F. W. HEADLEY : WIND AND FLIGHT. 145 



di'ives him onward. It must do so as the accompanying 

 diagram (Fig. 5) will show. 



Fig. 5. — B D, tke bird. W, the -wind acting in the direction F M. 

 The force represented by F M is resolved into F E, F S. 



In Algeria I once witnessed a splendid jDerformance by 

 two eagles. They advanced for a good mile and a half in 

 the teeth of the wind without a motion of their wings, as 

 far as I could judge neither losing nor gaining- altitude. 

 They then returned, flying with vigorous strokes. After 

 this, their wings held rigid as before, they travelled once 

 more over the same mile and a half, but at a higher 

 altitude. The wind was blowing over some high hills, 

 which gave it an upward incline, of which even a hand- 

 kerchief tied to the end of my umbrella gave evidence. 



In Alderney I saw a Gull advancing tvith the wind and 

 without a motion of his wings. The wind, blowing at a 

 small angle against steep cliffs, had a marked uj)tilt. 

 This advance with the wind is a thing' not often seen. 

 The position of the bird is the same as when he advances 

 against it. Probably a more decidedly ujDward current 

 is wanted when it blows from behind, otherwise all the 

 feathers would be disarranged. 



Gulls often emj)loy another method when there is a 

 wind blowing at right angles, or nearly so, to a steamer 

 at sea. They face the wind which has an upward incline 

 due to its striking the side of the vessel, and hang- in the 



