SUPERIOR SANDSTONES. 427 



access to a whole series is not always to be ob- 

 tained, it is sometimes impossible to make the 

 requisite distinctions. 



C. Quartz sand with schistose clay. 



This variety, although akin to the former in 

 name, presents sufficient distinctness of character 

 to justify a separation. The clay is sometimes 

 more or less distinctly interlaminated, and the 

 rock passes into shale. 



D. Quartz sand with clay and carbonat of lime. 



a. Large grained, gravelly. 



b. Fine, arenaceous. 



E. Argillaceous or calcareo-argillaceous sand- 

 stone mixed wkh bitumen. 



This sometimes passes into bituminous shale. 



F. Quartz sand with clay and mica, or with clay, 

 carbonat'of lime, mica, and red oxyde of iron. 



The red marie of English geologists belongs 

 to this division. 



G. Quartz sand, with carbonat of lime, mica, and 

 green earth. Kentish rag. 



H. Sandstones of various quality, containing a 

 large proportion of rust of iron : that substance often 

 forming the cement of the other ingredients : ferrugi- 

 nous sandstone. 



The sandstones of the Second Division, like 

 .those of the former head, when in contact with 



