At the northern entrance of Robeson Channel the breadth of navigable water became much contracted, until off Cape Sheridan the ice was observed to be touching the shore. In Robeson Channel, except where the cliffs rose precipitously from the sea, and afforded no ledge or step on which the ice could lodge, the shore-line was noted to be fronted, at a few paces distance, by a nearly continuous ragged-topped “ice-wall,” from fifteen to thirty-five feet high. It was broken only off the larger ravines. After proceeding some distance north it became evident that their sailing season was rapidly coming to an end. Captain Nares, after a thorough investigation, found that he had to winter in a somewhat exposed place, no harbour being available. He had rounded the north-east point of Grant Land, but instead of finding a continuous coast-line, leading far towards the north, as expected, found himself on the border of an apparently extensive sea, with impenetrable ice on every side. The ice was of most unusual age and thickness, resembling in a marked degree, both in appearance and formation, low floating icebergs rather than ordinary salt-water ice. It has now been termed the “Sea of Ancient Ice.” Whereas ordinary ice is usually from two feet to ten feet in thickness, that in the Polar Sea, in consequence of having so few outlets by which to escape to the southward in any appreciable quantity, gradually increases in age and thickness until it measures from 80 to 120 feet, floating with its surface at the lowest part fifteen feet above the water-line. Strange as it may appear, the extraordinary thickness of the ice saved the ship from being driven on shore, for, owing to its great depth of flotation, on nearing the shallow beach it grounded, and formed a barrier, inside which the ship was comparatively safe. When two pieces of ordinary ice are driven one against the other and the edges broken up, the crushed pieces are raised by the pressure into a high, long, wall-like hedge of ice. When two of the ancient floes of the Polar Sea meet, the intermediate, lighter, broken-up ice which may happen to be floating about between them alone suffers; it is pressed up between the two closing masses to a great height, producing a chaotic wilderness of angular blocks of all shapes and sizes, varying in height up to fifty feet above water, and frequently covering an area of upwards of a mile in diameter. Captain Nares mentions pieces being raised by outward pressure and crashing together which must have weighed 30,000 tons! A ship between such opposing masses would be annihilated in an instant.