;io 



NA TURE 



[January 13, 19 10 



photographic means, is seen in Figs. 3 and 4; an 

 artificial line was used. By means of this apparatus 

 much valuable information has been obtained relative 



a contrary current is transmitted by means of a re- 

 verser, and this passes into the polarised relay R. The 

 relay actuates, through a local battery, a magnetic 





iiminishing intensity. 



|ipppnTniii|^rT]|r!i 



Fig. 4. — Dots of varying size in face ol a portrait ( 



to the effects of capacity and inductance in long 

 cables, some particulars of which 1 hope to publish 



tJ A-a^ iAwvt twi (^ 



shortly; the effect of capacity is to widen the "teeth 

 and make one run into the next. 



The telectrograph, which is at 

 present being extensively used for 

 transmitting news photographs from 

 Manchester and Paris to London, is a 

 modification of the Bakewell apparatus, 

 and its essential feature is the balancer 

 or compensator for overcoming the 

 capacity and inductance effects of the 

 line — distortion and " leads " of waves. 

 The apparatus is seen in Fig. 5. Here 

 A is a brass drum to which is attached 

 the half-tone photograph — printed upon 

 lead sheet, and pressed therein so that 

 an even surface is offered to the stylus, 

 which is provided with an iridium point 

 E is the sending battery. The current 

 received flows into two tongues, which 

 are ordinarily in contact with the 

 platinum pins PP, which lead the 

 current to the drum and stylus of the 

 receiver, on the former of which is 

 placed moist absorbent paper contain- 

 ing the necessary chemical matter to 

 give, by electrolysis, a coloured mark 

 when current passes through it. At 

 the end of the revolution, which is 

 finished before that of the transmitting 

 cylinder, a metal check arrests further Fig. a — lelecirog 

 movement, and the motor merely re- 

 volves a friction clutch. When the 

 transmitting cylinder has now completed its revolution, 

 the tongues being now in contact with the pins OO, 

 NO. 2098, VOL. 82] 



resented as waves with different maximum ordinates. 



release which draws away the check, so that the 

 receiving drum starts oft again. This means of 

 synchronising is one in frequent 

 commercial use, and was employed 

 by Prof. Korn in his telautograph, 

 and (with slight modification) in 

 his selenium machines. 



Now if a photograph transmitted 

 as above be received direct on the 

 chemically prepared paper, it would 

 be blurred beyond recognition, 

 owing to the distortion and the 

 secondary discharges due to the 

 line, A small dot would appear 

 elongated as follows : — Where a 

 succession of dots should be re- 

 ceived, each one would run into the next, and if at a 

 certain moment the action, after such a series of dots, 



raphed from M 



line i>f 2000 li by Thorne- Maker 

 telei-t'Ograph. 



should cease abruptly — corresponding to a '* white " or 

 " hig-h-light " in the photograph^it "^'ould, on the 



