Mercurius a Venere Occultatus Maii 17. 1737. in Observatorio Regio Grenovici, ab J. Bevis, M. D. Observatus.

XII. Mercurius a Venere occultatus Maii 17. 1737. in Observatorio Regio Grenovici, ab J. Bevis, M.D. observatus. Tem. Appar. P.M. H. M. S. I 37 03 Præcedens Limbus Veneris Meridianum transit, centro a Vertice 25° 46' 35". Mercurium vero intra telescopium ne- quaquam conspiciebam. 9 04 09 Centrum Mercurii Limbum Veneris præ- cedentem præcedebat 12" Temporis. 06 20 Repetit. eodem tempore præcedebat, quo prius. 28 00 Mercurio Filum parallelum Micrometri decurrente, Cuspis Veneris austrina ab eodem Filo rescinditur, unde Venerem Mercurium obtecturam, vel saltem stricturam colligebam; Micrometrum itaque extrahebam, quo melius instantem Contactum discer- nerem Tubo 24 Pedum. 43 04 Mercurius haud plus distat a Venere quam decima vel duodecima parte Diametri Veneris: Deinde inimicæ Nubes. 51 10 Venus iterum clarissime effulget, Mer- curius vero totus sub Venere latet. Nubes jam Venerem rursus excipiunt, ulteriorem tam rari spectaculi con- templationem prohibentes. Maii Maii 18. P. M. Distantia Meridiana Solis a Vertice 30° 04'. Limbus praecedens Veneris Meridian. transit. Centro distant a Vertice 25° 57' 15''. Mercurium culminantem neque hac die videre licuit, coelo licet admodum sereno. N. B. Distantiæ a vertice a refractionibus non purgantur. Vide Fig. 2. in Tab. XIII. The Use of a new Azimuth Compass for finding the Variation of the Compass or Magnetic Needle at Sea, with greater Ease and Exactness than by any ever yet contriv'd for that Purpose; by Captain Christopher Middleton, F. R. S. To discover the Declination of the Magnetic Needle, or Variation of the Compass at Sea, with some tolerable Degree of Certainty and Exactness, is a thing of great Use and Importance in the Art of Navigation. The Instruments and Methods hitherto used for this Purpose, (as we could easily demonstrate, if it were needful) are subject to several Inconveniencies, Errors and Defects; to remedy which, this new Azimuth Com-