SCROPE, GEORGE JULIUS POULETT (b. London, England, 10 March 1797; d. Fairlawn [near Cobham], Surrey, England, 19 January 1876), geology.

    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, after 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.

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