GLASS WATER GAUGE.
A Glass Water Gauge is a device attached to a boiler to show the level of water in the boiler. It consists of a glass tube ten or twelve inches long, with an angle valve attached at each end. The lower valve enters the boiler below the water line, the top valve enters the boiler above the water line in the steam space. The ends of the glass are made steam and water tight by means of rubber gaskets and stuffing boxes. As water will seek its own level, the height of water in the boiler will show a corresponding height in the glass, and the engineer at a glance knows just how high the water in the boiler is above the flues and crown sheet.
Lunkenheimer Water Gauge.