On the Alleged Conversion of Crystalline Schists into Igneous Rocks in County Galway

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Abstract
Introduction. The theory of the metamorphism of aqueous deposits into granite and other igneous rocks has been maintained by most Irish geologists, and is set forth with much detail in the elaborate memoirs of the Irish Geological Survey* on the district between Galway and Westport. It therefore seemed to me, after some preliminary work in Donegal†, that the Connemara region would probably afford rich material for the determination of the question. In this hope I was not disappointed; but while working at the relations between the igneous and the metamorphic rocks, another problem, the origin of the schists themselves, began to emerge. The result of my inquiries was a singular reversal of the theory I was examining. I found, not that the igneous rocks had been formed out of schists, but that some, at least, of the schists had been formed out of igneous rocks. The Galway region has, indeed, been most fruitful in suggestion, and has supplied me with a clue to the origin of some of the less complex gneisses. I have to acknowledge my obligations to Profi Bonney, F.R.S., who has been kind enough to look through my microscopic slides, and to give me his opinion on critical points. In discussing the origin of the igneous rocks, it will be desirable to state briefly the evidence upon which the theory of the Irish Survey has been based. I will give the chief points, as far as possible, in the words of the Survey Memoirs† Of the granite

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