t would be the hypothetical neutron masses we think are in
certain stars. But this is not matter as we know matter; it is something
new.

* * * * *

"Our theory is this: the hydrogen atom has been split, resolved into
components, not of electrons and the proton centers, but held at some
halfway point of decomposition. Matter composed only of neutrons would
be heavy beyond belief. This fits the theory in that respect. But the
point is this: When these solids are formed--they are dense--they
represent in a cubic centimeter possibly a cubic mile of hydrogen gas
under normal pressure. That's a guess, but it will give you the idea.

"Not compressed, you understand, but all the elements present in other
than elemental form for the reconstruction of the atom ... for a million
billions of atoms.

"Then the light strikes it. These dense solids become instantly a
gas--miles of it held in that small space.

"There you have it: the gas, the explosion, the entire absence of
heat--which is to say, its terrific cold--when it expands."

Slim Riley was looking bewildered but game. "Sure, I saw it snow," he
affirmed, "so I guess the rest must be O.K. But what are we going to do
about it? You say light kills 'em, and fires their bombs. But how can we
let light into those big steel shells, or the little ones either?"

"Not through those thick walls," said MacGregor. "Not light. One of our
anti-aircraft shells made a direct hit. That might not happen again in a
million shots. But there are other forms of radiant energy that do
penetrate steel...."

* * * * *

The car had stopped beside a grove of eucalyptus. A barren, sun-baked
hillside stretched beyond. MacGregor motioned them to alight.

Riley was afire with optimism. "And do you believe it?" he asked
eagerly. "Do you believe that we've got 'em licked?"

Thurston, too, looked into MacGregor's face: Riley was not the only one
who needed encouragement. But the gray eyes were suddenly tired and
hopeless.

"You ask what I believe," said the scientist slowly. "I believe we are
witnessing the end of the world, our world of humans, their struggles,
their grave hopes and happiness and aspirations...."

He was not looking at them. His gaze was far off in space.

"Men will struggle and fight with their puny weapons, but these monsters
will win, and they will have their way with us. Then more of them will
come. The world,