In the distance rose low hills. Toward these the craft was headed. As it approached them, a great promontory might have been seen from its deck, stretching out into what had once been a mighty ocean, and circling back once more to enclose the forgotten harbour of a forgotten city, which still stretched back from its deserted quays, an imposing pile of wondrous architecture of a long-dead past. The countless dismal windows, vacant and forlorn, stared, sightless, from their marble walls; the whole sad city taking on the semblance of scattered mounds of dead men’s sun-bleached skulls—the casements having the appearance of eyeless sockets, the portals, grinning jaws. Closer came the flier, but now its speed was diminishing—yet this was not Ptarth. Above the central plaza it stopped, slowly settling Marsward. Within a hundred yards of the ground it came to rest, floating gently in the light air, and at the same instant an alarm sounded at the sleeper’s ear. Carthoris sprang to his feet. Below him he looked to see the teeming metropolis of Ptarth. Beside him, already, there should have been an air patrol. He gazed about in bewildered astonishment. There indeed was a great city, but it was not Ptarth. No multitudes surged through its broad avenues. No signs of life broke the dead monotony of its deserted roof tops. No gorgeous silks, no priceless furs lent life and colour to the cold marble and the gleaming ersite. No patrol boat lay ready with its familiar challenge. Silent and empty lay the great city—empty and silent the surrounding air. What had happened? Carthoris examined the dial of his compass. The pointer was set upon Ptarth. Could the creature of his genius have thus betrayed him? He would not believe it. Quickly he unlocked the cover, turning it back upon its hinge. A single glance showed him the truth, or at least a part of it—the steel projection that communicated the movement of the pointer upon the dial to the heart of the mechanism beneath had been severed. Who could have done the thing—and why? Carthoris could not hazard even a faint guess. But the thing now was to learn in what portion of the world he was, and then take up his interrupted journey once more. If it had been the purpose of some enemy to delay him, he had succeeded well, thought Carthoris, as he unlocked the cover of the second dial, the first having shown that its pointer had not been set at all. Beneath the second dial he found the steel pin severed as in the other, but the controlling mechanism had first been set for a point upon the western hemisphere. He had just time to judge his location roughly at some place south-west of Helium, and at a considerable distance from the twin cities, when he was startled by a woman’s scream beneath him.