a history of science-2-第8部分

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ect　on　science　could　not　be　long　delayed。　Quite　independently　of　the　Byzantine　influence；　however；　the　striving　for　better　intellectual　things　had　manifested　itself　in　many　ways　before　the　close　of　the　thirteenth　century。　An　illustration　of　this　is　found　in　the　almost　simultaneous　development　of　centres　of　teaching；　which　developed　into　the　universities　of　Italy；　France；　England；　and；　a　little　later；　of　Germany。　The　regular　list　of　studies　that　came　to　be　adopted　everywhere　comprised　seven　nominal　branches；　divided　into　two　groupsthe　so…called　quadrivium；　comprising　music；　arithmetic；　geometry；　and　astronomy；　and　the　trivium　comprising　grammar；　rhetoric；　and　logic。　The　vagueness　of　implication　of　some　of　these　branches　gave　opportunity　to　the　teacher　for　the　promulgation　of　almost　any　knowledge　of　which　he　might　be　possessed；　but　there　can　be　no　doubt　that；　in　general；　science　had　but　meagre　share　in　the　curriculum。　In　so　far　as　it　was　given　representation；　its　chief　field　must　have　been　Ptolemaic　astronomy。　The　utter　lack　of　scientific　thought　and　scientific　method　is　illustrated　most　vividly　in　the　works　of　the　greatest　men　of　that　periodsuch　men　as　Albertus　Magnus；　Thomas　Aquinas；　Bonaventura；　and　the　hosts　of　other　scholastics　of　lesser　rank。　Yet　the　mental　awakening　implied　in　their　efforts　was　sure　to　extend　to　other　fields；　and　in　point　of　fact　there　was　at　least　one　contemporary　of　these　great　scholastics　whose　mind　was　intended　towards　scientific　subjects；　and　who　produced　writings　strangely　at　variance　in　tone　and　in　content　with　the　others。　This　anachronistic　thinker　was　the　English　monk；　Roger　Bacon。

ROGER　BACON　Bacon　was　born　in　1214　and　died　in　1292。　By　some　it　is　held　that　he　was　not　appreciated　in　his　own　time　because　he　was　really　a　modern　scientist　living　in　an　age　two　centuries　before　modern　science　or　methods　of　modern　scientific　thinking　were　known。　Such　an　estimate；　however；　is　a　manifest　exaggeration　of　the　facts；　although　there　is　probably　a　grain　of　truth　in　it　withal。　His　learning　certainly　brought　him　into　contact　with　the　great　thinkers　of　the　time；　and　his　writings　caused　him　to　be　imprisoned　by　his　fellow…churchmen　at　different　times；　from　which　circumstances　we　may　gather　that　he　was　advanced　thinker；　even　if　not　a　modern　scientist。　Although　Bacon　was　at　various　times　in　durance；　or　under　surveillance；　and　forbidden　to　write；　he　was　nevertheless　a　marvellously　prolific　writer；　as　is　shown　by　the　numerous　books　and　unpublished　manuscripts　of　his　still　extant。　His　master…production　was　the　Opus　Majus。　In　Part　IV。　of　this　work　he　attempts　to　show　that　all　sciences　rest　ultimately　on　mathematics；　but　Part　V。；　which　treats　of　perspective；　is　of　particular　interest　to　modern　scientists；　because　in　this　he　discusses　reflection　and　refraction；　and　the　properties　of　mirrors　and　lenses。　In　this　part；　also；　it　is　evident　that　he　is　making　use　of　such　Arabian　writers　as　Alkindi　and　Alhazen；　and　this　is　of　especial　interest；　since　it　has　been　used　by　his　detractors；　who　accuse　him　of　lack　of　originality；　to　prove　that　his　seeming　inventions　and　discoveries　were　in　reality　adaptations　of　the　Arab　scientists。　It　is　difficult　to　determine　just　how　fully　such　criticisms　are　justified。　It　is　certain；　however；　that　in　this　part　he　describes　the　anatomy　of　the　eye　with　great　accuracy；　and　discusses　mirrors　and　lenses。　The　magnifying　power　of　the　segment　of　a　glass　sphere　had　been　noted　by　Alhazen；　who　had　observed　also　that　the　magnification　was　increased　by　increasing　the　size　of　the　segment　used。　Bacon　took　up　the　discussion　of　the　comparative　advantages　of　segments；　and　in　this　discussion　seems　to　show　that　he　understood　how　to　trace　the　progress　of　the　rays　of　light　through　a　spherical　transparent　body；　and　how　to　determine　the　place　of　the　image。　He　also　described　a　method　of　constructing　a　telescope；　but　it　is　by　no　means　clear　that　he　had　ever　actually　constructed　such　an　instrument。　It　is　also　a　mooted　question　as　to　whether　his　instructions　as　to　the　construction　of　such　an　instrument　would　have　enabled　any　one　to　construct　one。　The　vagaries　of　the　names　of　terms　as　he　uses　them　allow　such　latitude　in　interpretation　that　modern　scientists　are　not　agreed　as　to　the　practicability　of　Bacon's　suggestions。　For　example；　he　constantly　refers　to　force　under　such　names　as　virtus；　species；　imago；　agentis；　and　a　score　of　other　names；　and　this　naturally　gives　rise　to　the　great　differences　in　the　interpretations　of　his　writings；　with　corresponding　differences　in　estimates　of　them。　The　claim　that　Bacon　originated　the　use　of　lenses；　in　the　form　of　spectacles；　cannot　be　proven。　Smith　has　determined　that　as　early　as　the　opening　years　of　the　fourteenth　century　such　lenses　were　in　use；　but　this　proves　nothing　as　regards　Bacon's　connection　with　their　invention。　The　knowledge　of　lenses　seems　to　be　very　ancient；　if　we　may　judge　from　the　convex　lens　of　rock　crystal　found　by　Layard　in　his　excavations　at　Nimrud。　There　is　nothing　to　show；　however；　that　the　ancients　ever　thought　of　using　them　to　correct　defects　of　vision。　Neither；　apparently；　is　it　feasible　to　determine　whether　the　idea　of　such　an　application　originated　with　Bacon。　Another　mechanical　discovery　about　which　there　has　been　a　great　deal　of　discussion　is　Bacon's　supposed　invention　of　gunpowder。　It　appears　that　in　a　certain　passage　of　his　work　he　describes　the　process　of　making　a　substance　that　is；　in　effect；　ordinary　gunpowder；　but　it　is　more　than　doubtful　whether　he　understood　the　properties　of　the　substance　he　describes。　It　is　fairly　well　established；　however；　that　in　Bacon's　time　gunpowder　was　known　to　the　Arabs；　so　that　it　should　not　be　surprising　to　find　references　made　to　it　in　Bacon's　work；　since　there　is　reason　to　believe　that　he　constantly　consulted　Arabian　writings。　The　great　merit　of　Bacon's　work；　however；　depends　on　the　principles　taught　as　regards　experiment　and　the　observation　of　nature；　rather　than　on　any　single　invention。　He　had　the　all…important　idea　of　breaking　with　tradition。　He　championed　unfettered　inquiry　in　every　field　of　thought。　He　had　the　instinct　of　a　scientific　workera　rare　instinct　indeed　in　that　age。　Nor　need　we　doubt　that　to　the　best　of　his　opportunities　he　was　himself　an　original　investigator。

