An instrument for determining temperature usually by means of a scale graduated directly in temperature units and consisting typically of (1) a device having a bimetallic element, the expansion or contraction of which indicates a change in temperature, or (2) a glass bulb attached to a fine tube of glass with a numbered scale etched on it or fastened to it and containing a liquid (as mercury or cooled alcohol) that is sealed in and rises and falls with changes of temperature and that indicates the temperature by the number at the top of the column of liquid.