Chapter XIII. A Successful Test

"It took you long enough," Ned remarked as Tom entered the main office of the plant, having been to see Mary off on her trip to Newmarket. This was following his call of the night before to learn more particulars of her unexpected visit.

"Yes, I didn't plan to be gone so long," apologized Tom. "But I thought while I was there I might as well go all the way with her."

"And did you?"

"Yes. In the electric runabout. I wanted to come back and get the airship, but she said she wanted to look nice when she met her relatives, and as yet airship travel is a bit mussy. Though when I get my cabined cruiser of the clouds I'll guarantee not to ruffle a curl of the daintiest girl!"

"Getting poetical in your old age!" laughed Ned. "Well, here is that statement you said you wanted me to get ready. Want to go over it now?"

"No, I guess not, as long as you know it's all right. I'm going to start right in and get ready for a bang-up test."

"Of what--your new aerial fire fighting apparatus?"

"Yes. Mr. Baxter and I are going to make up a lot of the chemical compound that--we discovered through using it on the blazing tree--will best do the trick. Then I'm going to try it on a pit fire, and after that on a big blaze with an airship."

"Let me know when you do," begged Ned. "I want to see you do it."

"I'll send you word," promised the young inventor.

Then he began several days and nights of hard work. And he was glad to have the chance to occupy himself, for, though Tom professed not to be much affected by the departure of Mary Nestor, he really was very lonesome.

"How is her uncle, Barton Keith, by the way?" asked Ned, when he called on his chum one day, to find him reading a letter which needed but half an eye to tell was from Mary.

"About as usual," was the answer. "He sends word by Mary that he'll be glad to see us any time we want to call. He has some nice offices in the Landmark Building."

"Those papers proving his right to the oil land, which you recovered from the sunken ship for him, must have made his fortune."

"Well, yes--that and other things," agreed Tom. "Say, we had some exciting times on that undersea search, didn't we?"

"Did you call on Mr. Keith when you went to Newmarket with Mary?" Ned wanted to know, for he and Tom had taken quite a liking to Miss Nestor's uncle.

"No, I didn't get a chance. Besides, I wanted to keep away from the Landmark Building."

"Why?"

"Oh, I might run into Field and Melling, and I don't want to see them until I can accuse them, and prove it, of having taken Mr. Baxter's dye formulae."

"Oh,