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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.
NOTES
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), 210-211 (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. Volcanos (London, 1872), Preface.