230 ON THE ORIGIN, MATERIALS, COMPOSITION, 



ginary consolidation of such a mass, would form a 

 local conglomerate ; and thus it may be understood 

 why the angles of the fragments are so little rounded, 

 and why the separated parts are so capable of being 

 re-adapted. It is easy to conceive also, that the in- 

 filtration of a solution of lime would convert them 

 into a solid rock, and that the same effect might, 

 under other circumstance/, take place from carbonat 

 or rust of iron, or from some other of the causes 

 which produce the consolidation of rocks. The seve- 

 ral conditions thus hypothetically stated, appear to 

 have frequently existed in nature ; and thus have 

 arisen the number of local conglomerates now seen. 



The fractures of the rock, and the consequent pro- 

 duction of fragments on the surface, have probably, 

 in all such cases, originated, jointly, from the ordi- 

 nary causes of waste, and from mechanical violence. 

 In some instances, where the conglomerates lie be- 

 tween two rocks, they seem to have resulted from 

 the motion of the parts on each other, in consequence 

 of sudden and violent fractures, accompanied by a 

 partial comminution of the materials. Where one 

 rock alone has been engaged, a conglomerate of one 

 ingredient, united by a general cement, is the result ; 

 and this case is frequent in the calcareous rocks. 

 When the fractures have taken place at the meeting 

 of two strata of different rocks, or when two have 

 been in any other mode implicated, the compound 

 is more intricate. Thus also there are formed con- 

 glomerates of limestone arid serpentine, or of lime- 

 stone and argillaceous schist, or of other substances. 



There is yet one origin for the local conglomerates 

 to be stated, which, if somewhat analogous, possesses 

 a distinct interest. It may also be added as a super- 



