the life of thomas telford-第69章

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archstones；　being　in　the　form　of　a　segment；　have　the　same　chord；

with　only　13　feet　rise。　　〃This　complex　form；〃　says　Mr。　Telford；

〃converts　each　side　of　the　vault　of　the　arch　into　the　shape　of　the

entrance　of　a　pipe；　to　suit　the　contracted　passage　of　a　fluid；　thus

lessening　the　flat　surface　opposed　to　the　current　of　the　river

whenever　the　tide　or　upland　flood　rises　above　the　springing　of　the

middle　of　the　ellipse；　that　being　at　four　feet　above　low　water；

whereas　the　flood　of　1770　rose　twenty　feet　above　low　water　of　an

ordinary　spring…tide；　which；　when　there　is　no　upland　flood；　rises

only　eight　or　nine　feet。〃*＇1＇　　The　bridge　was　finished　and　opened　in

1828。



＇Image＇　Dean　Bridge；　Edinburgh。



The　last　structures　erected　after　our　engineer's　designs　were　at

Edinburgh　and　Glasgow：　his　Dean　Bridge　at　the　former　place；　and　his

Jamaica　Street　Bridge　at　the　latter；　being　regarded　as　among　his

most　successful　works。　　Since　his　employment　as　a　journeyman　mason

at　the　building　of　the　houses　in　Princes　Street；　Edinburgh；　the　New

Town　had　spread　in　all　directions。　　At　each　visit　to　it　on　his　way

to　or　from　the　Caledonian　Canal　or　the　northern　harbours；　he　had

been　no　less　surprised　than　delighted　at　the　architectural

improvements　which　he　found　going　forward。　　A　new　quarter　had　risen

up　during　his　lifetime；　and　had　extended　northward　and　westward　in

long　lines　of　magnificent　buildings　of　freestone；　until　in　1829　its

further　progress　was　checked　by　the　deep　ravine　running　along　the

back　of　the　New　Town；　in　the　bottom　of　which　runs　the　little　Water

of　Leith。　　It　was　determined　to　throw　a　stone　bridge　across　this

stream；　and　Telford　was　called　upon　to　supply　the　design。　　The　point

of　crossing　the　valley　was　immediately　behind　Moray　Place；　which

stands　almost　upon　its　verge；　the　sides　being　bold；　rocky；　and

finely　wooded。　　The　situation　was　well　adapted　for　a　picturesque

structure；　such　as　Telford　was　well　able　to　supply。　　The　depth　of

the　ravine　to　be　spanned　involved　great　height　in　the　piers；　the

roadway　being　106　feet　above　the　level　of　the　stream。　　The　bridge

was　of　four　arches　of　90　feet　span　each；　and　its　total　length　447

feet；　the　breadth　between　the　parapets　for　the　purposes　of　the

roadway　and　footpaths　being　39　feet。*＇2＇　　It　was　completed　and

opened　in　December；　1831。



But　the　most　important；　as　it　was　the　last；　of　Mr。　Telford's　stone

bridges　was　that　erected　across　the　Clyde　at　the　Broomielaw；

Glasgow。　　Little　more　than　fifty　years　since；　the　banks　of　the　river

at　that　place　were　literally　covered　with　broomand　hence　its

namewhile　the　stream　was　scarcely　deep　enough　to　float　a

herring…buss。　　Now；　the　Broomielaw　is　a　quay　frequented　by　ships　of

the　largest　burden；　and　bustling　with　trade　and　commerce。　　Skill　and

enterprise　have　deepened　the　Clyde；　dredged　away　its　shoals；　built

quays　and　wharves　along　its　banks；　and　rendered　it　one　of　the

busiest　streams　in　the　world；



It　has　become　a　great　river　thoroughfare；　worked　by　steam。　　On　its

waters　the　first　steamboat　ever　constructed　for　purposes　of　traffic

in　Europe　was　launched　by　Henry　Bell　in　1812；　and　the　Clyde　boats

to　this　day　enjoy　the　highest　prestige。



The　deepening　of　the　river　at　the　Broomielaw　had　led　to　a　gradual

undermining　of　the　foundations　of　the　old　bridge；　which　was

situated　close　to　the　principal　landing…place。　　A　little　above　it；

was　an　ancient　overfall　weir；　which　had　also　contributed　to　scour

away　the　foundations　of　the　piers。　　Besides；　the　bridge　was　felt　to

be　narrow；　inconvenient；　and　ill…adapted　for　accommodating　the

immense　traffic　passing　across　the　Clyde　at　that　point。　　It　was；

therefore；　determined　to　take　down　the　old　structure；　and　Build　a

new　one；　and　Mr。　Telford　was　called　upon　to　supply　the　design。

The　foundation　was　laid　with　great　ceremony　on　the　18th　of　March；　1833；

and　the　new　bridge　was　completed　and　opened　on　the　1st　of　January；

