably, we should see that the 
wing always presents its lower surface to the air, as the only one which can 
find in it a point of resistance.” 
In this modified statement, as may readily be perceived, 
we have simply a repetition of Dr. Pettigrew’s view, viz., 
“ that the under surface of the wing acts as a kite, both when 
the wing rises and falls.” 
We might greatly multiply these parallel passages in 
proof of our original assertion, that in all Professor Marey’s 
writings and experiments in flight, Dr. Pettigrew’s original 
discoveries and experiments may be traced, and we may fairly 
