Part 3 (1/2)
The big scientist kept an eye on his odometer, or mileage counter, while the boys watched for a clearing. It was slightly over a mile before they found one, and Zircon pulled off the road to let Brad Connel and Ruiz go by.
The jeep stopped as the two came abreast and the geologist called, ”Want to trade stations?”
”We like this one,” Zircon replied with a grin.
”Don't blame you. I have another three miles through this stuff. Well, so long.”
The jeep started off and was soon lost as the path curved slightly.
Zircon looked at his watch. ”Plenty of time, but we might as well get ready.”
A few minutes search disclosed a spot far enough away from the clearing for safety, with no trees to be uprooted by the blast. Zircon took two of the dynamite sticks Rick carried and one of the caps. He placed the cap over one stick and used a special tool, like a jar opener, to crimp it into place.
”This is the only really delicate part of the operation,” he said. ”If the crimpers slip, they could set off the cap and the dynamite. So be careful when you do it. Keep the crimpers low on the f.l.a.n.g.e of the cap.”
He found a rubber band in his pocket and used it to hold the two sticks together. A coil of wire was produced next, and the connection made to the dynamite cap. Zircon dug a shallow hole with his heel and put the dynamite sticks in, then backed off unwinding wire as he went.
The detonator had been left in the jeep. Rick got it and carried it to where Zircon waited with the pair of wires.
”How does this thing work?” Scotty asked.
”It's a dynamo,” Zircon replied. ”When the handle is pushed down it engages gears that spin a flywheel, which operates the dynamo long enough to send an electrical charge through the wires.”
”So don't sit on the handle,” Rick joked.
”And don't kick it,” Scotty added.
Zircon connected the wires to a pair of terminals on top of the detonator, then looked at his watch. ”Plenty of time. We might as well take it easy. Anyone hungry?”
No one was. It was too soon after breakfast. Instead, Rick took the opportunity to ask questions.
”I can understand the general principle of what we're doing, but can you tell us exactly what happens?”
”Sure. When the dynamite charge goes off, it sends shock waves through the earth in all directions. Whenever a shock wave strikes something of different density, its direction and velocity change. For instance, if there is denser rock a few hundred feet down, that will cause a change of both velocity and direction. With me so far?”
”I think so,” Scotty said. ”The denser the stuff the wave strikes, the faster it moves. Like sound waves. I mean, sound moves faster in water than in air, and faster in a steel rail than in water. Is it the same?”
”Just about,” Zircon agreed. ”The shock waves radiate away from us, through the earth, and eventually reach the recorders on the other side of the mountain. You can see what happens, I think. Waves will arrive at different times, depending on the path they took and the kind of material they went through.”
Rick nodded. ”So if there's molten rock, or magma somewhere in the way, the shock wave that goes through it will slow down and arrive at the recorder later?”
”That's it. The tracings we get can be a.n.a.lyzed to give us a kind of cross-sectional look at the mountain. You see, we know how fast the waves travel through different kinds of earth structure. Also, we will know the point of the explosion and the location of the recorder for each shot. Which reminds me. We'd better get out the equipment and locate ourselves precisely.”
”How?” Rick asked. ”What will we use for landmarks?”
”The top of the mountain, for one, and if you'll look carefully to a point slightly south of east between those two banana palms, you'll see the top of the control tower at the airport.”
Rick shook his head. ”Good thing you're with us. I completely forgot to watch for landmarks.”
”That was the first thing I had in mind in looking for a spot,” Zircon told him.