young banker took a seat on a box, and silently watched Tom. The inventor shifted several switches, pressed one button after another, and tilted the polished metal plate at different angles. Then he closed the door of the little telephone booth, and Ned, through the ground glass door, saw a light shining.

"I wonder what new game Tom is up to?" Ned mused.

Presently the door opened, and Tom stuck out his head.

"Ned, come here," he invited. "Look at that metal plate and see if you can notice anything on it. I've been staring at it so steadily that my eyes are full of sticks. See what you can make out."

"What is this?" asked Ned. "No trick; is it? I won't be blown up, or get my eyes full of pepper; will I?"

"Nonsense! Of course not. I'm trying to make a photo telephone. I have the telephone part down pat, but I can't see anything of the photo image. See if you can."

Ned stared at the polished plate, while Tom did things to it, making electrical connections, and tilting it at various angles.

"See anything, Ned?" asked Tom.

The other shook his head.

"Whom am I supposed to see?" he asked.

"Why, Koku is at the other end of the wire. I'm having him help me."

Ned gazed from the polished plate out of a side window of the shop, into the yard.

"Well, that Koku is certainly a wonderful giant," said Ned, with a laugh.

"How so?" asked Tom.

"Why he can not be in two places at once. You say he ought to be at the other end of this wire, and there he is out there, spading up the garden."

Tom stared for a second and then exclaimed:

"Well, if that isn't the limit! I put him in the telephone booth in the machine shop, and told him to stay there until I was through. What in the world is he doing out there?"

"Koku!" he called to the giant, "why didn't you stay at the telephone where I put you? Why did you run away?"

"Ha!" exclaimed the giant, who, for all his great size was a simple chap, "little thing go 'tick-tick' and then 'clap-clap!' Koku no like--Koku t'ink bad spirit in telumfoam--Koku come out!"

"Well, no wonder I couldn't see any image on the plate!" exclaimed Tom. "There was nobody there. Now, Ned, you try it; will you, please?"

"Sure. Anything to oblige!"

"Then go in the other telephone booth. You can talk to me on the wire. Say anything you like--the telephone part is all right. Then you just stand so that the light in the booth shines on your face. The machine will do the rest--if it works."

Ned hurried off and was soon talking to his chum over the wire from the branch telephone in the machine shop. Ned stood in the glare of an electric light, and looked at a polished plate similar to the one in the other booth.

"Are you there, Ned?" asked Tom.

"Yes, I'm here."

"Is the light on?"

"Yes."

"And you're looking at the plate?"

"Sure. Can you see any reflection in your plate?"

"No, not a thing," answered Tom, and there was great discouragement in his voice. "The thing is a failure, Ned. Come on back," and the young banker could hear his chum hang up the telephone receiver at the other end.

"That's too bad," murmured Ned, knowing how Tom must feel. "I'll have to cheer him up a bit."

Chapter IV Run Down

When Ned Newton got back to where Tom sat in the small telephone booth, the young banker found his chum staring rather moodily at the polished metal plate on the shelf that held the talking instrument.

"So it was no go; eh, Tom?"

"No go at all, Ned, and I thought sure I had it right this time."

"Then this isn't your first experiment?"

"Land no! I've been at it, off and on, for over a month, and I can't seem to get any farther. I'm up against a snag now, good and hard."

"Then there wasn't any image on your plate?"

"Not a thing, Ned. I don't suppose you caught any glimpse of me in your plate?" asked Tom, half hopefully.

"No. I couldn't see a thing. So you are going to try and make this thing work both ways, are you?"

"That's my intention, But I can fix it so that a person can control the apparatus at his end, and only see the person he is talking to, not being seen himself, unless he wishes it. That is, I hope to do that. Just now nobody can see anybody," and Tom sighed.

"Give it up," advised Ned. "It's too hard a nut to crack, Tom!"

"Indeed, I'll not give it up, Ned! I'm going to work along a new line. I must try a different solution of selenium on the metal plate. Perhaps I may have to try using a sensitized plate, and develop it later, though I do want to get the machine down so you can see a perfect image without the need of developing. And I will, too!" cried Tom. "I'll get some new selenium."

Eradicate, who came into the shop just then, heard the end of Tom's remarks. A strange look came over his honest black face, and he exclaimed:

"What all am dat, Massa Tom? Yo'ah gwine t' bring de new millenium heah? Dat's de end of de world, ain't it-dat millenium? Golly! Dish yeah coon neber 'spected t' lib t' see dat. De millenium! Oh mah landy!"

"No, Rad!" laughed Tom. "I was speaking about selenium, a sort of metallic combination that is a peculiar conductor of electricity. The more light that shines on it the better conductor it is, and the less light, the poorer."

"It must be queer stuff," said Ned.

"It is," declared Tom. "I think it is the only thing to use in this photo telephone experiment, though I might try the metal plate method, as they did between Monte Carlo and Paris. But I am not trying to make newspaper pictures."

"What is selenium, anyhow?" asked Ned. "Remember, Tom, I'm not up on this scientific stuff as you are."

"Selenium," went on Tom, "was discovered in 1817, by J. J. Berzelius, and he gave it that name from the Greek word for moon, on account of selenium being so similar, in some ways, to tellurium. That last is named after the Latin 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.