“Why is it that there is no bituminous coal of any account in Ireland?” This is a question which I have often been asked by well-informed people, and the answer is comprised in the one descriptive word “Denudation.” In truth, there is no reason why, at one period of our geological history, the great mass of the bituminous coal-bearing strata occurring in England should not have extended over what is now Ireland; but, strange to say, while this store of inestimable wealth was being preserved in England, and covered by the New Red Sandstone and probably Tertiary rocks, the adjoining portion of the earth's crust was being gradually raised from beneath the sea, and wellnigh effectually denuded of its carbonaceous covering. Ireland, therefore, for the most part, presents an older geological surface than England, especially over the areas now occupied by the Devonian and Carboniferous rocks; and I believe that all we have now remaining to us in the upper portion of the latter, is some of the basal beds of the English coal-measures, represented by three thin layers of bituminous coal, capping the mountains at either side of Lough Allen, in the counties of Roscommon and Leitrim, and extending into the Co. Sligo.

The most important coal-beds of the Arigna district, or those which are being worked at present, occur to the west of Lough Allen, and near the summits of the mountains of Kilronan and Altagowlan; the former being 1081 feet, and the latter 1377 feet above the sea, having the valley of the Arigna river between them. From an examination of these coal-fields, which I made in the month of March, 1862, I am enabled to add some information to that which we already possess regarding them, which, I have no doubt, will be acceptable to those who are interested in the subject of the Irish bituminous coals.