01
Preface — the oldest clock on Earth
READ AT SLACK WATER
No engine drives it and no hand winds it. The tide is the one machine that has run without pause since the sea was young — and the only clock that has never once been wrong. This bulletin is a field guide to its face.
- Period, principal lunar
- 12 h 25 m 14 s — the M2 constituent, the metronome
- Governing body
- One (1) moon, gravitational, no moving parts
- Service interruptions
- None recorded in ≈ 4 billion years of operation
- Accuracy
- Predictable to the minute, a century in advance
02
The Six-Hour Pulse
SCROLL TO RUN THE CLOCK · T+48 H
A tide is not a wave that arrives. It is the whole ocean tilting — six hours and twelve minutes up, the same back down, in a rhythm set 384,400 kilometres away.
Keep scrolling and the Bureau's pen will trace two full days of water: the great lunar swing, shaded by its solar and diurnal undertones.
03
The Engine, in Eight Positions
ONE ORBIT · 29.53 DAYS · READ LEFT TO RIGHT
AT POSITIONS I & V, SUN AND MOON PULL TOGETHER — SPRING TIDES
AT III & VII THEY QUARREL — NEAP TIDES
04
Where the Sea Swings Hardest
STATION INDEX · MEAN SPRING RANGE, DESCENDING
In the open ocean the tide is a polite half-metre. Funnel it into the right bay and it becomes a five-storey building of water, arriving and leaving twice a day, on schedule.
RANGES ARE MEAN SPRING VALUES, ROUNDED TO 0.1 M
HOVER A STATION FOR ITS SIGNATURE
THE MOON DOES NOT hurry, AND THE SEA DOES NOT wait.
MOTTO OF THE BUREAU · CARVED ABOVE THE DOOR, 1893