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MURCHISON, RODERICK IMPEY (b. Tarradale,
Ross and Cromarty, Scotland, 19 February 1792;
d. London, England, 22 October 1871), geology.
suggestion of William Lonsdale's, they concluded that
even these older strata were not pre-Silurian, as they
had originally thought, but were the lateral equivalents
of the Old Red Sandstone. This definition of a
Devonian system was at first criticized as being based
purely on paleontological criteria and not on any
plain evidence of superposition; but Murchison and
Sedgwick soon showed that the distinctive Devonian
invertebrate fauna occurred in Westphalia in
the expected position immediately below the
Carboniferous strata. The following year (1840)
Murchison resolved the matter by discovering in
European Russia a sequence of undisturbed strata
in which the Devonian was clearly underlain by
Silurian and overlain by Carboniferous, and in which
Devonian invertebrates were interbedded with Old
Red Sandstone fish. This established the temporal
equivalence of the Devonian and Old Red Sandstone
despite their contrasting lithology and fauna.
A second expedition to Russia in 1841 took
Murchison as far as the Urals and confirmed this
Paleozoic sequence. At the same time it showed him
how undisturbed and unaltered sediments could
change their appearance radically when traced laterally
into a region of mountain-building, and this convinced
him of the validity of Lyell's hypothesis of metamorphism.
He also found a vast development of
Paleozoic strata overlying the Carboniferous and
named them Permian after the Perm region near the
Urals.
In 1839 Murchison's financial position had greatly
improved, and he had moved into a grander house,
which thereafter became a fashionable salon of the
London intelligentsia. His enhanced social position,
coupled with the many distinctions conferred on him
for his work in Russia, unfortunately made him
increasingly conscious of social prestige and increasingly
arrogant and intolerant of opposition in
scientific matters.
Murchison's capacity for transforming scientific
controversies into paramilitary “campaigns” against
opponents had already been evident in his treatment
of de la Beche over the Devonian problem. It was now
shown much more seriously in his controversy with
Sedgwick over the base of the Silurian. In the same
year that Murchison had first investigated the
Transition strata, Sedgwick had begun to unravel
still older strata in Wales; and when Murchison
first established the Silurian, Sedgwick had suggested
the name Cambrian system (after the Latin name for
Wales) for the older rocks. During their only joint
fieldwork in Wales (in 1834) Murchison had assured
Sedgwick that the latter's Upper Cambrian lay below
his own Lower Silurian strata, although, as expected,
there was a faunal gradation between the two. But
when Murchison later realized that the fossils of the
Upper Cambrian Bala series were indistinguishable
from his own Lower Silurian Caradoc series, he
boldly proclaimed their identity and annexed the
Upper Cambrian into his Silurian system.
Sedgwick protested that the Cambrian had been
clearly defined by reference to an undisputed
succession of strata in northern Wales and that it was
wrong to alter the meaning of the term just because
its upper part contained Silurian fossils. But
Murchison continued to annex more and more of the
Cambrian into his Lower Silurian, until the two terms
were virtually synonymous. Sedgwick claimed that this
unjustified annexation was designed to cover two
major mistakes of Murchison's. He had misinterpreted
the Lower Silurian succession in its type area and had
therefore believed that these strata were younger than
the Upper Cambrian when in fact they were of the
same age; and--an even more serious mistake--he
had wrongly incorporated some Upper Silurian strata
(May Hill sandstone) into the Lower Silurian Caradoc
series, despite their very different faunas, thus giving
the Silurian fauna a spurious uniformity down into
Sedgwick's Cambrian.
But there was even more to the controversy than
technical mistakes and a priority dispute over
stratigraphical nomenclature. Each geologist, as a firm
believer in a progressionist interpretation of the fossil
record, ardently desired the distinction of showing
that his own system contained the evidence for the
origin of life on earth. Thus, when Murchison wrote
his Geology of Russia (1845), he asserted that the
“unequivocal base-line of palaeozoic existence” was
to be seen in the Lower Silurian strata, within which
there was a “gradual decrement and disappearance of
fossils” toward the base. Furthermore, in Scandinavia
(where he had traveled in 1844) these strata were
immediately underlain by “Azoic” crystalline schists,
in which Murchison believed that it was “hopeless to
expect” to find fossils. This was not because they had
been metamorphosed (although he agreed that they
resembled the metamorphic rocks of later periods)
but because they had been formed under conditions
too hot to support life. He therefore argued, against
Lyell, that geology provided “undeniable proofs of a
beginning” to life on earth. His desire to have sole
credit for providing these “proofs” is shown by his
obstinate insistence that the Silurian fauna was the
earliest. Thus when Joachim Barrande first described
a distinctive “primordial” fauna (the Cambrian of
modern geology) below the previously known Lower
Silurian faunas, Murchison did not allow it as a
possible paleontological basis for Sedgwick's