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Inside the Radcliffe Observatory's Stevenson screen are four thermometers. The dry bulb thermometer (vertical left) measures the still air temperature. The wet bulb thermometer (vertical right) has a fabric sleeve surrounding the bulb, connected by a wick to a reservoir of distilled water. The two horizontal thermometers register the maximum (upper) and minimum (lower) temperatures. See Wet and dry bulb thermometers, MI006, maximum and minimum thermometers, MI007.