STRUCTURE 05 THE EARTH'S CRUST. 393 



shewn in the cut, and also in the lower diagram in the 

 frontispiece. 



1st. The Lower Silurian. This is a most extensive forma- 

 tion, no less than eight stages of which have been made out 

 geologists in North America, composed of various lime- 

 stones and sandstones.* 



iM. The Upper Silurian. It is also a very extensive forma- 

 tion, since about ten stages of it are found in the State of 

 v York.f 



3d. The Devonian, including in North America no less than 

 eleven stages. It occurs also in Russia and Scotland, where 

 it was first made out as a distinct formation. 



4th. The Carboniferous Formation, consisting of three grand 

 di visions. 



5th. The Trias, or Saliferous Formation, contains the richest 

 deposits of salt on the continent of Europe, and comprises 

 three stages, || to one of which the sandstone of the Con- 

 necticut valley belongs. 



6th. The Oolitic Formation, only faint traces of which exist 

 on the continent of America. It comprises at least four dis- 

 tinct stages.^]" 



7th. The Cretaceous, or Chalk Formation, of which three 

 principal stages have been recognized : two of these are 

 feebly represented in the Southern and Middle States of North 

 America. 



* 1. Potsdam Sandstone; 2. Calciferous Sandstone; 3. Chazy Lime- 

 stone ; 4. Bird's-eye Limestone ; 5. Black River Limestone ; 6. Trenton 

 Limestone ; 7. Utica Slate ; 8. Hudson River Group ; beinaj all found in 

 the western parts of the United States. 



f 1. Oneida Conglomerate ; 2. Medina Sandstone ; 3. Clinton Group ; 

 4. Niagara Group ; 5. Onondaga Salt Group ; 6. Water Limestone ; 

 7. Pentamerus Limestone; 8. Delthyris Shaly Limestone; 9. Encrinal 

 Limestone ; 10. Upper Pentamerus Limestone. 



J 1. Oriskany Sandstone; 2. Cauda-Galli Grit; 3. Onondaga Lime- 

 stone ; 4. Corniferous Limestone ; 5. Marcellus Shale ; 6. Hamilton 

 Group ; 7. Tully Limestone ; 8. Genesee Slate ; 9. Portage Group ; 

 10. Chemung Group ; 11. Old Red Sandstone. 



1. The Permian, extensively developed in Russia, especially in the 

 government of Perm ; 2. The coal measures, containing the rich deposits 

 of coal in the Old and New World; 3. The Magnesian Limestone of 

 England. 



|| 1. New Red Sandstone ; 2. Muschelkalk; 3. Keuper. 



f 1. The Lias ; 2. The Lower Oolite ; 3. The Middle Oolite ; 4. The 

 Upper Oolite. 



