7A. FINAL OUTCOMES
The "controversy" over the glacial theory rumbled on through the 1860s, as these two contrasting images from the 1850s and 60s attest to:
“The Deluge of the north of Europe” (Figuier, L. 1863 p.321)
(Note the ice-bergs transporting boulders; trees give relative scale)
“The period of the Diluvium, or Ice Age, with a glacier invading the land” (Unger 1851).
(USGS Photographic library: http://libraryphoto.cr.usgs.gov/htmllib/btch528/btch528j/btch528z/lwt01322.jpg )
Lyell and Darwin never fully reconciled themselves to the new theory (e.g. Darwin 1855) but Murchison, above all, carried on the fight actively:
"Until lately geologists seemed to be generally agreed that most of the numerous deep openings and depressions which exist in all lofty mountains were primarily due to cracks, rents, and denudations, which took place during the various movements which each chain had undergone at various periods. These apertures, it was supposed, were necessarily enlarged by long diurnal atmospheric agency and the action of torrents carrying down boulders and detritus; such action being most intense in those mountains where snows and glaciers prevailed, the melting of which necessarily produced great debacles. In the place of this modus operandi, another theory has been applied to all those mountains, which, like the Alps, have been for long periods the seat of glaciers."
"I have had strong doubts as to whether the great blocks derived from Mont Blanc, and which lie on the slopes of the Jura, were ever borne thither by a vast solid glacier which advanced from the Lake of Geneva over the Cantons of Vaud and Neufchatel. Whilst fully believing in the great power of glaciers and their agency, my opinion was that these blocks were rather transported to their present habitats on the Jura on ice-rafts, which were floated away in water to the N.N.W., when the great glaciers melted, and the low countries were flooded. . . . there is still in it nothing which supports the opinion, as indeed Sir Charles has himself observed, that the deep cavity in which the lake lies [Lake Geneva] was excavated by ice."
Murchison even argued that ice could not flow into the Lake Geneva basin, but would flow across it as a bridge.
Nevertheless, the older paradigms of "Diluvium" and "Drift" were spent -- they had nothing new to offer and the glacial paradigm, steered now by a younger generation, rolled on, incorporating new and more varied facts. If Murchison had thought that "the glacier theory" was speculative and lacking in inductive observation, the tables were completely turned on him in the 1860s.
Thomas Francis Jamieson (1829-1913) revisited the Parallel Road of Glen Roy and effectively disposed of Darwin's "marine submergence" theory using a variety of evidence, primarily of a positive nature. Of particular importance was his finding of moraines as barriers in several instances, recognizing that deposition into water had modified them. "The absence, therefore, of any good positive evidence in favour of the marine theory, and so many considerations urging themselves against it, seemed to me to render it untenable."
His paper on the "ice-worn" rocks of Scotland is a classic observation and reasoning. He described a major flood in 1859 that had no impact on bedrock and failed to erase in any way striations that pre-dated the flood. In addition the material left behind was well-sorted (the finer material having been carried away).
Regarding the ice-berg drift theory of striations and erratics, he wondered why interior valleys and slopes are just as striated and grooved as coastal valleys. Plus, sources of rock show they moved towards the sea rather than inland. "But the instances I have mentioned above, being all purposely taken from localities close upon the present shores of Scotland, in my opinion go to prove that even in the low grounds this glacial erosion has radiated from the interior; and that not only in the mountain-glens has this action been due to glaciers, but down to the present coast-line we must still ascribe it to an agent moving off the land, and not to sea-ice."
Jamieson's (1862) map showing the direction of striae outwards towards the coast.
In addition he pointed to observations on icebergs from Greenland that showed icebergs milling around in different directions with near-shore currents -- which would give no clear direction to striae (also, for example, see iceberg scours in the "Glen Roy Revisited" Episode).
