THE POLAR GLACIERS. 25 



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 summer, of the 

 winter's increase. 



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

 spective 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 increase, the center 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, uncovering lands, and leaving 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 antarctics 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 perma- 

 nent arrangement whether we of the north side are always to 

 have the advantage of extent of territory, of fertile lands and 

 healthful homes in middle latitudes, in short, of all that makes 

 the rivalry of nations, and civilization a necessity. To answer 

 this question it will be necessary to turn again to astronomy, and 

 to study for a few moments some of its more abstruse problems. 



In addition to the rotation of the earth on its axis once every 

 day, and its revolution about the sun once in a year, there is also 

 a slow rolling motion of the equator, caused by the attraction 

 of the sun on the excess of matter in equatorial diameters over 

 the polar. It is precisely as when one touches the rim of a top 

 in rapid motion ; there is set up at once a slow gyrating or tilting 

 roll, and the upper end of the stem describes a small circle. 



