224 MR ALFRED HARKER ON 



of foreign boulders from the area. The exceptions to this latter generalisation are of 

 a kind which go to emphasize the rule. Boulders of rocks foreign to the district 

 (which farther S.E. occur at all altitudes) are found in central Skye only near the 

 shore ; usually about high- water mark, but occasionally up to 50 or even 75 feet above 

 sea-level. It is to be noted that occasional relics of the ' hundred foot ' raised beach 

 prove that the land stood lower by that amount about the close of the glacial period. 

 Since these foreign erratics are never embedded in the boulder-clay, but lie exposed 

 on the surface, there is no difficulty in supposing that they have been transported by 

 floating ice at a late stage of the Glacial period.* 



Both the Cuillins and the Eed Hills afforded gathering-ground for the ice. The 

 latter, though less lofty, are not less extensive than the former ; and it appears from 

 the thick accumulations of drift on the edge of the granite tract, and from the wide 

 dispersal of granite boulders, that this group of hills played, in some respects, almost 

 as important a part as the other. The nature of the granite of the Eed Hills, however, 

 does not lend itself to the preservation of glacial scorings, while the generally uniform 

 character of the rock makes it impossible to trace the movement of the ice in detail 

 by the distribution of boulders. For these and other reasons it is much less easy to 

 obtain precise data in the Red Hills than in the Cuillins with their adjacent basaltic 

 tract, and it is to these latter that we shall confine our attention. It is not to be 

 understood that the Cuillins and the Red Hills were in any sense two distinct centres 

 of glaciation. They formed together a single gathering-ground about 12 miles long 

 in an E. to W. direction, with a breadth of 5 or 6 miles and an area of roughly 

 40 square miles. 



During the maximum glaciation the central part of Skye was not merely a 

 feeding-ground for glaciers : it carried a true ice-cap, under which the mountains 

 were wholly buried. The evidence of this is cumulative, and is implicitly involved 

 in much of what follows. We may note in this place, however, that such a conclusion 

 appears inevitable from the consideration that the local ice was able to withstand the 

 pressure of the ice-sheet from the mainland. It is certain that throughout a long- 

 time the two were in equilibrium along their line of confluence, indicated approximately 

 in the small sketch map (fig. 1). Here the thickness of the Skye ice must have been 

 equal to that of the Scottish, i.e., probably not less than 3000 feet. A very moderate 

 rate of rise from here towards the mountains would suffice to carry the surface well 

 above the highest summits. The ice was presumably thickest over the broad double 

 strath which divides the Cuillins on the west from Blath-bheinn and the Red Hills on 

 the east, and is formed by the lower portions of the Camasunary and Sligachan valleys, 

 the one running south and the other north. The watershed dividing these two valleys 



* This remark applies to the occasional boulders, some of large size, found in places along and above the sea- 

 lochs. Where the present coast-line lies near what was the boundary of the Scottish ice, as in many places between 

 Bioadford and Loch Ainort, we find on the beach more numerous fragments of foreign rocks, doubtless washed out 

 of the ground-moraine of the Scottish ice-sheet. 



