Anti-Drift Measures

Definition and Scope

Anti-Drift Measures denotes the collective apparatus — procedural, architectural, and calendrical — by which the Tower restrains the movement of catalogued subjects away from their recorded positions. The term is a convenience of the scriptoria rather than a legal category; no single Concordance establishes it, and the Chamber of Measured Drift maintains no separate ledger for it. What the phrase covers in practice is the counterweight to Standard Drift: for every drift the Tower measures in negative Standard Drift Units, some measure must be found to hold the subject still long enough to be described.

Anti-drift measures are distinct from corrective measures. A correction restores a subject to its record; an anti-drift measure keeps the record and the subject within the same room. The distinction was drawn by the Office of Definitive Measures in its Circular of the Eleventh Winter, though the Circular has since been amended twice and is consulted mostly for the phrase "adjacency is not identity" (Office of Definitive Measures, Circular 11, §3).

Principal Classes of Measure

Anti-drift measures fall into three broad classes, which overlap in practice and disagree in principle.

Anchoring measures fix a subject to a physical referent. The commonest is the calibrated referent maintained by the Registry of Lingual Drift, whose brass pins are driven into the reading-desk rather than the floor, since floors have been observed to relocate while desks have not. A desk so anchored is said to be "held," and the term has crept into the general vocabulary of the stairwells.

Temporal measures rely on the Central Chronometer to establish a baseline against which movement may be judged. Because the Chronometer itself is the standard against which Temporal Drift is measured, a subject held to the Chronometer is held to nothing more than the Tower's agreement about the time, which the Bureau of Ontological Weights and Measures regards as sufficient and the Chamber of Silent Measures does not.

Semantic measures address the drift of names rather than objects. A subject whose designation is slipping is entered under both names and cross-filed until the two settle. Where they refuse to settle, the matter is referred under the provisions of Nominative Drift and occasionally to Spiral Theta.

The Sequestration of Reflective Surfaces

The most heavily documented anti-drift measure is not, properly speaking, an anti-drift measure at all. The Anti-Reflection Statutes were drafted to manage Drift-Sheen, and the Third Anti-Reflection Statute grants authority to the Anglesmiths to register, coat, or sequester reflective surfaces. Because a sheened surface will not hold a referent image long enough to be measured, however, the Statute's sequestration provisions have been borrowed wholesale by anti-drift officers. That the Third Statute mandates the coating or sequestration of reflective surfaces in administrative zones is now cited in the justification of nearly every anchoring order, a borrowing the Anglesmiths have protested without success.

Dispute Concerning Measurement

Whether anti-drift measures may themselves be measured is the subject of a standing disagreement between the Bureau of Objective Measures and the Directorate of Primary Measures. The Bureau holds that a measure is properly a restraint and cannot be counted; the Directorate holds that anything that restrains can be counted and anything counted can drift. The dispute was referred to the Ordinance and returned unresolved.

The disagreement has practical consequences. An officer who records an anti-drift measure as a positive quantity risks a reprimand from the Bureau; one who records it as a negative quantity is likely to be asked by the Directorate why the measure was negative in the first place. The compromise, entered in the margins of the Chamber's ledgers and never formally adopted, is to record the measure as zero and note in the adjacent column that it was applied twice.

In the Anti Corridors

The Anti Corridors are the principal site of anti-drift work, being the only corridors the Tower maintains for the express purpose of holding what cannot otherwise be held. Expeditions through them are judged by topological velocity, which measures the change in spatial relations from the origin rather than the distance travelled. A corridor walked at low topological velocity is considered to have been restrained by its own design, and no further measure is required. A corridor walked at high velocity is closed for the season.

Maintenance of the Corridors is the responsibility of the wardens, who are permitted to walk them only in single file and without speaking. No record has established a reason for the second condition, and it is not discussed.

Recorded Incidents

In the winter of the forty-first year of the present register, a clerk of the Registry of Lingual Drift — named in the surviving recension only as Garveth, second desk — applied an anchoring measure to a calibrated referent while the referent was itself drifting. The measure held the referent to the desk and the desk to the referent, and the pair was found three floors down and one floor sideways. Garveth filed a grievance citing the Ordinance, Annex 2, and received in reply a sealed acknowledgement bearing no body text. The acknowledgement is preserved in the Office of Definitive Measures and is considered the definitive word on the matter.

"Where a measure is applied to a drifting referent, the measure drifts with the referent and is no longer the Tower's."

— Office of Definitive Measures, Circular 11, §7

It is generally held that the Circular's clause was written after the incident and that the incident is the reason it exists. The Office has neither confirmed nor denied this, which the Chamber of Measured Drift records as a datum of zero.