ELLET, C. Report on a suspension bridge across the Potomac, for rail road and common travel: addressed to the Mayor and City Council of Georgetown, D.C. Philadelphia, John C.Clark 1852
Small 4to. 36pp, folding engraved frontis. (repaired) and 3 engraved plates. The whole rebound on new stubs (a few leaves repaired at corners) in quarter calf but an acceptable copy of a rare work. Ellet had first proposed a bridge across the Potomac to replace an older timber structure when he returned from France in 1831. By 1852, when he put forward this scheme, he had had actual experience of building suspension bridges and the design is thus far more ambitious than the earlier one. Half a mile above Georgetown, the bridge was to have been 60ft above high water with a span of 1000ft as against the earlier 600ft span with 46ft headroom. In addition, the new design provided a deck 32ft in width to accomodate rail as well as road traffic. The report discusses the design and proves the all-important strength of the cables. Weight, as with all Ellet's bridges, was of prime consideration, for he considered that the heavier the bridge the smaller would be the deflection set up by moving load of a locomotive. He calculated the weight of the Potomac structure to be four times heavier than his recently completed Wheeling bridge. A second edition of this report appeared in 1854.
£450
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