Norman grinned. "There'll be more. If I'm right about this thing we won't need to hop it--its own atmosphere will pick us up."

Both looked anxious as the motor sputtered briefly. But in a moment it was again roaring steadily. Norman shook his head.

"Maybe a fool's errand after all. No--I'm still sure we're right! But it seems that we don't prove it this time."

"Going down?" asked Hackett.

"We'll have to, in minutes. Even with its own air-feed the motor can't stand this height for--"

Norman never finished the words. There was a sound, a keen rising, rushing sound of immense power that reached their ears over the motor's roar. Then in an instant the universe seemed to go mad about them: they saw the gray ball of Earth and the sun above skyrocketing around them as the plane whirled madly.

The rushing sound was in that moment thunderous, terrible, and as winds smashed and rocked the plane like giant hands, Hackett glimpsed another sphere that was not the sphere of Earth, a greenish globe that expanded with lightning speed in the firmament beside their spinning plane! The winds stilled; the green globe changed abruptly to a landscape of green land and sea toward which the plane was falling!

Norman was fighting the controls--land and sea were gyrating up to them with dizzy speed--crash!

With that cracking crash the plane was motionless. Sunlight poured through its windows, and great green growths were all around it.

Hackett, despite Norman's warning cry, forced the door open and was bursting outside, Norman after him. They staggered and fell, with curious lightness and slowness, on the ground outside, then clutched the plane for support and gazed stupefiedly around them.

The plane had crashed down into a thicket of giant green reeds that rose a yard over their heads, its pancake landing having apparently not damaged it. The ground beneath their feet was soft and soggy, the air warm and balmy, and the giant reeds hid all the surrounding landscape from view.

In the sky the sun burned near one horizon with unusual brilliance.

But it was dwarfed, in size, by the huge gray circle that filled half the heavens overhead. A giant gray sphere it was, screened here and there by floating white mists and clouds, that had yet plain on it the outlines of dark continents and gleaming seas. A quaking realization held the two as they stared up at it.

"Earth!" Norman was babbling. "It's Earth, Hackett--above us; my G.o.d, I can't believe even yet that we've done it!"

"Then we're on--the satellite--the second satellite!--" Hackett fought for reality. "Those winds that caught us--"

"They were the atmosphere of this world, of the second satellite! They caught us and carried us on inside this smaller world's atmosphere, Hackett. We're moving with it around Earth at terrific speed now!"

"The second satellite, and we on it!" Hackett whispered, incredulously. "But these reeds--it can't all be like this--"

They stepped together away from the plane. The effort sent each of them sailing upward in a great, slow leap, to float down more than a score of feet from the plane. But unheeding in their eagerness this strange effect of the satellite's lesser gravitational power, they moved on, each step a giant, clumsy leap. Four such steps took them out of the towering reeds onto clear ground.

It was a gentle, gra.s.sy slope they were on, stretching away along a gray-green sea that extended out to the astoundingly near horizon on their right. To the left it rose into low hills covered with dense ma.s.ses of green junglelike vegetation. Hackett and Norman, though, gazed neither at sea or hills for the moment, but at the half-score grotesque figures who had turned toward them as they emerged from the reeds. A sick sense of the unreal held them as they gazed, frozen with horror. For the great figures returning their gaze a few yards from them were--frog-men!

Frog-men! Great mottled green shapes seven to eight feet in height, with bowed, powerful legs and arms that ended in webbed paws. The heads were bulbous ones in which wide, unwinking frog-eyes were set at the sides, the mouths white-lipped and white-lined. Three of the creatures held each a black metal tube-and-handle oddly like a target-pistol.

"Norman!" Hackett's voice was a crescendo of horror. "_Norman!_"

"Back to the plane!" Norman cried thickly. "The plane--"

The two staggered back, but the frog-men, recovering from their own first surprise, were running forward with great hopping steps! The two fliers flung themselves back in a floating leap toward the reeds, but the green monsters were quick after them. A croaking cry came from one and as another raised his tube-and-handle, something flicked from it that burst close beside Norman. There was no sound or light as it burst, but the reeds for a few feet around it vanished!

A hoa.r.s.e cry from Hackett--the creatures had reached him, grasped him at the edge of the reeds! Norman swerved in his floating leap to strike the struggling flier and frog-men. The scene whirled around him as he fought them, great paws reaching for him. With a sick, frantic rage he felt his clenched fist drive against cold, green, billowy bodies. Croaking cries sounded in his ears; then, Hackett and he were jerked to their feet, held tightly by four of the creatures.

"My G.o.d, Norman," panted Hackett, helpless. "What are they--frog-things?--"

"Steady, Hackett. They're the people of the second satellite, it seems; wait!"

