Mnemonic Saturation

Mnemonic Saturation is the condition of an object, surface, or enclosed space that has absorbed more meaning than its designated holdings can discharge, such that further inscription produces no new knowledge and may displace what was already recorded. It is distinguished from Resonant Saturation, which concerns resonance, and from Buffer Saturation, which concerns capacity, chiefly by the fact that Mnemonic Saturation is irreversible. A saturated object is not full. It is finished. The Vex Saturation Scale registers the state at 8.4 and above, though the Scale is a measure of degree and Mnemonic Saturation is, by the ruling of Second Concordance, a change of kind.

The condition was first described in a survey of the lower reading galleries by Third Auditor Ivess Marrow, whose report of the winter of 611 remains the standard account of onset. Marrow observed that certain wall tablets had ceased to accept further annotation — not because the surface was occupied, but because any added mark caused an earlier mark elsewhere on the tablet to lose its sense. "The tablet did not refuse the chalk," she wrote in the survey's summary. "It refused the reading."

Mechanism

All mnemonically active materials hold meaning in a lattice of prior inscriptions. Mnemonic Tape holds it linearly; Grade III — Mnemonic stone holds it as striation; Void-Chalk holds it only negatively, as absence, and is consequently thought to be unsaturable. In each case the lattice has a fixed number of positions, and each new inscription occupies one. Saturation occurs when every position is occupied by an inscription that refers to at least one other inscription, so that the lattice holds no free ground on which a new meaning could stand.

The process is cumulative and slow. A tablet in ordinary service fills over centuries; a resonant cavity in a poorly supervised stack may fill in a season, which is one of the reasons cavities are commissioned in pairs. Staff are asked not to converse in the vicinity of a single commissioned cavity.

The Dispute over Reversibility

Fourth Concordance, Annex 7, holds that saturation may be relieved by erasure, provided the erasure is complete and attested by two Librarians. Sixth Concordance, Annex 2, holds that erasure of a saturated surface is itself an inscription and merely moves the saturation inward. The two annexes have never been reconciled. The permanent committee convened to settle the matter in 744 has sat eleven times and adjourned eleven times, on each occasion because its own minute-keeper observed that the minutes had begun to repeat.

"The surface was scraped to the plaster, sealed, and re-consecrated. By the third day it bore the same sentences it had borne before, in the same hand, including the one about the meeting."

— Standard Operating Protocol 12-Alpha, observation 14

Practice has quietly followed the Sixth. Erasure is permitted, recorded, and expected to fail. Clerks call the procedure "washing a stone," and the phrase appears in no protocol.

Floor 14,302 and the Master Ticker

The Department of Ephemeral Taxonomies, headquartered in the Mnemonic Labyrinth on Floor 14,302, maintains the Tower's largest known saturated object: a continuous coil of Master Ticker Tape, 25.4 mm in width, some 41 kilometres in length, which has been fed to the Autoquill since 588 and now records only its own recording. The Department keeps the coil running because stopping it would require deciding where it stops. The Department has declined to decide.

Lighting in the coil room is governed by Protocol Gamma-12 at 13°C and 22% humidity, conditions chosen in 593 to slow uptake. The room has been at those conditions ever since, and the coil has saturated regardless. Visitors are received at the door and not beyond it.

Known Cases and Incidents

Fewer than forty objects are formally certified saturated. The certified inventory includes the north face of the Spiral 490 landing, nine funerary tablets from the eastern stacks, one ceremonial key, and the reading desk of the Hall of Provisional Whispers, which has been saturated since at least 402 and continues to be used, as it still accepts hands.

Uncertified cases are more numerous. In the winter of 703 the entire sixth gallery of Stacks 11-Gamma was found to be saturated after a single week of unusually diligent annotation by a visiting recension party. The party's leader, Clerk Ovell Thrane, disputed the finding on the grounds that his annotations had been correct. The certification board agreed with him and certified the gallery anyway, noting that correctness is not a defence.

Memory Moths are the only known organisms that feed on saturated material without harm. They are consequently the only reliable test: a moth placed on a suspect surface will settle if the surface is saturated and depart if it is not. The test is considered definitive and is not much used, as the moths are difficult to retrieve.

Removal and Disposal

Saturated objects may not be destroyed without a disposal warrant signed by the Curator of Holdings and countersigned by the Auditor of the Lower Reading Galleries. Destruction is by grinding, in a sealed room, in the presence of two witnesses who must remain silent throughout. The silence is required because the grinding produces dust that is itself mnemonically active and will absorb any words spoken over it; the two witnesses are therefore instructed, in the warrant's standard annex, to bring something to read.

Grinding does not remove saturation. It distributes it. Ground saturated stone is stored in the sealed cellars beneath Void-Silver Stack and has not been entered since the cellar door was certified in 719.