the gun would shoot luminous charges?" "Yes."

"Well, I'm going to try that, now. I wish we had another image to
shoot at, but I'll take a big dry-goods box, and make believe it's
an elephant. Now, this is going to be a hard test, such as we'd meet
with, if we were hunting in Africa. I want you to help me."

"What am I to do?" asked Ned.

"I want you to go outside," explained Tom, "set up a dry-goods box
against the side of the little hill back of the shed, and not tell
me where you put it. Then I'll go out, and, by means of the luminous
charge, I'll locate the box, set the distance gage, and destroy it."

"Well, you can see it anyhow, in the moonlight," objected Ned.

"No, the moon is under a cloud now," explained Tom, looking out of a
window. "It's quite dark, and will give me just the test I want for
my new electric rifle."

"But won't it be dangerous, firing in the dark? Suppose you misjudge
the distance, and the bullet, or charge, files off and hits some
one?"

"It can't. I'll set the distance gage before I shoot. But if I
should happen to make a mistake the charge will go into the side of
the hill, and spend itself there. There is no danger. Go ahead, and
set up the box, and then come and tell me. Mr. Jackson will help
you."