Tom Swift hesitated a moment before giving the final word that would send the metal container of powerful chemicals down into the midst of the crackling flames. He wanted to make sure, in his own mind, that he had done everything possible to insure the success of his undertaking. The young inventor never attempted the solution of any problem without going into it with his whole energy. So he wanted this experiment to succeed.

He quickly reviewed, mentally, the composition of the chemical compound. He had made it as strong as possible, and he had spared no pains to insure a hot fire, so that the test would not be too simple.

"What's the matter, Tom?" asked Ned, as his chum appeared to hesitate about giving the word that would send the chemicals hurtling down into the fire.

"Nothing. I was just making sure I hadn't forgotten anything," Tom answered. "I guess I haven't."

He paused a moment, looked up at his assistant on the overhanging arm of the tower, glanced down at the flames, now at their height, and then suddenly cried:

"Let her go!"

"Right!" came back the man's voice, and then a dark object, like a bomb, was seen descending from the skeleton framework above the flames.

There was a scattering of the fire in the pit as the extinguisher bomb fell among the blazing embers. Then followed a slight explosion when the bomb broke, as it was intended it should.

Tom and Ned leaned forward to peer through the pall of smoke which swirled this way and that. Here was to come the real test of the device. Would the fumes of the liberated chemicals choke the fire, or would it burn on in spite of them? That was the question to be settled for Tom Swift.

Almost immediately he had his answer. For after a fierce burst of the tongues of fire following the fall of the bomb, there was a distinct dying down of the conflagration in the pit. Great clouds of smoke arose, but the fire was quenched in a great measure, and as the fire-blanketing gas continued to be generated from the chemicals liberated from the bomb, there was a further dying down of the crackling fire.

"Tom, you've struck it!" yelled Ned in delight. "You have the right combination this time!"

Tom did not answer. He leaned forward and looked eagerly down into the pit. He was about to join with Ned in agreeing that he had, indeed, solved the problem, when, to his surprise, the flames started up again.

"What's this?" asked the young financial manager. Are you going to have a second test, Tom?"

"Not that I know of," was the puzzled answer. "I don't exactly understand this myself, Ned. By all calculations this fire ought to have died a natural death, but now it is breaking out again. I think what must have happened is that a quantity of the oil they poured on collected in a pool and didn't get all the effects of the chemicals from the bomb. Then the oil started to blaze."

"What can you do about it?" Ned wanted to know.

"Oh, I've got another bomb up there," and Tom pointed to his helper who was still perched on the overhanging arm. "I was prepared for some such emergency as this. Drop the other one!" Tom yelled, and again a dark object fell. bursting in the pit and again liberating the gas that was supposed to choke any fire.

The flames that had started up for the second time instantly died down, and Ned, leaning over the edge of the pit, cried:

"Hurray, Tom! That does the business!" But the young inventor shook his head. "I'm not quite satisfied," he remarked. "It didn't work quickly enough. What I want is a chemical combination that will choke the fire off first shot."

"Well, you pretty nearly have it," observed Ned.

"Yes. But 'good enough' isn't what I want," Tom said. "I've got to work on that chemical compound again. I think I know where I can improve it."

"Well, if I were a fire, and I had this happen to me," remarked Ned, laughing and pointing to the heap of blackened embers in the pit, "I should feel very much discouraged."

"But not enough," declared Tom. "I want the fire to be out more quickly than this one was. I think I can improve that chemical compound, and I'm going to do it."

"All right! Come on down!" he called to his helper, who was still perched on the overhanging arm. "We won't do any more today."

"What is your next move?" asked Ned, as Tom started for his small, private laboratory.

"Oh, I'm going to fiddle around among those sweet-smelling chemicals," answered the young inventor.

"Bless my vest buttons! then I'm not coming in, exclaimed a voice which could proceed from none other than Mr. Damon. And he it proved to be. He had driven over from Waterford in his automobile and had arrived just as the fire test was concluded.

"Oh, come on in!" called Tom. "You can visit with dad, and Eradicate will be glad to see you."

"Poor Rad! How is he?" asked Mr. Damon, walking along with Tom and Ned.

"No change," was the sad answer of the young inventor, for he felt responsible for the mishap to the colored man. "They can't operate on his eyes yet."

"And when they do will he be able to see?" asked Mr. Damon.

"That is what we are all hoping," answered Tom with a sigh. "But do go in to see him, Mr. Damon. It will cheer him up."

"I will," promised the eccentric man. "At any rate I'll not venture near your perfume shop, Tom Swift!"

"And I don't see that I can be of any service," added Ned, "so I'm off to my work."

"All right," assented Tom. "I've got several new schemes to try. Some of them ought to work."

Tom Swift was very busy for the next few days--so busy, in fact, that even Mary saw little of him. He was closeted with Mr. Baxter more than once, and that individual seemed to lose some of his bitter feelings over the loss of his formulae as he found he could be of service to the young inventor. For he was of service in suggesting new ways of combining fire-fighting chemicals, gained by his association with the fireworks concern.

"And that's about all the benefit I derived from being with those scoundrels, Field and Melling," said Mr. Baxter gloomily.

