“Over there is the oldest country on this side of the world,” said Peter Fenton, pointing over the rail of the vessel and across the smooth waters of the Caribbean sea. “We are now on the famous Spanish Main,” he continued, “where adventurers from the Windward Islands laid in wait for the galleons of Spain. Just ahead, rising out of the sea, is the Isthmus of Panama. Down there to the left is the continent of South America, where there were cathedrals and palaces when Manhattan Island was still populated by native Indians.”

The minds of the Boy Scouts were filled with splendid dreams as they followed with their eyes the directions indicated by the pointing hand. It was all a fairyland to them. Peter talked for some time on the causes which had brought the scum of the seven seas to the Isthmus, and then Ned Nestor interrupted the talk by inviting them all to the stateroom he occupied in common with Frank Shaw.

When all were seated on chairs and bunks Ned opened the door and looked out on the passage which ran along in front of the apartment. When he turned back into the room there was a humorous twinkle in his eyes.

“His Nobbs is in sight,” he said.

“The same party?” asked Frank.

“The same dusky gentleman who has followed us since the night of the theft of the emerald necklace,” Ned replied.

“He ought to receive a Carnegie medal for always being on the spot,” Frank said.

“We ought to turn the hose on him,” Jimmie corrected.

“We should feel lost without him,” laughed George Tolford. “When I first saw him in the newspaper building, while you were investigating the chaos of papers in Mr. Shaw’s rooms,” he went on, “I had a hunch that we shouldn’t be able to lose him.”

“Well, we haven’t been able to lose him,” Peter Fenton said. “He reminds me, the way he floats about, of the ghost of some pirate who sailed about the Spanish Main four hundred years ago in a long, low, rakish craft adorned with a black flag.”

“I saw him in the newspaper building that night,” Jimmie said, “an’ he looked glad because we got no clues there.”

“Why didn’t Ned have him arrested in New York?” asked Jack Bosworth.

“What for?” demanded Jimmie.

“For making a nuisance of himself. Then he couldn’t have followed us on board the ship. Also, he might have been able to get a little sleep nights.”

“I reckon we have kept him going,” Frank observed, with a laugh.

Ever since the night of the robbery the man called “His Nobbs” for want of a better name had kept Ned Nestor in sight most of the time. He had followed him home after the profitless visit to the newspaper office on the night of the theft, had chased about after him while the details of the trip to Panama were arranged the next day, and had turned up on the ship after she was under way.

The fellow did not seem to be overly anxious to keep his watchfulness a secret. He acted like any first cabin passenger on the ship. But, somehow, he managed to keep Ned in view most of the time. Now and then he was caught watching the door of Ned’s stateroom. He never spoke to the boy, and never even looked at him when the two passed one another.

Taking advantage of this preference for Ned’s company, the boys had put up all sorts of jobs on the fellow, and some of their pranks had kept him watching Ned’s odd moves all night. It was a new and strange experience to Ned, this being spied upon so openly, and he was at a loss to account for the mental processes which inspired the strange surveillance.

“Well,” said Ned presently, “let him watch outside if he wants to. We came in here to talk about something else. I have just been talking with Lieutenant Gordon, and he says we are to go into camp in the jungle not far from the Gatun dam. He will stop at the Tivoli, at Ancon, adjoining Panama. When we have anything to communicate to him, one of us can go down to Panama after supplies and leave word at an office where one of the lieutenant’s associates in the case will always be in waiting. We are not to know the lieutenant if we meet him in our soup.”

“We’ll be eaten alive out there in the jungle,” protested Jimmie.

“Besides, it would be more natural for us to go to Gatun for our supplies,” Peter Fenton said.

“There are reasons why he wants us to remain in the jungle near Gatun for a time,” Ned replied, and the boys separated, Jimmie strolling off in the wake of “His Nobbs,” “just to see if he couldn’t make him cough up something,” as he expressed it.

The mystery of the theft of the emerald necklace was still unsolved, the man whose picture Ned carried in his brain had not been found, Pedro had been among the missing ever since he had walked out of the Shaw residence on the morning after the robbery. When the boys landed at Colon the next morning the case upon which they were engaged was still new ground before them.

Frank Shaw continued to take the loss of his emeralds very seriously, and at no time during the trip to Colon had he failed to keep an eye out for Pedro, whom he suspected of having admitted the thief to the house.

