1824.] Thirty-Seven Principal Stars. 39 



I know by experience, that less than three minutes will not suf- 

 fice to procure with care, the correction in right ascension for 

 each star : and he must have little experience, or less candour, 

 who will not acknowledge that, with all his circumspection, he 

 has not occasionally taken out a false quantity from a wrono- 

 column, or applied one correction to the other with a wrong 



sign 



But it may be said, a reference to preceding observations will 

 immediately detect the error : not so perhaps ; many days may 

 have elapsed since a transit of the same star may have been 

 observed ; or it may be urged, that the amount of error, should 

 it escape unnoticed, will be such as not materially to invalidate 

 the result. Now as far as small instruments, such as are usually 

 stuck out of a window, are concerned, I will concede the point, 

 for with these, an erroneous computation, amounting to two or 

 three-tenths of a second, may really do no harm ; but where an 

 instrument is used, adequate under favourable circumstances, to 

 assign to any star south of our zenith, its right ascension by a 

 single observation, accurate to the largest of these quantities, an 

 error in the calculation of the correction becomes extremely 

 injurious ; for it may so far vitiate others, as to require many 

 additional observations to invalidate its force. We shall then, 

 perhaps, be told, reject it when reduced to the 1st day of the 

 year ; this may certainly be done, but I hold it a bad principle 

 to discard any observation, unless posted as bad at the time of 

 entering it in the rough journal; it leads to temptation which 

 ought in limine to be checked. Observations, be it never for- 

 gotten, are not less entitled to our confidence because they are 

 not always uniform ; and were I asked why the observations 

 made at our Royal Observatory have acquired the influence they 

 have over Europe, I should reply, not only because its instru- 

 ments are superior, but because every observation, good, bad, 

 and indifferent, which has been entered in the Observatory 

 Journal, has been honestly recorded in the printed copies. 



The remaining process of computing is extremely simple. 

 When, however, 50 or 60 stars are observed daily, its irksomeness 

 is quite sufficient ; a circumstance which induced me some time 

 since to remove as much of the drudgery as could be removed, 

 by computing a table, in which the clock's daily rate and error 

 at a particular time of the day being known, its corresponding 

 error at any given time might be found by inspection. 



( To he concluded in our next.) 



The accompanying Corrections are computed from Dr. Maske- 

 lyne's tables, except those of the pole star, which are derived 

 from its apparent right ascension, given in the Nautical Alma- 

 nac for 1824. For the mean right ascensions, 1 am indebted to 

 the kindness of the Astronomer Royal. 



Note.— It being generally admitted that something in the shape of an Astronomical 

 Ephemeris in much needed, I shall publish in the Journal of Science and the Arts for 

 January next, a list of astronomical phenomena arranged in order of succession for the 

 first three months of the year l»'i4. 



