heroes of the telegraph-第23章

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every　quarter　of　the　globe；　both　by　land　and　sea。　　The　most　important　aerial　line　erected　by　the　firm　was　the　Indo…European　telegraph　　line；　through　Prussia；　Russia；　and　Persia；　to　India。　　The　North　China　cable；　the　Platino…Brazileira；　and　the　Direct　United　States　cable；　were　laid　by　the　firm；　the　latter　in　1874…5　So　also　was　the　French　Atlantic　cable；　and　the　two　Jay　Could　Atlantic　cables。　　At　the　time　of　his　death　the　manufacture　and　laying　of　the　Bennett…Mackay　Atlantic　cables　was　in　progress　at　the　company's　works；　Charlton。　　Some　idea　of　the　extent　of　this　manufactory　may　be　gathered　from　the　fact　that　it　gives　employment　to　some　2；000　men。　　All　branches　of　electrical　work　are　followed　out　in　its　various　departments；　including　the　construction　of　dynamos　and　electric　lamps。

On　July　23；　1859；　Siemens　was　married　at　St。　James's；　Paddington；　to　Anne；　the　youngest　daughter　of　Mr。　Joseph　Gordon；　Writer　to　the　Signet；　Edinburgh；　and　brother　to　Mr。　Lewis　Gordon；　Professor　of　Engineering　in　the　University　of　Glasgow；　He　used　to　say　that　on　March　19　of　that　year　he　took　oath　and　allegiance　to　two　ladies　in　one　dayto　the　Queen　and　his　betrothed。　　The　marriage　was　a　thoroughly　happy　one。

Although　much　engaged　in　the　advancement　of　telegraphy；　he　was　also　occupied　with　his　favourite　idea　of　regeneration。　　The　regenerative　gas　furnace；　originally　invented　in　1848　by　his　brother　Friedrich；　was　perfected　and　introduced　by　him　during　many　succeeding　years。　　The　difficulties　overcome　in　the　development　of　this　invention　were　enormous；　but　the　final　triumph　was　complete。

The　principle　of　this　furnace　consists　in　utilising　the　heat　of　the　products　of　combustion　to　warm　up　the　gaseous　fuel　and　air　which　enters　the　furnace。　　This　is　done　by　making　these　products　pass　through　brickwork　chambers　which　absorb　their　heat　and　communicate　it　to　the　gas　and　air　currents　going　to　the　flame。　　An　extremely　high　temperature　is　thus　obtained；　and　the　furnace　has；　in　consequence；　been　largely　used　in　the　manufacture　of　glass　and　steel。

Before　the　introduction　of　this　furnace；　attempts　had　been　made　to　produce　cast…steel　without　the　use　of　a　cruciblethat　is　to　say；　on　the　'open　hearth'　of　the　furnace。　　Reaumur　was　probably　the　first　to　show　that　steel　could　be　made　by　fusing　malleable　iron　with　cast…iron。　　Heath　patented　the　process　in　1845；　and　a　quantity　of　cast…steel　was　actually　prepared　in　this　way；　on　the　bed　of　a　reverberatory　furnace；　by　Sudre；　in　France；　during　the　year　1860。　　But　the　furnace　was　destroyed　in　the　act；　and　it　remained　for　Siemens；　with　his　regenerative　furnace；　to　realise　the　object。　　In　1862　Mr。　Charles　Atwood；　of　Tow　Law；　agreed　to　erect　such　a　furnace；　and　give　the　process　a　fair　trial；　but　although　successful　in　　producing　the　steel；　he　was　afraid　its　temper　was　not　satisfactory；　and　discontinued　the　experiment。　　Next　year；　however；　Siemens；　who　was　not　to　be　　disheartened；　made　another　attempt　with　a　large　furnace　erected　at　the　Montlucon　Works；　in　France；　where　he　was　assisted　by　the　late　M。　le　Chatellier；　Inspecteur…General　　des　Mines。　Some　charges　of　steel　were　produced；　　but　here　again　the　roof　of　the　furnace　melted　down；　and　the　company　which　had　undertaken　the　trials　gave　them　up。　　The　temperature　required　for　the　manufacture　of　the　steel　was　higher　than　the　melting　point　of　most　fire…bricks。　　Further　endeavours　also　led　to　disappointments；　but　in　the　end　the　　inventor　was　successful。　　He　erected　experimental　works　at　Birmingham；　and　gradually　matured　his　process　until　it　was　so　far　advanced　that　it　could　be　trusted　to　the　hands　of　others。　　Siemens　used　a　mixture　of　cast…steel　and　iron　ore　to　make　the　steel；　but　another　manufacturer；　M。　Martin；　of　Sireuil；　in　France；　developed　the　older　plan　of　mixing　the　cast…iron　with　wrought…iron　scrap。　　While　Siemens　was　improving　his　means　at　Birmingham；　Martin　was　obtaining　　satisfactory　results　with　a　regenerative　furnace　of　his　own　design；　and　at　the　Paris　Exhibition　of　1867　samples　of　good　open…hearth　steel　were　shown　by　both　manufacturers。　　In　England　the　process　is　now　generally　known　as　the　'Siemens…Martin；'　and　on　the　Continent　as　the　'Martin…Siemens'　process。

