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ings. The ruins of the broken arches, whichhad fallen between their piers, formed excel-lent, solid foundations upon which to place thetrestles; but there was a good deal of difficultyin adjusting the legs to a firm footing onthe asperities of this dyke of ruined masonry;and as the least inequality in bearing at thebase would, obviously, have operated with vastforce, at such an elevation as that to which thesuperstructure was raised, to destroy the wholeby its own weight, so the greatest nicety wasrequired in making that adjustment. Whenthe first trestle was placed, the beams andfloor to its head were laid: the second trestlewas then established in like manner, and thework continued in this way till completed.The trestles were about 15 feet long, and placed16 feet asunder: five beams were used fromtrestle to trestle, and the floor formed of tworows of 1|- inch plank. Braces, strutting con-siderably, were driven down as far as possibleinto the bottom of the river, at each end of thetrestles; and these were further strengthenedby additional props placed vertically under thecentres of the ridge-pieces: strong side-railswere then constructed, and the ends of allthe trestles were moreover secured to cablesstretched across on each side of the bridge.