[Count von Brühl and Duke of Marlborough.] Autograph Letter Signed from Marlborough and Autograph Notes by von Brühl, about the 'Difference of Level between a Blenheim Barometer in the Duke of Marlborough's dressing Room, & the Harefield Barometer'.

Hans Moritz von Brühl (1736-1809) [John Maurice, Count of Brühl], German diplomat and astronomer; George Spencer, 4th Duke of Marlborough (1739-1817), FRS, English nobleman and amateur astronomer
Publication details: 
Marlborough's letter from Blenheim [Woodstock, Oxfordshire], 9 November 1796. [von Brühl's notes from Harefield, circa 1796?]
SKU: 15650

A Fellow of the Royal Society, Marlborough's main scientific interest was astronomy, a subject on which he corresponded with von Brühl. The four items in good condition, with light signs of age and wear. They are accompanied by a typewritten (1960s?) report (3pp., folio), whose purpose is to disprove any connection between them and 'the name of Henry Cavendish and his work on the barometer'. According to the anonymous author of the typescript, 'their purpose seems to have been to calculate the height above sea level of the floor of the Observatory [...] at Blenheim Palace, Woodstock, by determining its elevation above that of the observatory set up by John Maurice, Count of Brühl in his villa at Harefield, Middlesex, some four miles to the NE of Uxbridge'. ONE: Marlborough to von Brühl. Woodstock. 9 November 1796. The letter signed 'M.' and addressed to 'His Excellenty | The Cte. de Bruhl &c &c &c | Old Burlington Street | London'. The cover franked 'Marlborough', with broken red wax seal. 2pp., 4to. Bifolium. Discussing observations he has made by barometer ('I have a Barometer with a Gauge point in my own Room as well as in the Observatory'), and arranging another set of readings. Concludes: 'I have not observed the Decl[ination]. of all the Stars in your Paper, but I have of some - I shall observe the same this Winter to ascertain them & will then read them to you'. TWO: Manuscript table of 'Barometical Observations at Blenheim in Novr. 1796', compiled on Marlborough's behalf. 1p., 12mo. Readings from between 20 November and 1 December 1796, neatly written and divided into: [date]; 'Blenheim'; 'Bar[omete]r.'; 'Attached Therm[omete]r.' At foot of table: 'From the Observatory floor to His Grace's dressing room Floor is 36ft. 8 inches - From His Graces dressing rom Floor to the Top of the Cistern of the Bar[omete]r. is 3 ft. 2 ¾ inches'. Short note in Marlborough's hand at foot, dated 1 December 1796. THREE: Autograph table by von Brühl. 1p., 12mo. Divided into five columns: 'Haref[ield].'; 'Barom A.M.'; 'Therm A.M.'; 'Barom. P.M.'; 'Therm P.M.' Accompanying note (followed by a few calculations): 'With these corresponding observations were made at Blenheim from which this was found 110, 1 higher than Harefield which being 348,6 above the Sea, make the Blenheim 458,7 above the same Level.' FOUR: Autograph notes by von Brühl, regarding the 'Difference of Level between a Blenheim Barometer in the Duke of Marlborough's dressing Room, & the Harefield Barometer in the Observatory'. 2pp., folio. The first page with reference to the 'Elevation of the floor of the Blenheim observatory above that of the Harefield Observatory'; the second page entirely consisting of calculations.