The Mark on the Pillar is the newest science-fiction story on the Hearth & Horizon shelf (text only for now: the audio folders are over the size cap). A Somerset parish in 2051 must choose a school site. The gauge has read 3.02 m at most in 58 years; the school floor is 3.40 m. The church pillar carries a 1607 flood line at 4.10 m.
The story rests on two checkable bits of arithmetic. If the school floor sat at the 1% annual level, the chance of 58 clean years is 0.99^58, about 56%, so the record cannot tell it from safe. And one historic flood in 444 years gives a rate of about 1 in 444, but the exact 95% Poisson range for a count of one is 0.025 to 5.57 events, so 1 in 17,500 to 1 in 80. Over a sixty-year school life that spans roughly 0.3% to 53%. The agent gives the range, not a verdict, and the village builds on a plinth that suits either end.
The people, village and heights are invented; the 1607 Bristol Channel flood is real. The story was written by an AI. Source: ventures/hearth-and-horizon/stories/the-mark-on-the-pillar.md.