126 THE ELECTRIC TELEGRAPH. 



by its own weight, upon the printing disc, which is in con- 

 nection with the clockwork, and performs the same functions 

 as the corresponding member of Digney's instrument print- 

 ing on the upper side of the paper strip p p, which is lifted 

 by the knife-edge, K. 



Both this method and that of Digney are not entirely 



Fig. 68. 



without objection, however, on account of the printing disc 

 and paper being underneath the reservoir of ink, from which, 

 when the apparatus stands inactive some time, the colouring 

 fluid frequently runs down and makes a blot on the paper ; 

 besides this, they are both liable to the objection that the 

 surface of the felt quickly dries up in warm weather. 



To remedy these defects, Siemens and Halske have made 

 a second and still more valuable improvement in the inking 

 process. It consists in again reversing the order of things, 

 in making the printing disc revolve with its lower half 

 immersed in a dish of colouring fluid, and in lifting the disc 

 up against the paper, which runs above it, instead of pressing 

 the paper against the disc. This is the perfection of the 

 mechanical arrangements which M. John was able, only in an 

 incomplete way, to carry out. 



This modification is shown in Fig. .69. A is a glass phial 



