birds pass over the field of his telescope at a height of from 

 1500 to 15,000 feet ; and the most remarkable thing of all 

 was the fact that the lowest birds were flying upwards, as 

 if they had risen from the immediate neighbourhood and 

 were seeking the proper elevation to continue their flight. 



As has already been remarked, when nearing their destina- 

 tion migrating birds descend, though still many miles from 

 land. Should a gale be raging they fly so low that they 

 barely top the waves. And this, apparently, to escape, 

 so far as is possible, the force of the wind. Larks, starlings, 

 thrushes, and other small birds, can sometimes be seen 

 during daylight crossing the North Sea in their thousands. 

 At such times many will often afford themselves a brief 

 rest in the rigging of ships, homeward bound, but the main 

 host hurry on. The beautiful golden-crested wren, our 

 smallest British migrant, is one of these. A glance at our 

 charming coloured Plate will show at once that the wing is 

 not that of a bird of strong flight. There is no more inter- 

 esting experience to the bird-lover than that of watching the 

 tired travellers drop earthwards, as they leave the dreadful 

 sea behind them. 



With all birds yet retaining the power of flight there is 

 always a liberal " margin of safety " in regard to the wing 

 area. That is to say, this is always in excess of the minimum 

 area necessary to make flight possible. This much, indeed, is 



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