A valuable monograph on “The Glacial Geology of the North-West of Ireland” (Proc. R. Irish Acad., xxxvi, 1924, pp. 174–314, pls. 8 and 9) by Professor J. K. Charlesworth describes the complex glacial phenomena of Tyrone. He endorses the main conclusion of my paper on the Irish Bskers (Phil. Trans. Roy. Soc., 1920, vol. 210, pp. 115–51) that they are usually deposited along the margin of a glacier, and are not due to subglacial rivers. The two works further agree in their rejection of the long advocated theory that Irish glaciation was dominated by a huge dome of ice which accumulated as snow above the Central Plain and over-rode the surrounding mountains. That view, due to Hull (Physic. Geol. and Geogr. Ireland, 1878, p. 228), has in later years been advocated, amongst others, by Mr. T. Hallissy (Proc. R. Irish Acad., xxxi, part 7, 1914, p. 9), and also by him in association with the late Professor Cole (Handb. Reg. Geol, Ireland, 1924, p. 46; Cole, ibid., British Isles, 1916, p. 328). The lines of ice movement marked on my map (op. cit., 1920, p. 143) illustrating the distribution of the Irish eskers are fundamentally inconsistent with the traditional theory; I am therefore glad to find that theory emphatically rejected by Professor Charlesworth. He adduces convincing evidence that the ice was formed on the mountains and flowed from them on to the plains. In two minor questions Professor Charlesworth differs from the views of my paper. I remarked (op. cit., p. 133) that the eskers of Tyrone are “different in several respects” from those of the Central Plain. I did not state the differences as I mentioned the Tyrone eskers only in reference to the subglacial formation of eskers; and as they gave no support to that process, I briefly referred to them as having had the same marginal origin as the typical eskers of the Central Plain.