Chap, xviii.] TAMBOUR OF MAREY. 185 



membrane b ; and to the centre of the membrane is 

 cemented a disc of aluminium c, from which two light 

 supports rise for pivoting a lever d. The lever can 

 be made of any required 

 length, and terminates in 

 a fine point for writing 

 on the revolving cylinder. 



The attached end of the Fig. 91. Tambour of Marey. 



lever is freely movable 



round a horizontal axis. Now the membrane covering 

 the capsule moves with every change in the volume of 

 air which the capsule contains, and this movement is 

 communicated by the aluminium disc and its uprights 

 to the lever supported by them. The apparatus has 

 arrangements for increasing or diminishing the move- 

 ment communicated from the membrane to the lever. 

 Thus the attached end of the lever is split and the 

 supports springing from the membrane can slide back- 

 wards or forwards upon it. If the supports be pushed 

 towards the attached end the movement of the lever 

 is increased, and vice versa. When the supports are 

 moved one way or other they cease to be vertically on 

 the membrane. This is corrected by the screw s, 

 which moves the tambour, and by means of it the 

 tambour may be brought directly under the point of 

 support of the lever. By these arrangements the sen- 

 sibility of the lever can be altered. 



Such a tambour as this is brought into commu- 

 nication, with another similar instrument by means 

 of an indiarubber tube, which is attached at 

 each end to the tube f of each tambour. When two 

 tambours are thus connected with tubing they form a 

 closed system, and we may consider them as simply a 

 tube terminating at each end in an air-bag. When 

 the air is compressed in one tambour, e.y. by its 

 membrane being pressed downwards, the compression 

 passes through the tube to the other tambour, and 



