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GEOLOGY DIAGRAM 19. 



Lakes. When several springs unite, they form streams, which 

 in their turn unite to form a river, which flows to the sea where 

 the formation of the country permits it. But if this is not the 

 case, and the formation of the country opposes its course, the 

 waters accumulate, and form a lake or a pool. When the water 

 from rain, or from a river, is discharged into broad plains where 

 it can neither flow into the sea, nor accumulate to form a lake, 

 these plains become marshes and peat bogs. 



Banks and Cliffs. If rain water daily tends to remove pebbles 



from the mountains, and 

 to deposit gravel in low- 

 lying plains, the sea also 

 plays a double part on 

 its banks. It encroaches 

 on the land in some 

 places, and is encroached 

 upon by the land in 

 others. This is especially noticeable at the mouths of rivers. 

 The earth and gravel carried down by the current after rain 

 gradually accumulates at the mouths of rivers and streams, and 

 form flats which advance further and further into the sea. The 

 sea in its turn throws up heaps of sand on some coasts, while at 

 other points it wears away its banks, and advances into the land. 

 When this is elevated a cliff is the result. 



Volcanoes. There are mountains in some countries with a 

 large hole in the summit called a crater, whence issue stones, 





Cliffs. 



Volcuuo in Eruption, 

 dust, smoke, and flames. These mountains are called volcanoes. 



