heroes of the telegraph-第56章

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！


tially　the　same　as　that　now　used　for　the　purpose　in　cable　factories。

In　1848；　when　the　war　broke　out　with　Denmark；　he　was　sent　to　Kiel　where；　together　with　his　brother…in…law；　Professor　C。　Himly；　he　laid　the　first　submarine　mines；　fired　by　electricity　and　thus　protected　the　town　of　Kiel　from　the　advance　of　the　enemies'　fleet。

Of　late　years　the　German　Government　has　laid　a　great　network　of　underground　lines　between　the　various　towns　and　fortresses　of　the　empire；　preferring　them　to　overhead　lines　as　being　less　liable　to　interruption　from　mischief；　accident；　hostile　soldiers；　or　stress　of　weather。　　The　first　of　such　lines　was；　however；　laid　as　long　ago　as　1848；　by　Werner　Siemens；　who；　in　the　autumn　of　that　year；　deposited　a　subterranean　cable　between　Berlin　and　Frankfort…on…the…Main。　　Next　year　a　second　cable　was　laid　from　the　Capital　to　Cologne；　Aix…la…Chapelle；　and　Verviers。

In　1847　the；　subject　of　our　memoir　had；　along　with　Mr。　Halske；　founded　a　telegraph　factory；　and　he　now　left　the　army　to　give　himself　up　to　scientific　work　and　the　development　of　his　business。　　This　factory　prospered　well；　and　is　still　the　chief　continental　works　of　the　kind。　The　new　departure　made　by　Werner　Siemens　was　fortunate　for　electrical　science；　and　from　then　till　now　a　number　of　remarkable　inventions　have　proceeded　from　his　laboratory。

The　following　are　the　more　notable　advances　made：In　October　1845；　a　machine　for　the　measurement　of　small　intervals　of　time；　and　the　speed　of　electricity　by　means　of　electric　sparks；　and　its　application　in　1875　for　measuring　the　speed　of　the　electric　current　in　overland　lines。

In　January　1850；　a　paper　on　telegraph　lines　and　apparatus；　in　which　the　theory　of　the　electro…static　charge　in　insulated　wires；　as　well　as　methods　and　formula：　　for　the　localising　of　faults　in　underground　wires　were　first　established。　　In　1851；　the　firm　erected　the　first　automatic　fire　telegraphs　in　Berlin；　and　in　the　same　year；　Werner　Siemens　wrote　a　treatise　on　the　experience　gained　with　the　underground　lines　of　the　Prussian　telegraph　system。　The　difficulty　of　communicating　through　long　underground　lines　led　him　to　the　invention　of　automatic　translation；　which　was　afterwards　improved　upon　by　Steinheil；　and；　in　1852；　he　furnished　the　Warsaw…Petersburg　line　with　automatic　fast…speed　writers。　The　messages　were　punched　in　a　paper　band　by　means　of　the　well…known　Siemens'　lever　punching　apparatus；　and　then　automatically　transmitted　in　a　clockwork　instrument。

In　1854　the　discovery　（contemporaneous　with　that　of　Frischen）　of　simultaneous　transmission　of　messages　in　opposite　directions；　and　multiplex　transmission　of　messages　by　means　of　electro…magnetic　apparatus。　　The　'duplex'　system　which　is　now　employed　both　on　land　lines　and　submarine　cables　had　been　suggested　however；　before　this　by　Dr。　Zetsche；　Gintl；　and　others。

In　1856　he　invented　the　Siemens'　magneto…electric　dial　instrument　giving　alternate　currents。　　From　this　apparatus　originated　the　well…　known　Siemens'　armature；　and　from　the　receiver　was　developed　the　Siemens'　polarised　relay；　with　which　the　working　of　submarine　and　other　lines　could　be　effected　with　alternate　currents；　and　in　the　same　year；　during　the　laying　of　the　Cagliari　to　Bona　cable；　he　constructed　and　first　applied　the　dynamometer；　which　has　become　of　such　importance　in　the　operations　of　cable　laying。

In　1857；　he　investigated　the　electro…static　induction　and　retardation　of　currents　in　insulated　wires；　a　phenomenon　which　he　had　observed　in　1850；　and　communicated　an　account　of　it　to　the　French　Academy　of　Sciences。

'In　these　researches　he　developed　mathematically　Faraday's　theory　of　molecular　induction；　and　thereby　paved　the　way　in　great　measure　for　its　general　acceptance。'　His　ozone　apparatus；　his　telegraph　instrument　working　with　alternate　currents；　and　his　instrument　for　translating　on　and　automatically　discharging　submarine　cables　also　belong　to　the　year　1857。　　The　latter　instruments　were　applied　to　the　Sardinia；　Malta；　and　Corfu　cable。

