a history of science-1-第35章

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！


ity　or　completed　his　studies；　he　returned　to　Syracuse　and　spent　his　life　there；　chiefly　under　the　patronage　of　King　Hiero；　who　seems　fully　to　have　appreciated　his　abilities。　Archimedes　was　primarily　a　mathematician。　Left　to　his　own　devices；　he　would　probably　have　devoted　his　entire　time　to　the　study　of　geometrical　problems。　But　King　Hiero　had　discovered　that　his　protege　had　wonderful　mechanical　ingenuity；　and　he　made　good　use　of　this　discovery。　Under　stress　of　the　king's　urgings；　the　philosopher　was　led　to　invent　a　great　variety　of　mechanical　contrivances；　some　of　them　most　curious　ones。　Antiquity　credited　him　with　the　invention　of　more　than　forty　machines；　and　it　is　these；　rather　than　his　purely　mathematical　discoveries；　that　gave　his　name　popular　vogue　both　among　his　contemporaries　and　with　posterity。　Every　one　has　heard　of　the　screw　of　Archimedes；　through　which　the　paradoxical　effect　was　produced　of　making　water　seem　to　flow　up　hill。　The　best　idea　of　this　curious　mechanism　is　obtained　if　one　will　take　in　hand　an　ordinary　corkscrew；　and　imagine　this　instrument　to　be　changed　into　a　hollow　tube；　retaining　precisely　the　same　shape　but　increased　to　some　feet　in　length　and　to　a　proportionate　diameter。　If　one　will　hold　the　corkscrew　in　a　slanting　direction　and　turn　it　slowly　to　the　right；　supposing　that　the　point　dips　up　a　portion　of　water　each　time　it　revolves；　one　can　in　imagination　follow　the　flow　of　that　portion　of　water　from　spiral　to　spiral；　the　water　always　running　downward；　of　course；　yet　paradoxically　being　lifted　higher　and　higher　towards　the　base　of　the　corkscrew；　until　finally　it　pours　out　（in　the　actual　Archimedes'　tube）　at　the　top。　There　is　another　form　of　the　screw　in　which　a　revolving　spiral　blade　operates　within　a　cylinder；　but　the　principle　is　precisely　the　same。　With　either　form　water　may　be　lifted；　by　the　mere　turning　of　the　screw；　to　any　desired　height。　The　ingenious　mechanism　excited　the　wonder　of　the　contemporaries　of　Archimedes；　as　well　it　might。　More　efficient　devices　have　superseded　it　in　modern　times；　but　it　still　excites　the　admiration　of　all　who　examine　it；　and　its　effects　seem　as　paradoxical　as　ever。　Some　other　of　the　mechanisms　of　Archimedes　have　been　made　known　to　successive　generations　of　readers　through　the　pages　of　Polybius　and　Plutarch。　These　are　the　devices　through　which　Archimedes　aided　King　Hiero　to　ward　off　the　attacks　of　the　Roman　general　Marcellus；　who　in　the　course　of　the　second　Punic　war　laid　siege　to　Syracuse。　Plutarch；　in　his　life　of　Marcellus；　describes　the　Roman's　attack　and　Archimedes'　defence　in　much　detail。　Incidentally　he　tells　us　also　how　Archimedes　came　to　make　the　devices　that　rendered　the　siege　so　famous：　〃Marcellus　himself；　with　threescore　galleys　of　five　rowers　at　every　bank；　well　armed　and　full　of　all　sorts　of　artillery　and　fireworks；　did　assault　by　sea；　and　rowed　hard　to　the　wall；　having　made　a　great　engine　and　device　of　battery；　upon　eight　galleys　chained　together；　to　batter　the　wall：　trusting　in　the　great　multitude　of　his　engines　of　battery；　and　to　all　such　other　necessary　provision　as　he　had　for　wars；　as　also　in　his　own　reputation。　But　Archimedes　made　light　account　of　all　his　devices；　as　indeed　they　were　nothing　comparable　to　the　engines　himself　had　invented。　This　inventive　art　to　frame　instruments　and　engines　（which　are　called　mechanical；　or　organical；　so　highly　commended　and　esteemed　of　all　sorts　of　people）　was　first　set　forth　by　Architas；　and　by　Eudoxus：　partly　to　beautify　a　little　the　science　of　geometry　by　this　fineness；　and　partly　to　prove　and　confirm　by　material　examples　and　sensible　instruments；　certain　geometrical　conclusions；　where　of　a　man　cannot　find　out　the　conceivable　demonstrations　by　enforced　reasons　and　proofs。　As　that　conclusion　which　instructeth　one　to　search　out　two　lines　mean　proportional；　which　cannot　be　proved　by　reason　demonstrative；　and　yet　notwithstanding　is　a　principle　and　an　accepted　ground　for　many　things　which　are　contained　in　the　art　of　portraiture。　Both　of　them　have　fashioned　it　to　the　workmanship　of　certain　instruments；　called　mesolabes　or　mesographs；　which　serve　to　find　these　mean　lines　proportional；　by　drawing　certain　curve　lines；　and　overthwart　and　oblique　sections。　But　after　that　Plato　was　offended　with　them；　and　maintained　against　them；　that　they　did　utterly　corrupt　and　disgrace；　the　worthiness　and　excellence　of　geometry；　making　it　to　descend　from　things　not　comprehensible　and　without　body；　unto　things　sensible　and　material；　and　to　bring　it　to　a　palpable　substance；　where　the　vile　and　base　handiwork　of　man　is　to　be　employed：　since　that　time；　I　say；　handicraft；　or　the　art　of　engines；　came　to　be　separated　from　geometry；　and　being　long　time　despised　by　the　philosophers；　it　came　to　be　one　of　the　warlike　arts。　〃But　Archimedes　having　told　King　Hiero；　his　kinsman　and　friend；　that　it　was　possible　to　remove　as　great　a　weight　as　he　would；　with　as　little　strength　as　he　listed　to　put　to　it：　and　boasting　himself　thus　（as　they　report　of　him）　and　trusting　to　the　force　of　his　reasons；　wherewith　he　proved　this　conclusion；　that　if　there　were　another　globe　of　earth；　he　was　able　to　remove　this　of　ours；　and　pass　it　over　to　the　other：　King　Hiero　wondering　to　hear　him；　required　him　to　put　his　device　in　execution；　and　to　make　him　see　by　experience；　some　great　or　heavy　weight　removed；　by　little　force。　So　Archimedes　caught　hold　with　a　book　of　one　of　the　greatest　carects；　or　hulks　of　the　king　（that　to　draw　it　to　the　shore　out　of　the　water　required　a　marvellous　number　of　people　to　go　about　it；　and　was　hardly　to　be　done　so）　and　put　a　great　number　of　men　more　into　her；　than　her　ordinary　burden：　and　he　himself　sitting　alone　at　his　ease　far　off；　without　any　straining　at　all；　drawing　the　end　of　an　engine　with　many　wheels　and　pulleys；　fair　and　softly　with　his　hand；　made　it　come　as　gently　and　smoothly　to　him；　as　it　had　floated　in　the　sea。　The　king　wondering　to　see　the　sight；　and　knowing　by　proof　the　greatness　of　his　art；　be　prayed　him　to　make　him　some　engines；　both　to　assault　and　defend；　in　all　manner　of　sieges　and　assaults。　So　Archimedes　made　him　many　engines；　but　King　Hiero　never　occupied　any　of　them；　because　he　reigned　the　most　part　of　his　time　in　peace　without　any　wars。　But　this　provision　and　munition　of　engines；　served　the　Syracusan's　turn　marvellously　at　that　time：　and　not　only　the　provision　of　the　engines　ready　made；　but　also　the　engineer　and　work…master　himself；　that　had　invented　them。　〃Now　the　Syracusans；　seeing　themselves　assaulted　by　the　Romans；　both　by　sea　and　by　land；　were　marvellously　perplexed；　and　could　not　tell　what　to　say；　they　were　so　afraid：　imagining　it　was　impossible　for　them　to　withstand　so　great　an　army。　But　when　Archimedes　fell　to　handling　his　engines；　and　to　set　them　at　liberty；　there　flew　in　the　air　infinite　kinds　of　shot；　and　marvellous　great　stones；　with　an　incredible　noise　and　force　on　the　sudden；　upon　the　footmen　that　came　to　assault　the　city　by　land；　bearing　down；　and　tearing　in　pieces　all　those　which　came　against　them；　or　in　what　place　soever　they　lighted；　no　earthly　body　being　able　to　resist　the　violence　of　so　heavy　a　weight：　so　that　all　their　ranks　were　marvellously　disordered。　And　as　for　the　galleys　that　gave　assault　by　sea；　some　were　sunk　with　long　pieces　of　timber　like　unto　the　yards　of　ships；　whereto　they　fasten　their　sails；　which　were　suddenly　blown　over　the　walls　with　force　of　their　engines　into　their　galleys；　and　so　sunk　them　by　their　over　great　weight。〃

