a history of science-2-第36章

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〃venomous　exhalations〃　that　produced　diseases。　He　suggested　also　that　the　air　might　play　an　important　part　in　some　processes　of　calcination；　which；　as　we　shall　see；　was　proved　to　be　true　by　Lavoisier　late　in　the　eighteenth　century。　Boyle's　notions　of　the　exact　chemical　action　in　these　phenomena　were　of　course　vague　and　indefinite；　but　he　had　observed　that　some　part　was　played　by　the　air；　and　he　was　right　in　supposing　that　the　air　〃may　have　a　great　share　in　varying　the　salts　obtainable　from　calcined　vitriol。〃＇5＇　Although　he　was　himself　such　a　painstaking　observer　of　facts；　he　had　the　fault　of　his　age　of　placing　too　much　faith　in　hear…say　evidence　of　untrained　observers。　Thus；　from　the　numerous　stories　he　heard　concerning　the　growth　of　metals　in　previously　exhausted　mines；　he　believed　that　the　air　was　responsible　for　producing　this　growthin　which　he　undoubtedly　believed。　The　story　of　a　tin…miner　that；　in　his　own　time；　after　a　lapse　of　only　twenty…five　years；　a　heap；　of　earth　previously　exhausted　of　its　ore　became　again　even　more　richly　impregnated　than　before　by　lying　exposed　to　the　air；　seems　to　have　been　believed　by　the　philosopher。　As　Boyle　was　an　alchemist；　and　undoubtedly　believed　in　the　alchemic　theory　that　metals　have　〃spirits〃　and　various　other　qualities　that　do　not　exist；　it　is　not　surprising　that　he　was　credulous　in　the　matter　of　beliefs　concerning　peculiar　phenomena　exhibited　by　them。　Furthermore；　he　undoubtedly　fell　into　the　error　common　to　〃specialists；〃　or　persons　working　for　long　periods　of　time　on　one　subjectthe　error　of　over…enthusiasm　in　his　subject。　He　had　discovered　so　many　remarkable　qualities　in　the　air　that　it　is　not　surprising　to　find　that　he　attributed　to　it　many　more　that　he　could　not　demonstrate。　Boyle's　work　upon　colors；　although　probably　of　less　importance　than　his　experiments　and　deductions　upon　air；　show　that　he　was　in　the　van　as　far　as　the　science　of　his　day　was　concerned。　As　he　points　out；　the　schools　of　his　time　generally　taught　that　〃color　is　a　penetrating　quality；　reaching　to　the　innermost　part　of　the　substance；〃　and；　as　an　example　of　this；　sealing…wax　was　cited；　which　could　be　broken　into　minute　bits；　each　particle　retaining　the　same　color　as　its　fellows　or　the　original　mass。　To　refute　this　theory；　and　to　show　instances　to　the　contrary；　Boyle；　among　other　things；　shows　that　various　colorsblue；　red；　yellowmay　be　produced　upon　tempered　steel；　and　yet　the　metal　within　〃a　hair's…breadth　of　its　surface〃　have　none　of　these　colors。　Therefore；　he　was　led　to　believe　that　color；　in　opaque　bodies　at　least；　is　superficial。　〃But　before　we　descend　to　a　more　particular　consideration　of　our　subject；〃　he　says；　〃　'tis　proper　to　observe　that　colors　may　be　regarded　either　as　a　quality　residing　in　bodies　to　modify　light　after　a　particular　manner；　or　else　as　light　itself　so　modified　as　to　strike　upon　the　organs　of　sight；　and　cause　the　sensation　we　call　color；　and　that　this　latter　is　the　more　proper　acceptation　of　the　word　color　will　appear　hereafter。　And　indeed　it　is　the　light　itself；　which　after　a　certain　manner；　either　mixed　with　shades　or　other…wise；　strikes　our　eyes　and　immediately　produces　that　motion　in　the　organ　which　gives　us　the　color　of　an　object。〃＇6＇　In　examining　smooth　and　rough　surfaces　to　determine　the　cause　of　their　color；　he　made　use　of　the　microscope；　and　pointed　out　the　very　obvious　example　of　the　difference　in　color　of　a　rough　and　a　polished　piece　of　the　same　block　of　stone。　He　used　some　striking　illustrations　of　the　effect　of　light　and　the　position　of　the　eye　upon　colors。　〃Thus　the　color　of　plush　or　velvet　will　appear　various　if　you　stroke　part　of　it　one　way　and　part　another；　the　posture　of　the　particular　threads　in　regard　to　the　light；　or　the　eye；　being　thereby　varied。　And　'tis　observable　that　in　a　field　of　ripe　corn；　blown　upon　by　the　wind；　there　will　appear　waves　of　a　color　different　from　that　of　the　rest　of　the　corn；　because　the　wind；　by　depressing　some　of　the　ears　more　than　others；　causes　one　to　reflect　more　light　from　the　lateral　and　strawy　parts　than　another。〃＇7＇　His　work　upon　color；　however；　as　upon　light；　was　entirely　overshadowed　by　the　work　of　his　great　fellow…countryman　Newton。　Boyle's　work　on　electricity　was　a　continuation　of　Gilbert's；　to　which　he　added　several　new　facts。　He　added　several　substances　to　Gilbert's　list　of　〃electrics；〃　experimented　on　smooth　and　rough　surfaces　in　exciting　of　electricity；　and　made　the　important　discovery　that　amber　retained　its　attractive　virtue　after　the　friction　that　excited　it　bad　ceased。　〃For　the　attrition　having　caused　an　intestine　motion　in　its　parts；〃　he　says；　〃the　heat　thereby　excited　ought　not　to　cease　as　soon　as　ever　the　rubbing　is　over；　but　to　continue　capable　of　emitting　effluvia　for　some　time　afterwards；　longer　or　shorter　according　to　the　goodness　of　the　electric　and　the　degree　of　the　commotion　made；　all　which；　joined　together；　may　sometimes　make　the　effect　considerable；　and　by　this　means；　on　a　warm　day；　I；　with　a　certain　body　not　bigger　than　a　pea；　but　very　vigorously　attractive；　moved　a　steel　needle；　freely　poised；　about　three　minutes　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　ac