VOL. LII.] PHILOSOPHICAL TJ^IANSACTIONS. 567 



exactness, within 2 seconds; and did not differ more than 5 seconds in excess 

 from the computed place. The place of Venus was computed from Dr. Halley's 

 tables, only adding 31" to the mean motion, and l' 45''' to the place of the node ; 

 by which corrections, they had been found to agree better with observations 

 made near the inferior conjunction in 1753. 



According to these numbers, the ecliptic conjunction of the sun and Venus 

 was June 5, 1761, n.s. at 17^ 51"^ 20% meantime, at Greenwich; and the place 

 of the sun and Venus 2" 1 5^ 36' 33'^; and the geocentric latitude of Venus south 

 g' AA".g. The places of the sun and Venus being computed for 3 hours before, 

 and 3. hours after the ecliptic conjunction, the horary motion of the sun is 2' 

 23".45, of Venus retrograde V 33''.68; the horary motion of Venus from the 

 sun therefore 3' 57^.13, retrograde. The horary motion of Venus in latitude is 

 south 35'''.46. The angle of the visible way with the ecliptic 8° 30' 10'^; the 

 horary motion in that way 3' 59''.77. The right ascension of the sun, supposing 

 the apparent obliquity of the ecliptic 23° 28' 18", was then 74° 22' 19'^2; and 

 the horary motion of the sun in right ascension was 2' 34".55. The declination 

 of the sun was then 22^ 4l' 35''.9; the horary motion in declination was iS'^SS 

 northwards. The angle formed by the axis of the ecliptic, and the axis of the 

 equator, was 6° 9' 34'', decreasing hourly one minute. 



The right ascension of Venus at the ecliptic conjunction was 74° 23' 27^.2: 

 and the horary motion of Venus in right ascension l' 36 '.7 5 retrograde. The 

 horary motion of Venus from the sun in right ascension was therefore 4' 1 1'''.3 

 retrograde. The declination of Venus was then 22° 3l' 54''''.2: and the horary 

 motion in declination was 45^.29 southwards: the horary motion of Venus from 

 the sun in declination was therefore \' 0".Q2 southwards. 



The logarithm of the earth from the sun was then 5.006642; the logarithm 

 of Venus from the sun was 4.86 1 192; and the logarithm of Venus from the 

 earth was 4.460874. If we suppose the horizontal parallax of the sun to be 

 104-", then the horizontal parallax of Venus, as seen from the earth, will be 

 36^.31; which, diminished by that of the sun, is 25".97. If the parallax in 

 longitude and latitude be computed from these data, the visible horary motion 

 of VenuB from the sun in longitude will be 3' 58".35 retrograde, and in latitude 

 33".75 south. The longitude and latitude of the centre of Venus from the sun's 

 centre, answering to the several right ascensions and declinations observed, 

 may be determined in the following manner. 





