120 



ANIMAL LOCOMOTION. 



a level with the body, or on either side of it, the body almost 

 instantly attained a position of rest. The body was, in fact, 

 equally suspended and balanced from all points. 



Rapidity of Wing Movements j?(xr//?/ accounted for.- — Much 

 surprise has been expressed at the enormous rapidity with 

 which some wings are made to vibrate. The wing of the 

 .insect is, as a rule, very long and narrow. As a consequence, 

 a comparatively slow and very limited movement at the root 



Fig. 56.1 



confers great range and immense speed at the tip ; the speed 

 of each portion of the wing increasing as the root of the wing 

 is receded from. This is explained on a principle well under- 

 stood in mechanics, viz. that when a rod hinged at one end 

 is made to move in a circle, the tip or free end of the rod 

 describes a much wider circle in a given time than a portion 

 of the rod nearer the hinge. This principle is illustrated at 

 1 In this diagram I have purposely represented the right wing by a straight 

 rigid rod. The natural wing, however, is curved, flexible, and elastic. It 

 likewise m.oves in curves, the curves being most marked towards the end of 

 the up and down strokes, as shown at m n, o p. The curves, which are 

 double figure-of-8 curves, are obliterated towards the middle of the strokes {a r). 

 This remark holds tine of all natural wings, and of all artifioial wings properly 

 constructed. The curves and the reversal thereof are necessary to give con- 

 tinuity of motion to the wing during its vibrations, and what is not less 

 important, to enable the wing alternately to seize and dismiss the air. 



