Scrope, George Julius Poulett
Scrope, George Julius Poulett
SCROPE, GEORGE JULIUS POULETT
(b. London. England, 10 March 1797: d Fairlawn [near Cobham], Surrey, England, 19 Jannuary 1876) geology.
Scrope was the son of John Poulett Thomson, head of a firm engaged in trade with Russia, and Charlotte Jacob. Scrope’s younger brother was Charles Edward Poulett Thomson, Lord Syndenham. Scrope was educated at Harrow: at Pembroke College, Oxford (1815–1816); and at St. John’s College, Cambridge (1816–1821). Upon his marriage (22 March 1821) to Emma Phipps Scrope, heiress of William Scrope, of Castle Combe, Wiltshire, he assumed her name (which is pronounced Scroop).
Scrope was elected to the Geological Society in 1824 and served as secretary in 1825; he was later awarded the Society’s Wollaston Medal (1867). He was elected also to the Royal Society (1853–1855). From 1833 to 1868 he was a Liberal member of Parliament for Stroud, Gloucestershire. He was an advocate of free trade and various social and economic reforms, especially the poor law, but he took no part in parliamentary debate. He instead wrote extensively on a variety of political and economic subjects. He was said to have written nearly seventy anonymous pamphlets earning him the nickname “Pamphlet Scrope.” About 1867, after the death of his wife, who had been an invalid as the result of a riding accident soon after their marriage, he sold Castle Combe and moved to Fairlawn, near Cobham, Surrey. On 14 November 1867 he married Margaret Elizabeth Savage. Who survied him. there were no children from either marriage.
Scrope’s interest in geology was first aroused in Italy by the sight of Vesuvius in continual eruption during the winters of 1817–1818 and 1818–1819. In 1819–1820 he visited Sicily and the Lipari Islands, studying Mount Etna and Stromboli. On the advice of Edward Clarke and Adam Sedwoick at Cambridge, he studied the extinct volcanic region of Auvergne in central France in the summer and fall of 1821. He then went to northern Italy and eventually to Naples, where he arrived in time to observe the violent eruption Vesuvius in October 1822. During his return to England in the summer of 1823. he visited the volcanic regions of the Eifel in Germany.
On the basis of his geological fieldwork, Scrope wrote two books. The first book. Considerations on Volcanos (1825), has been called “the earliest systematic treatise on vulcanology.”1 It was poorly received by geologists, since it put forth in a dogmatic fashion hypotheses about every phase of volcanic activity and concluded with a “new the ory of the earth.” At this time Scrope was an ardent advocate of the theory of a cooling earth, which implied that the frequency and intensity of earthquakes and volcanic eruptions had declined over geological time. He believed that the forces of heat within the earth were still capable of producing, on rare occasions, cataclysmic pheavals (perhaps of whole mountain ranges or continents), causing destructive diluvial waves. At the same time he argued that
The laws or processes of nature we have every reason to believe invariable. Their results from time to time vary, according to the combinations of influential circumstances [p. 242]... . Until, after a long investigation, and with the most liberal allowances for all possible variations, and an unlimited series of ages, [present-day processes] have been found wholly indequate to the purpoose, it would be the height of absurdity to have recourse to any gratuitous and unexampled bypothesis [pp. v-vi].
These ideas were indebted in part to the writings of James Hutton, John Playfair, and James Hall, but Scrope’s restatement in combination with the theory of a cooling earth was to provide the basis for a catastrophist opposition to the uniformitarianism of Lyell.
Scrope’s second book, Memoir on the Geology of Central France (1827, but written in 1822), was more uniformitarian in approach, being devoted to a small region during geologically recent times. Improving upon the work of French geologists in Auvergne, he showed that currents of lava, which had flowed into valleys at various times, appeared at different heights above the river beds, marking successive steps in the progress of erosion of the valleys by the rivers. Scrope refuted the arguments for a recent deluge in the region and showed the untenability of attempts to classify the volcanic cones into antediluvian and postdiluvian on the basis of the amount of erosion they had undergone. As additional evidence that rivers are capable of producing impressive valleys unaided by a deluge, he cited in 1830 the presence of entrenched meanders in the valleys of the Meuse and Moselle.2 These arguments were effective in undermining the Cuvier-Buckland theory of a recent universal deluge, identical with the Biblical flood, that had deposited debris and had carved the major valleys. The theory was eventually abandoned by its remaining supporters in the Geological Society.
