^8 ^ On the Comet of 1 807. 



try, but by many others in different parts of the world ; aa 

 that the elements of its orbit will be ascertained with great 

 precision. 



I had an opportunity of observing it fourteen times be- 

 tween the 4th of October and the 12th of November, but 

 none afterwards. The right ascensions and declinations were 

 corrected for refraction, and from them the geocentric longi- 

 tudes and latitudes were deduced. With these data I eoia- 

 puted the elements of the orbit according to the rules laid 

 down in sir Henry Englefield's excellent Treatise upon Co- 

 mets, and hope that, though not quite accurate, they will not 

 be found to err much. 



The drawing (see Fig.) represents the comet's orbit simply 

 applied to, but not projected on the plane of the ecliptic. 

 The outer circle t> 25,=^, "l^, is drawn at pleasure with 

 any radius. — A B C D is the earth's, and E V F part of the 

 comet's orbit : X S V its axis : © gj the line of nodes ; 

 V the perihelion point, and S V the perihelion distance. 



The elements of the orbit are nearly as follows : The 

 perihelion distance = 0-64802; the distance of the earth 

 from the sun S A or S B being = 1*00000. 



The time of the comet's passing the perihelion at V wa^ 

 September 1 8th, 22 hours 10 minutes M. T. 



The longitude of V on the orbit was 28° 4l' in Scospio. 



The longitude of the ascending node 26° 3(5' in Sagit- 

 tarius. 



The comet passed the ascending node September 29th, 

 18*^48'". 



The longitude of the axis S X as seen from the sun,, was 

 in 13° 11' af Gemini; and its elevation or north latitude 

 24° 43'. — The inclination of the orbit 63° 15': — this is 

 easily conceived, by supposing the visible part of the orbit 

 from n to F to revolve upon the line of nodes gj n till any 

 point in the orbit, as F, is elevated 63^-° above the plane of 

 the ecliptic. 



The comet was seen here soon after it passed V; the earth 

 at that time was nearly at A, moving from thence towards B ; 

 while at the same time the comet moved from V towards 

 F ; and consequently its motion was direct. 



