alexandria and her schools-第6节

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。　　They　have　all　perished；like　ninety…nine　hundredths　of　the　labours　of　that　great　literary　age；　and　perhaps　the　world　is　no　poorer　for　the　loss。　　But　one　thing；　which　he　attempted　on　a　sound　and　practical　philosophic　method；　stands；　and　will　stand　for　ever。　　And　after　all；　is　not　that　enough　to　have　lived　for？　to　have　found　out　one　true　thing；　and；　therefore；　one　imperishable　thing；　in　one's　life？　　If　each　one　of　us　could　but　say　when　he　died：　　〃This　one　thing　I　have　found　out；　this　one　thing　I　have　proved　to　be　possible；　this　one　eternal　fact　I　have　rescued　from　Hela；　the　realm　of　the　formless　and　unknown；〃　how　rich　one　such　generation　might　make　the　world　for　ever！

But　such　is　not　the　appointed　method。　　The　finders　are　few　and　far　between；　because　the　true　seekers　are　few　and　far　between；　and　a　whole　generation　has　often　nothing　to　show　for　its　existence　but　one　solitary　gem　which　some　one　manoften　unnoticed　in　his　timehas　picked　up　for　them；　and　so　given　them　〃a　local　habitation　and　a　name。〃

Eratosthenes　had　heard　that　in　Syene；　in　Upper　Egypt；　deep　wells　were　enlightened　to　the　bottom　on　the　day　of　the　summer　solstice；　and　that　vertical　objects　cast　no　shadows。

He　had　before　suggested；　as　is　supposed；　to　Ptolemy　Euergetes；　to　make　him　the　two　great　copper　armillae；　or　circles　for　determining　the　equinox；　which　stood　for　centuries　in　〃that　which　is　called　the　Square　Porch〃probably　somewhere　in　the　Museum。　　By　these　he　had　calculated　the　obliquity　of　the　ecliptic；　closely　enough　to　serve　for　a　thousand　years　after。　　That　was　one　work　done。　　But　what　had　the　Syene　shadows　to　do　with　that？　　Syene　must　be　under　that　ecliptic。　　On　the　edge　of　it。　In　short；　just　under　the　tropic。　　Now　he　had　ascertained　exactly　the　latitude　of　one　place　on　the　earth's　surface。　　He　had　his　known　point　from　whence　to　start　on　a　world…journey；　and　he　would　use　it；　he　would　calculate　the　circumference　of　the　earthand　he　did　it。　　By　observations　made　at　Alexandria；　he　ascertained　its　latitude　compared　with　that　of　Syene；　and　so　ascertained　what　proportion　to　the　whole　circumference　was　borne　by　the　5000　stadia　between　Alexandria　and　Syene。　He　fell　into　an　error；　by　supposing　Alexandria　and　Syene　to　be　under　the　same　meridians　of　longitude：　　but　that　did　not　prevent　his　arriving　at　a　fair　rough　result　of　252；000　stadia31；500　Roman　miles；　considerably　too　much；　but　still；　before　him；　I　suppose；　none　knew　whether　it　was　10；000；　or　10；000；000。　　The　right　method　having　once　been　found；　nothing　remained　but　to　employ　it　more　accurately。

One　other　great　merit　of　Eratosthenes　is；　that　he　first　raised　Geography　to　the　rank　of　a　science。　　His　Geographica　were　an　organic　collection；　the　first　the　world　had　ever　seen；　of　all　the　travels　and　books　of　earth…description　heaped　together　in　the　Great　Library；　of　which　he　was　for　many　years　the　keeper。　　He　began　with　a　geognostic　book；　touched　on　the　traces　of　Cataclysms　and　Change　visible　on　the　earth's　surface；　followed　by　two　books；　one　a　mathematical　book；　the　other　on　political　geography；　and　completed　by　a　mapwhich　one　would　like　to　see：　　but　not　a　trace　of　all　remains；　save　a　few　quoted　fragments　…


