^24 ON THE RED SANDSTONE OF THE 



of the earth is more firmly built than is admitted 

 by some speculators. 



The strata sometimes rest on the primitive or 

 transition rocks in a conformable position, or they 

 are unconformably disposed ; for in some exten- 

 sive tracts, the primitive and transition rocks dip 

 to the S. E., while the superimposed strata of red 

 sandstone, dip to the S. W. The sandstone is 

 generally composed of roundish and angular grains 

 of quartz and felspar, with scales of mica. These 

 are either connected together by a basis of iron- 

 clay, ironshot slate-clay, which is occasionally 

 marly, quartz, or calcareous matter, or no per- 

 ceptible basis or ground is to be detected. When 

 the common basis or connecting material of the 

 grains is awanting, then the sandstone has much 

 of the aspect of a crystallised rock, and we can 

 observe portions of the grains of quartz and fel- 

 spar, and of the scales of mica shooting into each 

 other in the same manner as occurs in granite, 

 gneiss, and other crystallised rocks. 



Some varieties of the sandstone might be mis- 

 taken for grey-wacke : indeed, so strong is the 

 resemblance, that even experienced mineralogists 

 have occasionally committed the error of describ- 

 ing as grey-wacke varieties of red sandstone. 

 But this error will always be avoided, if we re- 

 collect, that formations are to be distinguished 

 by the characters of the rocks as they occur on 

 the great scale, and not from such accidental va* 



