OF UNSTRAT1FIED ROCKS AND VEINS. 145 



trap veins should generally be posterior to all mineral 

 reins, follows, of course, from the period at which 

 these appear, relatively, to have been formed. 



Many chemical and mechanical changes occur in 

 the including strata at the places where they are 

 traversed by veins, whether these be of trap or 

 granite. But these are numerous and minute, and 

 will be required hereafter for the purpose of esta- 

 blishing the igneous origin of those two rocks. But, 

 in this place, where the question of veins has been 

 treated generally, as far as that was possible, it is im- 

 portant to observe that the effects are, in both in- 

 stances, not only similar, but as exactly identical as 

 could be expected when the various differing circum- 

 stances attending them are considered. 



On the Origin of the umtratified Rocks. 



The reasons for believing that all the unstratified 

 rocks are alike of igneous origin, or that they are 

 substances crystallized from a fluid of fusion, will be 

 given in a more proper place hereafter. The follow- 

 ing remarks on the mode in which these rocks as- 

 sumed their present forms, and on the probable 

 causes and effects of their fluid state, proceed on this 

 supposition. In a science in which there is so uni- 

 versal a reaction of all the parts, and where every set 

 of facts is necessary to illustrate every other, all can- 

 not have that first place in consideration to which so 

 many have a claim. 



As it is apparent that granite has been in a state of 

 fluidity beneath the strata, and that, during this 

 state, these have been elevated in an irregular man- 

 ner, it is easy to account for the irregularity of its 



VOL. i. L 



