Tom Swift and Ned Newton were so accustomed to acting quickly and in emergencies that it did not take them long to run out the airship, which Tom had in readiness, not especially for this emergency, but to demonstrate his new apparatus to a committee of fire underwriters whom he had invited to call in a few days.

"Take this, if you will, Mr. Baxter!" cried Tom, giving the chemist a metal container. "It's a little different combination from the extinguisher I already have in the machine. Maybe I'll get a chance to try it."

"You're going to have all the chance you want, Tom, by the looks of that blaze," commented Ned Newton.

"It does look like quite a fire," observed Tom, as he gazed up at the sky, where the reflection was turning to a brighter red.

Outside in the streets near the Swift house and shops could be heard the rattle of fire apparatus, the patter of running feet, and many shouts from excited men and boys.

"Any idea what it is, Ned?" asked Tom, as he motioned to Mr. Baxter to climb into the aircraft.

"Some one said it was the new Normal School. But that's farther to the north," was Ned's answer. "By the way the blaze has increased since I first saw it, I'd take it to be the lumberyard."

"That would make a monster blaze!" observed Tom. "I don't believe I'll have chemicals enough for that," and he looked at the rather small supply in his craft. "However, I haven't time to get any more. Besides, they'll have the regular department on the job, and this isn't a skyscraper, anyhow."

"No, we'll have to go to New York or Newmarket for one of those," observed Ned. "All ready, Tom?"

"All ready," said the young inventor, as Ned took his place beside Mr. Baxter.

"What's the matter, Tom?" asked the voice of Mr. Swift, as he came out into the yard, having been attracted by the flashing lights and the noise of the aircraft motor, as Tom gave it a preliminary test.

"There's a fire in town," Tom answered. "I'm going to see if they need my services."

"Guess there isn't any question about that," said his business manager.

Tom's father, who was suffering the infirmities of age, was in the habit of retiring early, and he had dozed off in his chair directly after supper, to be awakened by the shouting and confusion about the place.

"Take care of yourself, my boy!" he advised, as there came a moment of silence before the throttle of the aircraft was opened to send it on its upward journey. "Don't take too many risks."

"I won't," Tom promised. "We'll be back soon."

Then came the roar of the motor as Tom cut out the muffler to gain speed and, a moment later, he and his two friends were sailing aloft with a load of fire-extinguishing chemicals.

Up and up rose the aircraft. It was not the first time Mr. Baxter had enjoyed the sensation, but he was not enough of a veteran to be immune to the thrills nor to be altogether void of fear. And it was his first night trip. Still he gave few evidences of nervousness.

"These she is!" cried Ned, for when the exhaust from the motor was sent through the new muffler Tom had attached it was possible to talk aboard the Lucifer. The young manager pointed down toward the earth, over which the craft was then skimming, though at no great height.

"It is the lumberyard!" exclaimed Mr. Baxter presently.

"It sure is," assented Tom. "I know I haven't enough stuff to cover as big a blaze as that, but I'll do my best. Fortunately there is no wind to speak of," he added, as he guided the craft in the direction of the fire.

"What has that to do with it--I mean as far as the working of your chemical extinguisher is concerned?" asked Mr. Baxter. "Can't you drop the bomb containers accurately in a wind?"

"Well, the wind has to be allowed for in dropping anything from an aeroplane," Tom answered. "And, naturally, it does spoil your aim to an extent. But the reason I'm glad there is no wind to speak of is that the chemical blanket I hope to spread over the fire won't be so quickly blown away."

"Oh, I see," said Mr. Baxter. "Well, I'm glad that you will be able to have a successful test of your invention."

"The regular land apparatus is on hand," observed Ned, for they were now so near the fire that they could look down and, in the reflection from the blaze, could see engines, hose-wagons and hook and ladder trucks arriving and deploying to different places of advantage, from which to fight the lumberyard fire that was now a roaring furnace of flames.

"No skyscraper work needed here," observed Tom. "But it will give me a chance to use the latest combination I worked out. I'll try that first. Are you ready with it, Mr. Baxter?"

