SUPERIOR SANDSTONES. 415 



of each in a separate division, so, in their geolo- 

 gical recurrence, they resemble the analogous 

 primary strata, in which no such distinctions 

 were thought necessary. Among these, argilla- 

 ceous schist, and quartz rock, occur in as many 

 positions and alternations as do these sandstones 

 in general. The record of these is the business 

 of geology ; and, in the case of the secondary 

 sandstone, also, it seemed unavoidable to leave 

 these differences, such as they may be, to those 

 who treat of the geological history of strata, 

 whether local or general. Had a different pro- 

 ceeding been here adopted, it would have been 

 necessary to enter on the details of these local 

 connections ; and had each stratum or formation 

 of sandstone which enters into the structure of 

 England, for example, been described under a 

 separate title, the descriptive catalogues of varie- 

 ties would have been little else than mere repe- 

 titions of the same unvarying characters. 



It is true, that one, or more, of these, such as 

 the red marie of the English geologists, might 

 have been placed under a separate head : but as 

 .nothing was here admissible on the subject of its 



