[f. THERMO- + Gr. στατός standing: cf. HELIOSTAT.] An automatic apparatus for regulating temperature; esp. a device in which the expansive force of metals or gas acts directly upon the source of heat, ventilation, or the like, or controls them indirectly by opening and closing an electric circuit.
1831. Ure, in Proc. Roy. Soc., 16 June, 67. On the Thermostat or Heat Governor, a self-acting physical Apparatus for regulating Temperature. Ibid. (1835), Philos. Manuf., 26. The instrument, for which I have obtained a patent, under the name of the heat-governor, or thermostat.
1877. W. Thomson, Voy. Challenger, I. i. 34. The size of the iron frame was arranged so as to receive one of Bunsen’s thermostats in ordinary use in laboratories.
1899. Cagney, Jaksch’s Clin. Diagn., ii. (ed. 4), 107. The test-tube containing the infected serum is now placed in a thermostat, maintained at 36.5°–37° C.
b. An apparatus which gives notice of undue increase of temperature; an automatic fire-alarm.
1881. Philad. Record, No. 3462. 4. The thermostat, which gives an alarm as soon as the temperature of the room where it may be rises to 100°.
1908. Daily Chron., 24 Aug., 6/3. The thermostat is usually attached to the ceiling, and immediately an abnormal and dangerous rise of temperature occurs the metal bars expand.
So Thermostatic a., of, pertaining to, or of the nature of a thermostat; Thermostatically adv., by means of a thermostat; Thermostatics sb. pl. [after hydrostatics], name suggested for the theory of the equilibrium of heat.
1839. Ure, Dict. Arts, etc., 1237. A single thermostatic bar, consisting of two or more bars or rulers of differently expansible solids … firmly riveted or soldered together, face to face…. A thermostatic hoop.
1871. Thermostatics [see thermokinematics, THERMO-]
1877. Knight, Dict. Mech., Thermostatic Alarm, a device to give a signal when a certain temperature is attained.
1883. Cassell’s Fam. Mag., Aug., 537/2. Frost tell-tales … can be readily constructed by employing a thermostatic spring.
1891. Cent. Dict., s.v., A thermostatically adjusted radiator.
