The Democratic advocate. [volume] (Westminster, Md.) 1865-1972, 1874-09-12
Art Nlpsteries.
Glass and its Manufacture.

! uSASu ~ hSAlDit ttiht ~ haJ bo ihouiucu
with the utmost ease into any form We
choose. When heated il can be drawn
out into threads Of the utmost conceivable
fneness, and these when cold are elastic
in remarkable degree.
The time at which glass was invented is
very uncertain. The popular opinion is
that it was discovered by accident 1t is
said by an ancient writer, Pliny, " that
some mariners, who had cargo Of nitrunl
(salt, or, as some have supposed, soda, } on
board, having landed on the bank Of the
river Belus, small stream at the base of
Mount Carmel, in Palestine, and finding
no stones to rest their pots on, placed un-
der them some masses of nitrum, which
being fused by the heat with the sand of
the river produced liquid and clear
stream; such was the origin Of glass. y
The ancient Egyptians were certainly ac-
quainted with the art of glass-making.
The earthenware beads found in some
mummies have an outer coat Of colored
glass and among the ruins of Thebes,
pieces Of blue glass have been found. The
manufacture of this important substance
was long carried on at Alexandria, from
which city the Romans were supplied with
it; but before the time Of Pliny it had
been also introduced into Italy, France
and Spain. Glass utensils Of various kinds
have been found among the ruins of Her
culaneum and in Cyrus.
Glass is formed by the fusion of flint, OIL
hinty matter such as fne sand, together
with some alkali-soda, potash, ammonia,
or the like. The nature Of the glass pro
duced will depend upon the quality and
proportions Of the ingredients employed
and thus an infinite variety of kinds Of
glass may be made. But in commerce
five kinds only are recognized first, bot
tie or coarse green glass second, broad
or coarse window glass third, crown glass
or the best window-glass; fourth, plate glass
or glass of pure soda fifth, fint-glass oil
glass of lead.
Glass-houses are commonly constructed
of brick, made in the form of a cone
varying from eighty to hundred feet in
diameter, and about as much in height
Furnaces of various kinds are erected in
them formed Of such materials as are
found best to resist the effects of intense
heat and in these furnaces earthen pot:
or crucibles are placed, containing the
substances-fint, alkali, etc-to be mel
ted into glass. The size and shape Of the
crucibles vary according to the purpose
for which they are intended, the usual
dimensions being forty inches in depth
forty inches at the top, and thirty at the
bottom. Those for bottle and crown glass
are open at the top, and are from three to
four inches thick those for fint-glass arc
covered at the top, and are made from
two to three inches in thickness.
Twelve crucibles are commonly placed,
at equal distances from each other, round
the circumference Of the furnace, each be-
ing opposite to an opening in the wall, so
that they may be charged, or filed from
time to time, by the workman from with
out. The furnace may be approached on
all sides, and ends in chimney, the inte,
rior being an arched dome. When the
glass has been melted and fashioned into
the shape required, it is carried to another
furnace or oven not quite so hot as that
necessary for fusion, and is suffered to re-
main there for several days; the heat
being allowed to diminish by slow degrees
until the fire is quite extinguished. This
is called the aaaeaiing furnace, and the
process of cooling the glass in it is called
anneaiing. Unless this operation be care
fully managed, the articles formed in the
glass-house can be of no use, because of
the ease with which they are broken, the
slightest scratch, or even change of tenn
perature, often causing them to fly in
pieces.
1t is impossible to describe here all the
several processes employed in making the
glass articles which in such great variety
We daily see and use. If my readers
should have at any time an opportunity to
visit glass-house, let them by all means
embrace it. They will be surprised aud
delighted, particularly with the manufac-
ture of Aint-glass. There is perhaps no
process in the arts which excites so much
the admiration of stranger, as that of
fashioning this material into all the yari-
GUS objects of convenience and ornament
for which it is employed To see sub
stance, proverbially brittle, Gin the state
in which it is used by us) blown with the
human breath, pulled, twisted, cut, and
then Joined again with the greatest ease,
never fails to strike with astonishment
those who are accustomed to the sight.
The tools with which all these operations
are performed are of the simplest descrip-
tion, and do not appear to have received
any improvement from the beginning Of
the manufacture.
A MECHANICAL WoNDER.--A won
derful piece Of mechanism has recently
been produced in Europe by F. Schroeder,
an Amsterdam jeweller, it is called the
"Great Mechanical City" and is twenty
feet long by fifteen feet wide. There are
houses, castles, churches and stores in Il,
just as they appear in almost any Europe
an city. People walk and ride about.
Horses and wagons and railway nara nass