Hy grometer

— An instrument for measuring the proportion of aqueous vapor in the atmosphere; a usual form is that known as the wet and dry bulb thermometer. This consists of two equal thermometers mounted side by side, the bulb of one being kept moist by means of a wick tied around it, which dips into a ve el of water. Owing to the evaporation from this bulb, its temperature is lower than that of the other, the difference depending upon the’ amount of moisture in the air., There is no real relation between the hygrometric readings and the actual state of the atmosphere, but the hygrometric state is deduced from reference to tables compiled from accurate observations with most elaborate instruments.