Page:Tom Swift and His Photo Telephone.djvu/38

32 "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,