men of invention and industry-第17节

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year　after　his　death。　　No　Life　of　him　has　since　appeared。　　Had　he

been　a　destructive　hero；　and　fought　battles　by　land　or　sea；　we

should　have　had　biographies　of　him　without　end。　　But　he　pursued　a

more　peaceful　and　industrious　course。　　His　discovery　conferred　an

incalculable　advantage　on　navigation；　and　enabled　innumerable

lives　to　be　saved　at　sea；　it　also　added　to　the　domains　of　science

by　its　more　exact　measurement　of　time。　　But　his　memory　has　been

suffered　to　pass　silently　away；　without　any　record　being　left　for

the　benefit　and　advantage　of　those　who　have　succeeded　him。　　The

following　memoir　includes　nearly　all　that　is　known　of　the　life

and　labours　of　John　Harrison。



He　was　born　at　Foulby；　in　the　parish　of　Wragby；　near　Pontefract；

Yorkshire；　in　March；　1693。　　His　father；　Henry　Harrison；　was

carpenter　and　joiner　to　Sir　Rowland　Winn；　owner　of　the　Nostell

Priory　estate。　　The　present　house　was　built　by　the　baronet　on　the

site　of　the　ancient　priory。　　Henry　Harrison　was　a　sort　of

retainer　of　the　family；　and　long　continued　in　their　Service。



Little　is　known　of　the　boy's　education。　　It　was　certainly　of　a

very　inferior　description。　　Like　George　Stephenson；　Harrison

always　had　a　great　difficulty　in　making　himself　understood；

either　by　speech　or　writing。　　Indeed；　every　board…school　boy　now

receives　a　better　education　than　John　Harrison　did　a　hundred　and

eighty　years　ago。　　But　education　does　not　altogether　come　by

reading　and　writing。　　The　boy　was　possessed　of　vigorous　natural

abilities。　　He　was　especially　attracted　by　every　machine　that

moved　upon　wheels。　　The　boy　was　'father　to　the　man。'　When　six

years　old；　and　lying　sick　of　small…pox；　a　going　watch　was　placed

upon　his　pillow；　which　afforded　him　infinite　delight。



When　seven　years　old　he　was　taken　by　his　father　to　Barrow；　near

Barton…on…Humber；　where　Sir　Rowland　Winn　had　another　residence

and　estate。　　Henry　Harrison　was　still　acting　as　the　baronet's

carpenter　and　joiner。　　In　course　of　time　young　Harrison　joined

his　father　in　the　workshop；　and　proved　of　great　use　to　him。　　His

opportunities　for　acquiring　knowledge　were　still　very　few；　but　he

applied　his　powers　of　observation　and　his　workmanship　upon　the

things　which　were　nearest　him。　　He　worked　in　wood；　and　to　wood　he

first　turned　his　attention。



He　was　still　fond　of　machines　going　upon　wheels。　　He　had　enjoyed

the　sight　of　the　big　watch　going　upon　brass　wheels　when　he　was　a

boy；　but；　now　that　he　was　a　workman　in　wood；　he　proposed　to　make

an　eight…day　clock；　with　wheels　of　this　material。　　He　made　the

clock　in　1713；　when　he　was　twenty　years　old；＇4＇　so　that　he　must

have　made　diligent　use　of　his　opportunities。　　He　had　of　course

difficulties　to　encounter；　and　nothing　can　be　accomplished

without　them；　for　it　is　difficulties　that　train　the　habits　of

application　and　perseverance。　　But　he　succeeded　in　making　an

effective　clock；　which　counted　the　time　with　regularity。　　This

clock　is　still　in　existence。　　It　is　to　be　seen　at　the　Museum　of

Patents；　South　Kensington；　and　when　we　visited　it　a　few　months

ago　it　was　going；　and　still　marking　the　moments　as　they　passed。　

It　is　contained　in　a　case　about　six　feet　high；　with　a　glass

front；　showing　a　pendulum　and　two　weights。　　Over　the　clock　is　the

following　inscription：



〃This　clock　was　made　at　Barrow；　Lincolnshire；　in　the　year　1715；　

by　John　Harrison；　celebrated　as　the　inventor　of　a　nautical

timepiece；　　or　chronometer；　which　gained　the　reward　of　20；000L。；

offered　by　the　Board　of　Longitude；　A。D。　1767。



〃This　clock　strikes　the　hour；　indicates　the　day　of　the　month；　and

with　one　exception　（the　escapement）　the　wheels　are　entirely　made

of　wood。〃



This；　however；　was　only　a　beginning。　　Harrison　proceeded　to　make

better　clocks；　and　then　he　found　it　necessary　to　introduce　metal；

which　was　more　lasting。　　He　made　pivots　of　brass；　which　moved

more　conveniently　in　sockets　of　wood　with　the　use　of　oil。　　He

also　caused　the　teeth　of　his　wheels　to　run　against　cylindrical

rollers　of　wood；　fixed　by　brass　pins；　at　a　proper　distance　from

the　axis　of　the　pinions；　and　thus　to　a　considerable　extent

removed　the　inconveniences　of　friction。



In　the　meantime　Harrison　eagerly　improved　every　incident　from

which　he　might　derive　further　information。　　There　was　a　clergyman

who　came　every　Sunday　to　the　village　to　officiate　in　the

neighbourhood；　and　having　heard　of　the　sedulous　application　of

