THE

"I tell you, electricity is the thing. Beats gasoline a million ways," chimed in Tom Jesson. Tom sat beside his cousin, Jack Chadwick, on the driver's seat of a curious-looking automobile which was whizzing down the smooth, broad, green-bordered road that led to Nestorville, the small town outside Boston where the Boy Inventors made their home.

The car that Jack Chadwick was driving differed in a dozen respects from an ordinary automobile. There was no engine hood in front. Instead of a bonnet the car, which was low slung, long and painted black, had a sharp prow of triangular shape. Its body, in fact, might be roughly compared to the form of a double-ended whaleboat.

As it sped along outside the city limits, and immune from hampering speed laws, the car emitted no sound.

It moved silently, without the usual sharp staccato rattle of the exhaust. Behind it there was no evil-smelling trail of gasoline and oil smoke. The car glided as silently as a summer breeze on its wire-wheels, like those of a bicycle enlarged.

"I'll get a great story out of this," declared Dick Donovan, who, as readers of other volumes of this series know, was a reporter on a Boston paper. "That is, if you'll let me write it," he added, leaning forward over the front seat from the tonneau as he spoke.

"How about it, Jack?" asked Tom with an amused smile. "Shall we let Dick here get famous at our expense again?"

"I don't see why not," said Jack. "Everything about the Electric Monarch is patented. The new reciprocating device, and the self-feeding storage batteries are fully covered. If Dick wants to write a romance about it he can, provided he leaves our pictures out."

"Oh, I'll do that," Dick readily promised. "Are you making top speed now, Jack?"

"Nowhere near; I wouldn't dare to. I believe that the Monarch is capable of ninety miles an hour. I wish we had a place like Ormond Beach to try her out on."

"You can count me out on that," chuckled Dick. "This is fast enough for me."

The boys were trying out their latest invention, an electric car capable of making the speed of a gasoline-driven vehicle, and one which could be operated at a minimum of cost, almost a nominal expense, as compared with the high price of a vehicle run by an explosive engine.

It was the trial trip of the Electric Monarch, as they had decided to call it, and so far the performances of the machine had exceeded, instead of fallen below, their expectations. Dick, who had been invited to the "tryout," was full of questions as they sped silently, and with an absolute lack of vibration, along the road.

"How do you generate your electricity?" he asked eagerly.

"By a device geared to the rear axle," answered Tom. "It runs a sort of dynamo, though it would be difficult for you to understand it if I went into details. It's something like the ordinary generator and turns a constant stream of 'juice' into the storage batteries that, in turn, feed the engines."

"Yes, that's all plain enough," said the inquisitive Dick, "but how do you get your power for starting?"

"If there is not enough juice in the storage batteries for the purpose we resort to compressed air," was the reply from Tom, for Jack, with keen eyes on the unrolling ribbon of road, was too busy to have his attention distracted.

"And that?" Dick paused interrogatively.

"Is pumped into a pressure tank as we go along. See that gauge?" he pointed to one on the dashboard of the car in front of the driver's seat.

Dick nodded.

"Well, that's a pressure gauge. You see, we have sixty pounds of air in the tank now. That can generate enough electricity to start the car going. After that the process is automatic."

"Yes, you explained that. Suppose the tank should, through an accident, be empty, and you wanted to start?"

"We've provided for that"

"I expected so. Wabbling wheels of Wisconsin, you fellows are certainly wonders."

"Nothing very wonderful about it," disclaimed Tom. "Well, if we find the tank is empty we have a powerful, double-acting hand pump by which, without much effort, we can get up any pressure we need."

"And then you turn a valve?"

"Exactly, and the air-motor turns over the dynamo which starts generating electricity right away."

"Then, except for the first cost of the car, the expense of operating it is comparatively nothing?" asked Dick.

"Yes, you might say we get our power out of the air, and that's free—so far."

"And there's no limit, then, to what you can do or where you can go with the Electric Monarch?"

"None; that is, so long as the machinery holds out. We are independent of fuel and the lubricating system is so devised that the oiling is automatic and requires attending to only once a month. We could easily carry a year's supply of lubricant."

"Tall timbers of Taunton!" burst out Dick enthusiastically. "You've solved the problem of the poor man's car. All the owner of an Electric Monarch has to do is to pump a little pump-handle or press a little button and he's off without it costing him a cent. My story will sure make a big sensation!"

"Well, you want to tone down that part about its not costing a cent," chimed in Jack as they coasted down a hill. "The expense of the motor and the self-lubricating bearings and so on is pretty steep. But we hope in time to be able to cheapen the whole car."

They were shooting swiftly down the hill as he spoke. The next moment he looked ahead again as they shot round a curve. As they did so his hand sought a button and an ear-splitting screech arose from a powerful siren.

In the center of the road, quite oblivious to the oncoming automobile, was an odd figure, that of a small man in a rusty, baggy suit of black.

He had a hammer in his hand and was hitting some object in the roadway over which he was bending with a concentrated interest that made him quite unconscious of the onrushing car.

"Hi! Get out of the way!" yelled the boys.

But the man did not look up. Instead, he kept tapping away with his hammer at whatever it was that absorbed his attention so intently.

CHAPTER II.

AN ENCOUNTER WITH A "CHARACTER."

Jack jammed down the emergency brakes, which were pneumatic and operated from the pressure tank, with a suddenness that sent Dick Donovan almost catapulting out of the tonneau.

"Jumping jiggers of Joppa!" he shouted, for he had not yet seen the obstacle in the road, "what's happened? Are we bust up?"

"No, but if I hadn't stopped when I did we'd have bust someone else up," declared Jack. "Look there!"

"Can you beat it?" exclaimed Tom.

As the brakes brought the car to a stop within a foot of his stout, rotund figure, the little man in the center of the road looked up with a sort of mild surprise through a pair of astonishingly thick-lensed eyeglasses secured to his ears by a thick, black ribbon. He wore a broad-brimmed black hat and wrinkled, baggy clothes of bar-cloth, and a huge pair of square-toed boots that looked as if their tips had been chopped off with an ax.

Over his shoulder was slung a canvas bag which appeared to be heavy and bulged as if several irregularly shaped, solid substances were inside of it. The spot where this odd encounter took place was some distance from any town, but a bicycle leaning against a tree at the roadside showed how the little man had got there.

"Say, would you mind letting us get by?" asked Jack.

The little man raised a hand protestingly.

"I'll be delighted to in just a moment," he said, "but just now it's impossible. You see, I've just discovered a vein of what I believe to be Laurentian granite running across the road. I am trying to trace it and—what's that? Good gracious! Back up your machine, please. I believe it runs under your wheel. I must make sure."

Jack obligingly threw in the reverse to humor the little man, who darted forward and began scraping up the dust in the road with his hands as if he had been a dog scratching out a rabbit hole. He began chipping away eagerly with his hammer at some rock that cropped up out of the road.

He broke off a piece with his hammer, which was an oddly shaped tool, and drawing out a big magnifying glass scanned the chip intently. He appeared to have forgotten all about the waiting boys. But now he seemed to remember them. He looked up, beaming.

"A magnificent specimen. One of the finest I have ever seen. Most remarkable!"

And with that he popped the bit of stone into his bag, which the boys now saw was filled with similar objects.

"Maybe he'll let us get by now," remarked Tom, but a sudden exclamation from Dick Donovan cut him short.

"Why, hullo, professor," he said, "out collecting specimens?"

The little man peered at him sharply. And then broke into a smile of recognition.

"Why, it's Dick Donovan!" he beamed, hastening up to the car, "the young journalist who wrote an article about my specimens once and woefully mixed them up. However, to an unscientific mind——"

"They are all just rocks," finished Dick with a grin.

"I have had unusual success to-day," said the professor, who appeared not to have heard the remark. "I must have at least fifty pounds of specimens on my back at this minute."

He broke off suddenly. The next moment he darted off to the side of the road and chipped off a fragment of rock from a bank that overhung it.

"This is lucky, indeed," he exclaimed, holding it up to the light so that some specks in the gray stone sparkled. "An extremely rare specimen of mica that I had no idea existed in this part of New England."

The odd little man opened his bag and introduced his latest acquisition into it While he was doing this Dick had been explaining to the boys:

"He's a queer character. Professor Jerushah Jenks. They say he's a great authority on mineralogy and so on. I interviewed him once. He's always out collecting."

"Does he always carry a quarry like that around on his back?" asked Tom.

"Always when he's getting specimens," Dick whispered back.

By this time the professor, his eyes agleam over his latest discovery, was back at the side of the car.

"Ah, my beauty, I have you safe now," he said, patting the side of the bagful of specimens. "Boys, this is my lucky day."

The boys could hardly keep from smiling at the little man's delight. It appeared hard to believe that anyone could find pleasure in packing about a sackful of heavy rocks on a hot day. But the professor's eyes were sparkling. It was clear he considered himself one of the most fortunate of men.

Dick introduced the boys and, to their surprise, the professor declared that he had read of their various adventures and inventions.

"We are actually fellow adventurers in the field of science," he cried, rattling his bag of specimens enthusiastically. "Some time I should like to call on you and see your workshops."

"You will be welcome at any time," said Jack cordially, and then the professor declared that he must be getting home.

"If we are going your way we can give you a ride," said Tom.

"Thank you, I'll accept that invitation. But what an odd-looking automobile you have there."

The boys explained to him that it was a new type of car that they were trying out for the first time and then Dick helped the scientist lift his bicycle into the tonneau. He would have helped him with his weighty load of specimens, but the professor refused to be parted from them. As they started off again he sat with the bag firmly gripped between his knees, as if afraid someone would separate him from it.

The professor lived with a spinster sister to whom his specimens were the bane of her life. As the car rolled swiftly along, he occupied his time by peeping into the bag at frequent intervals to see that none of the specimens, by some freak of nature, flew out.

All at once he reached forward and clutched Jack by the shoulder.

"Stop! My dear young friend, please stop at once!"

"What's the matter?" asked Jack, slowing down at the urgent summons.

"Look! Look there at that rock!"

To Jack the rock in question was just an ordinary bit of stone in a wall fencing in a pasture in which some cattle were grazing. But evidently the professor thought otherwise.

"It's a fine specimen of green granite," he exclaimed. "I must have it. How did such a fine piece ever come to be placed in a common wall?"

The car having now been brought to a stop, he leaped nimbly out, clutching his geological hammer in one hand and his precious sack of specimens in the other. He rushed up to the wall and stood for a minute with his head on one side, like an inquisitive bird.

"Too bad. That stone's a large flat one and goes right through the center of the wall," he mused. "The wall must come down."

And then, to the boys' consternation, he began demolishing the wall, pulling down the stones and throwing them right and left.

"Professor, you'll get in trouble," warned Dick in alarm. "Those cattle will get out. The farmer will be after us."

But the professor paid not the slightest attention. Taking off his coat, he resumed his operations with even greater vigor than before. The cattle in the field eyed him curiously. Then they began to move toward him. In front of the rest of the herd was a big black-and-white animal with sharp horns and big, thick neck.

It gave a sudden bellow and then rushed straight at the considerable gap the man of science had made in the stone fence.

"It's a bull!" yelled Dick suddenly. "Run, professor! Run or he'll toss you!"

With lowered horns the bull rushed down upon the unconscious scientist at locomotive speed. But the professor was oblivious to everything else but uncovering the odd-looking green stone embedded in the heart of the wall.

The boys shouted to him but he didn't hear them. On rushed the bull, bellowing, charging, ready to annihilate the scientist.

"Run!" yelled the boys at the top of their lungs. "Run!"

But the professor, with his precious bag in one hand and his hammer in the other, stood staring at the advancing bull through his thick glasses as if the maddened creature had been some sort of new and interesting specimen.

"Gracious! He's a goner!" groaned Dick.

CHAPTER III.

THE PROFESSOR'S DILEMMA.

But the professor was seen to suddenly dart, with an activity they would hardly have expected in him, across the road. He was only in the nick of time.

Almost opposite to the gap in the fence he had made was a tree with low-hanging boughs. As the bull charged through the gap, right on his heels, the professor, still with his bag, slung by its leather strap across his shoulders, swung himself up into the lower limbs.

The boys set up a cheer.

"Good for you, professor!" cried Dick, as the bull, with lowered head and horns, charged into the tree and made it shake as if a storm had struck.

"Wow! That's the time he got a headache!" cried Tom excitedly, as the professor, clinging desperately to his refuge, was almost flung from it by the shock.

"Gracious, boys, what shall I do?" he asked, looking about him from his leafy perch with a glance of despair that would have been comical had the situation not been serious, for the bull, instead of accepting his defeat, stood under the tree pawing and ramping ferociously.

"Well, here's a fine kettle of fish!" exclaimed Jack. "What are we going to do now?"

"Blessed if I know," said Dick helplessly. "By the bucking bulls of Bedlam, this is a nice mess."

"Maybe we could throw rocks at him and chase him away," suggested Tom.

"No chance; he's got his eye on the professor," returned Jack, "and if we did get out he would chase us and that wouldn't do the professor any good."

"Can't you help me, boys," inquired the professor in an agonized tone. "This tree limb is not exactly—er—comfortable."

"You're in no danger of falling, are you?" called Jack, in an alarmed voice.

"No—er—that is, I don't think so. But this is an extraordinary position. Most—er—undignified. I'm glad my sister can't see me."

"Try throwing some of the rocks out of your satchel at him," suggested Dick.

But the professor waxed indignant at this proposal.

"And cast my pearls before swine! or rather my specimens before a bull!" exclaimed the professor, in helpless indignation. "No, young gentlemen, not a pebble from this bag is wasted on that creature."

"I'd drop the whole bag on him," said Dick, "if I was in that position. It's heavy enough to knock out an elephant, let alone a bull."

"Can't you suggest anything?" wailed the professor.

"I'm trying to think of something right now," declared Jack, racking his brains for some way out of the predicament.

"I wish the farmer that owned him would come along and get his old bull out of there," said Dick.

"Yes, and then there would be fresh complications," declared Jack.

"How do you make that out?" came from Dick.

"He'll probably know how to handle him," supplemented Tom.

"Yes, he would if he's a bull-fighter," scoffed Dick, "and I never heard of there being any matadors in the vicinity of Nestorville."

"Lots of doormats, though," grinned Tom.

"Say, if you do that again I'll throw you out of the car," cried Jack at this atrocious pun.

"Sorry, couldn't help it. Just slipped out," said Tom contritely.

"Well, you'll slip out if the offense is repeated," retorted Dick. "But," he went on, "seriously, fellows, we've got to do something."

"Try blowing the horn," suggested Tom. "It has scared everything else we met. Horses shy at it, so do other autos. Maybe it will get the bull's goat."

