Bridges

The origin of cantilever (Figure 4.1) and suspension bridges almost certainly lay to the east of our area. In the south and west of China, in the Himalayan regions and in Afghanistan, cantilever bridges had been built from, at latest, the fifth century ad. Simple cantilever bridges were built in Savoy throughout the Middle Ages, and several sketches of them appear in the notebooks of Villard de Honnecourt (c. 1235), but there is no record of their use in western Asia or Europe in earlier times. Being made of timber, they do not have a long life nor do they leave traces, particularly since in many cases modern bridges may have been built at their sites. It would be surprising, however, if they were not built in mountainous areas such as the Zagros and the Taurus, since they are an excellent method of crossing deep ravines in hilly country. Usually a timber substructure is built into a masonry abutment on either bank, and the longitudinal and transverse beams to carry the roadway extend from the top of this supporting structure. At the centre the two cantilever spans support a short beam section. There is no need to build piers and no need to descend to the bottom of the ravine. In the tenth century a bridge over the River Tāb in Iran was described briefly by Ibn Hawqal. He says that the river was crossed by a wooden bridge ‘suspended between the sky and the water, its height above the water about 10 cubits’. ¹ He may, of course, have seen a suspension bridge, but the cantilever type seems more likely, especially since he makes no mention of ropes. The evidence is tenuous, but it seems a reasonable conjecture that this method of construction was transmitted from East Asia to western Europe via Iran, Anatolia and the Balkans. ²