June, 1905. 



KNOWLEDGE & SCIENTIEIC NEWS. 



123 



opened under the influence of an air current as shown 

 by the arrow. 



This is doubtless due to the formation of eddies by 

 the air flowing over the rigid lip. 



It is obvious that a bird's wing both as a gliding 

 and a propelling surface is a beautifully efficient instru- 

 ment. 



To test these views, in 1902, Mr. Frost and the 

 writer, with the co-operation of Mr. C. R. D'Esterre, 

 arranged the apparatus shown in Fig. i. A pair of 

 dried natural wings (area about three square feet) were 

 arranged with a small electric motor and a reduction 

 gear to flap up and down, the arrangement being 



various authorities as that obtaining with birds, and 

 is not in marked contrast with the ratio obtained (ac- 

 cording to puljli.shed reports) with the large machine 

 of Messrs. Wright in U.S.A. 



One may describe a flying lift and a hovering lift. 



The hovering lift obtained in a confined space, and 

 only three feet above the floor with the figure i 

 apparatus with i h.p. gave a lift of 10 lbs. 



We considered we had justification for proceeding 

 with a larger model. This has been constructed and 

 partly tested and I'igs. j and 3 show it o,i the rough 

 carriage. 



It is intended to run this car on a special trough 



Fig. 2. 



suspended bv a spring balance from the balanced arm. 

 The best result was obtained as hereunder : — 



Amps 



24 12 10 75% 350 to 400 5 lbs. 



The effect was striking. The " bird " flapped itself 

 round and round, although it fell between the down 

 strokes. But against this must be set the fact that its 

 rate of progression was only four or five miles an hour, 

 no doubt owing to air resistance and friction, which 

 were considerable, for the apparatus was crude. .'Mso 

 the "bird" weighed about 21 lbs., which would, of 

 course, pull it down on tlie up strokes. The oscilla- 

 tions to .1 iiii.rked extent diminished after the tail was 

 lilted. 



It will be noted that the ratio of h.p. to lift was 

 I h.p. to 50 lbs. This ratio tallies with that given by 



section track, and to arrange in the frame 4 \ertical 

 guides, one at each corner, of stretched cord or wire. 



The machine will be suspended from a spring balance. 

 The model has certain crudities in the motive portion, 

 although the workmanship (which, apart from the 

 wings, was carefully carried out by Messrs. Pyc, 

 scientific instrument makers, of Cambridge, and the 

 Cambridge .'\utocar Co., Ltd.) is good. But it is a 

 testing model only, and is merely intended to obtain 

 data from. 



The wings are of special construction, designed in 

 accordance with the above enunciated principles. The 

 total wing area is about 20 times that. of the No. I 

 model {i.e., about fio square feet). The machine 

 measures about 20 feet across. 



The transmission is by coned friction clutch, and 

 chains in two stages, to connecting rod. The crank 

 throw is adjustable for altering the size of angle of 



