310 GEOLOGY OF THE COMSTOCK LODE. 



BEIEF EEVIEW OF THE WOEK OF PEEVIOUS INVESTIGATOES. 



Fox/ in his original experiments, secured electric contact with the vein 

 by wedging copper plates against it. These were put in connection Avith a 

 galvanometer by copper wire. Earth currents, if present, entei'ed the wire 

 atone end, pas.sing through the galvanometer and finally back into the earth 

 at the other. 



As a general result of his investigation Fox found that the intensity 

 and direction of the cixrrents bore no relation to the cardinal points, but 

 could be explained by a consideration of the distribution of ores." Between 

 two points of a continuous vein on the same level no current was observa- 

 ble; but when the points tapped were on different levels, or when there 

 intervened between them an area of barren rock (horse), or when two appar- 

 ently distinct veins were connected, the effect was invariably decisive. At 

 times the currents were so powerful as to throw the needle of his by no means 

 delicate galvanometer (3^-inch needle in twenty-five turns of wire) several 

 times ai'ound the circle. After enumerating a number of facts with reference 

 to the relative position of the veins. Fox remarks that "many of the phe- 

 nomena referred to bear a striking resemblance to common galvanic combi- 

 nations, and the discovery of electricity in veins seems to complete the 

 resemblance." In other parts of this paper, however, he expresses the opinion 

 that "mineral veins and internal heat are connected with electric action," 

 and, moreover, anticipates greater effects with increasing heat and dejith. 



The experiments of v. Strombeck' were made at Werlau and Holzappel 

 on a large vein, in which quartz, blende, galena, copper-pyrites, and tetra- 

 hedrite occurred in irregular distribution, and are distinguished by the care 

 with which all known sources of error were avoided. Contact was secured 

 by drilling into the vein holes 2 to 3 inches in depth, into which the ends of 

 the wire, spirally wrapped and held in position by a cork, were inserted. In 



'R. W. Fox, "On the electro-magnetic properties of metalliferons veins in the mines of Corn- 

 wall." Phil. Trans., II., p. 399, 1830. 



-Galena, copper, and iron pyrites were the minerals met with. 



^A. V. Stronibeck, "Ueber die von Herru Fox angestellteu Untersuchnugen in Bezug nuf die 

 electro-uiaguetiHchen Aeusserungen der Mbtallgiinire." Knrsten's Archiv., VI., 431, 1H33. 



