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Canadian Record of Science. 



dykes, the largest only a foot in width, cutting the 

 essexite. These are all very fine in grain and much 

 decomposed, but represent two varieties of rock. Two of 

 the smallest are composed of a camptonite consisting of a 

 groundmass of brownish hornblende and plagioclase, with 

 lath-shaped plagioclase phenocrysts. The other two 

 dykes consist of a rusty weathering rock, made up of 

 feldspar laths and a mass of pseudomorphs of limonite 



Fig. 5. — Quarry in andose, Mount Johnson, showing vertical flow 

 structure on right. 



after some prismatic mineral, probably either segerin or 

 arfvedsonite. Professor Rosenbusch considers it to be a 

 highly altered tinguaite or solvsbergite, probably the latter. 

 The several dykes, while small and unimportant in 

 themselves, are of interest in that they present the 

 petrographical types regularly associated with the alka- 

 line rich intrusions of the class represented in Mount 

 Johnson." 



