Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/719

Rh least, one important value—that they will strictly define the limits of the coal-bearing tracts.

I propose in this paper to show to what extent the British Carboniferous rocks have their representatives in Ireland; after which I will endeavour to point out the significance, as bearing on the question of classification, of that remarkable series of beds already referred to, known as the "Gannister Beds" of the late Professor Phillips; and lastly I shall state the conclusions which seem to me to arise from the above considerations, and which seem to render desirable a fresh mode of classifying the Carboniferous beds, with a view to the introduction of a "Middle Carboniferous series" to include all the strata lying between the Mountain Limestone and the Middle Coal-measures, and including the Yoredale Beds, Millstone Grit, and Gannister Beds.

Arrangement of the Subject.—In considering the subject of the Carboniferous beds of Ireland, it will be desirable to divide it into three portions, taking:—I. The Southern Coal-districts; II. The Northern Coal-districts; and III. The Ballycastle Coal-district in Co. Antrim, which differs from both. But before doing so it will be desirable, for the sake of comparison, to state the succession of the strata in the British Carboniferous districts, as now very generally recognized ; and for the purpose of easy reference I have arranged them into stages.