During the next two weeks the young inventor worked hard in his laboratory, Mr. Swift sometimes helping him, but more often Koku and Eradicate. Mr. Baxter had recovered sufficiently to leave the Swift home. But though the chemist seemed well physically, his mind appeared to be brooding over his loss.

"If I could only get my secret formulae back!" he sighed, as he thanked Tom for his kindness. "I'm sure Field and Melling have them. And I believe they got them the night of the fireworks blaze; the scoundrels!"

"Well, if I can help you, please let me," begged Tom. And then he dismissed the matter from his mind in his anxiety to hit upon the right chemical mixture for putting out fires from the air.

One afternoon, at the end of a week in which he had been busily and steadily engaged on this work, Tom finally moved away from his laboratory table with a sigh of relief, and, turning to Eradicate, who had been helping him, exclaimed:

"Well, I think I have it now!"

"Good lan' ob massy, I hopes so!" exclaimed the colored man. "It sho' do smell bad enough, Massa Tom, to make any fire go an' run an' drown hisse'f! Whew-up! It's turrible stuff!"

"Yes, it isn't very pleasant," Tom agreed, with a smile. "Though I am getting rather used to it. But when it's in a metal tube it won't smell, and I think it will put out any fire that ever started. We'll give it a test now, Rad. Just take that flask of red stuff and pour it into this one of yellow. I'll go out and light the bonfire, and we'll make a small test."

Leaving Rad to mix some of the chemicals, a task the colored man had often done before, Tom went out into the yard near his laboratory to start a blaze on which his new mixture could be tested.

He had not got far from the laboratory door when he felt a sudden jar and a rush of air, and then followed the dull boom of an explosion. Like an echo came the voice of Eradicate:

"Oh, Massa Tom, I'se blowed up! It done sploded right in mah face!"

CHAPTER VI

TOM IS WORRIED

Dropping what he had in his hands, Tom Swift raced back to the laboratory where he had left Eradicate to mix the chemicals. Again the despairing, frightened cry of the colored man rang out.

"I hope nothing serious has happened," was the thought that flashed through Tom's mind. "But I'm afraid it has. I should have mixed those new chemicals myself."

Koku, the giant, who was at work in another part of the shop yard, heard Rad's cry and came running up. As there was always more or less jealousy between Eradicate and Koku, the latter now thought he had a chance to crow over his rival, not, of course, understanding what had happened.

"Ho! Ho!" laughed Koku. "You much better hab me work, Master Tom. I no make blunderstakes like dat black fellow! I never no make him!"

"I don't know whether Rad has made a mistake or not," murmured Tom. "Come along, Koku, we may need your help. There has been an explosion."

"Yep, dat Rad he don't as know any more as to blow up de whole place!" chuckled Koku.

He thought he would have a chance to make fun of Eradicate, but neither he nor Tom realized how serious had been the happening. As the young inventor reached the laboratory, which he had left but a few seconds before, he saw the interior almost in ruins. All about were scattered various pieces of apparatus, test tubes, alembics, retorts, flasks, and an electric furnace.

But what gave Tom more concern than anything else was the sight of Eradicate lying in the midst of broken glass on the floor. The colored man was moaning and held his hands over his face, and the young inventor could see that the hands, which had labored so hard and faithfully in his service, were cut and bleeding.

"Rad! Rad! what has happened?" cried Tom quickly.

"It sploded! It done sploded right in mah face!" moaned Eradicate. "I—I can't see no mo', Massa Tom! I can't see to help yo' nevah no mo'!"

"Don't worry about that, Rad!" cried Tom, as cheerfully as possible under the circumstances. "We'll soon have you fixed up! Come in here, Koku, and help me carry Rad out!"

Though the fumes from the chemicals that had exploded were choking, causing both Tom and Koku to gasp for breath, they never hesitated. In they rushed and picked up the limp figure of the helpless colored man.

"Poor Rad!" murmured the giant Koku tenderly. "Him bad hurt! I carry him, Master Tom! I take him bed, an' I go for doctor! I run like painted pig!"

Probably Koku meant "greased pig," but Tom never thought of that. All his concern was for his faithful Eradicate.

"Me carry him, Master Tom!" cried Koku, all the petty jealousy of his rival passing away now. "Me take care ob Rad. Him no see, me see for him. Anybody hurt Rad now, got to hurt Koku first!"

It was a fine and generous spirit that the giant was showing, though Tom had no time to speculate on it just then.

"We must get him into the house, Koku," said the young inventor. "And two of us can carry him better than one. After we get him to a bed you can go for the doctor, though I fancy the telephone can run even quicker than you can, Koku."

"Whatever Master Tom say," returned the giant humbly, as he looked with pity at the suffering form of his rival—a rival no longer. It seemed that Rad's working days were over.

Tenderly the aged colored man was laid on a lounge in the living room, Mr. Swift and Mrs. Baggert hovering over him.

"Where are you worst hurt, Rad?" asked Tom, with a view to getting a line on which physician would be the best one to summon.

"It's all in mah face, Massa Tom," moaned the colored man. "It's mah eyes. Dat stuff done sploded right in 'em! I can't see—nevah no mo'!"

"Oh, I guess it isn't as bad as that," said Tom. But when he had a glimpse of the seared and wounded face of his faithful servant he could not repress a shudder.

A physician was summoned by telephone, and he arrived in his automobile at the same time that Mr. Damon reached Tom's house.

"Bless my bottle of arnica, Tom!" exclaimed the eccentric man, with sympathy in his voice. "What's this I hear? One of your men tells me old Eradicate is killed!"

"Not as bad as that, yet," replied Tom, as he came out, leaving the doctor to make his first examination. "It was an explosion of my new aerial fire-fighting chemicals that I left Rad to mix for me. If anything serious results to him from this I'll drop the whole business! I'll never forgive myself!"

"It wasn't your fault, Tom. Perhaps he did something wrong," said Mr. Damon.

"Yes, it was my fault. I should not have let him take the chance with a mixture I had tried only a few times. But we'll hope for the best. How is he, Doctor?" Tom asked a little later when the physician came out on the porch.

"He's doing as well as can be expected for the present," was the answer. "I have given him a quieting mixture. His worst injury seems to be to his face. His hands are cut by broken glass, but the hurts are only superficial. I think we shall have to get an eye specialist to look at him in a day or two."

"You mean that he—that he may go blind?" gasped Tom.

"Well, we'll not decide right away," replied the doctor, as cheerfully as he could. "I should rather have the opinion of an oculist before making that statement. It may be only temporary."

"That's bad enough!" muttered Tom. "Poor old Rad!"

"Me take care ob him," put in Koku, who had been humbly standing around waiting to hear the news. "Me never be mad at dat black man no more! Him my best friend! I lub him like I did my brudder!"

"Thank you, Koku," said Tom, and his mind went back to the time when he had escaped in his airship from the gigantic men, of whom Koku and his brother were two specimens. The brother had gone with a circus, and Koku, for several years, only saw him occasionally.

Everything possible was done for Eradicate,