Dictionary of Scientific Biography

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 hot 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 molten 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.