80 Dr. T. Archibald Dukes on 
up Glen Roy be moved lower down the valley. When it gets past 
Glen Glas Dhoire, obviously the water will rush up that glen 
and flow over its “col,” which is at a lower level than that of 
the old lake in Glen Roy, until the lake settles to the level of 
this second ‘‘col.’”? Thus the second parallel ‘‘ road” is formed. 
Now move the obstruction lower down, and old Loch Roy runs 
directly into the Spean Valley; but if we suppose the mouth of 
this Spean Valley to be itself blocked up, the waters of the glen, 
dammed back to form a huge lake, would again overflow at the 
lowest available spot. This is the ‘‘col’’ which we have seen 
at Makoul in the far end of the valley beyond Loch Laggan; so 
at this level, 850 ft., the lowest ‘‘road”’ is formed in both Glen 
Roy and Glen Spean. 
What could have formed this slowly moveable obstruction ? 
An obstruction which has now completely gone, and left not a 
trace behind? Ice, certainly. And there is abundant evidence 
of ice action in the Spean Valley—moraines, scratches, and striz ; 
while, in places, obstructing rocks of hard schist are rounded off 
and smoothed down by the grinding glaciers which flowed over 
them. And there, opposite the mouth of Glen Roy, stands the 
highest mountain in the kingdom—Ben Nevis—with his neigh- 
bours Aonach Beg and Stob Coire an Easan, which are supposed 
to supply the required glacier. I believe, however, no one has 
ventured to draw upon a map the position and course of a glacier 
thus obstructing the glens. The configuration of the hills makes 
it mechanically impossible that any glacier should take such a 
course, for when it has reached the bottom of the Spean Valley, 
consider the forces acting upon it. From Glen Roy there comes 
a pressure of a mass of water, 850 ft. high, forcing the glacier 
towards the west. There is nothing to prevent the glacier going 
in that direction downhill some 200 ft. to the river Lochy, four 
or five miles off. But instead of taking this widely open unob- 
structed passage to the sea, we are asked to believe that it turns 
eastward, and, in the face of that enormous pressure, runs uphill 
more than 200 ft. for some four miles into a steep narrow valley. 
There is no moraine nor other sign of the former existence of 
such a glacier, and Glen Gloy, which is a branch of the Lochy 
Valley, would require another glacier to block its entrance; and 
to this there are further objections. 
All these difficulties disappear, however, if we remember that 
ice is not always liquid, it is sometimes solid ; it is not always a 
flowing glacier, it is sometimes a stationary mass. How it came 
about was, I imagine, something like this:—During the Glacial 
Epoch Scotland was covered deep with ice, because year by year 
more snow fell than got melted. This accumulated till it flowed 
off the mountains as glaciers, filled up the valleys, and perhaps 
covered up the tops of the mountains in one uniform snow-field, 
