Elizabeth Yale

Color—its chemical basis, how our minds perceive it, how one color transforms into another—has fascinated scientists and scholars for millennia. In 1664, British natural philosopher Robert Boyle tried to make sense of it with his book Experiments and Considerations Touching Colours. In “Experiment X,” he described a 17th-century scientist’s practical joke, astonishing visitors to his laboratory by asking them to wet their skin with spit and then rub silver nitrate, a white compound, on it. On his guests’ white skin, the silver nitrate instantly turned a deep, indelible black, “as if the stains had been made with Ink.”

In 1842, Charles Darwin and his wife Emma moved their young family to Down (now Downe), a village about 15 miles south of central London. They were seeking a country retreat, a place to raise their children away from the city, where the air was filled with coal smoke and the streets with sewage. But Charles also sought a sanctuary for his scientific work: a place far off enough from London to deter casual visitors.