1879.] 



of the Parallel Roads of Lochaber. 



11 



Burn, and the other ravines of that chain, and coming into collision 

 with those of the Ben Nevis range. In the same way, the valley of 

 Loch Eil, Glen Nevis, Glen Mhuilinn, Glen Loy, and others were 

 focussing their glaciers upon the end of the Great Glen north of Ben 

 Nevis, barring in that direction the passage of the ice down Glen 

 Spean, and diverting it northward towards Loch Lochy and Loch 

 Oich. 



The ice therefore descending Glen Spean, in consequence of these 

 obstructions, accumulated in mass in the lower part of that valley 

 opposite Glen Roy, until overcoming further resistance and confluent 

 with the Ben Nevis glaciers it wheeled round into the Great Glen at 

 Loch Lochy, where the united stream found not only a more con- 

 tracted passage, but met also at right angles the glacier issuing from 

 Glen Arkaig, by which it was forced against and up the entrance to 

 Glen Gluoy opposite. 



This direction of the flow is in accordance with ice striae noticed by ■ 

 Mr. Jamieson on the flank of Strone-y-Vaa, and by Mr. J. Campbell, 

 of Islay, to the west of Spean Bridge ; but it is not so readily recon- 

 cileable with those at the entrance of Glen Gluoy. It may be a 

 question, however, whether the striae, in the Spean Valley, facing and 

 flanking the entrance to Glen Treig, are all to be interpreted in the 

 way suggested by Mr. Jamieson. There is no doubt from the direction 

 of the striae, and the position of the transported boulders, that the 

 mass of the Treig glacier struck across the valley of the Spean, and 

 turned down its channel westward ; but that a part ascended to the 

 Col of Glen Glaster, and another passed up the Spean Valley is 

 doubtful. It is more probable that this glacier after traversing Strath 

 Spean, met with glaciers coming down Glen Feitheil and the Rough 

 Burn, which caused it to turn down the Spean Valley, while it barred 

 the passage of these other glaciers and diverted them up the valley 

 in the direction of Loch Laggan and over the Pass of Makoul. The 

 direction of the striae observed by the author between the Bough Burn 

 and Moy, points, he considers, to ice coming down from the hills on 

 the north and joining the main east stream. 



The effects of these great conflicting ice streams were not confined 

 to the piling up and accumulation of the ice only. Although glaciers 

 confined by the walls of narrow glens, and descending steep slopes 

 exercise great abrading power, the observations of Charpentier and 

 others show that when they emerge into broader and flatter valleys, they 

 may pass over beds of loose detritus without disturbance except that of 

 pressure. The terminal moraines of the many glaciers emerging into 

 Glen Spean may, according to the varying conditions of the ice, have 

 been pushed forward or rolled over by the ice, while the meeting of 

 conflicting glaciers must have led to the deposition and heaping up of 

 the glacial debris at the points of junction. The many checks and 



