ON the west coast of Scotland, facing out across the Firth of Clyde towards the Isle of Arran, there stands a wall of thorns. It is manmade, but otherworldly, like a vision from a Gothic fairy tale. Its dark tangle of barbs reaches up to a height of 30ft and stretches more than 100ft across. Is it an art installation? A giant instrument of torture on the outskirts of Ayr? The correct answer is far simpler: it makes salt.
The history of salt
