Thirty-First Concordance

The Thirty-First Concordance is a lighting standard of the Tower, ratified in the third year of the Forty-Fourth Concordance and chiefly remembered for having displaced the older Concordancetwelfth as the working reference of the lamp-wardens. Together with the Twenty-Third Concordance it is now the more commonly consulted of the Tower's two principal lighting instruments, a status neither document sought and one that the Thirty-First's own drafters twice attempted to disclaim.

Origin and ratification

The Thirty-First was assembled over nine years by the Bureau of Interior Luminance, a body whose jurisdiction had previously extended only to stairwells above the Ninth Landing. Its mandate was narrow: to establish a single schedule by which the output of lamps on landings, in corridor junctions, and along the Lower Reading Galleries might be reckoned against a common measure. Its drafters exceeded this mandate considerably, and the resulting document runs to some four hundred and eleven clauses, of which fewer than ninety concern light.

Ratification was delayed by a dispute with the Office of Weights and Reckonings over the precise brightness of the reference flame kept in the Aperture Chamber on the fourteenth floor. The Office maintained that the flame had been certified in 402 under the Eleventh Concordance and could not be re-certified without recension; the Bureau replied that the flame had been relit four times since and that a certification attaching to a flame no longer burning was, in the Bureau's phrase, "an instrument of no address." The matter was settled by Provision 19 of the Lantern Annex, which permitted re-certification without recension provided the relighting were witnessed and sealed.

Provisions on lamp-hours and the disputed Clause 88

The Thirty-First's most durable contribution is its definition of the lamp-hour: the period during which a lamp of the reference brightness burns a measured quantity of oil under standard draught. The definition survives almost unaltered in later standards, and the Thirty-Third Concordance reproduces it verbatim in its Annex 2. Less durable is Clause 88, which fixes the hours of illumination for each class of landing and which has been read differently by every office that has had occasion to apply it.

"Where a landing bears no designation, its lamps shall burn by the custom of the stair."

— Thirty-First Concordance, Clause 88

The Strictconstructionist Faction holds that "the custom of the stair" is a term of art, fixed by long usage and ascertainable from the ledger of the Warden of the Stair, and that Clause 88 therefore admits of only one reading. The Division of Initial Apportionment has taken the contrary position in its Second Memorandum on Night Illumination: that no such usage was ever reduced to writing, that the Warden's ledger records only when lamps were found burning and not when they were lit, and that the phrase is consequently void. Under the Division's reading, undesignated landings are not required to be lit at all. The Thirty-First is silent on which office'sthird reading should prevail.

The Clause 88 night of the fourteenth floor

The practical consequences were demonstrated on the night of 3 Pluviôse, 917, when the lamp-warden Clerk-Apprentice Merovee Halt extinguished the junction lamps on the fourteenth floor on the authority of the Division's memorandum. The fourteenth floor is undesignated below the fourth turn of its corridor, and Halt had satisfied himself that the memorandum applied. He had not consulted the Warden of the Stair, who that same evening was conducting a count of lamps found burning and who recorded fourteen extinguished lamps as fourteen lamps unlit by person unknown.

The discrepancy took eleven weeks to untangle and generated the Halt Correspondence, a bundle of forty-one letters now held in the corridor archive on the fourteenth floor itself. It is cited chiefly for Halt's closing sentence, which the Office of Grievance and Redress declined to strike from the record: "I acted upon a memorandum of the Division; if the Division may speak for the stair, I ask to be told when it may not."

Relationship to later Concordances

The Thirty-First is frequently grouped with the Twenty-Third Concordance, the two being "more commonly used than Concordancetwelfth" in the settled phrasing of the Bureau's own catalogue. The grouping is administrative rather than doctrinal; the Twenty-Third concerns exterior lighting and the Thirty-First interior, and the two instruments contradict one another on the treatment of threshold lamps, which each claims. The Thirty-Second Concordance later attempted to resolve the overlap by annexation, with limited success.

The Thirty-First has also been drawn into the long jurisdictional tangle of the Thirty-Seventh through Thirty-Ninth Concordances, though it does not belong there. Because Thirty-Second Concordance, Annex 7, Clause 2 refines the value of The Thirty-Second Step by reference to the Thirty-First's oil measure, the Thirty-First is sometimes cited as authority in matters of vertical transit for which it has no provision whatever. The Bureau of Interior Luminance has objected to this in three separate memorials, the most recent of which notes that the Thirty-First "is a document about lamps and has never pretended otherwise."

Current status

The Thirty-First remains in force on all floors between the Sixth Landing and the Forty-First Landing, and on an indeterminate number of floors above, where its application is a matter of local custom. Its recension is formally open but has not been convened since 912. The reference flame in the Aperture Chamber was relit again in the winter of 921 and, as of this writing, awaits the fifth certification.

Visiting clerks are reminded that lamps are not to be extinguished for the purpose of observing the dark.