GLASS. 
it any bigger, in the equa trial diameter gg, 
fig. 11, he lays the pipe on a hook driven in 
the side of the stool, and turns it round very 
quickly, the centrifugal force soon enlarges 
it in the equator. If on the other hand he 
wishes to lengthen its polar diameter, he 
holds the pipe perpendicular, the glass 
hanging downwards, its weight lengthen- 
ing it, and to shorten the polar diameter 
he holds the pipe upright, the glass at the 
top ; by blowing through the pipe the ca- 
pacity is increased, and the thickness of 
the glass of the vessel diminished. 
We now suppose that by a very dexterous 
application of the above methods, the work- 
men has brought it to the shape of fig. 11, 
he now carries it to the mouth of the fur- 
nace, and holds it in to get a fresh heat, 
(for by this time it is become too stiff to 
work easily,) taking care to turn it round 
slowly, that it may not alter its figure. The 
vessels in this stage is delivered to the se- 
cond, or principal workman, the other two 
being only assistants, he is seated upon the 
stool, figs. 1 and 2, and lays the blowing 
pipe with the glass at its end across its arm 
a b, and with his left hand rolls the pipe 
along the arms, turning the glass and pipe 
round at the same time ; in Ids right hand 
lie holds the pliers, fig. 3, whose blades 
are rubbed over with a small piece of bees- 
wax, and as the glass turns r ound presses 
the blade of the shears against it, following 
it with the shears as it rolls, at the eild or 
side as occasion requires, until he has 
brought it to the proper size which he de- 
termines by the compasses, fig. 4, though 
not materially altering its figure, the first 
workman kneeling on the ground and blow- 
ing with his mouth at the end of the pipe, 
which hangs over the arm b when directed 
by his principal. The third workman now 
produces the small rod, fig. 8, which is dip- 
ped into the melting pot to take up a small 
piece of metal to serve as cement, the end 
of this rod he applies to the centre of the 
glass just opposite the blowing pipe, the 
principal workman directing it, by holding 
its end between his pliers, the rod by the 
small piece of glass on its end immediately 
sticks to the glass vessel, and the third work- 
man draws it away, both workmen turning 
their rods round, but in contrary directions ; 
this operation forms a short tube on the 
end, as in fig. 12. The principal workman 
then takes the short tube at i, between the 
blades of a pair of pliers, exactly like the 
others, but which are not covered with 
bees-wax, the cold of these pliers, instantly 
cracks the glass all round, and a very slight 
jerk struck upon the rod 8, breaks it off. 
A hole is now made in the end of the glass, 
which is enlarged by the pliers while the 
glass is turned, as in fig. 13, until the neck 
is brought to the proper size and length to 
fit the brass cap as before described, and 
the inferior half of the lamp is brought to 
its shape and size in the same manner. 
In order to form the upper half, the third 
workman has in the mean time being pre- 
paring a round lump of glass K, fig. 14, on 
the end of one of the rods fig. 8, this he ap- 
plies hot to the end of the neck, it being 
guided by the principal workman, and it 
immediately holds tight, he then breaks off 
the other neck at 7, by the cold pliers, and 
thus separates it from the blowing pipe. 
The glass is now heated a third time, and 
brought from the furnace in the state, fig. 
15, to the principal w orkman, who enlarges 
the small orifice at the end by turning it 
round, and holding the pliers against it, until 
he enlarges it, as in fig. 16, to the shape of 
fig. 10, it is now finished, and the third 
workman takes it to a stool strewed over 
with small coals, he rests the rod upon the 
edge of the stool, and with the file, fig. 6, 
files the joint at the bottom neck and soon 
breaks otf, and the lamp falls upon the 
coals, the distance being so very small, as 
to be in no danger of breaking; a boy 
now puts the end of a long stick into the 
open mouth of the glass, and thus carries 
it up the steps before described, places it 
in the annealling oven, where it remains 
some hours, when taken out it must be 
cooled gradually, and is fit for sale. 
In the history of glass there is a fact de- 
serving record ; it is related by Pliny, that 
the discovery was owing to the following 
accident. Some merchants with soda as 
part of their freight, had cast anchor at the 
mouth of the river Belus, in Phoenicia, and 
were dressing their dinner on the. sand, 
making use of large lumps of the soda as sup- 
ports for their kettles. The heat of the fire 
melted the soda, and the siliceous earth to- 
gether ; the result was glass. The hint was 
not lost, and a manufacture in that trading 
country was instantly established, and to 
this place it was for a long time confined. 
Glass was undoubtedly made in great per- 
fection among the ancients. In their ac- 
counts we read of drinking glasses, glass 
prisms, and coloured glasses of various kinds. 
Glass was first used for windows in the third 
