154 



FALLING OF GLACIERS. 



To these causes we might add the falling of gla- 

 ciers in Alpine countries. These are large bodies of 

 ice found in elevated districts, above the line of con- 

 gelation. These are continually descending to- 

 wards the valleys ; and they assist in the degrada- 

 tion of the land by breaking away fragments from 

 the* rocks, and transporting all the loose substances 

 with which they come into contact. There are, 

 therefore, usually found in the front of glaciers 

 heaps of rocks and trees, which have been driven 

 before them in their course. Sometimes they trans- 

 port blocks of large dimensions, which could not 

 otherwise have been forced into the valleys. 



Such are some of the chief agents concerned in 

 the destruction of rocks and the other solid portions 

 of the globe ; we are now prepared to consider the 

 compensating powers of renovation. 



CHAPTER XV. 



AGENTS WHICH FORM ROCKS. 



Quantity of Sediment in River-water. — In the Rhine— In the 

 Yellow River — In the Ganges. — Deltas. — Delta in the Lake 

 of Geneva— Lake Mareotis— North American Lakes. — Delta 

 of Inland Seas— Of the Rhone— Of the Po— Of the Nile— Of 

 the Ganges— The Mississippi. 



We have seen that various causes are in contin- 

 ual operation to break down the solid parts of the 

 earth's surface ; let us now inquire what becomes 

 of all these fragments. As there is no loss of mat- 

 ter, it follows that there must be a reproduction, as 

 well as a destruction, of the land. Indeed, where- 

 ever water is found, there earthy deposites are go- 

 ing on ; and the substance of all the strata which 



