THE PARALLEL ROADS OF GLEN ROY. 219 



indubitable. One of the proofs most convenient for 

 reference, is a great rounded rock by the roadside, 

 1,000 yards east of the milestone marked three-quarters 

 of a mile from Roy Bridge. Farther east other cases 

 occur, and they leave no doubt upon the mind that 

 Glen Speanwas at one time filled by a great glacier. To 

 the disciplined eye the aspect of the mountains is per- 

 fectly conclusive on this point; and in no position can 

 the observer more readily and thoroughly convince 

 himself of this than at the head of Glen Glaster. The 

 dominant hills here are all intensely glaciated. 



But the great collecting ground of the glaciers 

 which dammed the glens and produced the parallel 

 roads, were the mountains south and west of Glen 

 Spean. The monarch of these is Ben Nevis, 4,370 feet 

 high. The position of Ben Nevis and his colleagues, in 

 reference to the vapour-laden winds of the Atlantic, is 

 a point of the first importance. It is exactly similar to 

 that of Carrantual and the Macgillicuddy Reeks in the 

 south-west of Ireland. These mountains are, and were, 

 the first to encounter the south-western Atlantic winds, 

 and the precipitation, even at present, in the neigh- 

 bourhood of Killaraey, is enormous. The winds, 

 robbed of their vapour, and charged with the heat set 

 free by its precipitation, pursue their direction oblique- 

 ly across Ireland; and the effect of the drying process 

 may be understood by comparing the rainfall at Ca- 

 ll irciveen with that at Portarlington. As found by 

 Dr. Lloyd, the ratio is as 59 to 21 fifty-nine inches 

 annually at Cahirciveen to twenty-one at Portarling- 

 ton. During the glacial epoch this vapour fell as snow, 

 and the consequence was a system of glaciers which 

 have left traces and evidences of the most impressive 

 character in the region of the Killarney Lakes. I have 

 referred in other places to the great glacier which, 



