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ANNUAL REPORT SMITHSONIAN INSTITUTION, 1934 



diagram the two constituent tides have such time relations that their 

 low waters occur at the same time. The resultant tide in this case 

 resembles the tide at Seattle, the differences between morning and 

 afternoon tides being wholly in the low waters. The middle diagram 

 represents the case in which the high waters of the two constituent 

 tides occur at the same time, and now the resultant tide resembles 

 that at Honolulu, the differences between morning and afternoon 

 tides being exhibited wholly in the high waters. Finally, the lower 



diagram represents the 

 conditions resulting when 

 the two constituent tides 

 are at sea level at the same 

 time. Now the resultant 

 tide resembles that at San 

 Diego, the differences in 

 the morning and after- 

 noon tides being exhibited 

 in equal degree by both 

 high and low waters. 



It appears, therefore, 

 that the varieties of tides 

 represented by such tides 

 as at Seattle, Honolulu, 

 and San Diego arise from 

 a mixture of daily and 

 semidaily tides of ap- 

 proximately equal range. 

 Such tides are known as 

 the mixed type. 



Tides in which a stand 

 occurs, as at Galveston 

 and Manila, can be shown 

 to arise from a combina- 

 tion of a daily and a semi- 

 daily constituent in which 

 the former has twice the range of the latter. If in the case repre- 

 sented by the lower diagram of figure 4, we take the range of the 

 daily constituent twice that of the semidaily, it is found that the 

 resultant tide will have but one high and one low water with a stand 

 on the rising tide. If we take the two constituents such that are at 

 sea level at the same instant, but both rising instead of falling, as in 

 figure 4, the stand will occur on the falling tide. And it is to be 

 noted that both the daily and semidaily tide-producing forces vary 

 in intensity from day to day, the former being greatest when the 



FiGUEE 4. — Combination ot daily and semidaily 

 constituent tides 



