the history of the telephone-第15部分

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emergencies；　began　in　1882　a　series　of　actual　experiments　at　Attleborough；　Massachusetts；　to　find　out　exactly　what　could；　and　what　could　not；　be　done　with　wires　that　were　buried　in　the　earth。

A　five…mile　trench　was　dug　beside　a　railway　track。　The　work　was　done　handily　and　cheaply　by　the　labor…saving　plan　of　hitching　a　locomotive　to　a　plough。　Five　ploughs　were　jerked　apart　before　the　work　was　finished。　Then；　into　this　trench　were　laid　wires　with　every　known　sort　of　covering。　Most　of　them；　naturally；　were　wrapped　with　rubber　or　gutta…percha；　after　the　fashion　of　a　submarine　cable。　When　all　were　in　place；　the　willing　locomotive　was　harnessed　to　a　huge　wooden　drag；　which　threw　the　ploughed　soil　back　into　the　trench　and　covered　the　wires　a　foot　deep。　It　was　the　most　professional　cable…　laying　that　any　one　at　that　time　could　do；　and　it　succeeded；　not　brilliantly；　but　well　enough　to　encourage　the　telephone　engineers　to　go　ahead。

Several　weeks　later；　the　first　two　cables　for　actual　use　were　laid　in　Boston　and　Brooklyn；　and　in　1883　Engineer　J。　P。　Davis　was　set　to　grapple　with　the　Herculean　labor　of　putting　a

complete　underground　system　in　the　wire…bound　city　of　New　York。　This　he　did　in　spite　of　a　bombardment　of　explosions　from　leaky　gas…　pipes；　and　with　a　woeful　lack　of　experts　and　standard　materials。　All　manner　of　makeshifts　had　to　be　tried　in　place　of　tile　ducts；　which　were　not　known　in　1883。　Iron　pipe　was　used　at　first；　then　asphalt；　concrete；　boxes　of　sand　and　creosoted　wood。　As　for　the　wires；　they　were　first　wrapped　in　cotton；　and　then　twisted　into　cables；　usually　of　a　hundred　wires　each。　And　to　prevent　the　least　taint　of　moisture；　which　means　sudden　death　to　a　telephone　current；　these　cables　were　invariably　soaked　in　oil。

This　oil…filled　type　of　cable　carried　the　telephone　business　safely　through　half　a　dozen　years。　But　it　was　not　the　final　type。　It　was　preliminary　only；　the　best　that　could　be　made　at　that　time。　Not　one　is　in　use　to…day。　In　1888　Theodore　Vail　set　on　foot　a　second　series　of　experiments；　to　see　if　a　cable　could　be　made　that　was　better　suited　as　a　highway　for　the　delicate　electric　currents　of　the　telephone。　A　young　engineer　named　John　A。　Barrett；　who　had　already　made　his　mark　as　an　expert；　by　finding　a　way　to　twist　and　transpose　the　wires；　was　set　apart　to　tackle　this　problem。　Being　an　economical　Vermonter；　Barrett　went　to　work　in　a　little　wooden　shed　in　the　backyard　of　a　Brooklyn　foundry。　In　this　foundry　he　had　seen　a　unique　machine　that　could　be　made　to　mould　hot　lead　around　a　rope　of　twisted　wires。　This　was　a　notable　discovery。　It　meant　TIGHT　COVERINGS。　It　meant　a　victory　over　that　most　troublesome　of　enemiesmoisture。　Also；　it　meant　that　cables　could　henceforth　be　made　longer；　with　fewer　sleeves　and　splices；　and　without　the　oil；　which　had　always　been　an　unmitigated　nuisance。

