a history of science-2-第48节

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viously　made　similar　demonstrations　on　various　inflammable　substances；　both　liquid　and　solid；　and　it　seems　highly　probable　that　he　had　done　so；　as　he　was　constantly　experimenting　with　the　sparks；　and　must　almost　certainly　have　set　certain　substances　ablaze　by　accident；　if　not　by　intent。　At　all　events；　he　carried　on　a　series　of　experiments　along　this　line　to　good　purpose；　finally　succeeding　in　exploding　gun…powder；　and　so　making　the　first　forerunner　of　the　electric　fuses　now　so　universally　used　in　blasting；　firing　cannon；　and　other　similar　purposes。　It　was　Bose　also　who；　observing　some　of　the　peculiar　manifestations　in　electrified　tubes；　and　noticing　their　resemblance　to　〃northern　lights；〃　was　one　of　the　first；　if　not　the　first；　to　suggest　that　the　aurora　borealis　is　of　electric　origin。　These　spectacular　demonstrations　had　the　effect　of　calling　public　attention　to　the　fact　that　electricity　is　a　most　wonderful　and　mysterious　thing；　to　say　the　least；　and　kept　both　scientists　and　laymen　agog　with　expectancy。　Bose　himself　was　aflame　with　excitement；　and　so　determined　in　his　efforts　to　produce　still　stronger　electric　currents；　that　he　sacrificed　the　tube　of　his　twenty…foot　telescope　for　the　construction　of　a　mammoth　electrical　machine。　With　this　great　machine　a　discharge　of　electricity　was　generated　powerful　enough　to　wound　the　skin　when　it　happened　to　strike　it。　Until　this　time　electricity　had　been　little　more　than　a　plaything　of　the　scientistsor；　at　least；　no　practical　use　had　been　made　of　it。　As　it　was　a　practising　physician；　Gilbert；　who　first　laid　the　foundation　for　experimenting　with　the　new　substance；　so　again　it　was　a　medical　man　who　first　attempted　to　put　it　to　practical　use；　and　that　in　the　field　of　his　profession。　Gottlieb　Kruger；　a　professor　of　medicine　at　Halle　in　1743；　suggested　that　electricity　might　be　of　use　in　some　branches　of　medicine；　and　the　year　following　Christian　Gottlieb　Kratzenstein　made　a　first　experiment　to　determine　the　effects　of　electricity　upon　the　body。　He　found　that　〃the　action　of　the　heart　was　accelerated；　the　circulation　increased；　and　that　muscles　were　made　to　contract　by　the　discharge〃：　and　he　began　at　once　administering　electricity　in　the　treatment　of　certain　diseases。　He　found　that　it　acted　beneficially　in　rheumatic　affections；　and　that　it　was　particularly　useful　in　certain　nervous　diseases；　such　as　palsies。　This　was　over　a　century　ago；　and　to…day　about　the　most　important　use　made　of　the　particular　kind　of　electricity　with　which　he　experimented　（the　static；　or　frictional）　is　for　the　treatment　of　diseases　affecting　the　nervous　system。　By　the　middle　of　the　century　a　perfect　mania　for　making　electrical　machines　had　spread　over　Europe；　and　the　whirling；　hand…rubbed　globes　were　gradually　replaced　by　great　cylinders　rubbed　by　woollen　cloths　or　pads；　and　generating　an　〃enormous　power　of　electricity。〃　These　cylinders　were　run　by　belts　and　foot…treadles；　and　gave　a　more　powerful；　constant；　and　satisfactory　current　than　known　heretofore。　While　making　experiments　with　one　of　these　machines；　Johann　Heinrichs　Winkler　attempted　to　measure　the　speed　at　which　electricity　travels。　To　do　this　he　extended　a　cord　suspended　on　silk　threads；　with　the　end　attached　to　the　machine　and　the　end　which　was　to　attract　the　bits　of　gold…leaf　near　enough　together　so　that　the　operator　could　watch　and　measure　the　interval　of　time　that　elapsed　between　the　starting　of　the　current　along　the　cord　and　its　attracting　the　gold…leaf。　The　length　of　the　cord　used　in　this　experiment　was　only　a　little　over　a　hundred　feet；　and　this　was；　of　course；　entirely　inadequate；　the　current　travelling　that　space　apparently　instantaneously。　The　improved　method　of　generating　electricity　that　had　come　into　general　use　made　several　of　the　scientists　again　turn　their　attention　more　particularly　to　attempt　putting　it　to　some　practical　account。　They　were　stimulated　to　these　efforts　by　the　constant　reproaches　that　were　beginning　to　be　heard　on　all　sides　that　electricity　was　merely　a　〃philosopher's　plaything。〃　One　of　the　first　to　succeed　in　inventing　something　that　approached　a　practical　mechanical　contrivance　was　Andrew　Gordon；　a　Scotch　Benedictine　monk。　He　invented　an　electric　bell　which　would　ring　automatically；　and　a　little　〃motor；〃　if　it　may　be　so　called。　And　while　neither　of　these　inventions　were　of　any　practical　importance　in　themselves；　they　were　attempts　in　the　right　direction；　and　were　the　first　ancestors　of　modern　electric　bells　and　motors；　although　the　principle　upon　which　they　worked　was　entirely　different　from　modern　electrical　machines。　