335,051. Mines Domaniales de Potasse d'Alsace. Feb. 21, 1929, [Convention date]. Prospecting for minerals.-In a method of exploring the subsoil for minerals &c., the resistance of the earth is measured between two electrodes T', T2 sunk in the earth and arranged in series in a circuit comprising a source D of alternating current and a voltmeter V of known internal resistance, each passage of current giving on the voltmeter a reading which enables the resistance between the electrodes T1, T2 to be calculated. A number of tests are made with the electrodes sunk at different places, and by plotting the various resistances as ordinates and the distances between the places of the tests as abscissal, a graph corresponding to the line of mineral &c. deposit is obtained.
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