Strictly speaking, the term geomancy refers to an ancient form of divination in which, simply put, handfuls of soil or other materials were scattered on the ground, or markings made in the earth or sand, to generate a range of dot configurations which could then be read by a seer.

Practitioner list

See also:
Feng Shui
Geopathic Stress

In the 19th century, however, geomancy came to be applied to the Chinese practice of feng shui by which the location and orientation of houses and tombs was determined with close regard to the topography of the local landscape. The feng shui master or geomant employed a circular magnetic compass, called a iuopan, which was marked off in rings containing data relating to astrology, directions, the elements, landscape forms, times of day, and so on. The aim was to locate a site where the energies or ch'i of the land and sky were brought into perfect balance. The harmony of these energies ensured good fortune.
The science of feng shui recognized that certain powerful currents and lines of magnetism run invisible through the landscape over the whole surface of the earth. The task of the geomancer was to detect these currents and interpret their influences on the land through which they passed.
These lines of magnetic force, known in China as the dragon current, or lung-mei, existed in two forms: the yin, or negative, current represented by the white tiger, and the yang, or positive, current, represented by the blue dragon. The landscape will display both yin and yang features; gently undulating country is yin, or female, while sharp rocks and steep mountains are yang, or male.
It was the aim of the geomancer to place every structure precisely within the landscape in accordance with a magic system by which the laws of music and mathematics were expressed in the geometry of the earth's surface. The landscape itself may be manipulated in order to achieve the harmony sought through the placement or adjustment, or removal, of trees or rocks, or bodies of water. Every feature of the landscape may be contrived to produce an effect which ultimately is perceived as beautiful; indeed, perceived beauty in a landscape may in fact be simply when the lines of the dragon current are in balance.
At the outset, a geomancer must locate the course of the major lines of the dragon current in his or her area. These days, it is claimed that such energy lines can be detected, and traced, through dowsing.
In the 1960s, the ley lines discovered by Alfred Watkins forty years earlier, came to be identified with the dragon lines of Chinese feng shui. This gave a whole new meaning to ley lines which now ceased to be simply straight tracks but in fact mapped on the surface of the landscape lines of energy coursing through the earth. The presence of prehistoric sites - megalithic tombs, stone circles, standing stones - along ley lines indicated that these energy currents were known in prehistoric times and that the sites did not merely mark the route but somehow also tapped into this energy source.
Frequently, important prehistoric monuments occupy sites where two or more ley lines intersect. Also located along these ley lines are sites associated with Dragons and Dragon-killers.
Article by: Chris Witcombe, Professor of Art History,
Sweet Briar College, Virginia, 24595 USA