THE METAMORPHIC ROCKS OF ADEL1E LAND. STILL WELL. 103 



In another part of the memoir we have noticed a description (p. 127) of the nodular 

 granite of Pine Lake, township of Cardiff. The granite is metamorphic, and shows 

 in part curious nodules which average 2in. to Sin. in diameter. The nodules are 

 composed chiefly of quartz, muscovite, and sillimanite. Muscovite and sillimanite 

 are especially metamorphic minerals, and it is therefore likely that the nodules are 

 formed under metamorphic conditions. The chemical composition of the nodules is 

 decidedly not that of an igneous rock, and yet they occur in granite ! It seems, 

 therefore, feasible to appeal to metamorphic differentiation. The nodules have been 

 described as sometimes aggregating and forming foliated veins, and in this case the whole 

 vein must be looked upon as a metamorphic differentiate. The instance is in some 

 respects analogous to the courts of crystallisation that have been described in No. 143 

 from Cape Denison, but in the Canadian instance the product is coarser and more readily 

 recognised as metamorphic. 



Summary. 



Summing up, it seems that the positive statements by Adams and Barlow in the 

 memoir, and by Adams in his published summaries, concerning the origin of amphibolites. 

 are not sufficient. It cannot be considered as proved that normal amphibolites can be 

 formed by the alteration and recrystallisation of impure calcareous sediments. The 

 evidence that has been presented in detail can be shown to be explicable on the 

 supposition that the amphibolites are recrystallised basic intrusive rocks. It is suggested 

 that unrecognised examples of metamorphic diffusion have been interpreted as proof 

 of the change of limestone to amphibolite. The amphibolite inclusions in the gneiss 

 have not been shown not to be the alteration of primary basic differentiation magma 

 products or the isolated fragments of fractured and disrupted basic igneous dykes. 

 The authors have stated (p. 62) that it is a remarkable fact that the amphibolites 

 originating in the two very diverse manners often resemble one another so closely that 

 it is impossible to tell them apart. Such resemblance is to be expected on our alternative 

 hypothesis of igneous intrusion. 



4. HIGHLANDS OF NEW JERSEY. 



The results of the Cape Denison observations are also applicable to the phenomena 

 described by Fenner in the Highlands of New Jersey*. Fenner describes hornblendic 

 bands which may show (p. 598) remarkable continuity and parallelism and which may 

 pinch out for a distance, recontinue after an interval, and appear as knots or inclusions. 

 There is no mashing or granulation. There is frequently a sharp contact between the 

 " inclusions " and granite, although an interlocking of crystals may occur. Fenner 

 states (p. 601) that it appears in some cases that the basic minerals at the immediate 

 contact have become involved in the granitic magma without losing their parallelism, 

 so that a perfect transition is produced from the hornblende or biotite gneiss with 



" Mode of Formation of Certain Gneisses in the Highlands of New Jersey," C. N. Fenner, Journ. Geol., voL XXII., 

 pp. 594-612, 694-702. Under this head numbers in brackets refer to this publication. 



