OF ARKANSAS. 157 
Where fuel is cheap, the calcination is advantageously performed in heaps. 
The heaps are formed by alternate layers of wood and carbonate of zinc; 
fire is set to the lowest layer of wood, and the ore left to the influence of 
heat and air; by this means the water is removed, but not the carbonic 
acid, and the state of cohesion lessened. 
In the Enexisu process, the calcined ore is mixed with about one-seventh 
of its weight of coal, and filled into large crucibles or pots. These pots 
are made of fire-clay, and cement of old pounds finely ground; they are 
covered with a lid, through an orifice of which the charge is introduced, 
-and are provided, at the bottom, with an aperture; to this aperture a long 
sheet iron pipe is joined, which dips, at its end, into a vessel filled with 
water. On heat being applied, the oxide of zinc becomes reduced, the 
metal is vaporized, passes through the iron pipe, and collects in drops in 
the water vessel. From 6 to 8 pots are placed in a furnace; a furnace 
will work up from 6 to 10 tons of ore in 14 days, consuming from 22 to 24 
tons of coal, and yielding 2 tons of zinc, on an average. A pot lasts 
about four months. 
In the Beteran process, the reduction furnace is filled with long, hori- 
zontal earthen tubes, from 3 to 4 feet long, and from 4 to 5 inches in 
diameter; 22 tubes in each furnace; the tubes are filled with a mixture of 
ground ore and coal, (1 volume of ore to $ to 3 volumes of coke or char- 
coal, broken to pieces the size of nuts); to each tube a conical piece of 
cast-iron is attached, in a slightly slanting position; these conical pipes 
serve as receivers and condensers of the vaporized zinc, and are raked 
out every two hours. Each earthen tube holds 40 ibs of the mixture of 
ore and coal; the distillation is completed in 12 hours, and each furnace 
yields every 12 hours, 100 ibs. of crude zinc; on being remelted and cast 
into moulds, the crude zine loses 10 per cent. For every pound of zine, 
about 28 ibs. of coal are used. 
In the Sruzsian processs, the small earthen tubes are replaced by muffles, 
made of fire-clay mixed with ground potsherds; the muffles are from 8 to 
4 feet long, and have adiameter of from 14 to 18 inches. The number of 
muffles in a furnace varies from 5 to 10; in Upper Silesia, double furnaces, 
holding 20 muffles, are in use. The charge consists of calcined ore mixed 
with an equal volume (about one-fifth by weight) of cinders. A single 
muffle will produce from 40 to 50 ibs. of zinc daily. A muffle will last 
several months. 
The crude zinc obtained by any of the above described processes has to 
be remelted; in this operation the heat must not rise above a low red-heat, 
and the surface covered with a layer of charcoal. Experience has shown 
that, with careful management, 100 tbs. of crude zinc will yield from 92 
