Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/182

 yielding to the action of the elements. I remarked formerly that these strata, however separated in position, were analogous to the white sandstone which occurs at Portree and elsewhere in the north-eastern portion of Sky, and is accompanied by limestone, shale, and coal. Having then but little acquaintance with that part of the island, the description of these strata was avowedly left imperfect, and it is now necessary to supply the deficiency.

As I remarked not long ago that a description of the neighbouring islands was requisite to throw light on the obscure connection of the red sandstone with the limestones of Strath and of Sligachan, so I may here repeat that the history of the uppermost strata of Sky, which I now propose to sketch, would be materially elucidated by that of Rasay. But as the description of this island would be here inadmissible, I can only say generally, that the deficiencies of connection which occur in Sky, and which compel me on many occasions to have recourse to inference and analogy, are in a great measure supplied by the structure of that island, which, while it is more continuous and accessible, is at the same time such as to leave no doubt respecting the identity of strata separated at present by a narrow arm of the sea.

It has been seen that as the gryphite limestone immediately follows the red sandstone, so it is succeeded by the calcareous white and grey sandstone of Strathaird. The same succession may be traced in a more circuitous manner by comparing the strata of Sligachan, Scalpa, and Rasay. But it is apparent on considering the map of Sky, that the portion of these uppermost strata which occupies the district of Trotternish is separated from the gryphite limestone by an interval, partly the result of the direction of the shores, and partly produced by the intervening mass of trap and syenite. There is no actual contact of the two to be seen, but the