BY THE REV. J. MILNE CURRAN. 205 



rock may be rearranged so as to give rise to a rock that may not 

 be distinguished from granite. The evidence advanced in support 

 of the metamorphic origin of many granites broke down when the 

 rocks were subjected to the test of microscopical examination. 

 But there are still cases where all the refinements of modern 

 geology have been employed without shaking the conclusion that 

 some granites, at least, and certainly some crystalline schists, can 

 be produced by the metamorphism of rocks in situ* 



There is little doubt, then, but that the granite was intruded 

 into Silurian rocks after their folding and elevation. Possibly the 

 granitic intrusion formed an anticlinal, and lifted the sediments 

 yet higher. Silurian rocks once occupied the place now taken by 

 the granite. Were the former rocks simply lifted or thrust aside, 

 or were they absorbed by the molten or plastic granite % Lifted, I 

 should say. There is little proof to show in support of this view, 

 but it is an impression left after a study of the whole district. I 

 have no doubt at all but that portions of the Silurian rocks were 

 absorbed by the granite in its intrusion. When we examine the 

 outer edges of the granite, we find that for a short distance from the 

 contact it differs from the typical rock. There is, for instance, an 

 absence of hornblende, the mica is in nests, and the minerals, 

 generally, are not arranged as in a normal granite. Quartz, 

 instead of filling up the spaces left by the other constituents, is 

 found in grains and blebs through a much larger body of felspar. 

 All this might be accounted for by the more rapid cooling of the 

 margins of any intrusive rock. But I consider it as the result of 

 the absorption of a certain amount of the pre-existing phyllites. 



In this connection I would like to draw attention to some views 

 on the origin of crystalline rocks as set forth in the volume of the 

 International Geological Congress for 1888.f 



In a paper on the " Archaean Geology of the Region N.W. of 

 Lake Superior," Dr. A. C. Lawson points out that the archaean 



* See Green's " Physical Geography," Chapter ix., second edition. 

 + Congres G^ologique International 4me Session — Londres, 1888. Etudes 

 sur les Schistes Cristallins. 



