43 



by averaging the hourly tidal heights at the 12-hour period of this 

 component. For example, the hourly tidal heights at Sitka. Alaska, 

 for the first 3 days, and the average of both the morning and after- 

 noon hourly tides for a 15-day period beginning July 1, 1893, are shown 

 below, the heights during the other days of the period being omitted 

 for brevity. 



Hourly height of tide, in feet 



The average heights derived in the last column are then the ap- 

 proximate hourly heights of the S2 component, and its overtides, 



\S' 



10 - 



-p 



o 



bO 



•H 

 0) 



AM 



s 



Cranplete Tide - 



S 2 c omponent 



Z 



?IV) 

 e 



9 



a 



Mean Solar Hours 



Figure 24.— S2 componeut at Sitka, .\laska. 



above datum. The recorded hourly heights for the first day, and of 

 the S2 component as thus computed, are plotted in figure 24. 



81. The amplitude of the S2 component at Sitka shown by the plotted 

 curve conforms well with value of 1.137 feet found from a year's 

 observations. The symmetry of the curve indicates that this com- 



192750—40 4 



