140 



THE FLIGHT OF BIRDS 



not exactly straight in the bird's face, but very 

 slightly from the right. A very little shove is enough, 

 as the air offers no great resistance to so well-built 

 an aeroplane travelling at no more, at any rate, than 

 twenty miles an hour, and generally slower. A 

 man-made aeroplane is bound to move at a great 

 pace or the air will not support it. But in the case 

 we are considering it is the wind that must have the 



7m) t 





Fig. 27. 



Gull gliding sideways, the left wing leading. The wind 



(represented by the arrow to the left) is deflected upward 



by the cliff. 



pace. Poised upon the strong, upward stream, the 

 Gull goes gently on his way. Some years ago, when 

 I was at Port Erin, in the Isle of Man, it was inter- 

 esting to see the Gulls returning in the evening to 

 the little island called the Calf, at the southern 



