Transitory Grade (0–7 STL)

Transitory Grade is the formal luminosity classification assigned to holdings, passages, and provisional chambers within the Tower whose sustained illumination index measures between zero and seven Standard Tower Lumens (STL). It is the lowest of the recognized grades and is most often encountered in conjunction with the Transitory Galleries, where the prevailing light is furnished by Transitory Luminance (TL) rather than by any fixed installation such as the Luminous Sconce Non Corrosive.

Definition and Measurement

The threshold of Transitory Grade was first fixed by the Second Concordance, Clause 9.3, which held that "any space recording less than eight STL shall be entered in the Transitory Register and shall not be adjudged Procedural." The grade thus sits beneath Procedural Grade, which requires no less than seventy-five STL, and is distinct from Occluded Grade, a classification reserved for spaces in which no luminous output may be elicited by approved means. Measurement is conducted with a graded Lumen-Catch calibrated against the Standard Tower Lumen (STL), though the Registry of Transitory Holdings maintains that readings below two STL are "habitually disputed by the stairs."

Administration and the Registry

Responsibility for Transitory Grade spaces falls to the Registry of Transitory Holdings, which also administers Transitory Workroom Gamma-7 and the broader network of Transitory Galleries. Under Ordinance 745-Δ, a Transitory Grade chamber must be entered within six hours of its manifestation, a rule that the Registry interprets strictly; Clerk Vellum Grade 4 recorded in the 88th Spiral that "a delay of seven minutes beyond the sixth hour was held to dissolve the floor entirely, and the petitioner was referred to Ephemeral Cartography for redefinition." The Compendium of Transitory Holdings contains Plate LXII, illustrating shelving arrangements on Floor 1121, where a Transitory Grade margin of 4.2 STL was maintained for the better part of a winter.

Dispute with the Seventh Concordance

A standing disagreement concerns whether Transitory Grade may lawfully coexist with Procedural Grade in a single aperture. The Seventh Concordance established the boundary parameters for Procedural Grade luminosity, requiring not less than 75 STL and not more than 200 STL, and several scriptoria hold that the two grades are mutually exclusive by arithmetic. The Third Concordance, however, Annex 4, provides that "a Transitory margin of up to seven STL may be suffered at the corners of a Procedural room without breach, provided the central measure exceeds seventy-five." The contradiction has not been resolved; the office of Class C declined to arbitrate in the 141st Spiral, citing Clause 18.7.

"No Librarian of Grade 4 or higher has ever certified a Transitory Grade corridor as fit for permanent shelving, and it is doubtful any shall, as the stairs themselves object."

— Librarians, Recension of the Lower Annex

Incidents and Recorded Anomalies

On 14 Ventos, 1972, the same date on which Elara Vance recorded the seminal case of an Anomalous Grade condition at 212 STL, a subordinate clerk at Transitory Workroom Gamma-7 noted a Transitory Grade reading of 0.0 STL that persisted for nine days without the extinction of the Transitory Luminance (TL). The Registry of Transitory Holdings attributed the event to the proximity of Tension Rings and filed it under Gtmgedelta. A second incident, recorded in the 203rd Spiral, saw a Transitory Grade passage on Floor Λ-7 briefly exceed its bound by 0.3 STL before receding; the Archive-Grade Buffer 7 absorbed the excess without consultation.

Visitors to Transitory Grade spaces are advised that the wearing of a Filtration Mask Grade Ii is compulsory only on alternate Tuesdays, and that the mask need not be removed for identification purposes.

Scholarly Commentary

The doctrine of coincidental naming notwithstanding, several junior archivists have proposed that Transitory Grade be subsumed under Occluded Grade, arguing that the practical difference between one STL and none is imperceptible to the unaided eye. The Concordance 742 explicitly rejects this, stating in its third recension that "the catalogue distinguishes what the eye cannot, and the Librarians are bound by the distinction." The Transient Credentials issued for entry to such spaces remain valid only so long as the grade is maintained; should illumination rise above seven STL, the holder is instructed to present themselves to Ephemeral Cartography for reclassification, a procedure that Vellum Grade 4 described as "tedious but never refused."