FLIGHT OF BIRDS. 



to those who like to understand what is going 

 on around them. It is still very puzzling that 

 small fishes should be able to dart so swiftly 

 with apparent ease through a medium so re- 

 sist ent as water is to motion at high velocities. 



But the flight of birds, though it has points 

 that still need clearing up, can for the most 

 part be explained in accordance with the 

 accepted principles of physical science. There 

 is so much in it, however, that is contrary 

 to ordinary expectation that it may be strictly 

 and literally called paradoxical. 



One point which has been much discussed 

 is the soaring of large birds, the means by 

 which they keep aloft in the air for hours to- 

 gether without any apparent motion of the 

 wings. This seems at first sight puzzling ; but 

 it is capable of explanation under known laws. 



In the first place a bird with a large area 

 of wings outspread sinks very slowly, just as 

 a parachute does, because it offers so large an 

 area, in proportion to its weight, over which 

 the air can resist its downward movement 

 in other words, support it. 



But when the bird is gliding forward this 

 resisting or supporting action of the air is more 

 effectual to uphold it than when it is sinking 

 straight down. For, in the latter case, the 

 air which it has moved downwards in the 

 previous part of its fall joins its downward 

 impetus to the weight of the bird in moving 



71 



