My first exposure to dowsing was watching an older gentleman using an L-shaped brass rod to accurately pinpoint both the location and the depth of an underground electrical conduit.
I have thought many times about this experience. Over the years it has become evident dowsing actually works, and that it has been used throughout history by ancient civilizations in locating treasure and in locating underground water sources.
Throughout recorded history dowsing has been mentioned in written texts. The first mention I have found is in Deuteronomy 18:10 where divining is equated to idolatry in 1600 BC. More recently Martin Luther also made the same comparison in the 1500's. Unfortunately, due to a lack of understanding it is still considered by many to be some type of satanic force acting on the dowsing device, or pseudoscience.
I am sure ancient civilizations did not understand the scientific explanations, or theories, as to how dowsing works. I do think the evidence suggests they were successful in applying the applications such as finding underground water as well as precious metals. I would be very interested in seeing their dowsing equipment.
My first device was a commercial long-range locator. It worked great with limitations far too numerous to be very useful. After I understood the theory of operation I made my own using over the counter parts with a portable frequency generator. It worked much better, but still got too many false readings for meteorite location. I have spent many hours over the past 20+ years building and using dowsing rods, and in understanding the dowsing theory of operation.
I am amazed there has never been a legitimate scientific investigation into the actual science of dowsing. I suspect there have been so many fraudulent claims science has never viewed it as a serious field. Also, the fear and lack of understanding of an unknown force actually causing rotational movement has prevented a more widespread understanding and use.
No, you won't find water using only a brass rod. A brass rod will respond only to the metals of the alloy of the rod which are basically copper and iron. Also, the energy field of the human operator is induced into the rod so the rod will offer a slight response to other human beings.
A simple test is to purchase a 3 foot by 3/16 inch diameter welding rod, cut off an inch or so, and bend a 4 inch, 90 degree ell at either end. Lay the 1" piece on the ground while loosely holding the 4" ell . The rod will point to the piece on the ground. I think it will work for everybody.