One thing, however, he did discover, a very great thing indeed, although Ma-Ya did not know, then, how great it was. He found out how to make the wind move his boat, by using a sail. And like nearly all of the discoveries of the early people, it was made by accident. Sometimes, in the middle of the summer, the sun on the water became so hot and burning that the men paddling the boat could hardly stand it. It was warmer in summer, in those days, than it is now, and the blazing rays of the sun often made the handles of the paddles so hot the men could scarcely hold them. To keep off the sun, Ma-Ya would lash some upright poles to the sides of the boat and hang from them a cover, or awning, made of grass-cloth. One day, while paddling up the broad mouth of the river, a squall came up behind them, and striking the awning, turned it sideways, like a sail. At once the boat began to fly through the water so fast ahead of the squall that the paddlers found their work of no use, and drew in their paddles. Ma-Ya set up a great shout and pointed to the sail. His companions did not understand at first, but when they saw the boat sailing along without their paddles being used, they too understood, and also began to shout. Not knowing how to stop, they sat doing nothing while the heavy squall carried them far up the river and finally drove them ashore on a sand bar. Ma-Ya was delighted. He lashed a stronger upright pole near the front of the boat, with another pole across it, from which he hung a large piece of grass matting, and the next time they went out, the wind took them along in fine fashion. Coming back, however, they had to use their paddles, for Ma-Ya did not know how to sail against the wind, nor did the sea people discover how to do this for a very long time. Ma-Ya was a great inventor. He gave to the sea folk boats and sails. But he was never able to cross the Great Water. When he died, he called his children and grandchildren about him, and told them to keep on trying, and some day they would find the land of the flying birds. CHAPTER XVII THE CONQUERORS MANY hundreds of years had passed, since Ka-Ma and his wife Tula left the valley, and the tribe of the cave people had grown very large. The whole valley was now filled with them, and they had spread out over the hills which surrounded it, and far into the country beyond. The head man, or chief of the tribe lived in the largest of the rock caves, and had many wives and children. Those who had gone outside the valley formed separate tribes of their own, each with a smaller chief, but all of them were under the rule of the head chief. The rocks all about the valley sides were honeycombed with caves, and as the tribe grew, and there were not enough caves for all, these bands of adventurers would leave the valley, and make new homes of their own on the hillsides, and in other valleys beyond them.