258 MINING INDUSTRY. 



built, in 1868, at tlie Eising Star mine, in Idaho, but, owing to the stopping 

 of the mine, were not long in operation. 



In the first furnace of the kind, built at the Merrimac mill, on the Car- 

 son River, experiments, on a large scale, showed that slimes could be roasted 

 at a cost varying from $5 to $7 50 per ton, according to the price of fuel, and 

 chloridized to such a degree that from seventy-five to eighty per cent, of the 

 assay value could be extracted, after the roasting, by working in pans. The 

 treatment of the roasted material, in pans, should not cost more than $4 or 

 $5 per ton. 



Another furnace, known as the ''Stetefeldt," designed for the cheaper 

 roasting and chloridizing of ores, will be described further on, 



CoNCENTEATiON OF Tailings. — Tailings, in the Washoe district, have 

 generally been found more profitable than slimes. It has been already said 

 that the stream of water, carrying the tailings out of the mill, is usually 

 passed over blanket-tables, in order to save aU that can possibly be obtained 

 in that way. 



The blanket-table, the most common means of concentration, is a long 

 shallow trough, about 20 inches wide, with sides only an inch or two high, 

 and of indefinite length, according to the supply of tailings, water, the char- 

 acter of the ground, and other conditions, A number of these tables are 

 usually established side by side, sometimes only two, three, or four together, 

 sometimes as many as fifteen or twenty. They are inclined gently, usually 

 having a fall of six or twelve inches in twelve feet of length. They are 

 covered with coarse blankets, made especially for the purpose, in strips about 

 two feet wide, and cut in such lengths, usually ten or fifteen feet, as may be 

 deemed convenient for removal and washing. As the stream of tailings runs 

 over the blankets the heavier portions of the ore, sulphurets, &c., and particles 

 of amalgam, are retained in the blankets, while the poorer sand is washed 

 away. The quantity of water must be carefully adapted to the purpose, suffi- 

 cient to prevent the accumulation of sand and not enough to carry away the 

 heavier particles. The operation is usually assisted by a man who, with a 

 broom, sweeps the surface of the table lightly, aiding the even distribution of 

 the material and exposing the particles more thoroughly to the action of the 



