andescent molasses, forced its way upward under enormous pressure.
Sometimes the magma remained quiet for hours, pulsing slightly like a
living thing. Then it would melt its way through to a weakness in the
earth's structure, creating a new channel for its upward flow.

In one new channel was basaltic rock with a higher moisture content than
the magma had encountered before. As the moisture turned instantly to
steam, it expanded with sudden violence, and the earth shook with the
force of the explosion.

Far above the pocket, Rick Brant felt the earth tremble, and shook his
head. The temblors were increasing in frequency, although none had been
as violent as that first day's earthquake. The boy looked at Scotty. His
pal's face was grim.

The scientists around the worktable had paused, too, as they felt the
earth tremble.

Esteben Balgos said quietly, "El Viejo is getting ready. If we are going
to act, it must be soon."

"Act?" Connel demanded. "How?"

Balgos shrugged. "That is what we are here to decide."

Rick watched the geologist's face. He was sure that Connel, for reasons
unknown, was trying to slow down the project. He was satisfied that the
man had stolen both the initial tracings and the dynamite. He also knew
that Connel lied. On their return from trailing him to Casa Guevara, the
boys had found Connel having a cup of coffee in the dining room and had
asked casually where he had gone. He had muttered something about going
into Calor for a supply of cigars.

Hartson Brant asked, "What do you make of this series of tracings? My
own opinion is that we have found a structural weakness through which
the magma will move. But the weakness does not extend far enough upward
to give any idea of the channel the magma will take to the surface."

The scientist pointed to a series of blue lines as he spoke. Dr.
Williams examined the lines, then took his pencil and began to sketch
rapidly on his cross-section drawing of the volcano and the earth under
it. Rick watched as the sketch took shape. From the upper lens-shaped
magma front Williams was drawing a series of lines that changed
direction, moving toward the western side of the island. Then, across
the top of the upward-moving lines Williams drew a horizontal line.

"Those upward strokes are the fissures shown by the tracings," he said.
"Notice that they stop at the horizontal line. My guess is that the
horizontal line represents an unbroken stratum that will pro