“His name isn’t Pedro at all,” he said, as the train sped out of the network of tracks behind Colon, “but Pedrarias. That was the name of the robber who succeeded Balboa as governor of New Granada, the pirate who stood Balboa up against a wall and shot him. Pedro, as I call him for short, declares that he is a direct descendant of that old stiff. He says the Spanish blood in his veins is pure. Great Scott! if I had such a pirate for an ancestor, I’d keep mighty still about it.”

Peter Fenton was in his element now. As the train moved away from Colon he pointed out various points of interest, and supplied such information about them as he had gleaned from the maps and books he had consulted. The ruins of the old French workings were soon in sight, the locality where millions had been squandered in graft. And there was Mount Hope Cemetery, where thousands who had perished from fever had been buried.

“The doctors have cleaned out the fever now,” he said, “by cleaning out the mosquitoes – the poison kind with the long name,” he added. “The Canal Zone is about as healthy now as the city of New York.”

Then came thickets where the trees were tied together with vines and creepers, all in gorgeous bloom. The great trees lifting their heads out of the jungle reminded the boys of the electric towers of New York, the twists of vines resembling the mighty cables which convey light, heat and power to the inhabitants of Manhattan.

As if in rivalry of the wealth of blossoms, bright-plumaged birds darted about like butterflies of unnatural growth. Now and then they saw evil looking lizards, some of them a yard in length, scuttling off through the marshes or looking down from high limbs. There was a swampy atmosphere over all the landscape.

Then, as the Boy Scouts looked, thinking of the glory of a camp in the thicket – of a retired nook on some dry knoll – the jungle disappeared as if by magic, and the train was winding up grassy hills. Beyond, higher up, the scattered houses of a city of fair size came into view.

“That’s Gatun,” cried Fenton. “I’ve read half a dozen descriptions of it lately. Great town, that.”

“The houses look like boxes from here,” Jimmie observed.

“Of course,” Peter replied, “they are all two-story houses, square, with double balconies all screened in. Might be Philadelphia, eh?”

There were smooth roads in front of the houses, and there were yards where flowers were growing, and where neatly dressed children were playing. Jimmie turned from the homelike scene to Frank.

“I thought there would be something new down here,” he complained. “This is just like a town up the Hudson.”

“Jimmie expected to find people living in tents made out of animal skins,” laughed George. “He thinks the natives eat folks alive.”

“You wait until you get out of the country,” Frank said, “before you talk of cottages up the Hudson. There will be something stirring before we get off the Isthmus.”

“I hope so,” Jimmie replied. “There surely will be if we camp back there in the jungle, among the snakes and lizards.”

“Why not camp on the hills back there?” asked Jack.

“We may soon camp anywhere we like,” said Ned. “The Zone government understands that we are a lot of kids out after specimens.”

“Specimens of what?” asked Jimmie.

“Tall, slender men with black hair turning gray,” replied Frank.

“Quit your kiddin’,” grinned Jimmie.

The boys left the train at a modern depot, passed through the train-shed, crossed a level sward, and looked down into a mighty chasm.

“Great Scott!” cried Frank. “Is that the bottom of the world?”

He pointed below as he spoke.

“There seems to be a thin crust of rock between the bottom and the other side of the world,” laughed George. “See! There are tunnels and pits down there. The men are still digging. Look like ants, don’t they?”

It was a wonderful sight, and the Boy Scouts gazed long at the scene of activity before turning away toward the Gatun dam itself. This, Peter Fenton explained, was one of the big cuts of the canal, and ran from the marshy valley above down through the rocky ridge which held the rains in check and made a swamp of the upland.

Along the margins of the excavation ran shining steel rails upon which were mounted tapering structures of steel, from which cables crossed the gorge, carrying great buckets of concrete for the work below. Heavy walls were growing out of the depths.

“The ships will come up out of the sea through this cut,” Peter explained.

“Then they’ll climb the hill,” scorned Jimmie.

“They will stop down there,” said Peter, “and the lock gates will be closed, and the water will lift them to the level of the lake.”

“I don’t see no lake,” observed the skeptical Jimmie.

“The lake will lie where the low land is, over there,” replied Peter, pointing. “The Gatun dam will block the water and make a lake 85 feet above sea level, covering one hundred and sixty-four square miles of earth.”

