They could create currents of any velocity, from the deep, slow current of the Gulf Stream to the fast tidal currents past some constriction.
Amos thought about that laboratory as he began to swim again toward the wall.
The lieutenant assigned to give the lecture was evidently irritated about the interruption of his work by civilian students pretending to be naval officers, and so made his lecture about as interesting as a dial tone.
He talked in a fast, monotonous, flat voice about wave action, tidal movements, ocean currents. Then he showed them models of ships and rattled on about hull design and skin friction and the signature ships made in the water.
He also told them about hydrostatic pressure, demonstrating that the pressure at any point in the ocean is fixed by its depth, and changes as the depth changes.
Amos remembered the shape of one graph the lieutenant had shown them, because, at the time, it had looked to him like the outline of a tongue hanging down from smiling lips.
He swam slowly through the tunnel and out into the dimly lit pool of the cave.
As he came to the surface, he saw Max sitting beside Tanaka, giving him water through the tube, while John unpeeled some of the K-rations. "When a ship passes over a definite point in the water, does the pressure on that point increase or decrease?" Amos almost yelled at them.
"Do who do what?" Max asked.
"Come on! Does it increase or decrease?"
"Now everybody's crazy," John said. "Tanaka's crazy, and you're crazy."
Amos stood waist deep in the water and stared at the diaphragm, its edges ragged where he had cut it. The light was dim in the cave, and he could hardly see the little hole.
He shoved the diaphragm at John. "This is what fires those mines. The . . ." His voice trailed off as he remembered the dangling tongue and smiling lips.
"I think it increases," Max said. "The weight of the ship would make it increase."
"John!" Amos said. "I've got it! I've got it all!"
"Is it catching?"
"Those mines are hot all the time. . . . Yeah! That's it!"
Amos came on out of the water. "How is he?" he asked, nodding at Tanaka.
"Bad. What is it, Amos?"
"Pressure," Amos said, unbuckling the harness. "Remember that lecture on hydrostatics? How the pressure on a point fixed in the ocean is the same at
that depth everywhere? The only way you can change the pressure is to change the depth of the water. The deeper, the more pressure."
Amos got the pack and belt off and unzipped his wet suit. As he struggled to peel it off, he said, "A ship passing over that point doesn't increase the pressure, it decreases it, because, no matter what the ship weighs, the hull displaces a certain amount of water." He grinned at John. "So simple. There's a diaphragm on the mine with a wire attached to it. When a ship passes over the mine, the pressure graph looks like this. . . ." He drew the lips and tongue in the wet pebbles. "At first, at the bow, the pressure goes up a little, but then it drops sharply down, like this tongue here, then goes up again at the stern. The faster the ship goes, the further this tongue hangs out—the greater the decrease in pressure. That's all there is to it!"
"To what?" Max asked.
"When the pressure on that diaphragm decreases, it is pushed upward by the higher pressure under it. That pulls a little wire up, which releases a sort of monster rat trap inside the mine. When that trips, it yanks a bale shackle off a pelican hook and the mine shoots straight up through the water, and wham it hits whatever is up there."
John took the piece of rubber and looked at it. "Just a decrease in pressure?" he asked, his voice vague.
"That's all."
"So do all the mines explode twice a day when the tide goes out?" John asked.
"That's what took me so long," Amos told them. "But you see that little hole in the rubber? Hold it up so you can see it. That hole is to equalize any slow change of pressure, like a wave or the tides. Water can flow through it, making the pressure equal on both sides. But the hole's too small to let it equalize for the fast change of pressure that a ship causes when it goes over. Unless the ship goes so slow that it gives the hole time to work. That's the whole secret. Speed."
"You smart," Max said.
"You wouldn't think so if you'd seen what I did to that mine, when all I really had to do was spot that little hole and sit down and figure it out."
John studied the diaphragm. "Very clever, these Japanese. Because if I was an admiral, I'd come in full speed ahead, four bells and a jingle, so I'd be a harder target to hit. And this little thing would blow me out of the water. They'd bust me back to radioman, sure."
"That's all we've got to tell Pearl Harbor," Amos said. " 'Go slow and you've got it made.'"
Tanaka's voice sounded as though it came from nowhere, a faint voice from space. "Write," he said.
Max moved over to him. "Yeah, Commander, you're okay."
"No," Tanaka said, "write it down."
They stared at him as he lay there with his eyes closed. "The key for the nineteenth is King Fox
George William Charlie. For the twentieth, Able Fox Baker Mike Victor. For the twenty-first ... for the twenty-first. . . Charlie . . . Charlie . . . No . . ." "Take it easy," Max said. "We've got it." "King Fox George William Charlie," Tanaka said. 'The nineteenth."
John got the coding board out of the case and sat down with it, slowly turning the knobs. "Go . . . slow . . . and . . . you . . . have . . . got ... it . . . made." Then he said in a mincing voice, "Please acknowledge receipt of this message." He looked up at them. "We can send it by tapping it out on the tomtoms of the natives."
