"5. Careful and critical examination shows that certain dowsers (not all in whose hands the twig turns) have a genuine facility or faculty for finding underground water beyond that possessed by ordinary well-sinkers. "Part of this success is due (1st) to shrewd observation and the conscious and unconscious detection of the surface signs of underground water. (2nd) A residue, say ten per cent or fifteen per cent of their successes cannot be so explained, nor can these be accounted for by chance nor lucky hits, the proportion being larger than the doctrine of probabilities would account for. "This residue no known scientific explanation can account for. Personally, I believe the explanation will be found in some faculty akin to clairvoyance; but as the science of to-day does not recognize such a faculty, I prefer to leave the explanation to future inquirers, and to throw on the skeptic the task of disproving my assertions, and giving his own explanations." This unexplained residue, "akin to clairvoyance," as admitted by a scientist of to-day who wears a top-hat and rides in taxi-cabs, clothes the divining rod in the same alluring mystery which so puzzled those childlike and credulous observers of remote and misty centuries. The Abbé de Vallemont, writing in 1697, found the problem hardly more difficult to explain than does this Professor of Experimental Physics in the Royal College of Science. The wise men of the seventeenth century strove hard to comprehend the "unexplained residue," each after his own fashion. Michael Mayerus, in his book entitled _Verum Inventum, hoc est, Munera Germanæ_, claimed that the world was indebted to Germany for the invention of gunpowder, and stated that the first wood-charcoal used in its manufacture, mixed with sulphur and saltpeter, was made from the hazel tree. This lead him to refer to the sympathy existing between hazel wood and metals, and to add that for this reason the divining rod was made of this particular wood, which was peculiarly adapted to the discovery of hidden gold and silver. Philip Melanchthon, 1497-1560, famously learned in Natural Philosophy and Theology, discoursed on Sympathy, of which he recognized six degrees in Nature, and in the second of these he named that sympathy or affinity which is found to exist between plants and minerals. He used as an illustration the forked hazel twig employed by those who search after gold, silver, and other precious metals. He attributed the movement of the rod to the metallic juices which nourish the hazel tree in the soil, and he was therefore convinced that its peculiar manifestations were wholly sympathetic and according to natural law.