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Darwin and the geological controversies over the steady-state worldview in the 1830s
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Darwin and the geological controversies over the steady-state worldview in the 1830s Gabriel Gohau Centre Franc¸ois Vie`te, Universite´ de Nantes, 2 rue de la Houssinie`re, 44 000 Nantes, France
Introduction Works by Charles Darwin are so varied we often forget that, before being the author of books on such topics as barnacles (cirripedia), orchids, expression of emotions, earthworms, natural selection (On the Origin of Species) and human evolution (The Descent of Man), he was actually a geologist.1 After reading Sandra Herbert’s beautiful book one may well ask: should Darwin have stuck with such a well-begun geological career.2 His works in the field of geology after his return from a five-year expedition on the Beagle are confined to the third volume of the Beagle’s Captain, Robert FitzRoy, entitled Narrative of the Surveying Voyages. Darwin’s works are deployed in three distinct parts: (1) ‘The structure and distribution of coral reefs’, 1842; (2) ‘Geological observations on the volcanic islands . . . together with some brief notices on the geology of Australia and the Cape of Good Hope’, 1844; and (3) ‘Geological observations on South
America’, 1846. From November 1835,3 Darwin also began writing papers for the Geological Society of London. The purpose of the present paper is to study the content of these works, beginning with Lyell’s influence on Darwin, as well as scholars like Herschel, von Buch, and Humboldt. As is well-known, Darwin had with him on board the Beagle the first volume of Principles of Geology published by Charles Lyell in 1830 (Figure 1). Captain FitzRoy was particularly interested in geology, and he himself gave Darwin a copy of Lyell’s first volume.4 During the voyage, the young Darwin devoted most of his time and attention to geology.5 Before that voyage, the young man learned geology through the lectures of Reverend Sedgwick at Cambridge University. During the preceding months, he had read Alexander Humboldt’s Personal Narrative and John Herschel’s Preliminary Discourse on the Study of Natural Philosophy. He was led to science by John Henslow, a professor of botany, whom he later befriended and encouraged him to study geology with Sedgwick. During the Summer of 1831, Darwin accompanied the famous geologist to Wales.6 Henslow also encouraged him to study Lyell’s book, but by no means accepted its point of view. Darwin, however, rapidly became interested in Lyell’s approach, which differed significantly from that of Sedgwick. The name for Lyell’s approach originates with William Whewell, who in his review of the second volume of Principles of Geology (1832) identified its essential characteristic as one of ‘geological uniformity’: the process of slow and gradual geological changes, opposing it to the reverse approach which was, incidentally, that of Sedgwick and of many other geologists. Whewell coined the name of ‘catastrophism’ to refer to this latter approach.7 By so doing, Whewell meant to contrast progressive changes (uniform in their intensity) to paroxysmal catastrophic changes. Let us begin by examining Darwin’s own geological observations, comparing them with those of his
Corresponding author: Gohau, G. ([email protected]). Gabriel Gohau, ‘Darwin the geologist. Between Lyell and von Buch. Darwin le ge´ologue. Entre Lyell et von Buch’, Comptes Rendus Biologies, 333 (2010), 95–98. 2 Sandra Herbert, Charles Darwin, Geologist (Ithaca, 2005). 3 Charles Darwin, ‘Geological notes made during a survey of the East and West Coasts of South America in the years 1832, 1833, 1834 and 1835, with an account of a transverse section of the Cordilleras of the Andes between Valparaiso and Mendoza’, Proceedings of the Geol. Soc of London, vol. II, 1833–38, number 40 (1835), 210–212. Available online 13 November 2014
4 Charles Darwin, Voyage of the Beagle, introduction by Janet Browne and Michael Neve (London, 1989), 12. 5 Charles Darwin, Geological Observations on South America, Critical Introduction by John W. Judd, 3rd ed. (London, 1890), 270. 6 Martin J.S. Rudwick, Worlds before Adam: The Reconstriction of Geohistory in the Age of Reform (Chicago, 2008), 487. 7 William Whewell, ‘Review of Principles of Geology by C. Lyell’, Quart. Review, XL (1832), 126. Also, William Whewell, History of the Inductive Sciences, from the Earliest to the present Time, 2nd ed., Tome III (1847), The two antagonist doctrines of Geology, 658–677.
In the first part of this paper, I will show that although Darwin’s geological works only covered the first years of his scientific career, these played a non-negligible role in the earth sciences of the mid-nineteenth century. His intellectual proximity with Charles Lyell often made him his disciple. This is indeed the case with respect to debates over ‘gradual’ soil movements and ‘catastrophic’ soil movements, and for ‘steady-state’ cycles as opposed to ‘directionalistic’ ones. This being said, it is also true that in South America Darwin saw geological processes which were incompatible with Lyell’s explanations. It must therefore be recognized that Darwin held a middle-of-the-road position between uniformitarianism (Lyell) and catastrophism (Humbolt and von Buch), at least as far as some geological questions were concerned. In the second part of the paper, debates on geological issues during Darwin’s active years will be put in the methodological context of the Scientific Revolution of the seventeenth century.
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Figure 2. Ring-shaped coral atoll illustrated in Charles Darwin’s Structure and Distribution of Coral Reefs, 2nd ed, Smith, Elder and Co, 1874. Photograph by Patrice Maurin-Berthier.
during Darwin’s time and the Scientific Revolution, begun several centuries before.
Figure 1. Ruins of the Temple of Serapis in Rome, Italy. Frontispice of Charles Lyell’s Principles of Geology, vol. 1, 1830. Photograph by Patrice Maurin-Berthier.
contemporaries. We shall see how the earlier observations of Darwin supported the uniformitarian approach; we shall also see, however, that a few of his other observations were more in line with the opposing view. Despite being short, Darwin’s geological career played a non-negligible role in the controversies that shook the earth sciences in the 1830s. Indeed, it was his worldwide travel on the Beagle between 1831 and 1836 that allowed him to make this contribution. In addition to Lyell’s Principles of Geology, from which Darwin adopted uniformitarianism, his Beagle readings also included works from catastrophist opponents, such as Humboldt. Darwin’s observation of disordered layers of land in the Cordillera gave him the opportunity to go beyond Lyell’s own explanation when it came to the formation of mountain chains. It will be seen that Darwin’s eclectic approach to geology can be seen in three key issues, all founded on the principle of a cyclical, eternal recurrence which accounts for the stability of features observed on the earth’s surface: (1) The vertical movements of the ground: upheavals and subsidence (2) Periodic climate change (3) The problem of the formation of mountains This paper will conclude with a section reflecting on the intellectual relationships between the earth sciences www.sciencedirect.com
To what extent was Darwin Lyell’s disciple? Vertical movements of the ground Darwin witnessed first-hand the earthquake that occurred in Valdivia, Chile, on February 20, 1835. He noted a ground elevation which, for him, was the cause of the earthquake. He observed numerous marine remains then at 14,000 feet above sea bottom level.8 By chance, in the first volume of Lyell’s Principles, Darwin had actually read about the 1822 destructive earthquake on the Chilian coast.9 In a communication made to the Geological Society, dated January 4, 1837, Darwin noted the imperceptible rise of the coast of Chile since 1822.10 In Patagonia, he had already observed the recent elevation of the whole coast to a considerable height, and assumed that the successive terraces of the shores of the Pacific had been formed recently and very gradually.11 Curiously, Lyell, who explained all geological actions by causes now in operation (including earthquakes and other natural catastrophes), rejected the idea of a recent elevation in the Baltic area. In this particular respect, Darwin was more of a uniformitarian than Lyell himself. Similarly, Darwin assumed that the subsidence of coral islands was a slow and continued process. For a long time, travelers have been struck by the presence of lagoon islands: an annular coral formation with a central lagoon, isolated in the middle of the ocean (Figure 2). Lyell, in his Principles, explained this simply: ‘they are . . . the crest of submarine volcanoes, having the rims and bottoms of their craters overgrown by corals’.12 Darwin’s solution, however, consisted in creating a link between coral formation and the slow elevation of coasts. On his view, a crater was no 8 Charles Darwin, loc.cit. (London, 1989), 245. See also Charles Darwin, chap. VII ‘Central Chile—structure of the Cordillera’, Geological observations on South America (London, 1846). 9 Charles Lyell, Principles of Geology. Being an Attempt to Explain the Former Changes of the Earth’s Surface by Reference to Causes Now in Operation, t I (London, 1830), 401–403. 10 Charles Darwin, ‘Observations of proofs of recent elevation on the coast of Chili, made during the survey of his Majesty’s ship Beagle commanded by Capt. Fitzroy’, Proceed. Geol. Soc. London, II (1837), 448–449. 11 Ibid., 159. See also Geological Observations on South America, chap. I and II, on the elevation of the eastern and of the western coasts. And Sandra Herbert (Ithaca, 2005), 160 sqq. 12 Charles Lyell, Op. cit., II (London, 1832), 290.
