THE SOOTY ALBATROSS 



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round and round in great circles, always keeping their wings 

 horizontal. 



Sailing flight depends upon the principle of the inclined plane. 

 The bird acquires momentum by flapping its wings, and then 

 holding them extended and motionless, waits until its momentum 

 is nearly exhausted, when it once more propels itself forward as 

 before. In the case of the sooty albatross, the interval may, 

 under favourable conditions, be about half-an-hour, and the 



Sooty Albatross. 



(Afti'i- Gould.) 



difficulty is to explain why the friction of the air does not sooner 

 bring the bird to a standstill. It was pointed out in 1889, by 

 Mr. A. C. Baines, that the birds usually rise in a slanting direc- 

 tion against the wind, turn round in a rather large circle, and 

 make a rapid descent down the wind. They subsequently take 

 a longer or shorter flight in various directions, almost touching 

 the water. After that comes another ascent in the same manner, 

 followed by another series of movements. As the velocity of the 

 wind near the surface of the sea is diminished by the friction of 

 the waves, when the bird ascends into the more rapidly-moving 



