Eigenvalue Enthusiast T-Shirt

Once upon a time there was a river, and next to the river was a village. The river did not flow from north to south nor east to west. Neither did it flow from south to north nor west to east. It just flowed the way it did and the villagers never gave it a moment's thought. This because all roads in the village lay either parallel to the river or at right angles to it. If a stranger appeared, say, asking directions to the wenchkeep, a villager might respond thusly: "you walk toward the river three blocks, along the river for four blocks, then away from the river for a block." Then the villager would beam, proudly hooking thumb though a buttonhole in his woollen over-shirt, "there may you procure the finest wenches in all the land." One day the King came to town...