Next；　having　made　the　cable　tight；　Barrett　set　out　to　produce　it　more　cheaply　and　by　accident　stumbled　upon　a　way　to　make　it　immensely　more　efficient。　All　wires　were　at　that　time　wrapped　with　cotton；　and　his　plan　was　to　find　some　less　costly　material　that　would　serve　the　same　purpose。　One　of　his　workmen；　a　Virginian；　suggested　the　use　of　paper　twine；　which　had　been　used　in　the　South　during　the　Civil　War；　when　cotton　was　scarce　and　expensive。　Barrett　at　once　searched　the　South　for　paper　twine　and　found　it。　He　bought　a　barrel　of　it　from　a　small　factory　in　Richmond；　but　after　a　trial　it　proved　to　be　too　flimsy。　If　such　paper　could　be　put　on　flat；　he　reasoned；　it　would　be　stronger。　Just　then　he　heard　of　an　erratic　genius　who　had　an　invention　for　winding　paper　tape　on　wire　for　the　use　of　milliners。

Paper…wound　bonnet…wire！　Who　could　imagine　any　connection　between　this　and　the　telephone？　Yet　this　hint　was　exactly　what　Barrett　needed。　He　experimented　until　he　had　devised　a　machine　that　crumpled　the　paper　around　the　wire；　instead　of　winding　it　tightly。　This　was　the　finishing　touch。　For　a　time　these　paper…wound　cables　were　soaked　in　oil；　but　in　1890　Engineer　F。　A。　Pickernell　dared　to　trust　to　the　tightness　of　the　lead　sheathing；　and　laid　a　〃dry　core〃　cable；　the　first　of　the　modern　type；　in　one　of　the　streets　of　Philadelphia。　This　cable　was　the　event　of　the　year。　It　was　not　only　cheaper。　It　was　the　best…talking　cable　that　had　ever　been　harnessed　to　a　telephone。

What　Barrett　had　done　was　soon　made　clear。　By　wrapping　the　wire　with　loose　paper；　he　had　in　reality　cushioned　it　with　AIR；　which　is　the　best　possible　insulator。　Not　the　paper；　but　the　air　in　the　paper；　had　improved　the　cable。　More　air　was　added　by　the　omission　of　the　oil。　And　presently　Barrett　perceived　that　he　had　merely　reproduced　in　a　cable；　as　far　as　possible；　the　conditions　of　the　overhead　wires；　which　are　separated　by　nothing　but　air。

By　1896　there　were　two　hundred　thousand　miles　of　wire　snugly　wrapped　in　paper　and　lying　in　leaden　caskets　beneath　the　streets　of　the　cities；　and　to…day　there　are　six　million　miles　of　it　owned　by　the　affiliated　Bell　companies。　Instead　of　blackening　the　streets；　the　wire　nerves　of　the　telephone　are　now　out　of　sight　under　the　roadway；　and　twining　into　the　basements　of　buildings　like　a　new　sort　of　metallic　ivy。　Some　cables　are　so　large　that　a　single　spool　of　cable　will　weigh　twenty…six　tons　and　require　a　giant　truck　and　a　sixteen…horse　team　to　haul　it　to　its　resting…place。　As　many　as　twelve　hundred　wires　are　often　bunched　into　one　sheath；　and　each　cable　lies　loosely　in　a　little　duct　of　its　own。　It　is　reached　by　manholes　where　it　runs　under　the　streets　and　in　little　switching…boxes　placed　at　intervals　it　is　frayed　out　into　separate　pairs　of　wires　that　blossom　at　length　into　telephones。

Out　in　the　open　country　there　are　still　the　open　wires；　which　in　point　of　talking　are　the　best。　In　the　suburbs　of　cities　there　are　neat　green　posts　with　a　single　gray　cable　hung　from　a　heavy　wire。　Usually；　a　telephone　pole　is　made　from　a　sixty…year…old　tree；　a　cedar；　chestnut；　or　juniper。　It　lasts　twelve　years　only；　so　that　the　one　item　of　poles　is　still　costing　the　telephone　companies　several　millions　a　year。　The　total　number　of　poles　now　in　the　United　States；　used　by　telephone　and　telegraph　companies；　once　covered　an　area；　before　they　were　cut　down；　as　large　as　the　State　of　Rhode　Island。

