Lyell's Oak

In 1835, the Scottish geologist Charles Lyell was in Stockholm gathering evidence for one of the founding ideas of modern geology, that Scandinavia's land was slowly rising out of the sea, a process now called postglacial rebound. To measure how much the land had lifted, Lyell needed a fixed reference point old enough to have been growing when earlier surveyors recorded the water line, and he found one in this oak on Norra Djurgarden, alongside a second oak, Fiskartorpseken, by a nearby royal fishing cottage. He measured the oak's girth and height above the water of Husarviken bay and used its estimated age to help calculate how much the shoreline had shifted, fieldwork now considered a small but real contribution to a theory Charles Darwin would later draw on directly. The oak has kept growing steadily in the two centuries since serving as scientific apparatus: 4.04 metres around in Lyell's own 1835 measurement, 5.20 metres when the Swedish botanist Rutger Sernander surveyed Djurgarden's oaks in 1926, and 6.30 metres by a 2011 measurement, a slow, legible record of exactly the kind of long, undisturbed growth that made it useful to Lyell in the first place.