J^ezo Method of determining the Longitude^ 1 1 1 



very great, the correction resulting from that part of the 

 formula immediately connected with these signs, (depend- 

 ing on the variation in the semi-diameter and declination 

 of the moon,) may be neglected, and the equation becomes 

 simply 



The values of t and t are obtained by observation, and 

 those of and h might easily be deduced therefrom, if ob- 

 servers record their observations entire ; since, the sidereal 

 time of the transits being given, vie might easily compute 

 the apparent time to the nearest minute, which will be 

 quite sufficient. The values of r, ^, c?, and 5, may be ta- 

 ken from an ephemeris, and computed for the apparent 

 times of observation as shown at the meridian for which 

 such ephemeris is calculated ; and the values of a and b 

 may be obtained from the same ephemeris bj second dif- 

 ferences. See p. 9. 



" I have already remarked that these formulae are adapt- 

 ed to sidereal time only : if therefore the clock, by which 

 any of the comparisons are made, should be adjusted to 

 mean solar time, the observed interval, denoted by t or t, 

 must be multiplied by 1,0027379." p. 10. 



We shall now present a case, selected from those Mr. 

 Baily has furnished, of the application of this formula to 

 practice. The differences between the culmination of the 

 first border of the moon and three stars were observed 

 March 3d, 1822, by M. Nicolai at Manheim, and by M. 

 Struve at Dorpat, as follows : 



1822. Stars. Manheim. Dorpat. Difference. 



i= «r= («-t) = 



March 3. 309 Mayer-f 13"" 18% 30+10"* \T, 56 + 3" 0S74 



82Gemin. + 8 9,43+ 5 8, 55 + 3 0,88 



M-'Gancri — 9 41,11-12 41,89+3 0,78 



Mean +3 0, 80 



The times of the moon's culmination are not here given, 

 and it becomes necessary to take them from an ephemeris. 

 By the Con. des Terns it appears, that the moon passed the 

 meridian of Paris March 3d, at 8A. bhn. apparent time ; 

 and as the estimated longitude of Manheim is Oh. 24m. 31s. 



