Mr Dunlop's observations on the Comet of 1825. 91 



very similar, and may be suspected to be returns of the same 

 epoch ; and Figures 2, 5, and 9, together with that of October 21, 

 which was hastily taken from a view of the comet through 

 an opening of the clouds, may also be suspected to be returns 

 of another epoch ; and also figures 8, 12, 14, 15 and 16, to be 

 returns of another epoch , — and the singular appearances on 

 October 19th and November 1st, or Figures 11 and 13, are 

 very similar, and are probably returns of the same epoch. 



These four epochs agree to prove something like a rotation, 

 or a regular succession of the same appearances ; and if we take 

 the observations of the 18th, 19th, 20th, and 21st of October, 

 or Figures 10, 11, 12, and October 21st, the period must be at 

 least eight days, or less than one day. 



Or the observations of October the 5th and 10th, Figures 1 

 and 3, would give a period of somewhat more than five days, as 

 Figure 3 is evidently short of the epoch of Figure first ; also the 

 observations of the 7 tn ant * l^th October, Figures 2 and 5, 

 would give a period of more than five days, as Figure 5 is evi- 

 dently not so far advanced as the epoch of Figure 2. 



But the observations of the 14th October show that the 

 change of figure is very sensible in a short time, and the ob- 

 servations of the 14th at 13 hours mean time, Figure 8 ; and 

 the observations of the 15th at 9 h 5' Figure 9, plainly show 

 that the body must have made a revolution and somewhat more 

 in 20 h and 5' of time ; for it is very evident that Figure 9 is 

 farther advanced from the epoch of Figure 6 than Figure 8 is, 

 and consequently the period of a revolution must be less than 

 20 h and 5', by a quantity equal to the difference between 

 Figures 8 and 9- 



From October 5th, at 9 h 30' to the 18th at ll h 13' gives 

 sixteen revolutions, and the time of revolution 19 h and 36'. 



From October 5th at 9 h 30' to the 14th at 8 h 10' gives eleven 

 revolutions, and the time of the revolution 19 h and 31/. 



From October 7th, at ll h 0', to the 15th at 10 h 15', gives 

 eleven revolutions, and the time of the revolution 19 h and 35'. 



From October 14th, at 13 h 0', to November 7th, at 8 h 56', 

 gives twenty-nine revolutions ; and the time of each revolution 

 19 h 42/. 



From October 19th, at 10 h 40', to November 1st, at 10 h 33' 



