=A Gauge Cock= is a stop cock attached to a boiler to ascertain the
height of water in the boiler. There are generally two and sometimes
three gauge cocks attached to a boiler. The lower one enters the boiler
as low down as it is deemed safe to allow the water to get, while the
upper one enters the boiler sufficiently high to avoid getting too much
water. Where three gauges are used, the middle one enters the boiler at
about the proper water level. They should be opened frequently to keep
them free from corrosion, being sure to close them tightly to prevent
leaking.
[Illustration: Lunkenheimer Gauge Cock.]