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Figure 3. Coral reef barrier illustrated in Charles Darwin’s Structure and Distribution of Coral Reefs, 2nd ed, Smith, Elder and Co, 1874. Photograph by Patrice Maurin-Berthier.
longer necessary to explain the lagoon formation, as an island which has its highest point at its center forms the same lagoon (Figures 3 and 4).13 Lyell eventually came to accept Darwin’s point of view in the next editions of the Principles, perhaps unsurprisingly, since Darwin had produced an even more Lyellian theory about atolls than Lyell’s own. Reflecting upon these two sorts of movement, elevation and subsidence, Darwin wrote: ‘when beholding more than one hemisphere divided into symmetrical areas, which within a limited period of time had undergone certain known movements, we obtain some insight into the system by which the crust of the globe is modified during the endless cycle of changes’ [italics mine].14 Here, Darwin seems to subscribe to a steady-state view of geological processes, just as Lyell had done before him: There can be no doubt, that periods of disturbance and repose have followed each other in succession in every region of the globe, but it may be equally true, that the energy of the subterraneous movements has been always uniform as regards the whole earth. The force of earthquakes (. . .) may then have gradually shifted its position.15 To more clearly define what seems to be a position common to Darwin and Lyell with respect to the notion of a steady-state worldview, a review of the two conflicting theories (as they appeared in the 1830s) is here required. Lyell’s uniformitarian thesis is rightly classified as steadystate, according to Martin Rudwick’s terminology. In fact, uniformitarianism and catastrophism, the terms used by Whewell, represent only one side (continuity) of Lyell’s thesis. Rudwick commented on a letter from William Conybeare (1787–1857) to Lyell, noting that: . . . it is perhaps unfortunate that Whewell should have dubbed the opponents of uniformitarianism ‘catastrophists’ for sudden and violent geological 13 Charles Darwin, Voyage. . ., loc. Cit., chap. XXII, p. 333sq. Also ‘‘On certain areas of elevation and subsidence in the Pacific and Indian Oceans as deduced from the study of Coral Formations’’, Proceedings G. S. L., vol. II, 50 (1837), 552–554. 14 Charles Darwin, ‘‘On certain areas of elevation and subsidence in the Pacific and Indian oceans, as deduced from the study of Coral Formations", Proceed. Geol. Soc. London, II 5 (1837) 554. See also The structure and distribution of Coral Reefs, loc. cit. (1842). 15 Charles Lyell, Loc. cit., I (London, 1830), 64.
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Figure 4. Geological process of erosion of a volcanic crater illustrated in Charles Darwin’s Structure and Distribution of Coral Reefs, 2nd ed, Smith, Elder and Co, 1874. Photograph by Patrice Maurin-Berthier.
events were not essential to their outlook. More important was their conviction that the earth’s history comprised a sequence of unique events so that each geological period represented a distinctive phase in the earth’s development.16 Rudwick finds particularly noteworthy the following aspect of the letter: ‘Conybeare’s insistence that rival models of earth history – historical and steady state – lay at the root of the debate’.17 A few years later, the famous paleontologist George G. Simpson, declaring his agreement with Rudwick, underscored that the disagreement between Lyell and Conybeare – the archetypal uniformitarian and the catastrophist, respectively – ‘was not in fact on the subject of catastrophe as usually understood, but on that of a steady-state versus a historical model of earth and life history’.18 The terms ‘historical’ and ‘steadystate’ coined in 1967 by Rudwick are now standard elements of scientific discourse: in fact, he borrowed the term steady-state from the vocabulary of astrophysicists.19 Rudwick would use it again in 1971: 16 Martin J. S. Rudwick, ‘A Critique of Uniformitarian Geology. A letter from W.D. Conybeare to Ch Lyell’, Proceed American Phil Soc, CXI (1967), 272–287, 272. 17 Ibid., 273. 18 Ceorge G. Simpson, loc.cit. (Stroudsburg, 1975) 265. 19 Hermann Bondy and Thomas Gold, The steady-state theory of the expanding Universe, MNRAS, vol. 108, 3 (1948), 252–270.
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I think we can identify four logical distinct types of uniformity on this level (. . .) First there is the theological status of a past geological ‘cause’; in relation to the creative activity of God (. . .) Second, there is the methodological status (. . .) Thirdly, there is the rate at which a geological ‘cause’ may be acted (. . .) Fourth and last, there is the overall pattern of a past geological ‘cause’, when its action is traced over the whole known time-span of earth-history. It might be steadystate, exhibiting relatively minor fluctuations around a constant mean; at least when the overall state of the whole globe is taken into account. This is clearly the original meaning of ‘uniformitarian’. Or the pattern might be directional, or in more familiar terms ‘developmental’ or ‘progressive’, in that, underlying the local fluctuations in its activity, a general overall trend can be detected on a global scale.20 We can clearly understand how the term catastrophism does not adequately reflect Conybeare’s thinking. In defining these terms, Whewell speaks of alternating periods of disruption and periods of tranquility. Continuity and steady-state appear as two components not identical to Lyell’s uniformitarianism. What makes the problem difficult is that authors such as Conybeare or Sedgwick (to mention but two examples) who believe in the directional evolution of the Earth do not preclude the possibility of periodic variations (catastrophism) through the rare combination of common physical causes. Nonetheless, Conybeare’s argument mainly focuses on directionalism. As Rudwick says, the ‘historical picture of directional change in the course of earth history is the most natural interpretation of all the facts of geology and philosophically preferable to Lyell’s uniformitarian model’.21 On this understanding, it seems that Darwin and Lyell are, indeed, united in the promotion of a somewhat marginal view called steady-state geology, a view opposed to historicity or directionalism and founded on the notion of relatively minor fluctuations around a constant mean. Climatic change The first problem concerned with the issue of climatic change did not oppose Conybeare to Lyell. In his letter of 1841, Conybeare writes: ‘I am a good deal caught by your new articles on the causes of changes of temperature in geological periods’.22 Nevertheless, mountains which bear traces of land modifications (erratic boulders carried to plains) are proof of forces which do not exist in nature today. This constitutes a key argument on the side of catastrophism. Catastrophists invoked more intense forces only because presently observable streams were not capable of eroding valleys, which have been cut out by ancient glaciers.23 Interestingly, Darwin also adopted this theory: erratic boulders could not be explained without referring to ice movement. Darwin’s mistake, however, was to base this 20 Martin J. S. Rudwick, ‘Uniformity and Progression: Reflections on the Structure of Geological theory in the Age of Lyell’, in D.H.D. Roller (ed.), Perspectives in the History of Science and Technology (Norman, 1971), 209–227, 211–212. 21 Ibid., 279. 22 Rudwick, loc. cit. 1967, p. 279. 23 Gordon. L. Davies, The Earth in Decay. A History of British Geomorphology, 1578 to 1878, chap. 8 (Amsterdam, London, 1969), 263 sq.
