Higher and higher went the Black Hawk, far above the earth, until the old elephant hunter, looking down, said in a voice which he tried to make calm and collected, but which trembled in spite of himself:

"Of course I'm not an expert at this game, Tom Swift, but it looks to me as if we'd never get down. Don't you think we're high enough?"

"For the time being, yes," answered the young inventor. "I didn't think she'd climb so far without the use of the gas. She's doing well."

"Bless my topknot, yes!" exclaimed Mr. Damon. "She beats the Red Cloud, Tom. Try her on a straight-away course."

Which the youth did, pointing the nose of the craft along parallel to the surface of the earth, and nearly a mile above it. Then, increasing the speed of the motor, and with the big propellers humming, they made fast time.

The old elephant hunter grew more calm as he saw that the airship did not show any inclination to fall, and he noted that Tom and the others not only knew how to manage it, but took their fight as much a matter of course as if they were in an automobile skimming along on the surface of the ground.

Tom put his craft through a number of evolutions, and when he found that she was in perfect control as an aeroplane, he started the gas machine, filled the big black bag overhead, and, when it was sufficiently buoyant, he shut off the motor, and the Black Hawk floated along like a balloon.

"That's what we'll do if our power happens to give out when we get over an African jungle, with a whole lot of wild elephants down below, and a forest full of the red pygmies waiting for us," explained Tom to Mr. Durban.

"And I guess you'll need to do it, too," answered the hunter. "I don't know which I fear worse, the bad elephants wild with rage, as they get some times, or the little red men who are as strong as gorillas, and as savage as wolves. It would be all up with us if we got into their hands. But I think this airship will be just what we need in Africa. I'd have been able to get out of many a tight place if I had had one on my last trip."

While the Black Hawk hung thus, up the air, not moving, save as the wind blew her, Tom with his father and Mr. Jackson made an inspection of the machinery to find out whether it had been strained any. They found that it had worked perfectly, and soon the craft was in motion again, her nose this time being pointed toward the earth. Tom let out some of the gas, and soon the airship was on the ground in front of the shed she had so recently left.

"She's all right," decided the young inventor after a careful inspection. "I'll give her a couple more trials, put on the finishing touches and then we'll be ready for our trip to Africa. Have you got everything arranged to go, Ned?"

"Sure. I have a leave of absence from the bank, thanks to your father and Mr. Damon, most of my clothes are packed, I've bought a gun and I've got a lot of quinine in case I get a fever."

"Good!" cried the elephant hunter. "You'll do all right, I reckon. I'm glad I met you young fellows. Well, I've lived through my first trip in the air, which is more than I expected when I started."

They discussed their plans at some length, for, now that the airship had proved all that they had hoped for, it would not be long ere they were under way. In the days that followed Tom put the finishing touches on the craft, arranged to have it packed up for shipment, and spent some time practicing with his electric rifle. He got to be an expert shot, and Mr. Durban, who was a wonder with the ordinary rifle, praised the young inventor highly.

"There won't many of the big tuskers get away from you, Tom Swift," he said. "And that reminds me, I got a letter the other day, from the firm I collect ivory for, stating that the price had risen because of a scarcity, and urging me to hurry back to Africa and get all I could. It seems that war has broken out among some of the central African tribes, and they are journeying about in the jungle, on the war path here and there, and have driven the elephants into the very deepest wilds, where the ordinary hunters can't get at them."

"Maybe we won't have any luck, either," suggested Ned.

"Oh, yes, we will," declared the hunter. "With our airship, the worst forest of the dark continent won't have any terrors for us, for we can float above it. And the fights of the natives won't have any effect. In a way, this will be a good thing, for with the price of ivory soaring, we can make more money than otherwise. There's a chance for us all to get a lot of money."

"Bless my piano keys!" exclaimed Mr. Damon, "if I can get just one elephant, and pull out his big ivory teeth, I'll be satisfied. I want a nice pair of tusks to set up on either side of my fireplace for ornaments."

