^10 



ON CONGLOMERATED ROCKS, 



In all true conglomerated rocks^ the fragment^ 

 of which they are composed, are either water- 

 worn, or present distinct fractured surfaces ; they 

 are not intermixed at their edges with the basis 

 in which they are contained ; we do not observe 

 the substance of the fragment gradually passing 

 into that of the basis, and we never see the basis 

 by a series of gradations assuming the form of 

 fragments. Such appearances, however, occur 

 in rocks having a conglornerated aspect, but which 

 appear to have been deposited from a state of che- 

 mical solution. These characters, therefore, when 

 taken in conjunction v/ith other geognostic rela- 

 tions, afford us the means of distinguishing true 

 conglomerated rocks from such as are probably 

 only so in appearance. 



The following short examination of the parti- 

 cular characters exhibited by certain conglome- 

 rated rocks, will afford us proofs of the plausibility 

 of the opinion just stated, vi?,. that many conglo- 

 merated rocks are chemical deposites. 



In the conglomerated gneiss, mica-slate, and gra- 

 nite, the imbedded masses are only apparent, not 

 true fragments ; for, upon examining them, we 

 do not find either water- worn or fractured surfaces ; 

 on the contrary, they are intimately mixed with 

 the basis at their junction with it ; and they are 

 observed passing into it in so gradual and imper- 

 ceptible a manner, that we cannot say where the 

 one begins and the other terminates. The same 

 is the case with the conglomerated rock which ^c- 