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theory on sea-ice forming icebergs rather than on continental glaciers.24 On that specific issue, Darwin shared Lyell’s viewpoint, who eventually came to accept the glacial theory but only after prolonged resistance to the idea.25 This being said, Darwin’s position against continental glaciers led him to a grave error: the problem of Glen Roy. The case began during the voyage of the Beagle. In the 3rd volume of the Principles of Geology (1833), Lyell held that parallel roads observed in Coquimbo (Chile) constituted ancient marine beaches, noting the existence of analogous parallel roads in Glen Road, Scotland.26 During the Beagle voyage, in May 1835, Darwin visited Coquimbo and commented as follows: I spent two or three days in examining the stepformed terraces of shingle first described by captain Basil Hall, in his work, so full of spirited descriptions, in the west coast of America. Mr. Lyell concluded from the account, that they must have been formed by the sea during the gradual rising of the land. Such is the case: on some of the steps which sweep round from within the valley, so as to front the coast, shells of existing species both lie on the surface, and are embedded in a soft calcareous stone. This bed of the most modern tertiary epoch passes downward into another, containing some living species associated with others now lost. Amongst the latter may be mentioned shells of an enormous perna and an oyster, and the teeth of a gigantic shark, closely allied to, or identical with the Carchiarias Megalodon of ancient Europe.27 Yet, two independent observers of the Glen Roy formation, MacCulloch, in 1816 (published in 1817) and Lauder, in 1821 (published in 1823) concluded that the parallel roads were in reality lake beaches and not marine beaches. Only after his return to England did Darwin visit Glen Roy, from June 28th to July 5th, 1838. His observations there about the ‘buttresses of alluvium’ seen at the upper end of the neighboring lake (Loch Dochart)28 prompted him to conclude that ‘Rivers could not have deposited it. Barrier of lake very lofty, & no trace of it; to the Sea more probable’.29 Unfortunately for Darwin, Louis Agassiz (1807–1873) would establish two years later that the roads were of glacial origin. Martin Rudwick30 and Sandra Herbert31 have reconstituted the controversy. The final solution eventually came from Jamieson, who visited Glen Roy in 1861: Jamieson concluded that both lack of good and positive evidence in favour of the marine hypothesis and availability of such evidence in favour of Agassiz 24 Charles Darwin, ‘On the distribution of the Erratic Boulders and on the contemporaneous unstratified Deposits of South America’, Proceed. Geol. Soc. London, III (1842), 425–430. See also Transactions of the G. S. L., (2), vol. VI (1841), 415–431. 25 Gordon L. Davies, loc. cit. (Amsterdam, London, 1969), p. 286 sq. 26 Charles Lyell, loc. cit., III (London, 1833), 131. 27 Charles Darwin, loc. cit. (London, 1989), 261. 28 Charles Darwin, ‘Observations on the Parallel Roads of Glen Roy, and of Other Parts of Lochaber in Scotland, with an Attempt to Prove that They Are of Marine Origin’, Philosophical Transactions of the Royal Society of London (1839), 39–81. 29 Sandra Herbert, loc. cit. (Ithaca, 2005), 266. 30 Martin Rudwick, ‘Darwin and Glen Roy. A ‘Great Failure’ in Scientific Method’, Studies in Hist. and Phil. of Science, 5 (1974), 97–185. 31 Sandra Herbert, loc. cit. (Ithaca, 2005), 262 sq.
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hypothesis rendered Darwin’s theory completely untenable (. . .) Two decades later Darwin recalled that (. . .) he ‘had given up the ghost with more sighs and groans than on almost any other occasion in [his] life’.32 The change in temperature implied by the Glen Roy geological formation was, however, hotly debated at the time. The majority of geologists then believed that the temperature of the Earth had gradually decreased since its formation, when the Earth was an igneous body assumed to have originated from the primitive nebula at the origin of our solar system, and for which the model had been provided by the calculations of Joseph Fourier (1824). This hypothesis was supported by the elevation of temperature observed in deep mines (Cordier 1827). Lyell, however, objected: . . . all this is precisely what we should have expected to arise from variations in the intensity of volcanic heat, and from that change of position, which the principal theatres of volcanic action have undergone at different periods, as the geologist can distinctly prove. But M. Cordier conjectures that there is a connection between such phenomena and the secular refrigeration and contraction of the internal fluid mass, and that the change of climate, of which there are geological proofs, favour this hypothesis.33 In Lyell’s view, ceaseless changes in the distribution of land and sea have been the norm everywhere, and have provoked continual fluctuations in the mean temperature.34 As Rudwick puts it, ‘[Lyell] suggests that the global climate might oscillate between what he terms metaphorically the ‘‘winter’’ and ‘‘summer’’ of the ‘‘great year’’’.35 We have seen that Darwin had reluctantly given up on some empirical facts supporting the interpretation of a steadystate view at Glen Roy. Mountain building The major geological problem of the Beagle’s voyage for Darwin was the explanation of mountain building (Figure 5). The elevation of the Andes was the most recent episode of this phenomenon, according to Elie de Beaumont. By chance, Darwin was in the area and he was more impressed by the elevation than by the folds. Indeed, it was easier for a uniformitarian to explain an elevation by a gradual movement than by a shortening of crust (folding). During his travel in the Cordillera, he observed a ‘great pile of strata (. . .) penetrated, upheaved, and overturned, in the most extraordinary manner, by masses of injected rock, equaling mountains in size’.36 In a communication to the Geological Society, Darwin claimed that ‘the conclusion that mountain-chains are formed by a long succession of small movements, may, as it appears to me, be rendered 32 Narasimhan M. G., ‘Controversy in science’, Journal of Biosciences, 26, 3 (2001), 299–304. 33 Charles Lyell, Op. cit., t.I (London, 1830), 142–143. 34 Ibid., 115. 35 Martin Rudwick, loc.cit. (Chicago, 1990), XXI. 36 Charles Darwin, loc. cit. (London, 1989), 245.
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Figure 5. Graphics theorizing the lift of mountain chains in Charles Darwin’s ‘‘On the Connexion of Certain Volcanic Phenomena in South America . . .’’, appearing in the Transactions of the Geological Society of London, (2), V, 1840, p. 625. Photograph by Patrice Maurin-Berthier.
also probable by simple theoretical reasoning’.37 He added: ‘We shall be deeply impressed with the grandeur of the one motive power, which, causing the elevation of the continent, has produced, as secondary effects, mountain-chains and volcanoes’.38 When he explains earthquakes in South America by ‘the interjection of liquefied rocks between masses of strata’,39 ‘proving by their intersections, successive periods of violence . . . [along] great lines of dislocation’,40 he is closer to catastrophic theories of von Buch and Humboldt than to the uniformitarism of Charles Lyell. Following the thesis of these former authors, Darwin thought that St Helena and other such islands were craters of elevation.41 Simultaneously, however, Darwin adopted Lyell’s idea of metamorphic actions on those geological formations.42 A question is worth been raised here: can mountain building be entirely explained using only Charles Lyell’s theory? It is difficult to subscribe to a positive answer. In fact, mountain formation remained difficult to explain for 37 Charles Darwin, ‘On the Connexion of certain Volcanic Phenomena in South America; and the Formation of Mountain Chains and Volcanos, as the Effect of the same Power by which Continents are elevated’, Trans. Geol. Soc. London, (2), V, (1840), 601–631, at 625. See also S. Herbert, loc. cit. (2005), 225–230, and particularly, 228, a figure showing Hopkin’s sketches. 38 Ibid., 630. 39 Ibid., 615. 40 Charles Darwin, loc. cit. (London, 1989), 245. 41 Charles Darwin, Geological Observations on the Volcanic Islands. . . (London, 1844), 93–96. Also Sandra Herbert, loc. cit., (Ithaca, 2005), 241–242. 42 Voyage, loc. cit., 245. Also Geological Observations in South America, loc. cit., (London, 1846), chapter VI plutonic and metamorphic rocks—cleavage and foliation. On Darwin, Buch and Humboldt, see Sandra Herbert, loc. cit, (Ithaca, 2005), 13–17, 58, 125, 141, 167, 198, 248. Particularly 198 sq.
