quickly at the port-opening switch, and the big steel disk backed slowly out of its threaded seat and swung wide.

Chet drew back one involuntary step as a blast of icy wind drove stinging snow into his face. Then, without a word, he gave Spud O'Malley a joyous grin and threw himself out into the void....

And, later, as he released the 'chute where a wind was dragging him violently across an icy expanse, he was laughing exultantly to see another 'chute whirled into the enshrouding drifts, while the chunky figure of a man came scrambling to his feet that he might shake a fist into the air toward some hidden enemy and shout into the storm epithets only half-heard.

"—and be damned to ye!" Chet heard him conclude; then was close enough to throw one arm about the figure and draw him after where he made his way toward a building that was like a mountain of snow.

Spud must have marveled at the craft within; at her sleek, shining sides; the flat nose that ended in a black exhaust port. He was examining the other exhausts that ringed her round when Chet pulled out a lever from the streamlined surface and swung open an entrance port.

He motioned Spud into the brilliantly lighted interior, where nitron illuminators were almost blinding as they shone of gleaming levers and dials of a control room like none that Spud O'Malley had ever seen.

Chet had thrown the building's doors open wide; a whirling motor had drawn them back on hidden tracks. Now he closed the entrance port with care, then glanced at his instruments before he placed his hand on a metal ball.

It hung suspended in air within a cage of curved bars. It was a modification of the high-liner ball-control, and it was new. Walt Harkness had had it installed to replace a more crudely fashioned substitute that had brought them safely back from the Dark Moon. The name of that new satellite was on Chet's lips as his thin hand rested delicately upon the ball.

"It's not the Dark Moon this time, old girl," he told the ship, "though you've taken me there twice. But we're going up just the same, and I told the Commander he hasn't Patrol Ships enough to hold us back." His fingers were gripping the little ball—lifting it—moving it forward....

And, as if he lifted the ship itself, the silent cylinder came roaring into life. Within the great building was a thundering blast that made the voice of the storm less than a whispering breath. It came but faintly through the heavily insulated walls, but Chet felt the lift of the ship, and that joyous smile was crinkling about his eyes as the silvery cylinder floated smoothly out of her shelter into the grip of the wind.

His eyes were on an upper lookout, where clouds were driving away like a curtain unrolled. More cloud banks were coming, but, for a time, the heavens were clear where the great red hull of a rusty freighter hung helpless beneath a red and silver Patrol Ship whose magnets held fast to its prey.

There were other shapes in the markings of the Service that shot slantingly down. Chet thought again of the carrion birds; then he saw the gold star on the bow of a great cruiser and knew from that ship that the Commander must be seeing their own below. Then he eased gently forward on a tiny ball—forward and forward, while the compensating floor of the control room swung up behind them and seemed thrusting up with unbearable weight.

There were flashes from the cruisers above, and flashes of red on the ice behind with fountains of shattered ice and rock; detonite works its most terrible destruction on a surface that is brittle and hard. But of what avail are detonite shells against a craft whose speed builds up to something greater than the muzzle velocity of a shell?—a silvery craft that sweeps out and out toward a black mountain range; then swings slowly up in a curve of sheer beauty that bends into banked masses of clouds—and ends.

But within the control room, Chet Bullard, no longer Master Pilot of the World, but master, in all truth, of space, knew that his ship's flight was far from ending. He turned to grin happily at his companion.

"We're off!" he shouted. "And it's thanks to you that we made it. If Haldgren's alive he'll have you to thank; for it's you that has done the trick so far!"

But Spud O'Malley answered soberly as he stared up and out into the blackness of levels he had never seen.

"I've helped," he admitted; "I've helped a bit. But it's a divil of a job of navigatin' that's ahead. And that's up to you, Chet Bullard; 'tis no job for an old omadhaun like mesilf!"

Chet felt the lift of the Repelling Area as they shot through. Ahead was the black velvet night that he knew so well; its silent emptiness was pricked through with bright points of fire.

"I found the Dark Moon," he said slowly, "and that you can't see at all. This other will be easy."

There was no boastfulness in the tone, and Spud O'Malley nodded as he glanced respectfully at the young man who threw back his disheveled mop of hair from a lean face and marked down some cryptic figures on a record sheet.

Chet Bullard was on the job ... and his passenger, it would seem, was satisfied that his unbelievable adventure was well begun.

CHAPTER IV

Life Monstrous and Horrible

"It looks," said Spud O'Malley, "as if some bad little spalpeen of the skies had thrown pebbles at it when 'twas soft. It's fair pockmarked with places where the stones have hit."

He was staring through a forward lookout, where the whole sky seemed filled with a tremendous disk. One quarter was brilliantly alight; it formed a fat crescent within whose arms the rest of the globe was held in fainter glowing. By comparison, this greater portion was dark, though illuminated by earthlight far brighter than any moonlight on Earth.

But light or dark, the surface showed nothing but an appalling desolation where the rocky expanse had been still further torn and disrupted—pockmarked,as O'Malley had said, with great rings that had been the walls of tremendous volcanoes.

Chet was consulting a map where a similar area of circular markings had been named by scientists of an earlier day.

"Hercules," he mused, and stared out at the great circle of the moon. "The crater of Hercules! Yes, that must be it. That dark area off to one side is the Lake of Dreams; below it is the Lake of Death. Atlas! Hercules! Suffering cats, what volcanoes they must have been!"

"I don't like your names," objected O'Malley. "Lake of Death! That's not so good. And I don't see any lake, and the whole Moon is wrong side up, according to your map."

Chet reached for the ball-control, moved it, and swung their ship in a slow, rotary motion. The result was an apparent revolution of the Moon.

"There, it's right side up," Chet laughed; "that is, if you can tell me what direction is 'up' out here in space. And, as for the names, don't let them disturb you; they don't mean anything. Some old-timer with a little three-inch telescope probably named them. The darker areas looked like seas to them. Astronomers have known better for a long time; and you and I—we're darned sure of it now."

The great sea of shadow, a darker area within the shaded portion whose only light came from the Earth, was plainly a vast expanse of blackened rock. An immense depression, like the bottom of some earlier sea, it was heaved into corrugations that Chet knew would be mountain-high at close range. Marked with the orifices of what once had been volcanoes, the floor of that Lake of Death was hundreds of miles in extent.

But as for seas and lakes, there was no sign of water in the whole, vast, desolate globe. An unlikely place, Chet admitted, for the beginning of their search, and yet—those flashes of light!—the S O S! They had been real!

The bow blast had been roaring for over an hour; their strong deceleration made the forward