The Island of Longstone is at the head of the group, and serves as a sort of vanguard, and is, perhaps, the most dangerous of all. A gloomy collection of black rocks, full of crevices worn by the action of the winds, the waters, and the tempests, it does not nourish a single plant; not an atom of soil adheres to its surface; it is naked and barren; its steep sides bristle with cockle shells which encrust the rock.