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quite some time with reference to causes currently at work. As noted by Rudwick: Yet it is significant that when Lyell is faced with an example of modern elevation that has not been accompanied by earthquakes, he refuses to accept its reality at all. He ridicules von Buch’s ‘extraordinary notion’ that the land around the Baltic is ‘slowly and insensibly rising although there are exceptionally careful historic records available to support it’ . . . Lyell changed his mind on this point while visiting the area in 1834 . . . and made it the subject of his substantial first paper (1835) to the Royal society in London.43 Turning to another geographical area, the problem of the uplift of Scandinavia is an old problem. In the language of modern geologists, the elevation of Scandinavia is an ‘epirogenesis’: a slow lifting of a continent produced by the melting ice which had encumbered it during a glacial period. Epirogenesis is a different process altogether from the one responsible for mountain formation and called ‘orogenesis’: the process of mountain formation, both by folding (tectogenesis) and uplifting (orogeny narrowly defined). Lyell was puzzled by ideas seen in Darwin’s works which were in contradiction to his own uniformarian model. Throughout successive editions of Principles of Geology (later renamed Elements of Geology), Lyell remained confused by the problem of the origin of mountains, a problem he would never be able to solve. Certainly, after 1834, he recognized the lifting of Scandinavia. This being said, he remained an opponent to the main tectonic theories of his time. At times, he invoked an elevation of temperature causing uplifting and folding through tightening edges44; at other times, he spoke of subsidence analogous to packing down (creeps) that occur in mines and fold the collapsed layers.45 To summarize Darwin’s geological position, then, we can say that from a doctrinal perspective he remained close to Lyell insofar as he embraced his steady-state worldview. Yet, Darwin’s observations of disturbed strata in South America required another explanation than the one promoted by Lyell. One could even ask whether Darwin would not eventually have moved beyond Lyell’s doctrine had he continued with his geological career.
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Newton’s ‘Rules of Reasoning in Philosophy’ which appeared in the 3rd edition of his Mathematical Principles of Natural Philosophy (1726), often referred to as the Principia. These rules became golden methodological rules for scholars following the way opened by Newton. Rule II reads as follows: ‘Therefore to the same natural effects we must, as far as possible, assign the same causes’. Conybeare, the directionalist, for instance, acts like a conscientious Newtonian methodologist when he replies to Lyell: ‘I do agree & have always agreed with you in believing the absolute uniformity of the laws of nature & general physical causes’. Newton’s rule II is preceded in the Principia by Rule I, which reads: ‘We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances’. Rule I implicitly refers to the notion of ‘true causes’, also called verae causae. The search for these ‘true causes’ allow us to establish an intellectual connection between the Scientific Revolution and the revolution in geology. Traces of the past that scholars of the 1780s called the ‘archives of nature’ are indisputable witnesses of causes that have acted in the Earth’s past. But can we, after interpreting these witnesses, rest assured that we have discovered their ‘true causes’ rather than imagined ones? Here lies the whole question. The reasoning behind interpreting the past is called an abduction, which is to say, the transition of effects to their cause is not logically guaranteed. Nonetheless, the notion of vera causa, a concept specific to this time, permeated the minds of many scholars, in particular those of Lyell and Darwin. In geology, both tried to establish a methodological continuation with the Newtonian Revolution. The Newtonian concept of vera causa was taken up by Darwin in John Herschel’s (1792–1871) Preliminary Discourse on Natural Philosophy (1831) shortly before his departure on the Beagle. It is certainly interesting to note that Herschel’s tomb lies at Westminster Abbey next to Newton’s. In his book, Herschel wrote: Causes competent under different modifications to the production of a great multitude of effects, besides those which originally led to knowledge of them. To such cause Newton has applied the term of verae causae; that is causes recognised as having a real existence in nature and not being mere hypotheses or figments of the mind.46
Darwin, the end of the scientific revolution? Scholars like Lyell, Darwin, Conybeare, von Buch, and Humboldt participated from the controversies previously discussed, controversies responsible for forging what must be called a revolution in the earth sciences. This revolution obviously took place much later than the Scientific Revolution recognized by historians and epistemologists of physics and astronomy, and which links Copernicus to Newton. By way of conclusion, let us reflect upon a possible link between these two revolutions. To link the Scientific Revolution with the geological revolution, let us go back to
In other words, verae causae are analogous to causes that are already known to have produced similar effects in other cases. When not directly observable, verae causae ‘are not to be arbitrarily assumed, they must be such as we have good inductive grounds to believe do exist in nature and do perform a part in phenomena analogous to those we would render an account of’.47 With respect to such methodological rules, Herschel acts like a genuine uniformitarian, explicitly following Lyell’s brand of geology. As Jonathan Hodge says:
43 Martin Rudwick, loc.cit. (Chicago, 1990), XXVII On his conversion see also Leonard G. Wilson, Charles Lyell, the years to 1841, (1972), 385, 398–407. 44 Charles Lyell, Principles of Geology (London, 1872), chap. XXXIII. It is true that he never explained more than the case of Scandinavia. 45 Charles Lyell, Elements of Geology, 6th ed. (London, 1865) chap. V.
46 John Herschel Preliminary Discourse on the study of Natural Philosophy (London 1831), 144–145. 47 Ibid., 197.
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Like his friend, (. . .) the physicist John Herschel, Lyell followed earlier writers, most notably the Scottish philosopher Thomas Reid (1710–1796); who had drawn this moral from the superior evidential credentials of the Newtonian gravitational force over the Cartesian ethereal vortices: any causes invoked in an explanatory theory should, ideally, be known to exist through direct observation independently of the facts they are supposed to explain.48 And as Rachel Laudan added some years later: Lyell’s commitment to the vera causa method permeates the [Principles of Geology]. Yet in spite of the impressive bulk of the work, Lyell never discussed it explicitly, perhaps because the method was so thoroughly treated in philosophical works that he could assume that his audience would be completely familiar with it. However we can reconstruct what he had in mind. In those many cases where the observational handicaps of the geologist were so great that he could not use the method of induction, what reasonable limits should be put on the method of hypothesis? Lyell’s answer was that all hypotheses about unobserved causes or effects must be found squarely on what we have observed.49
in Darwin traced it back to his transmutation notebooks (starting from 1838) or to the end of Darwin’s geological career in the 1830s. In order to remain true to our subject, let us simply add that the uniformitarian background was strongly criticized at the time by some catastrophists, particular by William Whewell, who: rejected this interpretation of vera causa principle believing to be overly restrictive. He agreed with Herschel that causes are not to be ‘arbitrarily assumed’ and that we must have ‘good inductive grounds’. Thus he explained in Philosophy of Inductive Science that verae causae are those which are justly and rigorously inferred. However he disagreed with Herschels’s condition that there must be an analogous connection to known causes (. . .) Whewell criticized Lyell (and unifomitarian geology in general) for using vera causa principle to rule out the possibility of catastrophic causes of geological change?.50
It should be noted in passing that Darwin uses the term ‘vera causa’ in the Origin of Species, although his biological works are beyond the scope of this paper. Modern historians and philosophers who studied the notion of vera causa
In accepting catastrophism in geology as in other scientific areas, Whewell discarded the idea of a science under the methodological principles of ‘true causes’. To this, Lyell, Herschel, and Darwin responded in the 1830s by walking in the footsteps of Newton. It is by following this intellectual path that one can go from the Scientific Revolution to the revolution in geology, from Copernicus to Darwin, as seen in the successive incorporation of scientific areas such as astrophysics, geology, and eventually biology.
48 Martin J. S. Hodge, ‘The development of Darwin’s general biological theorizing, in DS Bendall’, (ed) Evolution from molecules to men (Cambridge, 1983), 43–62, at 45. 49 Rachel Laudan, From mineralogy to geology. The foundations of a science 1650– 1830 (Chicago,1987), 204.
50 Laura J. Snyder, Reforming philosophy. A victorian debate on science and society (Chicago, 2006), 201. On Darwin’s report to Herschel and Whewell regarding the real cause see also Jean Gayon, ‘Mort ou persistance du darwinisme? Regard d’un e´piste´mologue’, CR Palevol 8 (2–3) 2009, 321–340.