"I'll try it, at all events," said Jack.

He pressed the button and the unearthly screech of the electric auto's siren split the air. But the bull merely cast an inquiring glance in their direction and then resumed his vigil over the professor.

"Boys," wailed the unhappy geologist, "can't you do something, anything? I can't roost in this tree all night, like a bird."

The boys couldn't help grinning at this. With his sharp nose, big spectacles and flapping black garments, the professor did look like a mammoth black crow.

"Reminds me of the fox and the crow," said Dick, in a low voice, to his companions.

"Only, in this case, the fox is a bull, and the piece of cheese is the bag of specimens," added Tom.

They looked about helplessly. There was no farmhouse in sight and the road did not appear to be much traveled.

"We'll have to go for help," declared Jack.

"The only thing to do," agreed Tom.

The professor was hailed. He had climbed to another limb with infinite difficulty, because of the encumbering bag of rocks on his back. He declared that he could manage to get along till the boys came back.

"By a merciful provision of providence," he said whimsically, "bulls can't climb trees. The situation might be worse if it was a bear."

"It would be unbearable," declared Dick to Tom.

"But just the same there's trouble a brewin'," retorted Tom. "I wish that farmer would show up."

"As I said before—I don't," responded Jack, as he prepared to start off.

"Why?"

For answer Jack waved an eloquent hand toward the gap in the stone fence.

"I guess he wouldn't be best pleased to find that his fence had been torn down," explained Jack, as the car drove off, leaving the professor marooned in his tree with the sentinel bull waiting patiently below.

Some distance down the road the boys came to a farmhouse. Several men were working in the field under the direction of a stout, red-faced man. Jack shouted to them, and when the red-faced man came up he explained the situation to him. The man was good-natured, or perhaps he rather liked the idea of a ride in such a novel-looking car. Anyhow, he called three of his hands and told them to get pitchforks.

"Never see a bull I couldn't handle," he said as the men, having returned, scrambled into the car.

"Do you know who it belongs to?" asked Jack, as he turned round and headed back to where they left the luckless professor.

"I reckon it's that big Holstein of Josh Crabtree's. He's pretty near as mean as his owner, and that's considerable."

Jack thought of the hole in the wall and hoped they would reach there before farmer Crabtree, and so avoid serious complications.

He drove at top speed, while the friendly farmer and his workmen clung to the sides of the car and looked rather scared at the rate they were going.

"There's the tree," exclaimed Jack, as they came in sight of it, "and there's the gap in the fence."

"And where's the bull?" asked Tom.

"And where's the professor?" added Dick.

Not a trace of the man of science or of the ferocious animal was to be seen.

"Are you sure you boys didn't dream all this?" asked the red-faced farmer suspiciously.

"There ain't even a cow in sight in the pasture lot," said one of the men.

"I reckon this is some sort of a fool joke," added another.

"It isn't. Indeed, it isn't," protested Jack.

"The professor is some place around," said Tom.

But a lengthy search of the vicinity failed to show anything except that the professor had vanished as if the earth had swallowed him.

CHAPTER IV.

"WHERE IS HE?"

"Professor!" hailed Dick, at the top of his lungs.

"Professor!" bawled the farm hands.

The red-faced farmer himself regarded the boys quizzically.

"What sort of a chap is this professor of yours?" he asked with an odd intonation.

"He's a geologist," replied Dick. "Why?"

"Oh, I thought he might be a conjurer," was the rejoinder. "He seems to be pretty good at hiding himself."

"Hark!" exclaimed Jack suddenly, standing at pause and listening intently.

"What's up?" demanded Dick, instantly on the alert, too.

"I heard something. It sounded like——"

"There it is again," cried Tom.

A faint, far-off cry, impossible to locate, was borne to their ears.

"It's a call for help," declared Dick.

"That's what it is," agreed the red-faced farmer. "Must be that perfusser of yours, but where in the name of Sam Hill is he?"

It was a puzzling question. The faint cries appeared to be muffled in some way. They looked about them, endeavoring to locate their source. Suddenly one of the farm hands spoke.

"I used to work fer old Crabtree," he said. "There's an old well hereabouts somewheres and maybe he's fell down that."

"Where is it?" demanded Jack.

"Back in the meadow yonder," said the man, pointing in the direction of the pasture lot.

"Let's go over there and see at once," said Dick. "Frantic frogs of France, if the professor's tumbled into a well he may be in serious trouble."

They set off on the run to where a pile of stones showed a well-curb had once been. The hoards at the top, which had covered it over, had rotted, and there was a jagged hole in them. Jack cautiously bent over and placed his mouth at the edge of the hole.

"Professor, are you down there?" he hailed.

"Y-y-y-y-yes," came up in feeble, stuttering tones. "I'm almost frozen. I'm hanging above the water but I can't hold on much longer. The bag of specimens is too heavy."

"Throw it away," urged Jack.

"N-n-n-not for worlds," was the reply. "I was looking for another rare bit of quartz when I fell in here."

"I'll run to the car," said Jack, who had made out that the well was not very deep. "Fortunately, we've got a rope and tackle in there. Hold on, professor, we'll soon have you out."

He hurriedly explained the situation to the others and ran at top speed to the car, in which the boys—like most careful motorists, who never know when such a piece of apparatus may come in useful for hauling a car out of mud or sand, for instance, or for towing an unlucky autoist home—had a block and tackle stowed.

He was soon back, and the rope was lowered to the professor, who made it fast under his arms. Then, aided by the husky muscles of the farm hands, they soon drew him to the surface. But his weight was materially added to by the stones, and it was no light task to rescue him, dripping and shivering, from the dark, cold shaft.

He explained that soon after they had gone some men came up and drove the bull away. But they had seen the gap in the stone wall first.

"They were positively violent," declared the professor, "and said that they'd have the man who did it arrested if they could find him. Under the circumstances, I deemed it prudent to stay up in the tree, where they could not see me. They drove the bull off into another pasture. As soon as the coast was clear I climbed down, but I happened to see a rare bit of quartz sparkling in the sun on the edge of the well-curb. Imprudently I stood on the planking and fell in."

"Gracious, it's a lucky thing you weren't drowned, with all that weight round your neck," declared Jack.

"It was fortunate," said the scientist mildly, as if such a thing as drowning was an everyday occurrence. "As a matter of fact, if I hadn't succeeded in grasping a projecting stone and held on, I might have gone down. It was an—er—a most discomforting experience."

"Well, of all things," exclaimed the red-faced man, "to go trapesing round the country collecting rocks!"

"Not rocks, sir—geological specimens," rejoined the professor with immense dignity, "and—great Huxley! Under your foot, sir! Under your foot!"

"What is it, a snake?" yelled the farmer, jumping backward as the scientist dashed at him with a wild expression.

"No, sir, but a remarkably fine specimen of what appears to be a granolithic substance," exclaimed the professor, and he began energetically chipping at a rock upon which the farmer had been standing.

"Crazy as a loon," declared the farmer, winking at his men. "Gets nearly drowned in a well and then begins chopping at a rock as soon as he gets out."

"Oh, this has been a lucky day for me," said the professor with huge satisfaction, as he placed his latest acquisition in the satchel. "As fine a specimen, boys, as ever I encountered," he declared, turning to the boys.

"Gracious," exclaimed Tom and Dick in low tones, "does he call getting chased by a bull and then tumbling down a well a satisfactory day?"

"I should call it a rocky time," grinned Dick.

But at this moment further conversation was cut short by the sudden arrival of a gray-haired, short little old man with a tuft of gray whiskers on his chin.

"Josh Crabtree!" exclaimed the red-faced farmer.

"Wow! now the music starts," declared Dick.

Josh Crabtree, his face ablaze, and his small, malignant eyes sparkling angrily, emitted a roar like that of his Holstein that had caused the professor so much tribulation.

"Say, be you the pesky varmints that tore down my fence and scared my bull out'n two years' growth?" he bellowed.

"I removed some stones from your fence, sir," said the professor, "but it was in the interests of science. You may not have been aware of it, but embedded in your enclosing structure was a fine specimen of green granite."

"Great hopping water-melyuns!" roared Old Crabtree, "and you tore down my fence to git at a pesky bit of rock?"

"Rock to you, sir," responded the scientist calmly, "like the man in the poem a 'primrose by the river's brim, a yellow primrose is to you, and it is nothing more.'"

"Dad rot yer yaller primroses," yelled Old Crabtree, dancing about in his rage. "You make good for tearing down my fence, d'ye hear me?"

"I shall take great pleasure in forwarding you a check for any damage I may have done," said the professor.

"I want ther money now," said the farmer truculently.

"I regret that I have left my wallet at home," said the professor. Then he brightened suddenly. "I can leave my bag of specimens with you as security," he said, "if you will promise to be careful with them."

He unslung his bag and tendered it to the angry farmer who received it with a look of amazement that the next moment turned to wrath when he saw its contents.

"By hickory, what kind of a game is this?" he demanded. "Nothing but a lot of old rocks. By heck, thar's enough here to build a new fence!"

He flung the bag down indignantly just as the professor darted forward with one of his odd, swift movements. He shoved Old Crabtree back without ceremony and bending swiftly to the spot where the angry farmer had been standing he picked up and pocketed a small rock.

"Wa'al land o' Goshen," gasped out the farmer, bewildered. "What in ther name of time is this?"

"A splendid specimen of gneiss," explained the professor triumphantly, "and now, Mr.—er—you were saying?"

"That I wants ter be paid fer ther damage ter my fence."

"How much do you want?" asked Jack, coming to the rescue.

"Reckon a dollar'll be about right."

"If you will let me lend it to you till we reach your home, I'll be very glad to pay him," said Jack aside to the professor.

"But, my dear young friend, there is no necessity. He has ample security till I can send him a check. Why, that bag of specimens is worth fifty dollars at least."

"Them old rocks," sniffed the farmer, who had overheard this last remark, "I wouldn't give yer ten cents fer a cartload uv 'em. They're too small fer fences an' too big to throw at cows."

"You'd better let me pay him," said Jack, and the professor finally consented to this arrangement.

This done, they started back on the run to the professor's home, which was about three miles off. On the way they dropped the red-faced farmer and his hands, who clearly regarded the professor as some sort of an amiable lunatic. But that worthy man, supremely happy despite his wet clothes, was quite contented, and from time to time dipped into his satchel, like a bookworm into a favorite volume, and drew out a particularly valued specimen and admired it.

They soon reached his home, a pretty cottage on the outskirts of Creston, a small town with elm-shaded streets. The professor invited the boys to accompany him into the house. They were met in the passage by a shrill-voiced woman who looked like the professor in petticoats.

"My sister, Miss Melissa," said the professor. "My dear, these are——"

But he got no further in his introduction. Miss Melissa's hands went up in the air and her voice rose in a shrill shriek as she saw her brother's condition.

"Lan's sakes, Jerushah, where have you been?" she exclaimed.

"My dear, I must apologize for my condition," said the professor mildly. "You see I——"

"You're dripping a puddle on my carpets. You're wringing wet through!" shrilled Miss Melissa.

"Yes, you see, my dear, I've been down a well," explained the man of science calmly.

"Do tell! Down a well, Jerushah? At your time of life!"

"You see I was after specimens, my dear," went on the professor.

"Specimens!" exclaimed Miss Melissa. "The whole house is full of old rocks now, Jerushah, an' you have ter go down a well to get more."

"These are very valuable, my dear," said the professor, floundering helplessly.

"Oh, don't tell me. A passel of old rocks. I'm going to get you a hot mustard footbath and some herb tea right away," and without another word, except something about "death of cold, passel of boys," the good lady flounced off.

"She's like that sometimes, but she means well, Melissa does," explained the professor, with a rather sheepish look as he stood in the midst of a puddle that was rapidly converting him into an isolated island in the midst of Miss Melissa's immaculate hall carpet. Suddenly, with one of his impulsive movements, he darted off into a room opening off the hall and came back with a dollar bill he had unearthed from a desk. He handed it to Jack, and then, raising his finger to his lips, he said:

"Don't let Melissa see it. She's the best of women, is Melissa, but peculiar about some things—er—very peculiar."

"Je-ru-shah!" came Miss Melissa's voice.

"Yes, my dear, coming," said the professor, and shouldering his bag of specimens he shook hands with the boys and hastened off to answer his sister's dictatorial call.

"I guess we'd better be going," said Jack, with a smile that he could not repress.

The others agreed, and they were soon speeding back to High Towers, as the estate of Jack's father, also a noted inventor, was called, with plenty to talk about as a result of the events of the day.

CHAPTER V.

CHESTER CHADWICK—INVENTOR.

As readers of the preceding volumes of this series, know, Jack Chadwick and Tom Jesson, his cousin, had won the titles of Boy Inventors through their ingenuity and mechanical genius. Jack's father, Chester Chadwick, was an inventor of note, and unlike the majority of inventors, he had turned his devices to such good account that he had accumulated a substantial fortune and was able to maintain a fine estate, already referred to as High Towers where, with splendidly equipped workshops and a miniature lake, he could experiment and work out his ideas.

In the first book of this series it was related how Tom Jesson, Jack's cousin, came to make his home at High Towers. Tom's father, an explorer of international fame, had departed on an expedition to Yucatan and had not been heard from since that time. This volume, which was called the Boy Inventors' Wireless Triumph, told of the boys' exploits in the radio-telegraphic field and the uses to which they were able to turn them. In a flying machine, the invention of Mr. Chadwick, they discovered Tom's father, under remarkable circumstances, a prisoner of a tribe of savages, and also found a fortune in precious stones.

In the succeeding story of their adventures, the boys helped an inventor in trouble. The Boy Inventors' Vanishing Gun, as this volume was entitled, set forth in a graphic way the triumph of the boys over the machinations of a gang of rascals intent on stealing the plans of the wonderful implement of warfare which they had helped bring to successful completion.

We next encountered the lads in the Boy Inventors' Diving Torpedo Boat. Here they were placed in a new environment on the surface and in the depths of the ocean. The way in which the wonderful diving craft aided Uncle Sam in a crisis with enemies of the United States was told, and their ingenuity and bravery played no small part in the affair.

The Boy Inventors' Flying Ship was devoted to a detailed narrative of the boys' long and unexpected cruise to the unexplored regions of the Upper Amazon. The boys were shipwrecked and cast away without an apparent hope of rescue on a yacht belonging to a German scientist, the crew of which had mutinied. The boys' capture by a strange tribe and subsequent escape in their Flying Ship formed thrilling portions of this story, while Dick Donovan's researches in natural history provided the boys with a lot of fun.

