View of the Coffer Dam, at Oswego, N.Y.

The picture herewith presented is a representation of an excavation made during the last winter, in the bed of the river forming the harbor at the city of Oswego. The excavation was made by means of a coffer dam, erected so as to embrace an area of about three acres, extending from the toll-bridge 700 feet down stream, upon the east bank of the Oswego River, studded with flouring mills and grain warehouses, whose machinery is driven by water power obtained from a canal running upon the bank and in rear of the mills. Upon the completion of the dam, the water was pumped out, and the enclosed space kept clear by two patent pumps propelled by water power from the canal, and kept running night and day, while the work of excavation was going on. One thousand yards, mostly of solid rock, was taken out in about thirty days, at an expense of $20,000, incurred by the few enterprising owners of the property directly benefited by the improvement. Where loaded vessels could not before float, eleven and twelve feet of water is obtained by the improvement, admitting the largest vessels navigating the lakes. Vessels of 350 and 400 tons now discharge and receive their cargoes up to the bridge, the highest point of the excavation, where canal boats could scarcely pass before. The importance of the improvement will be better understood and appreciated by a glance at the vast hydraulic power of the river, and the commercial advantages and facilities of the geographical position of Oswego. The city is situated upon the southern shore of Lake Ontario, and built on both sides of Oswego river. The river forms the outlet of the Oneida, Cayuga, Seneca, and the whole family of the lakes of Central New York. The vast hydraulic power of the river in connection with its commercial advantages, natural and artificial, are unsurpassed, and perhaps unequalled, on the continent. The Oswego flouring mills contain near 100 run of stones and can manufacture 8000 barrels of flour per day More flour is made there per annum, than at any other point in the United States. Oswego is within a few hours' sail of the Canadian ports on Lake Ontario, and forms the natural outlet to market for the vast regions lying north. She has also a direct ship navigation with the upper lakes by the Welland Canal, forming the cheapest freight channel between the East and the Great West, and will also be in the direct line of the shortest and most expeditious route of travel, on the completion of the Great Western Railroad, now building across the peninsula of Upper Canada, from Hamilton to Detroit. Oswego has also a water communication with the Hudson at Troy and Albany, by the Oswego and Erie Canal, and by railroad with Boston and New York. She has a population of 13,000, and a rapidly growing commerce; the property transhipped there in the season of 1851, amounting to over thirty millions of dollars. In short Oswego has the elements of commercial importance, and the natural resources of a great city.