Classifications of Rocks. 41 



classes, whenever the mere character of a specimen is used 

 to determine either ; but, in this case, we can always prevent 

 any error by having recourse to their actual positions in the 

 great series of rocks, which are, comparatively, of a very de- 

 cided nature. 



I have thus examined the objections to this class, taking it 

 only on the general broad view which has been given of it. 

 But it would not be doing the geological student that justice 

 which he is entitled to claim from a writer who undertakes to 

 tell him the truth as far as it can be discovered, if I did not 

 state them more particularly. Its ingredients, or members, 

 the reader may perceive, have never been named or defined, 

 so that it answers any temporary purpose that may be wished ; 

 adopting or renouncing at pleasure, and thus, like other 

 visionary things, remaining unassailable. That which is no 

 where is nothing ; the place of that which may be any where 

 can never be known. 



If, with some writers, it comprises the later schists and 

 limestones of the primary class which contain shells, it is still 

 undistinguishable, even in this arrangement ; since, according 

 to a celebrated writer on the Pyrenees, the transition rocks 

 there alternate with micaceous schist, which is admitted to be 

 primary. But it is easy to show that it involves both the 

 primary and the secondary classes, that the only easily assign- 

 able rocks in it belong to the latter, and that it has probably 

 arisen from an entire misconception respecting these. It 

 would be easy to show, had I here space for that purpose, that 

 the inventor of this system had mistaken the upper red sand- 

 stone for the lower ; and hence certain strata inferior to that, 

 but still in the secondary division, became members of his 

 transition class. Proceeding then to assume a wrong crite- 

 rion, namely, the presence of organic remains and of frag- 

 ments, one or both, some members of the primary class pos- 

 sessing these characters, also fell into it. The effect of this 

 invention, in the details, has therefore been to confound and 

 intermix the two chief classes, in addition to all the objections 

 already stated. It is easy to comprehend the inextricable 

 confusion which it has introduced into geological writings ; a 

 confusion indeed so great, as to render nearly unintelligible 



