Or UNSTRATIFIED ROCKS AND VEINS. 137 



been elevated by the same cause. If, in any case of 

 this nature, we cannot prove that a given effect 

 originates in a proposed cause, it is still important to 

 show that such a connexion is not impossible. 



It is evident now, that the relative position of any 

 two masses of granite to particular strata in the ge- 

 neral series, can afford no proofs respecting the relative 

 antiquity of these masses to each other. The veins 

 of the most recent may have been limited, like those 

 of the most antient, to the lowest stratum in the 

 series. That criterion must be sought, as I have 

 just said, by inquiring whether the veins of one mass 

 of granite penetrate another. And as this will here- 

 after be shown to be the case, it becomes proved that 

 granite has been produced at distinct successive pe- 

 riods. It appears that even three periods can be 

 proved; but it must be evident, that, from numberless 

 causes which cannot here be considered, the difficulty 

 of proving successive productions of it must increase 

 at each stage. 



The fact of even two generations of granite, is how- 

 ever important in that view which considers it as 

 having been the immediate cause or concomitant of 

 the elevation of the strata. It is shown in its proper 

 place, (chapters viii. and xxi.) that the strata have 

 actually been elevated at successive periods, in such a 

 manner as to prove that the inferior series was at least 

 twice moved ; and the theory of granite provides the 

 means of producing both the effects as easily as the 

 one. 



The question of the relative antiquity of Trap rests 

 on somewhat different grounds, and requires a separate 

 explanation. In some place or other, the veins of 

 this substance have been found penetrating every 

 rock from granite upwards; as far at least as the 



