introduce a key…stone of cast iron； occupying only a few feet at
the crown of the arch。 This plan was； however； given up as
unsuitable； and another； with the entire arch of cast iron； was
designed under the superintendence of Mr。 Darby。 The castings were
made in the works at Coalbrookdale； and the bridge was erected at a
point where the banks were of considerable height on both sides of
the river。 It was opened for traffic in 1779； and continues a most
serviceable structure to this day； giving the name to the town of
Ironbridge； which has sprung up in its immediate vicinity。 The
bridge consists of one semicircular arch； of 100 feet span； each of
the great ribs consisting of two pieces only。 Mr。 Robert Stephenson
has said of the structure〃If we consider that the manipulation of
cast iron was then completely in its infancy； a bridge of such
dimensions was doubtless a bold as well as an original undertaking；
and the efficiency of the details is worthy of the boldness of the
conception。〃*＇1＇
＇Image＇ The first Iron Bridge； Coalbrookdale。
It is a curious circumstance that the next projector of an iron
bridgeand that of a very bold designwas the celebrated； or
rather the notorious； Tom Paine； whose political writings Telford
had so much admired。 The son of a decent Quaker of Thetford； who
trained him to his own trade of a staymaker； Paine seems early to
have contracted a dislike for the sect to which his father
belonged。 Arrived at manhood； he gave up staymaking to embrace the
wild life of a privateersman； and served in two successive
adventures。 Leaving the sea； he became an exciseman； but retained
his commission for only a year。 Then he became an usher in a
school； during which he studied mechanics and mathematics。 Again
appointed an exciseman； he was stationed at Lewes in Sussex； where
he wrote poetry and acquired some local celebrity as a writer。
He was accordingly selected by his brother excisemen to prepare their
petition to Government for an increase of pay； *＇2＇ the document
which he drew up procuring him introductions to Goldsmith and
Franklin； and dismissal from his post。 Franklin persuaded him to go
to America； and there the quondam staymaker； privateersman； usher；
poet； an a exciseman； took an active part in the revolutionary
discussions of the time； besides holding the important office of
Secretary to the Committee for Foreign Affairs。 Paine afterwards
settled for a time at Philadelphia； where he occupied himself with
the study of mechanical philosophy； electricity； mineralogy； and
the use of iron in bridge…building。 In 1787； when a bridge over
the Schnylkill was proposed； without any river piers； as the stream
was apt to be choked with ice in the spring freshets； Paine boldly
offered to build an iron bridge with a single arch of 400 feet
span。 In the course of the same year； he submitted his design of
the proposed bridge to the Academy of Sciences at Paris； he also
sent a copy of his plan to Sir Joseph Banks for submission to the
Royal Society； and； encouraged by the favourable opinions of
scientific men； he proceeded to Rotherham； in Yorkshire； to have
his bridge cast。*＇3＇ An American gentleman； named Whiteside； having
advanced money to Paine on security of his property in the States；
to enable the bridge to be completed； the castings were duly made；
and shipped off to London； where they were put together and
exhibited to the public on a bowling…green at Paddington。
The bridge was there visited by a large number of persons； and was
considered to be a highly creditable work。 Suddenly Paine's attention
was withdrawn from its further prosecution by the publication of
Mr。 Burke's celebrated 'Thoughts on the French Revolution；' which
he undertook to answer。 Whiteside having in the meantime become
bankrupt； Paine was arrested by his assignees； but was liberated by
the assistance of two other Americans； who became bound for him。
Paine； however； was by this time carried away by the fervour of the
French Revolution； having become a member of the National
Convention； as representative for Calais。 The 〃Friends of Man；〃
whose cause he had espoused； treated him scurvily； imprisoning him
in the Luxembourg； where he lay for eleven months。 Escaped to
America； we find him in 1803 presenting to the American Congress a
memoir on the construction of Iron Bridges； accompanied by several
models。 It does not appear； however； that Paine ever succeeded in
erecting an iron bridge。 He was a restless； speculative； unhappy
being； and it would have been well for his memory if； instead of
penning shallow infidelity； he had devoted himself to his original
idea of improving the communications of his adopted country。
In the meantime； however； the bridge exhibited at Paddington had
produced important results。 The manufacturers agreed to take it
back as part of their debt； and the materials were afterwards used
