Surveyors’ Atrium

Surveyors' Atrium is the formal designation of Floor 317, a cartographic and spatial-reconciliation floor occupying the north-eastern quadrant of the Tower's three hundred and seventeenth storey. It is the seat of the Office of Spatial Reconciliation, the archival repository of the Surveyors' League, and the customary meeting-place of the Guild of Surveyors and Calibrators during those sessions the Guild declines to hold in its own administrative spire. The Atrium is among the most frequently revised floors in the Tower; its plan has been officially superseded eleven times since Year 588, though visitors continue to navigate by the original.

Layout and function

The Atrium is a single vaulted hall roughly four hundred paces on its long axis, ringed by measurement bays, calibration alcoves, and a locked scriptorium in which the primary resonance ledgers of the Surveyors of Transience are held under seal. The hall's floor is inlaid with a graduated meridian of brass and basalt, re-laid in Year 602 to correct an accumulated drift of some nine inches; the correction is recorded on a small plate at the threshold, which reads, in full: Meridian re-set. Do not measure from the old meridian.

Bays are assigned by seniority of measurement, not seniority of surveyor, a distinction the Guild of Surveyors has disputed in writing at least six times. Each bay carries a numbered plate corresponding to the floor's internal inventory, and the inventory is maintained in triplicate, one copy retained in the bay, one submitted to the Atrium's office of record, and one forwarded to the archives on Floor 317 proper, since the Atrium is the floor and the floor is the Atrium, and the duplication is therefore unavoidable.

The Office of Spatial Reconciliation

The Office of Spatial Reconciliation occupies the eastern apses and is charged with reconciling the measurements submitted by certified surveyors against those already catalogued. In practice the Office reconciles the surveyors against one another. Its ruling of Year 641, issued after the winter the north aisle was found to be four feet shorter on Tuesdays, established that a measurement may be altered (a) once, (b) in writing, and (c) only by an officer of the Guild of Surveyors and Calibrators. The same ruling permits a surveyor to file an unchanged measurement, but requires a fee, as the Office considers an unaltered submission to be a claim the surveyor has not troubled to examine.

"Where two measurements of the same span are submitted in the same week, the Office shall prefer the later, unless the earlier was taken in the presence of a witness, in which case both shall be returned for re-taking on a dry day."

— Fourth Concordance, Annex 12, clause 4

The League's archive

The archival records of the Surveyors' League are maintained in the sub-stacks beneath the western bays, accessible by a stair the Atrium's plan labels Service Stair C and the sub-stacks' own plan labels Principal Ascent. The League was dissolved in Year 588, and its records passed into the custody of the Surveyors' Guild, which maintains them in place rather than relocating them, on the ground that the League's surveyors measured the stair frequently and would object. The Topographical Surveyors are the only body permitted to take new measurements in the sub-stacks, and they are required to submit one copy to the Atrium archives and one to the Guild's own store, where the two copies have not agreed since Year 613.

The disposition dispute

Scholars disagree as to whether the Atrium is properly a floor with an office on it or an office that has been granted a floor. The Third Concordance treats Floor 317 as an administrative division of the Tower and the Atrium as its furnished interior; the Ninth Concordance, Annex 2, reverses the relation, describing the floor as "the floor of the Atrium, being the Atrium extended to the walls." The Office of Spatial Reconciliation has declined to resolve the question, noting in a minute of Year 649 that it would have to measure the floor to do so, and that the measurement would then require reconciliation. The Chronicles of the Mutable Atrium record the dispute as ongoing and, in the same entry, as settled.

A further dispute concerns the resonance bay. The Surveyors’ Revolt led to allegations of hoarding primary resonance data by the Surveyors of Transience, and the bay was sealed pending inquiry. The seal has never been lifted, though the inquiry concluded in Year 597 and its findings are filed inside the bay. Access is granted twice yearly to a named officer, who is instructed to retrieve the findings and does not.

Access and notes

The Atrium is open to all surveyors of certified standing between the hours of the first and ninth bell. Non-surveyors may enter on the arm of a surveyor of certified standing, or on written application to the Office, and must remain within the visitor's aisle, which is marked in ochre. The ochre is renewed each spring. Visitors are asked not to step over the meridian.

Maintenance of the Atrium falls to the eastern apses, which also hold the keys to the west. The arrangement is recorded in the office inventory under the heading Keys, custody of, anomalous, and has not been altered since it was first found to be anomalous in Year 571.