a history of science-2-第49节

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r　discoveries。　Musschenbroek　was　one　of　the　foremost　teachers　of　Europe；　and　so　widely　known　that　the　great　universities　vied　with　each　other；　and　kings　were　bidding；　for　his　services。　Naturally；　any　discovery　made　by　such　a　famous　person　would　soon　be　heralded　from　one　end　of　Europe　to　the　other。　And　so　when　this　professor　of　Leyden　made　his　discovery；　the　apparatus　came　to　be　called　the　〃Leyden　jar；〃　for　want　of　a　better　name。　There　can　be　little　doubt　that　Musschenbroek　made　his　discovery　entirely　independently　of　any　knowledge　of　Von　Kleist's；　or；　for　that　matter；　without　ever　having　heard　of　the　Pomeranian；　and　his　actions　in　the　matter　are　entirely　honorable。　His　discovery　was　the　result　of　an　accident。　While　experimenting　to　determine　the　strength　of　electricity　he　suspended　a　gun…barrel；　which　he　charged　with　electricity　from　a　revolving　glass　globe。　From　the　end　of　the　gun…barrel　opposite　the　globe　was　a　brass　wire；　which　extended　into　a　glass　jar　partly　filled　with　water。　Musschenbroek　held　in　one　hand　this　jar；　while　with　the　other　he　attempted　to　draw　sparks　from　the　barrel。　Suddenly　he　received　a　shock　in　the　hand　holding　the　jar；　that　〃shook　him　like　a　stroke　of　lightning；〃　and　for　a　moment　made　him　believe　that　〃he　was　done　for。〃　Continuing　his　experiments；　nevertheless；　he　found　that　if　the　jar　were　placed　on　a　piece　of　metal　on　the　table；　a　shock　would　be　received　by　touching　this　piece　of　metal　with　one　hand　and　touching　the　wire　with　the　otherthat　is；　a　path　was　made　for　the　electrical　discharge　through　the　body。　This　was　practically　the　same　experiment　as　made　by　Von　Kleist　with　his　bottle　and　nail；　but　carried　one　step　farther；　as　it　showed　that　the　〃jar〃　need　not　necessarily　be　held　in　the　hand；　as　believed　by　Von　Kleist。　Further　experiments；　continued　by　many　philosophers　at　the　time；　revealed　what　Von　Kleist　had　already　pointed　out；　that　the　electrified　jar　remained　charged　for　some　time。　Soon　after　this　Daniel　Gralath；　wishing　to　obtain　stronger　discharges　than　could　be　had　from　a　single　Leyden　jar；　conceived　the　idea　of　combining　several　jars；　thus　for　the　first　time　grouping　the　generators　in　a　〃battery〃　which　produced　a　discharge　strong　enough　to　kill　birds　and　small　animals。　He　also　attempted　to　measure　the　strength　of　the　discharges；　but　soon　gave　it　up　in　despair；　and　the　solution　of　this　problem　was　left　for　late　nineteenth…century　scientists。　The　advent　of　the　Leyden　jar；　which　made　it　possible　to　produce　strong　electrical　discharges　from　a　small　and　comparatively　simple　device；　was　followed　by　more　spectacular　demonstrations　of　various　kinds　all　over　Europe。　These　exhibitions　aroused　the　interest　of　the　kings　and　noblemen；　so　that　electricity　no　longer　remained　a　〃plaything　of　the　philosophers〃　alone；　but　of　kings　as　well。　A　favorite　demonstration　was　that　of　sending　the　electrical　discharge　through　long　lines　of　soldiers　linked　together　by　pieces　of　wire；　the　discharge　causing　them　to　〃spring　into　the　air　simultaneously〃　in　a　most　astonishing　manner。　A　certain　monk　in　Paris　prepared　a　most　elaborate　series　of　demonstrations　for　the　amusement　of　the　king；　among　other　things　linking　together　an　entire　regiment　of　nine　hundred　men；　causing　them　to　perform　simultaneous　springs　and　contortions　in　a　manner　most　amusing　to　the　royal　guests。　But　not　all　the　experiments　being　made　were　of　a　purely　spectacular　character；　although　most　of　them　accomplished　little　except　in　a　negative　way。　The　famous　Abbe　Nollet；　for　example；　combined　useful　experiments　with　spectacular　demonstrations；　thus　keeping　up　popular　interest　while　aiding　the　cause　of　scientific　electricity。

WILLIAM　WATSON　Naturally；　the　new　discoveries　made　necessary　a　new　nomenclature；　new　words　and　electrical　terms　being　constantly　employed　by　the　various　writers　of　that　day。　Among　these　writers　was　the　English　scientist　William　Watson；　who　was　not　only　a　most　prolific　writer　but　a　tireless　investigator。　Many　of　the　words　coined　by　him　are　now　obsolete；　but　one　at　least；　〃circuit；〃　still　remains　in　use。　In　1746；　a　French　scientist；　Louis　Guillaume　le　Monnier；　bad　made　a　circuit　including　metal　and　water　by　laying　a　chain　half…way　around　the　edge　of　a　pond；　a　man　at　either　end　holding　it。　One　of　these　men　dipped　his　free　hand　in　the　water；　the　other　presenting　a　Leyden　jar　to　a　rod　suspended　on　a　cork　float　on　the　water；　both　men　receiving　a　shock　simultaneously。　Watson；　a　year　later；　attempted　the　same　experiment　on　a　larger　scale。　He　laid　a　wire　about　twelve　hundred　feet　long　across　Westminster　Bridge　over　the　Thames；　bringing　the　ends　to　the　water's　edge　on　the　opposite　banks；　a　man　at　one　end　holding　the　wire　and　touching　the　water。　A　second　man　on　the　opposite　side　held　the　wire　and　a　Leyden　jar；　and　a　third　touched　the　jar　with　one　hand；　while　with　the　other　he　grasped　a　wire　that　extended　into　the　river。　In　this　way　they　not　only　received　the　shock；　but　fired　alcohol　as　readily　across　the　stream　as　could　be　done　in　the　laboratory。　In　this　experiment　Watson　discovered　the　superiority　of　wire　over　chain　as　a　conductor；　rightly　ascribing　this　superiority　to　the　continuity　of　the　metal。　Watson　continued　making　similar　experiments　over　longer　watercourses；　some　of　them　as　long　as　eight　thousand　feet；　and　while　engaged　in　making　one　of　these　he　made　the　discovery　so　essential　to　later　inventions；　that　the　earth　could　be　used　as　part　of　the　circuit　in　the　same　manner　as　bodies　of　water。　Lengthening　his　wires　he　continued　his　experiments　until　a　circuit　of　four　miles　was　made；　and　still　the　electricity　seemed　to　traverse　the　course　instantaneously；　and　with　apparently　undiminished　force；　if　the　insulation　was　perfect。