The volume immediately preceding this showed the boys coming to the rescue of a poor lad, a waif and orphan, who yet had a fortune in the plans and specifications of a new type of craft invented by his dead father who had lacked the capital to develop it. Enemies strove desperately to secure the papers, and even went to the length of forging a will for the purpose, but partly through the agency of an odd German lad, Heiney Pumpernickel Dill, their schemes were frustrated and the invention was developed and set upon a working basis. This book was called the Boy Inventors' Hydroaëroplane, and dealt with some astonishing adventures and perils all of which the boys encountered with plucky spirits and resourceful minds.

For some weeks preceding the opening of the present book relating of the Boy Inventors, Mr. Chadwick had been closeted in his own private laboratory. The boys had seen him only at rare intervals, and then he had appeared abstracted and preoccupied. This, the boys knew, was a sure sign that he was at work on a new idea.

Sometimes the lights burned in his laboratory far into the night and in the morning he would appear at breakfast pale and silent. The boys had indulged in much speculation as to what the new invention could be, but had arrived at no satisfactory conclusion when, two days after their experience with the eccentric professor, Mr. Chadwick summoned them to his private workshop. The boys, who had been at work on the Wondership, the flying automobile with which they had met such surprising adventures in Brazil, obeyed the summons with alacrity. It was delivered to them by Jupe, the negro factotum of the place.

"Massa Chadwick send me on de bustelbolorium," explained Jupe, who had a vocabulary that was all his own, "for yo' alls to come right away by his laburnumtory."

"All right, Jupe, we'll be right over," said Jack, "just as soon as we've got some of this grease off our hands."

The boys' workshop was equipped with a washbasin and they soon made themselves presentable. Then they hurried to Mr. Chadwick's workshop. They found him standing before a roughly-built table on which were ranged some odd-looking bits of apparatus.

There was a gasoline motor in one corner, geared to a generator—or what appeared to be one—from which feed wires led to a square metal box on the table. Attached to this metal box was a sort of horn-shaped mouthpiece something like the transmitter of a telephone. Hanging from its side was what looked like an enlarged telephone receiver. Jack regarded his father questioningly.

"You sent for us, dad?"

"Yes, Jack," was the reply. "I'm in a quandary. Have you any idea what this apparatus is?"

Both boys shook their heads.

"Looks like some kind of a telephone," ventured Tom.

"It is a telephone," replied Mr. Chadwick.

"But—but—where are the wires?" asked Jack, glancing about him, "or haven't you connected it up yet?"

"It's connected up as much as it will ever be," said Mr. Chadwick with a smile. "Can't you guess what it is?"

"I've got it," cried Jack suddenly. "It's a wireless telephone."

"That's right," admitted his father, and, in response to a flood of questions from the boys, he told them how he had been working day and night to bring the device to perfection.

"Now," he said, as he concluded, "I want you boys to go down to that shed that was put up last week at the northwest corner of the orchard."

"The one that was put up to store gasoline?" asked Tom.

"I said it was for that purpose in order to avoid questions till I had my work completed," said Mr. Chadwick with a smile. "Here is the key to it. Inside you will find an apparatus similar to this one. Start the dynamo and then stand in front of the transmitter and place the receiver to your ear. If you don't hear anything at once use the inductor to tune your aërial earth circuit to the transmitted current from my end just exactly as you would tune up a wireless telegraph instrument to catch certain wave lengths from another instrument"

"Then the principle of the radio telephone is the same as that of the wireless telephone?" asked Tom.

"I'll explain that to you later in as plain language as I can," said the inventor, "but now I am anxious to see how this instrument will transmit sound."

The boys were excited. Anything novel in the way of science attracted their bright, active minds as an electromagnet attracts steel. The idea of a wireless telephone, of the possibility of transmitting actual speech through space, just as the dots and dashes of the wireless telegraph are sped through the ether, quickened their inventive faculties to the highest pitch. Both felt a glow of pride that they had been selected, even before their father's scientific friends, to make the first test of this wonderful new invention.

They hurried across the broad lawn that intervened between the workshops and the orchard where the newly erected shed stood, and which, it had been given out, was to serve for the storage of gasoline. Unlocking the door, they found inside an apparatus resembling in almost every detail the one in Mr. Chadwick's workshop.

Jack's hands fairly trembled as he started up the motor and the generator began to buzz. With shining eyes and throbbing pulses he placed the receiver to his ear as his father had directed. But the next moment a flood of disappointment swept through him.

"Well?" demanded Tom, himself a tiptoe with expectation.

"Nothing doing," replied Jack, shaking his head. "I guess the thing isn't at a practical stage yet."

"Wait a minute, give it a chance," urged Tom. "By the way, how about that tuning device, have you tried that yet?"

"No, good gracious, my head must be turning into solid ivory from the neck up. I guess that's just what the trouble is."

Jack began carefully sliding a small block connected to the instruments up and down the coiled wire which formed the tuning apparatus, and brought the sending and receiving ends into harmony just as if they had been two musical instruments. When the right electric "chord" was struck he should be able to hear, just as in wireless he would be able to catch the message of an instrument whose wave lengths were attuned to his.

Suddenly Tom saw his chum and cousin give a start and then a shout. Over the space between the workshop and the small shed a human voice had been borne on electric waves. Sharp and clear as though he had been listening to a "wire" 'phone, Jack caught and recognized his father's voice:

"Hul-lo!"

CHAPTER VI.

THE RADIO TELEPHONE.

Back and forth through space they talked for quite a time. The boys were jubilant. The despair of many inventors, the wireless or radio telephone appeared to be an accomplished fact. But they didn't dream how much yet remained to be done. At length Mr. Chadwick told them to "hang-up" and come back to the workshop.

The boys were glad to do this for they were extremely anxious to learn something of the forces controlling this aërial method of conversation. So far, they had not the least understanding, beyond a general idea, of how the thing was done. Of the details by which Mr. Chadwick had worked out this radical departure in telephony, they knew nothing.

"Well, what did you think of it, boys?" asked Mr. Chadwick when they returned to the workshop.

"Wonderful, beyond anything I could have imagined," declared Jack.

"How far will it work?" asked Tom.

"That's just the point," said Mr. Chadwick. "That's where I'm at sea. I need a metal of greater conductivity than any attainable to get real results. The carbon that I am using does not throw off enough radio activity to produce a sufficient number of electric impulses to the atmosphere."

Jack and Tom looked puzzled.

"You don't understand me I see," said Mr. Chadwick.

"No, I must say I don't," said Jack; "you see——"

"It's pretty technical," broke in Tom.

"Well, then I'll try to explain to you, in simple language, the general principles of radio telephony," said Mr. Chadwick. "In the first place you know, of course, from your wireless studies, that an electric wave sent into the air will travel till it strikes something, such as an aërial."

"To use the old illustration, an electric impulse sent into the air spreads out in all directions just like the ripples from a stone chucked into a mill-pond," said Jack.

"That's it," said Mr. Chadwick. "Now then, as you also know the wire telephone works by a metal disc in the receiver, vibrating in exactly the same way as does the microphone in the transmitter. According to the vibrations of the voice of the person sending the spoken message, the electric current along the wire, acted upon by the microphone in the transmitter, increases or decreases. This increasing and decreasing current acts on a thin metal disc or diaphragm in the receiver which is held to the ear of the person listening to the message."

"That's plain sailing so far," said Jack. "For instance, when you say 'Hullo' over a phone, the microphone or transmitter gets busy and records it in electrical impulses and shoots it all along the wire where the receiver picks it up and wiggles the metal disc inside it to just the same tune."

"That's it exactly," said Mr. Chadwick. "Now we are ready to go a step further. Now, as this metal disc is attracted or released by the current coming over the wire, it compresses or rarefies the air between it and the ear-drum of the person to whose oral cavity it is held. In this way the sensation of the same sound as was spoken at the transmitter end is reproduced at the receiver end. In other words, the transmitter jerks and jumps just as the needle of a phonograph does in traveling over a record, and transmits these jerks and jumps over the wire to the metal disc which by aërial pressure on the ear drums of the receiver of the message, causes the aural membrane to translate the words, or vibrations along the nerves, to the brain.

"Following up this line," said Mr. Chadwick, "we find that the problem in radio telephony is the same as that met with in ordinary wire telephony. That is to say, we are required to cause a distant metal disc to repeat every inflection of the transmitter. But in the case of radio telephony the result is to be obtained by Hertzian waves, instead of by a current passing through an insulated wire."

"The same sort of waves that are employed in wireless telegraphy?" asked Tom.

"Just the same, only in radio telephony we are confronted by a problem not met with in wireless telegraphy. We have not only to transmit sound, such as isolated dots and dashes, but to send through the air every rise and fall and inflection of the human voice just as it is recorded in the minute lines of a phonographic record.

"Experiments have shown that articulation, that is, understand, a speech, depends upon overtones and upper harmonies of a frequency of 5,000 or 8,000 or more."

"What do you mean by frequency?" asked Tom.

"Speaking in reference to radio telephony it means the number of electrical vibrations per second required to produce a certain sound. In electric currents 100 per second is a low frequency current, 100,000 per second is spoken of as high frequency. In early experiments with radio telephony it was found that the chief difficulty lay in obtaining a current of sufficiently high frequency to transmit the human voice, the currents used in wireless telephony being much too weak for this purpose.

"I had, therefore, to invent my own alternator, which is attached to that gasoline motor. There is a similar one in the shed from which you just talked with me."

"But why does radio telephony require a stronger current than wireless telegraphy?" Tom wanted to know.

"Because, up to the present, no way has been found of utilizing in radio telephony the entire energy of the electric waves sent out," replied Professor Chadwick. "Only the variations in the waves can be detected, or transformed into sound at the receiving end of a radio telephone system. Therefore an immense amount of electrical energy has to be manufactured in order that the voice vibrations may register their variations as powerfully as possible."

"What percentage of the electrical energy manufactured by a high frequency alternator can be transformed into variations of sound?" asked Jack.

"Not more than five to eight per cent. of the total energy. So therefore the waste is enormous. In wireless telegraphy, on the other hand, the entire energy radiated from a sending station can be picked up to the limit of the receiver's capacity to detect it."

"Isn't there any way in which this difficulty could be overcome?" inquired Tom.

"Yes, there is," said Mr. Chadwick, after a moment's thought, "and I believe that I am the only man in the world employed with radio telephonic problems who knows of it."

"Why can't you use it, then?" asked Jack.

"Because there are almost insurmountable difficulties in the way. There is a substance chemically known Z. 2. X. which, if it could be applied to purposes of transmission and detection, has such immense powers of electrical absorption that messages could be sent almost any distance, and with far greater economy of power than at present."

"How far can you send them now?" asked Jack.

"About five miles. At least I think so. I'm not even sure of that," was Mr. Chadwick's reply.

But Jack was impatient to get back to Z. 2. X.

"Why can't you use this Z. 2. X.," he questioned, "if it would practically wipe out your troubles in sending and receiving?"

"Because there is even less of it in the world than there is of radium," was the startling reply. "At present Z. 2. X. costs far more than radium. It is the most intensely radio-active stuff in the world. It is capable of being wrought into metal if anybody had ever found enough of it, but except for a small deposit in South Africa, which has been devoted to experimental purposes, nobody has any.

"But enough of that now. That is only a dream. I am anxious, though, to test out my present apparatus thoroughly, and to do it I shall need the help of you boys."

"In what way?" asked Jack.

"In giving it a thorough trial to ascertain over how great a space I can transmit wireless speech."

"Are you going to put up another station outside the grounds?" asked Tom.

"No; I don't want to attract attention to my experiments. You boys have a wireless telegraph outfit on your Wondership?"

Jack nodded. He was curious, as was Tom, to know the Professor's plan. They did not have long to wait.

"I wish you would get the machine ready to install a radio-telephone outfit in its place. In that way I can gauge the limits of my invention without attracting undue attention, as everybody in this vicinity has seen you in flight and would imagine that you were merely taking a trip through the air."

"But can you get out an apparatus light enough for us to take up?" asked Jack.

"I am working on that now," said Mr. Chadwick. "I'll have it ready in a week."

"We'll be ready for you," promised Jack.

CHAPTER VII.

THE GREAT TEST.

A week later to the day on a sunshiny, windless morning, the Wondership was run out of its shed, glistening with new paint and with every bit of bright work burnished till it shone and sparkled like newly-minted silver. Amidships on the craft, the general construction of which is familiar to readers of foregoing volumes of this series, was a square metal box with small wires leading to long copper wires stretched from end to end of the Wondership's body.

These long copper wires were to form the aërials by which the messages from Mr. Chadwick's workshop were to be caught. The smaller wires underneath were connected with the metal work of the engine. These wires formed a "ground" similar to the kind employed in aërial wireless telegraphy.

The details of the Wondership having been fully described in the Boy Inventors' Flying Ship, we shall not enter here into any but a brief and general description of the craft. The Wondership, then, was a combination of dirigible balloon, automobile and boat. Her motive power was furnished by engines driven by an explosive volatile gas which was also used when occasion arose to inflate the bag of the balloon feature of her design. The gas was generated in the lower part of the craft's semi-cylindrical metal body.

On land two big aërial propellers, geared to the engine, drove the Wondership swiftly along on four solid-tired wheels. When it was desired to take to the air the balloon bag, which was neatly folded on a framework supported by upright stanchions above the body of the car, was inflated by turning on a valve connecting with the gas tanks in the base of the body.

When the Wondership was intended to navigate the water she was driven by the same aërial propellers that afforded her motive power on land or in the air. She then became what may be called a hydromobile. If it chanced to be rough weather, special hermetically sealed panels could be drawn together, completely enclosing the body and making the craft a water-tight "bottle." Ventilation was provided in such a case by a hollow telescopic tube which reached twenty-five feet into the air. It was divided in two. Fresh air was drawn by a fan down one section, while the stale air in the "cabin" was forced out by a similar device up the other part of the tube. Stability was afforded by hollow pontoons, which worked on toggle joints, and could be raised or lowered as desired.

With the aid of Jupe, the gas bag was inflated to a point where only a slight additional quantity of gas would cause the craft to shoot upward to the sky. When all was ready a test of the instruments was made and they were found to be working perfectly. The powerful alternator on the Wondership was, of course, worked by the same motor that drove the big propellers.

"Well, I guess there's nothing to keep you back now," said Mr. Chadwick, who looked pale and ill after his long days and nights of work on his invention.

"No, we're as ready as we ever will be," said Jack, making ready to climb into the machine above which the big yellow balloon bag was billowing and sending impatient quiverings through the Wondership.

