THE MASTERY OF THE AIR 251 



Hawaii seem to think nothing of setting out 

 for Alaska; it means some sense of direction 

 that we do not understand, for a young bird 

 that has never been more than a few miles 

 from home will start gaily in the autumn for 

 tropical Africa and will reach its goal in 

 safety, and, what is more, will sometimes 

 come back again the following spring to the 

 precise place of its birth. 



THE FOURTH SOLUTION OF FLIGHT 



The fourth solution of the problem of flight 

 was discovered by bats. In its idea it is 

 nearest that of the Flying Dragons, but it is 

 quite independent and by itself. Bats are, of 

 course, true mammals, covered with hair, and 

 giving milk to their offspring. They are most 

 nearly related to the Insectivores, such as 

 shrew and mole, and it is interesting to notice 

 that there is in the Far East an aberrant in- 

 sectivore called Galeopithecus, placed by 

 some authorities in a special order, which has 

 a sheet of skin stretched between fore- and 

 hind-limbs, and is a very expert parachutist. 



The wing of the bat is formed of a fold of 

 skin, which usually begins at the shoulder and 



