400 COMETS. 



g8, very pale, and exceeding thin ; its matter 

 more dispersed, and no distinct nucleus at 

 all appearing; and I shall only revert to* 

 the Comets alluded to before, which Dr. 

 Herschell discovered^ and which he was in-* 

 timately persuaded to be mere collections 

 of vapors, condensed about a centre, without 

 any nucleus whatever ; to show the probability 

 which exists, that Comets are nothing more than 

 atmopheric matter, in a state of combustion. 

 The rapidity and intensity of the combustion 

 which is thus going on in Comets, may, in some 

 degree, be estimated from the colorific, and ca- 

 lorific rays, which issue from them. Two 

 Comets described by JUSTIN, lib. 37, according 

 to his account, " shined so bright, that the 

 whole heaven seemed to be on fire, and by their 

 greatness filled up a fourth part of the heavens, 

 and by their splendor exceeded that of the 

 sun ; and it is affirmed, with regard to the 

 Comet of 1401, that the sun being got be- 

 low the horizon, there appeared in the west, 

 a bright and shining Comet, sending out a 

 tail, upward, in splendor like a flame of fire, 

 and in a form like a spear, darting its rays 

 from west to east ; by the lustre of its own rays, 

 it enlightened ail the borders of the earth, not 

 permitting the other stars to show their lights, 

 or the shades of night to darken the air, be- 

 cause its light exceeded that of the others, and 



