part of the ship seem "down." And down it was, too, by reason of the pull of the great globe they were approaching. But the roaring exhaust up ahead was checking their speed; Chet measured and timed the apparent growth of the Moon-disk and nodded his satisfaction at their reduced speed.

"This will stop us," he said. "I didn't know but we would have to swing off, shoot past, and return under control. But we're all right, and there is the place we are looking for—the big ring of Hercules, the level floor of rock inside it. And over at one side the smaller crater—"

He was gazing entranced at the mammoth circle that had been a volcano's throat—the very one he had seen flashed on the screen. He moved the control to open a side exhaust and change their direction of fall. He was still staring, with emotions too overwhelming for words, and Spud O'Malley was silent beside him, as the great ring spread out and became an up-thrust circle of torn, jagged mountains some thirty or more miles across and directly below.

They fell softly into that circle. Its mountainous sides were high; they blocked off the view of the enormous terraces beyond that had been the crater's sloping sides.

From the direction that had suddenly become "east," the rising sun's strong light struck in a slant to make the bar rocks seem incandescent. On one side the giant rim of the encircling mountains was black with shadow. The shadow reached out across the vast, rocky floor almost to the foot of the opposite wall many miles away. It enveloped their falling ship like a cushioning, ethereal sea: velvety, softly black, almost palpable.

It was wrapping them about in the darkness of night as Chet's slender hand touched so delicately upon the ball-control—checked them, eased off, drew back again until the thundering exhausts echoed softly where their ship hung suspended a hundred feet above a rocky floor. The shrouding darkness erased the harsh contours of mountain and plain; it seemed shielding this place of desolation and horror from critical, perhaps unfriendly eyes of these beings from another world. And Chet laid their ship down gently and silently on the earthlit plain as if he, too, felt this sense of intrusion—as if there might be those who would resent the trespass of unwanted guests.

But Spud O'Malley must have experienced no such delicacy of feeling. He let go one long pent-up breath.

"And may the saints protect us!" he said. "The Lake of Death outside, and inside here is purgatory itself, or I don't know my geography. But you made it, Chet, me bhoy; you made it! What a sweet little pilot you are!"

"There's air here," Chet was telling his companion later; "air of a sort, but it's no good to us."

He pointed to the spectro-analyzer with its groupings of lines and light bands. "Carbon dioxide," he explained, "and some nitrogen, but mighty little of either. See the pressure gage; it's way down.

"But that won't bother us too much. We've got some suits stowed away in the supplies that will hold an atmosphere of pressure, and their oxygen tanks will do the rest. We were ready for anything we might find on our Dark Moon trip, but we didn't need them there. Now they'll come in handy."

"That's all right," O'Malley assured him; "I've gone down under water in a diving suit; I've gone outside a ship for emergency repairs in a suit like yours when the air was as thin as this; I can stand it either way. But what I want to know is this:

"What the divil chance is there of findin' your man, Haldgren, in such a frozen corner of purgatory as this? How could he live here? Here you've come in a fine, big ship, and his was a little bit of a bullet by comparison. Yet I doubt if you could live here for five years with all your big oxygen supply. Now, how could he have done it with his little outfit?

"And what has he eaten? Does this look like a likely place for shootin' rabbits, I ask you? Can a man catch a mess of fish in that empty Lake of Death? Or did Haldgren bring a sandwich with him, it may be?"

Chet Bullard shook his head doubtfully.

"Don't get sarcastic!" he grinned. "You can't think of any wilder questions than I have asked myself.

"He couldn't have lived here, Spud; that's the only answer. It just isn't humanly possible. All I know is that he did it. I can't tell you how I know it, but I do. Those lights were a human call for help. No living man but Haldgren could have flashed them. He's alive—or he was then; that's all I know."

Spud crossed the control room as he had done a score of times to look through a glass port at the world outside. Chet, too, turned to the lookout by which he stood and stared through it. The men had found themselves surprisingly light within the ship. They had been compelled to guard against sudden motion; a step, instead of carrying them one stride, might hurl them the length of the room. This lowered gravitational pull helped to explain to the pilot that outer world.

There, close by, was the rocky plain on which he had landed the ship: Smooth and shiny as obsidian in places, again it was spongy gray, the color of volcanic rock, bubbling with imprisoned gases at the instant of hardening. It stretched out and down, that gently rolling plain, for a thousand yards or more, then ended in a welter of nightmare forms done in stone. It was like the work of some demented sculptor's tortured brain.

Jutting tongues of rock stood in air for a hundred—two hundred—feet. Chet hardly dared estimate size in this place where all was so strange and unearthly. The hot rock had spouted high in the thin air, and it had frozen as it threw itself frantically out from the inferno of heat that had given it birth. The jets sprayed out like spume-topped waves; they were whipped into ribbons that the winds of this world could not tear down, and the ribbons shone, waving white in the earthlight. The tortured stone was torn and ripped into twisted contortions whose very writhing told of the hell this had been. Its grotesque horror struck through to the deeper levels of Chet's mind with a feeling he could not have depicted in words.

From the higher elevation where their ship lay he could look out and across this welter of storm-lashed rock to see it level off, then vanish where another crater mouth yawned black. Here was the inner crater! It had seemed small before; it was huge now—a place of mystery, a black, waiting throat into which Chet knew he must go—a place of indefinable terror.

But it was the place, too, whence strange flashes had come, flashes that had told of the distress and suffering of men since the time when wireless waves had been widely used. The old call—the S O S!—it had come from that throat; it had seemed a call sent directly to him! And Chet Bullard's eyes held steadily toward that place of mystery and of a sender unknown.

"I'm going down," he told himself more than O'Malley. "There's something about it I can't understand, something pretty damnable about it, I admit. But, whatever it is, that's what I am here to find out."

"'Tis a divil of a place to die," said O'Malley, "and not one I'd pick out at all. But it may be we won't have to. I'm goin' along, of course."

The master pilot was reaching for the flexible metal suit he had brought from the store room. It was air-tight, gas-proof; it would hold an internal pressure far beyond anything the wearer would demand; and its headpiece was flexible like the body of the suit, and would fit him closely.

He drew the suit up over the clothes he wore and closed the front with one pull of a metal tab. Within, soft rubber-faced cushions had interlocked; the body would fasten to the headpiece in the same way. But Chet paused with the headpiece in his hand.

He looked at the glass window that would be before his eyes; at the thin diaphragms that would come over his ears and that would admit all ordinary sounds; and he tried out the microphone