One of the guards gave a low exclamation, instantly checked at a cold stare from Norbith. And meanwhile the boy was being placed just below, and a little to one side of the big clock.
"Remove the lower half of the clock-case!"
It was done in a few seconds. The instrument's pendulum now vibrated freely in the air, its weight swinging almost to the boy's head where he sat.
"Move him until I drop my hand," said Norbith.
A slight push, and instantly the doctor became aware that the heavy pendulum of the clock, on reaching the outward extremity of its swing, was now gently tapping at the boy's left temple. TAP-TAP-TAP-TAP it went, with the peculiar quickness due to the planet's powerful gravity.
"Keep him there until I tell you to move him."
The tapping continued. To the doctor, of course, the thing was entirely devoid of pain. It made much the same noise the dentist makes with his mallet, only it went on and on, until perhaps two minutes had passed.
"Stop!"
Instantly the boy was moved away. The student said nothing; neither did the father. Yet the doctor noticed something which meant volumes to his trained senses.
The boy's gaze was no longer clear. Instead, dancing lights appeared wherever he looked; tiny flashes of violet and orange, which shimmered before his pupils even though he closed his lids.