the life of thomas telford-第49章

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！



sides；　until　it　seemed　to　die　away　along　the　shores　in　the　distance。

Three　foolhardy　workmen；　excited　by　the　day's　proceedings；　had　the

temerity　to　scramble　along　the　upper　surface　of　the　chainwhich

was　only　nine　inches　wide　and　formed　a　curvature　of　590　feetfrom

one　side　of　the　Strait　to　the　other！*＇2＇　　Far　different　were　the

feelings　of　the　engineer　who　had　planned　this　magnificent　work。

Its　failure　had　been　predicted；　and；　like　Brindley's　Barton　Viaduct；

it　had　been　freely　spoken　of　as　a　〃castle　in　the　air。〃　　Telford　had；

it　is　true；　most　carefully　tested　every　part　by　repeated　experiment；

and　so　conclusively　proved　the　sufficiency　of　the　iron　chains　to

bear　the　immense　weight　they　would　have　to　support；　that　he　was

thoroughly　convinced　as　to　the　soundness　of　his　principles　of

construction；　and　satisfied　that；　if　rightly　manufactured　and

properly　put　together；　the　chains　would　hold；　and　that　the　piers

would　sustain　them。　　Still　there　was　necessarily　an　element　of

uncertainty　in　the　undertaking。　　It　was　the　largest　structure　of

the　kind　that　had　ever　been　attempted。　　There　was　the　contingency

of　a　flaw　in　the　iron；　some　possible　scamping　in　the　manufacture；

some　little　point　which；　in　the　multiplicity　of　details　to　be

attended　to；　he　might　have　overlooked；　or　which　his　subordinates

might　have　neglected。　　It　was；　indeed；　impossible　but　that　he

should　feel　intensely　anxious　as　to　the　result　of　the　day's

operations。　　Mr。　Telford　afterwards　stated　to　a　friend；　only　a　few

months　before　his　death；　that　for　some　time　previous　to　the　opening

of　the　bridge；　his　anxiety　was　so　great　that　he　could　scarcely

sleep；　and　that　a　continuance　of　that　condition　must　have　very　soon

completely　undermined　his　health。　　We　are　not；　therefore；　surprised

to　learn　that　when　his　friends　rushed　to　congratulate　him　on　the

result　of　the　first　day's　experiment；　which　decisively　proved　the

strength　and　solidity　of　the　bridge；　they　should　have　found　the

engineer　on　his　knees　engaged　in　prayer。　　A　vast　load　had　been

taken　off　his　mind；　the　perilous　enterprise　of　the　day　had　been

accomplished　without　loss　of　life；　and　his　spontaneous　act　was

thankfulness　and　gratitude。



＇Image＇　Menai　Bridge



The　suspension　of　the　remaining　fifteen　chains　was　accomplished

without　difficulty。　　The　last　was　raised　and　fixed　on　the　9th　of

July；　1825；　when　the　entire　line　was　completed。　　On　fixing　the　final

bolt；　a　band　of　music　descended　from　the　top　of　the　suspension　pier

on　the　Anglesea　side　to　a　scaffolding　erected　over　the　centre　of

the　curved　part　of　the　chains；　and　played　the　National　Anthem

amidst　the　cheering　of　many　thousand　persons　assembled　along　the

shores　of　the　Strait：　while　the　workmen　marched　in　procession　along

the　bridge；　on　which　a　temporary　platform　had　been　laid；　and　the

St。　David　steam…packet　of　Chester　passed　under　the　chains　towards

the　Smithy　Rocks　and　back　again；　thus　re…opening　the　navigation　of

the　Strait。



In　August　the　road　platform　was　commenced；　and　in　September　the

trussed　bearing　bars　were　all　suspended。　　The　road　was　constructed

of　timber　in　a　substantial　manner；　the　planking　being　spiked

together；　with　layers　of　patent　felt　between　the　planks；　and　the

carriage　way　being　protected　by　oak　guards　placed　seven　feet　and　a

half　apart。　　Side　railings　were　added；　the　toll…houses　and

approach…roads　were　completed　by　the　end　of　the　year；　and　the

bridge　was　opened　for　public　traffic　on　Monday；　the　30th　of　January；

1826；　when　the　London　and　Holyhead　mailcoach　passed　over　it　for　the

