a history of science-2-第3章

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out　of　their　language　into　mediaeval　Latin。　It　remains　to　inquire；　however；　through　what　channels　the　Greek　works　reached　the　Arabs　themselves。　To　gain　an　answer　to　this　question　we　must　follow　the　stream　of　history　from　its　Roman　course　eastward　to　the　new　seat　of　the　Roman　empire　in　Byzantium。　Here　civilization　centred　from　about　the　fifth　century　A。D。；　and　here　the　European　came　in　contact　with　the　civilization　of　the　Syrians；　the　Persians；　the　Armenians；　and　finally　of　the　Arabs。　The　Byzantines　themselves；　unlike　the　inhabitants　of　western　Europe；　did　not　ignore　the　literature　of　old　Greece；　the　Greek　language　became　the　regular　speech　of　the　Byzantine　people；　and　their　writers　made　a　strenuous　effort　to　perpetuate　the　idiom　and　style　of　the　classical　period。　Naturally　they　also　made　transcriptions　of　the　classical　authors；　and　thus　a　great　mass　of　literature　was　preserved；　while　the　corresponding　works　were　quite　forgotten　in　western　Europe。　Meantime　many　of　these　works　were　translated　into　Syriac；　Armenian；　and　Persian；　and　when　later　on　the　Byzantine　civilization　degenerated；　many　works　that　were　no　longer　to　be　had　in　the　Greek　originals　continued　to　be　widely　circulated　in　Syriac；　Persian；　Armenian；　and；　ultimately；　in　Arabic　translations。　When　the　Arabs　started　out　in　their　conquests；　which　carried　them　through　Egypt　and　along　the　southern　coast　of　the　Mediterranean；　until　they　finally　invaded　Europe　from　the　west　by　way　of　Gibraltar；　they　carried　with　them　their　translations　of　many　a　Greek　classical　author；　who　was　introduced　anew　to　the　western　world　through　this　strange　channel。　We　are　told；　for　example；　that　Averrhoes；　the　famous　commentator　of　Aristotle；　who　lived　in　Spain　in　the　twelfth　century；　did　not　know　a　word　of　Greek　and　was　obliged　to　gain　his　knowledge　of　the　master　through　a　Syriac　translation；　or；　as　others　alleged　（denying　that　he　knew　even　Syriac）；　through　an　Arabic　version　translated　from　the　Syriac。　We　know；　too；　that　the　famous　chronology　of　Eusebius　was　preserved　through　an　Armenian　translation；　and　reference　has　more　than　once　been　made　to　the　Arabic　translation　of　Ptolemy's　great　work；　to　which　we　still　apply　its　Arabic　title　of　Almagest。　The　familiar　story　that　when　the　Arabs　invaded　Egypt　they　burned　the　Alexandrian　library　is　now　regarded　as　an　invention　of　later　times。　It　seems　much　more　probable　that　the　library　bad　been　largely　scattered　before　the　coming　of　the　Moslems。　Indeed；　it　has　even　been　suggested　that　the　Christians　of　an　earlier　day　removed　the　records　of　pagan　thought。　Be　that　as　it　may；　the　famous　Alexandrian　library　had　disappeared　long　before　the　revival　of　interest　in　classical　learning。　Meanwhile；　as　we　have　said；　the　Arabs；　far　from　destroying　the　western　literature；　were　its　chief　preservers。　Partly　at　least　because　of　their　regard　for　the　records　of　the　creative　work　of　earlier　generations　of　alien　peoples；　the　Arabs　were　enabled　to　outstrip　their　contemporaries。　For　it　cannot　be　in　doubt　that；　during　that　long　stretch　of　time　when　the　western　world　was　ignoring　science　altogether　or　at　most　contenting　itself　with　the　casual　reading　of　Aristotle　and　Pliny；　the　Arabs　had　the　unique　distinction　of　attempting　original　investigations　in　science。　To　them　were　due　all　important　progressive　steps　which　were　made　in　any　scientific　field　whatever　for　about　a　thousand　years　after　the　time　of　Ptolemy　and　Galen。　The　progress　made　even　by　the　Arabs　during　this　long　period　seems　meagre　enough；　yet　it　has　some　significant　features。　These　will　now　demand　our　attention。