“So the most of the canal will be lake?” asked the boy.

“Quite a lot of it,” was the reply.

“And if any one should blow up the dam, after it gets on its job, the ships would have to climb a ladder if they got over to Panama,” he exclaimed.

“Something like that,” Peter said.

“Where is the Gatun dam?” asked Jack.

“It is going up over there,” Peter replied, pointing out a low, broad ridge which appeared to link two hills together. “That is what will make the inland sea, and that is the lump of earth we came here to look after.”

“It is a busy place night and day,” Ned said. “See the electric towers and wires? Work never stops.”

“Something like His Nobbs,” grinned Jimmie. “I wonder if he has had any sleep since he struck our trail?”

“I haven’t seen him since we left the train,” Jack said. “Perhaps he has delivered us over to the Panama division of the Anti-Canal Benevolent Society. In that case, we shall see no more of him.”

After a time the boys strolled over to a neat little hotel on the principal street of the town, and there saw Lieutenant Gordon, who strolled up to Ned, just as any two Americans meeting there might have affiliated.

“Your camp in the jungle is ready for you,” the officer said, as the two walked about the lobby of the hotel. “You will find a movable cottage there, all furnished, and a good cook. Until further orders you are all to remain there.”

“Pretty quick work,” said Ned.

“The orders for the cottage camp were sent over by wire before we left New York,” the lieutenant replied. “You are at liberty to roam about the works at will, only you ought to leave some one at the cottage always.”

“As I understand it, we are boys looking for adventure?” asked Ned.

“Exactly.”

“And an emerald necklace,” added the boy with a laugh.

“I have a notion that if you find Pedro you will find the necklace, unless you find him too late – after he has disposed of it.”

“That may be,” Ned replied, doubtingly, “but we are not likely to run across Pedro over here. Neither shall we see His Nobbs. They have played their roles, and we shall have new ones to contend with now.”

That night the boys took possession of the cottage in the jungle, dancing and prancing about it like wild Indians. It all seemed to them to be too good to be true. Here they were, at last, on the Canal Zone, and, in a way, in the secret service of the government. It was late when they retired, and no guard was set.

This Ned regretted, after the others were asleep, and so lay awake a long time, watching. Then, about midnight, he saw some one looking in at the porch door.

CHAPTER VI.
A BOMB AND A RUINED TEMPLE

Ned lay perfectly still and the door was closed again, with the figure still on the outside. There were no lights inside the cottage, and it was a fairly clear night, so the boy could see the man standing on the porch, the wire screen in the door robbing his figure of sharp outline.

The intruder appeared to be listening for some sound within. Now and then he bent his head forward toward the door, and once, when Jimmie snorted out in his sleep, he darted a hand toward his hip, as if reaching for a weapon.

“His Nobbs, or his substitute, has arrived,” thought Ned.

After a moment the man left the porch, closing the outer door carefully behind him. Ned was out of bed in an instant, following on after him. When he gained the porch, the intruder was turning the corner of the house.

Fearful of being seen, Ned crouched in a dark corner of the porch and waited. He could hear the fellow moving about, but could not see him, as he kept away from the front of the cottage.

The situation did not change for five minutes. The unwelcome visitor was still moving about outside and Ned was waiting for some decisive move to be made. The cottage did not rest on the knoll itself, but was set up on blocks a foot or more in height, and before long the boy heard sounds which indicated that the man he was watching was creeping in under the floor.

Waiting only long enough to make sure of this, Ned left the porch and hid himself in the jungle, which, on the south, came to within a few feet of the wall. The fellow was indeed under the house, as the boy knew by the sounds he made. It was perfectly dark under there, so his movements could not be observed.

In five minutes more the fellow backed out and arose to his feet. Then Ned saw that he held something in his right hand which looked like a fuse. It seemed that it was the man’s benevolent idea to deprive the jungle of the society of the boys by blowing up their cottage.

Ned’s first impulse was to shoot the fellow where he stood. He had no doubt that the fellow had put enough explosive under the floor to kill every person in it. That would be murder, and the boy’s impulse was to deal out to the ruffian the fate of a murderer.

