Base Medium

Base Medium is the collective designation, established by Fifth Concordance Annex 2, for any substance capable of receiving and retaining a designation without alteration of its own nature. The term is administrative rather than material: a Base Medium is defined not by what it is made of but by what it will consent to hold. Forgotten Resin is a Base Medium; so is Cardstock Laminates, unbaked clay, and — under a reading contested since the winter of the year the Tower recorded as 4471 — the ambient air of certain sealed stairwells.

The designation is conferred, never claimed. A substance becomes a Base Medium only upon registration with the Office of Substance and Endurance, which maintains the Register of Consenting Materials on Floor 212. There are, at last count, 1,144 registered Base Media. The Register has 1,151 entries. The discrepancy is a matter of long standing and no one at the Office will discuss it.

Definition and scope

The operative clause of the Fifth Concordance is unambiguous in its wording and troublesome in its consequences: "a designated subject persists as its medium, and the medium is the Tower" (Fifth Concordance, Annex 2, clause iii). Read strictly, the clause implies that any registered Base Medium is itself a portion of the Tower, and therefore that the Tower contains, as constituent parts, the very substances used to catalogue it. The Office resolved this in 4473 by ruling that a Base Medium is "a portion of the Tower held in suspension from its own substance," a formula that has satisfied every subsequent inquiry without clarifying anything.

Silent Medium is classified as a Binding Base Medium, a subclass whose members hold a designation by resisting rather than receiving it. Binding Base Media are not permitted in the scriptoria above Floor 300, following the Thickening of 4402, in which an unlabelled cask of Silent Medium was mistaken for a sealing wax and used to close some four hundred dispatch tubes; the tubes have not been opened since and the correspondence within them is presumed intact.

Relationship to the Concordances

The Third Concordance treats Base Medium as coterminous with "whatever the hand of the Scribe rests upon," a formulation that made the category useless for archival purposes, since it described an act rather than a material. The Seventh Concordance attempted a corrective, distinguishing a Base Medium (a substance that accepts a designation) from a Medium of Record (a substance that accepts a designation and is cited for having done so). The distinction is observed in the scriptoria and ignored in the courts.

Amended Concordance 1199-γ, which bounds the Scribe's influence by a line of contemplation one pace from its base, rendered in a medium befitting silence, has been read by some as an implicit ruling that the Scribe's own base must itself be a Base Medium. The Office has neither affirmed nor denied this reading, which is its customary way of denying things.

Measurement

Base Media are measured by capacity, not quantity. The unit is the Poliad of conceptual mass, indexed against Standard Conceptual Units (SCU), and the quotient of the two — a medium's capacity to hold designation per unit of its own mass — is called its retention. Retention is determined by the Refraction Index method, in which a standard specimen is repeatedly designated and undesignated and the drift recorded. A medium with a retention below 0.4 is struck from the Register; four substances were struck in 4468 and petitioned for reinstatement in 4469, and their petition remains before the Office.

Positioning on a floor is given by Base-707 Vectorial Addressing, which locates any registered medium by three vectors and a naming convention inherited from the older spiral notation. In practice the addressing is used chiefly to find the Register itself, which was moved twice in the same year and never formally re-addressed.

Cultivation media

Certain Base Media are held not for documents but for growth. The cultivation of lumen-moss requires a nutrient solution in which Hepatic Delta Base is the humectant of record; it is the only Base Medium on the Register whose registration is proprietary, and its schedule of permitted uses runs to forty pages. The Cartilaginous Expedition carried a sealed stock of cultivated Base Medium from Base Spire 7 and returned without it, reporting only that the medium had "performed as expected." Base Spire 7 is, under the Third Concordance and again under the Seventh Concordance, a base in the logistical rather than the substantive sense, and its baseness is consequently not a Base Medium.

The Winter Dispute of 4471

The disputed registration concerned the still air of Stairwell 88-C, which the Office's inspector, a clerk named Ondrej Pell, certified as a Base Medium after observing that dust held its shape in the stairwell for eleven days without settling. Pell's certification was countersigned by no one, which was later held to be fatal. The Stairwell was registered provisionally, and the provisional entry stood for two years before the Office convened a tribunal.

"The air of 88-C received the designation without alteration of its own nature, and its nature is to be altered."

— Ondrej Pell, testimony before the Office of Substance and Endurance, 4473

The tribunal found against Pell, on the grounds that a medium which only retains a designation while unobserved cannot be said to retain it at all. Pell was reassigned to the Register and, by his own account, "corrected the number of entries upward." The air of Stairwell 88-C was struck. It continues to hold dust for approximately eleven days, though no one now records how many.

Notable registered media

The Register's more frequently cited entries are:

• Forgotten Resin, the archival standard against which all other retention is indexed;
• Cardstock Laminates, the substrate of record for Conceptual Laminates;
• Permastone, retained for load-bearing designations only;
• Sorrow-Stained Marble, a Medium of Record under the Seventh Concordance, though not a Base Medium, its sorrow being antecedent to its designation;
• Silent Medium, restricted above Floor 300.

Neither Attenuated Nickel-Silver nor The Simple Ouroboros is registered, the first for reasons the Office has not published and the second because it does not accept designations, only returns them.