The newspapers had taken a dim view of the robbery. They protested against the carelessness which would enable the theft, in broad daylight, of such a valuable, secret, and hazardous thing as a radioactive isotope.
The blame, of course, fell primarily upon Mr. Taylor’s shoulders.
“Eddie,” Teena said, “you’re not even listening to me.”
“I—I’m sorry,” Eddie answered. “What did you say?”
“I merely said that some important blueprints are missing from my father’s department at Acme Aircraft,” Teena explained.
“Maybe someone put them in the wrong drawer or something,” Eddie suggested.
“They’ve looked everywhere, Eddie,” Teena said. “That’s why my father’s been getting home late every day. They’ve searched absolutely everywhere.”
“Well, I guess they can always make new blueprints,” Eddie said. He really couldn’t see why it was so important, especially not if you compared it to stolen radioisotopes.
“That’s not the point,” Teena said sharply. “They were top-secret blueprints—something to do with guiding a new missile Acme Aircraft is getting ready to make. If the plans were stolen—well, you know what that could mean.”
The importance of what Teena was saying struck Eddie suddenly. Could there be any connection between the missing blueprints and the stolen isotope?
The idea sent a chill along Eddie’s spine. Perhaps there was a whole spy ring operating around Oceanview!
He mentioned it to Teena.
“I thought the same thing,” she said. “But, Eddie, we’re not at war or anything. It’s silly to think there are spies and things like that running around. That’s comic-book stuff.”
“Not to me, it isn’t,” Eddie said. “There’s plenty of spying going on, war or no war. Every once in a while you hear about it.”
“Aw, you’re just trying to scare me,” Teena said. She stopped and picked up a shell, looked it over, then skipped it into the surf. Sandy chased it, yipping happily, but turned and scurried back just ahead of the foaming surf.
Eddie smiled. “Maybe I am,” he said. “Maybe I’m scaring myself, too. Anyway, if we’re going to hike all the way to the lighthouse, we’ll have to hurry up.”
As they walked on up the coast, the sandy beach gave way to rock formations which jutted out into the ocean. They picked their way carefully over the rocks. Now and then they stopped to inspect some tide pool for small crabs and other sea life left by the receding water. Sandy was beside himself with joy as he chased small crabs into rock crevices.
Teena found a starfish which she dropped into a small cloth sack she had brought along. Eddie had never been very interested in gathering shells and other sea souvenirs, but Teena had quite a collection at home.
They crossed over the rocks and dropped down into a sandy cove.
“There’s someone with a boat,” Teena said, pointing along the curving beach. A rowboat was pulled up on the sand. Two men stood beside it.
“Fishermen,” Eddie said. “Let’s see if they caught anything.”
There were several other small boats out on Moon Bay. Eddie and his father had fished the bay several times themselves. Although shallow in places, there were spots in the bay where good-sized perch and bass, and occasional halibut were caught.
Eddie and Teena hurried along the beach. The two men looked up as they approached.
“Hi, there,” Eddie greeted. “Any luck?”
The two men glanced at each other, seeming to pass a silent question back and forth.
Eddie laughed. “It’s O.K.,” he said. “I know most of the fishing spots out there. You won’t be giving away any secrets.”
“Hi, there,” Eddie greeted. “Any luck?”“Hi, there,” Eddie greeted. “Any luck?”
“Hi, there,” Eddie greeted. “Any luck?”
“Secrets?” one of the men said. He was tall and thin. His cheekbones pushed sharply outward against the sides of his face. His skin was strangely white for that of a fisherman in midsummer. Most week-end fishermen around Oceanview had pretty good tans by this time. Both men wore faded blue denims, white sneakers, and bright-colored sports shirts. The fact that their clothes looked new made Eddie think it might be the first time they had fished Moon Bay. The orange-and-white rowboat pulled up on the sand had been rented from Anderson’s Landing. Both Eddie and Teena knew Mr. Anderson well.
“We know fishermen don’t like to give away their fishing secrets,” Teena said, “so if you caught any, you don’t need to tell us where you got them.”
