170 THE REIGN OF LAW. 



They are greatly assisted in this beautiful 

 evolution by an adverse current of air; and it 

 will always be observed that the Kestrel, when 

 hovering, turns his head to wind, and hangs his 

 whole body at a greater or less angle to the 

 plane of the horizon. When there is no wind, or 

 very little, the sustaining force is kept up by a 

 short rapid action of the pinions, and the long tail 

 is spread out like a fan to assist in stopping any 

 tendency to onward motion. When there is a 

 strong breeze, no napping is required at all — the 

 force of the wind supplying the whole force neces- 

 sary to counteract the force of gravity ; and in pro- 

 portion to the increasing strength of the wind, the 

 amount of vane which must be exposed to it be- 

 comes less and less. I have seen a Kestrel stand 

 suspended in a half gale with the wings folded 

 close to the body, and with no visible muscular 

 motion whatever. And so nice is the adjustment 

 of position which is requisite to produce this exact 

 balance of all the forces bearing on the bird, 

 that the change in that position which again in- 

 stantly results in a forward motion is very often 

 almost insensible to the eye. It is generally a 



