Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/447

434 phenomena to which I have referred. Some very ingenious experiments by Mr. Robert Were Fox, in which he produced the lamination of clay by long-continued yoltaic action tend rather to the confirmation of this view.

3. The theory of M. Ampère supposes the magnetic condition of the earth to be due to currents of electricity, which traverse the globe from east to west, and it has been thought by those who are inclined to attribute the phenomena of lamination and of chemical change in rocks and minerals to electricity, that those circulating currents are the great agents on which these effects depend. It would, however, appear, that in many cases the effects arise from some merely local cause; and the peculiar conditions must therefore have arisen from some agency originating within confined limits, and to a certain extent independent of the great general electric current. That electric excitation may occur within exceedingly limited areas is quite certain, for we find that no case of chemical action can arise without producing voltaic phenomena, and that exceedingly feeble currents are capable of effecting considerable chemical changes. From a consideration of these matters, the natural inference is, certainly, that the molecular and crystalline structure of the earth's strata are dependent upon some modification of electricity, but it becomes highly necessary that this hypothesis should be examined by the test of experiment.

4. With this view many of the experiments, the results of which are detailed in this memoir, were undertaken, particularly those which relate to the lamination of clay and other substances by very weak voltaic action; and those which describe the decomposition of copper ores under the influence of the same agency. Some of these are only repetitions in modified forms, of experiments made by Mr. R. W. Fox, and published several years since by that gentleman; but they have been considerably extended and tried under such conditions as appeared desirable to remove any source of error likely to affect the results. It became of the utmost importance when entering on an inquiry of this extensive character, in which the absence of intensity of force, had to be met by the introduction of the element Time, that the experiments of other investigators should be confirmed, to prevent, if possible, after having waited many months for a result, the annoying disappointments which might occur, and with this especial object, the experiments described in the