The　motor　was　simply　a　wheel　with　several　protruding　metal　points　around　its　rim。　These　points　were　arranged　to　receive　an　electrical　discharge　from　a　frictional　machine；　the　discharge　causing　the　wheel　to　rotate。　There　was　very　little　force　given　to　this　rotation；　however；　not　enough；　in　fact；　to　make　it　possible　to　more　than　barely　turn　the　wheel　itself。　Two　more　great　discoveries；　galvanism　and　electro…magnetic　induction；　were　necessary　before　the　practical　motor　became　possible。　The　sober　Gordon　had　a　taste　for　the　spectacular　almost　equal　to　that　of　Bose。　It　was　he　who　ignited　a　bowl　of　alcohol　by　turning　a　stream　of　electrified　water　upon　it；　thus　presenting　the　seeming　paradox　of　fire　produced　by　a　stream　of　water。　Gordon　also　demonstrated　the　power　of　the　electrical　discharge　by　killing　small　birds　and　animals　at　a　distance　of　two　hundred　ells；　the　electricity　being　conveyed　that　distance　through　small　wires。

THE　LEYDEN　JAR　DISCOVERED　As　yet　no　one　had　discovered　that　electricity　could　be　stored；　or　generated　in　any　way　other　than　by　some　friction　device。　But　very　soon　two　experimenters；　Dean　von　Kleist；　of　Camin；　Pomerania；　and　Pieter　van　Musschenbroek；　the　famous　teacher　of　Leyden；　apparently　independently；　made　the　discovery　of　what　has　been　known　ever　since　as　the　Leyden　jar。　And　although　Musschenbroek　is　sometimes　credited　with　being　the　discoverer；　there　can　be　no　doubt　that　Von　Kleist's　discovery　antedated　his　by　a　few　months　at　least。　Von　Kleist　found　that　by　a　device　made　of　a　narrow…necked　bottle　containing　alcohol　or　mercury；　into　which　an　iron　nail　was　inserted；　be　was　able　to　retain　the　charge　of　electricity；　after　electrifying　this　apparatus　with　the　frictional　machine。　He　made　also　a　similar　device；　more　closely　resembling　the　modern　Leyden　jar；　from　a　thermometer　tube　partly　filled　with　water　and　a　wire　tipped　with　a　ball　of　lead。　With　these　devices　he　found　that　he　could　retain　the　charge　of　electricity　for　several　hours；　and　could　produce　the　usual　electrical　manifestations；　even　to　igniting　spirits；　quite　as　well　as　with　the　frictional　machine。　These　experiments　were　first　made　in　October；　1745；　and　after　a　month　of　further　experimenting；　Von　Kleist　sent　the　following　account　of　them　to　several　of　the　leading　scientists；　among　others；　Dr。　Lieberkuhn；　in　Berlin；　and　Dr。　Kruger；　of　Halle。　〃When　a　nail；　or　a　piece　of　thick　brass　wire；　is　put　into　a　small　apothecary's　phial　and　electrified；　remarkable　effects　follow；　but　the　phial　must　be　very　dry；　or　warm。　I　commonly　rub　it　over　beforehand　with　a　finger　on　which　I　put　some　pounded　chalk。　If　a　little　mercury　or　a　few　drops　of　spirit　of　wine　be　put　into　it；　the　experiment　succeeds　better。　As　soon　as　this　phial　and　nail　are　removed　from　the　electrifying…glass；　or　the　prime　conductor；　to　which　it　has　been　exposed；　is　taken　away；　it　throws　out　a　pencil　of　flame　so　long　that；　with　this　burning　machine　in　my　hand；　I　have　taken　above　sixty　steps　in　walking　about　my　room。　When　it　is　electrified　strongly；　I　can　take　it　into　another　room　and　there　fire　spirits　of　wine　with　it。　If　while　it　is　electrifying　I　put　my　finger；　or　a　piece　of　gold　which　I　hold　in　my　hand；　to　the　nail；　I　receive　a　shock　which　stuns　my　arms　and　shoulders。　〃A　tin　tube；　or　a　man；　placed　upon　electrics；　is　electrified　much　stronger　by　this　means　than　in　the　common　way。　When　I　present　this　phial　and　nail　to　a　tin　tube；　which　I　have；　fifteen　feet　long；　nothing　but　experience　can　make　a　person　believe　how　strongly　it　is　electrified。　I　am　persuaded；〃　he　adds；　〃that　in　this　manner　Mr。　Bose　would　not　have　taken　a　second　electrical　kiss。　Two　thin　glasses　have　been　broken　by　the　shock　of　it。　It　appears　to　me　very　extraordinary；　that　when　this　phial　and　nail　are　in　contact　with　either　conducting　or　non…conducting　matter；　the　strong　shock　does　not　follow。　I　have　cemented　it　to　wood；　metal；　glass；　sealing…wax；　etc。；　when　I　have　electrified　without　any　great　effect。　The　human　body；　therefore；　must　contribute　something　to　it。　This　opinion　is　confirmed　by　my　observing　that　unless　I　hold　the　phial　in　my　hand　I　cannot　fire　spirits　of　wine　with　it。〃＇2＇　But　it　seems　that　none　of　the　men　who　saw　this　account　were　able　to　repeat　the　experiment　and　produce　the　effects　claimed　by　Von　Kleist；　and　probably　for　this　reason　the　discovery　of　the　obscure　Pomeranian　was　for　a　time　lost　sight　of。　Musschenbroek's　discovery　was　made　within　a　short　time　after　Von　Kleist'sin　fact；　only　a　matter　of　about　two　months　later。　But　the　difference　in　the　reputations　of　the　two　discoverers　insured　a　very　different　reception　for　their　discoveries。　Musschenbroek　was　one　of　the　foremost　teachers　of　Europe；　and　so　widely　known　that　th