"Yes," was the answer.

The young inventor, not heeding the cries of wonder that arose from below and paying no attention to the uplifted hands and arms pointing to him, steered his craft to a corner of the yard where there was a small isolated fire in a pile of boards. It was Tom's idea to try his new chemical first on this spot to watch the effect. Then he would turn loose all his other containers of the chemical mixture that had proved so effective in other tests.

Attention of those who had gathered to look at the fire was about evenly divided between the efforts of the regular department and the pending action by Tom Swift. The latter was not long in turning loose his latest sensation.

"Let it go!" he cried to Mr. Baxter, and down into the seething caldron of flame dropped a thin sheet-iron container of powerful chemicals. Leaning over the cockpit of the aircraft, the occupants watched the effect. There was a slight explosion heard, even above the roar of the flames, and the tongues of fire in the section where Tom's extinguisher had fallen died down.

"Good work!" cried Ned.

"No!" answered Tom, shaking his head. "I was a little afraid of this. Not enough carbon dioxide in this mixture. I'll stick to the one I found most effective." For the flames, after momentarily dying down, burst out again in the spot where he had dropped the bomb.

Tom wheeled the airship in a sharp, banking turn, and headed for the heart of the fire in the lumberyard. It was clearly getting beyond the control of the regular department.

"How about you, Ned?" called Tom, for he had given his chum charge of dropping the regular bombs containing a large quantity of the extinguisher Tom had practically adopted.

"All ready," was the answer.

"Let 'em go!" came the command, and down shot the dark, spherical objects. They burst as they hit the ground or the piles of blazing lumber, and at once the powerful gases generated by the mixture of several different chemicals were released.

Again the three in the airship leaned eagerly over the side of the cockpit to watch the effect. It was almost magical in its action.

The bombs had been dropped into the very fiercest heart of the fire, and it was only an instant before their action was made manifest.

"This will do the trick!" cried Ned. "I'm certain it will."

"I didn't have much fear that it wouldn't," said Tom. "But I hoped the other would be better, for it is a much cheaper mixture to make, and that will count when you come to sell it to big cities."

"But the fire is certainly dying down," declared Mr. Baxter.

And this was true. As container after container of the bomb type fell in different parts of the burning lumberyard, while Tom coursed above it, the flames began to be smothered in various sections.

And from the watching crowds, as well as from the hard-working members of the Shopton fire department, came cheers of delight and encouragement as they saw the work of Tom Swift's aerial fire-fighting machine.

For he had, most completely, subdued what threatened to be a great fire, and when the last of his bombs had been dropped, so effective was the blanket of fire-dampening gases spread around that the flames just naturally expired, as it were.

As Tom had said, the absence of wind was in his favor, for the generated gases remained just where they were wanted, directly over the fire like an extinguishing blanket, and were not blown aside as would otherwise have been the case.

And, by the peculiar manner in which his chemicals were mixed, Tom had made them practically harmless for human beings to breathe. Though the fire-killing gases were unpleasant, there was no danger to life in them, and while several of the firemen made wry faces, and one or two were slightly ill from being too close to the chemicals, no one was seriously inconvenienced.

"Well, I. guess that's all," said Tom, when the final bomb had been dropped. "That was the last of them, wasn't it, Ned?"

"Yes, but you don't need any more. The fire's out--or what isn't can be easily handled by the hose lines."

"Good!" cried Tom. "But, all the same, I wish I had been able to make the first mixture work."

"Perhaps I can help you with that," suggested Mr. Baxter.

And the following day, after Tom had received the thanks of the town officials and of the fire department for his work in subduing the lumberyard blaze, the young inventor called Josephus Baxter in consultation.

"I feel that I need your help," said the young inventor. "You have been at this chemical study longer than I, and I am willing to pay you well for your work. Of course I can't make up to you the loss of your dye formulae. But while you are waiting for something to turn up in regard to them, you may be glad to assist me."

"I will, and without pay," said the chemist.

But Tom would not hear of that, and together he and Mr. Baxter set about putting the finishing touches to Tom's latest invention.