TIDAL OBSERVATIONS. 



137 



MayG. 



G9. The following is a comparison for fourteen days, commencing 1859, 

 March 1 6, of the recorded heights at Fort Point, San Francisco Bay, Cali- 

 fornia, with the heights calculated from the analyzed tide-components (§ 66). 

 In the calculation of the heights, the mean level of the water as determined 

 by the observations for the whole year was used. The difference between 

 this mean level and the me;m of the twenty-four hoiirly heights (corrected 

 for all sensible lunar influence) for each day is also given. The effect of this 

 is to greatly improve the differences (C— R). The following tide-components 

 were omitted in the calculations : — the whole of the long-period tides, the 

 luni-solar semidiurnal tides X and /j, and the Helmholtz shallow-water quarter- 

 diurnal tide MS. The computations are for heal time. 



