in Norway and i? Canada, 9 



erally calcspar, fluorspar, quartz arid metalJic silver, and more 

 sparingly, bitterspar, stilbite, prehnit/ harmotome, laumontite, 

 anthracite, fibrous pyroxene, chrysi Je, asbestus, actinolite, 

 axinite, adularia, and perhaps albite, auriferous silver, metallic 

 gold, horn silver, metallic arsenic, silver glance, red silver ore, 

 galena, blende, magnetic, iron, and copper pyrites. These cross 

 veins are exceedingly well developed within the fiihlband, but 

 beyond its limits they exhibit little distinctness or regularity, and 

 moreover are totally destitute of silver. They do not however, 

 while intersecting the fahlband, uniformly contain that valuable 

 metal ; on the contrary its occurrence there is almost as uncertain 

 as that of a valuable ore in any other lode, but only within the limits 

 of the fahlband can one expect to find it. The only rule which 

 seems to have been ascertained to exist with regard to its distri- 

 bution in the vein, within the fahlbands, is this — that where the 

 latter is most strongly charged with the impregnating sulphurets, 

 the vein at that point is richest in silver. 



Such are the characters of the Kongsberg silver veins, striking 

 examples of the influence which the wall-rocks exert on the con- 

 tents of metallic lodes, and little liable to be neglected in theories 

 regarding the filling of such. The connection between the 

 pyritous impregnation of the fahlbands, and the argentiferous con- 

 tents of the veins, necessitates the deduction that the silver has 

 been derived from the pyrites, and as these have been found to 

 be arjxentiferous, the deduction assumes the character of a fact 

 itself. As to the mode in which the silver has been secreted 

 various opinions may exist ; the most probable appears to me to 

 be the following : — 



Through gradual contact with the waters containing oxygen, 

 percolating through the rocks, the sulphurets, especially the 

 iron pyrites, were decomposed, sulphates of protoxide and peroxide 

 of iron, and sulphate of protoxide of silver being the results. 

 The first named salt would be produced in the earlier stages 

 of the decomposition, and removed ; the two latter salts, pro- 

 duced towards the end of the process, can exist simultaneously 

 in solution. On reaching the fissure. thus, in solution, they were 

 met by some agent capable of precipitating the silver of the sul- 

 phate. The agent which seems to me to have accomplished this, 

 is the sulphate of protoxide of iron, already alluded to as a pro- 

 duct of the decomposition of the pyrites. The precipitation of 

 silver salts by a solution of copperas, is a well known chemical rcac- 



