they were thumping their metal thighs.

A Robot mob was gathered close outside the palace walls. The revolt of
the Robots had come!

CHAPTER XVIII

_Tugh, the Clever Man_

"Sit quiet, George Rankin. And you, Mistress Mary; you will both be
quite safe with Migul if you are docile."

Tugh stood before us. We were in a dim recess of a great cavern with
the throb of whirring machinery around us. It was the same day which I
have just described; Larry was at this moment asleep in the palace
room. Tugh and Tina had come searching for Migul; and Tugh had
contrived to send Tina back. Then he had come directly to us, finding
us readily since we were hidden where he had told Migul to hide us.

This cavern was directly beneath the Robot laboratory in which the
Time-traveling cage was placed. A small spiral stairway led downward
some two levels, opening into a great, luridly lighted room. Huge
inert machines stood about. Great wheels were flashing as they
revolved, turning the dynamos to generate the several types of current
used by the city's underground industrial activities.

It was a tremendous subterranean room. I saw only one small section of
it; down the blue-lit aisles the rows of machines may have stretched
for half a mile or more. The low hum of them was an incessant pound
against my senses. The great inert mechanisms had tiny lights upon
them which gleamed like eyes. The illumined gauge-faces--each of them
I passed seemed staring at me. The brass jackets were polished until
they shone with the sheen of the overhead tube lights; the giant
wheels flashed smoothly upon oiled bearings. They were in every
fashion of shape and size, these inert machines. Some towered toward
the metal-beamed ceiling, with great swaying pendulums that ticked
like a giant clock. Some clanked with eccentric cams--a jarring rhythm
as though the heart of the thing were limping with its beat. Others
had a ragged, frightened pulse; others stood placid, outwardly
motionless under smooth, polished cases, but humming inside with a
myriad blended sounds.

* * * * *

Inert machines. Yet some were capable of locomotion. There was a small
truck on wheels which were set in universal joints. Of its own
power--radio controlled perhaps, so that it seemed acting of its own
volition--it rolled up and down one of the aisles, stopping at set
intervals and allowing a metal arm lever in it to blow out a tiny jet
of oil. One