

Figure 113. Diagram of changes in amplitude of the tide upon progressing 

 into shallow water. Comparative value of amplitude is shown 

 by the vertically hatched strip. 



3 . Every horizontal movement on the earth is deflected to the right in the northern hemi- 

 sphere and to the left in the southern due to the force of the earth's rotation. This is also felt in 

 the tidal phenomena. Thus, due to this influence of the earth's rotation, everywhere in the 

 northern hemisphere the tidal amplitude is considerably greater on the right hand shores (with 

 relation to the spreading of the tidal wave) than on the left hand shores. 



Figure 114 shows the amplitudes of the spring tides along the shores of the White, Barents 

 and Kara Seas, which confirm this phenomenon. 



Depending on local conditions, the tidal variations of the water level and the current may be 

 extremely diverse. Nevertheless, three basic groups of tidal phenomena may be noted: along 

 the shore, in narrow straits, and in the open sea. 



Along the shore the extreme levels usually coincide with the change of the tidal currents. 

 The variations of level are of the greatest practical interest here. 



In narrow straits the extreme levels coincide approximately with the maximum speeds of 

 the tidal currents. The change of tidal currents occurs approximately at mean tide level. The 

 horizontal orbits represent very nearly straight lines extending approximately along the axis of 

 the straits. It is as if the water masses are carried back and forth along the axis of the strait. 



In the open sea the variations of level have almost no significance. The horizontal orbits 

 are nearly circular and the water particles, due to the deflecting force of the earth's rotation in 

 the northern hemisphere, move in a clockwise direction. In regard to this my observations in the 

 open part of the Barents Sea provide a typical example . 



Figure 115 shows the horizontal orbits of water particles during the period of the tidal 

 current at depths of 0, 25, and 50 m all in the same scale. These were obtained by simultaneous 

 observations on 5-6 July 1928 at 73° 16.6' north 38° 24.5' east to depths of 260 m. In all cases 

 the permanent current is excluded. In examining the drawings, attention is directed to the 

 following: 



1. The horizontal orbits of the particles are almost circular. 



326 



