To Charles Lyell 22 September 
Down Bromley Kent
My dear Lyell
I have read Mr Jamieson’s last letter, like the former ones, with very great interest.1 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 Terraces to be marine; & would remove one of my greatest difficulties, viz. vast contrast of Welch & Lochaber valleys.2 But then,, as far as I dare trust my observations, the sloping terraces run far up the Roy valley so as to reach not far below the Lower shelf.3 If the sloping fringes are marine & 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 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 moraine, (& which must have existed since glacial epoch) & above water, & I could perceive no difference.4 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 & 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 Spey strike me as very suspicious.
Mr. J. refers to absence of pebbles at considerable heights: he must remember that every storm, every deer, every Hare which runs tends to roll pebbles down hill, & not one ever goes up again.— I may mention that I particularly attended to this on S. Ventana in N. Patagonia,—a great, isolated, rugged Quartz mountain, 3000 ft high, & I could find not one pebble, except on one very small spot, where a ferruginous spring had firmly cemented a few to face of mountain.—5
If the Lochaber Lakes had been formed by a ice-period posterior to the (marine?) sloping terraces in the Spean; would not Mr. J. have noticed gigantic moraines across the valley, opposite opening of L. Treig? I go so far as not to like making the elevation of the land in Wales & Scotland considerably different with respect to ice-period; & still more do I dislike it with respect to E. & W. Scotland. But I may be prejudiced by having been so long accustomed to plains of Patagonia. But the equability of level (barring denudation) of even the Secondary formations in Britain, after so many ups & downs, always impresses my mind, that, except when crust cracks & mountains are formed, movements of elevation & subsidence are generally very equable.—6
But it is folly my scribbling thus.— You have a grand problem, & Heaven help you & Mr Jamieson through it. It is out of my line now a-days, & above & beyond me.—
Ever my dear Lyell | Yours truly | C. Darwin
(This is dreadfully untidy & useless, but I am too tired to rewrite it.—)
Additional discussion of Jamieson’s theory that the roads of Glen Roy were formed by a glacial lake. Suggests the possible marine origin of the Glen Spean terraces. Comments on the power of lakes to produce pebbles. Discusses elevation of Wales and Scotland during the glacial period.
Please cite as
Darwin Correspondence Project, “Letter no. 3260,” accessed on 29 March 2017, http://www.darwinproject.ac.uk/DCP-LETT-3260