138 



PHOTO-TELEGRAPHY 



be transmitted at a considerable speed with the 

 apparatus.* 



The transmitting apparatus consists, as before, 

 of a metal drum revolving under a stylus, a metal 

 foil print, the image of which consists of glue or 

 shellac lines, being wrapped round it. The battery 



FIG. 63. Quartz string and selenium cell arranged for 

 receiving and transforming up electrical oscillations. 



current flows through the cylinder, picture, and 

 stylus to a very lightly-built relay capable of work- 

 ing at a high speed ; this relay in turn actuates a 

 heavier one which causes the interruptions in the 

 primary of the alternator or induction coil. If a 

 coil be used, a turbine or other mercury brake is 

 essential. 



Prov, Patent 361/10, 



