THE TIDES 



Chaptee I 



GENERAL DEFINITIONS: THE TIDE-PRODUCING FORCES: 

 EQUILIBRIUM TIDES 



Paragraphs 



Definitions 1-6 



Lunitidal intervals 7-13 



Tide-producing forces 1 4-21 



Tide-producing potential 22-25 



Surface of equilibrium and equilibrium tide 26-32 



Effect of the earth's rotation 33 



Effect of the declination of the moon 34-42 



Effect of variation in the moon's distance 43 



Solar equilibrium tides 44 



Tidal components 45 



Actual tides ^ 46-48 



GENEEAL DEFINITIONS 



1. The tide is the regular periodic rise and fall of the surface of the 

 seas, observable along their shores. The concurrent horizontal move- 

 ments of the water, whether the almost imperceptible drift in the 

 open sea, or the strong flow through a, contracted entrance to a tidal 

 basiri, are designated, in accordance with the practise of the United 

 States Coast and Geodetic Survey, as tidal currents. 



2. High and low water. — The maximum height reached by each risuig 

 tide is called high water, and the maximum depression of the falling 

 tide is caJled low water. On the Atlantic coast of the United States 

 the tide rises and falls twice daily — or more accurately twice during 

 the lunar day of 24 hours and 50 minutes. The two high waters and 

 the two low waters are each so nearly equal that for ordinary purposes 

 no distinction need be made between them. On the Pacific coast the 

 two high waters and the two low waters occurring daUy are in general 

 markedly different, and are designated as the higher high water, the 

 lower high water, the lower low water, and the higher low water. On 

 the Gulf of Mexico the tides are small, and toward its western end 

 but one tide occurs each day during a part of the month. 



The heights of the high waters and of the low waters vary from day 

 to day. In many parts of the world, the high waters reach their 

 greatest height, and the low waters the least height, soon after the 



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