"I want you to promise me one thing, dad," said Jack, when he had climbed into the driver's seat, in front of Tom, whose duty it was to look after the engine.

"What is that, my boy?" asked the inventor.

"That after this test, whatever the result may be, you will take a long rest."

"Yes, I will, I must," agreed his father. "I've been working too hard, I guess, but in the excitement of perfecting the radio telephone I hardly noticed it. But recently I've had dizzy spells."

"Two weeks' rest will make you well," declared Jack, as he adjusted the controls.

"Good-by and good luck," said his father.

Both boys waved their hands.

"All ready, Tom?" hailed Jack.

The other boy nodded and then turned on a valve so that with a hissing sound additional gas rushed into the bag. Jack pulled a lever. The big motors roared and a queer, sickly smell of burned gas filled the air. The propellers began to revolve slowly and then increased their speed till they became a mere blur.

"Dere she go! Gollyumption, dere she go!" cried Jupe, capering about.

As the old black spoke, the Wondership shot up like a rocket, tilting her nose slightly into the air. But the next moment Jack had her on an even keel. In an incredibly short space of time those watching below saw her only as a glinting, golden speck against the blue sky, circling like some strange bird far above their heads.

"Now for the tests," said Mr. Chadwick, as he hastened to his workshop.

He set the big alternator at work at top speed. It droned like a gaunt bee. The inventor's face, worn by his anxious vigils at his experiments, was as keen as a hawk's, while he adjusted the instruments and placed his long, lean fingers on the tuning device.

Far above the earth Jack and Tom could look down upon a patchwork of villages, farms, green pastures, yellow grain fields and stretches of woodland. They were too far up to distinguish figures, but they could see the white steam of rushing trains along the railroad tracks, and even catch the sound of the engines' whistles.

Beyond glinted the blue of the sea flecked with sails and with here and there a steamer's smoke smudging the horizon. Both lads were in high spirits. It seemed good to be navigating the air again. Every now and then inquisitive, high-flying crows would swoop toward the machine and then dash off again with alarmed squawks.

Although they were making a high rate of speed, they hardly seemed to be moving as they soared in long circles. To get a sense of rapid motion, stationary objects must be in sight. In the lonely air it was hard to tell that they were moving at all except by looking down at the earth which, as they rose, appeared to be rushing from them, as if it were sinking through space.

But novel as all these sensations would be to an aërial novice, they were an old story to the boys. Jack devoted his attention to testing a new steering appliance he had equipped the craft with, and Tom watched his engines with an eagle eye to detect a skip or a "knock."

"How high now?" asked the young engineer after an interval.

Jack glanced at the barograph on the dashboard in front of him.

"Three thousand feet," he said.

"Might as well connect the alternator?" said Tom interrogatively.

Jack nodded, and Tom threw a lever which brought the generator of high frequency currents in contact with the motor by means of a friction fly-wheel. The alternator began to buzz and spark, crackling viciously.

A sort of metal helmet with two receivers attached to it, one on each side, lay handy at Jack's hand. In front of him was the transmitter joined to the metal box which contained the microphone, transformers and inductance tuning coil. Tuning in the aërial apparatus was effected by means of a small knob projecting through a slit in the metal box enclosing the delicate instruments including the detector. By working this knob the tuning block was moved up and down the coil till a proper "pitch" was obtained.

Jack experienced an odd thrill as he prepared to send the first spoken word ever exchanged between an airship in motion and a station on land. He and Tom had sent plenty of wireless messages while soaring through the ether, but somehow, the dot and dash system had not half the fascination and mystery of the possibility of exchanging coherent speech between land and air.

He placed his lips close to the receiver, and with his hand on the tuning knob sent forth a loud, clear hail:

"Hullo, High Towers!"

There was no answer for a few seconds while he patiently adjusted the tuning knob. But then came a faint buzz like the humming of a drowsy bee. Suddenly, sharp and distinct, as if his father was at his elbow, came Mr. Chadwick's voice in reply:

"Hullo!"

"This is the Wondership. Three thousand feet in the air," cried Jack.

"Congratulations, my boy. It's a success so far."

"What shall we do now?" asked Jack.

"I want you to fly in the direction of Rayburn, and try to keep in communication all the way."

"All right, dad," responded Jack, and altered the course of the Wondership.

Rayburn was a small village some twenty-five miles to the north of Nestorville. Jack kept the receivers on his ears as he flew along. From time to time he exchanged conversation with his father. So far everything appeared to be working as if there were no limit to the distance over which the voices from the air and land could converse.

But suddenly there came a startling interruption to the experiments.

Jack felt a sharp "Bang" at his ears as if a small cannon had been fired close at hand.

CHAPTER VIII.

TALKING THROUGH SPACE.

As the distance increased between air and land stations, the currents became stronger, and frequent tuning was necessary. But Jack was able to keep up a constant conversation with his father, telling him all the details of the country as they flew along. The sudden explosion, however, for it sounded like nothing else, startled him into a sharp exclamation.

"What in the world was that?"

As if he had spoken the question to someone close at hand, came back the explanation.

"Wireless telegraph wave crossing ours," said his father. "Some powerful land station is sending out a message, possibly to some ship."

"It almost broke my ear drum," said Jack, and inwardly resolved to devote some time to trying to solve the problem of avoiding such "collisions" in the future. It occurred to him that some sort of a circuit breaker might be devised to cut off, temporarily, the telephone talk by automatic means when a cross-wave of high energy struck its current.

The shock was not repeated, and the conversation went on, still as sharp and as clear as when they had started out. A few minutes later Jack was able to report they were passing over Rayburn.

"You'd better keep on," said his father, his voice aglow with enthusiasm. "It's working beyond my wildest expectations."

"It's dandy," agreed Jack.

They talked without raising their voices to any great extent, but it was necessary to articulate very clearly so that each variation of sound might be sent out into space as clearly as the notes of a singer come from the record of a phonograph. But it was amazing, almost uncanny to Jack that such results could be obtained at all.

"Goodness, if only we could get that mineral substance that dad was talking about I believe you could rig up a radio telephone that would talk across the ocean," he said to Tom, "and think what that would mean. For instance, instead of bothering with the cable you could step into a radio-telephone office and say: 'Give me the London Exchange.' In a few minutes the central would answer and you could tell her what number you wanted on some regular wire line. Before long you'd get it, and be talking to whoever you had called just as if they were twenty-five miles off instead of three thousand!"

"It seems like a dream," said Tom.

"Not much of a dream about it. All it needs is development. We've proved to-day it can be done," declared Jack, bubbling over with enthusiasm.

They flew over meadow land and pasture, farmhouses where tiny figures emerged from buildings and looked up at them, over rivers and railroads, and still the alternator spat and sparked and the messages between Jack and his father were interchanged in a steady stream. Rayburn had been left behind. They were now over a small town Jack believed to be Hempstead.

He looked at his map to make sure. It was one that he had specially plotted out himself from observations he had made when flying in the vicinity. Having verified their whereabouts he found that they had flown about fifty miles, possibly a fraction more.

But at this juncture he noticed that the voice of his father pulsing through space began to grow thin and weak. Obviously the limit of the radio 'phone's capacity had been reached.

"Better turn back," said Mr. Chadwick.

Jack turned to Tom and gave him the necessary instructions. Then he set over his guiding wheel, turning the big rudder at the stern of the Wondership and she acted as obediently as a sea-going craft answering her helm. Never had she behaved better.

They flew swiftly back toward High Towers and were soon in sight of Rayburn. In order to test what effect the magnetism of the earth had upon the radio messages, Jack brought the great flying craft close to the ground. They almost grazed the treetops as they flew along.

Skimming a patch of trees they roared above a farmhouse with a great red barn adjoining it. The barn attracted Jack's attention because of the fact that it had a flat roof, an almost unique feature in that part of the country. He supposed it was used to dry some sort of produce on and noted that there were several hop-fields near at hand. Undoubtedly the roof was used for exposing them to the sun and thus drying the moisture from them without the expense of wood for the drying fires usually used for the purpose.

He had hardly noted all this when there came a sudden tug at the Wondership as if a titanic hand had reached up from below and grasped her. She pitched wildly and, but for Jack's skill as an airman, there might have been a serious accident. But he brought the big craft under control by skillful manipulation.

The next instant he discovered what had occurred. The grapple of the aircraft had, in some way, dropped from its fastenings and, trailing behind the Wondership, had caught in the roof of the farmer's barn.

A great section of it was torn away and as Jack brought the Wondership to rest on the roof, the only available place, for the rope was in danger of fouling the propellers if he descended to the ground, the farmer and a number of his men came running from the farmhouse.

In the hands of the farmer was a formidable looking shotgun. As the Wondership settled on the roof of the barn the man began shouting angrily.

CHAPTER IX.

THE BOYS FACE TROUBLE.

"Phew! looks as if we are in for trouble," exclaimed Tom, as he saw the warlike expression on the farmer's face.

"It does that," agreed Jack. "Hop out, will you, Tom, and get that grapple clear? Confound it, I don't see how it came loose."

"Wore through the lashing," said Tom, who had been examining the place where the big hooked steel anchor was usually tied.

"We ought to have seen to it before we started out," said Jack. "We haven't had it loose since that time we anchored above the Brazilian forest."

The farmer's angry voice hailed them from below.

"Hey there! Don't yew move a foot till we've had a reck'nin'."

"I am awfully sorry," said Jack. "It was an accident you see. We——"

"Don't care what it was. Thet thar was a new roof. Don't you move a step till Si here gits ther constabule."

"We'll pay you for the roof," said Jack apologetically. "After all it isn't much damaged."

Indeed it appeared as if the damage was not so great as they had at first imagined. After tearing off some shingles the grapple had caught in a beam and was prevented from doing further harm.

"Yes, yew'll pay, and yew'll go ter jail tew," declared the farmer. "Consarn it all, what's the country comin' tew? Las' week tew pesky dod-ratted balloonists hit Hi Holler on ther head with a bag of sand, and now yew come along in thet thar contraption and try to bust up my dryin' roof. I'll have ther law on yer."

Matters began to look serious. Jack had no doubt but what the farmer would accept a money payment for the damaged roof. But it appeared that the old fellow was bent on more stringent vengeance.

In the meantime Tom had been busy in the stern of the craft and had succeeded in getting the grapnel loose from the beam into which its sharp points had dug. It was not till that moment that the farmer observed him.

He leveled his shotgun at the balloon of the Wondership.

"Don't yew dare ter move er I'll bust a hole right plumb through that ther airbag of yourn," he said.

"Can't you be reasonable?" asked Jack. "Here's my name." He wrote his name and address on a slip of paper and threw it down.

But the irate farmer paid no attention to the missive. He kept his gun steadily trained on the Wondership.

"Move an' I'll bust yer!" he said grimly.

A buggy drove out of the yard. It raced through the gate and then struck the highroad leading to Rayburn.

"Thar' goes Si arter ther constabule," said the farmer, licking his thin lips as if with relish. "Hi Ketchum is a rare one arter automobubblists. I reckon he'll be right smart tickled to death when he hears I got a whole airship fer him ter 'rest."

"Bother the old grouch," muttered Tom, as he climbed back into the Wondership, the bag of which was deflated just enough to keep her at rest on the roof.

"He's evidently mighty serious in his intentions," said Jack, with a troubled face. "What are we going to do?"

There was a sudden puff of wind and the big yellow balloon bag swayed slightly.

Instantly the farmer's finger crooked on his trigger. He thought the boys were going to give him the slip.

"No you don't," he shouted, "you don't fool Ezry Perkins that 'er way!"

"We're not trying to fool you," said Jack disgustedly. "Why can't you be sensible. You've our names and addresses on that paper I threw down to you. If you like I'll make a cash settlement right here for any damage we've done."

"I'm goin' ter git yer in ther court," insisted the farmer sullenly. "Las' week some autermobubblists killed three uv my chickens, week afore thet I had a hog knocked off ther road. I'm er goin' ter git even on yer fer ther lot uv them."

It was plain that the man was not to be moved by promises or persuasion. He had conceived in his mind a hatred against automobiles, with which, in a vague way, he classed airships and all such modern inventions. Jack thought, too, that Ezra Perkins was the kind of man who liked to shine out among his neighbors, and what better opportunity could he have to satisfy this ambition than by blossoming forth as a man who, single handed, had captured a great aircraft?

The boys looked down. The farmer was pacing grimly up and down like a sentry, his eyes never leaving the Wondership.

"I'd like to drop a bag of ballast on his head, the same as those balloonists did on Si's," muttered Tom.

"Wouldn't do any good," said Jack. "It would only bounce off again."

"I guess it would at that," agreed Tom with a grin.

"I've half a mind to take a chance," said Jack suddenly.

"And get a hole blown in the balloon bag," protested Tom. "We wouldn't be better off than before in that case."

"I wonder if he'd really shoot or if he's only bluffing," mused Jack.

"Take a look at him," advised Tom.

Jack did. One glance was enough. There was no bluffing about the grim, overalled farmer. The very way in which he held his gun expressed positive determination not to let the boys escape.

But as it so happened, by no action of the boys', matters were suddenly brought to a sharp crisis. Over the patch of woods beyond the farm there came a vagrant puff of wind. It was followed by a sharper gust.

The Wondership swayed and then, before Jack could check the motion, drifted off the roof like a piece of thistledown blown by the wind. Instinctively, to check the downward motion, Jack's hand sought the gas valve. With a hiss the volatile vapor rushed into the bag.

The big aircraft shot up like an arrow. For a second the farmer stood paralyzed at the suddenness of it all. His farm hands lounged about, gaping and looking upward like country folks at a fireworks display.

Then, without any warning:

"Bang!"

The farmer let loose with both barrels at once. But the Wondership still rose.

All at once, from below, came a yell of surprise and terror. The boys looked over the side. As they did so they uttered simultaneous gasps of consternation.

The trailing grapnel, for Tom had forgotten to tie it back in place in the excitement, had caught the farmer by the waistband of his overalls and he was being carried skyward by the Wondership, dangling at the end of the anchor rope like some sprawling spider.

His wife, screaming at the top of her voice, rushed from the kitchen door.

"Hey, you come back with my husband!" she shouted.

"Lemme go! Lemme go!" bawled the farmer as loudly as he could, for, held securely by his stout overalls, he was carried high above his own buildings. He kicked and struggled furiously.

"Keep still," shouted Jack, in serious alarm, from the side of the Wondership. "Keep still or you'll kick yourself off."

The farmer had sense enough to obey. He hung upside down like a limp scarecrow, while his farm hands gaped up at him and the hired girl was busy pouring buckets of water over his wife who was in hysterics.

"Gracious, now we've done it!" gasped Tom in dismay.

