Credit: ©The Royal Society
    Image number: RS.14908

    Hygroscope

    Date
    17 April 1685
    Creator
    Unknown, Artist
    Object type
    Archive reference number
    LBC
    Manuscript page number
    vol10 p156a
    Material
    Dimensions
    height (page): 248mm
    width (page): 151mm
    Subject
    Content object
    Description
    Design of a hygroscope reported in a letter from William Molyneaux to William Musgrave dated 17 April 1685.

    It was read at the Royal Society on 13 May 1685, and the figure was shown at the following meeting on 20 May when it was also ordered that Denis Papin make one after the design. Papin brought in the hygrometer the next week, on 27 May 1685.

    This instrument was printed as fig. 2 in William Molyneux, ‘Concerning a new hygroscope’, Phil. Trans., vol. 15, no. 172 (June 1685), pp. 1032-35.
    Transcription
    I shall breifly declare to you the Contrivance of a Hydroscope, which I have lately invented, and put in Execution with good Success...
    Transcribed by the Making Visible project
    Object history
    At the meeting of the Royal Society on 13 May 1685, ‘A letter of Mr. William Molyneux to Mr. Musgrave, dated at Dublin, April 17, 1685, was read, concerning a new sort of hygroscope contrived by himself. A piece of whip-cord about four feet long was fastened at one end to an hook: at the other end hung a pound-weight, so fitted, as to carry an index of a graduated circle. The moisture of the air twists the rope, and gives a motion to the index upon the circle; and the dryness of the air untwists the cord, and brings back the index’ (Birch 4:400).

    On 20 May 1685, ‘The figure of the hygrometer in Mr. William Molyneux’s letter to Mr. Musgrave, read at the last meeting, was shewn; and Dr. Papin ordered to make such an hygrometer against the next meeting’ (Birch 4:402).

    On 27 May 1685, ‘Dr. Papin brought in an hygrometer made after the manner of Mr. Molyneux’ (Birch 4:404).

    Printed as fig. 2 in William Molyneux, ‘Concerning a new hygroscope’, Phil. Trans. vol. 15, no. 172 (June 1685), pp. 1032-35.
    Related fellows
    William Molyneux (1656 - 1698, British) , Science writer
    William Musgrave (1735 - 1800, British) , Physician
    Associated place
    <The World>
       > Europe
          > Ireland
    <The World>
       > Europe
          > United Kingdom
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