BOOK THREE
The tide was high now, leaving them only a narrow strip of beach. They had moved Tanaka so that his back was against the rock wall and only his feet were in the water. For an hour he had been fading in and out, sometimes saying rational things, sometimes just words. At one point he had suddenly remembered the key code for the twenty-first, and John had written that down with the others.
It was pitch dark in the cave. The only light coming down through the hole was from the dim, early-evening stars, and most of that was blocked out by Amos' head and shoulders.
Amos was looking out of the hole in the roof. To
get him up that high, Max had to stand on the bottom with a scuba, his head a foot or so under the water. Amos was standing on his shoulders.
John sat beside Tanaka, feeding him bits of K-ration dipped in water.
As Amos waited for the moon to rise, he thought of the submarine that had been blown up in the channel. The explanation fitted his theory perfectly. The sub had gone into the lagoon at dead slow, feeling her way along, her pressure not disturbing the diaphragm. But on her way out, thinking that there were no mines, mission accomplished, she had been in a hurry. And her speed had killed her.
The moon was golden and enormous as it came up above a low, rolling mountain.
Looking shoreward, Amos saw a section of landscape about as bleak as he imagined the moon itself was. Just a wide band of lava, torn and twisted, where nothing grew.
Beyond that, the jungle started, tentatively at first along the edge of the lava, then growing thicker and higher—a black wall of trees.
To his left, Amos could make out the little village beside the beach. The native houses were built on stilts in a curve at the edge of what looked like a grove of coconut trees. There were several small fires going, and he could see the outlines of people moving between him and the fires.
Looking at the village, Amos remembered the excitement of Tanaka's crew when they had passed it that morning. It was their village. They were plan-
ning to go home that night, they had told Max, and had invited him to come along. It was going to be a good party.
Inland, there seemed to be nothing except jungle, but as Amos shifted his eyes, he was startled to see the glow of bright, electric light. Staring at it, he gradually made out the shape of a small, whitish-
looking building, slits of light streaming out of it.
From inside the cave he heard John calling him.
"Tanaka's talking," John said, then leaned close to the man, listening.
Amos could hear only the weak, hesitant sound of his voice.
"He says look for a little building . . ." John relayed.
Amos looked out again, and this time saw more buildings, off to the right, they, too, all lit up.
"I see a lot of buildings," he told John.
". . . with a tall tree behind it . . ." John said.
"It's too dark to make out the trees."
"You're fading, Commander," John said. "What's in the building?"
John slumped down. "He's gone again. Just a little building, on a hill, with a tall tree."
"I see a building on a hill," Amos said, dropping down into the water.
On the beach he felt around until he found the .45 and then picked up a coil of life line and one of the extra strips of copra sack. "Let's go out and take a look."
"Will that gun shoot?" John asked.
"It's supposed to. The Marines shot theirs at Tarawa and they'd been under water a lot longer than this one."
Max surfaced and waded ashore. "What's out there?"
"Keep your gear on, Max; we're going out. I'll go up first, then John. When you feel him lift off, shuck the gear and come on out."
Max looked over at Tanaka. "What about him?"
"What can we do?"
"Nothing, I guess. Kind of lonely, though."
"I don't think he'll even know we're gone," John said.
As Amos started to wade into the water, Max stopped him. "You two guys look like something that ought to be preserved in a bottle. You wander around on this island where everybody is either yellow or brown and you'll attract a whole lot of attention."
Amos looked down at himself. What tan he'd had had been wiped out by the days spent in that sweltering cabin.
"We'd better wear wet suits," John said.
Amos started to pick up his jacket but then let it drop. "If anybody sees us in wet suits they'll know exacdy how we got here."
"What difference does it make? If anybody sees us it won't make any difference to them where we came from."
"It might," Amos said. "We need clothes." He
picked up one of the empty copra sacks and held it against his chest. "Just right."
Using the knife, Amos cut a slit in the bottom seam big enough to get his head through. Then he cut two slits in the side seams for his arms. Pulling the thing on, he stood up and looked at himself, the dark gray sack coming almost to his feet. "How's that?"
"I've seen better. When's the last time you got a haircut?" Max asked.
"Month? Two months?"
John was pulling the spare air tanks out of another sack. "It's okay, except where you stick out."
Amos looked at his bare white arms. "We could spread mud on ourselves," he said vaguely, knowing that would not work very well on this island, where it rained every half hour.
His weight belt, still loaded with equipment, lay on the gravel beach. Amos went over and took one of the packets of shark repellent out of the canvas pouch. The stuff was about the size and shape of a cake of soap and was wrapped in waterproof waxed paper.
Amos hadn't met anybody who had actually repelled a shark with it, but the theory was good. If a shark got interested in you all you had to do was break open one of the cakes, which contained not only a chemical sharks didn't like but a black dye that was supposed to spread out all around you and hide you.
He broke open the cake, dipped the exposed end in the water, and rubbed it down his arm. "Very
fine," he said, looking at the streak it made on his skin. "We'll put it on after we get outside so it won't wash off in here."
