Yonder, on the one hand, are the Orkneys, rising dim and blue over the foam-mottled currents of the Pentland Frith; and yonder, on the other, the far-stretching promontory of Holborn Head, with the line of coast that sweeps along the opposite side of the bay; here sinking in abrupt flagstone precipices direct into the tide; there receding in grassy banks formed of a dark blue diluvium. The fields and dwellings of living men mingle in the landscape with old episcopal ruins and ancient burying-grounds; and yonder, well-nigh in the opening of the Frith, gleams ruddy to the sun,--a true blood-colored blush, when all around is azure or pale,--the tall Red Sandstone precipices of Dunnet Head. It has been suggested that the planet Mars may owe its red color to the extensive development of some such formation as the Old Red Sandstone of our own planet: the existing formation in Mars may, at the present time, it is said, be a Red Sandstone formation. It seems much more probable, however, that the red flush which characterizes the whole of that planet,--its oceans as certainly as its continents,--should be rather owing to some widely-diffused peculiarity of the surrounding atmosphere, than to aught peculiar in the varied surface of land and water which that atmosphere surrounds; but certainly the extensive existence of such a red system might produce the effect. If the rocks and soils of Dunnet Head formed average specimens of those of our globe generally, we could look across the heavens at Mars with a disk vastly more rubicund and fiery than his own. The earth, as seen from the moon, would seem such a planet bathed in blood as the moon at its rising frequently appears from the earth.