Through that low door they dragged us in our space-walkers, and across the adjoining compartment toward one of the great upright cylinders resting there. In another moment the Neptunians had pulled us inside the door of that cylinder into its dark opening, and I saw the one who had given the orders following, with a half-dozen of his fellows. The others were dispersing to the other cylinders, and in a moment the door of our own slid clanging shut behind us. Then there was a hissing and throbbing of strange machinery in the dark interior of the cylinder about us, and at the same moment the leader of the Neptunians motioned to us to emerge from our space-walkers, having removed their own glowing ball-heaters. I think that both Marlin and I hesitated for a long moment before complying with that command, yet we saw that upon us still were trained the tubes of the four Neptunians who guarded us, so reluctantly we threw open the lower doors of the space-walkers and emerged from them. As we did so, forgetful for the moment of the strange creatures about us, we gazed in amazed interest around us. The huge cylinder's interior, we saw, was divided into a half-dozen compartments by metal floors or ceilings set at intervals of ten or twelve feet from its bottom to its top. A light metal ladder ran up through openings in all of the those floors or divisions, and up that ladder now a few of the many-limbed Neptunians were hurrying toward the upper compartments. We ourselves were standing, with the Neptunian leader of the red-circle insignia, in the lowest or bottom compartment of the cylinder, his four tube-armed guards and a half-dozen green disk-bodied monsters about us. That lowest compartment held great gleaming-cased mechanisms, from which came the throbbing that we had already heard, and that was so exactly similar to the throb of our space-flier's generators as to remove all doubt but that these were the similar generators of the cylinder. As our eyes roved about them the Neptunian leader uttered a staccato command, at the same time pointing with one of his seven limbs, up toward the ladder. His meaning was unmistakable, and at once Marlin and I stepped toward the ladder and began to climb upward on it, the tubes of the four watchful guards just beneath us as they followed. As we passed up that ladder, through the upper sections of the cylinder's interior, I saw vaguely the things within those sections.