492 



GEOLOGIC AI, REMARKS 



Of the former description here alluded to, I 

 have lately found a striking instance, in the Cart- 

 lane Craig, which is a vast chasm, in the sand- 

 stone formation, above Lanark, traditionally cele- 

 brated as one of the places where the heroic but 

 unfortunate Wallace concealed himself from 

 the search of the English. It is evidently form- 

 ed by the under side or projecting shoulder of a 

 round backed mountain-mass, somehow detached 

 from the body or upper part. The general line 

 of this enormous and singular rent, which runs 

 nearly in the direction of N. E. and S. W., is 

 that of the segment of a circle, sweepihg to a 

 distance of at least three-fourths of a mile froni 

 the one extremity to the other. Its greatest 

 depth can hardly be less than 400 feet ; and its 

 width above, at the highest point, probably ex-' 

 ceeds 600 feet, although at the bottom, it is little 

 more than the breadth of a small stream, called 

 the Mouse, which finds its way, by this opening, 

 into the Clyde. Towards the extremities, the 

 height on both sides gradually declines, till the 

 chasm entirely disappears, as may be easily con- 

 ceived from the shape of the mass or projecting 

 shoulder in which it occurs, and which approaches 

 the figure of a spherical segment. From the up^- 

 per extremity to the lower, there is a considerable 

 descent of levej. 



