heroes of the telegraph-第13部分

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he　North　Sea；　from　Orfordness　to　the　Hague。　　It　was　laid　by　the　Monarch；　a　paddle　steamer　which　had　been　fitted　for　the　work。　　During　the　night　she　met　with　such　heavy　weather　that　the　engineer　was　lashed　near　the　brakes；　and　the　electrician；　Mr。　Latimer　Clark；　sent　the　continuity　signals　by　jerking　a　needle　instrument　with　a　string。　　These　and　other　efforts　in　the　Mediterranean　and　elsewhere　were　the　harbingers　of　the　memorable　enterprise　which　bound　the　Old　World　and　the　New。

Bishop　Mullock；　head　of　the　Roman　Catholic　Church　in　Newfoundland；　was　lying　becalmed　in　his　yacht　one　day　in　sight　of　Cape　Breton　Island；　and　began　to　dream　of　a　plan　for　uniting　his　savage　diocese　to　the　mainland　by　a　line　of　telegraph　through　the　forest　from　St。　John's　to　Cape　Ray；　and　cables　across　the　mouth　of　the　St。　Lawrence　from　Cape　Ray　to　Nova　Scotia。　　St。　John's　was　an　Atlantic　port；　and　it　seemed　to　him　that　the　passage　of　news　between　America　and　Europe　could　thus　be　shortened　by　forty…eight　hours。　　On　returning　to　St。　John's　he　published　his　idea　in　the　COURIER　by　a　letter　dated　November　8；　1850。

About　the　same　time　a　similar　plan　occurred　to　Mr。　F。　N。　Gisborne；　a　telegraph　engineer　in　Nova　Scotia。　　In　the　spring　of　1851　he　procured　a　grant　from　the　Legislature　of　Newfoundland；　resigned　his　situation　in　Nova　Scotia；　and　having　formed　a　company；　began　the　construction　of　the　land　line。　　But　in　1853　his　bills　were　dishonoured　by　the　company；　he　was　arrested　for　debt；　and　stripped　of　all　his　fortune。　　The　following　year；　however；　he　was　introduced　to　Mr。　Cyrus　Field；　of　New　York；　a　wealthy　merchant；　who　had　just　returned　from　a　six　months'　tour　in　South　America。　　Mr。　Field　invited　Mr。　Gisborne　to　his　house　in　order　to　discuss　the　project。　　When　his　visitor　was　gone；　Mr。　Field　began　to　turn　over　a　terrestrial　globe　which　stood　in　his　library；　and　it　flashed　upon　him　that　the　telegraph　to　Newfoundland　might　be　extended　across　the　Atlantic　Ocean。　　The　idea　fired　him　with　enthusiasm。　　It　seemed　worthy　of　a　man's　ambition；　and　although　he　had　retired　from　business　to　spend　his　days　in　peace；　he　resolved　to　dedicate　his　time；　his　energies；　and　fortune　to　the　accomplishment　of　this　grand　enterprise。

A　presentiment　of　success　may　have　inspired　him；　but　he　was　ignorant　alike　of　submarine　cables　and　the　deep　sea。　　Was　it　possible　to　submerge　the　cable　in　the　Atlantic；　and　would　it　be　safe　at　the　bottom？　　Again；　would　the　messages　travel　through　the　line　fast　enough　to　make　it　pay！　On　the　first　question　he　consulted　Lieutenant　Maury；　the　great　authority　on　mareography。　　Maury　told　him　that　according　to　recent　soundings　by　Lieutenant　Berryman；　of　the　United　States　brig　Dolphin；　the　bottom　between　Ireland　and　Newfoundland　was　a　plateau　covered　with　microscopic　shells　at　a　depth　not　over　2000　fathoms；　and　seemed　to　have　been　made　for　the　very　purpose　of　receiving　the　cable。　　He　left　the　question　of　finding　a　time　calm　enough；　the　sea　smooth　enough；　a　wire　long　enough；　and　a　ship　big　enough；'　to　lay　a　line　some　sixteen　hundred　miles　in　length　to　other　minds。　　As　to　the　line　itself；　Mr。　Field　consulted　Professor　Morse；　who　assured　him　that　it　was　quite　possible　to　make　and　lay　a　cable　of　that　length。　　He　at　once　adopted　the　scheme　of　Gisborne　as　a　preliminary　step　to　the　vaster　undertaking；　and　promoted　the　New　York；　Newfoundland；　and　London　Telegraph　Company；　to　establish　a　line　of　telegraph　between　America　and　Europe。　　Professor　Morse　was　appointed　electrician　to　the　company。

