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ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 34 



Fla., and San Francisco, Calif., for the last 4 days of May 1931. 

 These are shown in figure 1, the horizontal line associated with each 

 tide curve representing the undisturbed or mean level of the sea. 

 At Norfolk, it is seen, there are two high and two low waters in a 

 day, morning and afternoon tides differing but little, and the high 



FiGDEB 1. — Tide curves, Norfolk, Peusacola, and San Francisco, May 28-31, 1931. 



waters rising approximately the same distance above sea level as the 

 low waters fall below it. At Pensacola, on the same days, there were 

 but one high and one low water each day. And at San Francisco, 

 while there were two high and two low waters each day, the morn- 

 ing tides differed very considerably from the afternoon tides. 



It must be emphasized that the differences in the tides at the 

 three places shown in figure 1 are in no way due to the disturbing 



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