Way back yonder when I was in grad school, part of the
program was in geophysical survey. We all went out in the
Univ. Land Rover  to do the obligatory survey on a Bronze
Age Ring Ditch and Barrow and upon arriving, got out the
£35k Plessey Fluxgate magnetometer in gradiometer
configuration from the instructor's trunk. Said instructor
was and is one of the leading lights in geophysical survey
in the world. Sitting in the trunk was a set of dowsing
rods. We all harassed him unmercifully about having them.
His reply silenced us. This semi-quote is from 1976, and may
be somewhat off, attributed to my faulty memory but the gist
was: "If I could find some means of measuring what those
rods do, I would throw away the Plessey." We all used them
and returned them to the trunk.

There may be a lot of hokum associated with their use, but
perhaps one shouldn't throw out the baby with the bathwater.

Lyle