324 Horner''s Geological Address. 



miles to the north. But between the localities where they now 

 exist and that parent rock, there are ridges, over which they 

 must have travelled, that are 1500 feet above the present sea- 

 level. This, then, is a case analogous to that of the Valdai 

 Hills in Russia, on the southern flanks of which blocks of Scan- 

 dinavian granite are scattered, indicating that these hills, and, 

 in like manner, the summits of the barrier north of Gare Loch, 

 were a sea-bottom, upon which the blocks were dropped from 

 floating icebergs ; that sea-bottom being subsequently raised 

 to form the existing land. 



The principal object of Professor Forbes's paper is to de- 

 scribe the topography and geological structure of the Cuchul- 

 lin Hills in Skye. He gives us much new and interesting in- 

 formation respecting the igneous rocks, of which they are com- 

 posed, particularly that comparatively rare variety, hypers- 

 thene rock : but he also describes these same rocks as being 

 furrowed and polished in several of the valleys, but especially 

 in the valley of Coruisk, the furrows there radiating from a 

 centre to the sea-shore ; and, in his opinion, they demonstrate 

 in as clear a manner as the subject admits of, the former ex- 

 istence of a glacier in that locality. All will admit that the 

 opinion of Professor Forbes on this subject is one in which 

 we may place entire confidence. The hypersthene rocks " are 

 smoothed and shaven in a direction parallel to the length of 

 the valley wherever their prominent parts are presented to- 

 wards the head of the valley ; but towards the sea, they are 

 often abruptly terminated by craggy surfaces, shewing the usual 

 ruggedness of the natural fracture of the rock, and exhibiting 

 the phenomenon of Stoss Seite and Lee Seite, so often described 

 in the Scandinavian rocks.*" 



" When the same rock is traversed by claystone veins, or by 

 veins of crystallized hypersthene and magnetic iron, these va- 

 rious parts of such diff*erent hardness are all uniformly shaven 

 over, in conformity with the general form of the mass to which 

 they belong. This presents a striking analogy to the pheno- 

 mena of polished rocks in the Alps, where the quartz veins are 

 cut ofl" parallel to the surface of the bounding felspar. . . . The 

 furrows are not confined to the entrance of the valley, but ex- 

 tend to the upper part of it, and to a great height above its 