first　time；　followed　by　the　Commissioners　of　the　Holyhead　roads；

the　engineer；　several　stage…coaches；　and　a　multitude　of　private

persons　too　numerous　to　mention。



We　may　briefly　add　a　few　facts　as　to　the　quantities　of　materials

used；　and　the　dimensions　of　this　remarkable　structure。　　The　total

weight　of　iron　was　2187　tons；　in　33；265　pieces。　　The　total　length　of

the　bridge　is　1710　feet；　or　nearly　a　third　of　a　mile；　the　distance

between　the　points　of　suspension　of　the　main　bridge　being　579　feet。

The　total　sum　expended　by　Government　in　its　erection；　including　the

embankment　and　about　half　a　mile　of　new　line　of　road　on　the

Caernarvon　side；　together　with　the　toll…houses；　was　120；000L。



Notwithstanding　the　wonders　of　the　Britannia　Bridge　subsequently

erected　by　Robert　Stephenson　for　the　passage　across　the　same　strait

of　the　Chester　and　Holyhead　Railway；　the　Menai　Bridge　of　Telford　is

by　far　the　most　picturesque　object。　　〃Seen　as　I　approached　it；〃　says

Mr。　Roscoe；　〃in　the　clear　light　of　an　autumnal　sunset；　which　threw

an　autumnal　splendour　on　the　wide　range　of　hills　beyond；　and　the

sweep　of　richly　variegated　groves　and　plantations　which　covered

their　basethe　bright　sun；　the　rocky　picturesque　foreground；

villas；　spires；　and　towers　here　and　there　enlivening　the　prospect

the　Menai　Bridge　appeared　more　like　the　work　of　some　great　magician

than　the　mere　result　of　man's　skill　and　industry。〃



＇Image＇　Conway　Suspension　Bridge



Shortly　after　the　Menai　Bridge　was　begun；　it　was　determined　by　the

Commissioners　of　the　Holyhead　road　that　a　bridge　of　similar　design

should　be　built　over　the　estuary　of　the　Conway；　immediately

opposite　the　old　castle　at　that　place；　and　which　had　formerly　been

crossed　by　an　open　ferry　boat。　　The　first　stone　was　laid　on　the

3rd　of　April；　1822；　and　the　works　having　proceeded　satisfactorily；

the　bridge　and　embankment　approaching　it　were　completed　by　the　summer

of　1826。　　But　the　operations　being　of　the　same　kind　as　those

connected　with　the　larger　structure　above　described；　though　of　a

much　less　difficult　character；　it　is　unnecessary　to　enter　into　any

details　as　to　the　several　stages　of　its　construction。　　In　this

bridge　the　width　between　the　centres　of　the　supporting　towers　is

327　feet；　and　the　height　of　the　under　side　of　the　roadway　above

high　water　of　spring　tides　only　15　feet。　　The　heaviest　work　was　an

embankment　as　its　eastern　approach；　2015　feet　in　length　and　about

300　feet　in　width　at　its　highest　part。



It　will　be　seen；　from　the　view　of　the　bridge　given　on　the　opposite

page；　that　it　is　a　highly　picturesque　structure；　and　combines；

with　the　estuary　which　it　crosses；　and　the　ancient　castle　of　Conway；

in　forming　a　landscape　that　is　rarely　equalled。



Footnotes　for　Chapter　XII。



*＇1＇　In　an　article　in　the　'Edinburgh　Review；'　No。　exli。；　from　the

pen　of　Sir　David　Brewster；　the　writer　observes：〃Mr。　Telford's

principle　of　suspending　and　laying　down　from　above　the　centering　of

stone　and　iron　bridges　is；　we　think；　a　much　more　fertile　one　than

even　he　himself　supposed。　　With　modifications；　by　no　means

considerable；　and　certainly　practicable；　it　appears　to　us　that　the

voussoirs　or　archstones　might　themselves　be　laid　down　from　above；

and　suspended　by　an　appropriate　mechanism　till　the　keystone　was

inserted。　　If　we　suppose　the　centering　in　Mr。　Telford's　plan　to　be

of　iron；　this　centering　itself　becomes　an　iron　bridge；　each　rib　of

which　is　composed　of　ten　pieces　of　fifty　feet　each；　and　by

increasing　the　number　of　suspending　chains；　these　separate　pieces

or　voussoirs　having　been　previously　joined　together；　either

temporarily　or　permanently；　by　cement　or　by　clamps；　might　be　laid

