Wherever there is a mineral load the development of force is in some instances very great. For instance, Mr. R. W. Fox was able, by connecting two lodes with copper wires, and conducting the latter to the surface of the earth, and immersing them in a cell which contained a solution of sulphate of copper, to obtain an electrotype copy of an engraved copperplate. Thus "the earth itself may be made a _battery_," as Robert Hunt says. "We know," he repeats, "that, through the superficial strata of the earth, electric currents circulate freely, whether they are composed of clay, sand, or any mixture of these with decomposed organic matter; indeed, that with any substance in a moist state, electric currents suffer no interruption." The electricity of mineral veins has attracted the attention of some of the first philosophers of Europe, and has led to some highly-interesting experiments with regard to the action of this important agent in the formation, disposition, and direction of rocks and mineral veins. M. Becqueral and others have made use of these currents successfully in imitating Nature in her processes of making crystals and other mineral formations." "It is not, however, necessary to suppose that the agent of which we are treating particularly requires a chemical action to develop it, or the action of the electric force. Experiments have proved that it is developed in every form of material action--that even the substances of the earth, without sensible alteration, exert this force. To this agent the sensitive nerve centres are extremely susceptible. The celebrated Ritter, of Germany, devoted much time to an investigation of this subject, and, in 1809, published Supplementary Treatises upon it, together with Amoretti's celebrated work on the same subject--Physical and Historical Inquiries into Rhabdomancy, &c., in Germany. (See Dr. Ashburner's Translation of Rheinbach, first American edition; Redfield.) Schubert, in his work on Natural History, says, "It seems clear, from many observations, that the whole mineral (and much of the vegetable) kingdom _has a profound and mysterious relation with the organism of man_." "_This_ relation," says Rogers, "is that of matter with matter connected by an imponderable agent." "The phenomena which betray this, as a fact of nature, have been observable from the earliest ages. It is certain, however, that local causes often give developments to such strange phenomena, _that it requires all the science that can be mustered to keep back the tide of superstition which will be thus aroused in the breasts of those unacquainted with the action of these agents_."