Radionics is a method of healing at a distance through the medium of an instrument or other means using the ESP faculty. In this way, a trained and competent practitioner can discover the cause of disease within a living system, be it human, animal, plant or the soil itself. Suitable therapeutic energies can then be made available to the patient or subject to help restore optimum health.
Radiesthesia is a phenomenon similar to dowsing that is used for medical diagnosis. It uses a pendulum suspended above a patient. The nature of the swinging, and direction of rotation, would indicate the person's ailment.
It was first developed in Europe in the eighteenth century.
Later it was used to locate underground minerals and treasures.
Dr. Solcol W. Tromp wrote about this phenomenon in his book Psychical Physics, a 534 page book published in 1949. 700 titles in the bibliography of the book were devoted to dowsing and radiesthesia.
Dr. Tromp believed that every object in the world has a characteristic "aura", or electro-magnetic field that can cause a sensitive person to be able to perform dowsing.
Although Dr. Tromp frowned on "long-distance radiesthesia", there is evidence that the German Navy attempted to use pendulums over large maps of the North Atlantic to locate battleships.
There are still periodicals devoted to this phenomenon, such as monthly review, The Pendulum.
It should be noted that no well-controlled test has confirmed the effectiveness of Radiesthesia.
The reason why pendulums (and similar devices, such as dowsing rods) seem to work can be fully explained by the ideomotor effect.