TAMBOURS 



29 



into the interior of each, and the two tambours are through these connected 

 by a piece of rubber tubing. When thus connected a pushing-in of the 

 membrane of the receiving tambour causes a corresponding rise of the 

 membrane of the recording tambour, and to the same extent if the two 

 tambours are of the same size. The form of the receiving tambour varies 

 according to the purpose for which it is intended. The form of the recording 

 tambour is shown in fig. 34. The flat metal box, provided with a side tubular 

 /, is represented at a. This is covered above by the rubber membrane b, to 

 the centre of which is attached a metal disc c with a vertical jointed rod 

 which moves the recording lever d. The amount of magnification may be 

 varied by altering the position of the jointed rod with respect to the axis of 

 the writing lever. 



Another form of tambour is represented in fig. 35. It consists of an 

 oblong vulcanite base on whose upper surface is a shallow circular cavity into 

 which the metal tube t opens. This is covered with thin rubber membrane, 

 which is attached to the vulcanite with a little Canada balsam. The upper 

 surface of the rubber is covered by a brass plate p with a central circular 

 aperture through which the rubber R is seen. The movements of the mem- 

 brane are transmitted by the cork c to the writing lever L. The axis of this 

 lever is held on a rod, which can be clamped in any position by the screw R, 

 and adjusted to any height by a vertical rod passing through the vulcanite 

 base and fixed by the screw s 1 . The advantages of this form are that the 



Fig. 85. — A Second Form of Becokmng Tambour. 



rubber membrane is very quickly replaced, and is easily made air-tight. The 

 metal plate p is held on by two stout rubber bands, B 1 and b'-', and by changing 

 this for one with a larger or smaller central aperture the sensitiveness of the 

 tambour can be at once decreased or increased. 



