MacCulloch (522/5. "On the Parallel Roads of Glen Roy." "Geol. Trans."
Volume IV., page 314, 1817 (with several maps and sections).) and Dick.
(522/6. "On the Parallel Roads of Lochaber." "Trans. R. Soc. Edinb."
Volume IX., page 1, 1823.) Indeed, in showing that there is a passage at
Glen Glaster at the level of the intermediate shelf, he makes the
difficulty to my mind greater. (522/7. See Letter 521, note.) When I
think of the gradual manner in which the two upper terraces die out at Glen
Collarig and at the mouth of Glen Roy, the smooth rounded form of the hills
there, and the lower shelf retaining its usual width where the immense
barrier stood, I can deliberately repeat "that more convincing proofs of
the non-existence of the imaginary Loch Roy could scarcely have been
invented with full play given to the imagination," etc.: but I do not
adhere to this remark with such strength when applied to the glacier-lake
theory. Oddly, I was never at all staggered by this theory until now,
having read Mr. Milne's argument against it. I now can hardly doubt that a
great glacier did emerge from Loch Treig, and this by the ice itself (not
moraine) might have blocked up the three outlets from Glen Roy. I do not,
however, yet believe in the glacier theory, for reasons which I will
presently give.

There are three chief hostile considerations in Mr. Milne's paper. First,
the Glen [shelf?], not coinciding in height with the upper one [outlet?],
from observations giving 12 feet, 15 feet, 29 feet, 23 feet: if the latter
are correct the terrace must be quite independent, and the case is hostile;
but Mr. Milne shows that there is one in Glen Roy 14 feet below the upper
one, and a second one again (which I observed) beneath this, and then we
come to the proper second shelf. Hence there is no great improbability in
an independent shelf having been found in Glen Gluoy.

This leads me to Mr. Milne's second class of facts (obvious to every one),