BENJAMIN　FRANKLIN　Watson's　writings　now　carried　the　field　of　active　discovery　across　the　Atlantic；　and　for　the　first　time　an　American　scientist　appeareda　scientist　who　not　only　rivalled；　but　excelled；　his　European　contemporaries。　Benjamin　Franklin；　of　Philadelphia；　coming　into　possession　of　some　of　Watson's　books；　became　so　interested　in　the　experiments　described　in　them　that　he　began　at　once　experimenting　with　electricity。　In　Watson's　book　were　given　directions　for　making　various　experiments；　and　these　assisted　Franklin　in　repeating　the　old　experiments；　and　eventually　adding　new　ones。　Associated　with　Franklin；　and　equally　interested　and　enthusiastic；　if　not　equally　successful　in　making　discoveries；　were　three　other　men；　Thomas　Hopkinson；　Philip　Sing；　and　Ebenezer　Kinnersley。　These　men　worked　together　constantly；　although　it　appears　to　have　been　Franklin　who　made　independently　the　important　discoveries；　and　formulated　the　famous　Franklinian　theory。　Working　steadily；　and　keeping　constantly　in　touch　with　the　progress　of　the　European　investigators；　Franklin　soon　made　some　experiments　which　he　thought　demonstrated　some　hitherto　unknown　phases　of　electrical　manifestation。　This　was　the　effect　of　pointed　bodies　〃in　DRAWING　OFF　and　THROWING　OFF　the　electrical　fire。〃　In　his　description　of　this　phenomenon；　Franklin　writes：　〃Place　an　iron　shot　of　three　or　four　inches　diameter　on　the　mouth　of　a　clean；　dry；　glass　bottle。　By　a　fine　silken　thread　from　the　ceiling　right　over　the　mouth　of　the　bottle；　suspend　a　small　cork　ball；　about　the　bigness　of　a　marble；　the　thread　of　such　a　length　that　the　cork　ball　may　rest　against　the　side　of　the　shot。　Electrify　the　shot；　and　the　ball　will　be　repelled　to　the　distance　of　four　or　five　inches；　more　or　less；　according　to　the　quantity　of　electricity。　When　in　this　state；　if　you　present　to　the　shot　the　point　of　a　long；　slender　shaft…bodkin；　at　six　or　eight　inches　distance；　the　repellency　is　instantly　destroyed；　and　the　cork　flies　to　the　shot。　A　blunt　body　must　be　brought　within　an　inch；　and　draw　a　spark；　to　produce　the　same　effect。　〃To　prove　that　the　electrical　fire　is　DRAWN　OFF　by　the　point；　if　you　take　the　blade　of　the　bodkin　out　of　the　wooden　handle　and　fix　it　in　a　stick　of　sealing…wax；　and　then　present　it　at　the　distance　aforesaid；　or　if　you　bring　it　very　near；　no　such　effect　follows；　but　sliding　one　finger　along　the　wax　till　you　touch　the　blade；　and　the　ball　flies　to　the　shot　immediately。　If　you　present　the　point　in　the　dark　you　will　see；　sometimes　at　a　foot　distance；　and　more；　a　light　gather　upon　it　like　that　of　a　fire…fly　or　glow…worm；　the　less　sharp　the　point；　the　nearer　you　must　bring　it　to　observe　the　light；　and　at　whatever　distance　you　see　the　light；　you　may　draw　off　the　electrical　fire　and　destroy　the　repellency。　If　a　cork　ball　so　suspended　be　repelled　by　the　tube；　and　a　point　be　presented　quick　to　it；　though　at　a　considerable　distance；　'tis　surprising　to　see　how　suddenly　it　flies　back　to　the　tube。　Points　of　wood　will　do　as　well　as　those　of　iron；　provided　the　wood　is　not　dry；　for　perfectly　dry　wood　will　no　more　conduct　electricity　than　sealing…wax。　〃To　show　that　points　will　THROW　OFF　as　well　as　DRAW　OFF　the　electrical　fire；　lay　a　long；　sharp　needle　upon　the　shot；　and　you　cannot　electrify　the　shot　so　as　to　make　it　repel　the　cork　ball。　Or　fix　a　needle　to　the　end　of　a　suspended　gun…barrel　or　iron　rod；　so　as　to　point　beyond　it　like　a　little　bayonet；　and　while　it　remains　there；　the　gun…barrel　or　rod　cannot；　by　applying　the　tube　to　the　other　end；　be　electrified　so　as　to　give　a　spark；　the　fire　continually　running　ou