The　first　thing　to　be　done　was　to　finish　the　line　between　St。　John's　and　Nova　Scotia；　and　in　1855　an　attempt　was　made　to　lay　a　cable　across　the　Gulf　of　the　St。　Lawrence；　It　was　payed　out　from　a　barque　in　tow　of　a　steamer；　but　when　half　was　laid　a　gale　rose；　and　to　keep　the　barque　from　sinking　the　line　was　cut　away。　　Next　summer　a　steamboat　was　fitted　out　for　the　purpose；　and　the　cable　was　submerged。　　St。　John's　was　now　connected　with　New　York　by　a　thousand　miles　of　land　and　submarine　telegraph。

Mr。　Field　then　directed　his　efforts　to　the　completion　of　the　trans…　oceanic　section。　　He　induced　the　American　Government　to　despatch　Lieutenant　Berryman；　in　the　Arctic；　and　the　British　Admiralty　to　send　Lieutenant：　　Dayman；　in　the　Cyclops；　to　make　a　special　survey　along　the　proposed　route　of　the　cable。　　These　soundings　　revealed　the　existence　of　a　submarine　hill　dividing　the　'telegraph　plateau'　from　the　shoal　water　on　the　coast　of　Ireland；　but　its　slope　was　gradual　and　easy。

Till　now　the　enterprise　had　been　purely　American；　and　the　funds　provided　by　American　capitalists；　with　the　exception　of　a　few　shares　held　by　Mr。　J。　W。　Brett。　　But　seeing　that　the　cable　was　to　land　on　British　soil；　it　was　fitting　that　the　work　should　be　international；　and　that　the　British　people　should　be　asked　to　contribute　towards　the　manufacture　and　submersion　of　the　cable。　　Mr。　Field　therefore　proceeded　to　London；　and　with　the　assistance　of　Mr。　Brett　the　Atlantic　Telegraph　Company　was　floated。　　Mr。　Field　himself　supplied　a　quarter　of　the　needed　capital；　and　we　may　add　that　Lady　Byron；　and　Mr。　Thackeray；　the　novelist；　were　among　the　shareholders。

