the celebrated Comet qfl264i and 1556. 55 



With the above values for x, y and ;?, and those of X, Y, 

 Z, taken from the Nautical Almanac, the position of the comet 

 for different suppositions as to the time of passage through 

 perihelion may be readily obtained. If vi^e suppose March 0, 

 which is about the epoch fixed by Professor Madler, we shall 

 have the following ephemeris for facilitating the discovery of 

 the comet, mean noon at Greenwich : — 



It appears from this ephemeris, that according to the most 

 probable supposition we can make respecting the time of pe- 

 rihelion without actual calculation of the perturbations, the 

 position of the comet in the heavens during the approaching 

 reappearance will be extremely unfavourable for observation ; 

 and it is therefore the more desirable that those who look 

 out for comets should be on the alert. Nearly the whole of 

 the vast trajectory of this comet lies below the plane of the 

 ecliptic, and Jar Jt'om the paths of the larger planet s^ but it ex- 

 tends into space more than twice the distance of Neptune ; 

 and surely we are not yet able to say what causes may operate, 

 at this immense distance from the sun, to affect the time of the 

 next return to perihelion. If however the comet can be de- 

 tected and observed, we shall then have the means of ascer- 

 taining something more on these points 



