THE POLAR GLACIERS. 705 



over 3,000,000 miles nearer tlie earth, are said to be even some degrees 

 cooler than the same seasons in corresponding localities of the north- 

 ern hemisphere. And to take an extreme example. Mars, which is 

 50,000,000 miles farther from the sun than the earth is, has snow-lines 

 about its poles which reach no nearer the equator than on our planet 

 in corresponding seasons. But the excess or diminution of eight days, 

 in the winters of climates which even in their warmest seasons barely 

 balance on the thawing point of ice, is a true cause in polar conditions 

 and differences. Considering that these days affect chiefly the period 

 of briefest sunshine, it amounts to quite one-twentieth of the whole 

 power of the sun on a hemisphere. This difference would not be ap- 

 parent in the warm regions of the globe, where there is always an 

 excess of heat which is carried off by evaporation and ocean-currents; 

 but it would exert nearly its full force in polar regions which are un- 

 affected by those i)ifluences. 



It cannot be denied that it is the sun's heat which prevents the 

 temperature of the earth from sinking to, or very near to, the absolute 

 zero of cold, wherever in the thermometrical scale that may be. Chem- 

 ists have produced a cold estimated at 257 below zero, of Fahr.' It 

 is not by any means probable that this reaches the entire absence of 

 heat. But, on the supposition that it is so, and that polar regions are 

 unaffected by the air or water currents of the tropics, then an excess 

 of eight winter days would lessen a polar temperature 15, and 

 unquestionably amount to the difference of an accumulation of ice and 

 snow year after year, instead of the annual thawing during each sum- 

 mer, of the winter's increase. 



This is precisely what is, or has been, taking place at the respective 

 poles of the earth. Year after year, probably for a long period, there 

 has been a steady accumulation of ice-material about the south pole, 

 adding weight to that hemisphere. Then, in proportion to this in- 

 crease, the centre of gravity of the earth has moved a little toward the 

 south ; and the waters, always obedient to this controlling point, have 

 gradually gathered into the southern seas, covering the lowlands and 

 plains of islands and continents. At the same time the waters were 

 drawn away from the north-polar regions, uncoveiing lands, and leav- 

 ing bays and sounds and inlets innumerable. The geography of the 

 countries fully corresponds to these inferences. The seas of the arctics 

 are comparatively shallow and deeply cut up, and the lands are low- 

 lying. In the antai'ctics the oceans are deep and bayless, and all the 

 mainlands and islands are precipitous and craggy, as if they were the 

 peaks and table-lands of mountain-ranges. 



It is now the question whether this state of things is a permanent 

 arrangement whether we of the north side are always to have the 

 advantage of extent of territory, of fertile lands and healthful homes 



* The temperature of stellar space is estimated by Sir John Herschel and others at 

 239 Fahr. 



VOL. viii. 45 