The other man smiled then. He looked relieved, Eddie thought. In appearance, he was almost the opposite of his companion. He was short and squat, almost fat. Despite the slight cool breeze from the ocean, the warm sun made his chubby face glisten with sweat. He seemed a little more willing to smile than the tall man. Eddie didn’t feel uncomfortable under his gaze, as he did under the stare of the tall man.
“To tell you the truth,” the short man said, “we haven’t been fishing yet. So I guess you couldn’t say we’ve had any luck.”
“Oh, I see,” Eddie said thoughtfully. Sandy began sniffing around the rowboat.
“Get that mutt away from there,” the tall man said.
“He won’t hurt anything, mister,” Eddie assured him.
He went over, though, and took hold of Sandy’s collar. As he did so he glanced into the beached rowboat. There were no fish, or even signs of fish. There were a couple bamboo poles which Eddie recognized also as having been rented from Anderson’s Landing. There was a box, probably the men’s lunch.
And under the plank seat stretching across the beam Eddie saw a round metal cylinder. At first he thought it was the kind of tube used as a carrying case to hold the sections of a jointed trout rod, but as he got a better look, it didn’t seem long enough for that.
Besides, who would use a light trout rod for ocean fishing? It wouldn’t be any good to catch the big bass which were sometimes caught in the bay. It’d probably snap in two if you tried to horse a halibut in with it.
“What are you looking at, kid?” The tall man’s harsh voice jerked Eddie out of his thoughts.
“N-nothin’,” Eddie said.
“Then stay away from the boat.”
“Take it easy, Simms,” the short man said. “These kids don’t mean any harm. They—they’re not trying to steal our fishing secrets. Now, are you?” He smiled at Teena, displaying a mouthful of yellowish uneven teeth.
Looking at those teeth made Eddie mighty glad his teeth would never look like that. What little bother his braces and the cleaning were would sure be worth it in the long run. He never wanted yellow, uneven teeth like that man had.
“I should say we wouldn’t try to steal any fishing secrets,” Teena answered the fat man’s question. “You’re welcome to all the fish you can catch.”
“We don’t care how you catch them, or what with,” Eddie added, “long as it’s legal.”
“Anyway, we’re on our way to visit Captain Daniels at the lighthouse,” Teena said. “Come on, Eddie.”
“Don’t go away mad,” the heavy-set man said. “We didn’t mean any harm.”
“Let ’em go, Roy,” Simms said. “We’ve got work to do.”
Eddie motioned to Teena and called Sandy. He had intended to tell the men of a good fishing spot only a few hundred yards out from the cove, but the way the men acted made him change his mind.
At the far end of the cove, Eddie and Teena stopped and turned to watch the two men as they shoved the rowboat into the calm surf and climbed in clumsily over the side.
“Boy, I’m glad all fishermen aren’t like that,” Teena said. “That tall man sure acted mean. I hope they don’t catch any fish.”
“I don’t think they will,” Eddie said. “I saw their bait can. Know what they’re using?”
“Sand crabs?”
“No. That’s what they should be using. They had some old dried up mussels. The fish here in Moon Bay don’t bite on mussel. Dad and I have tried it.”
“Then I wonder why Mr. Anderson sold it to them,” Teena said. “Mr. Anderson usually helps the fishermen. It’s good for his boat-rental business to sell the right bait.”
“I’ll bet they didn’t even ask what kind of bait was best,” Eddie said. “They probably grabbed the first thing they came to. And Mr. Anderson always has a few mussels in his bait bins.”
“I didn’t think fishing was so good in the middle of the day,” Teena said. She pointed out across the water. “See, most of the boats have gone ashore.”
“That’s right,” Eddie said. “If those guys wanted to catch fish they should have been out there early this morning when the big ones were biting.”
“Guess they don’t know much about fishing, huh, Eddie?” Teena said, smiling.
“That’s what I figure,” Eddie agreed. “Besides, they didn’t even act like fishermen. That tall fellow really was a grouch. First time I ever ran across a grouchy fisherman.”
“Anyway, let’s quit worrying about them,” Teena suggested. “It’s almost noon. We want to reach the lighthouse before Cap has lunch. He can’t very well eat his lunch and ours, too.”
