280 



PHENOMENA OF FLIGHT IN THE ANIMAL KINGDOM. 



is in the same direction as that of the drum ; that is to say, if the drum 

 be raised, the lever also raises itself. It may happen, with an apparatus 

 of this kind, that in the motion of the wings rubbing may be produced 

 on the membrane of the drum, which will make confusion in the signals. 

 To avoid this I cover the upper part of the apparatus with a metallic 





network, as seen in Fig. 29. The drum is there represented in the 

 hand, held by the transmitting tube connecting with the registering 

 apparatus. If the drum is moved in the vertical plane, the lever is seen 

 to move in the same direction, at the same instant of time, and with an 

 amplitude proportionate to the motions of the hand. If, on the con- 



