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