The success which had attended the use of iron, as a material in bridge building, had now given such confidence to engineers, that works of the greatest magnitude were pro posed by the master-minds of Telford, Rennie, and others. At this period, the practicability of constructing a bridge over the Menai Straits had been much discussed. It was deemed expedient by government to facilitate, as much as possible, the intercourse between England and Ireland. For this purpose, an investigation was made as to the most effec tual mode of improving the mail-roads from Holyhead through North Wales.
The Island of Anglesea, as is well known, is separated from Carnarvonshire by the celebrated strait or arm of the sea, named the Menai, through which the tide flows with great velocity, and, from local circumstances, in a very pecu liar manner. This rendered the navigation difficult, and it had always been a formidable obstacle in the before-mentioned communication. The passage between Anglesea and the opposite mainland was maintained by six ferries, the chief of which was called Bangor Ferry, from its proximity to that town : lint a permanent connection, by means of a bridge, had been in contemplation, and various projects for one had been under consideration. From a report of the [louse of Commons, of dune 1810, it appears, that Mr. Rennie, the engineer, had given plans and estimates for bridges at this place in 180e, and had been called on to revise them in 1810. His plans, which appear in the last-mentioned report, are, 1st, One arch of east-irun, 450 feet span, over the narrowest part of the strait, at a prltjecting rock named Ynys-y-Moch: and, end, Another upon the Swillev rucks, consisting of' three cast-iron arches, each 350 feet span. The expense of that
at •nys-y-Moch is estimated at £259,140, and of that at the £290,117. Ile prefers the latter, because he says, " On account of the great span of the arch at Ynys-y-Moch, and the difficulty and hazard there will be in constructing a centre to span the whole breadth of the channel at low-water, without any convenient means of it in the middle, on account of the depth of water and rapidity of the tide, or of getting any assistance front vessels moored in the channel to put it up; I will not say it is impracticable, but I think it too hazardous to be recommended." And, again, in the same report: "I should be little inclined to undertake the building a bridge at Ynys-y-Mueh." But front the report of .June, 1811, it appears that, in May 1810, Mr. Telford was instructed by the Lords of the Treasury to survey, and report upon the best method of improving the lines of communication between I ioly head and Shrewsbury. and also between lIolvhead and Chester; and to consider, and give plans for passing the Menai. In the aforesaid report (of 1811), we have his plans and estimate. His explanations we shall give in his own words; but before doing so, it is necessary to observe that much of the following extract may, perhaps, more properly belong to the descrip tion of the Menai bridge, which will be found under the head