Tides in the Mediterranean and Adjacent Seas 



389 



likewise according to observations transformed into amphidromies; this is 

 particularly the case for the one in the eastern basin. The Mediterranean can 

 be considered to be divided by these three nodal lines of the longitudinal 

 oscillations in six sections, each of which extends from an antinode to a node 

 and vice versa. 



Fig. 163. Oscillating areas of the Mediterranean (numbers indicate average establishments 

 in central European time, those in the Black Sea in Eastern European time) (Sterneck). 



The interpretation of these basic facts, which were found rather early 

 (see Grablovitz, 1909, p. 191) goes back to two different fundamental ideas 

 (see Merz, 1914). One is based on an assumption expressed by Darwin that 

 the Mediterranean is so completely closed by the Strait of Gibraltar that 

 only independent tides can develop in this sea, like in a large lake, so that 

 in each basin only forced oscillations are possible. Sterneck (1912, p. 1245), 

 who at first accepted this conception, has explained the equal establishments 

 in the large basins of the western Mediterranean (between the Balearic Islands, 

 Corsica and Sardinia, on the one hand, and in the Thyrrhenian Sea on the 

 other hand) by assuming forced oscillations, such that in the coastal regions 

 of these basins high water occurs simultaneously, while at the same time 

 the central parts of the basins have low water, and vice versa. For such 

 oscillations the nodal lines would be closed in themselves. De Marchi (1908, 

 p. 12) has proven, however, that such oscillations caused by the vertical 

 component of the tide-generating forces can only be very small and that 

 they cannot deserve any consideration; unless the period of the impulses 

 coincide with the period of the basin, which is not the case. Later on, Sterneck 

 has found that these oscillations, which would require a constant water volume 

 in the individual basins, do not exist. A great amount of tidal energy pene- 

 trates through the Strait of Gibraltar into the western Mediterranean and 

 influences conditions in the western basin. 



A second mode of interpretation of the observations denies in advance 



