LOWEST RED SANDSTONE. 405 



right angles to the plane of the bed, or else la- 

 terally, or according to its extent. Occasionally 

 also, solitary fragments of a determinate bulk, 

 are found imbedded in the finer rock. 



The simple minerals which enter into the 

 composition of the red sandstone, are, quartz, 

 felspar, clay, mica, and carbonat of lime. These 

 are all apparently derived from the disintegration 

 of previous rocks, the larger fragments producing 

 the coarser or conglomerate varieties. Among 

 these, quartz sand is the leading ingredient. Clay 

 is the next, and to the colour of this substance, 

 that of the rock is generally owing. Mica is com- 

 paratively a rare ingredient ; or, rather, it is not 

 an abundant one. Its presence has been im- 

 properly supposed to be always sufficient to dis- 

 tinguish this sandstone from those, superior in 

 position, with which it might otherwise be con- 

 founded. Carbonat of lime is also rare ; and, of 

 the felspar, it may be remarked, that it is seldom 

 either abundant, or of common occurrence ; hav- 

 ing, apparently, been generally decomposed, so 

 as to form the clay already noticed. It is in the 

 frequent presence of this substance, that the dis- 



