TRANSACTIONS OF THE SECTIONS. 57^ 



A represents the observed station in a level 98 fathoms 

 under the surface. 



B, C, D, E, and F, show the points of contact where the metallic 

 plates or copper wires were pressed against the vein, mostly 

 by means of a wooden prop ; and the dotted lines represent 

 the copper wires employed. 



Copper and zinc plates were alternately, or rather succes- 

 sively, used at each of the points of contact with the vein, except 

 at D ; but these changes of metal did not affect the character 

 or dii'ection of the electricity, nor did the contact oi points only 

 with the ore do so. But in all cases the easterly wires were 

 positive with respect to the westerly ones. These experiments 

 were made in order to prove that the electrical action is derived 

 from the vein, and that it is not in any degree excited by the 

 mere contact of the metal with the ore, as some have sur- 

 mised. 



In order to obtain some idea of the electric energy of the vein, 

 the author placed a galvanic trough as in the circuit, at m, and 

 caused it to act with the electricity of the vein, and also against 

 it. In the former case, the deflections of the needle were con- 

 siderably increased ; and in the latter, when the electricity pro- 

 duced by the galvanic apparatus was opposed to that of the 

 vein, the positive electricity from C was reversed, the gal- 

 vanometer giving evidence of a slight negative action in that 

 direction. The electricity from D, however, was only just 

 neutralized, and that from E was merely diminished in intensity, 

 the deflection of the needle being in the same direction, and 

 equal to about 40°, from the magnetic meridian, instead of 100° 

 at least, produced by the vein alone. 



The galvanic apparatus consisted of a plate of copper, and 

 another of zinc, plunged into strong brine, to which some sul- 

 phuric acid was added, and each plate exposed about 180 

 square inches to the action of the liquid. The voltaic activity 

 was much diminished before the completion of the experiments ; 

 but even at the last, when the wires of the apparatus were 

 applied to the galvanometer without the intervention of the 

 vein, and the extensive circuit and comparatively imperfect 

 contacts which it involved, a violent agitation and rapid rota- 

 tion of the needle were produced. 



These experiments afford strong evidence of the energy of 

 the electricity of the vein ; and this method may become useful 

 to the practical miner, in helping him to appreciate the value of 

 his discoveries, and enabling him to ascertain whether the ores 

 in distant parts of a vein are connected or insulated, or whether 

 Tfhat appear to be parallel veins are really so, or ramifications 



