METALS AND THEIR ORES. 2/ 



crush the rock perfectly, or perhaps an additional pair of rollers might answer the pur- 

 pose. From the rollers the ore is carried as a powder to the roasting cylinders. These 

 cylinders are made of boiler-iron, and are placed in an almost horizontal position on 

 friction rollers, and heated to redness from the outside. Inside the cylinders are flanges 

 or shelves fixed to the shell, and running parallel with its axes. The ore drops in at 

 the feed end ; and as the cylinder revolves, is lifted by the flanges, dropped, and thor- 

 oughly stirred. From the declination of the cylinder, the ore slowly works its way 

 down to the discharge end, roasted or desulphurized. 



The ore is now cooled, ground to a fine powder in the burrhstone mills, washed, to 

 free it from soluble metallic salts, and amalgamated. The amalgamation is performed 

 in tubs provided with stirrers ; and by an ingenious arrangement the quicksilver is 

 strained, the amalgam separated, and free quicksilver continuously passed in a fine 

 shower through the pulp in the tank. 



To test the efficiency of the process, I caused 174 pounds of sulphuretted ore, 

 assaying $56.15 in gold, to be worked, and obtained 80 per cent, of the assay. Had 

 the ore been properly crushed previous to roasting, the returns must have been larger. 

 The powdered ore was of all degrees of fineness, from a fine powder to a gravel the 

 size of coffee beans. Of course the latter were not desulphurized ; and that we should 

 obtain 80 per cent, of the gold with such imperfect crushing was a matter of surprise. 

 The cost of reduction at Gold Hill, N. C, the mill working 18 tons a day, and allow- 

 ing one dollar per ton for wear and tear, is $3.27^ per ton. 



George Clenden, Jr. 



The results of twelve different trials with the same apparatus are also 

 given in the prospectus. The sum total was 96 tons; the product was 

 $1,629.29; the average value of the sampled assay, $17.69; and the pro- 

 duct, 80 per cent, of the assay value. 



Alluvial Washings. 



In all gold-bearing countries it is common to resort to the hydraulic 

 process for the extraction of the precious metal. Two circumstances 

 have stood in the way of its use in New Hampshire, where it might serve 

 an excellent purpose : first, the land in the Ammonoosuc field is valua- 

 ble for farming purposes, and the farmers do not desire to have it torn 

 up; second, there were operations of this nature upon Salmon Hole brook 

 in Lisbon, in 1866, whose managers "salted" the sluice-boxes, and thus 

 falsely obtained a large yield. There is no reason why a judiciously se- 

 lected locality would not furnish profitable results, particularly in Pitts- 

 burg, where the value of the land is but a trifle. 



