VOL. LXII.] PHILOSOPHICAL TRANSACTIONS. 277 



moon occulted i$^''. My time was within 2' or 3* the same ; but we did not 

 observe the emersion. This occultation was observed both at Greenwich, by 

 Mr. Maskelyne, and at Oxford, by Professor Hornsby ; by comparing which, it 

 appears that this place is west of Greenwich 4™ 24'-J- of time, and that Oxford is 

 west of Greenwich 4™ 58'-^. 



J 7 70, April 28, at Q^ 48*" 13', apparent time, Mr. Bradley and I, both at 

 the same instant, observed the immersion of ^ y ' by the moon. The emersion 

 was not taken. By comparing this with Mr. Maskelyne's observation, our 

 longitude comes out 4"" 23*4^ west from Greenwich. 



These observations were made before our observatory was finished ; but that 

 being completed in the month of September, and furnished with an excellent, 

 though small, mural quadrant and transit instrument, both made by that 

 eminent artist Mr. John Bird, we began to observe meridian transits, from which 

 I shall select those that were made for determining the solstices, and the opposi- 

 tions of the 3 superior planets, which I shall transcribe, just as they were taken, 

 excepting only making the necessary allowance for the error of the line of 

 collimation. 



Observations for determining the Solstices. 



By comparing these obs. together, I make the true zenith\o ,«/ lo//^ 



distance of the sun's centre, at the winter solstice, to bej 



And at the summer solstice 27 1 9 5 1 .6 



Therefore, the distance of the tropics 46 56 21 .8 



Its half is ... • 23 28 10 .9 



By Mr. Mayer's tables, the decrement of the obliquity, in 



3 months is 0.1 



Hence the mean obliquity, December 21, 1770, is 23 28 11 .0 



And June 21, 1771 23 28 10 .8 



Therefore the lat. of the observatory, by these observations is 50 48 2 .4 Nor. 



Next followed some observations, by Mr. W. on the oppositions of the 

 superior planets to the sun. 



y. Abstract of Mr. T. Barker's Meteorological Register at Lyndon, Rutland, p. 42. 

 This abstract contains the quantity of rain which fell last year, (1771), and an 

 abstract of his observations of the barometer and thermometer, with a general 

 account of the weather. The whole depth of rain was 17-588 inches. 



F'l. Directions for Using the Common Micrometer, taken from a Paper in the 

 late Dr. Bradlei/s Hand Writing ; communicated by Nevil Maskelyne, 

 Astron. Royal, and F. R. S. p. 46. 

 Micrometers, as first contrived, being only adapted to the measuring small 



angles, as the diameters of the sun and moon, or other planets, and taking the 



I 



