how you could contact a time a thousand years
beyond us. It is possible that you attempt a joke. A--a kid, as you
would say._"

* * * * *

Sergeant Bellews beamed into the screen which so remarkably functioned
as a transmitting-eye also.

"Hell!" he said cordially. "You know we wouldn't kid you! You or our
great-great-great-grandchildren! We depend on you! We got to get you to
tell us how not to get wiped out! In 3020 the whole business is
forgotten. It's a thousand years old, to them! But they're passin' back
some swell machinery--"

He turned his head as if listening to something the microphone could not
pick up. But he looked appealingly at Lecky. Lecky nodded and moved
toward the communicator.

"Look!" said Sergeant Bellews into the screen. "Here's Doc Lecky--one of
our top guys. You talk to him."

He gave his seat to Lecky. Out of range of the communicator, he mopped
his face. His shirt was soaked through by the sweat produced by the
stress of the past few minutes. He shivered violently, and then clamped
his teeth and fumbled out sheets of paper. He beckoned to Graves. Graves
came.

"We--we got to give him a doctored circuit," whispered Sergeant Bellews
desperately, "and it's got to be good--an' quick!"

Graves bent over the paper on which the sergeant dripped sweat. The
sergeant murmured through now-chattering teeth what had to be devised,
and at once. It must be the circuit-diagram for a transmitter to be
given to the man whose face filled the screen. The transmitter must be
of at least twenty-kilowatt power. It must be such a circuit as nobody
had ever seen before.

It must be convincing. It should appear to radiate impossibly, or to
destroy energy without radiation. But it must actually produce a
broadcast signal of this exotic type--here the sergeant described with
shaky precision the exact constants of the wave to be generated--and the
broadcaster from nowhere must not be able to deduce those constants or
that wave-type from the diagram until he had built the transmitter and
tried it.

"I know it can't be done!" said the sergeant desperately. "I know it
can't! But it's gotta be! Or they'll parachute a transmitter down on us
sure."

Graves smiled a quick and nervous smile. He began to sketch a circuit.
It was a wonderful thing. It was the product of much ingenuity and
meditation. It had been devised--by himself--as a brain-teaser for the
amusement of other high-le