Mercury-in-glass thermometer related to the rapid cooling (and contraction) of the glass. When Celsius decided to use his own temperature scale, he originally defined his scale "upside-down", i.e. he chose to set the boiling point of pure water at 0 °C (212 °F) and the freezing point at -100 °C (-32 °F). One year later, Frenchman Jean-Pierre Christin proposed to invert the scale with the freezing point at and the boiling point at . He named it Centigrade (100 grades). Finally, Celsius proposed a method of calibrating a thermometer: These points are adequate for approximate calibration but both vary with atmospheric pressure.
Indoor–outdoor thermometer Indoor–outdoor thermometer An indoor–outdoor thermometer is a thermometer that simultaneously provides a measurement of the indoor and outdoor temperatures. The outdoor part of the thermometer requires some kind of remote temperature sensing device. Conventionally, this was done by extending the bulb of the thermometer to the remote site. Modern instruments are more likely to use some form of electronic transducer. In an indoor–outdoor thermometer based on a conventional liquid-in-glass thermometer, the stem of the outdoor thermometer is connected to the bulb by a long, flexible or semi-rigid capillary. The temperature scale is marked on the stem as usual. However, the