2CO Mr . JPigott’s Obfervathns on 
The fecond of thefe, being compared to that of Nov. 20, 
1687, made by Kirch, gives 406 days exactly for one period, 
the interval between them being 35322 days, and divided by 
87 periods. I make the divifor 87, in order to get a refult 
neareft to that fettled by Maraldi and Cassini of 405, and 
by M. le Gentil of 405,3 days. We cannot fuppofe that 
thefe great aftronomers have made any miftake.; and on the 
other hand, it feems hardly poflible, that the mean of my 
obfervations alone, which makes the period 392 days, can 
err 14 ; but perhaps its period is irregular ; to determine which 
feveral intervals of 15 years ought to be taken, and I am 
much inclined to believe, that it will be found of only 396 
days 2 1 hours. 
Particulars of the .changes it undergoes. 
1. When at its full brightnefs it has no perceptible change 
for about a fortnight. 
2. It is about 3I months in increafing from the nth mag- 
nitude to its full brightnefs, and the fame in decreafing. 
3. Therefore it may be confidered as invifible during fix 
months. 
4. It does not attain the fame degreee of brightnefs at every 
period, being fometimes of the 5th, and other times of the 
7th magnitude. 
Its mean right afcenfion, computed from my obfervations. 
Mid reduced to Aug. 1, 1783, is 
2 95 
