CHAPTER VI 

 COLD AND ICE ON THE EARTH 



THE astronomers who look at the planet Mars tell 

 us that at the Northern and Southern Poles there 

 are great areas of snow, very much greater than 

 the arctic regions of the earth, for the south polar area 

 alone occupies 11,330,000 square miles. But the geo- 

 logical records of the earth show that our own arctic 

 regions once extended very much farther than they do 

 at present, a fact which need not in any way surprise 

 us, for as we have already remarked, snow and ice are 

 very largely a matter of the nearness of the sea to the 

 land. We may put the same thing in another way by 

 saying that winter cold and summer heat depend largely 

 on the distribution of sea and land. Thus Venice, which 

 is not very much farther from the North Pole than 

 Vladivostok, has an altogether different climate, and in- 

 habitants of the Shetland Isles have a very different kind 

 of climatic experience from those who delve by the 

 frozen Yukon. There is another consideration which is 

 sometimes overlooked. We do not think of the earth 

 as a very warm body. But at its very coldest part, where 

 the thermometer goes down to seventy or ninety degrees 



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