THE TELAUTOGRAPH 



67 



is constituted. We shall now see how this inter- 

 mittent current is utilised to form a photographic 

 image in the receiving apparatus. 



Fig. 3 1 gives a diagrammatic representation of 

 the sending and receiving stations . At the former 

 we have the drum D and stylus S and the battery B. 

 At the receiving station we have a drum DI half the 

 size of the transmitting drum, so that the received 



Sending 

 Station 



Receiving 

 Station 



FIG. 31. 



picture is one-quarter the size of the sketch trans- 

 mitted. This drum revolves in a light-tight box, 

 and is fitted with a steel shaft cut with a screw 

 thread 100 to the inch, or about four to the 

 millimetre. The shaft turns in a fixed nut, so that 

 a lateral motion is given to the revolving drum, 

 its motion thus corresponding precisely to, that .of 

 the transmitting cylinder. A sliding lens is fitted 

 in the centre of the front of the " dark box," and 

 in front of it is placed an ebonite screen, with an 

 adjustable slit fitted centrally and opposite the lens. 

 Any light passing through the slit is focussed by 

 the lens as a small spot of light on DI, and if the slit 



K 9. 



