Scotty led the way back to the jeep. Rick got into the driver's seat and started the motor. He backed and turned in the narrow s.p.a.ce Connel's jeep had created, and finally got his wheels straight for the run back.

From somewhere behind them a voice called, "Parada!"

"Who's that yelling at us to stop?" Rick asked.

"I can't see anyone," Scotty replied. His eyes were scanning the jungle. "But I don't know anyone around here we want to talk to. I've got a hunch we should get going."

Rick felt the same. He released the clutch and the jeep moved ahead.

"Parada!" the voice yelled again, and on the echo came the clear crash of a rifleshot. A jagged star suddenly appeared on the windshield between them!

Rick reacted instinctively. He shoved the gas pedal to the floor and bent low, the skin of his back crawling with the expectation of a rifle bullet hitting it. The jeep leaped ahead and he steered as best he could. He shifted into second and the vehicle picked up speed. The rifle snapped again and he heard the sound of the slug hitting metal in the rear of the jeep. Then the trail turned and there was heavy jungle growth between them and the unseen sniper.

Not until they reached the second station, a mile away, did Rick slow down. He looked at Scotty, his face grim. "The place was guarded. What else can you make out of it?"

"Just that," Scotty agreed. "The guard must have been making a tour around the shot station. He got back just as we were taking off."

"Funny he didn't hear the jeep when we came," Rick said.

"Not very. Sound gets lost pretty fast in this heavy growth. You couldn't hear us a hundred yards away. Probably there's just the one guard, and he goes around the station in a big circle."

"I'll buy it," Rick agreed. "But why? Why guard a chunk of jungle with nothing in it but some torn up yellow ground?"

"When I find out," Scotty replied, "I'll let you know first thing."

CHAPTER X.

THE VOLCANIC PIPE.

HARTSON BRANT and Julius Weiss were still at work in the conference room when Rick and Scotty returned. David Riddle had gone, and the others had evidently not finished placing the tiltometers.

The two listened to Rick's story in silence, then Hartson Brant sighed. "I don't know how you do it, Rick. But if there's trouble around, you and Scotty will find it. Are you sure the rifleman shot at you?"

"We've got a bullet hole in the windshield and one just under the rear seat," Scotty said. "One might be an accident, but not two."

"I agree." Hartson Brant nodded. "Let's see the samples of earth you brought back, Rick."

He took both the yellow and blue pieces from his pocket and put them on the table. Hartson Brant and Weiss examined them with interest.

"Unusual," Weiss said. "I think you are right in a.s.suming that the yellow is simply an oxidized form of the blue, Rick. But I can't tell you what the material is. I've never seen anything like it before."

"The grain is pretty fine," Hartson Brant added. "It could be igneous or sedimentary in origin. I'm not enough of a rock hound to know. David Riddle can tell us when he returns."

"Connel would know, too," Scotty reminded. "He's a geologist. Wouldn't you think he would have mentioned an unusual formation like this when he found it?"

"Perhaps it's not unusual to a geologist," Weiss pointed out.

"Where is Riddle?" Rick asked.

"He went to his room a few minutes ago. He should be back shortly. Rick, I think you'd better tell us the whole story. Why do you suspect Connel? Why was it important for you to look at his shot station?"

Rick started at the beginning. "It wasn't any one thing, it was a series of little offbeat things. We thought it was funny he didn't even want company after Ruiz was hurt. Then he reacted so violently when we proposed swapping stations. It just seemed odd. The theft of the tracings bothered us, too. No ordinary thief would steal papers and leave Dr. Williams' wallet in his pocket, or leave his pocket transistor radio and stuff like that."

"But you can't connect Connel with the theft of the papers," Weiss objected.

"No, sir, we can't. But we almost got caught in the stolen dynamite, and he could have set that off. It was while we were on the way to his third station."

Scotty added, "Today, when we got to the station, I took a look along the trail. There's only one bend in it. If he was keeping a watch at the bend, he could have seen us arrive at the second station, hurried down the trail, set off the charge, then returned through the jungle to get his jeep."

"But the fact that he could have, does not mean that he did," Hartson Brant stated.

"We can't prove it," Scotty agreed.

