On and upward--and now as we shot on, with the swarming cylinders hurtling hotly after us in wild pursuit, with the throb of our generators and the roar of air about us thundering in our ears, with the wild tumult of the massed Neptunians on Triton's surface coming dully up to us from beneath, Marlin and I were gazing with tense eyes ahead and upward. The great opening, the great sliding section of the roof down through which we had come--that was our one chance to escape from Triton. I knew that unless we could win through that opening, out of Triton's enclosed world, we were doomed. On and on we went--our eyes still upon the vast roof overhead in search of that opening in it, when suddenly Marlin cried hoarsely in my ear, and pointed ahead. And there from ahead were rushing toward us other scores of cylinders, other swarms of racing cylinders answering the spreading alarm, while still others were shooting up from below toward us! From behind, from ahead, from beneath, the cylinders' swarms were converging upon us in that moment, and as instinctively I slowed our cylinder's mad rush I looked upward, toward the great roof---- "The opening-section!" I cried suddenly. "But it's closed against us!" For there above, indeed, was that great circle in the vast transparent roof that we knew could be slid aside and opened by its Neptunian guards in the bright-lit little cage-room suspended beside it. My one hope had been that in our stolen cylinder we might deceive those guards of the great orifice into opening it for us to pass. But that hope was gone. Behind and below and before us were the pursuing swarms of cylinders and the Neptunians in the cage-room above knew that something was wrong, and had not opened the great circle for us. There were other similar circles, similar opening-sections, in Triton's roof, but it was too late now to seek them because from all about us the swarming, racing cylinders were rushing upon us. In another moment their rays would shatter us! I heard Marlin, beside me, utter a low exclamation of utter hopelessness as those cylinders rushed upon us, held our own cylinder for the moment motionless there in mid-air beneath the great roof's opening-section, and then suddenly reached toward the control-studs, even as Marlin's hoarse cry was sounding beside me. "The end, Hunt!" he was crying. "The cylinders are almost upon us--and the opening-section is closed!" "The end maybe--but not this way!" I shouted fiercely, at the same moment sending the cylinder flashing straight upward with all its speed. "Hold to your chair, Marlin--_we're going to smash through that opening-section of the roof_!"