490 HISTORICAL GEOLOGY. 



1. Canadian 

 Period. 



2. Chazy Epoch : that of the Chazy limestone, Emmons. 

 Final Rep. Geol. N. Y., 1843. 



1. Calgifekous Epoch : that of the Calciferous sandrock of 

 Amos Eaton, Geol. and Agric. Survey distr. adj. Erie Canal, 

 N.Y., under S. Van Rensselaer, 1824. Part of the Levis, of 

 Logan's Quebec group. 



In the Reports of the first Pennsylvania Geological Survey, Professor H. D. Rogers 

 uses the following terms and numbers: Primal, I., for Cambrian ; Auroral, II., for the 

 Calciferous and Chazy ; Matinal, III., for the Trenton. The Taconic series of Emmons, 

 along western New England and eastern New York, corresponds to the Cambrian and 

 Lower Silurian formations combined. The geologists of the New York Geological Survey 

 of 1836 to 1842 were Ebenezer Emmons, W. W. Mather, James Hall, Lardner Vanuxem, 

 and T. A. Conrad, the last acting as paleontologist. After the close of the general survey 

 of the State, Hall was given charge of the paleontology. 



ROCKS — KINDS AND DISTRIBUTION. 



The Lower Silurian formations are to a large extent limestone ; they are 

 partly calcyte, but more widely dolomyte. Arenaceous and shaly strata 

 are most common in the earlier and later part of the series, that is, in the 

 Calciferous epoch and the Hudson epoch ; but in the Interior Continental 

 region the larger part of the rocks of these earliest and latest divisions is 

 calcareous. The Trenton rocks are remarkable for their wide distribution 

 over the continent. Outside of the Archseo-Cambrian areas they extend for 

 the most part from the Atlantic to the Pacific, though covered in general by 

 later rocks. The larger part of the outcrops of the limestones follows the 

 outline of the Archaean areas, separated from them, if at all, only by out- 

 cropping belts of Cambrian, showing that the shore line in the Lower 

 Silurian era was not far distant from its Cambrian position. 



This is true around the Adirondack area in New York, and from central 

 New York westward to Wisconsin and Minnesota. It is also true along the 

 Appalachian protaxis from Canada and the Green Mountain region to Ala- 

 bama, on both its east and west sides ; also in the Ottawa region, Canada, 

 where there was a large Lower Silurian basin as successor to that of the 

 Cambrian era ; also along the St. Lawrence northeastward, along the western 

 arm of the Archsean V northwestward, and on some Arctic islands. It was 

 true, also, along portions of the Rocky Mountain protaxis; but here, owing 

 to the thickness of the later formations, the Lower Silurian beds are not 

 commonly at the surface. Some of the deep canons of the Pacific Border 

 region cut down to them through 1000 to 3000 feet of overlying beds. 



In the Continental Interior two isolated areas lie in a line, one over 

 southern Ohio, part of Kentucky, and the border of Indiana ; and the other 

 in Tennessee (C, T, on the map, page 536). The region is that of the 

 so-called " Cincinnati uplift," or anticline. 



On the borders of western New England and eastern New York, along 

 the Taconic Range and either side of it, the crystalline schists and limestone 