"You still think they took your dye formulae?'~ asked Tom.

"I'm positive of it, but I can't prove anything. They threatened to get the best of me when I would not sell them, for a ridiculously low sum, an interest in the secrets. And I believe they did get the best of me during that fire."

"I believe the same!" exclaimed Tom.

"How is that? What do you know? Can you help me prove anything against them?" eagerly asked the chemist.

"Well, I don't know," answered Tom slowly. "I'll tell you what I heard."

Thereupon he related the conversation he had overheard while with Mary at the wayside inn. The eyes of Josephus Baxter gleamed as he listened to this recital.

"So that was their game!" he cried, as he smote the table with his fist, thereby nearly upsetting a test tube of acid, which Tom caught just in time. "I knew something crooked was going on, and they thought I'd be so badly overcome in the fire that I wouldn't know, or wouldn't remember, what happened."

"What did happen?" asked Tom. "All I know is that you were overcome in the laboratory room."

"It's too long a story to tell in detail now," said Mr. Baxter. "But the main facts are that through misrepresentations I was induced to associate myself with Field and Melling. They had a good factory for the making of fireworks, and some of the chemicals used in that industry also enter into the manufacture of the kind of dyes I have in mind to make. So I associated myself with them, they agreeing to let me use their laboratory.

"One night they came to see me as I was working there over my formulae. They pretended to have discovered something in an expired patent that nullified what I had. I did not believe this to be so, and I brought out my formulae to compare with theirs-- or what they said they had. The next thing I remember was that the fire broke out and my formulae disappeared. Then I was overcome, and I did not care what happened to me, for, having lost the valuable dye formulae, I did not think life worth living.

"Perhaps I was foolish," said Mr. Baxter, "but I had tried so many things and failed, and I counted so much on these formulae that it seemed as if the bottom dropped out of everything when I lost them."

"I know," said Tom sympathetically. "I've been in the same boat myself. But are you sure they took the papers which meant so much to you?"

"I don't see who else could," answered the chemist. "The papers were in a tin box on the table in the room where I was overcome by fire gases, or where, perhaps, they drugged me. I am not clear on this point. And afterward the tin box could not be found. There wasn't enough fire in that room to have melted it."

"No," agreed Tom, "it was mostly smoke in there, and smoke won't melt tin. Nor did I see any box on the table when we carried you out."

"Then the only other surmise is that Field and Melling got away with my formulae during the excitement and when I was half unconscious," Went on Mr. Baxter bitterly. "But you can see how foolish I would be to accuse them in court. I haven't a bit of proof."

"Not much, for a fact," agreed Tom. "Well, with what I heard and what you tell me, perhaps we can work up a case against them later. I'll go over it with Ned. He has a better head for business than I."

"Yes, we inventors need some business brains; or at least the time to give to business problems," agreed the chemist. "But enough of my troubles. Let's get at this chemical compound of yours."

Tom and Mr. Baxter spent many days and nights perfecting the fire-extinguisher chemical, and, after repeated tests, Tom felt that he was nearer his goal.

One afternoon Ned called, and Tom invited him to go for a ride in a small but speedy aeroplane.

"Anything special on?" asked the young manager.

"In a way, yes," Tom answered. "I'm having a firm in Newmarket make me some different containers, and they have promised me samples today. I thought I'd take a fly over and get them. I have the chemical compound all but perfected now, and I want to give it another test."

"All right, I'm with you," assented Ned. "Newmarket," he added musingly. "Isn't that where Field and Melling are now?"

"Yes. They have a factory on the outskirts of the place, and their offices are in the Landmark Building. But we aren't going to see them, though we may call on them later, when you have that case better worked up." For Ned's services had been enlisted to aid Mr. Baxter.

"I shall need a little more time," remarked Ned. "But I think we can at least bluff them into playing into our hands. I have a report to hear from a private detective I have hired."

"I hope we can do something to aid Baxter," remarked Tom. "He has done me good service in this chemical fire extinguisher matter."

A little later Tom and Ned were speeding through the air on their way to Newmarket. The rapid flier was making good time at not a great height when Ned, leaning forward, appeared to be gazing at something in the near distance.

"What's the matter?" asked Tom, for he had his silencer on this craft and it was possible for the occupants to converse. "Do you hear one of the cylinders missing, Ned?"

"No. But what's that smoke down there?" and Ned pointed. "It looks like a fire!"

"It is a fire!" exclaimed Tom, as he took an observation. "Not a big one, but a fire, just the same. If only--"

He did not finish what he started to say, but changed the direction of his air craft and headed directly toward a pall of smoke about a mile away.

In a few seconds they were near enough to make out the character of the blaze.

"Look, Tom!" cried Ned. "It's an immense tree on fire!"

"A tree!" exclaimed Tom, half incredulously, for he was leaning forward to look at one of the aeroplane gages and did not have a clear view of what Ned was looking at.

"Yes, as sure as Mr. Damon would bless something if he were here! It's a tree on fire up near the top!"

"That's strange!" murmured Tom. "But it may give me just the chance I've been looking for."

Ned wondered at this remark on the part of his chum as the airship drew nearer the blazing monarch in the patch of woods over which they were then hovering.