Thermometer A is moistened with water and the gauze around thermometer B is moistened with ether. Ether is a volatile liquid. At the start of the experiment, both thermometers record the same temperature because both were kept under identical conditions at room temperature. Evaporation of volatile liquids from the respective gauzes will commence immediately after exposure, and the latent heat of vaporization will be collected from the surroundings, i.e. air and the thermometer bulbs. As a result both the thermometer bulbs will experience a cooling effect and both A and B will exhibit a lower reading. Owing to higher volatility of ether, the extent of evaporation in B will be far greater than that of A. Hence the observed result.