Prof. T. 8terry Hunt — On Camhrian and Silurian. 561 



rv. — History of the Names Cabibrian and Silurian in Geology. 



By Prof. T. Sterry Hunt, LL.D., F.E.S. 



[Concluded from p. 510.) 



3. Cambrian and Silurian EocTcs in North America (abridged).^ 



IN accordance with our plan, we now proceed to sketch the history of the Lower 

 Palseozoic rocks in North America. While European geologists were carry- 

 ing out the researches which have been described in the first and second parts of 

 this paper, American investigators were not idle. The geological studies of Eaton . 

 led the way to a systematic survey of the State of New York, the results of which 

 have been the basis of most of the subsequent geological work in eastern North 

 America, and which was begun by legislative enactment in 1836. The State was 

 divided into four districts, the work of examining and finally reporting upon which 

 was committed to as many geologists. The first or south-eastern district was 

 imdertaken by Mather, the second or north-eastern by Emmons, the third or 

 central by Vanuxem, and the fourth or western by James Hall ; the palaeontology 

 of the whole being left to Conrad, and the mineralogy to Beck. After various 

 annual reports, the final results of the survey appeared in 1842. The whole series 

 of fossiliferous rocks known, from the basal or Potsdam sandstone to the Coal- 

 formation, was then described as the New York system. 



At that time the published researches of British geologists furnished the means 

 of comparison between the organic remains found in the rocks of New York, and 

 those then known to exist in the Palaeozoic strata of Great Britain. Prof Hall was 

 thus enabled, in his Geology of the Fourth District of New York, to declare, from 

 the study of its fossils, that the New York system included the Devonian of 

 Phillips, the Silurian of Murchison, and the Cambrian of Sedgwick ; meaning by 

 the latter the Upper Cambrian, or Bala group, which alone was then known to be 

 fossiliferous. From the evidence then before him, he concluded that the Upper 

 Cambrian was represented, in the New York system, by the whole of the rocks 

 from the base of the Utica slate, downward, with the probable exception of the 

 Potsdam sandstone ; while he conceived, partly on lithological grounds, that the 

 Utica and Hudson River groups represented the Llandeilo and Caradoc, or the 

 Lower Silurian of Murchison. 



Emmons meanwhile had examined in eastern New York and western New 

 England a series of fossiliferous rocks, which, on lithological and stratigraphical 

 grounds, he regarded as older than any in the New York systenr; a view which had 

 been previously maintained by Eaton. Holding with Hall, that the lower members 

 of the New York system were the equivalents of the Upper Cambrian of Sedgwick, 

 he looked upon the fossiliferous rocks, which he placed beneath them, as the 

 representatives of the Lower Cambrian. 



Feeling satisfied that the sedimentary rocks which he had examined in eastern 

 New York were distinct from those which he, with Hall, regarded as corresponding 

 to the Bala group or Upper Cambrian (the Lower Silurian of Murchison), and 

 probably equivalent to the inferior portions of Sedgwick's Cambrian, and sup- 

 posing that the latter term was henceforth to be effaced from geology (as indeed 

 was attempted shortly after in the copy of Sedgwick's map published in 1844 by 

 the Geological Society), he devised for these rocks the name of the Laconic system, 

 as synonymous with the Lower (and Middle) Cambrian of Sedgwick. 



To Prof Hall, after the completion of the survey, had been committed the task 

 of studying and describing the organic remains of the State, and in 1847 appeared 

 the first volume of his great work on the " Palaeontology of New York." Since 

 1842 he had been enabled to examine more fully the organic remains of the lower 

 rocks of the New York system, and to compare them with those of the old world ; 

 and in the Introduction to the volume just mentioned (page xix) he announced the 

 important conclusion that the New York system itself contained an older fauna 

 than the Upper Cambrian of Sedgwick. According to Hall, the organic forms of 

 the Calciferous and Chazy formations had not yet been found in Europe, and our 

 comparison with European fossiliferous rocks must commence with the Trenton 

 group. He however excepted the Potsdam sandstone, which already, in 1842, he 

 had conceived to be below the Upper Cambrian of Sedgwick, and now regarded as 



• From the " Canadian Naturalist," new series, vol. vi. no. 4, p. 417. 

 VOL. X. — NO. CXIV. 36 



