210 THE LIFE OF TEE FIELDS. 



BIRDS CLIMBING THE AIR. 



Two hawks come over the trees, and, approaching each 

 other, rise higher into the air. They wheel about for 

 a little without any apparent design, still rising, when 

 one ceases to beat the air with his wings, stretches 

 them to their full length, and seems to lean aside. 

 His impetus carries him forward and upward, at the 

 same time in a circle, something like a skater on one 

 foot. Revolving round a centre, he rises in a spiral, 

 perhaps a hundred yards across ; screwing upwards, 

 and at each turn ascending half the diameter of the 

 spiral. When he begins this it appears perfectly 

 natural, and nothing more than would necessarily 

 result if the wings were held outstretched and one 

 edge of the plane slightly elevated. The impulse of 

 previous flight, the beat of strong pinions, and the 

 swing and rush of the bird evidently suffice for two or 

 three, possibly for four or ^yq, winding movements, 

 after which the retarding effects of friction and gravi- 

 tation ought, according to theory, to gradually bring 

 the bird to a stop. But up goes the hawk, round 

 and round like a woodpecker climbing a< tree ; only 