In　1859；　he　constructed　an　electric　log；　he　discovered　that　a　dielectric　is　heated　by　induction；　he　introduced　the　well　known　Siemens'　mercury　unit；　and　many　improvements　in　the　manufacture　of　resistance　coils。　　He　also　investigated　the　law　of　change　of　resistance　in　wires　by　heating；　and　published　several　formulae　and　methods　for　testing　resistances　and　determining　'faults'　by　measuring　resistances。　These　methods　were　adopted　by　the　electricians　of　the　Government　service　in　Prussia；　and　by　Messrs。　Siemens　Brothers　in　London；　during　the　manufacture　of　the　Malta　to　Alexandria　cable；　which；　was；　we　believe；　the　first　long　cable　subjected　to　a　system　of　continuous　tests。

'In　1861；　he　showed　that　the　electrical　resistance　of　molten　alloys　is　equal　to　the　sum　of　the　resistances　of　the　separate　metals；　and　that　latent　heat　increases　the　specific　resistance　of　metals　in　a　greater　degree　than　free　heat。'　In　1864　he　made　researches　on　the　heating　of　the　sides　of　a　Leyden　jar　by　the　electrical　discharge。　　In　1866　he　published　the　general　theory　of　dynamo…electric　machines；　and　the　principle　of　accumulating　the　magnetic　effect；　a　principle　which；　however；　had　been　contemporaneously　discovered　by　Mr。　S。　A。　Varley；　and　described　in　a　patent　some　years　before　by　Mr。　Soren　Hjorth；　a　Danish　inventor。　Hjorth's　patent　is　to　be　found　in　the　British　Patent　Office　Library；　and　until　lately　it　was　thought　that　he　was　the　first　and　true　inventor　of　the　'dynamo'　proper；　but　we　understand　　there　is　a　prior　inventor　still；　though　we　have　not　seen　the　evidence　in　support　of　the　statement。

The　reversibility　of　the　dynamo　was　enunciated　by　Werner　Siemens　in　1867；　but　it　was　not　experimentally　demonstrated　on　any　practical　scale　until　1870；　when　M。　Hippolite　Fontaine　succeeded　in　pumping　water　at　the　Vienna　international　exhibition　by　the　aid　of　two　dynamos　connected　in　circuit；　one；　the　generator；　deriving　motion　from　a　hydraulic　engine；　and　in　turn　setting　in　motion　the　receiving　dynamo　which　worked　the　pump。　　Professor　Clerk　Maxwell　thought　this　discovery　the　greatest　of　the　century；　and　the　remark　has　been　repeated　more　than　once。　　But　it　is　a　remark　which　derives　its　chief　importance　from　the　man　who　made　it；　and　its　credentials　from　the　paradoxical　surprise　it　causes。　　The　discovery　in　question　is　certainly　fraught　with　very　great　consequences　to　the　mechanical　world；　but　in　itself　it　is　no　discovery　of　importance；　and　naturally　follows　from　Faraday's　far　greater　and　more　original　discovery　of　magneto…electric　generation。

In　1874；　Dr。　Siemens　published　a　treatise　on　the　laying　and　testing　of　submarine　cables。　　In　1875；　1876　and　1877；　he　investigated　the　action　of　light　on　crystalline　selenium；　and　in　1878　he　studied　the　action　of　the　telephone。

The　recent　work　of　Dr。　Siemens　has　been　to　improve　the　pneumatic　railway；　railway　signalling；　electric　lamps；　dynamos；　electro…plating　and　electric　railways。　　The　electric　railway　at　Berlin　in　1880；　and　Paris　in　1881；　was　the　beginning　of　electric　locomotion；　a　subject　of　great　importance　and　destined　in　all　probability；　to　very　wide　extension　in　the　immediate　future。　　Dr。　Siemens　has　received　many　honours　from　learned　societies　at　home　and　abroad；　and　a　title　equivalent　to　knighthood　from　the　German　Government。



VI。　　LATlMER　CLARK。

MR。　Clark　was　born　at　Great　Marlow　in　1822；　and　probably　acquired　his　scientific　bent　while　engaged　at　a　manufacturing　chemist's　business　in　Dublin。　On　the　outbreak　of　the　railway　mania　in　1845　he　took　to　surveying；　and　through　his　brother；　Mr。　Edwin　Clark；　became　assistant　engineer　to　the　late　Robert　Stephenson　on　the　Britannia　Bridge。　　While　thus　employed；　he　made　the　acquaintance　of　Mr。　Ricardo；　founder　of　the　Electric　Telegraph　Company；　and　joined　that　Company　as　an　engineer　in　1850。　　He　rose　to　be　chief　engineer　in　1854；　and　held　the　post　till　1861；　when　he　entered　into　a　partnership　with　Mr。　Charles　T。　Bright。　Prior　to　this；　he　had　made　several　original　researches；　in　1853；　he　found　that　the　retardation　of　current　on　insulated　wires　was　independent　of　the　strength　of　current；　and　his　experiments　formed　the　subject　of　a　Friday　evening　lecture　by　Faraday　at　the　Royal　Institutiona　sufficient　mark　of　their　impo