On the electro-magnetic properties of metalliferous veins in the mines of cornwall

Abstract

The author having been led from theory to entertain the belief that a connexion existed between electric action in the interior of the earth, and the arrangement of metalliferous veins, and also the progressive increase of temperature in the strata of the earth as we descend from the surface, proceeded to the verification of this opinion by experiment. His first trial was unsuccessful; but in the second he obtained decisive evidence of considerable electrical action in the mine of Huel Jewel in Cornwall. His apparatus consisted of small plates of sheet copper, which were fixed in contact with one in the veins by copper nails, or else wedged closely against them with wood­en props stretched across the galleries. Between two of these plates at different stations, a communication was made by means of copper wire one twentieth of an inch in diameter, which included a gal­vanometer in its circuit. In some instances, 300 fathoms of copper wire were employed. The intensity of the electric currents was found to differ consider­ably in different places; it was generally greater in proportion to the greater abundance of copper ore in the veins, and in some de­gree also to the depth of the stations. Hence the discovery of the author seems likely to be of practical utility to the miner in discover­ing the relative quantity of ore in veins, and the directions in which it most abounds. The electricity thus perpetually in action in mines does not appear to be influenced by the presence of the workmen and candles, or even by the explosion of gunpowder in blasting.