Engineering Wonders of the World
Volume I

206 ENGINEERING WONDERS OF THE WORLD. city of Montreal, where the stream is about If miles broad, and, excepting in somewhat contracted channels, navigable only by vessels of very shallow draught. The bed is here of solid rock covered with clay, quicksand, and large boulders, some weighing many tons. On his return to England Mr. Ross drew out designs for a tubular bridge very similar in cannot be an easy matter under any condi- tions. In the case of the Montreal Bridge, the physical difficulties to be overcome were such as to include this structure among the most remarkable engineering feats of which there is record. At high-water the St. Lawrence runs at a pace of from eight to nine miles an hour. To THE OLD VICTORIA BRIDGE. (Photo, Grand Trunk Railway Company.) Mr. Stephen- son visits Canada. its main details to the Britannia Bridge, then recently erected across the Menai Straits by Robert Stephenson, who was now asked to undertake, jointly with Mr. Ross, the final designs for the new structure. He accordingly visited Canada in 1853, ex- amined the site selected, and approved it. The bridge for which he was partly responsible had twenty-four tubular spans of 242 feet, and one of 330 feet over the central channel. To give sufficient headroom for navigation, the tubes rose from the ends to the centre of the bridge on an incline of 1 in 130, thereby increasing the distance between the bottom of the tubes and summer water-level from 36 feet at the abutments to 60 feet under the central span. The construction of a bridge miles long build piers amid so rapid a current promised some very difficult work, rendered all the more arduous in winter by the ice and in the summer by the huge rafts of logs, which, at the period of which we are speaking, were floated down the river to the Quebec sawmills. As winter closes in, the early ice pens up the water, which rises behind it and impels it with terrific force down-stream. When a “ shoving,” as it is locally termed, occurs, the ice ploughs ««ghovkigs ” deeply into the banks, packs again, banks up the water, and continues its way until some obstacle or the tightening grip of winter cold brings it to rest—a chaos of hummocks piled up, in places, to a height of from twenty to thirty feet. When spring arrives, the ice begins to break up, and more shovings take place.