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CHAPTER VI. LIMESTONES OF IRELAND. The Carboniferous limestone occupies the greater part of the central plain of Ireland, and lias been largely used both in tlie ancient and modern buildings of this region. It is divisible into three members, i. Lower limestone ; 2. Calp, a Middle limestone ; 3. Upper limestone; the whole attaining a thickness from 2000 to 3000 feet. The marbles from this formation have already been described. As a building stone there is much variety. The lower and upper divi sions produce a good, crystalline, greyish limestone, sometimes dolomitic, and in a few instances oolitic. This later variety occurs along the shores of Killala Bay; and has been used in the construction of the beautiful, but ruined, Abbey of Moyne, where the sharpness of the sculpturing is still retained. 1 The Calp, or Middle division, consists of dark carbonaceous or earthy grey limestone, alternating with beds of dark shale and chert, and is very irregular in the stratifica tion. The Upper limestone resembles the lower, but is more evenly bedded and flaggy. These general 1 Mr. Gr. Wilkinson, Anc. Arch, of Ireland, p. 37.