The Victorian era produced many great engineers, but also some who seemed to have ideas which stretched practicality to its limits. One such scheme which caught my eye was in a booklet [The Anglo-French railway bridge and how it is to be constructed. 1868.8.285] which outlines a project by a French engineer, Charles Boutet, who had spent ten years considering his plan and constructing models to prove its viability.
His vision was for an iron bridge across the English Channel: on the face of it, not entirely impossible; except that he proposed to do this with an extraordinary structure, consisting only of ten spans, each of 3,282 yards in length – that is over a mile and a half each. So each single span would have been considerably longer than the entire length of the Humber Bridge.
He intended to support these enormous spans 120 yards (that’s the length of a football pitch) above the sea on nine metal piers. Boutet calculated that each of these 2,500 ton piers would be able to support the 14,000 tons of each arch.
It was proposed to construct the lower portions of the bridge – each measuring 130 by 87 yards across at the base – on land, before floating them out, lowering them down through the water by means of buoys and then securing them to the seabed with large integral screws.
The actual spans were to be arches constructed with two inch diameter iron wire cables, strung horizontally and then connected to each other by vertical cables and iron transoms, the whole to form a mesh. Small metal arches, rising above this, would support the roadway of the bridge. The word “ponderous” is used more than once to describe this huge structure and certainly my mind boggles at the thought of the whole thing.
Boutet had complete confidence in his design for the iron beams and tresses of the spans though, calculating that each span would support the weight of 24 fully loaded trains in its centre. He thought the entire construction would cost £8 million and be completed in three years. However, the whole thing never progressed any further than the formation of a company and the publication of the promotional booklet, so we will never know if it would have worked!
