Black bile

Black bile is a synthesized humour held in the Tower's registries as a substance of record. It is not mined, drawn, or harvested; it is produced at designated nodes and conveyed by the Splenic Ductwork to repositories established for its storage. The greater part of the present stock dates from the Humoral Purges and rests in the Splenic Swamp. Black bile is classified under Black Registry Maintenance and its movements are entered in the Black Ledger of Recursive Debt wherever the conveyance creates a debt of record between floor and floor. Readers are reminded that the humour's colour is a matter of registry, not of observation: the substance itself is clear, and appears black only once entered.

Production

Black bile is synthesized at production nodes, the first of which were established during the Humoral Purges under warrant of the Third Concordance. A node is not a vessel and not a room; it is a designation affixed to a stretch of floor, usually between two and four paces in length, within which synthesis is licensed to occur. Nodes are numbered in the order of their licensing rather than their position, so that Node 14 may stand two floors above Node 9 and neither will ever stand near Node 1.

Synthesis proceeds continuously and at a rate the Tower has never found it necessary to state. A node unattended for a full season will produce what the registry calls a surplus of assurance: humour for which no destination has been declared. Surpluses are not destroyed. They are entered against the nearest unclaimed landing and held there until a repository is named, a practice that has made certain landings unpopular with the clerks assigned to them.

"The node does not wait upon the Ductwork. The Ductwork waits upon the registry, and the registry waits upon the seal, and the seal waits upon the hour, which is not the node's concern."

— Third Concordance, Annex 4

Conveyance and Storage

Once synthesized, black bile is conveyed by the Splenic Ductwork, whose branches are laid according to a plan amended more often than it is surveyed. Conveyance is not instantaneous. A quantity leaving Node 14 bound for the Splenic Swamp may take eleven days, or eleven years, depending on which recension of the Ductwork's schedule is currently posted at the junction. Clerks are advised to record the dispatch and the arrival separately, and not to expect the two entries to agree.

The Splenic Swamp serves as the primary repository for Black Bile synthesized during the Humoral Purges and remains the largest single holding in the Tower. It is not a swamp in the geographical sense. It is a stack of sealed basins arranged across four floors, filled to varying depths, and named for the sound the contents make when the floor settles. Visiting is permitted on the second and fourth floors only. Footwear is removed at the threshold and left in the charge of the basin-keeper; the basin-keeper is not answerable for losses.

Smaller Requisitioned Repositories hold quantities diverted from the Swamp under authority of the Seventy-First Concordance, which sealed its findings with a black seal in the year the Swamp last required re-surveying. These diversions are the subject of a standing grievance lodged by the Swamp's own registry office, which maintains that a repository requisitioned from it has never once been returned.

Registry and Ink

Black bile is among the few substances whose registry and whose ink are governed by the same branch. Black Registry Maintenance is concerned both with registries kept in black ink and with the ink itself, and it has long maintained that the two concerns cannot be separated. Standing entries in a Master Log are written in a single ink identified as Register Black II, a compound whose precise preparation is not disclosed and whose colour deepens with each recension it survives.

The identification has not gone unchallenged. In the winter of the year the Swamp was re-surveyed, the clerk Ambrice Tollen noted that the ink in the earliest Master Log entries differed from Register Black II in weight and drying time, and concluded that the standing entries had been rewritten at a later date and were therefore not standing at all. Her finding was entered in the Black Ledger of Recursive Debt as a debt owed by the registry to itself. Tollen was reassigned to the surplus landings. The entries were not altered, and Black Registry Maintenance continues to cite them as standing, in ink, and correct.

Disputes over the humour's character are settled by citation, which is to say they are not settled. The Third Concordance treats black bile as a substance of storage — produced, conveyed, and held — while the Seventy-First Concordance treats it as a substance of account, owed and discharged. The two documents have never been reconciled. Black Registry Maintenance observes both, depending on which is being cited against it.

The Black Spire Comparison

The Black Spire of Landing 209.1 is frequently invoked in the literature on black bile and is not, strictly, relevant to it. The Spire's surface absorbs 99.7% of incident light, a figure much quoted in the Swamp's own reports by way of analogy. The analogy is inexact: the Spire absorbs light, whereas black bile absorbs nothing and merely declines to reflect. The Wandering Gallery has exhibited the two side by side on three occasions, each time under protest from the Spire's annex-keeper, who objects to the comparison on the grounds that the Spire is an Immovable Annex and the humour is not.

Handling Notes

Black bile is not dangerous and is not considered a hazard by any office that has ruled on the question. It stains. Clerks conveying samples between floors are instructed to carry them in vessels of Quietstone, which does not resonate and does not take the stain. Samples may not be carried through the Wandering Gallery while it is in motion. The humour should not be tasted, as its flavour is a matter of registry and the registry is not consulted before tasting.

For the declaration of a ceased subject in respect of black bile, see Black Ledger of the Tower. For the sealing of predictive records concerning its future production, see the Black Seal of Final Iteration. Neither entry may be amended except under The Seal of Unreview, which has not been granted for this subject since the Purges.