In one of the skirmishes with slave caravans some of our Sarians took a number of Sagoth prisoners, and among them were two who had been members of the guards within the building where we had been confined at Phutra. They told us that the Mahars were frantic with rage when they discovered what had taken place in the cellars of the buildings. The Sagoths knew that something very terrible had befallen their masters, but the Mahars had been most careful to see that no inkling of the true nature of their vital affliction reached beyond their own race. How long it would take for the race to become extinct it was impossible even to guess; but that this must eventually happen seemed inevitable. The Mahars had offered fabulous rewards for the capture of any one of us alive, and at the same time had threatened to inflict the direst punishment upon whomever should harm us. The Sagoths could not understand these seemingly paradoxical instructions, though their purpose was quite evident to me. The Mahars wanted the Great Secret, and they knew that we alone could deliver it to them. Perry's experiments in the manufacture of gunpowder and the fashioning of rifles had not progressed as rapidly as we had hoped--there was a whole lot about these two arts which Perry didn't know. We were both assured that the solution of these problems would advance the cause of civilization within Pellucidar thousands of years at a single stroke. Then there were various other arts and sciences which we wished to introduce, but our combined knowledge of them did not embrace the mechanical details which alone could render them of commercial, or practical value. "David," said Perry, immediately after his latest failure to produce gunpowder that would even burn, "one of us must return to the outer world and bring back the information we lack. Here we have all the labor and materials for reproducing anything that ever has been produced above--what we lack is knowledge. Let us go back and get that knowledge in the shape of books--then this world will indeed be at our feet." And so it was decided that I should return in the prospector, which still lay upon the edge of the forest at the point where we had first penetrated to the surface of the inner world. Dian would not listen to any arrangement for my going which did not include her, and I was not sorry that she wished to accompany me, for I wanted her to see my world, and I wanted my world to see her. With a large force of men we marched to the great iron mole, which Perry soon had hoisted into position with its nose pointed back toward the outer crust. He went over all the machinery carefully. He replenished the air tanks, and manufactured oil for the engine. At last everything was ready, and we were about to set out when our pickets, a long, thin line of which had surrounded our camp at all times, reported that a great body of what appeared to be Sagoths and Mahars were approaching from the direction of Phutra.