Præsidium

First Appearance and Context

Accounts describe ascending within the tower toward the rooftop Starhenge and, on descent, encountering a portcullis supervised by the Master of the Keys. Observers have noted periods—such as during Apert—when multiple corner‑tower gridirons stood closed at once, temporarily sealing the stair. The summit vault spans the top of the tower with power shafts penetrating the stonework; a stair coils around the largest shaft to a controlled door that opens onto the roof of the Mynster.

Access and Structure

• Upper access is gated by portcullises; when sealed, the buttress stair is inaccessible and the upper Præsidium is off limits.
• The belfry sits in the lower reaches of the Chronochasm; a small maintenance room near the bells shelters part of the ringing mechanism. From the Fendant Court, a ladder rises to this room and dead‑ends there, allowing bell maintenance without permitting ascent higher into the tower.
• The bells are open to the weather above this maintenance space. An old ventilation opening was boarded, leaving only a pinhole that, when the room is darkened, projects a small image of the sun onto a screen.

Functions and Use

• Timekeeping hub: the tower carries the great dials and mechanically couples rooftop instruments to the clock through vertical shafts.
• Bells and changes: the carillon can strike automatically at the hour; for rites and signals, ringers disengage the mechanism and ring changes manually. These changes include the distinct patterns that summon the community for Voco.
• Camera obscura workspace: when darkened, the machinery room near the carillon serves as a camera obscura. Using architectural drawings of the Mynster and direct measurements of the aperture‑to‑screen geometry, avout have used projected tracks to quantify angular changes in a sky‑borne object’s path, refining an inferred orbital inclination to roughly fifty‑one degrees relative to the equator.
• Administration: access patterns to the upper works are scheduled and enforced by the Master of the Keys and, when required, may be tightened to seal the stair entirely for a period.

Descriptions/Characteristics

• Central stone tower with high clock dials and an interior stair rising through tracery walls to the roof.
• An inward‑curving vault spans the summit; power shafts pierce the stone to drive and be driven by rooftop instruments.
• Below the bells, a compact machinery room provides shelter for parts of the ringing apparatus and ad‑hoc workspace for maintenance and observation.

Current Status

Active and central to timekeeping and observation. During periods of restricted access, the portcullis and buttress stair have been held closed so that the upper works remained off limits; the ladder route from the Fendant Court to the carillon level continued to be used for bell maintenance and practice. The automatic striking mechanism continues to engage at the hour, with manual ringing for special observances. Observational work using the camera‑obscura setup has been undertaken here to support trajectory measurements when rooftop access is limited.