"A mighty queer place for such-like ornaments," said Mr. Durban in a low voice. Then he added: "Well, the sooner we get started the better I'll like it, for I want to get that pair of big tusks for a special customer of mine."

"I'll give the Black Hawk one more trial flight, and then take her apart and ship her," decided Tom, and the final flight, a most successful one, took place the following day.

Then came another busy season when the airship was taken apart for shipment to the coast of Africa by steamer. It was put into big boxes and crates, and Eradicate and his mule took them to the station in Shopton.

"Don't you want to come to Africa with us, Rad?" asked Tom, when the last of the cases had been sent off. "You'll find a lot of your friends there."

"No, indeedy, I doan't want t' go," answered the colored man, "though I would like to see dat country."

"Then why don't you come?"

"Hu! Yo' think, Massa Tom, dat I go anywhere dat I might meet dem little red men what Massa Durban talk about? No, sah, dey might hurt mah mule Boomerang."

"Oh, I wasn't going to take the mule along," said Tom, wondering how the creature might behave in the airship.

"Not take Boomerang? Den I suttinly ain't goin," and Eradicate walked off, highly offended, to give some oats to his faithful if somewhat eccentric steed.

After the airship had been sent off there yet remained much for Tom Swift to do. He had to send along a number of special tools and appliances with which to put the ship together again, and also some with which to repair the craft in case of accident. So that this time was pretty well occupied. But at length everything was in readiness, and with his electric rifle knocked down for transportation, and with his baggage, and that of the others, all packed, they set off one morning to take the train for New York, where they would get a steamer for Africa.

Numerous good-bys had been said, and Tom had made a farewell call on Mary Nestor, promising to bring her some trophy from elephant land, though he did not quite know what it would be.

Mr. Damon, as the train started, blessed everything he could think of. Mr. Swift waved his hand and wished his son and the others good luck, feeling a little lonesome that he could not make one of the party. Ned was eager with excitement, and anticipation of what lay before him. Tom Swift was thinking of what he could accomplish with his electric rifle, and of the wonderful sights he would see, and, as for the old elephant hunter, he was very glad to be on the move again, after so many weeks of idleness, for he was a very active man.

Their journey to New York was uneventful, and they found that the parts of the airship had safely arrived, and had been taken aboard the steamer. The little party went aboard themselves, after a day spent in sight-seeing, and that afternoon the Soudalar, which was the vessel's name, steamed away from the dock at high tide.

"Off for Africa!" exclaimed Tom to Ned, as they stood at the rail, watching the usual crowd wave farewells. "Off for Africa, Ned."

As Tom spoke, a gentleman who had been standing near him and his chum, vigorously waving his hand to some one on the pier, turned quickly. He looked sharply at the young inventor for a moment, and then exclaimed:

"Well, if it isn't Tom Swift! Did I hear you say you were going to Africa?"

Tom looked at the gentleman with rather a puzzled air for a moment. The face was vaguely familiar, but Tom could not recall where he had seen it. Then it came to him in a flash.

"Mr. Floyd Anderson!" exclaimed our hero. "Mr. Anderson of--"

"Earthquake Island!" exclaimed the gentleman quickly, as he extended his hand. "I guess you remember that place, Tom Swift."

"Indeed I do. And to think of meeting you again, and on this African steamer," and Tom's mind went back to the perilous days when his wireless message had saved the castaways of Earthquake Island, among whom were Mr. Anderson and his wife.

"Did I hear you say you were going to Africa?" asked Mr. Anderson, when he had been introduced to Ned, and the others in Tom's party.

"That's where we're bound for," answered the lad. "We are going to elephant land. But where are you going, Mr. Anderson?"

"Also to Africa, but not on a trip for pleasure or profit like yourselves. I have been commissioned by a missionary society to rescue two of its workers from the heart of the dark continent."

"Rescue two missionaries?" exclaimed Tom, wonderingly.

"Yes, a gentleman and his wife, who, it is reported, have fallen into the hands of a race known as the red pygmies, who hold them captives!"