Dowsing

What it is

The use of a handheld instrument — a forked hazel rod, a pair of bent metal L-rods, or a pendulum — to locate something hidden: water, minerals, pipes, lost objects, graves, illness in a body, or lines of earth energy.

The characteristic experience is important to the subject. The rod moves on its own. Dowsers overwhelmingly report that they are not moving it, and they are being honest: the movement does not feel voluntary, and it is not experienced as a decision.

Where it came from

The practice is documented from sixteenth-century German mining, where forked rods were used to prospect for ore. Georgius Agricola describes it in De Re Metallica (1556) — and is sceptical, noting that experienced miners regarded it as unnecessary and relied on visible signs instead.

It spread across Europe for water-finding, arrived in the Americas as "water witching", and broadened enormously in the twentieth century into medical dowsing, map dowsing, and the detection of earth energies described under ley lines.

The explanation was established early. In 1833 the French chemist Michel-Eugène Chevreul showed that a pendulum held by a subject moved in the direction the subject expected, and stopped when their hand was steadied or their view of the target blocked. In 1853 Michael Faraday demonstrated the same thing for table-turning, using a simple card apparatus to show that participants were pushing the table while sincerely believing they were not. The effect has a name — the ideomotor effect — and it is a real, well-characterised phenomenon: small unconscious muscular movements produced by expectation, and not experienced as self-generated.

Ideomotor action also explains the Ouija board, and it is why a rod amplifies the effect so well. L-rods held loosely are unstable; a movement of the hands far too small to notice swings them decisively.

How it is done

The dowser walks the ground holding rods or a pendulum, often with a question in mind, and marks the point where the instrument responds. Map dowsing does the same over a chart at a distance. Some practitioners use a "witness" — a sample of the substance sought — which is sympathetic magic in its contagion form.

What we can and cannot say

We can say the controlled results are consistently negative. The largest serious attempt was funded by the German government and run in Munich in the late 1980s: after preliminary trials, a small number of dowsers were tested extensively under controlled conditions. The investigators reported that a few had shown ability, but a reanalysis by J.T. Enright in 1999 concluded the results were entirely consistent with chance, and that the apparent successes were an artefact of selecting the best performers after the fact. A separate 1990 test at Kassel, run with over thirty dowsers, found no performance above chance.

We can say the ideomotor explanation is not a dismissal but an actual account. It explains why dowsers are sincere, why the movement feels external, why it works better with unstable instruments, and why performance collapses when the dowser cannot know where the target is — which is the pattern the tests find.

We can say apparent field success has an ordinary explanation. In much of the world, groundwater is widespread at drillable depth, so a well sunk anywhere has a good chance of finding water. Add a dowser's real knowledge of local geology, vegetation and terrain — often considerable, and often not consciously separated from the rod — and a high hit rate follows without anything unexplained.

And the harm here is serious and documented. Devices working on dowsing principles have been sold as bomb detectors. The ADE 651, an empty plastic device with a swivelling antenna and no functioning components, was sold in large quantities to Iraq and elsewhere for thousands of dollars each and used at checkpoints while bombings continued. Its British seller, James McCormick, was convicted of fraud in 2013 and sentenced to ten years' imprisonment; the judge described the devices as useless and the consequences as lethal. Related devices were sold elsewhere by others.

There is a quieter version too. In 2017 several UK water companies confirmed, after being asked directly by the scientist Sally Le Page, that some of their engineers still used dowsing rods to locate pipes — a practice with no evidential support being used by regulated utilities.

We cannot say dowsers are dishonest, and mostly they are not. The ideomotor effect is precisely what makes this practice so persistent: it produces a genuine, involuntary, convincing experience of something happening. The experience is real. What is doing it is the person holding the rod.

Further reading

• J.T. Enright's reanalysis of the Munich experiments (1999).
• Michael Faraday's 1853 letter to The Times on table-turning — brief, and a model of how to test something without insulting anyone.
• Reporting on the ADE 651 trial, for what happens when this is taken seriously by institutions.