RED PRIMARY SANDSTONE. 



343 



purpose of rendering more complete the history 

 of this hitherto neglected rock. 



The only mineral which I have yet observed 

 in this sandstone is garnet. It occurs either in 

 indistinct crystals, or diffused ; and is only found 

 in the very compact varieties, which are charac 

 terized by an uncommon degree of hardness 

 wherever it is present. The presence of this 

 mineral, which is unknown in the secondary red 

 sandstone, may be regarded as an additional and 

 important characteristic mark of difference be- 

 tween the two; and, from analogy, as indicating 

 a much more antient origin, since it belongs ex- 

 clusively to the primary rocks. 



