men of invention and industry-第20节

按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！



according　to　my　reckoning　（and　others）；　ought　to　have　been　the

Start；　but；　before　we　knew　what　land　it　was；　John　Harrison

declared　to　me　and　the　rest　of　the　ship's　company　that；　according

to　his　observations　with　his　machine；　it　ought　to　be　the

Lizardthe　which；　indeed；　it　was　found　to　be；　his　observation

showing　the　ship　to　be　more　west　than　my　reckoning；　above　one

degree　and　twenty…six　miles；〃that　is；　nearly　ninety　miles　out

of　its　course！



Six　days　laterthat　is；　on　the　30th　Junethe　Board　of　Longitude

met；　when　Harrison　was　present；　and　produced　the　chronometer　with

which　he　had　made　the　voyage　to　Lisbon　and　back。　　The　minute

states：　　〃Mr。　John　Harrison　produced　a　new　invented　machine；　in

the　nature　of　clockwork；　whereby　he　proposes　to　keep　time　at　sea

with　more　exactness　than　by　any　other　instrument　or　method

hitherto　contrived；　in　order　to　the　discovery　of　the　longitude　at

sea；　and　proposes　to　make　another　machine　of　smaller　dimensions

within　the　space　of　two　years；　whereby　he　will　endeavour　to

correct　some　defects　which　he　hath　found　in　that　already

prepared；　so　as　to　render　the　same　more　perfect；　which　machine；

when　completed；　he　is　desirous　of　having　tried　in　one　of　His

Majesty's　ships　that　shall　be　bound　to　the　West　Indies；　but　at

the　same　time　represented　that　he　should　not　be　able；　by　reason

of　his　necessitous　circumstances；　to　go　on　and　finish　his　said

machine　without　assistance；　and　requested　that　he　may　be

furnished　with　the　sum　of　500L。；　to　put　him　in　a　capacity　to

perform　the　same；　and　to　make　a　perfect　experiment　thereof。〃



The　result　of　the　meeting　was　that　500L。　was　ordered　to　be　paid

to　Harrison；　one　moiety　as　soon　as　convenient；　and　the　other　when

he　has　produced　a　certificate　from　the　captain　of　one　of　His

Majesty's　ships　that　he　has　put　the　machine　on　board　into　the

captain's　possession。　　Mr。　George　Graham；　who　was　consulted；

urged　that　the　Commissioners　should　grant　Harrison　at　least

1000L。；　but　they　only　awarded　him　half　the　sum；　and　at　first　only

a　moiety　of　the　amount　voted。　　At　the　recommendation　of　Lord

Monson；　who　was　present；　Harrison　accepted　the　250L。　as　a　help

towards　the　heavy　expenses　which　he　had　already　incurred；　and　was

again　about　to　incur；　in　perfecting　the　invention。　　He　was

instructed　to　make　his　new　chronometer　of　less　dimensions；　as　the

one　exhibited　was　cumbersome　and　heavy；　and　occupied　too　much

space　on　board。



He　accordingly　proceeded　to　make　his　second　chronometer。　　It

occupied　a　space　of　only　about　half　the　size　of　the　first。　　He

introduced　several　improvements。　　He　lessened　the　number　of　the

wheels；　and　thereby　diminished　friction。　　But　the　general

arrangement　remained　the　same。　　This　second　machine　was　finished

in　1739。　　It　was　more　simple　in　its　arrangement；　and　less

cumbrous　in　its　dimensions。　　It　answered　even　better　than　the

first；　and　though　it　was　not　tried　at　sea　its　motions　were

sufficiently　exact　for　finding　the　longitude　within　the　nearest

limits　proposed　by　Act　of　Parliament。



Not　satisfied　with　his　two　machines；　Harrison　proceeded　to　make　a

third。　　This　was　of　an　improved　construction；　and　occupied　still

less　space；　the　whole　of　the　machine　and　its　apparatus　standing

upon　an　area　of　only　four　square　feet。　　It　was　in　such

forwardness　in　January；　1741；　that　it　was　exhibited　before　the

Royal　Society；　and　twelve　of　the　most　prominent　members　signed　a

certificate　of　〃its　great　and　excellent　use；　as　well　for

determining　the　longitude　at　sea　as　for　correcting　the　charts　of

the　coasts。〃　　The　testimonial　concluded：　　〃We　do　recommend　Mr。

Harrison　to　the　favour　of　the　Commissioners　appointed　by　Act　of

Parliament　as　a　person　highly　deserving　of　such　further

encouragement　and　assistance　as　they　shall　judge　proper　and

sufficient　to　finish　his　third　machine。〃　　The　Commissioners

granted　him　a　further　sum　of　500L。　　Harrison　was　already　reduced

to　necessitous　circumstances　by　his　continuous　application　to　the

improvement　of　the　timekeepers。　　He　had　also　got　into　debt；　and

required　further　assistance　to　enable　him　to　proceed　with　their

construction；　but　the　Commissioners　would　only　help　him　by

driblets。



Although　Harrison　had　promised　that　the　third　machine　would　be

ready　for　trial　on　August　1；　1743；　it　was　not　finished　for　some

years　later。　　In　June；　1746；　we　find　him　again　appearing　before

the　Board；　asking　for　further　assistance。　　While　proceeding　with

