838 Mr. T. Thome Baker [April 22, 



What happens, then, is that every brief current which passes 

 through the paper causes a mark to appear on it. The width of the 

 mark depends on the duration of the current — or should do — so that 

 you will see that these marks gradually combine to recompose the 

 photographic image. 



This method is all very well in the laboratory, but when we come 

 to try it over a long distance the capacity of the line at once causes 

 serious interference. It is well known that if a current be sent to 

 some apparatus such as a telegraph from a distance, the current 

 having to pass through long wires whose capacity is appreciable, a 

 certain time is taken for the current to charge the line, and the line 

 discharges itself into the apparatus with comparative slowness. If 

 the circuit be closed by means of a Morse key, the time of contact 

 at the key being a sixth of a second — a common time of duration of 

 a short tap — the discharge of current from the cable would be con- 

 siderably longer than one-sixth of a second. When, therefore, we 

 are sending signals through the line at the rate of 175 per second, 

 it is not difficult to see that every signal will run into the next dozen 

 or so at the receiving apparatus, and the result will be a hopelessly 

 confused mass of overlapping marks. This is well illustrated in 

 Fig. 2, where A shows a series of taps passed through a cable of 



Fig. 2. 



high capacity into the telectrograph receiver ; instead of getting a 

 series of sharp dots or short lines, we get elongated hues ending off 

 in tails. Without the capacity we get the short lines as shown in 

 the B series. These short definite lines are again obtained, even 

 when the capacity is present, in series C, but in this case I had 

 shunted on to the receiver what I have termed the line balancer, a 

 modified form of shunt apparatus embodying the principles of iciiiing 

 out residuary currents from the cable in the way frequently made use 

 of in duplex telegraphy. 



The use of this apparatus has rendered commercial the old ideas of 

 telegraphing by the electrolytic method, and as many as three hundred 

 sharply defined chemical marks can be recorded in one second by its 

 means. The method of application will be seen if we have the last 

 slide shown again (Fig. 1) ; here shunted on to the line (which is 