“O.K.,” Eddie agreed, taking one last glance at the two men rowing out on the blue water of the bay. “But something smells fishy about those two—and I don’t mean the kind you catch on a hook!”
The lighthouse was a tall concrete finger, painted dazzling white with broad red rings around it. It stood on the top of a rock palisade which rose steeply from the beach. Steel stairs spiraled upward on the outside, leading to the strong glass-enclosed electric eye at the top.
Eddie and Teena paused on the beach below and looked up. Crude steps hewn out of the rocks led up to the lighthouse.
“I’ll carry the lunch,” Eddie volunteered. “And be careful. The sea spray can make those steps slippery.”
They took their time getting to the top. Sandy went ahead, sniffing in every crevice on the way.
“Phew!” Teena gasped as they reached the base of the lighthouse. “There seem to be more steps every time we climb it.”
Eddie smiled and shifted the lunch sack to his other hand. “You’re getting old, Teena,” he teased.
“Welcome aboard, mates,” a deep, kindly voice spoke from nearby.
They turned and saw Captain Daniels standing outside the door of his living quarters, a tiny three-room cottage located about fifty feet from the base of the lighthouse.
“Oh, hello, Captain Daniels,” Teena called. “Sure glad you’re home.”
“Home?” the former sea captain said, smiling. “A lightkeeper is always home.”
In Eddie’s opinion, Captain Daniels looked exactly like an old ship’s captain or a lightkeeper should look. He wore a fringe of white beard which formed a half-circle, starting under one ear and curving across his chin and up the other side. His bushy white hair fairly exploded from beneath the battered dark-blue seaman’s cap which he wore even while eating. Eddie sometimes wondered if Captain Daniels wore the cap to bed.
The old mariner also had sharp blue eyes. Eddie pictured all stout seamen as having sharp blue eyes.
“We brought a little lunch with us, Captain Daniels,” Teena said. “Hope you haven’t eaten already.”
A twinkle came into Cap’s eyes. “I might have,” he said, “but I reckon I better confess that I saw you through my telescope coming up the beach. Thought I’d better hold off on lunch—just in case.”
“Can we eat outside?” Teena asked.
“The lawn’s nice and dry,” Cap said.
“Let’s make it a picnic,” Eddie suggested.
“Good idea, mate,” the retired seafarer said.
Captain Daniels took great pride in his small patch of grass. It seemed to grow right out of the rock on which the lighthouse stood. However, Captain Daniels had hauled in topsoil from miles away and spread it carefully to make the lawn. He tended it, and the flower beds which bordered it, with an affection that seemed strangely out of place for a swashbuckling ship’s captain who had roamed the seven seas.
The three of them sat down on the lawn. Teena passed around the sandwiches, opened the potato chips, and unwrapped the pickles and olives.
They ate for a while in silence, looking off across the blue water of the bay toward the open ocean beyond. Eddie’s gaze followed the curving shore line to the north. Land’s end in that direction was Cedar Point, which stuck its rocky finger out into the ocean. It was wildly rugged country, difficult to get to except by boat across the bay. Eddie supposed that was why the lighthouse had been built on the smaller point located on the more civilized curve of the bay. Yet the lighthouse was high and plainly visible to ships at sea.
Captain Daniels finished his lunch, dug a pipe from his pocket, and tamped tobacco into the bowl. “Mighty good,” he said. “Sure nice of you young folks to share your rations with me.”
“Oh, we like to do it, Captain Daniels,” Teena said. “It’s so much fun coming up here to visit you.”
“From what I’ve been reading in the papers,” the lightkeeper said, “I hardly expected to see you for a while.”
“You mean the stolen isotope?” Eddie asked.
“I don’t know much about isotopes,” Cap said, “but I do know that the newspapers have been making your father walk the plank for letting it be stolen.”
“It really wasn’t his fault,” Eddie defended.