into　their　place；　and　kept　there　by　a　single　chain　till　the　road

was　completed。　　The　voussoirs；　when　united；　might　be　suspended　from

a　general　chain　across　the　archway；　and　a　platform　could　be　added

to　facilitate　the　operations。〃　　This　is　as　nearly　as　possible　the

plan　afterwards　revived　by　Mr。　Brunel；　and　for　the　originality　of

which；　we　believe；　he　has　generally　the　credit；　though　it　clearly

belongs　to　Telford。



*＇2＇　A　correspondent　informs　us　of　a　still　more　foolhardy　exploit

performed　on　the　occasion。　　He　says；　〃Having　been　present；　as　a　boy

from　Bangor　grammar　school；　on　the　26th　of　April；　when　the　first

chain　was　carried　across；　an　incident　occurred　which　made　no　small

impression　on　my　mind　at　the　time。　　After　the　chain　had　reached　its

position；　a　cobbler　of　the　neighbourhood　crawled　to　the　centre　of

the　curve；　and　there　finished　a　pair　of　shoes；　when；　having

completed　his　task；　he　returned　in　safety　to　the　Caernarvon　side！

I　need　not　say　that　we　schoolboys　appreciated　his　feat　of

foolhardiness　far　more　than　Telford's　master　work。〃





CHAPTER　XIII。



DOCKS；　DRAINAGE；　AND　BRIDGES。



It　will　have　been　observed；　from　the　preceding　narrative；　how　much

had　already　been　accomplished　by　skill　and　industry　towards　opening

up　the　material　resources　of　the　kingdom。　　The　stages　of　improvement

which　we　have　recorded　indeed　exhibit　a　measure　of　the　vital　energy

which　has　from　time　to　time　existed　in　the　nation。　　In　the　earlier

periods　of　engineering　history；　the　war　of　man　was　with　nature。

The　sea　was　held　back　by　embankments。　　The　Thames；　instead　of　being

allowed　to　overspread　the　wide　marshes　on　either　bank；　was　confined

within　limited　bounds；　by　which　the　navigable　depth　of　its　channel

was　increased；　at　the　same　time　that　a　wide　extent　of　land　was

rendered　available　for　agriculture。



In　those　early　days；　the　great　object　was　to　render　the　land　more

habitable；　comfortable；　and　productive。　　Marshes　were　reclaimed；　and

wastes　subdued。　　But　so　long　as　the　country　remained　comparatively

closed　against　communication；　and　intercourse　was　restricted　by　the

want　of　bridges　and　roads；　improvement　was　extremely　slow。

For；　while　roads　are　the　consequence　of　civilisation；　they　are　also

among　its　most　influential　causes。　　We　have　seen　even　the　blind

Metcalf　acting　as　an　effective　instrument　of　progress　in　the

northern　counties　by　the　formation　of　long　lines　of　road。　　Brindley

and　the　Duke　of　Bridgewater　carried　on　the　work　in　the　same

districts；　and　conferred　upon　the　north　and　north…west　of　England

the　blessings　of　cheap　and　effective　water　communication。　　Smeaton

followed　and　carried　out　similar　undertakings　in　still　remoter

places；　joining　the　east　and　west　coasts　of　Scotland　by　the　Forth

and　Clyde　Canal；　and　building　bridges　in　the　far　north。　　Rennie　made

harbours；　built　bridges；　and　hewed　out　docks　for　shipping；　the

increase　in　which　had　kept　pace　with　the　growth　of　our　home　and

foreign　trade。　　He　was　followed　by　Telford；　whose　long　and　busy

life；　as　we　have　seen；　was　occupied　in　building　bridges　and　making

roads　in　all　directions；　in　districts　of　the　country　formerly

inaccessible；　and　therefore　comparatively　barbarous。　　At　length　the

wildest　districts　of　the　Highlands　and　the　most　rugged　mountain

valleys　of　North　Wales　were　rendered　as　easy　of　access　as　the

comparatively　level　counties　in　the　immediate　neighbourhood　of　the

metropolis。



During　all　this　while；　the　wealth　and　industry　of　the　country　had

been　advancing　with　rapid　strides。　　London　had　grown　in　population

and　importance。　　Many　improvements　had　been　effected　in　the　river；

But　the　dock　accommodation　was　still　found　insufficient；　and；