736 PHILOSOPHICAL TRANSACTIONS. [anNO 1776. 



But the clock showed 10*' 12™ 44'.5 when the star passed, consequently it was 

 2™ 28^0 too slow for mean time. 



Observers, who are not furnished with tables of the sun's right ascension, and 

 of the equation of time for the apparent noon of their meridian, may apply both 

 as they are given in the Nautical Ephemeris for the meridian of the Royal Ob- 

 servatory at Greenwich ; the result will be the mean time of the star's passing the 

 Greenwich meridian. And by applying the proportional part of the foregoing 

 acceleration of 3"" 55\gi, belonging to the difterence of longitude in time of the 

 place of observation from Greenwich, the mean time of the star's passing the 

 meridian of the place of observation will be found. If the place be to the east 

 of Greenwich, the acceleration will be additive ; if to the west, subtractive. 



In a similar manner, the mean time of any observation made with a clock, 

 regulated to sidereal time, may be inferred, provided the preceding transit of the 

 sun has been observed ; for if from the time of the observation by the clock, in- 

 creased if necessary by '24 hours, the time of the observed transit of the sun be 

 subtracted, the remainder, diminished by the proportional part of 3™ 55^91, 

 and duly corrected by the equation of time for the preceding noon, will give the 

 mean time required. It is understood that the clock keeps the rate of sidereal 

 time exactly ; for if not, a further correction for the loss or gain since noon must 

 be applied. 



END OF VOLUME THIKTEENTH. 



C. aai K. Baldwin, Printers. 

 New Bridge-Street, London- 