“Of course not,” Captain Daniels agreed. “But someone always gets blamed. Just like those missing blueprints I read about in this morning’s paper. Teena’s father probably has nothing to do with guarding them, but when they turn up missing, he’s the one who gets lashed to the mast. The captain of a ship takes the blame for everything that happens aboard. Actually, that’s the way it should be, I suppose.”
Eddie had to agree, but he didn’t like to think about the worry his father and Mr. Ross were going through. He had been trying not to think about it.
Captain Daniels seemed to sense this. He quickly changed the subject.
“Don’t seem to be many fishermen out today,” he said, looking off across the bay. “And there’s one boat out there that could just as well have stayed ashore. Won’t catch anything worth frying out there on top of the sand bar.”
The rowboat had been anchored over the light-blue strip of water which marked the familiar sand bar stretching nearly a half mile across the middle of the bay. The sand bar lay about ten feet beneath the surface of the water. It was marked by three buoys, one at each end and one in the middle. Deep-draft boats avoided the sand bar. Fishermen kept away from it, as the larger fish lay in deeper water.
“Isn’t that the boat with those two men, Eddie?” Teena asked.
“I think so,” Eddie said, squinting through the sunlight.
“What two men?” Cap asked.
Quickly Eddie told him about the two strangers he and Teena had come across at the cove. Captain Daniels reached into his pocket and brought out a small telescope. He pulled its sections out to full length and handed it to Eddie. “See for yourself,” he invited.
Eddie adjusted the lens to his vision. With the telescope it was easy to see that the two men in the rowboat were the tall one called Simms and the chunky one called Roy.
“Anyway,” Eddie said, “they don’t seem to be pulling in any fish.” He passed the telescope to Teena.
“It doesn’t look like they’re even trying,” Teena said. “There’s only one line in.”
“Maybe they’re just relaxing,” Captain Daniels said. “Some people don’t care whether they catch any fish or not. They rent a boat, row it out and anchor it, and then sit around soothing their nerves. People build up a lot of tensions these days, you know. Folks have different ways of getting rid of them.”
“They were nervous, all right,” Teena said. “Especially the tall one.” She handed the telescope back to Captain Daniels.
“Well, let’s forget about them,” Eddie suggested. “Captain Daniels, would you like us to help polish the light again today?”
“You know you’re always welcome to help with that,” the lightkeeper said, “but I don’t want you coming up here thinking I expect you to work.”
“Oh, but that isn’t work,” Teena said. “It’s fun.”
Eddie agreed with that. Not only was it fun, but it was a great thrill to climb up to the top of the lighthouse.
Captain Daniels got some rags and a can of window cleaner out of a small tool shed at the foot of the lighthouse.
“Why don’t you let us do it today, Captain Daniels?” Teena asked. “No use in your climbing all of those stairs.”
“You win,” the lightkeeper said, smiling. “I’ll wait down here.”
Eddie and Teena took the rags and cleaner and started up the steel stairs which spiraled up the outside to the top of the lighthouse. The stairs were perfectly safe, as a waist-high railing prevented any possibility of an accident.
Reaching the top, they paused on the narrow steel balcony that circled the light. The view across the bay was spectacular—blue water and whitecaps as far as they could see. A couple of steamers dragged banners of smoke across the distant horizon. In the other direction they saw Oceanview sprawling out inland from the shore of the bay. Both Acme Aircraft Company and the college campus were in plain view.
After filling themselves with the view, they got busy on the light. It was like polishing a giant lantern chimney. It had thick, wavy glass to magnify the beam of the enormous electric lamp which rotated inside, making three complete turns a minute. Being daytime, the light was turned off. In fact, Eddie never had seen the light up close at night. He imagined it would be very blinding, although he doubted if anyone ever would be foolish enough to climb up and look into it. It was bright enough, even from a distance, as it swept its white warning finger through the sky.
He and Teena worked away at spreading the window cleaner. After it had dried on the thick glass, they went over it carefully with their soft rags. The dirt and the white deposit left from the salt spray came off easily, leaving the glass bright as crystal.
“I guess that’s it,” Eddie said, after they had made a complete circle of the glass. He paused to take one last look around.
“We’d better be getting back home, too,” Teena suggested. “It must be three o’clock.”
