THE MOON S MERIDIAN ALTITUDE. 



281 



the calculated declination, might produce an error ot* a like 

 number of minutes of a degree in the longitude; those effects 

 though of less importance in the moon's right ascension, may 

 also be brought into calculation. 



EXAMPLE I. 



On the evening of the 10th of November, 1804, at Fort 

 Miro, on the river Washita, took the apparent double altitude 

 of the moon's lower limb (greatest) near the meridian, 89° 17' 

 20", index error + 13' 47" 5, the latitude of the place of ob- 

 servation 32° 29' 25". Required the longitude. 



Double altitude of 2>'s lower limb. 

 Index error 



Apparent altitude of 3's lower limb. 

 Effects of refraction and parallax. 



True altitude of S's lower limb. 

 2>'s semidiameter and augmentation. 



Altitude of 2>'s centre. 

 Correction by formula. 



True altitude of 2)'s centre on meridian. 

 Colatitude 



2>'s declination on the meridian. 



Rate of change of 3*3 de- 

 clination in 1 of time by 

 even proportion. . 13" 25 

 Correct by second dif- 

 ferences. . . — 39 



True rate of change per 

 minute at 12 h 40' Green- 

 wich time. . . 12 



11 50 33 42 



86 



h / ii 



Appt. time at Greenwich when the 3 had this declination by even proportion. 12 39 56 17 



Correct by the equation of second difference, -j- 1 15 09 



Apparent time at Greenwich when the 3 was on the meridian of Fort Miro. 12 41 11 26 

 ditto, at ditto, when the 3 was on the mer. of Greenwich interpolated. 6 22 39 22 



Diff. of appt. time corrected by the equation of time — 1" 74 gives mean time. 6 18 30 3 

 Difference of increase of A. K. of the 3 and during the interval. . . — 11 41 



Longitude of Fort Miro 



Comparison of the above with other results. 



6 6 49 3 



Longitude deduced from a mean of six distances of the sun west of the moon. 6 5 59 

 a mean of three distances of a Arietis east of ditto. 6 7 40 

 Longitude alunar eclipse 14th of Jan. 1805, (a fine observation.) 6 6 42 5 



Mean longitude of Fort Miro, differing from the result by the meridian 7 

 ;.ltitudf, only 2" 13, or about 32" of a degree. 5 



6 6 47 ir 



