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bridges and viaducts； he thus kept his heart open to the influences
of beauty in life and nature； and； at all events； the writing of
verses； indifferent though they might have been； proved of this
value to himthat it cultivated in him the art of writing better
prose。
Footnotes for Chapter VI。
*＇1＇ The Ellesmere Canal now pays about 4 per cent。 dividend。
*＇2＇ 'A General History of Inland Navigation； Foreign and
Domestic；' &c。 By J。 Phillips。 Fourth edition。 London； 1803。
*＇3＇ ＇Image＇ Section of Pier
Telford himself thus modestly describes the merit of this original
contrivance： 〃Previously to this time such canal aqueducts had been
uniformly made to retain the water necessary for navigation by
means of puddled earth retained by masonry； and in order to obtain
sufficient breadth for this superstructure； the masonry of the
piers； abutments； and arches was of massive strength； and after all
this expense； and every imaginable precaution； the frosts； by
swelling the moist puddle； frequently created fissures； which burst
the masonry； and suffered the water to escapenay； sometimes
actually threw down the aqueducts； instances of this kind having
occurred even in the works of the justly celebrated Brindley。
It was evident that the increased pressure of the puddled earth was
the chief cause of such failures： I therefore had recourse to the
following scheme in order to a void using it。 The spandrels of the
stone arches were constructed with longitudinal walls； instead of
being filled in with earth （as at Kirkcudbright Bridge）； and across
these the canal bottom was formed by cast iron plates at each side；
infixed in square stone masonry。 These bottom plates had flanches
on their edges； and were secured by nuts and screws at every
juncture。 The sides of the canal were made water…proof by ashlar
masonry； backed with hard burnt bricks laid in Parker's cement； on
the outside of which was rubble stone work； like the rest of the
aqueduct。 The towing path had a thin bed of clay under the gravel；
and its outer edge was protected by an iron railing。 The width of
the water…way is 11 feet； of the masonry on each side； 5 feet 6
inches； and the depth of the water in the canal； 5 feet。 By this
mode of construction the quantity of masonry is much diminished；
and the iron bottom plate forms a continuous tie； preventing the
side…walls from separation by lateral pressure of the contained
water。〃'Life of Telford；' p。 40。
*＇4＇ Letter to Mr。 Andrew Little； Langholm； dated Shrewsbury；
13th March； 1795。
*＇5＇ Matthew Davidson had been Telford's fellow workman at Langholm；
and was reckoned an excellent mason。 He died at Inverness；
where he had a situation on the Caledonian Canal。
*＇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 formal opening 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
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 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