AERIAL LOCOMOTION 227 



past occupied ourselves in determining the .nature of 

 the wing movements, and to this end we have adapted 

 every possible means of mechanical appliance. These 

 experiments furnished us with important information 

 regarding the frequency of movement, and the reasons 

 for variation. We also obtained records of the muscular 

 contractions which occurred in flight, and their varia- 

 tions among different species of birds. Even the 

 trajectory of the point of the wing, and the inclination 

 of the wing-surface during the different phases of 

 movement, have been determined by this method. It 

 is, however, chiefly by means of chronophotography 

 that the complicated actions involved in the flight of 

 birds has been fully explained. 



As we have fully described these experiments else- 

 where,* we need only refer briefly to the two methods 

 which have thrown new light upon this subject. 



Employment of Chronophotography in detennining the 

 Duration of the Rise and Fall of the Wings. — As in 

 the case of terrestrial locomotion, it is by mechanical 

 means that the frequency of a bird's movements, and 

 the phases of muscular activity which result in flight, 

 can be best ascertained. 



Chronography and myography have both been suc- 

 cessfully used in these determinations. To measure 

 the frequency of the wing movements an electric 

 chronograph was employed to register on a revolving 

 cylinder the make and break of an electric current, 

 the interruption being brought about directly by the 

 movements of the wing. For this purpose the bird 

 had a small flexible plate fixed to the extremity of 

 one of its remiges, which was bent in different direc- 

 tions by the resistance of the air as the wing was 

 raised or lowered. A double and very flexible wire 

 connected the bird with the chronograph and battery, 



* Le Vol des Oiseaux. Paris, Masson, 1890. 



