CLASSIFICATION OF ROCKS. 75 



position is evidence. Thus does Time cease to be 

 the basis of classification for these; or, at least, if ad- 

 opted, it can only be under very lax inferences and 

 great chance of error, or under some conventional 

 circumstances. I need scarcely say, that position 

 alone proves nothing, when the very same unstratified 

 rock is proved, as well by focts as by its theory and 

 nature, to be, at the same time, below the lowest and 

 above the highest stratum, in every class, and also in 

 contact with every member in all of them. 



Whatever Geologists might have known or thought 

 of these unstratified rocks, they have never yet seen 

 the extent of this difficulty as I have here pointed it 

 out. Though they might have believed granite the 

 produce of fusion, they had convinced themselves 

 that it must always be a primary rock in time, and 

 therefore referable to the primary class, as they thus 

 judged also of certain porphyries, and as, with equal 

 calmness, they assigned all the trap rocks to the secon- 

 dary. I have shown the fallacy of all this: and thus 

 have I, yet not I, but Nature, encreased the dif- 

 ficulty of separating the unstratified rocks into divi- 

 sions which shall truly rank with the several classes of 

 stratified ones. And hence must we forfeit all hopes 

 of a truly natural arrangement as to these, if Time at 

 least is to be the basis, while I do not now see what 

 other can be adopted. Therefore, in making granite, 

 porphyry, and trap, conventional distinctions, as I 

 have done, I have also classed the unstratified ones 

 as primary and secondary, under the best evidence 

 which can be procured respecting their relative dates. 

 In the former, it has been that they do not, whether 

 really or conventionally, interfere as veins with any 

 secondary strata; while the latter may obviously thus 



