The men stood still for a moment, for they did not know what to do. Fine snowflakes were now falling and the dark clouds threatened a heavy storm. But the men were hungry and they were not ready to give up the hunt at once. "Listen!" said Bighorn, as a low rumbling sound came from the upper valley. The Cave-men put their ears to the ground and heard a sound like distant thunder. As they listened it came nearer and nearer and the ground seemed to shake. The Cave-men were not afraid. They knew what the sound meant. The bison, too, knew what it meant. They knew that winter was coming, and that it was time for them to be gone. They knew that the laggard herds were racing with the storm. And so the sentinels of the scattered herds gave signals to the bison. And before the Cave-men were on their feet, the bison had started toward the ford. Louder and louder the rumbling sound grew as the great herd galloped on. The snow was now falling thick and fast, and a cold northwest wind was blowing. But in spite of the wind and the snow, the Cave-men pressed on toward the ford. Bighorn still hoped to get a bison as the great herd passed. By the time the herd reached the ford, the wind had become a strong gale. The air was so thick with the snow that it nearly blinded the men. Then Bighorn turned and said to the men, "We must find a shelter from the storm." The bison, too, tried to find a shelter. Some of them hugged up closely to the sheltered side of the cliffs. Others sought cover in the ravines. But many could find no protection, so they turned about and faced the storm. [Illustration: "_But many could find no protection, so they turned about and faced the storm._"] The Cave-men wished they were safe at home, but they dared not go through the storm. They huddled together and felt their way to a spot where the snow did not drift. There they lay down in the snow and waited for the storm to cease. #THINGS TO DO# _Name some bird that migrates. Tell all that you know about the way it migrates._ _When you go out to play, show how the bison migrated in warm weather. Show how they migrated in cold weather._ _Show in your sand-box where the deep drifts would be. Show places where the snow would not drift. If you cannot be sure about where the drifts would be, see if you can find out by watching the storms during winter._ _If the Cave-men are buried in the snow, how do you think they can get air to breathe? How can they tell when the storm is over?_ XIX THINGS TO THINK ABOUT What do you think those who stayed in the cave will do during the storm? Can you think of any way by which they could get food? Did you ever walk on snowshoes? How do you think people came to make snowshoes? _How Antler Happened to Invent Snowshoes_