CHAPTER X.

AN INVOLUNTARY AËRONAUT.

"Steady, Tom, steady," warned Jack, as he set the pumps to work drawing gas from the bag into the reservoir.

The Wondership, her buoyancy thus diminished, began to descend.

"What are you going to do?" asked Tom.

"Drop our passenger," said Jack, with a grin he could not suppress, for the struggling farmer was within a few feet of the ground now and even if he did kick himself loose, for his struggles had begun again, he could not have hurt himself much.

"Back up till we get over that haystack," said Jack, "and then play out rope till we lower him. It'll make a nice soft jumping-off place."

Tom obeyed, pulling a reverse lever. The Wondership, steered with skill by Jack's practiced hand, backed slowly up. At length they hung directly over the haystack. Jack turned and nodded. Tom sprang to the rope and lowered the indignant farmer into the soft hay. The man lost no time in disentangling himself. Then he sprang to his feet and began hurling vituperation at them at the top of his lungs.

"I'll have ther law on yer fer this," he yelled. "Tryin' ter kidnap me and bustin' down my barn. I'll see whether such goin's on is allowed in ther sufferin' state uv Massachusetts, yew see if I don't, consarn yer. I'll——"

But the Wondership, bearing the two boys who could not help laughing heartily, although they feared serious consequences might come of the accident, was winging its way onward out of earshot of the not unnaturally indignant Ezra Perkins.

They passed Rayburn before Jack noticed a peculiar smell in the atmosphere.

It was leaking gas. Then, for the first time, he recollected that the farmer might have hit the gas bag above them with his double shots, although, till then, there had been no indication that such was the case.

He called Tom to the wheel, explaining his suspicions and clambered out on the rigging to see if he could find any holes in the balloon. It would have made a less steady boy dizzy and sick to stand on the edge of the Wondership, clinging to one of the supports that held the body of the craft to the gas-bag, while the whole affair plunged and swayed five hundred feet above the earth. But Jack, used as he was to navigating the air, felt none of these qualms.

His suspicions were speedily confirmed. There was a jagged hole in the underbody of the balloon, from which gas was rushing. Jack's face grew grave. The situation was dangerous.

He knew, as does every balloonist, that out-rushing gas can make an electric spark in the atmosphere which, in turn, ignites the gas itself, sometimes with fatal results. Experts in aëronautics attribute the disasters befalling the long series of Zeppelins, the giant German dirigibles, to this cause.

"Tom, we must go down. Drop at once," he said. "That old fellow succeeded in blowing a hole in us all right."

The pumps were set to work and the Wondership fell rapidly. They dropped in a field by the roadside, landing on the running wheels as lightly as a feather, thanks to the shock absorbers, similar to those of an automobile, with which the Wondership was equipped.

"Now for the repair kit," said Jack, rummaging a locker.

He soon had balloon silk, big shears, a quick-drying gum solution and a pot of gasproof varnish, ready for the job of patching up the hole. But first they had to empty the big bag of gas. This was speedily done, for already enough had escaped to wrinkle the bag like a walnut, with hollows and creases.

Jack cut out a patch of balloon silk large enough to fit the hole and spread it with the adhesive gum solution. This he placed inside the hole, spreading it out so that when pressure was applied it would be pressed firmly against the aperture. Then he coated the patch with the gasproof varnish, and both boys sat down to give the job time to "set."

Their eyes turned idly to the high-road. It was about noon and there was a heavy sort of silence in the air. Far on the horizon they could make out great billowy masses of white cloud. Piled and castellated against the sky they assumed all kinds of odd shapes.

"Thunder heads," said Jack. "We shall have a storm before to-night."

"It's sultry enough for anything," said Tom, taking off his cap and mopping his forehead. "I'd hate to be walking in this weather like that fellow yonder."

A man had come into sight, plodding along with bent head and eyes on the ground as if he was very tired. The gray dust of the road coated him from head to foot. He walked with a kind of dragging gait.

Over his shoulder he carried some sort of a bundle on a stick. His hat was a broad sombrero, like a cowboy's. It was a kind of headgear seldom seen in the east and attracted the boys' attention. Round the man's neck was a red handkerchief, the only spot of color on his dust-covered person. He had a great yellow beard and rather long, unkempt hair.

"Tramp," hazarded Tom.

Jack shook his head.

"Doesn't look like that to me somehow," he said. "I rather think——"

Round the corner whizzed a big red automobile. It was coming fast. The driver, a young man, had his head turned and was talking to three companions who sat in the tonneau. He did not see the dusty traveler in the road ahead.

The boys set up a shout.

"Look out! you'll run him down. Look out——"

But their caution came too late. At top speed the auto struck the wayfarer, and before the boys' horrified eyes he was thrown high in the air, to fall, a confused sprawl of legs and arms, at the wayside.

CHAPTER XI.

BY THE ROADSIDE.

The boys ran forward across the few yards of meadow that intervened between the Wondership and the roadway. The autoists did not, apparently, notice them. They had stopped the car and were looking back.

"Come on and let's get out of this quick," one of them, a hawk-faced youth, with a long motoring duster on, was shouting to the driver.

"Yes, let's beat it while the going's good, Bill," came from his companion as he addressed the driver of the car.

"I guess we'd better," said the man addressed as Bill.

Before the boys could intervene the car was on its way again, at top speed, leaving the unconscious form of its victim at the roadside.

"Of all the cold-blooded scoundrels!" gasped Jack, horrified at such callousness.

"Never mind them now," advised Tom. "Let's see if this poor fellow is badly hurt. He may even be——"

He did not finish the sentence, but Jack knew what he meant. Hastily the boys scrambled down the low bank that separated the field from the road. They ran quickly to the man's side. To their great relief, for they had feared that he might have been killed, the man was breathing. But his breath came pantingly from his parted lips and there was a bad cut on his forehead.

"Get some water from the creek yonder," said Jack, and Tom hastened up the road to where, beneath the small wooden bridge, there flowed a rivulet of water.

He was soon back, with his handkerchief well soaked, and with an old can, that he had been lucky enough to find, filled with water. They bathed the man's wound and then bound it up as best they could. But he still lay senseless.

"Now what's to be done?" asked Tom.

"We ought to get him over to the Wondership and rush him to the hospital at Nestorville," said Jack.

"Yes, that would be the thing to do. But he's too heavy for us to carry," objected Tom.

"Why not fly over here alongside him. I guess we could lift him in; that patch ought to hold by this time," suggested Jack.

"That's a good idea. What a pack of cowardly sneaks those chaps in that car were."

"I wish we could have stopped them. It would give me real pleasure to see a gang like that get its just deserts. They might have killed this poor fellow."

The unconscious man was powerfully built, with face tanned brown above a yellow beard, from exposure to sun and wind. As Jack had said, he did not look like a tramp. Suddenly the boy noticed lying near him an object which had evidently fallen from the man's pocket when he was struck and flung through the air by the auto.

It was a small cylinder, apparently made of lead, and about three inches long. Jack picked it up, and for the time being did not attempt to examine it but thrust it into his pocket for safe keeping. Little did either of the boys think how much that little cylinder was to mean to them, and how it was to influence some of the most important adventures of their lives.

Making the man as comfortable as they could, by rolling up their coats and placing them under his head, the boys hurried back to the Wondership. When they arrived there they saw that a feature of the radio 'phone, which has not yet been mentioned, was working in urgent appeal. This was a tiny red electric light attached to the top of the case containing the sensitive parts of the apparatus.

By an ingenious device, worked as a call signal from the transmitting station, the electric waves converted a lighting circuit for this purpose.

It was winking and twinkling, and Jack knew that his father was trying to call them.

He sent out some flashes by starting the dynamo going and pressing a key devised for the purpose. This, he knew, would cause a similar light attached to his father's apparatus to flash a reply. This done he waited a second and then adjusted the receivers to his ears.

"What's the matter?" came his father's voice.

Jack gave him a rapid account of the accident, not stopping just then to say anything about the incident of the farmer and his barn.

"What are you going to do about it?" asked his father.

"He appears to be seriously hurt," said Jack. "I was thinking of rushing him to the hospital at Nestorville."

"That seems to be the best plan," said his father. "By the way, did those autoists get clear away?"

"I'm afraid so. They never even waited a second to see if the man was badly injured. They——"

Jack suddenly stopped short. An inspiration had come to him. The accident had happened on a road that, as he knew, led straight through Nestorville. He had thought of a plan to bring the autoists to book for their callousness and negligence.

"Dad—oh, dad!" he called.

"Yes, what is it?" came back Mr. Chadwick's voice.

"Those fellows will pass through Nestorville. I had a flash of the number of the car. It was 4206 Mass. It's a red car and a powerful one, with three men in it."

"What do you want to do?" asked Mr. Chadwick.

"Can't you 'phone to the Nestorville police, telling them what has happened and have those fellows stopped. I'm not vindictive, but they ought to be brought to book for running down a man and then speeding off and leaving him like that."

"I agree with you," replied Mr. Chadwick. "I'll do so at once. Good-by."

"Good-by," said Jack and "rang off."

"That was a great idea of yours, Jack, old boy," approved Tom. "I hope they land those fellows."

"Of course it was an accident," said Jack, "but that fellow who was driving was too busy talking to watch the road, and then going off like that—they deserve all they get."

Examination of the patch showed that it would hold fast and the bag was refilled. As soon as it was sufficiently inflated, the Wondership sailed over to the road and was brought down alongside the still unconscious man.

"Looks as if he's badly hurt," said Tom with some anxiety.

"It does. His skull may be fractured," agreed Jack. "If he is seriously injured those fellows may get into trouble."

It required all the boys' strength to raise the man and get him into the Wondership. Here they laid him out on the floor of the rear section. They had just done this when the red light signaled Jack again. It was Mr. Chadwick. He had notified the Nestorville police force, consisting of a chief and two men, and they were on the lookout for the offending auto.

"Good," said Jack. "Say, dad, the radio telephone has shown its usefulness on the first day out, hasn't it?"

They were soon in the air once more. The run to Nestorville was made quickly. On the outskirts of the town they came to earth and deflated the balloon bag, since the hospital stood in a group of trees and it would have been impossible to make a landing there. The Wondership was converted into an auto and sent speeding toward the main street of the village.

Suddenly they heard a whir of wheels behind them and an impatient tooting of a horn. They looked back and uttered a simultaneous cry of astonishment.

The red auto that had run down the yellow-bearded man was behind them. Its occupants were shouting and sounding their horn impatiently for the right of way.

CHAPTER XII.

MAKING ENEMIES.

The road was narrow where they were, and unless the boys' machine was run to one side of the road there was no chance for the red machine to pass. Jack made it clear that he didn't intend to let them.

He paid no attention to the shouts that came from behind.

"Hey, you kids, with that queer-looking car, get off the road and give a real machine a chance to get by," shouted the driver, he who had been addressed as Bill.

Jack did not turn his head.

"I'll knock your head off if you don't turn out—and turn out quick!" came another shout.

Still the boys did not pay any attention. In this order they came into Nestorville. Lined up, with a look of stern determination on his face, and with his nickel star of office newly polished, was Chief Biff Bivins. Behind him were Lena Hardy and Joe Curley, his "force."

"Say, boys," hailed Chief Biff, as the boys rolled up abreast of him and his men, "hain't seen hair nor hide of that car your dad was arter 'phonin' me about."

"Well, you soon will, chief," said Jack.

"Haow do yew know that?" asked the chief, his little eyes blinking curiously.

"Because it's right behind us now," declared Jack. "It's that red one."

"Ther dickens you say. How'd you come ter git erhead of 'em?"

"They must have stopped to fix a tire or something," said Jack.

But Biff was paying no attention to him. The majesty of the law was strong upon him. Calling his minions to his side he stepped into the middle of the road in front of the red car.

"Get out of the way!" shouted the man who was driving.

"Not much I won't," declared Biff valorously. "Halt that gasoline gadabout o' yourn instanter."

"What for, you old Rube?"

"Old Rube am I?" sputtered Biff, feeling that the law had been insulted in his person, "jes' fer thet yer under 'rest."

"What for?" demanded the driver of the red car angrily.

"Fer running daown and grievously wounding a man and then speedin' off without stoppin' ter see if you'd killed him dead or what all. That's what fer."

The driver of the red machine lost his blustering tone.

"Why, there's some mistake," he stammered, his face very pale, "I—er—we—er—that is, we didn't run anybody down."

"Oh, yes, you did," said Jack. "We saw you, and what's more we've got the man you struck right here in our car. You're a fine pack of cowards to run off like that. If we hadn't happened along he might have lain there for hours before help came."

"You saw us!" gasped the driver of the car, losing his bravado completely. "Well, I might as well admit we did run a man down. But we didn't think he was badly hurt and so we put on all speed to rush into town here and get a doctor for him. We'd have been here sooner only one of our tires punctured."

"Thet's a dern good story," said the chief, "but you'll hev ter 'splain that ter ther squire. Come on with me ter ther court-house. Too bad fer you thet them Chadwick boys had some sort of a do-funny dingus on their sky buggy that talks through the air, otherwise you'd hev got clar' away."

The man had, by this time, got out of the car which they halted at the side of the street. A crowd of curious villagers gathered and were staring at the scene and the actors in it.

At Chief Biff's words the driver of the red car flashed an angry look at the boys. His companions looked equally vindictive.

"So, it's to you we owe our arrest, is it?" he said in a low voice, coming quite close to Jack. "All right. You'll hear from me later. I'm not going to forget you or that other kid, either. Do you understand?"

Jack made no reply, and as he was anxious to get the injured man to the hospital as quickly as possible he drove off. At the institution the man was carried to a cot by two orderlies, and the doctor in charge told the boys that, so far as he could see, his injuries were not mortal, although he added that a fracture of the skull was possible.

"In which case," he said, "his recovery is problematical. How did you happen to pick him up?" asked the doctor, who knew the boys quite well.

Jack told him as briefly as he could, and received the physician's warm congratulations.

"It was fortunate that you happened along," he said. "Otherwise a long exposure to the sun, unattended, might have resulted in the man's death. Have you any idea who he is?"

"Not the least," replied Jack. "All that we know is that, just after he had plodded round the corner as if he was tired after walking a long way, that auto came whizzing round and struck him. Somehow he doesn't look like a tramp."

"No, he doesn't," agreed the doctor. "However, he should be conscious to-morrow if there are no complications, and we can find out. One thing is certain, he ought to be grateful to you."

"Oh, that's all right," laughed Jack, much relieved to hear that the man wasn't going to die. "It was all we could do."

