226 The Mediterranean Sea 



might have a sine or arc capable of being measured in feet and 

 inches when the radius is as much as 200 miles long. Thus at 

 Port Mahon, in the island of Minorca, according to the Admiralty 

 Sailing Directions, the water rises and falls according to the 

 direction of the wind. With wind from south-east or south- 

 west the water rises, but from north-west or north-east it 

 falls. When northerly or north-westerly winds prevail, and this 

 is the case for two-thirds of the year, a strong current sets to 

 the south-west off Ayre Island, which is reversed in seasons 

 when south-westerly winds prevail. This current is due to 

 the water escaping round the end of Minorca having been 

 driven southward so as to raise a head on the north coasts of 

 the island. Similarly, in the Faro or Strait of Messina the 

 currents, of which the famous Scylla and Charybdis are swirls 

 or eddies, are the evidence of a tendency towards equalizing 

 the levels of the eastern extremity of the western basin and of 

 the western extremity of the eastern basin. In addition to 

 this peculiarity of position with reference to the two basins, 

 it has been found that there is a very strong purely tidal 

 influence at work which alone produces an alteration in the 

 direction of the currents, and thus adds to the confusion of 

 the waters. At Capo di Faro the rise is scarcely perceptible, 

 at Messina it may attain a maximum of 10 to 13 inches. In 

 the Straits of Bonifacio, between Corsica and Sardinia, the 

 currents follow entirely the direction of the prevailing winds, 

 and are at times very rapid. In the channel between Sicily 

 and the African coast the currents also follow the winds. In 

 long periods of calm weather a steady easterly set is observed, 

 no doubt a prolongation or reproduction of the Gibraltar 

 current. 



Temperature. Nothing whatever was known of the 

 temperature of the deep water of the Mediterranean until 

 Saussure extended to it his classical investigation into that 

 of the Swiss lakes. In October 1780 he sank his thermometer 

 to a depth of 160 fathoms off Genoa and of 320 fathoms off 

 Nice, and at both depths he found the temperature of the water 

 to be 55*8 F. These observations have a special value, for, 

 owing to Saussure's method of experimenting, his results were 



