248 



SUCCESSION OF GEOGRAPHICAL CHANGES 



[Ch. XII 



clear, therefore, that we Have at present not only more than 

 the usual degree of cold in the polar regions, but also less 

 than the average quantity of heat within the tropics. 



The reader will at once perceive that if it be a legitimate 

 speculation on the part of the geologist to assume, that in 



polar regions had usually within them the 



times 



normal proportion of sea and land, of two and a half to one, 

 between lat. 60° and the poles, instead of so abnormal a pro- 

 portion as one to one, the climate of the temperate regions 

 would be much warmer ; and if there were periods when a 

 deep ocean interspersed with a few islands prevailed at both 



poles (an event 



would 



» 



permanent 



not be rare), there 



summit 



s 



If such were the 



case, currents of denser and cooler water would still flow 

 from high to low latitudes, but none of them would convey 

 floating ice to lower the temperature of the sea between the 

 arctic and antarctic circles and the tropics. In the present 

 geographical state of the globe, the Alps, in latitude 46°, are 

 covered with perpetual snow, and even under the equator 

 itself a mountain 20,000 feet high has lately been discovered 

 in Eastern Africa, which has its uppermost 4,000 feet always 

 above the lowest limit of snow ;* but these mountainous 



circum 



from 



tudes were not reduced in temperature by the wide extent 

 of snow and ice now prevailing in both polar areas at all' 

 seasons of the year. 



Succession of geographical changes revealed to us by geology. 

 —-To those whose attention has never been called to the former 

 changes in the earth's surface which geology reveals to us, 

 the position of land and sea appears fixed and stable. It 

 may not seem to have undergone any material alterations 

 since the earliest times of history; but when we enquire 



more 



is 



annually some small variation in the geography of the 



* Kellimandjaro, discovered by Hr. 

 Redmann in i848, and measured in 

 1862 by Baron Von der Decken, who 



found it to be 20,065 feet high. Geo- 

 graph. Journ. vols, xxxiv. xxxv. 







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