A. D. Bache on the Tidal Currents of New York Bay. 339 
and the mean velocities 0°6 of ebb against 02 of flood. The 
mean durations are more than 10 hours of ebb against less than 
2 hours of flood, 
In the middle of Sandy Hook Bay the ebb current begins 
nearly two hours before slack water in the main ship channel, 
its general course is south by east, that of the flood being east 
by north. The avcrage maximum velocities, given by the 5th line 
of table 6 are 0:6 of ebb, against 0°4 of flood; the mean rates are 
above 0:4 of ebb against 0°2 of flood. The durations are about 
84 hours for ebb and 84 for flood. In the western section of the 
Bay the ebb commences at nearly the same period as in the 
main ship channel. The average velocities are nearly equal, 
and the durations are more nearly so than for the other portions 
of the Bay. The scouring done by these currents will v 
_, Since the tide wave is gaps ne most rapidly in deep water, 
it follows that the fall of the tide 
ex y in shallow bays. 
With the flood streams the reverse must be true, and the tide 
teristics, the ebb and flood assume an unequa, ® 
moulding of sandy coasts. The ebb current, with its concentra- 
tion of forces, is a far more powerful agent than the flood, its 
rmal course wt be ae con- 
sider i tensive draught currents. e 
Siderable, and it creates more extensi Pb Hod ste a 
ranch where the primary ebb a1 
me the ebb stream wa : 
Shallow basins, in a narrow Str 
its Shatner purses the broadest possible path, and presses 
al ae : ever 
eae tr ecean, 30 ful the flood predominating over the ebb 
