Chapter IV. Run Down - Page 2

word tellus, the earth."

"Do they dig it?" Ned wanted to know.

"Well, sometimes selenium is found in combination with metals, in the form of selenides, the more important minerals of that kind being eucharite, crooksite, clausthalite, naumannite and zorgite--"

"Good night!" interrupted Ned, with a laugh, holding up his hands. "Stop it, Tom!" he pleaded. "You'll give me a headache with all those big words."

"Oh, they're easy, once you get used to them," said the young inventor, with a smile. "Perhaps it will be easier if I say that sometimes selenium is found in native sulphur. Selenium is usually obtained from the flue-dust or chamber deposits of some factory where sulphuric acid is made. They take this dust and treat it with acids until they get the pure selenium. Sometimes selenium comes in crystal forms, and again it is combined with various metals for different uses."

"There's one good thing about it. There are several varieties, and I'll try them all before I give up."

"That's the way to talk!" cried Ned. "Never say die! Don't give up the ship, and all that. But, Tom, what you need now is a little fun. You've been poking away at this too long. Come on out on the lake, and have a ride in the motor boat. It will do you good. It will do me good. I'm a bit rusty myself--been working hard lately. Come on--let's go out on the lake."

"I believe I will!" exclaimed Tom, after thinking it over for a moment. "I need a little fresh air. Sitting in that telephone booth, trying to get an image on a plate, and not succeeding, has gotten on my nerves. I want to write out an order for Koku to take to town, though. I want to get some fresh selenium, and then I'm going to make new plates."

Tom made some memoranda, and then, giving Koku the order for the chemist, the young inventor closed up his shop, and went with Ned down to Lake Carlopa, where the motor boat was moored.

This was not the same boat Tom had first purchased, some years ago, but a comparatively new and powerful craft.

"It sure is one grand little day for a ride," remarked Ned, as he got in the craft, while Tom looked over the engine.

"Yes, I'm glad you came over, and routed me out," said the young inventor. "When I get going on a thing I don't know enough to stop. Oh, I forgot something!"

"What?" asked Ned.

"I forgot to leave word about Mr. Railing's airship. It's all fixed and ready for him, but I put on a new control, and I wanted to explain to him about it. He might not know how to work it. I left word with father, though, that if he came for it he must not try it until he had seen me. I guess it will be all right. I don't want to go back to the house now."

"No,