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
                            
                        
                            
                            
                            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.
                            
                            
                        
                            
                            
                            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.
                            
                        
                            
                            
                            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