HISTORY AND PROGRESS. 



123 



which turns by the friction of the printing disc, and keeps 

 the periphery of the latter always freshly inked. The paper 

 strip passes underneath the disc, over a knife-edge, forming 

 the continuation of a beam, carrying, at its other end, the 

 armature of the electro-magnet. When the latter is attracted, 

 therefore, the knife-edge presses the paper against the revolv- 

 ing disc. John's idea is thus reversed, but the principle 

 remains the same. 



Fig. 67 represents an elevation of the apparatus, the clock- 



Fig. 67. 



work being in the interior. The parts directly turned by 

 the clockwork are the roller R, and the printing disc D. The 

 paper strip is drawn from the drum p through the slit G, 

 under the guide-pulley u, between the printing disc D, and 

 knife-edge K, between the rollers R and B I? and across the 



