Prof. T. Sterry Hunt — On Cambrian and Silurian. 565 



This essay by de Vemeuil was translated and abridged by Prof. Hall, and 

 published by him in the American Journal of Science, with critical remarks, 

 wherein he objected to the application of this disputed nomenclature to North 

 American geology. 



Meanwhile the Geological Survey of Canada was in progress under Logan, who, 

 in his preliminary report in 1842, and in his subsequent ones for 1844 and 1846, 

 adopted the nomenclature of the New York system, without reference to European 

 divisions. Subsequently however, the usage of Lyell and de Vemeuil was adopted 

 by Logan, who, in his report for 1848 (page 57), spoke of the Clinton group as the 

 base of the "Upper Silurian series," while in that for 1850 (page 34) he declared 

 the whole of a great series of fossiliferous rocks in Eastern Canada, including the 

 Trenton, Utica, and Hudson-River divisions, and the shales and sandstones of 

 Quebec (then supposed to be superior to these) to "belong to the Lower Silurian." 

 In the report for 1852 (page 64) the Lower Silurian was made by Mr. Murray to 

 include not only the Utica and Trenton, but the Chazy limestone, the Calciferous 

 sandrock and the Potsdam sandstone of the New York system. From this time 

 the Silurian nomenclature, as applied by Lyell and de Vemeuil to our North 

 American rocks, was employed by the officers of the Canadian Geological Survey 

 (myself among the others), and was subsequently adopted by Prof. Dana in his 

 Manual of Geology, published in 1863. 



The Geological Survey of Pennsylvania, under the direction of Prof. Henry 

 Darwin Rogers, was begun, like that of New York, in 1836, and the Palaeozoic 

 rocks of the State were at first divided, on stratigraphical and lithological grounds, 

 into groups, which were designated, in ascending order, by Roman numerals. 

 Subsequently, as he informs us in the preface to his final Report on the Geology of 

 Pennsylvania, Prof H. D. Rogers, in concert with his brother. Prof. William B. 

 Rogers, then directing the Geological Survey of Virginia, considered the question 

 of geological nomenclature. Rejecting, after mature deliberation, the classification 

 and nomenclature both of the British and New York Geological Surveys, they 

 proposed a new one for the whole Palaeozoic column to the top of the Coal- 

 measures, founded on the conception of a great Palaeozoic day, the divisions of 

 which were designated by names taken from the sun's apparent course through the 

 heavens. (Geology of Penn., I. vi. 105.) So far as regards the three great 

 groups which we have recognized in the Lower Palaeozoic rocks, the later names 

 of Rogers, and his earlier numerical designations, with their equivalents in the 

 New York system, were as follows : 



Primal {!.). This includes the miass of 2500 feet or more of shales and sand- 

 stones, which in Pennsylvania and Virginia, and farther southwards, form the 

 base of the Palaeozoic series, and rest upon crystalline schists. The Primal division 

 was regarded by the Messrs. Rogers as the equivalent both of the Potsdam and the 

 still lower members of the Cambrian. 



Auroral (II.). This division, which, with the last, includes the first fauna, 

 consists in great part of magnesian limestones, and corresponds to the Calciferous 

 and Chazy formations. Its thickness in Pennsylvania varies from 2500 to 5000 

 feet, and with the preceding division, it includes the first fauna. The representa- 

 tives of the Primal and Auroral divisions attain a great development in Eastern 

 Tennessee, where they have been studied by Safiford. 



Matinal (III.). In this, which represents the second fauna, were comprised the 

 limestones of the Trenton group, together with the Utica and Hudson- River shales. 



Levant (IV.). This division corresponds to the Oneida and Medina conglomerates 

 and sandstones. 



Surgent, Scalent and Pre- Meridional (V., VI.). In these divisions were included 

 the representatives of the Clinton, Niagara, and Lower Helderberg groups of New 

 York, making, with Division IV., the third fauna. 



The parallelism of these divisions with the British rocks was most clearly and 

 correctly pointed out by H. D. Rogers himself, in an explanation prepared, as I 

 am informed, with the collaboration of Prof William B. Rogers, and published in 

 1856, with a geological map of North America by the former, in the second edition 

 of Keith Johnston's Physical Atlas. The Palaeozoic rocks of North America are 

 there divided into several groups, of which the first, including the Primal, Auroral, 

 and Matinal, is declared to be the near representative of "the European Palaeozoic 

 deposits from the first-formed fossiliferous beds to the close of the Bala group ; 

 that is to say, the proximate representatives of the Cambrian of Sedgwick." A 



