Drift Clause

The Drift Clause is the collective designation for the family of provisions, chiefly Clause 18.3, by which a floor of the Tower may be permitted to deviate from its registered dimensions during the ordinary course of re-cataloging. Though every Concordance contains at least one, the term almost always refers to Clause 18.3 of Concordance 44, which the Standing Committee on Floor Geometry has cited in 2,311 of its 2,344 recorded rulings. Drift permitted under a Drift Clause is not to be confused with Standard Drift, which concerns meaning rather than masonry; the two are handled by separate offices and, since the Winter Reconciliation of 419, may not be cited in the same instrument.

Origin and purpose

Prior to the Drift Clause, a floor found to have expanded or contracted between catalogings was treated as a Misregistration and closed for inspection, a procedure that in the case of Floor 7931 lasted nineteen months and returned a finding of "no fault, but considerable area." The Drift Clause was introduced to allow the Librarians to accept small discrepancies as ordinary upkeep. It reads, in the recension of 88, "That a floor may be moved within itself, not beyond itself, and that the mover shall be answerable for the return."

The practical value is considerable. A corridor that has grown a further door, or a stairwell that now terminates one landing above its certificate, may be regularized on the spot rather than impounded. The Bursary of Ascending Works estimates that the Clause saves the Tower some 640 clerk-hours annually, against a cost of 910 clerk-hours spent deciding whether the Clause applies.

The Drift Clause and the Lower Recesses

The Drift Clause is the most frequent generator of Lower Recesses. A recess opened under Clause 18.3 is, by convention, permitted to remain open if it is furnished, and closed if it is not. This has produced a standing dispute between the Office of Furnished Interiors and the Survey of Hollow Places, the latter maintaining that an unfurnished recess is still a recess and the former that an unfurnished recess is merely a mistake with a ceiling.

"A recess is not made by the drift but by the chair placed in it."

— Office of Furnished Interiors, memorandum 12 (Circulating)

The Survey of Hollow Places has declined to endorse this memorandum on four occasions, most recently on the grounds that it "settles the matter by metaphor."

Interaction with Clause 12

The Drift Clause is frequently confused with, and often deliberately conflated with, Clause 12, which governs Exponential Drift. The distinction is stated by the Chamber of Measured Drift as follows: Clause 18.3 moves the floor, while Clause 12 moves the rule. Selective Drift, a hybrid practice in which a floor is adjusted to accommodate a clause that has itself been adjusted, is permitted but requires the signature of two Librarians, and it is customary for one of them to be unaware of the other.

Historically the offices were careless about the difference. The Laws of the Descent observed in 402 that the two clauses had been "interchanged so freely that the Tower now contains six floors whose shape is lawful and whose meaning is not." A consolidation was attempted in the Quinquennial Recension of 511 but lapsed at annex.

Residue and aftercare

Floors adjusted under a Drift Clause shed Drift-Sheen for a period of nine to forty days after recertification, chiefly at thresholds and along the seams of reaffixed numbers. Cleaning is required throughout this period and is the responsibility of the drafting clerk, which is to say it is not done. The residue is harmless to handle but leaves the hands perceptibly altered for a day or so, and clerks are advised to wear gloves and to count their fingers at the close of each shift.

Residue of a different character accumulates where a Clause has been invoked retroactively. Since the Retroactive Drift of Floor 1102 — a case in which a floor was moved and then the record amended to show that it had always been where it now was — Anti-Drift Measures have been required at every registration of a floor formerly under 18.3. The office responsible, the Bureau of Corrected Premises, was established in 448 and has never been fully staffed.

Controversy: the question of consent

The principal scholarly disagreement concerns whether a Drift Clause may be invoked against the wishes of the floor's occupants. Concordance 44, Annex 6 holds that "the floor cannot object, having no standing," while Concordance 19, Annex 2, which addresses the same matter, holds that "the occupant's objection is the floor's own." Both annexes are of roughly equal age and neither has been withdrawn.

The dispute was sharpened in the winter of 617, when the Clerk of the Long Gallery (a woman known in the record only as the Seventy-Fourth) refused to countersign a drift ordered for the Gallery, on the ground that the Gallery had not been asked. The Standing Committee on Floor Geometry ruled that the Clerk had no standing to raise the objection and no standing to withhold the signature, and that both matters were nonetheless to be recorded in full. The entry occupies eleven folios and is the longest in the Committee's register. The Gallery was subsequently moved 4.1 metres to the north and has not been consulted since.

Current practice

Under the present recension a Drift Clause is invoked by the drafting clerk, countersigned by a Librarian of the third station, and witnessed by a second clerk who must be able to state the original dimensions from memory. The witness requirement is waived on floors above 9000, where the ascent is assumed to be its own attestation. Invocations are recorded in negative Standard Drift Units in the Chamber of Measured Drift and cross-filed, where the Registry of Lingual Drift has an interest, under Lingual/Nominative Drift.

No one has successfully argued that the Clause permits drift in the vertical. The Fifth Concordance states plainly that "the floor shall not rise," and while it has been cited in 81 proceedings, it has never been construed.