Feather stonhaugh^s Geological Report. 25 



It having been already stated that the rocks belonging to 

 the superior division of this column are constituted princi- 

 pally of the ruins of those of the inferior division, brought into 

 a comminuted state by the action of water, and subsequently 

 deposited into levels, the obvious propriety of considering 

 the column in the ascending order will be perceived. Every 

 practical student will also see the necessity of having some 

 knowledge of the mineral structure of the older rocks, before 

 he can form a judicious opinion of the mineral origin of the 

 more modern ones. The greater number of the formations 

 of the inorganic division are put down approximatively as to 

 their order of succession. Some of them, as the granite, 

 are unstratified, whilst the gneiss and some others are strati- 

 fied. Although all of them are not of igneous origin, yet 

 most of them in their turn seem to have acted in the charac- 

 ter of intrusive rocks. In some countries we have evidence 

 of trappean matter having been ejected from beneath the 

 granite. Whilst, however, they are not found in all countries 

 in the order assigned to them in this column, yet they have 

 been found every where approximating to it. In the early 

 days of geology, when theoretical terms had more influence 

 than at present, they were called primitive, because it was 

 supposed they had been produced before all other rocks. 

 The term primary has since been substituted, as expressing 

 their antecedent state in the column, without any theoretical 

 assertion. Geologists, on account of the extreme interest at-= 

 tending the study of the fossiliferous rocks, have paid such 

 undivided attention to them, that the most ancient formations 

 have been comparatively neglected, and an ample field has 

 thus been left for the arrangement of this mineralogical 

 branch of geology, where the rarer minerals and crystals may 

 assist in pointing out, as fossils have hitherto done, the 

 natural classification of these primordial rocks. We are en- 

 couraged to believe that this will not be deferred a long 

 time, when we look to the splendid results of the Silurian 