They drove back through the village. Outside the court-house was quite a crowd. Events were few and far between in sleepy Nestorville, and the arrest of the autoists had caused quite a sensation. From a friend in the crowd the boys learned that the three men were being arraigned before Squire Stevens.

"Let's go in," suggested Tom.

"All right," nodded Jack, and they climbed out of the Wondership and ascended the long steps leading into the court-house. As they entered Squire Stevens' court-room, Chief Bivins spied them.

"Here they be now, Squire," he said. "Glad you came, boys. It saved me the trouble of serving subpoenas on you. These are the boys who saw the whole thing, judge."

"Was it an accident?" asked Squire Stevens, a dignified-looking old man with an imposing white beard.

"Yes, entirely so," said Jack, who did not bear any malice.

"But after they had struck the man, these young men ran away?"

"Yes," Jack was forced to admit. The men shot him a glance of hatred.

"I understand you have been to the hospital," went on Squire Stevens. "Did you learn how badly the man they hit is hurt?"

"The doctor told us that his injuries don't appear to be serious," said Jack, "but that it was possible there might be complications."

"In that case I shall have to hold you young men under bond," said the squire. "Will you be able to furnish it?"

"In any amount," said the man who had driven the car, in a loud, boastful voice. "My father, Evans Masterson, owns the Boston Moon, the evening paper. If I can telephone to him he will soon get us out of this scrape."

"Very well, then," said the Squire, frowning slightly at young Masterson's tone. "I shall fix your bond at $500, as you were driving the car and directly responsible for the accident, and that of your companions at $100 each."

Young Masterson gave an ironical bow. Chief Biff Bivins escorted him to the telephone. The elder Masterson, who had had a good deal of experience with his son's escapades, at first administered a lecture over the 'phone which ended by his saying that he would come post-haste to Nestorville and extricate his son and his chums from their unpleasant fix.

But the boys did not wait for this. As soon as the case was over they hastened back to the Wondership. The run home was made without incident and it was not till the Wondership was safely in its shed that Jack suddenly thought of the odd cylinder of lead that he had picked up by the man's side as he lay on the road.

"I ought to have left it at the hospital," he thought, "but I entirely forgot it."

He drew it out and looked at it. He now saw that the lead cylinder enclosed a glass vial carefully corked and sealed. The bottle was wrapped in flannel. Jack could not withstand the temptation of pulling it out and looking at it. He hardly knew what he had expected to see, but he was distinctly disappointed, as was Tom, to find that the carefully protected vial contained nothing more than some dark, almost black, stuff that looked like sand. In it were particles that glittered like mica.

"Pshaw!" he exclaimed in a disappointed tone, "nothing but a bottle full of sand. Wonder why in the world that fellow carried trash like that so carefully wrapped up for?"

The solution of the question, which was near at hand, was to have an important bearing on the lives of the Boy Inventors, and that in the immediate future.

CHAPTER XIII.

THE LEADEN TUBE.

The following day, while they were experimenting and practicing with the radio telephone, the boys received word that the man in the hospital was conscious and wished to see them, if possible.

"Perhaps now we shall get some explanation of that queer tubeful of sand," said Jack, as he hung up the telephone receiver, having informed the physician that they would be at the hospital shortly.

"It's certainly a queer sort of thing for a man to carry about—a glass vial full of black grit so carefully protected, unless he is crazy or something," commented Tom.

"I think that there is some explanation back of all this," said Jack, "and for my part the sooner we get to the hospital, the better I shall be pleased. The man told the doctor he was a miner and his name is Zeb Cummings. Perhaps that sand is gold-bearing or something like that."

"That might be the case," agreed Tom.

The boys decided to take out the electric car. It was in perfect running order and the indicator showed that there was plenty of electricity in storage for the start. They told Mr. Chadwick where they were going and then rolled out of the High Towers gates onto the broad, smooth road bordered with pleasant green elms.

They bowled along smoothly and silently with the car working as perfectly as delicate clockwork. They had gone about a mile from the house and were on a steep grade which the car took as easily as if it had been going down hill, when their attention was attracted by a sudden shout from the vicinity.

Jack brought the car to a halt. The voice came again.

"Hi! Help me! Ouch! Help!"

"What in the world is the matter now?" wondered Tom.

"Somebody in trouble in that field yonder. We'd better get out and see what's up," proposed Jack.

The shouts seemed to issue from beyond a high bank at one side of the road. On its summit was a hedge which prevented the boys seeing what was going on in the field that lay beyond.

As they got out of the car, however, Jack spied a bicycle at one side of the road. A satchel that he remembered very well was slung from its frame.

"It's the professor in trouble again!" declared Jack.

"I do believe you are right," replied Tom as they scrambled up the bank. "That's sure enough his wheel."

They found a gate in the hedge and on the other side an odd sight met their eyes. Kneeling on the ground was the professor. His right arm was thrust almost up to the shoulder into a hole in the ground. He was shouting lustily for help and appeared to be imprisoned in his queer posture.

"Some animal has got hold of his hand," cried Jack. "Come on, Tom."

"Oh, boys, thank goodness you've come," gasped the scientist.

"What's the matter?" demanded Jack.

"I can't get my arm out of this hole," declared the professor.

"How did you get it in?" asked Tom.

"A fine specimen that I dropped accidentally rolled into it," was the reply. "I reached in to get it and now I can't get my hand out."

"But you got it in easily enough," said Jack in a puzzled tone.

"Ah, yes," replied the professor, "but then I didn't have my hand clenched. Now my fist is closed and I have the specimen in it. Oh, boys, it's a beauty. One of the finest I have ever seen. It shows distinct monolithic traces."

"But if you don't drop it you can't get your hand out," argued Tom.

"I know that. That's why I shouted for help," said the professor simply.

"You'll have to let go of it," decided Jack, almost choking with laughter at the plight of the eccentric little man.

"Let go of it? My dear sir," murmured the professor in a shocked tone, "this specimen is worth at least twenty dollars, not to speak of its scientific value."

"But you can't stay here," said Jack decisively.

"And I won't let go of the specimen," declared the professor with equal firmness.

"What on earth are we to do?" said Jack, looking helplessly at Tom.

Not far off Tom had noticed a man digging potatoes. It gave him an idea.

"We can borrow that man's shovel and dig his arm out," he suggested.

"It's about the only thing to do, I guess," said Jack. "You go and see if you can get it. I'll keep the professor company."

Tom soon came back. The potato-digger accompanied him. The man was much interested in the eccentric man's plight.

"If that ain't the beatingest I ever heard on," he remarked, gazing at the professor, and then he tapped his head significantly and looked at the boys in a knowing way.

"Nobody home, eh?" he said with a grin. Fortunately the professor did not hear him; but the boys could hardly keep from laughing outright as they set to work with the spade. A few minutes of brisk digging set the professor at liberty and he was able to stand upright and triumphantly exhibit a small black rock which looked in no way remarkable, but which, it was evident, he esteemed highly.

"Ah, my little gem," he said, gazing at it fondly. "You thought you'd escape me; but you didn't. A wonderfully fine specimen, boys."

"Tell yer what," said the yokel, from whom they had borrowed the spade, "I'll pay you fifty cents a day to clean up my back pasture yonder. It's chock full of them black rocks."

"It is?" exclaimed the professor eagerly. "I must visit it some day. It would be worth writing a paper about. Most remarkable. A whole field of these stones. Well, well, this is a great day for science. But how did you boys happen to come along so opportunely?"

Jack explained, and then, suddenly, he thought of the tube of queer-looking black sand. Possibly the professor would know what it was. He drew it out and briefly narrated how he came in possession of it. The professor took the little glass vial out of its protecting lead and flannel. He adjusted his glasses and held it up to the light. Then he uncorked it and sprinkled a few grains on the palm of his hand.

He regarded it carefully for a few minutes and then drew out a huge magnifying glass. The next instant he dropped his scientific calm and uttered a sharp exclamation of astonishment.

"Where is the man who owns this?" he exclaimed. "We must see him at once."

CHAPTER XIV.

IN THE HOSPITAL.

"We are on our way to see him now," said Jack. "He is in the Nestorville hospital."

"May I go with you?" asked the professor, with astonishing eagerness for him.

"Why, of course. But that black sand," said Jack. "What is it—gold-bearing material of some kind?"

"Gold!" exclaimed the professor with fine scorn, "gold would be dross beside it. Of course I haven't analyzed it yet, but if it is what I think it is, it is the most valuable stuff in the world."

The boys exchanged bewildered glances. Clearly their discovery of the injured man, Zeb Cummings, had an aspect they had not hitherto suspected. But the professor refused to tell them what the sand was, or what he thought it was, till he had seen Zeb Cummings himself.

Leaving the potato-digger under the firm impression that they were all crazy, they hurried back to the road, the professor's bicycle was placed in the tonneau, and Jack drove just within the speed law to the hospital.

They found the injured man sitting up in bed, his great yellow beard gleaming like gold. His head was bandaged but even the pallor induced by the accident had not materially altered the ruddy glow of his thick coat of tan.

"So these are the boys who saved me," he said, extending a big, gnarled hand. "Shake, pardners. The doc here tells me if I'd laid much longer out there in the sun, there might hev been a first-class funeral fer Zeb Cummings."

"Oh, that's all right," said Jack easily. "I'm only glad that we came along when we did."

"Well, you sure acted different from them other varmints," said Zeb with deep conviction. "The doc tole me all about it."

His face suddenly grew grave as he changed the subject.

"Did you find anything on the ground thereabouts after I got knocked out?" he asked.

"What sort of a thing?" asked Jack.

"Oh, nothing that looked very valuable. Jes' a little lead roll with a bottle full of what looked like black sand in it."

"Got it right here," said Jack, producing the bottle which the professor had given back to him.

"Glory be!" exclaimed Zeb Cummings, as he took the lead-wrapped vial as though it was something precious. "I was afeard that if anyone found it they might hev thrown it away, bein' as it don't look as if it amounted ter anything much."

"Is it valuable?" asked Jack, who could not restrain his curiosity.

"That's jes' what I don't rightly know," rejoined Zeb. "I reckon I'd better tell yer how I come ter git it an' then you kin judge fer yourselves."

"We'd like to hear," said Jack, who had felt all along that there was some mystery about the yellow-bearded giant.

"All right! Sit down and I'll tell yer ther yarn. But say, who is yer friend? No offense meant, ye understand."

"This is Professor Jerushah Jenks," said Jack.

"What, the guy that knows all about rocks and such like?" burst out the miner.

"I believe I have achieved some small fame in that line," said the professor.

"Wa'al if this don't beat pay dirt I'm a Piute," exclaimed the miner. "Give us your hand, Professor. I was on my way ter see you when that thar buzz wagon busted me higher nor a turkey buzzard."

"On your way to see me?" echoed the professor in amazed tones.

"Yes, siree bob, that very identical thing," was the bronzed miner's reply.

"But I don't quite understand. You see I——"

"That's all right, Professor. We'll git down ter pay dirt direc'ly," said the miner. "You know of the Scientific Society in Bosting, of course?"

"I am a member of that body, sir," was the dignified reply of the little man.

"Well, they giv' me your name. Said you was the biggest bug on rocks, minerals and sich in the country and so I sets out to pay a call on you."

"But you were many miles from where I live," said the professor. "The railroad, or the trolley——"

"Don't carry folks for nothing," interrupted Zeb, "and nothing's my capital right now."

"You mean that you were walking from Boston?" asked the professor.

"That's right," was the reply. "Landed there on ship from round the Horn last week. Got paid off but some sneak thief in the boarding house I was stopping at got my roll. So I had to hoof it."

"But what did you want with me?" asked the professor.

"I wanted you ter tell me ef that thar stuff in the glass tube is worth anything or nothing," was the reply.

"Why, do you know where there is more of it?" asked the professor, and the boys could see that he was oddly excited, although preserving an appearance of outward calm.

"Yes, siree," was the emphatic reply. "I know whar thar's enough of it to load a freight train."

"Shades of Huxley!" gasped the professor, actually turning pale. "Do you mean that?"

"I sure do, Professor. It's all down on a map what Blue Nose Sanchez give me afore he passed in his checks."

CHAPTER XV.

A TALE OF THE COLORADO.

"Do you fully realize what you are telling me?" asked the professor. The doctor and the nurse had left the room, and the miner, the scientist and the boys were alone.

"Course I do," was the rejoinder of the yellow-bearded giant with the bandaged head. "There ought ter be a fortune in it 'cording to what Blue Nose Sanchez said. Was he lyin', Professor?"

"I don't think so. But tell us your story," urged the man of science.

"Well, it begins some months ago. I was prospecting down along the Colorado River. It was in a mighty bad place. Don't rightly know just how I ever got thar, but thar I was. Wonder was I wasn't killed ten times over 'fore I got to whar I was. But I guess I'm pretty tough.

"That Colorado River is a pretty tough place down where I was. Nothing but desert all around, and just a swift dashing current at the bottom of a canyon that looks like it went into the middle of the earth with steep, dark walls that seem to go straight plum up to the sky.

"But I was lured on by the thought of making a big strike. At last I got down to a place where the banks was so high and steep that it was like twilight even at noon. Grub was gittin' to be a question with me, and I'd about made up my mind to turn back, but I thought I'd make one more last try.

"I set to work on a rocky bank with my pick but nary a color—that's what we call a trace of gold—could I uncover.

"Wa'al, says I to myself, it's up stakes fer you, Zeb, unless you want to starve afore you git back to civilization. But as it was evenin' then I decided to stay whar I was that night and strike back early the next day.

"Here's whar Blue Nose Sanchez comes inter ther story. They called him 'blue nose,' I guess, because of a premature blast that had blown powder into his nose and turned it that color. Anyway, he was a mighty homely specimen.

"It was just gittin' light in the canyon, although it must have been broad day up above, when I hears an almighty hollering up the gulch. The next thing I knows, round a bend comes a small boat. There's two men in it. They must have been crazy to try to make the passage, for the river is just a mass of rapids and whirlpools, and I never heard of anyone trying to shoot 'em.

"But thar was these two fellows in this boat, and they was scared, too, I kin tell you. Wa'al, I stood thar like a stuffed pig on the bank watching 'em as they came toward me at the speed of an express train. Suddenly one of 'em, the chap that was trying to steer, twisted the oar he was guiding the boat with and it cracked under his weight. He went overboard in a flash.

"The next moment, with a yell of fright that I kin hear yit, the boat was hurried past me on that water that boiled like yeast in a kittle, and in a flash it had disappeared round another bend. What became of it I never knew, but it must have been upset and the man in it drowned. No boat could have lasted long in that water, even with an oar to steer it, and that was gone.

