Electricity is the thing to use, I guess."

"Then you are really going off on this trip. Tom?" asked his father, rather wistfully.

"I'm afraid I am," replied his son. "I thought I could stay at home for a while, but it seems not."

"I was in hopes you could give me a little time to help me on my gyroscope invention," went on the aged man. "But I suppose it will keep until you come back. It is nearly finished."

"Yes, and I don't like stopping work on my noiseless motor," spoke Tom. "But that will have to wait, too."

"Do you know where you are going?" inquired Ned.

"Well, I'll have to do considerable traveling I suppose to get all the films he wants. But once I'm started I'll like it I guess. Of course you're coming, Ned."

"I hope so."

"Of course you are!" insisted Tom, as if that settled it. "And I'm sure Mr. Damon will go also. I haven't seen him in some time. I hope he isn't ill."

Tom started work on his Wizard Camera, as he called it, the next day—that is he began drawing the designs, and planning how to construct it. Ned helped him, and Koku was on hand in case he was needed, but there was little he could do, as yet. Tom made an inspection of his shop the morning after the chicken thief scare, but nothing seemed to have been disturbed.

A week passed, and Tom had all the plans drawn for the camera. He had made several experiments with different forms of electricity for operating the mechanism, and had decided on a small, but very powerful, storage battery to move the film, and take the pictures.

This storage battery, which would be inside the camera, would operate it automatically. That is, the camera could be set up any place, in the jungle, or on the desert, it could be left alone, and would take pictures without any one being near it. Tom planned to have it operate at a certain set time, and stop at a certain time, and he could set the dials to make this time any moment of the day or night. For there was to be a powerful light in connection with the camera, in order that night views might be taken. Besides being automatic the camera could be worked by hand.

When it was not necessary to have the camera operate by the storage battery, it could be connected to wires and worked by an ordinary set of batteries, or by a dynamo. This was for use on the airship, where there was a big electrical machine. I shall tell you more about the camera as the story proceeds.

One afternoon Tom was alone in the shop, for he had sent Koku on an errand, and Eradicate was off in a distant part of the grounds, doing some whitewashing, which was his specialty. Ned had not come over, and Mr. Swift, having gone to see some friends, and Mrs. Baggert being at the store, Tom, at this particular time, was rather isolated.

He was conducting some delicate electrical experiments, and to keep the measuring instruments steady he had closed all the windows and doors of his shop. The young inventor was working at a bench in one corner, and near him, standing upright, was a heavy shaft of iron, part of his submarine, wrapped in burlap, and padded, to keep it from rusting.

"Now," said Tom to himself, as he mixed two kinds of acid in a jar, to produce a new sort of electrical current, "I will see if this is any better than the first way in which I did it."

He was careful about pouring out the powerful stuff, but, in spite of this, he spilled a drop on his finger. It burned like fire, and, instinctively, he jerked his hand back.

The next instant there was a series of happenings. Tom's elbow came in contact with another jar of acid, knocking it over, and spilling it into the retort where he had been mixing the first two liquids. There was a hissing sound, as the acids combined, and a thick, white vapor arose, puffing into Tom's face, and making him gasp.

He staggered back, brushed against the heavy iron shaft in the corner, and it fell sideways against him, knocking him to the floor, and dropping across his thighs. The padding on it saved him from broken bones, but the shaft was so heavy, that after it was on him, Tom could not move. He was held fast on the floor of his shop, unable to use his legs, and prevented from getting up.

For a moment Tom was stunned, and then he called:

"Help! Help! Eradicate! Koku! Help!"

He waited a moment, but there was only a silence.

And then Tom smelled a strange odor—an odor of a choking gas that seemed to smother him.

"It's the acids!" he cried. "They're generating gas! And I'm held fast here! The place is closed up tight, and I can't move! Help! Help!"

But there was no one at hand to aid Tom, and every moment the fumes of the gas became stronger. Desperately the youth struggled to rid himself of the weight of the shaft, but he could not. And then he felt his senses leaving him, for the powerful gas was making him unconscious.

CHAPTER V

TOM GETS A WARNING

"Bless my shoe buttons!" exclaimed a voice, as a man came toward Tom's shop, a little later. "Bless my very necktie! This is odd. I go to the house, and find no one there. I come out here, and not a soul is about. Tom Swift can't have gone off on another one of his wonderful trips, without sending me word. I know he wouldn't do that. And yet, bless my watch and chain, I can't find any one!"

It was Mr. Damon who spoke, as my old readers have already guessed. He peered into one of the shop windows, and saw something like a fog filling the place.

"That's strange," he went on. "I don't see Tom there, and yet it looks as if an experiment was going on. I wonder—"

Mr. Damon heard some one coming up behind him, and turned to see Koku the giant, who was returning from the errand on which Tom had sent him.

"Oh, Koku, it's you; is it?" the odd man asked. "Bless my cuff buttons! Where is Tom?"

"In shop I guess."

"I don't see him. Still I had better look. There doesn't seem to be any one about."

Mr. Damon opened the shop door, and was met by such an outward rush of choking gas that he staggered back.

"Bless my—" he began but he had to stop, to cough and gasp. "There must have been some sort of an accident," he cried, as he got his lungs full of fresh air. "A bad accident! Tom could never work in that atmosphere. Whew!"

"Accident! What is matter?" cried Koku stepping to the doorway. He, too choked and gasped, but his was such a strong and rugged nature, and his lungs held such a supply of air, that it took more than mere gas to knock him out. He peered in through the wreaths of the acid vapor, and saw the body of his master, lying on the floor—held down by the heavy iron.

In another instant Koku had rushed in, holding his breath, for, now that he was inside the place, the gas made even him feel weak.

"Come back! Come back!" cried Mr. Damon. "You'll be smothered! Wait until the gas escapes!"

"Then Mr. Tom die!" cried the giant. "I get him—or I no come out."

With one heave of his powerful right arm, Koku lifted the heavy shaft from Tom's legs. Then, gathering the lad up in his left arm, as if he were a baby, Koku staggered out into the fresh air, almost falling with his burden, as he neared Mr. Damon, for the giant was, well-nigh overcome.

"Bless my soul!" cried the odd man. "Is he—is he—"

He did not finish the sentence, but, as Koku laid Tom down on the overcoat of Mr. Damon, which the latter quickly spread on the snow, the eccentric man put his hand over the heart of the young inventor.

"It beats!" he murmured. "He's alive, but very weak. We must get a doctor at once. I'll do what I can. There's no time to spare. Bless my—"

But Mr. Damon concluded that there was no time for blessing anything, and so he stopped short.

"Carry him up to the house, Koku," he said. "I know where there are some medicines, and I'll try to revive him while we're waiting for the doctor Hurry!"