Astronomical Society. 149 



the sum of the corrections for precession, aberration, lunar 

 and solar nutation, for every star at the time of observation, 

 and apply each sum with a contrary algebraic sign to each 

 true apparent right ascension ; the result will give their mean 

 right ascension for the beginning of the year. 13. Let a series 

 of these for each star be registered, and the mean of each 

 series (if the observations be good) may be expected to give 

 the mean right ascensions at the beginning of the year, with 

 considerable accuracy. — The author concludes with observing 

 that frequent applications of the level to the axis of the instru- 

 ment during a night's observations are indispensable. 



The same evening there was read, " An Appendix to a 

 former Paper on the Latitude of the Royal Observatory, by 

 the Astronomer Royal." The author of this Appendix defines 

 the latitude of a place to be the observed altitude of the centre 

 of a small circle described by the pole-star, the state of the 

 barometer and thermometer being given, minus the refraction 

 due to that altitude. The last correction he regards as alto- 

 gether arbitrary, and states that he employs Bradley's refrac- 

 tions. The observations of the last eighteen months at Green- 

 wich, with the two circles, as described in a former paper, in- 

 clude 720 of the pole-star, from which the co-latitude deduced 

 is 38° 31' 2l""045. 



There was next read, " A Summary of the Observations 

 made for the Determination of the Latitude of the Observatory 

 at Wilna, by M. Slawinski." The observations amount to 

 260, and were made in the months of October and November 

 1825. The author gives an account of his researches to de- 

 termine the flexure in the repeating circle, and explains that 

 his reductions are made both by means of the places of stars 

 given in Bessel's Tables, and the positions announced in the 

 Nautical Almanac for 1827. The latitude referred to the 

 centre of the transit instrument is 54° 40' 59"*09 deduced by 

 comparison with Bessel, and 54° 41' 0"*05 by comparison with 

 the Naut. Aim. The greatest of these determinations is less by 

 about 2" than the latitude of the same observatory as given by 

 M. Slawinski's predecessors Poczobut and Sniadecki. 



The reading of M. Slawinski's paper was followed by that 

 of one on " Micrometrical Observations of the Planet Saturn, 

 made with Fraunhofer's large Refractor at Dorpat, by Pro- 

 fessor Struve." These Observations were made with a re- 

 fracting wire micrometer attached to Fraunhofer's large tele- 

 scope now so well known : employing the power 540, Pro- 

 fessor Struve describes both the instrument and the manner 

 of observation ; but it will be simply necessary here to record 



the 



