The Ambulatory Annexes

The Ambulatory Annexes are a class of holdings catalogued in transit, whose location is recorded in the register not as a floor or a room but as a trajectory. They are conceptually secured to the principle of migratory cataloguing set out in Concordance 22, which permits a holding to satisfy its shelving obligation by remaining in continuous and documented motion. At the time of the most recent survey, eleven Ambulatory Annexes were active, four were dormant, and one was itself unsure.

The Annexes should be distinguished from The Ambulatory Annex, a single holding of contested definition, and from the Ambulatory Collection, which is a body rather than a class of holdings and which has never moved anywhere. The distinction is set out at length in Annexes and Outliers and is misstated in roughly one filing in nine.

Registration and the trajectory record

An Ambulatory Annex is registered by trajectory rather than position. The register entry takes the form of a line of bearings, distances and elapsed intervals, endorsed at each floor crossing by whichever clerk is nearest the stairhead. Movement is logged by the Algorithm of Shifting Annexes, which reconciles the trajectory against the Annex's own account of where it believes it has been. Discrepancies between the two are not errors; they are entered in a separate column and settled at the next Delta Measurement.

The Annexes are surveyed biannually at the hinge of winter and midsummer, a schedule fixed under Concordance 31 after the survey of the winter of 4-R went badly wrong. On that occasion three surveyors followed an Annex down eleven floors before establishing that they had been following one another. The report was filed as an incident, the surveyors were reassigned to the Prefecture of Juridical Annexes, and no finding was ever entered against the Annex itself, which had spent the interval on the floor above.

Types of movement

The Annexes do not all move in the same manner. The following inventory was compiled by the survey of midsummer and is reproduced without amendment:

• Four Annexes drift laterally along a single floor, never descending.
• Three descend by no more than one floor per quarter and are considered steady.
• One ascends. Its registration is unchallenged but its floor has not been confirmed since the survey of 4-R.
• Two move only when observed, which the survey records as a difficulty rather than a finding.
• One has not moved in ninety years and retains its designation out of respect for its former behaviour.

Movement is not unlimited. Under stride permitting, no Ambulatory Annex may cross a floor boundary before the third hour after the bell, and none may enter a stairwell occupied by a Courier-Sphere in transit. The rule is observed without exception, although no one has been able to say what would happen if it were not.

The question of the Annexes' status

Scholarly disagreement concerns not the movement of the Annexes but their legal character. The Third Concordance Annexes hold, at Annex 6, that an Ambulatory Annex in continuous motion never occupies a floor and therefore cannot be said to be shelved; it is, properly speaking, in transit always, and its obligation is discharged by the record rather than the room. Against this, Concordance 22 presumes the opposite: that the Annex is shelved wherever it happens to be, and that the trajectory is merely a description of how it arrived there.

"A holding that is nowhere is not a holding. A holding that is everywhere in turn is a route."

— Concordance 22, Annex 3

The dispute has never been resolved and is now older than the clerks who maintain it. The Lost Annexes of the Third were declared lost on the strength of the first reading and recovered on the strength of the second, and the archive has kept both rulings side by side since. A minority view, advanced by Surveyor Arn of the ninth reading room, holds that the Annexes are neither shelved nor travelling but are simply badly recorded, and that the register would settle the whole matter if anyone could find the register. Arn's view has not been adopted, though it has not been withdrawn.

Relation to the monitoring network

The Ambulatory Annexes are watched by a network of monitoring Annexes that do not themselves move. Annex Δ is the best documented of these and reports on the class as a whole; Annex 12-C reports on a subset and its jurisdiction overlaps, unhappily, with that of The Ambulatory Annex, producing a standing dispute over three flights of the eastern stair between the eleventh and twelfth landings. Annex 12c maintains seventeen variant designs for a stabilization cradle, none of which has ever been fitted, since stabilizing an Ambulatory Annex would defeat the purpose of the class.

The class has also been represented at the 309 Committee by delegation, most recently on the question of whether an Annex that has passed through a floor without stopping may claim to have visited it. The Committee has deferred the question twice. Supporting Annexes are invited to attend the next session, provided they arrive by the lower stair, since the upper is under repair.

Practices of care

The care of an Ambulatory Annex is the care of its record. Handlers are instructed to endorse the trajectory at each crossing, to note the hour, and to avoid speculation about the Annex's intentions. Case 745-B established that an Annex may not be held liable for a delay caused by its own movement, and the ruling has since been extended to delays caused by the handler's uncertainty about whether the Annex had moved. Where an Annex's floor and its trajectory disagree, the endorsed trajectory prevails; where both are missing, the matter is referred to the Prefect of Juridical Annexes and, on the Prefect's instruction, to the Logic Weasel, which has on four recorded occasions resolved the question by declining to consider it.

The Annexes are not to be followed below the ninth floor without a countersigned itinerary. This rule has been in force since the survey of 4-R and has been read with approval at every reading since.