EFFECTS OF COASTS. 



Norway, brings the tide to the east coast of England and to the 

 coasts of Holland, Denmark, and Germany. Continuing its 

 course, part of it passes through the strait of Dover and meets 

 in the English channel the tide from the Atlantic, which arrives 

 on the coast of Europe twelve hours later ; but in passing along 

 the English coast, another part of it is reflected from the pro- 

 jecting land of Norfolk upon the north coast of Germany, and 

 again meets the tide-wave on the shores of Denmark. Owing 

 to this interference of different tide-waves, the tides are almost 

 entirely obliterated on the coast of Jutland, where their place is 

 supplied by continual high water. 



In the Pacific Ocean the tides are very small ; but there are 

 not sufficient observations to determine the forms and progress 

 of the cotidal lines. Off Cape Horn, and round the whole shore 

 of Terra-del-Fuego, from the western extremity of Magellan's 

 Strait to Staten Island, it is very remarkable that the tidal wave, 

 instead of following the moon in its diurnal course, travels to 

 the eastward. This, however, is a partial phenomenon ; and a 

 little farther to the north of the last-named places, the tides set 

 to the north and west. In the Mediterranean and Baltic seas, 

 the tides are inconsiderable, but exhibit irregularities for which 

 it is difficult to account. The Indian Ocean appears to have high 

 water on all sides at once, though not in the central parts at the 

 same time. 



13. Since the tides on our coast are derived from the oscillations 

 produced under the direct agency of the sun and moon in the 

 Southern Ocean, and require a certain interval of time for their 

 transfer, it follows that, in general, the tide is not due to the 

 moon's transit immediately preceding, but is regulated by the 

 posftion which the sun and moon had when they determined the 

 primary tide. The time elapsed between the original formation 

 of the tide and its appearance at any place is called the age of 

 the tide, and sometimes, after Bernoulli, the retard. On the 

 shores of Spain and North America, the tide is a day and a half 

 old ; in the port of London, it appears to be two days and a half 

 old when it arrives. 



14. In the open ocean the crest of tide travels with enormous 

 velocity. If the whole surface were uniformly covered with 

 water, the summit of the tide-wave, being mainly governed by 

 the moon, would everywhere follow the moon's transit at the 

 same interval of time, and consequently travel round the earth in 

 a little more than twenty-four hours. But the circumference of 

 the earth at the equator being about 25000 miles, the velocity 

 of propagation would therefore be about 1000 miles per hour. 

 The actual velocity is, perhaps, nowhere equal to this, and is very 



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