TIDAL DATUM PLANES ii 
Fic. 5.—Tide curve, Pensacola, June 1934. 
The Mixed Type of Tide 
The mixed type of tide is defined as one in which two high waters and two low 
waters occur in a tidal day but with marked diurnal inequality. By its name this 
type of tide indicates that it arises as a mixture of daily and semidaily constituents of 
the tide. Strictly, all tides contain daily and semidaily constituents. In the semi- 
daily type, however, the daily constituent is relatively so small that it is overshadowed 
by the semidaily constituent in the resultant tide. Similarly, in the daily type of tide, 
the semidaily constituent is relatively so small that the resultant tide exhibits primarily 
the features of the daily constituent. It is only when the two constituents do not 
differ greatly in magnitude that the resultant tide clearly reveals the presence of both 
constituents and the term ‘‘mixed tide”’ is then employed. 
In the discussion of the combination of daily and semidaily constituent tides, it 
was found that the diurnal inequality in the height of the tide may be featured in three 
different ways: (1) principally in the high waters; (2) principally in the low waters; 
(3) in approximately equal degree by both high and low waters. The mixed type of 
tide, therefore, naturally divides itself into the above three classes. Figure 6, which 
reproduces the record of the rise and fall of the tide at Honolulu, Hawaii, for the month 
