accompanied by Mr. Barcoe Jenks, one of the castaways of Earthquake Island. They found the diamond makers, and had some surprising adventures, barely escaping with their lives.

This did not daunt Tom, however, and he once more started off on an expedition in his airship the Red Cloud to Alaska, amid the caves of ice. He was searching for a valley of gold, and though he and his friends found it, they came to grief. The Fogers, father and son, tried to steal the gold from them, and, failing in that, incited the Eskimos against our friends. There was a battle, but the forces of nature were even more to be dreaded than the terrible savages.

The ice cave, in which the Red Cloud was stored, collapsed, crushing the gallant craft, and burying it out of sight forever under thousand of tons of the frozen bergs.

After a desperate journey Tom and his friends reached civilization, with a large supply of gold. Tom regretted very much the destruction of the airship, but he at once set to work on another—a monoplane this time, instead of a combined aeroplane and dirigible balloon. This new craft he called the Humming-Bird and it was a “sky racer” of terrific speed. In it, as we have said, Tom brought a specialist to operate on his father, when, because of a broken railroad bridge, the physician could not otherwise have gotten to Shopton. He and Tom traveled through the air at the rate of over one hundred miles an hour. Later, Tom took part in a big race for a ten-thousand-dollar prize, and won, defeating Andy Foger, and a number of well-known “bird-men” who used biplanes and monoplanes of a more or less familiar type.

The government became interested in Tom’s craft, the Humming-Bird, and, as told in the ninth book of this series, Tom Swift and His Sky Racer, they secured some rights in the invention.

And now Tom, who had done nothing for several months following the great race—that is, nothing save to work on his new rifle—Tom, we say, sighed for new adventures.

“Well, Tom, what is on your mind?” asked his father at the supper table that evening. “What is worrying you?”

“Nothing is worrying me, Dad.”

“You are thinking of something. I can see that. Are you afraid your electric rifle won’t work as well as you hope, when Ned comes over to try it?”

“No, it isn’t that, Dad. But I may as well tell you, I guess. I’ve been reading in the paper about a big elephant hunt in Africa, and I—”

“That’s enough, Tom! You needn’t say any more,” interrupted Mr. Swift. “I can see which way the wind is blowing. You want to go to Africa with your new rifle.”

“Well, Dad, not exactly—that is—”

“Now, Tom, you needn’t deny it,” and Mr. Swift laughed. “Well, I don’t blame you a bit. You have been rather idle of late.”

“I would like to go, Dad,” admitted the young inventor, “only I’d never think of it while you weren’t well.”

“Don’t worry about me, Tom. Of course I will be lonesome while you are gone, but don’t let that stand in the way. If you want to go to Africa, you may start to-morrow, and take your new rifle with you.”

“The rifle part would be all right, Dad, but if I went I’d want to take an airship along, and it will take me some little time to finish the Black Hawk, as I have named my new craft.”

“Well, there’s no special hurry, is there?” asked Mr. Swift. “The elephants in Africa are likely to stay there for some time. If you want to go, why don’t you get right to work on the Black Hawk and make the trip? I’d like to go myself.”

“I wish you would, Dad,” exclaimed Tom eagerly.

“No, son, I couldn’t think of it. I want to stay here and get well. Then I am going to resume work on my wireless motor. Perhaps I’ll have it finished when you come back from Africa with an airship load of elephants’ tusks.”

“Perhaps,” admitted the young inventor. “Well, Dad, I’ll think of it. But now I’m going after my rifle, and—”

Tom was interrupted by a ring of the front-door bell, and Mrs. Baggert, the housekeeper, who was almost like a mother to the youth, went to answer it.

“It’s Ned Newton, I guess,” murmured Tom, and, a little later, his chum entered the room.

“Oh, I guess I’m early,” said Ned. “Haven’t you had supper yet, Tom?”

“Yes, we’re just finished. Come on out and we’ll try the gun.”

“And practice shooting elephants,” added Mr. Swift with a laugh, as he mentioned to Ned the latest idea of Tom.

“Say! That would be great!” cried the bank clerk. “I wish I could go!”

“Come along!” invited Tom cordially. “We’ll have more fun than we did in the caves of ice,” for Ned had gone on the voyage to Alaska.

The two youths went out to the shed where the rifle gallery had been built. The new electric weapon was out there, and Eradicate Sampson, the colored man, who was a sort of servant and man-of-all-work about the Swift household, had set up the scarecrow figure at the end of the gallery.

“Now we’ll try some shots,” said Tom, as he took the gun out of the case. “Just turn on a few more lights, will you, Mr. Jackson,” and the engineer, who was employed by Tom and his father to aid them in their inventive work, did as requested.

The gallery was now brilliantly illuminated, with the reflectors throwing the beams on the big stuffed figure, which, save for a face, looked very much like a human being, standing at the end of the gallery.

“I don’t suppose you want to go down there and hold it, while I shoot at it; do you, Rad?” asked Tom jokingly, as he prepared the electric rifle for use.

“No indeedy, I don’t!” cried Eradicate. “Yo’-all will hab t’ scuse me, Massa Tom. I think I’ll be goin’ now.”

“What’s your hurry?” asked Ned, as he saw the colored man hastily preparing to leave the improvised gallery.

“I spects I’d better fro’ down some mo’ straw fo’ a bed fo’ my mule Boomerang!” exclaimed Eradicate, as he hastily slid out of the door, and shut it after him.

“Rad is nervous,” remarked Tom. “He doesn’t like this gun. Well, it certainly does great execution.”

“How does it work’” asked Ned, as he looked at the curious gun. The electric weapon was not unlike an ordinary heavy rifle in appearance save that the barrel was a little longer, and the stock larger in every way. There were also a number of wheels, levers, gears and gages on the stock.

“It works by electricity,” explained Tom.

“That is, the force comes from a powerful current of stored electricity.”

“Oh, then you have storage batteries in the stock?”

“Not exactly. There are no batteries, but the current is a sort of wireless kind. It is stored in a cylinder, just as compressed air or gases are stored, and can be released as I need it.”

“And when it’s all gone, what do you do?”

“Make more power by means of a small dynamo.”

“And does it shoot lead bullets?”

“Not at all. There are no bullets used.”

“Then how does it kill?”

“By means of a concentrated charge of electricity which is shot from the barrel with great force. You can’t see it, yet it is there. It’s just as if you concentrated a charge of electricity of five thousand volts into a small globule the size of a bullet. That flies through space, strikes the object aimed at and—well, we’ll see what it does in a minute. Mr. Jackson, just put that steel plate up in front of the scarecrow; will you?”

The engineer proceeded to put into place a section of steel armor-plate before the stuffed figure.

“You don’t mean to say you’re going to shoot through that, do you?” asked Ned in surprise.

“Surely. The electric bullets will pierce anything. They’ll go through a brick wall as easily as the x-rays do. That’s one valuable feature of my rifle. You don’t