142 ASTRONOMICAL OBSERVATIONS. 



The following are the results of the observations : 



Lower culmination of Polaris, June 4, 1840, 41° 14' 40". 4 



8, 40 .2 



9, 42 .2 

 13, 42 .3 



15, 42 .6 



16, 41 .3 

 ■ 18, 45 .0 



19, 43 .1 



23, 43 .4 



Mean of nine culminations, 41 14 42 .3 



The result of last year's observations of Polaris was 41° 14' 38". 1. The 

 places of Polaris were taken from the Nautical Almanac, and the above results 

 are both affected by the error of the tables, but with opposite signs, as the lat- 

 ter result was derived from upper, and the former from lower culminations. 

 The mean of the two is 41° 14' 40". 1, the value which I at present employ. 



II. Observed Transits of the Moon and Moon culminating Stars at 



Hudson Observatory. 



The following list is supplemental to that given on pages 49, 50. The 

 observations are all reduced to the central wire. When the object is observed 

 at all the wires, the reduction is equal to 0M12 x secant of the declination, 

 which correction is readily taken from a table, and is sensibly constant for all 

 the following stars. When an object is not observed at all the wires, each ob- 

 servation is separately reduced to the central wire. For a star, this reduction 

 is equal to the equatorial interval multiplied by the secant of the declination. 

 For the moon this factor is computed by the formula 



1 — sin n cos d sec S o^nn s 



-f^ . dbOO sec 



3600 — A 



Where n = the moon's horizontal parallax. 

 ^ = latitude of the place. 

 5 = moon's true declination. 



A = moon's hourly motion in right ascension, expressed in seconds of 

 time. 



