The beaches of Orkney are thick with seaweed. Worthless today, two hundred years ago seaweed meant wealth and well-being to the inhabitants of these windswept islands north of Scotland.
Air-dried, then burned in shallow sand pits until it liquefied and hardened into cakes, seaweed was a source of alkali, a substance critical for making glass and soap. The product was called "kelp," after one abundant seaweed. The Orcadians sold it to the British, whose usual source of alkali had been cut off by the Napoleonic wars.