214 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jail. 4, 



the meridian, well displays this phseiiomenon and the general ap- 

 pearance of the overlying deposits. 



To the south-westward of this district the country presents to the 

 sea a perpendicular wall, rising at Spanish Head to a height of 300 

 feet. 



The great drift-current would pass along the face of this wall, 

 and no doubt would originally mark it with groovings. But as the 

 groovings would be in the strike of the bedding of the clay-schist, it 

 would be difficult to separate them from the lines of bedding ; and 

 they would be greatly effaced by the action of the sea at the subse- 

 quent upheaval. Indeed a large portion of this cliff has fallen, and 

 other portions annually fall into the sea. 



But all the way on the face of the mountain to the westward of 

 Port of St. Mary, we have accumulations of the boulder-clay very 

 distinctly, up to a height of 400 feet. Then, at a height of 460 feet 

 above high water, we have, on the surface of the rock, a couple of 

 hundred yards from the hamlet of Creggneese, by the road-side, 

 distinct glacial groovings, having a direction a little more to the 

 southward than those at Perwick Bay ; but this direction the drifting- 

 current would be compelled to take in passing through the slight 

 depression which exists between the highest point of the Mull Hills 

 and the point which lies to the eastward, in the direction of Spanish 

 Head. The highest point of the Mull Hills is 500 feet above the 

 level of the sea. 



If we pass over northward to the mountain-range extending from 

 Brada Head to South Barrule, we find the whole of the eastern face, 

 to a height of 800 feet, covered with patches of the boulder-clay 

 deposits, which remain wherever they have been protected from the 

 action of the sea during the subsequent upheaval. These abound 

 chiefly in boulders of the South Barrule granite, mixed with quartz 

 and fragments of the clay-schist. Above this limit we find very little 

 clay, but immense quantities of boulders lie both on the eastern and 

 western side of the mountain, up to the very summit, though de- 

 creasing very fast the higher we ascend. 



The summit of South Barrule is 1595 feet above the sea. To this 

 depth, therefore, at least, the submergence would appear to have taken 

 place. 



We have few mountains on the Island whose summits are much 

 higher than this, though Snea-fell reaches a trifle over 2000 feet. 

 There is good reason to believe that they were all submerged, though 

 I have not distinct proof of a similar kind to that which we find on 

 South Barrule. The presumption arises from the character of the 

 Insular Flora, destitute as it is of the plants of the true Scan- 

 dinavian type, as compared with the flora of the opposite Cumber- 

 land jMountains. 



With regard to the nature of the emergence, my impression is 

 that it was also of a quiet and continuous character. The proofs of 

 this seem to lie in the circumstance, to be observed here (as in the 

 case of the parallel roads of Glen Roy and the neighbouring Cale- 

 donian Valleys), of terraces being found at the same level as con- 

 tiguous mountain-j)asses. 



