1887.] 35 (Haupt. 
the ebb and require more work of it for its removal. He 
should also see that the ebb be not diverted from its course, but 
be protected and defended by a line of detached breakwaters. 
This will further have the effect of confining the ebb waters, 
which would otherwise escape in the swash or weir channels, 
to the main stream, and so concentrate their energy upon a single 
point of the bar, and that point the one where the bar-building 
Forces are the weakest. 
This barricade should not in general be joined to the beach at 
the shore end, but there should be left a wide opening across 
that portion of the bar which corresponds to the flood or 
beach channel. This should be deepened by the concentration 
of the flood currents, and the sand carried through the gorge 
would make fast land inside of the spit. Its quantity could 
be regulated by the extent of the opening. Thus the tendency 
of the flood to build its own barrier upon which to break 
would be aided, and the ebb would be protected in its escape. 
It also appears that but one such line of breakwater would in 
general be required, and hence the cost would be materially 
reduced. As it would occupy asite already dangerous to ves- 
sels, it would not increase the risks to navigation, but on the 
contrary, as it would project above the surface, it would be a 
beacon as well as a breakwater, and would greatly diminish 
the difficulties of effecting an entrance by sailing vessels over 
the case of a double line of extended jetties with a narrow 
pass between them, especially if submerged. 
INTERNAL PROJECTS. 
In connection with these external works there will be re- 
quired in certain harbors regulating deflectors, or reaction 
dikes, to prevent the current interferences which produce 
hummocks, mounds, and even islands just inside the entrances 