Eddie glanced up at the sun. “You’re about right,” he said.
They made their way back down the stairs. Cap was waiting at the bottom.
“It’s as bright as the northern star, mates,” he said, craning his neck to get a good look at their handiwork. “I sure do thank you both.”
“We’re the ones to thank you for letting us come out here to visit you, Captain Daniels,” Eddie said.
“Any time,” the old mariner invited. “You’re always welcome. And I don’t expect you to bring a lunch or polish the light, either.”
“We have to go now,” Teena said. “But we’ll come out to see you again before long. Come on, Sandy.”
“I’ll be looking for you,” Captain Daniels called after them, as they started down the rock steps toward the beach.
Later, when they reached the cove they noticed that the rowboat was no longer anchored out over the sand bar. Then Eddie saw it in close to shore, heading for Anderson’s Landing. He didn’t give it any more thought.
As they approached Anderson’s Landing, the two strangers were tying up at the dock.
“Let’s see if they caught anything,” Eddie suggested.
“Let’s not,” Teena objected. “They weren’t very nice to us.”
“They didn’t mean anything,” Eddie said. “Maybe someone should tell them that the fishing is no good over the sand bar.”
“I’ll bet they found that out for themselves,” Teena said.
But Eddie already had started walking out onto the plank boat dock. Teena followed.
“Here, mister, I’ll help you,” Eddie offered as the heavy-set man removed the oars from the oarlocks and moved toward the prow of the boat.
“O.K.,” the man said, trying to keep his balance in the rocking boat. Then he glanced up. “Hey, you’re the kids we saw earlier, aren’t you? You following us or something?”
“No, sir,” Eddie said. “We were on our way home. Just thought we’d come out and see what kind of luck you had.”
“We did all right, didn’t we, Roy?” the tall man said.
“But where are your fish?” Teena asked.
“We left them in the bay,” Roy, the portly man, said.
“I guess so,” Eddie said, smiling. “No one ever catches any fish out over the sand bar. The fish hang around in the deeper water.”
“Well, we don’t care much for fish, anyway,” Roy said.
“Then why do you go fishing?” Teena wondered.
“We do it to get away from kids who ask silly questions,” Simms said curtly. “Now beat it and leave us alone.” He tossed the two fishing poles onto the dock and climbed out of the boat.
“Sure, mister,” Eddie said. “We didn’t mean to bother you.”
“Don’t get sore, kids,” Roy said. “Simms is a little sunburned, that’s all. Makes him cranky.”
The tall man was sunburned, all right. Eddie had noticed that. But then, he had expected it. Neither man boasted any kind of a tan, and the sun had been hot all afternoon.
Eddie also had noticed something else. It struck him as strange, although he didn’t know what to make of it. The metal tube which he had noticed in the bottom of the boat when they had first met the men in the cove was no longer in sight.
If it had contained a collapsible fishing rod as he had guessed, why wasn’t it still there in the bottom of the boat? Eddie was certain the men hadn’t put in to shore between the time they had left the cove and now. If they had he and Teena would have noticed it from the lighthouse.
A metal tube like the one Eddie had seen earlier in the bottom of the rowboat simply would not disappear. Perhaps it hadn’t contained a collapsible fishing rod, as he had guessed. If not, what was in the cylinder?
And where was it now?
Nearly a week went by. The lead capsule containing the stolen radioisotope had not been found. In fact, as far as Eddie knew, there had been no worthwhile clues on which to base a search. Curious as he was, Eddie still managed to keep from asking his father a lot of questions. Around home, Mr. Taylor had been thoughtfully silent. Eddie knew that his father must be very worried.
Eddie gathered enough from the conversations between his parents to know that the search for the stolen isotope was still going on. In fact, it was pretty well known that FBI agents had arrived in Oceanview to lend a hand. Eddie hadn’t seen them, but several of his friends had. It was hard to keep secrets in a college town like Oceanview.
The newspapers had temporarily dropped the story. After all, when the radioisotope had been stolen it had made a big story, but nothing more had happened, so there was nothing more to write about.
