A U-shaped thermometer, designed by J. W. Six, with a bulb that contains creosote. Mercury occupies the bend in the tube and a spring-loaded index rests on the mercury's meniscus in each leg of the tube. These indexes are displaced by the expansion and contraction of the mercury, remaining at their extreme positions to give readings of the maximum and minimum temperatures. They are reset by the use of a magnet.
Subjects: Meteorology and Climatology.