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Darwin and the geological controversies over the steady-state worldview in the 1830s Gabriel Gohau Centre Franc¸ois Vie`te, Universite´ de Nantes, 2 rue de la Houssinie`re, 44 000 Nantes, France
Introduction Works by Charles Darwin are so varied we often forget that, before being the author of books on such topics as barnacles (cirripedia), orchids, expression of emotions, earthworms, natural selection (On the Origin of Species) and human evolution (The Descent of Man), he was actually a geologist.1 After reading Sandra Herbert’s beautiful book one may well ask: should Darwin have stuck with such a well-begun geological career.2 His works in the field of geology after his return from a five-year expedition on the Beagle are confined to the third volume of the Beagle’s Captain, Robert FitzRoy, entitled Narrative of the Surveying Voyages. Darwin’s works are deployed in three distinct parts: (1) ‘The structure and distribution of coral reefs’, 1842; (2) ‘Geological observations on the volcanic islands . . . together with some brief notices on the geology of Australia and the Cape of Good Hope’, 1844; and (3) ‘Geological observations on South
America’, 1846. From November 1835,3 Darwin also began writing papers for the Geological Society of London. The purpose of the present paper is to study the content of these works, beginning with Lyell’s influence on Darwin, as well as scholars like Herschel, von Buch, and Humboldt. As is well-known, Darwin had with him on board the Beagle the first volume of Principles of Geology published by Charles Lyell in 1830 (Figure 1). Captain FitzRoy was particularly interested in geology, and he himself gave Darwin a copy of Lyell’s first volume.4 During the voyage, the young Darwin devoted most of his time and attention to geology.5 Before that voyage, the young man learned geology through the lectures of Reverend Sedgwick at Cambridge University. During the preceding months, he had read Alexander Humboldt’s Personal Narrative and John Herschel’s Preliminary Discourse on the Study of Natural Philosophy. He was led to science by John Henslow, a professor of botany, whom he later befriended and encouraged him to study geology with Sedgwick. During the Summer of 1831, Darwin accompanied the famous geologist to Wales.6 Henslow also encouraged him to study Lyell’s book, but by no means accepted its point of view. Darwin, however, rapidly became interested in Lyell’s approach, which differed significantly from that of Sedgwick. The name for Lyell’s approach originates with William Whewell, who in his review of the second volume of Principles of Geology (1832) identified its essential characteristic as one of ‘geological uniformity’: the process of slow and gradual geological changes, opposing it to the reverse approach which was, incidentally, that of Sedgwick and of many other geologists. Whewell coined the name of ‘catastrophism’ to refer to this latter approach.7 By so doing, Whewell meant to contrast progressive changes (uniform in their intensity) to paroxysmal catastrophic changes. Let us begin by examining Darwin’s own geological observations, comparing them with those of his
Corresponding author: Gohau, G. ([email protected]). Gabriel Gohau, ‘Darwin the geologist. Between Lyell and von Buch. Darwin le ge´ologue. Entre Lyell et von Buch’, Comptes Rendus Biologies, 333 (2010), 95–98. 2 Sandra Herbert, Charles Darwin, Geologist (Ithaca, 2005). 3 Charles Darwin, ‘Geological notes made during a survey of the East and West Coasts of South America in the years 1832, 1833, 1834 and 1835, with an account of a transverse section of the Cordilleras of the Andes between Valparaiso and Mendoza’, Proceedings of the Geol. Soc of London, vol. II, 1833–38, number 40 (1835), 210–212. Available online 13 November 2014
4 Charles Darwin, Voyage of the Beagle, introduction by Janet Browne and Michael Neve (London, 1989), 12. 5 Charles Darwin, Geological Observations on South America, Critical Introduction by John W. Judd, 3rd ed. (London, 1890), 270. 6 Martin J.S. Rudwick, Worlds before Adam: The Reconstriction of Geohistory in the Age of Reform (Chicago, 2008), 487. 7 William Whewell, ‘Review of Principles of Geology by C. Lyell’, Quart. Review, XL (1832), 126. Also, William Whewell, History of the Inductive Sciences, from the Earliest to the present Time, 2nd ed., Tome III (1847), The two antagonist doctrines of Geology, 658–677.
In the first part of this paper, I will show that although Darwin’s geological works only covered the first years of his scientific career, these played a non-negligible role in the earth sciences of the mid-nineteenth century. His intellectual proximity with Charles Lyell often made him his disciple. This is indeed the case with respect to debates over ‘gradual’ soil movements and ‘catastrophic’ soil movements, and for ‘steady-state’ cycles as opposed to ‘directionalistic’ ones. This being said, it is also true that in South America Darwin saw geological processes which were incompatible with Lyell’s explanations. It must therefore be recognized that Darwin held a middle-of-the-road position between uniformitarianism (Lyell) and catastrophism (Humbolt and von Buch), at least as far as some geological questions were concerned. In the second part of the paper, debates on geological issues during Darwin’s active years will be put in the methodological context of the Scientific Revolution of the seventeenth century.
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Figure 2. Ring-shaped coral atoll illustrated in Charles Darwin’s Structure and Distribution of Coral Reefs, 2nd ed, Smith, Elder and Co, 1874. Photograph by Patrice Maurin-Berthier.
during Darwin’s time and the Scientific Revolution, begun several centuries before.
Figure 1. Ruins of the Temple of Serapis in Rome, Italy. Frontispice of Charles Lyell’s Principles of Geology, vol. 1, 1830. Photograph by Patrice Maurin-Berthier.
contemporaries. We shall see how the earlier observations of Darwin supported the uniformitarian approach; we shall also see, however, that a few of his other observations were more in line with the opposing view. Despite being short, Darwin’s geological career played a non-negligible role in the controversies that shook the earth sciences in the 1830s. Indeed, it was his worldwide travel on the Beagle between 1831 and 1836 that allowed him to make this contribution. In addition to Lyell’s Principles of Geology, from which Darwin adopted uniformitarianism, his Beagle readings also included works from catastrophist opponents, such as Humboldt. Darwin’s observation of disordered layers of land in the Cordillera gave him the opportunity to go beyond Lyell’s own explanation when it came to the formation of mountain chains. It will be seen that Darwin’s eclectic approach to geology can be seen in three key issues, all founded on the principle of a cyclical, eternal recurrence which accounts for the stability of features observed on the earth’s surface: (1) The vertical movements of the ground: upheavals and subsidence (2) Periodic climate change (3) The problem of the formation of mountains This paper will conclude with a section reflecting on the intellectual relationships between the earth sciences www.sciencedirect.com
To what extent was Darwin Lyell’s disciple? Vertical movements of the ground Darwin witnessed first-hand the earthquake that occurred in Valdivia, Chile, on February 20, 1835. He noted a ground elevation which, for him, was the cause of the earthquake. He observed numerous marine remains then at 14,000 feet above sea bottom level.8 By chance, in the first volume of Lyell’s Principles, Darwin had actually read about the 1822 destructive earthquake on the Chilian coast.9 In a communication made to the Geological Society, dated January 4, 1837, Darwin noted the imperceptible rise of the coast of Chile since 1822.10 In Patagonia, he had already observed the recent elevation of the whole coast to a considerable height, and assumed that the successive terraces of the shores of the Pacific had been formed recently and very gradually.11 Curiously, Lyell, who explained all geological actions by causes now in operation (including earthquakes and other natural catastrophes), rejected the idea of a recent elevation in the Baltic area. In this particular respect, Darwin was more of a uniformitarian than Lyell himself. Similarly, Darwin assumed that the subsidence of coral islands was a slow and continued process. For a long time, travelers have been struck by the presence of lagoon islands: an annular coral formation with a central lagoon, isolated in the middle of the ocean (Figure 2). Lyell, in his Principles, explained this simply: ‘they are . . . the crest of submarine volcanoes, having the rims and bottoms of their craters overgrown by corals’.12 Darwin’s solution, however, consisted in creating a link between coral formation and the slow elevation of coasts. On his view, a crater was no 8 Charles Darwin, loc.cit. (London, 1989), 245. See also Charles Darwin, chap. VII ‘Central Chile—structure of the Cordillera’, Geological observations on South America (London, 1846). 9 Charles Lyell, Principles of Geology. Being an Attempt to Explain the Former Changes of the Earth’s Surface by Reference to Causes Now in Operation, t I (London, 1830), 401–403. 10 Charles Darwin, ‘Observations of proofs of recent elevation on the coast of Chili, made during the survey of his Majesty’s ship Beagle commanded by Capt. Fitzroy’, Proceed. Geol. Soc. London, II (1837), 448–449. 11 Ibid., 159. See also Geological Observations on South America, chap. I and II, on the elevation of the eastern and of the western coasts. And Sandra Herbert (Ithaca, 2005), 160 sqq. 12 Charles Lyell, Op. cit., II (London, 1832), 290.
