An automatic device actuated by temperature changes designed to control the gas supply to the burner(s) in order to maintain temperature between predetermined limits, and in which the thermal actuating element is an integral part of the device: 1. Electric Switch Type: A device which senses changes in temperature and control electrically, by means of separate components, the flow of gas to the burner(s) to maintain selected temperature. 2. Graduating Thermostat: A thermostat in which the motion of the thermostat valve is in direct proportion to the effective motion of the thermal element induced by temperature change. 3. Quick-Acting Graduating Thermostat: A thermostat which changes from the completely closed position, or vice versa, but not with a snap. 4. Snap-Acting Thermostat: A thermostat in which the thermostatic valve travels instantly from the closed to the open position, or vice versa.