HUTTONIAN TliEORr. 



103 



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fcuffiori, or fome powerful torrent, had open- 

 ed at once the channel by which its waters 

 are conduaed to the ocean; but, when the 

 ufual form of a river is confidered, the trunk 

 divided into many branches, which rife at a 

 great diftance from one another, and thefe agairi 

 fubdivided into an infinity of fmaller ramifica- 

 tions, it becomes ftrongly imprefled upon the 

 mind, that all thefe channels have been cut by 

 the waters themfelves ; that they have been 

 llowly dug out by the wafliing and erofion of 

 the land ; and that it is by the repeated touch^ 

 es of the fame initrument, that this curious 

 affemblage of lines has been engraved fo deeply 



on the furface of the alobe. 



100. The changes which have taken place in 

 the courfes of rivers, are alfo to be traced, in ma- 

 ny inftances, by fucceffive platforms of flat al- 

 luvial land, riling one above another, and mark- 

 ing the different levels on which the river has 

 run at different periods of time. Of thefe, the 

 number to be diftinguifhed, in fome inftances, 

 is not lefs than four, or even five ; and this ne- 

 eelTarily carries us back, like all the operations 

 we are now treating of, to an antiquity ex- 

 tremely remote : for, if it be confidered, that 

 each change which the river makes in its bed 

 obliterates at leaft a part of the monuments of 

 former changes, we fliall be convinced, that 



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