Observations from a fortnight in Lochaber. Found the entrance to Loch Treig to present the clearest evidence of intense glacial action. States, in contradiction of David Milne-Home, that there is glacial scoring in Glen Spean, as Louis Agassiz described, and moraine around the mouth of Loch Treig. There is little sign of water erosion on the rocks crossed by the lines in Glen Roy. Believes the smoothed rocks at the eastern end of Loch Laggan are due to flow from the lake and not tidal action. The lines in Glen Roy are too neat for a lake shore subject to tides. Given the glacial scoring sweeping round from Glen Spean into Glen Treig, and all the boulders, TFJ is astonished that anyone could deny that there had been glaciers there. [See 3247.]
I returned a few days ago from a trip to Lochaber where I spent a fortnight and now
hasten to present you with some of the results of my visit,
and I may at once state that all I saw tended to impress upon me the conviction that
these parallel roads have been formed along the margin of freshwater lakes and finding
the marks of ice action so plain over the whole district I cannot help thinking that
Agassiz hit upon the true solution of the problem when he pronounced these marks to be
the effect of glacier-lakes. I attentively examined the
entrance to Loch Treig, and found both sides of the gorge to present the clearest
evidence of most intense glacial action, and that to heights of many hundred feet above
the like-rounded rocks, scores, flutings & perched blocks abound and all these
phenomena are most conclusively seen to have been effected by a great volume of ice
flowing down the valley now occupied by the Lake, and issuing out by this gorge into
Glen Spean. M
[DIAG HERE] Loch Treig direction of glacier markings E W Glen Spean
I went up to the head of Loch Treig and explored a wild glen which runs from the S.W. corner of the Lake to Spean-bridge & called the Larig or Larig Leachach.
There is no trace of any line round the head of Loch Treig, nor in fact round any part of it, altho' Sir Lauder Dick says it is visible on the W. side. There are some indications of alluvial detritus here & there towards the lower end of the Col.—but a marked absence of such at the upper end & instead I found hillocks of what seems to be Moraine matter abounding in blocks. There is an absence of all deltas at the mouths of the streams that come into the head of the lake at levels above the present upper limit of its waters which leads me to think that the upper end of the lake must have been occupied by the glacier during the time when the waters in Glen Spean stood at the level of the lowermost line of Glen Roy. In traversing the Larig glen I found much evidence of glacier action but not lines like those of Glen Roy.
The only place where I observed any wearing away of solid rock due to the action of the waters that had formed these Glen Roy lines was at the head of Glen Roy or rather what has been called the head of Lower Glen Roy, where there is a sort of pass caused by a set of rocky eminences in the hollow of the glen.
Here also there had been previous glacial action so that it is not easy to determine how much is properly due to the effect of water. This pass is a notable place for wind (as I can testify, having been nearly blown off my feet there) which coming up the long hollow of the glen rushes over this high narrow pass with immense force, and when the water stood at the levels of the two uppermost lines of Glen Roy it would lash against these rocks with considerable force during gales from the S. W.
On the face of the hill marked Tom Brahn in your map the shelves are more broadly & rudely marked than any where else that I saw. This broad marking however consists of a protrusion of loose matter, and I could find no noticeable erosion of rock along any of the lines. The middle line crosses a mass of solid rock in situ here which I examined with the view of detecting traces of such erosion but the angles were quite similar to such as are usually to be found on weathered rocks not exposed to the flow of water.
At the West end of Loch Laggan there is clear evidence of the water having formerly
stood at a height of probably 40--50 feet above their present level, there
being a great bank of alluvial matter to that height which seems to have been the delta
of the Gulban river Along the shores of Loch Laggan however there is no
clear trace of any line that I could see, most of it indeed is so encumbered with block
& rocks that the mark of a line could scarcely be expected. At the
E. end there is also evidence of the lake having formerly stood at a higher
level than at present and that to such a height as would, I have no doubt, cause its
waters to flow eastward by Makoul towards Spey at the pass of Makoul (or Muckul as it
has been written by some) or rather a little to the Eastward of it there is clear
evidence of a large stream of water having flowed out towards the basin of the Spey,
although I should describe it somewhat differently from M
Again the delta at the mouth of the Turret is out of all proportion too large for the size of the stream. I estimated the waters of the Roy as 3 or 4 times greater than those of the Turret at their point of junction whereas the Turret delta is 2 or 3 times bigger than the Roy delta. This I think can be explained only by supposing the Turret delta to be partly due to the outflow from Loch Gluoy. The glacier streams that had blocked up the mouth of Glen Spean have probably been those issuing from Glen Arkarg & the other glens at the mouth of the Caledonian Canal. At Fort Augustus the traces of glacial action are very noticeable.
In Glen Spean to N.E. of Bridge of Roy the scores run E. & W. but further up they sweep beautifully round into the mouth of Glen Treig opposite which they run N. & S. The glacial markings on the syenitic granite on the N. side of Glen Spean opposite the entrance to Loch Treig are amongst the finest specimens of ice-work I have seen, this with the heaps of moraine matter & the perfect wilderness of boulders made me stare with astonishment how any one, after Agassiz had drawn attention to all this, could go on the ground & yet deny that there had been any glacier here! I do not suppose there is any place in Britain where the traces of a great ice stream are more complete.
