They have worn the rock smooth, so that it glistens like glass in the morning sun, for, as if aware of the folly of urging on its regiments of well-mounted cavalry to come dashing in upon the wild white-maned sea-horses, or the more sober lines of heavy infantry in uniforms of green and blue, the sea has for countless ages bombarded Carn Du with stone-shot in the shape of great boulders.  These have ground and polished off every scrap of seaweed, every barnacle, limpet, and sea-anemone, leaving the rock all smooth and bare, while the boulders lie piled to the east in a heap, where the waves that try to take the rock in flank leap amongst them, and roll them over higher and higher, to come rumbling down as if they were tiny pebbles instead of rounded masses of granite and spar-veined stone a quarter, half, and a hundredweight each.