44 



applies very well to the granites in question, save that they 

 are generally exotic. There are, however, two important 

 considerations which, in my estimation, throw the weight of 

 evidence against the view that these granites are Laurentian. 

 These have already been stated. First, the relations of the 

 granite to the petrosilex make it necessary to regard these two 

 rocks as members of the same series, so that if one is Lauren- 

 tian, the other must be also. Now, the petrosilex is taken as 

 the most typical Huronian rock in this region ; and, if it is 

 included in the Laurentian system, there is really no reason 

 why the other rocks, here referred to the Huronian age, should 

 not be disposed of in the same way ; for they appear to be as 

 intimately associated with the petrosilex on one side as the 

 granite is on the other. Second, this granite overlies the 

 Naugus Head series, and hence, if the former is Laurentian, the 

 latter must be a distinct formation below the Laurentian ; which 

 is, to say the least, highly improbable. It might be urged by 

 some that we have here an inversion of the natural order ; that 

 the granite, though belonging to an older system, overlies the 

 Naugus Head series in consequence of some gigantic fault, 

 overturn fold, or igneous overflow ; the extravasation of the 

 Naugus Head series through the granite having occurred sub- 

 sequently to the inversion. This violent hypothesis, however, 

 is entirely unsupported by facts, except that evidences of 

 stratification are more frequently met with in the Naugus Head 

 series than among the granites , indicating that the latter are the 

 older rocks ; and this indirect evidence is offset by the fact that 

 the Naugus Head rocks, especially the feldspathic varieties, are, 

 as a rule, much more perfectly and coarsely crystalline than the 

 granite. 



Of course, that the granite occupies the geologic horizon here 

 claimed for it can be proved directly and conclusively only with 

 respect to those portions of this rock showing either a passage 

 to petrosilex, or intersection by rocks of the Naugus Head 

 series, — a small part of the entire granite formation. Hence 

 the way may be considered open for the introduction of evidence 



