628 D. MILNE HOME ON THE PARALLEL ROADS OF LOCHABER. 
glacier would have a less rise to make, because Loch Treig stands at a level of 
750 feet above the sea. But its course towards Cranachan, in Glen Roy, 
would be so obstructed, as to render it impossible that it should ever have 
reached Glen Roy at the place required, in the condition of a solid body of 
ice. First, it would have to descend into Glen Spean, (which must there 
have been filled by a lake flowing out at Mukkoul) which is about 200 feet 
below Loch Treig, and then it would have to climb up the ridge separating 
Glen Spean from Glen Glaster, requiring a rise of 500 feet, in which case it 
would have risen above its own fountain head to the extent of no less than 
400 feet. After getting over this ridge it would, before it could reach Glen 
Glaster, have to wheel round the S.E. corner of Craig Choinichte, and on 
passing through Glen Glaster make another bend before it reached Glen Roy. 
Even if, on reaching Glen Roy, it struck against Bohuntine Hill, and did not 
flow down Glen Roy, is it possible to suppose that the ice, on reaching Glen 
Roy, could have formed a solid body sufficiently strong to resist “ the hydrostatic 
pressure of a column of water some hundreds of feet high?” This difficulty, 
suggested by Mr Jamreson himself, seems to me insurmountable. 
(3.) There is afurther difficulty. The lake of Glen Roy, at the middle shelf, 
discharged through Glen Glaster ; but if the Treig Glacier came through Glen 
Glaster to block Glen Roy for Shelf 3, as suggested by Messrs Jamieson and 
JOLLY, any overflow of the lake through that glen would be impossible. 
(4.) Mr Jotty thinks that the barrier in Glen Collarig for Shelves 2 and 3 
might have been made by the glacier from Corry N‘Eoin pushing across the 
Spean into the mouth of Glen Roy and up into Glen Collarig. To say nothing 
of the very tortuous course which the ice would have to take before it could 
reach the middle of Glen Collarig, it is enough to observe that a glacier coming 
out of Corry N‘Eoin must, in virtue of the existing levels of the country, have 
flowed in an exactly opposite direction. The only use which Mr JAmMriEson made 
of the Corry N‘Eoin Glacier was to find a dam for the lake of Shelf 4, which 
extended down to Unichan. He supposed that this glacier extended across the 
Unichan Moor in a strait line to Teandrish. But as this barrier required to be 
four or five miles in length, it is hardly possible to suppose that this Corry 
N‘Eoin glacier could have formed a solid barrier along its whole course. Every 
winter and every summer it must have changed its position and its internal 
structure, in such a way as to allow the water to escape through or under it. 
(5.) Reference has been made to the Marjelen See. This lake, as I have 
just observed, is very small in size. Sir CuArLes LYELL, who visited it in the 
year 1865, says it was only two miles in circumference. Professor Favre, of 
(published by the Philosophical Society of Glasgow in 1850). Mr Bryce shows from the geographical 
position of Loch Arkaig that even supposing a glacier to have been formed in that valley, any moraines 
which it might have produced, ould not have been so situated as to block Glen Gluoy. He does not 
think it necessary even to entertain the question of a blockage by the glacier itself. 

