pilot had respected the other man's need of silence, but his curiosity could not be longer restrained.

"What's back of it all?" he demanded. "What caused it? The shock was like no earthquake I've ever known. And this tidal wave—" He was reaching for a small switch. He turned a dial to the words: "News Service—General," and the instrument broke into hurried speech.

It told of earth shocks in many places—the whole world had felt it—some tremendous readjustment among the inner stresses of the earth—most serious on the Atlantic seaboard—the great Harkness Terminals destroyed—some older buildings in the business district shaken down—loss of life not yet computed....

"But what did it?" Chet Bullard was repeating in the cabin of their floating ship. "A tremendous shake-up like that!" Harkness silenced him with a quick gesture of his hand. Another voice had broken in to answer the pilot's question.

"The mystery is solved," said the new voice. "This is the Radio-News representative speaking from Calcutta. We are in communication with the Allied Observatories on Mount Everest. At eleven P. M., World Standard Time, Professor Boyle observed a dark body in transit across the moon. According to Boyle, a non-luminous and non-reflecting asteroid has crashed into the earth's gravitational field. A dark moon has joined this celestial grouping, and is now swinging in an orbit about the earth. It is this that has disturbed the balance of internal stresses within the earth—"

 dark moon!" Chet Bullard broke in, but again a movement from Harkness silenced his exclamations. Whatever of dull apathy had gripped young Harkness was gone. No thought now of the devastation below them that spelled his financial ruin. Some greater, more gripping idea had now possessed him. The instrument was still speaking:

"—Without light of its own, nor does it reflect the sun's light as does our own moon. This phenomenon, as yet, is unexplained. It is nearer than our own moon and smaller, but of tremendous density." Harkness nodded his head quickly at that, and his eyes were alive with an inner enthusiasm not yet expressed in words. "It is believed that the worst is over. More minor shocks may follow, but the cause is known; the mystery is solved. Out from the velvet dark of space has come a small, new world to join us—"

The voice ceased. Walter Harkness had opened the switch.

"The mystery is solved," Chet Bullard repeated.

"Solved?" exclaimed the other from his place at the controls. "Man, it is only begun!" He depressed a lever, and a muffled roar marked their passage to a distant shaft of blue, where he turned the ship on end and shot like a giant shell for the higher air.

There was northbound travel at thirty-five, and northward Harkness would go, but he shot straight up. At forty thousand he motioned the master-pilot to take over the helm.

"Clear through," he ordered; "up into the liner lanes; then north for our own shop." Nor did he satisfy the curiosity in Chet Bullard's eyes by so much as a word until some hours later when they floated down.

n icy waste was beneath them, where the sub-polar regions were wrapped in the mantle of their endless winter. Here ships never passed. Northward, toward the Pole, were liner lanes in the higher levels, but here was a deserted sector. And here Walter Harkness had elected to carry on his experiments.

A rise of land showed gaunt and black, and the pilot was guiding the ship in a long slant upon it. He landed softly beside a building in a sheltered, snow-filled valley.

Harkness shivered as he stepped from the warmth of their insulated cabin, and he fumbled with shaking fingers to touch the combination upon the locked door. It swung open, to close behind the men as they stood in the warm, brightly-lighted room.

Nitro illuminators were hung from the ceiling, their diffused brilliance shining down to reflect in sparkling curves and ribbons of light from a silvery shape. It stood upon the floor, a metal cylinder a hundred feet in length, whose blunt ends showed dark openings of gaping ports. There were other open ports above and below and in regular spacing about the rounded sides. No helicopters swung their blades above; there were only the bulge of a conning tower and the heavy inset glasses of the lookouts. Nor were there wings of any kind. It might have been a projectile for some mammoth gun.

Harkness stood in silence before it, until he turned to smile at the still-wondering pilot.

"Chet," he said, "it's about finished and ready—just in time. We've built it, you and I; freighted in the parts ourselves and assembled every piece. We've even built the shop: lucky the big steeloid plates are so easily handled. And you and I are the only ones that know.

"Every ship in the airlanes of the world is driven by detonite—and we have evolved a super-detonite. We have proved that it will work. It will carry us beyond the pull of gravitation; it will give us the freedom of outer space. It is ours and ours alone."

"No," the other corrected slowly, "it is yours. You have paid the bills and you have paid me. Paid me well."

"I'm paying no more," Harkness told him. "I'm broke, right this minute. I haven't a dollar—and yet I say now that poor Warrington was right: this is my lucky day."

e laughed aloud at the bewilderment on the pilot's face.

"Chet," he said slowly, and his voice was pitched to a more serious tone, "out there is a new world, the Dark Moon. 'Tremendous density,' they said. That means it can hold an atmosphere of its own. It means new metals, new wealth. It means a new little world to explore, and it's out there waiting for us. Waiting for us; we will be the first. For here is the ship that will take us.

"It isn't mine, Chet; it's ours. And the adventure is ours; yours and mine, both. We only meant to go a few hundred miles at first, but here's something big. We may never come back—it's a long chance that we're taking—but you're in on it, if you want to go...."

He paused. The expression in the eyes of Chet Bullard, master-pilot of the world, was answer enough. But Chet amplified it with explosive words.

"Am I in on it?" he demanded. "Try to count me out—just try to do it! I was game for a trial flight out beyond. And now, with a real objective to shoot at—a new world—"

His words failed him. Walt Harkness knew that the hand the other extended was thrust forth blindly; he gripped at it hard, while he turned to look at the shining ship.

But his inner gaze passed far beyond the gleaming thing of metal, off into a realm of perpetual night. Out there a new world was waiting—a Dark Moon!—and there they might find.... But his imagination failed him there; he could only thrill with the adventure that the unknown held.

CHAPTER II

Escape

wo days, while a cold sun peeped above an icy horizon! Two days of driving, eager work on the installation of massive motors—yet motors so light that one man could lift them—then Harkness prepared to leave.

"Wealth brings care when it comes," he told Chet, "but it leaves plenty of trouble behind it when it