secondary strata, and of an entirely new character. Their upper edge is generally even, and their faces quite perpendicular, but they rarely exceed 60 feet in height. They are most remarkable for the very extraordinary number of the caves which are found in them, and of the fissures by which they are intersected. These are rarely of any great dimensions, but they are so numerous that they sometimes occupy nearly as much space in a given distance as the solid parts of the cliffs themselves. I have counted twenty or thirty of them in the course of a few hundred yards, the interstices having a resemblance to the ends of detached walls placed in a parallel manner. They are the consequences of trap veins which have been washed away, but as they present important geological facts, I shall describe them more particularly hereafter. Few of these caves have been explored, but one of them has acquired historic celebrity from the circumstance of its having been among the numerous places of temporary refuge inhabited by Prince Charles during his concealment. Another has recently become the cause of great resort to Sky on account of its stalactitic concretions; and it is popularly distinguished by the name of the Spar Cave: it lies on the estate of Mr. Macalister, and is too well known to require any more accurate description of its locality. This cave is accessible from the cliffs above, for a short time only at low water, but by means of a boat it may be visited at any time in moderate weather, or with the wind of the shore. The entrance is little less striking than the cave itself, and to the admirer of the picturesque it presents a scene even more attractive. It is formed by a fissure in the cliff, extending for a considerable way and rising into high and parallel walls on each side, its gloom being partially illuminated by reflected light, and its silence scarcely disturbed by the wash of the surf without. A narrow and obstructed opening leads unexpectedly into the cave: hence for a distance of
