The quiet of the afternoon was broken by a piercing childish yell which lacked no element of earnestness. Ab leaped to his feet and was by the youngsters in a moment. He saw the terrified Beechleaf standing, screaming still, with a fat arm outheld, from which dangled a little shaft of wood which had pierced the flesh just deeply enough to give it hold. Bark stood looking at her, astonished and alarmed. Understanding nothing of the circumstances, and supposing the girl's hurt came from Bark's careless flinging of sticks toward her, Ab started toward his brother to administer one of those buffets which were so easy to give or get among cave children. But Bark darted behind a convenient tree and there shrieked out his innocence of dire intent, just as the boy of to-day so fluently defends himself in any strait where castigation looms in sight. He told of the queer plaything he had made, and offered to show how all had happened. Ab was doubtful but laughing now, for the little shaft, which had scarcely pierced the skin of Beechleaf's arm had fallen to the ground and that young person's fright had given way to vengeful indignation and she was demanding that Bark be hit with something. He allowed the sinner to give his proof. Bark, taking his toy, essayed to show how Beechleaf had been injured. He was the most unfortunate of youths. He succeeded but too well. The mimic arrow flew again and the sound that rang out now was not the cry of a child. It was the yell of a great youth, who felt a sudden and poignant hurt, and who was not maintaining any dignity. Had Bark been as sure of hand and certain of aim as any archer who lived in later centuries he could not have sent an arrow more fairly to its mark than he sent that admirable sliver into the chest of his big brother. For a second the culprit stood with staring eyes, then dropped his toy and flew into the forest with a howl which betokened his fear of something little less than sudden death. Ab's first impulse was to pursue his sinful younger brother, but, after the first leap, he checked himself and paused to pluck away the thing which, so light the force that had impelled it, had not gone deeply in. He knew now that Bark was really blameless, and, picking up the abandoned plaything, began its examination thoughtfully and curiously. The young man's instinct toward experiment exhibited itself as usual and he put the splinter against the string and drew it back and let it fly as he had seen Bark do--that promising sprig, by the way, being now engaged in peering from the wood and trying to form an estimate as to whether or not his return was yet advisable. Ab learned that the force of the bent twig would throw the sliver farther than he could toss it with his hand, and he wondered what would follow were something like this plaything, the device of which Bark had so stumbled upon, to be made and tried on a greater scale. "I'll make one like it, only larger," he said to himself.