But　the　highest　triumph　of　wire…laying　came　when　New　York　swept　into　the　Skyscraper　Age；　and　when　hundreds　of　tall　buildings；　as　high　as　the　fall　of　the　waters　of　Niagara；　grew　up　like　a　range　of　magical　cliffs　upon　the　precious　rock　of　Manhattan。　Here　the　work　of　the　telephone　engineer　has　been　so　well　done　that　although　every　room　in　these　cliff…buildings　has　its　telephone；　there　is　not　a　pole　in　sight；　not　a　cross…arm；　not　a　wire。　Nothing　but　the　tip…ends　of　an　immense　system　are　visible。　No　sooner　is　a　new　skyscraper　walled　and　roofed；　than　the　telephones　are　in　place；　at　once　putting　the　tenants　in　touch　with　the　rest　of　the　city　and　the　greater　part　of　the　United　States。　In　a　single　one　of　these　monstrous　buildings；　the　Hudson　Terminal；　there　is　a　cable　that　runs　from　basement　to　roof　and　ravels　out　to　reach　three　thousand　desks。　This　mighty　geyser　of　wires　is　fifty　tons　in　weight　and　would；　if　straightened　out　into　a　single　line；　connect　New　York　with　Chicago。　Yet　it　is　as　invisible　as　the　nerves　and　muscles　of　a　human　body。

During　this　evolution　of　the　cable；　even　the　wire　itself　was　being　remade。　Vail　and　others　had　noticed　that　of　all　the　varieties　of　wire　that　were　for　sale；　not　one　was　exactly　suitable　for　a　telephone　system。　The　first　telephone　wire　was　of　galvanized　iron；　which　had　at　least　the　primitive　virtue　of　being　cheap。　Then　came　steel　wire；　stronger　but　less　durable。　But　these　wires　were　noisy　and　not　good　conductors　of　electricity。　An　ideal　telephone　wire；　they　found；　must　be　made　of　either　silver　or　copper。　Silver　was　out　of　the　question；　and　copper　wire　was　too　soft　and　weak。　It　would　not　carry　its　own　weight。

The　problem；　therefore；　was　either　to　make　steel　wire　a　better　conductor；　or　to　produce　a　copper　wire　that　would　be　strong　enough。　Vail　chose　the　latter；　and　forthwith　gave　orders　to　a　Bridgeport　manufacturer　to　begin　experiments。　A　young　expert　named　Thomas　B。　Doolittle　was　at　once　set　to　work；　and　presently　appeared　the　first　hard…drawn　copper　wire；　made　tough…　skinned　by　a　fairly　simple　process。　Vail　bought　thirty　pounds　of　it　and　scattered　it　in　various　parts　of　the　United　States；　to　note　the　effect　upon　it　of　different　climates。　One　length　of　it　may　still　be　seen　at　the　Vail　homestead　in　Lyndonville；　Vermont。　Then　this　hard…drawn　wire　was　put　to　a　severe　test　by　being　strung　between　Boston　and　New　York。　This　line　was　a　brilliant　success；　and　the　new　wire　was　hailed　with　great　delight　as　the　ideal　servant　of　the　telephone。

Since　then　there　has　been　little　trouble　with　copper　wire；　except　its　price。　It　was　four　times　as　good　as　iron　wire；　and　four　times　as　expensive。　Every　mile　of　it；　doubled；　weighed　two　hundred　pounds　and　cost　thirty　dollars。　On　the　long　lines；　where　it　had　to　be　as　thick　as　a　lead　pencil；　the　expense　seemed　to　be　ruinously　great。　When　the　first　pair　of　wires　was　strung　between　New　York　and　Chicago；　for　instance；　it　was　found　to　weigh　870；000　poundsa　full　load　for　a　twenty…two…car　freight　train；　and　the　cost　of　the　bar