274 THE STRUCTURE AND LIFE OF BIRDS ch. vn 



important questions of balance have yet to be decided. 

 Moreover, it cannot as yet leave the earth without iron 

 rails on which to get up pace. Wherever it might 

 alight, it would remain helpless as a stranded ship. 

 But the man who has got so far towards solving the 

 problem of flight may well get further. 



Conclusion. 



This ends my account of flight. Much, I hope, 

 has been made clear, but much remains that is 

 inexplicable. Mathematici?ns will, no doubt, some 

 day arrive at a formula of flight that will claim to 

 be a complete solution of the problem. Nevertheless 

 birds will still excite the wonder of men. Even those 

 who can quote the formula at a moment's notice will, 

 when they look at a Swift doing his sixty miles an 

 hour for mere play, or if they happen to see a soaring 

 Adjutant, relapse for a moment into blank astonish- 

 ment, the mental state of the Pacific islander when a 

 steamship first invades his lonely seas and claims a 

 place in his philosophy. It will always be difficult to 

 forget for long together, that, however much is learnt 

 on such a subject as flight, a great deal more remains 

 to be learnt. 



Some of the Literature of the Subject. 



Marey's Vol des Oiseanx. 



Marey's Animal Mechanism (International Sci. Series). 

 Alix's Appareil Loco?noteur des Oiseanx. 

 The article on " Flight " in Newton's Dictionary of Birds. 

 Pettigrew's Animal Locomotion (International Sci. Series). 

 Books and papers referred to in the footnotes in the course of 

 this chapter. 



