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V. 



ON THE GROWTH OF CRYSTALS IN THE CONTACT-ZONE 

 OF GRANITE AND AMPHIBOLITE. 



By GRENVILLE A. J. COLE, M.R.I.A., F.G.S., 

 Professor of Geology in the Royal College of Science for Ireland. 



Read April 10. Ordered for publication April 12. Published Mat 1, 1905. 



In 1893 Professor W. J. Sollas presented to the Royal Irish Academy 

 his conclusions on the relations of granite and gabbro at Barnavave ; 

 and the first publication of them^ marks an important step in the 

 petrography of the British Isles. Though his work at Carlingford is 

 still met in certain quarters by the assertion of a theory of strictly 

 local differentiation, yet the immense change of opinion that has 

 taken place in regard to the nature and extent of contact-meta- 

 morphism has been continuously in favour of his views. The school 

 of Michel-Levy, Barrels, and Lacroix, despite the serviceable criticism 

 which has been directed on it, has proved its contentions in area after 

 area, and notably in those regions where other modes of thought have 

 long prevailed. 



While the occurrence of basic igneous masses traversed by veins 

 of granite may in many cases be due to a separation of material in a 

 single caldron down below, this separation remains, in the vast 

 majority of cases, a pure assumption. It has been fashionable — and 

 the term may be used with all seriousness — to suggest a common 

 origin for all the igneous rocks of a district, without regard for the 

 endless chances offered for the admixture of any given rock with 



1 ** On the Origin of Intermediate Varieties of Igneous Rocks by Intrusion and 

 Admixture, as observed at Barnavave, Carlingford," Rep. British Assoc., 1893 

 (1894), p. 765. The full statement of results is in Trans. R. I. Acad., vol. xxx. 

 (1894). 



R.I.A. PROC, VOL. XXV., SEC. B.] X 



