TIDAL DATUM PLANES ; Sl 
1 a) 10 1 20 aBID5 30 
DA 
Atlantic City 
Los Angeles 
Pensacola 
Fic. 39.—High waters, Atlantic City, Los Angeles, and Pensacola, October 1947, referred to instantaneous sea level. 
with the variation in phase and in parallax, the highest high waters coming at the times 
of new and full moon, or when the moon is in perigee, while the lowest high waters come 
at the times of the moon’s Ist and 3d quarters, or when the moon is in apogee. The 
effect of the moon’s declination is also evident, giving greater inequalities in the high 
waters at the time of the moon’s northing and southing, and least inequality, near 
the times when the moon is over the Equator. ‘These are the typical variations in the 
semidaily type of tide. 
At Los Angeles the variations are much the same as at Atlantic City, except that 
the inequality in the high waters is much greater. At Pensacola the variations in re- 
