ASTRONOMY. 199 



more than an arch of a few degrees, these extraor- 

 dinary apparent changes of place can only have 

 proceeded from vicinity to the Earth. 



07. It appears that Comets contain very lit- 

 tle matter, and have but a very feeble action on 

 other bodies. 



In the year 1454, a Comet is said to have eclipsed 

 the Moon $ so that it must have been very near 

 to the Earth ; yet it had no sensible effects. 

 The Comets just mentioned produced none. A 

 Comet in 1770 came very near to the satellites of 

 Jupiter, but caused no derangement in the sys- 

 tem. 



208. The number of Comets observed and re- 

 corded, with more or less accuracy, exceeds 

 350. 



PINGRE', who wrote in 1783, enumerates 324 ; and 

 32 are now to be added. 



Of these, not so many as a third have been observed 

 with such accuracy, as to allow the elements of 

 their orbits to be asceratined. The elements of 98 

 have been computed, going back as far as the 

 year 837, and coming down to the Comet of 1807. 

 See FERGUSSON'S Astronomy, (BREWSTER'S edit.) 

 vol. II. p. 360. 



SECT. 



