1in a short
strake, at the head of which stands the washer, who draws the water
upward with a wooden hoe. The water running down again, carries all
the light particles into a trough placed underneath. I shall deal more fully
with this method of washing a little later.
upward with a wooden hoe. The water running down again, carries all
the light particles into a trough placed underneath. I shall deal more fully
with this method of washing a little later.
Ore is burned for two reasons; either that from being hard, it may become
soft and more easily broken and more readily crushed with a hammer or
stamps, and then can be smelted; or that the fatty things, that is to say,
sulphur, bitumen, orpiment, or realgar3 may be consumed. Sulphur is
frequently found in metallic ores, and, generally speaking, is more harmful
to the metals, except gold, than are the other things. It is most harmful of
all to iron, and less to tin than to bismuth, lead, silver, or copper.
Since very rarely gold is found in which there is not some silver, even gold
ores containing sulphur ought to be roasted before they are smelted, because,
in a very vigorous furnace fire, sulphur resolves metal into ashes and makes
slag of it. Bitumen acts in the same way, in fact sometimes it consumes
silver, which we may see in bituminous cadmia4.
soft and more easily broken and more readily crushed with a hammer or
stamps, and then can be smelted; or that the fatty things, that is to say,
sulphur, bitumen, orpiment, or realgar3 may be consumed. Sulphur is
frequently found in metallic ores, and, generally speaking, is more harmful
to the metals, except gold, than are the other things. It is most harmful of
all to iron, and less to tin than to bismuth, lead, silver, or copper.
Since very rarely gold is found in which there is not some silver, even gold
ores containing sulphur ought to be roasted before they are smelted, because,
in a very vigorous furnace fire, sulphur resolves metal into ashes and makes
slag of it. Bitumen acts in the same way, in fact sometimes it consumes
silver, which we may see in bituminous cadmia4.
I now come to the methods of roasting, and first of all to that one which
is common to all ores. The earth is dug out to the required extent, and
thus is made a quadrangular area of fair size, open at the front, and above
this, firewood is laid close together, and on it other wood is laid trans
versely, likewise close together, for which reason our countrymen call this
pile of wood a crate; this is repeated until the pile attains a height of one
or two cubits. Then there is placed upon it a quantity of ore that has been
broken into small pieces with a hammer; first the largest of these pieces,
next those of medium size, and lastly the smallest, and thus is built up a
gently sloping cone. To prevent it from becoming scattered, fine sand of the
is common to all ores. The earth is dug out to the required extent, and
thus is made a quadrangular area of fair size, open at the front, and above
this, firewood is laid close together, and on it other wood is laid trans
versely, likewise close together, for which reason our countrymen call this
pile of wood a crate; this is repeated until the pile attains a height of one
or two cubits. Then there is placed upon it a quantity of ore that has been
broken into small pieces with a hammer; first the largest of these pieces,
next those of medium size, and lastly the smallest, and thus is built up a
gently sloping cone. To prevent it from becoming scattered, fine sand of the
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