Sigma-Class Logging

Sigma-Class Logging is the mandatory documentary regime by which every observation, handling, count, and non-event pertaining to Sigma-class materials is entered into the permanent record of Line Sigma. It is distinct from measurement itself: a Sigma-class quantity may be measured by any authorized instrument, but until it is logged it is, in the phrase of Descent Protocol Sigma-3, "held in the air and owned by no one." Logging is the act that assigns an observation to the archive; the archive then assigns it, in turn, to a floor.

Origins and the Sigma-Chron

The regime descends from the earliest custodial practice at Aperture Sigma, where the continuous detection and recording of the Sigma Pulse required a written trace before any reading could be certified. The instrument built for this purpose, the Sigma-Chron, does not merely measure the Pulse; it archives each measurement in sequence, and the sequence is itself a logged object. Security Protocol Sigma treats the Sigma-Chron's continuous register as the primary evidentiary record of Line Sigma, subordinate only to the Annual Register Sigma-14,022 into which its daily extracts are bound.

Earlier practice was looser. Until the recension of Protocol 9033-β in the winter of the year recorded as 11,614, readings taken at Dock Sigma were entered on loose slips and filed by the initials of the observing clerk. The slips were not numbered, and a slip found on the floor of the dock in that winter, bearing a reading of 0.029 syllogistic radians and no date, could not be attributed to any hour or any clerk and was accordingly ruled inadmissible by the Office of Sequential Records. The Protocol's response was to require that every Sigma-class reading carry, at the moment of its taking, a time, a station, an instrument, an observer, and a count of the observers present.

The five-field entry

A Sigma-class entry is valid only when all five fields are complete and legible. The count of observers is included because of the Halved Bell incident, in which two clerks logging the same Pulse disagreeing by a single observer produced entries that could not be reconciled, and the resulting dispute occupied the Concordance on Conflicting Counts for the better part of a decade. Where an observer is present but does not observe — a porter waiting at the door, a courier awaiting a signature — the entry must say so, and the porter and courier are not counted.

Legibility is judged strictly. An entry corrected in the margin is valid; an entry overwritten is void; an entry corrected by a second hand requires the second hand to be logged as an observer, which alters the count and therefore voids the entry it was attempting to repair. Clerks are advised, in the margin of Protocol Sigma-6, simply to begin again.

Rolls and the binding schedule

Sigma-class entries are kept on rolls of not fewer than forty leaves, bound at Dock Sigma under the seal of the Keeper of the Rolls of Line Sigma. The binding schedule is set by Atmospheric Protocol Sigma, since the rolls are stored in the open galleries and damp affects both the ink and, according to a persistent minority view, the readings themselves. The Reroute Authorization for Line Sigma permits rolls to be moved by Vertical Tram Line Sigma only when sealed and only at hours when the Pulse is not under active measurement.

The current inventory of active rolls is short and is reproduced here in full:

• Roll Sigma-A, the Sigma-Chron extracts, continuous since 11,591.
• Roll Sigma-B, dock weighings and pane counts.
• Roll Sigma-C, breaches and near-breaches, including all Sigma-Glass fractures above 0.03 syllogistic radians.
• Roll Sigma-D, the Peregrine-Sigma sightings, all of which are logged as probable and none of which has been promoted.

Scholarly disagreement

The central dispute concerns whether an entry may be made after the fact. The Second Concordance on the Recording of Intervals, Annex 2, holds that "a thing observed and not at once written was not observed," and that retroactive entry is therefore a fabrication. The Fourth Concordance on the Recording of Intervals, Annex 2, holds the opposite with equal force, distinguishing observation from inscription and permitting retroactive entry where the observer can swear to the interval and an independent clerk can swear to the observer. Both annexes are numbered 2, and both are in force. The Office of Sequential Records has adopted the practice of entering such readings twice, once under each annex, with the reconciling note kept in a separate file that is itself not entered into Roll Sigma-A.

"The interval is not the entry. The interval is what the entry is about."

— Fourth Concordance on the Recording of Intervals, Annex 2

A secondary dispute concerns the status of Sigma-class descent operations conducted below the lowest logged station. The Fifth Concordance on Descent Records maintains that a descent not logged at its every stage is logged in its entirety as a single entry; the Descent Protocols hold that no descent may be compressed, and that a compressed descent is not a descent but a fall.

Notable irregularities

The Clerk of the Lower Landings, one Marrowby, logged a continuous Pulse reading across a period of nine days during which he was, by his own later admission, absent from the Tower. The entry was discovered in 11,708 by a collator comparing the Sigma-Chron's own trace against the roll, and the discrepancy ran to some four hundred readings. Marrowby's defense — that the trace and the roll agreed, and that the question of where he stood while they agreed was not a logging question — was rejected, and his entries for the period were struck. The episode is the reason the five-field entry now includes the station, and the reason the station field is checked against the Vertical Tram Line Sigma's passenger rolls.

Sigma-class logging is not to be performed in the reading galleries above the ninth landing. The galleries are unventilated, and the ink does not dry.