Mr. P. W, BARLOW directed attention to an interesting experiment, recently tried in America., in the adaptation of the suspension principle to a railway bridge : this should, if possible, be discussed, while the subject of the relat,ive advantages of different girders was under c,onsideration. Mr. BAKER, in answer to the PRESIDENT, said, he possessed but little accurate information on the subject. The bridge alluded to, over the Niagarq, was opened for tra& on the 18th of March last, since he left Canada: and Mr. Roebling, the Engineer, had not yet furnished him with the particulars of the structure. It was understood, that there had been, hitherto, eight trains over the bridge each way, conveying daily, 1,400 tons of goods, and fourteen, or fifteen hundred persons, at the rate of 10 miles per hour, causing a deflection of only half an inch in the centre. The weight of the trains was about 130 tons, the engine and tender weighing 35 tons; but this was only one-sixtieth of the weight which it was calculated to bear. The span of the bridge was 833 feet ; and it had three lines of rails upon the latform, of the various gauges of 3 feet 6 inches, 4 feet 84 inc K es, and 5 feet 6 inches. I n the absence of more reliable information than he could supply, it would be well for the Members to suspend their final judgment upon the bridge, until the details could be laid before them. Mr. C. MhNBY,-Secretary,-was enabled, through the kindness of Mr. Gillespie, an American Engineer, to afford some particulars which had been communicated by Mr. Roebling. The bridge was situated immediately above the Falls, at Niagara. The span was stated to be 822 feet 6 inches, and the height of the railway-track platform, above the river, was 250 feet ;-with a lower platform, for common-road vehicles, suspended beneath that which carried the three tracks for the%railways. There were four wire cables, of 10 inches diameter? each containing 3,640 wires, No. 9, W. G. The ultimate direct strength was 12,400 tons, and the ultimate supporting strength of the cables, was 7,000 tons. The total weight of the superstructure was 750 tons. The first freight train which passed over, was purposely extended, to cover the whole length of the platform; it consisted of twenty double cars, each weighing 7 tons, and carrying 10 tons of freight, with an engine weighing 26 tons,-making in all 366 tons. The ordinary camber of the platform, when unloaded, was 2.75 feet, which, under a load of 366 tons, was reduced to 1-93 foot. Under the ordinary circumstances of the traffic, ten cars would 'constitute a full train. There did not appear to be any undulatory motion, even when the cars attained a good speed, and there was an entire freedom from all vibration. A few heavy
