494 



TIDES. 



[Ch. XX. 



according to Rennell, of five feet.* In the Syrtes, also, of 

 the ancients, two wide shallow gulfs, which penetrate very 

 far within the northern coast of Africa, between Carthage 

 and Cyrene, the rise is said to exceed five feet.f 



In islands remote from any continent, the ebb and flow of 

 the ocean is very slight, as at St. Helena, for example, where 

 it is rarely above three feet. $ In any given line of coast, the 

 tides are greatest in narrow channels, bays, and estuaries, 

 and least in the intervening tracts where the land is promin- 

 ent. Tims, at the entrance of the estuary of the Thames and 

 Medway, the rise of the spring tides is eighteen feet ; but 

 when we follow our eastern coast from thence northward, to- 

 wards Lowestoff and Yarmouth, we find a gradual diminution, 

 until, at the places last mentioned, the highest rise is only 



From this point there begins again to 



seven or eight feet. 



be an increase, so that at Cromer, where the coast again re- 

 tires towards the west, the rise is sixteen feet ; and towards 

 the extremity of the gulf called ' the Wash/ as at Lynn and 

 in Boston Deeps, it is from twenty-two to twenty-four feet, 



From 



and in some extraordinary cases twenty-six feet, 

 thence again there is a decrease towards the north, the ele- 

 vation at the Spurn Point being from nineteen to twenty feet, 



Head and the Yorkshir 



§ 



Milford H 



•4- 

 L 



■he 



Bristol Channel, the tides rise thirty-six feet ; and at King- 

 Eoad near Bristol, forty-two feet. At Chepstow on the Wye, 

 a small river which opens into the estuary of the Severn, they 

 reach fifty feet and sometimes sixty-nine, and even seventy- 

 two feet. || A current which sets in on the French coast, to 

 the west of Cape La Hague, becomes bent up by Guernsey, 

 Jersey, and other islands, till the rise of the tide is from 

 twenty to forty-five feet, 

 Jersey, and at St. Malo, a seaport of Brittany. The tides in 



which last height it attains at 



* Geog. of Herod, vol. ii. p. 331. 



t Ibid. p. 328. 



| Homme, Vents et Courans, vol. ii. E.N. 



The heights of 



these tides were 



given me by the Lite Captain Hewett 



) 



p. 2. Eov. F. Fallows, Quart. Journ. of 

 Science, March 1829. 



|| On the authority of Admiral Sir E 



Beaufort, E.N. 



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