the　young　carpenter；　he　lent　him　a　manuscript　copy　of　Professor

Saunderson's　discourses。　　That　blind　professor　had　prepared

several　lectures　on　natural　philosophy　for　the　use　of　his

students；　though　they　were　not　intended　for　publication。　　Young

Harrison　now　proceeded　to　copy　them　out；　together　with　the

diagrams。　　Sometimes；　indeed；　he　spent　the　greater　part　of　the

night　in　writing　or　drawing。



As　part　of　his　business；　he　undertook　to　survey　land；　and　to

repair　clocks　and　watches；　besides　carrying　on　his　trade　of　a

carpenter。　　He　soon　obtained　a　considerable　knowledge　of　what　had

been　done　in　clocks　and　watches；　and　was　able　to　do　not　only　what

the　best　professional　workers　had　done；　but　to　strike　out

entirely　new　lights　in　the　clock　and　watch…making　business。　　He

found　out　a　method　of　diminishing　friction　by　adding　a　joint　to

the　pallets　of　the　pendulum；　whereby　they　were　made　to　work　in

the　nature　of　rollers　of　a　large　radius；　without　any　sliding；　as

usual；　upon　the　teeth　of　the　wheel。　　He　constructed　a　clock　on

the　recoiling　principle；　which　went　perfectly；　and　never　lost　a

minute　within　fourteen　years。　　Sir　Edmund　Denison　Beckett　says

that　he　invented　this　method　in　order　to　save　himself　the　trouble

of　going　so　frequently　to　oil　the　escapement　of　a　turret　clock；

of　which　he　had　charge；　though　there　were　other　influences　at

work　besides　this。



But　his　most　important　invention；　at　this　early　period　of　his

life；　was　his　compensation　pendulum。　　Every　one　knows　that　metals

expand　with　heat　and　contract　by　cold。　　The　pendulum　of　the　clock

therefore　expanded　in　summer　and　contracted　in　winter；　thereby

interfering　with　the　regular　going　of　the　clock。　　Huygens　had　by

his　cylindrical　checks　removed　the　great　irregularity　arising

from　the　unequal　lengths　of　the　oscillations；　but　the　pendulum

was　affected　by　the　tossing　of　a　ship　at　sea；　and　was　also

subject　to　a　variation　in　weight；　depending　on　the　parallel　of

latitude。　　Graham；　the　well…known　clock…maker；　invented　the

mercurial　compensation　pendulum；　consisting　of　a　glass　or　iron

jar　filled　with　quicksilver　and　fixed　to　the　end　of　the　pendulum

rod。　　When　the　rod　was　lengthened　by　heat；　the　quicksilver　and

the　jar　which　contained　it　were　simultaneously　expanded　and

elevated；　and　the　centre　of　oscillation　was　thus　continued　at　the

same　distance　from　the　point　of　suspension。



But　the　difficulty；　to　a　certain　extent；　remained　unconquered

until　Harrison　took　the　matter　in　hand。　　He　observed　that　all

rods　of　metal　do　not　alter　their　lengths　equally　by　heat；　or；　on

the　contrary；　become　shorter　by　cold；　but　some　more　sensibly　than

others。　　After　innumerable　experiments　Harrison　at　length

composed　a　frame　somewhat　resembling　a　gridiron；　in　which　the

alternate　bars　were　of　steel　and　of　brass；　and　so　arranged　that

those　which　expanded　the　most　were　counteracted　by　those　which

expanded　the　least。　　By　this　means　the　pendulum　contained　the

power　of　equalising　its　own　action；　and　the　centre　of　oscillation

continued　at　the　same　absolute　distance　from　the　point　of

suspension　through　all　the　variations　of　heat　and　cold　during　the

year。＇5＇



Thus　by　the　year　1726；　when　he　was　only　thirty…three　years　old；

Harrison　had　furnished　himself　with　two　compensation　clocks；　in

which　all　the　irregularities　to　which　these　machines　were

subject；　were　either　removed　or　so　happily　balanced；　one　metal

against　the　other；　that　the　two　clocks　kept　time　together　in

different　parts　of　his　house；　without　the　variation　of　more　than

a　single　second　in　the　month。　　One　of　them；　indeed；　which　he　kept

by　him　for　his　own　use；　and　constantly　compared　with　a　fixed

star；　did　not　vary　so　much　as　one　whole　minute　during　the　ten

years　that　he　continued　in　the　country　after　finishing　the

machine。＇6＇



Living；　as　he　did；　not　far　from　the　sea；　Harrison　next

endeavoured　to　arrange　his　timekeeper　for　purposes　of　navigation。



He　tried　his　clock　in　a　vessel　belonging　to　Barton…on…Humber；　but

his　compensating　pendulum　could　there　be　of　comparatively　little

use；　for　it　was　liable　to　be　tossed　hither　or　thither　by　the

sudden　motions　of　the　ship。　　He　found　it　necessary；　therefore；　to

mount　a　chronometer；　or　portable　timekeeper；　which　might　be　taken

from　place　to　place；　and　subjected　to　the　violent　and　irregular

motion　of　a　ship　at　sea；　without　affecting　its　rate　of　going。　　It

was　evident　to　him　that　the　first　mover　must　be　changed　from　a

weight　and　pendulum　to　a　spring　wound　up　and　a　compensating

balance。



He　n