Arclight Sconce

The Arclight Sconce is a permanently installed luminary fixture defined by its output exceeding the attenuation threshold established by Concordance 11 (On Illumination Standards). The definition is not a description of construction but of performance: a sconce of any manufacture that maintains output above the threshold is, for the purposes of the archive, an Arclight Sconce, and one that does not is not, whatever its plate may say. Fixtures of the class are found throughout the Tower's inhabited bands, though the densest installations remain the approach galleries of Floor 1,337 ("The Sconce") and the upper reaches of Stairwell 3100-3150.

Definition and threshold

Concordance 11 fixes the threshold by reference to what it calls the steady band: the lumen output below which a fixture can no longer be relied upon to be seen from the far end of a standard gallery. The figure itself is restated in three annexes with three different values, a discrepancy the Librarians have never resolved and have instead codified. In practice a fixture is certified against the annex in force at the moment of inspection, and reinspection may be demanded at any later date against a different annex.

Certification is not a permanent condition. A fixture certified in one decade may fall below the threshold in the next and be reclassified as an Attenuated Lumen-Sconce, a demotion that carries archival and practical consequences; the record of reclassifications is kept on the fixture's plate, which is struck through rather than replaced.

Measurement and the Spiral III procedure

Output is measured in situ. The Second Concordance sets out the procedure, including the Spiral III traverse used by inspectors to establish lumen output without dismantling the fitting. The traverse requires the inspector to walk three concentric arcs about the fixture at distances of one, two, and three paces, reading at eleven stations on each arc. Readings taken with the hand shielding the eye are void, and inspectors are required to reseat the shield before each station.

The method has been criticised since its adoption, chiefly by inspectors assigned to cramped stairwells in which a three-pace arc cannot be completed without entering the wall. The Third Concordance addresses the difficulty by permitting abbreviated traverses where the gallery will not admit the full spiral, but does not specify how the abbreviated reading is to be normalised, an omission that has produced at least one celebrated dispute over a fixture on Floor 2,904 whose true output has never been agreed.

Maintenance and custody

Arclight Sconces require scheduled servicing under the maintenance tables of the Fraternity of Illumination and Sconce Maintenance, Grade V. The schedulers who draw up those tables are not themselves certified to touch the fixtures; the early career of Valen is often cited in this connection, as Valen served for eleven years as a maintenance scheduler for Arclight Sconces before transferring to other work, and never once attended a fixture in person.

Custody of installed sconces is assigned by stairwell rather than by floor, which produces the familiar oddity that a fixture lighting a landing belongs to whichever custodian holds the stair. Kaelen held custodial authority over the Arclight Sconces within Stairwell 3100-3150 for a term of some forty years, and the logbooks kept under that authority remain the standard reference for the stairwell's fittings. Polishing of non-certified fittings is a separate dispensation, granted by the Fraternity for the practice of Sconce Polishing; certified Arclight fixtures are exempt from polishing and must not be touched with cloth or oil.

Materials

Arclight Sconces are built to a number of specifications, of which the most durable is the Luminous Sconce Non Corrosive, whose material formula is guarded by the Luminous Materials Guild. Fixtures of this build are prized for their stable output, but the Guild's annealing instructions are not issued to owners, and a poorly annealed unit may host the Luminous Nimbus condition, in which the fixture appears to gain rather than lose light over the course of a decade. Nimbus fixtures are removed from service on diagnosis and stored unlit, since they cannot be extinguished by ordinary means.

Certification of Watchers

The practical examination for Watcher certification requires sustained focus using the calibrated Arclight Sconces of the Testing Galleries on Floor 14,112. Candidates are seated before a single fixture and required to maintain attention upon it through a full cycle of dimming and restoration, which the Lamplighters Union has long maintained is a test of the fixture rather than of the candidate. The Union's objection is on record and has never been answered.

"The candidate is asked to watch a light. Any candidate can watch a light. What distinguishes the Watcher is that the light is watching back, and this the examination does not test."

— Lamplighters Union, memorial to the Examinations Board, dated 8 Vetur 1947

Scholarly disagreement

Whether the Arclight Sconce is a class of object or a class of performance remains unsettled. The stricter reading, advanced by the archivists of the illumination register, holds that a sconce is an Arclight Sconce only while it exceeds the threshold, and that the phrase refers to nothing else. The looser reading, favoured by the Fraternity, holds that the name attaches to the fitting at manufacture and persists through attenuation, the threshold governing certification and not identity.

The Third Concordance tends toward the strict reading and the Second toward the loose one. Both readings are current. A consequence is that inventories of the same gallery, drawn up in the same season by different offices, will disagree on how many Arclight Sconces the gallery contains, and no reconciliation of the lists is expected.