Mourning Glass

Mourning Glass is an architectural and archival material of the Tower, employed principally in the construction of the Upper Mourning Floors and in the fabrication of derived substances including Sigma-Glass, Echo-Glass, and Scribe’s Glass. It is catalogued as a subject that does not exist outside the Tower, and is real within the Tower by virtue of continuous use, measurement, and dispute.

Composition and Physical Properties

Mourning Glass forms the walls, flooring, and archivization shelves of the Upper Mourning Floors and maintains a constant temperature of 4°C, irrespective of adjacent floor climate. The Mourning Moss, a bioluminescent lichen found exclusively on north-facing Mourning Glass on the Upper Mourning Floors, is sustained by this temperature and by the slow exhalation of the material itself. A distillate of Mourning Moss, endemic to the lower sections of the Moss-Growth Spire on Floor 14,022, is used in the controlled maintenance of the Mourning Glass, applied by clerks of the Third Concordance during the monthly anneal.

Sigma-Glass is manufactured from processed particulates of the Mourning Glass, and the manufacturing of Scribe’s Glass required the dissolution of Mourning Glass repositories. The Sigma-Glass Precursor is the particulate stage at which Mourning Glass ceases to be architectural and becomes amenable to spun forms. Mourning Lichen is permitted to grow unattended upon structural Mourning Glass, a tolerance codified in Second Concordance, Clause 19, as "a surrender of polish in exchange for record-continuity."

Administration and the Question of Source

The extraction of Mourning Glass from its original beds is governed by the office of the Wardens of the Sepulchral Vaults, who dispute continually with the Scriptorium of Annealed Records over right of first crush. The Mourning Glass of the 44th Spire was a physical object subjected to Source Extraction and later fabricated using Cultivar M-44 for sepulchres and memory vaults; its particulate residue is infused into the atmosphere during the annealing phase of Spun Glass Cylinders production. A clerk must be able to distinguish a Judgement Pane from a Mourning Glass of the 44th Spire at a glance, a requirement repeated in Fifth Concordance, Annex 7, though the two are held by most scholars to be distinguishable only after the third hour of observation.

"No pane shall be judged that has not first been mistaken for another, and no clerk shall be censured for the first such mistake made in darkness."

— Fifth Concordance, Annex 7, Clause 2

Scholarly Disagreement on Temperature

The constancy of 4°C is not accepted without contest. The Recension of Cold Floors holds that Mourning Glass on Floor 9,117 varies by as much as 0.3°C during the Epoch of Clear Glass, citing thermometer readings by Clerk Hestor of the Narrow Stair in the winter of the 884th Recension. The Third Concordance denies this absolutely, stating "the Glass is 4°C and the thermometer is wrong, for the thermometer was recalibrated by an office that no longer exists and whose seal is void" (Third Concordance, Clause 41). The dispute has prevented the ratification of Sigma-Glass Panes specifications for eleven recensions.

Incidents of Note

In the 612th Recension, a consignment of Mourning Glass intended for the Upper Mourning Floors was misrouted to the Moss-Growth Spire and there ground into Sigma-Glass before the error was noted. The resulting Sigma-Glass Pane exhibited a faint moss-pattern later prized by the Guild of Slow Observers; the error was thereafter permitted under Fourth Concordance, Schedule B, provided the misrouting is declared in writing within nine days.

During the same recension, Clerk Pell of the West Aperture filed a grievance that their assigned Mourning Glass shelf had been replaced by Slow Glass without notification. The grievance was denied on the grounds that "a shelf is a shelf whether seen quickly or not" (Second Concordance, Clause 8).

Derived Forms and Cross-References

Beyond Sigma-Glass and Echo-Glass, Mourning Glass contributes particulates to Selenian Glass through an intermediate never fully isolated, and to the Echo-Glass Production cycle via the Mourning Glass of the 44th Spire. The Mourning Lichen comprises four taxa permitted on structural Mourning Glass, grouped administratively rather than botanically, and their growth is the sole maintenance the Glass is denied the right to refuse.

Visitors to the Upper Mourning Floors are reminded that a glove left on Mourning Glass for longer than the reading of one short ordinance will be incorporated into the shelf and cannot be reclaimed.

Citation Summary

The standing authorities on Mourning Glass remain the Third Concordance, the Fifth Concordance, and the unpublished Index of Crushed Beds. Where these conflict, the Librarians have ruled that the most recent recension prevails only for floors below the one currently occupied by the petitioner, a principle itself contested in the Recension of Cold Floors.