One of the armed frog-men approached and inspected them, and then croaked an order in a deep voice. Then, still holding the two tightly, the party of monsters began to move along the slope, skirting the sea's edge. In a few minutes they reached two curious objects resting on the slope. They seemed long black metal boats, slender and with sharp prow and stern. A compact mechanism and control-board filled the prow, while at the stern and sides were long tubes mounted on swivels like machine-guns.

The frog-men motioned Norman and Hackett into one, fastening the two prisoners and themselves into their seats with metal straps provided for the purpose. Four had entered the one boat, the others that of the captives. One at the prow moved his paws over the control-board and with a purring of power the boat, followed by the other, rose smoothly into the air. It headed out over the gray-green sea, land dropping quickly from sight behind, the horizons water-bounded on all sides.

From their nearness Norman guessed that this second satellite of Earth's was small indeed beside its mother planet. He had to look up to earth's great gray sphere overhead to attain a sense of reality.

Hackett was whispering beside him, the frog-men watchful. "Norman, it's not real--it can't be real! These things--these boats--intelligent like men--"

The other sought to steady him. "It's a different world, Hackett.

Gravitation different, light different, everything different, and evolution here has had a different course. On Earth men evolved to be the most intelligent life-forms, but here the frog-races, it seems."

"But where are they taking us? Could we ever find the plane again?"

"G.o.d knows. If we ever get away from these things we might. And we've got to find Fellows, too; I wonder where he is on this world."

For many minutes the two boats raced on at great speed over the endless waters before the watery skyline was broken far ahead by something dark and unmoving. Hackett and Norman peered with intense interest toward it. It seemed at first a giant squat mountain rising from the sea, but as they shot nearer they saw that its outline was too regular, and that colossal as it was in size it was the work of intelligence. They gasped as they came nearer and got a better view of it.

For it was a gigantic dome of black metal rising sheer from the lonely sea, ten miles if anything in diameter, a third that in greatest height. There was no gate or window or opening of any kind in it. Just the colossal, smooth black dome rearing from the watery plain. Yet the two boats were flashing lower toward it.

"They can't be going inside!" Hackett conjectured. "There's no way in and what could be in there? The whole thing's mad--"

"There's some way," Norman said. "They're slowing--"

The flying-boats were indeed slowing as they dipped lower. They were very near the dome now, its curving wall a looming, sky-high barrier before them. Suddenly the boats dipped sharply downward toward the green sea. Before the two fliers could comprehend their purpose, could do aught more than draw instinctive great breaths in preparation, the two craft had shot down into the waters and were arrowing down through the green depths.

Blinded, flung against his metal strap by the resistance of the waters they ripped through, Norman yet retained enough of consciousness to glimpse beams of light that stabbed ahead from the prows of their rushing boats, to see vaguely strange creatures of the deep blundering in and out of those beams as the boats hurtled forward. The water that forced its way between his lips was fresh, he was vaguely aware, and even as he fought to hold his breath was aware too that the frog-men seemed in no way incommoded by the sudden transition into the water, their amphibian nature allowing them to stay under it far longer than any human could do.

The boats ripped through the waters at terrific speed and in a few seconds there loomed before them the giant metal wall of the great dome, going down into the depths here. Norman glimpsed vaguely that the whole colossal dome rested on a vast pedestal-like mountain of rock that rose from the sea's floor almost to the surface. Then a great round opening in the wall; the boats flashed into it and were hurtling along a water-filled tunnel. Norman felt his lungs near bursting--when the tunnel turned sharply upward and the boats whizzed up and abruptly out of the water-tunnel into air!

But it was not the open air again. They were beneath the gigantic dome! For as Norman and Hackett breathed deep, awe fell on their faces as they took in the scene. Far overhead stretched the dome's colossally curving roof, and far out on all sides. It was lit beneath that roof by a clear light that the two would have sworn was sunlight.

The dome was in effect the roof of a gigantic, illuminated building, and upon its floor there stretched a mighty city.

The city of the frog-men! Their boats were rising up over it and Norman and Hackett saw it clear. Square mile upon square mile of structures stretched beneath the dome, black buildings often of immense size, varying in shape, but all of square, rectangular proportions. Between them moved countless frog-hordes, swirling throngs in streets and squares, and over the roofs darted thick swarms of flying-boats. And at the city's center, in a great, circular, clear s.p.a.ce, lay a wide, round, green pool--the opening of the water-tunnel up through which they had come.

Norman pointed down toward it. "That's your answer!" he cried. "The only entrance to this frog-city is from the sea, up through that water-tunnel!"

"Good G.o.d, an amphibian city!" Hackett was shaken, white-faced.

The two boats were driving quickly over the city, through the swarming craft. Norman glimpsed towering buildings that might have been palaces, temples, laboratories. They slowed and dipped toward one block-like building not far from the water-tunnel's opening. Armed frog-guards were on its roof, and other boats rested there. The two came to rest and the two captives were jerked out, the guards seizing them.