And the new theory was applied to the origin of "glacial" valleys: "Now I think the amount of rock which has been worn away, even at the mouths of the sea-lochs of the W. Highlands, as at Loch Fyne and at the Kyles of Bute, opposite the steamboat-quay at Colintrive, by the glacial action, is far too great to be accounted for by the passage of even a succession of such debacles. The rounded outlines of the tough gneiss and syenite, which I there saw, denoted to my mind the long-continued grinding action of ice slowly moving over them ; for I think the rapid, hurried rush of a sludgy mass, even although repeated, would not produce such finely rounded contours: neither would the grooves and furrows be so persistent and rectilinear in their direction ; for the ice being in broken masses, and accompanied with water and melting snow, would have more freedom of movement than the rigid mass of a huge glacier or ice-stream filling the valley; and in the lower open grounds, where there were no heights to confine the torrent, the straight persistent direction of the scores is even more striking than in the glens and gorges, and to my mind still more inexplicable by such a catastrophe or series of catastrophes."
Jamieson's (1862) map showing a Loch Treig glacier moving syenite from a source in both directions and up a slope, something he believed impossible by sea ice.
Sir Andrew Crombie Ramsay (1814-1891) provided a detailed account of how lake basins, such as Lake Geneva, might be formed by glacial action, showing quite specifically that they were not associated with structural features or faults or any other "cracks or rents" (Murchison). When Murchison gave an address to the Royal Geographical Society "On the relative powers of glaciers and floating icebergs in modifying the surface of the earth," Ramsay (1864) fumed in response against what he saw an an ad hominen attack: "I must needs be wrong because they are so eminent [geologists cited by Murchison]. . . . Assertions and crude ideas in all kinds of books and papers are "as plenty as blackberries; " but for clear demonstrations—none are given. . . . Unless I were to write a special elementary treatise on denudation, enough has now been said to show that the theory of formation of great systems of valleys by erosion in which water and ice are main agents, is not a mere absurdity, and I do not therefore care minutely to analyze the assertions that many of the Alpine rivers flow in fissures or deep chasms,.. . which water alone never could have opened out; or again, that the Rhine and the Danube never could have eroded those deep abrupt gorges through which they here and there flow, and which are manifestly due to original ruptures of the rocks."
Although Ramsay viewed Murchison as a respected senior colleague and friend, he saw his reasoning as deficient, if not non-existent.
James D. Forbes went on to establish more fully the science of glaciology. He developed a theory of viscous flow of glaciers and became embroiled in a dispute primarily involving priority over ideas. This dispute involved the physicist John Tyndall (1820-1893), who promoted a theory of regelation (melting and re-freezing – giving the appearance of flow) and Louis Agassiz. This was a very public dispute. Nevertheless, progress was made on a basic subject (i.e. how ice flows and under what conditions of terrain and slope) that had hindered acceptance of the theory overall.
Adding to this work, through the 60s and 70s, James Croll (1821 – 1890) extended formulae on the eccentricity of Earth's axis and orbit to generate cycles of colder and warm periods in Earth's history. Although not perfect -- it yielded too great a time since the end of the ice age and it suggested that glaciation in the northern hemisphere was not synchronized with that of the southern hemisphere -- his model included ice-albedo and ocean current feedback which intensified the "cosmical" effect and drove the climate into and out of alternating periods of cold and warmth. Croll thus advanced both a realistic, astronomical cause for glaciation as well as the notion of multiple glaciations. Lyell initially found these ideas highly speculative ("theoretical") and, besides, believed that terrestrial, geographical factors had more to do with any period of cold conditions than external factors. Croll, however, argued that "the theory of secular changes in climate follows, as a necessary consequence, from the admitted principle of physical science" (1875). Combined with geographical factors, Lyell was eventually persuaded by John Herschel that astronomical effects had a role to play. In the 20th Century a similar line of reasoning was developed by Milutin Milankovitch.
Croll also worked on the theory of ice flow but in a paper in 1870 Croll contributed another, crucial piece of the puzzle: in a study on "boulder-clay" (drift) in northern Scotland he showed that "The shells which the Boulder-clay of Caithness contains have . . . evidently been pushed out of the bed of the North Sea by the land ice which formed the clay itself." This was important because the existence of marine shells had been used to support the iceberg drift theory and continued to support Lyell and Darwin in their belief of lowland iceberg drift. By identifying species, Croll was able to argue that the species were not Arctic but were native to mid-latitudes and had pre-dated the coming of the ice.
