478 



Tides of the Oceans 



used for the prediction of the tides (p. 317, see also Shureman, 1924). 

 Dietrich (1944, p. 69; 1943, p. 123) used all these data to map the tides 

 of the ocean, which is much more reliable than previous attempts. The map 

 was limited to the oceans, omitting the adjacent and boundary seas, which 

 require a different approach. Table 79 shows the increase in the number 

 of constants used by Dietrich compared to those used by Harris in 1904 

 and Sterneck in 1920. The distribution of the data over the different oceans 



Table 79. Number of localities used for the study of the 

 tides of the oceans 



is still very irregular and by no means uniform. There are coasts which are 

 covered with localities for which harmonic constants have been computed 

 and, on the other hand, there are hundreds of miles of coastline for which 

 no constants are available at all. Many more data are needed for the coasts 

 of Africa, Australia and on the Pacific side of Central and South America; 

 also for the coasts of the Antarctic and for islands in the oceans which would 

 be of special importance for this problem. Very few data are available from 

 islands in the Pacific. The hydrographical work done by the Japanese has 

 provided us with data for the main islands, but we have only very few con- 

 stants for the islands of the eastern Pacific Ocean. It is easy to see that the 

 progress of our knowledge in the geographical distribution of the tides over 

 the ocean depends upon new observations of this kind. 



The published phase and amplitude values can only be used after scruti- 

 nizing them closely. Discrepancies in the phases must be rectified. These 

 discrepancies are mostly sudden variations of the phase by 180° or 90° in 

 neighbouring localities were this cannot be explained orographically, and 

 Dietrich has taken great pains in eliminating dubious values. He specially 

 refers to his list of dubious harmonic constants. The corrected phases which 

 are mostly referred to the local or zone time {x or g values) must be changed 

 into Greenwich Time. In this connection see p. 372. The data entered in 

 geographical maps show the phase at the coast and for the few islands, but 

 to connect these data across the oceans, the author needs a vast knowledge 