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Figure 3. Coral reef barrier illustrated in Charles Darwin’s Structure and Distribution of Coral Reefs, 2nd ed, Smith, Elder and Co, 1874. Photograph by Patrice Maurin-Berthier.
longer necessary to explain the lagoon formation, as an island which has its highest point at its center forms the same lagoon (Figures 3 and 4).13 Lyell eventually came to accept Darwin’s point of view in the next editions of the Principles, perhaps unsurprisingly, since Darwin had produced an even more Lyellian theory about atolls than Lyell’s own. Reflecting upon these two sorts of movement, elevation and subsidence, Darwin wrote: ‘when beholding more than one hemisphere divided into symmetrical areas, which within a limited period of time had undergone certain known movements, we obtain some insight into the system by which the crust of the globe is modified during the endless cycle of changes’ [italics mine].14 Here, Darwin seems to subscribe to a steady-state view of geological processes, just as Lyell had done before him: There can be no doubt, that periods of disturbance and repose have followed each other in succession in every region of the globe, but it may be equally true, that the energy of the subterraneous movements has been always uniform as regards the whole earth. The force of earthquakes (. . .) may then have gradually shifted its position.15 To more clearly define what seems to be a position common to Darwin and Lyell with respect to the notion of a steady-state worldview, a review of the two conflicting theories (as they appeared in the 1830s) is here required. Lyell’s uniformitarian thesis is rightly classified as steadystate, according to Martin Rudwick’s terminology. In fact, uniformitarianism and catastrophism, the terms used by Whewell, represent only one side (continuity) of Lyell’s thesis. Rudwick commented on a letter from William Conybeare (1787–1857) to Lyell, noting that: . . . it is perhaps unfortunate that Whewell should have dubbed the opponents of uniformitarianism ‘catastrophists’ for sudden and violent geological 13 Charles Darwin, Voyage. . ., loc. Cit., chap. XXII, p. 333sq. Also ‘‘On certain areas of elevation and subsidence in the Pacific and Indian Oceans as deduced from the study of Coral Formations’’, Proceedings G. S. L., vol. II, 50 (1837), 552–554. 14 Charles Darwin, ‘‘On certain areas of elevation and subsidence in the Pacific and Indian oceans, as deduced from the study of Coral Formations", Proceed. Geol. Soc. London, II 5 (1837) 554. See also The structure and distribution of Coral Reefs, loc. cit. (1842). 15 Charles Lyell, Loc. cit., I (London, 1830), 64.
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Figure 4. Geological process of erosion of a volcanic crater illustrated in Charles Darwin’s Structure and Distribution of Coral Reefs, 2nd ed, Smith, Elder and Co, 1874. Photograph by Patrice Maurin-Berthier.
events were not essential to their outlook. More important was their conviction that the earth’s history comprised a sequence of unique events so that each geological period represented a distinctive phase in the earth’s development.16 Rudwick finds particularly noteworthy the following aspect of the letter: ‘Conybeare’s insistence that rival models of earth history – historical and steady state – lay at the root of the debate’.17 A few years later, the famous paleontologist George G. Simpson, declaring his agreement with Rudwick, underscored that the disagreement between Lyell and Conybeare – the archetypal uniformitarian and the catastrophist, respectively – ‘was not in fact on the subject of catastrophe as usually understood, but on that of a steady-state versus a historical model of earth and life history’.18 The terms ‘historical’ and ‘steadystate’ coined in 1967 by Rudwick are now standard elements of scientific discourse: in fact, he borrowed the term steady-state from the vocabulary of astrophysicists.19 Rudwick would use it again in 1971: 16 Martin J. S. Rudwick, ‘A Critique of Uniformitarian Geology. A letter from W.D. Conybeare to Ch Lyell’, Proceed American Phil Soc, CXI (1967), 272–287, 272. 17 Ibid., 273. 18 Ceorge G. Simpson, loc.cit. (Stroudsburg, 1975) 265. 19 Hermann Bondy and Thomas Gold, The steady-state theory of the expanding Universe, MNRAS, vol. 108, 3 (1948), 252–270.
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I think we can identify four logical distinct types of uniformity on this level (. . .) First there is the theological status of a past geological ‘cause’; in relation to the creative activity of God (. . .) Second, there is the methodological status (. . .) Thirdly, there is the rate at which a geological ‘cause’ may be acted (. . .) Fourth and last, there is the overall pattern of a past geological ‘cause’, when its action is traced over the whole known time-span of earth-history. It might be steadystate, exhibiting relatively minor fluctuations around a constant mean; at least when the overall state of the whole globe is taken into account. This is clearly the original meaning of ‘uniformitarian’. Or the pattern might be directional, or in more familiar terms ‘developmental’ or ‘progressive’, in that, underlying the local fluctuations in its activity, a general overall trend can be detected on a global scale.20 We can clearly understand how the term catastrophism does not adequately reflect Conybeare’s thinking. In defining these terms, Whewell speaks of alternating periods of disruption and periods of tranquility. Continuity and steady-state appear as two components not identical to Lyell’s uniformitarianism. What makes the problem difficult is that authors such as Conybeare or Sedgwick (to mention but two examples) who believe in the directional evolution of the Earth do not preclude the possibility of periodic variations (catastrophism) through the rare combination of common physical causes. Nonetheless, Conybeare’s argument mainly focuses on directionalism. As Rudwick says, the ‘historical picture of directional change in the course of earth history is the most natural interpretation of all the facts of geology and philosophically preferable to Lyell’s uniformitarian model’.21 On this understanding, it seems that Darwin and Lyell are, indeed, united in the promotion of a somewhat marginal view called steady-state geology, a view opposed to historicity or directionalism and founded on the notion of relatively minor fluctuations around a constant mean. Climatic change The first problem concerned with the issue of climatic change did not oppose Conybeare to Lyell. In his letter of 1841, Conybeare writes: ‘I am a good deal caught by your new articles on the causes of changes of temperature in geological periods’.22 Nevertheless, mountains which bear traces of land modifications (erratic boulders carried to plains) are proof of forces which do not exist in nature today. This constitutes a key argument on the side of catastrophism. Catastrophists invoked more intense forces only because presently observable streams were not capable of eroding valleys, which have been cut out by ancient glaciers.23 Interestingly, Darwin also adopted this theory: erratic boulders could not be explained without referring to ice movement. Darwin’s mistake, however, was to base this 20 Martin J. S. Rudwick, ‘Uniformity and Progression: Reflections on the Structure of Geological theory in the Age of Lyell’, in D.H.D. Roller (ed.), Perspectives in the History of Science and Technology (Norman, 1971), 209–227, 211–212. 21 Ibid., 279. 22 Rudwick, loc. cit. 1967, p. 279. 23 Gordon. L. Davies, The Earth in Decay. A History of British Geomorphology, 1578 to 1878, chap. 8 (Amsterdam, London, 1969), 263 sq.
