254 flints respecting a New Theory 



carried from one vortex to another in right lines: but 

 Cassini supposed from his observations that they moved in 

 circles very eccentric, and containing the earth's orbit within 

 them ; and from hence was led to think the comet of 1680 

 and 1681 was the same as appeared in 1577. By means 

 of this and some others he had an opportunity of seeing, 

 he determined that comets moved through the constella- 

 tions Antinous, Pegasus, Andromeda, Taurus, Centaur, 

 Scorpio, and the bow of Sagittarius, which he called the 

 zodiac of comets. That this is not the case, later observa- 

 tions have proved. The comet that appeared in September 

 1808 was first seen in Serpentarius, it then passed through 

 the right shoulder of Hercules, the Lyre, and disappeared ill 

 the tail of the Swan, which is a course widely different from 

 the zodiac laid down by Cassini. James Bernouilli, in his 

 System of Comets, published in 1682, considers them to be 

 satellites moving about a primary planet, which revolved 

 around the sun, at a distance equal to 2583 semidiameters 

 of the Magnus orbis, in four years and 157 days, although 

 Saturn, who is 258 times nearer, makes only one revolu- 

 tion in about 30 years. This primary, he says, we can 

 never see, on account of its smallness and immense di- 

 stance, and these comets or satellites are only visible when 

 they descend towards us in perigeum. In this theory we 

 have a greater body revolving round and carried with a 

 smaller; which is contrary to what is observed with regard 

 to the other planets and their satellites. May we not con- 

 sider this as one of those theories which, had it not come 

 from so great a man, would have been buried long ago in 

 oblivion ? 



Sir Isaac Newton, Dr. David Gregory, Dr. Ualley, and 

 others, imagine them to move in very eccentric ellipses, 

 having the centre of the sun in one of their foci : but some 

 in their calculations have substituted a portion of a parabola 

 having the same vertex and focus, which they observe is its 

 tnte trajectory, if it never returns. This supposition only 

 leads us from one difficulty to another ; for we may next 

 ask, By what means did it come within the attraction of 

 the sun, and from whence ? Are we to suppose it passes 

 from one fixed star to another in a serpentine direction, 

 which is the theory adopted by Mr. Cole of Colchester ? 

 All the celestial phenomena with which we are acquainted, 

 are obedient to certain laws of attraction, and move either 

 in circles or ellipses, but none in the manner above men- 

 tioned. 



But to return to the former theory j that is, that they" 



move 