in the construction of the noble bridge over the Wear at Sunderland；
which was erected in 1796。
The project of constructing a bridge at this place； where the rocky
banks of the Wear rise to a great height oh both sides of the
river； is due to Rowland Burdon； Esq。； of Castle Eden； under whom
Mr。 T。 Wilson served as engineer in carrying out his design。
The details differed in several important respects from the proposed
bridge of Paine； Mr。 Burdon introducing several new and original
features； more particularly as regarded the framed iron panels
radiating towards the centre in the form of voussoirs； for the
purpose of resisting compression。 Mr。 Phipps； C。E。； in a report
prepared by him at the instance of the late Robert Stephenson；
under whose superintendence the bridge was recently repaired；
observes； with respect to the original design；〃We should probably
make a fair division of the honour connected with this unique
bridge； by conceding to Burdon all that belongs to a careful
elaboration and improvement upon the designs of another； to the
boldness of taking upon himself the great responsibility of
applying。 this idea at once on so magnificent a scale； and to his
liberality and public spirit in furnishing the requisite funds
＇to the amount of 22；000L。＇； but we must not deny to Paine the credit
of conceiving the construction of iron bridges of far larger span
than had been made before his time； or of the important examples
both as models and large constructions which he caused to be made
and publicly exhibited。 In whatever shares the merit of this great
work may be apportioned； it must be admitted to be one of the
earliest and greatest triumphs of the art of bridge construction。〃
Its span exceeded that of any arch then known； being 236 feet； with
a rise of 34 feet； the springing commencing at 95 feet above the
bed of the river； and its height was such as to allow vessels of
300 tons burden to sail underneath without striking their masts。
Mr。 Stephenson characterised the bridge as 〃a structure which； as
regards its proportions and the small quantity of material employed
in its construction； will probably remain unrivalled。〃
＇Image＇ Wear Bridge； at Sunderland。
The same year in which Burdon's Bridge was erected at Sunderland；
Telford was building his first iron bridge over the Severn at
Buildwas； at a point about midway between Shrewsbury and Bridgenorth。
An unusually high flood having swept away the old bridge in the
Year 1795； he was called upon； as surveyor for the county； to
supply the plan of a new one。 Having carefully examined the bridge
at Coalbrookdale； and appreciated its remarkable merits； he
determined to build the proposed bridge at Buildwas of iron； and as
the waters came down with great suddenness from the Welsh mountains；
he further resolved to construct it of only one arch； so as to
afford the largest possible water…way。
He had some difficulty in inducing the Coalbrookdale iron…masters；
who undertook the casting of the girders； to depart from the plan
of the earlier structure； but he persisted in his design； which was
eventually carried out。 It consisted of a single arch of 130 feet
span； the segment of a very large circle； calculated to resist the
tendency of the abutments to slide inwards； which had been a defect
of the Coalbrookdale bridge； the flat arch being itself sustained
and strengthened by an outer ribbed one on each side； springing
lower than the former and also rising higher； somewhat after the
manner of timber…trussing。 Although the span of the new bridge was
30 feet wider than the Coalbrookdale bridge； it contained less than
half the quantity of iron； Buildwas bridge containing 173； whereas
the other contained 378 tons。 The new structure was； besides；
extremely elegant in form； and when the centres were struck； the
arch and abutments stood perfectly firm； and have remained so to
this day。 But the ingenious design of this bridge will be better
explained by the following representation than by any description
in words。*＇4＇ The bridge at Buildwas； however； was not Telford's
first employment of iron in bridge…building； for； the year before
its erection； we find him writing to his friend at Langholm that he
had recommended an iron aqueduct for the Shrewsbury Canal；
〃on a principle entirely new；〃 and which he was 〃endeavouring to
establish with regard to the application of iron。〃*＇5＇ This iron
aqueduct had been cast and fixed； and it was found to effect so
great a saving in masonry and earthwork； that he was afterwards
induced to apply the same principle； as we have already seen；
in different forms； in the magnificent aqueducts of Chirk and
Pont…Cysylltau。
The uses of cast iron in canal construction became more obvious
with every year's successive experience； and Telford was accustomed
to introduce it in many cases where formerly only timber or stone
had been used。 On the Ellesmere； and afterwards on the Caledonial
Canal； he adopte