814 
SKETCH OF THB PROCESS OF MINING 
in motion. Each of the two opposite compartments, which in all 
respects are equal, contains, besides the furnace, an oblong excava¬ 
tion filled with sand, in which the moulds are formed for casting 
the metal, and, at the extremity, a similar excavation for macerating 
the Dross, which after pounding’, is fused a second time. At one 
corner in each extremity is a somewhat elevated platform for the 
convenience of the w r orkmen, spectators &c., 
The furnace has a regular oblong form ; it is ten feet long, four 
feet wide and four feet high: its posterior part is elevated into a 
narrow wall, extending about three feet above the rest which sepa¬ 
rates it from the ventilators, and prevents the communication of 
fire, wffien the furnace is ignited. The fire-place occupies the mid¬ 
dle portion of the furnace; its superior opening has the form of a 
section of an elipsis, the greatest diameter being 20 inches ; it des¬ 
cends perpendicularly three feet into the body of the furnace, and 
towards the lower extremity is somewhat oblique and contracted. 
From the exterior portion, descending somewhat lower than the 
rest, a rounded aperture conducts to that part which receives the 
smelted metal: for this purpose an oval basin exists at the bottom 
of the furnace, corresponding to which the anterior w’ali has a coni¬ 
cal excavation, which facilitates the taking it out when a sufficient 
quantity is collected for casting into moulds. The furnace is con¬ 
structed of clay and its body is proportioned to the degree of heat 
is must sustain. 
The bellows is a very large wooden tube which has externally an 
octangular form and diameter of 25 inches. It is always made of a 
single tree, and its construction requires considerable skill and care. 
The internal hollow', most finely polished, whose diameter is 17 
or 18 inches, admits a corresponding piston (consisting of a thick 
plank) which is attached to a long handle: by being forced in and 
drawn out, the air, alternately compressed from either side, is, (by 
means of two smaller tubes excavated into that side of the ventilator 
which faces the furnace, gradually narrowing and terminating in the 
middle) forced into the fire place and a constant blast kept up on 
the fire. Each of the ventilators is closed by a plank, which has two 
valves for the admission of the air. To conduct the blast more com¬ 
pletely into the heart of the furnace a cylindrical tube of clay is em¬ 
ployed, which is attached to the central aperture (or nozzle) of the 
ventilator, at the junction of the canals which convey the air com¬ 
pressed from each side. 
