10 The Compass Goes to Sea 1117 IT WAS LITTLE MORE than a magnet floating in a bowl of water, but without the nautical compass the millennium's great voyages of discovery could never have occurred. First used in feng shui (the Taoist system of environmental design), compasses appeared in China in the 4th century B.C. Lodestone pointers were replaced by flat slivers of iron, and then by needles, which arrived in the 6th century A.D. But the first account of seagoing compasses doesn't come until 1117, from Zhu Yu's P'ingchow Table Talk: "In dark weather, sailors look at the south-pointing needle." The compass reached Europe around 1190, almost certainly from China. (Its powers were so little understood that captains forbade their crews to eat onions, which were thought to destroy magnetism.) For Mediterranean sailors, used to long periods when overcast skies made navigation difficult, the device meant liberation. By the 15th century, they were ready to venture be- yond familiar seas.