ORNITHOLOGICAL OBSERVATIONS 273 



leeward it sails free and unrestrained, but as it comes 

 round to the wind its pace lessens, it seems almost 

 to struggle like a ship beating against the element. 

 Slower and slower grows its pace, greater and greater 

 is its contest with the wind, until at length its speed is 

 exhausted and the bird swerves to leeward and sails 

 gaily before the wind. 



Thirdly, we note that there is a change in the 

 attitude of the bird in the two different seL^ments. On 

 the windward side the bird inclines its body. To 

 leeward it appears naturally horizontal ; but as it comes 

 round with its head to the wind, its whole body inclines 

 so that the head is raised, the tail lowered, and the 

 under surface of the body and wings rest in a steep 

 incline upon the wind like the sails of a ship beating 

 close-hauled against the breeze. 



Fourthly, we note, and this perhaps is the most 

 important observation of all, that the bird ascends on 

 the windward side and descends on the leeward side. 

 It is dependent solely on the windward segment to 

 increase the height of its circles ; it can do nothing to 

 leeward. It is contesting against the stress of gravity ; 

 to windward it gains, to leeward it loses in the contest, 

 but the gain being greater than the loss it moves 

 higher in the air. 



These four facts supply us with definite information. 

 It is just this : that a kite can ascend in ever-rising 

 circles without the sliorhtest motion of its wings, and 

 that every time the bird comes to the windward side 

 of the circle it shortens the length of its course, it 

 lessens its speed, it inclines its body obliquely to the 

 wind, it ascends into the air ; and every time it falls 

 away to leeward, it lengthens its course, increases its 



