364 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Feb. 15, 





as 



\i 



and such an agency seemed further indicated by the fact that the 

 grooves and striae on the vertical faces of the rock are seldom quite 

 horizontal, but very generally dip somewhat to the southward ; that 

 is to say, they slope with the valley. Again, it is evident that under 

 glacier- conditions this is precisely a spot where immense grinding 

 action would be exerted ; for the two Highland valleys of the Tum- 

 mel and the Garry here unite, so that there would be a convergence 

 of two great ice-streams at this point, hemmed into a narrow valley 

 by high ridges on either side. 



Ascending the shoidder of this hill of Meal Uaine above the bed 

 of drift previously described, I found the hard quartz- 

 ose strata along its western side remarkably rounded 

 off in many places, and ground down into smooth 

 bosses, while occasional boulders of porphyry and 

 granite lay here and there on the surface. 



But what surprised me still more, on gaining the 

 top of the hill I found the stamp of the ice there as 

 vivid as in the ravine below. The coarse, hard, 

 gnarled gneiss that forms the scalp of the ridge 

 has all its angularities groimd off, and is fluted with 

 long scooping depressions, across the seams of the 

 strata, and pointing N. 45° W. (N.B. These bear- 

 ings are all true, and not magnetic.) These fluted 

 portions are smoother than the rest of the surface, 

 although all is rounded off. This is on precisely 

 the highest point of the summit. Thinking that 

 there was still a possibility of these appearances 

 being due to structure, or other causes, I searched 

 about, and soon noticed other scores and furrows a 

 few yards lower down, pointing N. 40° "W. Again, 

 60 feet below the summit, on the southern brow of 

 the hill, I came upon some surfaces showing the 

 most unmistakeable polish, striae, and scratches, to- 

 gether with scores and larger furrows, all parallel, 

 and also pointing N". 40° W. The rock is here of 

 an extremely hard and tough nature, to which is 

 doubtless owing the preservation of these markings. 

 It thus appeared that the whole flank of the hill 

 is marked from top to bottom ; for I had detected 

 these impressions at altitudes varying from 750 feet 

 up to the summit, which by aneroid measurement I 

 made 2095 feet high. 



I have already said that the polish on the flank 

 of this hill underneath the drift strongly suggested 

 the idea of glacier- action ; now as the strise and 

 furrows on the crest of the mountain are precisely 

 coincident in their direction, there is a presumption 

 that both are due to the same agency. If, then, 

 we adopt the instrumentality of a glacier, we are 

 driven to the admission that it must have been of 



\ 



