"But don't you think there is a chance of our getting them back?"
Frank's face grew grave.
"Of course we are going to try every means in our power, but once in the hands of that scoundrel Muley-Hassan it is doubtful if we ever see them again. There is only one thing for us to do."
"And that is—?"
"To get back to the Moon Mountains at once. But we have no gasoline."
This was a stunning blow; in the excitement their of fuel had not occurred even to the farseeing Frank. They had had, as our readers know, to leave most of their gasoline at the Moon Mountains in order to lighten the aeroplane. Without it they could not move an inch in their air-craft. Harry tested the tank. Only a few paltry gallons remained—not enough to drive the aeroplane ten miles.
As the boys stood, struck dumb by the realization of the disaster that had overtaken them, Ben Stubbs, who had been down to the river bank, reappeared.
"Look here!" he exclaimed, holding out at arms length a long white cloak. One glance at the garment was enough—it was an Arab article of dress. There was no further doubt about it, then. Muley-Hassan and his men had carried off Billy and Lathrop.
"But that's not the most extraordinary part of it," went on Ben; "while there are half a dozen of the Arabs' canoes down there, there are a lot of others, that must have belonged to a bunch of natives from their shiftless look—and I could see the bare imprint of the savages' feet in the mud, coming after the Arabs had trod around there."
This was a new mystery. Apparently, then, a tribe of cannibals had been on the trail of the Arabs who had carried off their two young companions. This could only mean one thing, that they meant to punish the Arab slave-dealers for some outrage and, while this would have been quite satisfactory to the boys under other conditions, as things were it meant that there would be a fight in which both Lathrop and Billy would probably be seriously wounded, if not killed. How wrong this surmise was we know, and it serves to show how very wide of the mark it is possible for the constructors of a theory to steer.