68 National GeographiG Magazine. 



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 

 Tieighbor. 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 at- 

 tempted, 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 suc- 

 cessful, the plan must conform to known general laws and the 

 peculiarities of local conditions, many of which are only ascer- 

 tainable 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 improve- 

 ments 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 de- 

 terioration, 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 Hydro- 

 graphy 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; 



