Chapter XIV 



Tides of the Oceans 



1. First Co-tidal Chart of the Oceans 



One could get a better picture of the tidal processes in the oceans if the 

 distribution of the phase and amplitude of the tidal wave would be given 

 for all points of the oceans. We would then have maps with co-tidal lines, 

 and maps with co-range lines places for the various parts of the oceans. 

 We have seen that from a pure mathematical standpoint, this problem cannot 

 be solved now. The theory can only tell us how various factors affect the 

 development of the tidal wave in the oceans and how they try to force certain 

 forms on the co-tidal lines and on the distribution of the amplitudes. At the 

 present time it seems fit to look at the observations from a geophysical view- 

 point, based on the harmonic constants of the principal tides which are avail- 

 able for coastal localities and islands, and to connect these constants into 

 an oscillating system extending all over the oceans. The main problem is then 

 to select from the large number of possible oscillating systems, the system 

 which is geophysically the most probable one on the basis of the theory of 

 the tides. The degree of reliability of such a picture depends, of course, upon 

 the number of available observations from coastal localities and islands far 

 away from the coast. It is very important to obtain reliable tidal constants 

 of islands if we want to further our knowledge of the ocean tides. 



Up to 1911 only two attempts had been made to present the tides of the 

 oceans in a map. Whewell (1833, 1836) has made a map for the Atlantic 

 Ocean, which he based on new data collected by himself for this purpose. 

 Whewell realised that his map could only be considered as rough approxima- 

 tion to the real conditions. It was limited to the semi-diurnal tides, as he could 

 only base it on the establishments. Berghaus (1845, 1892) incorporated this 

 map in an extended form in his atlas, thus giving it wider distribution though 

 Whewell (1848), had retracted his presentation of the ocean tides because 

 of the many criticism. Nowadays Whewell's map retains only an historical 

 interest. 



Whewell's map of the co-tidal lines indicates that the tidal wave in the 

 ocean is mostly a progressive wave and since that time this viewpoint was 

 adopted by the geographers. This is also the viewpoint taken by KrUmmel 

 in his textbook of oceanography. He was not very successful in trying to 



