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Doc. 205.] 53
SWEDENBORG’S TRAVELS IN 1733.
like a Krummofen, or a Stichofen, where the molten mass
may be drawn off either in front or at the side. The bellows
are of wood. The blast-hole is of iron, and its mouth round ;
its shape is conical and its opening large ; it is directed
towards the front wall, and about half a foot above the open
ing there.
August 9. I reached Platten, where only tin ore is exca
vated, partly in a matrix of sand stone and partly in slate.
Not far from it the blue colour is manufactured.
This colour is prepared in the following manner: 1. One
part or one hundred-weight of cobalt, one hundred-weight of
potash, and two hundred-weight of white sand are mixed. Wi
respect to the cobalt, this is brought from Joachimsthal. If
the potash is crude and black, it is first calcined in an oven,
which is like a baker’s oven. The sand is obtained from the
whitest quartz which is burnt at first in the open air, and
afterwards in an oven, which is close by, or attached to that
oven in which the above mixture is fused, so that the smelt
ing of the mass and the second calcining may be effected by
one and the same fire. There results hence a very white fine
sand. The proportions of the mixture are different when the
cobalt and the potash are not of an equally good quality.
2. This oven is almost round externally ; there are four open
ings, which lead to the retorts or pans enclosed in it, in which
the mixture is liquefied. There are also holes below leading
into these, through which the scoriæ are dropped out. In the
rear and in front are openings or doors leading to the fire,
through which pieces of wood are thrown in. The reverberated
flame can be tempered by opening the door in front more or
less. Attached to this is a square oven, in which, as said
above, the sand is burnt a second time. The large oven is
almost quadrangular in the interior; the retorts rest on a
paved surface with holes, through which the fire strikes in.
3. Four retorts are placed on this surface; they are made of
the hardest kind of clay; their diameter is one ell, and their
height three-quarters of an ell. 4. Into these retorts the
above-mentioned mixture is put, and is smelted by the fire
.
underneath ; every eighth hour or three times within twenty
four hours the mixture is poured out ; but during this time it
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