W6 ANIMAL MECHANISM. 



understand tho construction of the machine which we finally 

 employed. 



On t\vo solid feet carrying vertical supports, we placed 

 two horizontal arms parallel to each other. These were two 

 aluminium levers, which, by means of the apparatus we are 

 about to describe, will both execute the same movements. 

 Kadi of these levers is mounted on a Cardan joint, that is to 

 say, a universal joint which allows every kind of movement; 

 so that each lever can be carried upwards, downwards, to 

 the right or the left ; it can describe with its point the base 

 of a cone of which, the Cardan forms the apex ; in fact it will 

 execute any kind of movement which the experimenter may 

 please to give it. 



It was requisite to effect the transmission of the move- 

 ments of one of tliese levers to the other, and that at a dis- 

 tance of ten or fifteen metres. This is done by a method with 

 which the reader is already acquainted the employment of 

 air-drums and tubes. 



The lever, which in fig. 97 is seen to the left hand, is 

 fastened by a vertical metallic wire to the membrane of a 

 drum placed underneath it. In the vertical movements of 

 the lever, the membrane of the drum, alternately depressed 

 and raised, will produce a current of air, which will be trans- 

 mitted by a long air-tube to the membrane of a similar drum 

 belonging to the apparatus on the right hand. The second 

 diuiii, placed above the lever which corresponds with it, and 

 is fastened to it, will faithfully transmit all the vertical 

 movements which have been given to drum No. 1 (that on 

 the lefi). The motion of tho two levers will be in the sumo 

 direction, on account of the inversion of the position of the 

 drums. 



Let us suppose that we lower the lever No. 1 ; we com- 

 press the membrane of the drum beneath it; a current of 

 air is produced which r.iiM-s the membrane of the second 

 drum, ami consequently lowers lever No. 2. On the contrary, 

 the i.-v.itinn of Irver No. 1 will produce an inward current of 

 air. which will rai^e (lie menl'iane and the le\vr of No. 2. 



I'mcn-ding in the same manner for the transmission of 



vi mcnts, in the hori/ontal plane, we place to the right of 



