188 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



sea about as much as it has fallen below that level. At Pensacola the 

 tide has risen and fallen only once each day, and it is generally equally 

 above and below the mean level. At San Francisco there are two 

 highs and two lows each day, but there is a difference between the two 

 high waters and between the two low waters. 



The characteristic features of these tides are repeated throughout 

 the year, and are the normal characteristics of these three seaports. 



Typical tide curves at Seattle, Honolulu, and San Diego are shown 

 in figure 2. At each of these ports, there are two high and two low 



Figure 2. — Tide curves, Seattle, Honolulu, and San Diego. 



waters in a day. At Seattle the high waters do not differ much in 

 height, but the low waters exhibit a marked difference. Note that 

 on the last day, the difference in height of successive low waters is 

 10y 2 feet. At Honolulu the curve shows that the difference in height 

 of the high waters is more marked than for the low waters. If we 



