heroes of the telegraph-第14部分

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gear。　　Captain　（now　Sir）　James　Anderson；　of　the　Cunard　steamer　China；　a　thorough　seaman；　was　appointed　to　the　command；　with　Captain　Moriarty；　R。N。；　as　chief　navigating　officer。　　Mr。　（afterwards　Sir）　Samuel　Canning　was　engineer　for　the　contractors；　the　Telegraph　Construction　and　Maintenance　Company；　and　Mr。　de　Sauty　their　electrician；　Professor　Thomson　and　Mr。　Cromwell　Fleetwood　Varley　were　the　electricians　for　the　Atlantic　Telegraph　Company。　　The　Press　was　ably　represented　by　Dr。　W。　H。　Russell；　correspondent　of　the　TIMES。　　The　Great　Eastern　took　on　board　seven　or　eight　thousand　tons　of　coal　to　feed　her　fires；　a　prodigious　quantity　of　stores；　and　a　multitude　of　live　stock　which　turned　her　decks　into　a　farmyard。　　Her　crew　all　told　numbered　500　men。

At　noon　on　Saturday；　July　15；　1865；　the　Great　Eastern　left　the　Nore　for　Foilhommerum　Bay；　Valentia　Island；　where　the　shore　end　was　laid　by　the　Caroline。

At　5。30　p。m。　on　Sunday；　July　23；　amidst　the　firing　of　cannon　and　the　cheers　of　the　telegraph　fleet；　she　started　on　her　voyage　at　a　speed　of　about　four　knots　an　hour。　　The　weather　was　fine；　and　all　went　well　until　next　morning　early；　when　the　boom　of　a　gun　signalled　that　a　fault　had　broken　out　in　the　cable。　　It　turned　out　that　a　splinter　of　iron　wire　had　penetrated　the　core。　　More　faults　of　the　kind　were　discovered；　and　as　they　always　happened　in　the　same　watch；　there　was　a　suspicion　of　foul　play。　　In　repairing　one　of　these　on　July　31；　after　1；062　miles　had　been　payed　out；　the　cable　snapped　near　the　stern　of　the　ship；　and　the　end　was　lost。　　'All　is　over；'　quietly　observed　Mr。　Canning；　and　though　spirited　attempts　were　made　to　grapple　the　sunken　line　in　two　miles　of　water；　they　failed　to　recover　it。

The　Great　Eastern　steamed　back　to　England；　where　the　indomitable　Mr。　Field　issued　another　prospectus；　and　formed　the　Anglo…American　Telegraph　Company；　with　a　capital　of　L600；000；　to　lay　a　new　cable　and　complete　the　broken　one。　　On　July　7；　1866；　the　William　Cory　laid　the　shore　end　at　Valentia；　and　on　Friday；　July　13；。about　3　p。m。；　the　Great　Eastern　started　paying…out　once　more。　　＇Friday　is　regarded　as　　an　unlucky；　and　Sunday　as　a　lucky　day　by　sailors。　　The　Great　Eastern　started　on　Sunday　before　and　failed；　　she　succeeded　now。　　Columbus　sailed　on　a　Friday；　and　discovered　America　on　a　Friday。＇　　A　private　service　of　prayer　was　held　at　Valentia　by　invitation　of　two　directors　of　the　company；　but　otherwise　there　was　no　celebration　of　the　event。　　Professor　Thomson　was　on　board；　but　Dr。　W。　H。　Russell　had　gone　to　the　seat　of　the　Austro…Prussian　war；　from　which　telegrams　were　received　through　the　cable。

The　'big　ship'　was　attended　by　three　consorts；　the　Terrible；　to　act　as　a　spy　on　the　starboard　how；　and　warn　other　vessels　off　the　course；　the　Medway　on　the　port；　and　the　Albany　on　the　starboard　quarter；　to　drop　or　pick　up　buoys；　and　make　themselves　generally　useful。　　Despite　the　fickleness　of　the　weather；　and　a　'foul　flake；'　or　clogging　of　the　line　as　it　ran　out　of　the　tank；　there　was　no　interruption　of　the　work。　　The　'old　coffee　mill；'　as　the　sailors　dubbed　the　paying…out　gear；　kept　grinding　away。　　'I　believe　we　shall　do　it　this　time；　Jack；'　said　one　of　the　crew　to　his　mate。