"I waded out inter ther water as far as I dared and by some freak of the current the man who had toppled out of the boat came within my reach. I grabbed him and dragged him ashore, more dead than alive. I done what I could for him and he came to after a while. That was how I met Blue Nose Sanchez.

"Well, sir, Blue Nose was a mighty sick man, even then. He had fever and was a ravin' lunatic at times, but at intervals he made out to tell me suthin' of his story. Him and his partner, a fellow he called Foxy Joe, was on their way to find a little island down ther river where no white man but only one had been. This man was a friend of Foxy Joe's and the two met up in Yuma. Foxy's friend had a lot to tell him about a wonderful island some Injuns had told him about whar there was some sort of mysterious mineral. By what Joe could make out this mineral was nuthin' more nor less than radium."

"Radium!" exclaimed the boys.

"That's right," went on the miner. "Foxy's friend allowed that there was cartloads of it lyin' loose thar 'cording to the description the Injuns give him, and he showed Foxy a sample of the stuff. That sample is in this little lead-wrapped bottle. It's wrapped in lead 'cos otherwise it 'ud make sores on you when you carry it about. It's workin', workin' all the time, frum what I kin make out.

"Well, 'cordin' ter ther way Blue Nose Sanchez tells it, Foxy and the man who knew about the island and had a rough plan of it the Injuns drew fer him, had a fight, and Foxy kills him, or thinks he has. Blue Nose sees it and sees Foxy take the map and the little lead-wrapped bottle off the body. He suspects somethin' and tells Foxy that he'll give him up to the law if he don't let him in on it. So Foxy tells him all about it and him and Sanchez, who was then a mule rustler, agrees ter go partners and go git ther radium, or whatever it is.

"They builds this boat, the one that disappeared, and in order that Foxy shouldn't play no tricks, that bein' his disposition, Sanchez 'lows he'll take both the sample and the map. Foxy sees no way out of it but to give in and that's the way it's fixed.

"The boat is taken out of Yuma in sections and then put together in a place whar nobody ain't likely to come nosin' around. Then they starts out on what I guess was the most darn-fool enterprise any two locoed fortune-hunters ever undertook. How it ended you know. They both got fever, but Sanchez was the worst. He died that same evening, his tumble in the water havin' made him worse. I buried him there as best I could and then, as he had wished, I takes the sample and the map.

"'Some day,' he told me, just afore he closed his eyes for good, 'you'll be glad you saved me, even though it was too late.'

"Well, I beat it back and get out of the canyon more dead than alive and finally make a small strike. I go to San Francisco with it and try to git ther stuff analyzed, but everyone I tole about it laughed at me and said I was crazy. So, thinks I, I'll come East. My money was about all gone, so I shipped afore ther mast on a Cape Horn ship, and got here.

"Now, you have me tale, old top," grinned the good-natured miner, and added: "Well, has my toe-and-heeling been worth its salt?"

The professor nodded solemnly.

"What is it?" cried Jack, his heart beating with a strange, wild hope.

Tom and Zeb echoed Jack's eager question.

"My friends," declared the little man of science pompously, "we have reason to believe that a wonderful discovery has been made, namely, Z.2.X."

CHAPTER XVI.

ZEB CUMMINGS.

"Z.2.X., the most radio-active stuff in the world!" exclaimed Jack.

"I suppose that approximately describes it," said the professor, "but what do you know about it?"

Jack explained how ardently his father had wished for the missing element to make his system of radio telephony the most efficient in use.

"Well, if what Sanchez said was true, and the map is right, there is plenty of it right on that island," said the miner.

"Yes, that may all be," objected the professor, "but how are you going to get at it?"

"Wa'al that's a poser. You can't reach it in a boat and you can't reach it over the desert," said Zeb. "The country all round there is dry as an oven and, anyhow, if you got to ther banks of ther Colorado right by ther island ther's no way of gitting down to ther island. Sanchez says that the Injuns told Foxy's friend that a long time ago, when first they found the stuff on the island, there was a way of getting down to it. But an earthquake sunk the river bed and nobody had been thar since the Injuns that found it. He said that they first come to take notice of it by reason of the way it shined at night. But only a few of the tribe would go near on account of their thinking the place was haunted."

"Have you got that map?" asked the professor.

"Yes, if you'll reach my coat I'll show it you," said the miner.

Jack gave him the ragged garment off a hook at the back of the door. Zeb fumbled in the pockets for a minute and then brought out a knife.

"A rip more or less won't make no difference," he said, and cut a slash down the lining. There, carefully stowed inside, where it could not be suspected, was a folded, time-yellowed paper.

The miner opened it slowly and spread it out on the counterpane. The boys, not without a sense of shock, noted a dark, rusty-looking stain upon it. It struck them that the marks might be the life blood of the treacherous Foxy's friend who had met a tragic end in Yuma.

Zeb, with a broad and blackened forefinger, traced the course of the Colorado. At length his finger paused at an island marked in red. There was some fantastic Indian lettering, or sign-drawing, about it, and underneath, in a white man's handwriting, were the words: "Rattlesnake Island."

"I reckon Foxy Joe's friend must hev written that in," commented Zeb.

"It looks that way," said the professor, who had poured the sample of mineral-bearing sand back into the vial and restored it to Zeb Cummings.

"Rattlesnake Island," repeated Jack. "Are there any rattlers down that way?"

"Yes, and gila monsters and tarantulas and centipedes," replied Zeb cheerfully. "But you soon get used to 'em."

Some other islands were marked on the map, but Rattlesnake Island was the only one designated by name.

"That must be the place whar all that stuff is, then," decided Zeb. "I wish thar was some way of gittin' thar."

"If there is even only a small fraction of the mineral-bearing sand there," said the professor, "there's a fortune in it."

"Wa'al if you can't git it out what good is it?" said Zeb philosophically. "Anyhow, I'm glad that Sanchez spoke the truth with his dying words. Maybe thar is some way, except by water, in spite of what he said."

"Maybe there is," said Jack. "It seems a shame to think of all that rich stuff lying there neglected and unobtainable."

"It does indeed," agreed the professor. "In that sample I find traces of metals from which filaments for electric lights could be made and substances invaluable in medicine for X-ray purposes as well as the Z.2.X. which your father is convinced would make the radio telephone as practical as the wireless telegraph."

They would like to have stayed there all the morning poring over the map and asking further questions of the rugged miner, but at that moment the nurse came in and declared that the injured man must have quiet.

And so there, for the present, the matter rested. The professor departed for his home greatly excited over the events of the morning, but his excitement was a little allayed by the fear that he would be late for his mid-day meal with dire results from Miss Melissa.

As for the boys, they could talk of nothing else. The idea of that lonely island, lying at the bottom of an unscalable canyon in the midst of a burning, desolate desert, appealed powerfully to their imaginations. Their minds were in a whirl over the strange coincidence that had brought them in contact with a man who knew where possibly inexhaustible supplies of the mysterious Z.2.X. lay ready for the taking, provided it could be reached.

"I'd give a whole lot to be able to fix up an expedition to go out there and get that stuff," said Jack with a sigh.

"So would I," agreed Tom. "But I guess, as Zeb Cummings said, it will be a long time before anyone sets foot on Rattlesnake Island."

CHAPTER XVII.

IN THE LABORATORY.

That afternoon Jack broached to his father the events of the morning. Mr. Chadwick's enthusiasm may be imagined as his son told him of the professor's hasty analysis of the contents of Zeb Cumming's glass vial.

But there remained the insuperable obstacle of the remoteness of the island where the deposits lay, and the difficulties—in fact, almost the impossibilities—that barred the way. For the time being, however, the matter was set aside while further experiments with the radio telephone were conducted. As a means of increased transmitting power, Mr. Chadwick had in mind a series of sending devices attached to one mouthpiece. In this way he believed he could at least partially overcome the resistance of the atmosphere, and get a higher percentage of current.

He had been working on the idea all the morning and was anxious for a test. The Wondership was, therefore, wheeled out, and before long the boys were in the air once more. As before, they sailed in the direction of Rayburn. As they passed above the farm where they had met with their adventure the day before, they turned to each other with a laugh.

Below them they could see men working on the damaged roof of the barn and Tom burst into an uncontrollable fit of laughter as he recalled the queer sight the farmer presented dangling from the grapnel high above his broad acres.

"That reminds me," said Jack. "We must send him some money for that roof."

"How about his personal feelings?" grinned Tom.

"I guess he wiped that score out when he blazed away at the balloon bag."

"Just the same, I think we'd better go pretty high up," advised Tom. "He might fancy trying another shot at us."

"That's so," agreed Jack, studying the men moving about far below.

He pulled a lever and the Wondership began to rise. It was as well he did so perhaps, for as they shot upward they could see that their presence had been noted. They watched the men scurrying about and pointing upward. But whether the Wondership was too high, or his animosity had cooled after his involuntary ascension, the farmer made no hostile demonstration, and they were soon out of Perkins' sight.

Apparently the new device worked fine, for all through the afternoon, at various heights and distances, they kept in perfect touch with Mr. Chadwick. Every intonation of his voice was borne plainly to their ears, Tom at times taking the wheel and the receivers while Jack relieved him at the engines.

The storm which had threatened the night before, still was hovering about, as was evidenced by the white thunderheads piled on the horizon. But the electricity in the air did not, as is sometimes the case, interfere with the powerful impulses sent out from workshop and airship. Although the air felt heavy, the instruments worked perfectly.

The boys flew over hill and dale for more than seventy miles prior to any perceptible weakening in the current. But once it began to fail it reduced rapidly until the messages were scarcely audible. But the experiments were kept up till almost dusk, when Mr. Chadwick told the boys to come back.

As they returned the radio 'phones were kept working and as the distance decreased the impulses grew stronger.

"If only I had some of that Z.2.X.," said Mr. Chadwick, "I believe it would be possible to send a message across the ocean or the continent."

Not long after this Jack heard again from his father. It was a commonplace message enough. Sent merely to keep the air-line in operation.

"Here is Jupe with the afternoon mail," he said.

"Anything for us?" asked Jack, enjoying the novel sensation of talking through the air concerning such everyday matters.

"Yes, there's one from Ned Nevins," was the rejoinder, "and here is one for me from my New York brokers. Let me see—ah-h-h-h!"

The last was a sharp exclamation, as if Mr. Chadwick had received a sudden shock. It was followed by silence. Again and again Jack flashed the red signaling lamp but there was no reply.

He was seriously worried. The sudden sharp intake of breath, almost like an outcry, that he had heard, oppressed him with a sense of apprehension. What could have happened? Turning to Tom he called for full speed ahead for the trip back.

Tom was not slow in responding. He speeded the motors up to their top capacity. In the air there were no speed laws to look out for, or other motorists or pedestrians to avoid. It was a clear road. The steel stays and stanchions of the stanch Wonder ship fairly hummed as she shot forward, while an indefinable fear clutched at Jack's heart.

He knew that his father was subject to fainting spells and he had been overworking recently. Fast as the Wondership was cutting through the air it felt like an eternity to Jack before the gray walls and the well-laid-out grounds of High Towers came into view.

The boys lost no time in landing, and not waiting to place the Wondership in her shed, set out to look for Mr. Chadwick. Jupe came shuffling by on his way from the cornpatch.

"Where's dad, Jupe?" asked Jack.

"In his labveroratory, ah reckons," answered the old colored man. "Leastways ah ain't obfustucated any obserwations ob him round der contagiois atmosferics."

"Come on, Tom," said Jack. "Let's get to dad's workshop as quick as we can."

"Why, Jack, you—you don't think that anything has happened to him, do you?" asked Tom.

"I don't know. He was talking quite cheerfully to me and then, without any warning, he gave a sort of gasp and then everything was silent."

The next minute the boys entered the workshop of the inventor.

Jack's worst fears were realized as they gazed at the scene before them. On the floor, stretched out inanimate before the radio telephone apparatus, lay Mr. Chadwick. His right hand grasped a letter.

His head lay in a pool of blood, oozing from a cut at the back of his head.

"Dad! dad! What has happened?" cried Jack, in an agony of alarm, as he fell to his knees at his father's side.

But Mr. Chadwick did not answer. The next moment Tom's shout for help brought everybody about the place running toward the workshop where the alarming discovery had been made.

CHAPTER XVIII.

INTO THE STORM.

"Carry him into the house and get him to bed," cried Mrs. Bagley, the housekeeper, wringing her hands distractedly. "Oh dear! poor gentleman, he's bin a-workin' too hard, that's what's the matter."

Jupe and Hank Hawkins, the handy man, picked the unconscious man up and carried him to bed, where he was made comfortable.

Jack and Tom made an investigation of the workshop. At first the cut on Mr. Chadwick's head had given Jack the impression that he might have been the victim of foul play.

But a brief survey of the place soon dispelled these conclusions. When he fell, the inventor struck his head against the sharp corner of a table right behind him, Jack concluded, and in this way inflicted the wound.

The letter that his father had been reading when he was stricken still lay on the floor. Jack picked it up. It was from the brokers in New York, the same missive Mr. Chadwick had referred to over the radio 'phone just before the silence that so alarmed Jack.

Glancing over it Jack's eyes widened. He perceived at once that the cause of his father's sudden attack no doubt lay in the shock he had received when he opened the envelope. The letter was curt and to the point.

"Your securities wiped out in panic," it said. "Wire us and advise what to do."

That was all, but it was enough. Jack knew that most of his father's money was invested with the firm that had written the letter, and now they had been wiped out in a money panic. Jack had no idea how much of his father's fortune was affected, but it was evident from Mr. Chadwick's collapse that he had been dealt a heavy blow.

He was in the midst of talking to Tom about the letter when the housekeeper came running from the house.

"Oh, here you boys are!" she exclaimed. "You must get Dr. Mays at once. Those red drops he gave your father are finished and I can't find any more."

"I'll telephone," said Jack promptly, stuffing the letter into his pocket.

"I've already tried that," said Mrs. Bagley, "but the line is out of order."

"Can't we get some other doctor?" asked Tom.

Mrs. Bagley shook her head.

"Dr. Mays is the only one who understands your father's case," she said. "You must get him as soon as possible."

"Is dad conscious yet?" asked Jack anxiously.

"Yes, he has been trying to tell me something but I won't let him talk."

"We'll get Dr. Mays right away," said Jack, but then he suddenly recollected that the electric car was slightly out of order. There would be no time to stop and repair it then.

Luckily the Wondership still stood outside the shed. Five minutes later the boys were soaring aloft, bound for the doctor's house, which was some distance away. It was not till they had fairly started that they noticed the change in the weather.

