6 Professor Reich on the Electrical Currents 



nature of the discs applied to the ores is indifferent is this : — 

 that, in a connection of galena, of Frisch Gliick, and of silver- 

 ores in Neu Hoifnung, at the former point, a zinc disc was 

 laid between the copper and the galena, without the deviation 

 varying in the slightest. Perhaps still more striking is an ex- 

 periment in Frisch Gliick on the 5th drift, when a galena 

 point was connected with one of bleiide SS"" south from it, 

 without obtaming the least deviation ; — ^probably because 

 the two points were in uninterrupted metallic connection, — 

 which case will be further treated in the sequel. When, in 

 this case, a zinc disc was applied to the galena instead of a 

 copper one, there was still no action produced ; and here we 

 must expressly mention, that not only the current of a zinc- 

 copper element produced a deviation of 30°, but that also a 

 thermo-electric current, induced by heating one of the stations, 

 caused a deviation of the needle. The cause of this indiffe- 

 rence, as to the nature of the metallic disc applied to the 

 ores, is self-evident ; for in this case we must consider the 

 currents as produced bg the ores existing in the rock, whatever 

 may be its cause. These are the electrometers, and it is in- 

 different by means of what metal they are connected with one 

 another, and with the multiplicator. These experiments with 

 zinc discs may also serve to destroy the supposition, that the 

 current observed is only a consequence of the experiment. 

 When the discs are applied to non-metalliferous points, it is 

 then far from indifferent what be the nature of the discs ; — of 

 which hereafter. 



It might still be imagined that the discs themselves occa- 

 sioned the current as thermo-electric, by a slight difference of 

 temperature at the points of contact having place. The fol- 

 lowing observations shew that such a supposition is unfounded. 

 Deviation 18° ; temperature 19°.4 C, and lO^.G C. (about 

 67° F.) The latter point having been heated to such a de- 

 gree that the hand could not be held to it, the deviation de- 

 creased to 15°. 



Deviation 72° ; temperature 21°.! C. (70° F.), and 17°.8 C. 

 (61° F.) The first point having been heated as formerly, no 

 change took place, and the latter having been heated, the 

 deviation was decreased, but almost insensibly. 



