A thermometer for measuring temperature comprising: a heat receiving compartment containing a porous filler material impregnated with a heat transfer agent; a reservoir positioned adjacent to the compartment containing an indicating liquid; a transparent capillary tube communicating at one end with the reservoir; and a scale positioned along the capillary tube by which the temperature can be read, wherein vapors of the heat transfer agent exert a pressure on the indicating liquid in the reservoir causing the displacement of the indicating liquid into the capillary tube. The heat transfer agent and indicating liquid are preferably non-toxic, so that the thermometer combines high accuracy and minimal lag time in measurement with non-toxic components. The thermometer can be used in both medical and industrial applications. Also disclosed is a device for maintaining the maximum temperature reading.
