1 62 Mr. Goodricke’s Obfer nations 
becaufe in that point the ftar has been obferved of about the 
fourth magnitude at intervals much fhorter than in the third 
point, fo that, if it had continued to diminiffi, its diminution 
would have proceeded at a more rapid rate, which ftill fhews 
that there is at leaff a difference between thefe two points. 
With regard to the period of the variation, it is evident 
from a collation of the preceding obfervations in a coarfe way, 
that it is nearly twelve days and three quarters. To determine it 
with greater accuracy is a fubjedt of conliderable difficulty, in 
the prefent cafe ; for unlefs we can obtain very exadl points of 
comparifon, the period would come out erroneous, efpecially 
if deduced from intervals confiding of only a very few periods, 
as is the cafe here. However, as I have been able to obtain a 
few obfervations of the middle of its obfcuration in the third 
point accurate enough for our purpofe, I have formed the fol- 
lowing calculation. 
Times of the middle of its obfcuration 
in the third point. 
h. 
d. h. 
1784, Odh 6 
1 1 only a lingle period of 
12 21 
— 18 
22J 
Oft. 18 
22 1 D° — 
12 1 7 
— 3 l 
Odh 6 
1 1 two periods, each of 
12 ip 
- 3 J 
Hence the period on a mean is 
12 I9=t 
In ascertaining the above times, I attended 
particularly to 
the neareft obfervations both preceding and following. In the 
manner above ffated the period may alfo be deduced from the 
middle of its obfcuration in the feventh point ; but as thefe 
obfervations are not fo exadt as the above, I lh all only, as a 
.further 
