THERMOSTAT

is a device for con-| trolling the supply of heat to an apparatus. It utilizes the expansion and contraction of metals under heating, and may consjst in a column of mercury as in a thermometer which makes or breaks an electrical circuit according as it is heated or cooled. Or a more general form utilizes two strips of metal of different temperature coefficients, riveted or welded together. Such a composite strip, when heated will bend so that the strip which expands most will be on the outside of an arc, which will make or break an electric circuit, operate relay valves, etc. thus controlling the application of heat. some Fr. courtesan, who during revolution devoted herself to inciting mob to violence; seized by women, stripped, and flogged, 1793; went mad, 1794.