"The Feeding Machine is shown in Fig. 2. The castiron frame (A), which is placed on top of the shaft, is provided with a damper (B), which is drawn out when the furnace is in operation, but inserted when the feeding machine stops for any length of time, or if screens have to be replaced. C is a castiron grate, to the top of which is fastened the punched screen (D). The latter is made of Russian sheetiron, or of cast-steel plate, with holes of one-eighth to one-tenth of an inch in diameter. Above the punched screen is placed a frame (E), to the bottom of which is fastened a coarse wire screen (F), generally No. 3, made of extra heavy iron wire. The frame (E) rests upon friction rollers (G). The brackets (H) which hold the friction rollers can be raised or lowered by set screws, so that the wire screen (F) can be brought more or less close to the punched screen (D). The brackets (K) carry an eccentric shaft (L), connected with the shaft (M), from which the frame (E) receives an oscillating motion. To the brackets (N) are fastened transverse stationary blades (O), which come nearly in contact with the wire screen (F), and can be raised or lowered by the nuts (P). These blades keep the pulp in place when the frame (E) is in motion, and also act as distributors of the pulp over the whole surface of the screen. The hopper (I) receives the ore from an elevator which draws its supply from a hopper into which the pulverized ore is discharged from the crushing machinery. The ore is generally pulverized through a No 40 screen. By means of a set of cone pulleys the speed of the frame (E) can be changed from twenty to sixty strokes per minute, whereby the amount of ore fed into the furnace is regulated. This can also be done to some extent., by changing the distances between the punched screen (D), the wire screen (F), and the blades (O).

The largest sized furnace, as represented in the drawing - the scale of which is 1 in. = 12 ft., capable of roasting from 50 to 70 tons of ordinary ores, and from 30 to 35 tons of very base sulphuret ores in 24 hours, requires the following amount of materials, from which the cost of construction can be easily calculated by any architect or millwright, viz:

1,500 fire-bricks, for fire boxes and arches exposed to flame.

200,000 common bricks, of good quality, for furnace, large system of dust chambers, chimney, and cooling floor. 2,500 lbs. in bolts and nuts for anchoring furnace and dust chambers. 4,500 lbs. in wrought iron braces, flat iron for car-guides, tools, etc. 16,000 lbs. in castings.

All the castings are very plain and simple, the water-jacket on top of furnace, and the water damper having been discarded. Considerable work is only required on the feeding-machine, feeding-machine damper, and discharge damper, and some on the fire-doors, which will be covered by an additional charge of about $700 added to the ordinary price of castings.

The cost of three iron discharge cars is $125. For a furnace of 15 to 20 tons capacity, without hopper discharge, and a less extensive system of dust chambers, the amount of materials required may be estimated at two-thirds the figures given above."