MAKING AND LAYING SUBMARINE GABLES. 153 
gutta-percha ; but since wires insulated with Hooper’s india- 
rubber have, after they have been laid, exhibited new and some¬ 
what unexplained phenomena, these may no doubt be referred to 
chemical actions arising from the mixture of various substances 
in the only specimen of india-rubber that has hitherto proved 
successful. 
The electrical resistance of gutta-percha is, like that of india- 
rubber, much reduced by increase of the temperature. By 
Shore Cable. 
Deep Sea Cable. 
Fig. 94.—Cable between Marseilles and B6ne (Algeria). 
electrical resistance we mean, the non-conducting power that 
renders the substance more or less insulating. The loss of 
current occasioned by increase of temperature, rises more 
rapidly in gutta-percha than in india-rubber. In this respect, 
therefore, the latter is superior to the former, and it also, for 
the reason mentioned above, allows a greater number of words 
per minute to be transmitted, the weights or dimensions being 
equal. That is to say, if two cables having like conductors be 
covered respectively with equal weights of gutta-percha and 
india-rubber, twice as many words can be transmitted through 
the india-rubber cable as through the other. We have already 
stated that with Willoughby Smith’s gutta-percha, by reason of 
its superior insulating power and feeble induction, nearly as 
many words can be transmitted as with Hooper’s india-rubber. 
