1875.) Aérial Locomotion. 249 
. 
running in the direction of the length of the wing, the other 
in the direction of its breadth), and that the action of the 
wing resembles the action of an oar in sculling. (Trans. 
Ringe. 50c., vol. xxvi., pp. 206, 229, 231, and 206 ;. Proc. 
Roy. Inst. of Gt. Britain, March 22, 1867). Thus, he states 
that :— 
“In the fish, the lower half of the body and the broadly expanded tail are 
applied to the water very much as an oar is in sculling.”’ .... The fish may 
be said to drill the water in two directions, viz., from behind forward, by a 
twisting or screwing of the body on its long axis, and from side to side by 
causing its anterior and posterior portions to assume opposite curves. The 
pectoral and other fins are also thrown into curves in action, the movement, as 
in the body itself, travelling in spiral waves; and it is worthy of remark that 
the wing of the insect, bat, and bird obeys similar impulses. 
“The fins are rotated or twisted, and their free margins lashed about by 
spiral movements, which closely resemble those by which the wings of insects 
are propelled... = = That the wing twists upon itself structurally, not only 
in the insect, but also in the bat and bird—anyone may readily satisfy himself 
by a careful examination; and that it twists upon itself during its action I have 
had the most convincing and repeated proofs.”” ‘ The wing of the bird ats as a 
twisted inclined plane. In this respect it intimately agrees with the wing of 
both the inse@ and bat. .... The twisting in question is most marked in the 
posterior, or thin margin of the wing, the anterior or thicker margin per- 
forming more the part of an axis. As the result of this arrangement, the 
anterior or thick margin cuts into the air quietly, and as it were by stealth, 
the posterior one producing on all occasions a violent commotion, especially 
perceptible if a flame be exposed behind the inset.” 
Professor Marey goes over the same ground in much the 
Same way. Lhus, at pages 107, 109, 198, 208,, 210, 2m, 
259, and 261, he states :-— 
““ The oar is found in many inseé&ts which move on the surface of the water. 
A contrivance is employed by other animals, which resembles the aétion of an 
oar used at the stern of a boat in the process called sculling. To the latter 
motive power may be referred all those movements in which an inclined plane 
is displaced in the liquid, and finds in the resistance of the water which it 
presses obliquely two component forces, of which one furnishes a movement 
of propulsion.” .... ‘* When a fish strikes the water with his tail, in order 
to drive himself forward, he executes a double work, a part tends to drive 
behind him a certain mass of fluid with a certain velocity, and the other 
to drive the animal forward, in spite of the resistance of the surrounding 
Waters. i... Aérial Locomotion.—This mechanism is still the same; the 
motion of an inclined plane, which causes motion through the air, the wing in 
faét, in the insect as well as in the bird, strikes the air 7x an oblique manner, 
repels it in a certain direction, and gives the body a motion directly opposite.” 
..... ‘Each stroke of the wing acts upon the air obliquely, and neutralises 
its resistance, so that a horizontal force results, which impels the inse& 
forward. An effect is produced analogous with that which takes place when 
an oar is used in the stern of a boat in the action of sculling.” ‘‘ Most of the 
propellers which act in water overcome the resistance of the fluid by the action 
of an inclined plane. The tail of the fish produces a propulsion of this kind. 
Even the screw may be considered as an inclined plane, whose movement is 
continuous, and always in the same direction..... We see the main rib 
(anterior margin) of the wing remain sensibly immovable, and around it turns 
the membranous portion (posterior margin)..... “If this motion as ona 
pivot did not exist, the wing would cut the air with its edge, and would be 
utterly incapable of producing flight.” .... The wing presents very 
remarkable changes of plane at the inner part towards the body; the wing 
