Atmospheric Vestigials

Atmospheric Vestigials are the particulate residues of spent emotional and cognitive substrate that persist in the air of enclosed floors after the originating state has ceased to be recorded. They are not emotions, nor memories of emotions, but the measurable remainder of both — a fine suspension, visible only in slanting light, that settles without ever wholly settling. The Eighth Concordance formally established the Ambient Reservoirs to contain and modulate them, and every subsequent amendment to the Concordance has widened that remit without ever defining its object.

Vestigials are classified as a substrate rather than a substance. Filing them as a substance was attempted once, under Concordance 4402, and abandoned after eleven months; the schedule of substances has never been reprinted. What can be said with confidence is that Vestigials accumulate, drift, thicken near occupied chambers, and respond to pressure changes in ways no catalogue entry has yet adequately described.

Composition and behaviour

Sampling at Atmospheric Reclamation Station 7 indicates a stable profile of four fractions: a mineral fraction (chiefly stair-dust), a fibrous fraction, a fraction described in the assay returns only as residual warmth, and a fourth fraction that resists assay entirely and is recorded on the returns as a blank ruled space. The blank is not an omission. Assayers are instructed to leave it blank and to initial beside it, and the initials are collated quarterly.

Under ordinary conditions Vestigials disperse at roughly one floor per season in still air. Under the draughts maintained by the Ventilation System they may travel eight floors in a night, which is why the reading rooms near the intakes are sampled twice weekly and the ones near the exhausts not at all.

Conductivity and the Intent Meter

Vestigials are mildly conductive of intent. This is the principle of the Atmospheric Intent Meter, whose earliest prototype was simply a brass vane hung in a stairwell on Floor 1140 to see which way the residue leaned. Modern instruments are more guarded, but the underlying finding has not been overturned: a chamber with a high Vestigial load will register the intentions of its occupants before the occupants have formed them, and occasionally will register intentions no occupant has formed at all. Readings of this second kind are annotated unattributed and are not counted in the monthly totals. The Rota for unattributed readings is drawn on the first Monday of the quarter.

The Textual Primacy dispute

What Vestigials are remains the longest-running disagreement in the archival literature. The Primacy School holds that Vestigials are the skeletal remains of the Tower's original, inscrutable design — that the atmosphere was once load-bearing and its present suspended content is the powdered form of that structure. Proponents cite the Treatise on Pre-Procedural Forms, which speaks of "the air's former members, since dissolved into their own catalogue" (Book II, fol. 14r).

The Ambient Reservoirs reject this reading in their standing preface, arguing that the Treatise is a devotional text and was never intended as a materials specification. The Reservoirs maintain that Vestigials are wholly procedural in origin: byproducts, like sawdust, and no more mysterious than sawdust, though the Reservoirs concede in the same preface that they have not established what the procedure is. The dispute is renewed each time the Eighth Concordance is amended, which is to say very often.

"The air remembers nothing. It holds what was left when the remembering stopped, and holds it in suspension out of administrative convenience."

— Ambient Reservoirs, standing preface to the Sampling Returns, 3rd recension

The Spiral crisis and its aftermath

During the Western Atmospheric Spiral calibration crisis, Vestigial density in the Spiral's lower reaches rose to nineteen times the permitted ceiling, and the Atmospheric Calibration schedules were found to have been compensating for the load without recording it for nine years. The Atmospheric Integrity Guild reviewed the matter under its oversight of the Spiral and issued the Report on Atmospheric Anomalies (TY 7124), which remains the foundational document of the Guild. The Office of Atmospheric Cataloguing was constituted shortly afterwards, chiefly to ensure that compensation of this kind is written down as it is performed.

A ritual survives from the crisis. Before any recalibration of the Spiral, a junior cataloguer reads the density figures aloud to the empty chamber and waits thirty seconds. The reading is transcribed into the day-book even when no one is present to hear it. The Protocols Office has twice proposed abolishing the practice and has twice withdrawn the proposal without debate.

Handling and provision

Vestigials cannot be removed, only managed. Atmospheric Parity requires that all chambers in a linked range be held within two percent of one another's load, so that no room is emptied at another's expense — a provision the Guild of Atmospheric Balancers enforces by unglamorous arithmetic. Where local density exceeds the ceiling, Condensation Conduits draw off the surplus and return it to the Ambient Reservoirs for assay, reclassification, and eventual re-release at a floor specified in the transfer order and not disclosed to the receiving floor.

Under Atmospheric Protocol Sigma, an Atmospheric Readiness Assessment precedes every adjustment exceeding four percent. The assessments are conducted by assessors who are not informed of the adjustment they are assessing, a safeguard introduced after the assessment of Floor 1140 was found to have been completed before the adjustment it described. Visitors are asked not to brush the shelves. The Environmental Contingencies schedule lists Vestigial surge as Contingency 11 and provides no guidance for it beyond the words close the windows and wait, which the schedule's compiler appended in a smaller hand.

Inventory of holdings, Floor 1140, Vestigial store, sealed TY 7091:

• Forty-one sealed assay jars, fourth fraction, contents blank; forty-one initials.
• One brass vane, bent, with a note reading it leaned east on a still day.
• Nine transfer orders, unopened, addressed to a floor not listed in the register.
• One broom.