Variolite of the Lleyn, and associated Volcanic Rocks

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Abstract
I. Introduction. Although much has now been written about the igneous rocks of the Lleyn, especially in Mr. Alfred Harker's valuable essay, yet, as he expressly excludes most of the district of which I am treating, and as it receives only slight mention in other writings, some of the most interesting examples from the part coloured on the Geological Survey map as ‘metamorphosed Cambrian’ have remained unnoticed. I have therefore put together a few notes on the rocks which I have collected in the course of many visits during the last six years. The specimens not hitherto described include a variolite —a spherulitic, somewhat basic rock. A short summary of its occurrence will at least serve to show that we have on the mainland of our island (apart from any example in Anglesey) a mass of variolitic diabase with characters very similar to those of German and Alpine localities, corresponding closely in many particulars with that graphically described by Mr. J. W. Gregory from the Fichtelgebirge, and also, although perhaps less markedly, with that of the Durance, as shown by Prof. Cole and Mr. Gregory. I am limiting myself mainly to the rocks which can be clearly recognized as igneous, and have given only a short notice of others in the last section of the present paper. The extensive masses of a rather indefinite and schistose character in many parts are ashy or agglomeratie, but include crushed examples of igneous origin. The exact nature of some rocks, however, even when

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