THE ANCIENT and esoteric art of dowsing, or divining, consists of holding a pair of outstretched rods - traditionally a forked branch of hazel or willow, but a wire coat-hanger or a pair of knitting needles will do in an emergency - which when manipulated by the diviner, twitch or incline towards a place where lies a concealed spring or a metallic lode. The attitude of scientists to this practice could best be summed up in the forthright words in another context of the great American news editor H. L. Mencken: "Nine times out of ten, there is actually no truth to be discovered - only error to be exposed."
If and how dosing works has been hotly debated over the years. In the majority of tested cases the results have proved almost entirely negative, but a few dowsers are successful often enough for the phenomenon not to be totally dismissed as chance, coincidence or subterfuge. Indeed the technique has a faithful following in parts of the commercial world, particularly in the mining industry in some countries where it is presented as the BPM Technique, the "Bio-Physical Method".
Insofar as explanations have been sought, most focus on the assumption that dowsers are for some reason unusually sensitive to the earth's magnetic field, and pick up very small changes in it cause by water or metal underground. By this theory, when such persons detect a magnetic anomaly, it, sends a signal to the dowser's musdes, which experience a small contraction causing the lightly held dowsing-rod to deflect. Other experimenters claim that dowsers respond to anomalous electrical fields in the vicinity, which they say affect their blood pressure and pulse rates.
Adherents to the former view received a boost some time ago when researchers at the Californian Institute of Technology announced that they had identified in human brains tiny crystals of magnetite, the iron oxide that helps migrating birds to navigate. Experiments are still going on to discover if this might give humans an unconscious and rudimentary directional sense, similar to that enjoyed by homing pigeons. Dowsing enthusiasts, however, say that this new discovery may well be the basis of their gift.
The idea is that some individuals may be more generously endowed with magnetite than others, which, enthusiasts maintain, would explain why some people are dowsers while others achieve no reaction whatsoever. Critics, on the other hand, remain adamant that successful dowsing owes more to a thorough knowledge of the local geology that to any innate ability to detected magnetic or electrical anomalies in the vicinity.