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"This hygrometer consists of two thermometers a and b similar to each other in all respects except that one of them has a piece of muslin tied closely over the surface of its bulb c, and kept constantly wet by a few threads of cotton which connect it with the water in the vessel d. the water then which rises from the vessel by capillary attraction spreads over the muslin, and evaporates from its surface with more or less rapidity according to the dryness or moistness of the air; and the greater the dryness of the air the greater is the difference between the observed readings of the dry and the wet thermometers." — Encyclopedia Britannica, 1893

Bulb Hygrometer

"This hygrometer consists of two thermometers a and b similar to each other in all respects except that…

An instrument developed by Edison used to measure humidity.

Hygrometer

An instrument developed by Edison used to measure humidity.

"Hair hygrometer." — Waldo, 1896

Hair hygrometer

"Hair hygrometer." — Waldo, 1896

"Leslie's hygrometer, which is an adaptation of his differential thermometer, is formed by uniting two tubes having a ball blown on the end of each, into which some colored sulphuric ether has been previously introduced. When both bulbs are at the same temperature, the fluid stands at the zero of the scale, but when one of them is covered with wetted paper the instrument shows the depression of temperature of the wetted bulb." — Encyclopedia Britannica, 1893

Leslies Hygrometer

"Leslie's hygrometer, which is an adaptation of his differential thermometer, is formed by uniting two…

The psychrometer (showing wet and dry bulb thermometers) is an instrument used for determining the humidity by the temperature of evaporation.

Psychrometer

The psychrometer (showing wet and dry bulb thermometers) is an instrument used for determining the humidity…

"It consists of a glass tube or capsule A, having on the bottom and a little way up a highly polished silver surface, and closed by a cork with two holes. through one of these holes the stem of a thermometer B passes, having its bulb at the bottom of the silvered capsule, and the other end may, if desired, be connected with an aspirator or air-pump. In making an observation as much either is introduced into the capsule A as will cover the bulb of the thermometer, and then by transmitting air through the tube C the ether vapor is withdrawn from the capsule A through another tube D." — Encyclopedia Britannica, 1893

Regnaults Hygrometer

"It consists of a glass tube or capsule A, having on the bottom and a little way up a highly polished…