112 U. S. COAST AND GEODETIC SURVEY 
1925 1930 1935 1940 1945 
Los Angeles 
Foot 
1.0 
0.5 
Seattle 
Ketchikan 0.0 
Fic. 53.—Yearly lower low water, Los Angeles, Seattle, and Ketchikan. 
yearly height of lower low water from the corresponding yearly height of sea level. 
Figure 54 shows the result for the three Pacific coast stations used above. 
The horizontal line of each of the diagrams of Figure 54 represents the average fall 
of lower low water below mean sea level, the figures to the left of each line giving this 
fall in feet. The yearly values are seen to range themselves more or less closely along 
the sine-like curves drawn for each diagram. The period of this periodic variation is 
18.6 years and is associated with the period of the change in longitude of the moon’s 
node. At Los Angeles the range of this variation in yearly lower low water is 0.2 foot; 
at Seattle, 0.6 foot and at Ketchikan 0.15 foot. 
