Steadily I drove northward, in a daze of fevered pain. It seems an eternity when I look back upon it, but it could not have been many hours. Automatically I kept in the shelter of the purple trees. At last I emerged on the edge of a great plateau, covered with the green vegetation, many miles across. On the south and west, from whence I had come, it was surrounded by purple trees--by the thick purple wood in which I had halted. On the north the great cliffs towered up to the sharp-edged scarlet roof, four miles above. It was strange to see the blue walls cut off so abruptly by the red. The sky was like a red lake seen inverted in a mirror. Those blue cliffs were hardly a dozen miles away now--I had to bend back my head to see the sharp line where the roof cut them off. On the east side of that plateau, there was--nothing! Beyond, lay the pit of Xath, with the faint ruby mist above it, filled as always with the wavering reflections of violet flames. And a half dozen miles before me, on the brink of that pit, stood--Mutron! The City of the Sleepers! A strange scene it was! A city of silver metal! Domes and towers and pyramids of argent whiteness! Vast incredible machines! Huge and oddly wrought structures! Titanic cubes and cylinders and cones! All of gleaming silver! The city shone with a cold light. It was as weird, as unearthly, as a dead city of the moon! It had the silent, ghostly gleam of moonlight! It was wrapped in mystery, clad in frozen fear! And the city was not idle. Those vast amazing machines were moving. Silver globe-ships were drifting in silent haste above it! And ever and anon, one of them dropped over the rim, into the pit of Xath, or one floated unexpectedly up out of that abyss! As I stood there in the Omnimobile, in the shadow of the last of the purple trees, my heart grew sick again with doubt. What, indeed, could I, with my puny machine, do against the great science that that city of mystery represented? The men of one once mighty empire were now slaves to it! What hope was there for me? Was not the human race, like the bison or the dodo, about to fall before a superior power? But there would be no turning back. I saw to it that all the machinery was in order, and returned to the conning-tower. Before me was the instrument board that controlled the electric arc and the rocket tubes, as well as the machinery. I started the hydrodyne generators at their full capacity, and then threw the switch. As the half-million horse-power went through the resistance coils, jets of super-heated steam roared out of the nozzles, condensing in white rushing clouds. The terrific force of the jets uprooted the purple trees, and the machine vibrated to the mighty blast. I was hurled into the air. With a speed that swiftly increased to many hundreds of miles per hour, I hurtled the broad plain, and over the ghostly white city of silver--and into the abyss!