The psalm ended, our boat with most of its passengers retraces its course and is rowed back to the steamer,--the Bailie and I, however, having first disembarked and clambered up to the rough gallery, with a view of imitating the parties who are pursuing their explorations on foot. This gallery, or causeway, which runs along the eastern side of the cave, is about two feet in width, and consists of the bases of broken pillars, whose dark purple hexagons, cemented together by crystallizations or a white calcareous deposit, form a rough mosaic flooring. The inequality of its surface, and the fact that the stones are worn smooth and slippery by the action of the sea, render it a very precarious pathway; and as soon as we have proceeded far enough to gratify our curiosity and obtain satisfactory points of view, we are content to abandon the enterprise of penetrating to the remotest depths, preferring to reserve our time for a ramble over the exterior surface of the island. Emerging from the cavern and skirting its eastern side, we still find ourselves stepping from hexagon to hexagon over a massive bed of refuse material, and gazing upward at the columnar wall on our left which upholds the table-land of the island. No traveller, however ignorant or inappreciative of science, can fail to realize the immense interest which these evidences of some great natural convulsion must possess for the geologist; and a knowledge of the recent geological discoveries in this and other of the Western Islands is not needed to impress us with the conviction that treasures of truth are beneath and around us everywhere, waiting to be revealed. But we have not the key, nor can we pause to pick the lock.