mechanical
control rooms, with their humming, vibrating mechanisms were here. And
an instrument room with signaling apparatus, senders, receivers,
mirror-grids and audiphones of several varieties. And an
electro-telescope, small but modern, with dome overhead like a little
Earth observatory.

From this instrument building, beside the connecting pedestrian
passage, wire cables for light, and air tubes and strings and bundles
of instrument wires ran to the main structure--gray snakes upon the
porous, gray Lunar rock.

The third building seemed a lean-to banked against the cliff wall, a
slanting shed-wall of glassite fifty feet high and two hundred in
length. Under it, for months Grantline's bores had dug into the cliff.
Braced tunnels were here, penetrating back and downward into the vein
of rock.

The work was over. The borers had been dismantled and packed away. At
one end of the cliff the mining equipment lay piled in a litter. There
was a heap of discarded ore where Grantline had carted and dumped it
after his first crude refining process had yielded it as waste. The
ore slag lay like gray powder flakes strewn down the cliff. Trucks and
ore carts along the ledge stood discarded, mute evidence of the weeks
and months of work these helmeted miners had undergone, struggling
upon this airless, frowning world.

But now all that was finished. The catalytic ore was sufficiently
concentrated. It lay--this treasure--in a seventy foot pile behind
the glassite lean-to, with a cage of wires over it and an insulation
barrage hiding its presence.

The ore shelter was dark; the other two buildings were lighted. And
there were small lights mounted at intervals about the camp and along
the edge of the ledge. A spider ladder, with tiny platforms some
twenty feet one above the other, hung precariously to the cliff-face.
It descended the five hundred feet to the crater floor; and, behind
the camp, it mounted the jagged cliff-face to the upper rim height,
where a small observatory platform was placed.

Such was the outer aspect of the Grantline Treasure Camp near the
beginning of this Lunar night, when, unknown to Grantline and his men,
the _Planetara_ with its brigands was approaching. The night was
perhaps a sixth advanced. Full night. No breath of cloud to mar the
brilliant starry heavens. The quadrant Earth hung poised like a giant
mellow moon over Grantline's crater. A bright Earth, yet no air was
here on this Lunar surface