DE PETTIGREW ON THE PHYSIOLOGY OF WINGS. 405 



The model was forced by its propellers along a wire at a great speed, but, so 

 far as I could determine, failed to lift itself notwithstanding its extreme lightness 

 and the comparatively very great power employed.* 



Mr Henson's t aerial machine was very similar in principle to Mr 

 Stringfellow's. "The chief feature of the invention was the very great 

 expanse of its sustaining planes, which were larger in proportion to the weight 

 it had to carry than those of many birds. The machine advanced with its front 

 edge a little raised, the effect of which was to present its under surface to the 

 air over which it passed, the resistance of which, acting upon it like a strong 

 wind on the sails of a windmill, prevented the descent of the machine and its 

 burden. The sustaining of the whole, therefore, depended upon the speed at which 

 it travelled through the air, and the angle at which its under surface impinged on 

 the air in its front. . . . The machine, fully prepared for flight, was started 

 from the top of an inclined plane, in descending which it attained a velocity 

 necessary to sustain it in its further progress. That velocity would be gradually 

 destroyed by the resistance of the air to the forward flight ; it was, therefore, 

 the office of the steam engine and the vanes it actuated simply to repair the loss 

 of velocity ; it was made therefore only of the power and weight necessary for that 

 small effect. . . ." The editor of "Newton's Journal of Arts and Science" 

 speaks of it thus — -" The apparatus consists of a car containing the goods, passen- 

 gers, engines, fuel, &c, to which a rectangular frame, made of wood or bamboo 

 cane, and covered with canvas or oiled silk, is attached. This frame extends on 

 either side of the car in a similar manner to the outstretched wings of a bird ; but 

 with this difference, that the frame is immovable. Behind the wings are two vertical 

 fan wheels, furnished with oblique vanes, which are intended to propel the 

 apparatus through the air. The rainbow-like circular wheels are the propellers, 

 answering to the wheels of a steam-boat, and acting upon the air after the 

 manner of a windmill. These wheels receive motion from bands and pulleys 

 from a steam or other engine contained in the car. To an axis at the stern of 

 the car a triangular frame is attached, resembling the tail of a bird, which is 

 also covered with canvas or oiled silk. This may be expanded or contracted 

 at pleasure, and is moved up and down for the purpose of causing the machine 

 to ascend or descend. Beneath the tail is a rudder for directing the course of 

 the machine to the right or to the left ; and to facilitate the steering a sail is 

 stretched between two masts which rise from the car. The amount of canvass 

 or oiled silk necessary for buoying up the machine is stated to be equal to one 

 square foot for each half pound of weight.^ 



* Mr Stringfellow stated that his machine occasionally left the wire, and was sustained by its 

 superimposed planes alone. 



t Mr Henson designed his aerostat in 1843. 



X Astra Castra, by Hatton Turner, Esq. London, 1865, pages 311 and 312. 



