See E. Bouly, Histoire de Cambrai et du Cambrésis (Cambria, 1843).
CAMBRIA, the Med. Lat. name for Wales. After the end of the western Roman empire the Cymric Celts held for a while both Wales and the land round the Solway (now Cumberland and adjacent regions), and the former came to be called Cambria, the latter Cumbria, though the two names were sometimes interchanged by early medieval writers.
CAMBRIAN SYSTEM, in geology, the name now universally employed to designate the earliest group of Palaeozoic rocks which possesses a connected suite of fossils. The strata of this system rest upon the Pre-Cambrian, and are succeeded by the Ordovician system. Until the fourth decade of the 19th century all stratified rocks older than the Carboniferous had been grouped by geologists into a huge and indefinite “Transition Series.” In 1831 Adam Sedgwick and Sir Roderick I. Murchison began the herculean task of studying and sub-dividing this series of rocks as it occurs in Wales and the bordering counties of England. Sedgwick attacked the problem in the Snowdon district, where the rocks are highly altered and displaced and where fossils are comparatively difficult to obtain; Murchison, on the other hand, began to work at the upper end of the series where the stratigraphy is simple and the fossils are abundant. Murchison naturally made the most of the fossils collected, and was soon able to show that the transition series could be recognized by them, just as younger formations had fossils peculiar to themselves; as he zealously worked on he followed the fossiliferous rocks further afield and continually lower in the series. This fossil-bearing set of strata he first styled the “fossiliferous greywacke series,” changing it in 1835 to “Silurian system.”
In the same year Sedgwick introduced the name “Cambrian series” for the older and lower members. Murchison published his Silurian system in 1839, wherein he recognized the Cambrian to include the barren slates and grits of Harlech, Llanberis and the Long Mynd. So far, the two workers had been in agreement; but in his presidential address to the Geological Society of London in 1842 Murchison stated his opinion that the Cambrian contained no fossils that differed from those of the Lower Silurian. Whereupon Sedgwick undertook a re-examination of the Welsh rocks with the assistance of J.W. Salter, the palaeontologist; and in 1852 he included the Llandeilo and Bala beds (Silurian) in the Upper Cambrian. Two years later Murchison brought out his Siluria, in which he treated the Cambrian system as a mere local facies of the Silurian system, and he included in the latter, under J. Barrande’s term “Primordial zone,” all the lower rocks, although they had a distinctive fauna.
Meanwhile in Europe and America fossils were being collected from similar rocks which were classed as Silurian, and the use of “Cambrian” was almost discarded, because, following Murchison, it was taken to apply only to a group of rocks without a characteristic fauna and therefore impossible to recognize. Most of the Cambrian rocks were coloured as Silurian on the British official geological maps.
Nevertheless, from 1851 to 1855, Sedgwick, in his writings on the British palaeozoic deposits, insisted on the independence of the Cambrian system, and though Murchison had pushed his Silurian system downward in the series of rocks, Sedgwick adhered to the original grouping of his Cambrian system, and even proposed to limit the Silurian to the Ludlow and Wenlock beds with the May Hill Sandstone at the base. This attitude he maintained until the year of his death (1873), when there appeared his introduction to Salter’s Catalogue of Cambrian and Silurian Fossils.
It is not to be supposed that one of these great geologists was necessarily in the wrong; each had right on his side. It was left for the subsequent labours of Salter and H. Hicks to prove that the rocks below the undoubted lower Silurian of Murchison did indeed possess a characteristic fauna, and their work was confirmed by researches going on in other countries. To-day the recognition of the earliest fossil-bearing recks, below the Llandeilo formation of Murchison, as belonging to the Cambrian system, and the threefold subdivision of the system according to palaeontological evidence, may be regarded as firmly established.
It should be noted that A. de Lapparent classifies the Cambrian as the lowest stage in the Silurian, the middle and upper stages being Ordovician and Gothlandian. E. Renevier proposed to use Silurique to cover the same period with the Cambrian as the lowest series, but these differences of treatment are merely nominal. Jules Marcou and others have used Taconic (Taconian) as the equivalent of Cambrian, and C. Lapworth proposed to apply the same term to the lowest sub-division only; he had also used “Annelidian” in the same sense. These names are of historical interest alone.