282 PHENOMENA OF FLIGHT IN THE ANIMAL KINGDOM. 



Fior. 32, 



Fig, 30. Line 1, Chronographic trace of a tnning-fork, vibrating 100 times a second; 

 2. Vertical oscillations of the wild duck during flight. 3. OaciUatioua of the hen-hawk. 

 4, Of tlie screech-owl; and 5, of the harrier. 



Fig. 32. Simultaneous tracing of both kinds of oscillations executed by a harrier 

 during flight. 



