*[6] Mr. Hughes, C.E., in his 'Memoir of William Jessop,' published
in 'Weale's Quarterly Papers on Engineering,' points out the bold

and original idea here adopted, of constructing a water-tight
trough of cast iron, in which the water of the canal was to be

carried over the valleys, instead of an immense puddled trough,
in accordance with the practice until that time in use; and he adds,

"the immense importance of this improvement on the old practice is
apt to be lost sight of at the present day by those who overlook

the enormous size and strength of masonry which would have been
required to support a puddled channel at the height of 120 feet."

Mr. Hughes, however, claims for Mr. Jessop the merit of having
suggested the employment of iron, though, in our opinion, without

sufficient reason.
Mr. Jessop was, no doubt, consulted by Mr. Telford on the subject;

but the whole details of the design, as well as the suggestion of
the use of iron (as admitted by Mr. Hughes himself), and the

execution of the entire works, rested with the acting engineer.
This is borne out by the report published by the Company

immediately after the formalopening of the Canal in 1805, in which
they state: "Having now detailed the particulars relative to the

Canal, and the circumstances of the concern, the committee, in
concluding their report, think it but justice due to Mr. Telford to

state that the works have been planned with great skill and
science, and executed with much economy and stability, doing him,

as well as those employed by him, infinite credit. (Signed)
Bridgewater."

*[7] Letter to Mr. Andrew Little, Langholm, dated Shrewsbury,
16th Sept., 1794.

*[8] lbid.
*[9] Letter to Mr. Andrew Little, Langholm, dated Salop, 20th Aug.,

1797.
CHAPTER VII.

IRON AND AND OTHER BRIDGES.
Shrewsbury being situated in the immediate neighbourhood of the

Black Country, of which coal and iron are the principal products,
Telford's attention was naturally directed, at a very early period,

to the employment of cast iron in bridge-building. The strength as
well as lightness of a bridge of this material, compared with one

of stone and lime, is of great moment where headway is ofimportance,
or the difficulties of defective foundations have to be encountered.

The metal can be moulded in such precise forms and so accurately
fitted together as to give to the arching the greatest possible

rigidity; while it defies the destructive influences of time and
atmospheric corrosion with nearly as much certainty as stone itself.

The Italians and French, who took the lead in engineering down almost
to the end of last century, early detected the value of this material,

and made several attempts to introduce it in bridge-building;
but their efforts proved unsuccessful, chiefly because of the

inability of the early founders to cast large masses of iron,
and also because the metal was then more expensive than either stone

or timber. The first actual attempt to build a cast iron bridge was
made at Lyons in 1755, and it proceeded so far that one of the

arches was put together in the builder's yard; but the project was
abandoned as too costly, and timber was eventually used.

It was reserved for English manufacturers to triumph over the
difficulties which had baffled the foreign iron-founders. Shortly

after the above ineffectual attempt had been made, the construction" target="_blank" title="n.建设；修建；结构">construction
of a bridge over the Severn near Broseley formed the subject of

discussion among the adjoining owners. There had been a great
increase in the coal, iron, brick, and pottery trades of the

neighbourhood; and the old ferry between the opposite banks of the
river was found altogether inadequate for the accommodation of the

traffic. The necessity for a bridge had long been felt, and the
project of constructing one was actively taken up in 1776 by

Mr. Abraham Darby, the principal owner of the extensive iron works
at Coalbrookdale. Mr. Pritchard, a Shrewsbury architect, prepared

the design of a stone bridge of one arch, in which he proposed to
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 considerableheight 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
bridge--and that of a very bold design--was 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 studiedmechanics 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 mechanicalphilosophy, 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" target="_blank" title="n.建设；修建；结构">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