246 PBOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 21, 



Glen Gluoy and Glen Spean, and on the angle of the ridge, between 

 Loch Lochy and the Spean (known, I believe, as Strone-y-Yaa), I 

 found the rock much worn in many places, as if by the pressure of 

 ice from the west. The surface, however, of these masses has 

 yielded to the influence of the weather, so that it required much 

 search to discover any reliable markings. Several clear instances I 

 did at length find. At an elevation of probably 800 or 900 feet 

 glacial scoring occurred, pointing "W. 5° N., a little lower W. 20° N., 

 running not horizontally, but up and down the slope, as if by ice 

 mounting over it from Loch Lochy. Again, W. 26° N., "W". 45° K, 

 and "W. 12° N., pointing generally towards the mouth of Glen 

 Arkaig. Further round the angle of the hill towards Glen Spean 

 and lower down, W. 15° N. and W. 45° N., or due N.W. ; and the 

 western sides of the rock being most worn showed that the action had 

 come from that side, and not down the Spean Yalley. The rocks 

 were also most bared where the pressure of a glacier, wheeling round 

 from the Great Caledonian Yalley into the mouth of Glen Spean, 

 would have applied most strongly. All this seemed to show that 

 the Glen Arkaig glacier not only blocked up Glen Gluoy, but also 

 largely contributed to close the mouth of Glen Spean. 



At a place called Brackletter, on the south side of the Spean, near 

 its junction with the Lochy, I observed glacial scores pointing more 

 nearly due west, but still inclining a little to north, as if caused by 

 the pressure of ice from Glen Lui, a valley lying to the south of 

 Glen Arkaig, and opening in front of Glen Spean. 



The south side of the Spean, from its mouth eastward to Loch 

 Treig, is bounded by a range of lofty hills, which may be looked upon 

 as an extension of the Ben Nevis ridge. The highest peaks exceed 

 3000 feet in height, but they are not disposed around a basin that 

 could collect their snows into one ice-stream. The most extensive, 

 however, of the numerous gullies that intersect their flanks is "Corry 

 N'Eoin" (the " Bird-Corry "), a grand place to the east of a large 

 mountain called the Aonach More. This ravine presents a series 

 of rocky amphitheatres, or great caldrons, whose walls have been 

 ground down by the long- continued action of the ice. The quartz- 

 veins are all shorn to the level of the rounded gneiss, and streaked 

 with fine scratches pointing up and down the hollow. These signs of 

 glacial action extend far up the rocks on either side. I should have 

 therefore considered it a good objection to Agassiz's theory, had any 

 of the parallel roads been visible in this gully. But it is interesting 

 to remark, that although the lowest line can be traced from Loch 

 Treig all along to here, yet it stops short just as it approaches the 

 entrance of this ravine, and further west I could not trace it. The 

 conclusion, therefore, seems reasonable, that the extension of the 

 lake was cut off here by a glacier issuing from Corry N'Eoin, and 

 on the opposite side by the ice of Glen Arkaig and the Great Glen 

 flowing over the shoulder of Strone-y-Yaa to near Tiendrish, where 

 the line on the north side of Glen Spean vanishes. 



Probably all the Great Caledonian Yalley was at this time filled 

 with ice, from its summit-level at Loch Oich to Fort William ; the 



