th knew the principles
of operation. They roped together and started the long climb. It was
easy at first. The slopes low down were not steep, and the broken lava
gave plenty of hand and footholds. But as they reached a point Rick
estimated to be about two hundred feet above the water, the slope
steepened sharply.

"Rest a moment," Scotty suggested. "We'll last longer if we take a
breather once in a while."

Rick knew Scotty was right, but he resented the need for sitting idly
for even a few minutes. He used the five-minute rest period to report to
Zircon that all was well.

Rick led the way again as soon as the luminous dial of his wrist watch
showed that five minutes had elapsed. Twice he and Scotty were stalled
for a brief time, but finally found a route and improved it by hammering
the steel spikes in clefts in the rock. With the hammer padded, the
sound was muffled to a point where it couldn't be heard more than a few
feet away. The spikes could be used to belay their rope on the way down.

The last stage of the upward journey was to the top of the cone. It was
nearly vertical, but wide cracks made it less difficult than some of the
areas below. Scotty was leading now. He reached the top, then waited for
Rick to join him.

Silently the two boys looked out over the dark sea, and Rick wished for
a moment that he could see the view by daylight.

"Let's check the crater," Scotty suggested. He drew his flashlight, then
inched forward across the rubble of the rim. Rick stayed beside him.

"Any danger of the beam being seen?" Scotty asked softly.

"No. The angle is wrong. If you keep it directed toward the crater, it
will be invisible from the sea."

Rick watched as Scotty switched the light on. The pencil of light swept
downward, and finally lost itself in nothingness.

The two boys stared at each other.

"The whole island's hollow!" Rick breathed. "I'll say this thing has a
crater!"

"Plenty deep," Scotty agreed. "Well, that tears it. Nothing to do but go
around. You lead the way."

Rick felt his way down until at last he was standing on the shoulder of
the ancient volcano just below the final sweep upward to the crest. In a
moment Scotty joined him. Slowly and carefully they started the long
journey around, taking the southern slope as previously agreed.

It was hard going. In spots the lava was crumbly and gave under foot or
hand. In others it was dense as steel slag.

When Rick estimated that over