The thunderheads they had seen earlier in the day now spread and covered the whole sky with a dark pall. The air was very still, as if nature was holding her breath. Far off, though in plain view, the sea was lying like a smooth sheet of steel-gray velvet. A sailing ship, with sails flapping, was becalmed some distance from shore.

"Going to rain," said Tom.

"Worse than that, I think," said Jack. "We're in for the storm that's been making up for two days now."

"Well, we can get there and back before it breaks."

"Easily. Let those motors out, Tom, we want to make good time."

It was oppressively hot, and had it not been for Jack's anxiety he would have enjoyed the swift cooling passage through the thundery air. But he was strangely troubled. Did that letter mean that his father was on the verge of ruin?

Suddenly he bethought himself of Ned Nevins' letter. He opened it, having pushed it into his pocket when they entered the workshop, where Mr. Chadwick had placed it before opening the ominous epistle from his brokers. It was a friendly, chatty note from the boy, and enclosed the checks covering the joint dividends of Jack and Tom in the Hydroaëroplane Company.

"Well, at any rate, that's something," declared Jack to Tom, as he handed him the letter and his check.

"Yes, but if Uncle Chester is ruined, it's only a drop in the bucket," said Tom.

"Well, it's no use crossing your bridges till you come to them," said Jack, "and anyhow, that letter may be only a false alarm. I've heard they get these financial panics in Wall Street just like kids get the measles, and they get over them as quickly."

"I trust it will be so in this case," said Tom.

"So do I," said Jack hopefully, but a cold fear that his father was ruined possessed him, and made his heart feel heavy as lead.

Suddenly, from the purple firmament, came the sound of distant thunder. Following it a puff of wind, hot as the exhalation of an opened oven, blew in their faces. In the distance they saw a ragged streak of lightning tear the cloud curtains.

CHAPTER XIX.

THE "LIGHTNING CAGE."

"Look at that, will you!" exclaimed Tom.

"What, you are not scared, are you?" asked Jack.

"N-no, but I must say I'm not fond of thunderstorms Particularly when we are carrying all that gas over our heads."

"That new invention of mine will take care of that all right," said Jack confidently.

He referred to a new device of his with which the Wondership was equipped for protecting balloon bags from lightning. In a thunderstorm a balloon, or gas-filled dirigible, is subject to sudden variations of electric charge which, under certain conditions, might produce sparks leading to its annihilation.

More especially was this the case with such a craft as this Wondership, carrying as she did so much metal and steel wiring. The netting of the bag, with the idea of making it as conductive as possible, was of metal, connecting with the other metal parts of the craft so that when a steel drag rope was lowered to the ground a discharge of lightning striking the balloon would be passed off harmlessly into the earth, as is the case with a lightning conductor.

It might be supposed that making the outside of a balloon a good conductor would invite danger from lightning. But the Boy Inventors knew that this was not the case. While the ordinary balloon envelope is a fairly good insulator against low voltage, it is unable to resist the high tension of atmospheric electricity.

Jack ascertained these facts by touching an electroscope with a bit of balloon cloth of the kind used on the Wondership, and charged with 2,000 volts of electricity. The electroscope instantly responded.

This showed that the balloon bag increased the electrical tension immediately above and below it as much as it would do if it was a perfect conductor, but the destructive action of a lightning bolt would be greater in proportion to the resistance opposed to it. So that, in reality, Jack's device was one of the safest that could be imagined for protecting balloonists in a heavy storm.

In effect, the occupants of the Wondership were enclosed in a cage. Lightning might zip through the wires and stays, but it could not touch them. As to the danger of letting out gas through the valve in a strong electric field, which is almost certain to produce sparks, the boys did not have to worry about that for to deflate the bag they simply pumped some of its contents back into the reservoir with the powerful gas pumps.

But after all, Jack's device had never been tested. It looked as if it was due to be. The wind came in sharp puffs, now hot and now cold.

Ragged, white clouds, like wind-driven fragments of filmy lace, began to whip across the dark heavens. The sea turned a peculiar light green and was flecked with whitecaps.

"We're in for it," said Jack. "Better get up the storm curtains, Tom."

While Jack steered, Tom drew up the waterproof curtains and top which, in rainy weather, made the Wondership quite dry and weather-tight. Mica portholes gave light inside this extemporized cabin, and enabled the steersman to see.

This had hardly been done when a wild gust of wind struck the Wondership and sent it staggering off its course. But in a jiffy Jack regained control of the craft and headed her straight for the white house occupied by Dr. Mays, which could now be seen, its lofty cupola poking up above the trees surrounding it.

"Glad we're nearly there," said Tom. "I don't much like this."

"We're O.K.," Jack assured him. "We went through a lot worse than this in that circular storm in Yucatan."

"Can't we drop and run along the road?"

"It's much longer by the road than by the air line, and remember we are in a big hurry."

"That's so. But we've got the return trip ahead of us."

"Well, if it gets too bad, we'll have to come back by road," said Jack, "but I haven't got a doubt that she'll stand anything that will come out of this storm."

Crash!

The sky was rent from end to end by jagged lightning. With a deafening roar the thunder broke, rumbling and crashing in the sultry air.

S-w-i-s-h!

The rain came in torrents, tearing at the storm curtains. It beat frantically at them with a noise like that of surf on a beach. But inside the boys were snug and dry, and the Wondership forged steadily forward. It was a weird experience for the boys. About them the artillery of heaven thundered and flashed. They could see each other's faces and the black outlines of their craft in the livid flare of flash after flash of lightning.

Jack, with his hands firmly gripping the steering wheel, anticipating every move of the storm-tossed Wondership like a skillful pilot, felt his pulses throb. There was something fine in battling with the elements like this in a stanch craft they had perfected. He felt that no other airship then in existence would have been able to keep up the fight.

All at once there came a crash that drove his eardrums in. The Wondership staggered and then seemed to leap into lambent flame. Blinded, Jack threw his hands before his eyes, utterly forgetting for the minute the steering wheel.

Tom gave a shout of alarm, as he felt the craft stagger as if dealt a mortal blow, and then begin to drop earthward.

"We've been struck!" he yelled in panic.

CHAPTER XX.

THROUGH THE AIR.

For the fraction of a second the faculties of both boys were paralyzed. A tingling sensation was in their limbs. Jack was the first to recover his wits. He snatched his hands from his eyes and seized the wheel. In a jiffy the Wondership's earthward plunge was checked. Once more she regained an even keel.

"Wh-what happened?" stuttered Tom anxiously.

"We were hit by lightning," replied Jack.

"Goodness! I thought we were goners, for a minute."

"I confess that I did, too. But I guess the 'electric cage' worked. Everything seems to be shipshape."

Jack was right. Thanks to his ingenious invention, the lightning, which had struck the aircraft, had been diffused through the safety "cage" and safely convoyed to the earth by the ground chain made of light manganese bronze, which had been lowered when the storm broke.

"Just the same I don't want to get hit again," said Tom. "I thought for a minute the world had come to an end."

"My fingers are tingling yet," said Jack, "and I can see stars, but I think if it hadn't been for the cage we would have likely been blown to smithereens."

By this time they were almost over the doctor's house and extensive grounds. Jack manipulated the Wondership against the storm, flying in a circle, and snapped on the powerful searchlight. With the help of its rays he picked out a good landing place, and having set the pumps at work abstracting gas from the bag, they soon made a good landing.

Doctor Mays stood on his porch as they left the ship and ran through the downpour for the house.

"Gracious, boys!" he exclaimed, "but you certainly gave me a fright. I thought when that bolt hit you that you were going to be annihilated."

"How did it look from below?" asked Jack.

"As if you were enveloped in blue flame. Then suddenly a ball of red fire slid from the ship to the ground——"

"Down the conducting rope," put in Jack.

"And exploded with a loud bang when it struck the ground," continued the doctor. "But all's well that ends well, and now tell me what brings you here, for I know it must be urgent business or you'd never have ventured through such a storm."

Jack hastily told the doctor of his father's stroke. The medical man looked grave.

"I'll go with you just as soon as I can pack my bag," he said. "Your father had been overworking. I warned him of what would happen if he did not rest up, some time ago, but he has, seemingly, disregarded my advice."

In a few minutes the doctor, muffled up in a raincoat, was ready to start. But he stipulated that the run to High Towers should be made by the road.

"I like excitement as well as anybody," he said, "and I've been up in your Wondership before——"

"When it was the Roadracer," interpolated Jack.

"Exactly; but I must confess that when I saw you a short time ago looking like a floating ball of fire, I lost my taste for aërial travel."

"We'll go back by road, then," said Jack, as through the rain, which was falling in torrents, they ran to the Wondership.

"My, but you have it snug in here," said the doctor, as he entered the tight, waterproof cabin.

"Hang up your coat, doctor," said Tom, and he took the physician's dripping mackintosh and slung it on a hook attached to one of the stanchions. Then the start was made, with the bag partially deflated and lying in limp, wet folds on its framework.

Through the night, under skies fretted with lightning, the Wondership shot forward. Out on the open road Jack ordered full speed, the great searchlights illuming the roadway as if it were day. He felt little apprehension of meeting other vehicles. The night was too bad to permit of any save emergency traveling.

The roads were deep in mud, and water spurted up from the wheels of the flying car as it raced through the storm. But seated snug and dry in the cabin none of them bothered about this. Little was said. Jack had to concentrate his mind on handling the Wondership, for driving under the conditions, and at such speed, required all the wheel-handler's attention.

On and on they flew, down hills and over bridges, under which, ordinarily, quiet streams flowed, but now swollen by the rains, they boiled and raced like angry torrents. They flashed through villages and past farmhouses without encountering a soul, while overhead the tempest roared and raged and flared.

They were shooting down a hill at top speed when Jack suddenly gave a gasp. Right in front of them, vividly outlined in the searchlight's glare, was an obstacle. A big wagonload of hay, covered with a tarpaulin, and deserted by its driver who, despairing of mounting the hill in the storm, had unhitched his horses and driven off till the weather cleared.

The wagon was in such a position that it blocked the road, which was sunken between high banks at that point. Jack ground down his brakes in chagrin.

"Blocked!" he exclaimed disgustedly.

CHAPTER XXI.

VAULTING TO THE RESCUE.

"What awful luck," muttered Tom.

"Isn't there any way we can get by?" inquired the doctor anxiously. "It's important that I should reach Mr. Chadwick as soon as possible."

Jack made no reply, but bent over the gas-valve. In an instant the gas was hissing into the balloon bag. Its wet folds swelled out, and presently Jack started the propellers. Like a racehorse leaping a barrier, the Wondership rose skyward.

"Hold fast!" cried the boy in a triumphant voice.

"Wow!" yelled Tom, "there are more ways of killing a cat than by choking it with cream."

The next moment the Wondership was in the road on the other side of the hay wagon, having hurdled it like a high jumper, and was once more on her way.

"Jove, you boys are marvels!" exclaimed the doctor. "Is there anything you can't do with this craft, or auto, or whatever it is, of yours?"

"Lots of things, I guess," said Tom, "but we haven't found many of them yet."

At uninterrupted speed the journey was resumed. At times so swift was the pace that the Wondership seemed to be half flying. Thanks to her shock absorbers, but little motion was felt, although in places the roadway had been washed out by the torrential downpour and was very rough.

"Whereabouts are we?" shouted Tom, as they rushed along.

"Near the Coon Creek Bridge," flung back Jack over his shoulder. "We ought to sight it at any moment now."

He peered through the blackness ahead. The searchlights failed to show any bridge. But the young driver saw an abandoned cottage by the roadside which had formerly been used as a toolhouse. Just beyond it he knew the bridge should loom up with its white railings.

But there was not a sign of it.

Not till it was too late to stop did Jack realize what had happened. The bridge had been washed away by the rising waters of the creek and he was tearing at top speed for the steep banks.

It was a moment for lightning thinking. Right ahead loomed a black pit which he knew marked the water course.

Suddenly it flashed into Jack's mind that in former times, before the bridge had been built, there had been a ford at the point.

The banks, steep elsewhere, almost wall-like in fact, were still graded at the place where the old crossing spot had been.

He jerked over the steering wheel with a suddenness that threatened to overturn the Wondership. The auto-craft plunged wildly to one side and then rushed downward.

Before he realized it, Jack had steered her into the rushing waters of the swollen creek.

"All the power you've got," he cried to Tom, as the Wondership careened and tipped madly and then recovered an even keel. Jack headed her up stream while Tom, who hardly knew what had happened, blindly obeyed orders.

Jack's chief fear was that the rush of the torrential water would carry him too far down to make a landing on the opposite side of the old ford. In that case they would be in a bad fix, for the creek ran for some distance between steep walls of limestone rock.

It was a hard struggle. The twin propellers beat the air furiously, clawing the Wondership up stream, while the water hissed and roared all about her, and the engine labored with a noise like that of a giant locust.

And then, almost before he knew it, and before either Tom or the doctor realized in the least what had happened, they found themselves safe on the other side. They had gained the opposite slope of the ford with hardly an inch to spare, but that was enough.

The Wondership sped up the bank as if glad to be free of the battle with the swollen creek, and not half an hour afterward they rolled up to High Towers.

Dr. Mays was met almost tearfully by Mrs. Bagley.

"How is he?" was his first question.

"He seems to be better, doctor, but something is worrying him," said the worthy woman.

"I'll go up to him at once. You boys had better stay here," said the doctor.

The physician was upstairs a long time. When he came down he looked grave.

"Is dad any better?" asked Jack anxiously.

"He is suffering from a nervous breakdown due to overwork," said the doctor. "The cut on his head is a mere flesh wound. But he appears to have something on his mind. Do you know what it is?"

Then, and not till then, for in the rush of events he had completely forgotten it, Jack remembered the letter from the brokers.

"Dr. Mays," he said, "you are an old friend?"

"I hope so, my boy. You may confide in me freely if you know any reason for your father's disquiet."

"If you will read this, doctor, you will understand," and Jack handed him the letter.

Dr. Mays read it with knitted brows.

THE

BOY INVENTORS' RADIO-

TELEPHONE

BY

RICHARD BONNER

AUTHOR OF "THE BOY INVENTORS' WIRELESS TRIUMPH," "THE BOY

INVENTORS AND THE VANISHING GUN," "THE BOY INVENTORS'

DIVING TORPEDO BOAT," "THE BOY INVENTORS' FLYING

SHIP," "THE BOY INVENTORS' ELECTRIC

HYDROAEROPLANE," ETC., ETC.

WITH ILLUSTRATIONS BY

CHARLES L. WRENN

NEW YORK

HURST & COMPANY

PUBLISHERS

CONTENTS

The Boy Inventor's Radio-

Telephone.

CHAPTER I.