Four granitic intrusions in south-eastern Scotland

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The Silurian strata of Mid Lothian, East Lothian, and Berwickshire were invaded in early Devonian times by numerous igneous masses. Most of these intrusions are quartz-porphyrites, but a few are of more granitic texture, notably those of Broad Law in Mid Lothian, of Priestlaw in East Lothian, and of Cockburnlaw and Lamberton Beach in Berwickshire. These four igneous masses form the subject of the present communication. The Cockburnlaw intrusion will be considered first as it is the largest in area and shows the greatest variety of rock-types. All the rock names employed in the description are used in accordance with the recommendations made by the Committee on British Petrographic Nomenclature,1 with the following exceptions:— When the names granite and syenite are enclosed by inverted commas their old field significance is implied. The term hyperite is only used with particular reference to the Galloway rocks described under that name by Sir J. J. H. Teall. Cockburnlaw. The ‘ granite ’ mass which forms the eminences of Cockburnlaw and Stoneshiel Hill lies some three miles to the north of Duns and is admirably dissected by the River Whiteadder. W. Stevenson2 and Sir Archibald Geikie 3 have fully described the field relations of the intrusion, and a further detailed account is thus rendered superfluous. The igneous rock covers an area of about one square mile and is intrusive into grey wackes of Upper Silurian age which have undergone intense thermal metamorphism. At Cockburn Mill (see Fig. 1) the igneous rock