322 



GEOLOGY OF THE COMSTOCK LODE. 



Table IV. — Experiments made in the Ophir mine. 



[Steel gads.] 



Table V. — Experiments in the Consolidated Virginia and Califorma mines. 



[Steel gads.] 



Table VI. — Experiments in the Ophir and Mexican mines, 



[Copper terminals.] 



In small quartz seam ; barren. 



Do. 



Do. 



Do. 

 In large quartz seam ; low-grade ore. 



Do. 

 lu quartzose clay. 



Discussion. — From a comparison of Tables I. and II. with Tables IV., V., 

 and VI. it appears at once that the electromotive forces due purely to chem- 

 ical difference and polarization of the terminals are of the same order as the 

 data expressing the electric activity of the Lode. The latter therefore can 

 serve no other purpose than that of affording information as to the magni- 

 tude of the forces to be determined. To assure myself as to the certainty 

 of this conclusion, I made a measurement of the electromotive force (e) ob- 

 tained by using terminals of copper and zinc conjointly, and found, as a mean 



of three experiments, 



£=0.82. 



In consequence of polarization, the current speedily diminished in 



