There was a humming in the air. The telegraph wires that ran along on high poles past the house of Tom Swift sung a song like that of an Aeolian harp. The very house seemed to tremble.

"Jove! This is a wind!" cried Tom as he awakened on a morning a few days after his air glider was nearly completed. "I never saw it so strong. This ought to be just what I want I must telephone to Mr. Damon and to Ned."

He hustled into his clothes, pausing now and then to look out of his window and note the effects of the gale. It was a tremendous wind, as was evidenced by the limbs of several trees being broken off, while in some cases frail trees themselves had been snapped in twain.

"Coffee ready, Mrs. Baggert?" asked our hero as he went downstairs. "I haven't got time to eat much though."

In spite of his haste Tom ate a good breakfast and then, having telephoned to his two friends, and receiving their promises to come right over, our hero went out to make a few adjustments to his air glider, to get it in shape for the trial.

He was a little worried lest the wind die out, but when he got outside he noted with satisfaction that the gale was stronger than at first. In fact it did considerable damage in Shopton, as Tom learned later.

It certainly was a strong wind. An ordinary aeroplane never could have sailed in it, and Tom was doubtful of the ability of even his big airship to navigate in it. But he was not going to try that.

"And maybe my air glider won't work," he remarked to himself as he was on his way to the shed where it had been constructed. "The models went up all right, but maybe the big one isn't proportioned right. However, I'll soon see."

He was busy adjusting the balancing weights when Ned Newton came in.

"Great Scott!" exclaimed the lad, as he labored to close the shed door, "this is a blow all right, Tom! Do you think it's safe to go up?"

"I can't go up without a gale, Ned."

"Well, I'd think twice about it myself."

"Why, I counted on you going up with me."

"Burr-r-r-r!" and Ned pretended to shiver. "I haven't an accident insurance policy you know."

"You won't need it, Ned. If we get up at all we'll be all right. Catch hold there, and shift that rear weight a little forward on the rod. I expect Mr. Damon soon."

The eccentric man came in a little later, just as Tom and Ned had finished adjusting the mechanism.

"Bless my socks!" cried Mr. Damon. "Do you really mean to go up to-day, Tom?"

"I sure do! Why, aren't you going with me?" and Tom winked at Ned.

"Bless my--" began Mr. Damon, and then, evidently realizing that he was being tested he exclaimed: "Well, I will go, Tom! If the air glider is any good it ought to hold me. I will go up."

"Now, Ned, how about you?" asked the young inventor.

"Well, I guess it's up to me to come along. but I sure do wish it was over with," and Ned glanced out of the window to see if the gale was dying out. But the wind was as high as ever.

It was hard work getting the air glider out of the shed, and in position on top of a hill, about a quarter of a mile away, for Tom intended "taking off" from the mound, as he could not get a running start without a motor. The wind, however, he hoped, would raise him and the strange craft.

In order to get it over the ground without having it capsize, or elevate before they were ready for it, drag ropes, attached to bags of sand were used, and once these were attached the four found that they could not wheel the air glider along on its bicycle wheels.

"We'll have to get Eradicate and his mule, I guess," said Tom, after a vain endeavor to make progress against the wind. "When it's up in the air it will be all right, but until then I'll need help to move it. Ned, call Rad, will you?"

The colored man, with Boomerang, his faithful mule, was soon on hand. The animal was hitched to the glider, and pulled it toward the hill.

"Now to see what happens," remarked Tom as he wheeled his latest invention around where the wind would take it as soon as the restraining ropes were cast off, for it was now held in place by several heavy cables fastened to stakes driven in the ground.

Tom gave a last careful look to the weights, planes and rudders. He glanced at a small anemometer or wind gage, on the craft, and noted that it registered sixty miles an hour.

"That ought to do," he remarked. "Now who's going up with me? Will you take a chance, Mr. Petrofsky?"

"I'd rather not--at first."

"Come on then, Ned and Mr. Damon. Mr. Petrofsky and Rad can cast off the ropes."

The wind, if anything, was stronger than ever. It was a terrific gale, and just what was needed. But how would the air glider act? That was what Tom wanted very much to know.

"Cast off!" he cried to the Russian and Eradicate, and they slipped the ropes.

The next moment, with a rush and whizzing roar, the air glider shot aloft on the wings of the wind.