12 Prof'essiur Reich on the Electrical Currents 



undertaken ; when, at the same time, might be examined, 

 Whether, when two non-metalliferons points are connected, a 

 current ensues I If, Avith two homogeneous discs, this should 

 never be the case, even when ores are in the vicinity, it must 

 be tried with heterogeneous (zinc and copper) discs, which 

 probably would almost always give a cuiTent, and perhaps the 

 more intense when ores were in the vicinity. 



VI. Upon the cause of the electrical currents observed in 

 metalliferous veins, three diffei'ent opinions, as far as my know- 

 ledge extends, have been put forward. These currents have 

 been attributed to, 



a, General electrical currents at the earth's surface, pro- 

 duced either entirely or in part, by the earth's magnetism. 



b, Hydro-electric ; and 



c, Thermo-electric action of the various metallic components 

 of the vein. 



The fii'st hypothesis seems to be refuted by the indepen- 

 dence of the direction of the currents of their position rela- 

 tive to the earth's axis. Also, on this supposition, two points 

 betiveen which lay a sufficiently conducting medium, even 

 without the presence of ores, shoidd induce a current in a con- 

 necting wire. I have convinced myself, however, that two 

 copper-plates, placed in moist gi-ound, and connected by a wire, 

 give rise to no current, although that of a zinc-copper element 

 introduced, is easily transmitted, Avhether the connecting line 

 of the two discs be in the magnetic meridian, or perpendicular 

 to it. 



Thermo-magnetism, which Henwoodmore especially adopt- 

 ed, I hold incapable of producing such strong cm-rents as have 

 been observed, unr.er the circumstances above detailed, where 

 the chain was generally broken by the intervening of bad con- 

 ductors, particularly when it is considered that the difference 

 of temperature between the A^arious components of a vein can 

 be but very slight. We learn also from the above experi- 

 ments, that, by the connection of two ore masses, separated by 

 non-metalliferous rocks, a strong heating of one of the discs 

 eflPects no alteration in tlie deviation of the needle of the mul- 

 tiplicator, or at least very small in proportion to the intensity 

 of the ciu'rcnt ob:icrvcd. When a metallic connection subsists 



