384 PROPOSED MODIFICATION [Oh. XVL 



becomes very siliceous, the granite at the same time being 

 very quartzose ; and when a crystalline schist has a granular 

 texture, and meets with a fine-grained porphyritic granite, so as 

 to render the junction apparently abrupt ; then large crystals 

 of felspar traversing both rocks have occurred, removing all 

 doubt as to their identity. And this view of the primary 

 rocks is farther confirmed, by the numerous instances that 

 have been recorded, concerning the coincident composition of 

 adjacent granitic and schistose groups ; an agreement which 

 has not only been observed in several countries, but also, in 

 various parts of the hornblendic, shorlaceous, talcose, and 

 other formations. 



And lastly, the structure, composition, and modes of union 

 with the containing rocks, render it exceedingly probable 

 that the conglomerated and brecciated concretions, and the 

 granitic and mineral veins, are not of mechanical origin, but 

 have been formed during the cooling and consolidation of the 

 primary igneous mass. To recapitulate the evidence in favour 

 of this opinion is not necessary, since it may be readily 

 gathered from the last chapter, or may be deduced from the 

 objections enumerated in this against the prevailing opinion. 



Such, we presume, was the condition of the primary rocks 

 at the time of their formation from the refrigerating igneous 

 mass, and when the causes now in operation were first called 

 into action. It may, perhaps, be deemed incumbent on us to 

 explain how the bearings of strata, of beds or courses of 

 granitic rocks, and of veins, always exhibit, in certain local- 

 ities, a considerable degree of regularity, which the prevailing 

 theory attributes to the expansive power of the internal fire 

 fracturing and elevating the strata, in various but determinate 

 directions. It appears to us that these conditions of the 

 primary rocks have been effected by the same influence as 

 that which caused the laminae diagonally arranged within 

 strata, and contemporaneous veins, to assume certain positions ; 

 occurrences which cannot be supposed to have originated in 

 the application of any extraneous force. Is it not within the 



