And with mutual hand-wavings and dipping of colours the two craft separated, the _Walrus_ bearing up to intercept her boats, and the _Flying Fish_ heading northward at a speed of about twenty knots. For about a couple of hours the adventurous voyagers were able to maintain that speed; but toward noon they found themselves once more surrounded by ice; and they had no choice but either to materially reduce their speed and slowly thread their way through narrow and tortuous channels, or once more take flight into the air. They chose the latter alternative; and for the next two hours the flying ship sped northward through Smith's Sound, for the most part over an unbroken field of pack-ice which, to any ordinary vessel, would have opposed an utterly impassable barrier. At two o'clock in the afternoon, however, the Greenland shore suddenly trended to the north-eastward; and after following it for a short time the ice once more began to be intersected with water channels, short and narrow at first, but wider as they proceeded, until at length they found themselves once more able to descend in a water lane some four miles in width. "And now," said the professor, as they were nearing a bold rocky headland on their starboard bow, "we are about to be introduced to one of _the_ sights _par excellence_ of the Arctic regions." "What is it?" was the question which burst simultaneously from the lips of his three companions. "Wait and see," answered the professor, nodding mysteriously. Sure enough, the moment that the _Flying Fish_ rounded the point a magnificent spectacle burst upon the travellers' enraptured gaze. It was neither more nor less than an immense cliff of the clearest crystal ice, towering some three hundred feet above the water's edge, and extending so far northward along the coast that its northern extremity lay far below the horizon. It was the magnificent Humboldt Glacier. The afternoon sun was shining full upon its rugged face, causing the enormous mass to flash and gleam like a gigantic diamond. As they coasted slowly along, at a distance of about half a mile from its face, the dazzling flashes of light were reproduced one after the other, changing rapidly from one colour to another through every conceivable tint of the rainbow, until the beholders' eyes fairly ached with the contemplation of so much splendour, all of which was reflected with the most charming variation in the mirror-like surface of the deep still water below. The wind had died away to a dead calm, as if to give the bold explorers an opportunity of witnessing this unrivalled sight to the best advantage; and every now and then the still air resounded with the sharp rifle-like _crack_ which told that, though apparently so motionless and solid, hidden forces were at work within the heart of the glacier, slowly but surely tending to its ultimate dismemberment.