you'd come back with us. But we'll help you repair your ship. We'll give
you all the supplies we can spare."

Russ rose to his feet. "That," he said, "calls for a little drink."

He opened a cabinet and took out bottles and glasses.

"Only three," said Chambers. "Craven doesn't drink."

Craven interrupted. "Pour one for me, too, Page."

Chambers looked at the scientist, astounded. "I never knew you to take a
drink in your life."

Craven twisted his face into a grin. "This is a special occasion."

* * * * *

The _Invincible_ was nearing Mars, heading for Earth, which was still a
greenish sphere far to one side of the flaming Sun.

Russ watched the little green globe, thinking.

Earth was home. To him it always would be home. But that would be
changed soon. Just a few more generations, and, to millions upon
millions of human beings, Earth no longer would be home.

With the new material energy engines, life on every planet would be
possible now, even easy. The cost of manufacture, mining, shipping
across the vast distances between the planets would be only a fraction
of what it had been when man had been forced to rely upon the unwieldy,
expensive accumulator system of supplying life-giving power.

Now Mars would have power of her own. Even Pluto could generate her own.
And power was ... well, it was power. The power to live, the power to
work, to establish and maintain commerce, to adjust gravity to Earth
standard or to any standard. The power to remake and reshape and rebuild
planetary conditions to suit man exactly.

Earthmen and Earthwomen would be moving out en masse now to the new and
virgin fields of endeavor--to the farms of Venus, to the manufacturing
centers that were springing up on Mars, to the mines of the Jovian
worlds, to the great laboratory plants that would spring up on Titan and
on Pluto and on the other colder worlds.

The migration of races had started long ago. In the Old Stone Age, the
Cro-Magnon had swept out of nowhere to oust the Neanderthal. Centuries
later the barbarians of the north, in another of those restless
migrations, had overwhelmed and swept away the Roman Empire. And many
centuries later, migration had turned from Europe to a new world across
the sea, and fighting Americans had battled their way from east to west,
conquering a continent.

And now another great migration was on--man was leaving the Earth,
moving into space. He was leaving