There were still articles in the newspapers about the Acme Aircraft Company problem of the missing blueprints. Actually, it seemed to Eddie that the newspapers were making more of a mystery out of the missing blueprints than of the stolen radioisotopes. Perhaps that was because it had not yet been decided whether the blueprints had been stolen, destroyed by accident, or simply lost. In an aircraft plant, where thousands and thousands of plans are being used at all times, some carelessness is apt to occur. Eddie found it hard to believe that anyone could get careless with top-secret blueprints, yet such things did happen.
Maybe the reason people remained curious about the missing blueprints was that everyone knew what a blueprint was. Even the word “radioisotope” meant very little to most readers. What they were and what they did were even less well known.
Friday morning Teena came whistling up to the back door at Eddie’s house to see if he wanted to do anything.
“Mom’s gone shopping,” Eddie said. “She’ll be back in a few minutes. Then maybe we could take the Geiger counter and—”
His words were interrupted by the telephone ringing inside.
“Be right back,” he said, hurrying into the house.
His father was on the other end of the line.
“Eddie,” he said, “there’s a dark-green notebook on my desk in the study. I forgot it this morning. Can’t get away from here, and I need it.”
“I’ll bring it over, Dad,” Eddie volunteered quickly.
“Good. I’ll be outside the botany building. Know where that is?”
“Botany? Where they raise all the plants and stuff?” Eddie asked.
“That’s right.”
“I know where it is,” Eddie said. “Be there in five minutes.”
He went into the study, got the notebook off the desk, and went back outside.
“I’ve got to tear over to school with this notebook,” he explained to Teena. “That was my dad.”
“I’ll go with you,” Teena said.
“O.K.”
It was only a few blocks to the college campus. Reaching the grounds, they took a short cut past the men’s gymnasium, crossed the athletic field, and arrived at the Botany Building.
“I see Dad over there,” Eddie said, pointing. There were several men standing in a group in the small cultivated field which the botany department used to grow test plants of various kinds. Eddie and Teena picked their way carefully between the rows.
“You made good time, Eddie,” his father said, taking the notebook. “Morning, Teena. Hope I didn’t interrupt any big plans.”
“Oh, no, Mr. Taylor,” Teena said. “We weren’t doing anything special.”
Eddie was about to turn and leave, when he noticed that several of the young men—students, no doubt—were wearing strange-looking, long, heavy gloves.
“Why the gloves, Dad?” he asked.
Mr. Taylor glanced up from the notebook. “We’re experimenting with radioactive tracers,” he said. “They’re weak—certainly not dangerous—but there’s no harm in taking a little extra precaution. The gloves are lead-lined and absorb any of the rays which might possibly be picked up from handling the plants.”
“What are tracers, Mr. Taylor?” Teena asked.
Eddie shot her a quick scowl. He doubted that his father wanted to be bothered with questions at the moment. Then Eddie noticed one of the students holding the wandlike probe—or diode—of a Geiger counter down close to the leaves of one plant. It seemed a strange thing to be doing. Who would prospect for uranium in plants.
“That’s a good question, Teena,” Mr. Taylor said. “Glad to see you’re interested.” He turned and spoke to the student with the Geiger counter. “Jim, you want to explain to this young lady, and my son here, what tracers are?”
Eddie smiled to himself. His father was the kind of a professor who believed his students should have the chance to use their knowledge whenever possible.
“Maybe we should all listen to this,” Eddie’s father said to the others.
They gathered around as the dark-haired student switched off the Geiger counter, swallowed a bit uncomfortably, and turned to face the outdoor classroom which Teena’s question had formed on the spot.
“Well, er—” Jim began, addressing Teena, “a tracer is a radioactive isotope which we—well, send out on a journey, then follow it with a Geiger counter.”
“I’m afraid that’s not too clear, Jim,” Mr. Taylor said. “Teena’s not an atomic scientist. Can you simplify it for her?”
“Oh, I know what a radioactive isotope is, Mr. Taylor,” Teena said proudly.
“You do?” Eddie’s father said in surprise.
“It’s something—I think you call it an element—which they put in an atomic reactor, and—and cook it until it becomes radioactive. Kind of like a sponge soaking up water.”
