/ 



1824.] Thirty-Seven Principal Stars. 139 



Hence diff. for 10 days = + (Ho" 



And diff. for 1 day = + 0-015 



The equation, therefore, for Nov. 27 = — 0-235'". The sign 

 is to reduce mean to apparent N. P. D. 



Equation for Variation. 



Gr. obs. 1813, p. 260, equation for Nov. 26 = +2-71 



Dec. 6 = + 2-78 



Hence diff. for 10 days = + 0-07" 



And diff. for 1 day = 0-007 



The equation, therefore, for Nov. 27 = + 2-717". This sign 

 is to reduce the observed N. P. D. to the mean. 



Hence the correction for N. P. D. is + 13.05" + 9-04" 

 - 7-66" + 0-235" + 2-717" = + 17-382". 



On inspecting these calculations, remembering that they alone 

 refer to observations of a single star on a particular day, and 

 aware that similar are needed for every zero star, as often as it is 

 observed, few I apprehend will be found to dispute the point, 

 that corrections in right ascension, and north polar distance, 

 cannot be procured at the time ofivantingthem, without frequent 

 error, and disgusting labour. 



Proceed we now to investigate the nature, and extent of the 

 advantages, which would result, were we but supplied annually 

 with a publication containing the daily corrections of the 46 zero 

 stars. These would be comprised, in the equality upon which 

 it would place the British, with the foreign observer — in the 

 inducements which it would hold out, to the study of practical 

 astronomy — in the comparative ease with which it would enable 

 astronomers employed on scientific missions, to obtain accurate 

 astronomical observations — in the facilities which it would afford 

 us in the examination of published observations — in the superior 

 accuracy with which our most important observations would be 

 reduced; and lastly, in the immense labour which would be 

 saved. We will consider them in order. 



1 . As to the equality to which it would raise the British with the 

 foreign observer. — On the continent by the industry of a Danish 

 astronomer, and by the aid of the Danish government, the appa- 

 rent places of the 46 zero stars for every tenth day of the year, have 

 been published annually some time past ; but as the mean places 



