MECHANICAL PARADOXES. 



Nature^s active and independent travellers 

 through the air all employ one or both of two 

 proceedings either, like birds, bats, and in- 

 sects, they actively beat the air with their 

 wings, or like most large birds and many small 

 ones, they occasionally perform a soaring move- 

 ment with wings outspread and motionless, or 

 nearly motionless, gliding through the air from 

 a position of greater height or swifter move- 

 ment. 



Some of the movements of birds will be 

 considered more fully in the next section. 

 Meantime, we may note that the air-ship 

 engineers who get their aerial support after the 

 manner of soaring birds by means of aeroplanes 

 that is, large smooth surfaces gliding through 

 and resting upon the air avoid the necessity 

 for having a very large volume, and are left 

 with difficulties which, though great, are not 

 beyond human ingenuity to solve, since they 

 involve no incompatibles. Travelling by such 

 machines is never likely to be over-safe or 

 reasonably cheap, but they will probably be 

 very useful in war and meteorology, and for 

 emergency work generally. 



5. The Way of a Bird in the Air. 



Since the days of the ancient Hebrews " the 

 way of a bird in the air " and " the way of a 

 fish in the sea " have been standing puzzles 



70 



