metal just entering the mould, which instantly takes its form by
sharp blowing; the brim is then finished, as before explained, by the
gaffer, or workman, at the chair. This is an expensive principle of mould
making; but it decidedly gives a more polished surface to the bottles,
and produces excellent apothecaries' phials of uniform size and capacity.
The phial cannot, however, be made of a perfect cylindrical form,
as it needs the upper part of the mould to be a slight degree larger
than the lower, to allow of the delivery of the bottle from the mould.
It is closed by a treadle acting upon two levers with inside springs,
which again open the mould when the foot is removed.
All bottle moulds, while working, require
to be kept nearly at a red-heat, by means either of a small furnace,
or a piece of hot Glass, which is held by a lad inside the mould upon a
punty-iron, during the intervals it may be unoccupied by the two blowers.
Without this precaution, the surface of the bottles will be
. The heat of the moulds is essential to the polish;
but care is requisite to keep the metal moulds, whether brass or iron,
a little below red heat, or the Glass will adhere to them.
MOULDED ROMAN PILLARS.
Moulded Glass, as recently introduced by
the English manufacturer, owes its refractive and cut-like effect to its
inequalities of substance—the interior having no indentations to
correspond with its exterior projections. It requires, in addition to the
usual Glass-maker's tools, only a metal mould of about one third the size
of the object to be manufactured. The metal is first gathered upon a rod
in the ordinary manner, except that the first gathering should be