what on earth is he
using?"

"It looked like a flash of red light when it came from the submarine."

"Yes, but it couldn't be light. Let me think."

The doctor sat for a few minutes with corrugated brows. Suddenly he
sprang to his feet.

"I deserve to be beaten," he cried. "Why didn't I think of that
possibility before?"

* * * * *

He hurried into his laboratory and brought out a small box with a
glass front. From the top projected a spike topped with a ball.
Through the glass, Carnes could see a thin sheet of metal hanging
pendant from the spike.

"An electroscope," explained the doctor. "That sheet of metal is
really two sheets of gold-leaf, at present stuck together. If I rub a
piece of hard rubber with a woolen cloth, the rod will become charged
with static electricity. If I then touch the ball with it, the charge
is transferred to the electroscope and causes the two sheets of
gold-leaf to stand apart at an angle. Watch me."

He took a hard rubber rod and rubbed it briskly on his coat sleeve. As
he touched the ball of the electroscope the sheets of gold-leaf
separated and stood apart at a right angle.

"As long as the air remains non-conducting, the two bits of gold-leaf
will hold that position. The air, however, is not a perfect insulator
and the charge will gradually leak off. If I bring a bit of
radioactive substance, for instance, pitchblende, near the
electroscope, the charge will leak rapidly. Do you understand?"

"Yes, but how is that going to help us?"

"Saranoff is accomplishing his result by artificially compressing the
atoms. It is inevitable that he will do it imperfectly, and some
electrons will be loosened and escape. These electrons, traveling up
through the earth will make the air conducting. To-morrow we will have
a means of locating the borer under ground."

"Once you locate it, how will you fight it?"

"That is the problem I must work out to-night."

"Could we bury a charge of explosive and blow it up?"

* * * * *

"Ordinary explosives would be useless," the doctor answered. "They
would react in the same manner as other substances, and would be
rendered harmless. Radite might do the work if it could be placed in
the path, but it couldn't be. We may locate the position and depth of
the borer, but long before we could dig and blast a hole deep enough
to place a charge of radite before it, it would have passed on or