Long Waxes in Canals and Standing Waves in Closed Basins 189 



canals under consideration, a plausible explanation based on Merian's for- 

 mula for most observed periods. In general, the oscillations in these bays 

 and harbours have a period smaller than half an hour. Only on Trieste there 

 is sometimes a seiche with an average duration of 3-2 h which is always ac- 

 companied by great variations in water level (the average of fifteen cases 

 was approximately 75 cm, with a maximum of 156 cm). These are oscilla- 

 tions of the whole Gulf of Trieste, which can be imagined to be closed off 

 from the open sea by a line drawn from Capo Salvadore to a point located 

 somewhat to the west of Grado. This line is, in fact, the nodal line of the 

 oscillation. Merian's formula with a correction for the opening of 1-2943 

 gives a period of 3 1 h, in good agreement with the average observed period 

 (see Caloi, 1938). It seems, however, that part of the Adriatic west of this 

 nodal line participates in the oscillation, because the tide gauge at Falconera 

 (about 30 km to the west of Grado) clearly shows an antinode with a phase 

 opposite to that of Trieste. Smaller oscillations (0-78 h and less) registered 

 in Trieste are oscillations of the Bay of Muggia and of the harbour. For the 

 causes of the great seiche of 3-2 h we refer to p. 224. 



In the eastern part of the Mediterranean there occur also seiches at any 

 point where the configuration of the coast is appropriate for free oscillations 

 of the water-masses. If the amplitude of the tide is small and the seiches 

 rather large, then it happens that the tides are concealed by the seiches. 



The most famous example of standing waves in the Mediterranean is 

 considered to be the currents in the narrows between the Greek mainland 

 (Phokin and Voiotia) and the island Euboea. Forel (1879, p. 859) was the 

 first to relate the rapidly changing currents (4 m/sec) in the narrows of Khalkis 

 with the seiches in the northern and southern channels. Kruemmel (1888, 

 p. 331), submitted the observations of Miaulis to a thorough discussion, 

 which confirmed to him the correctness of Forel's assumption. Endros (1914) 

 and Sterneck (1916) (see also Defant, 1917, p. 329) have solved the Euripus 

 problem, on the basis of hydrodynamical considerations. The narrows at 

 Khalkis are composed of two parts each of 18 m length and approximately 

 6 m respectively 1 m depth (total cross-section 126 m 2 ), and separated by 

 a small island. The currents in these narrows are very irregular, which is to 

 be attributed to differences in the level of the sea surface north and south 

 of the narrows. Endros considers these differences in the water level to be 

 caused by (1) difference in the tides north and south of the narrows; (2) the 

 occurrence of seiches in the northern and southern channels; (3) piling up 

 of water in the channels by the winds. 



The tides of the Aegean Sea reach the narrows of Khalkis from the north 

 through the Trikeri and Oreos channel and from the south-east through the 

 Gulf of Petali. Both Endros and Sterneck were able to compute from the 

 observations of Miaulis the tidal constants of the semi-diurnal tides for the 

 northern and southern harbour of Khalkis. They found that the large dif- 



