During the trip from Westerlo to Pokeville the case of Ralph Ingersoll had been discussed in all its bearings, and it had been decided that, for the present at any rate, he was to make his home with the boys. Ralph appeared a bright little fellow, and his evident fear of being sent to some institution decided Mr. Jesson not to carry out his first intention.

Besides, Jack and Tom had argued that the lad would be useful to them around their inventions, and they needed an assistant, anyway. So, to Ralph’s great joy, matters were arranged as described above. But Mr. Jesson warned Ralph that, in the event of the circus people proving a legal right to him, he might have to be returned to them. This idea; however, proved so disquieting to the lad that the kind-hearted explorer forebore to press it.

Ralph declared that he had no knowledge of his parents, but that he had been placed with the circus men at an early age. Thus all that he could recall of his past was misery and privation.

As they turned into Mr. Peregrine’s grounds, the inventor himself came toward them. Even at a distance they could see that he was perturbed and excited. His face was flushed, and as soon as he got within speaking distance he began to talk, almost more explosively than usual.

“My stars! I’m glad you’ve come!” he exclaimed. “Queer doings—strange men—frightened them off—but afraid they’ve seen more than I want ’em to.”

“Jump in and tell us about it as we drive to the house,” said Mr. Jesson; “we, too, have had some odd adventures on our way here.”

Just then Mr. Peregrine caught sight of Ralph Ingersoll, who still wore his gaudy tights.

“Bless my soul—what’s this?—circus—bing-bang—through a hoop—whoop-la!” he exclaimed.

“Not exactly,” said Mr. Jesson, with a smile at the inventor’s rapid-fire speech; “but I’ll explain later on. First tell us about the strange men. Possibly we can throw some light on the matter. The boys told me about encountering two men on the road last night, who asked about you, and whom we saw again just now.”

“One of them with a red beard—long one—other chap had black moustache—eh?”

“Yes, that describes the fellows as accurately as we could size them up for their goggles,” struck in Jack, who meanwhile had started the machine again. He drove it up to the front door of Mr. Peregrine’s home, and when they had all alighted a man was detailed to take it to the barn. Within they found a good lunch awaiting them, and Mrs. Peregrine came to meet them with a smile of ready welcome.

As all the passengers were rather grimy, they first had a good wash, and Ralph was provided with a suit which had belonged to Mr. Peregrine’s son, now a lad of nineteen and away at college. During the meal Mr. Peregrine described how, on visiting the shed which housed his invention that morning, he had surprised a strange man with a red beard peeping through a window at it.

“I must tell you,” he continued, “that a powerful syndicate has tried to purchase my invention; but I have refused to sell. Since that time I have been harassed in many ways, and I am afraid that this is their latest move against me.”

When Mr. Peregrine was very much in earnest he dropped his odd way of talking, and there was no doubt but that he was very serious now. His wife, too, looked troubled. Clearly his enemies were powerful, and determined enough to cause the inventor considerable alarm.

“But surely your invention is patented, and you have nothing to fear on the score of their stealing your ideas?” asked Mr. Jesson.

“That’s just it,” said the inventor, with a troubled look; “I have taken no steps in the matter of a patent yet, as I feared a leak somewhere. These people who are after my vanishing gun are aware of this, too, as they have spies in Washington.”

“Well, that does make the matter serious,” agreed Mr. Jesson, and then, as Mrs. Peregrine looked rather alarmed, the subject was changed.

After lunch Mr. Peregrine asked if they would care to see his invention and try to ascertain what the trouble was with it.

“We can’t look it over too soon for me,” exclaimed Jack.

“I do hope you’ll be able to suggest something that will get me over the sticking point,” responded Mr. Peregrine, as the party donned their hats and, following him, made their way to the shed where stood the gun of which so much was expected.

The boys could hardly restrain their curiosity while Mr. Peregrine unlocked the door of the shed, which was furnished with quite an elaborate system of protection. Besides the heavy locks of a novel variety, it was fitted with a burglar alarm connecting with the house.

The door being opened, the boys saw a strange-looking piece of apparatus. Imagine a dull gray-colored submarine boat on wheels of solid steel with wide tires, and you have something of an idea of what they gazed upon. The cigar-shaped body of this odd vehicle was apparently of steel with riveted plates, and about twelve or thirteen feet in length. “Amidships,” so to speak, was a low sort of hood, pierced with slits. From the top of this projected a slender rod of steel tubing with a small, square, boxlike terminal on its top.

“But where does the gun part of it come in?” asked Jack, much mystified.

Mr. Peregrine smiled, and then, motioning to them to come closer, he indicated, what they had not before noticed, a break in the continuity of the “shell” of his invention. This was in the form of a band, completely encircling the diameter of the fore part of the machine. In two places in this band, at opposite points, appeared round openings.

“There,” said the inventor, pointing to this band and the two holes, “is the vital part of my invention. You see those holes?—yes—well, they are the muzzles of my vanishing guns.”

The group about the inventor nodded; but as yet they had only a very vague idea of the details of this strange invention.

“That slender shaft of tubing rising from the conning tower,” said Mr. Peregrine, who in his enthusiasm had lost his jerky manner of talking, “is nothing more nor less than a periscope; you know what that is, I presume.”

“A device which will show whatever is occurring outside, while the operator of the machine to which it is attached remains hidden,” said Jack.

“Correct. But this is an improved periscope. It gives the operator of the ‘gun carriage’ a wide view of the sky in every direction. But to explain my invention more fully I must invite you inside.”