The　design　of　the　cable　was　a　subject　of　experiment　by　Professor　Morse　and　others。　　It　was　known　that　the　conductor　should　be　of　copper；　possessing　a　high　conductivity　for　the　electric　current；　and　that　its　insulating　jacket　of　gutta…percha　should　offer　a　great　resistance　to　the　leakage　of　the　current。　　Moreover；　experience　had　shown　that　the　protecting　sheath　or　armour　of　the　core　should　be　light　and　flexible　as　well　as　strong；　in　order　to　resist　external　violence　and　allow　it　to　be　lifted　for　repair。　　There　was　another　consideration；　however；　which　at　this　time　was　rather　a　puzzle。　　As　early　as　1823　Mr。　（afterwards　Sir）　Francis　Ronalds　had　observed　that　electric　signals　were　retarded　in　passing　through　an　insulated　wire　or　core　laid　under　ground；　and　the　same　effect　was　noticeable　on　cores　immersed　in　water；　and　particularly　on　the　lengthy　cable　between　England　and　the　Hague。　　Faraday　showed　that　it　was　caused　by　induction　between　the　electricity　in　the　wire　and　the　earth　or　water　surrounding　it。　　A　core；　in　fact；　is　an　attenuated　Leyden　jar；　the　wire　of　the　core；　its　insulating　jacket；　and　the　soil　or　water　around　it　stand　respectively　for　the　inner　tinfoil；　the　glass；　and　the　outer　tinfoil　of　the　jar。　　When　the　wire　is　charged　from　a　battery；　the　electricity　induces　an　opposite　charge　in　the　water　as　it　travels　along；　and　as　the　two　charges　attract　each　other；　the　exciting　charge　is　restrained。　　The　speed　of　a　signal　through　the　conductor　of　a　submarine　cable　is　thus　diminished　by　a　drag　of　its　own　making。　　The　nature　of　the　phenomenon　was　clear；　but　the　laws　which　governed　it　were　still　a　mystery。　　It　became　a　serious　question　whether；　on　a　long　cable　such　as　that　required　for　the　Atlantic；　the　signals　might　not　be　so　sluggish　that　the　work　would　hardly　pay。　　Faraday　had　said　to　Mr。　Field　that　a　signal　would　take　'about　a　second；'　and　the　American　was　satisfied；　but　Professor　Thomson　enunciated　the　law　of　retardation；　and　cleared　up　the　whole　matter。　　He　showed　that　the　velocity　of　a　signal　through　a　given　core　was　inversely　proportional　to　the　square　of　the　length　of　the　core。　That　is　to　say；　in　any　particular　cable　the　speed　of　a　signal　is　diminished　to　one…fourth　if　the　length　is　doubled；　to　one…ninth　if　it　is　trebled；　to　one…sixteenth　if　it　is　quadrupled；　and　so　on。　　It　was　now　possible　to　calculate　the　time　taken　by　a　signal　in　traversing　the　proposed　Atlantic　line　to　a　minute　fraction　of　a　second；　and　to　design　the　proper　core　for　a　cable　of　any　given　length。

The　accuracy　of　Thomson's　law　was　disputed　in　1856　by　Dr。　Edward　O。　Wildman　Whitehouse；　the　electrician　of　the　Atlantic　Telegraph　Company；　who　had　misinterpreted　the　results　of　his　own　experiments。　　Thomson　disposed　of　his　contention　in　a　letter　to　the　ATHENAEUM；　and　the　directors　of　the　company　saw　that　he　was　a　man　to　enlist　in　their　adventure。　　It　is　not　enough　to　say　the　young　Glasgow　professor　threw　himself　heart　and　soul　into　their　work。　　He　descended　in　their　midst　like　the　very　genius　of　electricity；　and　helped　them　out　of　all　their　difficulties。　　In　1857　he　published　in　the　ENGINEER　the　whole　theory　of　the　mechanical　forces　involved　in　the　laying　of　a　submarine　cable；　and　showed　that　when　the　line　is　running　out　of　the　ship　at　a　constant　speed　in　a　uniform　depth　of　water；　it　sinks　in　a　slant　or　straight　incline　from　the　point　where　it　enters　the　water　to　that　where　it　touches　the　bottom。

To　these　gifts　of　theory；　electrical　and　mechanical；　Thomson　added　a　practical　boon　in　the　shape　of　the　reflecting　galvanometer；　or　mirror　instrument。　　This　measurer　of　the　current　was　infinitely　more　sensitive　than　any　which　preceded　it；　and　enables　the　electrician　to　detect　the　slightest　flaw　in　the　core　of　a　cable　during　its　manufacture　and　submersion。　　Moreover；　it　proved　the　best　apparatus　for　receiving　the　messages　through　a　long　cable。　　The　Morse　and　other　instruments；　however　suitable　for　land　lines　and　short　cables；　were　all　but　useless　on　the　Atlantic　line；　owing　to　the　retardation　of　the　signals；　but　the　mirror　instrument　sprang　out　of　Thomson's　study　of　this　phenomenon；　and　was　designed　to　match