a history of science-2-第33部分

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！


　after　I　had　left　off　rubbing　it。〃＇8＇

MARIOTTE　AND　VON　GUERICKE　Working　contemporaneously　with　Boyle；　and　a　man　whose　name　is　usually　associated　with　his　as　the　propounder　of　the　law　of　density　of　gases；　was　Edme　Mariotte　（died　1684）；　a　native　of　Burgundy。　Mariotte　demonstrated　that　but　for　the　resistance　of　the　atmosphere；　all　bodies；　whether　light　or　heavy；　dense　or　thin；　would　fall　with　equal　rapidity；　and　he　proved　this　by　the　well…known　〃guinea…and…feather〃　experiment。　Having　exhausted　the　air　from　a　long　glass　tube　in　which　a　guinea　piece　and　a　feather　had　been　placed；　he　showed　that　in　the　vacuum　thus　formed　they　fell　with　equal　rapidity　as　often　as　the　tube　was　reversed。　From　his　various　experiments　as　to　the　pressure　of　the　atmosphere　he　deduced　the　law　that　the　density　and　elasticity　of　the　atmosphere　are　precisely　proportional　to　the　compressing　force　（the　law　of　Boyle　and　Mariotte）。　He　also　ascertained　that　air　existed　in　a　state　of　mechanical　mixture　with　liquids；　〃existing　between　their　particles　in　a　state　of　condensation。〃　He　made　many　other　experiments；　especially　on　the　collision　of　bodies；　but　his　most　important　work　was　upon　the　atmosphere。　But　meanwhile　another　contemporary　of　Boyle　and　Mariotte　was　interesting　himself　in　the　study　of　the　atmosphere；　and　had　made　a　wonderful　invention　and　a　most　striking　demonstration。　This　was　Otto　von　Guericke　（1602…1686）；　Burgomaster　of　Magdeburg；　and　councillor　to　his　〃most　serene　and　potent　Highness〃　the　elector　of　that　place。　When　not　engrossed　with　the　duties　of　public　office；　he　devoted　his　time　to　the　study　of　the　sciences；　particularly　pneumatics　and　electricity；　both　then　in　their　infancy。　The　discoveries　of　Galileo；　Pascal；　and　Torricelli　incited　him　to　solve　the　problem　of　the　creation　of　a　vacuuma　desideratum　since　before　the　days　of　Aristotle。　His　first　experiments　were　with　a　wooden　pump　and　a　barrel　of　water；　but　he　soon　found　that　with　such　porous　material　as　wood　a　vacuum　could　not　be　created　or　maintained。　He　therefore　made　use　of　a　globe　of　copper；　with　pump　and　stop…cock；　and　with　this　he　was　able　to　pump　out　air　almost　as　easily　as　water。　Thus；　in　1650；　the　air…pump　was　invented。　Continuing　his　experiments　upon　vacuums　and　atmospheric　pressure　with　his　newly　discovered　pump；　he　made　some　startling　discoveries　as　to　the　enormous　pressure　exerted　by　the　air。　It　was　not　his　intention；　however；　to　demonstrate　his　newly　acquired　knowledge　by　words　or　theories　alone；　nor　by　mere　laboratory　experiments；　but　he　chose　instead　an　open　field；　to　which　were　invited　Emperor　Ferdinand　III。；　and　all　the　princes　of　the　Diet　at　Ratisbon。　When　they　were　assembled　he　produced　two　hollow　brass　hemispheres　about　two　feet　in　diameter；　and　placing　their　exactly　fitting　surfaces　together；　proceeded　to　pump　out　the　air　from　their　hollow　interior；　thus　causing　them　to　stick　together　firmly　in　a　most　remarkable　way；　apparently　without　anything　holding　them。　This　of　itself　was　strange　enough；　but　now　the　worthy　burgomaster　produced　teams　of　horses；　and　harnessing　them　to　either　side　of　the　hemispheres；　attempted　to　pull　the　adhering　brasses　apart。　Five；　ten；　fifteen　teamsthirty　horses；　in　allwere　attached；　but　pull　and　tug　as　they　would　they　could　not　separate　the　firmly　clasped　hemispheres。　The　enormous　pressure　of　the　atmosphere　had　been　most　strikingly　demonstrated。　