“‘I made inquiries. But from none could I learn more than I have told. Slave traders come and go. Within the memory of the oldest of us, reaching back fifteen or twenty years, this stranger had come once each year to the slave marts. For how long before that he had come, I do not know. None ever had pursued him into the east, to see whence he came. That is all.’

“So,” concluded Ali, “I have since been thinking. That man was a big chief among the Athensians, if not the greatest leader himself. Who he is, how he has acquired a knowledge of many languages, I do not know. That he and his people are white, of course, is not so marvellous, as the Berbers and Arabs are white races, and so are the Kabyles who inhabit the mountains of Morocco.”

Mr. Hampton nodded. “An offshoot of the white race which has maintained a splendid isolation in those mountains south of us, undoubtedly. Yet how this leader acquired his knowledge of civilization puzzles me. And why, Ali, are these annual expeditions to Gao made? And only the strongest slaves selected?”

Ali shrugged. “It is for Allah to say,” he replied, and lapsed into silence. Evidently, for that night, the loquacious Ali had said all he intended to say.

His story, however, furnished Mr. Hampton with food for reflection and on several occasions he discussed the matter with the boys. Especially, did he note that the slave trader’s account, as repeated by Ali, betrayed that the Athensians possessed rifles. This made them more dangerous enemies.

“In fact, boys,” he concluded, one day, after a lengthy discussion, “I have become pretty firmly convinced that these Athensians cannot be peacefully approached as had been our original intention. Therefore, we shall have to abandon the expedition. I shall wait a few days more to see whether this man recovers sufficiently to be moved, and then, if we can gain nothing from him in response to questioning, we shall set out to return.”

“What,” cried Jack in dismay, “leave without attempting to learn what we came all this way to discover?”

His father nodded gravely. “Professor Souchard and Ben Hassim have been slain,” he said. “Sheik Abraham and all his tribe have been carried into slavery. Quite evidently, the Athensians want no intruders and we would only imperil our lives by pursuing our investigations further.”

“But what’ll you do, Dad?”

“I shall lay the matter before the French and British governments. Now that the Great War is over, it may receive attention. They can send embassies, supported with sufficient power to compel recognition. Then, it is possible, the Athensians will yield on being shown no menace to their freedom threatens, and may admit scientists to their mountains to study the ruins of Korakum and the library of Athensi, if such really exists.”