FROM CART TO AUTOMOBILE 



be disposed to admit that the teal or the canvasback at 

 full speed might give the automobile a race. 



There is, to be sure, one way in which the bird might 

 get the better of a machine, thanks to its capacity to 

 rise to a height. This would be by taking a sloping 

 course downward. The little shore-lark often gives 

 an exhibition of the possibilities open to the bird 

 in this direction. After rising to a cloudhke height 

 it soars about for a time singing, then suddenly 

 sweeps downward, and, closing its wings, launches 

 itself directly toward the earth, falling with meteoric 

 speed till it almost reaches the surface, when it makes 

 a parachute of its wings and swoops away in safety. 

 During this performance the little lark is, I veritably 

 believe, the swiftest-moving animate thing in all the 

 world. But there is a reason why the bird could not 

 increase its speed indefinitely by imitating the lark's 

 feat in a modified form, and this is the obstacle of 

 atmospheric pressure. Air moving at the rate of sixty 

 feet a second constitutes a serious storm; at ninety 

 feet it becomes a tornado, and at one hundred and 

 fifty feet it is a tornado at its worst — a, storm that 

 tears up trees and overthrows houses, and against 

 which no man can stand any more than that he could 

 breast the current of Niagara. Now, of course, it is 

 all one whether the air moves at this rate against 

 you or whether you move at a corresponding rate 

 against the air — action and reaction being equal. 

 Therefore a very serious check is put upon the bird's 

 flight; and it is this consideration which makes it 

 seem doubtful whether any bird, except when aided by 



[169] 



