OF THE EARTH'S SURFACE. 197 



This hill is stated to be four hundred and seventy feet 

 above the sea. If we consider our stream as double the 

 depth, or one thousand feet, we shall probably not go beyond 

 the truth. This height is nearly sixteen times the altitude of 

 the wave at Cadiz, which was sixty feet. The phenomena of 

 the Alps, though very imperfectly known, indicate a magni- 

 tude double of this, by the mere position of the blocks on Ju- 

 ra, two thousand feet above the level of the Lake of Geneva. 

 While I thus, however, ascribe great magnitude to the dilu- 

 vian torrent, I am upon my guard against the excess of such 

 impressions, and the means have already occurred, as I shall 

 presently state, by which limits are assigned even to this colos- 

 sal agent. 



The geological truth supported by this concurrence of facts, 

 both vast and minute, is confirmed by innumerable circum- 

 stances, which present themselves to view on all hands in this 

 neighbourhood. 



No. 16. At a place called Dickson's Craig, upon the road to 

 Queensferry, about two or three hundred paces west of Barn- 

 bougie Gate, is an example of whinstone rock dressed like 

 those mentioned, having a direction of three degrees south of 

 west. 



No. 17. Another also occurs at the sandstone quarry of 

 Redhall, at the distance of about two miles south of Corstor- 

 phine Hill, and occupying the side of the valley directly oppo- 

 site to it. This quarry is opened in one of the diluvian ridges, 

 and the rock is covered by a bed of about twenty feet thick of 

 the blue clay, having various large blocks of whinstone suspend- 

 ed in it, one of which is not less than forty cubic feet. The 

 dressings point eight degrees south of west. 



No. 18. On the hill of Ravelrig, in a young wood, near the 

 eighth milestone from Edinburgh, on the road to Lanark, is a 



fine 



