Mr. J. N. Hearder on the Atlantic Cable. 35 



acted upon by the primary electric current intended to produce 

 the signal, but by the static charge which has been taken up by 

 the gutta-percha coating from the wire whilst the electricity was 

 passing through it, and which returns into the wire and escapes 

 through it, and through the instruments, after the primary cur- 

 rent has passed, and which continues to influence them until 

 the whole of that residual quantity has been discharged. 



3rd. The static charge which is taken up from the wire by 

 the gutta-percha coating increases even in a higher proportion 

 than the intensity of the current itself, and therefore with a long 

 attenuated wire these static effects increase, not only with the 

 length of the wire, but with the intensity of the current working 

 through it, and as gutta percha is analogous to crown glass and 

 some other insulating substances in its power of taking up elec- 

 tricity quickly, and parting with it again slowly, the delay occa- 

 sioned by waiting for the wire to clear itself of this static charge 

 and regain a neutral condition suited for the transmission of a 

 new current, is so considerable as to interfere most seriously with 

 the rapid transmission of signals. The recording instrument, 

 after being affected by the primary current, remains still acted 

 upon by the residual charge, though in a gradually decreasing 

 degree for a second or more, and consequently no new signal can 

 be transmitted whilst these effects are taking place, whereas with 

 an overland line the transmission of the electrical impulse is so 

 instantaneous and abrupt, that as many as twenty or more dis- 

 tinct impulses can be recognized and recorded in a single 

 second. 



4th. This disadvantage leads to another, viz. the necessity of 

 working very slowly, and employing recording or indicating tele- 

 graphs, the varied signals of which combine to form letters ; and 

 as these letters are often composed individually of four or five 

 separate signals, each occupying a second or two for its distinct 

 and perfect transmission, and as words contain on the average 

 five or six letters, it follows that each word will require from fifty 

 to sixty seconds for its transmission. This was actually the rate 

 at which, under the most favourable circumstances, the Atlantic 

 Cable worked in Keyham Dockyard, although from various news- 

 paper reports the public were led to believe that as many as four 

 words per minute had been transmitted through it. This might 

 probably have been the case if words only had been selected 

 composed of one or two signals, but in ordinary messages one 

 word per minute was the average rate of transmission. 



The loss of force in the current of electricity by the resistance 

 of the long wire, may be comprehended when I state that a flow 

 of electricity from a pair of huge induction coils capable of pro- 

 ducing the brilliant combustion of thick pieces of copper wire 



D2 



