took time to wonder at this statement.

"Then who are you?" he inquired, at length.

"The Demon of Electricity," was the solemn answer.

"Good gracious!" exclaimed Rob, "a demon!"

"Certainly. I am, in truth, the Slave of the Master Key, and am forced
to obey the commands of any one who is wise and brave enough--or, as in
your own case, fortunate and fool-hardy enough--to touch it."

"I--I've never guessed there was such a thing as a Master Key, or--or a
Demon of Electricity, and--and I'm awfully sorry I--I called you up!"
stammered the boy, abashed by the imposing appearance of his companion.

The Demon actually smiled at this speech,--a smile that was almost
reassuring.

"I am not sorry," he said, in kindlier tone, "for it is not much
pleasure waiting century after century for some one to command my
services. I have often thought my existence uncalled for, since you
Earth people are so stupid and ignorant that you seem unlikely ever to
master the secret of electrical power."

"Oh, we have some great masters among us!" cried Rob, rather nettled at
this statement. "Now, there's Edison--"

"Edison!" exclaimed the Demon, with a faint sneer; "what does he know?"

"Lots of things," declared the boy. "He's invented no end of wonderful
electrical things."

"You are wrong to call them wonderful," replied the Demon, lightly.
"He really knows little more than yourself about the laws that control
electricity. His inventions are trifling things in comparison with the
really wonderful results to be obtained by one who would actually know
how to direct the electric powers instead of groping blindly after
insignificant effects. Why, I've stood for months by Edison's elbow,
hoping and longing for him to touch the Master Key; but I can see
plainly he will never accomplish it."

"Then there's Tesla," said the boy.

The Demon laughed.

"There is Tesla, to be sure," he said. "But what of him?"

"Why, he's discovered a powerful light," the Demon gave an amused
chuckle, "and he's in communication with the people in Mars."

"What people?"

"Why, the people who live there."

"There are none."

This great statement almost took Rob's breath away, and caused him to
stare hard at his visitor.

"It's generally thought," he resumed, in an annoyed tone, "that Mars
has inhabitants who are far in advance of ourselves in civilization.
Many scientific men think the people of Mars have been trying to signal
us for years,