on finding the Mean Solar Time. 297 



for reducing sidereal into mean time, the other for reducing 

 mean into sidereal time, to any instant required, they would 

 have been an acquisition in stellar calculations, and found to 

 be more generally useful than his* 



In order to obtain apparent solar time by an observed alti- 

 tude of a known star, nothing more seems necessary than to 

 reduce the sun's right ascension to apparent time of observa- 

 tion, and apply a correction for longitude (if any) from the 

 meridian of Greenwich. The right ascension and the polar 

 distance of the star, if it be one of the 24- in the table of stars 

 at the end of the Nautical Almanack, may be taken out for 

 the given day by inspection at once, as the variations in 24 

 hours under these circumstances seldom amount to an appre- 

 ciable correction, except for Polaris. Then to the apparent 

 time found by the method in Mackay's, Norie's, or Riddle's 

 Navigation, apply the reduced equation of time in the same 

 sign as expressed in the Nautical Almanack, the result will be 

 the mean solar time, at the place of observation, when the al- 

 titude was taken ; the difference between this time and that 

 shown by the chronometer or clock, will be the error sought. 



The following are the tables I have alluded to, with an ex- 

 ample to each. 



Vol 64. No. 318. Oct. 1824. 



Pp 



Reduced 



