Jim did not like the feeling of nervousness he had in realizing how deep they were below the desert and how narrow and oppressive were the canyon walls. He was glad that the strenuous day sent them off to bed and to sleep as soon as they had finished supper. They were up at dawn. Charlie's purpose was to work down the river, surveying as he went until he found a level where the river would flow through a tunnel out onto the valley. And this level, too, must be at a point where construction work was possible. The river was incredibly rough and treacherous. From the first they packed everything in waterproof bags. The canvas canoes were impractical. The river was full of hidden rock and by the third day the second canoe was torn to pieces and they were depending on rafts made from the air mattresses. After the canoes were gone, they spent practically all the daylight in the water, swimming or wading and towing or pushing the mattresses. The water was very cold but they were obliged to work so hard that they scarcely felt the chill until they made camp at night. Jim discovered that a transit could be used in a cauldron of water or on a peak of rock where a slip meant instant death or clinging to steep walls that threatened rock slide at the misplacing of a pebble. One arduous task was the locating of a camp at night. The second night in the camp they were lucky. They found a broad ledge in a spot that at first seemed hopeless, for the blank walls appeared here almost to meet above the deep well of water. There was a little driftwood on the ledge and they had a fire. The following two nights they were less fortunate. The best they could find were chaotic heaps of fallen rock on which to lay their mattresses, and they slept with extreme discomfort. The fifth day was a black day. They were swimming slowly behind their laden mattresses through deep, smooth black water when, without warning, the river curved and swept over a small fall into heavy rapids. Instantly the mattresses were whirling like chips. The two men fought like mad to tow them to a rock ledge, the only visible landing place the crevice had to offer. But long before this haven was reached the mattresses were torn to shreds and Jim and Charlie were glad to reach the ledge with their surveying instruments and two bags of "grub." Here they sat dripping and exhausted. It was nearly dark. Night set in early in the canyon. They dared not try to look for a better camping ground that night. The ledge was just large enough for the two of them, with what remained of their dunnage. Charlie grinned. "Welcome to our city. Well, it's as good as a Pullman berth at that." "And no harder to dress on," said Jim, standing up carefully and beginning to peel off his wet clothes. "I guess if we wring these duds out and rub with alcohol, they won't feel so cold." Charlie rose and began to undress gingerly. "You can stand up to make your toilet," he said, "which is more than the Pullman offers you."