On　the　evening　of　Friday；　July　27；　the　expedition　made　the　entrance　of　Trinity　Bay；　Newfoundland；　in　a　thick　fog；　and　next　morning　the　Great　Eastern　cast　her　anchor　at　Heart's　Content。　　Flags　were　flying　from　the　little　church　and　the　telegraph　station　on　shore。　　The　Great　Eastern　was　dressed；　three　cheers　were　given；　and　a　salute　was　fired。　　At　9　a。m。　a　message　from　England　cited　these　words　from　a　leading　article　in　the　current　TIMES：　　'It　is　a　great　work；　a　glory　to　our　age　and　nation；　and　the　men　who　have　achieved　it　deserve　to　be　honoured　among　the　benefactors　of　their　race。'　'Treaty　of　peace　signed　between　Prussia　and　Austria。'　The　shore　end　was　landed　during　the　day　by　the　Medway；　and　Captain　Anderson；　with　the　officers　of　the　telegraph　fleet；　went　in　a　body　to　the　church　to　return　thanks　for　the　success　of　the　expedition。　Congratulations　poured　in；　and　friendly　telegrams　were　again　exchanged　between　Her　Majesty　and　the　United　States。　　The　great　work　had　been　finally　accomplished；　and　the　two　worlds　were　lastingly　united。

On　August　9　the　Great　Eastern　put　to　sea　again　in　order　to　grapple　the　lost　cable　of　1865；　and　　complete　it　to　Newfoundland。　　Arriving　in　mid…　ocean　she　proceeded　to　fish　for　the　submerged　line　in　two　thousand　fathoms　of　water；　and　after　repeated　failures；　involving　thirty　casts　of　the　grapnel；　she　hooked　and　raised　it　to　surface；　then　spliced　it　to　the　fresh　cable　in　her　hold；　and　payed　out　to　Heart's　Content；　where　she　arrived　on　Saturday；　September　7。　　There　were　now　two　fibres　of　intelligence　between　the　two　hemispheres。

On　his　return　home；　Professor　Thomson　was　among　those　who　received　the　honour　of　knighthood　for　their　services　in　connection　with　the　enterprise。　　He　deserved　it。　　By　his　theory　and　apparatus　he　probably　did　more　than　any　other　man；　with　the　exception　of　Mr。　Field；　to　further　the　Atlantic　telegraph。　　We　owe　it　to　his　admirable　inventions；　the　mirror　instrument　of　1857　and　the　siphon　recorder　of　1869；　that　messages　through　long　cables　are　so　cheap　and　fast；　and；　as　a　consequence；　that　ocean　telegraphy　is　now　so　common。　　Hence　some　account　of　these　two　instruments　will　not　be　out　of　place。

Sir　William　Thomson's　siphon　recorder；　in　all　its　present　completeness；　must　take　rank　as　a　masterpiece　of　invention。　　As　used　in　the　recording　or　writing　in　permanent　characters　of　the　messages　sent　through　long　submarine　cables；　it　is　the　acknowledged　chief　of　'receiving　instruments；'　as　those　apparatus　are　called　which　interpret　the　electrical　condition　of　the　telegraph　wire　into　intelligible　signals。　Like　other　mechanical　creations；　no　doubt　its　growth　in　idea　and　translation　into　material　fact　was　a　step…by…step　process　of　evolution；　culminating　at　last　in　its　great　fitness　and　beauty。

The　marvellous　development　of　telegraphy　within　the　last　generation　has　called　into　existence　a　great　variety　of　receiving　instruments；　each　admirable　in　its　way。　　The　Hughes；　or　the　Stock　Exchange　instruments；　for　instance；　print　the　message　in　Roman　characters；　the　sounders　strike　it　out　on　stops　or　bells　of　different　tone；　the　needle　instruments　indicate　it　by　oscillations　of　their　needles；　the　Morse　daubs　it　in　ink　on　paper；　or　embosses　it　by　a　hard　style；　while　Bain's　electro…chemical　receiver　stains　it　on　chemically　prepared　paper。　　The　Meyer…Baudot　and　the　Quadruple　　receive　four　messages　at　once　and　record　them　separately；　while　the　harmonic　telegraph　of　Elisha　Gray　can　receive　as　many　as　eight　simultaneously；　by　means　of　notes　excited　by　the　current　in　eight　separate　tuning　forks。

