THE TELECTROGRAPH 89 



name I have designated my own modification 

 of Bakewell's apparatus, has proved successful, 

 because (i.) all the mechanical parts have been 

 most carefully modelled on lines dictated by 

 innumerable failures and experiments, and (ii.) by 

 means of the line -balancer I have made the 

 receiving instrument of such a character that the 

 distortion, lag and line -surges met with when 

 working with long-distance cables can be instantly 

 overcome by simple regulation. 



Mr. Sanger Shepherd, whose workmanship is 

 perhaps the most accurate and effectual of any 

 instrument maker in the world, undertook from 

 the start the constructional work, and to him 

 largely belongs the credit of the success of the 

 Daily Mirror's photo -telegraphic work. In trans- 

 mitting a photograph seven inches by five, made 

 up of fifty lines to the inch, the Caselli 

 stylus has to traverse 7 X 50 or 350 lines per 

 revolution. With one revolution of the transmit- 

 ting drum in two seconds we have 175 dots 

 per second recorded on the receiving paper. If 

 one dot were j^th of a second later than it should 

 be it would fall into line with the dot of the next 

 line in the line photograph. The figure of merit 

 in synchronisation requires to be within an error 

 of at least i in 500 to obtain intelligible results. 

 Thus the synchronising mechanism lias to be very 

 fairly " perfect," and it has been necessary to 



