
D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 627 
glacier, the ice would likely push itself across the Spean into the mouth of Glen Roy, and up 
Glen Collarig” (MSS. p. 25). 
The existence of an ice stream which passed from Loch Treig through 
Glen Glaster, Mr Jotty thinks is proved by the existence in that glen of what 
he considers to be moraines. These, he says :— 
“Prove the presence of ice at the head of Glen Glaster to dam back the water of the 
middle shelf in Glen Roy. They also point to an extension of the ice in that glen above the 
middle shelf to form in conjunction with the glacier extensions from the glens west of Ben 
Chlinaig, the required dam for the highest shelf in Glen Roy at Cranachan, where that shelf 
suddenly ends on both sides of the glen” (MSS. p. 29). 
2. Having thus explained in what manner the ice dams are supposed to 
have been formed to suit the different glens and levels, and from what sources 
the ice came to make these dams, I proceed to notice the difficulties which 
this theory has to contend with. 
(1.) Is it likely that in this Lochaber district, some of the glens should have 
been filled with solid ice and others with water ? 
The temperature must have been much the same in all the glens. If there 
was any difference, one might have supposed that in the glens furthest from the 
sea, in winter at least, there should have been more cold; and yet Glens Gluoy, 
Roy, and Spean, which were occupied by lakes, are farther from the sea than _ 
Corry M‘Eoin and Loch Arkaig, which are supposed to have supplied great 
glaciers. 
There is only one case in the known world of a lake among mountains the 
waters of which were dammed up by a glacier. The Marjelen See in 
Switzerland, is a small lake occasionally dammed up by the Aletch glacier, as 
it flows past one end of the lake. This lake is at a level of 7000 feet above the 
sea; and the glacier comes from hills having a height of 12,000 feet above the 
sea. In this case, it is therefore intelligible how there should be a lake at the 
one place, and a glacier at the other. But in the Lochaber district, there is no 
such difference of altitude to cause a greatly lower temperature in the glens 
where Messrs JAMIESON and JOLLY say that glaciers were formed. 
Indeed, some of the hills adjoining Glens Gluoy, Roy, and Spean, are quite 
as high as the hills from which the glaciers are supposed to have come. 
(2.) Another difficulty is suggested by the levels of the country. 
The barrier for the highest shelf in Glen -Gluoy must have been at a height 
of 1170 feet above the sea. But the valley of Arkaig is only about 200 feet 
above the sea, and if a glacier emerged from its mouth, it would naturally flow 
westward towards the sea, instead of climbing 900 feet up a steep hill on the 
opposite side of the valley.* 
The highest shelf in Glen Roy being 1150 feet above the sea, the Treig 
* There is a very instructive paper ‘On the Parallel Roads,’ by Mr James Brycs, junior, F.G.S. 
VOL. XXVII. PART IV. 22 € 