John finished making the slit in his sack, but as he started to put it on, he stopped and looked at Amos and Max. "What are we going out there for?"
"We've got some information the Navy wants," Amos said. "We've got the code to send it in and the man to send it. All we need is a radio."
John pulled the sack down over his head. "So we're just going to walk in someplace where a million Japanese are sitting around playing acey-deucey and say, 'Pardon me, may I borrow your radio to blow you up?'"
Max was breaking some lengths of rope off the life line. "We got to get some more chow anyway. Here, you guys, tie this around your waist. It'll give you some shape and something to hang that gun on."
John tied the rope around his waist and posed. "How's that, Max?"
"You're not my type, but it's not bad."
Amos and John went up through the hole first and then dropped a line down to Max. Crouched on the barren stretch of the lava flow, John and Amos daubed themselves with the shark repellent as Max sat looking at the little village. "They would have been home tonight," he said. "Only—Reeder wiped them out. I never liked Reeder."
"You think you could talk those people into letting us stay there? Hiding us?" Amos said.
Max thought about it. "They told me on the boat
that the Japanese come around every day or so and ransack the place, take all the food they have. They'd find us. And when they did they'd finish off those people."
"Yeah," Amos said, covering the last white patch of John's skin. "Okay. If they catch us, nothing but name, rank, and serial number."
"I hope they give me time to say that much," John said.
At the edge of the lava the jungle began, growing thicker as they moved inland.
The sound of the engine was absolutely unreal, but when the headlights lit the jungle, they were startled by the sight of a road that had been cut through it only a few feet ahead of them.
Crouching in the dripping ferns, they watched the big truck crawling along, it's dual wheels deep in the dirt ruts. As it passed them, they could see that it was loaded with what looked like at least 16-inch projectiles, the pointed ends banded with yellow and red paint.
"Them ain't BBs," Max whispered.
"They're getting ready for us," Amos said quietly. "Only—we aren't coming."
The building squatted in the jungle like a small fort, completely concealed from the sky by a canopy of trees. Square, low, and flat-roofed, it was made of thick concrete, the roof at least two feet thick and heavily reinforced. There were no windows; the light came through narrow gun ports in the walls. The only door was in the solid wall facing the road and was made of metal.
Staying concealed in the jungle, they carefully circled the building, studying it.
Behind the fort there was another, smaller building, also of thick concrete. The doors and windows
were open, and in the moonlight they could see two big diesel generators, one of which was running.
Motioning for Max and John to wait, Amos went over to the side of the main building and looked in through one of the slits in the wall.
The room was made up of alcoves, one on each of the three walls he could see. The partitions were of concrete, sticking out into the room and supporting the roof.
In one of the alcoves he could see the end of a double-decker wooden bunk and the feet of two men apparently asleep on thin, straw mattresses.
In the alcove directly across from him was a makeshift kitchen, with a hot plate, utensils, bottles, and some painted metal canisters.
In the alcove to his right, opposite the door, the partition almost blocked his view, and all he could see was what appeared to be an electrical device of some sort. There were knobs and dials and a row of switches. Someone was behind the partition, for Amos could see little clouds of cigarette smoke occasionally and could just make out the curved back of a wooden chair.
In the center of the room two Japanese in uniform were sitting at a table playing a game.
Standing up as high as he could to look down along the inside of the wall nearest him, he could see only a low bench and what appeared to be yellow raincoats hanging on nails.
He moved around to
the front of the building to
inspect the metal door and was surprised to find that there was no knob and apparently no lock that could be worked from the outside. It was just a blank slab of metal set into the concrete, and when he touched it he could tell that this was a massive thing.
Going back to Max and John, Amos looked up behind the generator shack and now saw what Tanaka must have meant by the tall tree. In the moonlight it was hard to tell, but this single tree was much taller than any of those around it and was narrow and almost limbless.
"Go take a look, John," Amos whispered. "I think there's a radio in there."
"Yeah?" John asked, his voice excited. "Transmitter?"
"You'll know. But watch it, there's at least five of them in there."
Max and Amos watched him going cautiously toward the building.
Max's voice sounded a little excited too. "Can we take it?"
"Wouldn't do any good now. We haven't got the coding board."
"Want me to go get it?"
John came running back into the jungle. "Oh, man! Now that's a big ma-moo."
"Transmitter?" Amos asked.
"The works."
"I'll go get the coding board," Max said.
"No, wait; we better stick together." Amos stood
looking at the squat little building. "Anyway, weve still got to get in there."
"How many did you say there were?" Max asked. "Five? Then why not just blast through the door."
"Not through that door," Amos said. "It's solid steel, locked on the inside."
"Well . . . then through the window. As soon as you start shooting they'll probably come piling out of there. John and I'll take them at the door."
"It's no good," Amos said. "Whatever we do has got to guarantee opening that door."
John laughed. "Just go up and knock on it."
"Yeah, how do you say in Japanese, 'Ain't nobody out here but us chickens'?" Amos asked. "Well, I guess we better get the coding board first."