CHAP. VII. IRON AND OTHER BRIDGES, 



CHAPTER VII. 



IRON AND OTHER BRIDGES. 



SHREWSBURY being situated in the immediate neigh- 

 bourhood of the Black Country, of which coal and 

 iron are the principal products, Telford's attention was 

 naturally directed, at a very early period, to the employ- 

 ment of cast iron in bridge-building. The strength as 

 well as lightness of a bridge of this material, compared 

 with one of stone and lime, is of great moment where 

 headway is of importance, or the difficulties of defective 

 foundations have to be encountered. The metal can be 

 moulded in such precise forms and so accurately fitted 

 together as to give to the arching the greatest possible 

 rigidity ; whilst it defies the destructive influences of 

 time and atmospheric corrosion with nearly as much 

 certainty as stone itself. 



The Italians and French, who took the lead in en- 

 gineering down almost to the end of last century, early 

 detected the value of this material, and made several 

 attempts to introduce it in bridge-building ; but their 

 efforts proved unsuccessful, chiefly because of the in- 

 ability of the early founders to cast large masses of iron, 

 and also because the metal was then more expensive 

 than either stone or timber. The first actual attempt to 

 build a cast iron bridge was made at Lyons in 1755, 

 and it proceeded so far that one of the arches was put 

 together in the builder's yard ; but the project was 

 abandoned as too costly, and timber was eventually 

 used. 



It was reserved for English manufacturers to triumph 



2 A 2 



