ABSTRACT

In 1840 cast iron was firmly established as the modern structural material and when people talked of "iron" in bridges and buildings they meant cast iron. At this time wrought iron was rare and, for beams virtually unheard of, yet less than 10 years later no engineer would have thought of making a major beam or girder of anything else. By 1850 cast iron had been completely eclipsed. This was not just a time of change from one material to another, but also of unprecedented advances in our understanding oftheir use. This particular progress was nearly all made in England1 and, in the first instance, almost wholly in the field of railway bridges. Perhaps this is not surprising, for Britain led in the development of railways, which in turn needed countless bridges. In the early railway days the existing types of bridge were frequently found wanting and this triggered off the search for new ones.