of a propeller, driven at incredible speed, its immobile wings 

 sustaining the weight. The wings of the bird, on the other 

 hand, not only lift the body from the earth, but they sustain 

 it in the air by their marvellously complbx movements. And 

 this is true, in varying degrees of bird, and bat, and butterfly : 

 of dragon-fly and beetle. 



Even they who must perforce dwell in crowded cities see 

 daily the miracle of flight performed. For even here sparrows 

 and pigeons, at least, are everywhere, and it is just because 

 this is so, just because they have become so " commonplace," 

 that their very presence escapes notice. Yet the wonder of 

 their movements in the air might become a never-ending 

 source of delight if only we went about our business with 

 open eyes and minds alert. 



Watch the wary sparrow spring from the ground and dart 

 across the road, or up to the nearest house-top. How is it 

 done with such incredible speed and accuracy ? 



To understand even the broad principles of flight, it is 

 necessary to realize, at the very beginning, that the wing, 

 in the case of the bird, or the bat, is a specially modified 

 fore-leg. So also is the human arm and hand. But its 

 transformation has not been so drastic as that of the bird, 

 or the bat. Wherein the hand has been, as it were, com- 

 pletely re-modeUed to fulfil the peculiar and complex functions 

 demanded of it. 



