the _Sagittarius_, out of Mercury.

Capt. Go Sian-tek, a Chinese Planeteer officer, arrived in one of the
cruiser's boats with three enlisted men.

Captain Go greeted Rip and his men, then handed over a plastic stylus
plate ordering Rip to deliver six cubic meters of thorium for use on
Mercury. While Koa supervised the cutting of the block, Rip and the
captain chatted.

The Mercurian Planeteer base was in the twilight zone, but the Planeteers
always worked on the sun side, wearing special alloy suits to mine the
precious nuclite that only the hot planet provided.

At some time during its first years, Mercury had been so close to the
sun that its temperature was driven high enough to permit a subatomic
thermonuclear reaction. The reaction had shorn some elements of their
electrons and left a thin coating of material composed almost entirely
of neutrons. The nuclite was incredibly dense. It could be handled only
in low gravity because of its weight. But nothing else provided the
shielding against radiation and meteors half so well, and it was in great
demand.

"Things aren't so bad," Go told Rip. "The base is comfortable, and we
only work a two-hour shift out of each ten. We've had a plague of silly
dillies recently. They got into one man's suit while we were working, but
mostly they're just a nuisance."

Rip had heard of the creatures. They were like Earth armadillos, except
that they were silicon animals and not carbon like those of Earth. They
were drawn to oxygen like iron to a magnet, and their diamond-hard
tongues, used for drilling rock in order to get the minerals on which
they lived, could drive right through a space suit. Or, if these animals
worked undetected for a while, they could drill through the shell of a
space station.

_Scralabus primus_ was the scientific name of the creature, but the fact
that it looked like a silicon armadillo had given it the popular name of
"silly dilly." Apart from its desire for oxygen, it was harmless.

Koa reported, "Sir, the block of thorium is ready. We've hung it on a
line behind the landing-boat. The blast won't hurt it, and it's too big
to get inside the boat."

"Fine, Koa. Well, Captain, that does it."

The Mercurian Planeteers got into their craft and blasted off, trailing
the block of thorium in their exhaust. Rip watched the cruiser take the
craft and thorium aboard, then drive toward Mercury, brilliant sunlight
reflecting from its sleek sides. The planet w