Royal Astronomical Society. 305 



at Buenos Ayres, in June 1832. In a letter from Mr. Henderson 

 to Professor Airy. 



These positions have been computed by Mr. Henderson from the 

 observations, and he has compared them with those interpolated 

 from Mr. Encke's accurate Ephemeris, communicated to the Society 

 in May 1832. Mr. Henderson considers, as a definitive result ob- 

 tained from the Cape observations, that the mean correction of the 

 ephemeris in right ascension is -f-2' 25" reduced to a great circle, 

 and in declination + 1'30", the mean corresponding date being 

 June 5, 1832. 



V. Catalogue of the North Polar Distances of 60 Stars, reduced 

 to January 1, 1830, derived from Observations made at Greenwich 

 by the two circles and six microscopes, 1S25-1833. From the 

 Astronomer Royal. An Abstract of this paper is given in the 

 Monthly Notices. 



VI. Stars observed with the Moon at the Royal Observatory, 

 Greenwich, from February 1833 to March 1834. 



June 13. — The following communications were read: 



I. Some remarks on the Greenwich mural circles, by the Astro- 

 nomer Royal. 



The memoir lately published by Professor Airy, in which he 

 notices some discordances in the zenith points of the Cambridge 

 circle as determined by different stars observed directly and by re- 

 flection, induced Mr. Pond to examine whether one or both the 

 mural circles of Greenwich exhibited the same defects. The ob- 

 servations of 1825 and 1826 being very numerous and carefully 

 made, Mr. Pond has selected a series of differences of declinations 

 between certain stars observed in those years. As the altitude of 

 each star is obtained with each circle by direct and reflected vision, 

 independently, (the stars being in fact observed as church steeples 

 are with a theodolite,) it is evident that there are four combinations 

 of differences between every pair of stars, wholly free from any 

 hypothesis as to the absolute declinations, the agreement or dis- 

 agreement of which will show the accuracy or defects of the in- 

 struments. From the near coincidence of each result with the 

 mean, Mr. Pond concludes that the circles were at that time in a 

 satisfactory state. 



II. Observations of the Solar Eclipse, July 16, 1833, at the 

 Cambridge Observatory. By Professor Airy. 



Professor Airy considers the beginning or end of a solar eclipse 

 so unsatisfactory an observation compared with the mode adopted 

 by him on the present occasion, that he did not think it worth 

 while to note them at all. The instrument employed was a 5-feet 

 equatorial by T. Jones, magnifying power 100, which has been 

 noticed in the determination of the elongations of Jupiter's fourth 

 satellite and of the parallax of Mars. The only sensible error in 

 its adjustment was that in azimuth, which was unimportant in the 

 present instance, as the middle of the eclipse was almost exactly at 

 6 h from the meridian. The observations were of differences of 

 N.P.D. and differences of R.A. When differences of N.P.D., as 



Third Series. Vol. 5. No. 28. Oct. 1834. 2 R 



