heroes of the telegraph-第42章

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properties　of　matter　to　the　production　of　new　inventions。　　For　love　of　science　or　the　hope　of　gain；　men　had　experimented　before；　and　worked　out　their　inventions　in　the　laboratories　of　colleges　and　　manufactories。　　But　Edison　seems　to　have　been　the　first　to　organise　a　staff　of　trained　assistants　to　hunt　up　useful　facts　in　books；　old　and　modern；　and　discover　fresh　ones　by　experiment；　in　order　to　develop　his　ideas　or　suggest　new　ones；　together　with　skilled　workmen　to　embody　them　in　the　fittest　manner；　and　all　with　the　avowed　object　of　taking　out　patents；　and　introducing　the　novel　apparatus　as　a　commercial　speculation。　He　did　not　manufacture　his　machines　for　sale；　he　simply　created　the　models；　and　left　their　multiplication　to　other　people。　There　are　different　ways　of　looking　at　Nature：

　　　　　　　'To　some　she　is　the　goddess　great；　　　　　　　　To　some　the　milch…cow　of　the　field；　　　　　　　　Their　business　is　to　calculate　　　　　　　　The　butter　she　will　yield。'

The　institution　has　proved　a　remarkable　success。　　From　it　has　emanated　a　series　of　marvellous　inventions　which　have　carried　the　name　of　Edison　throughout　the　whole　civilised　world。　　Expense　was　disregarded　in　making　the　laboratory　as　efficient　as　possible；　the　very　best　equipment　was　provided；　the　ablest　assistants　employed；　and　the　profit　has　been　immense。　　Edison　is　a　millionaire；　the　royalties　from　his　patents　alone　are　said　to　equal　the　salary　of　a　Prime　Minister。

Although　Edison　was　the　master　spirit　of　the　band；　it　must　not　be　forgotten　that　his　assistants　were　sometimes　co…inventors　with　himself。　No　doubt　he　often　supplied　the　germinal　ideas；　while　his　assistants　only　carried　them　out。　　But　occasionally　the　suggestion　was　nothing　more　than　this：　　'I　want　something　that　will　do　so…and…so。　　I　believe　it　will　be　a　good　thing；　and　can　be　done。'　The　assistant　was　on　his　mettle；　and　either　failed　or　triumphed。　　The　results　of　the　experiments　and　researches　were　all　chronicled　in　a　book；　for　the　new　facts；　if　not　then　required；　might　become　serviceable　at　a　future　time。　　If　a　rare　material　was　wanted；　it　was　procured　at　any　cost。

With　such　facilities；　an　invention　is　rapidly　matured。　Sometimes　the　idea　was　conceived　in　the　morning；　and　a　working　model　was　constructed　by　the　evening。　　One　day；　we　are　told；　a　discovery　was　made　at　4　P。M。；　and　Edison　telegraphed　it　to　his　patent　agent；　who　immediately　drew　up　the　specification；　and　at　nine　o'clock　next　morning　cabled　it　to　London。　Before　the　inventor　was　out　of　bed；　he　received　an　intimation　that　his　patent　had　been　already　deposited　in　the　British　Patent　Office。　　Of　course；　the　difference　of　time　was　in　his　favour。

When　Edison　arrived　at　the　laboratory　in　the　morning；　he　read　his　letters；　and　then　overlooked　his　employees；　witnessing　their　results　and　offering　his　suggestions；　but　it　often　happened　that　he　became　totally　engrossed　with　one　experiment　or　invention。　His　work　was　frequently　interrupted　by　curious　visitors；　who　wished　to　see　the　laboratory　and　the　man。　　Although　he　had　chosen　that　out…of…the…way　place　to　avoid　disturbance；　they　were　never　denied：　　and　he　often　took　a　pleasure　in　showing　his　models；　or　explaining　the　work　on　which　he　was　engaged。　There　was　no　affectation　of　mystery；　no　attempt　at　keeping　his　experiments　a　secret。　　Even　the　laboratory　notes　were　open　to　inspection。　　Menlo　Park　became　a　kind　of　Mecca　to　the　scientific　pilgrim；　the　newspapers　and　magazines　despatched　reporters　to　the　scene；　excursion　parties　came　by　rail；　and　country　farmers　in　their　buggies；　till　at　last　an　enterprising　Yankee　even　opened　a　refreshment　room。

The　first　of　Edison's　greater　inventions　in　Menlo　Park　was　the　'loud…　speaking　telephone。'　Professor　Graham　Bell　had　introduced　his　magneto…　electric　telephone；　but　its　effect　was　feeble。　　It　is；　we　believe；　a　maxim　in　biology　that　a　similarity　between　the　extremities　of　a　creature　is　an　infallible　sign　of　its　inferiority；　and　that　in　proportion　as　it　rises　in　the　scale　of　being；　its　head　is　found　to　differ　from　its　tail。　Now；　in　the　Bell　apparatus；　the　transmitter　and　the　receiver　were　alike；　and　hence　Clerk　Maxwell　hinted　that　it　would　never　be　good　for　much　until　they　became　differentiated　from　each　other。　　Consciously　or　unconsciously　Edison　accomplished　the　feat。　　With　the　hardihood　of　genius；　he　attempted　to　devise　a　telephone　which　would　speak　out　loud　enough　to　be　heard　in　any　corner　of　a　large　hall。