Rick continued. "Then we trailed him to Casa Guevara. He couldn't have been paying a social call, because he wasn't there long enough. And what business does he have with Guevara? I don't know, but I'll bet his business is the reason we can't get Guevara to move."

"Possibly," Hartson Brant agreed. "I can see the reason for your suspicions, but you lack proof of anything, Rick. What motive could Connel have?"

"We hoped to find out at the shot station," Rick replied. "But we drew a blank."

Dr. David Riddle came into the room and joined them. Before anyone could speak, the geologist spotted the samples on the table and sucked in his breath sharply.

"Where did these come from?" he demanded.

"Connel's third shot station," Rick replied. "Do you know what the stuff is?"

Riddle sank into a chair and picked up one of the samples, testing it between his fingers. "Yes," he said, "I do. I've seen it only once before, in Africa. It occurs in what is known as a volcanic pipe, actually an ancient channel that gets filled with the stuff for reasons we do not know."

"A volcanic pipe," Hartson Brant said softly. "I'm beginning to see."

Rick wasn't. "But what is it?" he asked.

"The most valuable kind of ground in the world," Riddle said. "So far as anyone knew up to now, such pipes have occurred only in Africa. The one I saw was at Kimberley. The name came from there. This is kimberlite."

Rick knew of only one kind of valuable that was a.s.sociated with Kimberley, and the thought was so staggering that he was almost afraid to say it out loud. "You mean that this is the stuff diamonds are found in?"

"Exactly," Riddle said.

Rick fished the handful of crystals from his pocket and stared at them unbelievingly. "Then these," he said hoa.r.s.ely, "must be diamonds!"

CHAPTER XI.

EARTHQUAKE!.

"EVERYTHING adds up," Rick Brant said grimly. "And it isn't a pretty picture."

Hartson Brant agreed. "It certainly seems to add up, Rick. I suggest you put those crystals in a safe place until we can find out for certain whether or not there is real value there."

"Is there any doubt?" Scotty asked.

David Riddle answered, "Yes, Scotty. There are many grades of diamonds. Until an expert takes a look at those Rick collected, we won't be sure that they're of gem quality. He may have industrial grade diamonds, of the type called bort."

"Connel may already have had an expert take a look," Weiss pointed out.

Rick examined the handful of crystals. It was hard to believe he had simply picked up diamonds like so many pebbles. What's more, he couldn't be sure whether he held a king's ransom in his hand or a few dollars' worth of industrial abrasives.

"Why didn't Connel clean out all diamonds in the area?" he demanded.

"How could he?" Hartson Brant retorted. "When has he had time for a real effort? I suspect he has picked up quite a few, but you found those just by kicking around, which would indicate he hasn't sifted that loose ground very thoroughly."

David Riddle frowned. "It's odd that Rick found so many. Perhaps he was lucky enough to kick open a pocket that Connel missed. Diamonds just don't occur with such frequency, even in Kimberley."

"They were pretty close together," Rick remembered. "It may have been a pocket, all right."

"There is one other possibility," Riddle added, "and it's staggering to think of it. These crystals may have come from a single large crystal. Perhaps the dynamite explosions shattered the big one into a number of smaller ones."

Scotty gulped. "But the original crystal would have had to be nearly the size of a grapefruit!"

"True, Scotty. There have been crystals that big, or close to it. Usually the diamond that is cut from such a crystal is much smaller. There is considerable loss. But it's a possibility."

Rick said abruptly, "I think we ought to sort of review the situation. To see where we stand."

"A good idea," his father agreed. "Suppose you start?"

Rick considered. "Well, Connel must have discovered the yellow ground the very first thing, probably while he was kicking a hole to lay the charge in. The reason I think so is because of Ruiz. That accident has always bothered me. Ruiz just wouldn't walk back to the charge while Connel was ready to set it off. He just wouldn't."

Julius Weiss asked, "Are you implying that Connel deliberately blew Ruiz up?"

"What else can we make of it?" Rick replied. "That kind of accident just doesn't happen. Not to an expert. Rut if Connel found the yellow ground while setting the charge, and took time to dig a little and be sure there was blue ground under it, he would certainly have known that he was standing on top of a volcanic pipe. He might even have picked up a crystal."

