114 On the Formation of the Tails of Comets. 



It appears, therefore, that the most probable conception, to say 

 the least, that can be formed of the distribution of matter in the 

 tail of the recent comet, is that there was the same quantity of 

 matter in each section perpendicular to its axis. And if this con- 

 ception be in accordance with fact, (in case we have regard only 

 to the absolute quantity of matter, and not to the density, which 

 is all that calculation to be made requires,) it is plain that the tail 

 may, so far as we know, have extended to a vastly greater dis- 

 tance than it appeared to do. As to its probable apparent length 

 at the perihelion, had it been seen in the evening, the lengths 

 observed after this date, in connection with the history of previ- 

 ous comets, would make it, at least, 25,000,000 miles. If it be 

 admitted that the tail was seen by Mr. Walker, at Philadelphia, 

 on the 23d of February, (who represents it to have extended 30° 

 in the heavens,) it must have been more than 50,000,000 miles 

 in length at that date. In view of all these considerations it 

 would seem that we might safely take the actual length of the 

 tail at the perihelion as great as 50,000,000 miles. After having 

 made the calculation upon this supposition it will be easy to de- 

 termine the effect upon our results of any supposed diminution in 

 the length. In fact, it will be seen that the principal conclusions 

 arrived at cannot be overthrown by any changes, that are at all 

 admissible, in the two hypotheses in respect to the length of the 

 tail and the distribution of its matter, that have been adopted. 



Another requisite datum, in the calculation, is the proportion 

 between the quantities of matter in the head and tail of the comet. 

 It appears that the nucleus, as seen by the different observers had 

 not the appearance of being a solid. Amici of Florence, who 

 saw the comet on Feb. 28th, compares the whole mass, without 

 making any distinction between the nucleus and the tail, to " a 

 flame :" and Mr. Clarke of Portland, compares its appearance on 

 the same day, to "a white cloud of great density." Other ac- 

 counts convey a similar idea. Mr. Clarke also represents the nu- 

 cleus to have been no brighter than the tail. From his account 

 and Amici's, it may certainly be inferred that there was no mate- 

 to my knowledge some three months after the date at which the comet was seen ; 

 and so much time was afterwards consumed in the endeavor to identify the date 

 that it was concluded to defer their publication to the present time. I have found 

 it impossible to fix upon the day with positive certainty : but a collection of all 

 the circumstances, leaves little room to doubt that it was the 28th of February. 

 [The true date is probably the 27th ; for, the comet was certainly seen on the 28th 

 as late as 3 P. M. : see this Journal, Vols, xliv, 412 : xlv, 230. — Eds.] 