The　regenerative　furnace　is　the　greatest　single　invention　of　Charles　William　Siemens。　　Owing　to　the　large　demand　for　steel　for　engineering　operations；　both　at　home　and　abroad；　it　proved　exceedingly　remunerative。　Extensive　works　for　the　application　of　the　process　were　erected　at　Landore；　where　Siemens　prosecuted　his　experiments　on　the　subject　with　unfailing　ardour；　and；　among　other　things；　succeeded　in　making　a　basic　brick　for　the　lining　of　his　furnaces　which　withstood　the　intense　heat　fairly　well。

The　process　in　detail　consists　in　freeing　the　bath　of　melted　pig…iron　from　excess　of　carbon　by　adding　broken　lumps　of　pure　hematite　or　magnetite　iron　ore。　　This　causes　a　violent　boiling；　which　is　kept　up　until　the　metal　becomes　soft　enough；　when　it　is　allowed　to　stand　to　let　the　metal　clear　from　the　slag　which　floats　in　scum　upon　the　top。　　The　separation　of　the　slag　and　iron　is　facilitated　by　throwing　in　some　lime　from　time　to　time。　　Spiegel；　or　specular　iron；　is　then　added；　about　1　per　cent。　more　than　in　the　scrap　process。　　From　20　to　24　cwt。　of　ore　are　used　in　a　5…ton　charge；　and　about　half　the　metal　is　reduced　and　turned　into　steel；　so　that　the　yield　in　ingots　is　from　1　to　2　per　cent。　more　than　the　weight　of　pig　and　spiegel　iron　in　the　charge。　　The　consumption　of　coal　is　rather　larger　than　in　the　scrap　process；　and　is　from　14　to　15　cwt。　per　ton　of　steel。　　The　two　processes　of　Siemens　and　Martin　are　often　combined；　both　scrap　and　ore　being　used　in　the　same　charge；　the　latter　being　valuable　as　a　tempering　material。

At　present　there　are　several　large　works　engaged　in　manufacturing　the　Siemens…Martin　steel　in　England；　namely；　the　Landore；　the　Parkhead　Forge；　those　of　the　Steel　Company　of　Scotland；　of　Messrs。　Vickers　&　Co。；　Sheffield；　and　others。　　These　produced　no　less　than　340；000　tons　of　steel　during　the　year　1881；　and　two　years　later　the　total　output　had　risen　to　half　a　million　tons。　　In　1876　the　British　Admiralty　built　two　iron…clads；　the　Mercury　and　Iris；　of　Siemens…Martin　steel；　and　the　experiment　proved　so　satisfactory；　that　this　material　only　is　now　used　in　the　Royal　dockyards　for　the　construction　of　hulls　and　boilers。　Moreover；　the　use　of　it　is　gradually　extending　in　the　mercantile　marine。　Contemporaneous　with　his　development　of　the　open…hearth　process；　William　Siemens　introduced　the　rotary　furnace　for　producing　wrought…iron　direct　from　the　ore　without　the　need　of　puddling。

The　fervent　heat　of　the　Siemens　furnace　led　the　inventor　to　devise　a　novel　means　of　measuring　high　temperatures；　which　illustrates　the　value　of　a　broad　scientific　training　to　the　inventor；　and　the　happy　manner　in　which　William　Siemens；　above　all　others；　turned　his　varied　knowledge　to　account；　and　brought　the　facts　and　resources　of　one　science　to　bear　upon　another。　　As　early　as　1860；　while　engaged　in　testing　the　conductor　of　the　Malta　to　Alexandria　telegraph　cable；　then　in　course　of　manufacture；　he　was　struck　by　the　increase　of　resistance　in　metallic　wires　occasioned　by　a　rise　of　temperature；　and　the　following　year　he　devised　a　thermometer　based　on　the　fact　which　he　exhibited　before　the　British　Association　at　Manchester。　　Mathiessen　and　others　have　since　enunciated　the　law　according　to　which　this　rise　of　resistance　varies　with　rise　of　temperature；　and　Siemens　has　further　perfected　his　apparatus；　and　applied　it　as　a　pyrometer　to　the　measurement　of　furnace　fires。　　It　forms　in　reality　an　electric　thermometer；　which　will　indicate　the　temperature　of　an　inaccessible　spot。　　A　coil　of　platinum　or　platinum…alloy　wire　is　enclosed　in　a　suitable　fire…proof　case　and　put　into　the　furnace　of　which　the　temperature　is　wanted。　　Connecting　wires；　properly　protected；　lend　from　the　coil　to　a　differential　voltameter；　so　that；　by　means　of　the　current　from　a　battery　circulating　in　the　system；　the　electric　resistance　of　the　coil　in　the　furnace　can　be　determined　at　any　moment。　Since　this　resistance　depends　on　the　temperature　of　the　furnace；　the　temperature　call　be　found　from　the　resistance　observed。　　The　instrument　formed　the　subject　of　the　Bakerian　lecture　f