d about them.

Beyond it, nothing was visible. Within, only the screens glowed still,
wired through the screen.

The beams appeared, and swiftly they drew closer. They struck, and as
Trest and Roal looked, the dome quivered, and bellied inward under them.

F-2 was busy. A new machine was appearing under his lightning
force-beams. In moments more it was complete, and sending a strange
violet beam upwards toward the roof.

Outside more of the green beams were concentrating on this one point of
resistance. More--more--

The violet beam spread across the canopy of blackness, supporting it
against the pressing, driving rays of pale green.

Then the gathering fleet was driven off, just as it seemed that that
hopeless, futile curtain must break, and admit a flood of destroying
rays. Great ray projectors on the ground drove their terrible energies
through the enemy curtains of blankness, as light illumines and
disperses darkness.

And then, when the fleet retired, on all Earth, the only life was under
that dark shroud!

* * *

"We are alone, Trest," said Roal, "alone, now, in all the system, save
for these, the children of men, the machines. Pity that men would not
spread to other planets," he said softly.

"Why should they? Earth was the planet for which they were best fitted."

"We are alive--but is it worth it? Man is gone now, never to return.
Life, too, for that matter," answered Trest.

"Perhaps it was ordained; perhaps that was the right way. Man has always
been a parasite; always he had to live on the works of others. First, he
ate of the energy, which plants had stored, then of the artificial foods
his machines made for him. Man was always a makeshift; his life was
always subject to disease and to permanent death. He was forever useless
if he was but slightly injured; if but one part were destroyed.

"Perhaps, this is--a last evolution. Machines--man was the product of
life, the best product of life, but he was afflicted with life's
infirmities. Man built the machine--and evolution had probably reached
the final stage. But truly, it has not, for the machine can evolve,
change far more swiftly than life. The machine of the last evolution is
far ahead, far from us still. It is the machine that is not of iron and
beryllium and crystal, but of pure, living force.

"Life, chemical life, could be self-maintaining. It is a complete unit
in itself and could commence of itself. Chemicals migh