Vol. 52.] FOLIATED GRANITES IN EASTERN SUTHERLAND, 



647 



With regard to the granites, it is difficult to believe that they are 

 wholly foreign matter ; though here it is necessary to observe the 

 utmost caution, the chemical difficulties being so great. 



In all probability, we must wait for satisfactory solutions of these 



Eig. 5. — Veins of granite and pegmatite in liornblende-schist, 

 north-eastern corner of Armadale Bag. 



[Face of cliff = about 4 feet square.] 



and other problems in metamorphism until much more is known of 

 the behaviour of the compounds of silicon under high temperature 

 and pressure. The chemical analogies between silicon and carbon 

 are known to be close, but whereas the carbon compounds are 



Fig. 6. — Details of the smaller vein in Jig. 5. 



T = Pegmatite. FG = Foliated granite. 



singularly tractable under conditions attainable in experiment, 

 those of silicon are as strikingly intractable. It is not unreasonable 

 to suppose that the silicon atom may have powers of forming groups 

 and compound radicals comparable to those of the carbon atom, 



