102 AUSTBALASIAN ANTAKCTIC EXPEDITION. 



the Canadian amphibolites are portions of intrusive igneous rocks, frequently in the 

 form of dykes. It is very interesting, therefore, to read the footnote (p. 121) which 

 states that B. Frosterous, in his work in Finland, finds that the amphibolites which are 

 characteristic associates of the granite gneiss of Southern Finland are probably for the 

 most part altered dyke rocks. How far the dyke theory is applicable in Canada 

 cannot be at present determined. 



There remains the third class of amphibolite which are considered to be derived 

 from the metamorphism of impure bands in the limestone series. The cause of the 

 metamorphism is assumed to be (p. 164) " undoubtedly the granite lying below and 

 exerting its action upward." The evidence relied upon is the interbanded character 

 (p. 165) of thin amphibolite bands in crystalline limestone on the Hastings Road on 

 lots 31 and 57, near the village of Ormsby. To the north of this the limestone bands 

 disappear and the amphibolite covers a great area. This evidence could be adequately 

 interpreted by the supposition of a primary intrusive mass which sends out tongues 

 into the surrounding limestone. Hence it is difficult to see how the evidence can carry 

 the burden of proof placed upon it by Adams and Barlow. 



The " feather amphibolite," for which a sedimentary origin is claimed, seems to be 

 a different type of rock from the above amphibolites which the authors have called 

 the granular amphibolites. It is questionable whether the " feather amphibolite " 

 is a typical amphibolite. No analysis is given of the rock, so that it is impossible to 

 strictly correlate it with the normal amphibolites and to see whether it, like them, falls 

 into Grubeumann's group of amphibolites. The hand specimen (Plate XXXVII.) 

 shows striking differences, and to group the rock types illustrated in the memoir by 

 microphotographs (Plates IV., XXXVIII.) under the one generic term " amphibolite " 

 without modification is scarcely justified. The mode of occurrence, too, is different, 

 because the " feather amphibolite " is not found (p. 62) as inclusions in the granite 

 gneiss. The scientific term "amphibolite" will have much decreased value if made to 

 include dissimilar things. 



The amphibolite containing orthorhombic amphibole, which is described as a product 

 of the extreme alteration of limestone by a granitic magma, is also an abnormal type 

 and grouped among the amphibolites without a consideration of its chemical composition. 

 It contains abundant gedrite and garnet associated with cordierite, quartz, biotite, 

 iron ore, rutile, and sillimanite. No felspar is present, and the rock could be better 

 described as a cordierite-bearing garnet gedrite schist. Though it is not stated whether 

 the rock is schistose or massive, the microphotograph (Plate XXXIX.) shows a schistose 

 character. Anthophyllite has been found in dyke rocks in the Lewisian gneiss*, but 

 this mineral composition suggests a chemical composition quite unlike an igneous rock. 

 No actual evidence of the nature of the origin of this rock is stated, but its composition 

 could be expected to be that which would result by the recrystallisation of an impure 

 magnesian limestone. 



'^British Geological Survey Memoir, 1907, op. oit., p. 49. 



