ON THE ELECTRICAL CURRENTS OF THE EARTH. 



By Carlo Matteucci. 



ITntnslaicd for the Smithsonian Institution, from the ''Memoirs* of the Italian Society of 

 Sciences founded hy Anton Mario Lorgna."} 



The object of tliis memoir is to describe a long series of experiments, 

 commenced in 1803 and only iuterrapted by brief intervals, on the phe- 

 nomena called electric currents of the earth, meaning by those words the 

 electric cnrrents which circulate in a mixed circuit formed of a metallic 

 line and of a terrestrial stratum, and which do not depend on causes 

 known and existing either in the metallic part of the circuit or in its 

 extremities communicating w ith the ground. The conclusions arrived 

 at in this inquiry do not comprise, to any great extent, an explanation 

 of these currents founded on a known i)hysical theory, or the thorough 

 knowledge of the laws of the phenomena. We trust, however, that the 

 results obtained are of sufficient importance and exactness to recom- 

 pense the long and persevering efforts which were necessary to obtain 

 them. We hope also to be pardoned by any one who shall undertake 

 seriously to study this subject, if we have not carried these researches 

 to such a point as might be desired, since it must appear evident from 

 the experiments made that the means requisite to extend and complete 

 them exceed the resources of a private individual. 



HISTORICAL TART. 



Even from the time when the galvanometer was discovered — that is 

 to say, shortly after the celebrated exi^eriments of Oersted and Ampere — 

 l)henomena of electrical currents are cited as having been obtained by 

 introducing the extremities of the instrument into different points of a 

 terrestrial stratum. 



We believe that Fox was the first who observed the deviation of the 

 needle of the galvanometer, on inserting the copper i)oints attached to 

 the ends of the wire of this instrument in various places of a mineral 

 vein of copper. Becquerel, soon after Fox, published a long series of 

 experiments on the electric currents, which he obtained by sinking the 

 electrodes of the galvanometer in earth taken in different conditions of 

 humidity and of composition. 



It is scarcely necessary to say that all these experiments were but 

 different cases of the general principle of the galvanic pile ; that is to 

 say, of heterogeneity in the metallic laminoe in contact with the ground 

 and the liquids with which the ground was imbued at the points in . 

 contact with the electrodes. It would be easy, even supposing the em- 

 ployment of homogeneous electrodes, by which electric currents are not 

 l)roduced through their immersion in water, to exhibit distinct signs of 

 electric currents by using liquids of different chemical composition or 

 of different temperature in contact with the electrodes. This would be 



* Serie ter:a : Tomo I, Farte I. — Fironze, 1887. 