II。　MEDIAEVAL　SCIENCE　AMONG　THE　ARABIANS　The　successors　of　Mohammed　showed　themselves　curiously　receptive　of　the　ideas　of　the　western　people　whom　they　conquered。　They　came　in　contact　with　the　Greeks　in　western　Asia　and　in　Egypt；　and；　as　has　been　said；　became　their　virtual　successors　in　carrying　forward　the　torch　of　learning。　It　must　not　be　inferred；　however；　that　the　Arabian　scholars；　as　a　class；　were　comparable　to　their　predecessors　in　creative　genius。　On　the　contrary；　they　retained　much　of　the　conservative　oriental　spirit。　They　were　under　the　spell　of　tradition；　and；　in　the　main；　what　they　accepted　from　the　Greeks　they　regarded　as　almost　final　in　its　teaching。　There　were；　however；　a　few　notable　exceptions　among　their　men　of　science；　and　to　these　must　be　ascribed　several　discoveries　of　some　importance。　The　chief　subjects　that　excited　the　interest　and　exercised　the　ingenuity　of　the　Arabian　scholars　were　astronomy；　mathematics；　and　medicine。　The　practical　phases　of　all　these　subjects　were　given　particular　attention。　Thus　it　is　well　known　that　our　so…called　Arabian　numerals　date　from　this　period。　The　revolutionary　effect　of　these　characters；　as　applied　to　practical　mathematics；　can　hardly　be　overestimated；　but　it　is　generally　considered；　and　in　fact　was　admitted　by　the　Arabs　themselves；　that　these　numerals　were　really　borrowed　from　the　Hindoos；　with　whom　the　Arabs　came　in　contact　on　the　east。　Certain　of　the　Hindoo　alphabets；　notably　that　of　the　Battaks　of　Sumatra；　give　us　clews　to　the　originals　of　the　numerals。　It　does　not　seem　certain；　however；　that　the　Hindoos　employed　these　characters　according　to　the　decimal　system；　which　is　the　prime　element　of　their　importance。　Knowledge　is　not　forthcoming　as　to　just　when　or　by　whom　such　application　was　made。　If　this　was　an　Arabic　innovation；　it　was　perhaps　the　most　important　one　with　which　that　nation　is　to　be　credited。　Another　mathematical　improvement　was　the　introduction　into　trigonometry　of　the　sinethe　half…chord　of　the　double　arcinstead　of　the　chord　of　the　arc　itself　which　the　Greek　astronomers　had　employed。　This　improvement　was　due　to　the　famous　Albategnius；　whose　work　in　other　fields　we　shall　examine　in　a　moment。　Another　evidence　of　practicality　was　shown　in　the　Arabian　method　of　attempting　to　advance　upon　Eratosthenes'　measurement　of　the　earth。　Instead　of　trusting　to　the　measurement　of　angles；　the　Arabs　decided　to　measure　directly　a　degree　of　the　earth's　surfaceor　rather　two　degrees。　Selecting　a　level　plain　in　Mesopotamia　for　the　experiment；　one　party　of　the　surveyors　progressed　northward；　another　party　southward；　from　a　given　point　to　the　distance　of　one　degree　of　arc；　as　determined　by　astronomical　observations。　The　result　found　was　fifty…six　miles　for　the　northern　degree；　and　fifty…six　and　two…third　miles　for　the　southern。　Unfortunately；　we　do　not　know　the　precise　length　of　the　mile　in　question；　and　therefore　cannot　be　assured　as　to　the　accuracy　of　the　measurement。　It　is　interesting　to　note；　however；　that　the　two　degrees　were　found　of　unequal　lengths；　suggesting　that　the　earth　is　not　a　perfect　spherea　suggestion　the　validity　of　which　was　not　to　be　put　to　the　test　of　conclusive　measurements　until　about　the　close　of　the　eighteenth　century。　The　Arab　measurement　was　made　in　the　time　of　Caliph　Abdallah　al…Mamun；　the　son　of　the　famous　Harun…al…Rashid。　Both　father　and　son　were　famous　for　their　interest　in　science。　Harun…al…Rashid　was；　it　will　be　recalled；　the　friend　of　Charlemagne。　It　is　said　that　he　sent　that　ruler；　as　a　token　of　friendship；　a　marvellous　clock　which　let　fall　a　metal　ball　to　mark　the　hours。　This　mechanism；　which　is　alleged　to　have　excited　great　wonder　in　the　Wes