The ingredients to be made into glass (of whatever kind it may be)
are thoroughly mixed together and thrown a little at a time into
large crucibles or melting-pots placed in a circle (A A, fig. 1) in a
furnace resting on buttresses (B B, fig. 1), and heated to whiteness
by means of a fire in the centre, C, blown by a blowing machine,
the tube of which is seen at D. This furnace is shown in perspective
in fig. 2. The ingredients melt and sink down into a clear fluid,
throwing up a scum, which is removed from time to time. This clear
glass in the fused state is now kept at a white heat till all
air-bubbles have disappeared; the heat is then lowered to a bright
redness, when the glass assumes a consistence and ductility suitable
to the purposes of the glass blower.