"If word got out, he couldn't exploit the pipe," Scotty added. "So, Ruiz had to be eliminated. It would have been pretty easy. Connel had the watch. He could have kept track of the time, then asked Ruiz to make a final check and set the charge off while the poor guy was taking a look at the connections."

"It could have happened that way," Hartson Brant agreed. "But I hate to think any human being could be so ruthless."

"Connel had to keep others away, too," Rick went on. "Also, he had to slow things down so he could have time to set something up to exploit his find. So, he stole the tracings and the dynamite. That bought him a little time, didn't it? Then he tried to get Scotty and me, because we were following him and he was afraid we might find out what was going on."

"It seems reasonable," Hartson Brant agreed.

"Connel couldn't develop a diamond field in a foreign place without help, could he? He had to let someone in on it, locally. He sized up Guevara and figured the lieutenant governor could certainly help him out, so he brought Guevara in on it."

"Pure speculation," Weiss said.

"Yes, sir. But it fits. Guevara certainly wouldn't want people running around over there, so it's to his advantage to keep us from operating. If he thinks there's a fortune in the pipe, it's even to his advantage to kidnap the governor to make sure we can't follow our plans!"

David Riddle shook his head. "A man would have to be insane to hold up an effort to save the island just to make himself rich."

"He would if he believed the island was in danger," Scotty agreed. "But suppose he doesn't? I don't think Connel has the true picture. His time estimate was much longer than yours, and he hasn't been in on many of the discussions."

The three scientists looked at each other. "You know," Riddle said, "Scotty is right. Connel has shown little interest in the magma flux. He may not have a true understanding of the situation at all!"

"It's possible." Hartson Brant nodded. "Quite possible. After all, we borrowed him only to have another experienced man to handle the shots. His training certainly doesn't qualify him to understand the physics involved. He has concentrated on locating oil deposits, using standard data. This kind of thing is new to him."

"We didn't get him to handle data a.n.a.lysis," Weiss remarked. "There are enough of us who can do that."

Rick picked up his argument again. "If Connel doesn't believe there are only a couple of weeks, he would give the lieutenant governor his views, and he'd be believed, just because Guevara is so greedy he would believe anything that will make him rich. Of course I don't know for sure that Guevara is like that, but he certainly brushed us off, didn't he? And he didn't seem surprised when you told him about the danger."

"The thing that bothers me," Scotty stated, "is why Connel and Guevara haven't started to mine the diamonds."

"It takes organization," Rick pointed out. "Also, it couldn't be done while the governor was around, could it? He'd be sure to get wind of it. Connel and Guevara have to keep this quiet, or there will be a rush that will make the Klondike look like a picnic."

Scotty nodded. "That must be why they put a guard up there, too. Probably just one trusted man, who has to make the rounds alone. We were lucky he was on his rounds when we got there, or we'd never have had a chance for a close look."

"Well," Julius Weiss demanded, "what do we do now?"

A sudden earth tremor made the group pause. It lasted only a few seconds.

"Whatever we do, we'd better do it fast," Hartson Brant stated.

"Find the governor," Rick said. "That's the first thing. We can't move unless we have official backing, and we certainly won't get it from Guevara!"

Esteben Balgos walked in, closely followed by Brad Connel. "We placed the instruments without difficulty," Balgos began-and Connel's eye caught sight of the kimberlite samples on the table. The geologist realized instantly that his secret was known, and he knew, too, the conclusions that would be drawn. Among other things, he was guilty of the attempted murder of Ruiz.

Connel bolted for the door.

The geologist was fast, but Scotty was faster. The dark-haired boy charged across the room, then dove headlong. His extended arms caught the fleeting geologist around the thighs, then Scotty's shoulder smashed into him. Connel went down like a tackled ball carrier. Before he could recover, Scotty had shifted his grip and the geologist was helpless in a punishing hold.

The scientists and Rick arrived a split second later.

"Let him up," Riddle ordered. "But keep a grip on him."

Scotty did so, and the geologist glared at the group with angry eyes. He didn't try to bluff; he knew it was useless.

Rick hurried to find the hotel manager, who directed them to a tool closet on the outside of the hotel near the parking lot. It had no windows, a single, small ventilating duct, and only one door. Connel was pushed inside, and the door locked. Hartson Brant pocketed the key.