Engineering Wonders of the World
Volume I

THE BRIDGES OF THE MENAI STRAITS. 147 mouth of the Conway River, to benefit trav- on the Chester-Holy- road, by abolishing the for ferrying across the The Conway Bridge, which has a central span of 327 feet and a width of 32 feet, was also opened for traffic in 1826. The Conway Suspension ellers head need river. When Robert Stephenson took over the con- struction of the railway from his father, it was decided that special bridges for trains should be thrown across the Conway and the Menai Straits, and he was asked to draw out designs. The site selected by him was about a mile south of the sus- A Bridge required for the Menai Straits. Though now more than eighty years old, both these bridges are, to all appearance, “ as good as new,” and there is pension bridge, where the water- way is some 900 feet across at high tide, and where a rock, named the no reason to doubt that for many years to come they will stand as a memorial to the engineer who greatly dared and successfully ac- complished. THE BRITANNIA BRIDGE. In countries of old civili- zation first comes the road, then the railway. The twelve years that fol- lowed the completion of Telford’s suspension bridges were re- markable for the develop- ment of the steam railway. By 1838 George Stephenson was surveying with chain line of the Chester-Bangor north coast of Wales, with The Chester- Holyhead Railway. ROBERT STEPHENSON, Designer and Engineer of the Britannia Tubular Bridge. {From the. Rischgitz Collection.) Britannia Rock, rising in mid-channel, venient base for a cen- tral pier. Like Tel- ford, Steph- enson first offered a con- An Arch Bridge projected but disallowed. designed an arch bridge, his having two main spans of 450 feet each ; and, like Telford, he incurred the dis- pleasure of the Admiralty, who demanded a bridge which should give a clear headway of 100 feet right across the channel, not at certain points only. Fur- thermore, My Lords forbade the obstruction of the water- and level the road along the a view to con- way while the bridge, of whatever type it should be, was in course of construction. The arch principle having been ruled out, and the suspension principle being structing a railway to Holyhead. For the crossing of the Conway estuary of the Menai Straits the bridges then existing could, so Stephenson maintained, be used for trains, though he considered that it would be advis- able to relieve the Menai Bridge by moving trains over it by living horse power, as the concentrated weight of a locomotive might be expected to cause serious undulations of the roadway. unsuitable, Stephenson’s choice was narrowed down to a stiff truss of some kind. It occurred to him that huge iron tubes, large enough for trains to run through them, might be made of sufficient stiffness to span a gap of 450 feet or more. The most efficient form, and Plans for a Tubular Bridge. the disposition of metal in the tube, were made the subject of exhaustive experiments,