IN EELATION TO AERONAUTICS. 333 



by simply twisting the enveloping' wires in opposite directions. It therefore 

 represents the most primitive form of screw. This apparatus, simple as it may 

 appear, curiously enough furnishes the mechanical appliance Ity which a Ixxly 

 may be elevated, or elevated and carried in a horizontal direction at one and the 

 same time. By applying the necessary power the si)iralifer can be made to act 

 vertically or horizontally, or at any intermediate angle, so that we have in it an 

 easily regulated and perfect driving power. The position taken up by the advo- 

 cates of the screw is the reverse of that occupied by the advocates for the bal- 

 loon; so that the aeronaut promises at no distant day to be fairly im})aled on the 

 horns of a dilemma, b}' liaving'on the one hand a motor power which (because 

 of the space occupied by it) no human ingenuity can direct; and on the other a 

 thoroughly manageable and docile elevating and driving apparatus, minus an 

 adequate motor power. The problem of flight will probably be solved by one 

 employing a certain proportion of gas to assist him in overcoming the inertia of 

 his machine while he uses the screw as a propeller and partial elevator. Of the 

 two systems propounded, if they be judged separately, I incline to that which 

 proposes to employ the screw both in elevating and propelling, and this for two 

 reasons : 1st, Because the screw or a modification of it is the instrument by 

 which, as I have shown, the insect, bat, and bird rises and progresses ; and, 2d, 

 Because a certain degree of weight is necessary to overcome the air and make it 

 useful for the purposes of aerostation. 



That the principle of the helice as applied to the air is correct is proved by 

 the very remarkable experiments of MM. Pontin d'Amecourt and De la Lan- 

 delle, both of whom have constructed within the last three years helicojiteric 

 models, which not only rise l)y themselves into the air, ]:)ut also carry graduated 

 weights.* The difficulties therefore attendine: aerial locomotion bv means of the 

 screw are already partially surmounted. 



The advantages which will accrue from the employment of the screw in aeros- 

 tation may be briefly stated. 



It occupies little space, is strong without being heavy, and is prodigiously 

 powerful. 



It rigidly economizes the motor power by keeping the inclined planes of 

 which it is composed closely applied to the air throughout its entire revolution. 



The speed of the screw can be increased at pleasure — increased velocity, as I 

 have shown in the insect and bird, conferring enormously increased propelling 

 and lifting power. 



By a judicious combination of horizontal, vertical, and oblique screws, almost 

 any degree of speed may be attained, and any course, whether upwards, down- 

 wards, or forwards, pursued. 



A machine elevated and propelled by screws will be necessarily a conqiact 

 machine — a machine Avhich will navigate the air as a master ; its weight and 

 the small surface occupied by it rendering it superior even to moderately high 

 winds. 



The nearer such machine is kept to the earth, and the greater the density of 

 the atmosphere, the greater will be its facility and power — the inconveniences 

 arising from temperature and excessively rarefied air being thus avoided. 



The aerial screw machine should be constructed, whenever practicable, of 

 hollow cylinders fixed into a floor, composed of one or more flattened cyliudroid 

 chambers filled with hydrogen or other gas to diminish weight. The flattened 

 cylinders, if laid horizontally or inclined in a slightly npwaixl direction, would 

 act mechanically as sustainers and gliders, as do the wings in sailing and glid- 

 ing l)irds. It is just possible that the motor power required for the helicopteric 

 flying-machine may be derived from compressed atmosphere, the air being com- 



* Extracts from a paper, by Mons. Nadir, 1863, quoted in Astra Castra: By Hattoc 

 Turuor, London, ld65, pp. 34U. 