LEONARDO　DA　VINCI　The　relative　infertility　of　Bacon's　thought　is　shown　by　the　fact　that　he　founded　no　school　and　left　no　trace　of　discipleship。　The　entire　century　after　his　death　shows　no　single　European　name　that　need　claim　the　attention　of　the　historian　of　science。　In　the　latter　part　of　the　fifteenth　century；　however；　there　is　evidence　of　a　renaissance　of　science　no　less　than　of　art。　The　German　Muller　became　famous　under　the　latinized　named　of　Regio　Montanus　（1437…1472）；　although　his　actual　scientific　attainments　would　appear　to　have　been　important　only　in　comparison　with　the　utter　ignorance　of　his　contemporaries。　The　most　distinguished　worker　of　the　new　era　was　the　famous　Italian　Leonardo　da　Vincia　man　who　has　been　called　by　Hamerton　the　most　universal　genius　that　ever　lived。　Leonardo's　position　in　the　history　of　art　is　known　to　every　one。　With　that；　of　course；　we　have　no　present　concern；　but　it　is　worth　our　while　to　inquire　at　some　length　as　to　the　famous　painter's　accomplishments　as　a　scientist。　From　a　passage　in　the　works　of　Leonardo；　first　brought　to　light　by　Venturi；＇1＇　it　would　seem　that　the　great　painter　anticipated　Copernicus　in　determining　the　movement　of　the　earth。　He　made　mathematical　calculations　to　prove　this；　and　appears　to　have　reached　the　definite　conclusion　that　the　earth　does　moveor　what　amounts　to　the　same　thing；　that　the　sun　does　not　move。　Muntz　is　authority　for　the　statement　that　in　one　of　his　writings　he　declares；　〃Il　sole　non　si　mouve〃the　sun　does　not　move。＇2＇　Among　his　inventions　is　a　dynamometer　for　determining　the　traction　power　of　machines　and　animals；　and　his　experiments　with　steam　have　led　some　of　his　enthusiastic　partisans　to　claim　for　him　priority　to　Watt　in　the　invention　of　the　steam…engine。　In　these　experiments；　however；　Leonardo　seems　to　have　advanced　little　beyond　Hero　of　Alexandria　and　his　steam　toy。　Hero's　steam…engine　did　nothing　but　rotate　itself　by　virtue　of　escaping　jets　of　steam　forced　from　the　bent　tubes；　while　Leonardo's　〃steam…engine〃　〃drove　a　ball　weighing　one　talent　over　a　distance　of　six　stadia。〃　In　a　manuscript　now　in　the　library　of　the　Institut　de　France；　Da　Vinci　describes　this　engine　minutely。　The　action　of　this　machine　was　due　to　the　sudden　conversion　of　small　quantities　of　water　into　steam　（〃smoke；〃　as　he　called　it）　by　coming　suddenly　in　contact　with　a　heated　surface　in　a　proper　receptacle；　the　rapidly　formed　steam　acting　as　a　propulsive　force　after　the　manner　of　an　explosive。　It　is　really　a　steam…gun；　rather　than　a　steam…engine；　and　it　is　not　unlikely　that　the　study　of　the　action　of　gunpowder　may　have　suggested　it　to　Leonardo。　It　is　believed　that　Leonardo　is　the　true　discoverer　of　the　camera…obscura；　although　the　Neapolitan　philosopher；　Giambattista　Porta；　who　was　not　born　until　some　twenty　years　after　the　death　of　Leonardo；　is　usually　credited　with　first　describing　this　device。　There　is　little　doubt；　however；　that　Da　Vinci　understood　the　principle　of　this　mechanism；　for　he　describes　how　such　a　camer