

1 









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rer 



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tlie 

 it, 



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at 



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3 



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the 



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Ch. XII.] 



POLAIl LAND NOW IN EXCESS. 



247 



Tlie current which flows from the Indian Ocean through 

 the Mozambique Channel, having a breadth of nearly a 



region 



f conveys warm water from a tropical to a temperate 

 ' A current which flows in an opposite direction 

 „ v — -ape Horn northwards, along the west coast of South 

 America, conveys colder water towards the tropics. 



These oceanic rivers, as they have been called, exercise a 

 great control over the temperature of the air in certain 

 areas, causing deviations in the isothermal lines already 

 alluded to (p. 239). Their course being to a great extent 

 dependent on the position of the land, they add greatly to 

 the influence which geographical conditions exert on the 

 state of the climate at any given period. 



Present 



>/ 



abnormal. — It lias been 

 y an ocean, in tlie midst 

 many smaller ones ; for 



the whole of the continents and islands occupy an area 

 not much exceeding one-fourth, of tlie whole superficies of 



Now, according to this analogy, we may 



the spheroid. 



fairly speculate on the probability that there would not be 

 usually, at any given epoch of the past, more than about 

 one-fourth dry land in a particular region ; as, for example, 

 near the poles, or between them and the 60th parallels of 

 N. and S. latitude. If, therefore, at present there should 

 happen to be, in both these quarters of the globe, much 

 'more than this average proportion of land, if the land should 

 actually be equal in area to the sea, and some of it in the 

 arctic region 8,000 feet in height, and in the antarctic 

 15,000 feet, this alone affords ground for concluding that, 

 in the present state of things, the mean heat of the climate 



_ « • • 1 



moi 



would 



This presumption is greatly heightened when we discover 

 that there is a deficiency of land between the tropics, where, 

 in consequence of its being exposed to the direct, or nearly 

 direct rays of the sun, it would produce the greatest heat 



For in the inter-tropical regions of the globe, the sea is to the 



land as four to one, instead of two and a half to one. It is 



