"If they'd only conserved their resources," declared von Hofe, "they might be running out slaves yet. But it was more than slavers, my friend." He had advanced to the door of a hut and now drew back. "It is not a good place to stay. There are skeletons--perhaps of the plague." "That's more like it," exclaimed Charlie, as they rode on. "Mowbray said that he had found the Arab place plague-swept, and had burned the whole thing, prob'ly for fear of infection. That would account for the absence of human life a whole lot better than by laying it all on the slavers." There was another thought running through Charlie's head, however--something of which no one had yet spoken openly. He wondered if Schoverling had paid any attention to Mowbray's narrative of the big cache of ivory "underneath the left gate-post." He had been long enough in Africa to know the tremendous value of tusks, and resolved to talk things over with Jack at the first opportunity. Von Hofe, meanwhile, had been thinking along more practical lines. "If we had a large party, Schoverling, and plenty of time, we could make money," he announced suddenly, and pointed to the hills on their left. "Those hills must be of old volcanoes. Why should the Arabs have come so far to settle here in a terrible land? Not for slaves or ivory alone. No. In these lakes and rivers there is gold." "What!" exclaimed the explorer sharply. Then, more slowly, "I shouldn't wonder if you're right, Doctor. I'd like to take a little trip with a washing-pan up through there! If that is so, as it well might be, there'd be some rich pickings for the taking. However, we're here for elephant first and last, and I'm not inclined to linger with this outfit." This excited the boys hugely, but both realized that on this expedition there would be small opportunity for any gold-hunting, even if the supposition should prove to be true. The sight of that big python and the giant buffalo had been a good indication of what they might expect if they lingered long hereabouts, and the fate of Mowbray's expedition was vivid in their minds still. The day passed with no exciting feature, as all kept close to the slow advance of the cattle and wagon. The Masai spread out fearlessly enough, and brought in enough game for the party. That terrific battle with the herd of buffalo had made great inroads on their stock of ammunition, and the explorer cautioned them not to waste a shot in useless hunting. No sign of the expected lake appeared during the afternoon, and in the evening they camped in a little valley between two kopjes, beside a waterhole that welled out and sank again almost immediately into the thirsty earth. "We'll need those traps here, I guess," declared Charlie when the outspanning was going on. "Prob'ly every one of these water-holes is pretty well frequented by animals, so we can look out for visitors. Who's on guard to-night?"