280 On Enckc's Comet. 



From these elements it would follow that if the comet pass 

 the perihelion between the months of October and February, 

 it would appear, upon its approach towards the earth, so much 

 to the north of the ecliptic, as to render it visible in our northern 

 climates. But if it should happen at an opposite season of the 

 year, it would not, in general, be visible, except in places south 

 of the equator : unfoi'tunately, this will in some measure be the 

 case at its next appearance in May 1 822. 



To determine with precision the time and place when the 

 comet will next appear, would require a complete calculation 

 of the disturbing forces of all the planets upon the comet from 

 the year 1 795 to 1 822. The methods of doing this (though 

 much abridged and simplified from what they were when 

 Clairaut and his associates, witli immense labour, calculated 

 the return of Halley's comet) are yet extremely laborious ; and 

 the difficulty in the present instance may sometimes be very 

 much increased, from the circumstance that the comet may 

 pass very near to Mercury, and the attraction of this planet 

 might be so much augmented by its proximity, that its disturb- 

 ing force, notwithstanding the smallness of its mass, might ex- 

 ceed that of Jupiter, the greatest planet in the system. 



The calculations made by Professor Encke, to ascertain 

 nearly the effect of the disturbing forces of the planet upon the 

 comet, ai-e given in the diird of the papers mentioned at die 

 beginning of this article. It is unnecessary to go into any par- 

 ticular detail relative to this subject. We shall merely ob- 

 serve, that the result of his inquiries leaves an uncertainty of 

 about one day in the time of passing the perihelion. He has 

 therefore used two sets of elements, in computing the places 

 of the comet. T\\ejirst set, which he supposes to be the most 

 accurate, is as follows : counting the mean time from the meri- 

 dian of Seeberg, and the longitudes from the mean equinox of 

 May 24., 1822. 



(1. Jt. 

 Time of passing the perihelion, 1822, May 24, 0. 

 Log. of the mean distance - - 0.-34722 



Long, of die pevilielion - - 157° 12' 7" 



Long, of the ascending node - - 334 23 24- 



Liclination of the oibit to the ecliptic 13 20 36 



Eccentricity - - 0.84472 



In the second set, the time of passing the perihelion is Ma}' 

 25*^0''; the log. of the mean distance 0.34746; the rest of 

 the elements are not altered. 



Professor Encke lias calculated, in both these hypotheses, 

 the places of the comet, at intervals of four an<l of two days, 



fn)n\ 



