424 



DR PETTIGKEW ON THE PHYSIOLOGY OF WINGS. 



This form of wing is made to oscillate upon two centres (a? and / of fig. 63), to 



bring out the peculiar eccentric action of the pinion. 



If I wish to produce a very delicate light wing, I do so by selecting a fine 



tapering elastic reed, as represented at a b of figure 64, p. 425. 



To this I add successive layers (t, h, g,f, e,) of some flexible 



e _ material, such as parchment, buckram, tracing cloth, or even 



paper. As the layers overlap each other, it follows that there 

 are five layers at the anterior margin (a b), and only one at the 

 posterior (c d). This form of wing is not twisted upon itself 

 structurally, but it twists and untwists, and becomes a true screw 



\y 



during its action. 



How to Construct a Wave Wing ivhich shall evade the superim- 



Fig. 03.* 



posed Air during the Up Stroke. — To construct a wing which shall elude the air 

 during the up stroke, it is necessary to make it valvular, as shown at fig. 65, p. 425. 



* Fig. 63. Artificial Wing with Driving Apparatus. 



a b, Strong elastic rod, which tapers towards the tip of the wing. 



d, e,f, g, h, i,j, k, Tapering curved reeds, which ran obliquelyf rom the anterior to the posterior margin of the wing, 

 and whili radiate towards the tip. 



m, Similar curved reeds, which run still more obliquely. 



a, n, o, p, q, Tapering curved reeds, which run from the anterior margin of the wing, and at right angles to it. These 

 support the two sets of oblique reeds, and give additional strength to the anterior margin. 



x, Ball and socket joint, by which the root of the wing is attached to the cylinder. 



s, Steam cylinder. 



r, Piston, with cross bar, with which driving gear (t) is connected by ball and socket joint (I), and by a hinge 

 joint (m). The hinge joint is mounted on a tube, through which the root of the wing passes, and within which it can 

 rotate in the direction of its length (long axis). The hinge joint and the tube on which it is mounted can be moved out 

 and in upon the root of the wing, and fixed by the aid of pins. By this means the range of the wing, i.e., the length of 

 the stroke, can be increased or diminished. The driving gear is arranged on a similar principle. Thus, by causing the 

 portion marked u to move within the tube (t) in an upward direction, the wing vibrates on a higher level than natural. 

 If, on the other hand, the portion marked u be moved in a downward direction, the wing vibrates on a lower level. The 

 range of the wing and its arc of vibration are thus easily regulated. 



1, 2, Cross bar attached to steam chest (7) and to cylinder (.•?). To this anterior (v) and posterior (w) elastic 

 bands are affixed. Those elastic bands (anterior and posterior) are bound to the anterior and posterior portions of the 

 ring c ; y, superior elastic band ; z, inferior ditto. 



3, 4, Steel springs running at right angles to each other, and attached respectively to the cross bar and the root of the 

 wing anteriorly. They come in contact when the wing descends, and prevent the anterior margin of the wing from dipping, 

 i.e., from diving downwards during the down stroke. This result is also secured by inserting the superior elastic band (y) 

 into the upper and anterior portion of the ring c. Indeed, by employing a cross bar or lever, similar to that marked 4, 

 in place of the ring c, the amount of rotation of the posterior margin round the anterior one can be regulated both 

 during the down and up strokes. If the superior elastic band (y) be moved towards the tip of the lever, the degree of 

 rotation is increased ; if it be moved towards the root of the lever, it is diminished. 



5. Rod fixed to posterior of cylinder, and bearing cross bar (6), to which the superior elastic band (y) is attached. 



Note. — In the present arrangement the steam chest (7) and valve occupy the centre of the cylinder posteriorly, the 

 valve being opened and closed by the aid of an idle rod (furnished with two kickers), which passes through a loop pro- 

 jecting from the piston anteriorly. The idle rod and kickers move a small lever (9), which in turn moves the spindle 

 (8), to which the steam valve is attached. The cylinder is fixed to the top of the boiler, and the ports for the admission of 

 steam to the cylinder are unequal in size, the upper port being larger than the under one. Unequal quantities of steam 

 are thus admitted to the top and bottom of the cylinder respectively, the greater quantity admitted to the top causing 

 the wing to descend much more quickly than it ascends. From the above figure it will be seen that the movements cf 

 the wing are communicated directly from the piston, a great saving in weight and power being thus effected. 



