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26 SWEDENBORG’S TRAVELS AND DIARIES. [Doc. 205.
Afterwards I went to see the works where plates of glass
are ground and polished, so that foils may be applied to them
and mirrors formed, which is a very interesting operation.
Plates of glass and mirrors are manufactured there, which are
frequently of the height of four ells. With regard to the
work itself, the following particulars may be mentioned :
1. When the plates of glass are first brought from the fur
nace and are still in the rough, they are more than an inch
thick, but by the process of polishing they are made so thin,
that they are scarcely half the original thickness. The process
of polishing is described as follows : 2. The plate is inserted
in a frame, and placed on a smooth stone, to which it is
closely fitted, and fastened by means of plaster of Paris or
yellowish red clay; it is inserted into this mass in such a
manner, that it firmly adheres thereby to the stone. Frequent
ly three, four, six or ten plates are attached to one stone,
and they all receive their polish at the same time. 3. This
stone, with the plates of glass adhering to it, is placed upon
a table, and under this stone on the same table is placed an
other machine, also of stone [on which likewise plates of glass
are fastened]. On the top of the first stone, however, is put
a wooden frame with six or seven compartments, in which sand
as well as weights are placed, so that this frame lies more
evenly and presses equally upon the glass underneath which
is to be polished. It is to be borne in mind that the
operation of polishing is always performed by two sets of
glass plates, one lying upon the other, and by these two
sets the whole of the polishing is done. 4. The machine
is set in motion by a water-wheel, which turns a hook bent
into the form of a triangle, and by this four arms are turned,
each in its turn. To each of these arms four or five hooks
are attached, eighteen in all, which are inserted in little balls
turning in all directions, and fastened to the upper stone ;
and by the reciprocal motion of this upper stone or table to
which the plate of glass is attached the polishing is effected.
5. It is to be observed, that this upper table moves in all
directions; for it may be revolved like a wheel or in a circle,
so that it should not always move in the same way, and by the
interposition of the sand become deeper in some places
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