I. I ntroduction . In the Summary of Progress of the Geological Survey for 1898 (pp. 104–11), Sir Archibald Geikie & Mr. Strahan, in a description of a ‘Volcanic Group in the Carboniferous Limestone of North Somerset,’ published for the first time the evidence for the contemporaneity of these igneous rocks. The authors refer briefly to the basalt and associated tufts at Spring Cove, immediately to the west of the town of Weston, and describe in more detail the basalt-lava and beds of tuff interbedded with the fossiliferous limestone along the ridge of Middle Hope, 2 miles north of Weston. At the time of the publication of this account, I had already made a detailed examination of these rocks in the field, and of microscopic and chemical preparations ; but as my results seemed in general accord with those of the authors named, especially in regard to the rocks of Middle Hope, I felt that little or nothing was to be gained by the publication of my work as a whole. In the rocks at Spring Cove, Weston, however, there appear to me to be points of considerable interest which are only briefly touched upon, or not mentioned at all, in the account to which I have referred, and I therefore venture to submit some additional observations in regard to them. II. General Description of the Rocks . The basalt at Spring Cove, immediately north of Weston Pier, runs obliquely to the high road, and is exposed from low-water mark along the foreshore