198 



TTTE WORLD'S ADVANCE 



pressure at that depth is about five tons 

 per square inch, and as it would be quite 

 impossible to recover an injured cable at 

 that point, a wide detour was made. 

 Most of this cable, incidentally, lies in 

 water deeper than three miles. 



In the tele- 

 graph code the 

 letter "e" is 

 translated into 

 a single dot. 

 T h e electrical 

 impulse which 

 carries this 

 signal down 

 under the At- 

 lantic, from 

 America to 

 England, con- 

 sumes, in time, 

 about one-sixth 



second an eye-wink reckon- 

 ing the speed of electricity at 

 180,000 miles per sec- 

 ond. When the first 

 cable was laid, 500 

 volts of electricity 



l 



enough to drive a street 

 car propelled the dots 

 and dashes from one 

 side to the other. The 

 life of the cable under 

 that terrific strain was 

 ally short. It 

 performed fit- 

 fully during a 

 brief two 

 months, from 

 August 17, 

 1858, until the 

 latter part of 

 October. Then 

 the powerful 

 currents, c o n- 

 tinually seek- 

 ing an escape, 

 finally broke 

 through the 

 weakened insulation of the cable. 



The mirror galvanometer, an invention 

 of Kelvin, was then adopted, because 

 only a fraction of the original current 

 was required to operate it a battery the 

 size of a child's thimble was sufficient 

 and it increased the speed of transmis- 



Above: A Section of an Ocean 

 Cable on the Deck of the "Makay- 

 Bennett," Ready to be Repaired. 

 Below: Another Near View of an 

 Ocean Cable, Showing How Dam- 

 aged the Covering May Become, 

 Especially in the Instance of 

 Cables Near Shore. 



sion six times. Twenty years later, 

 Lord Kelvin, who has been most aptly 

 named "The Father of the Cablegram," 

 perfected the siphon recorder, which 

 prints a graphic record of all messages. 

 Additional improvements came in the 



form of the 

 automatic 

 printing ma- 

 chine, which 

 entirely e 1 i in- 

 mates the error 

 of the human 

 equation, and a 

 duplex circuit 

 system which 

 ingeniously 

 permits two 

 messages to go 

 over one wire 

 at the same 



time. These improvements and 

 others of later origin and lesser 

 HBH^I importance are incor- 

 porated in the majority 

 of present - day cable 

 systems, although the 

 old mirror-galvanome- 

 ter can still be found 

 in a few out-of-the- 

 way corners of the 

 world. 



accidents may 

 happen to a 

 cable to inter- 

 rupt the flow 

 of conversation 

 between conti- 

 nents. In very 

 deep water the 

 sea bottom 

 consists of de- 

 composed shell 

 matter known 

 a s globigerina 

 ooze. This sub- 

 stance is harm- 

 less, and cables 



recovered from a globigerinous floor af- 

 ter a repose of thirty years were as sound 

 as the day they were laid. Greater danger 

 lurks in shoal waters. One of the tiniest 

 but most terrible enemies of the cable is 

 the teredo worm ; apparently it thrives on 

 a diet of gutta percha ! The attacks of 



