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 clearly as to render the descriptions in the deed intelligible. This is but a single instance of the practical application of the knowledge gained; and if its general usefulness may be judged by the numerous inquiries made of the Bureau, it is not unreasonable to assume that time will bear increasing testimony of its great economic value from those who traverse the land, as well as those who sail on the waters.

The study of the recurrence of the tides along our extensive Coast lines, and determination of laws that would satisfy the great variance in the different periods, was a problem of no little magnitude but the greatest possible importance to our commerce. Much of the traffic along the coasts literally moves with the tides, and the cost of transportation is enhanced or diminished as the tide retards or advances it. Hundreds of dollars of expense may be incurred on a single cargo that must enter on the high water, but through imperfect knowledge of the master of the ship, is forced after sighting his port, to wait for the next tide, perhaps over night, and is driven to sea by a sudden storm and the voyage made several days longer. Such mishaps are not infrequent, and even at the great port of New York certain classes of vessels must "wait for the tide." The investigation of this complex subject has resulted in the acquirement of a knowledge that enables the prediction of the time of high and low water, and the height of the tidal wave, years in advance; and the mariner may now carry with him the tables published on the subject wherever he goes, and be independant of the doubtful communications he may otherwise receive from the shore. How many lives, how many dollars, have been saved by the knowledge gained?

But the investigation of the Tidal phenomena is of great scientific importance also; and a practical assistance in the great problems involved in the preservation and improvement of our harbors, but in this connection it probably falls more properly under the head of that greater study of the currents and their effects in the erosion, and building of the shores; the movement of the sands and formation of shoals and channels; termed "Physical Hydrography." Our commerce depends largely on this study for its perpetuation, for without harbors commerce must cease; and without harbors that will admit vessels of the largest class it must deteriorate. If commerce finds increased profits in large vessels it demands increased facilities, and the bars to the har-