CONGLOMERATE ROCKS. 577 



chanical, or of crystalline matter ; this latter case 

 commonly occurring in the calcareous conglo- 

 merates. 



The conglomerates of the trap rocks are often 

 distinguished by peculiar geological features, 

 which cannot be discussed in this place as they 

 deserve. Although, in one sense, strictly local, 

 their union is often effected by operations pecu- 

 liar to the rocks that form this family, and differ- 

 ing from those by which the consolidation of the 

 other local conglomerates is produced. These 

 sometimes contain bituminized wood, and other 

 organic remains. When firmly compacted, they 

 have thus led to an erroneous train of reasoning 

 respecting the origin of the trap rocks in general. 

 In that circumstance they bear no resemblance 

 to these rocks, as they are evidently of more 

 recent date, formed from their ruins, and con- 

 solidated under the action of water. 



p P 



