Comets. 249 



system, are as much unknown as ever. No distinct and sa- 

 tisfactory account has yet been rendered of those immensely 

 voluminous appendages which they bear about with them, 

 and which are known by the name of their tails (though im- 

 properly, since they often precede them in their motions), any 

 more than of several other singularities which they present. 



The number of comets which have been astronomically- 

 observed, or of which notices have been recorded in history, 

 is very great, amounting to several hundreds ; and when we 

 consider that, in the earlier ages of astronomy, and indeed 

 in more recent times, before the invention of the telescope, 

 only large and conspicuous ones were noticed, and that, since 

 due attention has been paid to the subject, scarcely a year 

 has passed without the observation of one or two of these 

 bodies, and that sometimes two, and even three, have ap- 

 peared at once, — it will be easily supposed that their actual 

 number must be at least many thousands. Multitudes, in- 

 deed, must escape all observation, by reason of their paths 

 traversing only that part of the heavens which is above the 

 horizon in the day-time. Comets so circumstanced can only 

 become visible by the rare coincidence of a total eclipse of 

 the sun, — a coincidence which happened, as i-elated by Se- 

 neca, sixty-two years before Christ, when a large comet was 

 actually observed very near the sun. Several, however, stand 

 on record as having been bright enough to be seen with the 

 naked eye in the day-time, even at noon and in bright sun- 

 shine. Such were the comets of 1402, 1532, and 1843, and 

 that of 43 B.C. which appeared during the games celebrated 

 by Augustus in honour of Venus shortly after the death of 

 Caesar, and which the flattery of poets declared to be the soul 

 of that hero taking its place among the divinities. 



That feelings of awe and astonishment should be excited 

 by the sudden and unexpected appearance of a great comet, 

 is no way surprising ; being, in fact, according to the ac- 

 counts we have of such events, one of the most imposing of 

 all natural phenomena. Comets consist for the most part 

 of a large and more or less splendid, but ill-defined nebu- 

 lous mass of light, called the head, which is usually much 

 brighter towards its centre, and offers the appearance of a 



