In the next article we shall consider the glacial phenomena as they exist in America.
FOOTNOTES:
[A] See January No., p. 61.
[B] Having enumerated the characteristic features of the glacial phenomena in the preceding pages, I throw into this note some explanation which may render my views of the parallel roads more intelligible, not to interrupt again the exposition with details. It would be desirable, however, that the reader should first make himself thoroughly familiar with the localities concerned, before proceeding any farther. I would therefore state here, that, in the wood-cut opposite, G. R. indicates the valley of Glen Roy, with the three parallel roads marked 1, 2, 3. Glen Spean is designated by G. S., and the river flowing at its bottom by S. Loch Laggan, out of which the River Spean rises, is marked L. G. indicates Glen Gloy, a little valley to the northwest of Glen Roy, with a single terrace. Loch Treig is designated by T., Loch Lochy by L. O., Loch Arkeig by A., and Moeldhu Hill by M., while E. indicates Loch Eil. The Great Glen of Scotland, through which the Caledonian Canal runs, extends in the direction of L. O. and E. The position of Ben Nevis is designated by N. The dotted area between N. and M. marks the place occupied by the great glacier of Ben Nevis, when it extended as far as Moeldhu; while the close continuous lines in front of Loch Treig indicate the direction of the glacial scratches left across Glen Spean by the glacier of Loch Treig, when it extended as far as the eastern termination of the two upper terraces. It ought to be remembered, in this connection, that the bottom of the valley of the Spean, as well as that of Glen Roy, is occupied by loose materials, partly drift, that is, materials acted upon by glaciers, and partly decomposed fragments of rocks brought down by the torrents, greatly impeding the observation of the polished surfaces. The river-bed is cut through this deposit, and here and there through the underlying rock. Besides the parallel roads, there are also peculiar accumulations of loose materials in Glen Roy and Glen Spean, more particularly connected with the lowest terrace, which Mr. Darwin and Professor Jamieson have shown to be little deltas formed during the existence of the lake of Glen Roy at the bottom of the gullies intersecting the shelves of the upper roads. The outlet for the water at the period during which the second terrace was formed, not known when I visited Glen Roy, has been discovered by Mr. Milne-Holme, and also observed by Professor Jamieson. During the formation of the upper terrace, the waters escaped through the westernmost tributary of the River Spey, in the direction of the northeast corner of the wood-cut, and during that of the lowest terrace, at the eastern end of Loch Laggan, also through the valley of the Spey. The state of preservation of the parallel roads is such as to prove that no disturbance of any importance can have taken place in the country since they were formed. Far from believing, therefore, that these remarkable shelves are ancient sea-beaches, I am prepared to maintain, that, had the area occupied by them been submerged only for a few days, under an ocean rising and falling for several feet with every tide, no vestige would have been left of their former existence.
[C] The wood-cut on p. 730 is a reproduction of the little map accompanying a paper of mine upon "The Glacial Theory and its Recent Progress," printed in the "Edinburgh New Philosophical Journal" for October, 1842. I might have greatly improved the topography, and represented more accurately the details of the phenomenon, by availing myself of the much larger and very minute map recently published by Professor Thomas F. Jamieson, of Aberdeen; but I thought it advisable to leave my first sketch as I presented it twenty-two years ago, in order to show that Sir Charles Lyell is mistaken in ascribing (see "Antiquity of Man," pp. 260, 261) the discovery of the glacier of Loch Treig to Professor Jamieson. A comparison of his statements with mine will show that the solution of the problem offered by him is identical with that proposed by me, as he himself candidly admits ("Quarterly Journal of the Geological Society" for August, 1863, p. 239). I have only one fault to find with his observations, and, as I have never revisited the locality since, this remark may satisfy him that my examination of its features was not so hurried as he supposes. Professor Jamieson confounds the effects of two distinct glaciers moving in different valleys as the action of one and the same glacier. In my paper, it is true, I made no allusion to the great glacier of Glen Spean, the existence of which I had recognized along the river from Loch Laggan nearly to the Caledonian Canal. I publish my observations upon this great central glacier for the first time in the present article, having omitted them in my contributions upon this subject to the scientific periodicals of the day simply because I thought best not to complicate my exposition of the facts concerning the parallel roads by considerations foreign to their origin, convinced as I was, from the manner in which the glacial theory was then received, that they would not be understood, and still less admitted. But now that all the geologists of Great Britain seem to have given their adhesion to it, I may be permitted to state that I already knew then, what Professor Jamieson has overlooked in his latest paper, that a separate glacier had occupied the valley of the Spean prior to the formation of the parallel roads, and that at that time the glacier of Loch Treig was only a lateral tributary of the same, just as the glacier of the Thierberg is a tributary of the glacier of the Aar. It was not until the Glen Spean glacier had retreated to the hills east of Loch Laggan that the glacier of Loch Treig could form a barrier across Glen Spean, and thus dam the waters in Glen Roy which produced the parallel roads. The marks left by the great Glen Spean glacier in the valley are mistaken by Professor Jamieson for indications, that, in its greatest extension, the glacier of Loch Treig not only advanced across Glen Spean, but divided into two branches, one moving westward down Glen Spean, the other eastward up Glen Spean, as far as Loch Laggan. Any one sufficiently familiar with existing glaciers to compare their action with the phenomena referred to above will at once see the impossibility of such a course for any glacier coming down from Loch Treig. At the time the Grampians had become a separate centre of glacial action a great glacier must have moved down, towards the Caledonian Canal, through Glen Spean, receiving as tributaries lateral glaciers not only from Loch Treig and Glen Roy, but also from all the other minor lateral valleys emptying into Glen Spean, the largest of which must have come from the range of Ben Nevis,—just as the great glacier of the valley of the Rhone once received as tributaries all the glaciers coming down into that valley from the southern slope of the Bernese Oberland, and from the northern slope of the Valesian Alps, and at one time also from the eastern slopes of the range of Mont Blanc. And when the large glacier occupying the lower, and therefore warmer, level gradually disappeared and retreated far away to levels where it could maintain itself against the effect of a returning milder climate, the opening spring of our era, as we may call it, the lateral glaciers, arising from the nearer high grounds, could extend across the valleys, but not before.
UNDER THE CLIFF.
"Still ailing, Wind? Wilt be appeased or no?
Which needs the other's office, thou or I?
Dost want to be disburthened of a woe,
And can, in truth, my voice untie
Its links, and let it go?
"Art thou a dumb, wronged thing that would be righted,
Intrusting thus thy cause to me? Forbear!
No tongue can mend such pleadings; faith, requited
With falsehood,—love, at last aware
Of scorn,—hopes, early blighted,—
"We have them; but I know not any tone
So fit as thine to falter forth a sorrow:
Dost think men would go mad without a moan,
If they knew any way to borrow
A pathos like thy own?