1863.] JAJIIESON PARALLEL ROADS OP GLE3" ROY. 245 



some 1200 feet or so, and yet have preserved its horizontal] ty so 

 perfect that all the observations hitherto made have failed to detect 

 any fault in the lines, or any deviation from a dead "water-level. 



The absence, therefore, of any good positive evidence in favour of 

 the marine theory, and so many considerations urging themselves 

 against it, seemed to me to render it untenable. 



c. Agassiz's theory. — Let us now see what help is to be got from 

 the glaciers ; and first as regards Glen Gluoy. This glen opens into 

 the great valley of the Caledonian Canal (or 'the Great Glen/ as it is 

 called in pre-eminence), right opposite Loch Arkaig. A glacier, then, 

 issuing out there might have blocked up Glen Gluoy ; or we may 

 conceive the Great Glen itself to have been the bed of a large ice- 

 stream, fed by the lateral valleys. 



I therefore went to Glen Arkaig, and at its very mouth, close to 

 Loch Lochy, found the gneiss much ground down, as if by ice coming 

 from the west. From this to the Lake is known as 'the dark mile/ 

 the road winding along the bottom of the glen beneath the shade 

 of oak, birch, alder, and ash. On reaching Loch Arkaig I ascended 

 the hill on its north side, and found the gneiss much ice-worn as 

 far up as I went, which was about 700 feet above the lake. The 

 crystalline schist is here highly mineralized and of a very metamor- 

 phic nature. The bedding seems nearly vertical, and the layers 

 often twisted and gnarled. These rocky masses show an evident Stos 

 JSeite, as Sefstrom would have called it, the west faces being smoothed 

 down, and the eastern more rugged and unworn. The scores and 

 striae have mostly weathered out, but I succeeded in finding some 

 well-marked instances, the direction being up and down the valley. 

 This was nearly 400 feet above the Loch ; and, judging from the ap- 

 pearance of the ridge as far up as I could see, the glacial action had 

 extended to a great height. There was an absence of any super- 

 ficial detritus, and also of large boulders. Glen Arkaig shows a wide 

 basin encompassed with large, broad-flanked hills. The ridge be- 

 tween it and Glen Garry is very high, three of the peaks reaching 

 about 3000 feet, and the highest exceeding that a little. Glen 

 Arkaig, therefore, would seem to possess the qualities suited for 

 turning out one of the largest glaciers in the district. This, then, 

 was so far favourable. 



On coming to examine the mouth of Glen Gluoy, I found on the 

 north side, upon the angle of the ridge between it and Loch Lochy, 

 glacial scores pointing "W. 25° N., as if caused by a pressure of ice 

 from Loch Arkaig. This was at a height of about 260 feet above 

 the bridge, the markings being discovered by tearing off the peel 

 of turf that covered the rock, so as to expose a fresh surface. On 

 walking up the glen to the point where Glen Fintaig branches off, I 

 found scores here and there, generally parallel to the valley ; but on 

 the spur of the hill that divides Glen Gluoy from Glen Fintaig, the 

 scoring runs right up and down the slope that faces down the valley. 

 This had been previously noticed by Sir. Milne-Home, who attri- 

 buted it to diluvial action. 



I now examined the shoulder of the hill between the mouths of 

 vol. xix. — part i. s 



