413 



SUPERIOR SANDSTONES 



IT has already been observed, that whatever 

 variety in a mineralogical sense, and whatever 

 important distinctions of a geological nature, 

 may exist among the secondary strata, they are 

 nearly all comprised under the heads of sand- 

 stone, limestone, and shale. Among the numer- 

 ous varieties of the former rock, that which was 

 described in the preceding chapter, is generally 

 very distinguishable from the rest by many im- 

 portant mineral characters, as well as by the 

 steady and peculiar nature of its geological posi- 

 tion. But, among those which follow it in 

 order, which alternate with the other members 

 of the same class, it is very difficult to make such 

 mineral distinctions as to render it either neces- 

 sary or useful, to treat of them separately. 



In a geological view however, the distinctions 

 are often of great importance. In many coun- 

 tries, or districts, these strata occur in a certain 

 order, and under certain relations to the accom- 



