an autobiography-第67部分

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ing　by　his　devotion　to　astronomical　pursuits　and　his　profound　knowledge　of　the　subject。　　He　had　acquired　much　technical　skill　in　the　construction　of　reflecting　telescopes；　and　the　companionship　between　us　was　thus　rendered　very　agreeable。　　There　was　an　intimate　exchange　of　opinions　on　the　subject；　and　my　friendship　with　him　continued　during　forty　successive　years。　　I　was　perhaps　a　little　ahead　of　him　in　certain　respects。　　I　had　more　practical　knowledge　of　casting；　for　I　had　begun　when　a　boy　in　my　bedroom　at　Edinburgh。　　In　course　of　time　I　contrived　many　practical　〃dodges〃　（if　I　may　use　such　a　word）；　and　could　nimbly　vault　over　difficulties　of　a　special　kind　which　had　hitherto　formed　a　barrier　in　the　way　of　amateur　speculum　makers　when　fighting　their　way　to　a　home…made　telescope。　　I　may　mention　that　I　know　of　no　mechanical　pursuit　in　connection　with　science；　that　offers　such　an　opportunity　for　practising　the　technical　arts；　as　that　of　constructing　from　first　to　last　a　complete　Newtonian　or　Gregorian　Reflecting　Telescope。　Such　an　enterprise　brings　before　the　amateur　a　succession　of　the　most　interesting　and　instructive　mechanical　arts；　and　obliges　the　experimenter　to　exercise　the　faculty　of　delicate　manipulation。　If　I　were　asked　what　course　of　practice　was　the　best　to　instil　a　true　taste　for　refined　mechanical　work；　I　should　say；　set　to　and　make　for　yourself　from　first　to　last　a　reflecting　telescope　with　a　metallic　speculum。　　Buy　nothing　but　the　raw　material；　and　work　your　way　to　the　possession　of　a　telescope　by　means　of　your　own　individual　labour　and　skill。　　If　you　do　your　work　with　the　care；　intelligence；　and　patience　that　is　necessary；　you　will　find　a　glorious　reward　in　the　enhanced　enjoyment　of　a　night　with　the　heavensall　the　result　of　your　own　ingenuity　and　handiwork。　　It　will　prove　a　source　of　abundant　pleasure　and　of　infinite　enjoyment　for　the　rest　of　your　life。

I　well　remember　the　visit　I　received　from　my　dear　friend　Warren　de　la　Rue　in　the　year　1840。　　I　was　executing　some　work　for　him　with　respect　to　a　new　process　which　he　had　contrived　for　the　production　of　white　lead。　I　was　then　busy　with　the　casting　of　my　thirteen…inch　speculum。　He　watched　my　proceedings　with　earnest　interest　and　most　careful　attention。　　He　told　me　many　years　after；　that　it　was　the　sight　of　my　special　process　of　casting　a　sound　speculum　that　in　a　manner　caused　him　to　turn　his　thoughts　to　practical　astronomy；　a　subject　in　which　he　has　exhibited　such　noble　devotion　as　well　as　masterly　skill。　　Soon　after　his　visit　I　had　the　honour　of　casting　for　him　a　thirteen…inch　speculum；　which　he　afterwards　ground　and　polished　by　a　method　of　his　own。　He　mounted　it　in　an　equatorial　instrument　of　such　surpassing　excellence　as　enabled　him；　aided　by　his　devotion　and　pure　love　of　the　subject；　to　record　a　series　of　observations　and　results　which　will　hand　his　name　down　to　posterity　as　one　of　the　most　faithful　and　patient　of　astronomical　observers。

＇Image＇　　Fireside；　Patricroft。　　After　a　drawing　by　James　Nasmyth

But　to　return　to　my　own　little　work　at　Patricroft。　　I　mounted　my　ten…inch　home…made　reflecting　telescope；　and　began　my　survey　of　the　heavens。　　Need　I　say　with　what　exquisite　delight　the　harmony　of　their　splendour　filled　me。　　I　began　as　a　learner；　and　my　learning　grew　with　experience。　　There　were　the　prominent　stars；　the　planets；　the　Milky　Way　with　thousands　of　far…off　sunsto　be　seen。　　My　observations　were　at　first　merely　general；　by　degrees　they　became　particular。　I　was　not　satisfied　with　enjoying　these　sights　myself；　I　made　my　friends　and　neighbours　sharers　in　my　pleasure；　and　some　of　them　enjoyed　the　wonders　of　the　heavens　as　much　as　I　did。

In　my　early　use　of　the　telescope　I　had　fitted　the　speculum　into　a　light　square　tube　of　deal　to　which　the　eye…piece　was　attached；　so　as　to　have　all　the　essential　parts　of　the　telescope　combined　together　in　the　most　simple　and　portable　form。　　I　had　often　to　remove　it　from　place　to　place　in　my　small　garden　at　the　side　of　the　Bridgewater　Canal；　in　order　to　get　it　clear　of　the　trees　and　branches　which　intercepted　some　object　in　the　heavens　which　I　wished　to　see。　　How　eager　and　enthusiastic　I　was　in　those　days！　　Sometimes　I　got　out　of　bed　in　the　clear　small　hours　of　the　morning；　and　went　down　to　the　garden　in　my　night…shirt。　　I　would　take　the　telescope　in　my　arms　and　plant　it　in　some　suitable　spot；　where　I　might　get　a　peep　at　some　special　planet　or　star　then　above　the　horizon。

