Thermometer

An instrument for indicating the intensity of heat. Three scales of degrees of heat are used in practise, the Fahrenheit, Réamur, and Centigrade, each of which is described under its own title. (See Zero, Thermometric-Zero, Absolute.) The ordinary thermometer depends on the expansion of mercury; in some cases alcohol is used. Besides these the compound bar principle as used in the thermostat (see Thermostat, Electric) is employed.