bors with but six or eight feet of water on them a few years ago, must have ten, perhaps fifteen feet now, or the people must suffer their trade to pass to some more fortunate or energetic neighbor. This may be a hardship; but the demands of trade are inexorable, the profits must be reasonably assured, and those who would have the trade must comply with the requirements. Thus we see the striving for harbor improvements; the weakest making the greatest outcry that they shall not be left in the race. And the improvements must come in the end, or at least be attempted, for it is as much a law of commerce not to be hampered by small freights, as it is the law of nature that water flows down hill.
The outcry for "improvements" never grows weaker; it is the expression of a sincere conviction that the life of the community and the welfare of the "back country" depend upon its success for prosperity; it will not admit a rebuff and knows no such word as failure. Alleged authorities are consulted, a scheme of improvement is proposed and Congress is asked to vote the money, and finally the improvements are attempted. To be successful, the plan must conform to known general laws and the peculiarities of local conditions, many of which are only ascertainable by comparison of surveys at different periods. Theories advanced on data collected by one survey, may be strengthened or disproved by the facts ascertained in a subsequent survey; and it is only when the plan proposed meets the general laws and the local conditions at the same time, that it holds out promise of success. The study of the questions involved has been greatly aided by the work of the Coast Survey in improvements already attempted, and will be of greater assistance in the future. A positive knowledge of what the local conditions were when a harbor was at its greatest capacity, is of the greatest help in indicating the improvements necessary to restore it, after deterioration, or to maintain it in the full measure of its usefulness. Reliable charts do this, but they tell only half the story. A cause must be found for the effects that have been produced, and the remedy suggested must overcome that cause or control it, that it may work good instead of evil. In Physical Hydrography we learn the forces that nature has given us in the tides, the currents and the winds, and divert them from powers of destruction, as man in his ignorance may have led them, or in their warfare with one another they may have led themselves;