We　are　such　stuff　As　dreams　are　made　of。


But　if　Eratosthenes　had　hold　of　eternal　fact　and　law　on　one　point；　there　was　a　contemporary　who　had　hold　of　it　in　more　than　one。　　I　mean　Archimedes；　of　whom；　as　I　have　said；　we　must　speak　as　of　an　Alexandrian。　It　was　as　a　mechanician；　rather　than　as　an　astronomer；　that　he　gained　his　reputation。　　The　stories　of　his　Hydraulic　Screw；　the　Great　Ship　which　he　built　for　Hiero；　and　launched　by　means　of　machinery；　his　crane；　his　war…engines；　above　all　his　somewhat　mythical　arrangement　of　mirrors；　by　which　he　set　fire　to　ships　in　the　harbourall　these；　like　the　story　of　his　detecting　the　alloy　in　Hiero's　crown；　while　he　himself　was　in　the　bath；　and　running　home　undressed　shouting　＇Greek　text：　　eureeka＇all　these　are　schoolboys'　tales。　　To　the　thoughtful　person　it　is　the　method　of　the　man　which　constitutes　his　real　greatness；　that　power　of　insight　by　which　he　solved　the　two　great　problems　of　the　nature　of　the　lever　and　of　hydrostatic　pressure；　which　form　the　basis　of　all　static　and　hydrostatic　science　to　this　day。　　And　yet　on　that　very　question　of　the　lever　the　great　mind　of　Aristotle　babblesneither　sees　the　thing　itself；　nor　the　way　towards　seeing　it。　　But　since　Archimedes　spoke；　the　thing　seems　self…evident　to　every　schoolboy。　　There　is　something　to　me　very　solemn　in　such　a　fact　as　this。　　It　brings　us　down　to　some　of　the　very　deepest　questions　of　metaphysic。　　This　mental　insight　of　which　we　boast　so　much；　what　is　it？　　Is　it　altogether　a　process　of　our　own　brain　and　will？　　If　it　be；　why　have　so　few　the　power；　even　among　men　of　power；　and　they　so　seldom？　　If　brain　alone　were　what　was　wanted；　what　could　not　Aristotle　have　discovered？　　Or　is　it　that　no　man　can　see　a　thing　unless　God　shows　it　him？　　Is　it　that　in　each　separate　act　of　induction；　that　mysterious　and　transcendental　process　which　cannot；　let　logicians　try　as　they　will；　be　expressed　by　any　merely　logical　formula；　Aristotelian　or　otheris　it　I　say；　that　in　each　separate　act　of　induction　we　do　not　find　the　law；　but　the　law　is　shown　to　us；　by　Him　who　made　the　law？　Bacon　thought　so。　　Of　that　you　may　find　clear　proof　in　his　writings。　May　not　Bacon　be　right？　　May　it　not　be　true　that　God　does　in　science；　as　well　as　in　ethics；　hide　things　from　the　wise　and　prudent；　from　the　proud；　complete；　self…contained　systematiser　like　Aristotle；　who　must　needs　explain　all　things　in　heaven　and　earth　by　his　own　formulae；　and　his　entelechies　and　energies；　and　the　rest　of　the　notions　which　he　has　made　for　himself　out　of　his　own　brain；　and　then　pack　each　thing　away　in　its　proper　niche　in　his　great　cloud…universe　of　conceptions？　　Is　it　that　God　hides　things　from　such　men　many　a　time；　and　reveals　them　to　babes；　to　gentle；　affectionate；　simple…hearted　men；　such　as　we　know　Archimedes　to　have　been；　who　do　not　try　to　give　an　explanation　for　a　fact；　but　feel　how　awful　and　divine　it　is；　and　wrestle　reverently　and　stedfastly　with　it；　as　Jacob　with　the　Angel；　and　will　not　let　it　go；　until　it　bless　them？　　Sure　I　am；　from　what　I　have　seen　of　scientific　men；　that　there　is　an　intimate　connection　between　the　health　of　the　moral　faculties　and　the　health　of　the　inductive　ones；　and　that　the　proud；　self…conceited；　and　passionate　man　will　see　nothing：　　perhaps　because　nothing　will　be　shown　him。

But　we　must　leave　Archimedes　for　a　man　not　perhaps　so　well　known；　but　to　whom　we　owe　as　much　as　to　the　great　SyracusanHipparchus　the　astronomer。　　To　his　case　much　which　I　have　just　said　applies。　　In　him　astronomic　science　seemed　to　awaken　suddenly　to　a　true　inductive　method；　and　after　him　to　fall　into　its　old　slumber　for　300　years。　　In　the　meantime　Timocharis；　Aristyllus；　and　Conon　had　each　added　their　mites　to　the　discoveries　of　Eratosthenes：　　but　to　Hipparchus　we　owe　that　theory　of　the　heavens；　commonly　called　the　Ptolemaic　system；　which；　starting　from　the　assumption　that　the　earth　was　the　centre　of　the　universe；　attempted　to　explain　the　motions　of　the　heavenly　bodies　by　a　complex　system　of　supposed　eccentrics　and　epicycles。　　This　has　of　course　now　vanished　before　modern　discoveries。　　But　its　value　as　a　scientific　attempt　lies　in　this：　　that　the　method　being　a　correct　one；　correct　results　were　obtained；　though　starting　from　a　false　assumption；　and　Hipparchus　and　his　successors　were　enabled　by　it　to　calculate　and　predict　the　changes　of　the　heavens；　in　spite　of　their　clumsy　instruments；　with　almost　as　much　accuracy　as　we　do　now。

For　the　purpose　of　working　out　this　theory　he　required　a　science　of　trigonometry；　plane　and　spherical：　　and　this　he　accordingly　seems　to　have　invented。　　To　him　also　we　owe　the　discovery　of　that　vast　gradual　change　in　the　position　of　the　fixed　stars；　in　fact；　of　the　whole　celestial　system；　now　known　by　the　name　of　the　precession　of　the　equinoxes；　the　first　great　catalogue　of　fixed　stars；　to　the　number　of　1080；　attempts　to　ascertain　whether　the　length　of　years　and　days　were　constant；　with　which；　with　his　characteristic　love　of　truth；　he　seems　to　have　been　hardly　satisfied。　　He　too　invented　the　planisphere；　or　mode　of　representing　the　starry　heavens　upon　a　plane；　and　is　the　father　of　true　geography；　having　formed　the　happy　notion　of　mapping　out　the　earth；　as　well　as　the　heavens；　by　degrees　of　latitude　and　longitude。

Strange　it　is；　and　somewhat　sad；　that　we　should　know　nothing　of　this　great　man；　should　be　hardly　able　to　distinguish　him　from　others　of　the　same　name；　but　through　the　works　of　a　commentator；　who　wrote　and　observed　in　Alexandria　300　years　after；　during　the　age　of　the　Antonines。　I　mean；　of　course；　the　famous　Ptolemy；　whose　name　so　long　bore　the　honour　of　that　system　which　really　belonged　to　Hipparchus。

This　single　fact　speaks　volumes　for　the　real　weakness　of　the　great　artificial　school　of　literature　and　science　founded　by　the　kings　of　Egypt。　　From　the　father　of　Astronomy；　as　Delambre　calls　him；　to　Ptolemy；　the　first　man　who　seems　really　to　have　appreciated　him；　we　have　not　a　discovery；　hardly　an　observation　or　a　name；　to　fill　the　gap。　　Physical　sages　there　were；　but　they　were　geometers　and　mathematicians；　rather　than　astronomic　obse