How Does It Work
The short answer is that no-one really knows—it just does!
The scientific world, geologists and archaeologists and so on appear to put their heads in the sand because here is something that cannot be PROVED nor can it be DISPROVED scientifically. However it is surprising how many water, mining, oil companies and so on use Dowsers in exploration work-- it is never admitted because it may take away the credibility of the large concerns.
All that can be said that it is an inbuilt ability within man from the beginning of time, it helped him to find his food and water and his minerals. Gradually over the centuries our so called sophistication and civilization etc. have stifled these natural abilities, plus, of course , condemnation by the Church particularly in the period of about 1610 until the late 1700's and even today when it was and is, by some , considered the work of the devil. I firmly believe that it is some primeval and natural instinct that lies deep within us all, the Mind which has the ability to receive communication from the Universal Mind that knows and controls everything that their has ever been, that there is and ever will be –GOD. I firmly believe that it is a God given gift—to everyone who is prepared to develop and use it.—to be used for the benefit of our fellow man and the world in which we live.