STUDIES IN NATURE 



ranges, which in their turn are now being de- 

 stroyed by the constant wearing away of rain 

 and ice. Such movements are still taking place, 

 although we can hardly hope to notice them ; 

 except perhaps at the sea-side, where it is easier 

 to find out year by year how far the sea comes 

 up the face of the cliffs or goes out over the 

 sand. 



Great sudden changes must also have oc- 

 curred in the dim past, but such movements of 

 the earth as these, have now, happily for us, for 

 the most part ceased; although something of 

 the same kind still occurs when there are 

 earthquakes and volcanic eruptions. 



Sometimes we come across large tracts of 

 country which seem almost flat ; there are 

 neither hills nor valleys to be seen, and the 

 rivers, if there are any, crawl through them 

 as though they hardly knew which way to 

 flow to reach the sea. These tracts of 

 country are called plains, and at first sight are 

 apt to appear uninteresting. If they are on 

 high ground we shall probably find them dry 

 and waterless, for the rain will sink into the 

 ground, since there are no little hollows and 

 slopes for it to gather in and run down ; unless 

 indeed the rock will not let the water through, 

 when it will collect in dull flat-edged lakes and 

 swamps on the top. If the plain is low, the 

 ground will be wet and marshy ; there is a great 

 deal of water, but it seems to get entangled in 



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