20 U. S. COAST AND GEODETIC SURVEY 
above sea level. The average difference between the two low waters of the day, there- 
fore, was 7.30 feet, or very nearly as much as the average difference between the high 
waters and low waters. For the high waters, the average difference between the higher 
high and lower high waters was 1.97 feet. 
For the greater part of the month it is seen that the higher low water did not fall 
as low as mean sea level which, for each ten-day group of the observations, is repre- 
sented by the corresponding horizontal line. The differences between the two low 
waters of a day are seen to be most marked near the times when the moon is in the 
tropics. In June 1934, the moon was at its maximum semimonthly declination on the 
11th and on the 26th. On the 27th, the difference between morning and afternoon 
low waters was 11.5 feet. 
Around the days when the moon was over the Equator, which occurred on the 
Ath and 19th of the month, it will be noted that the tide at Seattle exhibits the inequality 
principally in the high waters. This emphasizes the fact which was noted in connection 
with the Honolulu tides, that at least a month of observations is required to determine 
the character of the tide at any place. 
The third form of the mixed type of tide, in which the inequality is exhibited in 
approximately equal degree by both high and low waters, is exemplified by the tide 
at San Pedro (Los Angeles Harbor), California. The tide curve for the month of June 
1934 at that place is shown in Figure 8. 
[\ LN /\ n/n ee [\ 
MAY 
nee 
Fia. 8.—Tide curve, Los Angeles Harbor, June 1934. 