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theory on sea-ice forming icebergs rather than on continental glaciers.24 On that specific issue, Darwin shared Lyell’s viewpoint, who eventually came to accept the glacial theory but only after prolonged resistance to the idea.25 This being said, Darwin’s position against continental glaciers led him to a grave error: the problem of Glen Roy. The case began during the voyage of the Beagle. In the 3rd volume of the Principles of Geology (1833), Lyell held that parallel roads observed in Coquimbo (Chile) constituted ancient marine beaches, noting the existence of analogous parallel roads in Glen Road, Scotland.26 During the Beagle voyage, in May 1835, Darwin visited Coquimbo and commented as follows: I spent two or three days in examining the stepformed terraces of shingle first described by captain Basil Hall, in his work, so full of spirited descriptions, in the west coast of America. Mr. Lyell concluded from the account, that they must have been formed by the sea during the gradual rising of the land. Such is the case: on some of the steps which sweep round from within the valley, so as to front the coast, shells of existing species both lie on the surface, and are embedded in a soft calcareous stone. This bed of the most modern tertiary epoch passes downward into another, containing some living species associated with others now lost. Amongst the latter may be mentioned shells of an enormous perna and an oyster, and the teeth of a gigantic shark, closely allied to, or identical with the Carchiarias Megalodon of ancient Europe.27 Yet, two independent observers of the Glen Roy formation, MacCulloch, in 1816 (published in 1817) and Lauder, in 1821 (published in 1823) concluded that the parallel roads were in reality lake beaches and not marine beaches. Only after his return to England did Darwin visit Glen Roy, from June 28th to July 5th, 1838. His observations there about the ‘buttresses of alluvium’ seen at the upper end of the neighboring lake (Loch Dochart)28 prompted him to conclude that ‘Rivers could not have deposited it. Barrier of lake very lofty, & no trace of it; to the Sea more probable’.29 Unfortunately for Darwin, Louis Agassiz (1807–1873) would establish two years later that the roads were of glacial origin. Martin Rudwick30 and Sandra Herbert31 have reconstituted the controversy. The final solution eventually came from Jamieson, who visited Glen Roy in 1861: Jamieson concluded that both lack of good and positive evidence in favour of the marine hypothesis and availability of such evidence in favour of Agassiz 24 Charles Darwin, ‘On the distribution of the Erratic Boulders and on the contemporaneous unstratified Deposits of South America’, Proceed. Geol. Soc. London, III (1842), 425–430. See also Transactions of the G. S. L., (2), vol. VI (1841), 415–431. 25 Gordon L. Davies, loc. cit. (Amsterdam, London, 1969), p. 286 sq. 26 Charles Lyell, loc. cit., III (London, 1833), 131. 27 Charles Darwin, loc. cit. (London, 1989), 261. 28 Charles Darwin, ‘Observations on the Parallel Roads of Glen Roy, and of Other Parts of Lochaber in Scotland, with an Attempt to Prove that They Are of Marine Origin’, Philosophical Transactions of the Royal Society of London (1839), 39–81. 29 Sandra Herbert, loc. cit. (Ithaca, 2005), 266. 30 Martin Rudwick, ‘Darwin and Glen Roy. A ‘Great Failure’ in Scientific Method’, Studies in Hist. and Phil. of Science, 5 (1974), 97–185. 31 Sandra Herbert, loc. cit. (Ithaca, 2005), 262 sq.
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hypothesis rendered Darwin’s theory completely untenable (. . .) Two decades later Darwin recalled that (. . .) he ‘had given up the ghost with more sighs and groans than on almost any other occasion in [his] life’.32 The change in temperature implied by the Glen Roy geological formation was, however, hotly debated at the time. The majority of geologists then believed that the temperature of the Earth had gradually decreased since its formation, when the Earth was an igneous body assumed to have originated from the primitive nebula at the origin of our solar system, and for which the model had been provided by the calculations of Joseph Fourier (1824). This hypothesis was supported by the elevation of temperature observed in deep mines (Cordier 1827). Lyell, however, objected: . . . all this is precisely what we should have expected to arise from variations in the intensity of volcanic heat, and from that change of position, which the principal theatres of volcanic action have undergone at different periods, as the geologist can distinctly prove. But M. Cordier conjectures that there is a connection between such phenomena and the secular refrigeration and contraction of the internal fluid mass, and that the change of climate, of which there are geological proofs, favour this hypothesis.33 In Lyell’s view, ceaseless changes in the distribution of land and sea have been the norm everywhere, and have provoked continual fluctuations in the mean temperature.34 As Rudwick puts it, ‘[Lyell] suggests that the global climate might oscillate between what he terms metaphorically the ‘‘winter’’ and ‘‘summer’’ of the ‘‘great year’’’.35 We have seen that Darwin had reluctantly given up on some empirical facts supporting the interpretation of a steadystate view at Glen Roy. Mountain building The major geological problem of the Beagle’s voyage for Darwin was the explanation of mountain building (Figure 5). The elevation of the Andes was the most recent episode of this phenomenon, according to Elie de Beaumont. By chance, Darwin was in the area and he was more impressed by the elevation than by the folds. Indeed, it was easier for a uniformitarian to explain an elevation by a gradual movement than by a shortening of crust (folding). During his travel in the Cordillera, he observed a ‘great pile of strata (. . .) penetrated, upheaved, and overturned, in the most extraordinary manner, by masses of injected rock, equaling mountains in size’.36 In a communication to the Geological Society, Darwin claimed that ‘the conclusion that mountain-chains are formed by a long succession of small movements, may, as it appears to me, be rendered 32 Narasimhan M. G., ‘Controversy in science’, Journal of Biosciences, 26, 3 (2001), 299–304. 33 Charles Lyell, Op. cit., t.I (London, 1830), 142–143. 34 Ibid., 115. 35 Martin Rudwick, loc.cit. (Chicago, 1990), XXI. 36 Charles Darwin, loc. cit. (London, 1989), 245.
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Figure 5. Graphics theorizing the lift of mountain chains in Charles Darwin’s ‘‘On the Connexion of Certain Volcanic Phenomena in South America . . .’’, appearing in the Transactions of the Geological Society of London, (2), V, 1840, p. 625. Photograph by Patrice Maurin-Berthier.
also probable by simple theoretical reasoning’.37 He added: ‘We shall be deeply impressed with the grandeur of the one motive power, which, causing the elevation of the continent, has produced, as secondary effects, mountain-chains and volcanoes’.38 When he explains earthquakes in South America by ‘the interjection of liquefied rocks between masses of strata’,39 ‘proving by their intersections, successive periods of violence . . . [along] great lines of dislocation’,40 he is closer to catastrophic theories of von Buch and Humboldt than to the uniformitarism of Charles Lyell. Following the thesis of these former authors, Darwin thought that St Helena and other such islands were craters of elevation.41 Simultaneously, however, Darwin adopted Lyell’s idea of metamorphic actions on those geological formations.42 A question is worth been raised here: can mountain building be entirely explained using only Charles Lyell’s theory? It is difficult to subscribe to a positive answer. In fact, mountain formation remained difficult to explain for 37 Charles Darwin, ‘On the Connexion of certain Volcanic Phenomena in South America; and the Formation of Mountain Chains and Volcanos, as the Effect of the same Power by which Continents are elevated’, Trans. Geol. Soc. London, (2), V, (1840), 601–631, at 625. See also S. Herbert, loc. cit. (2005), 225–230, and particularly, 228, a figure showing Hopkin’s sketches. 38 Ibid., 630. 39 Ibid., 615. 40 Charles Darwin, loc. cit. (London, 1989), 245. 41 Charles Darwin, Geological Observations on the Volcanic Islands. . . (London, 1844), 93–96. Also Sandra Herbert, loc. cit., (Ithaca, 2005), 241–242. 42 Voyage, loc. cit., 245. Also Geological Observations in South America, loc. cit., (London, 1846), chapter VI plutonic and metamorphic rocks—cleavage and foliation. On Darwin, Buch and Humboldt, see Sandra Herbert, loc. cit, (Ithaca, 2005), 13–17, 58, 125, 141, 167, 198, 248. Particularly 198 sq.
