134 



SKETCHES OF CREATION. 



which were soon to be followed by a more or less general 

 disruption. We may generally distinguish, therefore, some 

 calcareous shales constituting the uppermost beds of a 

 group ; and, in rare instances, the disturbance proceeded 

 so far before the extinction of the faunas that the upper- 

 most beds have been rendered finely fragmental. To illus- 

 trate and confirm these generalizations, I introduce the fol- 

 lowing table: 





Coarse-fragmen tal. 



Fine-fragmental. 



Calcareous. 



Calcareo-fragmental. 



* 5, 



Potsdam sand- 

 stone. 



Calciferous and 

 Chazy formations. 



Trenton Group. 



Cincinnati Group. 



la 



Oneida conglom- 

 erate. 

 Medina sand- 

 stone. 



Clinton Group. 

 Niagara shale. 



Niagara lime- 

 stone. 



Salina Group. 



la 



ft "5 



Oriskany sand- 

 stone. 



Schoharie Grit. 



Corniferous lime- 

 stone. 



Hamilton Group, 

 followed by Che- 

 mung. 



g-s 



>3« 



Waverly sand- 

 stone 

 (Marshall phase). 



Waverly sand- 

 stone 

 (Chouteau phase). 



Mountain lime- 

 stone. 



False coal-meas- 

 ures. 



P.S 



Parma cong.om- L^X^yl ^S^ 

 erate> short epochs). stone ' 



Permian Group. 



In this exhibit I take no account of the St. John's Group, 

 since we know so little of its lithological characters. It 

 thus appears that the recognized succession of strata in 

 each of the great divisions of Paleozoic time is wonderful- 

 ly similar in lithological characters. In each great group 

 is a great limestone mass, which stands out conspicuously 

 in the geology of the region underlaid by the group. These 

 limestone masses are prominent landmarks in the progress 

 of the ages. They mark the successive culminations of the 

 geological periods. Each mass outcrops in a protruding 

 belt, sweeping from east to west over a wide extent of 

 country. The oldest is the more northern, and the others 

 follow in regular succession. The Trenton mass sweeps 

 across along the north of Lake Ontario and to Georgian 

 Bay. The Niagara mass lies to the south of Lake Ontario 