Scrope always believed that his two books had greatly influenced the development of Lyell’s uniformitarian views; and Lyell’s dependence is traceable in two articles that he wrote in 1826 and 1827 for the Quarterly Review. The latter was a very favorable review of Scrope’s second book. Lyell soon after verified Scrope’s observations in central France and Italy (1828–1829). Therefore, Scrope can, paradoxically, be regarded as a parent of both uniformitarianism and its catastrophist opposition in Great Britain. He never committed himself to either side and always occupied a middle ground.
As one of a number of younger geologists who wished, as he expressed it, to free geology “from the clutches of Moses,” Scrope assisted Lyell in the completion of the first volume of his Principles of Geology (1830), which had as a principal objective the extermination of theological influence on geology. A favorable review was ensured, since the publisher also owned the Quarterly Review; and its editor, after consulting Lyell, chose Scrope as the reviewer. Scrope wrote the review with Lyell’s advice, and he also reviewed Lyell’s third volume for the same journal (1835). In these and later reviews, Scrope argued strongly against religious influence in geology, yet he asserted that there was no conflict between the Bible and geology and wrote enthusiastically about the great contributions of geology to natural theology. He put forth, in opposition to Lyell, the evidence for progressive change in the histories of the earth and of life; and he was unimpressed by Lyell’s hypothesis of a chemical source of heat within the earth.
Scrope rejected Lyell’s metamorphic theory, which asserted that the “stratified primary rocks,” such as gneiss and schist, were normal sedimentary rocks altered by internal heat. He contended instead that the stratified primary rocks had originally been disintegrated granite deposited in hot agitated water when the primitive earth was not and barren.3 He later gave up this explanation but continued to believe that the foliation of these rocks was caused by differential movement. Scrope regarded the earth as essentially solid in its interior, kept in this state by intense pressure brought about by the expansive forces of heat and steam. The subterranean matter was thus in a state of tension so that any slight reduction of external pressure, caused perhaps by a change in atmospheric pressure or by the tidal action of the sun and moon, or an increase in internal temperature brought about by a local influx of heat would be sufficient to cause local melting accompanied by fracturing of the surrounding rock and the penetration of the fractures by the molton rock.
Scrope saw no essential difference between the causes of volcanoes and of earthquakes; a volcano was the result of fracturing at shallow depths, which allowed the fluid material to reach the surface. In 1856 he argued that this same cause could also produce a violent fracture and elevation of the overlying crust and the extrusion through a fissure of a ridge of crystalline matter. As the central axis of this protruded ridge or mountain range rose, the hot and partially fluid matter on the sides would be subject to friction, causing differential movement and the formation of parallel striations. In support of this theory he argued that mountain ranges typically show granite in the center, passing on the sides into gneiss (or “squeezed granite”) and, further on, into schist.4
To the end of his life, Scrope continued to believe in the possibility of rare cataclysmic earth movements far in excess of anything that Lyell would allow, although Scrope’s early catastrophism was soon modified to the extent that he believed that a mountain range had been formed by a succession of upheavals rather than by one grand upheaval, as advocated by Élie de Beaumont. Scrope adopted a mean position between the two extremes following the analogy with volcanic eruptions, which vary greatly in violence. By 1872 he had also sufficiently changed his views so that he could regard the theory of a cooling earth as only a conjecture, belonging rather to astronomy than to geology. He therefore rejected T. H. Huxley’s attempt to replace the uniformitarian interpretation of earth history by an evolutionary one, asserting that there was no evidence to show that the overall rate of earth movement had varied perceptibly during geological time. He did not, however, contest the evidence for biological evolution.5
Scrope’s original scientific work virtually ceased for many years after he entered Parliament. He returned to geology in the mid-1850’s, prompted by his desire to assist Lyell in combating a revival of the theory of “craters of elevation” of Humboldt, Buch, and Élie de Beaumont–a theory that he had first attacked in 1825. This theory regarded some volcanic cones as produced by a single explosive upheaval of strata rather than being built slowly by successive deposits of volcanic materials erupted from a vent, as Scrope and Lyell had always maintained. In two articles (1856, 1859) Scrope helped to refute the theory, pointing out its inconsistencies and the lack of agreement among its supporters as to the criteria for distinguishing these cones from cones formed by ordinary eruptions.6
After revisiting Auvergne in the summer of 1857, Scrope published a revised edition of his work on central France (1858); he dedicated the work to Lyell. This was followed by a greatly altered edition of his work on volcanoes (1862). During the last fifteen years of his life, he wrote many letters and short articles, which appeared mostly in the Geological Magazine. These writings served to correct the errors of others, to reaffirm or revive theories that Scrope had published in his first books, and to remind the world of his priority. He gave a general summary of his views in a new preface that accompanied the reissue of his work on volcanoes in 1872.