But　it　is　one　thing　to　demonstrate；　another　to　convince；　and　many　of　the　good　people　of　Magdeburg　shook　their　heads　over　this　〃devil's　contrivance；〃　and　predicted　that　Heaven　would　punish　the　Herr　Burgomaster；　as　indeed　it　had　once　by　striking　his　house　with　lightning　and　injuring　some　of　his　infernal　contrivances。　They　predicted　his　future　punishment；　but　they　did　not　molest　him；　for　to　his　fellow…citizens；　who　talked　and　laughed；　drank　and　smoked　with　him；　and　knew　him　for　the　honest　citizen　that　he　was；　he　did　not　seem　bewitched　at　all。　And　so　he　lived　and　worked　and　added　other　facts　to　science；　and　his　brass　hemispheres　were　not　destroyed　by　fanatical　Inquisitors；　but　are　still　preserved　in　the　royal　library　at　Berlin。　In　his　experiments　with　his　air…pump　he　discovered　many　things　regarding　the　action　of　gases；　among　others；　that　animals　cannot　live　in　a　vacuum。　He　invented　the　anemoscope　and　the　air…balance；　and　being　thus　enabled　to　weight　the　air　and　note　the　changes　that　preceded　storms　and　calms；　he　was　able　still　further　to　dumfound　his　wondering　fellow…Magde…burgers　by　more　or　less　accurate　predictions　about　the　weather。　Von　Guericke　did　not　accept　Gilbert's　theory　that　the　earth　was　a　great　magnet；　but　in　his　experiments　along　lines　similar　to　those　pursued　by　Gilbert；　he　not　only　invented　the　first　electrical　machine；　but　discovered　electrical　attraction　and　repulsion。　The　electrical　machine　which　he　invented　consisted　of　a　sphere　of　sulphur　mounted　on　an　iron　axis　to　imitate　the　rotation　of　the　earth；　and　which；　when　rubbed；　manifested　electrical　reactions。　When　this　globe　was　revolved　and　stroked　with　the　dry　hand　it　was　found　that　it　attached　to　it　〃all　sorts　of　little　fragments；　like　leaves　of　gold；　silver；　paper；　etc。〃　〃Thus　this　globe；〃　he　says；　〃when　brought　rather　near　drops　of　water　causes　them　to　swell　and　puff　up。　It　likewise　attracts　air；　smoke；　etc。〃＇9＇　Before　the　time　of　Guericke's　demonstrations；　Cabaeus　had　noted　that　chaff　leaped　back　from　an　〃electric；〃　but　he　did　not　interpret　the　phenomenon　as　electrical　repulsion。　Von　Guericke；　however；　recognized　it　as　such；　and　refers　to　it　as　what　he　calls　〃expulsive　virtue。〃　〃Even　expulsive　virtue　is　seen　in　this　globe；〃　he　says；　〃for　it　not　only　attracts；　but　also　REPELS　again　from　itself　little　bodies　of　this　sort；　nor　does　it　receive　them　until　they　have　touched　something　else。〃　It　will　be　observed　from　this　that　he　was　very　close　to　discovering　the　discharge　of　the　electrification　of　attracted　bodies　by　contact　with　some　other　object；　after　which　they　are　reattracted　by　the　electric。　He　performed　a　most　interesting　experiment　with　his　sulphur　globe　and　a　feather；　and　in　doing　so　came　near　anticipating　Benjamin　Franklin　in　his　discovery　of　the　effects　of　pointed　conductors　in　drawing　off　the　discharge。　Having　revolved　and　stroked　his　globe　until　it　repelled　a　bit　of　down；　he　removed　the　globe　from　its　rack　and　advancing　it　towards　the　now　repellent　down；　drove　it　before　him　about　the　room。　In　this　chase　he　observed　that　the　down　preferred　to　alight　against　〃the　points　of　any　object　whatsoever。〃　He　noticed　that　should　the　down　chance　to　be　driven　within　a　few　inches　of　a　lighted　candle；　its　attitude　towards　the　globe　suddenly　changed；　and　instead　of　running　away　from　it；　it　now　〃flew　to　it　for　protection〃　the　charge　on　the　down　having　been　dissipated　by　the　hot　air。　