THE WING OF A BIRD. 



Now we will see how wings are fitted for flying. 



That a good wing must be large, strong, light, and safe 

 against accidents hardly needs to be said ; and yet not until 

 we compare a bird's wing with a bat's do we observe that 

 a wing may have all these points and yet be an inferior 

 wing. The great skinny hand of the bat is badly shaped 

 for speed and it baffles with the wind, not being made to 



FIG. 14. WING-BONES OF BAT. 



shed it on the upward stroke. The superiority of the bird's 

 wing is that it is practically made of slats which swing 

 in their places to let the air pass through on the up-stroke. 

 A very simple change it seems to be, and yet to make it 

 practical there have been a hundred and one alterations from 

 the primitive hand-wing of the bats and of the ancient flying 



75 



