BIRDS ON THE WING. 55 



air-ships that can be successfully operated is an 

 open question; but long before such inventions 

 were even dreamed of by the human mind the 

 Creator had solved the problem by making our 

 feathered aerial navigators. How do birds propel 

 themselves through their native element ? It will 

 be seen that they are wonderfully adapted to that 

 purpose. Many of m}^ older readers may already 

 understand the philosoph}^ of bird flight, as far as 

 it has been explained by scientists ; but for younger 

 readers and others not informed on the subject, I 

 will say a few words in regard to it. 



Of course the best fliers are very light and buoy- 

 ant, their bodies being quite small compai'ed with 

 the bulk of their feathers. This causes them to 

 float with little effort on the air. In proportion to 

 their weight they present a large surface to the up- 

 buoyiiig atmosphere. Their wings serve as oars 

 to beat the air with, and also increase the amount 

 of resistance to the atmosphere, while their tails 

 answer the purpose of a keel with which to steer 

 their feathered craft. Then, by turning their 

 heads from side to side and variously inclining 

 their wings, they help to guide themselves. 



But how do they contrive to elevate and lower 

 themselves so deftly and easily ? That may be 



