William Edson, a civil engineer in Boston, designed a "Hygrometrical Index" that, when connected to a common wet and dry bulb hydrometer, "will enable any one, by simple inspection of the instrument, to ascertain the relative humidity and dew-point of the air, also the absolute amount of moisture in the air, without the aid of tables or calculation." In this example, which came from Cornell College, the paper chart is marked "EDSON'S HYGRODEIK MANUFACTURED BY N.M. LOWE, BOSTON." Nathaniel M. Lowe is known to have manufactured Edson's Hygrodeik from 1866 until the early 1890s.
Ref: William Edson, "Hydrometer," U.S. Patent 48620 (1865), as well as similar patents in England and France.
William Edson, The Use of Edson's Hygrodeik (1865).
Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.
If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.