Tides in the Mediterranean and Adjacent Seas 



395 



explained by the position of the nodal line of the semi-diurnal tides in the 

 western part of the western basin, where at the same time the diurnal tides 

 have an antinode. The Ligurian Sea, which is not close to a nodal line 

 neither of the semi-diurnal nor of the diurnal tides, has an ratio of 56, 

 which does not deviate essentially from the normal value of 49. In the 



Ug. 

 seo 



Tyrrh. Ionian 

 seo seo 



Fig. 



166. Distribution of the amplitude of the diurnal partial tides in the Mediterranean 

 (Sterneck). , co-oscillation with Atlantic ocean, independent tide. 



Tyrrhenian Sea with an antinode of the semi-diurnal tides there is a decrease 

 of the ratio to 0-30, which continues in the Ionian Sea to 0-24, because here 

 lies the nodal line of the diurnal tides. In Alexandria the ratio is also not 

 much greater, as the amplitudes of the semi-diurnal tides increase towards 

 the east. 



6. The Tides in the Strait of Messina 



There are in the Strait of Messina strong currents which have the rhythm 

 of the tides and which are known since antiquity by the Homeric description 

 of Scylla and Charybdis. It was already known to Aristotle that these currents 

 are associated with the tides in neighbouring seas. The first compilation of 

 the basic facts (1824) is due to the French Vice-Consul in Messina, Ribaud. 

 A detailed description of the current conditions throughout the whole strait 

 was given by Marini in 1917. Later on, these phenomena were investigated 

 from a biological viewpoint without dealing with the geophysical process as 

 such. A first extensive oceanographical survey of the entire phenomenon was 

 made by Vercelli (1925) aboard the research ship "Marsigli" in 1922-23. 

 These observations were the basis of a geophysical explanation given by 

 Defant (1940, p. 145). An extensive description of the eddies and currents 

 within the strait has been given recently by Mazzarelli (1938). The stationary 

 currents at the narrowest point of the strait flow in a southward direction, 



