648 MESSES. J. HORNE AND E. GREENLY ON [JSToV. 1 896, 



giving rise to similar series of Protean changes l ; but that these 

 powers are exerted only under conditions which, as yet, preclude 

 experimental investigation. If we consider, however, what amazing 

 results have followed the successful investigation of such a series as 

 C w H2n+2, for example, it may well give us pause to reflect on what 

 may happen under conditions which set the silicon atom also free 

 to move. 



Let us hope that the door to further knowledge of these matters 

 may not always remain closed, though of its opening there is yet 

 no sign. 



Meanwhile the facts described render certain : 



1. The existence of relations between granites and crystalline 



schists so intimate as to amalgamate the two rocks into 

 one gneissose complex. 



2. That in such regions the schists become more coarsely crystal- 



line than they are elsewhere. 



3. That some of these schists are of sedimentary origin, and that 



aluminous silicates abound in the most highly crystalline 

 varieties. 



4. That the foliated structures in the granites are assignable to at 



least two modes of origin. 



5. That, in spite of powerful earth- movements, there is a general 



absence of cataclastic structure. 



Discussion. 



Sir Archibald Geikie remarked that it was curious to see how 

 the oscillations of geological theory were reviving the views formerly 

 held, but more recently abandoned, as to the metamorphic origin of 

 some granites. The Authors of the record of careful observations 

 contained in this paper were cautious in drawing deductions, but it 

 was obvious that they were disposed to believe that the granite 

 described by them, though an eruptive rock, had assimilated the 

 surrounding schists and was not separated from them by any 

 sharply-defined differences of composition or structure. Their work 

 ran on lines closely parallel to that of the French Geological Survey 

 under M. Michel-Levy. They were evidently dealing with the 

 same class of phenomena that had been so closely studied in the 

 Plateau Central of France. A new line of research had in recent 

 years been opened up by the study of the intimate blending of 

 granitic laminae with granulitic and other schists, and though it 

 was still perhaps too early to formulate a definite theory, a marked 

 advance had been made towards a comprehension of the conditions 

 under which granitic intrusions and regional metamorphism are 

 linked together. 



Gen. McMahon congratulated the Authors on their interesting 

 paper, and concurred with them in their main conclusions. He 



1 It is not meant that ' hydrosilicons ' play the part of the hydrocarbons, but 

 merely to suggest how much we may have yet to learn regarding silicon. 



