ter immediate need. He and his allies worked twice around the clock
to assemble the replaced parts with the repaired elements of the pilot
gyros. They grew groggy from the desperate need both for speed and for
absolute accuracy, but they put the complex device together, and
adjusted it, and surveyed the result through red-rimmed eyes, and were
too weary to rejoice.

Then Joe threw a switch and the reconstituted pilot gyro assembly began
to hum quietly, and the humming rose to a whine, and the whine went
deliberately up the scale until it ceased to be audible at all.
Presently a dial announced the impossible, and they gazed at a device
that seemed to be doing nothing whatever. The gyros appeared quite
motionless. They spun with such incredible precision that it was not
possible to detect that they moved a hairbreadth. And the whole complex
device looked very simple and useless.

But the four of them gazed at it--now that it worked--with a sudden
passionate satisfaction. Joe moved a control, and the axis of the device
moved smoothly to a new place and stayed there. He moved the control
again, and it moved to another position and stayed there. And to another
and another and another.

Then the Chief took Joe's place, and under his hand the seemingly static
disks--which were actually spinning at forty thousand revolutions per
minute--turned obediently and without any appearance of the spectacular.
Then Haney worked the controls. And Mike put the device through its
paces.

Mike left the gyros spinning so that the main axis pointed at the sun,
invisible beyond the Shed's roof. And then all four of them watched. It
took minutes for this last small test to show its results. But visibly
and inexorably the pilot gyros followed the unseen sun, and they would
have resisted with a force of very many tons any attempt to move them
aside by so little as one-tenth of a second of arc, which would mean
something like one three-hundred-thousandth of a right angle. And these
pilot gyros would control the main gyros with just this precision, and
after the Platform was out in space could hold the Platform itself with
the steadiness needed for astronomical observation past achievement from
the surface of the Earth.

The pilot gyros, in a word, were ready for installation.

Joe and Haney and the Chief and Mike were not beautiful to look at. They
were begrimed from head to toe, and their eyes were bloodshot, and they
were exhausted to the