Polybius　describes　what　was　perhaps　the　most　important　of　these　contrivances；　which　was；　he　tells　us；　〃a　band　of　iron；　hanging　by　a　chain　from　the　beak　of　a　machine；　which　was　used　in　the　following　manner。　The　person　who；　like　a　pilot；　guided　the　beak；　having　let　fall　the　hand；　and　catched　hold　of　the　prow　of　any　vessel；　drew　down　the　opposite　end　of　the　machine　that　was　on　the　inside　of　the　walls。　And　when　the　vessel　was　thus　raised　erect　upon　its　stem；　the　machine　itself　was　held　immovable；　but；　the　chain　being　suddenly　loosened　from　the　beak　by　the　means　of　pulleys；　some　of　the　vessels　were　thrown　upon　their　sides；　others　turned　with　the　bottom　upwards；　and　the　greatest　part；　as　the　prows　were　plunged　from　a　considerable　height　into　the　sea；　were　filled　with　water；　and　all　that　were　on　board　thrown　into　tumult　and　disorder。　〃Marcellus　was　in　no　small　degree　embarrassed；〃　Polybius　continues；　〃when　he　found　himself　encountered　in　every　attempt　by　such　resistance。　He　perceived　that　all　his　efforts　were　defeated　with　loss；　and　were　even　derided　by　the　enemy。　But；　amidst　all　the　anxiety　that　he　suffered；　he　could　not　help　jesting　upon　the　inventions　of　Archimedes。　This　man；　said　he；　employs　our　ships　as　buckets　to　draw　water：　and　boxing　about　our　sackbuts；　as　if　they　were　unworthy　to　be　associated　with　him；　drives　them　from　his　company　with　disgrace。　Such　was　the　success　of　the　siege　on　the　side　of　the　sea。〃　Subsequently；　however；　Marcellus　took　the　city　by　strategy；　and　Archimedes　was　killed；　contrary；　it　is　said；　to　the　express　orders　of　Marcellus。　〃Syracuse　being　taken；〃　says　Plutarch；　〃nothing　grieved　Marcellus　more　than　the　loss　of　Archimedes。　Who；　being　in　his　study　when　the　city　was　taken；　busily　seeking　out　by　himself　the　demonstration　of　some　geometrical　proposition　which　he　ha