forbidden, which would be conclusive. I will hear the holy one."

"There is indeed a forbidden idea. It is known from tradition and old texts that the mathematic of accelerated movement through time involves imaginary numbers. At the conference of 1480 DRC it was confirmed that imaginary numbers are a metaphysical concept forbidden to scientists."

"I will hear the Candidate's master."

A light cloud was filtering the sunlight, and the old man seemed cool and calm. He took a step to a little mound of good grass as if he were climbing to a rostrum.

"Wise one! Neither the holy one nor our own Grandmaster—both devoted patriots with their minds on the welfare of the City—thought to bring one very important fact to your attention. My apprentice's demonstration is not an original experiment; it is a reconstructed experiment. By Acknowledged Custom, reconstructed experiments are permitted regardless of mysteries and ideas so long as the experimenter does not comprehend any impious theory but merely follows the practical directions of old texts.

"I declare that my apprentice is ignorant of the theory of his demonstration—and who is in a better position to know than his master?"

Snubnose rejoiced. He was ready to forgive even the bread and water. In a few sentences Crookback had excused the Grandmaster's rashness, had made good the Grandmaster's oversight, and had set forth a strong case for Bump-arch.

"I will hear the holy one."

"Let him prove that!" the godsman shouted.

"I will hear the Candidate's master."

"I regret that I cannot prove it absolutely. Negatives are difficult of proof. I suggest that the Candidate swear to his ignorance by the God Mother-Father."

"You should know that apprentices are not eligible to take oaths," the High Arbiter said impatiently, dropping the formal manner as if in a hurry to finish the proceedings—and finish Bump-arch.

Encouraged, the godsman cried, "Let Crookback swear to it. He was willing to declare it."

"Will you?" the High Arbiter asked Crookback.

"Though I am sure of the truth, my reverence for the God Mother-Father is too great to permit me to swear to the contents of another's mind—"

"That, and not wanting to be tried for false swearing," Snubnose muttered. He admired his old master a lot less.

"—but I will swear by the God Mother-Father that I myself am ignorant of the theory."

"What good is that?" the godsman demanded.

Cleverly, the master stood in respectful silence. There was an awkward pause—awkward for the godsman and the High Arbiter—and then the High Arbiter collected himself and said, "The question may be answered. I will hear the Candidate's master."

"I am shocked and saddened," said Crookback, "that the holy one believes that apprentices, still wearing their neckbands, excel in wisdom the masters of the guilds."

The High Arbiter's driver, who had been squatting meekly by the elephant, suddenly let loose a screaming laugh, which he cut off just as suddenly with a scared catch of breath.

"I will hear the oath," the High Arbiter said.

Crookback swore by the God Mother-Father while the godsman glowered. The High Arbiter said, "The demonstration may proceed. My apprentices will present my bills tomorrow, including commutation of fees for twenty journeyman lawyers, since you did not place the issue in King's Courts."

Everybody winced, and the elephant rumbled away.

The doors of the Ready Hall opened, and the whole body of apprentice scientists marched on the Field. They carried sections of steel sheet, lengths of magnesium tubing, and parts of machines unfamiliar to the guildfolk. Under Bump-arch's direction they began to assemble the equipment and to enclose it in a small building.

Bump-arch had planned well. They put the components together quickly, and marched from the Field. They had erected a cubical chamber of bright steel with an opening near the ground just big enough for