4 Professor Reich on fhc Etec/rical t'tirn'/i/s 



element be introduceil, to prove that no defect that might 

 prevent the deviation of tlie needle exists in any part of the 

 apparatus. The points tried lay either on the same level, 

 and at distances of frona 10'" to 120" asunder, or the one 

 above the other, at heights varying from 8'" to 60'". When 

 the points lay near one another, there intervened either a 

 cross-vein or a shaft ; when wide apart, the same was the 

 case, or they were sepai-ated by a non-metalliferous mass. 



Six times galena at a point in " Friseh Gllick," was united 

 with points in another vein, viz. twice with silver-ores of 

 Neu HofFnung, twice with a friable pyrites of the same, once 

 with an isolated eye of galena, in the midst of heavy-spar in 

 this vein, and once with massive fresh pyrites of Isaac, N. 

 and S. vein, in the vicinity of Neu Hoffnung, which crosses 

 it. In every case the current went in the direction of " Friseh 

 Gluck," and thus appeared to be positive. The two experi- 

 ments on silver-ores, consisting of silver-glance, brittle silver- 

 glance, and the dark and light red ores of silver, were made 

 on the 6th drift (about 180 fathoms deep, Tr.), and on differ- 

 ent days, but in very similar circumstances. The first time, 

 however. I obtained only 32", whereas the second 72^ to 73° of 

 deviation. This case shews that the deviation may be very 

 different in amount in, on the whole, vevy similar circum- 

 stances, which depends probably less on an inconstancy in 

 the intensity of the cm-rent, which cannot be conceived, than 

 on secondary causes, especially on the more or less perfect 

 contact of the disc with the minerals, or of the wire with the 

 disc. The fact is, that in these two cases the latter connec- 

 tion was effected in a different manner for each, and in the 

 case of the greater deviation it was the more perfect. The 

 two experiments on the friable pyrites gave 68" and 47^ de- 

 viation. In the first case Ai'as a short string of pyrites 8 inches 

 wide, in the other case this was only 1 inch. The isolated 

 eye of galena caused a deviation of 26°. The massive pyrites 

 in Isaac vein was only of small extent, imbedded in quartz, 

 and caused a deviation of 20". 



I made eleven experiments in one and the same vein, viz. 

 ten on the 6th and 5th drifts of Friseh Gliick, N. and S. vein, 

 and one on the 2d drift of Gottlob, K. and W. vein. Eight 