1836；　rather　more　than　a　year　after　the　engineer's　death。　　It　is　a

very　fine　work；　consisting　of　seven　arches；　segments　of　circles；

the　central　arch　being　58　feet　6　inches；　the　span　of　the　adjoining

arches　diminishing　to　57　feet　9　inches；　55　feet　6　inches；　and　52

feet　respectively。　　It　is　560　feet　in　length；　with　an　open　waterway

of　389　feet；　and　its　total　width　of　carriageway　and　footpath　is　60

feet；　or　wider；　at　the　time　it　was　built；　than　any　river　bridge　in

the　kingdom。



＇Image＇　Glasgow　Bridge



Like　most　previous　engineers　of　eminencelike　Perry；　Brindley；

Smeaton；　and　RennieMr。　Telford　was　in　the　course　of　his　life

extensively　employed　in　the　drainage　of　the　Fen　districts。　　He　had

been　jointly　concerned　with　Mr。　Rennie　in　carrying　out　the

important　works　of　the　Eau　Brink　Cut；　and　at　Mr。　Rennie's　death　he

succeeded　to　much　of　his　practice　as　consulting　engineer。



It　was　principally　in　designing　and　carrying　out　the　drainage　of

the　North　Level　that　Mr。　Telford　distinguished　himself　in　Fen

drainage。　　The　North　Level　includes　all　that　part　of　the　Great

Bedford　Level　situated　between　Morton's　Leam　and　the　river　Welland；

comprising　about　48；000　acres　of　land。　　The　river　Nene；　which　brings

down　from　the　interior　the　rainfall　of　almost　the　entire　county　of

Northampton；　flows　through　nearly　the　centre　of　the　district。

In　some　places　the　stream　is　confined　by　embankments；　in　others　it

flows　along　artificial　outs；　until　it　enters　the　great　estuary　of

the　Wash；　about　five　miles　below　Wisbeach。　　This　town　is　situated　on

another　river　which　flows　through　the　Level；　called　the　Old　Nene。

Below　the　point　of　junction　of　these　rivers　with　the　Wash；　and

still　more　to　seaward；　was　South　Holland　Sluice；　through　which　the

waters　of　the　South　Holland　Drain　entered　the　estuary。　　At　that

point　a　great　mass　of　silt　had　accumulated；　which　tended　to　choke

up　the　mouths　of　the　rivers　further　inland；　rendering　their

navigation　difficult　and　precarious；　and　seriously　interrupting　the

drainage　of　the　whole　lowland　district　traversed　by　both　the　Old

and　New　Nene。　　Indeed　the　sands　were　accumulating　at　such　a　rate；

that　the　outfall　of　the　Wisbeach　River　threatened　to　become

completely　destroyed。



Such　being　the　state　of　things；　it　was　determined　to　take　the

opinion　of　some　eminent　engineer；　and　Mr。　Rennie　was　employed　to

survey　the　district　and　recommend　a　measure　for　the　remedy　of　these

great　evils。　　He　performed　this　service　in　his　usually　careful　and

masterly　manner；　but　as　the　method　which　he　proposed；　complete

though　it　was；　would　have　seriously　interfered　with　the　trade　of

Wisbeach；　by　leaving　it　out　of　the　line　of　navigation　and　drainage

which　he　proposed　to　open　up；　the　corporation　of　that　town

determined　to　employ　another　engineer；　and　Mr　Telford　was　selected

to　examine　and　report　upon　the　whole　subject；　keeping　in　view　the

improvement　of　the　river　immediately　adjacent　to　the　town　of

Wisbeach。



Mr。　Telford　confirmed　Mr。　Rennie's　views　to　a　large　extent；　more

especially　with　reference　to　the　construction　of　an　entirely　new

outfall；　by　making　an　artificial　channel　from　Kindersleys　Cut　to

Crab…Hole　Eye　anchorage；　by　which　a　level　lower　by　nearly　twelve

feet　would　be　secured　for　the　outfall　waters；　but　he　preferred

leaving　the　river　open　to　the　tide　as　high　as　Wisbeach；　rather　than

place　a　lock　with　draw…doors　at　Lutton　Leam　Sluice；　as　had　been

proposed　by　Mr。　Rennie。　　He　also　suggested　that　the　acute　angle　at

the　Horseshoe　be　cut　off　and　the　river　deepened　up　to　the　bridge　at

Wisbeach；　making　a　new　cut　along　the　bank　on　the　south　side　of　the

town；　which　should　join　the　river　again　immediately　above　it；

thereby　converting　the　intermediate　space；　by　draw…doors　and　the

usual　contrivances；　into　a　floating　dock。　　Though　this　plan　was

approved　by　the　parties　interested　in　the　drainage；　to　Telford's

great　mortification　it　was　opposed　by　the　corporation　of　Wisbeach；

and　like　so　many　other　excellent　schemes　for　the　improvement　of　the

Fen　districts；　it　eventually　f