DE PETTIGEEW ON THE PHYSIOLOGY OF WINGS. 433 



of the wing, and the amount of resistance which it experiences from the air. 

 The flexible and elastic nature of my peculiar form of wing (wave-wing), as- 

 sisted by certain springs to be presently explained, ensure a continuous vibra- 

 tion where neither halts nor dead points are observable. I obtain the varying 

 power required by a direct piston action, and by working the steam expansively 

 (vide figs. 62, 63, and 69, pages 423, 424, and 430). The power employed is 

 materially assisted, particularly during the up stroke, by the reaction of the air 

 and the elastic structures about to be described. An artificial wing, propelled 

 and regulated by the forces recommended, is in some respects as completely 

 under control as the wing of the insect, bat or bird. 



Necessity for supplying the root of artificial wings with elastic structures in 

 imitation of the muscles and elastic ligaments of flying animals. — Borelli, Durck- 

 heim, and Marey, who advocate the perpendicular vibration of the wing, make 

 no allowance, so far as I am aware, for the wing leaping forward in curves dur- 

 ing the down and up strokes. As a consequence, the wing is jointed in their 

 models to the frame by a simple joint which moves only in one direction, viz., 

 from above downwards, and vice versa. Observation and experiment have, 

 however, convinced me that an artificial wing, to be effective as an elevator and 

 propeller, ought to be able to move not only in an upward and downward direc- 

 tion, but also in a forward, backward, and oblique direction, nay, more, that it 

 should be free to rotate along its anterior margin in the direction of its length : 

 in fact, that its movements should be universal. Thus it must be able to rise 

 or fall, to advance or retire, to move at any degree of obliquity, and to rotate 

 along its anterior margin. To secure the several movements in question I fur- 

 nish the root of the wing with a ball and socket-joint, i.e., a universal joint (see 

 x of fig. 62, page 423 ; and a? of fig. 63, page 424). To regulate the several move- 

 ments when the wing is vibrating, and to confer on the wing the various in- 

 clined surfaces requisite for flight, as well as to delegate as little as possible to 

 the air, I employ a cross system of elastic bands. These bands vary in length, 

 strength, and direction, and are attached to the anterior margin of the wing 

 (near its root), and to the cylinder (or a rod extending from the cylinder) of the 

 model respectively (vide m, n of fig. 62, page 423). The principal bands are four 

 in number: a superior (fig. 63, page 424, y), inferior (z), anterior (v), and posterior 

 (iv). The superior band extends between a rod proceeding from the upper part 

 of the cylinder (5) of the model, and the upper surface of the anterior margin 

 (a, b,) of the wing; the inferior band (z), extending between the under part of 

 the cylinder or boiler and the inferior surface of the anterior margin (d, e, f) of 

 the pinion. The anterior (v), and posterior (iv), bands are attached to the anterior 

 and posterior portions of the wing and to rods extending from the centre of the 

 anterior and posterior portions of the cylinder. Oblique bands are added (vide 

 p, q of fig. 65, page 425), and these are so arranged that they give to the wing 



