Credit: ©The Royal Society
    Image number: RS.14468

    Hygroscope and wheel barometer

    Date
    7 October 1663
    Creator
    Unknown, Artist
    Object type
    Archive reference number
    Manuscript page number
    p128
    Dimensions
    height (page): 365mm
    width (page): 233mm
    Description
    Drawings of a hygroscope and wheel barometer. These images appear in a paper on the history of the weather by Robert Hooke. The hygroscope is used to make measurement of the dryness and moisture in the air. The instrument relies on a ripe wild-oat beard attached to a dial, which curls and straightens depending on the moisture in the air. Hooke indicates that the dial should be created in the manner described by Emmanuel Maignan (Perspectiva Horaria (Rome, 1648), p. 89 and illustration).

    The drawing of the barometer shows a tube and dial for taking barometric readings. The equipment is similar to that illustrated in Hooke's Micrographia (London, 1665), but here it is depicted from an angle so that the mechanism at the rear of the dial is visible.

    These figures are coped from RBO/3/001 and RBO/3/002. The original drawings are in Cl.P/4i/25/001 and Cl.P/20/32/001.
    Object history
    At the meeting of the Royal Society on 7 October 1663, ‘Mr. Hooke’s paper concerning the observables for making a history of the weather was read, and ordered to be reviewed by the president and Sir Robert Moray, and then to be registered, and sent to the several persons, who had been engaged in this work of observing the changes of weather, as Dr. Power, Mr. Beal, etc.’ (Birch 1:311).

    A figure of Hooke's wheel barometer is printed in:
    Robert Hooke, Micrographia (London: for Jo. Martyn and Ja. Allestry, 1665), scheme I, fig. 1;
    Robert Hooke, 'A new contrivance of wheel-barometer', Phil. Trans., vol. 1, no. 13 (June 1666), pp. 218-19, fig. 1; and
    Thomas Sprat, The History of the Royal-Society of London for the Improving of Natural Knowledge (London: Printed by T. R. for J. Martyn and J. Allestry, 1667), p. 173.
    Related fellows
    Robert Hooke (1635 - 1703, British) , Natural philosopher
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