ell in ruins. The rest paused and drew off.

"They're retreating, Jim!" I cried.

"Cease firing until they come on again," he replied is he took the
shells from the magazines of the other guns and piled them near the bow
gun.

I held my fire for a few minutes. The Mercurians retreated a short
distance and then came on again with a rush. Twenty times my gun went
off as fast as I could align it and press the trigger, and eighteen of
the enemy ships were in ruins. Again the Mercurians retreated. I held my
fire. We were falling more rapidly now and far below we could see the
black spots which were the guard ships. I told Jim that they were in
sight; he stepped to the radio telephone and ordered them to keep well
away from the hole.

* * * * *

Again the Mercurian ships came on with a rush, this time with beams of
orange light stabbing a way before them. When I told Jim of this he
jumped to the controls and shot our ship down at breakneck speed.

"I don't know what sort of fighting apparatus they have, but I don't
care to face it," he said to me. "Fire if they get close; but I hope to
get out of the hole before they are in range."

Fast as we fell, the Mercurians were coming faster, and they were not
over eight hundred yards from us when he reached the level of the guard
ships. Jim checked our speed; I managed to pick off three more of the
invaders before we moved away from the hole. Jim stopped the side motion
and jumped to the radio telephone.

"Hello, Williams!" he shouted into the instrument. "Are you ready down
there? Thank God! Full power at once, please!

"Watch what happens," he said to me, as he turned from the instrument.

Some fifty of the Mercurian flyers had reached our level and had started
to move toward us before anything happened. Then from below came a beam
of intolerable light. Upward it struck, and the Mercurian ships on which
it impinged disappeared in a flash of light.

"A disintegrating ray," explained Jim. "I suspected that it might be
needed and I started Williams to rigging it up early this morning. I
hated to use it because it may easily undo the work that six years have
done in healing the break in the layer, but it was necessary. That ends
the invasion, except for those ten or twelve ships ahead of us. How is
your marksmanship? Can you pick off ten in ten shots?"

"Watch me," I said grimly as the ship started to move.

* * * *