Chapter XI 



Tides and Tidal Currents 

 in the Proximity of Land 



1. Preliminary Remarks 



The following paragraphs are part of the more recent developments in the 

 tidal theory. It is not so much intended to consider the tides of the oceans 

 as a whole, but rather to explain the actual tides in certain adjacent seas. 

 Starting out from the dynamical theory, the phenomena are treated from 

 a geophysical viewpoint. Above all, the important relations between the 

 vertical tide and the tidal currents are studied in detail. 



In studying the tides synthetically, it was found best to proceed from the 

 elementary to the more complicated questions and to study separately the 

 modifying effects of single factors, amongst which the most important are 

 the influences of the configuration of shore and bottom, the change caused 

 by the earth's rotation and the distortion caused by friction. The results 

 were applied first to the tidal phenomena of shallow parts of the ocean com- 

 municating with the vast expansions of the open oceans by straits and chan- 

 nels. The tides of these adjacent seas seem often to be independent and, 

 apparently, their relationship with the tides of the open oceans is often very 

 limited. These shallow waters are located without exception on the wide con- 

 tinental shelf; shallow water and complicated orographical coastal contours 

 can strongly influence the tides. The friction caused by the sea bottoms is 

 so powerful here that it is able to influence the motions of the entire water 

 layer up to the surface. In this sense we then speak of tides "in the proximity 

 of land". 



2. General Considerations on the Influence of the Earth's Rotation and of the 

 Friction on Tides and Tidal Currents 



(a) Influences Due to the Earth's Rotation 



In Chapter VI, 1/a (p. 142) is explained the form of the progressive tide 

 waves in a non-rotating canal of uniform depth, if friction is neglected. 

 The vertical tide and the tidal currents are given by the equations (VI. 3 and 6); 

 they have the form 



t) = rj sm((7t—xx) , 