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quite some time with reference to causes currently at work. As noted by Rudwick: Yet it is significant that when Lyell is faced with an example of modern elevation that has not been accompanied by earthquakes, he refuses to accept its reality at all. He ridicules von Buch’s ‘extraordinary notion’ that the land around the Baltic is ‘slowly and insensibly rising although there are exceptionally careful historic records available to support it’ . . . Lyell changed his mind on this point while visiting the area in 1834 . . . and made it the subject of his substantial first paper (1835) to the Royal society in London.43 Turning to another geographical area, the problem of the uplift of Scandinavia is an old problem. In the language of modern geologists, the elevation of Scandinavia is an ‘epirogenesis’: a slow lifting of a continent produced by the melting ice which had encumbered it during a glacial period. Epirogenesis is a different process altogether from the one responsible for mountain formation and called ‘orogenesis’: the process of mountain formation, both by folding (tectogenesis) and uplifting (orogeny narrowly defined). Lyell was puzzled by ideas seen in Darwin’s works which were in contradiction to his own uniformarian model. Throughout successive editions of Principles of Geology (later renamed Elements of Geology), Lyell remained confused by the problem of the origin of mountains, a problem he would never be able to solve. Certainly, after 1834, he recognized the lifting of Scandinavia. This being said, he remained an opponent to the main tectonic theories of his time. At times, he invoked an elevation of temperature causing uplifting and folding through tightening edges44; at other times, he spoke of subsidence analogous to packing down (creeps) that occur in mines and fold the collapsed layers.45 To summarize Darwin’s geological position, then, we can say that from a doctrinal perspective he remained close to Lyell insofar as he embraced his steady-state worldview. Yet, Darwin’s observations of disturbed strata in South America required another explanation than the one promoted by Lyell. One could even ask whether Darwin would not eventually have moved beyond Lyell’s doctrine had he continued with his geological career.
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Newton’s ‘Rules of Reasoning in Philosophy’ which appeared in the 3rd edition of his Mathematical Principles of Natural Philosophy (1726), often referred to as the Principia. These rules became golden methodological rules for scholars following the way opened by Newton. Rule II reads as follows: ‘Therefore to the same natural effects we must, as far as possible, assign the same causes’. Conybeare, the directionalist, for instance, acts like a conscientious Newtonian methodologist when he replies to Lyell: ‘I do agree & have always agreed with you in believing the absolute uniformity of the laws of nature & general physical causes’. Newton’s rule II is preceded in the Principia by Rule I, which reads: ‘We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances’. Rule I implicitly refers to the notion of ‘true causes’, also called verae causae. The search for these ‘true causes’ allow us to establish an intellectual connection between the Scientific Revolution and the revolution in geology. Traces of the past that scholars of the 1780s called the ‘archives of nature’ are indisputable witnesses of causes that have acted in the Earth’s past. But can we, after interpreting these witnesses, rest assured that we have discovered their ‘true causes’ rather than imagined ones? Here lies the whole question. The reasoning behind interpreting the past is called an abduction, which is to say, the transition of effects to their cause is not logically guaranteed. Nonetheless, the notion of vera causa, a concept specific to this time, permeated the minds of many scholars, in particular those of Lyell and Darwin. In geology, both tried to establish a methodological continuation with the Newtonian Revolution. The Newtonian concept of vera causa was taken up by Darwin in John Herschel’s (1792–1871) Preliminary Discourse on Natural Philosophy (1831) shortly before his departure on the Beagle. It is certainly interesting to note that Herschel’s tomb lies at Westminster Abbey next to Newton’s. In his book, Herschel wrote: Causes competent under different modifications to the production of a great multitude of effects, besides those which originally led to knowledge of them. To such cause Newton has applied the term of verae causae; that is causes recognised as having a real existence in nature and not being mere hypotheses or figments of the mind.46
Darwin, the end of the scientific revolution? Scholars like Lyell, Darwin, Conybeare, von Buch, and Humboldt participated from the controversies previously discussed, controversies responsible for forging what must be called a revolution in the earth sciences. This revolution obviously took place much later than the Scientific Revolution recognized by historians and epistemologists of physics and astronomy, and which links Copernicus to Newton. By way of conclusion, let us reflect upon a possible link between these two revolutions. To link the Scientific Revolution with the geological revolution, let us go back to
In other words, verae causae are analogous to causes that are already known to have produced similar effects in other cases. When not directly observable, verae causae ‘are not to be arbitrarily assumed, they must be such as we have good inductive grounds to believe do exist in nature and do perform a part in phenomena analogous to those we would render an account of’.47 With respect to such methodological rules, Herschel acts like a genuine uniformitarian, explicitly following Lyell’s brand of geology. As Jonathan Hodge says:
43 Martin Rudwick, loc.cit. (Chicago, 1990), XXVII On his conversion see also Leonard G. Wilson, Charles Lyell, the years to 1841, (1972), 385, 398–407. 44 Charles Lyell, Principles of Geology (London, 1872), chap. XXXIII. It is true that he never explained more than the case of Scandinavia. 45 Charles Lyell, Elements of Geology, 6th ed. (London, 1865) chap. V.
46 John Herschel Preliminary Discourse on the study of Natural Philosophy (London 1831), 144–145. 47 Ibid., 197.
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Like his friend, (. . .) the physicist John Herschel, Lyell followed earlier writers, most notably the Scottish philosopher Thomas Reid (1710–1796); who had drawn this moral from the superior evidential credentials of the Newtonian gravitational force over the Cartesian ethereal vortices: any causes invoked in an explanatory theory should, ideally, be known to exist through direct observation independently of the facts they are supposed to explain.48 And as Rachel Laudan added some years later: Lyell’s commitment to the vera causa method permeates the [Principles of Geology]. Yet in spite of the impressive bulk of the work, Lyell never discussed it explicitly, perhaps because the method was so thoroughly treated in philosophical works that he could assume that his audience would be completely familiar with it. However we can reconstruct what he had in mind. In those many cases where the observational handicaps of the geologist were so great that he could not use the method of induction, what reasonable limits should be put on the method of hypothesis? Lyell’s answer was that all hypotheses about unobserved causes or effects must be found squarely on what we have observed.49
in Darwin traced it back to his transmutation notebooks (starting from 1838) or to the end of Darwin’s geological career in the 1830s. In order to remain true to our subject, let us simply add that the uniformitarian background was strongly criticized at the time by some catastrophists, particular by William Whewell, who: rejected this interpretation of vera causa principle believing to be overly restrictive. He agreed with Herschel that causes are not to be ‘arbitrarily assumed’ and that we must have ‘good inductive grounds’. Thus he explained in Philosophy of Inductive Science that verae causae are those which are justly and rigorously inferred. However he disagreed with Herschels’s condition that there must be an analogous connection to known causes (. . .) Whewell criticized Lyell (and unifomitarian geology in general) for using vera causa principle to rule out the possibility of catastrophic causes of geological change?.50
It should be noted in passing that Darwin uses the term ‘vera causa’ in the Origin of Species, although his biological works are beyond the scope of this paper. Modern historians and philosophers who studied the notion of vera causa
In accepting catastrophism in geology as in other scientific areas, Whewell discarded the idea of a science under the methodological principles of ‘true causes’. To this, Lyell, Herschel, and Darwin responded in the 1830s by walking in the footsteps of Newton. It is by following this intellectual path that one can go from the Scientific Revolution to the revolution in geology, from Copernicus to Darwin, as seen in the successive incorporation of scientific areas such as astrophysics, geology, and eventually biology.
48 Martin J. S. Hodge, ‘The development of Darwin’s general biological theorizing, in DS Bendall’, (ed) Evolution from molecules to men (Cambridge, 1983), 43–62, at 45. 49 Rachel Laudan, From mineralogy to geology. The foundations of a science 1650– 1830 (Chicago,1987), 204.
50 Laura J. Snyder, Reforming philosophy. A victorian debate on science and society (Chicago, 2006), 201. On Darwin’s report to Herschel and Whewell regarding the real cause see also Jean Gayon, ‘Mort ou persistance du darwinisme? Regard d’un e´piste´mologue’, CR Palevol 8 (2–3) 2009, 321–340.
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