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BELL 



bottom. The sloping sides measured 3 meters and the length 

 from fore to aft at the square bottom was 3 meters. It is obvious 

 that this kite might be extended laterally at the top to twice its 

 length without forming an immoderately large structure. It 

 would then be 12 meters on the top (39 ft.) and 9 meters on the 

 bottom from side to side, without changing the fore and aft 

 dimensions, or the height. It would then contain more than 

 double the number of cells and so should be able to sustain in 

 the air more than double the load ; so that such a structure 

 would be quite capable of sustaintng both a man, and an engine 

 of the weight of a man, and yet be able to fly as a kite in a 

 breeze no stronger than that which supported the " Frost 

 King." 



An engine of the weight of a man could certainly impart to 

 the structure a velocity of 10 miles an hour, the estimated veloc- 

 ity of the supporting wind, and thus convert the kite into a free 

 flying-machine. The low speed at which I have been aiming 

 — for safety's sake — is therefore practicable. 



In the "Frost King" and other kites composed exclusively 

 of tetrahedral winged cells, there are no horizontal surfaces (or 

 rather surfaces substantially horizontal as in ordinary kites), but 

 the framework is admirably adapted for the support of such 

 surfaces. Horizontal aeroplanes have much greater lifting- 

 power than similar surfaces obliquely arranged as in the tetra- 

 hedral construction, and I have made many experiments to com- 

 bine horizontal surfaces with winged cells, with greatly im- 

 proved results so far as lifting-power is concerned. But there 

 is always an element of instability in a horizontal aeroplane, 

 especially if it is of large size ; whereas kites composed exclu- 

 sively of winged cells are wonderfully steady in the air under 

 varying conditions, though deficient in lifting-power ; and the 

 kites composed of the largest number of winged cells seem to 

 be the most stable in the air. 



In the case of an aeroplane of any kind the center of air-pres- 

 sure rarely coincides with the geometrical center of surface, but 

 is usually nearer the front edge than the middle. It is liable to 

 shift its position, at the most unexpected times, on account of 

 some change in the inclination of the surface or the direction of 



