140 THE FLIGHT OF BIRDS 
not exactly straight 3 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 
PG. 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 
