THE PARALLEL ROADS OF GLEN ROY 233 



arch of these is Ben Nevis, 4,370 feet high. The position 

 of Ben Nevis and his colleagues, in reference to the vapor- 

 laden winds of the Atlantic, is a point of the first impor- 

 tance. It is exactly similar to that of Carrantual and the 

 Macgillicuddy Eeeks in the southwest of Ireland. These 

 mountains are, and were, the first to encounter the south- 

 western Atlantic winds, and the precipitation, even at 

 present, in the neighborhood of Killarney, is enormous. 

 The winds, robbed of their vapor, and charged with the 

 heat set free by its precipitation, pursue their direction 

 obliquely across Ireland; and the effect of the drying 

 process may be understood by comparing the rainfall at 

 Cahirciveen 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 Portarlington. During the 

 glacial epoch this vapor fell as snow, and the consequence 

 was a system of glaciers which have left traces and evi- 

 dences of the most impressive character in the region of 

 the Killarney Lakes. I have referred in other places to 

 the great glacier which, descending from the Keeks, moved 

 through the Black Valley, took possession of the lake- 

 basins, and left its traces on every rock and island emer- 

 gent from the waters of the upper lake. They are all 

 conspicuously glaciated. Not in Switzerland itself do we 

 find clearer traces of ancient glacier action. 



What the Macgillicuddy Reeks did in Ireland, Ben 

 Nevis and the adjacent mountains did, and continue to 

 do, in Scotland. We had an example of this on the 

 morning we quitted Roy Bridge. From the bridge west- 

 ward rain fell copiously, and the roads were wet; but the 

 precipitation ceased near Loch Laggan, whence eastward 

 the roads were dry. Measured by the gauge, the rainfall 



