429
Controlling the temperature or smoking.
If the
temperature
is
raised above
the proper point, the metal is speedily impaired, the slugs are caused to adhere tightly in the mould, so that ejection is difficult, the bodies of the slugs are rendered porous,
The temperature
is
and the matrices are injured. controlled by regulating the
mercurial governor at the side of the pot. As the column of mercury expands with the increasing heat of the pot, it rises in the glass tube and checks the flow of gas to the burner. The height of the
mercury
is
adjusted by means of a small stem or
When
the spindle in the side of .the governor. thermometer shows that the metal is at the proper temperature, the mercury should be at the foot of the small central gas-tube. If too high or too low, adjust the spindle to bring it to the proper level.
The pressure of the gas received from city mains varies widely at different hours of the day and Each machine plant is therefore provided night. with a pressure governor or regulator. These governors, for use on the main supply-pipe, contain a
diaphragm or
float,
which may be loaded
to a
greater or less extent. The load should be regulated so that the governor will permit the flow of
gas at moderate pressure only.
TREATMENT OF MATRICES The perfection of the type-characters produced depends wholly on the condition of the matrices,