Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/117

 that of Glen Tilt in aspect and composition, renders it probable that like this it lies in mica slate, forming beds parallel to and interstratified with that rock: that the others have similar relations to the primary rocks, we should have concluded on general geological principles, had we not already seen that the white marble of Sky which has given rise to this discussion belongs to the secondary strata.

We have now to examine the white marbles which have been discovered in our own islands, for the purpose of comparing their relative properties and the value which they are likely to possess in sculpture. I am unfortunately unable to give any account of those found in Ireland, neither having seen their places, nor being possessed of any specimens.

That which has been found at Cape Wrath in Scotland, is of a grain much larger than even the Parian, and is consequently useless for the purpose of sculpture; and this indeed is by much the most common character of the Scottish specimens. Those of Blairgowrie, of Glenavon, and of Balahulish, are all equally characterized by this large sparry texture, and are all equally unlit for sculpture, however applicable to the purposes of architecture. The marble of Iona has been long since exhausted, and consequently requires no particular notice: however valuable from the purity of its colour and compactness of its texture, yet the uncertainty of its splintery fracture before the chisel, (that tool without which no spirited work was ever finished,) combined with its great hardness would probably have rendered it useless in the arts, even if it were still to be procured.

In a paper on Assynt I have already described the white marble of that district: it is of a very close texture, and although it contains