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Dec. 16, 1887.] 1 9 (Haupt. 
THE PHYSICAL PHENOMENA 
or 
HARBOR ENTRANCES. 
THEIR CAUSES*-AND REMEDIES. 
DEFECTS OF PRESENT METHODS OF IMPROVEMENT. 
By Lewis M. Haupt, C.E. 
(Professor of Civil Engineering, University of Pennsylvania, Phila.) 
This Paper was awarded the Magellanic Premium at a Stated Meeting 
of the American Philosophical Society, held December 16, 1887. 
Every well-considered plan for improving the entrance to a 
harbor must take into account the existing physical conditions 
or features of the site, and the causes which have produced 
them. These features are composed of the land-drainage, the 
inner basin, the gorge, the outer basin, the bar and the ocean. 
In passing from the fresh to the salt water system, there may 
be one or more channels having some peculiar characteristics, 
which are not mere accidents, but the results of certain 
forces. Before any radical or permanent improvement can be 
effected it is necessary that the forces operating at any point 
should be fully understood, and, so far as possible, be measured. 
In tracing step by step the causes from their effects, I have 
found the circle of investigation unavoidably widening, until 
it embraced many of the physical phenomena pertaining to the 
North Atlantic Ocean. 
The initial point in this study is the form of the bed or 
mould of alluvial harbors, supposed to be of material suf- 
ficiently plastic to reveal the effect of the forces operating upon 
them. I have heretofore elsewhere called attention to the im- 
portant deductions to be obtained from noting the position of 
