John Snow and the Broad Street Pump

1854 CE — British Isles, Victorian Britain

Today: Soho, London

Cholera killed by the hundreds of thousands as it spread out of India along the new steamship and railway routes, and everyone knew it travelled in bad air. A London physician, John Snow, doubted it, and when an outbreak killed 600 people in a few streets of Soho he mapped every death, found they clustered around one water pump, and had the handle removed. He could not prove why — germ theory did not exist yet — but the map did the arguing. The pump was fed by a well dug three feet from a leaking cesspit.

Worth knowing: The authorities put the pump handle back once the outbreak subsided, because they did not accept his explanation. It took another thirty years and a German bacteriologist to prove Snow right, by which time he had been dead for a quarter of a century.

Pattern: Pandemic — A pathogen spreads through a population and reshapes its demography, economy, and beliefs at once.

Entry 192 of 240 in Precedent, a walk through the whole human story in order.