242, Aérial Locomotion. (April, 
margin of the wing should not be composed of a rigid rod may be demonstrated 
in a variety of ways. Ifa rigid rod be made to vibrate by the hand, the vibra- 
tion is not smooth and continuous; on the contrary, it is irregular and jerky, 
and characterised by two pauses, the one occurring at the end of the up stroke, 
the other occurring at the end of the down stroke. The wing to be effective as 
an elevating and propelling organ should have no dead points, and should be 
characterised by a rapid winnowing or fanning motion. .... If a longitudinal 
section of bamboo cane has added to it tapering rods of whalebone which 
radiate in an outward direction, and this (framework)* be covered by a thin 
sheet of india-rubber (gutta-percha tissue), an artificial wing, resembling the 
natural one in all its essential points, is atonce produced..... If this wing 
be made to vibrate by its root, a series of longitudinal and transverse waves are 
at once formed, the one series running in the direction of the length of the 
wing, the other in the direction of its breadth. The wing further twists and 
untwists during the down and up strokes..... This form of wing, which 
may be regarded as the realisation of the figure-of-8 theory of flight, elevates 
and propels both during the down and up strokes, and its working is accom- 
panied with almost no slip. It seems literally to float upon the air.t+ 
“No wing that is rigid in the anterior margin can twist and untwist during 
its action, and produce the figure-of-8 curves generated by the living wing. To 
produce the curves in question, the wing must be flexible, elastic, and capable 
of change of form in all its parts.’’{ 
In one part of his new work, indeed (viz., at p. 198), 
Professor Marey seems to have largely profited by the 
observations and experiments of Dr. Pettigrew, as given 
above; for he states that, if rapid to-and-fro movements in 
a vertical plane be given to a ‘‘ flexible shaft”’ (mark, the 
shaft is no longer described as 71gid), to which he affixes a 
membrane similar to that found in the wings of inseéts—to 
use his own words—this flexible shaft will then represent the 
main rib of the wing; and we shall see this contrivance 
execute all the movements which the wing of the insect 
describes in space.” “If,” he says, “‘ we illuminate the 
extremity of this artificial wing, we shall see that its point 
describes the figure 8 like a real wing; we shall observe also 
that the plane of the wing changes twice during each revolution, 
in the same manner as in the insect itself.”—(‘‘Animal 
Mechanism,”’ p. 198).|| 
Professor Marey, it will be observed, claims for his 
artificial wing similar properties to those originally claimed 
by Dr. Pettigrew for his artificial wing. Thus Dr. Pettigrew 
states (op. cit., pp. 421, 422), that if the anterior or thick 
margin of his artificial wave wing be directed upwards, and 
* The words in brackets are ours, 
+ Trans. Roy. Soc. Edin., vol. xxvi., 1870, pp. 408, 419, 420, and 422. 
+ Physiology of Wings. By J. Bett Petticrew, M.D., F.R.S., p. 422. 
(Trans. Roy. Soc. Edin., vol. xxvi., 1870). 
|| The above remarks of Professor Marey are worth studying; for two 
reasons: first, because they are so confirmatory of all Dr. Pettigrew had 
written about the flexibility of the main nervure of an insedct’s wing ; secondly, 
they contrast so strangely with the rigid main rib, at pp. 201 and 208 of 
Marey’s work before cited.”’ 
