men of invention and industry-第73节

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And　such　proved　to　be　the　case。　　I　have　the　mirror　still；　and　its

performance　is　very　good　indeed。



〃I　went　no　further　with　this　mirror；　for　fear　or　spoiling　it。　　It

is　very　slightly　grey　in　the　centre；　but　not　sufficiently　so　as

to　materially　injure　its　performance。　　I　mounted　it　in　a　wooden

tube；　placed　it　on　a　wooden　stand；　and　used　it　for　a　time　thus

mounted；　but　getting　disgusted　with　the　tremor　and　inconvenience

I　had　to　put　up　with；　I　resolved　to　construct　for　it　an　iron

equatorial　stand。　　I　made　my　patterns；　got　them　cast；　turned　and

fitted　them　myself；　grinding　all　the　working　parts　together　with

emery　and　oil；　and　fitted　a　tangent…screw　motion　to　drive　the

instrument　in　right　ascension。　　Now　I　found　the　instrument　a

pleasure　to　use；　and　I　determined　to　add　to　it　divided　circles；

and　to　accurately　adjust　it　to　the　meridian。　　I　made　my　circles

of　well…seasoned　mahogany；　with　slips　of　paper　on　their　edges；

dividing　them　with　my　drawing　instruments；　and　varnishing　them　to

keep　out　the　wet。　　I　shall　never　forget　that　sunny　afternoon　upon

which　I　computed　the　hour…angle　for　Jupiter；　and　set　the

instrument　so　that　by　calculation　Jupiter　should　pass　through　the

field　of　the　instrument　at　1h。　25m。　15s。　　With　my　watch　in　my

hand；　and　my　eye　to　the　eye…piece；　I　waited　for　the　orb。　　When

his　glorious　face　appeared；　almost　in　a　direct　line　for　the

centre　of　the　field；　I　could　not　contain　my　joy；　but　shouted　out

as　loudly　as　I　could；greatly　to　the　astonishment　of　old　George

Johnson；　the　miller；　who　happened　to　be　in　the　field　where　I　had

planted　my　stand！



〃Now；　though　I　had　obtained　what　I　wanteda　fairly　good

instrument；still　I　was　not　quite　satisfied；　as　I　had　produced

it　by　a　fortunate　chance；　and　not　by　skill　alone。　　I　therefore

set　to　work　again　on　the　other　disc　of　glass；　to　try　if　I　could

finish　it　in　such　a　way　as　to　excel　the　first　one。　　After　nearly

a　year's　work　I　found　that　I　could　only　succeed　in　equalling　it。　

But　then；　during　this　time；　I　had　removed　the　working　of　mirrors

from　mere　chance　to　a　fair　amount　of　certainty。　　By　bringing　my

mathematical　knowledge　to　bear　on　the　subject；　I　had　devised　a

method　of　testing　and　measuring　my　work　which；　I　am　happy　to　say；

has　been　fairly　successful；　and　has　enabled　me　to　produce　the

spherical；　elliptic；　parabolic；　or　hyperbolic　curve　in　my

mirrors；　with　almost　unvarying　success。　　The　study　of　the

practical　working　of　specula　and　lenses　has　also　absorbed　a　good

deal　of　my　spare　time　during　the　last　two　years；　and　the　work

involved　has　been　scarcely　less　difficult。　　Altogether；　I

consider　this　last　year　（1882…3）　to　mark　the　busiest　period　of　my

life。



〃It　will　be　observed　that　I　have　only　given　an　account　of　those

branches　of　study　in　which　I　have　put　to　practical　test　the

deductions　from　theoretical　reasoning。　　I　am　at　present　engaged

on　the　theory　of　the　achromatic　object…glass；　with　regard　to

spherical　chromatisma　subject　upon　which；　I　believe；　nearly　all

our　text…books　are　silent；　but　one　nevertheless　of　vital

importance　to　the　optician。　　I　can　only　proceed　very　slowly　with

it；　on　account　of　having　to　grind　and　figure　lenses　for　every

step　of　the　theory；　to　keep　myself　in　the　right　track；　as　mere

theorizing　is　apt　to　lead　one　very　much　astray；　unless　it　be

checked　by　constant　experiment。　　For　this　particular　subject；

lenses　must　be　ground　firstly　to　spherical；　and　then　to　curves　of

conic　sections；　so　as　to　eliminate　spherical　aberration　from　each

lens；　so　that　it　will　be　observed　that　this　subject　is　not

without　its　difficulties。



〃About　a　month　ago　（September；　1883）；　I　determined　to　put　to　the

test　the　statement　of　some　of　our　theorists；　that　the　surface　of

a　rotating　fluid　is　either　a　parabola　or　a　hyperbola。　　I　found　by

experiment　that　it　is　neither；　but　an　approximation　to　the

tractrix　（a　modification　of　the　catenary）；　if　anything　definite；

as　indeed　one；　on　thinking　over　the　matter；　might　feel　certain　it

would　bethe　tractrix　being　the　curve　of　least　friction。



〃In　astronomy；　I　have　really　done　very　little　beyond　mere

algebraical　working　of　the　fundamental　theorems；　and　a　little

casual　observation　of　the　telescope。　　So　far；　I　must　own；　I　have

taken　more　pleasure　in　the　theory　and　construction　of　the

telescope；　than　in　its　use。〃



Such　is　Samuel　Lancaster's　history　of　the　growth　and　development

of　his　mind。　　I　do　not　think　there　is　anything　more　interesting

