83 Mr. J. N. Hearder on the Atlantic Cable, 



The charge thus communicated to the siu-face of the gutta 

 percha endeavours to retuiii into the wire whenever the latter 

 regains its neutral condition; and if immediately after the trans- 

 mission of a current through the conductor^ its ends be con- 

 nected with the earth, this charge will be fouud to flow out at 

 each end, starting from a point near the centre, until the whole 

 is discharged. If telegraphic instruments be so connected with 

 the ends of the conductor as to form the channels by which 

 these discharges flow back again into the earth, after each sus- 

 pension of the battery current, they will, if they are constructed 

 so as to be influenced by statical electricity, be acted upon by 

 these discharges, just as if they had been transmitting signals 

 from a battery. It follows, therefore, that before fresh signals 

 can be transmitted with certainty and accuracy, the wire must 

 be permitted to clear itself entirely of this residuary charge; 

 otherwise the succeeding battery currents will be embarrassed 

 and confused. In submarine cables of moderate lengths this 

 difficulty has been partially met by modifying the character of 

 the telegraphic instruments, but not without a considerable sa- 

 crifice of rapidity in working, as compared with the rate of trans- 

 mission through atmospheric lines. With very long lines, how- 

 ever, even under the best circumstances, this clearing-time, 

 or, as it is improperly called, retardation, is very considerable, 

 amounting often to twice and thrice that required for the actual 

 transmission of the primary current. 



By a careful attention, however, to the due adjustment of the 

 length and thickness of the wires to the battery current, much 

 of this inductive action may be overcome, and the tendency to 

 take up charge be diminished. When the resistance of a wire 

 is very great, it requires high intensity in the battery current to 

 overcome it ; and as the tendency of the wire to charge the gutta 

 percha increases in a much higher proportion than the statical 

 intensity of the cm-rent, it follows that the lower this intensity 

 can be kept (and this can only be done by diminishing the resist- 

 ance), the less will be the embarrassment from residual charge. 

 The only way in which this resistance can be diminished, is by 

 increasing the bulk and conducting capability of the wire. It 

 may be argued, however, that this increase of bulk increases the 

 inner surface of the gutta percha exposed to the charging in- 

 fluence. Granted ; but it must be remembered that doubling the 

 diameter only doubles this charging surface, whereas the trans- 

 verse sectional area, and consequent conducting capability, are 

 quadrupled. The requisite intensity, therefore, and charging 

 power of the current will be only one-fourth ; and if the diameter 

 of the wire were four times as great, the charging surface would 

 also be four times as great, but the charging power of the current 



