206 THE LIFE OF TEE FIELDS. 



the moment he pauses gravitation exercises a force 

 much greater that when he glides. 



While hovering there are several forces balanced : 



first, the original impetus onwards; secondly, that of 



the depressed tail dragging and stopping that onward 



course ; thirdly, that of the wing beating downwards ; 



and fourthly, that of the wing a very little reversed 



beating forwards, like backing water with a scull. 



"When used in the ordinary way the shape of the 



wing causes it to exert a downward and a backward 



pressure. His slip is when he loses balance : it is 



most obviously a loss of balance; he quite oscillates 



sometimes when it occurs ; and now and then I 



have seen a kestrel unable to catch himself, and 



obliged to proceed some distance before he could 



hover again. Occasionally, in the slip he loses a foot 



or so of elevation, but not always. While actually 



hovering, his altitude does not vary an inch. All 



and each of these movements and the considerations 



to which they give rise show conclusively that the 



act of hovering is nothing more or less than an 



act of balancing; and when he has his balance he 



will rest a moment with outstretched wings kept still. 



He uses his wings with just sufficient force neither 



to rise nor fall, and prevents progress by a slightly 



different stroke. 



The next point is, Where does he hover ? He 

 hovers any and everywhere, without the slightest 

 choice. He hovers over meadows, cornfields; over 

 the tops of the highest downs, sometimes at the very 

 edge of a precipice or above a chalk quarry ; over 

 gardens, waste ground ; over the highway ; over 



