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.