A thermometer used to measure the cooling power of the air surrounding it, having its bulb covered with water-moistened material. The instrument is brought to a steady temperature of 100°F and then exposed to the air. The time taken for the temperature recorded by the thermometer to fall to 95°F gives an index of the air’s cooling power.
A device consisting of two thermometers, one a dry bulb and the other a wet bulb. Both are heated to 110°F (43.3°C) and the time required for each thermometer to fall from 100° to 90°F (37.8° to 32.2°C) is noted. The dry bulb gives the cooling power by radiation and convection, the wet bulb by radiation, convection, and evaporation.