David Milne, Esq., on Polished and Striated Pocks, 169 



bade to take place, sufficient to hurry over these surfaces not merely 

 sand and gravel, but also hard blocks a ton or more in weight, I have 

 no doubt that abundance of ruts and scratches would be formed on 

 them. 



That water was the agent in this case, is the more clear, from the 

 following considerations : — I have already alluded to the natural 

 rock fissures at Sampson's Ribs, and to the absence, in many places, 

 of a portion of the rock on the south side of the fissure. The pro- 

 bability is, that these south portions of the fissures were torn or 

 broken off by the force of the boulders in passing through the trough. 

 But the point to which I wish more particularly to direct attention 

 is the fact, that in very many cases, the angle formed by the north 

 side of the fissure and the east side of the gully is rounded off, as 

 shewn at 6 c in fig. 2 ; and not only so, but occasionally the rock 

 along the north side of the fissure itself has been smoothed ; that is 

 to say, whilst the agent (whatever it was) was passing mainly in a 

 direction from NW. to SE., and smoothing the wall-faces of the 

 trough or gully, this agent must have entered so far into this fissure, 

 and others in the same manner, in order to smooth their faces. The 

 amount of divergence from the general axis of the gully and direc- 

 tion of the moving and smoothing body, must have been from 20° 

 to 30°, Now, I can conceive no agent but water which could act in 

 this way. 



There is another circumstance which leads to the same conclusion. 

 I had the good fortune to find, in company with Mr R. Chambers, a 

 small trough of rock, the sides of which, when cleared out and washed, 

 were seen to be smoothed and furrowed in a manner precisely si- 

 milar to those in the larger trough or gully. This little trough was 

 only 4 feet in length, its width at the top or widest part was only 

 1 foot, and its depth not quite 2 feet. It was situated about 80 yards 

 to the north of the principal gully, and its direction was NNW. by 

 compass, so that this trough was evidently connected with, and a part 

 of, the phenomenon. Now, its dimensions were so small, that no 

 other agent than water can be conceived to have formed it. 



3. There is another question, in some respects subordinate, but still 

 bearing on the facts very materially, viz., from what direction did 

 the rush of waters come 1 



At Sampson's Ribs, the appearances indicate a NW. direction ; for 

 it is the NW. side of the hill on which these smoothed appearances 

 occur, and it is the SE. side where there is an accumulation of sand 

 and gravel, indicating a less tunmltuous state of waters, as if on the 

 lee side. 



On this hypothesis, it is easy to explain the direction of the 

 scratches on both sides of the guHy, and, in particular, the slope of 

 the deepest ruts upwards to the SE. To the north of the gully the 

 ground slopes to the north, so that, if a rush came from that direc- 

 tion, the blocks carried along by it, would move upwards to the 



