The observations recorded in this paper have reference chiefly to the coast-sections at St Abb's Head and Coldingham Shore. The district was geologically surveyed some twenty-five years ago by my brother, Dr A. Geikie, and subsequently described by him in the Memoirs of the Geological Survey. Since the publication of that memoir, no further examination of the ground in question appears to have been made. During the past summer I visited the neighbourhood, principally for the purpose of studying the igneous rocks which are so well exposed in sea-coast sections. At the date of the Government Survey of Eastern Berwickshire the aid of the microscope had not yet been invoked by field-geologists for the purpose of determining rock-species, and I was therefore curious to compare the igneous rocks of that region with those of similar age which I had studied elsewhere in Scotland, and more especially with the bedded and intrusive porphyrites and tuffs of the Cheviot Hills and the Sidlaws.