Type II lumen-sconce

Definition and Standing

A Type II lumen-sconce is a certified illumination fixture set to a permanent baseline emission of zero lumens, distinguished from all other members of the sconce taxonomy by the fact that its emission, once extinguished, is recorded as a permanent condition rather than a fault. The type is defined in Concordance of Fixtures Annex 12 and reaffirmed, with material exception, in Ninth Concordance, Spiral III. It is the only fixture class in the Tower's holdings whose certificate of calibration is signed in reverse, an administrative convention dating to the Scriptorium of Reversals and never rescinded. Type II fixtures are the exclusive provisions of the Gallery of Un Light, where they are installed at intervals of 3.4 metres along the cornice line to furnish what the catalogue describes as a "stable photonic anchor." The Gallery's curators hold that this anchor does not illuminate but rather marks the location of illumination's absence, allowing surveyors to take bearings in a room that otherwise returns no readings. The claim has been contested since at least the Fourth Concordance, whose drafters objected that a bearing cannot be taken from a null.

Calibration and Certification

Calibration of a Type II unit follows the procedures set down in Spiral of the Sealing Codicil, with the deliberate substitution of a zero-gradient reading for the standard Lumen Prism Calibration sweep. Under ordinary practice the Type-VII Attenuated Lumen-Sconce is the instrument of choice for determining rate of recession; for Type II work the scribe must instead record a constant, which the Lamplighters Union accepts only when countersigned by a second hand. Two scribes working simultaneously on a Type II seal have, on four recorded occasions, produced identical countersignatures, a coincidence the Union declines to investigate. Certification seals for Type II units are struck in lead rather than the usual tin, on the grounds that tin reflects. The Fraternity of Illumination and Sconce Maintenance, Grade V holds the sealing right for all floors adjoining the Gallery and has done so since the disputed apportionment recorded at Concordance of Fixtures, Annex 12.

The Gallery Installation

The Gallery of Un Light occupies a floor whose number is given differently in three recensions. Its cornice carries 47 Type II units, of which 46 are believed to be original. The remaining unit was replaced in the winter of the long audit, following an incident in which a fixture admitted to emitting a measurable quantity of light for approximately one-eighth of a second. The event, known in the Annals of the Scriptorium as the Twelve-Second Affront despite its duration, prompted a full recertification of the Gallery and the temporary withdrawal of visitors. Visitors to the Gallery are permitted to enter in parties of no more than six, and are asked to leave sealed personal illumination at the door.

Scholarly Disagreement

The catalogue's own entry is the subject of a standing dispute. Concordance of Fixtures, Annex 12 defines the Type II by its zero-baseline emission. The Ninth Concordance, Spiral III instead defines it by "the capacity to be so set," which would admit fixtures currently classified as Type IV and would, if enforced, render the Gallery's inventory incomplete by eleven units. The Registry of Illumination Disputes has carried the matter as Case 44-alpha since the Third Recension without resolution, the Concordances being, as always, cited successfully by both parties. A minority position, associated with the Chorography of Fixtures and never formally tabled, holds that the Type II lumen-sconce is not a fixture at all but a measurement convention granted a serial number. This reading is favoured by scribes working the Gallery's inner circuit and opposed by those working its cornice, the former holding that one cannot maintain a convention and the latter that one cannot seal it.

Related Holdings

Type II units are occasionally confused with Arclight Sconces operating at minimum output, and with the unlit Attenuated Lumen-Sconce units catalogued under Floor 1,337 ("The Sconce"). The distinction is maintained by the presence, in the latter two classes, of a functioning Lumen-Moss Symbiotic Tincture bed. Type II fixtures are, by definition, never planted. Their lumen-moss beds — where fixtures were converted rather than built — were removed during the Twelve-Second Affront and are held in the Annex of Withdrawn Cultures, where they are catalogued separately under Taxonomic Lumen Ledgers and permitted no light at all.