ELECTRICAL ACTIVITY OP ORE BODIES. 813 



Reich, "there being- still a tendency to deflection." Tlie exchange of ter- 

 minals of different metals also produced a change in the direction of the 

 current. 



In the next year Reich^ published his second paper, undertaken with 

 the especial object of studying more closely the currents probably existing 

 in the rocks surrounding the vein. His idea was that lode currents are 

 produced by the contact of the different ores in the deposit, the rock which 

 separates them more or less completely one from another performing the 

 function of the liquid of an ordinary galvanic couple. As Fox's method of 

 obtaining contacts with the earth was inapplicable, Reich had holes (12 

 inches deep) drilled in the rock, into which dilute sulphuric acid was poured. 

 Strips of copper foil plunged into the acid and connected with the ends of a 

 copper wire completed the circuit. Currents were obtained when at least 

 one point was near ore; they were completely absent when both points were 

 in barren rock. Though the deflections of the needle ranged from 2° to 

 30°, they seemed to obey no general law. The results are, moreover, diffi- 

 cult of interpretation, because the needle does not discriminate between 

 high and low grade, or between base and noble minerals,^ the deflection 

 being a function of both the quality and the quantity of the electrically 

 active material. Reich's mode of operation was derived from a considera- 

 tion of the currents of a galvanic cell in action. The paper' is interesting 

 and the reader's attention is especially called to it. I shall have occasion 

 to consider it again below. 



The reader is finally referred to the Proceedings Roy. Soc. Lond., III., 

 p. 123, 1832, and IV., p. 317, 1841, which were not at my disposal. 



Remarks on the foregoing. — Froui 1830 uutll 1844, therefore, the papers in 

 hand offer little more than a criticism of Fox's original investigation. In 

 1844, with the publication of Reich's second paper, in which the idea that 

 if local currents due to ore bodies are present at all they must be discover- 

 able in the rocks, was the basis of research, a second step may be considered 



'F. Reich, "Versuche uber die Aufsuchung von Erzen mittelst des Schweigertchen Multiplica- 

 tors." Berg- u.- huttenmiinn'sche Ztg., [3], pp. 342-346, 386-390, 1844. 



= The term "mineral" wherever nseil thronghout this chapter is intended to refer to those of the 

 heavy metals only — to those in short iu which we may expect to find metallic properties. 



'See, also, B. v. Cotta, " Erzlagerstatten," Vol. I. 



