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III.—On Changes of Climate during the Glacial Epoch

Published online by Cambridge University Press:  01 May 2009

James Geikie
Affiliation:
District Surveyor of the Geological Survey of Scotland.

Extract

In my first paper I gave the sequence of the Scottish Drift under three groups; but in order to compare these deposits more satisfactorily with the drifts of other countries, it is necessary to subdivide them more closely.

Type
Original Articles
Copyright
Copyright © Cambridge University Press 1872

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References

page 61 note 1 See Geol. Mag. Vol. VIII., Dec. 1871, p. 545.

page 61 note 2 To avoid confusion I have in this table omitted the “high-level beaches”, which mark the pauses in the re-elevation of the land. They are referred to in my second paper. I have of course left unmentioned the more recent raised beaches, etc. It is with the Glacial beds proper that I am dealing.

page 61 note 3 Ueber die erratischen Bildungen im Aargau, etc.; See Nature, vol. ii., p. 310. Mühlberg’s results agree with those obtained by M. Morlot, see Edinb. New Phil. Journal, 1855, p. 14, and Antiquity of Man, p. 320.

page 62 note 1 In a subsequent paper I shall return to the consideration of the inter-Glacial periods of the Swiss geologists, noticing especially the remarkable results obtained by Prof. Heer, see his Urwelt der Schweitz, p. 484, et seq.

page 62 note 2 From the descriptions given of some of the ösar or åsar, I strongly suspect that the equivalent of No 2 in the Scottish section occurs in Sweden; but without a personal examination one can hardly be sure of this. MM. Durocher and Martins distinguish two kinds of ösar—the one containing scratched stones and sometimes shells of Arctic species, and being often made up of very coarse materials; the other being more sandy and showing shells of Baltic species. The former may possibly represent some portion of the Scotch Boulder-earth and clay.

page 63 note 1 Acadian Geology, p. 63.

page 64 note 1 On the Glacial Phenomena of Labrador and Maine.

page 64 note 2 Geology of New York, part iv., p. 160 (Prof. W. Mather).

page 64 note 3 Smithsonian Contributions to Knowledge, vol. xv.

page 65 note 1 On the Surface Geology of the District round Glasgow, etc. Glasgow Geol. Trans, vol. iii., part i.

page 65 note 2 See Geology of Illinois, vol. iv., p. 179. The “shells” are of fresh-water species.

page 65 note 3 See Nature, June 22, 1871, p. 155.

page 66 note 1 Smithsonian Contributions. Illustrations of Surface Geology, etc.

page 66 note 2 Trans. of the Assoc. of Amer. Geol. and Natur. 1840–1842, p. 191.

page 66 note 3 See Report on the Geology of the Lake Superior Land District, p. 235. Also Geology of New York, part iii., p. 121, where Lardner Vanuxem says, “With some exceptions they (erratics) are generally found upon the surface, frequently upon the tops of hills or on their sides, appearing in almost all their localities as if but recently dropped,” etc.

page 67 note 1 Narrative of Arctic Land Expedition to the Mouth of the Great Fish. River, etc., pp. 140, 346. I cannot refrain from quoting a passage which the geologist will at once recognize as a faithful picture of a highly glaciated land-surface. The scene described by Back was just on the skirts of the barren grounds. “There was not the stern beauty of Alpine scenery, and still less the fair variety of hill and dale, forest and glade, which makes the charm of a European landscape. There was nothing to catch or detain the lingering eye, which wandered on without a check over endless lines of round-backed rocks, whose sides were rent into indescribably eccentric forms. It was like a stormy ocean suddenly petrified. Except a few tawny and pale green lichens there was nothing to relieve the horror of the scene; for the fire had scathed it, and the gray and black stems of the mountain pine which lay prostrate in mournful confusion seemed like the blackened corpses of departed vegetation” (p. 178).

page 67 note 2 See Sir J. Franklin’s “First Journey to the Shores of the Polar Sea”; and his “Second Journey”; also Sir J. Richardson’s “Journal of a Boat Voyage through Rupert’s Land”.

page 68 note 1 There is some uncertainty as to the height reached by the sea during the period of subsidence that followed upon the retirement of the ice-sheet. Perched blocks are not always safe guides, as these may sometimes haye been stranded along the sides of mountains by glaciers. In many, or rather in most cases, however, they would appear to have been earried by rafts of ice and dropped into their present positions. They seem to give evidence, therefore, that the land subsided to at least 2500 feet below the present level of the sea. But Dr. Packard thinks that some of the high-level terraces described by Hitchcock are not of marine but freshwater origin, and that they are relics of glacial lakes. In this case these terraces would resemble the parallel roads of Glenroy.

page 68 note 2 So much so indeed as to entitle them to be called “Boulder-clays”. They are more or less distinctly stratified, however. (Packard.)