Note 121 — CHAPTER THE FOURTH (continued 2)

The middle arch of 58 ft. span, 17 ft. rise, and 14 ft. in width across the soffit, has archstones which are only 18 ins. deep, and they vary in thickness from 5 to 16 ins.: many of them are 8 and 9 ins. Sometimes there are two headers to answer a course of common archstones; and sometimes two courses of archstones answer one header. The piers are 10 ft. thick, and the middle arch springs about 3 ft. above the river’s bed. A steep road over the bridge diminishes the weight upon the side arches; but Telford believed that if the spandrils had been hollowed the road could have been made with an easy gradient of 1 in 24. The workmanship is very light, and it appears to be stable, though a shivering bridge inspires no more confidence than a stammering man. In 1803, owing to a defect in the foundation of the western abutment, one of the side arches fell, yet the others remained uninjured while the broken one was being rebuilt. So the bridge in the proportion of all its parts must have been very well balanced, despite its quivering alertness and lightness.