Bentley felt the cold chills racing along his spine as he listened to the old man's flow of words. He behaved well, but Bentley could feel in spite of that, that there was a hidden current of menace in the old man's behavior. He wished that Ellen would keep him talking, would somehow make sure of his identity. Perhaps the same thought was in her mind, for it had scarcely come to him when the girl spoke again. "Before he disappeared Professor Barter wrote a learned treatise on--" "I am Professor Barter, I tell you, young woman. But if you wish proof the title of the treatise was 'The Language of the Great Apes.'" Ellen turned quickly to Bentley and nodded. She was satisfied that the man was the person he claimed to be. He didn't ask how Ellen happened to know about him, and Bentley himself considered the proof entirely lacking in conclusiveness. Anyone might know about the last treatise of Barter. However, they could but await developments. They followed Barter along the trail. Now and again apes challenged from the jungle, and Barter answered them with that strange laughter of his, or with a flow of gibberish that was like nothing human. Bentley shivered. Barter, by his laughter, was identifying himself to the great anthropoids. But with his gibberish was he actually conversing with them? "This experiment of yours," said Bentley when the period of silence became unbearable, "--won't you tell us about it?" The old man cackled. "You'll know all about it--soon! You'll know everything, but the secret will still rest with Caleb Barter. Do not be too curious, my friends." "We are anxious to reach civilization, Professor," said Bentley, deciding to be placative with the old man. "Perhaps you can arrange for guides for us?" Barter laughed. "I could not permit you to leave me for some time," he said. "I want you to witness my experiment. The world would never believe me without the evidence of reliable witnesses." Barter laughed again. * * * * * They entered a clean clearing which was a riot of flowers. At the further edge was a log cabin of huge proportions. The whole thing had a decidedly homely appearance, but it was a welcome sight to the castaways. There were cages in which strange birds chattered shrilly in their own language at sight of the three. A pair of tame monkeys chased each other on the roof of the house, whose corners were almost hidden by climbing vines whose growth one could almost see. Barter led the way at a swift walk across the clearing and into the house. Bentley gasped. Ellen Estabrook exclaimed with pleasure. The reception room was as neat as though it received the hourly attentions of a fussy housewife. It was cozily furnished, yet it was evident that the furniture had been made on the spot of rough wood and skins of various animals. Deep skin rugs covered the floor and walls. There were three doors giving off of the reception room, all three of which were closed.