94 



177. The annual mean tidal ranges at Fort Hamilton, as observed, 

 and after correction for the longitude of the moon's node, for the years 

 1893 to 1932 are plotted in figure 35 from the data given in Special 

 Publication, No. Ill of the United States Coast and Geodetic Survey 

 (1935 edition). 



The variation in the observed annual ranges with the longitude of 

 the moon's node, A^, is apparent in the figure. The increase in the 



SO 





A.6 



N 



180 



I 



180 



!i 



Oq C O 



4- 



I4Z5Z+' 



°o o 



Tsxr 



^«e- 



OoO 



I I ' I ' I ' M I I I 



o 

 CD 



I I I I I I ' I I I I ' I I I I I I ' I I I . I I , I 



Observed "Ranjge, o 



o 



Corrected + 



Figure 35.— Observed and corrected annual mean tidal range Fort Hamilton, New York, Harbor. 



corrected ranges between 1902 and 1912 coincides with the major 

 enlargement of the harbor entrance in the dredging of the Ambrose 

 Channel during this period. 



178. Table VI is not extended to give the values of i^(Mn) for values 

 of (Ki+0i)/M2 in excess of unity. When this ratio exceeds unity the 

 tides are decidedly of the mixed type, and the diurnal inequalities 

 become their important feature. A study included in Special Publica- 

 tion, No. 115, United States Coast and Geodetic Survey, of the annual 

 mean tidal ranges at San Francisco, Calif., where the ratio (Ki +0])/M2 

 is 1.1, shows that any effects of the longitude of the moon's node on the 

 annual mean tidal ranges during the 26-year period from 1898 to 1923 

 are completely overshadowed by accidental variations in the ranges, 

 and that the correction of the observed ranges for the longitude of 

 the moon's node serves little purpose in reducing the observations to 

 better concordance. 



179. The correction for the longitude of the moon's node is applied 

 only in an independent determination of mean low and high water 

 datums at a station. Ordinarily these datums are determined by a 

 comparison of the high and low waters with those at an established 

 base station (par. 196 et seq.) at which the correction already has 

 been applied. The approximations inherent to this correction are 

 practically eliminated when the datums are determined from observa- 

 tions extending over nine years, the period in which the moon's node 



