CHAP. VII. BUILDWAS IRON BRIDGE. 359 



is 236 feet, with a rise of 34 feet, the springing com- 

 mencing at 95 feet above the bed of the river ; and its 

 height is such as to allow vessels of 300 tons burden to 

 sail underneath without striking their masts. 



The same year in which Paine' 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 1.795, Telford was called upon, as 

 surveyor for the county, to supply the plan of a new 

 one. Being on intimate terms with Mr. Wilkinson, who 

 had strongly supported his appointment as engineer 

 to the Ellesmere Canal, he was well aware of his san- 

 guine views as to the capabilities of iron. He had also 

 carefully examined the bridge at Coalbrookdale ; and 

 while he had noted the defects in its construction, he 

 fully appreciated its remarkable merits. The conclusion 

 at which he arrived was, to build the proposed bridge 

 at Buildwas of this material ; and as the waters came 

 down with great suddenness and fury from the Welsh 

 mountains, he determined 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 material, 

 to depart from the plan of the earlier structure ; but 

 he persisted in his own 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 that tendency of the abutments to slide inwards 

 which had been the 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 Coalbrook- 

 dale bridge, it contained less than half the quantity of 



