Engineering Wonders of the World
Volume I

AN INTERESTING BRIDGE-BUILDING FEAT 435 Fig. 2.—FIRST FLOTATION OF A SPAN ON PONTOON. sections six feet long. On the whole, it was considered better to float out the complete spans at the full height. By this method the girders could be built in safety on shore, and be made perfectly safe when placed in position on the bridge. The only danger would be during the few hours when the girders were actually floating, and it was thought that by providing carefully against all contingencies, including heavy squalls, the operation could be accom- plished successfully. Preparations were therefore made early in March 1907. Fig. 1 shows a view of the staging on shore on which the girders were built. This staging was carried The “Dread- , ,, , nought ” UP ^ ie same level as the tops of the bridge piers. From the staging two jetties were run out to deep water. On each of these a pair of ordinary railway lines were laid, passing under the built girders. The girders were then lowered on to four strong trollies placed on the rails, and hauled out to the end of the jetties. A set of strong pontoons, intended eventually for us© as floating landing-stages at Moulmein, were made use of for carrying the girders. On these pontoons a strong wooden staging was erected. This floating mass was named the “ Dreadnought ”—a name calculated to inspire confidence. The pair of girders, with cross girders, bracings, etc., weighed about 100 tons, so it was necessary to calculate exactly how deep the “ Dreadnought ” would sink when the extra 100 tons were placed upon it. ■ Fig. 3.-THE SPAN FLOATING IN MID-STREAM. On May 1 there were still five spans to be finished. Three of these were in hand—two on river stagings, and one on the shore staging. On May 4 the rainy season opened most unexpectedly with A tremendous a tremendous storm, which at Moulmein actually brought down 21 inches of rain in the twenty-four hours. This was very disheartening. To add to the difficulties the labour supply began to fail. The girder- erecting contractors declined to have anything to do with the floating out, saying that it was too dangerous. However, more labour was collected from Rangoon, and the work was pushed on with all possible speed. On May 30 everything was ready for float- ing No. 4 span. Fig. 1 shows the span after it had been removed from its original staging and hauled out to the end of the jetties. The