se explosive copper projectiles--the heaviest projectiles that could
be used without endangering the planet itself--being directed under the
exposed edge of that unbreakable apron, which was in actuality anchored
to the solid core of the planet itself; lava flowing into and filling up
the vast craters caused by the explosions. The attack seemed fiercest at
certain points, perhaps a quarter of a mile apart around the circle, and
after a time the watchers perceived that at those points, under the edge
of the apron, in that indescribable inferno of boiling lava, destructive
rays, and disintegrating copper, there were enemy machines at work.
These machines were strengthening the protecting apron and extending it,
very slowly, but ever wider and ever deeper as the ground under it and
before it was volatilized or hurled away by the awful forces of the
Kondalian attack. So much destruction had already been wrought that the
edge of the apron and its molten moat were already fully a mile below
the normal level of that cratered, torn, and tortured plain.

Now and then one of the mechanical moles would cease its labors,
overcome by the concentrated fury of destruction centered upon it. Its
shattered remnants would be withdrawn and shortly, repaired or replaced,
it would be back at work. But it was not the defenders who had suffered
most heavily. The fortress was literally ringed about with the shattered
remnants of airships, and the riddled hulls of more than a few of those
mighty globular cruisers of the void bore mute testimony to the
deadliness and efficiency of the warfare of the invaders.

Even as they watched, one of the spheres, unable for some reason to
maintain its screens or overcome by the awful forces playing upon it,
flared from white into and through the violet and was hurled upward as
though shot from the mouth of some Brobdingnagian howitzer. A door
opened, and from its flaming interior four figures leaped out into the
air, followed by a puff of orange-colored smoke. At the first sign of
trouble, the ship next it in line leaped in front of it and the four
figures floated gently to the ground, supported by friendly attractors
and protected from enemy rays by the bulk and by the screens of the
rescuing vessel. Two great airships soared upward from back of the lines
and hauled the disabled vessel to the ground by means of their powerful
attractors. The two observers saw with amazement that after brief
attention from a