Tides in the Mediterranean and Adjacent Seas 



391 



basin through the Straits of Tunis and Messina. These co-oscillating tides 

 can be accurately determined by the method of the step-wise integration of 

 the hydrodynamical equations (p. 339), because we know the water-masses 

 which pass through the straits within a half-tidal period. According to the 

 current observations of Captain N. S. Nares there is from 3 to 9 h an inflow 

 of 69-8 km 3 into the western basin, which enables one to compute the co- 

 oscillating tide for all cross-sections. The co-oscillating tide is larger than 

 the independent tide (a little east of Gibraltar about at the ratio 5:3) and 

 it is evident that the influence of the tides of the Atlantic Ocean on those 

 of the Mediterranean is considerable. The nodal line of the oscillation in the 

 western section of the basin is between Cape de la Nao (between Valencia 

 and Alicante) and a point of the Algerian coast between Alger and Oran. 



Fig. 164. Longitudinal oscillations of the semi-diurnal tides in the western and eastern 



basins of the Mediterranean. , theoretical distribution of the springtide ranges; •••••, 



observed values; positive values: phase around 3 h; negative values: phase around 9h Central 



European Time. 



For the co-oscillation of the western basin with the eastern basin, we can 

 consider first the Strait of Messina. One can use the same cross-sections 

 as for the co-oscillation with the Atlantic Ocean and obtain at the western 

 end of the basin a range of only 3 cm; the nodal lines he in the centre of 

 the Tyrrhenian Sea. Somewhat greater is the influence of the co-oscillation 

 through the Strait of Tunis. On account of the position of this opening, 

 it was necessary to select another arrangement of the cross-sections. One 



