Royal Astronomical Society. 581 



The N. P. D.'s are compared with the Astronomical Society's 

 Catalogue, with Pond's, Johnson's, and Henderson's Catalogues, 

 and with the Greenwich observations of 1836 and 1837. 



June 1 1 . — The following communications were read :— 



A New Catalogue of Moon-culminating Stars, observed at South 

 Kilworth. By the Rev. Dr. Pearson. 



This catalogue contains 520 stars which fall within the passage 

 of the moon, in every situation of the nodes, and which had been 

 published in the Appendix to the first volume of the author's work 

 on Practical Astronomy *. The stars in this catalogue had been 

 selected by Caturegli from the determinations of different observers, 

 and therefore might be supposed to have their places assigned with 

 different degrees of accuracy, so as to require a new series of care- 

 ful observations, and reduction with improved constants, to ren- 

 der them suitable objects for so delicate a purpose as the deter- 

 mination of longitudes, by comparison with the moon's limb, upon 

 or near the meridian. This consideration induced Dr. Pearson to 

 confine his stellar observations to moon-culminating stars, employing 

 for the purpose, contemporaneously, the transit instrument and 

 circle, described in his work before referred to, and a clock by 

 Hardy, which is an exact fellow to the transit- clock at Greenwich 

 in its original state. The observations were continued uninter- 

 ruptedly from November 4, 1830, to May 7, 1834; when, on ac- 

 count of inconvenience arising from the smoke of the village, the 

 instruments were removed to another building in the author's pri- 

 vate grounds, lying in the same meridian and 4'' to the south of the 

 former. They were here continued till the end of the year 1837, 

 when it was found that, with very few exceptions, the whole of the 

 stars had been observed at least six times. 



The reductions were made with the constants given in the Astro- 

 nomical Society's Catalogue for the epoch 1830, for the purpose of 

 direct comparison with that catalogue, using the annual precessions 

 given in that work. Brinkley's refractions were used in the reduc- 

 tion of the circle observations, which include stars as low as 8° of 

 altitude, and may therefore possibly furnish data for correction of 

 the tables of refractions ; with which view the original observations 

 have been preserved. The telescopes used are by Tulley, and the 

 object-glasses, of 3£ inches aperture and nearly 44 inches focal 

 length, may be considered excellent in their definition of a large star. 

 The collimation in altitude was determined by a small collimating 

 telescope, by reversion of the azimuthal positions ; and comparison 

 of the sum of reversed readings with 90° proved highly satisfactory 

 in every instance. 



The resulting right ascensions of the stars used for clock-error 

 are given in an appendix, that their close agreement with the right 

 ascensions derived from a multiplicity of observations at Greenwich 

 may be exhibited. 



Numerical corrections were not applied for the instrumental 

 errors, but the instruments themselves were kept in adjustment by 

 [* See Phil. Mag., Second Series, vol. iv. p. 134.— En.] 



