In the spring, when the ice breaks up and is hurled irresistibly down stream on the swollen current, the same effect is reproduced on a vastly increased scale. Then the upper river breaks first, and a sudden rise of water from some great tributary starts the ice over the still solid barrier below. The huge cakes slide, jam, push, and crash over the still unbroken ice sheet, until they are piled in a vast gleaming mass seventy or eighty feet in height, from a quarter of a mile to one mile in length, and extending from bank to bank. This mighty gorge must give way at length, and when it does it goes with a roaring fury that is terrifying and grand beyond description. After grinding and tearing onward for several miles, or perhaps less than one, the furious impulse is again checked by another solid barrier, which must in turn be broken down and swept away, its added weight giving increased energy to the mighty force. So the ice crashes its resistless way down the whole Yukon Valley to Bering Sea, two thousand miles distant, sweeping everything before it, mowing down vast areas of forest, submerging islands, tearing out banks, and leaving everywhere traces of its terrible progress in the shape of huge ice cakes, weighing many tons, stranded high above ordinary water level. Although Phil Ryder and his companions were not to witness this grand exhibition of one of nature's mightiest forces, they were sadly inconvenienced and delayed by the uncomfortable fashion in which their frozen highway had been constructed some months earlier. If they could have left the river and followed along its banks, they would have done so; but this was out of the question, not only on account of their rugged character, but because on their timbered portions the snow lay many feet in depth, while from the river it had been so blown by strong north winds that for long stretches the ice was barely covered. This enabled the sledge men to walk without snow-shoes, which was a great comfort to all three, but especially to Jalap Coombs, who had not yet learned to use the netted frames with "ease and fluency," as Phil said. To this light-hearted youth the sight of his sailor friend wrestling with the difficulties of inland navigation as practised in arctic regions afforded a never-failing source of mirth. A single glance at Jalap's lank figure enveloped in firs, with his weather-beaten face peering from the recesses of a hair-fringed hood, was enough at any time to make Phil laugh. Jalap on snow-shoes that, in spite of all his efforts, would slide in every direction but the one desired, and Jalap gazing at a frosty world through a pair of wooden snow-goggles, were sights that even sober-sided Serge found humorous.