270 



ANIMAL MECHANISM. 



movement which we wish to investigate. For this purpose, the 

 two drums combined rectangularly must be connected with the 

 same inert mass. 



Let us refer to fig. 97 (p. 237), where we see the two 

 levers connected together and communicating with each other 

 by tubes, which transmit to one all the movements executed 

 by the other. When we give the first lever any kind of 

 movement, we see it reproduced by the second lever in the 

 same direction. 



Now, let each of these levers be loaded with a piece of lead, 

 and taking in our hand the support of the apparatus, let us 

 cause it to describe any kind of movement in a plane perpen- 

 dicular to the direction of the lever. We shall see that the 

 lever No. 2 executes movements of exactly an opposite kind. 

 In fact, since the motive force which acts on the membrane of 

 the drums is nothing more than the inertia of the mass of 

 lead, and the movements of this mass are always later than 

 those given t6 the apparatus, it is clear that if we raise 

 the whole system, the mass will keep the lever down, while 

 if we lower the instrument the mass will retain the lever 

 above ; that if we carry it forward, the inertia will keep the 

 lever back, &c. Therefore, the lever No. 2, only going 

 through the same movements as No. 1 , will give curves which 

 will be absolutely opposed to the movement which has been 

 given to the stand of the apparatus. This being assumed, let 

 us pass to the experiment; for this, let us employ the 

 apparatus represented in fig. 99 on the back of the buzzard 

 as it flies ; let us remove the rod which received the movements 

 of the wing, as well as the parallelogram which transmitted 

 them to the lever ; we will only retain the lever fastened to 

 the two drums, and the contrivance which fixes the whole 

 instrument on the back of the buzzard ; lastly, let us adapt a 

 piece of lead to this lever, and let the bird fly. The tracing 

 procured is represented in fig. 115. The analysis of this 

 curve is at first sight extremely difficult ; we hope, however, 

 to succeed in showing its signification. 



Analysis of the curve illustrating the oscillations of the bird. — 

 This curve is described on the cylinder in the same manner as 

 in fig. 100, which shows the different movements of the point 



