Thermometer

n.
  1. An instrument for measuring temperature, founded on the principle that changes of temperature in bodies are accompanied by proportional changes in their volumes or dimensions.
    2. Air thermometer, Balance thermometer ,
    etc. See under Air, Balance, etc.
    Metallic thermometer ,
    a form of thermometer indicating changes of temperature by the expansion or contraction of rods or strips of metal.
    Register thermometer, or Self-registering thermometer ,
    a thermometer that registers the maximum and minimum of temperature occurring in the interval of time between two consecutive settings of the instrument. A common form contains a bit of steel wire to be pushed before the column and left at the point of maximum temperature, or a slide of enamel, which is drawn back by the liquid, and left within it at the point of minimum temperature.