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Daniell Hygrometer
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
About this work
John Frederic Daniell, a young English natural philosopher, described this type of hygrometer in 1820. It consists of two glass balls, one partially filled with ether and the other covered with muslin, connected by a thin tube from which the air has been evacuated. There is a thermometer in the tube above the ball with the ether, and another on the supporting stand. When a few drops of ether are poured onto the muslin, their evaporation chills the covered ball; that in turn causes the ether vapor inside the instrument to condense, thereby cooling the other ball and causing dew to form on its surface.
National Museum of American History’s own descriptionSubjects
Credit lineDaniell Hygrometer. National Museum of American History, U.S. Military Academy. CC0.
