290, 291.)


LETTER 525. TO C. LYELL.
Down, September 22nd [1861].

I have read Mr. Jamieson's last letter, like the former ones, with very
great interest. (525/1. Mr. Jamieson visited Glen Roy in August 1861 and
in July 1862. His paper "On the Parallel Roads of Glen Roy, and their
Place in the History of the Glacial Period," was published in the
"Quarterly Journal of the Geological Society" in 1863, Volume XIX., page
235. His latest contribution to this subject was published in the
"Quarterly Journal," Volume XLVIII., page 5, 1892.) What a problem you
have in hand! It beats manufacturing new species all to bits. It would be
a great personal consolation to me if Mr. J. can admit the sloping Spean
terrace to be marine, and would remove one of my greatest difficulties--
viz. the vast contrast of Welsh and Lochaber valleys. But then, as far as
I dare trust my observations, the sloping terraces ran far up the Roy
valley, so as to reach not far below the lower shelf. If the sloping
fringes are marine and the shelves lacustrine, all I can say is that nature
has laid a shameful trap to catch an unwary wretch. I suppose that I have
underrated the power of lakes in producing pebbles; this, I think, ought to
be well looked to. I was much struck in Wales on carefully comparing the
glacial scratches under a lake (formed by a moraine and which must have
existed since the Glacial epoch) and above water, and I could perceive NO
difference. I believe I saw many such beds of good pebbles on level of
lower shelf, which at the time I could not believe could have been found on
shores of lake. The land-straits and little cliffs above them, to which I
referred, were quite above the highest shelf; they may be of much more
ancient date than the shelves. Some terrace-like fringes at head of the