The Hygrodeik is used to measure relative humidity. Like the Hygrometer , it uses wet and dry bulb thermometers. However, it has a nomograph which enables the user to set the wet and dry bulb temperatures and then read off the relative humidity.

   Loyd's Hygrodeik, below, was patented in 1902. This example, in the Greenslade collection, will also give the absolute humidity and the dew point. It is listed at $17.50 in the 1929 Chicago Apparatus Co. catalogue.

   The Lowe's Hygrodeik below is listed in the 1881 Queen Catalogue at $15.00. The two examples are from the National Museum of American History at the Smithsonian Institution.

Below are front and back views of Edson's Hygrodiek in the Smithsonian Collection.

   This example of Edson's hygrodiek in in the collection of the United States Military Academy at West Point, New York.

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