If you’ve ever downed a pint at the John Snow, in London’s Soho district, you may have walked right past the water pump mounted on Broad Street. What at first might appear to be an unremarkable fixture played a key role in medical science. In 1854, Londoners were dying at a rapid rate. The culprit was thought to be miasma, or bad air, but Dr. John Snow—in whose honor the pub is named—had a different theory. He suspected that diseases could travel in water. Via careful mapping, he traced the…
