On the abutments of the stone works are placed iron plates, with mortices, in which stand two upright pillars of the same. Against the foot of the inner pillar the bottom of the main rib bears on a base plate. This rib consists of two pieces connected by a dovetail joint in an iron key, and fastened by screws; each is seventy feet long. The shorter ribs pass through the pillar, the back rib in like manner, without coming down to the plate. The cross-stays, braces, circles in spandrils, and the brackets, connect the larger pieces, so as to keep the bridge perfectly steady, while the diagonal and cross-stays and top plates connect the pillars and ribs together in opposite directions. The whole bridge is covered with top plates, projecting over the ribs on each side, and on this projection stands the balustrade of cast iron. The road over the bridge, made generally of iron slag, is twenty-four feet wide, and one foot deep. The span of the arch is one hundred feet six inches, and the height from the base line to the centre is forty feet. The weight of iron in the whole is three hundred and seventy-eight tons, ten hundred-weight. Each piece of the long ribs weighs five tons, fifteen hundred. On the largest or exterior rib is inscribed in capitals—“This bridge was cast at Coalbrookdale, and erected in the year 1779.” [Picture: The Iron Bridge] During the construction of the bridge a model was prepared and sent up to the Society of Arts, who presented Mr. Darby with their gold medal in recognition of his merits as designer and erector; and a model and an engraving of the bridge may still be seen in the Society’s rooms, John Street, Adelphi. 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.” Mr. Stephenson adds “_that from a defect in the construction_ the abutments were thrust inwards at the approaches and the ribs partially fractured.” This was not the case. It arose from the nature of the land and its exterior pressure which was obviated by sinking and underbuilding the foundation, and to remedy the supposed defect, two small land arches were, in the year 1800, substituted for the stone approach on the Broseley side. While the work was in progress, Mr. Telford carefully examined the bridge, and thus spoke of its condition at the time:—