As civilisation advanced, and the value of the metals, of coal and salt, came to be more and more appreciated, nothing could be more natural than the desire of no longer relying upon the discoveries of chance or upon the mines bequeathed by former ages, but of sounding the mysterious recesses of the earth, and forcing her, by dint of patient exploration, to reveal the riches she conceals under her surface. Thus, as far back as the eleventh century, the _divining_ rod came into practice, and found full credence in a superstitious age. A forked branch of the hazel-tree, cut during a peculiar phase of the moon, was the means employed in Germany for the discovery of buried treasures, of veins of metal, of deposits of salt, or of subterranean sources. But the miraculous rod did not indiscriminately show its powers in every hand; it was necessary to have been born in certain months, and soft and warm— or, according to the modern expression, _magnetic_—fingers were indispensable for handling it with effect. The diviner possessing these necessary qualifications took hold of the rod by its branches so that the stem into which they united was directed upwards. On approaching the spot where the sought-for treasure lay concealed, the magical rod slowly turned towards it, until finally the stem had fully changed its position and pointed vertically downwards. To increase the solemnity of the scene, the wily conjurors generally traced magical circles that were not to be passed, burnt strong smelling herbs and spices, and uttered powerful charms to disarm the enmity of the evil spirits that were supposed to guard the hidden treasures. At present, the divining-rod has lost its old reputation, and more rational means are employed for the discovery of mineral wealth. Relying on experience, tact, and geological knowledge, the investigator carefully examines the country where ores or coal are supposed to be concealed, and having fixed upon an appropriate spot, has recourse either to experimental digging or to boring for testing the truth of his opinion. These expensive explorations, though often unsuccessful, frequently prove highly remunerative, and many a saline spring, or coal seam, or metallic vein would, without their assistance, have remained unknown and unproductive.