AERONAUTICS. 



257 



This screw, which for the sake of uniformity I denominate 

 the aerial wave screw, possesses advantages for aerial pur- 

 poses to which no form of rigid screw yet devised can lay 

 claim. The way in which it clings to the air during its 

 revolution, and the degree of buoying power it possesses, are 

 quite astonishing. It is a self-adjusting, self-regulating screw, 

 and as its component parts are flexible and elastic, it accom- 

 modates itself to the speed at Which it is driven, and gives 

 a uniform buoyancy. -The slip, I may add, is nominal in 

 amount. This screw is exceedingly light, and owes its efiicacy 

 to its shape and the graduated nature of its blades; the 

 anterior margin of each blade being comparatively rigid, 

 the posterior margin being comparatively flexible and 

 more or less elastic. The blades are kites in the same 

 sense that natural wings are kites. They are flown as such 

 when the screw revolves. I find that the aerial wave screw 

 flies best and elevates most when its blades are inclined at a 

 certain upward angle as indicated in the figure (130). The 

 aerial wave screw may have the number of its blades in- 

 creased by placing the one above the other ; and two or more 

 screws may be combined and made to revolve in opposite 

 directions so as to make them reciprocate ; the one screw pro- 

 ducing the current on which the other rises, as happens in 

 natural wings. 



The Aerial Wave Screw operates also upon Water,— The 

 form of screw just described is adapted in a marked manner 

 for water, if the blades be reduced in size and composed of 

 some elastic substance, which will resist the action of fluids, 

 as gutta-percha, carefully tempered finely graduated steel plates, 

 etc. It bears the same relation to, and produces the same 

 results upon, water, as the tail and fin of the fish. It throws 

 its blades during its action into double figure-of-8 curves, 

 similar in all respects to those produced on the anterior and 

 posterior margins of the natural and artificial flying wing. As 

 the speed attained by the several portions of each blade varies, 

 so the angle at which each part of the blade strikes varies; 

 the angles being alway is greatest towards the root of the blade 

 and least towards the tip. The angles made by the diff'erent 

 portions of the blades are diminished in proportion as the 