It　became　bruited　about　that　a　ghost　was　seen　at　Patricroft！　A　barge　was　silently　gliding　along　the　canal　near　midnight；　when　the　boatman　suddenly　saw　a　figure　in　white。　〃It　moved　among　the　trees　with　a　coffin　in　its　arms！〃　The　apparition　was　so　sudden　and　strange　that　he　immediately　concluded　that　it　was　a　ghost。　　The　weird　sight　was　reported　at　the　stations　along　the　canal；　and　also　at　Wolverhampton；　which　was　the　boatman's　headquarters。　　He　told　the　people　at　Patricroft　on　his　return　journey　what　he　had　seen；　and　great　was　the　excitement　produced。　　The　place　was　haunted：　　there　was　no　doubt　about　it！　　After　all；　the　rumour　was　founded　on　fact；　for　the　ghost　was　merely　myself　in　my　night…shirt；　and　the　coffin　was　my　telescope；　which　I　was　quietly　shifting　from　one　place　to　another　in　order　to　get　a　clearer　sight　of　the　heavens　at　midnight。

My　ambition　expanded。　　I　now　resolved　to　construct　a　reflecting　telescope　of　considerably　greater　power　than　that　which　I　possessed。　I　made　one　of　twenty　inches　diameter；　and　mounted　it　on　a　very　simple　plan；　thus　removing　many　of　the　inconveniences　and　even　personal　risks　that　attend　the　use　of　such　instruments。　　（For　illustration　of　the　plan　of　mounting　a　large　telescope；　see　p。　338）　It　had　been　necessary　to　mount　steps　or　ladders　to　get　at　the　eyepiece；　especially　when　the　objects　to　be　observed　were　at　a　high　elevation　above　the　horizon。　I　now　prepared　to　do　some　special　work　with　this　instrument。　In　1842　I　began　my　systematic　researches　upon　the　Moon。　　I　carefully　and　minutely　scrutinised　the　marvellous　details　of　its　surface；　a　pursuit　which　I　continued　for　many　years；　and　still　continue　with　ardour　until　this　day。　　My　method　was　as　follows：　

I　availed　myself　of　every　favourable　opportunity　for　carrying　on　the　investigation。　　I　made　careful　drawings　with　black　and　white　chalk　on　large　sheets　of　grey…tinted　paper；　of　such　selected　portions　of　the　Moon　as　embodied　the　most　characteristic　and　instructive　features　of　her　wonderful　surface。　　I　was　thus　enabled　to　graphically　represent　the　details　with　due　fidelity　as　to　form；　as　well　as　with　regard　to　the　striking　effect　of　the　original　in　its　masses　of　light　and　shade。　I　thus　educated　my　eye　for　the　special　object　by　systematic　and　careful　observation；　and　at　the　same　time　practised　my　hand　in　no　less　careful　delineation　of　all　that　was　so　distinctly　presented　to　me　by　the　telescopeat　the　side　of　which　my　sheet　of　paper　was　handily　fixed。　I　became　in　a　manner　familiar　with　the　vast　variety　of　those　distinct　manifestations　of　volcanic　action；　which　at　some　inconceivably　remote　period　had　produced　these　wonderful　features　and　details　of　the　moon's　surface。　　So　far　as　could　be　observed；　there　was　an　entire　absence　of　any　agency　of　change；　so　that　their　formation　must　have　remained　absolutely　intact　since　the　original　cosmical　heat　of　the　moon　had　passed　rapidly　into　space。　　The　surface；　with　all　its　wondrous　details；　presents　the　same　aspect　as　it　did　probably　millions　of　ages　ago。

This　consideration　vastly　enhances　the　deep　interest　with　which　we　look　upon　the　moon　and　its　volcanic　details。　　It　is　totally　without　an　atmosphere；　or　of　a　vapour　envelope；　such　as　the　earth　possesses；　and　which　must　have　contributed　to　the　conservation　of　the　cosmical　heat　of　the　latter　orb。　　The　moon　is　of　relatively　small　mass；　and　is　consequently　inferior　in　heat…retaining　power。　　It　must　thus　have　parted　with　its　original　stock　of　cosmical　heat　with　such　rapidity　as　to　bring　about　the　final　termination　of　those　surface　changes　which　give　it　so　peculiar　an　aspect。　　In　the　case　of　the　earth　the　internal　heat　still　continues　in　operation；　though　in　a　vastly　reduced　degree　of　activity。　　Again　in　the　case　of　the　moon；　the　total　absence　of　water　as　well　as　atmosphere　has　removed　from　it　all　those　denudative　activities　which；　in　the　earth；　have　acted　so　powerfully　in　effecting　changes　of　its　surfaces　as　well　as　in　the　distribution　of　its　materials。　Hence　the　appearance　of　the　wonderful　details　of　the　moon's　surface　presents　us　with　objects　of　inconceivably　remote　antiquity。

＇Image＇　　General　structure　of　Lunar　craters。

Another　striking　characteristic　of　the　moon's　surface　is　the　enormous　magnitude　of　its　volcanic　crater　formations。　　In　comparison　with　these；　the　greatest　on　the　surface　of　the　earth　are　reduced　to　insignificance。　Paradoxical　as　the　statement　may　at　first　appear；　the　magnitude　of　the　remains　of　the　primitive　volcanic　energy　in　the　moon　is　simply　due　to　the　smallness　of　its　mass。　　Being　only　about　one…eightieth　part　of　the　bulk　of　the　earth；　the　force　of　gravity　on　the　moon's　surface　is　only　about　one…sixth。　　And　as　eruptive　force　is　quite　independent；　as　a　force；　of　the　law　of　gravitation；　and　as　it　acted　with　its　full　energy　on　matter；　which　in　the　moon　is　little　h