146 Mr. Pigott's Investigation of the Changes 
obscure and another brightens, up in a different place, this 
latter will make the star appear at its next full splendour either 
sooner or later than the real rotation according to its position, 
thus, 
2d View. 
Fig. 1. A full brightness having been shewn by the same 
spot, it afterwards loses its light and another as bright is pro- 
duced 5 days motion ( or 29 degrees ) preceding it at E, see 
Fig. 2. This latter, when turned centrally to the earth, will 
appear 5 days sooner than the former one, now obscured, ( here 
marked P, ) and show the star at its full lustre, making the 
rotation 57 days instead of 62, which was the case in 1796, the 
observed revolution between September 17 and November 13. 
(See Table IX.) 
<gd View. 
Fig. 3. We will now apply a case of an interval of too great 
length, that of 72 days : the spot m alone having shewn us 
the star in its full lustre, its light disappears during the revo- 
lution, and another brightens forth ten days (or 58 degrees) 
follozvmg it at H ; when m returns to face us again in 6 2 days 
it being obliterated, the star will still appear obscured, and not 
recover its splendour until the new brightened part H becomes 
central, which being ten days later than the position in which 
m was seen, makes the revolution 72 days instead of 62, as 
was observed between July 14 and September 24, 1801. (See 
Table IX.) In the above case the alterations took place while 
behind the star, otherwise some irregularities would have been 
perceived, as will later be noticed. The same reasoning with 
proper alterations will, I apprehend, account for the other re- 
volutions, yet I shall soon again resume the subject with 
