THE MASTERY OF THE AIR 257 



adaptations for flight have been wrought out in 

 the bodies of bird and bat. Both are lightly 

 built as regards their skeleton, which means a 

 big surface for fastening muscles on to, with- 

 out great increase in weight Both show a keel 

 on the breastbone for the better fixing on of the 

 muscles of flight, but the bat's keel is much less 

 prominent than a bird's. Both show a solidi- 

 fying of the middle region of the backbone, 

 which affords a firm fulcrum for the wings to 

 work against. In almost every other respect 

 they are as different as different could be, but 

 it may be noted that most birds and most bats 

 are small, as if there were a size-limit to flying 

 creatures. A bird like an albatross, with a span 

 of 1 1 feet from tip to tip of the outstretched 

 wings, is quite out of the common, and so are 

 the very large fox-bats of the Far East. 



ATTEMPTS AT FLIGHT 



Apart from man, the problem of flight has 

 been successfully solved four times by in- 

 sects, Pterodactyls, birds, and bats; but how 

 often has its solution been attempted? It is 

 very interesting to study these attempts, some 

 of them splendid failures. 



