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THE WORLD. 



islands from 250 to 300 feet above the level qf the sea, have been 

 occasionally seen off" the Cape of Good Hope, and were there- 

 fore of immense bulk, as for every solid foot seen above, there 

 must have been at least eight cubic feet below water. The wood 

 cut below exhibits one of these ice-islands, sketched by Capt. 

 Horsburgh; it was seen off the Cape of Good Hope, in April 

 1829; it was two miles in circumference and about 150 feet high, 

 appearing like chalk when the sun was obscured, and having the 

 lustre of refined sugar when the sun was shining upon it. 





Undoubtedly the principal causes of Oceanic currents are the 

 trade-winds, of which we have already spoken. These blowing 

 at first directly from the north and south, over the surface of the 

 water, move the floating ice, and superficial water, in the same 

 general direction, thus at length generating a strong polar current. 

 The south polar current being less intercepted by the peculiar 

 formation of the antarctic lands, than the northern, is perceptible 

 in much higher southern latitudes than the current from the 

 north. A manifest influence is thus exerted upon the climate, to 

 which wo shall again allude. 



The rotation of the earth, when the waters have been set in 

 motion from the north to the south, causes a great change in the 

 general direction of these currents precisely upon the same princi- 

 ple which has long been recognized in the case of trade winds. 

 For example, the current which flows north from the Cape of Good 

 Hope towards the Gulf of Guinea, has a rotary velocity when it 

 doubles the Cape of about 800 miles per hour, but when it reaches 

 the equator, the surface of the earth is there whirled around at 



