CLIMATOLOGY. 323 



to its exposure to the prevailing west winds which have 

 blown across the ocean, to the sea free from ice which 

 separates it from the polar regions, and lastly, to the 

 existence and position of Africa, with its wide extent of 

 tropical land favourable to the ascending current, while the 

 equatorial region to the south of Asia is for the most part 

 covered by the ocean. The European climate would there- 

 fore become colder, ( 397 ) if Africa were to be overflowed by 

 the ocean, or if the fabulous Atlantis were to rise from the 

 waves, and connect the two continents, or, finally, if either 

 the Gulf stream were to cease to extend its warming in- 

 fluence to the Northern Sea, or if a tract of land were to be 

 elevated by volcanic forces between the Scandinavian penin- 

 sula and Spitzbergen. If in Europe the mean annual 

 temperature decreases as we proceed easterly on a parallel 

 of latitude, from the Atlantic coast of Prance through 

 Germany, Poland, and Eussia, to the chain of the Ural ; 

 the principal cause of this phsenomenon is to be sought 

 in the form of the continent being gradually less inter- 

 sected, and becoming more compact and extended, in the 

 increasing distance from the sea, and in the feebler influence 

 of westerly winds. Beyond the Ural, westerly winds blow- 

 ing over wide expanses of land covered during several 

 months with ice and snow, become cold land winds. It is 

 to such circumstances of configuration and of atmospheric 

 currents that the cold of western Siberia is due, and by no 

 means to a great elevation of the surface above the level of 

 the sea, as anciently assumed by Hippocrates and Trogus 

 Pompeius, ( 398 ) and still related by travellers of some celebrity 

 in the eighteenth century. 



If from differences of temperature at a uniform level, we 



