Granites from British Columbia, etc. 349 



The mode of occurrence is exactly the same as that des- 

 cribed by Dr. Geo. H. Williams in the case of the epidote oc- 

 curring in the Mica Diorite from Stony Point on the Hud- 

 son Biver (American Journal of Science, June, 1888). The 

 nearest analogy to it observed in other rocks, is the struc- 

 ture of the garnets in many garnetiferous gneisses. In 

 the garnetiferous gneisses of the Laurentian System which 

 I have had an opportunity of examining in thin sections, 

 the garnets, although sometimes forming compact indi- 

 viduals, in other specimens have a structure closely 

 resembling, and often apparently identical with that above 

 described. This structure in gneisses and in the granite 

 under consideration, does not seem to be due to the eating 

 away or partial solution of crystals which originally had 

 a perfect form, as in the quartz phenocrysts of quartz 

 porphyries, where fragments of what were evidently once 

 quartz crystals which have been eaten apart, can often be 

 found lying near each other having lost their common 

 orientation, nor are the bays which run into the epidote 

 always or generally large and well defined like the arms of 

 the groundmass in the quartz phenocrysts in question, but 

 on the contrary, they are generally long, slender curving 

 arms and little irregular canals, and are frequently found 

 closed at the outer end, forming cavities which then appar- 

 ently become filled up, leaving finally one or more minute 

 inclusions or little points of the quartz or feldspar com- 

 pletely isolated in the epidote individual. In other grains 

 these have apparently also disappeared, and a crystal free 

 from all inclusions is the result. The epidote, like the 

 garnets in the gneiss, presents the appearance rather of 

 having grown into the surrounding minerals by first send- 

 ing out little arm like extensions of its substance which 

 subsequently meet one another, in this way including some 

 of the foreign mineral which may or may not finally dis- 

 appear. The few grains of garnet which as above men- 

 tioned, occur in sections of the Wrangell Island granite 

 have this same structure. 



Where an allanite crystal is enclosed in the epidote this 