But he did not fire, for the intruder had not yet lighted the fuse. He stood for a moment with the end in his hand and then moved toward that part of the jungle where Ned was concealed. The boy moved cautiously aside, but even then, as the man crouched down in the vines, he could have touched him with a hand by crawling a yard to the front.

Deliberately the fellow lighted a match and applied it to the fuse. The end of the cord brightened for an instant and then became black again.

“It is wet.”

The words were whispered in English.

He struck another match, listened an instant to make sure that the noise of the lighting had not attracted attention inside the cottage, and applied it to the fuse. The fuse burned swiftly, and the boy heard the incendiary go crashing through the tangle of vines and creepers, heading toward the south.

Ned cut the fuse above the crawling coal and stood for a moment listening to the man struggling with the undergrowth. Then he hastened into the cottage and laid a hand on Frank Shaw’s shoulder.

“Get up,” he whispered. “The fireworks have begun.”

Frank sat up in his bunk and rubbed his eyes sleepily.

“What is it?” he asked. “Have you found the necklace?”

“Dress, quick.”

“Wonder you wouldn’t let a fellow sleep,” grumbled Frank.

While the boys were dressing there came a snicker from Jimmie’s bed.

“Don’t start anythin’ you can’t stop,” they heard the boy whisper.

“Want a midnight ramble among the snakes?” asked Ned, drawing on a pair of rubber boots which came up to his thighs.

“You bet I do,” was the reply.

“Then get up and dress, and put on your high boots, for there are crawling things in the jungle.”

Leaving the boys dressing, Ned hastened outside and listened. The man who had attempted the destruction of the cottage was still moving through the thicket. It seemed to Ned that an army could have made no more noise than he made. In a moment he was joined by Frank and Jimmie.

In as few words as possible Ned explained the situation to his amazed chums.

“What you goin’ to do?” Jimmie asked.

“I want to follow that fellow to his principal,” was the reply. “I want to know who set him at such cowardly work.”

“It won’t be difficult to follow him,” Frank said. “He makes a noise like a circus parade.”

“One of you must stay here and watch the cottage,” Ned said, then. “When the explosion does not come, he may circle back here to see what has happened. The other may go with me.”

Both boys insisted on accompanying Ned, but it was finally decided that it would be better policy to leave Frank at the cottage.

“You’ll have to make haste,” Frank said, regretfully, “for the sounds he is making are becoming fainter. What are you going to do with that fuse?” he added, as Ned drew on the line and hauled about half a foot of gas pipe from under the house.

“It will do no harm to take it with me,” Ned replied. “It is not very heavy to carry, and it may be of use.”

“I hope you’ll blow that chap up with it,” exclaimed Jimmie.

“Be careful that you don’t blow yourself up with it,” warned Frank.

“There are no cigarette smokers in the party, and so there is no danger,” was the reply.

“I’ll be here listening when the explosion comes,” grinned Frank.

The sounds out in the jungle were now growing fainter. The man was either finding the way easier or he was getting some distance away.

“Come on,” Jimmie urged. “He’ll get away from us.”

“If you make as much noise as he does,” Frank said, “he’ll stop and shoot you before you get anywhere near him.”

It was no part of Ned’s intention, however, to follow the intruder through the jungle. He was now waiting to make sure of the general direction the fellow was taking. He listened some moments longer, until the sounds grew very faint indeed, and then took the path which led from the cottage to a fairly well-made road ending five miles away at one of the streets of Gatun.

“You’re gettin’ the wrong steer,” Jimmie said, as they moved along. “You’ll have to go around the world if you catch him by going this way.”

“The fellow is making for the hills,” explained Ned, “and we may be able to catch him as he comes out of the jungle.”

The boys made good speed along the cleared lane until they came to a rolling, grassy hill, one of many leading up to the summit. Then they turned off to the east, still keeping their pace but taking precautions against being seen, as the night was clearer now than before, and a moon looked down from the sky.

Finally Ned paused in a little valley on a gentle slope.

It was one of the wonderful nights rarely experienced save under the equator, or very close to the middle girdle of the globe. The luxuriant growths of the jungle seemed to be breathing in long, steady pulsations, so uniform was the lifting and falling of the night breeze.

