When the other cave men saw what Ai-Ab had done, they made fires in their caves, as well, and if one went out, they would borrow some hot coals from a neighbour. Once, however, during the rainy season, when all the wood was wet, they came very near losing their precious fire, so after that, the head man of the tribe told two old men, who were not strong enough to go out after food, to watch the fire and keep it going in a cave by themselves, which they filled with dry wood, and while one watched, the other slept, and in this way the fire never went out. The Fire seemed something sacred to them, and after a time, they got into a way of coming to the cave and saying prayers or making wishes to it, and thought of it as a sort of god. And in worshipping Fire, or the Sun, or any of the other great forces that helped them, the cave men, although they did not know it, were really worshipping God, who made all these things for their use. CHAPTER X THE FIRST BOAT TUL the Swift, and Ni-Va the Fish, were always together. It made them angry not to be allowed to leave the valley with the hunting men, so they planned in secret to make a trip by themselves. The weather was warm, now, for the spring had come, and they talked a great deal about the country outside the valley, where they had never been, and planned to see it. Tul had a fine spear he had made, with a long sharp lizard's tooth for a point. He had found the tooth among some bones in the lower end of the valley, where the lake had once been, and was very proud of it. Ni-Va's spear was tipped with bone, for spearing fish. He had never killed one yet, but he wanted to very much, for he heard the older men talking about it, when they came back from the great marsh. He also carried a small stone-bladed axe, while Tul took a flint knife, such as the men used for skinning animals. Both had leather sandals, and belts from which the hair had been scraped with sharp stones. They took no food with them when they went, and they did not tell any one that they were going, but one morning, very early, they crept out of the cave, before the sun was up, and made their way down the banks of the stream toward the lower end of the valley. When they came to the waterfall, they climbed down over the path of rocks worn smooth by the feet of many hunting parties, and soon found themselves on the wide marshy plain which stretched out as far as their eyes could reach. The river, after it emptied into the plain, spread out into many small winding streams, and that was what made the great marsh they saw before them. Off to the right, however, they found that the ground was higher, so instead of following the paths through the marsh which the hunting parties usually took, the two boys circled off toward the higher ground, as the walking was easier that way. The ground was hard, and full of flat stones, between which the coarse grasses were springing up covering the Earth with a fresh coat of green.