406 DP PETTIGREW ON THE PHYSIOLOGY OF WINGS. 



The idea embodied by Henson, Stringfellow, and Wenham is plainly that 

 of a boy's kite sailing upon the wind. The kite, however, is a more perfect 

 flying apparatus than that furnished by Henson, Stringfellow, and Wenham 

 inasmuch as the inclined plane formed by its body strikes the air at various 

 angles— the angles varying according to the length of string, strength of breeze, 

 length and weight of tail, &c. Henson's, Stringfellow's, and Wenham's 

 methods, although carefully tried, have hitherto failed. The objections are 

 numerous. In the first place, the supporting planes (aeroplanes or otherwise) 

 are rigid. This is a point to which I wish particularly to direct attention. 

 Second, They stroke the air at a given angle. Here again, there is a departure 

 from nature. Third, A machine so constructed must be precipitated from a 

 height or driven along the surface of the land or water at a high-speed to supply 

 it with initial velocity. Fourth, It is unfitted for flying with the wind unless its 

 speed greatly exceeds that of the wind. Fifth, It would have considerable 

 difficulty in flying across the wind, and considerable risk would be incurred in 

 landing because of the velocity attained. Sixth, The sustaining surfaces are 

 comparatively very large. They are, moreover, passive or dead surfaces, i.e., 

 they have no power of moving or accommodating themselves to altered circum- 

 stances. In this respect they somewhat resemble the surfaces presented by a 

 balloon — their great extent rendering them liable to be seized and tossed by the 

 wind. 



The Aerial Screw. — Our countryman, Sir George Cayley, gave the first 

 practical illustration of the efficacy of the screw as applied to the air in 1796. 

 In that year he constructed a small machine consisting of two screws made of 

 quill feathers. The screws were each composed of four feathers stuck in a piece 

 of cork, the corks being drilled in the centre to receive a driving shaft or axis. 

 To the shaft a whalebone spring, with a string which coiled round the shaft (and 

 by which the spring was wound up), was affixed. By turning the upper screw 

 (the lower one being secured) a sufficient number of times, the proper degree of 

 tension was conferred on the spring ; and the instant the apparatus was 

 liberated it flew into the air. Cayley's screws were peculiar, inasmuch as they 

 were superimposed and rotated in opposite directions. He estimated that if 

 the area of the screws was increased to 200 square feet, and moved by a man, 

 they would elevate him. Cayley's interesting experiment is described at length, 

 and the apparatus figured in "Nicholson's Journal" for 1809, p. 175. In 1842 

 Mr Phillips also succeeded in elevating a model by means of revolving fans. Mr 

 Phillips's model was made entirely of metal, and when complete and charged 

 weighed 2 lbs. It consisted of a boiler or steam generator and four fans 

 supported between eight arms. The fans were inclined to the horizon at an 

 angle of 20°, and through the arms the steam rushed on the principle discovered 

 by Hero of Alexandria. By the escape of steam from the arms, the fans were 



