102 The Position of the Cincinnati Groiqh 



Calciferous, which has not been recognized in Canada. It thus appears 

 that the Levis formation not only lies above the Calciferous, but more 

 than 2,000 feet above it. Yet it holds a large number of trilobites of 

 tlie Potsdam type, and several species which certainly do occur in the 

 Calciferous. '(Billing's Pal, p. 876.) 



5th. The Chazy limestone, which takes its name from Chazy, Clinton 

 county, New York, has an extensive range over New York, the Island 

 of Anticosti, and Canada, but is seldom found over 300 feet in thick- 

 ness. 



6th. The Black river and Birdseye limestone, which is found in 

 Canada, and the Island of Anticosti, in New York, Missouri, and 

 other places, usually of no very important thickness, but in Pennsyl- 

 vania its maximum is estimated at 5,500 feet. (Geo. of Penn., vol. i., 



]). 105.) 



7th. The Trenton Group, which takes its name from Trenton, 

 Oneida county. New York, is highly fossiliferous, and is found almost 

 everywhere on the continent where the Lower Silurian rocks are ex- 

 posed. In New York, Pennsylvania, Missouri, Illinois, and Canada, 

 its greatest thickness does not exceed 1,000 feet, while on the Island 

 of Anticosti it reaches 1,700 feet, and in Tennessee 2,500 feet. (Geo. 

 of Tenn., p. 160.) 



8th. The Black slate or Utica shale, which is confined in its range 

 to Pennsylvania, New York, and Canada, and reaches its greatest 

 thickness in Pennsylvania, at 400 feet. (Geo. of Penn., vol. i., p. 

 105.) 



9th. The Cincinnati Group, which is situated at the top of the Low* 

 er Silurian, and has a total thickness exposed in Kentucky, Ohio, and 

 Indiana, of about 1,000 feet, is the equivalent of the Hudson River 

 Group of New York, whicli is exposed from 500 to 800 feet. It is the 

 equivalent of the Matinal Shales of Pennsylvania, which are 1,200 

 feet thick, and the Cape Girardeau limestone of Missouri, which is 

 165 feet in thickness. It is 150 feet thick at Green Bay, and other 

 places in Michigan, 250 feet at Chicago, as found by boring an artesian 

 Avell, and from 150 to 200 feet at other places in Illinois. It is 500 

 feet thick at Cape Rich, on Georgian Bay, 960 feet on the Island of 

 Anticosti, 800 feet at Colling wood, Canada, where it is interposed as 

 in New York between the Trenton and Medina Groups, while its 

 greatest thickness in Canada is 2,000 feet. (Geo. of Cau., 1863, p. 

 200.) 



The maximum thickness of the Lower Silurian, at the places men- 

 tioned, is thus seen to be 46,684 feet, and the fossiliferous part of the 

 metamorphic rocks, 36,500 feet. Total, 83,184 feet, or fifteen miles 



