nts, and
intermediate growths. And they fought endlessly for survival. Then more
millions of years passed, and there appeared a creature which slowly
gained ascendancy over the other struggling life forms that fought for
the warmth of rays of the hot, red sun.

"That sun had been old, even as the age of a star is counted, before its
planets had been born, and many, many millions of years had passed
before those planets cooled, and then more eons sped by before life
appeared. Now, as life slowly forced its way upward, that sun was nearly
burned out. The animals fought, and bathed in the luxury of its rays,
for many millennia were required to produce any noticeable change in its
life-giving radiations.

"At last one animal gained the ascendancy. Our race. But though one
species now ruled, there was no peace. Age followed age while
semi-barbaric peoples fought among themselves. But even as they fought,
they learned.

"They moved from caves into structures of wood and stone--and
engineering had its beginning. With the buildings came little chemical
engines to destroy them; warfare was developing. Then came the first
crude flying-machines, using clumsy, inefficient engines. Chemical
engines! Engines so crude that one could watch the flow of their fuel!
One part in one hundred thousand million of the energy of their
propellents they released to run the engines, and they carried fuel in
such vast quantities that they staggered under its load as they left the
ground! And warfare became world-wide. After flight came other machines
and other ages. Other scientists began to have visions of the realms
beyond, and they sought to tap the vast reservoirs of Nature's energies,
the energies of matter.

"Other ages saw it done--a few thousand years later there passed out
into space a machine that forced its way across the void to another
planet! And the races of the three living worlds became as one--but
there was no peace.

"Swiftly now, science grew upon itself, building with ever faster steps,
like a crystal which, once started, forms with incalculable speed.

"And while that science grew swiftly greater, other changes took place,
changes in our universe itself. Ten million years passed before the
first of those changes became important. But slowly, steadily our
atmosphere was drifting into space. Through ages this gradually became
apparent. Our worlds were losing their air and their water. One planet,
less favored than anothe