 | Debating Glacial Theory, 1800-1870 – Epilog, Part 2 |
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The "controversy" over
the glacial theory rumbled on through the 1860s, as these two contrasting images
from the 1850s and 60s attest to:
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.
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) 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.
QUESTION
Agassiz has often been credited with having been the "father" of the glacial
theory, and this attribution has equally often been criticized as inaccurate,
given the contributions of others. How would you assess Agassiz's contribution?
How "modern" was his conception of glaciation?
REFERENCES 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. 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 Jamieson, T.F.
1862 On the ice-worn rocks of Scotland. Quarterly Journal of the Geological
Society, London, v.18, p.164-184 Jamieson, T.F.
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)
http://books.google.com/books?id=kYs5AAAAcAAJ&pg=PA1#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 Ramsay, A.C.
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 |
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![[Deluge+of+the+North+of+Europe.jpg]](Final-outcomes_files/image002.jpg)
Adding to
this work, through the 60s
and 70s, 
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