OF TIDES. 323 



which may cause irregularities of various kinds. The southern tide 

 is, however, probably less considerable than has sometimes been 

 supposed, for, in the latitudes in which it must originate, the ex- 

 tent of the elevation can only be half as great as at tbe equator ; 

 and the Islands of Kerguelen's Land and South Georgia, in the lati- 

 tudes of about 50 and 55, have their tides delayed till the tenth 

 and eleventh hours, apparently because they receive them prin. 

 cipally from distant parts of the ocean, which are nearer to the 

 equator. 



On the western coasts of Europe, from Ireland to Cadiz, on 

 those of Africa, from Cape Coast to the Cape of Good Hope, and 

 on the Coast of America, from California to the streights of Ma- 

 gellan, as well as in the neighbouring islands, it is usually high 

 water at some time between two and four hours after the moon's 

 southing; on the eastern coast of South America between four and 

 six, on that of North America between seven and eleven; and on 

 the eastern coasts of Asia and New Holland between four and 

 eight. The Society islands are perhaps too near the middle of the 

 Pacific ocean to partake of the effects of its primitive tide, and their 

 tide, being secondary, is probably for this reason a few hours later. 

 At the Almirantes, near the eastern coast of Africa, the tide is af 

 the sixth hour; but there seem to be some irregularities in the 

 tides of the neighbouring islands. 



The progress of a tide may be very distinctly traced from its 

 source in the ocean into the narrow and shallow branches of the 

 sea which constitute our channels; Thus the tide is an hour or 

 two later at the Scilly Islands than in the Atlantic, at Plymouth 

 three, at Cork, Bristol, and Weymouth four, at Caen and Havre 

 six, at Dublin and Brighthelmstone seven, at Boulogne and Liver- 

 pool eight, at Dover near nine, at the Nore eleven, and at Lon- 

 don bridge twelve and a half. Another portion appears to proceed 

 round Ireland and Scotland into the North Sea ; it arrives from the 

 Atlantic at Londonderry in about three hours, at the Orkneys in 

 six, at Aberdeen in eleven, at Leith in fourteen, at LeostofFe in 

 twenty, and at the Nore in about twenty-four, so as to meet there 

 the subsequent tide coming from the south. From the time occu- 

 pied by the tide in travelling from the mouth of the English chan- 

 nel to Boulogne, at the rate of about fifty miles an hour, we may 



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