Cause of Glacial Epochs. 379 



whole country is nearly entirely shrouded in glacier-ice, 

 and is altogether uninhabitable by man, while in the 

 northern hemisphere, in equivalent latitudes, there are 

 no parts of North America and Europe totally un- 

 inhabited, and even the north of Norway in summer, 

 when the sun does not set, is often inconveniently 

 warm, and the traveller is troubled with clouds of mos- 

 quitoes. 



The present winter of the southern hemisphere being 

 when the earth is in aphelion, the result is this, that the 

 winter of the Antipodes is seven or eight days longer 

 than our own, for the further the earth is removed from 

 the sun, the more slowly it moves in its orbit, and the 

 nearer it is, it moves in proportion more rapidly, and 

 this somewhat lengthened winter, coupled with the 

 absence of heated water flowing south from equatorial 

 regions, has enabled the snows to accumulate, and being 

 but little affected even by the summer's sun, the country 

 is continually buried in ice, while in Norway and on the 

 shores of the Baltic, in equivalent latitudes, forests, grass, 

 and crops abound. The winter of our northern hemis- 

 phere is of course seven or eight days shorter than that 

 of the south, and the earth is at that season with us 

 nearest to the sun, and our summer being a little longer 

 though further from the sun. the effect of its heat 

 corresponds to the difference, irrespective of the power- 

 ful effect of the heated water of the Grulf Stream. 



If such marked results are produced with this com- 

 paratively small amount of eccentricity, it is reasonable 

 to suppose that with the greatest possible eccentricity 

 the effect must be much greater, and it has been calcu- 

 lated that when this by slow degrees takes place, the 

 earth in aphelion is distant from the sun about 98-J 

 millions of miles, or nearly 7 millions of miles further 



