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Several tidal datums of practical importance are described. Sources of detailed information are 

 identified. Difficulties associated with surveys which extend over a wide range of latitude and eleva- 

 tion are discussed. 



Statistical characteristics of the astronomical tides at various U.S. ports are investigated and 

 documented with graphs and tables. The distribution function for astronomical tidal heights is 

 found to be nearly symmetric at many stations. At many other continental tide stations, the astro- 

 nomical tide remains above mean sea level (MSL) more than half the time, but departs farther from 

 MSL in a negative rather than in a positive direction. At Honolulu, Hawaii, the predicted tide is 

 below the MSL more than half the time and positive departures are larger than negative departures. 



A technical glossary and supplementary tables are included. 



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