Tides in the Mediterranean and Adjacent Seas 445 



alternating current with velocities averaging 18 knots. The average time of 

 the reversal of the current is at the opening 35 min after high water at St. John. 

 This speaks also in favour of a standing wave as co-oscillating tide. Towards 

 the end of the bay the velocity increases somewhat with narrowing cross- 

 sections; in the Minas Basin velocities of 9 knots have been measured; this, 

 however, can only occur in a very limited region. 



In the Petit Coudiac (in the centre of the Chignecto Basin) a bore follows 

 the larger tidal ranges existing there, which impedes the practical use of the 

 waterway and requires very expensive constructions on the banks and at the 

 landing points (p. 469). Furthermore, with storms from the south-west water- 

 masses in the canal pile up so that storm tides can still increase the tidal 

 range by 2 m (6 ft) and more. Famous is the "Saxy" tide of 5 October, 1869, 

 when the water level in the Coudiac River was as high as 8 9m (29 ft) above 

 and 7-2 m (236 ft) below the normal sea level; so the range was 161 m 

 (52-5 ft) (see Dawson 1902, p. 85). Older reports mention tidal ranges of 

 21 3 m (70 ft) in the Coudiac River, according to Herschel (1875, p. 756), 

 even as high as 36-5 (120 ft). Dawson is of the opinion that these figures 

 are very much exaggerated. 



20. The Tides of the White Sea and of the Gorlo 



The orographical configuration of the White Sea seems very intricate; 

 it can be divided into three sections: The main basin with its greatest depths 

 of 350 m (1180 ft) extending from the north-west (Kandalakshskaya Bay) to 

 the south-east divided into the Dvinskaya Bay and the Bay of Onezhskaya, 

 20 m (65 ft) -40 m (1 30 ft) deep. This main basin communicates with the Barents 

 Sea by way of the bow-form Gorlo and later through the Woronka funnel. 

 There are a large number of tidal observations, with establishments and ranges, 

 for a number of localities. At the outer opening of the Gorlo the establishments 

 are about 7 h (Greenwich time), the tidal ranges at spring tide vary between 

 2-3 m. The tide wave retards little at first and then rapidly, to 8 and 9 h, 

 and attains about 1 h at the inner opening while the range decreases. The 

 entire north and north-west coast of the main basin has a phase of 1 h. At the 

 south coast the establishment becomes 3i h up to the opening into the Bay 

 of Onezhskaya. The same phase applies to the Bay of Arkhangelsk, whereas 

 in the Bay of Onezhskaya we find 6 h 40 min. 



Shoulejkin (1926, p. 321) has tried a hydrodynamical explanation of these 

 tides based on Airy's canal theory. He based his chart of co-tidal lines on 

 Airy's viewpoint that the crest of the tide wave has a different velocity of 

 propagation perpendicularly to the cross-section, which viewpoint, however, 

 proved to be erroneous (p. 148). Therefore, his presentation cannot be ex- 

 pected to agree with actual conditions. In interpreting the tides in the White 

 Sea, it should be borne in mind that the period of the free oscillation of the 

 entire basin is about 10 h or v =08 (see Defant, 1925, p. 71). This means 



