d afford to waste. It was a small figure--too
small, perhaps.

He turned to the radio. "Ganymede?"

"Where are you, Postal Ship?"

"I'm in a tight orbit about a hundred miles up," Preston said. "Give me
the figures on the circumference of your Dome, Ganymede?"

"Seven miles," the colonist said. "What are you planning to do?"

Preston didn't answer. He broke contact and scribbled some more figures.
Seven miles of iceworms, eh? That was too much to handle. He had planned
on dropping flaming fuel on them and burning them out, but he couldn't
do it that way.

He'd have to try a different tactic.

Down below, he could see the blue-white ammonia ice that was the frozen
atmosphere of Ganymede. Shimmering gently amid the whiteness was the
transparent yellow of the Dome beneath whose curved walls lived the
Ganymede Colony. Even forewarned, Preston shuddered. Surrounding the
Dome was a living, writhing belt of giant worms.

"Lovely," he said. "Just lovely."

Getting up, he clambered over the mail sacks and headed toward the rear
of the ship, hunting for the auxiliary fuel-tanks.

Working rapidly, he lugged one out and strapped it into an empty gun
turret, making sure he could get it loose again when he'd need it.

He wiped away sweat and checked the angle at which the fuel-tank would
face the ground when he came down for a landing. Satisfied, he knocked a
hole in the side of the fuel-tank.

"Okay, Ganymede," he radioed. "I'm coming down."

He blasted loose from the tight orbit and rocked the ship down on
manual. The forbidding surface of Ganymede grew closer and closer. Now
he could see the iceworms plainly.

Hideous, thick creatures, lying coiled in masses around the Dome.
Preston checked his spacesuit, making sure it was sealed. The
instruments told him he was a bare ten miles above Ganymede now. One
more swing around the poles would do it.

He peered out as the Dome came below and once again snapped on the
radio.

* * * * *

"I'm going to come down and burn a path through those worms of yours.
Watch me carefully, and jump to it when you see me land. I want that
airlock open, or else."

"But--"

"No buts!"

He was right overhead now. Just one ordinary-type gun would solve the
whole problem, he thought. But Postal Ships didn't get guns. They
weren't supposed to need them.

He centered the ship as well as he could on the Dome below and threw it
into automatic pilot. Jump