A vertical liquid area in a firebox or burning chamber within a steam boiler.
A support when it comes to centre of a tunnel.
A vertical liquid room in a fire box or burning chamber.
A support for center of a tunnel.
A hollow horizontal septum when you look at the furnace of a steam-boiler, which, becoming full of water, kinds a kind of water-bridge, under and over which the fire of the gas is caused to pass through.