Two thermometers, mercury-in-glass, ordinary pattern, Fahrenheit scale, 1956

Thermometers use the linear expansion of mercury to measure temperature. This example was calibrated to a temperature by the National Physical Laboratory, who certified thermometers accurate to within +/-0.2 C. Such thermometers would respond to temperature change within a minute or two (and subsequent instruments adopt this same level of response time). The Met Office phased out mercury thermometers from 2010 following restrictions on the use of mercury, and as a result of increasing instrument automation.

Thermometers use the linear expansion of mercury to measure temperature. This example was calibrated to a temperature by the National Physical Laboratory, who certified thermometers accurate to within +/-0.2 C. Such thermometers would respond to temperature change within a minute or two (and subsequent instruments adopt this same level of response time). The Met Office phased out mercury thermometers from 2010 following restrictions on the use of mercury, and as a result of increasing instrument automation.