In 1780 the scientist James Six devised a thermometer for meteorological observations. The observer himself did not have to be present to measure the maximum and minimum temperature. It concerns two tubes, in which the highest and lowest temperature respectively were measured by means of a mercury thread. When the temperature changed, the thread was first displaced, but it could not go back to its original position [See 706]. Six's minimum and maximum thermometer was copied by many instrument makers, sometimes with some small adjustments. The maximum thermometer shown here, is from Négretti, the minimum thermometer from Rutherford.
