*3® Mr. Pigott on the periodical Changes of 
From these observations the periodical changes were de«* 
duced as follows : 
The length of a single period being first settled of 67 days, 
from a succession of observations between March and May, 
and of 69 between April and June, we may proceed to obtain 
a greater exactness from distant dates, thus : 
Middle of its greatest brightness. 
DAYS. 
1795. Oct. 
1st. 1 Interval of four periods, making the 
1796. June 
18 J length of a single one 
® 5 * 
1 795 - Oct. 
1 1 Interval of three periods, making the 
1 796. April 
10 J length of a single one - 
(14 
Middle of its least brightness. 
1795. Nov. 
6 | Interval of three periods, making the 
1796. May 
10 J length of a single one 
62 
1 795 - Nov. 
6* ^Interval of two periods, making the 
1796. March 4 J length of a single one 
A single period, on a mean 
6q± 
Had it been requisite to have given any preference to one of 
these four results, I should have chosen the third ; not only on 
account of the exactness of the observations themselves, but 
particularly because the changes when near its least bright- 
ness are quicker ; however, they all agree more satisfactorily 
than I think could be expected ; still it must be remembered, 
that the mean period here determined is merely for this set of 
observations, it being yet unknown what kind of irregularities 
it is liable to ; for while I am now writing, in the month of 
August, its changes seem different from those of the four pre- 
ceding periods ; and how these perturbations will terminate, 
