VII 



FLKiIIT 241 



Gull flying at right angles to it without moving his 

 wings. A diagram will make clear the method. 



He descends swiftly at a gentle incline, making an 

 angle with the wind that, but for leeway, would be a right 

 angle, then suddenly turns and faces the wind, rising 

 by a short steep ascent to his former level, after which 

 he begins the process over again. He descends from 

 the more rapid current into the slower, and so has the 

 advantage of his relative velocity, after which he again 

 ascends, and profits by his passage from the slower to 

 the swifter. The upper current lends him pace, the 



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Fig. 64. 

 W shows the direction of the wind ; G the line of the Gull's flight. 



lower we may look upon as a floor off which he rebounds 

 like a ball. As he ascends into the more quickly moving 

 air, he has, belonging as he does now to the slower 

 current below, an inertia which makes the wind act 

 upon him as upon a kite. A glance at the line of his 

 course will show how he keeps making good his leeway 

 as he goes. The Albatross, those who have been lucky 

 enough to see him say, has brought this mode of pro- 

 gression to perfection, working onward by the hour 

 without a motion of his wings. A Gull is often reduced 

 to putting in a stroke or two, though I have seen them 

 cover a considerable distance without once resorting to 

 this. It is said that some birds make head directly 



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