420 CAMBRIAN AND SILURIAN IN NORTH AMERICA. [XV. 



wherein he objected to the application of this disputed nomen- 

 clature 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 nomen- 

 clature of the New York system, without reference to European 

 divisions. Subsequently, however, the usage of Lyell and De 

 Verneuil 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 divis- 

 ions, 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 sand-rock and the Potsdam 

 sandstone of the New York system. From this time the 

 Silurian nomenclature, as applied by Lyell and De Verneuil 

 to our North American rocks, was employed by the officers 

 of the Canadian geological survey (myself among the others), 

 and was subsequently adopted by Professor Dana in his Manual 

 of Geology, published in 1863. 



The geological survey of Pennsylvania, under the direction 

 of Professor 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, Professor H. 

 D. Rogers, in concert with his brother, Professor William B. 

 Rogers, then directing the geological survey of Virginia, con- 

 sidered 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 



