4 MANUAL OF CURRENT OBSERVATIONS 
approximates a true cosine curve, the mean velocity of the current throughout a flood 
or ebb period may be taken as 0.637 times the velocity at the strength of current. 
10. A reversing tidal current may be greatly modified when in combination with 
a nontidal current. The velocity of the current will be increased. in the direction in 
which the nontidal current is moving by an amount equal to the magnitude of the 
latter, and will be decreased by an equal amount in the opposite direction. The dura- 
tion of flow in the direction of the nontidal current will be increased and the duration 
Flood 
Knots k TE MAGNATE, ALO TEE Aiea owe Sen eas eal] cay PR Ck SEATS Can Rtas, Sei “| 
3 
2 
I 
(oe) 
I 
2 
: ( 
y Ebb 
FIGURE 5.—Diurnal current in Mobile Bay Entrance at time 1 tronie ides: (At time of equatorial tides tidal current is very weak 
and irregular. 
1 Flood 
inv) 
fo) 
i) 
Ebb 
FIGURE 6.—Diurnal current in Galveston Bay Entrance at time of tropic tides. (At time of equatorial tides a normal semidiurnal 
current prevails.) ( 