Variations in the
earth’s orbit over four million years (1 million after 1800)
(Croll, 1875, following p. 312)
James Geikie (1839-1915) was also one of the new generation and his "The Great Ice Age and its relation to the antiquity of Man" sums up much of the new the new work and stands in opposition to Lyell's work at this time which still referred to the lowland ice-berg drift theory. Increasingly, in all of this work, new observations from Greenland and Antarctica were used to corroborate elements of the theory as applied to Scotland and elsewhere.
Glacial scene of Northern Greenland
Finally, in same year as Ramsay and Jamieson were publishing their great papers on glacial action, Joseph Beete Jukes (1811-1869) also solved another piece of the puzzle: he showed how rivers can cut across regional rock structure through the mechanism of "superimposing" drainage -- that over time rivers can flow across an area on younger, horizontal rocks and then be let down upon older folded or tilted strata. Thus thus rivers like the Rhone can come to flow through complex structures, such as folds.
It should be noted, that Jamieson, Ramsay, Forbes, Croll, and Geikie were all Scottish – their interest in glaciers and glaciation having been piqued by Agassiz’s visit and by the challenges posed in explaining Scottish Highland landscapes. Thus, to some extent, the locus of work moved from central Europe to NW Europe in the final establishment of the theory of “land ice.”
Thus, the "fact" of glaciation, accepted by all scientists today, emerged slowly between 1835 and the 1870s. First accepted in the Alps, where there are glaciers, it was then extended to incorporate phenomena across northern Europe. The older "flood" theory proved hard to dislodge, especially in lowland areas, as it was well embedded in thinking and there appeared to be ample evidence to back it up. There were some individuals who "converted," such as Buckland and Ramsay -- Buckland compromised with his contemporaries, while Ramsay had been an iceberg drift proponent -- but its final acceptance was due as much to the passing of generations as anything else. Its greater explanatory power simply was not accepted by the older generation of geologists, but by the 1870s it incorporated so many ideas about the physical landscape, climate, and the workings of the planet in general that it had moved from speculation to highly probable to virtual certainty.
Croll, J. 1864 On the physical cause of the change of climate during geological epochs. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science v.XXVIII (4th Series; Jul-Dec 1864) p.121-137. http://books.google.com/books?id=J1cwAAAAIAAJ&pg=PA121#v
Croll, J. 1867 On the eccentricity of the Earth's orbit, and its physical relations to the glacial epoch. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science v.XXXIII (4th Series; Jan-Jun 1867) p.119-131. http://books.google.com/books?id=W1EEAAAAYAAJ&pg=PA119#v
Croll, J. 1867 On the change in the obliquity of the ecliptic, its Influence on the climate of the Polar Regions and on the level of the sea. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science v.XXXIII (4th Series; Jan-Jun 1867) p.426-445. http://books.google.com/books?id=W1EEAAAAYAAJ&pg=PA426#v
Croll, J. 1870 The boulder-clay of Caithness - a product of land-ice. The Geological Magazine v.VII (Jan-Dec 1870) p.271-278. http://books.google.com/books?id=ePVjAAAAIAAJ&pg=PA271#v
Croll, J. 1875 Climate and time and their geological relations: a theory of secular changes of the Earth's climate (London, Daldy, Isbister & Co.) http://books.google.com/books?id=mLYKAQAAIAAJ&pg=PR3#v
Darwin, C. 1855 On the
power of icebergs to make rectilinear, uniformly directed grooves across a
submarine undulatory surface. The London, Edinburgh, and Dublin Philosophical
Magazine and Journal of Science v.10 (Jul-Dec) p.96-98
Fleming, J.R. 2006 James Croll in Context: The Encounter between Climate Dynamics and Geology in the Second Half of the Nineteenth Century. History of Meteorology, v.3 p.43-53 http://www.meteohistory.org/2006historyofmeteorology3/3fleming_croll.pdf
Forbes, J.D. 1845 Travels
through the Alps of Savoy and other parts of the Pennine chain with observations
on the phenomena of glaciers. (Edinburgh, Adams and Charles Black; London,
Longman, Brown, Green, and Longmans)
Forbes, J.D. 1846 Illustrations of the Viscous Theory of Glacier Motion Part I. Containing Experiments on the Flow of Plastic Bodies, and Observations on the Phenomena of Lava . Philosophical Transactions of the Royal Society of London, v.136, p.143-155. http://rstl.royalsocietypublishing.org/content/136.toc
Forbes, J.D. 1846 Illustrations of the Viscous Theory of Glacier Motion Part II. An Attempt to Establish by Observation the Plasticity of Glacier Ice. Philosophical Transactions of the Royal Society of London, v.136, p.157-175. http://rstl.royalsocietypublishing.org/content/136.toc
Forbes, J.D. 1846
Illustrations of the Viscous Theory of Glacier Motion Part III.
