Poets never dreamed of anything more beautiful than these crystal vaults, which sometimes appear of a deep ultramarine blue, and at others of an emerald-green tint. One could fancy them the favourite haunts of mermaids and mermen, and of every kind of sea monster; but, in truth, no animal ever enters them; the water dashing in and out through their icy caves and tunnels makes a sonorous but rather monotonous and melancholy sound. In moderately calm weather many of these excavated bergs assume the form of gigantic mushrooms, and all kinds of fantastic outlines; but as soon as a breeze of wind arises they break up into little pieces with great rapidity. Icebergs are met with on every side of the Southern Pole, and on every meridian of the great Antarctic Ocean. But such is not the case in the North. In the 360th meridian of longitude which intersects the parallel of 70° N., icebergs spread over an extent only of about fifty-five degrees, and this is immediately in and about Greenland and Baffin Bay. Or, as Admiral Osborn puts it, for 1,375 miles of longitude we have icebergs, and then for 7,635 geographical miles none are met with. This fact is, as the same writer calls it, most interesting, and points strongly to the probability that no extensive area of land exists about the North Pole; a supposition strengthened by another fact, that the vast ice-fields off Spitzbergen show no signs of ever having been in contact with land or gravel. [Illustration: FALL OF AN ICEBERG.] Another difficulty which besets the Arctic navigator is the “pack-ice.” In winter, the ice from the North Pole descends so far south as to render the coast of Newfoundland inaccessible; it envelops Greenland, sometimes even Iceland, and always surrounds and blocks up Spitzbergen and Novaia Zemlaia. But as the sun comes north this vast frozen expanse, which stretches over several thousands of square miles, breaks up into enormous masses. When these extend horizontally for a considerable distance they are called _ice-fields_. A _floe_ is a detached portion of a field; a large area of floes, closely compact together, is known as _pack-ice_; while _drift-ice_ is loose ice in motion, and not so firmly welded as to prevent a ship from forcing her way through the yielding fragments. [Illustration: IN AN ICE-PACK, MELVILLE BAY.]