248 



AERONAUTICS. 



with a ball-and-socket joint, i.e., a universal joint (see x of 

 fig. 122, p. 239). To regulate the several movements when 

 the wing is vibrating, and to confer on the wing the various 

 inclined surfaces requisite for flight, as well as to delegate 

 as little as possible to the air, I employ a cross system of 

 elastic bands.- These bands vary in length, strength, and 

 direction, and are attached to the anterior margin of the wing 

 (near its root), and to the cylinder (or a rod extending 

 from the cylinder) of the model (vide m,n of fig. 122, p. 

 239). The principal bands are four in number — -a superior, 

 inferior, anterior, and posterior. The superior band (m) 

 extends between the upper part of the cylinder of the 

 model, and the upper surface of the anterior margin of the 

 wing ; the inferior band (n) extending between the under part 

 of the cylinder or the boiler and the inferior surface of the 

 anterior margin of the pinion. The anterior and posterior 

 bands are attached to the anterior and posterior portions of 

 the wing and to rods extending from the centre of the 

 anterior and posterior portions of the cylinder. Oblique 

 bands are added, and these are so arranged that they give to 

 the wing during its descent and ascent the precise angles 

 made by the wing with the horizon in natural flight. The 

 superior bands are stronger than the inferior ones, and are 

 put upon the stretch during the down stroke. Thus they 

 help the wing over the dead point at the end of the down 

 stroke, and assist, in conjunction with the reaction obtained 

 from the air, in elevating it. The posterior bands are 

 stronger than the anterior ones to restrain within certain 

 limits the great tendency which the wing has to leap forward 

 in curves towards the end of the down and up strokes. The 

 oblique bands, aided by the air, give the necessary degree of 

 rotation to the wing in the direction of its length. This 

 efi'ect can, however, also be produced independently by the 

 four principal bands. From what has been stated it will be 

 evident that the elastic bands exercise a restraining influence, 

 and that they act in unison with the driving power and with 

 the reaction supplied by the air. They powerfully contribute 

 to the continuous vibration of the wing, the vibration being 

 peculiar in this that it varies in rapidity at every stage of the 



