"I may as well clear this up once and for all. The rain and snow were
my doing. After I had told you to rely on the Mercurians and described
the landmark, I discovered that the Mercurians were nitwits and the
landmark a false alarm. That meant that, once you landed, you'd never
find me except by accident. That put it up to me to find you.
"As you may have heard, normally there's no such thing as rain or snow
on Mercury. But there is water. And there is a continual process of
transfer going on. The water flows through subterranean channels to the
Hot Side, evaporates, and is carried over in the air to the Cold Side.
There it deposits on the ground eventually as ice, melts, and goes
through the whole process again."
"Why doesn't it rain?"
"Because there's no dust in Mercury's air. The absence of a rapidly
alternating day and night means that the air doesn't circulate on the
same scale as on Earth. Practically no wind, combined with little
erosion, means little dust. The water-laden air cools off and becomes
super-saturated at the Twilight Zone. But there are no clouds, and
there's no precipitation because the water needs either dust or ions to
condense on. In a Wilson cloud chamber, an experimenter furnishes it
with ions. Here on Mercury I furnished it with dust.
"I gave the Mercurians rifles and explosive bullets, and taught them to
shoot into the air. It was quite a job, but they learned. The explosion
spreads a cloud of dust, the water condenses, and you have rain or
snow, depending on the temperature. I impressed it upon their brains,
such as they are, that the presence of human beings calls for a Fourth
of July celebration--shooting into the air. And there you are. I had
the occurrence of rain and snow reported to me, moved toward wherever
the snow was thickest, and found the ship."
"Another thing--"
"I've talked enough. That dame won't wait forever. Which will it be,
Carvalho, the Lady or the Tiger?"
They listened in curiosity as Carvalho, tight-lipped, tapped out a
short message in code. They didn't ask him what it was.
As the _Astrolight_ drove upward away from Mercury, Lamoureux had one
last glimpse of the Mercurians shooting into the air. The snow was
coming down in enormous flakes two inches across, and Carvalho, staring
after the ship, was shivering and cursing. After they reported the
facts to the Interplanetary Commission, a ship would be sent to pick
him up--but it might take some time.
"Let me tell you about this dame," said Kalinoff.
Lamoureux listened patiently, got out his contract, and waited, with
pen ready, for the interplanetary screwball's signature.