VIRGULA DIVINA, or Baculus divinatory, &c. a forked branch, in the form of a Y, cut off an hazel-stick, by means whereof people have pretended to discover mines, springs, &c. under ground. The method of using it is thus: The person who bears it, walking very slowly over the places where he suspects mines or springs may be, the effluvia exhaling from the metals, or vapour from the water, impregnating the wood, makes it dip or incline, which is the sign of a discovery.
Some dispute the matter of fact, and deny it to be possible. Others, convinced by the great number of experiments alleged in its behalf, look out for the natural causes thereof: The corpuleles, say those authors, rising from the springs or minerals, entering the rod, determine it to bow down, in order to render it parallel to the vertical lines which the effluvia describe in their rise.
The famous Father Kircher, in his Mundus Subterraneus, in which many interesting particulars are found concerning mines, derides these practices, and denies, from his own experience, the truth of the assertions concerning them. He seems, however, to have some faith in sympathies, and proposes even new divining wands of his own invention; the effects of which, though more dependent on physical causes, are not, however, more certain. He believes, for instance, that a wand, one end of which should be made of sal gem, and the other of wood, being suspended and balanced above a mine of salt, would be inclined towards the ground; and he supports his opinion by an experiment. This experiment consists in evaporating over the fire a solution of sal gem below the wand, which is by this means really made to incline. We need not be deeply learned in chemistry to discover, that the wand would have inclined in the same manner if Father Kircher had evaporated pure water instead of a solution of sal gem; because the water would have equally well attached itself to the saline end of the wand; consequently this experiment proves nothing.
The same author proposes also to discover mines of
mercury by employing a wand, one end of which is made of gold, and the other of wood, in hopes that the emanations of the mercury would attach themselves to the gold rather than to the wood, and would make it incline downwards. But this effect certainly cannot be produced unless the mercury was evaporating; for which purpose two conditions are necessary: 1. The mercury must be in a native metallic state, and not mineralised, as it is in cinnabar; and, 2. it must also be exposed to the heat of some subterranean fire, by which it is volatilised and sublimed, the ordinary heat of the earth being far too little for this purpose. This second physical or chemical divining wand proposed by Father Kircher is therefore no better than the former; and probably the same judgment may be passed upon all other wands made upon the same principles and in imitation of these. Lastly, the same author positively affirms, that he hung and balanced a wand, one half of which was made of alder-tree, and the other half of some wood that has no sympathy with water, over a subterranean water, and that he observed the end of the wand incline towards the earth.