Six's thermometer

Six's maximum and minimum thermometer is a registering thermometer that 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 the British scientist James Six, in 1780; the same basic design remains in use.

It is also commonly known as a maximum–minimum, minimum–maximum, maxima–minima or minima–maxima thermometer, of which it is the earliest practical design.

The thermometer indicates the current temperature, and the highest and lowest temperatures since the last reset.