AT THE OBSERVATORY AT PARAMATTA. 29 



From the known right ascensions of the Moon's culminating Stars, observed 

 on the given day, I deduce the true right ascension of the Moon's centre for 

 the apparent time of the Moon's limbs passing the middle wire. For the cor- 

 responding time at Greenwich (found here upon the supposition of the longi- 

 tude = 10'' 4™ 3^), I find also from the Nautical Almanac, the Moon's right 

 ascension, applpng thereto the correction found from the Observations made 

 on that day at Greenwich. The diflference between the two right ascensions, 

 divided by the Moon's horary motion, which need only to be known superficially, 

 is the error of the assumed Longitude, which in East Longitude is additive or 

 subtractive, accordingly as the Nautical Almanac gives the Moon's M greater 

 or less than the Observation. 



The above Longitudes rest merely upon a comparison with the Nautical 

 Almanac. When the errors thereof are once known, it will be suflicient to 

 apply double their quantities to the Longitudes in time found on the corre- 

 sponding days. 



The Longitude of the Observatory by a mean of all hitherto calculated 

 Observations, including the occultations, is lO"* 4™ 6^25. 



Port Jackson. 



The geographical position of Port Jackson being of nautical importance, I 

 think its determination here is not misplaced. 



The observations of Sir Thomas Brisbane with two reflecting circles of 

 Tboughton and one of Jecker, give the latitude of Government House at 

 Sydney 33° 51' 58" S. 



Sir Thomas Brisbane observed the eclipse of the sun l6th August 1822, at 

 the same place, as follows : 



b m s 



lT."!"':::22?o1:5}Me-ti">eatSidney. , 



Hence I find by a comparison with the Nautical Almanac the ^^ ^ ^ 

 longitude of Sydney * 10 5 17-89 



The solar eclipse of 9th December 1806, observed by Admiral 

 BuGH, gives, according to my calculation, 



Another, observed by Captain Philip Parker King, R.N. . . . 



By chronometers frequently carried backward and forward between Pa- 



