602 HISTORY OF GEOLOGY. 



morasses, which otherwise appear without aim or 

 meaning ; and thus this department of science can- 

 not fail to be constantly augmented by contribu- 

 tions from every side. At the same time it is clear, 

 that these contributions, voluminous as they must 

 become, must, from time to time, be resolved into 

 laws of greater and greater generality ; and that 

 thus alone the progress of this, as of all other 

 sciences, can be furthered. 



I need not attempt any detailed enumeration of 

 the modes of aqueous action which are here to be 

 considered. Some are destructive, as when the 

 rivers erode the channels in which they flow; or 

 when the waves, by their perpetual assault, shat- 

 ter the shores, and carry the ruins of them into 

 the abyss of the ocean. Some operations of the 

 water, on the other hand, add to the land ; 

 as when deltas are formed at the mouths of rivers, 

 or when calcareous springs form deposits of tra- 

 vertin. Even when bound in icy fetters, water is 

 by no means deprived of its active power; the 

 glacier carries into the valley masses of its native 

 mountain, and often floats with a lading of such 

 materials far into the seas of the temperate zone. 

 It is indisputable that vast beds of worn-down frag- 

 ments of the existing land are now forming into 

 strata at the bottom of the ocean ; and that many 

 other effects are constantly produced by existing 

 aqueous causes, which resemble some, at least, of 

 the facts which geology has to explain (E A). 



