256 



AERONAUTICS. 



the air has nn opportunity of reacting on its under sur- 

 face. 



The Artificial Wave Wing as a Propeller. — The wave 

 wing makes an admirable propeller if its tip be directed 

 vertically downwards, and the wing lashed from side to side 

 iVith a sculling figure-of-8 motion, similar to that executed by 

 the tail of the fish. Three wave wings may be made to act 

 in concert, and with a very good result ; two of them being 

 made to vibrate figure-of-8 fashion in a more or less horizontal 

 direction with a view to elevating ; the third being turned in 

 a downward direction, and made to act vertically for the 

 purpose of propelling. 



Fig. 130.— Aerial wave screw, whose blades are slightly twisted (a b,cd/ 

 ef,gJi), so that those portions nearest the root (rf /t) make a greater angle 

 with the horizon than those parts nearer the tip (&/). The angle is thus 

 adjusted to the speed attained by the different portions of the screw. The 

 angle admits of further adjustment by means of the steel springs z,Sy 

 these exercising a restraining, and to a certain extent a regulating, influ- 

 ence which effectually prevents shock. 



It will be at once perceived from this figure that the portions of the screw 

 marked m and n travel at a much lower speed than those portions marked 

 o and p, and these again more slowly than those marked q and r (compare 

 with fig. 56, p. 120). As, however, the angle which a wing or a portion of 

 a wing, as 1 have pointed out, varies to accommodate itself to the si^eed 

 attained by the wing, or a portion thereof, it follows, that to make the wave 

 screw mechanically perfect, the angles made by its several portions must 

 be accurately adapted to the travel of its several parts as indicated al>ove. 



X, Vertical tube for receiving driving shaft, v, lu. Sockets in which the 

 roots of the blades of the screw rotate, the degree of rotation being limited 

 by the steel springs z, s. ah, e/, Tapering elastic reeds forming anterior or 

 thick margins of blades of screw, dc, hg, Posterior or thin elastic margins 

 of blades of screw, m n, op,qr, Radii formed by the different portions of 

 the blades of the screw when in operation. The arrows indicate the direc- 

 tion of travel. — Original. 



A New Form of Aerial Screw. — If two of the wave wings 

 represented at fig. 122, p. 239, be placed end to end, and 

 united to a vertical portion of tube to ^ form a two-bladed 

 screw, similar to that employed in navigation, a most powerful 

 elastic aerial screw is at once produced, as seen at fig. 130. 



