"True enough--why not?" scoffed Jack. "Let's keep them to slide down hill on. Do you realize that the professor says we are still three hundred miles from Nigatuk and the mouth of the Coleville?" "That is the reason I suggest traveling by sled instead of dragging them behind us," said Mark, unruffled. "I've got an idea." Jack stopped then. When Mark said he had an idea his chum knew it was probably worth listening to, for Mark possessed an inventive mind. "We will have to strap the robes and blankets on our shoulders if we abandon the sleds," Mark Sampson said, quietly. "Let us utilize them to better advantage and save the sleds in addition." "How?" asked Phineas Roebach. "Make sails of the robes and propel the sleds, riding on them, too," declared Mark. "Such wind as there is is pretty steadily at our backs. Why not?" "Why not, indeed?" shouted Jack. "Hurrah for Mark!" "A splendid thought, my boy," declared the professor. Poles were cut for masts and Andy rigged a stout one on each sled, with cross-pieces, or spars, to hold the blankets spread as sails. Andy even rigged sweeps for rudders with which to steer these crude ice-boats. They got off under a fair wind as soon as the river was passable again, and ran fifty miles straight away without stopping. This was a great lift toward the end of their journey, and all plucked up courage. The Shanghai seemed to share the feeling of renewed hope, and began to crow again. They were obliged to rest over the sunlit day, as before, for the ice became covered with a sheet of water an hour after sunrise, and they were afraid the sled runners would cut through and let them all down into the stream. However, they saw very well that--barring some unforeseen accident--they would be able to reach the mouth of the river before the last of their scanty food supply ran out. All the way now they looked for signs of the traders from Aleukan, who had started for the coast ahead of them. These men, however, seemed to have left the rough path along the bank of the Coleville, and were either traveling on the ice ahead, or had struck off into the wilderness. When they set sail for a second time the heavens, for the first time since the final cataclysm that had shot them off into space, were beginning to be overcast. "There is so great an evaporation while the sun is shining that I am surprised that we have not had snow before," the professor observed. "These mists rising from the earth and the bodies of water would become heavy nightly rains in any other climate. Here they will result, now that the atmosphere has become saturated with moisture, in heavy hail storms and much snow. It is nothing more than I have looked forward to." The remainder of the party were not so much interested in the natural phenomena as he, however; they looked forward mainly to reaching some safe refuge--some place where there were supplies and the fellowship of other human beings.