During a visit to the Giant's Causeway in the month of September, 1857, I made a few notes and sketches on the spot, having reference more particularly to the determinating of the stratigraphical position of the Causeway itself, and to get if possible a clear idea of the structure of the exposed cliff-sections of the basalts in the immediate neighbourhood. On comparing my observations with an account of the causeway and the adjoining coast given by the Rev. John Dubourdien in his statistical survey of the county of Antrim in 1812, I was struck with the discrepancies which exist between them, the author's idea being that the bed of Basalt forming the Causeway extended eastward to Portmoon, a distance of two-miles (page 46), and that the whole of the strata are parallel to each other. These suppositions are, as far as I am aware of, adopted by all subsequent writers on the Causeway; and as they are errors, a transcript of my notes may not be unacceptable to the readers of the “Geologist;” they tend at least to illustrate more fully the structure of the Basaltic deposits to which I allude, and are a few additional facts added to our present information on this interesting subject.