Tides in the Mediterranean and Adjacent Seas 



387 



in the southern part of the North Channel. The opening in the north has 

 an amphidromy, as a transition to the oceanic tides. 



The extensive bays and sounds on the east coast of the Irish Sea have 

 a great influence on the development of the tides. The tides of the Bristol 

 Channel have been discussed by Taylor (1921, p. 320). The water-masses 

 in the area off Liverpool and in the Solway Firth, as well as in the Firth 

 of Clyde, co-oscillate with those of the Channel outside the opening and 

 a considerable part of the penetrating tidal energy is used up through friction. 



Borgen (1894, p. 395) has also in this case tried to explain the Irish tides 

 by assuming two progressive waves travelling in opposite directions; this expla- 

 nation, however, agrees only partly with the observations. The later used 

 hydrodynamical methods as applied by Defant have permitted the numerical 

 computation of the tides and tidal currents. On the basis of eighteen cross- 



700 

 cm 



600 

 500 

 400 

 300 

 200 

 100 



Irish Seo 



Fig. 162. Semi-diurnal tide in the Irish Sea (spring tide values of the tide tables). 



sections, Defant (1919) computed the co-oscillating tides of the water-masses 

 of the entire channel with the tides at the north and south openings, taking 

 into account all adjacent bays. As the difference in phase at these openings is 

 less than one hour and, as the amplitudes there are almost the same, the 

 superposition of the two co-oscillations does not essentially change the charac- 

 ter of a standing wave, and there are two places where the range is small and 

 the variation in the phase is rapid. Here again, as in the English Channel, the 

 rotation of the earth is not able to transform the nodal line into an amphi- 

 dromy; the crowding of the co-tidal lines, especially on the Irish side in the 



25" 