“Very good,” Mr. Taylor nodded, obviously impressed.
“Eddie explained it to me,” Teena said, smiling, “but he didn’t say anything about tracers.” She turned her attention back to Jim, the student.
“All right,” Jim said, seeming more at ease, “let’s look at it this way. Any radioisotope keeps shooting out rays. Of course, you can’t see the rays with your eyes. They’re almost too small to think about. But you can follow them with a Geiger counter.” He indicated the black metal instrument which he still held in his hand.
“Well,” Jim went on, “say, for instance, that you wanted to know how fast a stream of water flows. You might toss in a rubber ball and time how long it takes to float a mile downstream. That would give you its speed. Or say you wanted to know which way its currents twist and turn. You might dump in a gallon of ink and watch it follow the currents. In a way, the ball and the ink are tracers. Not radioactive tracers, of course, but by watching how they act, you learn what you want to know.”
“Let’s talk about radioactive tracers,” Eddie said eagerly.
“You’re crowding me, bub,” Jim said, smiling. Everyone laughed.
“How are we using tracers here, Jim?” Mr. Taylor prompted.
“We’re testing the use of phosphate in plant growth,” the student explained. “We want to know what the plant does with it. Does a phosphate fertilizer merely feed the plant’s roots, or is it pulled up into the stems and leaves? And we want to know how quickly the plant absorbs it, if at all. Of course, we can’t see it, but if we make the phosphate slightly radioactive, then we have what we call a tracer. By using a Geiger counter, we can follow or trace its movement.”
“Can you explain our method, Jim?” Mr. Taylor said.
“Well, we spread a little of the radioactive phosphate around the plant,” the student said. “Soon the roots start taking it in.”
“How do you know that, Jim?” Mr. Taylor asked.
“We hold the Geiger counter to the root. If it starts clicking faster than usual, we know the root has absorbed some of the phosphate tracer. We also hold the Geiger counter over the stems and leaves. As the tracer works upward into the plant, the Geiger counter reacts to it. Here, let me show you how it works on this cotton plant.”
Eddie and Teena moved over closer to the two-foot-high plant. Jim switched on the Geiger counter. Eddie saw the needle on the gauge flutter slightly, indicating the normal cosmic-ray background count.
“Teena,” Jim said, handing her the earphones which were attached by a long wire to the Geiger counter, “you take these earphones. Now, I’ll pass the probe down close to the base of the cotton bush.”
“What does the stick do?” Teena asked. Although Eddie had explained it to her, she seemed to feel that, as a pupil, she should ask some questions to help Jim out.
“Stick? Oh, you mean the probe. Actually, it’s called a diode, but probe’s easier to remember. Anyway, the probe is a vacuum tube filled with a special kind of gas. Whenever invisible radioactive particles shoot through the probe and into the gas, the Geiger counter clicks, and the needle on the dial moves forward. The more rays shooting through the probe, the more clicks; the more clicks, the more radioactivity. That’s why Geiger counters are so useful in hunting for uranium. Uranium is very, very radioactive. If you happen onto some uranium ore, the Geiger counter really goes wild.”
“We have a Geiger counter at home,” Eddie said eagerly. “Teena and I have gone uranium prospecting several times.”
“Haven’t found any uranium,” Teena said, “but we’ve had fun trying. Whoops. There’s some clicking!” She put her hands up to the earphones.
Jim had moved the probe down close to the stem of the cotton plant.
“Good,” he said. “We mixed a little radioactive phosphate into the ground around the roots this morning. See, the Geiger counter shows that the phosphate tracer has already started moving up into the plant. Helps show how important phosphate is to plant growth, and how eagerly the plants absorb it.”
“The plant sure looks healthy enough, all right,” Eddie said.
“Right,” Jim said. “Now let’s see how far up into the plant the tracer has gone.”
He moved the probe upward over the smaller twigs and leaves. On the lower leaves the Geiger counter kept clicking rapidly. Eddie watched the needle stay forward on the gauge.
“See, the leaves have taken a lot of it in already,” Jim explained.
