ies for the exacting tasks required of serious scientific research.
"Okay," he said, "I was hoping you'd move on soon, Dad. This looked like
a washout from the first. I'd say this place was sacked and ruined even
before the Incas fell."

The older man nodded. "I suppose so. Well, let's wash up and see what's
for supper."

They went down to the icy mountain stream to wash the dirt from their
hands. "It's been a nice day," Burl commented. "In spite of the Sun
being out steadily, it wasn't hot at all. Cooler than yesterday."

Mark Denning looked up at the sky and the Sun lowering toward the
horizon. "There must have been some volcanic dust in the heavens," he
said. "The Sun's been a bit dimmed, have you noticed?"

Burl squinted his eyes against the glare. "Wasn't any eruption around
here. Maybe in Ecuador?"

His father shrugged. "Could have been thousands of miles away," was his
slow reply. "Volcanic dust travels around the world, just as radioactive
dust permeated the atmosphere from atomic testings. They say that the
dust from the great Krakatoa explosion remained in the atmosphere for
three years before the last of it settled."

When they had finished supper and the Sun was casting its last red rays
over the rapidly purpling landscape, Burl got out the expedition radio,
set up its antenna, plugged in its compact atomic battery, and tried to
get the news from Lima. All he got was static.

He fiddled with the dials for a long time, twisting the antenna, ranging
the wavelengths, but there was static everywhere. "Strange," he said to
his father, "something's disturbed reception completely."

Pedro Gonzales, their official Peruvian guide, leaned over. "Could be
the battery she is broken, eh?"

Burl shook his head. "Not this battery," he said. "It's a brand-new one,
a real keen development. And I already checked the wiring. It's some
sort of disturbance that's blocking reception. Maybe we're in a dead
zone or something."

"Wasn't dead yesterday," said his father. "Maybe that eruption was
radioactive."

Burl looked up sharply. "I'll check the Geiger counters, Dad.
Something's blocking reception, something strong and powerful to
interfere with this set." But when he returned, he had to admit he had
found nothing.

When the Sun went down, they retired, for the temperature drops swiftly
in the high, thin air of the Andes.

In the rest of the world people watched their color-vision shows without
interruption. Rece