SECT. 5] TIDES 703 



of li, 89.05% of all differences are located in the interval ± 5 cm. For ^2 the 

 corresponding figure is 88.62%. In both cases the total number of differences 

 are restricted to the interval ± 26 cm with only one exception. The ^2 

 difference in the Wash reaches 68 cm. The difference method yields not only 

 the variation of sea-level but also the components of currents. In the North 

 Sea there is a relatively large number of records of tidal currents which render 



2.0 



1.5 



1.0 



0.5 



/ 



I- 



-1.0 



0.5 



1.0 



1.5 



2.0 m 



-1.0 -■ 



Fig. 22. Correlation between ob.served (vertical axis) and computed (horizontal axis) 

 elevation ^o of the M2 constituent in the North Sea. 



possible the comparison between observed and comptited currents. Fig. 25 

 contains on the a::-axis computed maximum values, and on the ?/-axis observed 

 maximum values of tidal currents. In Fig. 26 the x-axis represents the dif- 

 ference between the observed and computed velocity in cm/sec, the ^/-axis 

 represents the number of occasions on which, between integral numbers of 

 cm/sec, these differences existed. 73.68% of all differences are in the interval 

 ± 5 cm/sec and 91.02% are in the interval ±10 cm/sec. 



