Six's thermometer
（重定向自Maximum minimum thermometer）
![A maximum–minimum thermometer. The scales are Fahrenheit on the inside of the U and Celsius on the outside. The current temperature is 23 degrees Celsius, the maximum recorded is 25, and the minimum is 15, both read from the base of the small markers in each arm of the U tube. The bulbs are hidden by a plastic housing.](/Images/godic/202501/26/Max_Min_Thermometer5613.JPG")
![Detail of the thermometer bulbs of the maximum–minimum thermometer shown above. The left-hand (minimum arm) bulb is full of alcohol. This bulb measures the temperature by the expansion and contraction of the liquid. The right-hand (maximum arm) bulb contains alcohol and a bubble of low-pressure gas or alcohol vapour. This bulb accommodates the expansion in the other bulb and allows the train of alcohol and mercury to move in the U-shaped tube as the temperature changes.[3]](/Images/godic/202501/26/Max_min_bulbs5613.JPG")
![Marker showing the maximum temperature. Mercury has retreated to about 26.5°C as the temperature has dropped below its maximum of about 28.3°C.](/Images/godic/202501/26/Six's_thermometer_marker5613.png")
Six's thermometer is a registering thermometer which can record the maximum and minimum temperatures reached over a period of time, for example 24 hours. It is used to record the extremes of temperature at a location, for instance in meteorology and horticulture. It was invented by Englishman James Six in 1780; the same basic design remains in use.