of this to you, Carnes,"
said the doctor. "At four hundred-yard intervals are men with
electroscopes like this one. My attempt to locate Saranoff by means of
wave detectors was a failure. That proved that the ray he was using is
not of the wave type. The other common ray is the cathode ray type
which does not consist of vibrations but of a stream of electrons,
negative particles of electricity, traveling in straight lines of high
velocity. He must be knocking loose some of the electrons when he
collapses the atoms. The rate of discharge of these electroscopes will
give us a clue to the nearness of his device."

* * * * *

"Once you locate him, how do you propose to attack him?"

"The obvious method, that of using his own ray against him, fell down.
However, in attempting to produce it, I stumbled on another weapon
which may be equally effective. I am going to try to use an exact
opposite of his ray. The cathode ray, when properly used, will bombard
the atoms and knock electrons loose. I perfected last night a device
on which I have been working for months. It is a super-cathode ray. I
tested it on the yellow powder and find that I can successfully
reverse Saranoff's process. He can contract matter together until it
occupies less than one one-thousandth of its original volume. My ray
will destroy this effect and restore matter to something like its
original condition."

"And the effect will be?"

"Use your imagination. He blasts out a hole by condensing the rock to
a pinch of yellow powder. He moves forward into the hole he has made.
I come along and reverse his process. The yellow powder expands to its
original volume and the hole he has made ceases to exist. What must
happen to the foreign body which had been introduced into the hole
that is no longer a hole?"

Carnes whistled.

"At any rate, I hope that I am never in a hole when that happens."

"And I devoutly hope that Saranoff is. I met with one difficulty. My
ray will not penetrate the depth of solid rock which separates his
borer from the surface."

"Then how will you reach him to crush him? You don't expect to drill
down ahead of him?"

"That is my stroke of genius, Carnes. I am going to make him bore the
hole down which my ray will travel to accomplish his destruction. The
cathode ray and rays of that type--"

* * * * *

"Pardon me, Doctor," interrupted the radio operator. "I have jus