his　work　he　found　it　necessary　to　add　a　new　spring；　〃having　spent

much　time　and　thought　in　tempering　them。〃　　Another　500L。　was

voted　to　enable　him　to　pay　his　debts；　to　maintain　himself　and

family；　and　to　complete　his　chronometer。



Three　years　later　he　exhibited　his　third　machine　to　the　Royal

Society；　and　on　the　30th　of　November；　1749；　he　was　awarded　the

Gold　Medal　for　the　year。　　In　presenting　it；　Mr。　Folkes；　the

President；　said　to　Mr。　Harrison；　〃I　do　here；　by　the　authority　and

in　the　name　of　the　Royal　Society　of　London　for　the　improving　of

natural　knowledge；　present　you　with　this　small　but　faithful　token

of　their　regard　and　esteem。　　I　do；　in　their　name　congratulate　you

upon　the　successes　you　have　already　had；　and　I　most　sincerely

wish　that　all　your　future　trials　may　in　every　way　prove

answerable　to　these　beginnings；　and　that　the　full　accomplishment

of　your　great　undertaking　may　at　last　be　crowned　with　all　the

reputation　and　advantage　to　yourself　that　your　warmest　wishes　may

suggest；　and　to　which　so　many　years　so　laudably　and　so　diligently

spent　in　the　improvement　of　those　talents　which　God　Almighty　has

bestowed　upon　you；　will　so　justly　entitle　your　constant　and

unwearied　perseverance。〃



Mr。　Folkes；　in　his　speech；　spoke　of　Mr。　Harrison　as　〃one　of　the

most　modest　persons　he　had　ever　known。　　In　speaking；〃　he

continued；　〃of　his　own　performances；　he　has　assured　me　that；　from

the　immense　number　of　diligent　and　accurate　experiments　he　has

made；　and　from　the　severe　tests　to　which　he　has　in　many　ways　put

his　instrument；　he　expects　he　shall　be　able　with　sufficient

certainty；　through　all　the　greatest　variety　of　seasons　and　the

most　irregular　motions　of　the　sea；　to　keep　time　constantly；

without　the　variation　of　so　much　as　three　seconds　in　a　week；　a

degree　of　exactness　that　is　astonishing　and　even　stupendous；

considering　the　immense　number　of　difficulties；　and　those　of　very

different　sorts；　which　the　author　of　these　inventions　must　have

had　to　encounter　and　struggle　withal。〃



Although　it　is　common　enough　now　to　make　first…rate

chronometers　sufficient　to　determine　the　longitude　with　almost

perfect　accuracy　in　every　clime　of　the　worldit　was　very

different　at　that　time；　when　Harrison　was　occupied　with　his

laborious　experiments。　　Although　he　considered　his　third　machine

to　be　the　ne　plus　ultra　of　scientific　mechanism；　he　nevertheless

proceeded　to　construct　a　fourth　timepiece；　in　the　form　of　a

pocket　watch　about　five　inches　in　diameter。　　He　found　the

principles　which　he　had　adopted　in　his　larger　machines　applied

equally　well　in　the　smaller；　and　the　performances　of　the　last

surpassed　his　utmost　expectations。　　But　in　the　meantime；　as　his

third　timekeeper　was；　in　his　opinion；　sufficient　to　supply　the

requirements　of　the　Board　of　Longitude　as　respected　the　highest

reward　offered；　he　applied　to　the　Commissioners　for　leave　to　try

that　instrument　on　board　a　royal　ship　to　some　port　in　the　West

Indies；　as　directed　by　the　statute　of　Queen　Anne。



Though　Harrison's　third　timekeeper　was　finished　about　the　year

1758；　it　was　not　until　March　12；　1761；　that　he　received　orders

for　his　son　William　to　proceed　to　Portsmouth；　and　go　on　board　the

Dorsetshire　man…of…war；　to　proceed　to　Jamaica。　　But　another

tedious　delay　occurred。　　The　ship　was　ordered　elsewhere；　and

William　Harrison；　after　remaining　five　months　at　Portsmouth；

returned　to　London。　　By　this　time；　John　Harrison　had　finished　his

fourth　timepiecethe　small　one；　in　the　form　of　a　watch。　　At

length　William　Harrison　set　sail　with　this　timekeeper　from

Portsmouth　for　Jamaica；　on　November　18th；　1761；　in　the　Deptford

man…of…war。　　The　Deptford　had　forty…three　ships　in　convoy；　and

arrived　at　Jamaica　on　the　l9th　of　January；　1762；　three　days

before　the　Beaver；　another　of　His　Majesty's　ships…of…war；　which

had　sailed　from　Portsmouth　ten　days　before　the　Deptford；　but　had

lost　her　reckoning　and　been　deceived　in　her　longitude；　having

trusted　entirely　to　the　log。　　Harrison's　timepiece　had　corrected

the　log　of　the　Deptford　to　the　extent　of　three　degrees　of

longitude；　whilst　several　of　the　ships　in　the　fleet　lost　as　much

as　five　degrees！　　This　shows　the　haphazard　way　in　which

navigation　was　conducted　previous　to　the　invention　of　the　marine

chronometer。



When　the　Deptford　arrived　at　Port　Royal；　Jamaica；　the　timekeeper

was　found　to　be　only　five　and　one　tenth　seconds　in　error；　and

during　the　voyage　of　four　months；　on　its　return　to　Portsmouth　on

March　26th；　1762；　it　was　found　（after　allow