Among the “errors” attacked by Scrope in his last years were (1) the theory of a hot liquid earth with a thin crust, the contractions of which cause the earth to crumple, forming mountain ranges; (2) the tendency of German geologists to postulate a rigid law of succession of different types of lava from a volcanic vent; (3) the theory, held by Lyell, that the influx of seawater into the interior of the earth is the triggering cause of earthquakes and volcanic activity; and (4) any theory that ignored the primary importance of subterranean forces in the history of the earth. Thus, in a controversy with Jukes over the origin of valleys (1866), Scrope felt it necessary to remind the extreme fluvialists of the primacy of internal forces in creating the topography of the earth. Scrope believed that stream erosion was insignificant in comparison, yet he had long been among the leading advocates of “rain and rivers” as agencies of denudation in opposition to the tendency of Lyell and others to stress marine denudation.7 Later (1872) he warned the fluvialists of the probability of vast denudational effects produced in the past by gigantic waves accompanying cataclysmic earth movements.
One of Scrope’s favorite theories was that most lavas at the time of their appearance on the surface are not in a state of fusion but consist of solid crystals sliding over one another because of the expansive force of the steam mixed with them. In support of this theory he pointed to the rarity of glassy textures in most lavas. Despite the criticism his theory incurred from Lyell, aft he first proposed it in 1825, Scrope continued to advance it, although without much success.
Like Lyell, Scrope was virtually blind during his last years. He generously encouraged young geologists to continue his investigations of volcanic phenomena, and his financial support enabled Archibald Geikie (1870) and John W. Judd (1876) to study Vesuvius and the Lipari Islands.
Scrope remained an amateur in geology in the sense that his knowledge never extended far beyond his principal fields of interest. He had little knowledge of paleontology, and his theories on tectonic mechanisms and on the origin of metamorphic rocks exhibit a deficient knowledge of chemistry and physics. His books of the 1820’s showed considerable originality, and, principally by means of their influence on Lyell, helped steer geology into a more uniformitarian path. His later writings may have helped to keep geology on a middle course by combating extreme views from whatever side.
1. See John W. Judd, Volcanoes: What They Are and What They Teach, 6th ed. (London, 1903), p. 5, Judd credits Scrope with a number of contributions to vulcanology.
2.Philosophical Magazine, 7 (1830), 21–211 (Geological Society Proceedings).
3.Quarterly Review, 43 (1830), 411–469. and 53 (1835), 406–448.
4.Geological Society Quarterly Journal, 12 (1856), 326–350, cf. Volcanos (1862), pp. 265ff.
5.Volcanoes (London, 1872), Preface.
6.Geological Society Quarterly Journal, 12 (1856). 326–350. and 15 (1859). 505–549.
7.Geloogical Magazine3 (1866). Cf. Geology and Extinct Volcanos of Central France (1858), 208.
I. Original Works. Scrope’s major geological works are Considerations on Volcanos (London, 1825), 2nd ed., Volcanos (London, 1862; reissued with new preface, 1872), and Memoir on the Geology of Central France (London, 1827), 2nd ed., Geology and Extinct Volcanos of Central France (London, 1858). The Royal Society Catalogue of Scientific Papers lists some 36 scientific articles by Scrope, omitting at least four articles in the Geological Magazine, two letters in Nature (1875), and four reviews of geological works in the Quarterly Review (listed in the Wellesley Index to Victorian Periodicals, vol. I). Besides many pamphlets, Scrope wrote a number of reviews on nonscientific subjects, a biography of his brother, a history of Castle Combe., and works on economics and other subjects. Some 32 of Scrope’s letters to Lyell (1828–1874) are at the American Philosophical Society.
II. Secondary Works. There is no biography of Scrope. T. G. Bonney’s article in the Dictionary of National Biography, XVII (1897), 1073–1074. is rather uninformative about Scrope’s personal life, as are the various obituaries. Scrope’s contributions to geology are listed in Geological Magazine, 13 (1876), 96. His geological work is discussed in Karl Alfred von Zittel. History of Geology and Palaeontology (London, 1901), 259–263, and in R. J. Chorley, A. J. Dunn, and R. P. Beckinsale. History of the Study of Landforms. I (London, 1964), 125–130, 146–147, 357. 390–391, 400.
L. E. Page