They crossed one wide but shallow stream by throwing brush into the water, which raised the sleds enough to keep the loads dry. At another point a considerable delay was caused by a steep hill which the trail mounted at one side of the valley in order to avoid a difficult ford. Uncle Will pointed out a tree at the top of this hill, the bark of which was worn off in a circle a few feet above the ground, remarking that the Mysterious Thirty-six had evidently rigged a block and tackle there, and drawn up their sleds by a long rope. After following a rough, wooded ridge for perhaps a quarter of a mile, the trail led down again to the river flats. Each day brought them nearer the great range of snowy mountains, at the foot of which lay Pleasant Camp. There they would turn to the right and cross the mountains, which were in British territory, by the Chilkat Pass. The boys thought they had never seen a more beautiful valley than that of the Klaheena. In every direction were glistening peaks, their bases clothed with green spruce forests, which here and there spread out over the levels near the river, where they showed a sprinkling of bare-boughed poplars, willows, and alders. At one of their camps, where a small stream known as Boulder Creek flowed into the Klaheena from the north, the weather turned suddenly cold, with a bitter wind which the huge camp-fire hardly tempered. It was so cold in the tent that the boys slept in their Mackinaw coats, which usually they removed and rolled up for pillows. Nestling deep down into the blankets, they were warm enough, except when one or the other turned over, disturbing the coverlets, and drawing a blast of cold air over their necks and shoulders. They did not take the precaution to pull their caps over their ears, relying on the protection of the blankets, but unfortunately, while they slept, their heads became entirely uncovered. Both boys found their ears slightly frost-bitten and very painful in the morning. When they attempted to draw on their shoe-packs, which had been left outside the tent, the leather tops and lacings were frozen so stiffly that it was necessary to thaw them out before a fire. Mr. Bradford's pocket thermometer registered three degrees below zero when they crept out into the crisp morning air and with numb fingers took down the tents and made ready the sleds. "This is about as chilly as we shall have it," said Uncle Will, as he deftly turned the bacon in the frying-pan; "and it's nothing to what I had on my first trip in. Fifty below is a nice bit colder than three. It's too late in the season for any more of that, and I'm not sorry. We shall be unlucky though, if we don't reach the Alsek River before the ice breaks up, for cross-country travelling in that region is a hard proposition." "How far away is the Alsek?" asked David. "About thirty miles on the other side of the Pass." "And where do you suppose the mysterious gentlemen are now?"