in　the　'Pursuit　of　Knowledge　under　Difficulties。'　His　life　has

been　a　gallant　endeavour　to　win　further　knowledge；　though　too

much　at　the　expense　of　a　constitution　originally　delicate。　　He

pursues　science　with　patience　and　determination；　and　wooes　truth

with　the　ardour　of　a　lover。　　Eulogy　of　his　character　would　here

be　unnecessary；　but；　if　he　takes　due　care　of　his　health；　we　shall

hear　more　of　him。＇11＇



More　astronomers　in　humble　life！　　There　seems　to　to　be　no　end　of

them。　　There　must　be　a　great　fascination　in　looking　up　to　the

heavens；　and　seeing　those　wondrous　worlds　careering　in　the

far…off　infinite。　　Let　me　look　back　to　the　names　I　have

introduced　in　this　chapter　of　autobiography。　　First；　there　was　my

worthy　porter　friend　at　Coupar　Angus　station；　enjoying　himself

with　his　three…inch　object…glass。　　Then　there　was　the　shoemaker

and　teacher；　and　eventually　the　first…rate　maker　of　achromatic

instruments。　　Look　also　at　the　persons　whom　he　supplied　with　his

best　telescopes。　　Among　them　we　find　princes；　baronets；

clergymen；　professors；　doctors；　solicitors；　manufacturers；　and

inventors。　　Then　we　come　to　the　portrait　painter；　who　acquired

the　highest　supremacy　in　the　art　of　telescope　making；　then　to　Mr。

Lassell；　the　retired　brewer；　whose　daughters　presented　his

instrument　to　the　nation；　and；　lastly；　to　the　extraordinary　young

schoolmaster　of　Bainbridge；　in　Yorkshire。　　And　now　before　I

conclude　this　last　chapter；　I　have　to　relate　perhaps　the　most

extraordinary　story　of　allthat　of　another　astronomer　in　humble

life；　in　the　person　of　a　slate　counter　at　Port　Penrhyn；　Bangor；

North　Wales。



While　at　Birnam；　I　received　a　letter　from　my　old　friend　the　Rev。

Charles　Wicksteed；　formerly　of　Leeds；　calling　my　attention　to

this　case；　and　inclosing　an　extract　from　the　letter　of　a　young

lady；　one　of　his　correspondents　at　Bangor。　　In　that　letter　she

said：　〃What　you　write　of　Mr。　Christmas　Evans　reminds　me　very　much

of　a　visit　I　paid　a　few　evenings　ago　to　an　old　man　in　Upper

Bangor。　　He　works　on　the　Quay；　but　has　a　very　decided　taste　for

astronomy；　his　leisure　time　being　spent　in　its　study；　with　a

great　part　of　his　earnings。　　I　went　there　with　some　friends　to

see　an　immense　telescope；　which　he　has　made　almost　entirely

without　aid；　preparing　the　glasses　as　far　as　possible　himself；

and　sending　them　away　merely　to　have　their　concavity　changed。　　He

showed　us　all　his　treasures　with　the　greatest　delight；　explaining

in　English；　but　substituting　Welsh　when　at　a　loss。　　He　has

scarcely　ever　been　at　school；　but　has　learnt　English　entirely

from　books。　　Among　other　things　he　showed　us　were　a　Greek

Testament　and　a　Hebrew　Bible；　both　of　which　he　can　read。　　His

largest　telescope；　which　is　several　yards　long；　he　has　named

'Jumbo；'　and　through　it　he　told　us　he　saw　the　snowcap　on　the　pole

of　Mars。　　He　had　another　smaller　telescope；　made　by　himself；　and

had　a　spectroscope　in　process　of　making。　　He　is　now　quite　old；

but　his　delight　in　his　studies　is　still　unbounded　and　unabated。　

It　seems　so　sad　that　he　has　had　no　right　opportunity　for

developing　his　talent。〃



Mr。　Wicksteed　was　very　much　interested　in　the　case；　and　called　my

attention　to　it；　that　I　might　add　the　story　to　my　repertory　of

self…helping　men。　　While　at　York　I　received　a　communication　from

Miss　Grace　Ellis；　the　young　lady　in　question；　informing　me　of　the

name　of　the　astronomerJohn　Jones；　Albert　Street；　Upper

Bangorand　intimating　that　he　would　be　glad　to　see　me　any

evening　after　six。　　As　railways　have　had　the　effect　of　bringing

places　very　close　together　in　point　of　timemaking　of　Britain；

as　it　were；　one　great　townand　as　the　autumn　was　brilliant；　and

the　holiday　season　not　at　an　end；　I　had　no　difficulty　in

diverging　from　my　journey；　and　taking　Bangor　on　my　way　homeward。　

Starting　from　York　in　the　morning；　and　passing　through　Leeds；

Manchester；　and　Chester；　I　reached　Bangor　in　the　afternoon；　and

had　my　first　interview　with　Mr。　Jones　that　very　evening。



I　found　him；　as　Miss　Grace　Ellis　had　described；　active；　vigorous；

and　intelligent；　his　stature　short；　his　face　well…formed；　his

eyes　keen　and　bright。　　I　was　first　shown　into　his　little　parlour

downstairs；　furnished　　with　his　books　and　some　of　his

instruments；　I　was　then　taken　to　his　tiny　room　upstairs；　where　he

had　his　big　reflecting　telescope；　by　means　of　which　he　had　seen；

through　the　chamber　window；　the　snowcap　of　Mars。　　He　is　so　fond

of　philology　that　I　found　he　had　no　fewer　than　twenty…six

dictionari