He　also　noted　that　if　one　face　of　a　feather　had　been　first　attracted　and　then　repelled　by　the　sulphur　ball；　that　the　surface　so　affected　was　always　turned　towards　the　globe；　so　that　if　the　positions　of　the　two　were　reversed；　the　sides　of　the　feather　reversed　also。　Still　another　important　discovery；　that　of　electrical　conduction；　was　made　by　Von　Guericke。　Until　his　discovery　no　one　had　observed　the　transference　of　electricity　from　one　body　to　another；　although　Gilbert　had　some　time　before　noted　that　a　rod　rendered　magnetic　at　one　end　became　so　at　the　other。　Von　Guericke's　experiments　were　made　upon　a　linen　thread　with　his　sulphur　globe；　which；　he　says；　〃having　been　previously　excited　by　rubbing；　can　exercise　likewise　its　virtue　through　a　linen　thread　an　ell　or　more　long；　and　there　attract　something。〃　But　this　discovery；　and　his　equally　important　one　that　the　sulphur　ball　becomes　luminous　when　rubbed；　were　practically　forgotten　until　again　brought　to　notice　by　the　discoveries　of　Francis　Hauksbee　and　Stephen　Gray　early　in　the　eighteenth　century。　From　this　we　may　gather　that　Von　Guericke　himself　did　not　realize　the　import　of　his　discoveries；　for　otherwise　he　would　certainly　have　carried　his　investigations　still　further。　But　as　it　was　he　turned　his　attention　to　other　fields　of　research。

ROBERT　HOOKE　A　slender；　crooked；　shrivelled…limbed；　cantankerous　little　man；　with　dishevelled　hair　and　haggard　countenance；　bad…tempered　and　irritable；　penurious　and　dishonest；　at　least　in　his　claims　for　priority　in　discoveriesthis　is　the　picture　usually　drawn；　alike　by　friends　and　enemies；　of　Robert　Hooke　（1635…1703）；　a　man　with　an　almost　unparalleled　genius　for　scientific　discoveries　in　almost　all　branches　of　science。　History　gives　few　examples　so　striking　of　a　man　whose　really　great　achievements　in　science　would　alone　have　made　his　name　immortal；　and　yet　who　had　the　pusillanimous　spirit　of　a　charlatanan　almost　insane　mania；　as　it　seemsfor　claiming　the　credit　of　discoveries　made　by　others。　This　attitude　of　mind　can　hardly　be　explained　except　as　a　mania：　it　is　certainly　more　charitable　so　to　regard　it。　For　his　own　discoveries　and　inventions　were　so　numerous　that　a　few　more　or　less　would　hardly　have　added　to　his　fame；　as　his　reputation　as　a　philosopher　was　well　established。　Admiration　for　his　ability　and　his　philosophical　knowledge　must　always　be　marred　by　the　recollection　of　his　arrogant　claims　to　the　discoveries　of　other　philosophers。　It　seems　pretty　definitely　determined　that　Hooke　should　be　credited　with　the　invention　of　the　balance…spring　for　regulating　watches；　but　for　a　long　time　a　heated　controversy　was　waged　between　Hooke　and　Huygens　as　to　who　was　the　real　inventor。　It　appears　that　Hooke　conceived　the　idea　of　the　balance…spring；　while　to　Huygens　belongs　the　credit　of　having　adapted　the　COILED　spring　in　a　working　model。　He　thus　made　practical　Hooke's　conception；　which　is　without　value　except　as　applied　by　the　coiled　spring；　but；　nevertheless；　the　inventor；　as　well　as　the　perfector；　should　receive　credit。　In　this　controversy；　unlike　many　others；　the　blame　cannot　be　laid　at　Hooke's　door。　Hooke　was　the　first　curator　of　the　Royal　Society；　and　when　anything　was　to　be　investigated；　usually　invented　the　mechanical　devices　for　doing　so。　Astronomical　apparatus；　instruments　for　measuring　specific　weights；　clocks　and　chronometers；　methods　of　measuring　the　velocity　of　falling　bodies；　freezing　and　boiling　points；　strength　of　gunpowder；　magnetic　instrumentsin　short；　all　kinds　of　ingenious　mechanical　devices　in　all　b