390 



LOWEST (RED) SANDSTONE, 



THE rock which forms the subject of the pre- 

 sent chapter, has very frequently been designated 

 by the name of the old red sandstone, for the pur- 

 pose of distinguishing it from certain sandstones 

 of the same colour, which are found higher up in 

 the succession of the secondary strata. 



These, more recent red sandstones, are fre- 

 quently separated from the rock in question, by 

 intervening strata of sandstone, limestone, and 

 shale ; in which cases the geological distinction 

 is easily made : much more easily indeed than the 

 mineral distinction, which, if certain specimens 

 of both be compared, can scarcely be perceived 

 by the eye ; far less be rendered intelligible by 

 description. 



Occasionally, however, the more recent red 

 strata, are found in immediate contact with the old 

 red sandstone ; an occurrence which often proves a 



