To the north-west are found the highest range of pillars. Here they are bare to their base, and the stratum beneath is visible, as it rises several feet above the water. The surface of it is rough, with frequent large pieces of stone sticking in it, as if half immersed. The base, when broken, appears to be composed of many heterogenous parts, and much resembles lava. Many of the floating stones are of a similar substance with the pillars, a coarse kind of basalt, less beautiful than that of the Giant’s Causeway: the color is a dirty brown. The whole of this stratum dips gradually to the south-east. The thickness of the stratum of lava-like matter below the pillars, the hight of the pillars, and the thickness of the superincumbent stratum, at three different places westward of the mouth of the cave, beginning with the corner pillar of the cave, are described as follows by Sir Joseph Banks: Feet. In. Feet. In. Feet. In. Stratum below, 11 0 17 1 19 8 Hight of pillars, 54 0 50 0 55 1 Stratum above, 61 6 51 1 54 7 The stratum above the columns is uniformly the same, consisting of numberless small pillars, bending and inclining in all directions, sometimes so irregularly, that the stones can only be said to have an inclination to assume a columnar form; in others more regularly; but never breaking into, or disturbing the stratum of large pillars, whose tops keep everywhere an uniform line. On the opposite side of the island is a cavern, called Oua-na-scarve, or the Cormorant’s cave; here the stratum under the pillars is lifted up very high, and the pillars are considerably less than at the north-west side. Beyond, a bay cuts deep into the island, rendering it not more than a quarter of a mile across. On the sides of this bay, especially beyond a little valley, which almost divides the island, are two stages of small pillars, with a stratum between, exactly resembling that above, formed of innumerable little pillars shaken out of their places, and leaning in all directions. Beyond this, the pillars totally cease. The rock is of a dark-brown stone, without regularity, from the bay along the south-east end of the island; beyond which, a disposition to columnar formation is again manifested, extending from the west side, but in an irregular manner, to the bending pillars first described. OTHER GROTTOS AND CAVERNS. There are few countries which have not to boast of a variety of natural excavations; and these have, from their extent, structure, and the curious phenomena they exhibit, in the formation of petrifactions, &c., been at all times objects of popular attention. Among those particularly deserving of notice are the following.