e middle of the artificial cavern I
could see them stagger back in terror. Again the blinding flashes of a
few ray pistols, and instantaneous borings of the rays into the walls.
The red coats nearest the escape tunnels fled down them in panic. Those
whose escape I blocked dropped their weapons and shrank back against the
smooth, iridescent green walls.

I marshalled the rest of my string carefully into the cavern, and
counted the tunnel entrances, slowly swinging my "eye" around the
semicircle of them. There were 26 corridors diverging to the north and
west. I decided to send three balls down each, leave 12 in the cavern,
then detonate them all at once.

Assigning my operators to their corridors, I ordered intervals of five
miles between them, and taking the lead down the first corridor, I
ordered "go."

Soon my ball overtook the stream of fugitives, smashing them down
despite ray pistols and even rockets that were shot against it. On and
on I drove it, time and again battering it through detachments of
fleeing Hans, while the distance register on my board climbed to ten,
twenty, fifty miles.

Then I called a halt, and suspended my previous orders. I had had no
idea that the Hans had bored these tunnels for such distances under the
surface of the ground as this. It would be necessary to trace them to
their ends and locate their new underground cities in which they
expected to establish themselves, and in which many had established
themselves by now, no doubt.

Fifty miles of air in these corridors, I thought, ought to prove a
pretty good cushion against the shock of detonation in the cavern. So I
ordered detonation of the twelve balls we had left behind. As I
expected, there was little effect from it so far out in the tunnels.

But from our scopemen who were covering the city from the outside, I
learned that the effects of the explosion on the mountain were terrific;
far more than I had dared to hope for.

* * * * *

The mountain itself burst asunder in several spots, throwing out
thousands of tons of earth and rock. One-half the city itself tore loose
and slid downward, lost in the debris of the avalanche of which it was a
part. The remainder, wrenched and convulsed like a living thing in
agony, cracked, crumbled and split, towers tumbling down and great
fissures appearing in its walls. Its power plant and electro machinery
went out of commission. Fifteen of its scout ships hove