Manual of Temporal Calibration

The Manual of Temporal Calibration is a procedural handbook issued by the Bureau of Temporal Metrics for the adjustment of instruments that measure duration against the Tower's standard intervals. First circulated in the fourth recension of the Bureau's standing instructions, it is a narrower document than the Temporal Regulation Manual and is frequently confused with it, a confusion the Bureau has twice attempted to correct by typography and once by sealing the two volumes in differently coloured bindings. The Manual governs the calibration of Temporal Gauges and the conduct of Local Calibration at floor level; it does not govern the movement of time itself, a distinction its preface states three times in ascending degrees of emphasis.

Scope and relationship to other instruments

The Manual is to be read alongside the Manual of Temporal Cartography, which sets the procedures of Temporal Cartography and belongs to the Subbureau of Temporal Reconciliation. The two are often shelved together because both concern the recording of intervals, but the Cartography Manual fixes where an interval is deemed to have occurred, while the Calibration Manual fixes what the instrument said while it was occurring. Clerks who confuse the two produce readings that are internally consistent and geographically impossible; the resulting reports are filed, unread, under Schedule 9.

Calibration under the Manual requires a triplicate permit from the Office of Temporal Modulation before any gauge is opened, resealed, or struck. The Office issues the permit; it does not inspect the work. That duty falls to the Provosts of Calibration, whose seal appears on the closing page of every certified return. Where the Manual and the Manual of Dimensional Calibration (Rev. 44) address the same instrument, the more recent revision prevails, except in matters of drift, where Rev. 44 defers to the Manual by an arrangement no one has located in writing.

The seven checks

Calibration proceeds by seven checks, performed in order and recorded on Form T-14, which is printed on one side only. The sequence is not optional. Check four, the comparison against the Consensus Second, may be repeated as often as the operator wishes, but checks five and six may not be reversed, a prohibition introduced after the Marrowgate incident of the winter of 317, in which two Provosts calibrated a stairwell clock in reverse order and produced a reading that has never been reconciled.

Each check is witnessed by a second clerk, who signs the margin and is thereafter answerable for the reading even if absent at the time. The Bureau acknowledges the difficulty this creates and has declined to revise it. Instruments found to drift beyond the tolerances set in the Manual of Acceptable Tolerances are removed from service and conveyed to the Calibration Annex for the Dimensional Calibration Check, a procedure the Manual describes only by reference.

Incidents and rulings

The Manual's reputation for severity rests largely on the Central Chronophage affair. In the eleventh year of the current administration, a party of clerks attempted to calibrate gauges adjacent to the Chronophage on the reasoning that its rate was regular enough to serve as a reference. The readings obtained were regular, and wrong. Provision 3 was subsequently amended to forbid calibration within nine landings of the Chronophage, and the Manual's second chapter was rewritten to describe the device only as "a condition of the floor, not an instrument upon it" (Manual of Temporal Calibration, ch. 2, §6).

Disputes over the Manual are settled by citation of the Concordances, which is to say they are settled slowly. The Third Concordance, clause 17beta, holds that a gauge once sealed cannot be recalibrated in the same vertical year; the procedures issued under that clause extend the prohibition to instruments merely stored in the same alcove. The Fifth Concordance, annex 4, contradicts this directly and at length. The Chronometry Guild observes the Fifth in its own workshops and the Third everywhere else, and has done so without comment for over a century.

"Where two Concordances bind the same gauge, the operator shall follow the elder and record the younger in the margin. The margin is not to exceed one third of the page."

— Provosts of Calibration, Circular 22, item 9

Physical description and upkeep

The current edition runs to 214 leaves in octavo, bound in board covered with a grey cloth that darkens with handling. Chapter 3 contains the only fold-out diagram in the Tower's procedural literature: a cross-section of a Resonator Bell with its calibration collar removed. The diagram has been corrected by pasted slip in every copy examined since 402, and the slip itself is now catalogued as a separate holding in three libraries.

Copies held in reading rooms are chained. Copies held in calibration chambers are not, and are instead checked out against a brass token; the token must be returned before the chamber's door will close. Operators are reminded that the Manual is not to be used to level a gauge, steady a lamp, or hold a door open, and that the last of these caused the loss of four leaves from the Survey Station Theta copy, which remains in service with the gap noted in the register.

Textual history and disagreement

The Manual's first recension is lost; the second survives only in quotations within the revised edition and in a marginal note by Verifier Kael, whose own copy was audited and sealed in the year 388 and thereafter unavailable. The Manual of Radiance borrows its phrasing for Spectral Lamplight Calibration without acknowledgment, a borrowing the Bureau has chosen not to pursue.

Scholars disagree on whether the Manual's seven checks derive from the Guild of Exactitude's annex procedures or from an earlier Office schedule now known only through Local Calibration returns. The Guild of Quantitative Idealists holds the latter view and cites its own Manual of Ideal Calibration as evidence of a shared ancestor; the Provosts hold the former and cite Section 14 of the Manual of Acceptable Tolerances. Neither citation settles the question, and both are reprinted together in the current edition's appendix, facing one another, which the Bureau describes as a convenience.