OF UNSTRATIFIED ROCKS AND VEINS. 149 



position. It is on this ground also that we may 

 readily admit successive formations of trap rocks; 

 even if we had not those proofs of it which have al- 

 ready been mentioned : and it may thus even, prove, that 

 many of those now known, which are in contact, 

 separately, with different strata in the series, may 

 actually have been of different periods, and not the 

 consequences of a single deposit on rocks of different 

 natures; separated, itself, into distinct parts, by the 

 effects of waste. It is not a little remarkable, on this 

 view, that two deposits of trap, of which the distant 

 succession is proved by appearances that will hereafter 

 be fully detailed, are found in the same place; a phe- 

 nomenon exactly similar to the renewal of volcanoes 

 at distant intervals among the ruins of those long 

 since extinct. 



It must thus be apparent, that whatever differences 

 may exist between trap and granite, whether in their 

 relations to the strata, or their mineral characters, 

 they are strikingly analogous in almost every essential 

 general circumstance, and that the former may, in a 

 certain sense, be considered as a recent granite; as 

 the granite of the newer strata. The circumstances 

 respecting these analogies which have not yet been 

 noticed, will be found in their history in future chap- 

 ters. It remains to account for one difference, on 

 which much stress has been laid, not only by those 

 who deny the igneous origin of every rock, but by 

 those who, unable longer to blind themselves re- 

 specting that of trap, reserve all their force in favour 

 of the aqueous origin of granite. 



It has been said that granite, in a state of fusion and 

 protrusion, ought to have been erupted so as to flow 

 over the strata, and that, like the trap rocks, it ought 



