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.
Pages:
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46