The Harmonic Analysis of Tidal Observations 



307 



F: 0-25—1-5 mixed, mainly semi-diurnal type. There are daily two high 

 and two low waters which, however, show inequalities in height and time, 

 which attain their maximum when the declination of the moon has passed 

 its maximum. The mean spring tide range is 2(M 2 + SV). 



F: 1-5—3 mixed, mainly diurnal type. Occasionally only one high water 

 a day, following the maximum declination of the moon. At other times there 

 are two high waters in the day, which show, however, strong inequalities 

 in height and time, especially when the moon has passed through the equator. 

 The mean spring tide range is 2(AT 1 +0 1 ). 



F: 3 0— oo diurnal type. Only one high water daily, and the semi-diurnal 

 almost vanishes. At neap tide, when the moon has passed through the 

 equatorial plane, there can also be two high waters. The mean spring tide 

 range is 2(X 1 + # 1 ). 



Table 33. Harmonic constants of the principal component 



tides for four ports. 



Characteristic of the different types of tides 



In order to illustrate the influence of the type of tides in a harbour, Fig. 123 

 shows the tidal curves of four harbours with different types of tides calculated 

 in advance for the month of March 1936 according to the tidal constants 

 (see German tide tables, 1940). Table 33 contains the harmonic constanst 



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