170 



PROCEEDINGS OF THE AMERICAN ACADEMY 



given by the great refractor of Cambridge University, having been 

 obtained in every case from instrumental readings, and not from mi- 

 crometric comparisons, are not determined with the full accuracy which 

 the instrument is capable of affording. The mode of observation has 

 been, to bring the object, by estimation, to the centre of the field of 

 view, marking the time, and reading the circles for each in succession, 

 and thence deriving their relative positions ; a method which, howev- 

 er unpromising it may at first sight appear, affords, with practice, 

 better differences of declination than are easily obtained, with smaller 

 instruments, by the aid of the micrometer, and in high declinations 

 is often decidedly preferable for right-ascension differences. The 

 right ascensions and declinations of the comet were obtained by ap- 

 plying the observed differences to the place of the star of compari- 

 son referred to the mean equinox of Jan. 1st, 1847. 



Mr. Bond presented for publication a new series of moon 

 culminations, observed at the Cambridge Observatory during 

 the past and present year. 



Moon Culminations, 

 Observed at Camhridge, Corrected for Instrumental Errors, Clock 



Error, and Rate. 



B» is the initial of William. C. Bond ; B*, of G. P. Bond. 



