PHENOMENA OF FLIGHT IN THE ANIMAL KINGDOM. 273 



imparted to the first drum to the left. These movements will be in the 

 same direction in both levers on account of the inversion of the position 

 of the drums. If we depress the first lever it presses down the mem- 

 brane of the drum below it, inducing a pressure which lifts the mem- 

 brane of the second drum, and consequently lowers the second lever 

 conversely; the elevation of the first lever produces an influx of air 

 which raises the membrane of the second lever. ' 



Fig. 23. 



Proceeding in the same manner to transmit motions in a horizontal 

 plane, I have placed at the right of one of the levers and at the left of 

 the other a drum with the membrane in a vertical plane, which imparts 



