ore than a third of the way. In
mid-air it froze, as if paralysis had suddenly struck it. Harper
regarded it in seeming dumb astonishment. His face grew red, and sweat
broke out upon his forehead as if from the physical exertion of trying
to put his hand to the lever.

Paul grabbed a microphone and switched it on. "Touch the lever," he
commanded. "Draw it toward you."

Harper looked around as if in panic, but he completed the motion. He sat
staring at the panels for a full two minutes while alarm eyes went from
green to yellow to red.

"Alarm red!" Paul exclaimed into the microphone. "Correct course!"

Harper turned and glared about with hate in his eyes as if to find the
source of the sound. He began tearing at the wires and contacts fastened
to his head and body. "To hell with the course!" he cried. "I'm getting
out of here!"

He hurled the wiring harness at the panels. Then, he stood in a moment's
further paralysis and slumped finally into the chair. He put his arms
and head down on the instrument desk and began sobbing deeply.

Paul put away the microphone and moved to the door. "That's the end of
that," he said. "I hope our record is good. Harper might not like to go
through that again."

Nat Holt was still staring through the window at the sobbing engineer.
"I don't understand," he murmured. "What made him break down like that
for no reason at all?"

* * * * *

One by one, the top engineers of the Base went through the breakdown
test. Some broke down with an emotional storm as Harper had, others
simply ended in a swirl of confusion that put lights flashing all over
the panels. But all of them had a breaking point of some kind that could
be measured in a small number of hours.

The test was a stab in the dark. It was based on an old and well-known
principle that repeated tactile contact under command will break down
the motor responses of the body in a matter of hours. Paul did not know
whether it would actually provide a fertile lead to the problem of error
or not, but it seemed the closest possible approach at present.

Nat Holt, however, was astonished at the reaction of the men. He
insisted on trying it himself, determined that he would not break down
no matter what happened. He lasted six hours before the panel lit up
like a Christmas tree.

He subjected the resulting curves to an analyzer, and to his own he gave
the most detailed attention. At the end of a full we