nse.

"Guess you're not getting through, skipper," Bud commented with a grin.

"No," Tom agreed. "I can't predict what kind of energy this brain will
respond to. Being only energy, it must respond to other energy and sound
is our form of energy. The problem is the same as with radio waves,
which are also energy. We must figure out how we can vary the energy, so
it can transmit information to Exman."

"What _do_ we try?" Bud asked. "Or is it hopeless?"

"I'll try communicating with it via the electronic brain, which I have
adapted to fit this problem."

The boys cleaned up the wreckage caused by Exman in his dawn venturings.
Then Tom went by jeep to the computer laboratory, made connections to
his electronic brain, and wired it for remote control. Then he returned
to the private laboratory. There Bud watched as he hooked up the leads
from the computer to a transmitting-receiving decoder with a short-range
antenna.

"Speak, O Master!" Bud said, imitating a squeaky robot voice. "Sound off
loud and clear!"

Tom grinned and tapped out a command on the keyboard: _Move backward._

Exman rolled backward! Bud gave a whoop of delight.

Tom signaled: _Move forward._ Obediently Exman rolled toward him.

_Stop._ Exman stopped.

"Hey, how about that?" Bud exclaimed happily. "It really savvies those
electronic brain impulses!"

"And minds them--which is equally important," Tom added.

A moment later the brain energy seemed to become impatient. It spurted
off in its wheeled container toward a laboratory workbench.

_Crash!_ A rack of test tubes went sailing to the floor with an
explosion of tinkling glass.

_Stop!_ Tom signaled frantically. Again Exman obeyed the order.

"It's like a mischievous kid," Bud said.

Almost as if in defiance, Exman scooted off in another direction. Then
it stopped abruptly and swiveled around, one of its antenna arms
knocking a Bunsen burner to the floor as it did so.

_Come here!_ Tom signaled. As the culprit approached, he added sternly,
_Stop where you are. And stay there until you receive further orders._

This time Exman stood patiently, awaiting the next signal. Bud got a
brush and dustpan, and the boys cleaned up the broken test tubes and
replaced the burner on its shelf.

Then Tom began feeding more complicated instructions to Exman through
the electronic brain. He guided him through a number of dancelike
movements and other drills, and got him to send out a wave of heat whic