The fractures or rents frequently visible in the glittering cliffs of the icebergs are of an emerald green, and look like patches of beautiful fresh sward on cliffs of chalk; while pools of water of the most exquisite sapphirine blue shine resplendent on their surface, or leap down their craggy sides in luminous cascades. Even in the night they are readily distinguished from afar by their effulgence; and in foggy, hazy weather, by a peculiar blackness in the atmosphere. As the Greenland Current frequently drifts them to the south of Newfoundland, and even to the 40th or 39th parallel of latitude, the ships and steamers crossing between Europe and America sometimes meet them on their track. To come into collision with them is certain destruction; and it is probable that some of those ill-fated vessels which have left their harbours in safety, but have never since been heard of,--as, for example, the steamer _President_,--have perished through this cause. But if they are sometimes dangerous to the mariner, they often prove his security. As most of their bulk lies below the water-surface, they are either carried along by under-currents against the wind, or else from their colossal size they are able to defy the strongest gale, and to move along with majestic slowness when every other kind of ice is driven swiftly past them. And hence it happens that, when the wind is contrary, the whaler is glad to bring his ship into smooth water under their lee. In describing the difficulties of his passage through the loose and drifting ice near Cape York, and the broken ice-fields, Dr. Kane records the assistance he derived from the large icebergs, to which he moored his vessel, and thus was enabled, he says, to hold his own, however rapidly the surface-floes were passing by him to the south. Yet anchoring to a berg brings with it an occasional peril. As we have already said, large pieces frequently loosen themselves from the summit or sides, and fall into the sea with a far-resounding crash. When this operation, “calving,” as it is called, takes place, woe to the unfortunate ship which lies beneath! All ice becomes excessively brittle under the influence of the sun or of a temperate atmosphere, and a single blow from an axe will suffice to split a huge berg asunder, burying the heedless adventurer beneath the ruins, or hurling him into the yawning chasm.