Stack 451

Stack 451 is a catalogued floor of the Tower, designated on the spine-marks of its eastern staircase as a restricted-consultation stack and administered since at least the ninth century under the standing provisions of the Concordance of Assigned Numbers. It holds no collection of its own. Stack 451 is a stack of stacks: its shelves carry not books but the sealed accession ledgers of four hundred and twelve other floors, each ledger itself uncatalogued, so that the floor's holdings cannot be read without first consulting the ledger for the ledger, which is kept elsewhere and is not on Stack 451.

The floor is numbered, named, and — uniquely among the floors between the third and ninth galleries — cross-referenced against itself in the master index, a clerical error first recorded in the winter of 1128 and never corrected, on the ground that correction would require a Concordance.

Layout and access

Stack 451 occupies an irregular octagon measuring roughly forty by thirty paces, its north wall built into the flank of the Vertical Vector rather than parallel to it, so that the shelving converges toward the eastern stairwell and the last bay on each tier is narrower than the first by the width of a hand. Access is by the eastern stair only. The western stair was bricked in during the Recess of the Ninth Gallery and the brickwork has never been approved for removal; the Department of Stack Integrity has twice measured the wall and twice declined to certify it.

Consultation is permitted to holders of a Second-Tier Reading Warrant and requires the presence of a duty clerk, who is not permitted to assist. A notice fixed at the head of the stair since 1402 reads, in full:

"Readers are reminded that the ledgers of Stack 451 may be consulted but not opened, that the opening of a ledger is governed by the Ordinance of Closed Ledgers, and that the duty clerk has not been issued a key."

— Stack Notice 451-E, affixed 1402, reaffixed 1587

The Highfield recension

The floor's modern history begins with the survey of the clerk Annet Highfield, who between 1601 and 1604 attempted the first complete reconciliation of Stack 451's four hundred and twelve ledgers against the master index. Highfield's method — checking each ledger's spine against the index entry, then the index entry against the shelf, then the shelf against the spine — produced a closed loop in which every ledger was verified against nothing but itself. The survey was nevertheless accepted in full, and Highfield's recension remains the authoritative account of the floor. It records three hundred and ninety-eight ledgers. The floor's own count records four hundred and twelve. Neither figure has been revised, and readers are directed to consult whichever suits their warrant.

Highfield is also the source of the floor's most-quoted observation on its own holdings, in a memorandum to the Office of the Spine dated 12 November 1603: "The ledgers are all present and none of them can be shown to be present." The Office did not reply. Highfield died in 1611 and is buried, by the floor's own account, in the western stairwell.

Dispute over classification

Stack 451's standing is contested. The Third Concordance, Annex 6, holds that a floor holding only records of other floors is a derivative stack and takes its classification from the deepest floor it describes — which, on any reading, would make Stack 451 an Archive Stack and subject it to the completion requirements of the Sealed Stack provisions. The Fifth Concordance, Annex 2, holds the opposite in a single sentence: that a stack which describes all stacks cannot be a stack, and must therefore be an appendage of the Department of Stack Integrity and not a floor at all.

Practice has split the difference without resolving it. The floor is taxed as a stack, heated as an appendage, and appears in the Register of Standing Floors under both headings, at folios 88 and 91. Aris of the West Stack was asked to arbitrate in 1810 and declined, observing in his reply that the question was "of no consequence to anyone who has not tried to leave by the western stair."

The Möbius question

Because Stack 451 is at once a floor holding ledgers, a floor described by its own ledgers, and a floor whose description of itself is among the ledgers it holds, successive Librarians have proposed it for classification under the Möbius Stack designation — the administrative category for stacks both central and sealed at once. The designation has never been applied. The Department of Stack Integrity's survey of 1907 found that Stack 451 is not a Central Stack, since nothing is central to it, and not a Sealed Stack, since readers enter it daily; and concluded that it was therefore, in the surveyor's words, "not a Möbius Stack, but something the category had not anticipated." The file was closed without a finding and has been reopened three times.

Recent incidents

In 1953, during the Provisional Stack Relocation (1952-1954), a portion of the floor's third tier was moved to relieve pressure on the eastern staircase and moved back the following spring, the relocating officers having discovered that the ledgers on that tier belonged to floors which had themselves been relocated. The floor's shelves were returned to their original order, with the exception of the narrowest bay, which has since held nothing.

The duty clerks maintain a separate grievance, filed in 1788 and never heard: that the monthly heating inspection requires the ledger room to be unoccupied, and that the room cannot be cleared because clearing it requires the duty clerk, and the duty clerk cannot enter during the inspection, and the inspection cannot proceed until the room is cleared. The grievance is entered on the floor's own shelf list under Accession 451-0, which is itself one of the four hundred and twelve ledgers, and cannot be read without opening it.

Readers are asked to leave the eastern stair as they find it. The door does not lock.