166 Macfarlane on the Primitive Formations 



bichromate. At the manufactory, the ore in fine powder is simply 

 Ignited in a reverberatory furnace, with about 30 per cent, of cal- 

 cined potash, and little or no saltpetre. The resulting mixture- 

 yields, on lixiviation with water, a solution of neutral chrom ate of 

 potash, which separates as a granular salt on evaporation. It is 

 redissolved, and the solution is treated with a certain quantity 

 of sulphuric acid, when crystallized bichromate of potash is ob- 

 tained. The sulphuric acid is manufactured in the same establish- 

 ijient. One hundred parts of ore yield about thirty-seven of bi- 

 chromate, so that the ore used must contain only about twenty 

 per cent, of chromic oxide. 



The nickel mines of Espedal, which are now abandoned, fur- 

 nished an ore much of the same character as those of Ertelien in 

 Ringerike, described in the first part of this paper. The mode of 

 treatment was also similar. 



The rocks of the two areas just described, ofi'er, as we have 

 seen, very considerable lithological difi'erences. Those of the 

 northern region do not appear to present any striking resem- 

 blances with the Canadian rocks, but the region about Trondhjem 

 strongly resembles that of the Eastern Townships of Canada, and 

 garees with it in the very points in which it differs from the mica 

 schist region of Tromsen and Senjen. Among these are the pre- 

 dominance of clay slates, the presence of serpentines, with chro- 

 mic iron, and the occurrence of ores of copper disseminated in 

 the schists. These rocks of Eastern Canada have been traced 

 from the line of the state of Vermont, for 140 miles north-east- 

 ward to the Chaudiere River, and thence, at intervals, as far as 

 Gaspe. As described in the Reports of the Geological Survey, 

 they consist in great part of mica schists, passing into a gneiss, 

 sometimes granitoid, on the one hand, and into clay slates on the' 

 other. Roofing slates are abundant in this series, and beds of 

 steatite and chlorite slate are not uncommon. Quartzites, some- 

 times conglomerate, are met with, and limestones, which are very 

 often magnesian, and weather of a reddish or brownish color 

 from the presence of iron or manganese. They are sometimes re- 

 placed by carbonate of magnesia. Beds of serpentine are an 

 important feature in this series ; they are often mingled with lime- 

 stone, dolomite or magnesite, and always impregnated with 

 chrome and nickel. These serpentines are sometimes associated 

 with diallage and with feldspathic rocks, which constitute varieties 

 of diorite and diabase. These same rocks are traced southwards. 



