48 On the Comet of July— September 1SI9. 



The figure may be shortly explained, thus ; NC the orbit of 

 the comet projected on the plane of the ecliptic, with dots re- 

 presenting its place at intervals of 5, 10, 20, 30, &c. days from 

 the perihelion ; N n, the line of the nodes ; P p, that of the 

 apsis ; S, the sun ; the orbit of the earth shown by a portion of 

 a circle, with dots corresponding to the same epochs as those on 

 the comet's orbit; the dotted lines joining the two orbits point 

 out clearly the progressive increase of the comet's geocentric di- 

 stance and longitude. The dotted line NP'C shows the para- 

 bolic curve on its own plane, whence the perpendicular heights 

 of the comet above the plane of the ecliptic may be found, by 

 diminishing the ordinates of the curve in the proportion of radius 

 to sin. inclin. i. c. 11 to 76 nearly. 



The subjoined table gives the distances, &c. from the time of 

 passing the node, to 80 days from perihelion, or upwards of 141° 

 of anomaly. 



With respect to the length of the tail, it is impossible to give 

 any thing like an accurate statement, as different observers vary 

 greatly in their ectimations ; but if we assume the angular mea- 

 sure already given, to be correct, tlie length thence deduced will 

 be about 8| millions of miles. 



Lewes, Jan, 1, 1820. 



I am, &c. 



AXrPO<PIAOX. 



• The mean distance of Earth from Sun being assumed 93,7'6S,000 miles. 



VI. Parti- 



