98 Astronomical and Nautical Collections* 



In these calculations the difference of meridians is assumed 

 9' 20"'5, which has been deduced from the corresponding occulta- 

 tions of fixed stars by the moon, observed at both places, during 

 the period in question. 



On comparing the catalogues of fixed stars by different astrono- 

 mers, similar discordances are found to subsist between the places 

 of several stars relatively to those of the others by the respective 

 catalogues. For instance, the relative position of Castor, in right 

 ascension, differs 0"-31 of time, or 4"*6 of space, in Mr. Pond's 

 and M. BesseFs catalogues. Nautical Almanac for 1822, p. 179. 

 It would thus appear that the discordances alluded to are not pe- 

 culiar to observations of the sun and moon, but that they are com- 

 mon to all the celestial bodies, and are occasioned by the unavoid- 

 able imperfections in the present state of the art of observing. It 

 may be remarked that, while these imperfections continue, the dif- 

 ference of longitude determined from observations of the moon's 

 meridian right ascension cannot be so accurate as that deduced 

 from corresponding observations of occultations. Thus, while the 

 difference of longitude between Greenwich and Paris, by eight 

 occultations is 9' 20"*5, the above series of 395 observations of 

 right ascension makes the same difference of longitude 9' 24"*8. 



iii. The Latitude of Greenwich, as computed by Professor 

 Bessel. 



In the 73rd Number of Schumacher's Nachrichten, we find a 

 paper of Professor Bessel on the results of the Greenwich observa- 

 tions for 1822, comprehending a number of altitudes obtained by 

 reflection as well as by direct vision. The latitude, from the mean 

 of a great multitude of observations of different stars, becomes 

 51° 28' 38"-343 + b', b' t being a quantity so small that it may 

 be neglected, though it has not been precisely determined. The 

 mean error of each single observation is ;£ 0""799, and is no 

 greater for the observations made by reflection than for the others ; 

 a circumstance which proves the extreme care that must have been 

 taken to avoid the effects of agitation. 



