Fitted to the boiler in a locomotives cab the water gauge shows the level of water in the boiler The gauge is usually a strong glass tube, which lead to sayings such a ‘half a glass’ when referring to boiler water level It is often surrounded by a protective cage to prevent it being knocked, and also to prevent broken glass being sprayed around the cab if it should break
An instrument for measuring or ascertaining the depth or quantity of water, or for indicating the height of its surface, as in the boiler of a steam engine
Water Gauge - A scale of measurement for measuring the effectiveness of the suction of a vacuum One measures the effectiveness by attaching a vacuum to a column of water (such as in a tube) and then measuring how many inches the water rises as the vacuum exhausts the air from the tube