Observations of the Transit of Mercury, May 4, 1786, at Dresden. By M. Kohler, Inspector of the Mathematical Repository of the Elector of Saxony; Communicated by the Count De Bruhl, F. R. S.

IX. Observations of the Transit of Mercury, May 4, 1786, at Dresden. By M. Köhler, Inspector of the Mathematical Repository of the Elector of Saxony; communicated by the Count de Brühl, F. R. S. Read December 21, 1786. Apparent time. 9 21' 54" beginning of the planet's egress, doubtful. 9 25' 23" complete egress, or last contact, very certain. The telescope with which Mr. Köhler observed, was a 9-feet refractor of Dollond's, magnifying 104 times. He has made a comparison of his observation with that of Alexander Aubert, Esq. from which he has inferred the longitude of Dresden in the following manner. | Exterior contact observed by Mr. Aubert at | Mean time. | |------------------------------------------|------------| | Equation | + 3 28,3 | | Difference of parallax | + 0 13,4 | | Apparent time at Loam-pit Hill | 8 30 46,7 | | Loam-pit Hill west of Greenwich | + 0 5,4 | | Apparent time at Greenwich | 8 30 52,1 | | Apparent time at Dresden | 9 25 23,0 | Longitude of Dresden east of Greenwich 54 30,9