Then, as he moved the probe farther up toward the top of the plant, the clicking diminished until only the familiar slow background count remained.
“It quit,” Teena said.
“Shows that the phosphate has only reached about half of the plant so far,” Jim said. “You see, with the tracer and the Geiger counter we can tell just how far it has gone and how long it has taken. We can even tell how much has been absorbed by comparing the amount of radioactivity in the leaves and stems of the plant to what we know was contained in the original tracer.”
“Boy, that’s something!” Eddie exclaimed.
“By adding tracers to some fertilizers,” Jim went on, “we found that the plant made no use of the fertilizer. The Geiger counter didn’t pick up any radioactivity in the plant. Meant wasted money to any farmer or gardener who used it. Now do you see what we mean by a tracer? See how radioactive tracers can be helpful?”
“Oh, yes,” Teena said. “I do.”
“I’ll bet if I had some of that tracer I wouldn’t lose so many things,” Eddie said. “I could paint a little on my marbles or sling-shot. Then I could always find them with a Geiger counter.”
“You could, at that,” his father said. “And I wouldn’t be stepping on the marbles in my bare feet. But, of course, great care must be taken in handling radioisotopes, which is what tracers are.”
Jim had warmed up to the subject, and wasn’t quite ready to drop it. “Tracers are used in many ways,” he went on. “They are used in medicine to locate diseased tissue which attracts and absorbs certain isotopes. A radiation-sensitive instrument, similar to a super Geiger counter, sniffs out the isotope and locates the damaged tissue. Then the doctor knows what to treat, or where to operate. Radioisotopes are used in various food tests. By watching the tracer with electronic gadgets, they can tell whether the food is a muscle builder, a bone builder, or what.”
“You can make machine parts radioactive,” Mr. Taylor said. “Then by seeing how many radioactive particles are in the oil after the machine has been run, you can tell how much wear the machine has taken. Oh, there are hundreds of ways to use radioactive tracers. You might call them atomic signposts. Using a Geiger counter to read the signs, you are directed along the paths that lead to the answers of nature’s mysteries.”
“Wow!” Eddie exclaimed.
“Pretty flowery, at that, I guess,” his father said, smiling. “Well, anyway, Jim, you did a nice job of explaining it. Now, I think we’d better get back to our work. Thanks for bringing the notebook over, Eddie—and Teena.”
The two young people turned and started back toward Eddie’s house.
“Let’s go across the mall,” Teena suggested. “I haven’t been over here for a long time.”
The mall, as it was always called, was a broad ribbon of lawn which stretched for more than a block down the center of the college campus. It was bordered on both sides by the many buildings which made up Oceanview College. Sidewalks laced back and forth across the mall. During class changes, the area swarmed with students. Now, as Eddie and Teena walked along the mall, only a few students sauntered around or sat loafing in front of the buildings waiting for their next class.
Teena and Eddie walked past the library, the assembly hall, and the nuclear-science building. They were starting past the chemistry building, when Eddie tugged at Teena’s sleeve.
“Look,” he said, pointing to the back of a man walking about fifty yards ahead of them. “Who’s that?”
“Who’s who?” Teena asked. “You mean that man? Am I supposed to know him?”
“I think I do,” Eddie said. “He sure looks familiar.”
“How can you tell? All we can see is his back. Lots of backs look alike. He’s tall. Maybe he’s a basketball player. He looks older than most students, though. Why, his hair’s even a little gray, and—”
“I’ve got it now,” Eddie interrupted. “The tall and kind of gray part. You know who? Simms. That fellow we ran into down at the cove last week.”
“Well-ll, maybe,” Teena admitted thoughtfully. “We could tell for sure if he’d turn around. Anyway, I don’t see what difference it makes. Maybe he’s a student here. There are a lot of older students. Maybe he’s even a teacher. Lots of teachers fish on week ends. No reason to get excited.”
“Who’s excited?” Eddie challenged. “Can’t a fellow ask—”
“O.K., O.K.,” Teena said. “Anyway, there he goes into the chemistry building, so we’ll never know just who it was. And that’s the end of your mystery.”