For bridge-building the value of this metal has lately been much
disputed, though we have several notable examples of its use in the
earlier days for such structures. In fact, the use of cast iron for
structural purposes is not older than the time of Smeaton, who in 1755
employed it for mill construction, and about the same time the great
Coalbrookdale Viaduct was erected across the Severn near Broseley, which
gave an impetus to the use of cast iron for bridge construction. The
viaduct had a span of 100 feet, and was composed of ribs cast in two
pieces; it was erected from castings designed by Mr. Pritchard, of
Shrewsbury, an architect, and this circumstance is worthy of note as
showing that an architect really was the first to employ this material
for important structural work, and that the same profession was the
first to reject it upon traditional grounds. It is quite certain,
however, the bridge-builder lost no time in trying his hand upon so
tractable a material; for not long after Telford erected a bridge at
Buildwas of even a greater span, and the famous cast-iron bridge over
the river Wear at Sunderland was erected from the designs of Thomas
Paine, the author of the "Age of Reason.
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