320 



ON AEKIAL LOCOMOTION. 



These cousideratious bear uo relation to artificial wings ; so in de- 

 signing a iiying-macbiue, any deviations are admissible, provided the 

 theoretical conditions involved in flight are borne in mind. 



Having remarked how thin a stratum of air is displaced beneath the 

 wings of a bird in rapid flight, it follows that in order to obtain the 

 necessary length of. plane for supporting heavy weights, the surfaces may 

 be superposed, or placed in parallel rows, with an interval between 

 them. A dozen pelicans may fl^^ one above the other without mutual 

 impediment, as if framed together; and it is thus shown how 2 hun- 

 dred-weight may be supported in a transverse distance of only 10 feet. 



In order to test this idea, six bands of stiff paper, 3 feet long and 3 

 inches wide, were stretched at a slight upward angle, in a light rectan- 

 gular frame, with an interval of 3 inches between them, the arrange- 

 ment resembling an open Venetian blind. When this was held against 

 a breeze, the lifting power was very great, and even by running with 

 it in a calm it required much force to keep it down. The success of 

 this model led to the construction of one of a sufficient size to carry the 



Fig,3. 



weight of a man. Fig. 3 represents the arrangement : a a m a thin 

 plank, tapered at the outer ends, and attached at the base to a triangle, 

 h, made of similar plank, for the insertion of the body. The boards 

 a a were trussed with thin bauds of iron, c c, and at the ends were ver- 

 tical rods, d d. Between these were stretched five bands of holland, 15 

 inches broad and IG feet long, the total length of the web being 80 feet. 

 This was taken out after dark into a wet piece of meadow land, one 

 JS^ovember evening, during a strong breeze wherein it became quite 

 unmanageable. The wind acting upon the already tightly-stretched 

 webs, their united pull caused the central boards to bend considerably, 

 with a twisting, vibratory motion. During a lull, the head and shoul- 

 ders were inserted in the triangle, with the chest resting on the base- 

 board. A sudden gust caught up the experimenter, whc^ was carried 

 some distance from the ground, and the affair falling over sideways 

 broke up the right-hand set of webs. 



In all new machines we gain experience by repeated failures, which 

 frequently form the stepping stone to ultimate success. The rude con- 

 trivance just described (which was but the work of a few hours) had 

 taught first that the webs, or aero-planes, must not be distended in a 

 frame, as this must of necessity be strong and heavy, to withstand 

 their combined tension; second, that the planes must be made so as 

 either to furl or fold up, for t've sake of portability. 



