Rutherford maximum and minimum thermometer, 1794.
© Science Museum / Science & Society Picture Library
The innovative feature of tthe Rutherford maximum and minimum thermometer was the tiny steel springs inside the tubes. These would be pushed up by the mercury or down by the spirit in the tubes as temperature changed, and would lodge at the extreme positions, allowing the maximum and minimum temperatures experienced to be read. This example was made by Lake of Taunton, Somerset.