In　the　telephone　of　Bell；　the　voice　of　the　speaker　is　the　motive　power　which　generates　the　current　in　the　line。　　The　vibrations　of　the　sound　may　be　said　to　transform　themselves　into　electrical　undulations。　Hence　the　current　is　very　weak；　and　the　reproduction　of　the　voice　is　relatively　faint。　　Edison　adopted　the　principle　of　making　the　vibrations　of　the　voice　control　the　intensity　of　a　current　which　was　independently　supplied　to　the　line　by　a　voltaic　battery。　　The　plan　of　Bell；　in　short；　may　be　compared　to　a　man　who　employs　his　strength　to　pump　a　quantity　of　water　into　a　pipe；　and　that　of　Edison　to　one　who　uses　his　to　open　a　sluice；　through　which　a　stream　of　water　flows　from　a　capacious　dam　into　the　pipe。　　Edison　was　acquainted　with　two　experimental　facts　on　which　to　base　the　invention。

In　1873；　or　thereabout；　he　claimed　to　have　observed；　while　constructing　rheostats；　or　electrical　resistances　for　making　an　artificial　telegraph　line；　that　powdered　plumbago　and　carbon　has　the　property　of　varying　in　its　resistance　to　the　passage　of　the　current　when　under　pressure。　　The　variation　seemed　in　a　manner　proportional　to　the　pressure。　　As　a　matter　of　fact；　powdered　carbon　and　plumbago　had　been　used　in　making　small　adjustable　rheostats　by　M。　Clerac；　in　France；　and　probably　also　in　Germany；　as　early　as　1865　or　1866。　Clerac's　device　consisted　of　a　small　wooden　tube　containing　the　material；　and　fitted　with　contacts　for　the　current；　which　appear　to　have　adjusted　the　pressure。　Moreover；　the　Count　Du　Moncel；　as　far　back　as　1856；　had　clearly　discovered　that　when　powdered　carbon　was　subjected　to　pressure；　its　electrical　resistance　altered；　and　had　made　a　number　of　experiments　on　the　phenomenon。　　Edison　may　have　independently　observed　the　fact；　but　it　is　certain　he　was　not　the　first；　and　his　claim　to　priority　has　fallen　to　the　ground。

Still　he　deserves　the　full　credit　of　utilising　it　in　ways　which　were　highly　ingenious　and　bold。　　The　'pressure…relay；'　produced　in　1877；　was　the　first　relay　in　which　the　strength　of　the　local　current　working　the　local　telegraph　instrument　was　caused　to　vary　in　proportion　to　the　variation；　of　the　current　in　the　main　line。　　It　consisted　of　an　electro…　magnet　with　double　poles　and　an　armature　which　pressed　upon　a　disc　or　discs　of　plumbago；　through　which　the　local　current　Passed。　　The　electro…　magnet　was　excited　by　the　main　line　current　and　the　armature　attracted　to　its　poles　at　every　signal；　thus　pressing　on　the　plumbago；　and　by　reducing　its　resistance　varying　the　current　in　the　local　circuit。　According　as　the　main　line　current　was　strong　or　weak；　the　pressure　on　the　plumbago　was　more　or　less；　and　the　current　in　the　local　circuit　strong　or　weak。　　Hence　the　signals　of　the　local　receiver　were　in　accordance　with　the　currents　in　the　main　line。

Edison　found　that　the　same　property　might　be　applied　to　regulate　the　strength　of　a　current　in　conformity　with　the　vibrations　of　the　voice；　and　after　a　great　number　of　experiments　produced　his　'carbon　transmitter。'　Plumbago　in　powder；　in　sticks；　or　rubbed　on　fibres　and　sheets　of　silk；　were　tried　as　the　sensitive　material；　but　finally　abandoned　in　favour　of　a　small　cake　or　wafer　of　compressed　lamp…black；　obtained　from　the　smoke　of　burning　oil；　such　as　　benzolene　or　rigolene。　This　was　the　celebrated　'carbon　button；'　which　on　being　placed　between　two　platinum　discs　by　way　of　contact；　and　traversed　by　the　electric　current；　was　found　to　vary　in　resistance　under　the　pressure　of　the　sound　waves。　　The　voice　was　concentrated　upon　it　by　means　of　a　mouthpiece　and　a　diaphragm。

The　property　on　which　the　receiver　was　based　had　been　observed　and　applied　by　him　some　time　before。　When　a　current　is　passed　from　a　metal　contact　through　certain　chemical　salts；　a　lubricating　effect　was　noticeable。　　Thus　if　a　metal　stylus　were　rubbed　or　drawn　over　a　pr