Figure 44 is a photograph of the cast-iron bridge at Coalbrookdale. The bridge has a span of about 30 metres and it has an 18 metre clearance above the water below. The bridge comprises stone columns with iron arch structures between them. The largest iron structure is in the centre and spans the river. The pattern created by this iron structure is similar to the pattern created by the edges of the blocks in a stone arch. The structure looks like an assembly of similar components. There are in fact about 800 castings of 12 basic types.