So saying, the inventor opened a door in the side of the steel structure, which they had not previously noticed. Taking Jack by the arm, he gave him a half shove into the interior of the steel cigar.

As the space within was small, Mr. Peregrine explained that he would have to show the points of his invention to one of them at a time. When Jack was inside the inventor closed the door and, turning a switch, caused a flood of light to illuminate the interior of the wheeled cylinder. Jack found that they were standing within the conning tower. Through the slits he could see out into the shed, but his attention was speedily distracted by Mr. Peregrine.

The inventor indicated a seat, and invited Jack to occupy it. The boy was informed that he was seated in the operator’s position. In front of him was a sort of desk with a white top. This was divided into squares. The inventor explained that the white surface represented the expanse of sky commanded by the periscope.

“The instant an aËroplane is seen to enter one of those squares, each of which, as you see, is numbered,” he explained, “I press one of these buttons which are correspondingly marked.”

He reached up to a sort of switchboard above the periscope desk, and pressed one of the numbered buttons on it. A whirring sound followed.

“What’s that?” demanded Jack.

“That noise is caused by the cylindrical band which you observed on the fore part of the machine,” said Mr. Peregrine; “two guns, controlled by electricity, are set in that band. By pressing this button one of them is automatically aimed at the square of sky which the periscope shows is occupied by a supposedly hostile aËroplane.”

Jack nodded. It was plain to him that the band which they had noticed revolved on an axis, and that the muzzles of the ‘vanishing gun’ revolved with it.

“The guns fire explosive shells,” went on the inventor, “and when they burst in mid-air they do damage extending over a wide area. This is an essential feature of the machine, for of course it would be impossible, actually, to hit an aËroplane fair and square except by chance.”

After showing Jack several more unique features of his strange invention, Mr. Peregrine took the boy “forward” into the gun chamber. Jack then saw just how each gun’s magazine of six shells was worked, and how the steel cases on the walls were especially designed for reserve ammunition. The boy could not help feeling the warmest admiration for the inventive genius that the eccentric designer of this queer, modern implement of warfare had displayed.

“But it seems to me that you have solved every problem in connection with this invention, Mr. Peregrine,” said Jack, after he had inspected the storage batteries and engine, designed to supply motive power to the vehicle which housed the vanishing guns.

“Yes,” rejoined the inventor, with a return to his odd, jerky manner, “everything solved—all complete—guns work—everything all right—but won’t go.”

“Won’t go?” questioned Jack wonderingly, “how do you mean?”

“What I say—can’t get it to move—wheels won’t go round.”

The inventor went on to explain that, although he had solved almost all the problems in connection with his wonderful device, one of the most important was still unmastered—namely, the means of locomotion for his invention. To be of any use at all in the field, it must be able to move, and move fast.

Now, although the inventor had provided a gasolene engine of considerable power, still he had not, up to date, been able to make the wheels revolve. Till he could do this, therefore, his invention must be considered a failure.

“It’s this that I wanted you to help me out on, Jack Chadwick,” he said, after he had jerkily explained his trouble; “can you do it?”

Jack looked rather dubious.

“Your machine is so enormously heavy,” he said, “that I’m afraid it is going to be a difficult matter.”

“Not so heavy as it looks,” responded the inventor, tapping the plates; “these are not steel, as you may think, but a mixture of vanadium and aluminum. The machine is practically bomb-proof. Any explosive dropped from an aËroplane would have to be more deadly than any at present known to do it much harm.”

Jack inspected the driving motor, a six-cylinder affair located behind a bulkhead, which cut it off from the conning tower, although the motor controls and the steering apparatus led into that compartment. The young inventor made a thorough and careful examination of the motor, and of the means by which it was geared to the driving shaft.

Then he started it up. Sure enough, as Mr. Peregrine had said, it refused to move the driving wheels. Jack stopped it and made a further examination. Following this, he made some more tests and a series of calculations. Mr. Peregrine watched him with some anxiety. A good deal depended on the lad’s opinion. At length Jack spoke.

“I think we can overcome your difficulty,” he said.

Mr. Peregrine looked as if he would have liked to embrace him.

“You can?—Good!—Fine!—But how?”

“Well, for one thing, your gearing is wrong. We’ll have to change that. Then we shall have to put a carburetor on each cylinder instead of on one only, as at present. That alone will give you more power. Such a change, combined with the improved gearing I spoke of, should solve the trouble.”

“You think so—you really do?—Then my troubles are over!”

“Not just yet,” smiled Jack; “there is quite a lot of work ahead of us, but I think I can promise you that I can make it move at a fair speed.” After making a further examination, and noting down the changes he wished to make. Jack and Mr. Peregrine emerged from the queer machine. The others then took turns in examining it, although it is doubtful if Mr. Jesson or young Ralph understood its principles very clearly.

“Do you think you can make it go?” Tom asked of Jack, in a low voice, after the former had been through it, and Mr. Peregrine had explained his stumbling-block.

“I think so,” said Jack, “but I don’t want to brag. You and I will have to make a trip to Boston as soon as possible, to get several supplies and fittings. As soon as we have those we can go right ahead.”

“That’s the idea,” agreed Tom enthusiastically, but the next moment he broke off abruptly, and pointed to a small window at the back of the shed.

“There was a man with a red beard peeping in at us through that window an instant ago,” he exclaimed.

“It must have been one of the spies that Mr. Peregrine fears; one of the men we met on the road,” exclaimed Jack, and without a thought of the consequences he dashed out of the shed, followed closely by Tom.