392 LOWEST RED SANDSTONE. 



instance. They only serve to prove still fur- 

 ther, that which has been already fully shown, 

 that the most accurate knowledge of rocks in 

 specimens, or the most attentive examination of 

 their mineral characters, is not sufficient to super- 

 sede the necessity of geological investigations, 

 where questions of a geological nature are con- 

 cerned. 



In the case of the lowest red sandstone, there- 

 fore, as in many others where the chief interest is 

 of a general or geological nature, the mineral 

 description of the rock must be considered as 

 merely accessory, and as tending to enumerate 

 the varieties in structure and composition, which 

 may occur among the strata that appertain to it. 

 Yet, an accurate knowledge of those varieties 

 may often be of material use to a geologist, by 

 enabling him, sometimes even separately, but, 

 more frequently, in conjunction with other cha- 

 racters, to determine a question of this nature, 

 where the evidence derived from position is ob- 

 scure, or unsatisfactory, or difficult of access. 



The further remarks that might here be offered 

 on this, as on similar subjects, are the busines of 