There are however some facts connected with the former glaciation of Lochaber very remarkable but they refer to a period anterior to the formation of the parallel lines, and although very extraordinary they are consistent & harmonise with what I have seen in other parts of Scotland. They indicate however a climate more like that of the poles than any thing else we have at present on the face of the globe, & the state of things which they disclose seems to me one of the most curious & inexplicable in the whole range of the geological record
I have written the above notes very hastily but shall be happy to answer any queries you may wish to put. I may mention that I had most villainous weather, which prevented me making so long excursions as I otherwise might have done; and it was only by going doggedly to work with a waterproof & umbrella that I could get any thing done at all.
Yours ever | Thos. F. Jamieson
- f1 3242a.f1The original letter has not been found. The text has been taken from a copy entered into Charles Lyell's journal and headed: `Letter from Mr. Jamieson of Ellon to Cha
s. Darwin'. It is also printed in Wilson ed. 1970, pp. 518--23.
- f2 3242a.f2Lochaber is a district in southern Inverness-shire, near Fort William, Scotland; see map, p. 248. CD had visited the region in June 1838 in order to investigate the famous parallel terraces or `roads' of Glen Roy. His paper, `Observations on the parallel roads of Glen Roy, and of other parts of Lochaber, with an attempt to prove that they are of marine origin', was published in the Philosophical Transactions of the Royal Society of London (1839): pt 1, 39--81 (Collected papers 1: 87--137). CD had encouraged Jamieson to `take up Glen Roy' earlier in the year (see letter to Robert Chambers, 30 April , and Correspondence vol. 9, Appendix IX, letter from T. F. Jamieson to Charles Lyell, 14 May 1861). See also Barrett 1973 and Rudwick 1974.
- f3 3242a.f3Louis Agassiz had visited Lochaber in the company of the geologist William Buckland in the summer of 1840, after attending the Glasgow meeting of the British Association for the Advancement of Science. Agassiz subsequently published a brief notice stating his belief that the parallel roads of Glen Roy had been formed by glacial lakes (Agassiz 1840b). Two years later, he published a more complete report on the glacial phenomena of Scotland in which several pages were devoted to a discussion of the parallel roads of Lochaber (Agassiz 1842).
- f4 3242a.f4Milne 1849. The Scottish advocate and geologist David Milne (later Milne-Home) visited Glen Roy in 1845. His paper on the parallel roads, read to the Royal Society of Edinburgh, was privately printed in 1847 and published in the Transactions of the Royal Society of Edinburgh in 1849. There is an annotated copy of the earlier version in DAR 139: 5. Although Milne had originally subscribed to CD's view that the terraces were the remnants of former sea-beaches successively formed as the land was elevated, he became convinced, after visiting the region, that the roads were lacustrine in origin. See Rudwick 1974, pp. 140--5.
- f5 3242a.f5CD stated in his paper (see n. 2, above) that the water-worn rocks at the entrance of Loch Treig and at the head of Lower Glen Roy had helped to convince him that marine action had been involved in the formation of the parallel roads. These rocks appeared `as if they had lain for centuries on a sea coast … washed by the ancient waves' (Collected papers 1: 92).
- f6 3242a.f6In Chambers 1848, pp. 109--10, Robert Chambers outlined Louis Agassiz's glacial theory of the formation of the parallel roads (see n. 3, above). Chambers then claimed that a fatal objection to this theory was that it did not take into account `an opening at the head of Glen Glaster, by which all water above the No. 3 shelf must have been discharged' (ibid., p. 110).
- f7 3242a.f7The Scottish writer Thomas Dick Lauder published one of the earliest scientific accounts of the Lochaber terraces, suggesting that the roads were the remnants of former freshwater lakes (Lauder 1823).
- f8 3242a.f8In the map of Lochaber that accompanied CD's paper (taken from the map published in Lauder 1823, the hill labelled `Tombhran' is shown at the juncture of Glen Roy with Upper Glen Roy, near the intersection with Loch Spey.
- f9 3242a.f9CD did not visit the Pass of Muckul, which Milne identified as a major overflow channel for the supposed former lake in Glen Spean (see Rudwick 1974, p. 140). After reading Milne 1847a, however, CD still believed the site represented a channel of the sea (Correspondence vol. 4, letter to Charles Lyell, 8 [September 1847]):
I look at the pass of Muckul … as a channel just kept open, & the head of glen Roy (where there is a great Bay silted up) & of Kilfinnen, (at both which places, there are level-topped mounds of detritus above the level of the terraces) as instances of channels filled up at the stationary levels.For a comparison of the differing interpretations given to the same phenomena by proponents of the lacustrine hypothesis versus the marine hypothesis, see Rudwick 1974, pp. 138--9, Table 1.
- f10 3242a.f10In Bravais [1843?], the French geologist Auguste Bravais provided several drawings showing the lateral profiles of sections of the Norway coastline that exhibited lines marking the position of ancient sea levels. A shortened, English version of the work, published in the Quarterly Journal of the Geological Society (Bravais 1845), did not include the diagrams.
- f11 3242a.f11CD had made a similar statement about Roderick Impey Murchison after both had visited North Wales in 1842. As CD told Charles Lyell, whereas he had seen obvious signs of glaciation in the region, Murchison saw `no traces of glaciers, but only the trickling of water & of the roots of the Heath! It is enough to make an extraneous man think geology from beginning to end a work of imagination & not founded on observation … But I confess I am astonished, so glaringly clear after two or three days did the evidence appear to me.—' (Correspondence vol. 2, letter to Charles Lyell, [5 and 7 October 1842]). See also Autobiography, p. 70.
- f12 3242a.f12Martin Rudwick has noted that `as Jamieson clearly suspected, the relevant actualistic analogues [of the Lochaber roads] were not the glaciers of the Alps but those of the Polar regions.' (Rudwick 1974, p. 153 n. 98).