But　all　these　instruments　have　one　great　drawback　for　delicate　work；　and；　however　suitable　they　may　be　for　land　lines；　they　are　next　to　useless　for　long　cables。　　They　require　a　certain　definite　strength　of　current　to　work　them；　whatever　it　may　be；　and　in　general　it　is　very　considerable。　　Most　of　the　moving　parts　of　the　mechanism　are　comparatively　heavy；　and　unless　the　current　is　of　the　proper　strength　to　move　them；　the　instrument　is　dumb；　while　in　Bain's　the　solution　requires　a　certain　power　of　current　to　decompose　it　and　leave　the　stain。

In　overland　lines　the　current　traverses　the　wire　suddenly；　like　a　bullet；　and　at　its　full　strength；　so　that　if　the　current　be　sufficiently　strong　these　instruments　will　be　worked　at　once；　and　no　time　will　be　lost。　　But　it　is　quite　different　on　submarine　cables。　　There　the　current　is　slow　and　varying。　　It　travels　along　the　copper　wire　in　the　form　of　a　wave　or　undulation；　and　is　received　feebly　at　first；　then　gradually　rising　to　its　maximum　strength；　and　finally　dying　away　again　as　slowly　as　it　rose。　　In　the　French　Atlantic　cable　no　current　can　be　detected　by　the　most　delicate　galvanoscope　at　America　for　the　first　tenth　of　a　second　after　it　has　been　put　on　at　Brest；　and　it　takes　about　half　a　second　for　the　received　current　to　reach　its　maximum　value。　　This　is　owing　to　the　phenomenon　of　induction；　very　important　in　submarine　cables；　but　almost　entirely　absent　in　land　lines。　　In　submarine　cables；　as　is　well　known；　the　copper　wire　which　conveys　the　current　is　insulated　from　the　sea…water　by　an　envelope；　usually　of　gutta…percha。　　Now　the　electricity　sent　into　this　wire　INDUCES　electricity　of　an　opposite　kind　to　itself　in　the　sea…water　outside；　and　the　attraction　set　up　between　these　two　kinds　'holds　back'　the　current　in　the　wire；　and　retards　its　passage　to　the　receiving　station。

It　follows；　that　with　a　receiving　instrument　set　to　indicate　a　particular　strength　of　current；　the　rate　of　signalling　would　be　very　slow　on　long　cables　compared　to　land　lines；　and　that　a　different　form　of　instrument　is　required　for　cable　work。　　This　fact　stood　greatly　in　the　way　of　early　cable　enterprise。　　Sir　William　（then　Professor）　Thomson　first　solved　the　difficulty　by　his　invention　of　the　'mirror　galvanometer；'　and　rendered　at　the　same　time　the　first　Atlantic　cable　company　a　commercial　success。　　The　merit　of　this　receiving　　instrument　is；　that　it　indicates　with　extreme　sensibility　all　the　variations　of　the　current　in　the　cable；　so　that；　instead　of　having　to　wait　until　each　signal　wave　sent　into　the　cable　has　travelled　to　the　receiving　end　before　sending　another；　a　series　of　waves　may　be　sent　after　each　other　in　rapid　succession。　　These　waves；　　encroaching　upon　each　other；　will　coalesce　at　their　bases；　but　if　the　crests　remain　separate；　the　delicate　decipherer　at　the　other　end　will　take　cognisance　of　them　and　make　them　known　to　the　eye　as　the　distinct　signals　of　the　message。

The　mirror　galvanometer　is　at　once　beautifully　simple　and　exquisitely　scientific。　　It　consists　of　a　very　long　fine　coil　of　silk…covered　copper　wire；　and　in　the　heart　of　the　coil；　within　a　little　air…chamber；　a　small　round　mirror；　having　four　tiny　magnets　cemented　to　its　back；　is　hung；　by　a　single　fibre　of　floss　silk　no　thicker　than　a　spider's　line。　　The　mirror　is　of　film　glass　silvered；　the　magnets　of　hair…spring；　and　both　together　sometimes　weigh　only　one…tenth　of　a　grain。　　A　beam　of　light　is　thrown　from　a　lamp　upon　the　mirror；　and　reflected　by　it　upon　a　white　screen　or　scale　a　fe