Philosophical Transactions of the Royal Society of London, v.136, p.177-210
Geikie, J. 1877 (1874) The Great Ice Age and its relation to the antiquity of Man (D. Appleton &Co., New York) http://books.google.com/books?id=zjQaeq03ikIC&pg=PR3
Hamlin, C. 1982 James Geikie, James Croll, and the eventful ice age. Annals of Science v.39, p.565-583
Hevly, B. 1996 The heroic science of glacier motion. Osiris v.11, p.66-86
1862 On the ice-worn rocks of Scotland. Quarterly Journal of the Geological
Society, London, v.18, p.164-184
1863 On the Parallel Roads of Glen Roy,
and their Place in the History of the Glacial Period, Quarterly Journal of the
Geological Society, London v. 19, issue.1-2; p. 235-259
Jukes, J.B. 1862 On the mode of formation of some of the river-valleys in the south of Ireland. Quarterly Journal, Geological Society, London, v.18, p.378-403 http://books.google.com/books?id=RQQAAAAAMAAJ&pg=RA2-PA378#v
Murchison R.I. 1864 On
the relative powers of glaciers and floating icebergs in modifying the surface
of the earth. From the Address of the President of the Royal Geographical
Society, May 23, 1864. (London, W. Clowes and Sons)
REVIEW: Address at the Anniversary Meeting of The Royal Geographical Society, 23rd May, 1864 . By Sir Roderick I. Murchison, K.C.B., G.C.St.A. & St.S., D.C.L., LL.D., F.R.S., Director-General Geological Survey, President. London, 1864. 8vo. pp. 89. The Geological Magazine v.1(3) (July-December 1864) p.126-127 http://books.google.com/books?id=bhI-AAAAcAAJ&pg=PA126#v
Ramsay, A.C. 1857 On certain peculiarities of climate during part of the Permian Epoch. Proceedings of the Royal Institution of Great Britain v.2 (1854-1858) p.417-421 http://books.google.com/books?id=LxNcKnmdDTIC&pg=PA417#v
Ramsay, A.C. 1858 On the geological causes that have influenced the scenery of Canada and the north-eastern provinces of Canada. Proceedings of the Royal Institution of Great Britain v.2 (1854-1858) p.522-524 http://books.google.com/books?id=tfkAAAAAYAAJ&pg=PA522#v
1862 On the glacial origin of certain lakes in Switzerland, the Black Forest,
Great Britain, Sweden, North America, and elsewhere. Quarterly Journal,
Geological Society of London, v.18, p.185-204.
Ramsay, A.C. 1864 The physical geology and geography of Great Britain: six lectures to working men delivered in the Royal School of mines in 1863 (Edward Stanford, London) http://books.google.com/books?id=NMm7AAAAIAAJ&pg=PR1#v
Ramsay, A.C. 1864 On the Erosion of Valleys and Lakes; a Reply to Sir Roderick Murchison's Anniversary Address to the Geographical Society. The London, Edinburgh and Dublin Philosophical Magazine of Science, v.XXVIII (July-December 1864) p.293-311. http://books.google.com/books?id=J1cwAAAAIAAJ&pg=PA293#v
Tyndall, J., 1861 The glaciers
of the Alps – being a narrative of excursions and ascents, an account of the
origin and phenomena of glaciers, and an exposition of the physical principles
to which they are related (Boston, Ticknor and Fields)
Worsley, P. 2006 The British Geological Survey's glaciological expedition to Arctic Norway in 1865. Mercian Geologist v.16(4) p.263-275