Haupt. ] 20 (Dee. 16, 
the submerged crest line of bars, as well as from the relative 
slopes of sections along the thalweg of the channel or across 
the bar, as indicating the direction of movement of the sand 
and of the flexure of the outer ends of the channels, after pass- 
ing the gorge, either up or down the coast. The immediate 
cause of this flexure was asserted to be a littoral component 
which rolled up the sand on the flood tide and compressed the ebb 
stream against one or other of the adjacent shores. But why 
this resultant should have been so constantly operating in 
opposite directions at different entrances was not then fully 
understood or stated. 
It is the object of this paper to collate certain observed facts, 
for the purpose of explaining these phenomena and of deducing 
therefrom a conclusion of practical value in the economical 
solution of the problem of improving our harbor entrances. 
TypicaL Forms. (See Plate I.) 
In examining the plan of any entrance it is generally found 
that the ends of the islands forming the outlying cordon are 
elongated into spits or hooks, curving inward, with a smooth 
outer and a rugged inner shore line; that one of the points is 
sharp, and the other blunt or round headed; that the sharp 
point usually recedes from the general coast line; that the sea- 
ward slope of a cross section of the bar is less steep than the 
inner slope, except where the ebb streams cross it; that the 
flood tide usually approaches the entrance at first in a direc- 
tion more nearly parallel to the sharper lip and normal to the 
blunt one, rolling tp the gentler slope and depositing sand on 
or within the crest of the bar, where “breakers” are found ; 
that along the shore of the sharp point there is a shallow 
channel cut out by the flood, and curving around the blunt, e 
projecting lip of the gorge there is the main deep-water chan- 
