Magmtical Observatory of Dublin during the Years 1840-43. 81 



Epoch of greatest Weste^iy Elongation. 



Summer half-year, O* 58*" p. m. 



Winter half-year, 47 



Whole year, 54 



Epochs of greatest Easterly Elongation. 



Summer half-year, . . G'SO^a. m. . ll* 8" p. m. 

 Winter half-year, . . 7 59 . . . 9 38 

 Whole year, .... 7 12 ... 10 



The hours of mean declination (or those at which the curve crosses the 

 axis of abscissEe) are in like manner deduced from the equation 



^(Ai cos ix + Bi sin ix) = 0. 

 The following are the results : 



Epochs of Mean Declination. 



Summer half-year, . . 9* 36"' a. m. . 6* 3*" p. m. 

 Winter half-year, .. 9 30 ... 5 54 

 Whole year, .... 9 34 ... 5 59 



10. The critical hours for the separate months are given in the following 

 Table: 



Table IV. Hours of Greatest, Least, and Mean Declination. 



VOL. XXII. 



M 



