ON THE ALLUVIAL DEPOSITS. 367 



Scotland, on the red sandstone and on the coal strata, 

 to depths ranging from thirty to fifty feet, and covering 

 miles of country. That these have been the prepa- 

 ratory steps to many of the obscure denudations, I 

 cannot doubt : since it is impossible that any current 

 of mere water, or even of water charged with frag- 

 ments, could demolish mountains ; above all, within 

 that very brief time which must be allowed to " The 

 Deluge." Woodward's theory, suspending the laws 

 of cohesion, could alone produce such an effect: but 

 we smile at Woodward, and. forget that we are be- 

 lieving in him under another shape. 



If generally easy to assign, the alluvia of disintegra- 

 tion are sometimes rendered doubtful by the disappear- 

 ance of the parent rock, or obscured by the intermix- 

 ture of transported materials. Thus, beds of gravel, 

 or sand, or clay, are often found under circumstances 

 which render their origin uncertain ; while they have 

 occasionally been ranked with transported, and even 

 with "diluvian" deposits. But the discriminating 

 marks can often be traced, in veins or other appear- 

 ances, remaining, in the nature of the neighbouring 

 unchanged strata, or in the absence of indications of 

 transportation: while, in the unstratified rocks, where 

 the original mass has disappeared, their origin is 

 proved by finding a dark soil incumbent on a sand- 

 stone which could not have produced it, as I noticed 

 in treating of denudations. The induction is com- 

 plete, when nodules, fragments, or agates are found 

 in such alluvia. 



This disintegration, in conglomerate rocks, has often 

 given rise to the belief in transported or diluvian allu- 

 via, as just remarked: and thus may be explained many 

 of the blocks which have been invested with a myste- 

 rious origin : as well as the flints or gravel derived 



