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tenacity of wrought iron bars； with the object of employing this
material in his proposed structure。 After he had made upwards of
two hundred tests of malleable iron of various qualities； he
proceeded to prepare his design of a bridge； which consisted of a
central opening of 1000 feet span； and two side openings of 500
feet each； supported by pyramids of masonry placed near the
low…water lines。 The roadway was to be 30 feet wide； divided into
one central footway and two distinct carriageways of 12 feet each。
At the same time he prepared and submitted a model of the central
opening； which satisfactorily stood the various strains which were
applied to it。 This Runcorn design of 1814 was of a very
magnificent character； perhaps superior even to that of the Menai
Suspension Bridge； afterwards erected； but unhappily the means were
not forthcoming to carry it into effect。 The publication of his
plan and report had； however； the effect of directing public
attention to the construction of bridges on the suspension
principle； and many were shortly after designed and erected by
Telford and other engineers in different parts of the kingdom。
Mr。 Telford continued to be consulted by the Commissioners of the
Holyhead Roads as to the completion of the last and most important
link in the line of communication between London and Holyhead；
by bridging the Straits of Menai； and at one of their meetings in
1815； shortly after the publication of his Runcorn design； the
inquiry was made whether a bridge upon the same principle was not
applicable in this particular case。 The engineer was instructed
again to examine the Straits and submit a suitable plan and
estimate； which he proceeded to do in the early part of 1818。
The site selected by him as the most favourable was that which had
been previously fixed upon for the projected cast iron bridge；
namely at Ynys…y…mochthe shores there being bold and rocky；
affording easy access and excellent foundations； while by spanning
the entire channel between the low…water lines； and the roadway
being kept uniformly 100 feet above the highest water at spring tide；
the whole of the navigable waterway would be left entirely
uninterrupted。 The distance between the centres of the supporting
pyramids was proposed to be of the then unprecedented width of 550
feet； and the height of the pyramids 53 feet above the level of the
roadway。 The main chains were to be sixteen in number； with a
deflection of 37 feet； each composed of thirty…six bars of
half…inch…square iron； so placed as to give a square of six on each
side； making the whole chain about four inches in diameter； welded
together for their whole length； secured by bucklings； and braced
round with iron wire； while the ends of these great chains were to
be secured by a mass of masonry built over stone arches between
each end of the supporting piers and the adjoining shore。 Four of
the arches were to be on the Anglesea； and three on the
Caernarvonshire side； each of them of 52 feet 6 inches span。
The roadway was to be divided； as in the Runcorn design with a
carriage way 12 feet wide on each side； and a footpath of 4 feet in
the middle。 Mr。 Telford's plan was supported by Mr。 Rennie and other
engineers of eminence； and the Select Committee of the House of Commons；
being satisfied as to its practicability； recommended Parliament to
pass a Bill and to make a grant of money to enable the work to be
carried into effect。
＇Image＇ Outline of Menai Bridge
The necessary Act passed in the session of 1819； and Mr。 Telford
immediately proceeded to Bangor to make preparations for beginning
the works。 The first proceeding was to blast off the inequalities
of the surface of the rock called Ynys…y…moch； situated on the
western or Holyhead side of the Strait； at that time accessible
only at low water。 The object was to form an even surface upon it
for the foundation of the west main pier。 It used to be at this
point； where the Strait was narrowest； that horned cattle were
driven down； preparatory to swimming them across the channel to the
Caernarvon side； when the tide was weak and at its lowest ebb。 The
cattle were； nevertheless； often carried away； the current being
too strong for the animals to contend against it。
At the same time； a landing…quay was erected on Ynys…y…moch； which
was connected with the shore by an embankment carrying lines of
railway。 Along these； horses drew the sledges laden with stone
required for the work； the material being brought in barges from
the quarries opened at Penmon Point； on the north…eastern extremity
of the Isle of Anglesea； a little to the westward of the northern
opening of the Strait。 When the surface of the rock had been
levelled and the causeway completed； the first stone of the main
pier was laid by Mr。 W。A。 Provis； the resident engineer； on the
10th of August； 1819； but not the slightest ceremony was observed
on the occasion。
Later in the autumn； preparations were made for proceeding with the
foundations of the eastern main pier on the Bangor side of the
Strait。 After excavating the beach to a depth of 7 feet； a solid
mass of rock was reached； which served the purpose of an immoveable
foundation for the pier。 At the same； time workshops were erected；
builders； artisans； and labourers were brought together from
distant quarters； vessels and barges were purchased or built for
the special purpose of the work； a quay was constructed at Penmon
Point for loading the stones for the piers； and all the requisite
preliminary arrangements were made for proceeding with the building
operations in the ensuing spring。
A careful specification of the masonry work was drawn up； and the
contract was let to Messrs。 Stapleton and Hall； but as they did not
proceed satisfactorily； and desired to be released from the contract；
it was relet on the same terms to Mr。 John Wilson； one of Mr。 Telford's
principal contractors for mason work on the Caledonian Canal。
The building operations were begun with great vigour early in 1820。
The three arches on the Caernarvonshire side and the four on the
Anglesea side were first proceeded with。 They are of immense
magnitude； and occupied four years in construction； having been
finished late in the autumn of 1824。 These piers are 65 feet in
height from high…water line to the springing of the arches； the
span of each being 52 feet 6 inches。 The work of the main piers
also made satisfactory progress； and the masonry proceeded so
rapidly that stones could scarcely be got from the quarries in
sufficient quantity to keep the builders at work。 By the end of
June about three hundred men were employed。
The two principal piers； each 153 feet in height； upon which the
main chains of the bridge were to be suspended； were built with
great care and under rigorous inspection。 In these； as indeed in
most of the masonry of the bridge； Mr。 Telford adopted the same
practice which he had employed in his previous bridge structures；
that of leaving large void spaces； commencing above high water mark
and continuing them up perpendicularly nearly to the level of the
roadway。 〃I have elsewhere expressed my conviction；〃 he says； when
referring to the mode of constructing these piers； 〃that one of the
most important improvements which I have been able to introduce
into masonry consists in the preference of cross…walls to rubble；
in the structure of a pier； or any other edifice requiring strength。
Every stone and joint in such walls is open to inspection in the
progress of the work； and even afterwards； if necessary； but a
solid filling of rubble conceals itself； and may be little better
than a heap of rubbish confined by side walls。〃 The walls of these
main piers were built from within as well as from without all the
way up； and the inside was as carefully and closely cemented with
mortar as the external face。 Thus the whole pier was bound firml