a history of science-2-第38节

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own　poet　and　diplomatist。　Early　in　life　young　Huygens　began　his　career　in　the　legal　profession；　completing　his　education　in　the　juridical　school　at　Breda；　but　his　taste　for　mathematics　soon　led　him　to　neglect　his　legal　studies；　and　his　aptitude　for　scientific　researches　was　so　marked　that　Descartes　predicted　great　things　of　him　even　while　he　was　a　mere　tyro　in　the　field　of　scientific　investigation。　One　of　his　first　endeavors　in　science　was　to　attempt　an　improvement　of　the　telescope。　Reflecting　upon　the　process　of　making　lenses　then　in　vogue；　young　Huygens　and　his　brother　Constantine　attempted　a　new　method　of　grinding　and　polishing；　whereby　they　overcame　a　great　deal　of　the　spherical　and　chromatic　aberration。　With　this　new　telescope　a　much　clearer　field　of　vision　was　obtained；　so　much　so　that　Huygens　was　able　to　detect；　among　other　things；　a　hitherto　unknown　satellite　of　Saturn。　It　was　these　astronomical　researches　that　led　him　to　apply　the　pendulum　to　regulate　the　movements　of　clocks。　The　need　for　some　more　exact　method　of　measuring　time　in　his　observations　of　the　stars　was　keenly　felt　by　the　young　astronomer；　and　after　several　experiments　along　different　lines；　Huygens　hit　upon　the　use　of　a　swinging　weight；　and　in　1656　made　his　invention　of　the　pendulum　clock。　The　year　following；　his　clock　was　presented　to　the　states…general。　Accuracy　as　to　time　is　absolutely　essential　in　astronomy；　but　until　the　invention　of　Huygens's　clock　there　was　no　precise；　nor　even　approximately　precise；　means　of　measuring　short　intervals。　Huygens　was　one　of　the　first　to　adapt　the　micrometer　to　the　telescopea　mechanical　device　on　which　all　the　nice　determination　of　minute　distances　depends。　He　also　took　up　the　controversy　against　Hooke　as　to　the　superiority　of　telescopic　over　plain　sights　to　quadrants；　Hooke　contending　in　favor　of　the　plain。　In　this　controversy；　the　subject　of　which　attracted　wide　attention；　Huygens　was　completely　victorious；　and　Hooke；　being　unable　to　refute　Huygens's　arguments；　exhibited　such　irritability　that　he　increased　his　already　general　unpopularity。　All　of　the　arguments　for　and　against　the　telescope　sight　are　too　numerous　to　be　given　here。　In　contending　in　its　favor　Huygens　pointed　out　that　the　unaided　eye　is　unable　to　appreciate　an　angular　space　in　the　sky　less　than　about　thirty　seconds。　Even　in　the　best　quadrant　with　a　plain　sight；　therefore；　the　altitude　must　be　uncertain　by　that　quantity。　If　in　place　of　the　plain　sight　a　telescope　is　substituted；　even　if　it　magnify　only　thirty　times；　it　will　enable　the　observer　to　fix　the　position　to　one　second；　with　progressively　increased　accuracy　as　the　magnifying　power　of　the　telescope　is　increased。　This　was　only　one　of　the　many　telling　arguments　advanced　by　Huygens。　In　the　field　of　optics；　also；　Huygens　has　added　considerably　to　science；　and　his　work；　Dioptrics；　is　said　to　have　been　a　favorite　book　with　Newton。　During　the　later　part　of　his　life；　however；　Huygens　again　devoted　himself　to　inventing　and　constructing　telescopes；　grinding　the　lenses；　and　devising；　if　not　actually　making；　the　frame　for　holding　them。　These　telescopes　were　of　enormous　lengths；　three　of　his　object…glasses；　now　in　possession　of　the　Royal　Society；　being　of　123；　180；　and　210　feet　focal　length　respectively。　Such　instruments；　if　constructed　in　the　ordinary　form　of　the　long　tube；　were　very　unmanageable；　and　to　obviate　this　Huygens　adopted　the　plan　of　dispensing　with　the　tube　altogether；　mounting　his　lenses　on　long　poles　manipulated　by　machinery。　Even　these　were　unwieldy　enough；　but　the　difficulties　of　manipulation　were　fully　compensated　by　the　results　obtained。　It　had　been　discovered；　among　other　things；　that　in　oblique　refraction　light　is　separated　into　colors。　Therefore；　any　small　portion　of　the　convex　lens　of　the　telescope；　being　a　prism；　the　rays　proceed　to　the　focus；　separated　into　prismatic　colors；　which　make　the　image　thus　formed　edged　with　a　fringe　of　color　and　indistinct。　But；　fortunately　for　the　early　telescope　makers；　the　degree　of　this　aberration　is　independent　of　the　focal　length　of　the　lens；　so　that；　by　increasing　this　focal　length　and　using　the　appropriate　eye…piece；　the　image　can　be　greatly　magnified；　while　the　fringe　of　colors　remains　about　the　same　as　when　a　less　powerful　lens　is　used。　Hence　the　advantage　of　Huygens's　long　telescope。　He　did　not　confine　his　efforts　to　simply　lengthening　the　focal　length　of　his　telescopes；　however；　but　also　added　to　their　efficiency　by　inventing　an　almost　perfect　achromatic　eye…piece。　In　1663　he　was　elected　a　fellow　of　the　Royal　Society　of　London；　and　in　1669　he　gave　to　that　body　a　concise　statement　of　the　laws　governing　the　collision　of　elastic　bodies。　Although　the　same　views　had　been　given　by　Wallis　and　Wren　a　few　weeks　earlier；　there　is　no　doubt　that　Huygens's　views　were　reached　independently；　and　it　is　probable　that　he　had　arrived　at　his　conclusions　several　years　before。　In　the　Philosophical　Transactions　for　1669　it　is　recorded　that　the　society；　being　interested　in　the　laws　of　the　principles　of　motion；　a　request　was　made　that　M。　Huygens；　Dr。　Wallis；　and　Sir　Christopher　Wren　submit　their　views　on　the　subject。　Wallis　submitted　his　paper　first；　November　15；　1668。　A　month　later；　December　17th；　Wren　imparted　to　the　society　his　laws　as　to　the　nature　of　the　collision　of　bodies。　And　a　few　days　later；　January　5；　1669；　Huygens　sent　in　his　〃Rules　Concerning　the　Motion　of　Bodies　after　Mutual　Impulse。〃　Although　Huygens's　report　was　received　last；　he　was　anticipated　by　such　a　brief　space　of　time；　and　his　views　are　so　clearly　statedon　the　whole　rather　more　so　than　those　of　the　other　twothat　we　give　them　in　part　here：

