The dial and pointer devices upon which we depend in the modern world had originated in China by the third century AD. They were geomantic compasses, used for consultation on such questions as to where a house should be built, or a city laid out. Of course, much was superstition, but at the basis of the practice was the phenomenon of the north-south alignment of the magnetized magnetic needle. The fantastic array of readings which were possible to a geomancer's compass may be seen here, though this is by no means the most complicated. Some are known with forty concentric circles of readings. The outermost circle here marks the twenty-eight lunar mansions. The next circle is marked in the'New Degrees' of 360' adopted for the'circle under Jesuit influence, indicating that this compass cannot be earlier than the seventeenth century. A full description of the readings is obviously impossible in the space available. (Science Museum, London.)

A detail of an illustration showing the selection of the site for a new city. The geomancer studies his geomantic compass, which rests on a folding table. From Imperial illustrated Edition of the Historical Classic.