404 LOWEST RED SANDSTONE. 



The sizes of the parts of which this rock is 

 formed, are infinitely various ; and, although the 

 largest do not often exceed a few inches in dia- 

 meter, they sometimes attain to dimensions of 

 more than a foot. In all cases, their aspect varies 

 with respect to the marks of wear which they 

 exhibit ; as they are sometimes acutely angular, 

 and, at others, as far rounded as is possible. 

 The proofs which the latter display of distant 

 transportation, or of long continued friction, are 

 highly interesting in a geological view, but are 

 not objects for the present inquiry. It may 

 happen, that angular and rounded fragments are 

 contained in the same mass, or specimen ; but 

 it is more usual for a common character in this 

 respect, if not a very defined one, to pervade one 

 mass or stratum. 



It is not necessary that the whole of one 

 stratum should be formed of coarse fragments, or 

 of fine sand ; or that the sandstone and the con- 

 glomerate should occupy distinct places. On the 

 contrary, it is not unusual for one part of a bed 

 to be fine, and another coarse ; and this variation 

 of structure may occur, either vertically, or at 



