72 



The changes are the result of the transfusion into the 

 limestone of certain constituents which are present in the 

 granite magma. A remarkable fact in connection with the 

 alteration, is that the granite, which is an acid variety of 

 the rock containing a very small amount of biotite as its 

 only bisilicate, where the limestone was bathed by it or 



Amphibolite resulting from alteration of limestone, cut by pegmatite. 

 of Glamorgan batholith near Bear lake. 



Eastern border 



actually immersed in it as in the case of the included frag- 

 ments, has notwithstanding this fact transfused into the 

 limestone not only silica, alumina and alkalis, as might be 

 expected, but also large amounts of magnesia and iron. 

 The limestone evidently fixed certain constituents of the 

 granite magma in relatively greater abundance than others, 

 exerting a species of selective action. 



In the cutting just west of Maxwell's Crossing there 

 is an exposure of a coarse pegmatite rather rich in f erro • 

 magnesian constituents, holding an inclusion of limestone 



