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1887.] 23 {Haupt. 
basin is generally composed of three subdivisions, viz: One 
extending along the islands on either hand, and one stretching 
to the rear. Atthe ebb of the tide the prisms of discharge 
are all approaching the gorge at the same time. In consequence. 
of the inward flexure of the spit at this place, one or both of 
the lateral currents are reflected into the face of the main 
discharge, and thus diminish its energy, which it is the object 
of the engineer to conserve. 
These general effects can be seen by a comparison of the 
position and depth of the bar crossings along the coast line of 
the Middle and Southern States. One of the most striking 
and typical instances of the effect of the internal concentra- 
tion and conservation of energy is that of the Port Royal en- 
trance, where there is a depth of twenty-one (21) feet on the 
bar, due to the increased intensity of the resultant ebb, pro- 
duced by the confluence of the Beaufort, Broad and Cheches- 
see rivers, whose thalwegs approach in directions nearly par- 
allel. Here, too, is observed the flexure of the outer stream to 
the southward, showing clearly the existence of an excess of 
flood action from the northward, and the piling up of sand 
banks on this side to be eroded by the ebb. 
The opposite effect resulting from conflicting internal cur- 
rents is il'ustrated in the case of the Galveston entrance 
(Fig. 2), 
An examination of the various entrances leaves no doubt of 
the existence of such a littoral flood movement, whereby the 
sands of the beaches are transported to and deposited in front of 
the inlets, where the racing waves, no longer resisted by and 
reflected from the shore, escape through the break in the bar- 
rier which forms the outlying sandy cordon defending the coast. 
aaa 
