1826, J Astronomical Society. 231 



and the pole. 9. A proportional part of the daily rate must be 

 applied to every observation from the first. 10. The error of 

 each star from the true meridian, must be computed from tables 

 prepared for the purpose. 1 1 . To the time of transit of each 

 star, add the error of the clock (6), the proportional part of the 

 daily rate (9), and the error from the meridian (10) : the respec- 

 tive sums will give the true apparent right ascensions required. 

 12. Compute the sum of the corrections for precession, aberra- 

 tion, lunar and solar nutation, for every star at the time of obser- 

 vation, 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 consi- 

 derable accuracy. — The author concludes with observing, that 

 frequent applications of the level to the axis of the instrument^ 

 during a night's observations, are indispensable. ;^'''' ^*"' ' -■ -^ 



The same evening there was read, " An Appendii^tbii foi'mer 

 Paper on the Latitude of the Royal Observatory, by the Astro- 

 nomer 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 alti- 

 tude. The last correction he regards as altogether arbitrary, 

 and states that he employs Bradley's refractions. The obser- 

 vations of the last eighteen months at Greenwich, with the two 

 circles, as described in a former paper, include 720 of the pole- 

 star, from which the co-latitude deduced is 38° 31' 21''-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 determine 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 instru- 

 ment is 54° 40' 59''*09 deduced by comparison with Bessel, and 

 54° 4r 0''-05 by comparison with 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 Professor 

 Struve." These observations were made with a refracting wire 

 micrometer attached to Fraunhofer's large telescope, now so v^ell- 



