244 CONFIGURATION OF LAND AND WATER. SECT. XXV. 



the distribution of heat over the surface of the globe. Under 

 the equator only one-sixth part of the circumference is land ; 

 and the superficial extent of land in the northern and southern 

 hemispheres is in the proportion of three to one. The 

 effect of this unequal division is greater in the temperate 

 than in the torrid zones, for the area of land in the northern 

 temperate zone is to that in the southern as thirteen to one, 

 whereas the proportion of land between the equator and each 

 tropic is as five to four. It is a curious fact, noticed by Mr. 

 Gardner, that only one twenty-seventh part of the land of the 

 globe has land diametrically opposite to it. This disproportion- 

 ate arrangement of the solid part of the globe has a powerful 

 influence on the temperature of the southern hemisphere. But, 

 besides these greater modifications, the peninsulas, promontories, 

 and capes, running out into the ocean, together with bays and 

 internal seas, all affect temperature. To these may be added the 

 position of continental masses with regard to the cardinal points. 

 All these diversities of land and water influence temperature by the 

 agency of the winds. On this account the temperature is lower 

 on the eastern coasts both of the New and Old World than on 

 the western ; for, considering Europe as an island, the general 

 temperature is mild in proportion as the aspect is open to the 

 Atlantic Ocean, the superficial temperature of which, as far north 

 as the 45th and 50th degrees of latitude, does not fall below 48 

 or 51 of Fahrenheit, even in the middle of winter. On the con- 

 trary, the cold of Russia arises from its exposure to the northern 

 and eastern winds. But the European part of that empire has a 

 less rigorous climate than the Asiatic, because it does not extend 

 to so high a latitude. 



The interposition of the atmosphere modifies all the effects 

 of the sun's heat. The earth communicates its temperature so 

 slowly, that M. Arago has occasionally found as much as from 

 14 to 18 of difference between the heat of the soil and that of 

 the air two or three inches above it. 



The circumstances which have been enumerated, and many 

 more, concur in disturbing the regular distribution of heat over 

 the globe, and occasion numberless local irregularities. Never- 

 theless the mean annual temperature becomes gradually lower 

 from the equator to the poles. But the diminution of mean heat 

 is most rapid between the 40th and 45th degrees of latitude both 



