The New Yorker:

As the oceans ebb and surge, staggering ingenuity has gone into inventing the measure.

By Brooke Jarvis

In the mid-fifteen-hundreds, a Swedish peasant named Nils lived on an island called Iggön in the Baltic Sea. He was known to his neighbors as Rich Nils, apparently because of the plenitude of fish in the waters near his home and, even more lucrative, the seals that showed up to hunt them. There was one rock in particular where seals liked to haul themselves out of the ocean to rest and bask in the sun. Nils, for his part, liked to visit this rock with his harpoon.

Eventually, though, Nils noticed that the seals had begun gathering on a lower part of the rock, rather than on the high point, as they once did. It seemed that the water level no longer gave them access to the very top. This was a troubling development for Rich Nils’s income: the high point now obstructed the path of his harpoon when he approached the rock from the shore. Nils used fire to weaken the rock, chipping away at it until he’d not only removed the high point but also lowered the over-all height of the rock, so that seals would be able to rest on it even when the sea reached its lowest level of the year.

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