"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