a history of science-2-第62章

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ething　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　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　gener