This “pack-ice,” however, is the great obstacle to Arctic exploration; and frequently it presents a barrier which no human enterprise or skill can overpass. At times, it has been found possible to cut a channel through it, or it breaks up and opens a water-way through which the bold adventurer steers. In 1806, Captain Scoresby forced his ship through two hundred and fifty miles of pack-ice, in imminent peril, until he reached the parallel of 81° 50’,--his nearest approach to the Pole. In 1827, Sir Edward Parry gained the latitude of 82° 45’, by dragging a boat over the ice-fields, but was then compelled to abandon his daring and hazardous attempt, because the current carried the ice southward more rapidly than he could traverse it to the north. In warm summers this mass of ice will suddenly clear away and leave an open streak of silver sea along the west coast of Spitzbergen, varying in width from sixty to one hundred and fifty miles, and reaching as high as 80° or 80° 30’ N. latitude. It was through this channel that Scoresby bore his ship on the expedition to which we have just alluded. A direct course from the Thames, across the Pole, to Behring Strait is 3,570 geographical miles; by Lancaster Sound it is 4,660 miles. The Russians would be saved a voyage of 18,000 geographical miles could they strike across the Pole and through Behring Strait to British Columbia, instead of going by Cape Horn. [Illustration: CHANNEL IN AN ICE-FIELD.] Ice-fields, twenty to thirty miles across, are of frequent occurrence in the great Northern Ocean; sometimes they extend fully one hundred miles, so closely and solidly packed that no opening, even for a boat, intervenes between them; they vary in thickness from ten to forty or even fifty feet. At times these fields, which are many thousand millions of tons in weight, acquire a rapid rotatory motion, and dash against one another with a fury of which no words can give an accurate idea. The reader knows what awful results are produced by the collision of two railway trains, and may succeed, perhaps, in forming some feeble conception of this still more appalling scene when he remembers the huge dimensions and solidity of the opposing forces. The waters seethe and foam, as if lashed by a tremendous tempest; the air is smitten into stillness by the chaos of sounds, the creaking, and rending, and cracking, and heaving, as the two ice-fields are hurled against each other. [Illustration: “NIPPED” IN AN ICE-FIELD.] Woe to the ship caught between these grinding masses! No vessel ever built by human hands could resist their pressure; and many a whaler, navigating amid the floating fields, especially in foggy weather, has thus been doomed to destruction. Some have been caught up like reeds, and flung helplessly upon the ice; others have been overrun by the ice, and buried beneath the accumulated fragments; others have been dashed to pieces, and have gone down suddenly with all on board.