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GENERAL REPORT OF THE JUDGES OF GROUP XXVI. 33 The waters of that river, estimated to amount to 1,280,000 cubic feet per second, find their way through the Delta into the Gulf of Mexico mainly through three channels or passes, viz., the Southwest Pass, the South Pass, and the Pass a l’Outre; the centre or South Pass hitherto has not been used for commerce; and, though it is the most direct passage, yet before the works began not more than about one-tenth of the waters of the Mississippi found their way through it to sea. The object of the works, which are now in rapid progress, is to im prove this outlet, which in its original state at high tide had not more than 8 feet of water on its bar, and to secure if possible everywhere along it a depth of 20 to 26 feet. With this object, jetties 1000 feet apart, formed of mattresses covered with stone, are being constructed on each side of the channel, and the result of this work is awaited with great interest, for if successful it will be of vast importance to the traffic of that great river, and will produce changes in the direc tion of traffic to and from this vast continent difficult at present to estimate. HARBORS. The magnitude of the lakes and rivers, of sheltered bays, and arms of the sea, have spared the United States the necessity of con structing deep-sea artificial harbors like those which have in some cases in England, as at Holyhead and Portland, for instance, involved so much expenditure. But some of the American lakes are like in land seas, and sometimes call for works of magnitude such as the Harbor of Refuge now constructing on Lake Huron, where the breakwater will be 7000 feet long, and will inclose an area of 320 acres of 12-feet water. The method of constructing this and other breakwaters, much used in the country, is called crib-work. It consists in forming boxes or frames of timber of the width of the structure required, and of convenient lengths, and divided into com partments. The frames are floated to their place, then sunk, and after wards filled with stone. Where necessary, in very exposed situations they are protected outside by stone or pierre perdu, Of the models of similar works exhibited maybe mentioned—details of crib-work used in the breakwater, Oswego harbor, Lake Ontario, New York; model of crib-work used in the construction of United States breakwater at Dunkirk, New York, Lake Erie. LIGHT-HOUSES. Many models of the structures, varying in material and mode of con struction, were exhibited by the Government of the United States, with samples also of beautifully-constructed lenses of each class. 3