122 Mf. Bryce 071 the Geological Structure of Roseneaih. 



beds and of similar shelly deposits on the opposite coast at Ardencaple, 

 first noticed by the late Duke of Argyle, led Mr. Smith to that extensive 

 and most valuable series of investigations by which he established the 

 former existence of a sub-arctic climate, and a distinct place for the 

 Clyde beds among the tertiary strata. 



Within the Gareloch the cliflF bounding the ancient beach is not 

 marked with the same continuity or distinctness ; but where it is seen, 

 the levels appear to be Ihe same as those already mentioned. 



POSTCRIPT, August, 1850. 

 f. Scratched Bocks. 

 12. The striated and grooved rocks of Gareloch have been described 

 by Mr. Charles IM'Laren in several papers in late numbers of Jameson's 

 Journal ; and it is] therefore unnecessary to enter into any details respect- 

 ing them. I have verified his observations in several places, and have 

 no doubt that the phenomena ai'e described with that precision and strict 

 attention to facts which mark Mr. M'Laren's other productions. But I 

 cannot agree with his conclusion, that they are due to glacial action. 

 It seems much more reasonable to connect them with the deposit of the 

 boulder clay, and the transport over the plains of Lanarkshire of rocks 

 which exist only to the north-west, and which are often striated and 

 polished. The total absence of any such gravel deposits as could be 

 considered moraines is a serious objection; for though Mr. M'Laren 

 gives one instance in the shingle-bed at Row-ferry, I think it is perfectly 

 clear, from the sea-worn character of its materials, that this is a true 

 bank of shingle, fonned by the sea in consequence of the peculiar 

 movements of the tide at this part. Owing to the narrowness of the 

 outlet, and the great extent of water inside, the tide ebbs at Row-ferry 

 with a powerful current : between this and the sm-f the bank has been 

 thrown up, there being both at flood and ebb a stream on the western side 

 of the outlet, and an eddy on the eastern. This fact has been pointed 

 out to me by Mr. Smith, who also states that the shingle bank rests upon 

 the old boulder clay or supposed glacial deposit, and must therefore be of 

 later formation than the rock-striation and boulder-transport. Other 

 weighty objections are ably stated in Professor Oldham's anniversary 

 address of this year to the Dublin Geological Society ; and the sub- 

 ject need not therefore be pursued farther. The most accessible 

 points for seeing the striation and grooving are at the landing place at 

 Row ; at the point of divergence of the roads leading along the east and 

 west sides of the loch, about a quarter of a mile above Gareloch-head ; 

 and at several points on the road-side, between the latter place and the 

 summit level, particularly on the east side of the road, exactly at the 

 summit. But at none of the points which I visited were any marked 

 examples of polishing noticed, or of that peculiar " moutonnee " character 

 which is so extremely well defined in the case of rocks in the lake district 

 of Westmoreland, which I have lately described, and of some pointed out 



