. Soc." 1839, page 39.), the buttress-like
accumulations of stratified shingle on sides of valley, especially those
just below the lowest shelf in Spean Valley.

2nd. I can hardly conceive the extension of the glaciers in front of the
valley of Kilfinnin, where I found a new road--where the sides of Great
Glen are not very lofty.

3rd. The flat watersheds which I describe in places where there are
no roads, as well as those connected with "roads." These remain
unexplained.

I might continue to add many other such reasons, all of which, however,
I daresay would appear trifling to any one who had not visited the
district. With respect to equable elevation, it cannot be a valid
objection to any one who thinks of Scandinavia or the Pampas. With
respect to the glacier theory, the greatest objection appears to me the
following, though possibly not a sound one. The water has beyond doubt
remained very long at the levels of each shelf--this is unequivocally
shown by the depth of the notch or beach formed in many places in
the hard mica-slate, and the large accumulations or buttresses of
well-rounded pebbles at certain spots on the level of old beaches. (The
time must have been immense, if formed by lakes without tides.) During
the existence of the lakes their drainage must have been at the head of
the valleys, and has given the flat appearance of the watersheds. All
this is very clear for four of the shelves (viz., upper and lower in
Glen Roy, the 800-foot one in Glen Spean, and the one in Kilfinnin), and
explains the coincidence of "roads" with the watersheds more simply than
my view, and as simply as the common lake theory. But how was the Glen
Roy lake drained when the water stood at level of the middle "road"? It
must (for there is no other exit whatever) have been drained over the
glacier. Now this shelf is full as narrow in a vertical line and
as deeply worn horizontally into the mountain side and with a large
accumulation of shingle (I can give cases) as the other shelves. We
must, therefore, on the glacier theory, suppose that the surface of
the ice remained at exactly the same level, not being worn down by the
running water, or the glacier moved by its own movement during the very
long period absolutely necessary for a quiet lake to form such a beach
as this shelf presents in its whole course. I do not know whether I have
explained myself clearly. I should like to know what you think of this
difficulty. I shall much