[174]
we perceived the basaltic column to the left, very irregular in its form, but in hardness and texture similar to those of Staffa in the Hebrides, and the Giant's-Causeway in Ireland. Incorporated in it is crystallized quartz, approaching in appearance to chalcedony. This column is part of a vast un-shaped basaltic mass which stretches north and south about sixty yards; covered with a stratum of clay that has very much the look of scoria, and seems to indicate volcanic effects in these parts. It is of great thickness, and considerable dip. The toadstone, which ranges under the limestone in strata of different thickness, from three or four fathoms to above one hundred, and contains in its pores chalcedony, zeolite, and calcareous spar, occurs in the immediate neighbourhood of the basalt, but is sufficiently distinguishable from it by being less hard and compaft; indeed, there are great varieties of both, but especially of the toadstone, from a dark brown to a light-coloured ochre full of fine green spots. Opposite to this basalt is the mountain of limestone; and like most of the others in this neighbourhood, stratified; the strata separated by little beds of clay. The admirable lime burned from the stone renders the barren declivities that compose the mountains around productive of oats, the only grain attempted to be sown