Now and then the call of a night bird or the cry of a wild animal in the thickets came through the heavy air. From the distance came the clamor of the greatest work the world has ever undertaken. The thud and creaking of machinery mingled with the primitive noises of the forest. And far away over the cut flared the white light of the great electric globes which lighted the workers on their tasks.

As the boys looked forth from their depression in the side of the slope, two men came around the rise of the hill and stood at the edge of the jungle, not more than half a dozen yards away. Almost at the same instant it became apparent that some one was floundering about in the thicket immediately in front of them.

A low whistle cut the air, and then the creepers parted and a man’s head and shoulders appeared. Ned and Jimmie crouched lower in their dent in the grassy hill.

The man emerged from the thicket and stood with the others, tearing clinging vines and leaves from his clothing as he did so.

“What is wrong?” a voice asked. “There has been no explosion.”

“The fuse was wet,” was the reply.

“Then why didn’t you go back and fix it?” demanded the first speaker. “The sooner the job is done the better.”

“I heard some one stirring in the jungle,” was the reply.

“A nice man to be given such a task,” roared another voice. “You must go back.”

“You’ve landed the plotters, all right,” whispered Jimmie. “I’ll bet there’s plenty more bombs like the one you have, waiting to be tucked under the Gatun dam. Gee! I’d like to take a shot at them gazabos.”

Still standing in the moonlight, only a short distance from the listening boys, the three men argued in low tones for a moment. It was clear that the man who had placed the bomb was refusing to obey the orders given by the others.

“I’m not in love with the job, anyway,” the fellow snarled, “and you may do it yourselves if you want it done to-night.”

The others did not appear to relish the murderous job they were urging the speaker to undertake, and in a few moments the party moved around the base of the hill and then struck for the higher ground by way of a gully which cut between two elevations.

When the boys, mounting the breast of the hill and crouching at the summit, saw the men again, two were making for the cloud of light which lay over the workings while the other was following the crest of the hill toward the east.

Presently the two swung down into a valley, and then twin lights like those of a great touring car showed over a rise.

“What do you think of that?” asked Jimmie. “There must be a good road there.”

The car came on a few yards after the lamp showed, and the two men clambered aboard. In five minutes the motor car was speeding toward Gatun.

“Two for the city and one for the tall timber,” Jimmie snickered, as the car moved out of view. “There’s the solitary individual watching them from the summit.”

As the boy spoke the man who had laid the bomb so unsuccessfully faced away to the east and disappeared down the slope. It was not difficult to keep track of him, although the necessity for concealment was imperative, and the fellow proceeded at a swift pace for an hour.

At the end of that time he was in a lonely section of country, where rounded knolls were surrounded by the dense growth of the jungle. In spite of the wildness of the spot, however, Ned saw that civilization had at some distant time made its mark there. Here and there low, broken walls of brick lifted from the grass, and the vegetation was not quite so luxuriant. In numerous places, as they advanced, the boys saw that the ground had once been leveled off as if to make way for a building, the ruins of which were still to be seen.

“One of the ruined cities of the Isthmus,” Jimmie whispered. “If Peter could see this he would know all about it.”

“It wasn’t a very large city,” laughed Ned.

“There’s the ruins of a temple over there,” insisted the boy. “There’s a wall standing yet. And there’s the man we want going into it.”

As the boy spoke the man they were following disappeared behind the wall. Before he could be restrained Jimmie wiggled forward to the foot of the ruin. Nestor saw him peering around the end of the line of brick and hastened forward.

The man they had followed was nowhere in sight when Ned turned the angle, and Jimmie lay on the ground in the shadows, kicking up his heels.

“He went down through the earth,” the boy giggled, regardless of the danger of the situation. “He went right down through the ground. Say, but he’s a corker, to get out of sight like that.”

Ned caught the lad by the arm, to silence him, and listened. A steady click-click came from the ground beneath their feet. The sounds came continuously, almost with the regularity of the ticking of a clock.

“Where was he when he disappeared?” asked Ned.

“Over there in the corner,” was the reply. “He walked up to the wall and stepped out of sight. What’s that queer smell?” he added, sniffing the air.

“There must be a fire down there in the vaults of the old temple,” replied Ned. “They must have a fire, for the smoke is coming out of a crevice at the top of that wall, and they are working on metal.”

“Yes,” said Jimmie, “an’ I’ll bet they’re makin’ more bombs – bombs for the dam.”