SILVEE MINING IN COLORADO. 611 



It is usually made in sections, e, wliicli are held in grooves that are formed 

 in the ribs, f. These ribs are made in tubular form with open ends, which, 

 extending outward beyond the side of the cylinder, permit the passage of 

 air and are thus partially cooled. 



When the several sections are in place, the entire partition, or dia- 

 phragm, has the form of a rhomb, whose ends are obtuse angles. It is placed 

 at an angle of 10° or 15° with the longitudinal axis of the cylinder, so that 

 as the cylinder, containing a charge of ore, is revolved, the diaphragm causes 

 a continuous passing and repassing of the material from one end to the other 

 and insures at the same time an intimate mixture of the whole mass. A 

 door, d^ for the charging and discharging of the ore, is placed in the surface 

 of the cylinder opposite the partition. The outside of the cylinder is pro- 

 vided with ribs or flanges, g, concentric with the axis of revolution, which 

 rest on the rollers, % ; also with a toothed rib with which the pinion is placed 

 in gear at h, causing the whole to revolve. The fireplace and chimney are 

 built of brick or stone, with funnels large enough for the ends of the cylin- 

 der, which may fit into their place easily and revolve. Between the end of 

 the cylinder and the stack there is a dust chamber, in which the fine mate- 

 rial that is carried through with the draught may have an opportunity of 

 settling, 



The charge of ore for this cylinder consists of 3,000 to 4,000 pounds 

 mixed with from 6 to 10 per cent, of salt. The cylinder revolves slowly, 

 making only one or two turns per minute. It consumes about three-quarters 

 of a cord of wood per day. The chlorination is said to be very thoroughly 

 effected. A detailed statement of the cost of roasting and chlorination was 

 not available, but according to Mr. Huepeden, who has employed these cylin- 

 ders during two or three years, it is much less than in the reverberatory 

 furnaces. It is probably not far from $6 to $7 per ton. 



There are two of these cylinders in Mr. Huepeden's establishment, one 

 of which has been at work two years or more, wearing very well and costing 

 but little for repair. 



The amalgamation of the roasted material is performed in barrels, of 

 which there were four in place, and four more were soon to be supplied. 

 The capacity of each barrel was about 2,000 pounds per charge. The details 



