114 MR DAVID MILNE HOME: MEMOIR ON THE 
has ventured to point out any other valleys than two, viz., Loch Treig and 
Corry N’Eoin, from which glaciers might have come into Glen Spean. 
But it now turns out, that at the very time that lakes filled Glen Roy and 
Glen Spean, a lake existed in Loch Treig also; nay, it was the same lake which 
existed in these three glens,—Shelf 4 being traceable in all of them. The exist- 
ence of this shelf in Loch Treig is assumed by AGAssiz and CHAMBERS. Sir 
THomas Dick LAUDER describes this shelf as surrounding Loch Treig. He so 
represents itin his map. I can myself vouch for having seen traces of Shelf 
4, in the lower parts of Loch Treig,—the only parts examined by me: What is 
more, the map annexed to Dr TyNDALL’s lecture represents Loch Treig as sur- 
rounded by the same “ Parallel Road” as that in Glen Roy and Glen Spean! 
With regard to Corry N’Eoin, any glacier from it, mstead of flowing up 
towards Glen Roy, would, in consequence of the levels of the country, have 
flowed in a direction nearly opposite. 
The barriers at Bohenie and in Glen Collarig admittedly necessary for 
keeping in the lakes which formed Shelves 2 and 3, are 7 or 8 miles distant from 
Corry N’Eoin. Before any glacier formed in that Corry could have pushed 
out a tongue of ice to form a barrier,—it had to cross a large extent of 
uneven surface of country, and must also have wheeled round several project- 
ing hills, and have risen up at least 400 feet above its own original level ! 
But in this glen also, the existence of any glacier at the period when the 
Parallel Roads were formed, is more than doubtful. Having twice visited that 
Corry, I satisfied myself that the lowest shelf, or Parallel Road No. 4, exists at 
the Corry, near its south side; and that a mass of detritus exists at the mouth 
which would have been swept away had any glacier issued from that glen. 
(See Diagram on upper part of Plate XIV.) 
In concluding and bidding farewell to the whole discussion, I offer the 
following programme of the various changes which appear to me to have taken 
place. 
1st. Local glaciers occupied the valleys of the Highlands, so that the rocks 
occupying the floors of the valleys were smoothed and striated. Moraines 
were occasionally formed at the mouths of these valleys. 
2d. A change then took place in the relative levels of sea and land. The 
land sunk, or the sea rose, so that the mountains of the country were submerged 
to the extent of 3000 feet or more. An oceanic current from the W.N.W. 
prevailed, bringing masses of ice loaded with boulders. The effect was to 
grind and round off the tops and sides of our mountains, and deposit on na 
of them, especially on their N.W. sides, boulders of all sizes. 
3d. During this period of submergence, and asthe sea retired or subsided, 
beds of clay, sand, and gravel were deposited, being the debris of rocks broken 
down and carried off by the sea and ice, from the submerged hills. 