〃1。　If　a　hard　body　should　strike　against　a　body　equally　hard　at　rest；　after　contact　the　former　will　rest　and　the　latter　acquire　a　velocity　equal　to　that　of　the　moving　body。　〃2。　But　if　that　other　equal　body　be　likewise　in　motion；　and　moving　in　the　same　direction；　after　contact　they　will　move　with　reciprocal　velocities。　〃3。　A　body；　however　great；　is　moved　by　a　body　however　small　impelled　with　any　velocity　whatsoever。　〃5。　The　quantity　of　motion　of　two　bodies　may　be　either　increased　or　diminished　by　their　shock；　but　the　same　quantity　towards　the　same　part　remains；　after　subtracting　the　quantity　of　the　contrary　motion。　〃6。　The　sum　of　the　products　arising　from　multiplying　the　mass　of　any　hard　body　into　the　squares　of　its　velocity　is　the　same　both　before　and　after　the　stroke。　〃7。　A　hard　body　at　rest　will　receive　a　greater　quantity　of　motion　from　another　hard　body；　either　greater　or　less　than　itself；　by　the　interposition　of　any　third　body　of　a　mean　quantity；　than　if　it　was　immediately　struck　by　the　body　itself；　and　if　the　interposing　body　be　a　mean　proportional　between　the　other　two；　its　action　upon　the　quiescent　body　will　be　the　greatest　of　all。〃＇10＇

This　was　only　one　of　several　interesting　and　important　communications　sent　to　the　Royal　Society　during　his　lifetime。　One　of　these　was　a　report　on　what　he　calls　〃Pneumatical　Experiments。〃　〃Upon　including　in　a　vacuum　an　insect　resembling　a　beetle；　but　somewhat　larger；〃　he　says；　〃when　it　seemed　to　be　dead；　the　air　was　readmitted；　and　soon　after　it　revived；　putting　it　again　in　the　vacuum；　and　leaving　it　for　an　hour；　after　which　the　air　was　readmitted；　it　was　observed　that　the　insect　required　a　longer　time　to　recover；　including　it　the　third　time　for　two　days；　after　which　the　air　was　admitted；　it　was　ten　hours　before　it　began　to　stir；　but；　putting　it　in　a　fourth　time；　for　eight　days；　it　never　afterwards　recovered。。。。　Several　birds；　rats；　mice；　rabbits；　and　cats　were　killed　in　a　vacuum；　but　if　the　air　was　admitted　before　the　engine　was　quite　exhausted　some　of　them　would　recover；　yet　none　revived　that　had　been　in　a　perfect　vacuum。。。。　Upon　putting　the　weight　of　eighteen　grains　of　powder　with　a　gauge　into　a　receiver　that　held　several　pounds　of　water；　and　firing　the　powder；　it　raised　the　mercury　an　inch　and　a　half；　from　which　it　appears　that　there　is　one…fifth　of　air　in　gunpowder；　upon　the　supposition　that　air　is　about　one　thousand　times　lighter　than　water；　for　in　this　experiment　the　mercury　rose　to　the　eighteenth　part　of　the　height　at　which　the　air　commonly　sustains　it；　and　consequently　the　weight　of　eighteen　grains　of　powder　yielded　air　enough　to　fill　the　eighteenth　part　of　a　receiver　that　contained　seven　pounds　of　water；　now　this　eighteenth　part　contains　forty…nine　drachms　of　water；　wherefore　the　air；　that　takes　up　an　equal　space；　being　a　thousand　times　lighter；　weighs　one…thousandth　part　of　forty…nine　drachms；　which　is　more　than　three　grains　and　a　half；　it　follows；　therefore；　that　the　weight　of　eighteen　grains　of　powder　contains　more　than　three　and　a　half　of　air；　which　is　about　one…fifth　of　eighteen　grains。。。。〃　From　1665　to　1681；　accepting　the　tempting　offer　made　him　through　Colbert；　by　Louis　XIV。；　Huygens　pursued　his　studies　at　the　Bibliotheque　du　Roi　as　a　resident　of　France。　Here　he　published　his　Horologium　Oscillatorium；　dedicated　to　the　king；　containing；　among　other　things；　his　solution　of　the　problem　of　the　〃centre　of　oscillation。〃　This　in　itself　was　an　important　step　in　the　history　of　mechanics。　Assuming　as　true　that　the　centre　of　gravity　of　any　number　of　interdependent　bodies　cannot　rise　higher　than　the　point　from　which　it　falls；　h