He solved his problem in a very simple fashion. He dug a hole and he covered it with branches and leaves and a little grass. A bear came by and fell into this artificial cave. Man waited until the creature was weak from lack of food and then killed him with many blows of a big stone. With a sharp piece of flint he cut the fur of the animal's back. Then he dried it in the sparse rays of the sun, put it around his own shoulders and enjoyed the same warmth that had formerly kept the bear happy and comfortable. Then there was the housing problem. Many animals were in the habit of sleeping in a dark cave. Man followed their example and searched until he found an empty grotto. He shared it with bats and all sorts of creeping insects but this he did not mind. His new home kept him warm and that was enough. Often, during a thunderstorm a tree had been hit by lightning. Sometimes the entire forest had been set on fire. Man had seen these forest-fires. When he had come too near he had been driven away by the heat. He now remembered that fire gave warmth. Thus far, fire had been an enemy. Now it became a friend. A dead tree, dragged into a cave and lighted by means of smouldering branches from a burning forest filled the room with unusual but very pleasant heat. Perhaps you will laugh. All these things seem so very simple. They are very simple to us because some one, ages and ages ago, was clever enough to think of them. But the first cave that was made comfortable by the fire of an old log attracted more attention than the first house that ever was lighted by electricity. When at last, a specially brilliant fellow hit upon the idea of throwing raw meat into the hot ashes before eating it, he added something to the sum total of human knowledge which made the cave-man feel that the height of civilization had been reached. Nowadays, when we hear of another marvelous invention we are very proud. "What more," we ask, "can the human brain accomplish?" And we smile contentedly for we live in the most remarkable of all ages and no one has ever performed such miracles as our engineers and our chemists. Forty thousand years ago when the world was on the point of freezing to death, an unkempt and unwashed cave-man, pulling the feathers out of a half-dead chicken with the help of his brown fingers and his big white teeth--throwing the feathers and the bones upon the same floor that served him and his family as a bed, felt just as happy and just as proud when he was taught how the hot cinders of a fire would change raw meat into a delicious meal. "What a wonderful age," he would exclaim and he would lie down amidst the decaying skeletons of the animals which had served him as his dinner and he would dream of his own perfection while bats, as large as small dogs, flew restlessly through the cave and while rats, as big as small cats, rummaged among the left overs.