SU a aaa 
200 OBSERVATORY AT WEST POINT. 
These values substituted in eq. (8) give 
1925.68, 50°.75 _ 9 39367, 
2000” 130°.75 
THE COMET OF 1843. 
The instrument just described was hardly in working condition, before the announce- 
ment of a comet within our system gave hopes of a speedy opportunity to test its quali- 
ties. 
The weather was unfavourable till the 24th of March, when the first observations upon 
the new visiter were made; the last were on the 2d of April. Of the intermediate days, 
the only ones admitting of observation were the 25th and 29th of March. I have taken 
those of 25th and 29th of March, and of 2d April, to compute the elements of the orbit. 
The observations were commenced by the usual simple and accurate method of mea- 
suring differences of right ascension and declination of the comet, and certain small stars, 
which were in the field at the same time; but recollecting that I had no catalogue more 
extensive than that of the Royal Astron. Society, in which the stars in question could 
not be found, I was obliged to have recourse to another method. 
It is obvious that the difference of the instrumental places of two bodies, corrected for the 
change of instrumental errors arising from a change of position, is equal to the difference of 
their true places. "This corrected difference may be found from Kriel’s formule ( 1) and 
(2), as soon as A, @, w and » are known. If then, some well known star be observed on 
the same evening with the comet, the true place of the latter becomes known, since that 
of the former is obtained from the catalogue, and the quantity by which it differs from 
the place of the comet, by observation. To keep the instrument as nearly as possible in 
the same bearings during the observations on both bodies, « cetd, in the neighbourhood of 
the comet, was selected and used throughout. 
TO FIND AND 4. 
The co-ordinates of a known star, corrected for refraction, when on the meridian, and 
six hours to the east or west, being substituted in equations (6) and (7), we obtain by 
squaring, adding, and taking square root, 
nat No ™H™) +78). 
and dividing eq. (7) by eq. (6) 
Tan, =— PR PI Ra POOL TAG ¢ |-> 
